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  • 1. Andersson, Patrik U.
    et al.
    Ojekull, Jenny
    Pettersson, Jan B. C.
    Markovic, Nikola
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, Anneli
    Stockholm University, Faculty of Science, Department of Physics.
    Österdahl, Fabian
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Uggerud, Einar
    Danared, Hakan
    Kallberg, Anders
    Formation of Highly Rovibrationally Excited Ammonia from Dissociative Recombination of NH4+2010In: The journal of physical chemistry letters, ISSN 1948-7185, Vol. 1, no 17, p. 2519-2523Article in journal (Refereed)
    Abstract [en]

    The internal energy distribution of ammonia formed in the dissociative recombination (DR) of NH4+ with electrons has been studied by an imaging technique at the ion storage ring CRYRING. The DR process resulted in the formation of NH3 + H (0,90 +/- 0.01), with minor contributions from channels producing NH2 + H-2 (0.05 +/- 0.01) and NH2 + 2H (0.04 +/- 0.02). The formed NH3 molecules were highly internally excited, with a mean rovibrational energy of 3.3 +/- 0.4 eV, which corresponds to 70% of the energy released in the neutralization process. The internal energy distribution was semiquantitatively reproduced by ab initio direct dynamics simulations, and the calculations suggested that the NH3 molecules are highly vibrationally excited while rotational excitation is limited. The high internal,excitation and the translational energy of NH3 and H will influence their subsequent reactivity, an aspect that should be taken into account when developing detailed models of the interstellar medium and ammonia-containing plasmas.

  • 2. Best, T.
    et al.
    Otto, R.
    Trippel, S.
    Hlavenka, P.
    von Zastrow, A.
    Eisenbach, S.
    Jezouin, S.
    Wester, R.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    ABSOLUTE PHOTODETACHMENT CROSS-SECTION MEASUREMENTS FOR HYDROCARBON CHAIN ANIONS2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 742, no 2, p. 63-Article in journal (Refereed)
    Abstract [en]

    Absolute photodetachment cross sections have been measured for the hydrocarbon chain anions C(n)H(-), n = 2, 4, and 6, which are relevant for an understanding of molecular clouds in the interstellar medium. Data have been obtained for different photon energies within approximately 1 eV of the detachment threshold. With our recently developed method we have achieved a precision of better than 25% on these absolute cross sections. The experiments have been carried out by means of photodetachment tomography of the mass-selected molecular anions in a multipole radio-frequency ion trap. The measured absolute cross sections are in accordance with the empirical scaling law of Millar et al. and have allowed us to determine its free parameters. These results are important for predicting the photostability and thus the abundance of carbon chain anions in planetary atmospheres, in circumstellar envelopes, and in photon-dominated regions of interstellar molecular clouds.

  • 3. Calabrese, C.
    et al.
    Vigorito, A.
    Feng, G.
    Favero, L. B.
    Maris, A.
    Melandri, S.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Caminati, W.
    Laboratory rotational spectrum of acrylic acid and its isotopologues in the 6-18.5 GHz and 52-74.4 GHz frequency ranges2014In: Journal of Molecular Spectroscopy, ISSN 0022-2852, E-ISSN 1096-083X, Vol. 295, p. 37-43Article in journal (Refereed)
    Abstract [en]

    In order to facilitate the detection of acrylic acid in space, for which a possible mechanism of formation is proposed, we extended the measurements of the rotational spectrum of this molecule to the 6-18.5 GHz (time domain Fourier transform) and 52-74.4 GHz (frequency domain) ranges in supersonic expansions. 77 new lines were assigned to the s-cis conformer and 83 new lines to the s-trans conformer. In addition, the rotational spectra of the three single C-13 isotopologues have been measured in natural abundance for both conformers. High resolution measurements of the carboxylic deuterated isotopologues allowed for the determination of the deuterium nuclear quadrupole coupling constants. All the spectroscopic experimental parameters were compared to the ones obtained with quantum chemical methods at the MP2(fc)/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels of calculation.

  • 4. Calabrese, Camilla
    et al.
    Maris, Assimo
    Dore, Luca
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Fathi, Pantea
    Stockholm University, Faculty of Science, Department of Physics.
    Melandri, Sonia
    Acrylic acid (CH2CHCOOH): the rotational spectrum in the millimetre range up to 397 GHz2015In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 113, no 15-16, p. 2290-2295Article in journal (Refereed)
    Abstract [en]

    In order to facilitate its detection in astronomical observations, the measurement of the rotational spectrum of acrylic acid has been extended to 397 GHz using a free space cell at room temperature. 295 new lines were assigned to the s-cis conformer and 286 new lines to the s-trans conformer of acrylic acid. Using the determined experimental parameters, the predictions of the rotational transition frequencies up to 900 GHz and their intensities were obtained at temperatures of 100 and 200 K and at room temperature. Based on these predictions, a search of the most intense transitions of acrylic acid in star-forming regions was performed using published data from the HERSCHEL Science Archive. No lines were found but the possibility of observing rotational transitions of acrylic acid in astronomical objects is discussed.

  • 5. Calabrese, Camilla
    et al.
    Vigorito, Annalisa
    Maris, Assimo
    Mariotti, Sergio
    Fathi, Pantea
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Melandri, Sonia
    Millimeter Wave Spectrum of the Weakly Bound Complex CH2=CHCN center dot H2O: Structure, Dynamics, and Implications for Astronomical Search2015In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 119, no 48, p. 11674-11682Article in journal (Refereed)
    Abstract [en]

    The weakly bound 1:1 complex between acrylonitrile (CH2=-CHCN) and water has been characterized spectroscopically in the millimeter wave range (59.6-74.4 GHz) using a Free Jet Absorption Millimeter Wave spectrometer. Precise values of the rotational and quartic centrifugal distortion constants have been obtained from the measured frequencies of the normal and isotopically substituted water moiety (DOH, DOD, (HOH)-O-18). Structural parameters have been estimated from the rotational constants and their differences among isotopologues: the complex has a planar structure with the two subunits held together by a O-H center dot center dot center dot N (2.331(3) angstrom) and a C- H center dot center dot center dot O (2.508(4) angstrom) interaction. The ab initio intermolecular binding energy, obtained at the counterpoise corrected MP2/aug-cc-pVTZ level of calculation, is D-e = 24.4 kJ mol(-1)

  • 6. Carrascosa, E.
    et al.
    Bawart, M.
    Stei, M.
    Lindén, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Carelli, F.
    Meyer, J.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Gianturco, F. A.
    Wester, R.
    Nucleophilic substitution with two reactive centers: The CN- + CH3I case2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, no 18, article id 184309Article in journal (Refereed)
    Abstract [en]

    The nucleophilic substitution reaction CN- + CH3I allows for two possible reactive approaches of the reactant ion onto the methyl halide, which lead to two different product isomers. Stationary point calculations predict a similar shape of the potential and a dominant collinear approach for both attacks. In addition, an H-bonded pre-reaction complex is identified as a possible intermediate structure. Submerged potential energy barriers hint at a statistical formation process of both CNCH3 and NCCH3 isomers at the experimental collision energies. Experimental angle-and energy differential cross sections show dominant direct rebound dynamics and high internal excitation of the neutral product. No distinct bimodal distributions can be extracted from the velocity images, which impedes the indication of a specific preference towards any of the product isomers. A forward scattering simulation based on the experimental parameters describes accurately the experimental outcome and shows how the possibility to discriminate between the two isomers is mainly hindered by the large product internal excitation.

  • 7.
    Danielsson, Mathias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Paál, Andreas
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitaly
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, Anneli
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard
    Stockholm University, Faculty of Science, Department of Physics.
    Österdal, Fabian
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    The cross-section and branching fractions for dissociative recombination of the diacetylene cation C4D2+2008In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 273, no 3, p. 111-116Article in journal (Refereed)
    Abstract [en]

    In this paper we report the results of a study on the dissociative recombination (DR) of the diacetylene cation, C4D2+, which has been carried out at the ion storage ring CRYRING in Stockholm, Sweden. The energy-dependent absolute DR cross-section as well as the branching fractions at 0 eV collision energy were measured. The DR cross-section was best fitted using the expression σ(E) = (7.5 ± 1.5) × 10−16 × E−(1.29±0.03) cm2 over the collision energy range 1–100 meV. The thermal rate coefficient was deduced from the cross-section to be α(T) = (1.10 ± 0.15) × 10−6 × (T/300)−(0.79±0.03) cm3/s. The reported branching fractions for C4D2+ agree with previous experiments on the DR of C4H2+ performed at the ASTRID storage ring in Aarhus, Denmark, and furthermore, indicate that the DR of C4D2+ possesses only two channels leading to the following products: C4D + D (75%) and C2D + C2D (25%).

  • 8.
    Fathi, Pantea
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Ascenzi, D.
    Experimental and theoretical investigations of the ion-neutral reaction of C2H2N+ with C2H6 and implications on chain elongation processes in Titan's atmosphere2016In: International Journal of Mass Spectrometry, ISSN 1387-3806, E-ISSN 1873-2798, Vol. 411, p. 1-13Article in journal (Refereed)
    Abstract [en]

    In this study we report theoretical and experimental evidence for the formation of ionic products by the ion-neutral reaction of C2H2N+ with C2H6. Our investigations consist of laboratory measurements using a guided ion beam mass spectrometer together with complementary ab initio quantum chemical computations, at the MP2/6-311++G(d,p) level of theory, in order to elucidate the energetics and geometries of the intermediates and transition states that are involved in the production of the observed product ions. This study also provides insights on the isomeric nature of the observed product ions, their formation pathways together with collision energy and pressure dependences. The experimental data agrees well with the predictions of the ab initio calculations. Despite data provides evidence for the occurrence of C2H5+ as the most salient product ion, the production of CH3+, C2H3+, C3H5+, C3H7+ and C2H4N+ is also evident. A reaction scheme was proposed to elucidate the mechanisms responsible for the formation of the observed product ions. These processes might be intermediate steps in the generation of long chain carbon and nitrogen-bearing compounds in Titan's ionosphere, the interstellar medium or circumstellar envelopes.

  • 9.
    Fathi, Pantea
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Kaiser, A.
    Ascenzic, D.
    Ion-neutral reaction of the C2H2N+ cation with C2H2: An experimental and theoretical study2016In: Molecular Astrophysics, ISSN 2405-6758, Vol. 2, p. 1-11Article in journal (Refereed)
    Abstract [en]

    The ion-neutral reactions of the C2H2N+ cation with C2H2 have been investigated using a Guided Ion Beam Mass Spectrometer (GIB-MS). The following ionic products were observed: CH3+, C2H2+, C2H3+, HNC+/HCN+, HCNH+, C3H+, C2N+, C3H3+, HCCNand C4H2N+. Theoretical calculations have been carried out to propose reaction pathways leading to the observed products. These processes are of relevance for the generation of long chain nitrogen-containing species and they may be of interest for the chemistry of Titan’s ionosphere or circumstellar envelopes.

  • 10.
    Fathi, Pantea
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Lindén, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Cernuto, A.
    Ascenzi, D.
    Ion-neutral reaction of C2H2N+ with CH4: An experimental and theoretical study2016In: Molecular Astrophysics, ISSN 2405-6758, Vol. 5, p. 9-22Article in journal (Refereed)
    Abstract [en]

    The current study was undertaken to probe the ionic products of the ion-neutral reaction of C2H2N+ with CH4 using guided ion beam mass spectrometry (GIB-MS) in which the CH3+, C2H3+, HCNH+, C2H5+, C2H3N+ and C3H4N+ ions are identified as products. Theoretical calculations were performed to suggest reaction pathways leading to the detected products. These processes might be of relevance for the generation of long chain carbon-nitrogen bearing compounds in Titan's atmosphere, the interstellar medium or circumstellar envelopes.

  • 11.
    Gatchell, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Alexander, John D.
    Stockholm University, Faculty of Science, Department of Physics.
    Andler, Guillermo
    Stockholm University, Faculty of Science, Department of Physics.
    Björkhage, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Blom, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Brännholm, Lars
    Stockholm University, Faculty of Science, Department of Physics.
    Bäckström, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Chen, Tao
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Halldén, Per
    Stockholm University, Faculty of Science, Department of Physics.
    Hanstorp, Dag
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Leontein, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Liljeby, Leif
    Stockholm University, Faculty of Science, Department of Physics.
    Löfgren, Patrik
    Stockholm University, Faculty of Science, Department of Physics.
    Mannervik, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Paal, Andras
    Stockholm University, Faculty of Science, Department of Physics.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Rensfelt, Karl-Gunnar
    Stockholm University, Faculty of Science, Department of Physics.
    Rosén, Stefan
    Stockholm University, Faculty of Science, Department of Physics.
    Seitz, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, Department of Physics.
    Stockett, Mark H.
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    First results from the Double ElectroStatic Ion-Ring ExpEriment, DESIREE2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 488, p. 092003-Article in journal (Refereed)
    Abstract [en]

    We have stored the first beams in one of the rings of the double electrostatic ion-storage ring, DESIREE at cryogenic and at room temperature conditions. At cryogenic operations the following parameters are found. Temperature; T= 13K, pressure; p <10(-13) mbar, initial number of stored ions; N > 10(7) and storage lifetime of a C-2(-) beam; tau = 450 S.

  • 12.
    Gatchell, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Rosén, Stefan
    Stockholm University, Faculty of Science, Department of Physics.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Löfgren, Patrik
    Stockholm University, Faculty of Science, Department of Physics.
    Brännholm, Lars
    Stockholm University, Faculty of Science, Department of Physics.
    Blom, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Björkhage, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Bäckström, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Alexander, John D.
    Stockholm University, Faculty of Science, Department of Physics.
    Leontein, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Hanstorp, D.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Liljeby, Leif
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Mannervik, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Rensfelt, Karl-Gunnar
    Stockholm University, Faculty of Science, Department of Physics.
    Danared, Håkan
    Stockholm University, Faculty of Science, Department of Physics. European Spallation Source, Sweden.
    Paál, Andras
    Stockholm University, Faculty of Science, Department of Physics.
    Masuda, Masaharu
    Stockholm University, Faculty of Science, Department of Physics.
    Halldén, Per
    Stockholm University, Faculty of Science, Department of Physics.
    Andler, Guillermo
    Stockholm University, Faculty of Science, Department of Physics.
    Stockett, Mark H.
    Stockholm University, Faculty of Science, Department of Physics.
    Chen, Tao
    Stockholm University, Faculty of Science, Department of Physics.
    Källersjö, Gunnar
    Stockholm University, Faculty of Science, Department of Physics.
    Weimer, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Hansen, K.
    Hartman, H.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Commissioning of the DESIREE storage rings - a new facility for cold ion-ion collisions2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 488, p. 012040-Article in journal (Refereed)
    Abstract [en]

    We report on the ongoing commissioning of the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. Beams of atomic carbon anions (C-) and smaller carbon anion molecules (C-2(-), C-3(-), C-4(-) etc.) have been produced in a sputter ion source, accelerated to 10 keV or 20 keV, and stored successfully in the two electrostatic rings. The rings are enclosed in a common vacuum chamber cooled to below 13 Kelvin. The DESIREE facility allows for studies of internally relaxed single isolated atomic, molecular and cluster ions and for collision experiments between cat-and anions down to very low center-of-mass collision energies (meV scale). The total thermal load of the vacuum chamber at this temperature is measured to be 32 W. The decay rates of stored ion beams have two components: a non-exponential component caused by the space charge of the beam itself which dominates at early times and an exponential term from the neutralization of the beam in collisions with residual gas at later times. The residual gas limited storage lifetime of carbon anions in the symmetric ring is over seven minutes while the 1/e lifetime in the asymmetric ring is measured to be about 30 seconds. Although we aim to improve the storage in the second ring, the number of stored ions are now sufficient for many merged beams experiments with positive and negative ions requiring milliseconds to seconds ion storage.

  • 13. Gentry, Diana M.
    et al.
    Amador, Elena S.
    Cable, Morgan L.
    Chaudry, Nosheen
    Cullen, Thomas
    Jacobsen, Malene B.
    Murukesan, Gayathri
    Schwieterman, Edward W.
    Stevens, Adam H.
    Stockton, Amanda
    Tan, George
    Yin, Chang
    Stockholm University, Faculty of Science, Department of Physics.
    Cullen, David C.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Correlations Between Life-Detection Techniques and Implications for Sampling Site Selection in Planetary Analog Missions2017In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, no 10, p. 1009-1021Article in journal (Refereed)
    Abstract [en]

    We conducted an analog sampling expedition under simulated mission constraints to areas dominated by basaltic tephra of the Eldfell and Fimmvorouhals lava fields (Iceland). Sites were selected to be homogeneous at a coarse remote sensing resolution (10-100m) in apparent color, morphology, moisture, and grain size, with best-effort realism in numbers of locations and replicates. Three different biomarker assays (counting of nucleic-acid-stained cells via fluorescent microscopy, a luciferin/luciferase assay for adenosine triphosphate, and quantitative polymerase chain reaction (qPCR) to detect DNA associated with bacteria, archaea, and fungi) were characterized at four nested spatial scales (1m, 10m, 100m, and >1km) by using five common metrics for sample site representativeness (sample mean variance, group F tests, pairwise t tests, and the distribution-free rank sum H and u tests). Correlations between all assays were characterized with Spearman's rank test. The bioluminescence assay showed the most variance across the sites, followed by qPCR for bacterial and archaeal DNA; these results could not be considered representative at the finest resolution tested (1m). Cell concentration and fungal DNA also had significant local variation, but they were homogeneous over scales of >1km. These results show that the selection of life detection assays and the number, distribution, and location of sampling sites in a low biomass environment with limited a priori characterization can yield both contrasting and complementary results, and that their interdependence must be given due consideration to maximize science return in future biomarker sampling expeditions.

  • 14.
    Geppert, W.D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, R.D.
    Stockholm University, Faculty of Science, Department of Physics.
    Österdahl, F.
    Hellberg, F.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhauernerchyk, V.
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, A.
    Stockholm University, Faculty of Science, Department of Physics.
    Millar, T.J.
    Roberts, H.
    Semaniak, J.
    af Ugglas, M.
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Kaminska, M.
    Larsson, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of protonated methanol2006In: Journal of the Chemical Society, Faraday Transactions, ISSN 0956-5000, E-ISSN 1364-5455, Vol. 133, p. 177-190Article in journal (Refereed)
  • 15.
    Geppert, Wolf D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination in the interstellar medium and planetary ionospheres2008In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 106, no 16-18, p. 2199-2226Article, review/survey (Refereed)
    Abstract [en]

    Dissociative recombination is a corner-stone reaction in the synthesis of interstellar molecules and plays an important role in the ionised layers of the atmospheres of the Earth, other planets, and their satellites. The studies of dissociative recombination reactions was for a long time dominated by afterglow techniques, and these techniques are used in improved versions also today, but the bulk of the relevant data have in recent years been produced at ion storage rings. We review briefly these different experimental techniques. As examples of recent developments in the field, we discuss in particular the dissociative recombination of [image omitted], the role of dissociative recombination in the chemistry of hydrocarbons and sulphur compounds in the interstellar medium and planetary ionospheres, and the synthesis of interstellar methanol.

  • 16.
    Geppert, Wolf D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental Investigations into Astrophysically Relevant Ionic Reactions2013In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 113, no 12, p. 8872-8905Article, review/survey (Refereed)
  • 17.
    Geppert, Wolf
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Österdahl, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, Anneli
    Stockholm University, Faculty of Science, Department of Physics.
    Millar, Tom
    Queen's University Belfast.
    Roberts, Helen
    Queen's University Belfast.
    Semaniak, Jacek
    Jan Kochanowski University, Kielce.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Kaminska, Magdalena
    Jan Kochanowski University.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of protonated methanol2006In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 133, p. 177-190Article in journal (Refereed)
    Abstract [en]

    The branching ratios of the different reaction pathways and the overall rate coefficients of the dissociative recombination reactions of CH3OH2+ and CD3OD2+ have been measured at the CRYRING storage ring located in Stockholm, Sweden. Analysis of the data yielded the result that formation of methanol or deuterated methanol accounted for only 3 and 6% of the total rate in CH3OH2+ and CD3OD2+, respectively. Dissociative recombination of both isotopomeres mainly involves fragmentation of the C–O bond, the major process being the three-body break-up forming CH3, OH and H (CD3, OD and D). The overall cross sections are best fitted by s = 1.2 ± 0.1 × 10-15 E-1.15±0.02 cm2 and s = 9.6 ± 0.9 × 10-16 E-1.20±0.02 cm2 for CH3OH2+ and CD3OD2+, respectively. From these values thermal reaction rate coefficients of k(T) = 8.9 ± 0.9 ×10-7 (T/300)-0.59±0.02 cm3 s-1 (CH3OH2+) and k(T) = 9.1 ± 0.9 × 10-7 (T/300)-0.63±0.02 cm3 s-1(CD3OD2+) can be calculated. A non-negligible formation of interstellar methanol by the previously proposed mechanism via radiative association of CH3+ and H2O and subsequent dissociative recombination of the resulting CH3OH2+ ion to yield methanol and hydrogen atoms is therefore very unlikely.

  • 18.
    Hamberg, Mathias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    Danielsson, Mathias
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Österdahl, Fabian
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Jan Kochanowski University, Kielce, Poland.
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Paál, András
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental studies on the dissociative recombination of H13CO+ with electrons at energies between 2 – 50 000 meVManuscript (preprint) (Other academic)
    Abstract [en]

    Determination of dissociative recombination processes of H13CO+ using merged ion-electron beam methods has been performed at the heavy storage ring CRYRING, Stockholm, Sweden. We have measured the branching fractions at ~0 eV as: CO+H 87±2%, OH+C 9±2% and O+CH 4±2%. The channels leading to CO+H have the following branching fractions between the accessible electronic states of CO(X1S+)+H 46±3%, CO(a3Pg)+H 20±1% and CO(a’3S+)+H 34±3% respectively. The reaction cross section was fitted between 1-300 meV and followed the expression σ = 1.2±0.25×10-16 E-1.32±0.02 cm2 and the corresponding thermal rate constant was determined to k(T) = 2.0±0.4×10−7(T/300)−0.82±0.02 cm3s−1. The cross sections between ~2-50 000 meV were investigated showing resonant structures between 3-15 eV.

  • 19.
    Hamberg, Mathias
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Uppsala University, Sweden.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Roueff, Evelyne
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics. Uppsala University, Sweden.
    Danielsson, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Österdahl, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, Department of Physics.
    Paál, Andras
    Stockholm University, Faculty of Science, Department of Physics.
    Gerin, Maryvonne
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental Studies of (HCO+)-C-13 Recombining with Electrons at Energies between 2-50 000 meV2014In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 118, no 31, p. 6034-6049Article in journal (Refereed)
    Abstract [en]

    An investigation into the dissociative recombination process for (HCO+)-C-13 using merged ion-electron beam methods has been performed at the heavy ion storage ring CRYRING, Stockholm, Sweden. We have measured the branching fractions of the different product channels at similar to 0 eV collision energy to be the following: CO + H 87 +/- 2%, OH + C 9 +/- 2%, and O + CH 4 +/- 2%. The formation of electronically excited CO in the dominant reaction channel has also been studied, and we report the following tentative branching fractions for the different CO product electronic states: CO(X (1)Sigma(+)) + H, 54 +/- 10%; CO(a (3)Pi) + H, 23 +/- 4%; and CO(a' (3)Sigma(+)) + H, 23 +/- 4%. The absolute cross section between similar to 2-50 000 meV was measured and showed resonance structures between 3 and 15 eV. The cross section was fitted in the energy range relevant to astrophysics, i.e., between 1 and 300 meV, and was found to follow the expression sigma = 1.3 +/- 0.3 X 10(-16) E-1.29 +/- 0.05 cm(2) and the corresponding thermal rate constant was determined to be k(T) = 2.0 +/- 0.4 X 10(-7)(T/300)(-0.79 +/- 0.05) cm(3) s(-1). Radioastronomical observations with the IRAM 30 m telescope of HCO+ toward the Red Rectangle yielded an upper column density limit of 4 X 10(11) cm(-2) of HCO+ at the 1 sigma level in that object, indicating that previous claims that the dissociative recombination of HCO+ plays an important role in the production of excited CO molecules emitting the observed Cameron bands in that object are not supported.

  • 20.
    Hamberg, Mathias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Jan Kochanowski University, Kielce, Poland.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    Zhang, Mingwu
    Institute of Modern Physics.
    Trippel, Sebastian
    Albert-Ludwigs-Universität Freiburg, Tyskland.
    Österdahl, Fabian
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Paál, András
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental studies of the dissociative recombination for CD3CDOD+ and CH3CH2OH2+Manuscript (preprint) (Other academic)
    Abstract [en]

    Aims:  Determination of branching fractions, cross sections and thermal rate constants for the dissociative recombination of CD3CDOD+ and CH3CH2OH2+ at the low relative kinetic energies encountered in the interstellar medium.

    Methods: The experiments were carried out by merging an ion and electron beam at the heavy ion storage ring CRYRING, Stockholm, Sweden.

    Results: Break-up of the CCO structure into three heavy fragments is not found for either of the ions. Instead the CCO structure is retained in 23 ± 3% of the DR reactions of CD3CDOD+ and 7 ± 3% in the DR of CH3CH2OH2+, whereas rupture into two heavy fragments occurs in 77 ± 3% and 93 ± 3% of the DR events of the respective ions. The measured cross sections were fitted between 1-200 meV yielding the following thermal rate constants and cross-section dependencies on the relative kinetic energy: σ(Ecm[eV]) = 1.7 ± 0.3 × 1015(Ecm[eV])1.23±0.02 cm2 and k(T) = 1.9 ± 0.4 × 106(T/300)0.73±0.02 cm3s1 for CH3CH2OH2+  as well as k(T) = 1.1 ± 0.4 × 106(T/300)0.74±0.05 cm3s1 and σ(Ecm[eV]) = 9.2 ± 4 × 1016(Ecm[eV])1.24±0.05 cm2 for CD3CDOD+.

  • 21.
    Hamberg, Mathias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Österdahl, Fabian
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Jan Kochanowski University.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory.
    Paál, András
    Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory.
    Larsson, Mats
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental studies of the dissociative recombination processes for the dimethyl ether ions CD3OCD2+ and (CD3)2OD+2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 514, p. A83-Article in journal (Refereed)
    Abstract [en]

    Aims: Determination of branching fractions, cross sections and thermal rate coefficients for the dissociative recombination of CD3OCD2+ (0-0.3 eV) and (CD3)2OD+ (0-0.2 eV) at the low relative kinetic energies encountered in the interstellar medium.

    Methods: The measurements were carried out using merged electron and ion beams at the CRYRING storage ring, Stockholm, Sweden.

    Results: For (CD3)2OD+ we have experimentally determined the branching fraction for ejection of a single hydrogen atom in the DR process to be maximally 7% whereas 49% of the reactions involve the break up of the COC chain into two heavy fragments and 44% ruptures both C-O bonds. The DR of CD3OCD2+ is dominated by fragmentation of the COC chain into two heavy fragments. The measured thermal rate constants and cross sections are k(T) =1.7 ± 0.5 × 106(T/300)0.77±0.01 cm3s−1,  σ= 1.2 ± 0.4 × 1015(Ecm[eV])1.27 ± 0.01 cm2 and k(T) = 1.7 ± 0.6 × 106(T/300)0.70±0.02 cm3s1,σ= 1.7 ± 0.6 × 1015(Ecm[eV])1.20±0.02 cm2 for CD3OCD2+ and (CD3)2OD+, respectively.

  • 22. Kobayashi, Kensei
    et al.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Carrasco, Nathalie
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mousis, Olivier
    Palumbo, Maria Elisabetta
    Waite, J. Hunter
    Watanabe, Naoki
    Ziurys, Lucy M.
    Laboratory Studies of Methane and Its Relationship to Prebiotic Chemistry2017In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, no 8, p. 786-812Article, review/survey (Refereed)
    Abstract [en]

    To examine how prebiotic chemical evolution took place on Earth prior to the emergence of life, laboratory experiments have been conducted since the 1950s. Methane has been one of the key molecules in these investigations. In earlier studies, strongly reducing gas mixtures containing methane and ammonia were used to simulate possible reactions in the primitive atmosphere of Earth, producing amino acids and other organic compounds. Since Earth's early atmosphere is now considered to be less reducing, the contribution of extraterrestrial organics to chemical evolution has taken on an important role. Such organic molecules may have come from molecular clouds and regions of star formation that created protoplanetary disks, planets, asteroids, and comets. The interstellar origin of organics has been examined both experimentally and theoretically, including laboratory investigations that simulate interstellar molecular reactions. Endogenous and exogenous organics could also have been supplied to the primitive ocean, making submarine hydrothermal systems plausible sites of the generation of life. Experiments that simulate such hydrothermal systems where methane played an important role have consequently been conducted. Processes that occur in other Solar System bodies offer clues to the prebiotic chemistry of Earth. Titan and other icy bodies, where methane plays significant roles, are especially good targets. In the case of Titan, methane is both in the atmosphere and in liquidospheres that are composed of methane and other hydrocarbons, and these have been studied in simulation experiments. Here, we review the wide range of experimental work in which these various terrestrial and extraterrestrial environments have been modeled, and we examine the possible role of methane in chemical evolution.

  • 23. Kumar, S. S.
    et al.
    Hauser, D.
    Jindra, R.
    Best, T.
    Roucka, S.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Millar, T. J.
    Wester, R.
    PHOTODETACHMENT AS A DESTRUCTION MECHANISM FOR CN- AND C3N- ANIONS IN CIRCUMSTELLAR ENVELOPES2013In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 776, no 1, p. 25-Article in journal (Refereed)
    Abstract [en]

    Absolute photodetachment cross sections of two anions of astrophysical importance CN- and C3N- were measured to be (1.18 +/- (0.03)(stat)(0.17)(sys)) x 10(-17) cm(2) and (1.43 +/- (0.14)(stat)(0.37)(sys)) x 10(-17) cm(2), respectively, at the ultraviolet (UV) wavelength of 266 nm (4.66 eV). These relatively large values of the cross sections imply that photodetachment can play a major role in the destruction mechanisms of these anions particularly in photon-dominated regions. We have therefore carried out model calculations using the newly measured cross sections to investigate the abundance of these molecular anions in the cirumstellar envelope of the carbon-rich star IRC+10216. The model predicts the relative importance of the various mechanisms of formation and destruction of these species in different regions of the envelope. UV photodetachment was found to be the major destruction mechanism for both CN- and C3N- anions in those regions of the envelope, where they occur in peak abundance. It was also found that photodetachment plays a crucial role in the degradation of these anions throughout the circumstellar envelope.

  • 24.
    Larsson, Mats
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf. D.
    Stockholm University, Faculty of Science, Department of Physics.
    Nyman, G.
    Ion chemistry in space2012In: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 75, no 6, p. 066901-Article, review/survey (Refereed)
    Abstract [en]

    We review the gas-phase chemistry in extraterrestrial space that is driven by reactions with atomic and molecular ions. Ions are ubiquitous in space and are potentially responsible for the formation of increasingly complex interstellar molecules. Until recently, positively charged atoms and molecules were the only ions known in space; however, this situation has changed with the discovery of various molecular anions. This review covers not only the observation, distribution and reactions of ions in space, but also laboratory-based experimental and theoretical methods for studying these ions. Recent results from space-based instruments, such as those on the Cassini-Huygens space mission and the Herschel Space Observatory, are highlighted.

  • 25.
    Lenori, Francesca
    et al.
    Universitá di Perugia.
    Petrucci, Raffaelo
    Universitá di Perugia.
    Hickson, Kevin E.
    Université Bordeaux 1.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Casavecchia, Piergiorgio
    Universitá di Perugia.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Crossed-Beam and Theoretical Studies of the S(1D) + C2H2 Reaction2009In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 113, p. 4330-Article in journal (Refereed)
    Abstract [en]

    The reaction dynamics of excited sulfur atoms, S(D-1), with acetylene has been investigated by the crossed-beam scattering technique with mass spectrometric detection and time-of-flight (TOF) analysis at the collision energy of 35.6 kJ mol(-1). These studies have been made possible by the development of intense continuous supersonic beams of S(P-3,D-1) atoms. From product angular and TOF distributions, center-of-mass product angular and translational energy distributions are derived. The S(D-1) + C2H2 reaction is found to lead to formation of HCCS (thioketenyl) + H, while the only other energetically allowed channels, those leading to CCS((3)Sigma(-), Delta) + H-2, are not observed to occur to an appreciable extent. The dynamics of the H-elimination channel is discussed and elucidated. The interpretation of the scattering results is assisted by synergic high-level ab initio electronic structure calculations of stationary points and product energetics for the C2H2S ground-state singlet potential energy surface. In addition, by exploiting the novel capability of performing product detection by means of a tunable electron-impact ionizer, we have obtained the first experimental information on the ionization energy of thioketenyl radical, HCCS, as synthesized in the reactive scattering experiment. This has been complemented by ab initio calculations of the adiabatic and vertical ionization energies for the ground-state radical. The theoretically derived value of 9.1 eV confirms very recent, accurate calculations and is corroborated by the experimentally determined ionization threshold of 8.9 +/- 0.3 eV for the internally warm HCCS produced from the title reaction.

  • 26.
    Lindén, Carl Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Žabka, Ján
    Polášek, Miroslav
    Zymakb, Illia
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    The reaction of C5N- with acetylene as a possible intermediate step to produce large anions in Titan’s ionosphere2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 8, p. 5377-5388Article in journal (Refereed)
    Abstract [en]

    A theoretical and experimental investigation of the reaction C5N + C2H2 has been carried out. This reaction is of astrophysical interest since the growth mechanism of large anions that have been detected in Titan's upper atmosphere by the Cassini plasma spectrometer are still largely unknown. The experimental studies have been performed using a tandem quadrupole mass spectrometer which allows identification of the different reaction channels and assessment of their reaction thresholds. Results of these investigations were compared with the predictions of ab initio calculations, which identified possible pathways leading to the observed products and their thermodynamical properties. These computations yielded that the majority of these products are only accessible via energy barriers situated more than 1 eV above the reactant energies. In many cases, the thresholds predicted by the ab initio calculations are in good agreement with the experimentally observed ones. For example, the chain elongation reaction leading to C7N, although being slightly exoergic, possesses an energy barrier of 1.91 eV. Therefore, the title reaction can be regarded to be somewhat unlikely to be responsible for the formation of large anions in cold environments such as interstellar medium or planetary ionospheres.

  • 27.
    Lindén, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Alcaraz, Christian
    Ascenzi, Daniela
    Guillemin, Jean-Claude
    Koch, Leopold
    Lopes, Allan
    Polášek, Miroslav
    Romanzin, Claire
    Zabka, Jan
    Zymak, Illia
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Is the Reaction of C3N- with C2H2 a Possible Process for Chain Elongation in Titan's Ionosphere?2016In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 120, no 27, p. 5337-5347Article in journal (Refereed)
    Abstract [en]

    The reaction of C3N- with acetylene was studied using three different experimental setups, a triple quadrupole mass spectrometer (Trento), a tandem quadrupole mass spectrometer (Prague), and the CERISES guided ion beam apparatus at Orsay. The process is of astrophysical interest because it can function as a chain elongation mechanism to produce larger anions that have been detected in Titan's ionosphere by the Cassini Plasma Spectrometer. Three major products of primary processes, C2H-, CN-, and C5N-, have been identified, whereby the production of the cyanide anion is probably partly due to collisional induced dissociation. The formations of all these products show considerable reaction thresholds and also display comparatively small cross sections. Also, no strong signals of anionic products for collision energies lower than 1 eV have been observed. Ab initio calculations have been performed to identify possible pathways leading to the observed products of the title reaction and to elucidate the thermodynamics of these processes. Although the productions of CN- and C5N- are exoergic, all reaction pathways have considerable barriers. Overall, the results of these computations are in agreement with the observed reaction thresholds. Due to the existence of considerable reaction enenrgy barriers and the small observed cross sections, the title reaction is not very likely to play major role in the buildup of large anions in cold environments like the interstellar medium or planetary and satellite ionospheres.

  • 28. Losiak, A.
    et al.
    Wild, E. M.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Huber, M. S.
    Joeleht, A.
    Kriiska, A.
    Kulkov, A.
    Paavel, K.
    Pirkovic, I.
    Plado, J.
    Steier, P.
    Vaelja, R.
    Wilk, J.
    Wisniowski, T.
    Zanetti, M.
    Dating a small impact crater: An age of Kaali crater (Estonia) based on charcoal emplaced within proximal ejecta2016In: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 51, no 4, p. 681-695Article in journal (Refereed)
    Abstract [en]

    The estimates of the age of the Kaali impact structure (Saaremaa Island, Estonia) provided by different authors vary by as much as 6000years, ranging from similar to 6400 to similar to 400 before current era (BCE). In this study, a new age is obtained based on C-14 dating charred plant material within the proximal ejecta blanket, which makes it directly related to the impact structure, and not susceptible to potential reservoir effects. Our results show that the Kaali crater was most probably formed shortly after 1530-1450 BCE (3237 +/- 10 C-14 yr BP). Saaremaa was already inhabited when the bolide hit the Earth, thus, the crater-forming event was probably witnessed by humans. There is, however, no evidence that this event caused significant change in the material culture (e.g., known archeological artifacts) or patterns of human habitation on Saaremaa.

  • 29. Mousis, O.
    et al.
    Fletcher, L. N.
    Lebreton, J. P.
    Wurz, P.
    Cavalie, T.
    Coustenis, A.
    Courtin, R.
    Gautier, D.
    Helled, R.
    Irwin, P. G. J.
    Morse, A. D.
    Nettelmann, N.
    Marty, B.
    Rousselot, P.
    Venot, O.
    Atkinson, D. H.
    Waite, J. H.
    Reh, K. R.
    Simon, A. A.
    Atreya, S.
    Andre, N.
    Blanc, M.
    Daglis, I. A.
    Fischer, G.
    Geppertt, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Guillot, T.
    Hedman, M. M.
    Hueso, R.
    Lellouch, E.
    Lunine, J. I.
    Murray, C. D.
    O'Donoghue, J.
    Rengel, M.
    Sanchez-Lavega, A.
    Schmider, F. X.
    Spiga, A.
    Spilker, T.
    Petit, J. -M
    Tiscareno, M. S.
    Ali-Dib, M.
    Altwegg, K.
    Bolton, S. J.
    Bouquet, A.
    Briois, C.
    Fouchet, T.
    Guerlet, S.
    Kostiuk, T.
    Lebleu, D.
    Moreno, R.
    Orton, G. S.
    Poncy, J.
    Scientific rationale for Saturn's in situ exploration2014In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 104, p. 29-47Article in journal (Refereed)
    Abstract [en]

    Remote sensing observations meet some limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the superiority of in situ probe measurements is illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases' abundances and the precise measurement of the helium mixing ratio have only been made available through in situ measurements by the Galileo probe. This paper describes the main scientific goals to be addressed by the future in situ exploration of Saturn placing the Galileo probe exploration of Jupiter in a broader context and before the future probe exploration of the more remote ice giants. In situ exploration of Saturn's atmosphere addresses two broad themes that are discussed throughout this paper: first, the formation history of our solar system and second, the processes at play in planetary atmospheres. In this context, we detail the reasons why measurements of Saturn's bulk elemental and isotopic composition would place important constraints on the volatile reservoirs in the protosolar nebula. We also show that the in situ measurement of CO (or any other disequilibrium species that is depleted by reaction with water) in Saturn's upper troposphere may help constraining its bulk O/H ratio. We compare predictions of Jupiter and Saturn's bulk compositions from different formation scenarios, and highlight the key measurements required to distinguish competing theories to shed light on giant planet formation as a common process in planetary systems with potential applications to most extrasolar systems. In situ measurements of Saturn's stratospheric and tropospheric dynamics, chemistry and cloud-forming processes will provide access to phenomena unreachable to remote sensing studies. Different mission architectures are envisaged, which would benefit from strong international collaborations, all based on an entry probe that would descend through Saturn's stratosphere and troposphere under parachute down to a minimum of 10 bar of atmospheric pressure. We finally discuss the science payload required on a Saturn probe to match the measurement requirements.

  • 30. Mousis, Olivier
    et al.
    Chassefiere, Eric
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bouquet, Alexis
    Hunter Waite, Jack
    Geppert, Wolf Dietrich
    Stockholm University, Faculty of Science, Department of Physics.
    Picaud, Sylvain
    Aikawa, Yuri
    Ali-Dib, Mohamad
    Charlou, Jean-Luc
    Rousselot, Philippe
    Methane Clathrates in the Solar System2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 4, p. 308-326Article, review/survey (Refereed)
    Abstract [en]

    We review the reservoirs of methane clathrates that may exist in the different bodies of the Solar System. Methane was formed in the interstellar medium prior to having been embedded in the protosolar nebula gas phase. This molecule was subsequently trapped in clathrates that formed from crystalline water ice during the cooling of the disk and incorporated in this form into the building blocks of comets, icy bodies, and giant planets. Methane clathrates may play an important role in the evolution of planetary atmospheres. On Earth, the production of methane in clathrates is essentially biological, and these compounds are mostly found in permafrost regions or in the sediments of continental shelves. On Mars, methane would more likely derive from hydrothermal reactions with olivine-rich material. If they do exist, martian methane clathrates would be stable only at depth in the cryosphere and sporadically release some methane into the atmosphere via mechanisms that remain to be determined. In the case of Titan, most of its methane probably originates from the protosolar nebula, where it would have been trapped in the clathrates agglomerated by the satellite's building blocks. Methane clathrates are still believed to play an important role in the present state of Titan. Their presence is invoked in the satellite's subsurface as a means of replenishing its atmosphere with methane via outgassing episodes. The internal oceans of Enceladus and Europa also provide appropriate thermodynamic conditions that allow formation of methane clathrates. In turn, these clathrates might influence the composition of these liquid reservoirs. Finally, comets and Kuiper Belt Objects might have formed from the agglomeration of clathrates and pure ices in the nebula. The methane observed in comets would then result from the destabilization of clathrate layers in the nuclei concurrent with their approach to perihelion. Thermodynamic equilibrium calculations show that methane-rich clathrate layers may exist on Pluto as well.

  • 31. Novotny, O.
    et al.
    Becker, A.
    Buhr, H.
    Domesle, C.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Grieser, M.
    Krantz, C.
    Kreckel, H.
    Repnow, R.
    Schwalm, D.
    Spruck, K.
    Stuetzel, J.
    Yang, B.
    Wolf, A.
    Savin, D. W.
    DISSOCIATIVE RECOMBINATION MEASUREMENTS OF HCl+ USING AN ION STORAGE RING2013In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 777, no 1, p. 54-Article in journal (Refereed)
    Abstract [en]

    We have measured dissociative recombination (DR) of HCl+ with electrons using a merged beams configuration at the TSR heavy-ion storage ring located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We present the measured absolute merged beams recombination rate coefficient for collision energies from 0 to 4.5 eV. We have also developed a new method for deriving the cross section from the measurements. Our approach does not suffer from approximations made by previously used methods. The cross section was transformed to a plasma rate coefficient for the electron temperature range from T = 10 to 5000 K. We show that the previously used HCl+ DR data underestimate the plasma rate coefficient by a factor of 1.5 at T = 10 K and overestimate it by a factor of three at T = 300 K. We also find that the new data may partly explain existing discrepancies between observed abundances of chlorine-bearing molecules and their astrochemical models.

  • 32. Novotny, O.
    et al.
    Buhr, H.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Grieser, M.
    Hamberg, Matthias
    Stockholm University, Faculty of Science, Department of Physics. Uppsala University, Sweden.
    Krantz, C.
    Mendes, M. B.
    Petrignani, A.
    Repnow, R.
    Savin, D. W.
    Schwalm, D.
    Stutzel, J.
    Wolf, A.
    Dissociative Recombination Measurements of Chloronium Ions (D2Cl+) Using an Ion Storage Ring2018In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 862, no 2, article id 166Article in journal (Refereed)
    Abstract [en]

    We report our plasma rate coefficient and branching ratio measurements for dissociative recombination (DR) of D2Cl+ with electrons. The studies were performed in a merged-beams configuration using the TSR heavy-ion storage ring located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Starting with our absolute merged-beams recombination rate coefficient at a collision energy of approximate to 0 eV, we have extracted the cross section and produced a plasma rate coefficient for a translational temperature of approximate to 8 K. Furthermore, extrapolating our cross-section results using the typical low-energy DR behavior, we have generated a plasma rate coefficient for translational temperatures from 5 to 500 K. We find good agreement between our extrapolated results and previous experimental DR studies on D2Cl+. Additionally, we have investigated the three fragmentation channels for DR of D2Cl+. Here we report on the dissociation geometry of the three-body fragmentation channel, the kinetic energy released for each of the three outgoing channels, the molecular internal excitation for the two outgoing channels that produce molecular fragments, and the fragmentation branching ratios for all three channels. Our results, in combination with those of other groups, indicate that any remaining uncertainties in the DR rate coefficient for H2Cl+ appear unlikely to explain the observed discrepancies between the inferred abundances of HCl and H2Cl+ in molecular clouds and predictions from astrochemical models.

  • 33. Novotný, O.
    et al.
    Berg, M.
    Bing, D.
    Buhr, H.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Grieser, M.
    Grussie, F.
    Krantz, C.
    Mendes, M. B.
    Nordhorn, C.
    Repnow, R.
    Schwalm, D.
    Yang, B.
    Wolf, A.
    Savin, D. W.
    DISSOCIATIVE RECOMBINATION MEASUREMENTS OF NH+ USING AN ION STORAGE RING2014In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 792, no 2, article id 132Article in journal (Refereed)
    Abstract [en]

    We have investigated dissociative recombination (DR) of NH+ with electrons using a merged beams configuration at the TSR heavy-ion storage ring located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We present our measured absolute merged-beams recombination rate coefficient for collision energies from 0 to 12 eV. From these data, we have extracted a cross section, which we have transformed to a plasma rate coefficient for the collisional plasma temperature range from T-p1 = 10 to 18,000 K. We show that the NH+ DR rate coefficient data in current astrochemical models are underestimated by up to a factor of approximately nine. Our new data will result in predicted NH+ abundances lower than those calculated by present models. This is in agreement with the sensitivity limits of all observations attempting to detect NH+ in interstellar clouds.

  • 34.
    Schmidt, Henning T.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    Rosén, Stefan
    Stockholm University, Faculty of Science, Department of Physics.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Löfgren, Patrik
    Stockholm University, Faculty of Science, Department of Physics.
    Brännholm, Lars
    Stockholm University, Faculty of Science, Department of Physics.
    Blom, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Björkhage, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Bäckström, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Alexander, John D.
    Stockholm University, Faculty of Science, Department of Physics.
    Leontein, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Hanstorp, D.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Liljeby, Leif
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Mannervik, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Rensfelt, Karl-Gunnar
    Stockholm University, Faculty of Science, Department of Physics.
    Danared, Håkan
    Stockholm University, Faculty of Science, Department of Physics.
    Paal, A.
    Stockholm University, Faculty of Science, Department of Physics.
    Masuda, Masaharu
    Stockholm University, Faculty of Science, Department of Physics.
    Hallden, Per
    Stockholm University, Faculty of Science, Department of Physics.
    Andler, Guillermo
    Stockholm University, Faculty of Science, Department of Physics.
    Stockett, Mark H.
    Stockholm University, Faculty of Science, Department of Physics.
    Chen, Tao
    Stockholm University, Faculty of Science, Department of Physics.
    Källersjö, Gunnar
    Stockholm University, Faculty of Science, Department of Physics.
    Weimer, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Hansen, K.
    Hartman, H.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    First storage of ion beams in the Double Electrostatic Ion-Ring Experiment: DESIREE2013In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84, no 5, p. 055115-Article in journal (Refereed)
    Abstract [en]

    We report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. We have produced beams of atomic carbon anions and small carbon anion molecules (C-n(-), n = 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 keV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 keV C-2(-) molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s +/- 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10(-14) mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.

  • 35.
    Schmidt, Henning
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Johansson, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Haag, Nicole
    Stockholm University, Faculty of Science, Department of Physics.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Rosén, Stefan
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Danared, Håkan
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Rensfelt, K.-G
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Liljeby, Leif
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Bagge, Lars
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Björkhage, Mikael
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Blom, Mikael
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Löfgren, Patrik
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Källberg, Anders
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Paál, Andras
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    DESIREE as a new tool for interstellar ion chemistry2008In: International Journal of Astrobiology, ISSN 1473-5504, E-ISSN 1475-3006, Vol. 7, no 3-4, p. 205-208Article in journal (Refereed)
    Abstract [en]

    A novel cryogenic electrostatic storage device consisting of two ion-beam storage rings with a common straight section for studies of interactions between oppositely charged ions at low and well-defined relative velocities is under construction at Stockholm University. Here we consider the prospect of using this new tool to measure cross-sections and rate coefficients for mutual neutralization reactions of importance in interstellar ion chemistry in general and specifically in cosmic pre-biotic ion chemistry.

  • 36.
    Thomas, R. D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, Anneli
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Bahati, E.
    Bannister, M. E.
    Fogle, M. R.
    Vane, C. R.
    Petrignani, A.
    Andersson, P. U.
    Ojekull, J.
    Pettersson, J. B. C.
    van der Zande, W. J.
    Larsson, M.
    Hot Water from Cold. The Dissociative Recombination of Water Cluster Ions2010In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 114, no 14, p. 4843-4846Article in journal (Refereed)
    Abstract [en]

    Dissociative recombination of the Zundel cation D(5)O(2)(+) almost exclusively produces D + 2 D(2)O with a maximum kinetic energy release of 5.1 eV. An imaging technique is used to investigate the distribution of the available reaction energy among these products. Analysis shows that as much as 4 eV can be stored internally by the molecular fragments, with a preference for producing highly excited molecular fragments, and that the deuteron shows a nonrandom distribution of kinetic energies. A possible mechanism and the implications for these observations are addressed.

  • 37.
    Thomas, Richard D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, Anneli
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Bahati, E.
    Bannister, M. E.
    Fogle, M. R.
    Vane, C. R.
    Dissociative recombination of LiH2+2014In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 89, no 5, p. 050701-Article in journal (Refereed)
    Abstract [en]

    In this paper, we report results regarding how LiH2+ fragments as a result of a low-energy collision with an electron (dissociative recombination), a reaction that contains only elements and particles created during the very first phase of the universe. The collision-energy-dependent reaction rate and cross sections show detailed structures, more so than predicted by theory, suggesting significant rovibrational coupling in the ion and a complex reaction surface. From the structure of the molecule, the reaction predominantly results in the formation of Li + H-2. However, 23% of the reaction flux leads to more interesting products, with 17% producing Li + 2H and 6% producing LiH + H. These last two channels break the strongest molecular bond in the system and, in the case of the latter channel, form a significantly weaker ionic bond. Possible reasons behind this interesting behavior are discussed, together with the interaction between the available reaction channels.

  • 38.
    Thomas, Richard D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative Recombination of CH4+2013In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, no 39, p. 9999-10005Article in journal (Refereed)
    Abstract [en]

    CH4+ is an important molecular ion in the astrochemistry of diffuse clouds, dense clouds, cometary comae, and planetary ionospheres However, the rate of one of the common destruction mechanisms for molecular ions in these regions, dissociative recombination (DR), is somewhat uncertain. Here, we present absolute measurements for the DR of CH4+ made using the heavy ion storage ring CRYRING hi Stockholm, Sweden. From our collision energy dependent cross sections, we infer a thermal rate constant of k(T-e) = 1.71(+/- 0.02) X 10(-6)(T-e/300)(-0.66(+/- 0.02)) cm(3) s(-1) over the region of electron temperatures 10 <= T-e <= 1000 K. At low collision energies, we have measured the branching fractions of the DR products to be CH4 (0.00 +/- 0.00); CH3 + H (0.18 +/- 0.03); CH2 + 2H (0.51 +/- 0.03); CH2 + H-2 (0.06 +/- 0.01); CH + H-2 + H (0.23 +/- 0.01); and CH + 2H(2) (0.02 +/- 0.01), indicating that two or more C-H bonds are broken in similar to 80% of all collisions.

  • 39.
    Thomas, Richard D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    Rosén, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Reinhed, Peter
    Stockholm University, Faculty of Science, Department of Physics.
    Löfgren, Patrik
    Stockholm University, Faculty of Science, Department of Physics.
    Brännholm, Lars
    Stockholm University, Faculty of Science, Department of Physics.
    Blom, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Björkhage, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Bäckström, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Alexander, John D.
    Stockholm University, Faculty of Science, Department of Physics.
    Leontein, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Hanstorp, D.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Stockholm University, Faculty of Science, Department of Physics.
    Nascimento, Rodrigo
    Stockholm University, Faculty of Science, Department of Physics.
    Liljeby, Leif
    Stockholm University, Faculty of Science, Department of Physics.
    Källberg, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Simonsson, Ansgar
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Mannervik, Sven
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Rensfelt, Karl-Gunnar
    Stockholm University, Faculty of Science, Department of Physics.
    Paál, Andras
    Stockholm University, Faculty of Science, Department of Physics.
    Masuda, Masaharu
    Stockholm University, Faculty of Science, Department of Physics.
    Halldén, Per
    Stockholm University, Faculty of Science, Department of Physics.
    Andler, Guillermo
    Stockholm University, Faculty of Science, Department of Physics.
    Stockett, Mark H.
    Stockholm University, Faculty of Science, Department of Physics.
    Chen, Tao
    Stockholm University, Faculty of Science, Department of Physics.
    Källersjö, Gunnar
    Stockholm University, Faculty of Science, Department of Physics.
    Weimer, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Hansen, K.
    Hartman, H.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    DESIREE: Physics with cold stored ion beams2015In: DR2013: Ninth international conference on dissociative recombination: theory, experiment, and applications, 2015, Vol. 84, article id 01004Conference paper (Refereed)
    Abstract [en]

    Here we will briefly describe the commissioning of the Double ElectroStatic Ion Ring ExpEriment (DESIREE) facility at Stockholm University, Sweden. This device uses purely electrostatic focussing and deflection elements and allows ion beams of opposite charge to be confined under extreme high vacuum and cryogenic conditions in separate rings and then merged over a common straight section. This apparatus allows for studies of interactions between cations and anions at very low and well-defined centre-of-mass energies (down to a few meV) and at very low internal temperatures (down to a few K).

  • 40.
    Thomas, Richard
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, I.
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Indriolo, N.
    Yagi, K.
    Hirata, S.
    McCall, B. J.
    DISSOCIATIVE RECOMBINATION OF VIBRATIONALLY COLD CH+3 AND INTERSTELLAR IMPLICATIONS2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 758, no 1, p. 55-Article in journal (Refereed)
    Abstract [en]

    CH3+ is an important molecular ion in the astrochemistry of diffuse clouds, dense clouds, cometary comae, and planetary ionospheres. However, the rate of one of the major destruction mechanisms of CH3+, dissociative recombination (DR), has long been uncertain, hindering the use of CH3+ as an astrochemical probe. Here, we present the first absolute measurement of the DR of vibrationally cold CH3+, which has been made using the heavy storage ring CRYRING in Stockholm, Sweden. From our collision-energy-dependent cross sections, we infer a thermal rate constant of k(T) = 6.97(+/- 0.03) x 10(-7)(T/300)(-0.61(+/- 0.01)) cm(3) s(-1) over the region 10 K <= T <= 1000 K. At low collision energies, we have measured the branching fractions of the DR products to be CH3 (0.00(- 0.00)(+ 0.01)), CH2 + H (0.35(-0.01)(+ 0.01)), CH + 2H (0.20(-0.02)(+0.02)), CH + H-2 (0.10(-0.01)(+0.01)), and C + H-2 + H (0.35(-0.02)(+ 0.01)), indicating that two or more C-H bonds are broken in 65% of all collisions. We also present vibrational calculations which indicate that the CH3+ ions in the storage ring were relaxed to the vibrational ground state by spontaneous emission during the storage time. Finally, we discuss the implications of these new measurements for the observation of CH3+ in regions of the diffuse interstellar medium where CH+ is abundant.

  • 41. Tobie, G.
    et al.
    Teanby, N. A.
    Coustenis, A.
    Jaumann, R.
    Raulin, E.
    Schmidt, J.
    Carrasco, N.
    Coates, Aj.
    Cordier, D.
    De Kok, R.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Lebreton, J. -P
    Lefevre, A.
    Livengood, T. A.
    Mandt, K. E.
    Mitri, G.
    Nimmo, F.
    Nixon, C. A.
    Norman, L.
    Pappalardo, R. T.
    Postberg, F.
    Rodriguez, S.
    SchuizeMakuch, D.
    Soderblom, J. M.
    Solomonidou, A.
    Stephan, K.
    Stofan, E. R.
    Turtle, E. P.
    Wagner, R. J.
    West, R. A.
    Westlake, J. H.
    Science goals and mission concept for the future exploration of Titan and Enceladus2014In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 104, p. 59-77Article in journal (Refereed)
    Abstract [en]

    Saturn's moons, Titan and Enceladus, are two of the Solar System's most enigmatic bodies and are prime targets for future space exploration. Titan provides an analogue for many processes relevant to the Earth, more generally to outer Solar System bodies, and a growing host of newly discovered icy exoplanets. Processes represented include atmospheric dynamics, complex organic chemistry, meteorological cycles (with methane as a working fluid), astrobiology, surface liquids and lakes, geology, fluvial and aeolian erosion, and interactions with an external plasma environment. In addition, exploring Enceladus over multiple targeted flybys will give us a unique opportunity to further study the most active icy moon in our Solar System as revealed by Cassini and to analyse in situ its active plume with highly capable instrumentation addressing its complex chemistry and dynamics. Enceladus' plume likely represents the most accessible samples from an extra-terrestrial liquid water environment in the Solar system, which has far reaching implications for many areas of planetary and biological science. Titan with its massive atmosphere and Enceladus with its active plume are prime planetary objects in the Outer Solar System to perform in situ investigations. In the present paper, we describe the science goals and key measurements to be performed by a future exploration mission involving a Saturn-Titan orbiter and a Titan balloon, which was proposed to ESA in response to the call for definition of the science themes of the next Large-class mission in 2013. The mission scenario is built around three complementary science goals: (A) Titan as an Earth-like system; (B) Enceladus as an active cryovolcanic moon; and (C) Chemistry of Titan and Enceladus - clues for the origin of life. The proposed measurements would provide a step change in our understanding of planetary processes and evolution, with many orders of magnitude improvement in temporal, spatial, and chemical resolution over that which is possible with Cassini-Huygens. This mission concept builds upon the successes of Cassini-Huygens and takes advantage of previous mission heritage in both remote sensing and in situ measurement technologies. (C) 2014 Elsevier Ltd. All rights reserved.

  • 42. Tom, Brian A.
    et al.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Wiczer, Michael B.
    Mills, Andrew A.
    Crabtree, Kyle N.
    Kaminska, Magdalena
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    van der Zande, Wim J.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    McCall, Benjamin J.
    Dissociative recombination of highly enriched para-H-3(+)2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, no 3, p. 31101-Article in journal (Refereed)
    Abstract [en]

    The determination of the dissociative recombination rate coefficient of H-3(+) has had a turbulent history, but both experiment and theory have recently converged to a common value. Despite this convergence, it has not been clear if there should be a difference between the rate coefficients for ortho-H-3(+) and para-H-3(+). A difference has been predicted theoretically and could conceivably impact the ortho:para ratio of H-3(+) in the diffuse interstellar medium, where H-3(+) has been widely observed. We present the results of an experiment at the CRYRING ion storage ring in which we investigated the dissociative recombination of highly enriched (similar to 83.6%) para-H-3(+) using a supersonic expansion source that produced ions with T-rot similar to 60-100 K. We observed an increase in the low energy recombination rate coefficient of the enriched para-H-3(+) by a factor of similar to 1.25 in comparison to H-3(+) produced from normal H-2 (ortho:para=3:1). The ratio of the rate coefficients of pure para-H-3(+) to that of pure ortho-H-3(+) is inferred to be similar to 2 at low collision energies; the corresponding ratio of the thermal rate coefficients is similar to 1.5 at electron temperatures from 60 to 1000 K. We conclude that this difference is unlikely to have an impact on the interstellar ortho:para ratio of H-3(+).

  • 43. Vigren, E.
    et al.
    Galand, M.
    Shebanits, O.
    Wahlund, J. -E
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Lavvas, P.
    Vuitton, V.
    Yelle, R. V.
    INCREASING POSITIVE ION NUMBER DENSITIES BELOW THE PEAK OF ION-ELECTRON PAIR PRODUCTION IN TITAN'S IONOSPHERE2014In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 786, no 1, p. 69-Article in journal (Refereed)
    Abstract [en]

    We combine derived ion-electron pair formation rates with Cassini Radio Plasma Wave Science Langmuir Probe measurements of electron and positive ion number densities in Titan's sunlit ionosphere. We show that positive ion number densities in Titan's sunlit ionosphere can increase toward significantly lower altitudes than the peak of ion-electron pair formation despite that the effective ion-electron recombination coefficient increases. This is explained by the increased mixing ratios of negative ions, which are formed by electron attachment to neutrals. While such a process acts as a sink for free electrons, the positive ions become longer-lived as the rate coefficients for ion-anion neutralization reactions are smaller than those for ion-electron dissociative recombination reactions.

  • 44.
    Vigren, E.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, V.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, W. D.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Bahati, E.
    Vane, C. R.
    Bannister, M. E.
    Fogle, M. R.
    Hamberg, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Danielsson, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, M.
    Thomas, R. D.
    Stockholm University, Faculty of Science, Department of Physics.
    Collision-induced dissociation of similar to 2-MeV O-3(+) and N-3(+) ions2013In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 87, no 5, article id 052707Article in journal (Refereed)
    Abstract [en]

    We present a study into the collision-induced dissociation (possibly including electron stripping) of O-3(+) and N-3(+) with rest gas molecules (predominantly H-2) in the heavy-ion storage ring CRYRING. The projectile ions had kinetic energies of 1.96 MeV (O-3(+)) and 2.25 MeV (N-3(+)) and from the experimental data we could derive the relative importance of the channels that produce at least one neutral product fragment. The dominant type of fragmentation for both ions involves the production of a single neutral fragment, namely an individual atom. We also find pronounced dissimilarities when comparing the O-3(+) and N-3(+) results, which we link to the stronger chemical bonds in the nitrogen system.

  • 45.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Semaniak, Jacek
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    Millar, T. J.
    Walsh, Catherine
    Roberts, Helen
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative Recombination of Protonated Formic Acid: Implications for Molecular Cloud and Cometary Chemistry2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 709, no 2, p. 1429-1434Article in journal (Refereed)
    Abstract [en]

    At the heavy ion storage ring CRYRING in Stockholm, Sweden, we have investigated the dissociative recombination of DCOOD2+ at low relative kinetic energies, from similar to 1 meV to 1 eV. The thermal rate coefficient has been found to follow the expression k(T) = 8.43 x 10(-7) (T/300)(-0.78) cm(3) s(-1) for electron temperatures, T, ranging from similar to 10 to similar to 1000 K. The branching fractions of the reaction have been studied at similar to 2 meV relative kinetic energy. It has been found that similar to 87% of the reactions involve breaking a bond between heavy atoms. In only 13% of the reactions do the heavy atoms remain in the same product fragment. This puts limits on the gas-phase production of formic acid, observed in both molecular clouds and cometary comae. Using the experimental results in chemical models of the dark cloud, TMC-1, and using the latest release of the UMIST Database for Astrochemistry improves the agreement with observations for the abundance of formic acid. Our results also strengthen the assumption that formic acid is a component of cometary ices.

  • 46.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Millar, T. J.
    Walsh, Catherine
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    The Dissociative Recombination of Protonated Acrylonitrile, CH2CHCNH+, with implications for the Nitrile Chemistry in Dark Molecular Clouds and the Upper Atmosphere of Titan2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 695, no 1, p. 317-324Article in journal (Refereed)
    Abstract [en]

    Measurements on the dissociative recombination (DR) of protonated acrylonitrile, CH2CHCNH+, have been performed at the heavy ion storage ring CRYRING located in the Manne Siegbahn Laboratory in Stockholm, Sweden. It has been found that at similar to 2meV relative kinetic energy about 50% of the DR events involve only ruptures of X-Hbonds (where X = C or N) while the rest leads to the production of a pair of fragments each containing two heavy atoms (alongside H and/or H-2). The absolute DR cross section has been investigated for relative kinetic energies ranging from similar to 1 meV to 1 eV. The thermal rate coefficient has been determined to follow the expression k(T) = 1.78 x 10(-6) (T/300)(-0.80) cm(3) s(-1) for electron temperatures ranging from similar to 10 to 1000 K. Gas-phase models of the nitrile chemistry in the dark molecular cloud TMC-1 have been run and results are compared with observations. Also, implications of the present results for the nitrile chemistry of Titan's upper atmosphere are discussed.

  • 47.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Kaminska, Magdalena
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Trippel, Sebastian
    Wester, Roland
    Zhang, Mingwu
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory.
    Semaniak, Jacek
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative Recombination of Protonated Propionitrile, CH3CH2CNH+: Implications for Titan's Upper Atmosphere2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 722, no 1, p. 847-850Article in journal (Refereed)
    Abstract [en]

    The dissociative recombination of protonated propionitrile, CH3CH2CNH+, has been investigated at the heavy ion storage ring, CRYRING, at the Manne Siegbahn Laboratory, Stockholm University, Sweden. The thermal rate coefficient has been deduced to follow k(T) = (1.5 ± 0.2) × 10–6 (T/300)–0.76 ± 0.02 cm3 s–1 for electron temperatures ranging from ~10 to ~1000 K. Measurements of the branching fractions were performed at ~0 eV relative kinetic energy. It has been found that in 43% ± 2% of the reactions the four heavy atoms remain in the same product fragment. An equal portion of the reactions leads to products where one of the heavy atoms is split off from the other three and 14% ± 1% result in a breakup into two heavy fragments containing two heavy atoms each. We discuss the significance of the data to Titan's upper atmosphere.

  • 48.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Trippel, Sebastian
    Zhang, Mingwu
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Walsh, Catherine
    Wester, Roland
    Semaniak, Jacek
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of the acetaldehyde cation, CH3CHO+2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 37, p. 11670-11673Article in journal (Refereed)
    Abstract [en]

    The dissociative recombination of the acetaldehyde cation, CH3CHO+, has been investigated at the heavy ion storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm, Sweden. The dependence of the absolute cross section of the reaction on the relative kinetic energy has been determined and a thermal rate coefficient of k(T) = (1.5 +/- 0.2) x 10(-6) (T/300)(-0.70 +/- 0.02) cm(3) s(-1) has been deduced, which is valid for electron temperatures between similar to 10 and 1000 K. The branching fractions of the reaction were studied at similar to 0 eV relative kinetic energy and we found that breaking one of the bonds between two of the heavy atoms occurs in 72 +/- 2% of the reactions. In the remaining events the three heavy atoms stay in the same product fragment. While the branching fractions are fairly similar to the results from an earlier investigation into the dissociative recombination of the fully deuterated acetaldehyde cation, CD3CDO+, the thermal rate coefficient is somewhat larger for CH3CHO+. Astrochemical implications of the results are discussed.

  • 49.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Danielsson, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Semaniak, Jacek
    Andersson, Patrik U.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of fully deuterated protonated acetonitrile, CD3CND+: Product branching fractions, absolute cross section and thermal rate coefficient2008In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 10, no 27, p. 4014-4019Article in journal (Refereed)
    Abstract [en]

    The dissociative recombination of fully deuterated protonated acetonitrile, CD3CND+, has been investigated at the CRYRING heavy ion storage ring, located at the Manne Siegbahn Laboratory, Stockholm, Sweden. Branching fractions were measured at similar to 0 eV relative collision energy between the ions and the electrons and in 65% of the DR events there was no rupture of bonds between heavy atoms. In the remaining 35%, one of the bonds between the heavy atoms was broken. The DR cross-section was measured between similar to 0 eV and 1 eV relative collision energy. In the energy region between 1 meV and 0.1 eV the cross section data were best fitted by the expression sigma = 7.37 x 10(-16) (E/eV)(-1.23) cm(2), whereas sigma = 4.12 x 10(-16) (E/eV)(-1.46) cm(2) was the best fit for the energy region between 0.1 and 1.0 eV. From the cross section a thermal rate coefficient of alpha(T) = 8.13 x 10(-7) (T/300)(-0.69) cm(3) s(-1) was deduced.

  • 50.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Semaniak, Jacek
    Danielsson, Mathias
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of the deuterated acetaldehyde ion, CD3CDO+: product branching fractions, absolute cross sections and thermal rate coefficient2007In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 9, no 22, p. 2856-2861Article in journal (Refereed)
    Abstract [en]

    Dissociative recombination of the deuterated acetaldehyde ion CD3CDO+ has been studied at the heavy-ion storage ring CRYRING, located at the Manne Siegbahn Laboratory, Stockholm, Sweden. Product branching fractions together with absolute DR cross-sections were measured. The branching fractions were determined at a relative collision energy between the ions and the electrons of 0 eV. With a probability of 34% the DR events resulted in no ruptures of bonds between heavy atoms (i.e. no breakage of the C–C bond or the CO bond). In the remaining 66% of the events one of the bonds between the heavy atoms was broken. The energy-dependent cross-section for the DR reaction was measured between 0 and 1 eV relative kinetic energy. In the energy region between 1 meV and 0.2 eV the absolute cross section could be fitted by the expression σ(E) = 6.8 × 10−16E−1.28 cm2, whereas in the energy interval between 0.2 and 1 eV the data were best fitted by σ(E) = 4.1 × 10−16E−1.60 cm2. From these cross section data the thermal rate coefficient (as a function of the electron temperature), α(T) = 9.2 × 10−7 (T/300)−0.72 cm3 s−1 was obtained.

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