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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, E-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
    Annalisa, Vigorito
    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
    Structure, Dynamics, and Accurate Laboratory Rotational Frequencies of the Acrylonitrile-Methanol Complex2020In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 124, no 18, p. 3601-3608Article in journal (Refereed)
    Abstract [en]

    The hydrogen-bonded complex between acrylonitrile (CH2=CHCN) and methanol 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 centrifugal distortion constants were obtained from the measured frequencies of the complex of acrylonitrile with CH3OH and CD3OD. The analysis of the splittings of the rotational lines due to the hindered internal rotation of the methanol methyl group led to the determination of a V-3 value of 221.9(7) and 218(5) cm(-1) for the complexes of CH3OH and CD3OD, respectively, and these values are about 40% lower than that of free methanol. The structure of the observed conformation is in agreement with the global minimum determined at the MP2/aug-cc-pVTZ level of calculation, and the counterpoise corrected intermolecular binding energy, obtained at the same theoretical level, is D-e = 26.3 kJ mol(-1).

  • 5. 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.

  • 6. 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)

  • 7. 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.

  • 8.
    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%).

  • 9.
    Eklund, Gustav
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kristiansson, Moa
    Stockholm University, Faculty of Science, Department of Physics.
    Chartkunchand, K. C.
    Anderson, Emma K.
    Simpson, Malcolm
    Wester, Roland
    Schmidt, Henning T.
    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.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental lifetime of the a1Δ electronically excited state of CH2022In: Physical Review Research, E-ISSN 2643-1564, Vol. 4, no 1, article id L012016Article in journal (Refereed)
    Abstract [en]

    By repeatedly probing the a1Δ excited state and the X3Σ ground-state populations in a beam of CH ions stored in a cryogenic ion-beam storage ring for 100 s, we extract an intrinsic lifetime of 14.9±0.5 s for this excited state. This is far longer than all earlier experimental and theoretical results, exposing large difficulties in measuring and calculating slow decays and the need for benchmark quality experiments.

  • 10.
    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.

  • 11.
    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.

  • 12.
    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.

  • 13.
    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: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013), Institute of Physics (IOP), 2014, article id 092003Conference paper (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.

  • 14.
    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: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013), Institute of Physics (IOP), 2014, article id 012040Conference paper (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.

  • 15. 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.

  • 16.
    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)
  • 17.
    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.

  • 18.
    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)
  • 19.
    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, 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.

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  • 20.
    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.

  • 21.
    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.

  • 22.
    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+.

  • 23.
    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.

  • 24.
    Holm, Nils
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Introduction to a Series of Articles That Focus on Methane2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 4, p. 307-307Article, review/survey (Refereed)
  • 25. 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.

  • 26. Kopacz, Nina
    et al.
    Csuka, Joleen
    Baqué, Mickael
    Iakubivskyi, Iaroslav
    Guðlaugardóttir, Hrefna
    Klarenberg, Ingeborg J.
    Ahmed, Mahid
    Zetterlind, Alexandra
    Singh, Abhijeet
    ten Kate, Inge Loes
    Hellebrand, Eric
    Stockwell, Brent R.
    Stefánsson, Árni B.
    Vilhelmsson, Oddur
    Neubeck, Anna
    Schnürer, Anna
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    A Study in Blue: Secondary Copper-Rich Minerals and Their Associated Bacterial Diversity in Icelandic Lava Tubes2022In: Earth and Space Science, E-ISSN 2333-5084, Vol. 9, no 5, article id e2022EA002234Article in journal (Refereed)
    Abstract [en]

    Lava tubes on Mars hold exciting potential for the preservation of biosignatures, which may survive on geological timescales in these isolated, stable environments. To support the development of future astrobiological mission concepts, we turn to terrestrial lava tubes, host to a variety of microbial communities and secondary minerals. Following a multidisciplinary sampling protocol, we retrieved biological, molecular, and mineralogical data from several lava tubes in Iceland. We report on blue-colored copper-rich secondary minerals and their associated bacterial communities using a multi-method approach, and an amalgam of 16S rRNA gene sequencing, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy data sets. We found numerous bacterial genera known for their high metal resistance and ability to survive in low-nutrient environments. Both are characteristics to be expected for any potential life in Martian lava tubes, and should be considered when checking for contaminants in Mars mission preparations. Associated with the microbial mats, we identified several types of copper-rich secondary minerals, indicating localized copper enrichments in the groundwater, possibly stemming from overlying ash deposits and nearby hyaloclastite formations. Molecular analysis revealed carotenoid signals preserved within the copper speleothems. If found in Martian lava tubes, blue copper-rich mineral precipitates would be deserving of astrobiological investigation, as they have potential to preserve biosignatures and harbor life.

  • 27. 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.

  • 28.
    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.

  • 29.
    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.

  • 30. Li, Weixing
    et al.
    Maris, Assimo
    Calabrese, Camilla
    Usabiaga, Imanol
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Evangelisti, Luca
    Melandri, Sonia
    Atmospherically relevant acrolein-water complexes: spectroscopic evidence of aldehyde hydration and oxygen atom exchange2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 42, p. 23559-23566Article in journal (Refereed)
    Abstract [en]

    Direct spectroscopic evidence of a reaction occurring between acrolein and water and involving the exchange of an oxygen atom has been obtained by characterizing the non-covalently bound water complexes and their isotopic forms, via rotational spectroscopy. The experimental geometries of the binary and ternary water complexes have been determined, and other stationary points on the reaction path have been characterized using ab initio quantum chemical methods at the MP2/6-311++G(d,p) level. These results can enhance the understanding of the water-mediated atmospherically important reactions involving acrolein.

  • 31.
    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.

  • 32.
    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.

  • 33. 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.

  • 34. Marimuthu, Aravindh N.
    et al.
    Sundelin, David
    Stockholm University, Faculty of Science, Department of Physics.
    Thorwirth, Sven
    Redlich, Britta
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Brünken, Sandra
    Laboratory gas-phase vibrational spectra of [C3H3]+ isomers and isotopologues by IRPD spectroscopy2020In: Journal of Molecular Spectroscopy, ISSN 0022-2852, E-ISSN 1096-083X, Vol. 374, article id 111377Article in journal (Refereed)
    Abstract [en]

    Gas phase vibrational spectra of [C3H3]+ isomers and their fully deuterated isotopologues measured in a cryogenic 22-pole ion trap are presented. The widely tunable free electron laser for infrared experiments, FELIX, was employed to cover the frequency range 500–2400 cm−1, complemented with an OPO/OPA system covering 2800–3400 cm−1. Spectral assignments for both the linear and cyclic isomeric form (H2C3H+ and c-C3H3+, respectively) are made based on various high-level computational studies. The effect of ion source conditions and different precursors (allene and propargyl chloride) for the preferential production of a specific isomer is discussed. The perturbation of the vibrational band position due to complexation with neon in the recorded infrared-predissociation (IRPD) spectra are also reported in this study.

  • 35. 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.

  • 36. 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.

  • 37. Neubeck, Anna
    et al.
    Broman, Curt
    Ivarsson, Magnus
    Holm, Nils G.
    Whitehouse, Martin
    Nilsson, Sara
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Gervilla, Fernando
    Isotopic Signatures of Carbon in the 'Los Pobres' Graphite Mine, Ronda, Spain2020In: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 61, no 4, article id egaa042Article in journal (Refereed)
    Abstract [en]

    Graphite formation temperatures in the ‘Los Pobres’ mine within the Ronda peridotite, Spain, previously reported to be between 770 and 820 °C, have been reinterpreted based on new temperature measurements using Raman spectroscopy. Additional in situ and bulk stable carbon isotopic measurements and fluid inclusion studies contributed to improved understanding of parts of the graphite formation process. Raman spectroscopy revealed that the formation of the ‘Los Pobres’ graphite extends to temperatures as low as 500 °C, indicating a broader temperature range than previously reported. Stable carbon isotopes and temperature estimates suggest two different crystallization events, followed by a late hydrothermal alteration of the host rock. The first event occurred at temperatures higher than ∼600°C, in which crystalline graphite was formed with a mixed 13C composition as a result of the mixing of two different carbon-bearing sources. The second graphite formation event took place below ∼600°C, within the same system, but with lower purity and crystallinity of the graphite. In the third event, the temperature decreased to less than 550 °C, and hydrothermal fluids altered the host rock, precipitating silica and iron oxides in veins penetrating both the host rock and the deposited graphite.

  • 38. 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.

  • 39. Novotny, O.
    et al.
    Buhr, H.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Grieser, M.
    Hamberg, Mathias
    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.

  • 40. 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.

  • 41. Rader, Erika
    et al.
    Simpson, Anna
    Amador, Elena
    Fraser, Julia M.
    Holtzen, Samuel
    Hanna, Ashley
    Cable, Morgan L.
    Cullen, Thomas
    Duca, Zach
    Gentry, Diana
    Murukesan, Gayathri
    Rennie, Vincent
    Stevens, Adam H.
    Sutton, Scot
    Tan, George
    Cullen, David
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Stockton, Amanda
    Preferably Plinian and Pumaceous: Implications of Microbial Activity in Modern Volcanic Deposits at Askja Volcano, Iceland, and Relevancy for Mars Exploration2020In: ACS Earth and Space Chemistry, E-ISSN 2472-3452, Vol. 4, no 9, p. 1500-1514Article in journal (Refereed)
    Abstract [en]

    To search more efficiently for a record of past life on Mars, it is critical to know where to look and thus maximize the likelihood of success. Large-scale site selection for the Mars 2020 mission has been completed, but small (meter to 10 cm)-scale relationships of microenvironments will not be known until the rover reaches the surface. Over a 2 m transect at a modern volcanic deposit on the flank of Askja volcano in the barren highlands of Iceland, we compared two biological indicators (ATP activity and 16SrRNA amplicon sequence composition) to physical characteristics including bulk chemical composition, spectral signatures of mineralogy, and grain size. Using analytical instrumentation analogous to those available on Mars rovers, we were able to characterize the geological setting of the deposits and link physical parameters to microbial abundance and diversity. In general, methanogenesis, methanotrophy/methylotrophy, and nitrate reduction were the functional traits most associated with microbial community shift along the transect. Core microbiome members tended to be associated with nitrate reduction, and relative abundance of core microbes was strongly related to free water in the deposit. Community compositional shift of the rare microbiome was related to microenvironmental changes such as change in grain size, geochemistry, and age of deposit. These correlations lead us to suggest a sampling strategy that accounts for Martian geology, looking for undisturbed (not remobilized) explosive volcanic ash below pumice that could maximize diversity and abundance of different bioindicators. Our study also illustrates the importance of studying the variability across microenvironments in low biomass settings on earth.

  • 42. Richardson, V.
    et al.
    Alcaraz, C.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Polášek, M.
    Romanzin, C.
    Sundelin, David
    Stockholm University, Faculty of Science, Department of Physics.
    Thissen, R.
    Tosi, P.
    Žabka, J.
    Ascenzi, D.
    The reactivity of methanimine radical cation (H2CNH.+) and its isomer aminomethylene (HCNH2.+) with methane2021In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 775, article id 138611Article in journal (Refereed)
    Abstract [en]

    Experimental and theoretical studies are presented on the reactions of the isomeric radical cations H2CNH+ and HCNH2+ with CH4. Ionic isomers were generated selectively by VUV dissociative photoionization of azetidine and cyclopropylamine precursors respectively. Both exclusively give H2CNH2+ plus CH3 as products, but differences are observed related to a competition between stripping and complex-mediated H-transfer. Astrochemical implications for Titan’s atmosphere are briefly discussed, where the presence of methanimine (H2CNH), a key prebiotic molecule and a potential precursor for tholins, is proposed on the basis of atmospheric models and the observation of CH2NH2+ ions in Cassini mass spectrometric data.

  • 43. Richardson, Vincent
    et al.
    Ascenzi, Daniela
    Sundelin, David
    Stockholm University, Faculty of Science, Department of Physics.
    Alcaraz, Christian
    Romanzin, Claire
    Thissen, Roland
    Guillemin, Jean-Claude
    Polášek, Miroslav
    Tosi, Paolo
    Žabka, Jan
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Experimental and Computational Studies on the Reactivity of Methanimine Radical Cation (H2CNH+•) and its Isomer Aminomethylene (HCNH2+•) With C2H22021In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 8, article id 752376Article in journal (Refereed)
    Abstract [en]

    Experimental and theoretical studies are presented on the reactivity of the radical cation isomers H2CNH+• (methanimine) and HCNH2+• (aminomethylene) with ethyne (C2H2). Selective isomer generation is performed via dissociative photoionization of suitable neutral precursors as well as via direct photoionization of methanimine. Reactive cross sections (in absolute scales) and product branching ratios are measured as a function of photon and collision energies. Differences between isomers’ reactivity are discussed in light of ab-initio calculations of reaction mechanisms. The major channels, for both isomers, are due to H atom elimination from covalently bound adducts to give [C3NH4]+. Theoretical calculations show that while for the reaction of HCNH2+• with acetylene any of the three lowest energy [C3NH4]+ isomers can form via barrierless and exothermic pathways, for the H2CNH+• reagent the only barrierless pathway is the one leading to the production of protonated vinyl cyanide (CH2CHCNH+), a prototypical branched nitrile species that has been proposed as a likely intermediate in star forming regions and in the atmosphere of Titan. The astrochemical implications of the results are briefly addressed.

  • 44. Rodriguez, Sébastien
    et al.
    Vinatier, Sandrine
    Cordier, Daniel
    Tobie, Gabriel
    Achterberg, Richard K.
    Anderson, Carrie M.
    Badman, Sarah V.
    Barnes, Jason W.
    Barth, Erika L.
    Bézard, Bruno
    Carrasco, Nathalie
    Charnay, Benjamin
    Clark, Roger N.
    Coll, Patrice
    Cornet, Thomas
    Coustenis, Athena
    Couturier-Tamburelli, Isabelle
    Dobrijevic, Michel
    Flasar, F. Michael
    de Kok, Remco
    Freissinet, Caroline
    Galand, Marina
    Gautier, Thomas
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Griffith, Caitlin A.
    Gudipati, Murthy S.
    Hadid, Lina Z.
    Hayes, Alexander G.
    Hendrix, Amanda R.
    Jaumann, Ralf
    Jennings, Donald E.
    Jolly, Antoine
    Kalousova, Klara
    Koskinen, Tommi T.
    Lavvas, Panayotis
    Lebonnois, Sébastien
    Lebreton, Jean-Pierre
    Le Gall, Alice
    Lellouch, Emmanuel
    Le Mouélic, Stéphane
    Lopes, Rosaly M. C.
    Lora, Juan M.
    Lorenz, Ralph D.
    Lucas, Antoine
    MacKenzie, Shannon
    Malaska, Michael J.
    Mandt, Kathleen
    Mastrogiuseppe, Marco
    Newman, Claire E.
    Nixon, Conor A.
    Radebaugh, Jani
    Rafkin, Scot C.
    Rannou, Pascal
    Sciamma-O'Brien, Ella M.
    Soderblom, Jason M.
    Solomonidou, Anezina
    Sotin, Christophe
    Stephan, Katrin
    Strobel, Darrell
    Szopa, Cyril
    Teanby, Nicholas A.
    Turtle, Elizabeth P.
    Vuitton, Véronique
    West, Robert A.
    Science goals and new mission concepts for future exploration of Titan's atmosphere, geology and habitability: titan POlar scout/orbitEr and in situ lake lander and DrONe explorer (POSEIDON)2022In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 54, no 2-3, p. 911-973Article in journal (Refereed)
    Abstract [en]

    In response to ESA’s “Voyage 2050” announcement of opportunity, we propose an ambitious L-class mission to explore one of the most exciting bodies in the Solar System, Saturn’s largest moon Titan. Titan, a “world with two oceans”, is an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. Titan is also one of the few places in the Solar System with habitability potential. Titan’s remarkable nature was only partly revealed by the Cassini-Huygens mission and still holds mysteries requiring a complete exploration using a variety of vehicles and instruments. The proposed mission concept POSEIDON (Titan POlar Scout/orbitEr and In situ lake lander DrONe explorer) would perform joint orbital and in situ investigations of Titan. It is designed to build on and exceed the scope and scientific/technological accomplishments of Cassini-Huygens, exploring Titan in ways that were not previously possible, in particular through full close-up and in situ coverage over long periods of time. In the proposed mission architecture, POSEIDON consists of two major elements: a spacecraft with a large set of instruments that would orbit Titan, preferably in a low-eccentricity polar orbit, and a suite of in situ investigation components, i.e. a lake lander, a “heavy” drone (possibly amphibious) and/or a fleet of mini-drones, dedicated to the exploration of the polar regions. The ideal arrival time at Titan would be slightly before the next northern Spring equinox (2039), as equinoxes are the most active periods to monitor still largely unknown atmospheric and surface seasonal changes. The exploration of Titan’s northern latitudes with an orbiter and in situ element(s) would be highly complementary in terms of timing (with possible mission timing overlap), locations, and science goals with the upcoming NASA New Frontiers Dragonfly mission that will provide in situ exploration of Titan’s equatorial regions, in the mid-2030s. 

  • 45.
    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.

  • 46.
    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.

  • 47.
    Sundelin, David
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Ascenzi, D.
    Richardson, V.
    Alcaraz, C.
    Polášek, M.
    Romanzin, C.
    Thissen, R.
    Tosi, P.
    Žabka, J.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    The reactivity of methanimine radical cation (H2CNH•+) and its isomer aminomethylene (HCNH2•+) with C2H42021In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 777, article id 138677Article in journal (Refereed)
    Abstract [en]

    Experimental and theoretical studies are presented on the reactivity of H2CNH'+ (methanimine) and HCNH2'+ (aminomethylene) with ethene (C2H4). Selective isomer generation is performed via dissociative photoionization of suitable neutral precursors and reactive cross sections and branching ratios are measured as a function of photon and collision energies. Differences between isomers' reactivity are discussed in light of ab-initio calculations on reaction mechanisms. The main products, for both isomers, are H-elimination, most likely occurring from covalently bound adducts (giving c-CH2CH2CHNH+/CH2NHCHCH2+) and H' atom transfer to yield H2CNH2+. The astrochemical implications of the results are briefly addressed.

  • 48.
    Sundelin, David
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Marimuthu, Aravindh N.
    Thorwirth, Sven
    Brünken, Sandra
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Spectroscopic characterisation of the isomeric H2NCH+ and H2CNH+ radical cations2022In: Journal of Molecular Spectroscopy, ISSN 0022-2852, E-ISSN 1096-083X, Vol. 387, article id 111640Article in journal (Refereed)
    Abstract [en]

    The vibrational transitions and the relative abundances of the two isomeric ions H2CNH+ and H2NCH+ generated through electron impact ionisation have been investigated in a noble gas tagging experiment. It could be shown that both species were formed with an abundance of 70 and 30% for H2NCH+ and H2CNH+, respectively. The obtained vibrational bands of the two species have been assigned to vibrational transitions through comparison with the results of ab initio calculations. These computations also predict both species to be moderately polar. The present investigations show that both isomers should be included in chemical model calculations of dark interstellar clouds, protoplanetary disks, star-forming regions as well as planetary atmospheres.

  • 49. Tan, George K.
    et al.
    Simpson, Anna
    Holtzen, Samuel
    Amador, Elena
    Cable, Morgan L.
    Cantrell, Thomas
    Cullen, Thomas
    Duca, Zach
    Gentry, Diana
    Kirby, Jessica
    McCraig, Heather
    Murukesan, Gayathri
    Patel, Aditya
    Pital, Aaron
    Rader, Erika
    Rennie, Vincent
    Sutton, Scot
    Stevens, Adam
    Whitehead, Jarah
    Cullen, David C.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Stockton, Amanda M.
    Spatial Variation in Results of Biosignature Analyses of Apparently Homogeneous Samples from Mars Analogue Environments in Iceland2022In: ACS Earth and Space Chemistry, E-ISSN 2472-3452, Vol. 6, no 6, p. 1472-1481Article in journal (Refereed)
    Abstract [en]

    The search for signs of life on Mars and beyond is time consuming and labor-intensive; hence, it is critical to understand how to design sampling strategies that can maximize the likelihood of success. Two distinct Mars analogue environments in Iceland were selected to represent volcanic resurfacing and glacial environments where characterization of different biosignatures at various spatial scales (100 m, 10 m, 1 m, 10 cm) was performed. This study serves the twofold purposes of (1) understanding the different levels of biosignature distributions in these analogue environments and (2) the spatial distributions of biosignatures in these environments, with an overarching goal of drawing lessons from low biomass Mars analogue environments to inform the best sampling strategies for sample collection strategies on Mars. Our results show that samples should be collected for analysis at large (at least 100 m spacing) to capture most differences within an apparently homogeneous environment of the aged resurfaced volcanic region like Mælifellssandur, whereas a smaller spacing at 10 m scale is necessary for younger glacial–volcanic environments like Fimmvörduháls. This study also illustrates the importance of understanding the variability across spatial scales in sampling design for future planetary missions.

  • 50.
    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.

12 1 - 50 of 76
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