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

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

  • 2.
    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%).

  • 3.
    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)
  • 4.
    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.

  • 5.
    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+.

  • 6.
    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.

  • 7. Ojekull, J.
    et al.
    Andersson, P. U.
    Pettersson, J. B. C.
    Markovic, N.
    Thomas, R. D.
    Stockholm University, Faculty of Science, Department of Physics.
    Al Khalili, Ahmed
    Stockholm University, Faculty of Science, Department of Physics.
    Ehlerding, Anneli
    Stockholm University, Faculty of Science, Department of Physics.
    Osterdahl, F.
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Danared, H.
    Kallberg, A.
    Dissociative recombination of water cluster ions with free electrons: Cross sections and branching ratios2008In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, no 4, p. 44311-Article in journal (Refereed)
    Abstract [en]

    Dissociative recombination (DR) of water cluster ions H+(H2O)(n) (n=4-6) with ree electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, branching ratios have been determined for the dominating product channels and absolute DR cross sections have been measured in the energy range from 0.001 to 0.7 eV. Dissociative recombination is concluded to result in extensive fragmentation for all three cluster ions, and a maximum number of heavy oxygen-containing fragments is produced with a probability close to unity. The branching ratio results agree with earlier DR studies of smaller water cluster ions where the channel nH(2)O+H has been observed to dominate and where energy transfer to internal degrees of freedom has been concluded to be highly efficient. The absolute DR cross sections for H+(H2O)(n) (n=4-6) decrease monotonically with increasing energy with an energy dependence close to E-1 in the lower part of the energy range and a faster falloff at higher energies, in agreement with the behavior of other studied heavy ions. The cross section data have been used to calculate DR rate coefficients in the temperature range of 10-2000 K. The results from storage ring experiments with water cluster ions are concluded to partly confirm the earlier results from afterglow experiments. The DR rate coefficients for H+(H2O)(n) (n=1-6) are in general somewhat lower than reported from afterglow experiments. The rate coefficient tends to increase with increasing cluster size, but not in the monotonic way that has been reported from afterglow experiments. The needs for further experimental studies and for theoretical models that can be used to predict the DR rate of polyatomic ions are discussed.

  • 8.
    Thomas, Richard D.
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative Recombination of CH4+2013In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, no 39, p. 9999-10005Article in journal (Refereed)
    Abstract [en]

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

  • 9.
    Thomas, Richard
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, I.
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Indriolo, N.
    Yagi, K.
    Hirata, S.
    McCall, B. J.
    DISSOCIATIVE RECOMBINATION OF VIBRATIONALLY COLD CH+3 AND INTERSTELLAR IMPLICATIONS2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 758, no 1, p. 55-Article in journal (Refereed)
    Abstract [en]

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

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

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

  • 11.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Semaniak, Jacek
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    Millar, T. J.
    Walsh, Catherine
    Roberts, Helen
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative Recombination of Protonated Formic Acid: Implications for Molecular Cloud and Cometary Chemistry2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 709, no 2, p. 1429-1434Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Kaminska, Magdalena
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Trippel, Sebastian
    Wester, Roland
    Zhang, Mingwu
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics, The Manne Siegbahn Laboratory.
    Semaniak, Jacek
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative Recombination of Protonated Propionitrile, CH3CH2CNH+: Implications for Titan's Upper Atmosphere2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 722, no 1, p. 847-850Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Trippel, Sebastian
    Zhang, Mingwu
    Stockholm University, Faculty of Science, Department of Physics.
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Walsh, Catherine
    Wester, Roland
    Semaniak, Jacek
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of the acetaldehyde cation, CH3CHO+2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 37, p. 11670-11673Article in journal (Refereed)
    Abstract [en]

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

  • 14.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Semaniak, J.
    Hamberg, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, V.
    Kaminska, M.
    Thomas, Richard 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.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of nitrile ions with implications for Titan's upper atmosphere2012In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 60, no 1, p. 102-106Article in journal (Refereed)
    Abstract [en]

    Nitrile ions are abundant in Titan's upper atmosphere and are expected to be lost mainly via dissociative recombination with free electrons. We review in this paper a series of experimental results on the dissociative recombination reactions of nitrile ions known/expected to be present in Titan's upper atmosphere. The experiments were all performed at the heavy ion storage ring CRYRING in Stockholm, Sweden, and the results presented here include information on rate coefficients at electron temperatures relevant for Titan's upper atmosphere as well as information on the product branching fractions of the reactions. We discuss implications of the results for Titan's atmosphere. As an example the presented results support a statement by Krasnopolsky (2009) that nitriles do not degrade to yield N-2 again in Titan's atmosphere, indicating that condensation and polymerization with precipitation to the surface are their ultimate fate.

  • 15.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, M.
    Semaniak, J.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Reassessment of the dissociative recombination of n2h+ at cryring2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 757, no 1, p. 34-Article in journal (Refereed)
    Abstract [en]

    The dissociative recombination (DR) of N2H+ has been reinvestigated at the heavy ion storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm, Sweden. Thermal rate coefficients for electron temperatures between 10 and 1000 K have been deduced. We show that electron recombination is expected to play an approximately equally important role as CO in the removal of N2H+ in dark interstellar clouds. We note that a deeper knowledge on the influence of the ions' rotational temperature in the DR of N2H+ would be helpful to set further constraints on the relative importance of the different destruction mechanisms for N2H+ in these environments. The branching fractions in the DR of N2H+ have been reinvestigated at similar to 0 eV relative kinetic energy, showing a strong dominance of the N-2 + H production channel (93(-2)(+4)%) with the rest leading to NH + N. These results are in good agreement with flowing afterglow experiments and in disagreement with an earlier measurement at CRYRING.

  • 16.
    Zhaunerchyk, Vitali
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Rosen, Stefan
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Kashperka, Iryna
    Stockholm University, Faculty of Science, Department of Physics.
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, Department of Physics.
    Semaniak, Jacek
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Investigation into the vibrational yield of OH products in the OH plus H plus H channel arising from the dissociative recombination of H3O+2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, no 21, p. 214302-Article in journal (Refereed)
    Abstract [en]

    The vibrational population of the hydroxyl radical, OH, formed in the OH+H+H channel arising from the dissociative recombination of the hydronium ion, H3O+, has been investigated at the storage ring CRYRING using a position-sensitive imaging detector. Analysis shows that the OH fragments are predominantly produced in the v=0 and v=1 states with almost equal probabilities. This observation is in disagreement with earlier FALP experiments, which reported OH(v=0) as the dominant product. Possible explanations for this difference are discussed.

  • 17.
    Zhaunerchyk, Vitali
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    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.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Vane, C. Randy
    Bannister, Mark E.
    Bahati, Eric M.
    Österdahl, Fabian
    af Ugglas, Magnus
    Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
    Dissociative recombination study of PD2+ at CRYRING: absolute cross section, chemical branching ratios and three-body fragmentation dynamics2005In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Molecular Physics, ISSN 0026-8976, Vol. 103, no 20, p. 2735-2745Article in journal (Refereed)
    Abstract [en]

    The paper reports an investigation of the dissociative recombination of   at the heavy-ion storage ring CRYRING. The absolute cross-section has been measured as a function of centre-of-mass energy ranging from 1 meV to 0.1 eV. The experiment performed has shown the dissociative recombination of   to be dominated by three-body break-up, with a branching ratio of about 78%. Competition between the available three-body channels producing the ground state, P(4S), and the first two excited states, P(2D) and P(2P), is observed. The formation of the first excited state dominates over the other two almost equally probable channels with about 75% of all three-body events. The results indicate that the kinetic energy released in the three-body break-up of   is randomly shared between the deuterium atoms. The intra-molecular angle on dissociation has also been investigated. A comparative analysis of the dissociative recombination dynamics for the two isovalent systems,   and  , is undertaken.

1 - 17 of 17
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