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  • 1.
    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%).

  • 2.
    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)
  • 3.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative Recombination of Astrochemically Interesting Ions2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis the major work described concerns experimental determination of the dissociative recombination (DR) reaction for several molecular ions of astrochemical interest. DR is the process where an electron recombines with a molecular ion to form an excited neutral that disintegrates into two or more neutral fragments to release the gained excess energy. It is very efficient under cold conditions and therefore ubiquitously occurring in interstellar environments such as dark clouds and plays an important role in aeronomical plasmae, lightnings and in man-made plasmas such as in combustion engines and fusion reactors. Although DR reactions are crucial processes in all these environments, product branching fractions of DR reactions have proven to be very unpredictable and present one of the great remaining challenges for theoreticians. The experimental work includes determination of reaction rates and product distribution of DR of complex ions such as protonated alcohols and ethers. The following species have been investigated and are discussed in this thesis:

    CH3OH2+ (protonated methanol), CD3OD2+ (deuteronated methanol), CD3OCD2+ (methoxymethyl cation), CD3CDOD+ (deuteronated acetaldehyde), CH3CH2OH2+ (protonated ethanol) and (CD3)2OD+ (deuteronated dimethyl ether).

    The results of these measurements are used in astrochemical model calculations in which the rates used hitherto greatly have been based on educated guesses. Employing the outcome of the DR investigations of the CH3OH2+ and CD3OD2+ ions have shown a great impact on such models. The DR investigations have been followed up by astronomical observations. Theoretical models and laboratory experiments show that methanol should be formed from CO on cold grains. This scenario was tested by astronomical observations of gas associated with young stellar objects (YSOs). Two independent tests were showing consistency with methanol formation on grain surfaces.

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  • 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.
    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.

  • 8.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Millar, T. J.
    Walsh, Catherine
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    The Dissociative Recombination of Protonated Acrylonitrile, CH2CHCNH+, with implications for the Nitrile Chemistry in Dark Molecular Clouds and the Upper Atmosphere of Titan2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 695, no 1, p. 317-324Article in journal (Refereed)
    Abstract [en]

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

  • 9.
    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.

  • 10.
    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.

  • 11.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Danielsson, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Semaniak, Jacek
    Andersson, Patrik U.
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of fully deuterated protonated acetonitrile, CD3CND+: Product branching fractions, absolute cross section and thermal rate coefficient2008In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 10, no 27, p. 4014-4019Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Vigren, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Kaminska, Magdalena
    Hamberg, Mathias
    Stockholm University, Faculty of Science, Department of Physics.
    Zhaunerchyk, Vitali
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, Richard D.
    Stockholm University, Faculty of Science, Department of Physics.
    Semaniak, Jacek
    Danielsson, Mathias
    Larsson, Mats
    Stockholm University, Faculty of Science, Department of Physics.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of the deuterated acetaldehyde ion, CD3CDO+: product branching fractions, absolute cross sections and thermal rate coefficient2007In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 9, no 22, p. 2856-2861Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Zhaunerchyk, Vitali
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Thomas, R. D.
    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.
    Kaminska, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Vigren, E.
    Stockholm University, Faculty of Science, Department of Physics.
    Larsson, M.
    Stockholm University, Faculty of Science, Department of Physics.
    Dissociative recombination of D2H+: Comparison between recent storage-ring results and theoretical calculations2008In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 77, no 3, p. 34701-Article in journal (Refereed)
    Abstract [en]

    The most up-to-date theoretical calculation on the dissociative recombination (DR) of D2H+ predicts a 2-5 times lower rate coefficient than that obtained experimentally at the Test Storage Ring (TSR). In order to verify the validity either of the experimental results or the theoretical calculations we have studied the DR of D2H+ at the storage ring CRYRING. The rate coefficient has been measured over the interaction energy range from approximate to 0 eV to 50 eV and has been found to have a peak at about 10 eV with a value of 1.6 x 10(-8) cm(3) s(-1), which is in excellent agreement with the result reported from TSR. Taking into account the electron temperature distributions, excellent agreement between the two storage rings measurements is also obtained at smaller interaction energies. The branching fraction analysis has been performed at approximate to 0 eV interaction energy and revealed the following results at the 1 sigma confidence level: N(D+D+H)=76.5%+/-2.2%, N(D-2+H)= 10.0%+/-0.7%, and N(DH+D)=13.5%+/-1.5%. The value of 2N(D-2+H)/N(DH+D)=1.48+/-0.22 implies that formation of D-2 is more favorable than DH.

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