| 1. |
- Danielsson, Mathias, et al.
(författare)
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The cross-section and branching fractions for dissociative recombination of the diacetylene cation C4D2
- 2008
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 273:3, s. 111-116
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Tidskriftsartikel (refereegranskat)abstract
- 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%).
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| 2. |
- Geppert, Wolf D., et al.
(författare)
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Dissociative recombination in the interstellar medium and planetary ionospheres
- 2008
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Ingår i: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 106:16-18, s. 2199-2226
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Forskningsöversikt (refereegranskat)abstract
- 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.
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| 3. |
- Hamberg, Matthias, 1975-
(författare)
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Examination of Dissociative Recombination Processes of Importance for Astrochemically Evolving Interstellar Clouds
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Each single moment a myriad of processes is taking place throughout the universe. A great deal of them has been found to be dissociative recombination (DR) reactions. In this thesis the major work described are related to experimental determination of reaction rates and how the reaction products splits up into their final fragments. I focus on the study of ion formation of molecules that can function as life precursors.The following species have been investigated and are discussed in this thesis:CH3OH2+, CD3OD2+, N2O+, CH2OH+, CD2OD+, CD2OD2+ , CD3OCD2+ and (CD3)2OD+The result of these measurements are and will be 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 the great impact on such models.
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| 4. |
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| 5. |
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| 6. |
- Lenori, Francesca, et al.
(författare)
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Crossed-Beam and Theoretical Studies of the S(1D) + C2H2 Reaction
- 2009
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Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 113, s. 4330-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Schmidt, Henning, et al.
(författare)
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DESIREE as a new tool for interstellar ion chemistry
- 2008
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Ingår i: International Journal of Astrobiology. - 1473-5504 .- 1475-3006. ; 7:3-4, s. 205-208
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Tom, Brian A., et al.
(författare)
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Dissociative recombination of highly enriched para-H-3(+)
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:3, s. 31101-
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Tidskriftsartikel (refereegranskat)abstract
- 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(+).
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| 9. |
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| 10. |
- Vigren, Erik, et al.
(författare)
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Dissociative recombination of fully deuterated protonated acetonitrile, CD3CND+ : Product branching fractions, absolute cross section and thermal rate coefficient
- 2008
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 10, s. 4014-4019
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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