| 1. |
- Ehlerding, A., et al.
(författare)
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The dissociative recombination of fluorocarbon ions III : CF2+ and CF3
- 2006
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:4, s. 805-812
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Tidskriftsartikel (refereegranskat)abstract
- Cross sections and branching ratios are presented for the dissociative recombination of the CF2+ and C-3(+) ions with electrons. It is found that the channel producing CF + F is dominant for the reaction with CF2+ and the production of CF2 + F is dominant for the reaction with CF3+. The cross sections for these two ions are very similar.
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| 2. |
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| 3. |
- Geppert, W. D., et al.
(författare)
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Dissociative recombination of CD3OD2
- 2005
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 1, s. 117-124
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Tidskriftsartikel (refereegranskat)abstract
- The branching ratios of the different reaction pathways and the overall rate of the dissociative recombination of CD3OD2 + were measured at the CRYRING storage ring located at the Manne Siegbahn Laboratory in Stockholm, Sweden. A preliminary analysis of the data yielded that formation of methanol accounts for only 6±2% of the total reaction rate. Largely, dissociative recombination of CD3OD 2 + involves fragmentation of the C-O bond, the major process being the three-body break-up forming CD3, OD and D (branching ratio 0.59). A non-negligible formation of interstellar methanol by the previously proposed mechanism is therefore very unlikely.
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| 4. |
- Geppert, W.D., et al.
(författare)
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Dissociative recombination of protonated methanol
- 2006
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Ingår i: Faraday discussions. - Cambridge : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 133, s. 177-190
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Tidskriftsartikel (refereegranskat)abstract
- 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 sigma = 1.2 +/- 0.1 x 10(-15) E-1.15 +/- 0.02 cm(2) and sigma = 9.6 +/- 0.9 x 10(-16) E-1.20 +/- 0.02 cm(2) for CH3OH2+ and CD3OD2+, respectively. From these values thermal reaction rate coefficients of k(T) = 8.9 +/- 0.9 x 10(-7) (T/300) (- 0.59 +/- 0.02) cm(3) s(-1) (CH3OH2+) and k( T) = 9.1 +/- 0.9 x 10(-7) (T/ 300) (- 0.63 +/- 0.02) cm(3) 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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| 5. |
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| 6. |
- Al-Khalili, A, et al.
(författare)
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Dissociative recombination cross section and branching ratios of protonated dimethyl disulfide and N-methylacetamide
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:12, s. 5700-5708
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Tidskriftsartikel (refereegranskat)abstract
- Dimethyl disulfide (DMDS) and N-methylacetamide are two first choice model systems that represent the disulfide bridge bonding and the peptide bonding in proteins. These molecules are therefore suitable for investigation of the mechanisms involved when proteins fragment under electron capture dissociation (ECD). The dissociative recombination cross sections for both protonated DMDS and protonated N-methylacetamide were determined at electron energies ranging from 0.001 to 0.3 eV. Also, the branching ratios at 0 eV center-of-mass collision energy were determined. The present results give support for the indirect mechanism of ECD, where free hydrogen atoms produced in the initial fragmentation step induce further decomposition. We suggest that both indirect and direct dissociations play a role in ECD.
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| 7. |
- Geppert, W D, et al.
(författare)
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Dissociative recombination of nitrile ions : DCCCN+ and DCCCND
- 2004
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 613:2, s. 1302-1309
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Tidskriftsartikel (refereegranskat)abstract
- Branching ratios and absolute cross sections have been measured for the dissociative recombination of DCCCN+ and DCCCND+ using the CRYRING ion storage ring. In the case of DCCCN+ the dissociation yielding D + C3N and those leading to two fragments containing a pair of heavy atoms dominate, whereas pathways producing a fragment with three heavy atoms play only a minor role. Conversely, for DCCCND+, only those channels preserving the carbon chain or producing two fragments with a pair of heavy atoms each are detected. The cross sections of the reactions are very similar and can be fitted to the expressions sigma = (2.9 +/- 0.5) x 10(-15)E(eV)(-1.05 +/- 0.02) cm(2) and sigma = (2.3 +/- 0.4) x 10(-15)E(eV)(-1.10 +/- 0.02) cm(2) for DCCCN+ and DCCCND+, respectively. From these data, thermal reaction rates of k(T) = (1.5 +/- 0.3) x 10(-6)(T/300 K)(-0.60 +/- 0.02) cm(3) s(-1) and k(T) = (1.5 +/- 0.3) x 10(-6)(T/300 K)(-0.58 +/- 0.02) cm(3) s(-1) were calculated for DCCCN+ and DCCCND+, respectively. These rates and branching ratios are compared with those hitherto used in astrophysical models.
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| 8. |
- Geppert, W D, et al.
(författare)
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Dissociative recombination of (SO2+)-O-18 : Evidence for three-body breakup
- 2004
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 610:2, s. 1228-1233
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Tidskriftsartikel (refereegranskat)abstract
- Branching ratios and absolute cross sections have been measured for the dissociative recombination of (SO2+)-O-18 using the CRYRING ion storage ring. The branching ratio of the (SO2+)-O-18 + e(-)-->(SO)-O-18+O-18 channel amounts to 61%, while the three-body breakup (SO2+)-O-18 + e(-)-->S+2(18)O accounts for the remaining 39% of the total reaction. The cross section of the reaction could be fitted by the expression sigma=(1.2+/-0.4)x10(-15) E-0.96+/-0.02 cm(2), which leads to a thermal reaction rate of k(T)=(4.6+/-0.2)x10(-7)(T/300 K)(-0.52+/-0.02) cm(3) mol(-1) s(-1).
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| 9. |
- Hellberg, F, et al.
(författare)
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Investigating the breakup dynamics of dihydrogen sulfide ions recombining with electrons
- 2005
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 122:22, s. 224314-
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents results concerning measurements of the dissociative recombination (DR) of dihydrogen sulfide ions. In combination with the ion storage ring CRYRING an imaging technique was used to investigate the breakup dynamics of the three-body channel in the DR of (SD2+)-S-32. The two energetically available product channels S(P-3)+2D(S-2) and S(D-1)+2D(S-2) were both populated, with a branching fraction of the ground-state channel of 0.6(0.1). Information about the angle between the two deuterium atoms upon dissociation was obtained together with information about how the available kinetic energy was distributed between the two light fragments. The recombination cross sections as functions of energy in the interval of 1 meV to 0.3 eV in the center-of-mass frame are presented for (SH2+)-S-34. The thermal rate coefficient for the DR of (SH2+)-S-34 was determined to be (4.8 +/- 1.0)x10(-7)(T/300)(-0.72 +/- 0.1) cm(3) s(-1) over this interval.
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| 10. |
- Montaigne, Helen, et al.
(författare)
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Dissociative recombination of the thioformyl (HCS+) and carbonyl sulfide (OCS+) cations
- 2005
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 631:1, s. 653-659
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Tidskriftsartikel (refereegranskat)abstract
- Branching ratios and absolute cross sections have been measured for the dissociative recombination of HCS+ and OCS+ at the CRYRING ion storage ring. In the case of OCS+, the channel leading to CO + S ( 83%) dominates, whereas the other exoergic pathways leading to CS + O (14%) and C + SO (3%) are of lesser importance. In the case of HCS+, fracture of the C - S bond is predominant (81%), with the production of H + CS accounting for the remainder (19%). The cross section of the reaction could be fitted by the expressions sigma = 1.41 x 10(-15)E(eV)(-1.11) and 4.47 x 10(-16)E(eV) (-1.14) cm(2) for HCS+ and OCS+, respectively. The derived energy dependences of the thermal reaction rate coefficients can be fitted by k(T) 9.7 x 10(-7)(T/300)(-0.57) and 3.5 x 10(-7)(T/300)(-0.62) cm(3) s(-1) for HCS+ and OCS+, respectively. We use these data to perform model calculations on the HCS+/CS abundance ratio in dark clouds and find that the models using the UMIST and Ohio State University databases have even more difficulty in accounting for the large observed ratio.
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| 11. |
- Någård, M. B., et al.
(författare)
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Dissociative recombination of D+(D2O)(2) water cluster ions with free electrons
- 2002
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 117:11, s. 5264-5270
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Tidskriftsartikel (refereegranskat)abstract
- Dissociative recombination (DR) of the water cluster ion D+(D2O)(2) has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). Cluster ions were injected into the ring and accelerated to an energy of 2.28 MeV. The stored ion beam was merged with an almost monoenergetic electron beam, and neutral fragments produced by DR were detected by an energy-sensitive surface barrier detector. The first experimental determinations of the absolute DR cross section and branching ratios for a cluster ion are reported. The cross section for the process D+(D2O)(2)+e(-) is large and reaches 6.10(-12) cm(2) at a low center-of-mass collision energy of 0.001 eV. The cross section has an E-1.19+/-0.02 dependence in the energy range 0.001-0.0052 eV, and a steeper slope with an E-1.70+/-0.12 dependence for E=0.052-0.324 eV. The general trends are similar to the results for previously studied molecular ions, but the cross section is higher in absolute numbers for the cluster ion. Thermal rate coefficients for electron temperatures of 50-2000 K are deduced from the cross section data and the rate coefficients are consequently also large. Branching ratios for the product channels are determined with a grid technique. Break-up into 2D(2)O+D is the dominating dissociation channel with a probability of 0.94+/-0.04. The channel resulting in the fragments D2O+OD+D-2 has a probability of 0.04+/-0.02, and the probability for formation of D3O+D2O is 0.02+/-0.03. The results are compared with data for molecular ions, and the cluster dissociation dynamics are discussed.
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| 12. |
- Öjekull, Jenny, 1973, et al.
(författare)
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Dissociative recombination of ammonia clusters studied by storage ring experiments
- 2006
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 125:19, s. 194306-
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Tidskriftsartikel (refereegranskat)abstract
- Dissociative recombination of ammonia cluster ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for dissociative recombination of H+(NH3)(2), H+(NH3)(3), D+(ND3)(2), and D+(ND3)(3) in the collision energy range of 0.001-27 eV are reported, and thermal rate coefficients for the temperature interval from 10 to 1000 K are calculated from the experimental data and compared with earlier results. The fragmentation patterns for the two ions H+(NH3)(2) and D+(ND3)(2) show no clear isotope effect. Dissociative recombination of X+(NX3)(2) (X=H or D) is dominated by the product channels 2NX(3)+X [0.95 +/- 0.02 for H+(NH3)(2) and 1.00 +/- 0.02 for D+(ND3)(2)]. Dissociative recombination of D+(ND3)(3) is dominated by the channels yielding three N-containing fragments (0.95 +/- 0.05).
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| 13. |
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| 14. |
- Öjekull, Jenny, 1973, et al.
(författare)
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Dissociative recombination of H+(H2O)3 and D+(D2O)3 water cluster ions with electrons: Cross sections and branching ratios
- 2007
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Ingår i: The Journal of chemical physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127, s. 194301-194309
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Tidskriftsartikel (refereegranskat)abstract
- Dissociative recombination (DR) of the water cluster ions H+(H2O)3 and D+(D2O)3 with electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, absolute DR cross sections have been measured for H+(H2O)3 in the energy range of 0.001–0.8 eV, and relative cross sections have been measured for D+(D2O)3 in the energy range of 0.001–1.0 eV. The DR cross sections for H+(H2O)3 are larger than previously observed for H+(H2O)n (n=1,2), which is in agreement with the previously observed trend indicating that the DR rate coefficient increases with size of the water cluster ion. Branching ratios have been determined for the dominating product channels. Dissociative recombination of H+(H2O)3 mainly results in the formation of 3H2O+H (probability of 0.95±0.05) and with a possible minor channel resulting in 2H2O+OH+H2 (0.05±0.05). The dominating channels for DR of D+(D2O)3 are 3D2O+D (0.88±0.03) and 2D2O+OD+D2 (0.09±0.02). The branching ratios are comparable to earlier DR results for H+(H2O)2 and D+(D2O)2, which gave 2X2O+X (X=H,D) with a probability of over 0.9.
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| 15. |
- Öjekull, Jenny, 1973, et al.
(författare)
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Dissociative recombination of NH4+ and ND4+ ions : Storage ring experiments and ab initio molecular dynamics
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:16, s. 7391-7399
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Tidskriftsartikel (refereegranskat)abstract
- The dissociative recombination (DR) process of NH4+ and ND4+ molecular ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for DR of NH4+ and ND4+ in the collision energy range 0.001-1 eV are reported, and thermal rate coefficients for the temperature interval from 10 to 2000 K are calculated from the experimental data. The absolute cross section for NH4+ agrees well with earlier work and is about a factor of 2 larger than the cross section for ND4+. The dissociative recombination of NH4+ is dominated by the product channels NH3+H (0.85+/-0.04) and NH2+2H (0.13+/-0.01), while the DR of ND4+ mainly results in ND3+D (0.94+/-0.03). Ab initio direct dynamics simulations, based on the assumption that the dissociation dynamics is governed by the neutral ground-state potential energy surface, suggest that the primary product formed in the DR process is NH3+H. The ejection of the H atom is direct and leaves the NH3 molecule highly vibrationally excited. A fraction of the excited ammonia molecules may subsequently undergo secondary fragmentation forming NH2+H. It is concluded that the model results are consistent with gross features of the experimental results, including the sensitivity of the branching ratio for the three-body channel NH2+2H to isotopic exchange.
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| 16. |
- Geppert, W D, et al.
(författare)
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Dissociative recombination of C3H4+ : preferential formation of the C3H3 radical
- 2004
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 237:1, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- Branching ratios and absolute cross sections have been measured for the dissociative recombination of C3H4+ using the CRYRING ion storage ring. The pre-eminent channel involves the production of C3H3 and H, whereas processes involving rupture of carbon-carbon bonds are clearly disfavoured. The cross section of the reaction could be fitted to the expression sigma = 5.5 +/- 0.2 x 10(-15) E-1.01+/-0.02, which leads to a thermal reaction rate of k(T) = 2.95 +/- 0.1 x 10(-6) (T/300)(-0.67+/-0.02) cm(3) s(-1).
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| 17. |
- Geppert, W D, et al.
(författare)
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Dissociative recombination of N2OD
- 2004
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 6:13, s. 3415-3419
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Tidskriftsartikel (refereegranskat)abstract
- Branching ratios and absolute cross sections have been measured for the dissociative recombination of N2OD+ using the CRYRING ion storage ring. The most dominating pathways were found to be those eading to N-2 + OD (46%) and the three-body break-up producing N-2 + O + D (40%). The production of N2O is not observed. The cross section of the reaction could be fitted to the expression sigma = 1.25 +/- 0.25 x 10(-15)(E/eV)(-1.24+/-0.02), which leads to a thermal reaction rate of k(T) = 1.4 +/- 0.1 x 10(-6)(T/300)(-0.74+/-0.02) cm(3) s(-1). The findings are compared with those of the related dissociative recombination of DOCO+ as well as with earlier flowing afterglow measurements.
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| 18. |
- Geppert, W D, et al.
(författare)
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Extraordinary branching ratios in astrophysically important dissociative recombination reactions
- 2004
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Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 127, s. 425-437
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Tidskriftsartikel (refereegranskat)abstract
- Branching ratios of the dissociative recombination reactions of the astrophysically relevant ions DCO+, N2H+ and DOCO+ ( as substitute for HOCO+) have been measured using the CRYRING storage ring at the Manne Siegbahn Laboratory at the University of Stockholm, Sweden. For DCO+, the channel leading to D and CO was by far the most important one ( branching ratio 0.88), only small contributions of the CD+O and OD+C product pathways ( branching ratios 0.06 each) were recorded. In the case of N2H+ the surprising result of a break-up of the N-N bond to N and NH ( branching ratio 0.64) was found with the branching ratio of the N-2+H product channel therefore displaying a branching ratio of only 0.36. In the case of DOCO+, the three-body break-up into D+O+CO dominated ( branching ratio 0.68), whereas the contribution of the CO2+H channel was only minute (0.05). The remaining share ( branching ratio 0.27) was taken by the pathway leading to OH+CO. For the dissociative recombination of N2H+ and DOCO+ also absolute reaction cross sections were obtained in the collisional energy range between 0 and 1 eV. From these cross sections it was possible to work out the thermal rate constants, which were found to be k(T) = 1.0 +/- 0.1 x 10(-7) (T/300 K)(-0.51 +/- 0.02) cm(3) s(-1) and k(T) = 1.2 +/- 0.1 x 10(-6) (T/300 K)(-0.64 +/- 0.02) cm(3) s(-1) for N2H+ and DOCO+, respectively.
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| 19. |
- Salén, Peter, et al.
(författare)
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Complete dissociation branching fractions and Coulomb explosion dynamics of SO2 induced by excitation of O 1s pre-edge resonances
- 2015
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 143:13
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Tidskriftsartikel (refereegranskat)abstract
- Fragmentation processes of SO2 following excitation of the six main O 1s pre-edge resonances, as well as above the ionization threshold and below the resonances, are studied using a position-sensitive time-of-flight ion imaging detector, and the associated dissociation branching ratios and break-up dynamics are determined. In order to distinguish between the O+ and S2+ fragments of equal mass-to-charge ratio, the measurements have been performed with the isotopically enriched (SO2)-O-18 sample. By analysis of the complete set of the fragment momentum vectors, the beta values for the fragments originating from the SO+ + O+ break-up and the kinetic energy release for fragmentation channels of both SO22+ and SO23+ parent ions are determined. We also present results on the three-body break-up dynamics. (C) 2015 AIP Publishing LLC.
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| 20. |
- Zhaunerchyk, Vitali, et al.
(författare)
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Dissociative recombination study of PD2+ at CRYRING : absolute cross-section, chemical branching ratios and three-body fragmentation dynamics
- 2005
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Ingår i: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 103:20, s. 2735-2745
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Tidskriftsartikel (refereegranskat)abstract
- The paper reports an investigation of the dissociative recombination of PD2+ 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 PD2+ 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(S-4), and the. first two excited states, P(D-2) and P(P-2), 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 PD2+ 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, PD2+ and NH2+, is undertaken.
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| 21. |
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| 22. |
- Vigren, Erik, et al.
(författare)
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Dissociative recombination of nitrile ions with implications for Titan's upper atmosphere
- 2012
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 60:1, s. 102-106
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 23. |
- Vigren, Erik, et al.
(författare)
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Reassessment of the dissociative recombination of n2h+ at cryring
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 757:1, s. 34-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 24. |
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| 25. |
- Öjekull, Jenny, 1973, et al.
(författare)
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Dissociative recombination of water cluster ions with free electrons : Cross sections and branching ratios
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:4, s. 44311-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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