| 1. |
- Hamberg, Mathias, et al.
(författare)
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Experimental studies of the dissociative recombination for CD3CDOD+ and CH3CH2OH2
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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 × 10−15(Ecm[eV])−1.23±0.02 cm2 and k(T) = 1.9 ± 0.4 × 10−6(T/300)−0.73±0.02 cm3s−1 for CH3CH2OH2+ as well as k(T) = 1.1 ± 0.4 × 10−6(T/300)−0.74±0.05 cm3s−1 and σ(Ecm[eV]) = 9.2 ± 4 × 10−16(Ecm[eV])−1.24±0.05 cm2 for CD3CDOD+.
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| 2. |
- Hamberg, Mathias, et al.
(författare)
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Experimental studies of the dissociative recombination processes for the dimethyl ether ions CD3OCD2+ and (CD3)2OD
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 514, s. A83-
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Tidskriftsartikel (refereegranskat)abstract
- 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 × 10−6(T/300)−0.77±0.01 cm3s−1, σ= 1.2 ± 0.4 × 10−15(Ecm[eV])−1.27 ± 0.01 cm2 and k(T) = 1.7 ± 0.6 × 10−6(T/300)−0.70±0.02 cm3s−1,σ= 1.7 ± 0.6 × 10−15(Ecm[eV])−1.20±0.02 cm2 for CD3OCD2+ and (CD3)2OD+, respectively.
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| 3. |
- 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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