| 1. |
- Tom, Brian A., et al.
(author)
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Dissociative recombination of highly enriched para-H-3(+)
- 2009
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:3, s. 31101-
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Journal article (peer-reviewed)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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| 2. |
- Vigren, Erik, et al.
(author)
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The Dissociative Recombination of Protonated Acrylonitrile, CH2CHCNH+, with implications for the Nitrile Chemistry in Dark Molecular Clouds and the Upper Atmosphere of Titan
- 2009
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In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 695:1, s. 317-324
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Zhaunerchyk, Vitali, et al.
(author)
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Investigation into the vibrational yield of OH products in the OH plus H plus H channel arising from the dissociative recombination of H3O
- 2009
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:21, s. 214302-
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Zhaunerchyk, Vitali, et al.
(author)
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Sequential formation of the CH3+H+H channel in the dissociative recombination of CH5
- 2009
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 79:3, s. 30701-
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Journal article (peer-reviewed)abstract
- The fragmentation dynamics in the CH3+H+H channel arising from the dissociative recombination of protonated methane, CH5+, has been investigated with an imaging detector at the CRYRING storage ring. The experimental results imply that this channel proceeds via two-step break-up in which the intermediate CH4 molecule is sufficiently internally excited to further fragment. These observations could go some way to explaining the discrepancy in results reported from ion storage rings and FALP apparatus.
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| 5. |
- Kwiatkowski, A., et al.
(author)
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Magnetic properties of MnAs nanocrystals embedded in GaAs
- 2009
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In: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 321:18, s. 2788-2791
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Journal article (peer-reviewed)abstract
- A phenomenological model for explaining the magnetic properties of MnAs nanocrystals embedded in GaAs is proposed. It is shown that experimental data of DC magnetization as a function of temperature, obtained according to zero-field-cooled and field-cooled protocols, can be understood assuming a transition of the system from a low temperature state in which very slow dynamics is observed(frozen state) to a high-temperature state in which dynamics is fast(quasi superparamagnetic state). (C) 2009 Elsevier B. V. All rights reserved.
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