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Dissociative recombination of NH4+ and ND4+ ions: storage ring experiments and ab initio molecular dynamics.

Jenny Öjekull ; Patrik U Andersson ; Mats B Någård ; Jan B. C. Pettersson ; A M Derkatch ; A Neau ; S Rosén ; R Thomas ; M Larsson ; F Österdahl ; J Semaniak ; H Danared ; A Källberg ; M af Ugglas ; Nikola Markovic (Institutionen för kemi och biovetenskap, Fysikalisk kemi)
The Journal of chemical physics (0021-9606). Vol. 120 (2004), 16, p. 7391-9.
[Artikel, refereegranskad vetenskaplig]

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.

Denna post skapades 2007-10-15. Senast ändrad 2009-01-07.
CPL Pubid: 53725


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Institutioner (Chalmers)

Institutionen för kemi (2001-2011)
Institutionen för kemi och biovetenskap, Fysikalisk kemi (2004-2004)


Fysikalisk kemi

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