Dissociative recombination of NH4+ and ND4+ ions: storage ring experiments and ab initio molecular dynamics.
Artikel i vetenskaplig tidskrift, 2004

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.

Författare

Jenny Öjekull

Göteborgs universitet

Patrik U Andersson

Göteborgs universitet

Mats B Någård

Göteborgs universitet

Jan B. C. Pettersson

Göteborgs universitet

A M Derkatch

AlbaNova University Center

A Neau

AlbaNova University Center

S Rosén

AlbaNova University Center

R Thomas

AlbaNova University Center

M Larsson

AlbaNova University Center

F Österdahl

Kungliga Tekniska Högskolan (KTH)

J Semaniak

Akademia Swietokrzyska im. Jana Kochanowskiego w Kielcach

H Danared

Manne Siegbahn Laboratory

A Källberg

Manne Siegbahn Laboratory

M af Ugglas

Manne Siegbahn Laboratory

Nikola Markovic

Chalmers, Institutionen för kemi och biovetenskap, Fysikalisk kemi

Journal of Chemical Physics

0021-9606 (ISSN) 1089-7690 (eISSN)

Vol. 120 7391-9

Ämneskategorier

Fysikalisk kemi

DOI

10.1063/1.1669388

PubMed

15267649