title: Nuclear-spin selection rules in the chemistry of interstellar nitrogen hydrides.
abstract: Nitrogen hydrides are at the root of the nitrogen chemistry in interstellar space. The detailed modeling of their gas phase formation, however, requires the knowledge of nuclear-spin branching ratios for chemical reactions involving multiprotonated species. We investigate in this work the nuclear-spin selection rules in both exothermic and near thermoneutral ion–molecule reactions involved in the synthesis of ammonia, assuming full scrambling of protons in the reaction complexes. The formalism of Oka [ J. Mol. Spectrosc. 2004, 228, 635] is employed for highly exothermic ion–molecule and dissociative recombination reactions. For thermoneutral reactions, a simple state-to-state statistical approach is suggested, which is in qualitative agreement with both quantum scattering and microcanonical statistical calculations. This model is applied to the seven atom reaction NH4(+) + H2, of possible importance in the nuclear-spin thermalization of ammonia.
authors: IPAG, Observatoire de Grenoble, Université Joseph Fourier , CNRS UMR5571, B.P. 53, 38041 Grenoble Cedex 09, France.
authors: Claire
authors: C
authors: Rist
authors: Alexandre
authors: A
authors: Faure
authors: Pierre
authors: P
authors: Hily-Blant
authors: Romane
authors: R
authors: Le Gal