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Title: Effects of reactant rotational excitations on H{sub 2} + NH{sub 2} → H + NH{sub 3} reactivity

Rotational mode specificity of the title reaction is examined using an initial state selected time-dependent wave packet method on an accurate ab initio based global potential energy surface. This penta-atomic reaction presents an ideal system to test several dynamical approximations, which might be useful for future quantum dynamics studies of polyatomic reactions, particularly with rotationally excited reactants. The first approximation involves a seven-dimensional (7D) model in which the two non-reactive N–H bonds are fixed at their equilibrium geometry. The second is the centrifugal sudden (CS) approximation within the 7D model. Finally, the J-shifting (JS) model is tested, again with the fixed N–H bonds. The spectator-bond approximation works very well in the energy range studied, while the centrifugal sudden and J-shifting integral cross sections (ICSs) agree satisfactorily with the coupled-channel counterparts in the low collision energy range, but deviate at the high energies. The calculated integral cross sections indicate that the rotational excitation of H{sub 2} somewhat inhibits the reaction while the rotational excitations of NH{sub 2} have little effect. These findings are compared with the predictions of the sudden vector projection model. Finally, a simple model is proposed to predict rotational mode specificity using K-averaged reaction probabilities.
Authors:
;  [1]
  1. Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)
Publication Date:
OSTI Identifier:
22415425
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 24; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; AMMONIA; APPROXIMATIONS; CHEMICAL BONDS; CHEMICAL REACTIONS; COMPARATIVE EVALUATIONS; COUPLED CHANNEL THEORY; EXCITATION; HYDROGEN; INTEGRAL CROSS SECTIONS; POTENTIAL ENERGY; PROBABILITY; REACTIVITY; ROTATIONAL STATES; SPECIFICITY; SURFACES; TIME DEPENDENCE; WAVE PACKETS