Scattering of NH[sub 3] by [ital ortho]- and [ital para]-H[sub 2]: Expansion of the potential and collisional propensity rules

Journal Article · Mon Mar 15 04:00:00 EST 1993 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.464970· OSTI ID:5565902

Rist, C; Alexander, M H ^[1]; Valiron, P ^[2]

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1. Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742 (United States)
2. Groupe d'Astrophysique (URA 708 du CNRS), Observatoire de Grenoble, Universite Joseph Fourier, BP 53 X, 38041 Grenoble Cedex (France)

We present the general expansion of the interaction potential between a rigid, but invertible symmetric top and a linear molecule. The development is derived from the average over electronic coordinates of the fundamental electrostatic interaction. Our expansion for the electrostatic potential takes into account explicitly the symmetry under inversion of the position of all the nuclei, which was not included in earlier expansions. A numerical fit of calculated [ital ab] [ital initio] points for the NH[sub 3]--H[sub 2] system suggests the presence of a similar inversion symmetry for the total interaction potential. We then use our expansion to derive, in the Born and energy sudden limits, propensity rules for collisions of NH[sub 3] with [ital ortho]- and [ital para]-hydrogen. Although at a formal level these propensity rules are equally valid for both hydrogen rotomers, close coupling calculations show that they are considerably weakened for [ital o]-H[sub 2]. This is a manifestation of the additional anisotropy in the interaction between NH[sub 3] and a non-spherical collision partner. Notwithstanding, evidence of these propensity rules is clear, in contrast to earlier calculations based on a preliminary version of the NH[sub 3]--H[sub 2] interaction potential used here.

• OSTI ID: 5565902
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 98:6; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
AMMONIA
ANISOTROPY
BORN APPROXIMATION
CHAINS
COLLISIONS
COULOMB FIELD
COUPLING
ELECTRIC FIELDS
ELEMENTS
ENERGY TRANSFER
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
INELASTIC SCATTERING
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANIC SULFUR COMPOUNDS
SCATTERING
SERIES EXPANSION
SYMMETRY
TOPS