Monte Carlo trajectory study of Ar+H_{2} collisions. I. Potential energy surface and cross sections for dissociation, recombination, and inelastic scattering
Abstract
Modified statistical electrongas calculations using the methods of Gordon, Kim, Rae, Cohen, and Pack are carried out to obtain the interaction energy of Ar with H_{2} as a function of geometry. The results are combined with the accurate pairwise interactions, the longrange nonpairwise interaction, and the potential LeRoy and van Kranendonk fit to spectral data on the van der Waals' complex to obtain a potential energy surface which is as accurate as possible at all geometries. This surface and the pairwise additive surface are then used in a Monte Carlo quasiclassical trajectory study of the cross sections (under shocktube highenergy collision conditions) for complete dissociation, for production of quasibound states of H_{2}, and for VT, RT, and VRT energy transfer. Except for RT energy transfer, the accurate surface yields smaller cross sections than the pairwise additive surface does. The cross sections for dissociation are much smaller than predicted by the availableenergy hardsphere model but are larger than the inelastic cross sections for excitation to the highest bound vibrational energy levels. Initial vibrational excitation energy is more effective than rotational energy or relative translational energy in causing dissociation. Using the full potential surface the recombination cross section of the v=13, j=8 quasibound state of H_{2} is calculated at E_{rel}=0.026 eV and is in good agreement with the result previously calculated by Whitlock, Muckerman, and Roberts using a less accurate, pairwise additive potential surface.
 Publication:

Journal of Chemical Physics
 Pub Date:
 December 1976
 DOI:
 10.1063/1.433035
 Bibcode:
 1976JChPh..65.5335B
 Keywords:

 Argon;
 Gas Dissociation;
 Hydrogen;
 Inelastic Collisions;
 Potential Energy;
 Recombination Reactions;
 Trajectory Analysis;
 Error Analysis;
 Inelastic Scattering;
 Molecular Collisions;
 Molecular Oscillations;
 Molecular Rotation;
 Monte Carlo Method;
 Scattering Cross Sections;
 Atomic and Molecular Physics;
 82.20.Fd;
 82.20.Kh;
 34.50.Ez;
 Collision theories;
 trajectory models;
 Potential energy surfaces for chemical reactions;
 Rotational and vibrational energy transfer