Cross sections and rate constants for low-temperature $sup 4$He--H$sub 2$ vibrational relaxation

Journal Article · Thu Jan 15 04:00:00 EST 1976 · J. Chem. Phys., v. 64, no. 2, pp. 452-459

OSTI ID:4071300

Alexander, M H; McGuire, P

Converged coupled-states integral cross sections were determined for the vibrational relaxation of the v=1 j=0 level of p-H$sub 2$ in collisions with $sup 4$He. The collision energies ranged from 0.005 to 0.4 eV. The Gordon--Secrest (GS) potential was used with both a harmonic (HO) and rotating-Morse oscillator (MO) description of the H$sub 2$ molecule. Additional calculations incorporated modifications in the long-range and spherically symmetric (V$sub 0$) parts of the purely repulsive GS surface. Rotational coupling plays a major role in vibrational relaxation even at thermal energies. Although the relative importance of individual vibration--rotation transitions is a sensitive function of the choice of intramolecular potential, the HO and MO total relaxation cross sections are nearly identical. These total relaxation cross sections exhibit a power-law dependence on the initial translational energy down to approx.0.1 eV above threshold; below which point a positive curvature appears for all the surfaces considered. Rate constants for vibrational relaxation were computed and compared with experiment for 60 degreeK

• Research Organization: Department of Chemistry, University of Maryland, College Park, Maryland 20742
• NSA Number: NSA-33-021204
• OSTI ID: 4071300
• Journal Information: J. Chem. Phys., v. 64, no. 2, pp. 452-459, Journal Name: J. Chem. Phys., v. 64, no. 2, pp. 452-459; ISSN JCPSA
• Country of Publication: United States
• Language: English

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DE-EXCITATION
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VIBRATIONAL STATES