New semiclassical treatments of rotational and vibrational transitions in heavy-particle collisions. I. H--H$sub 2$ and He--H$sub 2$ collisions

Journal Article · Mon Dec 01 04:00:00 EST 1975 · J. Chem. Phys., v. 63, no. 11, pp. 4695-4707

OSTI ID:4084295

McCann, K J; Flannery, M R

Two new semiclassical methods: the multistate orbital treatment and the multichannel eikonal treatment: are proposed for the description of rotational and vibrational excitation in heavy-particle collisions. The first method includes appropriate trajectories determined from a certain optical potential designed to couple the response of the internal structure, which is described by a quantal multistate expansion, to the orbit for the relative motion and vice versa. While this approach is, in general, valid when the quantal imprecision in the classical trajectories is small (as for heavy particles) the second method based on the use of a straight-line eikonal for the relative motion, of different local momenta in the various channels and of a multistate expansion for the internal motions, is valid for scattering mainly about the forward direction. These procedures are applied to representative rotational transitions in H--H$sub 2$ and He--H$sub 2$ collisions at 0.25--1.5 eV and yield angular distributions and integral cross sections in very close accord with corresponding quantal results. The methods are particularly valuable at higher impact energies when the inclusion of the resulting many rotational and vibrational channels by full quantal treatments is prohibitively difficult. Various approximate schemes--the perturbed-rotating-atoms approximation and the effective potential method-- are also investigated. (AIP)

• Research Organization: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332
• NSA Number: NSA-33-015657
• OSTI ID: 4084295
• Journal Information: J. Chem. Phys., v. 63, no. 11, pp. 4695-4707, Journal Name: J. Chem. Phys., v. 63, no. 11, pp. 4695-4707; ISSN JCPSA
• Country of Publication: United States
• Language: English

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EV RANGE 01-10
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ROTATIONAL STATES
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