Computer-Graphics Studies of Dipole-Dipole Collisions: Evidence for Neutral Collision Complexes

Dugan, J. V.; Palmer, R. W.

doi:10.1063/1.1678525

The Journal of Chemical Physics

1972

DOI: 10.1063/1.1678525

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Computer-Graphics Studies of Dipole-Dipole Collisions: Evidence for Neutral Collision Complexes

J. V. Dugan

R. W. Palmer

Abstract: Three-dimensional computer-graphics studies of orientation-dependent forces are extended to multiple reflection behavior in dipole-dipole collisions. The collision pairs DCl–DCl and HCl–HCl are studied for rotational temperatures of 25, 77, and 300°K and translational temperatures of 77 and 300°K. The probability of a multiple reflection collision is a very sensitive inverse function of hard-core reflection distance Rc for fixed temperatures. A brief comparison of the results is made with two-dimensional resul… Show more

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Semiclassical theory of inelastic molecular collisions: Rotational transitions in small-angle dipole–dipole scattering

Gislason

Herschbach

1976

The Journal of Chemical Physics

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The angular distribution of small-angle scattering is calculated for collisions of polar molecules. As found in previous calculations of the total cross section, the magnitude and form of the scattering vary drastically with the amount of inelastic energy transfer between rotation and translation. Collisions with various orientations of the increments ajl and aj2 in the rotational momenta of the two molecules also give markedly different contributions. A semiclassical treatment of the inelastic scattering amplitude is used, with a random phase approximation for the strong-coupling realm at small impact parameters and the Born approximation for the weak-coupling realm at very large impact parameters. A classical timedependent perturbation calculation is also carried out using a "flywheel" approximation which averages over the unperturbed rotational motion of the molecules during the collision. These small-angle scattering calculations give good agreement with the angular distribution measurements on CsCI + SbCI 3 made by Helbing and Pauly. The resolution correction for total cross section measurements is also derived from these calculations and is found to bring theoretical and experimental cross sections into reasonable correspondence for several systems. The main results are given as simple, closed formulas in terms of reduced variables and are compared with those for the spherically symmetric r-3 and r-6 potentials.

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Semiclassical theory of inelastic molecular collisions: Rotational transitions in small-angle dipole–dipole scattering

Gislason

Herschbach

1976

The Journal of Chemical Physics

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Rotationally inelastic scattering of two HF molecules

DePristo

Alexander

1977

The Journal of Chemical Physics

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For rotationally inelastic HF–HF collisions we have determined fully quantum partial opacities and integral cross sections for the j1=0, j2=0→11, 02, and 22 transitions at total energies of 500, 1000, and 8000 cm−1 and the 11→02 transition at 1000 cm−1. The potential was obtained from a recent fit of an ab initio surface and consisted of a spherically symmetric component and an anisotropic term with dipole–dipole symmetry. The collision dynamics were treated using the recently developed decoupled l-dominant (DLD) and coupled-states (CS) methods as well as within the Born approximation (BA). Comparison with selected full close-coupling calculations indicates that the CS method is very accurate for processes where collisions at small impact parameter play a large role, while the DLD method is to be preferred when large parameter collisions make the major contribution. The BA is, unfortunately, consistently unreliable, overestimating cross sections by more than an order of magnitude except at high energy. Additionally, the BA does not predict correctly the relative ratio of the 11→02 to 11→00 cross sections.

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Computer-Graphics Studies of Dipole-Dipole Collisions: Evidence for Neutral Collision Complexes

Cited by 2 publications

References 7 publications

Semiclassical theory of inelastic molecular collisions: Rotational transitions in small-angle dipole–dipole scattering

Semiclassical theory of inelastic molecular collisions: Rotational transitions in small-angle dipole–dipole scattering

Rotationally inelastic scattering of two HF molecules

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