Ki Tung Lee

Sudden rotation reactive scattering: Theory and application to 3‐D H+H2

An approximate quantum mechanical theory of reactive scattering is presented and applied to the H+H2 reaction in three dimensions. Centrifugal sudden and rotational sudden approximations are made in each arrangement channel, however, vibrational states are treated in a fully coupled manner. Matching of arrangement channel wave functions is done where the arrangement channel centrifugal potentials are equal. This matching is particularly appropriate for collinearly favored reactions. Integral and differential cross sections are calculated for the H+H2 reaction for H2 in the ground and first excited vibrational states. These calculations employ the Porter–Karplus potential energy surface mainly to allow for comparisons with previous accurate and approximate quantal and quasiclassical calculations.

Reduced dimensionality quantum rate constants for the D+H2(v=0) and D+H2(v=1) reactions on the LSTH surface

Collinear exact quantum reaction probabilities for the D+H2(v=0) and D+H2(v=1) reactions were calculated using the ab initio surface of Liu and Siegbahn (as fit by Truhlar and Horowitz) with an adiabatic treatment of the ground state bend. These probabilities are used to obtain approximate three‐dimensional thermal rate constants which are compared with experiment and other calculations.

A comparative study of the reaction dynamics of several potential energy surfaces for O(3P)+H2 → OH+H. II. Collinear exact quantum and quasiclassical reaction probabilities

Exact quantum and quasiclassical reaction probabilities for the collinear O(3P)+H2 reaction are presented for five potential energy surfaces. These surfaces include the diatomics‐in‐molecules surface of Whitlock, Muckerman, and Fisher, the LEPS surface of Johnson and Winter, the ab initio fitted surface of Schinke and Lester, the ab initio fitted surface of Schatz, Wagner, Walch, and Bowman, and a modification of this last surface newly reported here. On each surface, the quantum and quasiclassical probabilities are compared and interpreted. A vibrationally adiabatic analysis based on recent work by Pollak proves useful in interpreting the dynamic thresholds and quantum oscillations in the reaction probability and other features. A systematic variation in both the quantum and quasiclassical reaction probabilities with the saddle point location of the surface is observed.

New approximate quantum cross sections for the H+H2 reaction

The H+H2 cross section is calculated using a transition state theory is used based on collinear exact quantum reaction probabilities. (AIP)

A comparative study of the reaction dynamics of the O(3P)+H2 → OH+H reaction on several potential energy surfaces. III. Collinear exact quantum transmission coefficient correction to transition state theory

Collinear exact quantum and quasiclassical rate constants and transmission coefficients are presented for the O(3P)+H2 (ν), ν = 0,1 reaction, using the quantum and quasiclassical trajectory reaction probabilities calculated in the preceding paper and by Clary, et al. [D. C. Clary, J. N. L. Connor, and C. J. Edge, Chem. Phys. Lett. 68, 154 (1979)] on a total of five potential energy surfaces.

Sudden rotation calculations of the H + H2(υ = 1, f = 0) reaction☆

Abstract Reaction cross sections are calculated with the sudden rotation (IOS) approximation for the H + H 2 (υ = 1, f = 0) exchange reaction, for total energies between 0.9 and 1 eV. It is found that product H 2 (υ′ = 1) is favored over H 2 (υ′ = o).

Sudden approximation calculations of reactive scattering: The H+H2 reaction

Approximate quantal calculations of the zero partial wave total indistinguishable reaction probability and the total reaction cross section for H+H2 are presented.

Tests of collinear quasiclassical trajectory transmission coefficient correction to transition state theory

We test the accuracy of a collinear quasiclassical trajectory transmission coefficient correction to conventional transition state theory. Comparisons are made between the so‐modified transition state theory, conventional transition state theory, and previously reported three dimensional quasiclassical trajectory rate constants for several reactions. They are the O(3P)+H2(ν = 0), H2(ν = 1) reactions on three different potential energy surfaces, the F+H2(ν = 0) reaction on the LEPS surface of Muckerman (no. 5), and the H+H2(ν = 0) reaction on the Porter–Karplus surface. Although each of these systems has a collinear transition state, they span a wide variation in saddle point location and classical barrier height. We find that the collinear quasiclassical trajectory transmission coefficient very successfully corrects the conventional transition state rate constant even for the O(3P)+H2(ν = 1) reaction where the latter differs from the 3D quasiclassical one by two orders of magnitude.

Reduced dimensionality quantum calculations of integral cross sections for H + H2(υ = 1) → H2(υ′ = 0), H2(υ′ = 1) + H

Abstract Reduced dimensionality quantum, rotationally energy averaged integral cross sections for the H + H 2 (υ = 1) → H 2 (υ′ = 0), H 2 (υ′ = 1) + H reactions are presented and compared to the recent centrifugal sudden results of Schatz, for the Porter-Karplus surface. A simple adiabatic analysis is also presented which accounts for the threshold behavior of the total cross section summed over υ′.

Reply to Comment by Thomas on ‘‘On rainbow scattering in inelastic molecular collisions’’

The comments of Thomas1 on the location of rainbows in inelastic molecular scattering of Ref. 2 are discussed and evaluated. It is contended that more insight into the nature of reainbows in rotatinally inelstic collisions is obtained by using the arguments in ref. 2. (AIP)