THEORETICAL STUDIES OF MOLECULAR COLLISION PROCESSES: (I) TWO-POTENTIAL APPROACH FOR ELECTRON-MOLECULE SCATTERING, (II) THREE-DIMENSIONAL QUANTUM-MECHANICAL STUDY ON ATOM-MOLECULE REACTIVE COLLISION WITH ROTATIONALLY PRE-EXCITED TARGET MOLECULE

Theoretical studies have been carried out on two categories of molecular collision processes: (I) molecule scattering with a light incident particle - electron, and (II) molecule scattering with a heavy incident particle atom.; For the electron-molecule scattering, a general approach, two-potential approach, has been formulated for elastic and vibrational transitions with intermediate- and high-energy impact electrons. In this approach, contributions to the scattering process come from the incoherent sum of two dominant potentials: a short-range shielded nuclear Coulomb potential from individual atomic center, and a permanent/induced long-ranged potential. Applications to e-N(,2), e-CO, and e-CO(,2) scatterings from 50-800 eV incident electron energy have yielded good agreement with absolutely calibrated experiments. This study has enabled us to understand the physical effects responsible for the structure in the differential cross section as well as to gain a clear physical picture of the detail of the electron-molecule scattering process.; The three-dimensional atom-molecule reactive collision has been studied quantum-mechanically within the T-matrix formalism with the adiabetic approximation. By formulating the problem in the body-fixed coordinate system, we have made it possible to study the scattering process with the rotationally pre-excited target molecule. Application to the D + H(,2) reaction on the ab initio Liu-Siegbahn-Truhlar--Horowitz (LSTH) surface has been made. Scattering cross sections of the rotationally pre-excited target molecule are in general 2-3 times smaller than those of the ground state molecule. Various dynamical scattering attributes are averaged at the beam temperature of the experiment of Geddes, Krause and Fite (GKF) and have yielded good agreement with the GKF experiment. The shape of the Arrhenius plot of the reaction rate constants is in excellent agreement with experimental measurements. In some energies, the overall reactivity of the LSTH surface is as much as an order of magnitude less than that of the Porter--Karplus (PK) surface, which is in agreement with classical trajectory calculations.