Albert C. Yates

A new H3 potential energy surface and its implications for chemical reaction

Abstract A new H 3 potential energy hypersurface for arbitrary nuclear arrangements is generated from Lius very accurate (≈0.3 kcal/mole error) collinear ab initio calculation and compared with other general geometry surfaces. Preliminary classical trajectory calculations on the new hypersurface are presented and compared with results on the Porter-Karplus surface.

Collinear classical dynamics on a chemically accurate H+H2 potential energy surface

Exchange in the hydrogen atom–molecule reaction is investigated via classical collinear dynamics on the Yates–Lester potential energy surface. A threshold kinetic energy of 6.4762 kcal/mole (0.2808 eV) is determined. Exchange probabilities are found to be, in general, slightly less than those obtained using the energy surface of Shavitt, Stevens, Minn, and Karplus. Energy banding is observed and discontinuities in the transition region are attributed to snarled trajectories. Reaction probabilities for all possible combinations of H, D, and T are determined. Isotopic variations in reaction probability are explained in terms of the mass‐dependent skew of the potential surface and differences in zero‐point vibrational energy.

Multiple‐Scattering Effects in High‐Energy Electron‐Molecule Collisions. II Polyatomic Molecules

The Glauber theory of multiple scattering is applied to the elastic collisions of fast electrons with polyatomic molecules in an effort to explain deviations between theory and experiment in recent molecular structure determination by electron diffraction. The full scattering amplitude is developed inclusive of all double‐scattering contributions, with the differential cross section for the process given up to terms representative of the interference between single and double scattering. For sufficiently energetic incident electrons, the multiple‐scattering contributions to the differential cross section are shown to reduce to simple analytic forms. In particular, the three‐atom single‐double interference term is shown to be an oscillatory function of momentum transfer. Application of the approximate formulas to the rhenium hexafluoride molecule gives excellent agreement with the experimental results of Jacob and Bartell.

On the term-wise analysis of the glauber eikonal series

Abstract For the case of charged particles colliding with atoms, an analytical procedure, capable of providing quantitative estimates of the Glauber cross section, is proposed.

On the reduction of the glauber exchange amplitude

Abstract The “post” and “prior” forms of the Glauber exchange amplitude are reduced in a manner consistent with the Bonham-Ochkur expansions. The application is with respect to the hydrogen atom, wherein the resulting reduced amplitude can be completely evaluated in closed form. Results are presented for the elastic scattering of 4.0 Rydberg electrons, and compared with the corresponding close-coupling and Bonham-Ochkur results. the effect of the Glauber modification is seen to be most important for small angles of scattering.

On a simple modification of the glauber collision amplitude

Abstract The connection between the Glauber many-particle amplitude function and the generalized Born series is demonstrated. The correspondence suggests the introduction of a mean excitation energy to improve the inclusion of virtual excitations of the target.

RELATIVISTIC EFFECTS IN HIGH-ENERGY INELASTIC ELECTRON--ATOM COLLISIONS.

Abstract In the approximation that electron-electron interactions at high incident electron energies (≈40 keV) may be taken as coulombic, an expression for the integral inelastic cross section for all inelastic collisions is given for the hydrogen atom and is easily generalizable to more complex atoms. Results are presented which indicate that relativistic effects in the above energy range can amount to upwards of 15% of the nonrelativistic results. For the differential cross sections, it is found that such corrections are most important for small-angle scattering.