Walter R. Thorson

Nonadiabatic Effects in the High‐Energy Scattering of Normal Helium Atoms

There is a large discrepancy (∼9 eV) between the calculated adiabatic electronic energy of the ground state (X 1Σg+) of the system He2 and the effective scattering potential deduced from experiments with high‐energy (2 keV) atomic beams, at small interatomic distances (R=0.53 A). It is shown that at least a significant part (25%) of this discrepancy arises from nonadiabatic effects of high relative angular velocity of the atoms in the collisions typical of the experiment. A perturbation‐theory treatment is included to give an estimate of the over‐all magnitude of the effect; but a variational calculation is employed with the nonadiabatic Hamiltonian to produce the minimum estimates of nonadiabatic energy shifts to which we refer above. The theory correctly predicts the observed approximate agreement between adiabatic energies and the experimental potentials at larger distances (R=1.06 A). A method of extending the variational calculation to include continuum contributions is described; it employs a pseudo...

Study of Electron Correlation in the H6 Ring, Using a Novel Approximation

Studies on electron behavior in finite model systems provide information relevant to electrons in lattices. Approximate schemes for testing electron correlation may be tested by such model calculations. We report here the results of a study on the 1Γ1 ground state of the H6 hexagonal ring, using a novel type of wavefunction containing both valence bond and molecular orbital components. The method has a number of significant advantages and gives results as good as those of the simple alternant molecular orbital (AMO) method. Possible implications of these results for molecular and solid‐state electron behavior are discussed briefly.

CORIOLIS SHIFTS IN ELASTIC SCATTERING POTENTIALS

Nonadiabatic effects (Coriolis shifts) have been studied in the 2Σu+ and 2Σg+ states of H2+, for elastic scattering at high relative kinetic energies. This study was made to explore the effects in a simplest prototype system; conclusions are also qualitatively applicable to the He2 system, for which earlier and incomplete studies were made by W. R. Thorson. The phenomenon is relevant to the existing large discrepancy between adiabatic theoretical calculations and the results of high‐energy scattering experiments determining the interaction potential in He2. The results of the study are useful in a study of the scattering proper in the H2+ system.

X 1Σg+—A 3Σu+ Excitation Energy in N2

The valence‐bond method is employed to calculate the energy separations of the potential surfaces for the X 1Σg+ and A 3Σu+ states of the nitrogen molecule for internuclear distances between the respective equilibrium positions (i.e., 1.094 to 1.29 A). The radiative π—π* transition between these states gives rise to the well‐known Vegard—Kaplan bands. The N2 molecule is treated as a 10‐electron problem. Separation into σ and π groups of electrons is made and excitation assumed to affect only the latter. The self‐energy of the σ core is not explicitly evaluated. The σ—π interactions are nearly insensitive to variations in the σ‐core bonds, a result which justifies the variational calculation of the π energy plus σ—π interactions as a valid determination of the π‐electron wavefunctions.The resulting energy separation has an almost constant error, 1.1 to 1.3 eV lower than experiment; the energies themselves are more sensitive to the wavefunction than is the separation. The invariance of the error, both as ob...