G D Meneses

The calculation of orientation and alignment parameters for the electron impact excitation of the 21P state of He in the first-order many-body theory

An attempt has been made to resolve an apparent disagreement between two very similar calculations, by Thomas et al. (1974) and Madison and Shelton (1973), for the electron impact excitation of He 21P at 80 eV impact energy. The present results are in good agreement with those of Thomas et al. Another parameter is calculated which has not been calculated previously in the first-order many-body theory, and the angular rate of the calculation is extended to compare it with newly obtained experimental data.

Coherence parameters, spin-asymmetry and spin-polarization functions for electron impact excitation of neon

Electron impact coherence parameters and fine-structure-effect spin-asymmetry and spin-polarization functions are reported for electron impact excitation of the first few low-lying excited states of Ne. First-order many-body theory was used in these calculations. Our results are in good agreement with recent experimental results for the Stokes parameters P1, P2 and P3 in the small scattering angle region.

Coherence and correlation parameters for thed3 Π u − (v=0,1,2,3;N=1) states of H2

We have applied the density matrix formalism and the distorted-wave approximation to calculate the Stokes parameters for thed3 Πu− (v=0,1,2,3;N=1) states of H2 excited from the X1 ∑g+ (v=0,N=1) state by electron impact at the incident energies ranging from 15 to 40 eV. Our results show that these parameters are nearly independent of the vibrational quantum number of the excited states. However, the polarization of the radiation emitted by the target in the subsequent decay process increases with increasing incident energies.

Electron impact polarization and correlation properties of the inert gases

For the heavier rare-gas targets, Ne, Ar, Kr, there is now a reasonable amount of experimental electron impact coherence parameter data available for excitation of the lowestJ=1 states. Theoretical results for those rare-gas targets, have been restricted to distorted-wave approximation (DWA) type theories. We present a systemization of the experimental data and compare them with available theoretical results. In the case of the heavy rare gases, we compare the experimental and theoretical data available for the three species, Ne, Ar, Kr, in order to identify trends. We compare the experimental data with results from available theories (mainly DWA type) and discuss the importance of spin-orbit coupling effects and “shell” effects. We present our point-of-view as to the physical picture that is emerging from all collisional data, and conclude by recommending future experimental and theoretical activities that will, from our perspective, provide new insight into the physics of these processes.

Analytical approach to the first-order Bethe-Goldstone equation

The first-order Bethe-Goldstone theory (BG1) is defined as the Bethe-Goldstone equation for the two-particle Greens function with the one-particle Greens function calculated in the Hartree-Fock approximation. It is shown that this equation is closely related to the fundamental equations of pair theories developed for electronic systems in atoms and molecules. With the aid of an analytical technique it is shown that this theory can be formulated in terms of coupled integrodifferential equations.