Accession Number : AD0682309

Title :   MONTE CARLO TRAJECTORY CALCULATIONS OF ATOMIC EXCITATION AND IONIZATION BY ELECTRON IMPACT.

Descriptive Note : Research rept.,

Corporate Author : AVCO EVERETT RESEARCH LAB EVERETT MASS

Personal Author(s) : Mansbach,Peter ; Keck,James

Report Date : JAN 1969

Pagination or Media Count : 57

Abstract : The excitation and de-excitation of atoms by electron impact has been investigated for states near the ionization limit using classical Monte Carlo trajectory calculations. The trajectories were sampled within the reaction zone with a weight proportional to the equilibrium reaction rate and integrated backward and forward in time to obtain complete histories for the collisions. This method is very much more efficient than the usual technique of sampling outside the reaction zone and makes an otherwise extremely expensive calculation feasible. The results indicate that for energy transfers less than a few kT the reaction cross-section is determined by adiabatic collisions, while for transfers greater than a few kT the impulse approximation is valid. The data have been used to obtain a convenient approximation for the equilibrium transition kernel valid near the ionization limit. This has been used in conjunction with a conventional master equation to obtain an exact expression for the steady state collisional recombination rate constant. Comparison with the available experimental data is reasonably good but there are indications that both radiative cascading and collisions with neutrals may be important under some experimental conditions. (Author)

Descriptors :   (*GAS IONIZATION, REACTION KINETICS), (*ATOMIC ENERGY LEVELS, EXCITATION), RECOMBINATION REACTIONS, MONTE CARLO METHOD, PARTICLE TRAJECTORIES, INTERACTIONS, ELECTRON IRRADIATION

Subject Categories : Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE