Elastic He~+ on He collision cross-sections and Monte Carlo calculation of the transport coefficients of He~+ ions in gaseous helium

摘要

Integral and differential cross-sections for elastic collisions of He~+ ions in the ground state (~2S) with neutral He atoms are calculated, for centre-of-mass energies between 0.001 and 10 eV, using the partial waves method. The scattering phase shifts are calculated using the JWKB semi-classical approximation, with modified Tang-Toennies ion-atom (TTIA) potential energy curves, that describe spectroscopic data, dissociation energies and equilibrium internuclear distances, and the long-range interaction potentials. These cross-sections are used in a detailed three-dimensional Monte Carlo simulation model to calculate the main transport coefficients describing the ion drift through the neutral gas, as a function of the gas temperature and the reduced uniform electric field. Calculated drift velocities, ion mobilities, as well as longitudinal and transverse diffusion coefficients for He~+ atomic ions in gaseous He, at temperature T=293 K and reduced electric fields, E/N, in the 1 to 300Td (1 Td=10~(-17)Vcm~2) range, are reported and compared with the limited experimental data available in the scientific literature. The calculated drift velocities range from 28.31 ms~(-1) at 1 Td to 3685.0ms~(-1) at 300Td.