Total scattering cross sections for the helium–argon system at low relative velocities

Abstract

Absolute vibrational and electronic cross sections for low-energy electron (2-12 eV) scattering from condensed pyrimidine Absolute total cross sections for He-Ar were measured in the relative velocity range of -800-2000 mls by passing a supersonic nozzle beam through a cell containing the target gas. The beam attenuation was determined by passing the unscattered beam particles into a quadrupole detector. The absolute number density of target gas particles in the target cell was obtained by a calibrated-flow method of introducing gas into the cell during an experiment. A correction was applied for the angular resolution of the apparatus. The average experimental uncertainty was estimated to be -3% to 3.5%. The present results, as well as other available data, were deconvoluted in a two-step process to yield QI and QU, the first and second approximations to the total cross section, as a function of the relative velocity. The composite results of all experimental data were compared to seven interatomic potentials and the Hartree-Fock-dispersion (HFD) potential represented the data best.