Penning ionization of He(2 3S)+Ar

Abstract
A new measurement of the differential cross sections for He(2 3S)+Ar has been carried out at 65 and 132 meV. A potential V0iVi is found which fits our data as well as the total ionization cross section results of Illenberger and Niehaus. Some sources of uncertainties inherent in our analysis are discussed. The first order semiclassical approximation, which has been employed by several groups, is critically examined. A guideline is proposed to define the region within which this approach can be safely adopted.