Laser-Induced Fluorescence Study of Penning Collision of HeI 21S Atom with Xe in He+Xe Gas Discharge Plasma

Abstract

This paper presents experimental results concerning the population of the 21S atom of HeI in a discharge plasma of a He+Xe gas mixture. The population measurement was made by the laser-induced fluorescence method with the laser light tuned to the HeI line of 5016 A(21S-31P). The fluorescence intensity of the HeI line was measured as a function of the discharge current at pressures ranging from 0.2 to 5.0 Torr, and the behavior of the fluorescence intensity was clarified in terms of the measured electron density. In the Xe-mixed gas, the fluorescence intensity was significantly reduced in the region of low electron density; this region extended to a higher electron density as the Xe gas content was increased. Thus, it was concluded that the population of the 21S state was dominated by Penning collisions with Xe atoms at low electron density.