Additional Excitation Transfer between Excited Helium Atoms and Neon in He–Ne Laser Discharges

Abstract

Measurements are given of the ratio of the excitation due to helium to the excitation due to electrons for a number of neon states in a He–Ne laser discharge. The ratio was obtained from spectral intensity measurements on dc discharges in pure neon at a pD of 2.2 Torr mm and in a helium-neon 5:1 mixture at a pD of 4 Torr mm, with a discharge tube diameter of 10 mm, at a current density of 0.23 A cm−2, where the electron temperature is deliberately chosen to be the same in both discharges. In Paschen notation, the ratios are 4d5−6; 5d4, 5d4′, 4d3, 4d1″, 4d1′, 4s3−7; 5d4, 5d4′, 5d3, 5d1′−8; 4s5−9, 4s4−51; 4s2−29; 5s3−3.5; and 5s2−12. It is shown that a selective-excitation reaction involving He 21P1 atoms is responsible for the excitation of neon atoms to the Ne-5s2 state. The reaction is spin conserved and has a cross section of about 10−16 cm2.