Excitation of He + in a hollow cathode arc discharge

Abstract

Population densities of the excited He(II) levels i=4 to i=10 in hollow cathode arc discharge have been determined and compared with those calculated from a collisional-radiative model. In the experiment the electron temperature was about 2x10 5K and the electron density about 3x10 19 m -3. The observed population densities agree within 50% with those calculated by Drawin and Emard, but differ by a factor 4–6 from the ones found by McWhirter and Hearn. The results of the present experiment suggest that near the threshold energies the cross sections for electronic excitation of He + levels from the He + ground state are half those expected from the calculations of Burgess. We conclude that Drawin and Emard's calculations should preferably be employed for the determination of the electron density and the electron temperature from observed population densities.