Signature of fast H atoms from cathode glow region of a dc discharge

Abstract

Asymmetric broadening of Hα line from cathode glow region has been studied. In the cathode glow, mean energy and fractional population of very fast hydrogen atoms were found to be ∼130 eV and ∼55%, respectively. These values reduced to ∼90 eV and ∼20% when measured at negative glow region. The observed asymmetry was attributed to the presence of the fast hydrogen atoms near the cathode surface. The mean energy and number density of excited fast hydrogen atoms were estimated from the velocity distribution of H +, H2+, and H3+ considering collisions inside the cathode sheath. The reduction in the mean energy and number density of the excited fast hydrogen atoms, at the other locations of the discharge, was explained by energy relaxation and thermalization of the neutrals with the background gas. © 2009 American Institute of Physics.