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

Abstract

Asymmetric broadening of H ␣ 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 ϳ130 eV and ϳ55%, respectively. These values reduced to ϳ90 eV and ϳ20% 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 + , H 2 + , and H 3 + 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.

Collisional kinetics of non-uniform electric field, low-pressure, direct-current discharges in H2

“…The shape of the H α profile seen with an optical probe at large distances from the cathode by Bharathi et al [62] is similar to the axial profiles of Barbeau and Jolly [11] at about the same pressure and discharge voltage. See section 4.2.…”

“…The shape of the H α profile seen with an optical probe at large distances from the cathode by Bharathi et al [57] is similar to the axial profiles of Barbeau and Jolly [10] at about the same pressure and discharge voltage (see section 4.2). Bharathi et al discuss the various reactions and excitation processes, but do not calculate H α profiles.…”