Abnormal broadening of boron emission lines in glow-discharge lamps: evidence for excitation in low-energy B-Ar(Kr or Xe) collisions

Abstract

The profiles of the boron resonance lines emitted from hollow-cathode and planar-cathode glow-discharge lamps have been studied for a variety of discharge conditions. For discharges operated in argon, krypton or xenon, the lines are extremely broad (halfwidths 0.13-0.27 AA) and are emitted very close to the cathode surface with unusually high intensity. The abnormal linewidths are due to Doppler broadening, which is unusually large because of a preferred excitation for those sputtered boron atoms possessing high kinetic energies of ejection. Investigations of the excitation process suggest that the energetic boron atoms are excited by inelastic collisions with rare-gas atoms. The high excitation efficiency at relatively low collision energies is interpreted in terms of curve crossings, which appear to be particularly favourable for some boron-rare-gas systems.