Excitation of vacuum ultraviolet transitions in a discharge of rare-gas mixtures with alkali-metal vapours

Abstract

Collisional energy transfer of excited rare-gas atoms with alkali-metal atoms was studied in a gas discharge of their mixtures by monitoring the vacuum ultraviolet (VUV) line intensities and by a comparison with the approximate solutions of the rate equations. The method used enabled us to obtain depletion cross sections of rare-gas atom resonance states by alkali-metal atoms in a discharge of their mixtures for the following atom pairs: He* by Rb sigma d=8.8*10-15 cm2, Ne* by Rb sigma d=2.0*10-16 cm2 and Ar* by Cs sigma d=1.2*10-15 cm2. The fundamental processes of atomic collisions producing alkali-metal quartet quasimetastable highly excited states in a discharge plasma were studied. The cross section of Rb(4p55s5p)4S32/ quasimetastable excitation in non-elastic collisions with neon metastable atoms was measured to be 2.0(+or-0.8)*10-15 cm2. The quasiresonant charge transfer from a caesium ion metastable to a caesium atom produces Cs(5p55d6s)4P52/ quasimetastable states with a cross section of 9(+or-3)*10-15 cm2. These reactions lead to quasimetastable level population in the discharge, which is important for applications in VUV laser schemes.