Vacuum ultraviolet afterglow emission of rare gases and their mixtures

Abstract

The results of a study of afterglow in the VUV spectral region of discharges in xenon, krypton and argon (at pressures of 0.2 to 6 Torr) are reported. Values have been obtained for recombination coefficients and formation rates of molecular ions from atomic ions, as well as for certain collisional excitation transfer constants for the 3p54s1P1 level of argon by comparing the experimental pressure dependence of resonance-line afterglow intensities with approximate analytical solutions of balance equations. The time dependence of xenon resonance lines in mixtures of helium, neon, argon and krypton were also compared with approximate solutions of the balance equations. The rate constant for the formation of xenon molecular ions in three-body collisions of Xe+ with two Xe atoms was measured to be k+(Xe)=0.8(+or-10.2)*10-31 cm6 s-1 with Ne as the third atom the same reaction had a constant of k+(Ne)=3.0(+or-0.8)*10-31 cm6 s-1 and with Ar as the third atom k+(Ar)=0.8(+or-10.2)*10-32 cm6 s-1. The Kr2+ formation constant in three-body collisions of Kr+ with two Kr atoms was measured to be 0.53(+or-0.15)*10-31 cm6 s-1 and, for Ar2+ formation in a similar reaction with two argon atoms, it is 1.9(+or-0.5)*10-31 cm6 s-1. The recombination constants alpha for the atomic ions were obtained: alpha 1(Xe)=1.5(+or-0.5)*10-9, alpha 1(Kr)=0.8(+or-0.2)*10-9, and alpha 1(Ar)=1.0(+or-10.2)*10-10 cm3 s-1.