Effect of ionization density on the time dependence of luminescence from liquid argon and xenon

Abstract

The time dependence of luminescence in liquid argon and xenon has been studied for electron, $\alpha$-particle, and fission-fragment excitation. The lifetimes of low excited molecular states (${}_{}{}^1{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$) do not depend on the density of excited species while the intensity ratio of ${}_{}{}^1{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ to ${}_{}{}^3{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ is found to be larger at higher deposited energy density. The lifetimes obtained for the ${}_{}{}^1{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ states are 7.0 ± 1.0 nsec and 1.6 ± 0.1 μsec, respectively, in liquid argon, and 4.3 ± 0.6 and 22.0 ± 2.0 nsec, respectively, in liquid xenon. The mechanism of quenching of luminescence at a high density of excited species in liquid argon and xenon is discussed.