Photo-injected electron current in cryogenic liquids: a comparison of liquid Ar, Ne, He, N2, and H2 near their boiling points

Collection efficiency of photoelectrons injected into near- and supercritical argon gas

“…Moreover, the residual content of O 2 impurities is so small that the concentration of slow O − 2 ions is negligible. Such a conclusion is supported by the analysis of the behavior of the photoelectric current measured at constant N in liquid argon at the normal boiling point T ≈ 87 K as a function of the electric field E 25,26 . At low injection level, the photocurrent rises ∝ E at first and shows a crossover to a E 1/2 -law at a field that roughly corresponds to 1 mTd.…”

“…12,18 Moreover, the residual content of O 2 impurities is so small that the concentration of slow O − 2 ions is negligible. Such a conclusion is supported by the analysis of the behavior of the photoelectric current measured at constant N in liquid argon at the normal boiling point T ≈ 87 K as a function of the electric field E. 25,26 At low injection level, the photocurrent rises ∝E at first and shows a crossover to a E 1/2 -law at a field that roughly corresponds to 1 mTd. As the injection level is raised, the field dependence at low field gradually changes towards a E 2 -law, typical of a space-charge-limited regime, and the crossover region shifts to increasingly larger field strengths.…”