A study of trapped electrons in LiCl/D2O and other aqueous glasses at temperatures down to 2 K by radiolysis, pulse radiolysis, photolysis, and stimulated luminescence

Abstract

Pulse radiolysis of 9.5 M LiCl/D2O glass at 6 K produces both types of trapped electrons, evis− and eir−, just as it does at 75 K. However, going from 75 K to 6 K increases the initial yield of eir− and decreases its decay rate, while the yield of evis− decreases and its decay rate increases. These results are attributed to fast trap-to-trap tunnelling of evis− from unrelaxed traps at 6 K and slower tunnelling from deeper traps at 75 K while the eir− traps seem to relax within 100 ns even at 6 K. In 12 M LiCl/D2O at 4–10 K the initial evis− band with λmax = 625 nm decays considerably over minutes revealing a stable band with λmax = 695 nm. The stimulation spectrum and absorption spectrum of this stable band indicate a bound–free transition of 2.0 eV and a bound–bound transition of 1.8 eV. Similar measurements of evis− at 77 K indicate a bound–free transition of 2.6 eV and a bound–bound transition of 2.1 eV. Tryptophan was photolyzed in 9.5 M LiCl/D2O at 2 K to produce eir−.