Detection of trapped electrons in organic glasses after gamma irradiation at 4.2 °K by electron spin resonance spectroscopy

Several organic glasses which are known to form trapped electrons when gamma irradiated at 77 °K have been irradiated at 4.2 °K and examined by electron spin resonance (e.s.r.) at the same temperature. In each case an absorption is observed which is probably due to trapped electrons. In three cases, the yield of trapped electrons at 4.2 °K seems to be as great as at 77 °K. In one case, a glassy alkane, the yield is enhanced at 4.2 °K. Trapped electrons in ethanol give a narrower e.s.r. line at 4.2 °K than at 77 °K, suggesting less orientation in the solvent cage.Trapped hydrogen atoms are not detected after irradiation at 4.2 °K. Contrary to prediction, hydrogen atoms are also not detected after post-irradiation photolysis of the trapped electrons.The results suggest that electron traps exist prior to irradiation and that molecular orientation via electronic dipole interaction is not a necessary condition for electron trapping. The results do not distinguish between trapping in solvent defects or trapping via electron-induced polarization of molecular orbitals.