High Energy Electron Induced Emission in Low Temperature Glasses Containing Adenine

The emission spectra and decay kinetics after pulsed electron irradiation of 10^-3 M adenine in an ethylene glycol:water (EGW) glass and of the solvent glass itself have been recorded at a temperature of 80°K under different gas pressures down to$10^{-6}\ \text{Torr}$. The effect of NaNO₃ and${\rm NClO}_{4}$ at several different concentrations on the luminescence from glasses with and without adenine has been studied. It is found that NaNO₃ at low concentration reduces the yield of solvent glass luminescence by an order of magnitude but has little effect on the adenine emission. High concentrations of both NaNO₃ and${\rm NClO}_{4}$ are required to reduce the phosphorescence yield of adenine. It is concluded that the excited state responsible for the long-lived emission from the solvent is formed by a process involving "mobile" electrons, probably a charge recombination process, while the triplet state of adenine is populated either by direct excitation by slow electrons or by geminate ion pair recombination.