Thermoluminescent charge recombination in saturated hydrocarbons

Thermoluminescence from the recombination of N,N,N ' ,N ' -tetramethylparap henylenediamin (TMPD) cations with trapped electrons in squalane and cis-de calin glasses and in microcrystalline methylcyclohexane is reported. The gl asses exhibit distributions of activation energies maximal at 0.20 eV in sq ualane and 0.19 eV in cis-decalin, with half-widths at half-height of appro ximately 0.03 eV. Microcrystalline methylcyclohexane exhibits a single acti vation energy at 0.30 eV. These activation energies for thermal electron re lease are much smaller than photoionization threshold energies determined o ptically in similar glasses, suggesting that the mechanism of electron rele ase is trap destruction, not electron excitation within a stable trap. The similarity between these activation energies and those determined for quenc hing of the TMPD phosphorescence also supports this interpretation.