Influence of primary charge distribution on charge recombination in an irradiated rigid glass: A deferred luminescence study

Abstract

Isothermal luminescence decay kinetics of doped methylcyclohexane, interpreted in terms of tunnelling electron-ion recombination, had been previously studied between 10 -6 and 10 4s and were shown to obey the analytical law I( t) ∝ t −1 throughout this whole time range. In the nanosecond time range, deviations from this law are observed. Different decay kinetics are ascribed to recombination in volumes with different primary ionization densities as the distribution of primary species created by ionizing particles is known to be inhomogeneous, and experimental results are shown to be qualitatively consistent with this interpretation. Evidence of the influence of primary charge distribution is given by the dependence of ITL kinetics on solute concentration and nature of ionizing radiation in the nanosecond time range. It is shown that total ITL intensity observed after β-irradiation is in fact a sum of two decays: one is ascribed to the recombination of isolated pairs in zones of low density of ionization and follows I i ( t) ∝ t −1; the other one, a faster process since it shows up as I m ( t) ∝ t −2, is attributed to recombination in zones of high primary ionization density, where pairs (“multipairs”) can no longer be considered as isolated. Observation of the kinetics ascribed to multipair recombination at very low solute concentration also indicates that positive charges, trapped on molecules which cannot be solute molecules, are present in the glass as well.