The effect of optical bleaching at selected photon energies on the thermoluminescence of LiF:Mg,Ti

A new interpretation of the optical absorption energy spectrum of LiF:Mg,Ti (TLD-100) is presented in which the 4.0 eV band is composed of two-sub-bands at 3.8 eV and 4.3 eV. The new interpretation is of central importance in the understanding of the geminate recombination mechanisms giving rise to composite glow peak 5 in the thermoluminescence (TL) of TLD-100. Photon bleaches at energies of 3.6 eV and 4.3 eV on samples of gamma irradiated TLD-100 were carried out in order to investigate the correlation of the 4.3 eV absorption band with the electron-hole configuration giving rise to glow peak 5a and the 3.8 eV absorption band with the e-only configuration giving rise to glow peak 5. The 4.3 eV bleach decreases peak 5a dramatically and increases peak 4 (a hole-only configuration). No such effect is observed following the 3.6 eV bleach. The results strongly support the suggested structures giving rise to the 4.3 eV and 3.8 eV bands observed in the optical absorption energy spectrum.