Localized and delocalized transitions and optical excitation of LiF:Mg,Ti following alpha and beta irradiation

It is shown that glow peak 5a (a low-temperature satellite of the major glow peak 5) arises from localized electron-hole recombination in a trapping center (TC)-luminescent center (LC) pair believed to be based on Mg²⁺ -Li_vac trimers (the TCs) coupled to Ti(OH)_n molecules (the LCs). Peak 5 arises from the same complex which has captured an electron only, and peak 4 arises from a very similar complex which has captured a hole only. It is demonstrated experimentally that optical excitation of irradiated LiF:Mg,Ti (TLD-100) by 4 eV photons has the same effect for both alpha particle (high ionization density) irradiation and photon/electron irradiation. In both cases, peak 5a converts to peak 4 causing peak 4 to increase following the bleach. Such an observation is consistent with the major premise of track structure theory, that radiation effects following heavy charged particle (HCP)/neutron irradiation are due exclusively to the interaction of the secondary electrons created by the HCP slowing down.