CHARGE MOVEMENTS IN QUARTZ AND THEIR RELEVANCE TO OPTICAL DATING

Combined thermoluminescence (TL), phosphorescence and optically stimulated luminescence (OSL) measurements hav been used to trace the movement of charge within the lattice of a geological quartz sample when it is exposed to light (514 nm from an Ar ion laser). The evidence suggests that optical stimulation evicts charge from traps in the crystal lattice associated with the 325 degrees C thermoluminescence (TL) emission and elevates it to the conduction band. Part of the charge recombines with luminescence centres to produce the observed optically stimulated luminescence (OSL), and a significant portion is re-trapped at the same or different localities in the lattice. Important implications for the optical dating of quartz are discussed, including the necessity of a pre-heat, the interpretation of the equivalent dose as a function of OSL measurement time and the ramifications of OSL recuperation.