Infra-red stimulated luminescence spectra of alkali feldspars

IRSL emission spectra from alkali feldspars show a UV emission peak, centred on 290 nm, which is associated with a sodium aluminosilicate lattice structure, either as the dominant phase in sodium feldspar (albite) or as exsolved features in perthitic potassium feldspars (orthoclases and microclines). The trapped charge population associated with recombination at the 290 nm centre during IRSL is thermally unstable. After laboratory irradiation, luminescence intensity in this emission band decays and in sodium feldspars, this decay results in charge transfer into other recombination centres. Use of a sustained preheating regime removes the unstable trapped charge population associated with the 290 nm emission and is essential in an IRSL dating routine. (C) 1997 Elsevier Science Ltd.