Many recent studies indicate that the post-IR IRSL signals from potassium-rich feldspar grains suffer negligible anomalous fading and have great potential for extending the luminescence dating range. In this study, using a museum specimen of perthitic feldspar, the characteristics of post-IR IRSL production at 200 ºC after different prior IR bleaching at 100 ºC were investigated. It was found that IR stimulation at low temperature (e.g. 100 ºC) causes photo-transfer with some of the electrons being retrapped in low temperature TL peaks during IRSL production. This results in a recuperated TL peak when no further dose is applied. These retrapped electrons are thermally evicted when subsequent post-IR IR stimulation is carried out at a higher temperature (e.g. 200 ºC), causing the post-IR IRSL signal to have an isothermal TL contribution from the recuperated TL traps. Since this isothermal contribution is derived from the same electron source as the IRSL signal and might exhibit anomalous fading, it is suggested that an extra step (a cut-heat to 300 ºC) is added to the post-IR IRSL dating protocols.

Related paper entitled “Investigating the contribution of recuperated TL to post-IR IRSL signals in a perthitic feldspar” by Wang X.L. and Wintle A.G. is published in Radiation Measurements (2013, 49, 82-87).