On the trap depth of the IR-sensitive trap in Na- and K-feldspar

The fast phosphorescence following IRSL in both crystals is likely the result of tunnelling from band-tail states in the vicinity of the excited state of the IR-trap. The post-OSL phosphorescence decay is an order of magnitude slower, owing to the contribution from tunnelling of charge from a range of occupied band-tail states. The lack of dependence of the phosphorescence decay rate on the excitation energy (in the range of 1.7-2.8 eV), unambiguously indicates that a single mechanism causes the post-OSL phosphorescence signal.