New perspectives on traps and radiative recombination centers for optically stimulated luminescence in LiF:Mg,Cu,P

Abstract

LiF:Mg,Cu,P (MCP) is well-known for its high thermoluminescence (TL) sensitivity and is widely used for TL dosimetry. Following recent studies, highlighting its optically stimulated luminescence (OSL), the properties of MCP have been studied for OSL-based 2D and 3D dosimetry. Here, we have measured the spectrally resolved OSL emission as a function of stimulation time, identifying the peak of the emission band to be at ∼355 nm during the early stimulation period before shifting to peaking at ∼382 nm during the remaining part of the experiment. By assuming the spectra to originate from radiative recombination centers with Gaussian emission bands, we identified two recombination centers with emission centered at ∼355 nm (RC1) and ∼394 nm (RC2), respectively. From the OSL decay curves, we have identified two dominating types of OSL traps (fast and slowly decaying OSL traps). We provide indicative values for the photoexcitation cross section of these OSL traps. The fast-decaying OSL traps were found to predominantly emit OSL through RC1. By depleting the fast-decaying OSL traps before TL measurements, we have identified these traps to be associated with a previously undetected TL peak at ∼87 ° C (1 °C/s heating rate), located between the TL peaks usually denoted as peaks one and two. We further found that the features related to the fast-decaying OSL traps were not observable for powder samples without a heat treatment at ∼560–700 °C. Pellet samples show these features without the heat treatment, but could potentially have undergone a similar treatment during sintering.