Influence of the photoionization cross-section on the OSL signal of LiF

Abstract

The understanding of the electron trapping and recombination processes is the key to successful applications of materials in ionizing radiation dosimetry, which unfortunately are not well known yet. In this work, the influence of the photoionization cross-section (𝜎) was investigated on the optically stimulated luminescence (OSL) response of the lithium fluoride (LiF) compound. The 𝜎 has been predicted through the expression proposed by Lima–Batista–Couto. In addition, OSL measurements were performed using the continuous-wave stimulation mode (CW-OSL), with 60 s of light stimulation. The samples were submitted to 10 Gy and 15 Gy of absorbed dose. Phonon dispersion and density calculations are presented by using the Density Functional Perturbation Theory. The results, obtained by a combination of different methodologies, show that the low sensitivity of LiF to the light stimulus (𝜆 = 470 nm) is due to the very low magnitude of 𝜎 at the used excitation wavelength. A comparison with Al2O3:C was also carried out, showing that the intensity and the pattern of the OSL curve decay are modified by the 𝜎. These results play an important role in understanding the luminescent properties of this material, and they open a new opportunity to improve the light sensitivity of this detector.