The effect of Mn concentration on the luminescence properties of NaMgF_3:Mn: Defect/Mn complex photoluminescence, radioluminescence, and optically stimulated luminescence for radiation dose monitoring

摘要

Luminescence measurements were made on NaMgF3 :Mn before and after irradiation with X-rays over a wide Mn concentration range from x = 0.1 0 /0-5%. Photoluminescence (PL) is seen from distorted Mn2+ sites that saturate for x >= 1% and non-distorted Mn2+ sites. The non-distorted Mn2+ crystal field parameter and crystal field splitting are independent of Mn concentration and they are B = 779 +/- 14 cm(-1) and 10Dq = 9250 +/- 160 cm(-1 ). F-centre/Mn complexes are seen for all concentrations with a PL emission at similar to 670 nm. The complexes have perturbed Mn2+ energy levels that shift by less than 1630 cm(-1) in the 320 nm-570 nm wavelength range. There is also a PL emission at similar to 730 nm that is likely to arise from F-3 -centres perturbed by nearby Mn. The PL from these two perturbed centres is linear in dose up to 3.8 kGy when probed in the 550 nm-650 nm region and it can be repeatedly probed without bleaching. Optically stimulated luminescence (OSL) occurs for all Mn concentrations from the non-distorted Mn2+ site after X-ray irradiation. The OSL intensity is linear up to similar to 270 Gy for 0.5% Mn and the trapped carriers can be selectively bleached. Radioluminescence (RL) is also observed in all samples from both Mn2+ sites. Not all Mn(2+ )displays RL and a larger fraction of distorted Mn2+ sites do not display RL, which may be due to a higher concentration of nearby non-radiative recombination sites. The ratio of the RL of the non-distorted Mn2+ to the distorted Mn2+ is nearly dose-history-independent after an initial predose for 0.1% Mn, and it is linear in dose up to 9.6 kGy for 5% Mn. Our results show that NaMgF3 :Mn has great potential for real-time and total dose measurements where there are complementary methods available to obtain the dose rate, the dose-history, the dose after each irradiation, and the cumulative dose up to very high doses.