Influence of Oxygen Centers on the Thermoluminescence of NaF Crystals

Abstract

The thermoluminescence (TL) of pure and doped NaF crystals has been intensively investigated for the last years, however, in many works the spectral distribution of the emission was not studied and the interpretation of the glow peaks is often contradictory /l/.This note gives some new results concerning the influence of oxygen ions o n the T L process. N a F single crystals were grown both in vacuum and air atmosphere from the reactive of high purity. All the samples were X-irradiated up t o l x l 0 R. The absorption spectra were measured on a Unicam SP8-100 spectrophotometer. Cooled photomultipliers sensitive in the range of 180 t o 800 nm were used while studying the TL; the constant heating rate was 1 0 K/min. The spectral composition of the emission was analysed using a MDR-2 monochromator. (Fig. 1); these bands are ascribed to O--V: complexes. At LNT there is also an absorption band a t 196 nm, conditioned by 0--ions. N a F ( 0 2 ) samples (NaF(vacuum), subjected to a prolonged thermal treatment in the air) show new absorption bands at 255 and 3#55 nm (curves 3 and 4 in Fig.

Electrolytic coloration of air-grown sodium fluoride crystals

“…The spectrum can be roughly decomposed into eleven Gaussian type absorption peaks (dashed curves) at 193.0 (peak 1), 220.0 (peak 2), 255.0 (peak 3), 280.0 (peak 4), 342.4 (peak 5), 355.2 (peak 6), 380.0 (peak 7), 414.4 (peak 8), 504.1 (peak 9), 575.5 (peak 10) and 639.2 nm (peak 11), and the corresponding widths are 0.711, 0.640, 0.600, 0.400, 0.600, 0.300, 0.230, 0.246, 0.494, 0.450 and 0.350 eV, respectively. The peaks 1-4 and 6 are due to oxygen impurities, among which the peak 1 associates to O 2À color centers [9], the peaks 2 and 4 to O 2À -V a + complexes, the peak 3 to O 2 À color centers and the peak 6 was observed previously but unidentified [10]; the peaks 7 and 8 associate probably to remanent magnesium impurities [11]; the peaks 5 and 9-11 associate to F, M, N 1 and N 2 color centers [12], respectively. Fig.…”

Oscillator rule of the trap activation energies in NaCl crystals

“…Unfortunately, we have not found current investigations devoted to the study of the role of oxygen in the TL of NaCl crystals, but a recent study [24] dealt with the in°uence of oxygen centers on the TL of NaF crystals, where it was reported that oxygen centers (mostly O 2¡ v + a complexes) can stabilize interstitial halogen atoms (H centres). This is important, in particular, for the ion model of Alvarez Rivaz et al [20,21].…”