Study of the phototransferred thermoluminescence in KC1:Eu²⁺ phosphors

The phototransferred thermoluminescence (PTTL) processes play an important role in the optical stimulated luminescence (OSL) and thermoluminescence (TL) dosimetric properties in KCl:Eu²⁺ crystals. In the present work, experimental evidence is presented about the participation of F and F_z centres in the associated recombination luminescence mechanisms involved with all three phenomena. An analysis of the TL glow curve of KCl:Eu²⁺ exposed to X ray ionising radiation shows three main thermoluminescence peaks around 370, 390 and 470 K. The 470 K highest intensity peak, considered the dosimetric peak due to its low fading and linear dose behaviour, is strongly correlated to the F and F_z centres. Through optical absorption spectra measuréments of an optically bleached specimen, it was found that a minimum occurs at 560 nm, coinciding with the F centre band in KCl:Eu²⁺. Moreover, the diminishing of the integrated TL 470 K peak intensity is also seen to have a minimum at 560 nm (F centres); it also happens simultaneously with an increase of the integrated TL peak associated to the F_z band. This supports the close relation of the F and F_z centres in the PTTL process in KCl:Eu²⁺.