Recombination luminescence between trapped electrons and self-trapped holes in SrCl2doped with alkali cations after X-irradiation

After X-irradiation in the range 10-145K, SrCl 2 doped with M + (M + =Na + ,K + ,Rb + ) gives rise to a post-luminescence whose spectrum, independent of the M + cation nature, is formed principally of a broad band at 500 nm. The hyperbolic law of isothermal decay of post-luminescence (I t =C N 0 -t where N 0 is the initial number of V k centres) suggests that this emission is due to a tunnelling recombination between V k and perturbed F-centres. While between 10 and 38K the coefficient C does not depend on T, at higher temperatures the value of C is very sensitive to the X-irradiation temperature. In particular, in the range 35-100K, the behaviour of the coefficient C with temperature is well explained by the motion of V k -centres viewed as small polarons.