LUMINESCENCE QUENCHING STUDIES OF CEF3 AND CEF3-LAF3 BY MEAN OF NANOSECOND TIME-RESOLVED VUV SPECTROSCOPY

The quenching mechanisms for fast luminescence in CeF3 and CeF3-LaF3 c rystals have been studied by means of time-resolved VUV spectroscopy u sing synchrotron radiation. The luminescence decay of these crystals r eveals at least three mechanisms of quenching: the first one, conventi onal for the VUV region, where the radiation penetration depth is very small similar to 10 nm, results from surface losses; the second one i s due to the energy transfer to defect centres in the bulk of the crys tal (very pronounced in CeF3-LaF3) and the third one, the least studie d, is attributed to the interaction of closely spaced electron excitat ions (secondary-electron excitation quenching). The temperature and en ergy dependencies of the decay kinetics clearly indicate that the last quenching mechanism comes into play above the energy corresponding to the threshold for the creation of secondary-electron excitations.