On the Luminescence and Photoconductivity of the F Centres in NaBr

Abstract

A model has recently been used by Bartram and Stoneham (1) to explain the occurrence o r non-occurrence of F centre luminescence in ionic crystals, in terms of a single two-state configuration coordinate diagram. In this model, which works for all known cases, luminescence i s quenched by a competing non-radiative pro-

Lifetime of Color Centers in NaBr

“…We studied F-luminescence in NaBr by using a single-photon technique [6] : we were thus able to measure signals corresponding to very low photon rates, muoh below the range of traditional analog detection techniques [ 3 ] . The sensitivity of the photomultiplier tube used in our experiincnt,s (a LNT cooled Philips 56CVP) extends in the infrared as far as about 1 eV (one of the best lilnit,s among the currently available photomultipliers): however, a t these energies, the sensitivity is very low (less than 0.1% quantum efficiency).…”

The absence of energy transfer between F and M centres in alkali halides: the case of NaF

“…The radiative transfer between two centres (transmitting and receiving) occurs when there is an appreciable overlap of the emission band of the transmitting centre (primary luminescence) and the absorption of the receiving centre (with a subsequent secondary luminescence): it is often referred to as 'trivial' since it implies a 'cascade' mechanism through the emission and reabsorption of photons. The radiative transfer does not imply change of the transmitting and receiving centre lifetime: a typical example is the energy transfer between M and M + centres in x-ray coloured NaF investigated and characterized by Bosi [27]. Since the F emission band and M absorption band scarcely overlap in NaF (as well as in KCl, RbCl and KBr), this kind of transfer is practically negligible.…”