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Experimental and computational studies of photophysical processes in silver halide imaging materials are presented. Recent investigations that have refined our understanding of carrier recombination paths, exciton behavior, quantum confinement effects, and the structure and function of small surface silver clusters are detailed. The theory and mechanism of electron and hole injection from photoexcited surface-adsorbed dye molecules are outlined. The carrier trapping properties and subsequent photophysics of transition-metal dopant complexes are presented. Particular emphasis is given to the role of relaxation processes in electron and hole trapping events.

Using magneto-optical and optically detected electron paramagnetic resonance methods, it is shown that in BaFBr single crystals grown using standard procedures the ubiquitous oxide impurity is primarily responsible for the X-irradiation-induced formation of F(Br-) centres. The bromide vacancy formed to charge compensate O2- is implicated in the direct trapping of electrons. F(F-) centres are also produced by irradiation, probably by an exciton collapse process requiring thermal activation. Cross relaxation measurements show that many of the F(F-) and F(Br-) centres are spatially correlated, more than expected on statistical grounds. The relevance of these results to the use of rare earth-activated BaFBr materials as storage phosphors is discussed.

A detailed investigation of the optical absorption and emission bands from the two types of F centre in BaFBr is reported, using optical, magneto-optical, and optically detected electron paramagnetic resonance and electron nuclear double resonance (ENDOR) techniques. With conventional ENDOR, the superhyperfine interactions of the F(Br-) centre are investigated in detail. It was found from the luminescence experiments that the two types of F centre are spatially correlated when they are created by X-irradiation in qualitative agreement with the observation of cross relaxation effects, as reported elsewhere.

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