| Summary: | The techniques of laser selective excitation have been successfully applied to study the multitude of spectroscopic sites present in hydrogenated SrF₂:Prᶾ⁺and CaF₂:Prᶾ⁺ crystals. Many optical transitions of the tetragonally sited Prᶾ⁺ions have been characterised using well defined polarisation rules, and comprehensive sets of energy levels have been established. For the hydrogenic C₄ᵥ Prᶾ⁺sites, the predictions of a single frequency multiphonon relaxation theory show excellent agreement with the results of a temporal study of these sites. The results show that the relaxation of the Prᶾ⁺electronic system is entirely determined by the hydrogenic ion local mode phonons.
Several low symmetry hydrogenic Prᶾ⁺centres show the, new to inorganics, property of reversible bleaching. Two mechanisms have been identified, where a photoproduct is formed with a different site orientation or at a different excitation wavelength. Site configurations have been developed that successfully account for many of the observed bleaching effects.
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