Laser selective excitation of praseodymium ions in hydrogenated fluorite crystals

• Main Author: Reeves, Roger J.
• Language: en
• Published: University of Canterbury. Physics 2013
• Online Access: http://hdl.handle.net/10092/8218

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.