Abstract

Low crystal-field octahedral complexes of Cr³⁺ exhibit broad-band (⁴T_2g→⁴A_2g) fluorescence, useful in tunable-laser applications (1), rather than the narrow-band (²E_g→⁴A_2g)phosphorescence of high-field complexes. This contrasting behavior his been demonstrated previously in a variety of host crystals which provide a range of octahedral crystal fields {2}. In the present investigation, photoluminescence spectra and lifetimes of K₂NaScF₆ Cr³⁺ and K₂NaGaF₆:Cr³⁺ were measured as a function of temperature and pressure. Experiments were performed with He-Cd laser excitation in a diamond-anvil cell at pressures between 0 and 65 kbars and temperatures between 200 and 300 K. In both compounds a transition from low-field to high-field behavior is evidenced by a pronounced blue shift of the featureless fluorescence spectrum and its ultimate replacement by a highly structured phosphorescence spectrum.

© 1985 Optical Society of America