Dye laser spectroscopy of trivalent samarium in calcium tungstate crystals

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Abstract
Tunable dye laser spectroscopy has been used to study energy transfer processes in CaWO3:Sm3+ crystals. Fluorescence and excitation transitions for samarium ions in different crystal-field sites have been identified and their changes in width and position with temperature studied. This information is used to characterize energy migration among samarium ions as a function of temperature, samarium concentration, time after the laser pulse, and pressure. The interaction mechanism causing energy migration is identified as electric quadrupole-quadrupole. At low temperatures it was found that only single-step transfer between nearby ions takes place, while at high temperatures multi-step diffusion of energy occurs. These results are interpreted in terms of the Anderson (1958) localization concepts for systems with inhomogeneously broadened transitions, and quantitative estimates of the transfer rates and diffusion parameters are obtained.