Optical Absorption and Fluorescence Intensities in Several Rare-Earth-Doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Y</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>and La<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">F</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Single Crystals

The absolute intensities of transitions occurring in the optical spectra of single crystals of ${\mathrm{Y}}_{2}$${\mathrm{O}}_{3}$ doped with small amounts of Pr, Nd, Eu, Er, and Tm; single crystals of La${\mathrm{F}}_{3}$ doped with small amounts of Pr and Nd; and single crystals of ${\mathrm{Er}}_{2}$${\mathrm{O}}_{3}$, ${\mathrm{Tm}}_{2}$${\mathrm{O}}_{3}$, and ${\mathrm{Yb}}_{2}$${\mathrm{O}}_{3}$ have been measured at room temperature. All observed transitions occur within the ground configurations of the trivalent rare-earth ions, and their intensities are accounted for using three phenomenological parameters for each system, whose values are determined by a a least-squares fitting calculation. A calculation of the relevant crystal-field terms is made, and theoretical values for the intensity parameters are calculated using free-ion radial wave functions and certain closure approximations. It is concluded that excited $4{f}^{n\ensuremath{-}1}$ $g$ configurations contribute to observed intensities more than is indicated by free-ion calculations, and that the excited $4{f}^{n\ensuremath{-}1}5d$ configuration contributes to the observed intensities an order of magnitude less than indicated by free-ion calculations. A hypersensitive transition in the neodymium systems is observed and its sensitivity is traced to a simple change in point symmetry of the host.

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