Spectra and energy levels of trivalent samarium in strontium fluorapatite

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Abstract
Absorption and fluorescence spectra are reported for Sm3+(4f5) as a dopant in crystals of strontium fluorapatite, Sr5(PO4)3F. Spectra were obtained at sample temperatures near 10, 100 K, and room temperature. The absorption spectra covered the wavelength range between 2840 and 520 nm and were analyzed for the detailed crystal-field splitting of the 6HJ, 6FJ, 4G(4)5/2, and 4F(3)3/2 multiplet manifolds of Sm3+(4f5). Fluorescence spectra were observed from the 4G(4)5/2 to the 6H5/2 (ground state), 6H7/2, 6H9/2, and part of the 6H11/2 manifolds. The strongest fluorescence is observed to the 6H9/2 manifold. The distribution of the fluorescence intensities is similar to that observed for the Sm3+-doped glass laser. A detailed crystal-field splitting calculation was carried out for the 14 multiplet manifolds of Sm3+ that are lowest in energy. A rms deviation of 8 cm−1 was obtained between 49 experimental and calculated energy Stark levels. The calculation also predicts fluorescence branching ratios and the 4G(4)5/2 radiative lifetime, in reasonable agreement with our measured values.