The effects of temperature on the fluorescence lines of Sm2plus;in CaF2, SrF2, and BaClF were studied. The results for the first two samples were obtained in the region 10deg;ndash;100deg;K. For CaF2a strong dependence of the linewidth on temperature was found; this width is sim;thinsp;1.7 cmminus;1at 15deg;K and sim;thinsp;40 cmminus;1at 95deg;K. For SrF2, the linewidth is constant and equal to sim;thinsp;2.15 cmminus;1up to sim;thinsp;77deg;K. This difference in behavior is explained qualitatively as due to the fact that in CaF2the metastable state belongs to the4f55dconfiguration and therefore, the electron charge is strongly affected by the thermal perturbations of the environment. We also measured the widths and positions of several fluorescence lines of BaClF:Sm2plus;in the 30deg;ndash;600deg;K region. The thermal broadening of most of these lines is explained as due to microscopic strains and Raman scattering of phonons, the thermal shifts as due to emission, and absorption of virtual phonons. A Debye model of phonon distribution was used with the sameTDfor both the lineshift and linewidth.
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