THERMAL EFFECTS ON FLUORESCENCE LINES OF SM2+ IN CRYSTALS

The effects of temperature on the fluorescence lines of Sm2+ in CaF2, SrF2, and BaCIF were studied. The results for the first two samples were obtained in the region 10°-100°K. For CaF 2 a strong dependence of the linewidth on temperature was found; this width is ∼1.7 cm-1 at 15°K and -∼40 cm-1 at 9S°K. For SrF2, the linewidth is constant and equal to ∼2.15 cm-1 up to ∼77°K. This difference in behavior is explained qualitatively as due to the fact that in CaF2 the metastable state belongs to the 4f55d configuration 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 BaCIF :Sm2+ in the 30°-600°K region. The thermal broadening of most of these lines is explained as due to microscopic strains and Eaman 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 same T D for both the lineshift and linewidth.