7F0→5DJ two-photon-absorption transitions of Sm2+ in SrF2

One-color two-photon excitation spectra of the 7F0→5D0 and 7F0→5D2 transitions of Sm2+ in SrF2 have been measured at low temperature and their dependences upon photon polarization analyzed. Linewidths on the order of 0.2, 0.6, and 1.0 cm-1 are obtained for the 7F0→5D0(A1g), 7F0→5D2(Eg), and 7F0→5D2(T2g) Stark components observed at 15 K, respectively. The 7F0→5D0(A1g) transition is observed to be isotropic within experimental error, while the Eg and T2g components of the 7F0→5D2 transition exhibit the anisotropic patterns expected in Oh symmetry. Calculations of two-photon transition intensities are conducted within the framework of the phenomenological model previously used for Sm2+ in MClF (M=Ba,Sr) and Eu3+ in LuPO4, where the rare-earth ion occupies sites of C4v and D2d symmetries, respectively. The present results are compared and contrasted with those obtained in these previous cases