Two-photon absorption spectroscopy of Cm3+ in LuPO4

Laser excitation spectroscopy has been used to investigate two-photon absorption (TPA) transitions of the actinide ion Cm3+ in a LuPO4 host crystal. One-color two-photon excitation spectra were recorded in the energy ranges corresponding to the S-8(7/2)-->D-6(7/2) (16 400-17 200 cm(-1)), S-8(7/2)-->P-6(5/2) (19 700-20 300 cm(-1)), and S-8(7/2)-->D-6(7/2) (27 700-28 100 cm(-1)) absorption transitions. The relative intensities and polarization dependences of the lines observed were measured. These results are compared to calculated intensities derived from the second-order theory of Axe and also from the second-order theory extended to include a third-order spin-orbit correction. There was poor agreement between experiment and theory for most of the TPA transitions investigated. Inclusion of an additional phenomenological imaginary term in the amplitude improved the agreement for these transitions.