CORRELATION CONTRIBUTIONS TO 2-PHOTON LANTHANIDE ABSORPTION INTENSITIES - DIRECT CALCULATIONS FOR EU2+ IONS

We calculate two-photon intensities for S-8(7/2) --> P-6(J), 6D(J) transitions in Eu2+-doped CaF2 using eigenstates of the Coulomb and spin-orbit interactions within both the ground 4f7 and excited 4f(6)5d configurations. Good agreement with experiment is achieved. In particular, we explain observed S-8(7/2) --> P-6(7/2) transition intensities, which previous calculations had overestimated by a factor of more than 100. We also examine the relationship between the direct calculations presented here and various perturbation methods.