Polarization dependences of a two-photon absorption in a 7Fo → 5Do channel for Sm2+ in BaC1F

For the 7Fo → 5Do transition of Sm2+ it is a somewhat unexpected fact that the contribution of the scalar part (a), which is independent of the angles, is only slightly different from the angular component (b), i.e., |a|/|b| ≅ 1.57. The point is that the value of the spin-orbital interaction (ζn ell = 1050 cm -1), making the main contribution to the scalar part of the two-photon absorption (TPA), very much exceeds the value of the crystalline field (CF) (causing a shift with respect to J) due to the angular matrix element of TPA. Therefore it is very desirable to evaluate the contribution to the TPA of various mechanisms determined by the CF (VCF), by the spin-orbital interaction (Vso), and the polarization of the surrounding ligands