Anisotropy of two-photon excited f-f transitions of Eu2+ in KMgF3

Polarization dependence of sharp intraconfigurational 4f(7) transitions of Eu2+ in KMgF3 have been studied by means of two-photon excitation spectrosc opy. A new puzzle appears connected with the site-symmetry distortion at th e Eu2+ ions and the weakness of third-order spin-orbit corrections, suggest ing a mechanism for intraconfigurational interaction independent from cryst al-field strength and from the site symmetry on the rare-earth ion. Intensi ty and polarization dependencies of the S-8(7/2)-->P-6(7/2), P-6(5/2), D-6( 9/2) transitions have been satisfactorily interpreted in terms of second-or der perturbation theory. (C) 1999 American Institute of Physics. [S0021-960 6(99)01101-0].