A new contribution to spin‐forbidden rare earth optical transition intensities: Analysis of all trivalent lanthanides

We expand upon recent quantitative calculations which show that numerous parity- and spin-forbidden linear optical transitions observed in trivalent rare earth ions acquire a major fraction of their intensity from hitherto neglected contributions involving spin-orbit linkages within excited configurations. Extending our revised analysis of observed linear absorption intensities for Gd3+ and Eu3+ to the other nine trivalent lanthanides with visible wavelength transitions, we find that the new contributions are at least as important in these other lanthanides, and are often comparable to standard contributions. We also show that spin-forbidden ΔS = 1 transitions are selectively modified over the spin-allowed ΔS = 0 transitions. In addition, we examine contributions from linkages with g orbital excited states in the light of recent electronic Raman scattering data for lanthanide phosphates, and show that these long neglected terms may actualy dominate the transition intensity. With substantial modification of previously fitted phenomenological parameters, however, the good fit with observed intensities is retained. © 1989 American Institute of Physics.