Direct calculation of optical absorption amplitudes for trivalent rare-earth ions in LiYF4 -: art. no. 045111

The approximations within the Judd-Ofelt theory are eliminated by an explicit reformulation of the absorption amplitude for f<---->f dipole transitions in terms of determinantal product states and perturbed functions. By considering the crystal-field and spin-orbit perturbations we obtain expressions for amplitudes of the type (phi(cf)(1)\d(q)(1)\phi(0)), (phi(cf)(1)\d(q)(1)\phi(so)(1)), and (phi(cf)(1)\d(q)(1)\phi(cf)(1)). The latter two are third-order results, going beyond the standard Judd-Ofelt theory. There are no experimentally fitted parameters used in the amplitude calculations. Crystal-field parameters A(tp) needed for the intensity calculations are calculated using the self-consistent electrostatic model. Polarized absorption spectra are calculated for Nd3+, Ho3+, Er3+, or Tm3+ in LiYF4. Very good agreement with experiment is, in general, observed. The contribution from the third-order terms (phi(cf)(1)\d(q)(1)\phi(so)(1)) and (phi(cf)(1)\d(q)(1)\phi(cf)(1)) are seen to be small in comparison with (phi(cf)(1)\d(q)(1)\phi(0)).