OSCILLATOR STRENGTH CALCULATIONS FOR ND2O3 AND ND3+LIYF4

In contrast to earlier work based on least-squares fitting of crystal- field (CF) parameters to experiment, the current study diagonalizes th e complete 364 x 364 energy matrix directly using a simple CF model us ing only four free parameters, These are the Slater integrals F-2, F-4 , F-6 and the spin-orbit coupling constant zeta. The various polarizab ilities and shielding parameters have been derived by ab initio method s [2]. All Stark levels within the Nd3+(4f(3)) configuration are prese nted. The calculated Stark splittings agree well with experiment for t he Nd3+ ion in both Nd2O3 and Nd3+:LiYF4; however the agreement is not so good at higher energies. This is expected when configuration inter action is neglected. The eigenvectors of the complete energy matrix ar e used to calculate polarized oscillator strengths. For the case of Nd 3+:LiYF4, our results indicate that the local structure around the Nd3 +-ion contracts compared to the structure around the Y3+-ions.