CORRELATION BETWEEN EU-151 MOSSBAUER ISOMER-SHIFT AND JUDD-OFELT OMEGA(6) PARAMETERS OF ND3+ IONS IN PHOSPHATE AND SILICATE LASER GLASSES

Eu-151 Mossbauer effect measurements were carried out for various silicate and phosphate laser glasses doped with Eu3+ ions instead of Nd3+, for which Judd-Ofelt OMEGA(t) parameters are known. The isomer shift (IS) for the silicate glasses decreased with an increase in the electronegativity of the network-modifying alkali and alkaline-earth metal ions, indicating a decreased 6s electron density of the rare-earth R3+ ions, i.e., covalency of the R-0 chemical bond. On the other hand, in phosphate glasses the IS increased with increased electronegativity. Among three OMEGA(t), parameters of Nd3+, OMEGA6, which dominates the radiative transition probability and branching ratio of the 1.3 and 1.06 mum emissions, showed a good correlation with the IS of EU3+ ions in the corresponding glasses, independent of compositions. The results were explained by the more sensitive dependence of the THETA(s, t) terms in OMEGA6 on the overlap integrals of 4f and 5d orbitals of rare-earth ions, compared with that in OMEGA2, which is sensitive to the odd-parity terms of the crystal field, A(sp).