RELATION BETWEEN THE OMEGA-6 INTENSITY PARAMETER OF ER3+ IONS AND THE EU-151 ISOMER-SHIFT IN OXIDE GLASSES

The OMEGA(t) intensity parameters (t=2,4,6) of Er3+ ions in several oxide glasses and the isomer shift (IS) of Eu-151 Mossbauer spectra in glasses of the same composition were determined. Among these OMEGA(t)'s the OMEGA6 parameter was found to have a good relation with IS; OMEGA6 decreases with an increase of IS which reflects the 6s electron density of rare-earth ions. From the theoretical expression of OMEGA(t), OMEGA6 is considered to be more affected by the overlap integrals of the 4f and 5d orbitals than OMEGA2 and OMEGA4, and to increase with an increase of these overlap integrals. These overlap integrals are supposed to decrease when the 6s electron density is larger, since the 6s electron density shields the 5d electron orbital.