R. Singhai et al., ELECTRONIC SPECTRAL STUDIES ON RARE-EARTH-DOPED PSEUDOGARNETS, Proceedings of the Indian Academy of Sciences. Chemical sciences, 107(5), 1995, pp. 523-531
Spectral parameters viz. oscillator strengths (P), Judd-Ofelt paramete
rs (tau(lambda)), inter-electronic repulsion (Racah) delta E(k) parame
ters (IERP) and nephelauxetic ratio (delta E(3)/delta E(1)) have been
determined using aqueous solutions of representative lanthanide (rare
earth) (III) ions, Pr(III), Nd(III), Sm(III), Eu(III), and Er(III) and
rare earth-doped concentrated (similar to 1.0 M) solutions of pseudog
arnets sodium m-silicate, sodium molybdate and sodium m-vanadate. Thes
e parameters have been studied as a function of (i) symmetry around th
e Ln(III) ions, and (ii) matrix environment due to different pseudogar
nets. The electronic transitions for various Ln(III) ions and changes
in their positions due to corresponding changes in matrix environment
are observed to show red shift. The oscillator strength values increas
e significantly in the sequence aqua < MoO42- < VO3- < SiO32-. The tau
(lambda) values are found to lie in the order tau(6) > tau(4) > tau(2)
. The delta E(k) and delta E(3)/delta E(1) values are observed to lie
in the theoretically calculated ranges. The nature of dopant-matrix in
teraction appears to change from ionic to ionocovalent on going across
the Ln(III) series.