CRYSTAL-FIELD DISTRIBUTION AND NONRADIATIVE-TRANSITIONS IN CR3-DOPED GALLOGERMANATES()

The large broadening of the fluorescence transitions in Cr3+-doped gal logermanates is attributed to variations in the distortions to the oct ahedron of nearest-neighbour oxygen ions. For the weak field sites tha t fluoresce via the T-4(2) --> (4)A(2) transition, this causes the Hua ng-Rhys factor to vary from site to site. Such a crystal field distrib ution results in strong broadening of the emission band, and also enha nces non-radiative decay processes. The non-radiative decay is describ ed in terms of an internal conversion process and modelling shows a co nfinement potential to reproduce the experimental data most accurately .