VIBRONIC TRANSITION-PROBABILITIES IN THE EXCITATION-SPECTRA OF THE PR-3+ ION

Vibronic features are observed in the excitation spectrum of Pr3+ in several host lattices. Vibronic transition probabilities, A(VIB), for the H-3(4) --> P-3(0) excitation transition on Pr3+ are reported. A(VIB) varies by two orders of magnitude from LaF3 to Y2O2S. These observations are discussed in terms of existing theories of the intensity of vibronic transitions in the intraconfigurational 4f(n) spectra. The observed variation can be qualitatively accounted for by the differences in covalency, polarizability and opposite-parity configuration admixing.