Environmental Effects on f–f Transitions. II. “Hypersensitivity” in Some Complexes of Trivalent Neodymium

The variations in the oscillator strengths of the “hypersensitive” I9/24 → 2G7/2, 4G5/2 transition of some complexes of Nd3+ are discussed. It is concluded that the order of magnitude of these oscillator strengths can be accounted for by means of vibronic mechanism. The variation in the oscillator strengths as a function of increasing “covalency,” as measured by the nephelauxetic effect, is also considered, and it is concluded that the phenomenon of “hypersensitivity” may be explained by the inclusion of covalency within the framework of a vibronic mechanism.