Pseudoquadrupole transitions

According to Jorgensen and Judd, hypersensitivity may occur due to pseudoquadrupole transitions [66]. Consequently an ion embedded in an inhomogeneous dielectric would exhibit hypersensitive behavior. These normally weak electric quadrupole transitions are probably intensified and become hypersensitive transitions. Hypersensitivity can also occur in symmetries of spherical harmonics (Ymk, with k = 1) which form totally symmetrical representations. Thus this permits their inclusion in the crystal field potential. 

C. K. Jorgensen and B.R. Judd, Hypersensitive pseudoquadrupole transitions in lanthanides. 

However, a theoretical treatment by J0rgensen and Judd [580] points out that these hypersensitive transitions occur due to the inhomogeneity of the dielectric and obey the selection rule AJ = 2. These authors believe that these transitions are pseudoquadrupole in nature. The author [581] has pointed out that the selection rule proposed by J0rgensen - Judd is not rigorously obeyed as they have claimed. Some comments on the validity of J0rgensen - Judd s theory may also be found elsewhere [582, 583. Recently Judd [584] tried to air a certain uneasiness caused by the theory [580], and pointed out that only the following symmetry classes will give rise to hypersensitive transitions. 

Fig. 3.9 Schematic representation of the pseudoquadrupole effect on two electronic levels I Ey and G> (not drawn to scale). Transitions 1 and 2 are weak at very low temperatures because of depopulation of the [ Ey levels...

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