Hypersensitive transitions absorption spectra

Both the calculated and observed energy levels of Tm(III) in ethyl sulphate matrix are given in Table 8.24. Theoretical analysis of the spectrum of Tm3+ in LaF3 matrix has been done [180]. The absorption spectrum of the aquo ion has also been analyzed [113]. The 3H4 — 3Hft transition is hypersensitive. The intensities of the bands have been well studied [61,112],... 

I. r + Optical absorption and NIR luminescence properties of ethanolic Er + ZnO (3.5-5 nm) colloids have been investigated (Schmidt et al., 1998). A significant band broadening and hyperchromic effect for the hypersensitive transitions to Gnn and were observed in the absorption spectrum. For colloids with high ZnO/Er ratio, the hyperchromic term splitting of was obvious, which was possibly related to stronger Er-O orbital... 

A possible breakdown of the Judd-Ofelt theory was suggested by Henrie and Henrie (1977) for the absorption spectrum between 18 400 cm and 22 600 cm for NdBre " in acetonitrile. In this region the observed intensities are much larger than the calculated ones. But in general, the Judd-Ofelt theory works very well for Nd ". The Judd-Ofelt theory is not very suitable for the ah initio calculation of intensity parameters. Especially the so-called hypersensitive transitions give problems (see sect. 8). Therefore, a number of refinements of the intensity theory have been published after the original papers of Judd and Ofelt. These models are discussed in detail in sections 6.2 and 8.2. 

The intensities of the induced electric dipole transitions in lanthanide ions are not much affected by the environment. The dipole strength of a particular transition of a lanthanide ion in different matrices will not vary more than a factor two or three. However, a few transitions are very sensitive to the environment, and these are usually more intense for a complexed lanthanide ion than for the lanthanide ion in aqueous solution. The intensity increases up to a factor 200 (Gruen and DeKock 1966, Gruen et al. 1967). Only in a few cases has a lower intensity than in the aqueous solution been reported for these transitions (e.g. Krupke 1966). Jorgensen and Judd (1964) have called such transitions hypersensitive transitions. They noted that all known hypersensitive transitions obey the selection rules A5 = 0, AI 2 and jAJj 2. These selection rules are the same as the selection rules of a pure quadrupole transition, but calculations have revealed that the intensities of hypersensitive transitions are several orders of magnitude too large for these transitions to have a quadrupole character. Therefore, hypersensitive transitions have been called also pseudo-quadrupole transitions. No quadrupole transitions have been observed for lanthanide ions, although Chrysochoos and Evers (1973) stated that the intensity of the hypersensitive transitions D2 Fq (in the absorption spectrum) and Do Fi (in the luminescence spectrum) of Eu " are mainly quadrupolar in nature. 

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