Rare-Earth Elements Luminescence in Minerals

The promise of luminescent methodology is based on many types of information that can be derived from mineralogical samples. These include RE from Ce to Yb, identities down to the ppb range, the valence states of the RE, the nature of the sites at which RE reside and the ways of compensating the charge, and features related to the presence of other ions (donors, activators). All this information can be used to determine the chemical, thermal, and deformational history of the material. 

Depending upon the site symmetry, the degeneracy of the 5d state is partially or completely removed. The overall splitting of the 5d manifold is typically in the order of 5,000-10,000 cm  

Electric-dipole transitions between the 4f ground state and the 5d excited state of Ce are parity and spin allowed and have a large oscillator strength and very short decay time. Contrary to a long lived emission of many 4f j-levels of several 

A narrow band with a main shoulder at 302 nm with a very short decay time of 25 ns, and another with shoulders at 330 and 360 nm with a longer decay of 75 ns (Fig. 4.74c, d) in time-resolved spectra have spectral-kinetic parameters suitable for Ce . It is known that narrow bands near 300 nm are especially strong in (Ba,Sr)S04 (baritocelestine), while in barite they are situated at a longer wavelength (Gaft et al. 1985). The ionic radius of Ce + is 128 pm and a possible accommodation is isomorphic substitution for Ba (156 pm) or Sr (140 pm). Thus, two types of Ce centers may be connected with Sr impurity, the presence of which in barite samples is confirmed by ICP analysis (450-720 ppm). Luminescence of Ce in anhydrite is seen under excitation at 266 nm (Fig. 4.30b) and it is 

Two types of Ce centers in calcite were detected by steady-state spectroscopy (Kasyanenko and Matveeva 1987). The first one has two bands at 340 and 370 nm and is coimected with electron-hole pare Ce -C03. The second one has a maximum at 380 nm and was ascribed to complex center with Ce and OH or H2O as charge compensators. Such center becomes stronger after ionizing irradiation and disappears after thermal treatment. The typical example of Ce luminescence in time-resolved luminescence of calcite, aragonite and dolomite consists of narrow band at approximately 350-360 nm with very short decay time of 30 ns, which is very characteristic for Ce (Figs. 4.18a, 4.22a and 4.25b). It was found that Ce excitation bands occur also in the Mn excitation spectrum, demmi- 

Narrow bands at 320-335 nm with very short decay time of 20-30 ns may be confidently ascribed to Ce luminescence (Fig. 4.98). In steady-state spectra different bands in this spectral range without decay time analyses, especially under X-ray and electron beam excitations may be mistakenly considered as 

The narrow band with two maxims at 335 and 360 nm in time-resolved emission spectra of datolite (Fig. 4.29a), with short decay time of 30 ns is connected with Ce +. 

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