VO6 Chrysoberyl, Pyromorphite and Beryl

Vanadium complex luminescence may be supposed in chrysoberyl where artificial chrysoberyl activated by V exhibits read broad band luminescence with decay time of approximately 5 ps under UV excitation (Fig. 5.98). Similarly, pyromorphite usually has orange to yeUow UV excited luminescence characterized by broadband peaking at 580 nm (Fig. 4.60). It was earlier supposed that such luminescence is connected with (V04) emission center (Gaft 1984), but the possible role of Ag also may be considered (Gorobets and Rogojine 2001). Beside, blue emission band in beryl luminescence spectrum with short decay time of 1 ps (Fig. 4.122a) can also be connected with (V04) complex, especially because the similar emission has been found in radioluminescence spectrum of beryl with elevated ccmcentration of vanadium (Chithambo et al. 1995). 

3 TiOg Benitoite, Chrysoberyl, Bahdadite, Baratovite and Aegirin 

According to our experience all benitoite samples have intensive blue emissimis under short wave and middle wave UV, and we have never seen or heard of any that did not. On the other hand, efficient luminescence has been observed from the Ti04 , TiOe and even TiOs complexes. In addition, bazirite BaZrSisOg with the benitoite stmcture demonstrates luminescence of zirconate complexes ZrOe (Blasse 1980). The blue luminescence of impurity Ti centers has been found in synthetic BaSnSisOg-Ti and BaZTSisOg-Ti with the benitoite structure (Konijenendijk 1981). 

We thus have strong evidences in favor of an intrinsic model for the blue luminescence in benitoite, connected with the TiOg octahedra. Hence we have tried to determine if the spectroscopic experimental data may be explained based on such a model (Gaft et al. 2004). 

Thus the excitation band at 240 nm may be assigned to the allowed Aig- T2u transition, and the weaker band at 290 nm assigned to the formally forbidden Aig- Tiu transition. Because of very long decay time, the emission at low temperatures must originate from the parent Ti triplet states, because the Ti state is the 

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