Apatite Luminescence Spectroscopy

13 Reabsorption Lines of Oxygen and Water 5.13.1 Apatite Luminescence Spectroscopy 

Nevertheless, these absorption lines though not previously mentioned in solids are well known to absorb the visible light in the atmosphere (Measures 1985 Peixoto and Oort 1992). The strongest absorption lines of molecular oxygen are named as A-band, or 760 nm, and B-band, or 687 nm. The 760 nm band is very 

The next interesting problem is why reabsorption lines disappear at liquid nitrogen temperature In emission-reabsorption process both centers behave as independent systems, and do not interact directly. Thus energy migration is not temperature dependent. The possible explanation is that at liquid nitrogen 

It is clearly seen that negative lines are much stronger then the noise. Besides that, the negative lines are always situated at the same places. The invariabihty of the spectral positions provides the evidence that they are not connected with fluctuations of the laser pulses and detection system. Thus it may be concluded that we a deaUng with a reabsorption mechanism. The optical absorption spectra of natural apatites in the range 600-900 nm contain several lines and bands connected with Nd , Pr , Mn , SOj (Gorobets 1975  

Gilinskaya and Mashkovtsev 1994) but they do not coincide with the negative lines detected in our study. The optical spectroscopy data connected with other minerals and solids have been also checked, but all attempts were unsuccessful (Platonov 1979). 

Thus the spectroscopic conclusion is in accordance with the crystallochem-istry of apatite, namely with possible accommodation of molecular oxygen and water in different ways by structural incorporation and by adsorption. 

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It was established by steady-state luminescence spectroscopy that minerals of Mn, such as rhodonite, rhodochrosite, helvine, triplite, Mn-apatite, Mn-milarite and others, show dark red luminescence, mainly at 77 K, which is uncommon to impurity Mn ". The excitation center proved to be regular Mn ", while the emission center is Mn ", situated near some lattice defect (Gorobets et al. 1978 Gaft et al. 1981). 

After a delay of several ps, the luminescence of Eu " is already very weak, and narrow long-lived lines of trivalent RE dominate in the spectrum. The lines at 589, 617, 651, and 695 nm (Fig. 4.1c) have never been detected in natural apatite by steady-state spectroscopy. According to their spectral position they may be ascribed to Eu ", but they are different from known lines in synthetic apatites activated by Eu (Jagannathan and Kottaosamy 1995 Morozov et al. 1970 Piriou et al. 1987 Piriou et al. 2001 Voronko et al. 1991). In order to clarify this problem we studied artificially activated samples by laser-induced time-resolved luminescence spectroscopy. 

The book deals mainly with theoretical approach, experimental results and their interpretation of laser-induced time-resolved spectroscopy of minerals in the wide spectral range from 250 to 2000 nm, which enables to reveal new luminescence previously hidden by more intensive centers. Artificial activation by potential luminescence centers has been accomplished in many cases, which makes the sure identification possible. The mostly striking example is mineral apatite, which has been extremely well studied by many scientists using practically all known varieties of steady-state luminescence spectroscopy photoluminescence with lamp and laser excitations. X-ray excited luminescence, cathodoluminescence, ionolumi-nescence and thermoluminescence. Nevertheless, time-resolved spectroscopy revealed that approximately 50 % of luminescence information remained hidden. The mostly important new information is connected with luminescence of trivalent... 

The presence of Pr in apatite samples, up to 424.4 ppm in the blue apatite sample, was confirmed by induced-coupled plasma analysis (Table 1.3). The luminescence spectrum of apatite with a broad gate width of 9 ms is shown in Fig. 4.2a where the delay time of500 ns is used in order to quench the short-lived luminescence of Ce + and Eu +. The broad yellow band is connected with Mn " " luminescence, while the narrow lines at 485 and 579 nm are usually ascribed to Dy and the fines at 604 and 652 nm, to Sm +. Only those luminescence centers are detected by steady-state spectroscopy. Nevertheless, with a shorter gate width of 100 ps, when the relative contribution of the short lived centers is larger, the characteristic fines of Sm " at 652 nm and Dy + at 579 nm disappear while the fines at 485 and 607 nm remain (Fig. 4.2b). It is known that such luminescence is characteristic of Pr in apatite, which was proved by the study of synthetic apatite artificially activated by Pr (Gaft et al. 1997a Gaft... 

Divalent europium is detected in apatite as a shoulder of Ce luminescence when studied by steady-state spectroscopy (Tarashchan and Marfunin 1969 ... 

Warren RW (1970) EPR of Mn in calcium fluorophosphates. 1. The Ca (11) site. Phys Rev B 2 4383-4388 Waychunas G (1989) Luminescence, X-ray emission and new spectroscopies. Rev Mineral 18 638-698 Wright AO, Seltzer MD, Graber JB, Zandi B, Merkle LD, Chai BHT (1996) Spectroscopic investigation of Pr in fluorapatite crystals. JPhys Chem Solids 57 1337-1350 Xiong J (1995) Cathodoluminescence studies of feldspars and apatites from the Coldwell alkaline complex. MSc thesis, Lakehead Univ, Thunder Bay, Ontario... 

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