Luminescence excited

Fig. 21.4 The X-ray-excited luminescence spectrum of Ba3BP30i2 host. The dotted lines are the Gaussian decomposition.

Therefore, there could exist rich defects in Ba3BP30i2, BaBPOs and Ba3BP07 powders. From the point of energy-band theory, these defects will create defect energy levels in the band gap. It can be suggested that the electrons and holes introduced by X-ray excitation in the host might be mobile and lead to transitions within the conduction band, acceptor levels, donor levels and valence band. Consequently, some X-ray-excited luminescence bands may come into being. 

The X-ray-excited Luminescence Properties of Ce -activated Ba3BP30i2, BaBPOs and Ba3BP07... 

Figures 21.16, 21.17 and 21.18 show the X-ray-excited luminescence properties of Ce -activated Ba3BP30i2, BaBPOs and Ba3BP07 respectively. They all show a broad emission band with peak center at about 351 nm for Ba3BP30i2 Ce, ...

The method of exchange-luminescence [46, 47] is based on the phenomenon of energy transfer from the metastable levels of EEPs to the resonance levels of atoms and molecules of de-exciter. The EEP concentration in this case is evaluated by the intensity of de-exciter luminescence. This technique features sensitivity up to-10 particle/cm, but its application is limited by flow system having a high flow velocity, with which the counterdiffusion phenomenon may be neglected. Moreover, this technique permits EEP concentration to be estimated only at a fixed point of the setup, a factor that interferes much with the survey of heterogeneous processes associated with taking measurements of EEP spatial distribution. 

For most people, BL is represented by the flash of the firefly or the phosphorescence that frequently occurs on agitating the surface of ocean water. Chemical excitation, luminescent reactions occurs in almost all zoological kingdoms (bacteria, dinoflagelates, Crustacea, worms, clams, insects, and fishes) except higher vertebrates BL is not found in any organisms higher than fish. In most cases this phenomenon occurs within specialized cells called photocytes [3-5], As shown in Table 1, BL occurs in many terrestrial forms but is most common in the sea, particularly in the deep ocean, where the majority of species are luminescent [6],... 

A luminescent mineral is a sohd, which converts certain types of energy into electromagnetic radiation over and above thermal radiation. The electromagnetic radiation emitted by a luminescent mineral is usually in the visible range, but can also occur in the ultraviolet (UV) or infrared (IR) range. It is possible to excite the luminescence of minerals by UV and visible radiation (photoluminescence), by a beam of energetic electrons (cathodoluminescence), by X-rays (X-ray excited luminescence) and so on. A special case is so-called thermoluminescence, which is stimulation by the heating of luminescence, prehminary excited in a different way. 

Ultra-violet X-ray excited luminescence of Pr was first observed in minerals in anhydrite, but have been mistakenly ascribed to transitions from Ijj2 and Ds/2 levels in Gd " (Gaft et al. 1985). According to CL spectra of anhydrite artificially acfivated by Pr " " (Baumer ef al. 1997 Blank ef al. 2000) the emission lines at 228, 239, 258 and 268 nm (Fig. 4.17a) belong to Pr " and may be connected with Sq and Sq -> 64 transitions. The lines... 

Together with Sm another group of lines is often detected with the main line at 685 nm, which also has a very long decay time of several ms (Fig. 4. lOd). It is very close to the known resonance line of Sm. Under low power UV lamp excitation, the luminescence of Sm in fluorite is known only at low temperatures, starting from approximately 77 K, and is composed of narrow /-/ transition lines and a broad band of 4f-5d transitions (Tarashchan 1978 Krasilschikova et al. 1986). Evidently, under strong laser excitation, luminescence of Sm + may be seen even at room temperature, where 4f-5d luminescence is usually quenched because of radiationless transition. 

Figure 4.26 demonstrates the time-resolved liuninescence of pyromorphite under 355 and 266 nm laser excitations. Luminescence lines of Eu + are clearly seen in both cases. 

Luminescence of Eu and Eu has been found in the X-ray excited luminescence spectra of synthetic leucophane activated by Eu (Prokofiev et al. 1982 Eig. 5.17), while in natural samples only Eu " " was detected. Laser-induced time resolved luminescence under 532 nm excitation enables us to detect clear lines of Eu " " with the strongest Dq- Fq electron transition at 573 nm (Eig. 4.25). 

Fig. 5.17. Steady-state X-ray excited luminescence of artificial leucophane activated by Eu (a-2% andb-0.5% EU2O3 in blend, respectively) (Prokofiev et al. 1982)...

For separation between microcline and plagioclase X-ray excited luminescence is used (Gorobets et al. 1997). The main problem is that their emission spectra are very close. Under laser excitation these minerals also demonstrate blue emissions connected with Eu ", which have close spectral and kinetic parameters. Nevertheless, the differences in excitation spectra (Fig. 8.5) enable effective sorting. 

E. R. Menzel, Detection of Latent Fingerprints by Laser-Excited Luminescence, Anal. Chem. 1989,61, 557A. 

Combined with photoemission, DRS provides quantitative data on excitation-luminescence behavior of powdered specimens which can be used to determine photoluminescence quantum efficiencies and the extent of resonant energy transfer among the bulk and surface activators and sensitizers. 

Fig. 14. Origin region of the low temperature excitation (luminescence monitored broad band below 20 200 cm 1) and luminescence (excitation at 457.9 nm with an Ar laser) spectra of [lr(ppy)2bpy]PF5 in [Rh(ppy)2bpy] PF6. M, C and D label electronic origins (from Ref. [45])...

Figure 11.10 Energy level diagrams for photoinduced electron transfer processed based on 11.8, showing excitation (--), luminescence (---) and nonradiative decay (—).

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