Photoluminescence thermoluminescence

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. 

Luminescence is defined as emission of light by materials in the visible, UV, and IR spectral range after input of energy [2], Emission of light quanta by molecules from a (photo) excited state proceeds via transition of an electron to a lower energy level. Depending upon the way in which the excited state is generated, a distinction is made between photoluminescence, chemoluminescence, radioluminescence, and thermoluminescence (Table 5.1). In the case of photo-... 

Energy Transfer Processes. Luminescence is a complex sequence of energy transfer processes. Figure 2 is a schematic of the most important of these for photoluminescence, cathodoluminescence, and candoluminescence. The ultimate source of energy is the excitation UV light, electron beam, ion beam, or radical recombination excitation. We are not concerned here about the triggered release of previously trapped energy such as occurs in thermoluminescence and triboluminescence. 

See also bioluminescence, chemiluminescence, dectro-generated chemiluminescence, fluorescence, phosphorescence, photoluminescence, radioluminescence, sono luminescence, thermoluminescence, triholuminescence. 

Key words Point defects, photoluminescence, photo-EPR, single crystals, hydrothermal method, exciton, donor, acceptor, thermoluminescence... 

Longitudinal diffusion term, Bin A term in chromatographic band-broadening models that accounts for longitudinal diffusion. Lower control limit, LCL The lower boundai7 that has been set for satisfactory performance of a process or measurement. Luminescence Radiation resulting from photoexcitation (photoluminescence), chemical excitation (chemiluminescence), or theiTnal excitation (thermoluminescence). 

Stokes shifted photoluminescence spectrum has been observed in arsenic chalcogenides. Luminescence can result from thermal excitations also which requires less energy as illustrated in the same figure by slanted arrow. The requirement of smaller energy in thermoluminescence is thought to, be due to the fact that the lattice has time to relax during the thermal transition and therefore, excitation occurs between potential minima. 

A luminescence spectrometer type CLA-FSl was employed to measure both thermoluminescence and photoluminescence of Ti02. Colour photographs of the photoluminescence for Ti02 were taken with a high sensitive camera Cube-2DI equipped with a sensitive colour CCD (a product of Bitran Co., Japan). Both types of the apparatus are available from the Tohoku Electronic Industrial Co., Japan. 

Luminescence The light emitted by something in response to a stimulus. Specific names are used for different stimuli, e.g., thermoluminescence, optically-stimulated luminescence, photoluminescence, triboluminescence etc. 

Luminescence of AIN ceramics was studied (i) during irradiation process, in the case of UV fight irradiation this type of luminescence is called photoluminescence (PL), (fi) after ceasing of irradiation - in the form of afterglow (AGL), (iii) during heating of the previously irradiated sample - in the form of thermoluminescence (TL), (iv) during illumination of the previously irradiated sample - in the form of optically stimulated luminescence (OSL). 

Optical clarity has received considerable attention from the research conununity, as well as industry, especially, since transparent ABS was introduced to the market. Although success in this area has been limited, nevertheless this property is pertinent when considering blend suitability to a particular application. Few significant innovations have come up in photoluminescence and thermoluminescence, but the subject is, however, not mature enough to make a comprehensive story of the subject. 

Emitters can be classified in terms of those which emit in the gas phase, the solution phase, or the solid state, and also by mode of excitation, i.e. electroluminescence, thermoluminescence, chemiluminescence, radioluminescence and photoluminescence. We are most concerned with photoluminescent materials, but thermoluminescence and electroluminescence, in both gas and solid phases, are important technologies. 

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... 

---