Radiation thermal luminescence

In the majority of cases the compatibility of the polymers is characterized by the glass-transition temperature Tg, determined by methods such as dilatometry, differential scanning calorimetry (DSC), reversed-phase gas chromatography (RGC), radiation thermal luminescence (RTL), dynamic mechanical spectroscopy (DMS), nuclear magnetic resonance (NMR), or dielectric loss. The existence of two... 

Fig. 5.65. Comparison of radiation-induced luminescence and EPR of different centers as a fimction of the heating temperature. Left integrated yellow liuninescence (upper) and EPR of TF, Yh, Nh and SiO (lower). Right yellow luminescence bands of different origin with different thermal stability (Gaft et al. 1986)...

Merely from the fact that even a true black body would yield less than half this amount (Table 7) at an estimated flame temperature of about 2500it becomes obvious that in intense pyrotechnic radiation thermal grey-body emission is heavily augmented by selective radiation and luminescent phenomena. This can be experimentally demonstrated by a comparison of light emission from binary mixtures where various alkali salts act as oxidizers. Table 9 (from Table 13.7, Shidlovsky ) shows these relations. He uses a fixed ratio of 40 % metal fuel and 60% of the nitrates of sodium, potassium, or barium. It is of course not... 

The Kirchhoff law defines one of the most important properties of thermal radiation, distinguishing it from other types of radiation (fluorescence, luminescent, etc.) thermal radiation is an equilibrium one. From eq. (6.6.9), it follows that the more a body absorbs, the more it radiates. Hence, in an isolated system of bodies their temperature will eventually be equalized, becoming identical. If a body absorbs more, it also radiates more. The values r(to,T) and a(to,T) can differ, but their ratio is identical. 

Principles and Characteristics The term luminescence describes the radiative evolution of energy other than blackbody radiation which may accompany the decay of a population of electronically excited chro-mophores as it relaxes to that of the thermally equilibrated ground state of the system. The frequency of the... 

Photodissociation of molecules may also be achieved by depositing energy directly in the vibrational degrees of freedom. With hi -power pulsed CO2 lasers dissociation of molecules which absorb CO2 -laser radiation has been observed to proceed at an initial rate that far exceeds the measured thermal rate 169 ). The appearance of luminescence spectra of dissociation products preceding the occurrence of gas breakdown 169b) indicates that a considerable degree of dissociation exists for some time before breakdown. 

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. 

Effect of turbulence on flame radiation) (Authors measured the radiation intensity from propane flames and found a decrease in radiation with turbulence. Radiation is not thermal, but appears to be a luminescent phenomenon) 11) T.E. Holland et al, JApplPhys 28, 1217(1957)... 

At temperatures above absolute zero, particles can emit as well as absorb and scatter electromagnetic radiation. Emission does not strictly fall within the bounds imposed in the first chapter it is more akin to such phenomena as luminescence than to elastic scattering. However, because of the relation between emission and absorption, and because emission can be an important cooling mechanism for particles, it seems appropriate to discuss, at least briefly, thermal emission by a sphere. 

As it is known, I centres are the most mobile radiation-induced radiation defects in alkali halides and therefore they play an essential role in low-temperature defect annealing. It is known, in particular, from thermally-stimulated conductivity and thermally-stimulated luminescence measurements, that these centres recombine with the F and F electron centres which results in an electron release from anion vacancy. This electron participates in a number of secondary reactions, e.g., in recombination with hole (H, Vk) centres. Results of the calculations of the correlated annealing of the close pairs of I, F centres are presented in Fig. 3.11. The conclusion could be drawn that even simultaneous annealing of three kinds of pairs (Inn, 2nn and 3nn in equal concentrations) results in the step-structure of concentration decay in complete agreement with the experimental data [82]. 

Spontaneous emission of radiation from an electronically and/or vibrationally excited species not in thermal equilibrium with its environment is called luminescence when the emission is accompanied by the formation of a molecular entity of the same spin multiplicity it is called fluorescence (F), whereas luminescence involving change in spin multiplicity (typically from triplet to singlet) is called phosphorescence (Ph) [1],... 

Luminescence Spontaneous emission of radiation from an electronically or vibra-tionaUy excited species not in thermal equilibrium with its environment... 

If, however, the population of the energy state 2 ii> a consequence of a non-thermal process, then the emission of radiation as a result of a transition from 2 to 1 is referred to as luminescence. There are different types of luminescence ... 

Luminescence processes usually produce incoherent radiation. The population of the energy states 2 and 1, according to Boltzmann s law, may be described by a temperature. These states are not usually in thermal equilibrium with the other energy states of the ensemble, which normally correspond to a low temperature. 

Luminescence, the emission of electromagnetic radiation in excess of that thermally generated, has been observed in several azides. The emission typically occurs in the ultraviolet, visible, or infrared regions of the electromagnetic spectrum. Some external stimulus is required prior to luminescent emission. The stimulus can take the form of photons, energetic particles, electric field, mechanical energy, or energy available from chemical reaction. 

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