Photons, radiation

Q is commonly referred as the sensor quantum yield. It gives the fraction of excited molecules that return to the ground state by emitting a photon. The steady-state sensor luminescence Iss is given by the number of photons radiated per unit of time by our sensor when excited by steady-state excitation. Iss is proportional to Q ... 

Koh W, Griffin TW, Laramore GE, et al. Neutron versus photon radiation therapy for inoperable nonsmall cell lung cancer results of a multicenter randomized trial. Int J Radiat Oncol Biol Phys 1993 27 499-505. 

Figure 3 Microdosimetric distributions for several photon radiations commonly used in brachytherapy. (From Ref. 36.)...

It is current medical practice to select the weighting factors as a function of two main criteria (1) late tolerance in normal tissues and (2) in relation to a daily fractionation of 2 Gy (photons or Co-gamma rays). Therefore among the published RBE values, those obtained for late elfects on normal tissues, with 2 Gy of photons per fraction as reference, are the most relevant for the selection of the RBE weighting factor and could be defined as reference conditions. The reference RBE is then, to some extent, an average or overall RBE for late tolerance of normal tissues at risk, evaluated vs. 2 Gy per fraction of photon radiation. 

Figure 1 shows the cooling behavior of neutron stars during the first one year after the explosion. The total luminosity of the surface photon radiation Lph (left) and the surface temperature Ts (right), both to be observed at infinity, are plotted as a function of time, for three nuclear models PS (stiff), FP (intermediate), and BPS (soft). The temperature scale refers to the FP model. 

As long as so little is known about the interstellar particle and photon radiation fields which provide the heating of the interstellar gas, one should not put too much faith in estimated equilibrium temperatures of dense gas clouds such as shown in Fig. 9. However, at least qualitatively it appears to be correct that dense condensations in the interstellar gas have low kinetic temperatures. In fact, gas-kinetic temperatures as low as 5 °K have been observa-tionally determined in the center of dark clouds. 

Davis and Okabe (1 ) have determined the dissociation energy of FCN to F(g) and CN(g) by measuring the threshold energies of incident photon radiation to produce B l CN which is monitored by its fluorescence. The dissociation energy determined by this technique is 111 kcal mol" with an uncertainty of about 1 kcal in the determination of the limit. 

Later, a secondary mode of EDS was developed to overcome this intrinsic limitation of the detector when handling a large influx of photons. In the secondary mode, a selected pure element standard with absorption filters is placed in the optical path between the primary X-ray source and the specimen. The element standard only allows the X-ray photons in a selected range of energy (secondary photons) to strike the sample. Thus, in secondary photon radiation, the amount of photons emitted from the sample is controlled by preventing unwanted X-ray excitation of the specimen. 

QED [17] where energy is coherently exchanged between the internal state and single-photon radiation field. The first blue sideband, at 8 = +co drives transitions between states 11, n) 11, n+l) with Rabi frequency 2 +i = gTi(n+l) . ... 

The equation of radiative transfer will not be solved here since solutions to some approximations of the equation are well known. In photon radiation, it has served as the framework for photon radiative transfer. It is well known that in the optically thin or ballistic photon limit, one gets the heat flux as q = g T[ - T ) from this equation for radiation between two black surfaces [13]. For the case of phonons, this is known as the Casimir limit. In the optically thick or diffusive limit, the equation reduces to q = -kpVT where kp is the photon thermal conductivity. The same results can be derived for phonon radiative transfer [14,15]. 

The second recent interesting application of lasers is concerned with the use of the narrow spectral bandwidth of the laser as a means of selectively exciting single components in mixtures, particularly in isotopic mixtures, thus achieving selective reaction and ultimately isotope separation. In order to obtain high selectivity, in general a two-step excitation process is required, but one-photon radiation of several species with i.r. lasers has been shown to lead to enhancement of reaction rates. Thus C02-laser-induced vibrational excitation of 03 leads to enhancement of reaction rates with SO (85), NO (86), and SF4-02 mixtures.222... 

NLO properties are provided by including chromophore compounds, such as an azo-t)q)e dye, which can absorb photon radiation. The chromophore may also provide adequate charge generation. Alternatively, a sensitizer may be added to provide or boost the mobile charge required for photorefractive properties. 

This definition is based on incident photons (radiation incident on the surface of a solid polymer or on the surface of a cell carrying a solution of the polymer). No corrections are made for scattering losses, back reflection, absorbance, or internal reflection effects. The action spectrum, therefore, depends on absorption characteristics of the polymer as well as on the quantum yield of the degradation process studied. 

The Bose-Einstein distribution (1.162) may be considered to recover the Planck law of black body radiation, i.e., the photon radiation modeling, by considering the following peculiarities ... 

Based on such statistics, the total energy of photon radiation is obtained by passing from the discreet definition to the continuous one by the sum-to-integral (statistical) conversion... 

However, another important quantity related to the energy density refers to the photon radiation pressure, phenomenological deduced from the general relations... 

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