Emitted radiation

In traditional Fan-Beam CT the radiation emitted from the X-ray tube is collimated to a planar fan, and so most of the intensity is wasted in the collimator blades (Fig. 2a). Cone-Beam CT, where the X-rays not only diverge in the horizontal, but also in the vertical direction, allows to use nearly the whole emitted beam-profile and so makes best use of the available LINAC photon flux (Fig. 2b). So fast scanning of the samples three-dimensional structure is possible. For Cone-Beam 3D-reconstruction special algorithms, taking in consideration the vertical beam divergence of the rays, were developed. 

The linear and nonlinear optical responses for this problem are defined by e, 2, e and respectively, as indicated in figure Bl.5.5. In order to detemiine the nonlinear radiation, we need to introduce appropriate pump radiation fields E(m ) and (co2)- If these pump beams are well-collimated, they will give rise to well-collimated radiation emitted tlirough the surface nonlmear response. Because the nonlinear response is present only in a thin layer, phase matching [37] considerations are unimportant and nonlinear emission will be present in both transmitted and reflected directions. 

From such a treatment, we may derive explicit expressions for the nonlinear radiation in tenns of the linear and nonlinear response and the excitation conditions. For the case of nonlinear reflection, we obtain an irradiance for the radiation emitted at the nonlinear frequency of... 

In 1896, only a few months after Roentgen aimounced the observation of x-rays, Becquerel reported the additional observation of penetrating radiation emitted from certain natural materials, a phenomenon that Marie Curie would later name radioactivity. This phenomenon had a much less glamorous development. Over a three-year period, Becquerel pubHshed three articles, decided there was Htfle else to learn about it, and went on to the study... 

The radiation from a flame is due to radiation from burning soot particles of microscopic andsubmicroscopic dimensions, from suspended larger particles of coal, coke, or ash, and from the water vapor and carbon dioxide in the hot gaseous combustion products. The contribution of radiation emitted by the combustion process itself, so-called chemiluminescence, is relatively neghgible. Common to these problems is the effect of the shape of the emitting volume on the radiative fliix this is considered first. 

The algorithm is based both on a mathematical simulation of a spectmm of secondary radiation emitted by a sample to be studied and the detector response function. The detection limit is given by criteria 3s ... 

Another consideration in the determination of the optimum Eq is the depth of X-ray production in bulk samples, especially if one component strongly absorbs the radiation emitted by another. This is often the case when there is a low-Z element in a high-2 matrix, e.g., C in Fe. Here X rays from carbon generated deep within the sample will be highly absorbed by the Fe and will not exit the sample to be detected. The usual result will be an erroneously low value for the carbon concentration. In these situations the best choice for Eq will be closer to Eq with U rather than a much higher value with U = 2.5. 

Fig. 4.15. Angular dependence of the fluorescence radiation emitted from a Co-layered Si substrate. The Co-Ka intensity is plotted semi-logarithmically for layers of different thickness (mm). The maxima forthe ultra-thin Co-layers are located at the critical angle of Si (dashed vertical line). They are shifted to the critical angle of Co (dotted vertical line) ifthe layer is more than 10 mm thick ([4.21], after Ref [4.41]).

Ion beam spectrochemical analysis (IBSCA) is a sputtering-based surface analytical technique similar to SIMS/SNMS. In IBSCA the radiation emitted by excited sputtered secondary neutrals or ions is detected. IBSCA was developed parallel to SIMS in the nineteen-sixties and early nineteen-seventies [4.246, 4.247]. It is also known... 

Show by a diagram why the energy of radiation emitted from an excited electronic state (by fluorescence or phosphorescence) is of lower energy than the exciting radiation. Would you expect the shift to lower energy to be more pronounced for fluorescence or phosphorescence Explain. 

The same type of radiation emitted by different isotopes may differ signifieantly in energy, e.g. y-radiation from potassium-42 has about four times the energy of y-radiation from gold-198. 

Since the K radiation emitted from a magnesium anode consists of the intense Kbinding energies by 8.0 and 10.2 eV [20]. The satellites excited by the Kas and K<,6 lines are usually too weak to be observed. Similar features can be observed in XPS spectra excited using Ko, X-rays from aluminum. 

UV Radiation Ultraviolet Radiation emitted from the sun, which can affect health and ecosystems at elevated levels. 

The radiation emitted by a body due to its temperature is defined by the factor , the emissivity,... 

Suppose two objects are in a hollow (Fig. 4.30) object A, which is black, and object B, which is gray (a body that does not absorb all the incoming radiation). The energy and mass are in balance when the temperatures of A, B, and C are equal. In the balanced state the radiation emitted by the bodies is equal to the radiation received. 

The noncontact measurement principle, usually called optical or radiation temperature measurement, is based on detecting electromagnetic radiation emitted from an object. In ventilation applications this method of measurement is used to determine surface temperatures in the infrared region. The advantage is that the measurement can be carried out from a distance, without contact with the surface, which possibly influences the heat balance and the temperatures. The disadvantages are that neither air (or other fluid) temperature nor internal temperature of a material can be measured. Also the temper-... 

High pressure xenon lamps are also employed in some TLC scanners (e.g. the scanner of Schoeffel and that of Farrand). They produce higher intensity radiation than do hydrogen or tungsten lamps. The maximum intensity of the radiation emitted lies between k = 500 and 700 nm. In addition to the continuum there are also weak emission lines below k = 495 nm (Fig. 14). The intensity of the radiation drops appreciably below k = 300 nm and the emission zone, which is stable for higher wavelengths, begins to move [43]. 

The radiation emitted is usually longer in wavelength (i.e. lower in energy) than the incident light (Store s law). It is only in the case of 0—0 transitions (shown in Figure 27 as thick arrows) that the wavelengths for fluorescence and activation are identical. 

Thermal radiation is electromagnetic radiation covering wavelengths from 2 to 16 p,m (infrared). It is the net result of radiation emitted by radiating substances such as HjO, CO2, and soot (often dominant in fireballs and pool fires), absorption by these substances, and scatter. This section presents general methods to describe... 

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