Radiation origin

The explanation of the hydrogen atom spectmm and the photoelectric effect, together with other anomalous observations such as the behaviour of the molar heat capacity Q of a solid at temperatures close to 0 K and the frequency distribution of black body radiation, originated with Planck. In 1900 he proposed that the microscopic oscillators, of which a black body is made up, have an oscillation frequency v related to the energy E of the emitted radiation by... 

The very close similarity between the x-ray spectra of the different elements shows that these radiations originate... 

Scattered radiation. In a transmission experiment, the Mossbauer sample emits a substantial amount of scattered radiation, originating from XRF and Compton scattering, but also y-radiation emitted by the Mossbauer nuclei upon de-excitation of the excited state after resonant absorption. Since scattering occurs in 4ti solid angle, the y-detector should not be positioned too close to the absorber so as not to collect too much of this unwanted scattered radiation. The corresponding pulses may not only uimecessarily overload the detector and increase the counting dead time, but they may also affect the y-discrimination in the SCA and increase the nonresonant background noise. 

Background Radiation—The amount of radiation to which a member of the general population is exposed from natural sources, such as terrestrial radiation from naturally occurring radionuclides in the soil, cosmic radiation originating from outer space, and naturally occurring radionuclides deposited in the human body. 

Radiation, Characteristic (Discrete)—Radiation originating from an excited atom after removal of an electron from an atom. The wavelength of the emitted radiation is specific, depending only on the element and particular energy levels involved. 

A type of radiation that was not available earlier came into existence and eventually became available to soil scientists. This is the radiation given off by synchrotrons that emit what is called synchrotron radiation (originally considered a waste product of acceleration electrons close to the speed of light). It is described as similar to bright X-rays. This electromagnetic radiation has been used to successfully elucidate the structure and oxidation states of metals in soil and thus their likelihood of becoming environmental pollutants [34],... 

In surface-enhanced Raman spectroscopy (SERS) samples are adsorbed onto microscopically roughened metal surfaces. Spectra are the intensities and frequencies of scattered radiation originating from a sample that has been irradiated with a monochromatic source such as a laser. SERS spectra are of molecules that are less than 50 A from the surface. 

It is quite apparent that if one must resort to such drastic and expensive measures to counteract flavor and color deterioration, any advantage that radiation originally had will be very much weakened. 

I often wondered whether the reporters were afraid to include my points about nuclear power, or whether they were edited out at a higher level. In any case, the media and the public view radiation from nuclear power and from radon in homes as entirely different and unrelated subjects. I repeatedly explained to reporters that when a cell in our bodies is hit by radiation, there is no way for it to know whether that radiation originated from nuclear power operations or from radon, but somehow that explanation never got reported. 

In addition to the penetrating power of the x-rays there are certain other characteristic phenomena encountered in radiography with the betatron not found with low voltage x-rays, such as a) A relative freedom from scattered radiation. The secondary radiation will tend to retain direction which the primary radiation originally had. Hence, no blocking is necessary around an irregular object or be-... 

Another particularly interesting limit of Eq. (5-134) occurs when A2 Ai, which might represent a small sphere irradiated by an infinite surroundings which can reflect radiation originating at Ab back to Ai. That is to say, even though A2 — , the self total exchange area does not necessarily vanish, to wit... 

Introduction Flame radiation originates as a result of emission from water vapor and carbon dioxide in the hot gaseous combustion... 

Gas Emissivities Radiant transfer in a gaseous medium is characterized by three quantities the gas emissivity, gas absorptivity, and gas transmissivity. Gas emissivity refers to radiation originating within a gas volume which is incident on some reference surface. Gas absorptivity and transmissivity, however, refer to the absorption and transmission of radiation from some external surface radiation source characterized by some radiation temperature 7. The sum of the gas absorptivity and transmissivity must, by definition, be unity. Gas absorptivity may be calculated from an appropriate gas emissivity. The gas emissivity is a function only of the gas temperature Tg while the absorptivity and transmissivity are functions ofboth Tg and Tt. 

Backscattering of radiation can be taken as the basis for surface analysis. It is due to electron-electron interaction, which is nearly independent of the atomic number Z of the material, and to scattering by atomic nuclei, which increases with Z. Both effects overlap, and the saturation value of backscattering increases approximately with fZ. Because the backscattered radiation originates from the layers near the surface, surface analysis is possible. An example is the determination of heavy elements in a solid or liquid matrix of light elements by use of the fi radiation of Sr. 

Unlike emissivity, the absorptivity of a material is practically independent of surface temperature. However, the absorptivity depends strongly on the temperature of the source at which the incident radiation is originating. This is also evident from Fig. 12 33, which shows the absorplivilies of various materials at room temperature as functions of the temperature of the radiation source. For example, the absorptivity of the concrete roof of a house is about 0.6 for solar radiation (source temperature 5780 K) and 0.9 for radiation originating from the surrounding trees and buildings (source leriiperaiurc 300 K), as illustrated in F ig. 12-34. 

The absorptivity of a material may be quite different for radiation originating from sources at different temperatures. 

C E. ptain why surfaces usually have quite different absorptivitics for solar radiation and for radiation originating from the surrounding bodies. 

Gamma ray—Electromagnetic radiation originating from the nucleus of an atom. 

Large amounts of gallium have also been used to study radiation given off by the sun. In experiments conducted at the National Laboratory at Gran Sasso, Italy, containers holding more than 33 short tons (30 metric tons) of gallium were used to detect and measure various types of radiation originating from the sun. These experiments were conducted from 1991 to 1997 and from 1998 to 2002. 

Here, t e is the reflectivity of the earth s surface for short wave radiation originating from the sun it is also known as the Albedo in meteorology. t e can be calculated from information about the absorptivity of solar radiation, given in the following section 5.4.5. The reflectivity of the atmosphere is indicated by rAti it is small and, according to [5.42], can be calculated from... 

B are special slits which define and collimate the incident and diffracted beams. The filter is usually placed in a special holder (not shown) in the diffracted, rather than the incident, beam a filter in the diffracted beam not only serves its primary function (suppression of radiation) but also decreases background radiation originating in the specimen. 

Placement of the monochromator in the diffracted beam has the advantage of suppressing background radiation originating in the specimen, such as fluorescent radiation and incoherent (Compton modified) scattered radiation. For example, if a steel specimen or any iron-rich material is examined with copper radiation in an ordinary diffractometer, the background due to fluorescent Fe K radiation will be unacceptably high. But if a monochromator is added and oriented to reflect only Cu Aa, the background is reduced practically to zero, because the fluoresced Fe Kol and Fe K(i do not enter the counter. A monochromator may therefore... 

A primary source is used which emits the element-specific radiation. Originally continuous sources were used and the primary radiation required was isolated with a high-resolution spectrometer. However, owing to the low radiant densities of these sources, detector noise limitations were encounterd or the spectral bandwidth was too large to obtain a sufficiently high sensitivity. Indeed, as the width of atomic spectral lines at atmospheric pressure is of the order of 2 pm, one would need for a spectral line with 7. = 400 nm a practical resolving power of 200 000 in order to obtain primary radiation that was as narrow as the absorption profile. This is absolutely necessary to realize the full sensitivity and power of detection of AAS. Therefore, it is generally more attractive to use a source which emits possibly only a few and usually narrow atomic spectral lines. Then low-cost monochromators can be used to isolate the radiation. 

An activity of 5 mCi (185 MBq) was injected into a healthy beagle dog. Whole body scans were obtained 1, 4 and 24 h post-injection, with an energy window centred on 140 keV but fully open to detect all bremsstrahlung. In most cases, the images could not be evaluated owing to the extremely dispersed nature of the incoming radiation originating from the animal. 

The given concepts also apply to incident radiation. Such radiation originates from emission and reflection occuring at other surfaces and have spectral and directional distributions determined by the spectral intensity Ix,i X, 9, (p). 

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