Radiation Sources table

Si 2p line, at about 100 eV BE, is also easily accessible at most synchrotron sources but cannot, of course, be observed using He I and He II radiation. On the other hand, the Zn 3d and Hg 4f lines can be observed quite readily by He I radiation (see Table 1) and the elements identified in this way. Quantitative analysis using relative peak intensities is performed exactly as in XPS, but the photoionization cross sections a are very different at UPS photon energies, compared to A1 Ka energies, and tabulated or calculated values are not so readily available. Quantitation, therefore, usually has to be done using local standards. 

TABLE 9.2. Effect on Humans from Two Radiation Source Models... 

Potential Mossbauer isotopes for nuclear resonance scattering, which are within the spectral reach of synchrotron radiation sources, are summarized in Table 9.5 [118-120], and the synchrotron radiation sources which provide dedicated beam lines for specific Mossbauer isotopes are listed in Table 9.6 (adopted from [85]). 

Table 9.5 Potential Mossbauer isotopes for nuclear resonance scattering, which are within the spectral reach of currently available synchrotron radiation sources...

Table 9.6 List of synchrotron radiation sources which provide dedicated nuclear resonance beamlines for specific isotopes...

Table 4.1. Performance of available point-focus setup. DORIS is an older storage ring at HASYLAB in Hamburg. The ESRF in Grenoble is an advanced synchrotron radiation source... 

If these concepts of curve analysis shall be applied to the anisotropic scattering of polymer fibers, one should choose to study either the longitudinal or the transversal density fluctuations. According to the decision made, the fiber scattering must be projected either on the fiber axis or on the cross-sectional plane. This results in scattering curves with a one- or a two-dimensional Porod s law. Because modern radiation sources always feature a point-focus, the required plots for the separation of fluctuation and transition zone are readily established (cf. Table 8.3). 

Typical irradiation facilities consist of a process chamber containing the radiation source, some sort of conveyor systems to transport products inside and outside the shielding walls, and sophisticated control and safety systems. Irradiation facilities are built with several layers of redundant protection to detect equipment malfunctions and protect employees from accidental exposure. Technical details depend on the type of irradiation. Typical processing parameters are compared in Table 2 [7]. 

Synchrotron radiation sources are ideal for this purpose, since they allow a continuous variation of excitation energy in a wide range. Usually a combination of UPS and XPS is employed, which allows a series of excitation energies in UV in the 10-48 eV range. Typical excitation energies for the laboratory case are presented in Table 1. 

There are two general classes of photoinitiators (1) those that undergo direct photofragmentation on exposure to uv or visible light irradiation and produce active free radical intermediates and (2) those that undergo electron transfer followed by proton transfer to form a free radical species. The choice of photoinitiator is determined by the radiation source, the film thickness, the pigmentation, and the types of base resin employed. Examples of typical photoinitiator systems used to cure reactive resins are shown in Table 14.2. Benzophenone is perhaps one of the most common photoinitiators. 

For a CCD detector the absorbance noise is independent of the spectral bandwidth, but it depends on the number of measurement pixels sam and reference pixels ref in such a way that sam should be as small as possible and rel should be larger than sam. The other component that influences the noise is the intensity I of the radiation source, in that the absorbance noise is inversely proportional to the square root of I [12]. As the intensity of the radiation source in CS AAS is in some cases up to two orders of magnitude higher than that of a typical LS for conventional AAS, an improvement in the SNR and limits of detection (LoD) by factors of 3-10 could be expected, unless other factors, such as flame noise, become dominant. The values given in Table 4.1 show that this expectation has in fact been realized for the majority of the elements. 

The reactive intermediates in the charge-transfer photochemistry of contact ion pairs can be identified by their time-resolved spectra immediately following the application of a 10-nsecond pulse consisting of the second harmonic at 532 nm of a mode-locked Nd3+-YAG laser (27). The wavelength of this radiation source is ideally suited for the specific excitation of the contact ion pairs (see Table II). Accordingly, the time-resolved spectra from Cp2Co+ Mn(CO)5- and Cp Co Co(CO)4- (Fig. 3) relate directly to the charge-transfer photochemistry. Most notably, the intense... 

At NS 175 local radiation sources above other compartments were also revealed mainly due to specific effects of RC. The results of performed measurements are generalized in Table 2. 

The radiant flux through a spectrometer at a given bandwidth equals = Lj Lj)-G A and B define a black body at higher and lower temperature, re.spectively. A radiant flux flows from the hot to the cold Planck black body, i.e., a radiation source, the sample, or the detector. Combinations of practical significance are listed in Table 3.4-3. 

Table 7.1. Comparative Characteristics of Energetic Radiation Sources...

Table 1. Comparison of existing synchrotron radiation sources. E particle energy, R magnetic radius, I maximum current, critical wavelength (Eq. 2-4) ... 

Further details about the different synchrotron radiation sources can be obtained from Table 1 and from the literature. 

The dose rate constant ky for y radiation depends on the energy of the y rays and on the decay scheme of the radionuclide. Values of ky for various radionuclides are listed in Table 22.3. For rough estimation, it is useful to know that a point-like radiation source of 1 GBq emitting y rays with energies of 1 MeV transmits an ion dose rate of about 0.03 R h at a distance of 1 m. 

Average equivalent dose rates received from natural radiation sources are listed in Table 22.8. The values vary appreciably with the environmental conditions. The influence of cosmic radiation increases markedly with the height above sea level, and terrestrial radiation depends strongly on the local and the living conditions. 

Table 22.8. Average radiation exposure by natural radiation sources.

Average equivalent dose rates due to artificial radiation sources are listed in Table 22.9. These dose rates originate from application of X rays and radionuchdes for diagnostic and therapeutic purposes, from various radiation sources applied in daily life and from radioactive fall-out. 

Table 22.9. Radiation exposure by artificial radiation sources.

Their stock of alpha radiation sources are listed in Table 4.18. 

Radiation sources including X-rays, y-rays, and ultraviolet produce preferential light absorption at color centers in glass by formation of free electrons and holes. These are trapped at a defect such a vacancy, an interstitial atom, a multivalent impurity, or a nonbridging oxygen T The types of color center induced in siliea, soda-lime-silica, borate, and phosphate glasses are elucidated by optical and electron spin resonance studies of irradiated samples. Table 1 summarizes composition variables and reaction types that induce damage. 

A summary of the contributions of the various natural and man-made radiation sources to our radiation background is given in Table 3. It can be seen that natural sources contribute 82% of the total, with radon being the largest single source (67% of natural radiation dose). Of the 18% contributed by man-made sources, medical exposure is the most prominent (83%). Attempts to significantly reduce population radiation doses would most likely be focused on the largest contributors, that is, indoor radon and medical radiation. 

A comprehensive list of the world s synchrotron radiation sources, including many still on the drawing boards, can be found at many of the web-sites maintained by the Light Sources (e.g. http //www.nsls.bnl.gov/AccPhys/synchros.htm). Table 1 provides the web addresses for some synchrotron facilities. These sites provide up to date information on characteristics of the beams provided, key experimental expertise, future construction plans, and resources for users including how to obtain access. 

Choice of X-ray radiation copper Ka is the most popular radiation source used in diffractometry because of its short wavelength. Table 2.4 lists the detection limitations of X-ray radiations commonly used in diffractometry and... 

Limitations to the spectroscopic measurement of the temperatures from line intensities lie in possible deviations from ideal thermodynamic behavior in real radiation sources, but also in the poor accuracy of transition probabilities. They can be calculated from quantum mechanics, and have been determined and compiled by Corliss and Bozman at NIST [10] from measurements using a copper dc arc. These tables contain line energy levels, transition probabilities and the so-called oscillator strengths for ca. 25000 lines between 200 and 900 nm for 112 spectra of 70 elements. Between the oscillator strength f (being 0.01-0.1 for non-resonance and nearer to 1 for resonance lines) there is the relationship [11] ... 

In addition, spectral line tables, in which the wavelengths of the spectral lines together with their excitation energy and a number indicating their relative intensity for a certain radiation source are tabulated, are very useful. They are available for different sources, such as arc and spark sources [330-332], but also in a much less complete form for newer radiation sources such as glow discharges [333] and inductively coupled plasmas [334],... 

Apart from the high power of detection, also the realization of the highest analytical accuracy is very important. This relates to the freedom of interferences. Whereas the interferences stemming from influences of the sample constituents on the sample introduction or on the volatilization, ionization and excitation in the radiation source differ widely from one source to another, most sources emit line-rich spectra and thus the risks for spectral interferences in AES are high. In the wavelength range 200-400 nm, as an example, only for arc and spark sources have more than 200 000 spectral lines yet been identified with respect to wavelength and element in the classical MIT Tables. Consequently, spectral interferences are much more severe than in AAS or AFS work. 

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