Exciter Radioactive Source

There are several types of source, e.g. Co, Sm, Gd, and " " Sn, which are applicable for varied samples, respectively. When probing Fe samples, the excited radioactive source Co/Rh ( Co in a rhodium matrix) decays via electron capture with emitted gamma rays at 122 and 14.4 keV with additionally imparted Doppler energy since the source moves relative to the absorber. The source under the control of a velocity transducer can move back and forth with constant velocity, sinusoidally, in a symmetric sawtooth, or any other complicated way therefore, the Doppler energy as well as the energy of gamma quanta can be modified in a controllable marmer. 

XRF spectrometry is based on the principle that primary X-rays (from an X-ray tube or radioactive source) are incident upon a sample and create inner shell (K, L, M) vacancies in the atoms of the surface layers. These vacancies de-excite by the production of a secondary (fluorescent) X-ray whose energy is characteristic of the elements present in the sample. Some of these characteristic X-rays escape from the sample and are counted and their energies measured. Comparison of these energies with known values for each element (e.g., Van Grieken and Markowicz 1993, Parsons 1997) allow the elements present in the sample to be identified and quantified. 

Radioactive sources and particle accelerators are used to initiate polymerizations. Electrons, neutrons, and a-particles (He2+) are particulate radiations, while gamma and X rays are electromagnetic radiations. The interactions of these radiations with matter are complex [Chapiro, 1962 Wilson, 1974]. The chemical effects of the different types of radiation are qualitatively the same, although there are quantitative differences. Molecular excitation may occur with the subsequent formation of radicals in the same manner as in photolysis, but ionization of a compound C by ejection of an electron is more probable because of the higher... 

As described in Section 5.6.2, argon/helium atoms are excited to a metastable state by beta radiation from a radioactive source. The species formed is then capable of ionizing all compounds with a lower ionization potential. The products formed are then subject to an electric field (500-1100 V) and the change in current measured. 

Resonance gamma spectrometry or Mossbauer spectrometry can be used to study the hyperfine interactions between a nucleus and its chemical neighborhood [142], In order to examine these interactions with the help of a Mossbauer spectrometer, the first-order Doppler effect shift of the wave emitted by a moving source is applied. The arrangement used for a Mossbauer spectrometer consists of a radioactive source containing a Mossbauer isotope in an excited state (see Figure 4.54)... 

In conventional Mossbauer spectroscopy, X-rays with energies corresponding to nuclear transitions (5-150keV) can be produced only by use of radioactive sources containing a parent isotope of the absorbing nucleus in an appropriate excited state from which it decays into the ground state with emission of a y-quantum. For spectroscopic applications, the y-radiation must be variable. The chemical perturbations... 

As was stated in Section II.A, the energy resolution of the radioactive sources used in conventional Mossbauer spectroscopy is typically 10 eV. This resolution is determined by the natural line width and the maximum energy range obtained by Doppler-shifting techniques. In the case of synchrotron radiation, the energy resolution, which is related to the time period following the excitation of the isotope, is superior to that in conventional Mossbauer spectroscopy. This period can be as short as 2.8 ps, which leads to an energy resolution of about 10 ° eV. However, the... 

In Table 12, the experimental results of Paic and Pecar [29] are also hsted for comparison. They observed almost 10% decrease for V and about 5% decrease for Cr. These results are much larger than the present theoretical values. Unfortunately there is no description about the chemical forms of the samples they used. It is possible that the chemical forms of their radioactive sources are different from those of the targets for PI. If the chemical forms of the samples are different, the relative ratios become a sum of two effects, the chemical effect and the effect of excitation modes, and can be larger values than those for the latter effect alone. For example, if we choose the smallest value for EC and the largest value for PI from... 

Another result of the low power requirement is that a low-intensity radioactive source, rather than an x-ray tube, can be used to excite the sample. Such sources have made possible various types of simple portable spectrometers, of limited capability but useful for such tasks as alloy sorting and ore prospecting. 

Hehum Ionization (fflD) He atoms excited 1 ng by radioactive source and ionize compounds with low ionization potential 10 Respond to aU gases and vapours except to Ne... 

Recent developments in Mossbauer spectroscopy may also lead to interesting high-pressure applications. Many years ago it was proposed that the special properties of synchrotron radiation could be used to provide nuclear excitation without the use of radioactive sources, and recently progress with modern synchrotron-radiation sources could mean that such experiments could be feasible for Fe. Due to the natural high collimation of the most favourable undulator radiation from synchrotron insertion devices, one can expect that high-pressure measurements will be one of the first applications of this technique, which will eventually be applied to isotopes for which no suitable radioactive sources exist. " ... 

Rb, Mo, Ag. Ba, Tb). In this way a number of excitation lines can be produced. The advantages of these radioactive sources lie in their simplicity and small size as well as their independence ofelectrical power. Thus they are suited to portable instruments. Spectra obtained from fluorescent emission show much better resolution than primary X-ray spectra as they lack the continuum background, figure 8.27. Consequently sensitivity and precision are rather better for fluorescence methods than they are for electron excitation techniques. ... 

Spectra from Radioactive Sources X-radiation is often a product of radioactive decay proccs.ses, Gamma rays, which are indistinguishable from X-rays, are produced in intranuclear reactions, Many a and /3 emission processes (see Section 32A-2) leave a nucleus in an excited state the nucleus then releases one or more quanta of gamma rays as it returns to its ground state. Efearon aipiure or K capture... 

Although it is feasible to excite an X-ray emission spectrum by incorporating the sample into the target area of an X-ray tube, this approach is extremely inconvenient for many types of materials. Instead, excitation is usually accomplished by irradiating the sample with a beam of X-rays from an, X-ray tube or a radioactive source. In this method, the elements in the sample arc excited In absorption of the primary beam and emit their own characteristic fluorescence X-ravs. 

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