Scatter radiations Compton

Fig. 6. Schematic illustration of the relationships of the original y-ray and the scattered radiations for Compton scattering where E is the energy of the incident photon, E is the energy of the recoiling electron, and E is the energy of the scattered photon.

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. 

Experimental chemists are rarely concerned with quantum effects and it s not unusual to find them ignoring this fundamental theory altogether. Even when an effort is made to explore the topic more deeply traditional quantum phenomena like black-body radiation, Compton scattering and even the photoelectric effect may appear to be of somewhat limited importance. Experimentalists who rely on spectroscopic measurements get by with interpretations based on a few simple semi-classical rules, and without ever appreciating the deep significance of quantum theory. Maybe there is a problem with the rigorous mathematical formulation of quantum theory and too little emphasis on quantum effects routinely encountered in chemistry. 

The EMD is closely related to intensities obtained from Compton scattering experiments, in which the obtained distribution depends on the incident wavelength and the scattering angle. The intensity of the scattered radiation is proportional to the theoretically obtained Compton profile given by the equation... 

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... 

The beam of secondary radiation issuing from the sample consists largely of fluorescent radiation, but there are some other weak components present as well. These are coherent scattered radiation, coherent diffracted radiation, and incoherent (Compton modified) radiation. These components appear as a background on which the spectral lines are superimposed. This background is normally low (see Fig. 15-3), but it may become rather high if the sample contains a large proportion of elements of low atomic number, because the sample will then emit a large amount of Compton modified radiation. 

Vol. III. Physical and Chemical Tables (1962). Includes data on characteristic wavelengths, absorption coefficients, atomic scattering factors, Compton scattering, etc. Also treatments of intensity measurements, texture determination, particle size broadening, small angle scattering, and radiation hazards. 

Experimentally, the momentum density is closely connected with the Compton profile, the spectrum of scattered radiation. Within the impulse approximation (Kilby, 1965 Eisenberger and Platzman, 1970), the directional Compton profile is given by... 

Equation (11.3) is valid for a narrow-beam geometry from a point source, and scattered radiations in the absorbing material are excluded. That is, each photon is either completely absorbed or transmitted. In reality, Compton scattering of 511 keV photons occurs within the shielding material, and some... 

Electrons also scatter radiation by another effect, the Compton effect. Compton scattering adds to the general background of scattered X-rays, and is usually ignored in structure determination. 

What is called the Compton effect is accounted for. When photons are scattered by matter their momentum is changed, presumably in accordance with the ordinary laws of impact. Since the momentum is hvjc, a calculable change of frequency is observed in the scattered radiation. 

According to Eq. (26.15), the linear attenuation coefficient for the Compton event can be separated into that due to absorption and that due to scattered radiation, so that... 

The most informative probe to extract the detailed hydride s band structure is a beam of particles with energy and momentum comparable to that of the band electrons. The obvious choice, the low energy electron beam, is not applicable in the condensed matter bulk properties studies, because its shallow penetration. Other choices, such as the photon beam emission and absorption spectroscopy, can provide information either about the electron s energy or about the electron s momentum, but not for both at the same time, because the photon dispersion relation is generally quite different from that of the band electrons. This is not however the case in Compton spectroscopy, where the spectra of incoherently scattered radiation are more informative because the probing "particle" has energy... 

Thus, the contribution of coherent and non-coherent (Compton) scattering in attenuation of primary radiation and fluorescence increase in comparison with the solid samples. 

Detection limits for various elements by TXRF on Si wafers are shown in Fig. 4.13. Synchrotron radiation (SR) enables bright and horizontally polarized X-ray excitation of narrow collimation that reduces the Compton scatter of silicon. Recent developments in the field of SR-TXRF and extreme ultra violet (EUV) lithography nurture our hope for improved sensitivity down to the range of less than 10 atoms cm ... 

We are interested in the transmission of y-quanta through the absorber as a function of the Doppler velocity. The radiation is attenuated by resonant absorption, in as much as emission and absorption lines are overlapping, but also by mass absorption due to photo effect and Compton scattering. Therefore, the number Tt E2)AE of recoilless y-quanta with energies EXo E + AE traversing the absorber is given by... 

The thickness of a Mossbauer sample affects not only the strength of the Mossbauer signal but also the intensity of the radiation arriving at the detector because the y-rays are inherently attenuated by the sample because of nonresonant mass absorption caused by the photo effect and Compton scattering as mentioned earlier. The counting rate C in the detector decreases exponentially with the density of the absorber,... 

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