Gamma quanta

Internal Conversion—Process in which a gamma ray knocks an electron out of the same atom from which the gamma ray was emitted. The ratio of the number of internal conversion electrons to the number of gamma quanta emitted in the de-excitation of the nucleus is called the "conversion ratio."... 

Broser, L Kallmann, H. On the elementary process of light excitation in phosphors by ot particles, fast electrons, and gamma quanta. Z. Naturforsch. 1950, 2A, 439. 

If we denote the conversion coefficient as Oj, it is equal to the ratio of K-electrons ejected (which we may denote with to that of gamma quanta emitted (7 ) ... 

The reaction shown in Fig. 5 is an example of a topo-chemical polymerization in which conjugate, 1,4-addition of 1,3-diyne units take place in the crystalline state. The reaction is performed by irradiating the crystals with visible or ultraviolet light. X-rays or gamma quanta, or by annealing the crystals at a temperature below their melting point. The unreacted monomer is then removed by extraction with a suitable solvent and leaves behind a single deeply coloured polydiacetylene crystal. This unique polymerization process has been intensively studied and has been the subject of many reviews [15]. 

The correlation between successive gamma quanta arising for instance in the de-excitation of an excited nucleus formed by radioactive decay is relatively... 

The presence of extended collimator essentially lowered the possibility ofthe resonance detector being entered by that very small part of gamma quanta (with a small possible spectrum self-broadening) that were emitted by the source at a big angle from the direction to the detector. Such quanta, having passed the path in the resonance absorber volume greater than its optical width for the direct beam quanta, could be scattered in the resonant detector direction and lead to a very small additional broadening of the measured spectral line of radiation. 

The influence of spatial position of nonresonant totally absorbing screen (6) upon the intensity of direct beam of gamma quanta filled circles—screen is put around the resonant absorber empty circles—screen is taken off. The case (a) corresponds to the source (1) situated in the center of the resonant absorber / = 2.5 cm) and the case (b)— the source is at /= 1 cm. 

In the second case, another cylinder (6) made of lead with diameter D = 2.2 cm, length L = 5 m, and thickness AR = 0.2 cm was put around the resonant absorber cylinder. It totally absorbs both resonant and nonresonant radiation in the range of energies close to Ey = 14.4 keV. This corresponds to completely nonselective absorber and leads to the intensity of registered flux of gamma quanta Jy, and N = J At. 

Such method excludes the uncontrolled influence of reverse scattering of resonant gamma quanta after changing resonant absorption to nonresonant (which would occur when resonant absorber cylinder is simply taken off the source). Each measurement lasted At= 100s. The results of measurements are presented in Fig. 14.6. 

I n fact, considering the scattering of nonresonant gamma quanta (in region Ey = 14.4 keV) from lead absorber, which increases this increase of lifetime r is even greater. 

UDPG-04R is intended for measurement of volumetric activity of gamma-radiation of radionuclides in live steam when the device is located in the close vicinity to the steam line under control. Recording of gamma-quanta is performed with the use of scintillation detection unit. The device may operate in the channel of an automated information and measuring system with the following kinds of measurements ... 

Figure 5.1 Schematic illustration of recording the resonance absorption line in a Mossbauer spectroscopy experiment and relative transmission of gamma quanta as a function of Doppler velocity. 2000 lOP Publishing Ltd.

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. 

In the course of Mossbauer measurement, the energy of gamma quanta is ordinarily modulated by a mechanical movement of the source relative to the absorber. The spectrum is essentially a plot of Mossbauer transition count rates as a function of velocity of the source relative to the absorber. If no resonance occurs, the spectrum would be a horizontal line with no variations while resonance occurs, there would be a decrease in the intensity at certain velocity values as shown in Figure 5.4. In interpreting the spectrum the Mossbauer parameters can be obtained, i.e. the isomer shift, the electric quadruple splitting, and the magnetic dipole splitting. 

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