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An isotropic electromagnetic field in a plasma of thermalized electrons undergoes changes in energy as a result of Compton scattering and an Einstein–Hopf drag force on the electrons, eventually approaching a Bose–Einstein photon distribution at the electron temperature. The rate of change of field energy due to the combined effects of Compton scattering and the drag force is shown to be described by the Kompaneets equation for photon diffusion in frequency space. A similarity is noted between this approach and Einstein's derivation of the Planck spectrum based on the recoil of atoms as they absorb and emit radiation. [ABSTRACT FROM AUTHOR]

The bismuth-based non-toxic and lead-free alloys have been investigated for their advanced photon attenuation and photon energy absorption characteristics over wide γ -ray energy regime from 1 keV to 20 MeV. For this study, we selected five bismuth containing alloys with composition: Bi50Sn (50 - x) Znx where x = 0 , 10 , 20 , 30 , 40 wt. % . The mass attenuation coefficient values computed by theoretical approach using the WinXCom software package show marked difference from the mass energy-absorption coefficient values particularly in the energy regime dominated by the Compton effect (CE). Photon interaction (attenuation) effective atomic number (Z PIeff ) and photon-energy absorption effective atomic number (Z PEAeff) values were compared for their mean, maximum and minimum values computed for these alloys. The optimum thickness range analysed using the attenuation and absorption coefficient values indicate saturation with respect to photon energy spanning Compton effect (CE) and pair-production (PP) processes. Kinetic energy released per unit mass of the absorbing material (KERMA) relative to air calculations indicated significant influence of the elemental composition of these alloys in the intermediate photon energy regime. We also performed calculations for the air-KERMA or exposure build-up factors of these Bi–Sn–Zn alloy compositions done within the framework of novel EXABCal programme code. The calculated exposure build-up factor was found to be minimum for the alloy composition Bi50Sn50. Present investigation of photon interaction and photon energy absorption characteristics would be of interest for addressing shielding efficiency of lead-free and environment friendly bismuth containing alloy systems. [ABSTRACT FROM AUTHOR]

The Compton profiles of methane and ethane molecules have been determined at an incident photon energy of 20 keV based on the third generation synchrotron radiation, and the statistical accuracy of 0.2% is achieved near pz = 0. The density functional theory with aug-cc-pVTZ basis set was used to calculate the Compton profiles of methane and ethane. The present experimental Compton profiles are in better agreement with the theoretical calculations in the whole z region than the previous experimental results, which indicates that the present experimental Compton profiles are accurate enough to serve as the benchmark data for methane and ethane molecules. [ABSTRACT FROM AUTHOR]