Experimental measurements of K and L3 subshell jump ratios and photon-attenuation Co-efficients in different media

Abstract

Interaction of electromagnetic radiation with matter is a complex phenomenon. Unlike charged particles, a well-collimated beam of gamma-rays shows a truly exponential absorption in matter. When the photon interacts with matter, it might be absorbed or scattered, with or without loss of energy while changing its direction of travel. Interactions of these photons with matter are thought to be independent of the mode of origin of the photon and dependent only upon its quantum energy. Various possible processes by which the electromagnetic field of the gamma-rays interact with matter are photoelectric absorption, Compton scattering, pair production, Rayleigh scattering, Thomson scattering by the nucleus, Delbruck scattering, Nuclear scattering resonance, Photodisintegration of nuclei, Meson production etc. Many of these processes are quite infrequent, and some have not yet been observed. However, in low energy region, photoelectric absorption, Compton scattering, and pair production are the prominent modes of interactions. In photoelectric interaction, if the energy of the incident photon is less than 0.1MeV, variation of the photoelectric cross-section with incident photon energy shows sharp discontinuities. These discontinuities are due to absorption edges and occur when a photon impinging on an atom carries energy just above the binding energy of the electron of a specific shell/sub-shell (K, LI, LII or MI etc). In this way the probability of interaction between photon and electron of a particular shell/subshell (K, LI, LII or MI etc) increases suddenly, which results into an abrupt change in the value of photoelectric cross-section. Ratio of values of photoelectric cross-section on the higher energy to that of lower energy side of an edge of a particular shell/subshell is called jump ratio of that shell/subshell. However, if the energy of the incident photon liesbetween 0.5 MeV to 5 MeV, Compton scattering and pair production plays a dominating role in interaction process.