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A gamma ray cross section is a measure of the probability that a gamma ray interacts with matter. The total cross section of gamma ray interactions is composed of several independent processes: photoelectric effect, Compton (incoherent) scattering, electron-positron pair production in the nucleus field and electron-positron pair production in the electron field (triplet production).
A typical absorption cross-section has units of cm 2 ⋅molecule −1. In honor of the fundamental contribution of Maria Goeppert Mayer to this area, the unit for the two-photon absorption cross section is named the "GM". One GM is 10 −50 cm 4 ⋅s⋅photon −1. [1] [2]
The knowledge of the cross section of a material can help to detect thin layers or 1D nanowires over a substrate. A right choice of the photon energy can enhance a small amount of material deposited over a surface, otherwise the display of the different spectra won't be possible. [1]
This cross section depends on the energy of the photon (proportional to its wavenumber) and the species being considered i.e. it depends on the structure of the molecular species. In the case of molecules, the photoionization cross-section can be estimated by examination of Franck-Condon factors between a ground-state molecule and the target ion.
The best previous constraint on the elastic photon–photon scattering cross section was set by PVLAS, which reported an upper limit far above the level predicted by the Standard Model. [10] Observation of a cross section larger than that predicted by the Standard Model could signify new physics such as axions , the search of which is the ...
Mass attenuation coefficients of selected elements for X-ray photons with energies up to 250 keV. The mass attenuation coefficient, or mass narrow beam attenuation coefficient of a material is the attenuation coefficient normalized by the density of the material; that is, the attenuation per unit mass (rather than per unit of distance).
Two-photon absorption is a third-order process, with absorption cross section typically several orders of magnitude smaller than one-photon absorption cross section. Two-photon absorption was originally predicted by Maria Goeppert-Mayer in 1931 in her doctoral dissertation. [2]
Klein–Nishina distribution of scattering-angle cross sections over a range of commonly encountered energies. Electron-photon scattering cross section In particle physics , the Klein–Nishina formula gives the differential cross section (i.e. the "likelihood" and angular distribution) of photons scattered from a single free electron ...