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In the context of ozone shielding of ultraviolet light, absorption cross section is the ability of a molecule to absorb a photon of a particular wavelength and polarization. Analogously, in the context of nuclear engineering , it refers to the probability of a particle (usually a neutron ) being absorbed by a nucleus.
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]
The mass attenuation coefficient (also called "mass extinction coefficient"), which is the absorption coefficient divided by density; The absorption cross section and scattering cross-section, related closely to the absorption and attenuation coefficients, respectively "Extinction" in astronomy, which is equivalent to the attenuation coefficient
To implement non-degenerate two photon excitation microscopy, two photon pulses of differing energies must be synchronized to interact with a specimen at the sample plane near-simultaneously. Due to the enhanced absorption cross section and VSL, more time is possible for excitation to occur, and thus perfect synchronization is unnecessary.
An absorption line is formed when an atom or molecule makes a transition from a lower, E 1, to a higher discrete energy state, E 2, with a photon being absorbed in the process. These absorbed photons generally come from background continuum radiation (the full spectrum of electromagnetic radiation) and a spectrum will show a drop in the ...
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).
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 ...
The total amount of scattering in a sparse medium is determined by the product of the scattering cross section and the number of particles present. In terms of area, the total cross section (σ) is the sum of the cross sections due to absorption, scattering, and luminescence: