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In physics, absorption cross-section is a measure of the probability of an absorption process. More generally, the term cross-section is used in physics to quantify the probability of a certain particle-particle interaction, e.g., scattering , electromagnetic absorption , etc. (Note that light in this context is described as consisting of ...
absorption cross section and scattering cross section are both quantitatively related to the attenuation coefficient; see absorption cross section and scattering cross section for details; The attenuation coefficient is also sometimes called opacity ; see opacity (optics) .
In physics, the cross section is a measure of the probability that a specific process will take place in a collision of two particles. For example, the Rutherford cross-section is a measure of probability that an alpha particle will be deflected by a given angle during an interaction with an atomic nucleus.
The oscillator strength for any transition between ground and excited state depends on these coefficients. The absorption cross-section (σ λ) is empirically determined from this oscillator strength and the broadening of the absorption/emission line by collisions, the Doppler effect and the uncertainty principle.
A collimated beam (directed radiation) with cross-sectional area S will encounter Sℓn particles (on average) during its travel. However, not all of these particles interact with the beam. Propensity to interact is a material-dependent property, typically summarized in absorptivity ϵ [12] or scattering cross-section σ. [13]
Image of a helium-4 nucleus; 4 H has a very small cross-section, less than 0.01 barn.. During Manhattan Project research on the atomic bomb during World War II, American physicists Marshall Holloway and Charles P. Baker were working at Purdue University on a project using a particle accelerator to measure the cross sections of certain nuclear reactions.
The absorption neutron cross section of an isotope of a chemical element is the effective cross-sectional area that an atom of that isotope presents to absorption and is a measure of the probability of neutron capture. It is usually measured in barns. Absorption cross section is often highly dependent on neutron energy. In general, the ...
The oscillator strength is defined by the following relation to the cross section for absorption: [19] = =, where e {\displaystyle e} is the electron charge, m e {\displaystyle m_{e}} is the electron mass, and ϕ ν {\displaystyle \phi _{\nu }} and ϕ ω {\displaystyle \phi _{\omega }} are normalized distribution functions in frequency and ...