## microscopic cross-section, $$\sigma$$

https://doi.org/10.1351/goldbook.M03911
A measure of the @[email protected] of a specified interaction or reaction between an incident radiation and a target particle or system of particles. It is the reaction rate per target particle for a specified process divided by the @[email protected] of the incident radiation. In general, a specification is added of the type of radiation (e.g. @[email protected], photon), the @[email protected] of the incident radiation (e.g. thermal, epithermal, fast) and the type of interaction of reaction (e.g. @[email protected], @[email protected], @[email protected]).