## Wikipedia - Cross section (physics) (en) Wikipedia - Nuklearni udarni presjek (sr) Wikipedia - Secțiune eficace (fizică) (ro) Wikipedia - سطح مقطع (فیزیک) (fa) reaction cross-section, $$\sigma_{\text{r}}$$

https://doi.org/10.1351/goldbook.R05169
A quantity used in collision theories of reactions in order to interpret calculated or experimental rates. In some collision theories the reaction cross-section is considered to be related to $$b_{\max }$$, the maximum value of the @I02987@ that allows reaction to occur, by: $\sigma _{\text{r}}=P_{\text{r}}\ \pi \ b_{\max }^{2}$ where $$P_{\text{r}}$$ is the @R05176@.
See:
collision cross-section
,
impact parameter
Source:
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 183 [Terms] [Paper]