https://doi.org/10.1351/goldbook.R05176
The probability that a reaction occurs when two particles undergo a collision. If \(N_{\rm{c}}\) is the number of collisions occurring in unit time, and \(N_{\rm{r}}\) the number of reactions occurring in unit time: \(P_{\rm{r}}=\frac{N_{\rm{r}}}{N_{\rm{c}}}\).