overlap integral, \(S_{\text{rs}}\)

https://doi.org/10.1351/goldbook.O04357
Integral over space of the type \(\int \psi _{\text{r}}^{*}\ \psi _{\text{s}}\ \text{d}\tau \) where \(\psi_{\text{r}}\) and \(\psi_{\text{s}}\) are different wavefunctions.
Source:
Green Book, 2nd ed., p. 17 [Terms] [Book]