electron transfer for which the relevant electronic interaction between the donor and acceptor sites is mediated either by direct orbital overlap or by superexchange interaction via intervening molecular entities not covalently bound to the donor or acceptor sites.
See also: through-bond electron transfer
Source:
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2280 (https://doi.org/10.1351/pac199668122223)