n → σ* transition

An electronic transition described approximately as promotion of an electron from a 'non-bonding' (lone-pair) n orbital to an 'antibonding' σ orbital designated as σ*. Such transitions generally involve high transition energies and appear close to or mixed with Rydberg transitions.
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2255 (https://doi.org/10.1351/pac199668122223)