Rydberg transition

An electronic transition described approximately as promotion of an electron from a 'bonding' orbital to a Rydberg orbital. Spectral bands corresponding to Rydberg transitions approximately fit the Rydberg formula:

$σ = I − R ( n − Δ ) 2$

where $σ$ is the wavenumber, $I$ the ionization potential of the atom or molecular entity, $n$ a principal quantum number, $R$ the Rydberg constant, and $Δ$ the quantum defect which differentiates between s, p, d, etc., orbitals. The notation used is, e.g. $π → ns$ .

Source:

PAC, 1996, 68, 2223 (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2272