https://doi.org/10.1351/goldbook.R05431
For an atom, an orbital with principal quantum number greater than that of any occupied orbital of the @[email protected] For a molecular entity, a @[email protected] which correlates with a Rydberg atomic orbital in an atomic fragment produced by @[email protected] Typically, the extension of the Rydberg orbital is large compared to the size of the atom or molecular entity.