excimer

An electronically excited dimer, 'non-bonding' in the ground state. For example, a complex formed by the interaction of an excited molecular entity with a ground state partner of the same structure.
See also: exciplex
Source:
PAC, 1996, 68, 2223 (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2240
PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1114