luminescence

https://doi.org/10.1351/goldbook.L03641
spontaneous emission of radiation from an electronically or vibrationally excited species not in thermal equilibrium with its environment.
See also: bioluminescence, chemiluminescence, electro-generated chemiluminescence, fluorescence, phosphorescence, photoluminescence, radioluminescence, sonoluminescence, thermoluminescence, triboluminescence
Sources:
PAC, 1994, 66, 2513. 'Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)' on page 2522 (https://doi.org/10.1351/pac199466122513)
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2252 (https://doi.org/10.1351/pac199668122223)
See also:
Orange Book, 2nd ed., p. 184 (http://media.iupac.org/publications/analytical_compendium/)
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2200 (https://doi.org/10.1351/pac199062112167)