From a phenomenological point of view, the term has been used to describe long-lived @L03641@. In mechanistic @P04588@, the term designates @L03641@ involving change in spin multiplicity, typically from triplet to singlet or vice versa. The @L03641@ from a @Q04993@ to a @D01853@ is also phosphorescence.
PAC, 1984, 56, 231. (Nomenclature, symbols, units and their usage in spectrochemical analysis-Part VI: molecular luminescence spectroscopy) on page 233 [Terms] [Paper]
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2258 [Terms] [Paper]
See also:
Orange Book, 2nd ed., p. 184 [Terms] [Book]