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