triplet-triplet annihilation
Two atoms or molecular entities both in a @T06503@ often interact (usually upon collision) to produce one atom or molecular entity in an excited @S05699@ and another in its ground @S05699@. This is often, but not always, followed by @D01579@.
See also:
annihilation (in radiochemistry, in photochemistry)
spin conservation rule
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2281 [Terms] [Paper]