Three types of delayed @F02453@ are known:
- E-type delayed @F02453@: The process in which the first excited @S05699@ becomes populated by a thermally activated @R05057@ from the first excited @T06503@. Since in this case the populations of the singlet and triplet states are in thermal equilibrium, the lifetimes of delayed @F02453@ and the concomitant @P04569@ are equal.
- P-type delayed @F02453@: The process in which the first excited @S05699@ is populated by interaction of two molecules in the @T06503@ (triplet-triplet @A00366@ ) thus producing one molecule in the excited @S05699@. In this @B00669@ the @L03515@ of delayed @F02453@ is half the value of the concomitant @P04569@.
- Recombination fluorescence: The first excited @S05699@ becomes populated by recombination of @R05073@ with electrons or by recombination of radical ions of opposite charge.