https://doi.org/10.1351/goldbook.E02116
From a phenomenological point of view, the term is used to describe the process by which a molecular entity absorbs light and a phenomenon originates from the
excited state
of another molecular entity. In mechanistic photochemistry
the term has been reserved for the photophysical process in which an excited state
of one molecular entity (the donor) is deactivated to a lower-lying state by transferring energy to a second molecular entity (the acceptor) which is thereby raised to a higher energy state. The excitation may be electronic, vibrational, rotational or translational. The donor and acceptor may be two parts of the same molecular entity, in which case the process is called intramolecular
energy transfer.See also:
Dexter excitation transfer
, Förster excitation transfer
, radiative energy transfer
, spectral overlap