heavy atom effect

The enhancement of the rate of a spin-forbidden process by the presence of an atom of high @A00499@, which is either part of, or external to, the excited molecular entity. Mechanistically, it responds to a @S05870@ enhancement produced by a heavy atom.
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2245 [Terms] [Paper]