QuoteFor particle physicists whose entire standard model assumes that decay rates cannot be influenced by external factors, the Purcell effect is a puzzle.
The Purcell effect is the enhancement of a quantum system's spontaneous emission rate by its environment. In the 1940s Edward Mills Purcell discovered the enhancement of spontaneous emission rates of atoms when they are incorporated into a resonant cavity. It has nothing to do with radioactive decay rate and its theory is elaborated well.