Inhibited spontaneous emission in solid-state electronics (A)

It has been recognized for some time1 that the spontaneous emission of atoms is not necessarily a fixed and immutable property of coupling between matter and space but that it can be controlled by modifying the properties of the radiation field. Recently there have been experiments in which the spontaneous emission of Rydberg atoms2 and Penning trapped electrons3 has been inhibited in a microwave cavity which had no electromagnetic modes at the transition frequency.