A nuclear system is treated in which a forbidden beta decay leads to a state metastable against gamma-ray emission. Considering both the beta and isomeric transitions to be accelerated by an applied electromagnetic field, the rate equation for emission from the isomeric state is solved for the case where the nucleus is subjected to alternating episodes of field on and field off. There are important qualitative differences in the solution between the cases where enhancement of the beta transition rate dominates enhancement of the isomeric transition rate, and vice versa. Application is made to the example of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Cs}$.

• Received 11 December 1984

DOI:https://doi.org/10.1103/PhysRevC.31.2238