Storage of Nuclear Excitation Energy through Magnetic Switching

The decay rate of ${}^{57}\mathrm{Fe}$ nuclei in an ${}^{57}{\mathrm{FeBO}}_3$ crystal excited by 14.4 keV synchrotron radiation pulses was controlled by switching the direction of the crystal magnetization. Abrupt switching some nanoseconds after excitation suppresses the coherent nuclear decay. Switching back at later times restores it, starting with an intense radiation spike. The enhanced delayed reemission is due to the release of the energy stored during the period of suppression. Suppression and restoration originate from drastic changes of the nuclear states and of the interference within the nuclear transitions.