Nuclear Isomer Research with FEL-Compton Scattering Photons

Publisher Summary When an isomer decays, the stored energy is usually released by emission of α, β, or γ rays. Gamma-ray transitions, which occur within the same nucleus, usually have transition strength larger than α or β decay. However, if the γ-ray half-life is long, the α or β-transition can proceed in competition with the γ decay. This is commonly seen at the lower excitation energy. The spin and parity selection rule governs the decays for that type of isomers. In case the transitions involve a larger spin difference and/or parity change, the isomer half-life increases depending on the branching ratios and the energies of transitions decaying out of the isomer. This chapter describes the processes of the photo-induced excitation or de-excitation of the isomers through intermediate K-mixing states. It discusses the photo-induced population and depopulation of the isomers in 176 Lu and 180 Ta. The chapter illustrates the use of photons generated by a superconducting wiggler at SPring-8 and by a laser-Compton scattering with free-electron Laser.