Coherent γ-ray optics

With the advent of high brightness synchrotron radiation sources, an important new field has been opened up involving coherent nuclear excitations induced by synchrotron radiation pulses traversing a piece of matter. We review the theory of coherent resonant gamma-ray optics, including some of the interesting new phenomena which occur when systems of nuclei are excited by synchrotron radiation pulses, such as the creation of nuclear exciton states, superradiant and subradiant decay, spatially coherent quantum beats, and temporal Pendellosung. We also discuss the relation between the nuclear exciton states and multi-photon Dicke superradiance and gamma-ray lasers, and comment on neutron phasors and neutron superradiance in resonant neutron optics. The interesting features of coherent enhancement, superradiant decay, and dynamical beats are discussed from the fundamental perspective of the radiative normal modes of a system of nuclear resonators.