Temporal optics of recoil-free gamma radiation

A discussion is given of the time-behavior of recoil-free γ-radiation passing through a resonant medium. The classical dispersion theory of Hamermesh is extended to account for different linewidths in source or absorber so that a synchrotron-radiation source can be simulated. A result, essentially the same as that of Kagan et al., follows in the limit of large source width. A review is given of the quantum beats which result from the absorption of one line of a frequency-modulation spectrum. An example is given of the measurement of second-order Doppler shift in Fe-Be by the method of quantum beats. Finally, there is a discussion of the measurement by quantum beats of the very small energy shift in a 57Co-Cu source by a magnetic field. (orig.)