Coherent transients with a single photon

Reversible coherent transients induced by a single photon in an ensemble of resonant particles are considered. It can be shown that a phase shift of a single photon wave packet produces its re-emission by these particles. As an example, the resonant interaction of a single gamma-photon with Mössbauer nuclei is theoretically analyzed. This example has interesting applications in such areas as information transmission and measuring of sub-angstrom vibrations of thin films for creating of sub-angstrom etalon displacements, which can be used for sensor calibration. We show that coherent transients that are governed by the time evolution of a population of nuclear excited states can be detected not only in the transmission of photons through resonant absorbers, but also directly in the time evolution of a population of nuclear excited states. These states experience radiative decay and also emit conversion electrons. The detection of conversion electrons provides information about the excited state population of nuclei located nearby the surface of the radiation incidence on the absorber. This is because of short mean free path (or escape depth) of these electrons in the bulk.