Time spectra of a nearly-single-line pure nuclear reflection excited by synchrotron radiation

The time dependence of the coherent response of a ${}_{}{}^{57}{}_{}{}^{}\mathrm{FeBO}_3^{}{}_{}{}^{}$ single crystal excited by synchrotron-radiation (SR) pulses was studied in the pure nuclear (333) Bragg reflection near the Néel temperature, where the Mössbauer reflection spectrum consists of nearly a single line of almost natural linewidth. The time spectra revealed a delayed reemission of γ quanta into the Bragg direction starting at zero intensity. This behavior was determined by two factors: the coherent decay of the nuclear excited state and the interference of two nearly coinciding hyperfine components.