Hyperfine Modulation of the Shape of the Primary and Stimulated Photon Echoes' Signals in Ruby in the Permanent Magnetic Field

The modulation of the temporal shape of the primary (PPE) and stimulated (SPE) photon echoes is for the first time observed in natural and enriched ruby in slow magnetic field. The modulation period is equal to 20 ns. This modulation can be explained by means of the hyperfine interaction of valent electrons of $^{53}$Cr-isotope with its own nuclei (the spin of which is equal to 3/2). The new echo-experiment is carried out on the sample of ruby enriched by isotope $^{53}$Cr$^{3+}$, in permanent magnetic field (200 G). The temporal decay of PPE and SPE are researched, and the time of phase relaxation (which is obliged of spectral diffusion) is estimated. The spectrum of SPE-signal in the ruby in magnetic field is investigated.