Incoherent photon echo in 7Li Y F$_4:^{167}$ Er3+

The effect of an incoherent photon echo is studied experimentally and theoretically in (LiYFEr3+)-Li-7 crystal ( transition). This is considered as a promising material for Raman optical quantum memory due to the extremely narrow optical transitions. Oscillations of the photon echo intensity versus the external static magnetic field are observed. The theory shows that the oscillation period is very sensitive to one of the parameters of the spin Hamiltonian in the excited state, thereby making the incoherent photon echo convenient for spectroscopic measurements.