Photoinduced Local Lattice Vibrations in a Ruby Crystal under Optical Pumping of the 2T1 State

The oscillatory behavior of a heavy substitutional impurity (Cr³⁺) in Al₂O₃ has been studied by the Brillouin scattering method. The oscillations of chromium ions are carried out by their photoexcitation. Discrete shifts of the ruby luminescence lines R₁ and R₂ at room temperature depending on the absorbed laser pump power upon excitation of the ²T₁ state observed for the first time. These shifts are caused by the excitation of quasi-local vibrations of chromium ions. The frequency of quasi-local oscillations is equal to 22 GHz, which corresponds to transverse acoustic oscillations in ruby. An explanation of the observed phenomenon is given based on the Born–Oppenheimer adiabatic approximation and the Pekar function.