Photoinduced local lattice vibrations in a ruby crystal under optical pumping of the 2T1 state

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