Observation of resonant relaxation of acoustic phonons by vibronic anti-Stokes luminescence in doped crystals
Akimov A. V. , Kaplyanskii A. A., Syrkin A. L.
We report experiments on the direct observation of nonequilibrium acoustic phonons generated in the nonradiative relaxation of electronic excitation of the impurity ions in the doubly activated crystals CaF2-Eu2+, Sm2+. Resonant phonons at ~ 1 THz given off in transitions between the electronic levels of the Eu2+ ion are detected by the vibronic luminescence of the Sm2+ ion.