LOW-ENERGY EXCITATIONS SPECTRUM OF KY(MOO 4)(2)-KER(MOO4)(2)

The low-frequency IR transmission spectra of the system of isostructur al crystals KY1-xErx(MoO4)(2) (x = 0; 0.05; 0.1; 0.2; 0.5; 0.7; 1.0) w ere measured in the energy range from 13 to 40 cm(-1) The interpretati on of the vibrational low-frequency modes was made. It is shown, that the vibrational spectrum of the crystals is adequately represented by the one-dimensional model. A supposition is made of the cross splittin g of the low-frequency acoustic branches of the spectrum due to intera ction with the lowest electronic excitation of Er3+ ions.