Absorption spectra peculiarities at the Jahn-Teller ordering in KDy(MoO4)(2)

The absorption spectra of KDy(MoO4)(2) are studied in the region of the low -temperature phase transition of cooperative Jahn-Teller ordering type. The parameters of the fine structure components of the absorption spectrum man ifest anomalies of different type in the temperature region 20-8K. Possible low-temperature phases accompanied with the doubling of the unit cell of i nitial rhombic phase D-2h(14) are analysed. It is shown that the Jahn-Telle r pseudo-effect occurs in KDy(Moo(4))(2) due to the interaction between the electron states of Dy3+ ions and the strains in the "pre-transition" tempe rature region.