Influence of the phase transition in CsDy(MoO4)2 on the electronic spectrum of the Dy3+ ion.

Comparison of the spectra of the two phases, above and below the first order phase transition (∼ 40 °K, has shown that the chane in the small j terms is insignificant, but the spectra of the lowest terms (6H15/2, 6H13/2, and 6H11/2) differ strongly. From the temperature dependence of the intensities of the additional bands in the spectrum we have determined the low-frequency electronic and phonon levels of cesium dysprosium molybdate in the high- and low-temperature phases of the crystal. We propose that acoustic phonons participate in the phase transition.