Polarized IR and Raman spectra of kdy(moo4)2 single crystals,and the 92MO-100MO isotope effect

Polarized IR and Raman spectra below 4000 cm^?1 for single crystals of KDy(MoO₄)₂ are presented and discussed in relation to molecular and crystal structures. The spectroscopic data indicate additional intermolecular interactions due to pair coupling of the molybdate tetrahedra. This effect, combined with the multilayer crystal structure, is found to restrict the vibrational degrees of freedom, disturbing the selection rules for vibrational transitions. The spectra of first and higher-order transitions are described on the basis of ⁹²Mo/¹⁰⁰Mo isotopic-exchange effects and Y/Dy and K/Na substitutions.