IR AND POLARIZED RAMAN-SPECTRA OF A SINGLE-CRYSTAL RB3H(SEO4)(2) IN THE FERROELASTIC PHASE

Infrared and polarized Raman spectra of a single crystal Rb3H(SeO4)(2) and the polycrystalline spectra of its deuterated analogue are record ed and analysed. Bands indicate the existence of SeO42- ions and HSeO4 - ions, in agreement with a non-centrosymmetric dimer in the crystal. The difference between v(Se-O) and v(Se-OH) bands is a measure of the hydrogen bond strength and it decreases on deuteration. The presence o f an absorption continuum along with a transmission window shows that the proton motion is coupled with those of the oxygen atoms in the SeO 42- ions. The ABC bands in the OH stretching region also support stron g hydrogen bonding in the crystal. The lower wave numbers for the stre tching OH mode show that the dimer formation is quite anharmonic, as j udged from the isotopic shift.