VIBRATIONAL-SPECTRA OF NH4SM(SO4)(2)CENTER-DOT-4H(2)O AND NH(4)LN(SO4)(2)CENTER-DOT-2H(2)O[LN=YB, TM]

The IR and Raman spectra of a single crystal NH4Sm(SO4)(2) . 4H(2)O an d that of two polycrystalline compounds NH(4)Ln(SO4)(2) . 2H(2)O [Ln = Yb, Tm] have been recorded and analyzed. Two types of SO4 groups pred icted by the X-ray data of the samarium compound are not observed in t he present study. However, the bands show two crystallographically dis tinct SO42- ions in the other two compounds. The absence of free rotat ion and broadness of the bands in the internal made region confirms th at NH: ions form hydrogen bonds in the crystals under study. The obser ved stretching and bending bands show the presence of three distinct t ypes of water molecules in NH4Sm(SO4)(2) . 4H(2)O. The water molecules form hydrogen bonds of medium strength in all three crystals. (C) 199 6 Academic Press, Inc.