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 and 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 predicted by the X-ray data of the samarium compound are not observed in the present study. However, the bands show two crystallographically distinct SO42- ions in the other two compounds. The absence of free rotation and broadness of the bands in the internal made region confirms that NH: ions form hydrogen bonds in the crystals under study. The observed stretching and bending bands show the presence of three distinct types of water molecules in NH4Sm(SO4)(2) . 4H(2)O. The water molecules form hydrogen bonds of medium strength in all three crystals. (C) 1996 Academic Press, Inc.