• Shashi P Gupta

      Articles written in Pramana – Journal of Physics

    • The infrared spectra of tutton salts 1. A comparative study of (NH4)2 M″(SO4)2·6H2O (M″=Ni, Co or Mg)

      B Singh Shashi P Gupta B N Khanna

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      The infrared spectra of (NH4)2M″(SO4)2.6H2O has been analysed in the region 4000–250 cm−1. The dynamics of each crystal has been discussed in terms of 234 phonon modes, including 3 acoustical ones, using the unit cell approximation. The ambiguity in the assignments of the bands in the region 900–500 cm−1 has been removed by assigning the bands in this region to the libratory modes of H2O molecules. It has been concluded that the NH4+ and SO42− ions have a symmetry lower thanTdand also the complex [M″(H2O)6]2+ has a symmetry lower than Oh. The hydrogen bonding is the strongest in the Ni-salt and the weakest in the Mg-salt.

    • Libratory modes of water molecules in tutton salts

      Shashi P Gupta Y Kumar B N Khanna

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      The existence of rocking, wagging and twisting librations of different types of water molecules in tutton salts has been established from their ir spectra. These bands have been identified, following the intensity criterion of Miyazawa. The present assignments indicate that the bands due to libratory motion of H2O III in NH4Mn-, KNi-, KCo and KMn- and of H2O I in KMn- and KCu- tutton salts are out-of-plane H-bonded. The strength of the hydrogen bonding is the weakest in the (NH4)2Fe(SO4)2.6H2O.

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