• Y Kumar

      Articles written in Pramana – Journal of Physics

    • 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.

    • Surface enhanced Raman scattering of 2-cyanopyridine adsorbed on silver colloidal particles

      Ekram Ali Shaikh Y Kumar B N Khanna

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      Surface-enhanced Raman scattering (SERS) spectra of 2-cyanopyridine (2 CP) adsorbed on silver colloidal particles have been investigated. The prominent SERS bands are observed at 556, 612, 778, 1002, 1060, 1072, 1150 and 1240 cm−1. The absolute enhancement factor of the Raman signals in SERS studies has been estimated to be of the order of 102–105 for various bands. The 2CP molecules have been ascribed to adsorb on colloidal particles in standing up fashion.

    • Inelastic light scattering in strontium borate glasses in the systemxSrO.(1−x)B2O3 and (SrCl2)y.[xSrO.(1−yx)B2O3]1−y

      M H Rahman B P Dwivedi Y Kumar B N Khanna

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      Raman spectra of strontium borate binary glasses in the systemxSrO.(1-x)B2O3 forx=0.20, 0.25, 0.30, 0.35, 0.40, and 0.50 and ternary glasses in the system (SrCl2)y.[xSrO.(1−yx)B2O3]1−y fory=0.10, 0.20, 0.30 and 0.40 andx=0.20 and 0.35, are reported. Raman spectra of the glasses show experimental evidence of glass network modifying nature of SrO in borate matrix. SrO causes a change of boron atom coordination number from 3 to 4 resulting in the complex structural groupings comprising of BO4 and BO3 units. Strontium cations are not easily accommodated in the glass structure and tend to break up the network at high concentration (x) of SrO, causing non-bridging oxygens. The effect of temperature variation of binary glasses has also been studied. The introduction of SrCl2 to the binary stronium borate glass causes a large change in intensity of low frequency Raman scattering whereas there is no change in the vibrational dynamics in the high frequency region. The temperature reduced Raman spectra represents true vibrational density of states. Martin-Brenig model developed for the low frequency region has been discussed to obtain the structural correlation range in the glass.

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