• K Balasubramanian

      Articles written in Proceedings – Section A

    • Raman spectrum of crystalline α-glycine

      R S Krishnan K Balasubramanian

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    • Raman spectrum of crystalline tri-glycine sulphate (NH3.CH3.COO)3H2SO4

      R S Krishnan K Balasubramanian

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    • Raman spectrum of triglycine selenate (G3Se), [(NH2CH2COOH)3 H2SeO4]

      K Balasubramanian R S Krishnan

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      The Raman spectrum of a single crystal of triglycine selenate G3Se which is ferroelectric below 22° C. has been photographed usingλ 2537 excitation. 42 Raman lines have been recorded of which 6 belong to the lattice spectrum, 3 are due to NH...O oscillations and the remaining 33 are due to internal oscillations of the ions of glycine and SeO4−−. There is a close similarity between the spectrum of triglycine selenate and the spectrum of its isomorph, triglycine sulphate, the frequency shifts due to the SO4−− ion being replaced by the frequency shifts due to the SeO4−− ion. The existence of glycine in the zwitterion form in the structure of G3Se is substantiated by the appearance in the Raman spectrum of lines which are attributable to NH3+ groups and COO groups. The appearance of the additional C-H line at 2982 cm.−1 in the spectrum of triglycine selenate which is absent in the spectrum ofα-glycine indicates the existence of planar monoprotonated glycine also in the structure, as indicated by X-ray studies.

    • Raman spectrum of diglycine barium chloride monohydrate

      R S Krishnan K Balasubramanian

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      The Raman spectrum of diglycine barium chloride monohydrate in the single crystal form has been recorded using λ 2536·5 excitation. 43 Raman lines (9 lattice and 34 internal) have been recorded. Satisfactory assignments have been given for most of the observed Raman lines. It is concluded from a comparison of the Raman spectrum of this compound with those of glycine and of other addition compounds of glycine, that the glycine unit exists in the zwitterion form in the structure of diglycine barium chloride monohydrate.

    • Polarisation studies of the Raman spectrum ofα-glycine and the orientation of CH2 groups

      K Balasubramanian R S Krishnan

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      The polarisation characteristics of the intense Raman lines ofα-glycine have been investigated using unpolarised incidentγ 2536·5 radiation. Six different orientations of the crystal with reference to the directions of incidence and observation have been used. From the observed depolarisation values, the classification of the Raman lines to the two different symmetry types Ag and Bg has been made. The orientation of the CH2 groups inα-glycine, deduced from polarisation studies, is slightly different from that given by Marsh by X-ray analysis and a quantitative estimate of this deviation has been made.

    • Raman spectrum of hydroxylamine hydrochloride (NH3OH.Cl)

      R S Krishnan K Balasubramanian

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      The Raman spectrum of hydroxylamine hydrochloride (NH3OH.Cl) in the form of a single crystal has been photographed usingλ 2536·5 excitation. 32 Raman lines with frequency shifts 40, 57, 78, 88, 111, 125, 135, 156, 187, 217, 250, 330, 550, 575, 1004, 1168, 1204, 1470, 1496, 1565, 1590, 1979, 2636, 2710, 2750, 2789, 2926, 2970, 3000, 3050, 3141 and 3220 cm.−1 have been recorded. Of these, the first 8 low-frequency lines belong to the external oscillation, while the four lines at 187, 217, 250 and 330 cm.−1 should be attributed to the vibrations of the hydrogen bond valence vibrations. The remaining Raman lines have been assigned to the vibrations of the NH3OH ion. The O-H and N-H stretching vibrations are very much influenced by the presence of the hydrogen bonds in the crystal.

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