• N Satyavathi

      Articles written in Pramana – Journal of Physics

    • Raman intensity analysis of LaCl3

      N Satyavathi N Rajeswar Rao

      More Details Abstract Fulltext PDF

      Raman intensity analysis of LaCl3 on lines adopted earlier for crystals like LiNO3, KNO3 or YVO4 is found to be unsuitable for LaCl3. The rotation of the LaCl3 pyramids in the unit cell of this crystal is represented by high frequencies, comparable to the internal oscillations of LaCl3 molecule. The intensity ofRz, rotation about the symmetry axis of the crystal, is higher than the total symmetric line. These two factors show that the two molecules in the unit cell cannot be treated separately. Also, the polarisability of the bonds between atoms connecting the molecules cannot be neglected. The intensity formulae have been derived for this crystal and using the directional Raman spectra, electro-optical constants of the LaCl and Cl-Cl bonds have been evaluated. It is found that while the polarisability of Cl-Cl bond between the molecules, is about 0·4 times that of LaCl bonds, in crystals like LiNO3 the polarisability of bonds like Li-O is found to be negligible.

    • Evaluation of photoelastic constants from first-order Raman intensities of MgF2

      G Swarna Kumari N Satyavathi N Rajeswara Rao

      More Details Abstract Fulltext PDF

      A formalism to connect first-order Raman intensities of MgF2 and its photoelastic constants is developed by developing a method of writing internal coordinates in terms of displacement gradientsuij which are not symmetric. It is found that for crystals containing only one line inA1 species, the ratiosP13/P33 and (P11 +P12)/P31 can be directly evaluated from the intensities, without having to derive the intensity formulae; while (P11 +P12)/P13 is independent of the intensities as well as the refractive index of the crystal. It is a function of only the dimensional parameters. In this crystal, since the speciesB1g andB2g also contain only one line each, the ratio (P11P12)/P66 can also be directly obtained from the intensities.

  • Pramana – Journal of Physics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2021-2022 Indian Academy of Sciences, Bengaluru.