P S Narayanan
Articles written in Pramana – Journal of Physics
Volume 1 Issue 3 September 1973 pp 161-164 Solids
The infrared spectrum of potassium ferrocyanide trihydrate has been recorded both in the para and ferroelectric phases. From a combined study of the IR and Raman spectra, it is concluded that there are two sets of water molecules present in the lattice, one set being involved in stronger hydrogen bonding than the other. The ferroelectric transition appears to be associated with an ordering of the water dipoles.
Volume 11 Issue 3 September 1978 pp 245-250 Solids
The Pippard-Janovec relations are derived for correlating the anomalous elastic coefficient and the anomalous specific heat near the phase transitions of ferroelectric crystals. These relations are verified in the case of ferroelectric triglycine selenate crystal.
Volume 19 Issue 2 August 1982 pp 117-124 Solid State Physics
In the case of cubic ionic crystals Havinga has shown that the temperature variation of dielectric constant could be described in terms of volume and temperature effects. By extending his formalism to anisotropic, ionic crystals it has been shown that unlike in cubic ionic crystals where the volume effect consists of a change in the number per unit volume of the polarizable particles and their polarizability with volume, in the case of anisotropic ionic crystals, in addition to these, a variation in the anisotropy of polarizability due to uneven thermal expansion also has to be taken into account. This method of analysis has been examined by taking rutile as an example.
Volume 21 Issue 1 July 1983 pp 41-50 Solid State Physics
The Raman spectra of mixed crystals of [(NH4)1−
Volume 24 Issue 4 April 1985 pp 545-557 Solid State Physics
Lithium caesium sulphate has been reported to undergo a phase transition from the room temperature orthorhombic phase with space group
Volume 34 Issue 6 June 1990 pp 461-471
The development of optical phase conjugation using thermally formed gratings in absorbing media, especially the dye solutions, has besides the high efficiencies, many other characteristics which are worthy of study. Here the wavelength dependence of phase conjugate reflectivity in relation to absorption spectrum of rhodamine-6G and rhodamine-B in water, methanol and ethanol is reported. Further the Bragg condition has been verified for the dominant diffracted beam which shows that the thermal grating behaves like an optically thick grating.
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