• T G Ramesh

      Articles written in Pramana – Journal of Physics

    • High pressure behaviour of liquid caesium

      T G Ramesh

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      This paper deals with the anomalous behaviour of liquid caesium at high pressures. A model for the phenomenon of electron collapse in the liquid phase, based on the anomalous density variation of liquid caesium with pressure has been proposed. The process of 6s→5d electron collapse is pictured as the formation of a virtual bound state and the tunnelling process accounts for the 6s⇌5d dynamic conversion. The same model together with the Friedel sum rule has been used to explain the resistivity variation of liquid caesium with pressure. The resistivity minimum observed in most of the liquid alkali metals in the low pressure region has been explained. The agreement with the experimental curve is good in the low pressure region whereas a large discrepancy exists at higher pressures. This may be due to the breakdown of the Ziman’s resistivity formula under conditions of resonance scattering.

    • Thermoelectric power of cerium at high pressures

      T G Ramesh A S Reshamwala S Ramaseshan

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      The electronic phase transition in cerium occurring near 7 kbar pressure at room temperature which is attributed to the 4f–5d electron promotion has been studied using thermoelectric power as a tool. The important results that have emerged out of this work are: (a) the relatively large variation in the absolute thermoelectric power ofγ-cerium (normal fcc phase) with pressure prior to the phase transition (in contrast to the rather small resistivity change with pressure in this region); (b) a sharp decrease in the thermoelectric power accompanying the iso-structuralγ-α phase transition; and (c) the continuous decrease in the thermoelectric power ofα-cerium (collapsed fcc phase) with pressure, ultimately changing sign at higher pressures. An explanation based on the “virtual bound state” model is proposed to account for these results.

    • An automatic technique for the measurement of thermoelectric power at high pressures

      T G Ramesh A S Reshamwala M T Srivatsa

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      We describe an automatic technique for direct recording of the themoelectric power of metals either as a function of temperature or pressure. This technique facilitates the process of measurement especially when one has to scan a wide temperature and pressure range. Typical experimental recordings of the γ-α electronic phase transition in cerium are also presented.

    • On the valence instability in CeAl2

      T G Ramesh W B Holzapfel

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      This paper reports the observation of an isostructural electronic phase transition in CeAl2 near 77 Kbar pressure at ambient temperature. The present volume compression data obtained under truly hydrostatic pressure conditions gives a clear indication of the first order nature of this phase transformation.

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