Articles written in Pramana – Journal of Physics

    • A simple apparatus for the measurement of thermoelectric power in the temperature range 4·2–300K

      K P Rajeev N Y Vasanthacharya

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      A simple apparatus to measure the absolute thermoelectric power of solids in the temperature range 4·2–300K is described. The cryostat and the associated instrumentation is simple to operate. Representative data of measurements on metallic wire and pressed pellets are given. An accuracy of better than 10% in absolute thermopower can be obtained in this apparatus.

    • An automated thermal relaxation calorimeter for operation at low temperature (0.5 K<T<10 K)

      S Banerjee M W J Prins K P Rajeev A K Raychaudhuri

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      We describe an automated calorimeter for measurement of specific heat in the temperature range 10 K>T>0.5 K. It uses sample of moderate size (100–1000 mg), has a moderate precision and accuracy (2%–5%), is easy to operate and the measurements can be done quickly with He4 economy. The accuracy of this calorimeter was checked by measurement of specific heat of copper and that of aluminium near its superconducting transition temperature.

    • Photon-induced low-energy nuclear reactions


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      We propose a new mechanism for inducing low-energy nuclear reactions (LENRs). The process is initiated by a perturbation which we assumed to be caused by absorption or emission of a photon. Due to the electromagnetic perturbation, the initial two-body nuclear state forms an intermediate state to make a transition into the final nuclear state through the action of another perturbation. In the present paper,we take the second perturbation to be also electromagnetic. We need to sum over all energies of the intermediate state. Since the upper limit on this sum is infinity it is possible to get contributions from very high energies for which the barrier penetration factor is not too small. By considering a specific reaction, we determine the conditions under which this mechanism may lead to significantly enhanced reaction rates. We find that the mechanism leads to very small cross-sections in free space. However, in a condensed medium, there exist several possibilities leading to enhanced cross-sections, which may lead to observable reaction rates even at relatively low energies. Hence we argue that LENRs are possible and provide a theoretical set-up which may explain some of the experimental claims in this field.

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