• D R Chakrabarty

      Articles written in Pramana – Journal of Physics

    • Unusual features of proton and 𝛼-spectra from low-energy heavy-ion reactions

      D R Chakrabarty

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      Proton and 𝛼-particle spectra have been measured in low-energy 12C and 16O-induced reactions on Nb and Y targets with the primary aim of measuring the excitation energy and angular momentum dependence of nuclear level density. In the 𝛾-multiplicity gated spectra, an unusual feature of a broad structure at high particle energies is observed in all the cases. In the case of proton spectra, the structures have compound nuclear origin and point towards an excitation energy and angular momentum-dependent enhancement which is beyond the conventional level density prescription. The broad structures in the 𝛼-spectra cannot be fully explained within the statistical model even with the enhanced level density. In this case, other reaction mechanisms like the transfer of 𝛼 or 8Be to the target could also be important.

    • Electromagnetic transition between molecular resonances in 8Be

      D R Chakrabarty

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      The nucleus 8Be has been conjectured to resemble a molecule of two interacting 𝛼-particles. A crucial test of this conjecture is the electromagnetic transition between the molecular resonances. This paper discusses the earlier indirect bremsstrahlung measurements and describes a recent experiment on the direct measurement of 𝛾-transition between the 4+ and 2+ resonances. Experimental results are compared with various theories. The outlook on the measurement of $2^+ \to 0^+$ transition will be presented.

    • Fission time-scale from the measurement of pre-scission light particles and 𝛾-ray multiplicities

      K Ramachandran A Chatterjee A Navin K Mahata A Shrivastava V Tripathi S Kailas V Nanal R G Pillay A Saxena R G Thomas D R Chakrabarty V M Datar Suresh Kumar P K Sahu

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      An overview of the experimental result on simultaneous measurement of pre-scission neutron, proton, 𝛼-particle and GDR 𝛾-ray multiplicities for the reaction 28Si+175Lu at 159 MeV using the BARC–TIFR Pelletron–LINAC accelerator facility is given. The data were analysed using deformation-dependent particle transmission coefficients, binding energies and level densities which are incorporated in the code JOANNE2 to extract fission time-scales and mean deformation of the saddle-to-scission emitter. The neutron, light charged particle and GDR 𝛾-ray multiplicity data could be explained consistently. The emission of neutrons seems to be favoured towards larger deformation as compared to charged particles. The pre-saddle time-scale is deduced as (0–2) × 10−21 s whereas the saddle-to-scission time-scale is (36–39) × 10−21 s. The total fission time-scale is deduced as (36–41) × 10−21 s.

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