• A Goswami

      Articles written in Pramana – Journal of Physics

    • Angular momentum transfer in incomplete fusion

      B S Tomar K Surendra Babu K Sudarshan R Tripathi A Goswami

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      Isomeric cross-section ratios of evaporation residues formed in 12C+93Nb and 16O + 89Y reactions were measured by recoil catcher technique followed by off-line 𝛾-ray spectrometry in the beam energy range of 55.7-77.5 MeV for 12C and 68-81 MeV for 16O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical de-excitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.

    • Effect of entrance channel parameters on the fusion of two heavy ions: Excitation functions of reaction products in16O +66Zn and37Cl +45Sc reactions

      Suparna Sodaye B S Tomar A Goswami

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      Excitation functions of reaction products formed in16O +66Zn and37Cl +45Sc systems, leading to the same compound nucleus,82Sr, were measured using recoil-catcher technique and off-line γ-ray spectrometry. The contribution of non-compound processes like transfer and incomplete fusion (ICF) reactions to the cross-sections of different evaporation residues were delineated by comparing the experimental data with the predictions of Monte Carlo simulation code PACE2. The results show that non-compound processes become a significant fraction of the total reaction cross-section in16O +66 systems in the beam energy range studied, while37Cl +45Sc gives mainly compound nucleus products. The mass asymmetry dependence of the fusion and non-compound cross-sections have been analysed in terms of the static fusion model and sum rule model

    • Odd–even effect in fragment angular momentum in low-energy fission of actinides

      B S Tomar R Tripathi A Goswami

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      Quantitative explanation for the odd–even effect on fragment angular momenta in the low-energy fission of actinides have been provided by taking into account the single particle spin of the odd proton at the fragment's scission point deformation in the case of odd-𝑍 fragments along with the contribution from the population of angular momentum bearing collective vibrations of the fissioning nucleus at scission point. The calculated fragment angular momenta have been found to be in very good agreement with the experimental data for fragments in the mass number region of 130–140. The odd–even effect observed in the fragment angular momenta in the low-energy fission of actinides has been explained quantitatively for the first time.

    • Measurement of 232Th$(n, \gamma)$ and 232Th$(n, 2n)$ cross-sections at neutron energies of 13.5, 15.5 and 17.28 MeV using neutron activation techniques

      Sadhana Mukerji H Naik S V Suryanarayana S Chachara B S Shivashankar V Mulik Rita Crasta Sudipta Samanta B K Nayak A Saxena S C Sharma P V Bhagwat K K Rasheed R N Jindal S Ganesan A K Mohanty A Goswami P D Krishnani

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      The 232Th$(n, \gamma)$ reaction cross-section at average neutron energies of 13.5, 15.5 and 17.28 MeV from the 7Li$(p, n)$ reaction has been determined for the first time using activation and off-line 𝛾-ray spectrometric technique. The 232Th$(n, 2n)$ cross-section at 17.28 MeV neutron energy has also been determined using the same technique. The experimentally determined 232Th$(n, \gamma)$ and 232Th$(n, 2n)$ reaction cross-sections from the present work were compared with the evaluated data of ENDF/BVII and JENDL-4.0 and were found to be in good agreement. The present data, along with literature data in a wide range of neutron energies, were interpreted in terms of competition between 232Th$(n, \gamma)$, $(n, f)$, $(n, nf)$ and $(n, xn)$ reaction channels. The 232Th$(n, \gamma)$ and 232Th$(n, 2n)$ reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were found to be in good agreement with the experimental data from the present work but were slightly higher than the literature data at lower neutron energies.

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