• B V Thirumala Rao

      Articles written in Pramana – Journal of Physics

    • Anomalous conversion in the decay of197mHg

      S Bhuloka Reddy D Sudhakara Reddy K L Narasimham B V Thirumala Rao V Lakshminarayana

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      The total andK-shell conversion coefficients of the 165 keV transition in the decay of197mHg are determined from intensity balance considerations and a coincidence technique using a Ge(Li)—NaI (Tl) system respectively. The resultant values areaT=274.8±19.2 andaK=47±12, whil the corresponding theoretical values are 344 and 77 respectively, indicating anomalous conversion. The gamma ray transition probability however, shows a hindrance of only about 6 and cannot be correlated with the present anomalous conversion data. TheK/L ratio of the 130 keV transition, determined using a summing method with a Ge(Li) detector, yielded 0.090±0.012, while the corresponding theoretical value is 0.048, indicating anomalous conversion. The corresponding gamma transition probability shows a hindrance of about 3000, in correlation with anomalous conversion.

    • Neutron induced reactions in antimony isotopes at 14 MeV

      N Lakshmana Das C V Srinivasa Rao B V Thirumala Rao J Rama Rao

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      Neutron activation cross-sections in antimony isotopes were measured at an incident neutron energy of 14.2±0.2 MeV. The versatile mixed powder technique and high resolution Ge(Li) detector gamma ray spectroscopy were employed. The measured cross-sections were compared with those reported in literature. The total (n, 2n) cross-sections were compared with the estimates based on statistical theory. The experimental values were found to be smaller than the statistical theory estimates and the resulting diminution was attributed to the precompound effects in (n, 2n) reactions at 14 MeV.

    • Pre-equilibrium effects in (n, 2n) reactions at 14.2 MeV+

      N Lakshmana Das C V Srinivasa Rao B V Thirumala Rao J Rama Rao

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      With a view to study the pre-equilibrium effects in neutron-induced reactions, the activation cross-sections for (n, 2n) reactions at 14.2±0.2 MeV in the heavy mass region have been measured using the versatile mixed powder technique and high resolution Ge(Li) detection. The experimental cross-sections are found to be consistently smaller than the predictions based on the statistical theory and this is attributed to the effect of pre-equilibrium decay in these reactions. The cross-sections due to pre-equilibrium decay were estimated using exciton, hybrid and unified models. When this cross-section was included in comparing the experimental cross-sections with theory, we obtained better agreement, within the limitations of the present-day preequilibrium theories.

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