Elastic scattering and total reaction cross sections using the weakly bound projectile 7Li on medium – mass target 116Sn
N. N. Deshmukh 1*, S. Mukherjee 1, B. K. Nayak 2, D. C. Biswas 2, S. Santra 2, S. Appannababu 1, E. T. Mirgule 2, A. Saxena 2, D. Patel 1, R. K. Choudhury 2, J. Lubian 3, P. Gomes 3
1 Physics Department, Faculty of Science, THE M.S.University of Baroda, Vadodara-390002, India
2 Nuclear Physics Division, B.A.R.C., Mumbai-400085, India
3 Instituto de Fisica, Universidade Federal Fluminense, Niteroi, R.J. 24210-340, Brazil
The elastic scattering experiments parallel with coincident experiments, in nuclear reactions, plays an essential role to provide the information of nuclear properties. It is a well established fact that the near barrier elastic scattering of tightly bound heavy ions shows up a behavior of the energy dependence of the interacting optical potential (OP) known as Threshold Anomaly (TA) [1 - 3], where the real and imaginary parts of the potential shows a rapid variation and is consistent with the dispersion relation [4,5]. In TA the coupling to the channels other than elastic introduces an attractive real potential and the result of the decrease of the imaginary potential is tacit by the closure of the nonelastic channels at energies near and below the Coulomb barrier. However, the scenario changes drastically when the weakly bound nuclei are involved which couples to the breakup channels; as a result the breakup cross section becomes larger than the fusion cross section at the sub barrier energies and the effect now is called BTA [5,6]. In any situation, the real and imaginary parts of the OP should satisfy the dispersion relation.
Thus to contribute in this field we performed elastic scattering experiment below and above the Coulomb barrier viz., 18, 19, 20, 21, 22, 23, 24, 26, 30 and 35 MeV energy range, using the weakly bound projectile 7Li. The beam was delivered by the 14UD Pelletron accelerator of the TIFR/BARC facility in Mumbai, India. The beam was bombarded on a 430 µg/cm2, self supported enriched 116Sn (≥ 98%) target and the elastically scattered 7Li ions were detected by four solid state silicon surface barrier ∆E + E telescopic arrangements. One monitor detector was used for the absolute normalization.
Results and Discussions
Optical model analysis has been carried out to extract the optical potential parameters and reaction cross sections using the potential model, namely, the Sao Paulo double folding potential (SPP) [7,8], which has been successfully used to describe a large variety of systems in a wide energy range, including fusion excitation functions and barrier distributions of weakly bound nuclei. Figure shows the elastic scattering angular distribution above and below Coulomb barrier and the lines show the double folding model fit to data. It is also observed that the total reaction cross section is largest for the neutron-halo other than the weakly and tightly bound nuclei. The detailed aspects of which will be presented in the Conference.
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Figure: For details see in text