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The fusion barrier studies at energies around the Coulomb barrier have been a topic of great interest. At these energies, the coupling between relative motion and internal degrees of freedom of colliding heavy ions is strongly affected, which results in a number of distributed barriers instead of a single barrier (Bfus) [1-6]. A barrier distribution (BD) can be extracted experimentally from the fusion excitation function {σfus(E)} using the relation Dfus =d2/dE2 (Eσfus) [3]. The extracted BD contains the fingerprint of the reaction dynamics. This is because the nature and strengths of the several couplings involved in the interaction give distinct peaks in the barrier distribution. Further, it was suggested that the same information can also be extracted from the cross-section of quasi-elastic scattering (QE) (as the total flux is conserved) measured at large angles using the prescription Dqel= d/dE(dσqel /dσR ), as an alternative representation of fusion BD [5]. In the present work, the QE measurements have been performed for the 14N+ 176Yb system, which will be translated into BD.
The experiment has been performed in the GPSC at the IUAC, New Delhi, employing the HYTAR detecting system, comprising 13 ∆E-E hybrid telescopes, where ∆E were gas ionization chambers and E detectors were passivated implanted planar silicon (PIPS) detectors [7]. Beam energy was varied in steps of 3 MeV ranging from 20% below to 20% above the barrier. Four telescope detectors, each at an angle of 1730, were arranged in a symmetrical cone geometry to measure the back-scattered quasi-elastic events. Two monitor detectors were placed at ±100 for beam monitoring and normalization purposes. The QE-excitation functions have been obtained, and the experimental BD for the 14N+ 176Yb system has been derived, as shown in Fig.1. In order to understand the observed nature of the experimentally deduced BD, theoretical calculations have been performed using the CCFULL code. As can been seen from Fig.1, the experimental BD significantly deviates from the one one-dimensional barrier penetration model (shown as a dotted curve), which reveals the presence of structural effects involved in the interaction of the 14N projectile with the 176Yb target. To gain a concrete understanding of these effects, the deformations of the interacting nuclei have been included in the CCFUL calculations. The analysis concludes that target deformation plays an important role in the interaction process. Further, the analysis of the data and results will be presented.
References:
[1] G. Kaur et al., Phys. Rev. C 94, 034613 (2016).
[2] Md. Moin Shaikh et al., Phys. Rev. C 91, 034615 (2015).
[3] N. Rowley, G.R. Satchler, and P.H. Stelson, Phys. Lett. B254, 25 (1991).
[4] M. Dasgupta et al., Annu. Rev. Nucl. Part. Sci. 48, 401 (1998).
[5] H. Timmers et al., Nucl. Phys. A 584, 190 (1995).
[6] K. Hagino, N. Rowley, and A. T. Kruppa, Comp. Phys. Comm. 123, 143 (1999).
[7] Akhil Jhingan et al., Nuclear Inst. and Methods in Physics Research, A 903, 326 (2018).
