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Channel coupling plays a crucial role in enhancing sub-barrier fusion in heavy-ion collisions by splitting a single potential barrier into a measurable barrier distribution (BD). Heavy- ion reactions near the Coulomb barrier are particularly sensitive to these coupling effects, making them ideal for investigating the interplay between the relative motion of nuclei and their intrinsic degrees of freedom. Quasielastic (QE) scattering provides a powerful tool to probe such couplings, as the resulting barrier distributions reveal valuable information about nuclear structure, intrinsic excitations, and the underlying reaction dynamics [1, 2]. While the Coupled Channels (CC) framework has successfully reproduced many experimental barrier distributions, remaining discrepancies suggest the involvement of additional weak couplings, such as non-collective excitations and nucleon transfer [3, 4, 5, 6]. Experimental QE barrier distributions (D𝑞𝑒 ) for several systems have been observed to be smoother than predicted by standard CC calculations. This behavior was first reported for the 20Ne+90,92Zr systems [3], where the 20Ne+92Zr barrier distribution was notably smoother than the 20Ne+90Zr one, unlike CC predictions based on dominant rotational modes in deformed 20Ne. Similar results were observed for 20 Ne+61 Ni [4] and 24 Mg+92Zr [5] systems. The discrepancy with CC predictions was attributed to a dissipative mechanism, i.e., internal non- collective excitations, mainly single-particle (s.p.). Theoretically, these effects were accounted by the extension of the CC method using random matrix theory (CC+RMT). Recently, similar study performed for the 20Ne + 92,94,95Mo [6] reactions also highlighted the significance of such dissipative effects on the QE barrier distributions. These findings motivated additional studies to further explore this dissipation cause using different strongly deformed projectiles and targets with varying s.p. level densities. In this context, quasielastic scattering measurements for the 24Mg + 92,94,95Mo systems were carried out at near-barrier energies employing the HI-13 tandem accelerator of the China Institute of Atomic Energy (CIAE), Beijing. The experiment utilized the backscattering technique with silicon (Si) detector arrays to obtain excitation functions for quasielastic scattering at various backward angles. The extracted barrier distributions are being analyzed to investigate the interplay between collective and non-collective couplings. The details of the experiment and the preliminary results of this ongoing study will be presented during the conference. References [1] M. Dasgupta et al., Annu. Rev. Nucl. Part. Sci. 48, 401 (1998). [2] H. Timmers et al., Nucl. Phys. A 584, 190 (1995). [3] E. Piasecki et al., Phys. Rev. C 80, 054613 (2009). [4] A. Trzcińska et al., Phys. Rev. C 92, 034619 (2015). [5] A. Trzcińska et al., Phys. Rev. C 102, 034617 (2020). [6] G. Colucci et al., Nucl. Phys. A 1063, 123197 (2025).
Authors: Kavita Rani1 , G. Colucci1 , A. Trzcińska1 , E. Piasecki1 , M. Wolińska-Cichocka1 , and C. J. Lin et al.2 1 Heavy Ion Laboratory, University of Warsaw, Warsaw, 02-978, Poland 2 China Institute of Atomic Energy, Beijing 102413, China
