Seminarium Fizyki Jądra Atomowego

Barrier distributions are an excellent tool for revealing detailed structures in the energy dependence of the measured fusion cross-sections at energies close to the Coulomb barrier. The Coupled Channels successfully indicated the couplings of the relative motion to intrinsic degrees of freedom as the main phenomena responsible for the strong enhancement of sub-barrier fusion cross sections as well as the observed structures in the barrier distributions for many systems [1]. However, there are several mechanisms whose influence on the fusion is still not clear, among these is the influence of dissipation: the partial conversion of the projectile-target kinetic energy into their heating. There are two main mechanisms of dissipation: excitation of non-collective levels by nuclear and electromagnetic interactions and projectile-target transfer of light particles. The first phenomenon has been treated by combining the Coupled Channels (CC) method with the Random Matrix Theory (RMT) with promising results [2, 3]. Concerning the transfers, the complicated nature of this many-body phenomenon makes the exact description of it arduous, particularly for heavier systems.
At the Heavy Ion Laboratory (HIL) of the University of Warsaw, an investigation of the influence of dissipation due to weak but numerous non-collective excitations and transfer reactions on quasielastic barrier distribution has been carried out. Details on the recent results and the plans for fusion and transfer cross-section measurements at HIL will be discussed in this seminar.

[1] K. Hagino and N. Takigawa, Prog. Theo. Phys. 128 (2012) 1061
[2] S. Yusa et al., Phys. Rev. C 82 (2010) 024606
[3] E. Piasecki et al., Phys. Rev. C 100 (2019) 014616