Role of neutron rearrangement channels in sub-barrier fusion

Abstract

Abstract. Different factors influencing the sub-barrier fusion enhancement owing to neutron rearrangement with positive Q values are studied. It was found that opposite to the previous opinion the presence of positive Q values is necessary but not sufficient to observe enhancement of the sub-barrier fusion. "Rigidity" of colliding nuclei with respect to collective excitations plays a crucial role for the sub-barrier fusion enhancement due to neutron rearrangement. Neutron binding energy has a strong impact but only in the case of fusion of light nuclei.

Survey of deep sub-barrier heavy-ion fusion hindrance phenomenon for positive and negative Q-value systems using the proximity-type potential

“…[4], as indicated by the gray solid curve, as a function of the system parameter . In two previous studies [26,27], we demonstrated that fusion hindrance appears at the energy threshold = 87.29, 88.9, 67.5, 73.42, and 72.95 MeV for the 58 Ni+ 56 Fe, 64 Ni+ 64 Ni, 28 Si+ 100 Mo, 32 S+ 89 Y, and 34 S+ 89 Y systems, respectively. These values are presented in Fig.…”

“…77 model significantly underestimates the measurements of the fusion-evaporation excitation functions at sub-barrier energies for a number of systems. However, it appears that this potential model achieves better performance for the lighter colliding systems 12 C+ 30 Si, 28 Si+ 30 Si, and 24 Mg+ 30 Si. These results can be understood by observing the radial behavior of the Coulomb plus nuclear potentials used in the CC calculations (see the inset in the figure).…”

“…The existence of heavy-ion reactions with positive and negative fusion -values allows us to investigate the effect of the sign of the -value on the energy-dependent behavior of the coefficient. According to the literature [28][29][30][31][32][33][34], an additional enhancement in the sub-barrier fusion process can be observed due to the coupling of the neutron transfer channels with the positive -values. Nevertheless, the effective -values for various neutron transfer channels, involving single-and multi-neutron (up to six neutrons) stripping (or pick-up), are negative for most of the reactions investigated in this study.…”

“…[25] indicated that a shallow pocket is formed in the inner part of the potential barrier when the standard M3Y nuclear interaction accompanied by the Pauli blocking potential of two colliding nuclei is applied. Furthermore, it was shown that the fusion hindrance phenomenon in the colliding systems 12 C+ 198 Pt, 16 O+ 208 Pb, 12 C+ 30 Si, 24 Mg+ 30 Si, and 28 Si+ 30 Si can be described well by introducing the Pauli blocking potential.…”

“…Recently, we proposed a dynamical approach to evaluate the heavy-ion fusion cross sections at deep sub-barrier energies within the framework of the energy-dependent nucleus-nucleus potential [26]. It was shown that when the effect of the surface energy coefficients and the temperature-dependence in the original proximity potential 1977 are taken into account, the theoretical fusion cross sections calculated using the CC calculations provide a good description of the steep falloff phenomenon at low energies for the 28 Si+ 100 Mo, 58 Ni+ 54 Fe, and 64 Ni+ 64 Ni systems. Very recently, we used this idea to explore the fusion hindrance phenomenon for the two fusion reactions 32,34 S+ 89 Y [27].…”