Abstract
We present the results of a high-precision quasi-elastic excitation function measurement for the ${}^{48}$Ca + ${}^{120}$Sn system at ${\ensuremath{\theta}}_{\mathrm{LAB}}$ = 160\ifmmode^\circ\else\textdegree\fi{} at near-barrier energies in steps of 1.0 MeV. The corresponding quasi-elastic barrier distribution is derived. A large-scale coupled-channel calculation was performed to investigate the role of several reaction channels in the reaction mechanism. An excellent agreement between theory and data was obtained for the barrier distribution. The first quadrupole vibrations of the ${}^{48}$Ca and ${}^{120}$Sn, the 2$n$, and the ${}^{4}$He transfers have a strong influence on the reaction mechanism and are responsible for the good agreement achieved. The 1$n$ transfer has a minor importance in the result when compared with the 2$n$ transfer, which suggests that the pairing correlation might play an important role in the 2$n$-neutron transfer process. However, if the octupole vibration of the projectile is included in the coupling scheme, the agreement with the data gets worse. The comparison of the coupled-channel calculations with experimental data leads to the conclusion that the nuclear matter diffuseness of the ${}^{48}$Ca nucleus is 0.56 fm in agreement with most of the double-magic nuclei.
Highlights
The double-magic 48Ca nucleus has largely been used in nuclear reactions with the aim of synthesizing superheavy elements [1,2] and to study neutron transfer reactions over a large number of systems [2,3,4,5,6]
The 1n transfer has a minor importance in the result when compared with the 2n transfer, which suggests that the pairing correlation might play an important role in the 2n-neutron transfer process
Large-scale coupled-channel calculations were performed to investigate the role of several reaction channels in the reaction mechanism of this system
Summary
The double-magic 48Ca nucleus has largely been used in nuclear reactions with the aim of synthesizing superheavy elements [1,2] and to study neutron transfer reactions over a large number of systems [2,3,4,5,6]. The nuclear charge distributions of 40Ca and 48Ca nuclei are quite similar as supported by electron scattering, isotope shift measurements, and large-scale nuclear shell model calculations [8,9,10], there is a lack of experimental data on their nuclear matter distribution. More recently, accurate fusion excitation functions of the 40Ca + 48Ca [4,6], 48Ca + 48Ca [6,12], and 40Ca + 40Ca [13,14] systems have been measured to extract the fusion barrier distribution and/or to investigate the origin of the fusion hindrance that was observed at deep sub-barrier energies [15,16]
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