Abstract
Recently, various two-neutron transfer studies using the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction were performed with a large success. This was achieved because of a combined use of the microscopic quantum description of the reaction mechanism and of the nuclear structure. In the present work we use this methodology to study the two-neutron transfer reaction of the $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ system at 84 MeV incident energy, to the ground and first ${2}^{+}$ excited state of the residual $^{66}\mathrm{Ni}$ nucleus. All the experimental data were measured by the large acceptance MAGNEX spectrometer at the Instituto Nazionale di Fisica Nucleare --Laboratori Nazionali del Sud (Italy). We have performed exact finite range cross section calculations using the coupled channel Born approximation (CCBA) and coupled reaction channel (CRC) method for the sequential and direct two-neutron transfers, respectively. Moreover, this is the first time that the formalism of the microscopic interaction boson model (IBM-2) was applied to a two-neutron transfer reaction. From our results we conclude that for two-neutron transfer to the ground state of $^{66}\mathrm{Ni}$, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of $^{66}\mathrm{Ni}$, the sequential process dominates. A competition between long-range and short-range correlations is discussed, in particular, how the use of two different models (Shell model and IBM's) help to disentangle long- and short-range correlations.
Highlights
It is well known that the atomic nucleus is a complex many-body system
From our results we conclude that for two-neutron transfer to the ground state of 66Ni, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of 66Ni, the sequential process dominates
In the previous section we have presented the description of one-step calculation of the two-neutron transfer reaction within the microscopic IBM-2, where a neutron boson is transferred
Summary
It is well known that the atomic nucleus is a complex many-body system. The knowledge of the internal degrees of freedom is crucial to understand nuclear structure features like single-particle and collective states, clustering, pairing correlations, and other properties [1,2]. Normal behavior of the 62,64Ni(18O,16O) reactions remains over a variety of incident energies They claim that the reason for this forward rising of the angular distributions for these two 58,60Ni(18O,16O) reactions lies in the fact that the absorption in the surface region, where the projectile and target interact, was decreased. To study the details of the two-neutron reaction on a target in this mass region, we have performed a high-precision measurement of the 64Ni(18O,16O)66Ni reaction to the ground and to the first excited state of the residual 66Ni nucleus. To describe these reactions, the structure of the relevant states of the interacting nuclei needs to be modeled as accurately as possible.
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