Experimental Study of the Pygmy Dipole Resonance in the $^{68}$Ni Nucleus

Abstract

It is known that the low-energy E1 strength, known as the Pygmy Dipole Resonance (PDR), can be excited by both isovector and isoscalar probes. In this work, we report on the results of an experiment, carried out at the LNS-INFN in Catania, with the aim to study the Pygmy Dipole Resonance induced in the 68 Ni nucleus through the interaction with a 12 C isoscalar target. The CHIMERA multidetector and the FARCOS array were used to detect, respectively, γ rays and charged particles. Details on the experimental setup , data analysis and results are reported.

Nuclear Physics Opportunities at European Small-Scale Facilities

“…The study of the cluster structure in exotic nuclei and the "pygmy resonance" manifestations of a particular collective nuclear motion carried out using the exotic beams produced by FRIBS have been performed. The isoscalar excitation of the Pygmy Dipole resonance in 68 Ni was investigated for the first time [67] (the term "Pygmy Dipole Resonance" (PDR) has been commonly used for the E1 strength around and below the neutron-separation energy, Sn). One of the PDR's main characteristics is the behavior of isoscalar and isovector transition densities, which have the same order of magnitude at the surface.…”

“…The goal of this research is to provide experimental data in unexplored energy regions and at beam energies where the available experimental data are insufficient to firmly constrain the theoretical model calculations. In recent studies, the 63 Cu(α,γ) 67 Ga reaction cross-section [109] was measured in the energy range between 5 and 9 MeV, relevant to p-process nucleosynthesis. The experiment was performed at a 4 MV Tandem accelerator by applying the 4π γ-summing method, using an aforementioned NaI(Tl) detector.…”

“…In the medium-mass region of nuclei approaching the N = 40 subshell closure with Z∼28, it is assumed from empirical observations and theoretical calculations that states with different structures such as single-particle, intruder, and collective states coexist at low-and medium-excitation energies [168,169]. The half-lives of the 9/2 + , 13/2 + , and 15/2 + yrast states in the neutronrich 67 Cu nucleus were determined by using the in-beam fast-timing technique [101]. The 67 Cu nuclei were produced in an α-induced reaction on a 64 Ni target at an incident energy of 18 MeV.…”