Coulomb and nuclear excitations of Zn70 and Ni68 at intermediate energy

Abstract

The reduced transition probabilities B(E2;0g.s.+→21+,22+) in Zn70 and the full B(E2;0g.s.+→2+) strength up to Sn=7.79MeV in Ni68 have been determined at the LISE/GANIL facility using the Coulomb-excitation technique at intermediate beam energy on a Pb208 target. The γ rays emitted in-flight were detected with an array of 46BaF2 crystals. The angles of the deflected nuclei were determined in order to disentangle and extract the Coulomb and nuclear contributions to the excitation of the 2+ states. The measured B(E2;0g.s.+→21+) of 1432(124) e2fm4 for Zn70 falls in the lower part of the published values which clustered either around 1600 or above 2000e2fm4, while the B(E2;0g.s.+→22+) of 53(7) e2fm4 agrees very well with the two published values. The relatively low B(E2;0g.s.+→21+) of 301(38) e2fm4 for Ni68 agrees with previous studies and confirms a local magicity at Z=28, N=40. Combining the results of the low-energy spectra of Ni68 and Zn70 and their shell-model interpretations, it is interesting to notice that four different shapes (spherical, oblate, prolate, and triaxial) are present. Finally, a summed E2 strength of only about 150e2fm4 has been found experimentally at high excitation energy, likely due to proton excitations across the Z=28 gap. The experimental distribution of this high-energy E2 excitation agrees with shell-model calculations, but its strength is about two times weaker.4 MoreReceived 19 May 2020Revised 8 April 2021Accepted 10 September 2021DOI:https://doi.org/10.1103/PhysRevC.104.034318©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsNuclear fragmentationNuclear structure & decaysProperties59 ≤ A ≤ 89Nuclear Physics