Coulomb excitation of Kr80,82 and a change in structure approaching N=Z=40

Abstract

Background: Nuclei approaching N = Z = 40 are known to exhibit strongly deformed structures and are thought to be candidates for shape coexistence. In the krypton isotopes 80,82 Kr are poorly characterized, preventing understanding of evolving deformation approaching N = 40.Purpose: The present work aims to determine electric quadrupole transition strengths and quadrupole moments of 80,82 Kr in order to better characterize their deformation.Methods: Sub-barrier Coulomb excitation was employed, impinging the isotopes of krypton on 196 Pt and 208 Pb targets. Utilizing a semi-classical description of the safe Coulomb-excitation process E2 matrix elements could then be determined.Results: Eleven new or improved matrix elements are determined in 80 Kr and six in 82 Kr. The new B(E2; 0 + 1 → 2 + 1 ) value in 82 Kr disagrees with the evaluated value by 3σ, which can be explained in terms of deficiencies in a previous Coulomb-excitation analysis.Conclusions: Comparison of measured Qs 2 + 1 and B(E2; 0 + 1 → 2 + 1 ) values indicates that neutron-deficient (N ≤ 42) isotopes of krypton are closer to axial deformation than other isotopic chains in the mass region. A continuation of this trend to higher Z may result in Sr and Zr isotopes exhibiting near-axial prolate deformation.