Electric Monopole Transition Strengths in ⁶²Ni

¹ TRIUMF, 4004 Wesbrook Mall, Vancouver BC, V6T 2A3, Canada
² Department of Physics, University of Surrey, Guildford, GU2 7XH, United Kingdom
³ Department of Nuclear Physics, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 2601, Australia
⁴ King Khaled University, Abha, Kingdom of Saudi Arabia

^a e-mail: evitts@triumf.ca

Published online: 5 September 2016

Abstract

Excited states in ⁶²Ni were populated with a (p, p’) reaction using the 14UD Pelletron accelerator at the Australian National University. Electric monopole transition strengths, ρ²(E0), were measured through simultaneous detection of the internal conversion electrons and γ rays emitted from the de-excitation of populated states, using the Super-e spectrometer coupled with a germanium detector. The strength of the 0₂⁺ to 0₁⁺ transition has been measured to be 77₋₃₄⁺²³ × 10⁻³ and agrees with previously reported values. Upper limits have been placed on the 0₃⁺ to 0₁⁺ and 0₃⁺ to 0₂⁺ transitions. The measured ρ²(E0) value of the 2₂⁺ to 2₁⁺ transition in ⁶²Ni has been measured for the first time and found to be one of the largest ρ²(E0) values measured to date in nuclei heavier than Ca. The low-lying states of ⁶²Ni have previously been classified as one- and two-phonon vibrational states based on level energies. The measured electric quadrupole transition strengths are consistent with this interpretation. However as electric monopole transitions are forbidden between states which differ by one phonon number, the simple harmonic quadrupole vibrational picture is not suffcient to explain the large ρ²(E0) value for the 2₂⁺ to 2₁⁺ transition.