Investigation of 0⁺ states in mercury isotopes after two-neutron transfer

¹ Wright Nuclear Structure Laboratory, Yale University, New Haven, CT-06520, USA
² Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany
³ National Institute for Physics and Nuclear Engineering, Bucharest, R-76900, Romania
⁴ Fakultät für Physik, Ludwig-Maximilians-Universität München, D-85748 Garching, Germany
⁵ Faculty of Physics, University of Sofia, 1164 Sofia, Bulgaria
⁶ Physik Department, Technische Universität München, D-85748 Garching, Germany

^a e-mail: christian.bernards@yale.edu
^b Present address: Physik Department, Technische Universität München, D-85748 Garching, Germany

Published online: 20 March 2014

Abstract

Using the high-resolution Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory (MLL) Tandem accelerator in Munich, we studied 0⁺ excitations in the mercury isotopes ¹⁹⁸Hg, ²⁰⁰Hg, and ²⁰²Hg after two-neutron transfer. We only observed 4-6 excited 0⁺ states per nucleus up to about 3-MeV excitation energy, far fewer than in other experiments of this (p, t) campaign. The results reveal a sharp drop in the number of low-lying 0⁺ states towards the ²⁰⁸Pb shell closure. We discuss the low-energy 0⁺ state density as a function of the valence nucleon number N_val. The 0⁺ excitation energies and the measured (p, t) transfer cross sections indicate a structural change throughout the Hg isotopes, with the most notable result being the peaking in the cross section of the low-lying excited 0₂⁺ state in ²⁰⁰Hg.