Shape coexistence and collectivity in neutron-deficient mercury isotopes

Abstract

Recoil Distance Doppler Shift measurements of 182Hg have been performed at the University of Jyväskylä utilising the Köln plunger device. Lifetimes of excited yrast states up to the 10+ state have been measured. The 2+ , 4+ , 6+ , 8+ and 10+ states were found to have lifetimes of 41(3) ps, 35.7(15) ps, 8.2(5) ps, 2.9(3) ps and 1.2(3) ps respectively. The high collectivity of the states with Iπ ≤ 4+ indicate their prolate deformed character. In 182Hg the 2+ yrast state was deduced to be a strong admixture of the coexisting prolate and oblate structures. Coulomb excitation measurements of 182,186Hg performed at REX-ISOLDE using the MINIBALL HPGe array examine the quadrupole moment and transitional matrix elements associated to the 2+_1 , 2+_2 and 4+_1 states in 182Hg and the 2+_1 state in 186Hg. The spectroscopic quadrupole moment of the 2+_1 state in 182Hg measured -0.45 eb, indicating prolate deformed character. Conversely, the 2+1 state in 186Hg was found to be oblate from the spectroscopic quadrupole moment of +1.74 eb. Transitional matrix elements for both 182Hg and 186Hg were found to be in agreement with those from lifetime measurements.