Fast-timing lifetime measurements of the 33/2+ and 25/2− states in 189Hg: oblate excitations

Abstract

Abstract The lifetimes of the I π = 33/2+ and I π = 25/2− states with E x = 2674.6 keV and E x = 1917.3 keV, respectively, in 189Hg have been determined by using the fast-timing techniques with the HPGe and LaBr3:Ce array via the 175Lu(19F, 5n)189Hg reaction at a beam energy of 100 MeV. The deduced B(E2) strengths have been discussed in relation to the systematics of the previously reported B(E2) strengths in the heavy mercury isotopes. The transition quadrupole moments Q t are derived from present experimental data. The Q t values together with the excitation energies of the (+, 0)(+, 1/2) and (+, 0)(−, 1/2) bands are interpreted in terms of the Nilsson–Strutinsky–Bogoliubov model (CNSB) calculations suggesting oblate excitations in 189Hg.