Abstract
Lifetime measurements of excited states in ¹⁷⁸Hg have been performed using the ¹⁰³Rh(⁷⁸Kr,p2n) reaction at a beam energy of 354 MeV. The recoil-decay tagging (RDT) technique was applied to select the ¹⁷⁸Hg nuclei and associate the prompt γ rays with the correlated characteristic ground-state α decay. Lifetimes of the four lowest yrast states of ¹⁷⁸Hg have been determined using the recoil distance Doppler-shift (RDDS) method. The experimental data are compared to theoretical predictions with focus on shape coexistence. The results confirm the shift of the deformed prolate structures to higher lying states but also indicate their increasing deformation with decreasing neutron number