Oblate-prolate transition in odd-mass light mercury isotopes

Anomalous isotope shifts in the chain of light Hg isotopes are investigated by using the Hartree-Fock-Bogoliubov method with the Skyrme SIII, SkI3 and SLy4 forces. The sharp increase in the mean-square radius of the odd mass $^{181-185}$Hg isotopes is well explained in terms of the transition from an oblate to a prolate shape in the ground state of these isotopes. We discuss the polarization energy of time-odd mean-field terms in relation to the blocked level by the odd neutron.