"Lifetime measurements in 98Zr and shape transition in Zr isotopes".

The equilibrium shape of an atomic nucleus is determined by a delicate interplay between macroscopic and microscopic effects. Thus its study is a very sensitive probe to nuclear quantum many-body correlations and serves as a testing ground for nuclear theories. In fact, one of the fundamental quest in nuclear physics is to study the various modes of excitation and the associated evolution of nuclear shapes along spin and isospin axes in atomic nuclei. The nuclei at closed shells tend to have spherical ground state, however, as one moves away, the polarizing effect of added nucleons leads to deformation.Throughout the nuclear landscape, this onset of deformation is usually a gradual process, however in mass 100-110 region the shape change is rather dramatic and abrupt. While the ground states of Sr, and Zr isotopes with neutron number, N ranging from the magic number N=50 up to N<60 are spherical, they undergo a rapid shape transition from nearly spherical to well deformed prolate deformations between N=58 and N=60. This sudden onset of deformation is reflected in a sharp drop by a factor of ~6 in the excitation energy of the 2+ state at N=60 which is the largest known change on the mass surface. Although first observed in 70s, this puzzling phenomenon has kept both experimentalists and theoreticians equally engaged since then.In this talk I will present some recent results highlighting our efforts at solving this puzzle through study of shape and collectivity in 98Zr, a nucleus which lies near the critical point of this shape transition. In addition to these results, some future prospects on study of shape evolution and shape coexistence in A~100-110 region nuclei will be presented. 
Referrences:
 [1] T. Togashi et al., Phys. Rev. Lett. 117, 172502 (2016). 
 [2] P. Singh et al., submitted