Ab initio computations from 78Ni towards 70Ca along neutron number N = 50
B. S. Hu, Z. H. Sun, G. Hagen, G. R. Jansen, T. Papenbrock
Abstract
We present coupled-cluster computations of nuclei with neutron number N = 50 “south” of 78 Ni using nucleon-nucleon and three-nucleon forces from chiral effective field theory. We find an erosion of the magic number N = 50 toward 70 Ca manifesting itself by an onset of deformation and increased complexity in the ground states. For 78 Ni, we predict a low-lying rotational band consistent with recent data, which up until now has been a challenge for ab initio nuclear models. Ground states are deformed in 76 Fe, 74 Cr, and 72 Ti, although the spherical states are too close in energy to unambiguously identify the shape of the ground state within the uncertainty estimates. In 70 Ca, the potential energy landscape from quadrupole-constrained Hartree-Fock computations flattens, and the deformation becomes less rigid. We also compute the low-lying spectra and B ( E 2 ) values for these neutron-rich N = 50 nuclei.