Quadrupole collectivity in the Si isotopes around N=20

The angular momentum projected generator coordinate method using the quadru pole moment as a collective coordinate and the Gogny force as the effective interaction is used to describe the properties of the ground and low-lying excited states of the neutron rich light nuclei Si-32,Si-34,Si-36. It is f ound that the ground state of the nucleus Si-34 is spherical. However, this is not due only to the N = 20 shell closure, since the ground state of Si- 34 contains a significant amount of the intruder f(7/2) neutron orbital. A rather good agreement with experimental data for many observables is obtain ed.