The Proton and Neutron Quadrupole Collectivity in ³²Si

The collective excitation is an important characteristic of nuclear structure. Proton and neutron collectivity are the same in most of stable nuclei; however, it has been found out that this can be broken for some of nuclei around magic number, such as ¹⁶C and ³⁸Si. In this work, we investigate the collective property in the ground state of ³²Si, which has Z=14 semi-magic number and N=18 close to magic number 20, by ³²Si (d, d') reaction in inverse kinematics.

The experiment was performed at RI beam facility (EN course) RCNP. The ³²Si beam at the average energy of 18.5 AMeV bombarded a solid deuterium target. The final states of ³²Si were selected from the measurement of de-excitation γ rays using Clover Ge detector array CAGRA, in coincidence with the scattered ³²Si identified by ΔE-E method using Silicon telescope. The quadrupole collectivity was deduced from the angular distribution of differential cross section of the (d, d') reaction to the first 2⁺ state. By combining with proton quadrupole collectivity deduced from the known B(E2) value, proton  and neutron quadrupole parameters were determined separately.