The interference of Coulomb and nuclear excitation in the scattering of 16O from 58Ni, 88Sr and 142Nd

Abstract

The interference of Coulomb and nuclear excitation has been studied for 16O ions bombarding targets of 58Ni, 88Sr and 142Nd in the energy region spanning the Coulomb barrier. The measurements include elastic and inelastic (to the first 2 + state) excitation functions at 175° lab for all targets, excitation functions at 60°, 75° and 90° lab for 58Ni and 88Sr, angular distributions at 44, 50 and 60 MeV for 58Ni, and angular distributions at 52 and 60 MeV for 88Sr. From the sub-Coulomb data, B(E2) values (in units of e 2·b 2) of 0.066 ± 0.004 for 58Ni (1.45 MeV), 0.114 ± 0.015 for 88Sr (1.84 MeV) and 0.27 ± 0.03 for 142Nd (1.57 MeV) were obtained. The cross section data can be well reproduced by the optical model and the distorted-wave Born approximation with a collective model form factor for nuclear excitation. Absolute values for the real part of the optical model potential are obtained for the interaction of 16O and 58Ni in the region 1 fm to 3 fm beyond the nuclear surface. For r 0 = 1.3 fm, the DWBA fits to the data require r′ 0 > r 0, a′ < a and nuclear deformation parameters, ( βR) nucl., of 0.94 fm, 0.64 fm and 0.34 fm for 58Ni, 88Sr and 142Nd, respectively.