Neutron orbit sizes from measurements of the ⁶⁰Ni(t,d) reaction in the sub-Coulomb regime

Angular distributions of the deuteron groups from the ⁶⁰Ni(t,d) reaction populating the J^pi =3^-/2 ground state, the J^pi =3^-/2 first excited state at 68 keV and the J^pi =1^-/2 second excited state at 284 keV of the final nucleus, ⁶¹Ni, have been measured at incident energies near the Coulomb barrier of 2.5, 3.0, 3.5 and 4.0 MeV. Values of the root-mean-square radii of the orbits into which the neutron is transferred (2p₃2/, 1f₅2/, and 2p₁2/) are obtained from a DWBA analysis of the data. The sensitivity of the results to variations in the optical-model parameters and uncertainties in the single neutron spectroscopic factors of the states excited is discussed. A comparison is made of the RMS radius of the neutron excess in ⁶²Ni, calculated from the results of this work, with the value extracted from the Coulomb energy difference of the ⁶²Ni-⁶²Cu pair.