The reactions 14N(p, 3He) 12C, 14N(d, α) 12C, 13C(p, d) 12C and the 4 + level of 12C

Abstract

In a study of the two-nucleon transfer reaction 14N(p, 3He) 12C at 50 MeV, strong transitions are observed to the ground state, 4.43, 12.71, 14.08, 15.11 and 16.11 MeV levels of 12C. The first four of these levels are also strongly excited in the 14N(d, α) 12C reaction, which is investigated at incident energies of 15 and 20 MeV. A detailed comparison of the data is made with the theory of direct reactions, using intermediate coupling, shell-model wave functions for 12C, and a finite-range non-local formulation of the DWBA. Good agreement between theory and experiment is obtained with realistic optical-model potentials for all reaction channels. The analysis identifies the 14.08 MeV level as the lowest 4 + state of 12C. This assignment is supported by a study of the single-nucleon transfer reaction 13C(p, d) 12C at 50 MeV in which a 4 + state cannot be reached by 1p shell neutron pick-up. In this reaction the 14.08 MeV level is not observed. The angular distributions for the observed levels at 0.0, 4.43, 12.71, 15.11 and 16.11 MeV are satisfactorily explained with a finite-range non-local DWBA theory and with spectroscopic factors derived from intermediate coupling shell-model wave functions.