Excitation of analog isovector giant resonances via the (n, p) reaction on 14N and 16O at 60MeV

Abstract

Data were accumulated for the (n, p) reaction on 14N and 16O using 60MeV neutrons. Angular distributions of the cross sections for eight proton groups were extracted and compared to distorted-waves Born approximation (DWBA) calculations using a simple macroscopic model. Enhancements in the spectra were seen in each case in the region of excitation corresponding to the giant dipole resonance (GDR) of the target nucleus. DWBA calculations show that these excitations are primarily dipole and favor the use of the Goldhaber-Teller form factor. Comparison with photo-absorption measurements suggests that there may also be significant contributions to the (n, p) reaction from “spin-flip” dipole excitations. The other proton groups could be correlated with the results of other experiments and include excitations of analogs of the giant isovector “magnetic” dipole mode of 14N.