Single-Particle States of the Neutron from Gross Structure in the Proton Spectra of (d, p) Reactions

Abstract

Systematic gross-structure peaks have been observed in the proton spectra from ($d, p$) reactions on nuclei in the region of atomic weight 60. Measurements at deuteron energies of 4, 10, and 21.6 Mev were made with the energy resolution in the proton detectors considerably worse than the known spacing of levels in these nuclei. In all these measurements, the peaks in the proton spectra stayed at a fixed energy of the captured neutron. Angular distributions obtained with 10-Mev deuterons were analyzed in terms of the Butler theory of stripping reactions. It was found that each peak in the proton spectrum corresponded to a specific value of the orbital angular momentum of the captured neutron. The peaks are interpreted as being caused by the shell-model single-particle states of the captured neutron, when these states are smeared out among the many actual levels of the nucleus. Thus the observed gross-structure peaks are believed to correspond to the giant resonances of the complex-potential model of Feshbach, Porter, and Weisskopf. Peaks have been assigned to the $1f_{\frac{7}{2}}$, $2p_{\frac{3}{2}}$, $1f_{\frac{5}{2}}$, $2p_{\frac{1}{2}}$, $1g_{\frac{9}{2}}$, $2d_{\frac{5}{2}}$, $3s_{\frac{1}{2}}$, and $2d_{\frac{3}{2}}$ shell-model states, although these states could not all be identified in every nucleus that was studied. The relative intensities of the peaks are also consistent with this interpretation, except for the $l=0\mathrm{}$ peaks at high excitation energies. Information on the ground-state configurations of the target nuclei has also been obtained from the intensities.