Detailed measurements of the angular distribution for the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$→${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ single neutron transfer reaction as a function of bombarding energy from just above the Coulomb barrier to approximately four times the barrier energy are reported. The distorted-wave Born approximation for the transfer process does not reproduce the strong oscillations observed in both the experimental angular distributions and excitation functions, while analyses using a two-pole model for the transfer amplitude indicate significant multistep contributions. We show that the cross section in the 90° region in the center of mass is characteristic of an increased collision delay time and of an effective $Q$ value 1 MeV smaller than the asymptotic observable $Q$ value. Angular distributions calculated using the dynamic two-center shell model of Konnecke et al. also succeed in reproducing the salient features of the data. The present experiment provides evidence for the occurrence of single-particle nuclear molecular behavior in a heavy-ion neutron transfer reaction. Data for the elastic scattering of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ are also presented and analyzed. We conclude that the elastic scattering excitation functions are consistent with the occurrence of orbiting in the dynamic interaction.

NUCLEAR REACTIONS ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$,${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$,${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, measured $\sigma (E;\theta )$, $E\left(\mathrm{lab}\right)=16.0-50.0\mathrm{}$ MeV, $\theta \left(\mathrm{lab}\right)=17.8\mathrm{}°-51.4\mathrm{}°$, comparison with DWBA calculations, analysis using two-pole model, interpreted as evidence for reduced effective $Q$ value in the surface region and an increase in the collision delay time compared to values expected for a single step process; ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$,${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, measured $\sigma \mathrm{}\left(E\right)\mathrm{}$, $\theta \left(\mathrm{lab}\right)=25\mathrm{}°, 30°, 35°, 40°, 45°$, $E\left(\mathrm{lab}\right)=14.5-71.0\mathrm{}$ MeV, optical model calculations, analysis using one pole model, gross structure oscillations interpreted as a geometrical effect.

• Received 28 February 1983

DOI:https://doi.org/10.1103/PhysRevC.28.168