The differential cross sections for the reaction ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}({}_{}{}^{14}{}_{}{}^{}\mathrm{N}, \alpha ){}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ leading to the lower excited states of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ were measured at ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ energies of 25 and 35 MeV. The excitation functions of those states were also measured at 0, 30, and 110° over the range $5.2\le E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<13\mathrm{}$ MeV. The data were analyzed in terms of the statistical compound nucleus model. The average behavior of this reaction is fairly reproduced by these calculations with reasonable values of the level density and spin cutoff parameters for this excitation energy region. Some features, however, could not be explained by this model. In particular, a large structure was seen in the 0° excitation function at 10 MeV(c.m.) in many channels, which is clearly not of statistical origin. A possible explanation is the presence of a doorway state in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ at the corresponding excitation energy.

NUCLEAR REACTIONS ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}({}_{}{}^{14}{}_{}{}^{}\mathrm{N}, \alpha ){}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, $E=13-35\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$ at $E=25, 35$ MeV and $\sigma \mathrm{}\left(E\right)\mathrm{}$ at ${\theta }_{\mathrm{lab}}=0, 30, 110°$. Enriched targets; Hauser-Feshbach and correlation analysis; deduced resonance energy and width.

• Received 24 June 1975

DOI:https://doi.org/10.1103/PhysRevC.12.1878