Excitation functions and angular distributions of protons and alpha particles emitted from the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ + ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ reaction were measured in the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ energy range from 8.05 to 20.425 MeV. The excitation functions show large, uncorrelated structures. Analysis on the basis of the autocorrelation function and the spectral density method yields largely varying values of the coherence energy, which can be attributed to the different steps of the statistical multistep compound emission chain. This process explains the average shape of the excitation functions, and also the absolute value of the emitted proton spectrum, measured at 13 MeV incident ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ beam.

NUCLEAR REACTIONS ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $p$), (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $\alpha$), $E=8.05-20.425\mathrm{}$ MeV; measured $\sigma (E;\theta )$; calculated $\sigma \mathrm{}\left(E\right)\mathrm{}$, $\sigma \left(E_p\right)$; deduced coherence widths.

• Received 6 August 1981

DOI:https://doi.org/10.1103/PhysRevC.25.717