The $\alpha$-particle energy spectra from bombardment of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ with 9.1-MeV protons have been obtained for $2.5°\le {\theta }_{\alpha }\le 120°$. The high-energy portions of the $\alpha$ spectra are interpreted as due to the ${}_{}{}^1{}_{}{}^{}S$, $p$+${}_{}{}^3{}_{}{}^{}\mathrm{H}$ finalstate interaction through the first excited state of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at 20.06 MeV. The factored-wave-function method is used to deduce the resonance parameters of this state. Consistency in the use of this method is obtained by a plane-wave Born-approximation calculation based on triton-transfer mechanisms to account for the forward peaking in the angular distribution. Coincidence measurements between $\alpha$ particles and other charged reaction products give additional evidence for the $0^{+}$ assignment to the state and indicate the importance of the $\alpha$+${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and $\alpha$+${}_{}{}^1{}_{}{}^{}\mathrm{H}$ final-state interactions at still higher excitation energy of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ system.

• Received 28 August 1969

DOI:https://doi.org/10.1103/PhysRevC.1.816