The cross section of the bremsstrahlung process ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\alpha ,\alpha \alpha )\gamma$ has been measured at five energies between 11.4 and 13.5 MeV with detector lab angles of ${\theta }_1={\theta }_2={37}^{\circ }$, and at 9.35 MeV with ${\theta }_1={\theta }_2={35}^{\circ }$. The results agree well with predictions based on the work of Feshbach and Yennie, Signell, and Green. No significant enhancement is found at the final state energy corresponding to the 2.9 MeV resonance in ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$. A single measurement of the process ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\tau ,\alpha \alpha )\gamma$ made at 7.4 MeV with ${\theta }_1={\theta }_2={37}^{\circ }$ is also in good agreement with theory. Details of the experimental technique and of finite geometry corrections are discussed.

[NUCLEAR REACTIONS ${}_{}{}^3{}_{}{}^{}\mathrm{H}\mathrm{e}-\alpha$ and $\alpha -\alpha$ bremsstrahlung, $E=7.4,9.35,11.4-13.5\mathrm{}$ MeV, measured $\frac{d^2\sigma }{d{\Omega }_{1}d{\Omega }_2}$.]

• Received 7 September 1973

DOI:https://doi.org/10.1103/PhysRevC.8.2132