A study of inelastic events induced by the bombardment of helium nuclei with 32-Mev protons has been made.

No low energy group of protons has been found which would indicate the existence of an excited, heavy-particle stable state of the helium nucleus. The absence of a bump on the continuum of protons from the reactions $p+{\mathrm{He}}^4\to {\mathrm{He}}^3+n+p^{\prime },$ $p+{\mathrm{He}}^4\to {\mathrm{H}}^3+p^{\prime \prime }+p^{\prime },$ indicates a maximum cross section of 0.1 mb/sterad at 45° c.m. for the production of a single excited helium level as high as 23.3 Mev above the ground state. Further, the observed rather flat shape of the continuum requires the existence of at least two levels of about 1-Mev half-width, separated by about 1 Mev.

The angular variation of the differential cross section for the production of deuterons from the reaction $p+{\mathrm{He}}^4\to {\mathrm{He}}^3+d$ has been measured. When the principle of detailed balancing is invoked, good agreement with the prediction of the theory of Butler is obtained for $r_0\left(\mathrm{range}\mathrm{of}\mathrm{nuclear}\mathrm{forces}\mathrm{plus}\mathrm{radius}\mathrm{of}{\mathrm{He}}^3 \mathrm{nucleus}\right)=4.2\mathrm{}\times {10}^{-13\mathrm{}}$ cm.

• Received 4 August 1952

DOI:https://doi.org/10.1103/PhysRev.89.422