Scattering of 22-MevαParticles byC12

Abstract

The elastic and inelastic scattering of 22-Mev $\alpha$ particles by carbon has been observed at a number of angles. Groups corresponding to the excitation of ${\mathrm{C}}^{12}$ to the known 4.4-, 7.7-, and 9.6-Mev levels were found. There was no evidence for the higher states reported by others, except possibly at ∼12.7-Mev excitation. A strong angular dependence and a marked lack of symmetry around 90° was observed. The excitation function for $E_{\alpha }=20.4\mathrm{} \mathrm{to} 22.6$ Mev indicates a resonance at $E_{\alpha }=21.85\mathrm{}\pm 0.1$ Mev, and the angular asymmetry indicates that there is at least one other level of opposite parity in this region. The $Q$-value for the second excited state was measured to be -7.64±0.07 Mev. By looking for the appropriate ${\mathrm{C}}^{12}$ recoil ions it was established that this state decays to ${\mathrm{Be}}^8$+$\alpha$ with >80% probability.