High-Energy Alpha Particles fromB12

Abstract

An earlier investigation of the alpha-particle spectrum associated with the beta decay of ${\mathrm{B}}^{12}$ has been extended to an alpha-particle energy of approximately 3 Mev. The high-energy spectrum appears to indicate a broad level in ${\mathrm{C}}^{12}$ having an excitation energy of 10.1±0.2 Mev and a width at half-maximum of $\Gamma \approx 2.5$ Mev. The most probable spin and parity assignment for this level is $J=0^{+}$, although $J=2^{+}$ cannot be definitely excluded; for $J=0^{+}$ the width is approximately the Wigner limit. It is found that (0.13±0.04)% of all decays of ${\mathrm{B}}^{12}$ lead to this state.