Decay ofBe9*(2.43-Mev State)

Abstract

The decay of the 2.43-Mev state of ${\mathrm{Be}}^9$ is treated theoretically. Of the open two-body decay channels all but one involve a nuclear state, the energy of which is not well defined. The usual formalisms have been generalized to take this into account. The estimate of the decay rates is made by means of a variational internal wave function for the ${\mathrm{Be}}^{9*}$ state, based upon the alpha-particle model. It is found that the principal mode of decay is to ${\mathrm{He}}^5$+${\mathrm{He}}^4$. Model—dependent arguments are given to show that decay to the ground state of ${\mathrm{Be}}^8$ should be inhibited. Furthermore, the momentum and angular distributions of alphas emitted in the decay through several two-particle decay modes are computed. These latter calculations do not assume any specific nuclear model, but depend on the weak assumption that the state is excited by a direct reaction. Comparison with recent measurements indicates that in addition to the ${\mathrm{He}}^5$+${\mathrm{He}}^4$ decay, approximately 7% of the decay occurs to the ground state of ${\mathrm{Be}}^8$, which is consistent with our calculations.