Theory of the Photo- and Electrodisintegration ofBe9

Cross sections for the photo- and electrodisintegration processes at relatively low energies have been calculated as a function of energy on the basis of a simple model of the ${\mathrm{Be}}^9$ nucleus in which a neutron is assumed to move in the potential well provided by the remainder of the nucleus. According to the theory, the disintegration at low energies results primarily from electric dipole transitions from the ground $P_{\frac{3}{2}}$ state to $S$ and $D$ states in the positive energy continuum. Magnetic dipole disintegration does not seem to play an important role. In order to obtain agreement between the theoretical and empirical photo-disintegration cross sections, it seems necessary to make the plausible assumption that the interaction between the prospective photo-neutron and the remaining nucleons of the nucleus is a function of the orbital angular momentum of the system (Majorana interaction). Furthermore, complete neglect of the $P_{\frac{3}{2}}-P_{\frac{1}{2}}$ splitting of the lowest $P$ state leads to an angular distribution of the ejected neutrons which does not agree with the (preliminary) empirical results.