Electron scattering from Be 9

The structure of $^{9}\mathrm{Be}$ is investigated using electron scattering measurements at 90\ifmmode^\circ\else\textdegree\fi{} and 160\ifmmode^\circ\else\textdegree\fi{} for momentum transfers between about 1.0 and 2.5 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$. In addition to the 3/${2}^{\mathrm{\ensuremath{-}}}$ ground state and the narrow 5/${2}^{\mathrm{\ensuremath{-}}}$ state at 2.43 MeV, detailed line-shape analysis was used to extract cross sections for broad states at 1.68, 3.05, 4.70, 6.38, 6.76, 11.28, and 13.79 MeV. The previously unknown state at 6.38 MeV was isolated from the known 6.76 MeV state in both (e,e') and (p,p') data using the dependence of peak position upon momentum transfer. On the basis of the form factor, the 6.38 MeV state replaces the 6.76 MeV state as the 7/${2}^{\mathrm{\ensuremath{-}}}$ member of the ground-state rotational band and the 6.76 MeV state is identified with the lowest 9/${2}^{+}$ state predicted by the shell model. The data for all states are compared with a shell-model calculation that uses the full 0\ensuremath{\Elzxh}\ensuremath{\omega} and 1\ensuremath{\Elzxh}\ensuremath{\omega} model spaces. Calculations are also presented for the narrow states between 14 and 18 MeV excitation.