Partial level scheme for . Excited states are labeled by their excitation energy and are given in . Parity assignments enclosed in parentheses are consistent with the data, but an opposite parity assignment, while unlikely, cannot be ruled out. States associated with the ground state (positive parity) and the octupole-vibrational (negative parity) configurations are given in blue and are well understood within the framework of the shell model. States with odd spin and positive parity (far left) and even spin negative parity (far right) that cannot be explained by the shell model are given in red. Arrows connecting these states with the shell model states indicate the observed electric-dipole transitions () whose lifetimes have been measured by Astier et al. to be picoseconds. These transitions are labeled by their energy in . The red states as well as their decay properties are explained by a cluster model which assumes they are associated with a configuration.