Ab initio configuration interaction calculations of the ground and singlet A′ and A″ excited states have been performed, with all possible single and double excitations from the 10 highest occupied orbitals to the lowest 17 virtual orbitals being included, the previous C s symmetry molecular structure being used. Some of the states can be identified with excitation from individual occupied (SCF) orbitals to members of the virtual set, but some are not well represented by single configuration concepts. The results suggest that the three broad UV-spectral maxima observed in solution are not single excitations, but groups of excited states, with a total of 8 states. The closeness of some of these states makes positive assignment difficult. The most probable assignment is 455 nm (1 A″), 377 nm (2A″ + 1A′+ 2A′), ~ 277 nm (3A″ + 3A′), 232 nm (4A′ + 4A″).