This section addresses why 3 n* phosphorescence is faster than 3 * one in aromatic carbonyls. We will take BA as an example and focus our discussion on T1→S0 phosphorescence. First, we must remember that state symmetry should consider both the usual symmetry representation of the spatial wave function and the symmetry representation generated by the spin wave function. The spin wave function of the singlet state always transforms as the totally symmetric representation of the group (1), while the spin wave function Cartesian components belong to the representations generated by the Rx, Ry, and Rz rotations . Thus,