Ab initio calculations of the electronic states of acetyl radical

Four excited states, A2A″, B2A′, C2A′, and D2A″ of the acetyl radical CH3CO, which is the intermediate of the Norrish type I photolysis reaction of acetone, were found by MR(SD)CI calculations. Their vertical excitation energy from the ground state X2A′ is 60.0, 113.0, 154.5 and 161.4 kcal/mol, respectively. The A2A″ state is a bound state while the X2A′ state has a low dissociative energy barrier to form CH3 and CO. Based on these calculations, a state-specific reaction path of one photon and two photon photodissociation of acetone is described.