A CASSCF/MR-CCI study of the excited states of Fe(CO)5

CASSCF/MR-CCI calculations have been performed to determine excited states of Fe(CO)5 in the VUV region as well as the corresponding dipole moments. In spite of the high density of states between 25 000 and 45 000 cm−1, only three allowed transitions, with rather high oscillator strengths, 1A1′ → a 1E′, 1A1′ → 1A2″, 1A1′ → b 1E′ are present. The a 1E′ state is metal-centered (3d to 3d excitation) whereas the 1A2″ and b 1E′ correspond to 3d to πCO∗ excitations. The importance of these states for dissociation processes is discussed.