Interference dips in molecular absorption spectra calculated for coupled electronic state potential surfaces

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Abstract
Interference effects in electronic absorption spectra caused by coupling between excited states are calculated and interpreted by using numerical integration of the time‐dependent Schrödinger equation and the time‐dependent theory of electronic spectroscopy. The interference between nearby spin‐forbidden doublet and spin‐allowed quartet states of chromium (III) and vanadium (II) metal complexes causes sharp decreases of intensity or dips in the envelopes of absorption bands. The states are coupled by spin–orbit coupling. The origin of the dips is explained in terms of interference between wave packets moving on potential energy surfaces representing the states. The importance of curve crossing and amplitude transfer between the states is analyzed quantitatively. The theory is applied to the absorption spectrum of a chromium (III) complex.