Non-adiabatic direct dynamics study of chromium hexacarbonyl photodissociation

The photodissociation of Cr(CO)(6) has been studied using direct dynamics including trajectory surface hopping. The dissociation takes place on a steep excited-state potential surface leading to ejection of a CO ligand within 100 fs in reasonable agreement with time-resolved studies by Fubeta et al.(1-3) Our dynamics studies of the Cr(CO)(5) photoproduct allow us to determine mechanistic details of the relaxation of the excited state of this species. We find that Cr(CO)(5) decays to the ground state via a Jahn-Teller (symmetry-induced) conical intersection, at a trigonal bipyramid geometry. The molecule then oscillates in the well of the "moat" surrounding this conical intersection. Our results provide evidence for the dissociation mechanism proposed by Fubeta et al.(1-3) Both the computed frequency of the coherent oscillation and the delay time until this motion is observed are in good agreement with experimental results.