Wavepacket dynamics study of Cr(CO)5after formation by photodissociation: relaxation through an (E ⊕ A) ⊗ e Jahn–Teller conical intersection

In the ultrafast photodissociation of Cr(CO)6, Cr(CO)5 is formed within 50 fs. Initially in an excited state, a Jahn–Teller (E ⊗ e) conical intersection is believed to then act as an efficient decay funnel to the ground state. Here, we present a Hamiltonian representing the first three electronic states of Cr(CO)5, obtained by fitting the linear vibronic coupling model to calculations using a complete active space self-consistent field (CASSCF) wavefunction. The intersection is in fact found to involve (( E ⊕ A) ⊗ e) pseudo-Jahn–Teller coupling, with the singly degenerate state playing an important role. The results of wavepacket dynamics using the multi-configuration time-dependent Hartree (MCTDH) method show that this model is consistent with the experimental data.