Imaging correlated nuclear motion mediated by passage through a conical intersection

Observing the coupled electronic and nuclear dynamics and the energy flow between electronic and vibrational degrees of freedom during photochemical reactions represent a key challenge in ultrafast photochemistry. Even for simple triatomic molecules, the correlated dynamics are too complex to be fully captured by state-of-the art experiment and theory. Here we use time-resolved Coulomb explosion imaging, coupled with ab initio quantum wavepacket calculations, to image the non-adiabatic dynamics of UV-excited NO₂ as it evolves toward, and relaxes through, a conical intersection, and the ensuing energy transfer between bending and asymmetric-stretch vibrational modes on the electronic ground state. Due to the highly multidimensional information contained in coincident Coulomb explosion imaging data, we can visualize the the dynamics of the highly delocalized nuclear wavepackets in unprecendented detail.