Electronic Symmetry Sensitive Vacuum-ultraviolet Spectroscopy of Carbon Dioxide in the Molecular Frame

Ultrafast electronic dynamics in molecules are governed by the symmetry and anisotropy of dipole-allowed transitions in the molecular frame. We probe these dynamics using align-excite transient absorption spectroscopy of molecules in the vacuum-ultraviolet (VUV) regime, which enables us to extract the molecular-frame differential absorption. Measurements in carbon dioxide reveal two regions of distinct electronic symmetry in the 7.5–7.9 eV photon energy range. The angular dependence of the absorption directly reflects the anisotropy of the underlying transition dipole moments, allowing symmetry assignment of the probed states. These results provide insight into molecular-frame electronic structure of CO2 in the VUV region where strong non-adiabatic coupling is present. We also discuss experiments probing the ultrafast evolution of electronic coherences in the presence of non-adiabatic dynamics.