Direct observation of strong-field enhanced ionization in CO and N$_{2}$

Enhanced ionization (EI) of molecules has been predicted as a common process in molecular dissociative ionization in strong fields over two decades ago. However, direct evidence for EI has only been found in I$_{2}$ and H$_{2}$. In this work, we perform the first direct study of EI in CO and N$_{2}$. We find a new dissociation channel in each of these two molecules following double ionization that has not been previously resolved. Interestingly, EI occurs only in the newly discovered channels with a lower kinetic energy release but, surprisingly, does not happen in the commonly-seen dissociation channels that were previously assigned undergoing EI.