Direct detection of enhanced ionization in CO andN2in strong fields

Enhanced ionization (EI) of molecules has been extensively studied over the past two decades as a common process in molecular dissociative ionization in strong laser fields. Direct evidence for EI has been found only in ${\mathrm{I}}_{2}$ and ${\mathrm{H}}_{2}$. However, in this work we perform a direct study of EI in CO and ${\mathrm{N}}_{2}$, and find enhanced ionization in an alternate dissociation channel in each of these two molecules following double ionization. Surprisingly, EI does not happen in the commonly seen dissociation channels that were previously assigned undergoing EI. Instead, EI occurs only in the alternate channels seen here with a lower kinetic-energy release.