Ellipticity effects on single and double ionization of diatomic molecules in strong laser fields

By studying high-precision ion yield measurements in diatomic molecules N₂ and NO with 30-fs linearly (LP) and circularly (CP) polarized light, we extend to molecular systems the study of ellipticity effects on both single and double ionization in strong laser fields. Competing ionization rates between LP and CP light, as predicted in the Ammosov-Delone-Krainov model, is observed experimentally by studying singly ionized N₂ and NO. We further observe an anomalously high NO²⁺ signal with CP, which shows a nonsequential ionization signature. A hypothesis is given that ties this observation to the influences of electronic structure on ellipticity effects in strong-field ionization.