Strong field dissociation dynamics of NO2+: A multiphoton electronic or vibrational excitation?

Abstract

A coincidence 3-D momentum imaging technique is employed to study the dissociation of a metastable NO2+ beam in an intense ultrafast laser field. We find that dissociation into N+ + O+ is aligned perpendicular to the laser polarization for intensities below 1015 W/cm2 while higher intensities (~1016 W/cm2) yield a prominent contribution from molecules breaking parallel to the field. The latter feature may be due to direct 2-photon transition to the vibrational continuum of the X2Σ+ ground state, a surprising multiphoton vibrational excitation.