Exploring the influence of experimental parameters on the interaction of asymmetric ω/2ω fields with water isotopologues.

Abstract

Water isotopologues are doubly ionized by phase-controlled asymmetric ω/2ω laser fields, and their two-body fragmentation channels leading to pairs of OH+/H+ [channel (I)] and H2 +/O+ [channel (II)] are systematically investigated. The dependence of the ionic fragments on phase distinguishes between two dissociation channels, while a quantity that is proportional to the directionality of the ejected fragments, called asymmetry parameter (β), is measured as a function of composite field's phase. The dependence of the two channels' asymmetry amplitude (β0) on the experimental parameters that characterize the composite field (wavelength, anisotropic shape, and total intensity) is found to differ significantly. The channel leading to H2 + and O+ ions' ejection shows increased asymmetry compared to the other channel and is found to be dependent on excitation of overtones and combinations of vibrational modes as well as from the field's shape and intensity. The asymmetry (β) of the channel leading to the release of a H+ and an OH+ ions is far less sensitive to the experimental parameters. Inspection of the individual OH+ peak's dependence on phase reveals information on the effect of the field's profile, which is unclear when asymmetry (β) is inspected.