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.

Helicity-dependent dissociative tunneling ionization of CF4 in multicycle circularly polarized intense laser fields

“…Among others, control of directional ejection of fragment ions with o-2o two-color laser fields has been demonstrated with a variety of molecules. [10][11][12][13][14][15][16][17][18] This includes the application to symmetric molecules such as CO 2 , where the selective breaking of the two equivalent C-O bonds was observed in the Coulomb explosion of CO 2 2+ -CO + + O + 14,15 by deformation of the potential energy surfaces of CO 2…”

Dissociative ionization and Coulomb explosion of CH4 in two-color asymmetric intense laser fields

“…16,17 In particular, asymmetric fragment ejections from symmetric molecules were observed for small molecules, such as D 2 , 18,19 CO 2 , 20,21 C 2 H 2 , 22 and H 2 O. 23,24 The origin of the asymmetry has been discussed in terms of coherent coupling between electronic states, 18,19 laser-induced coupling of highest-occupied molecular orbitals (HOMO) and HOMOÀ1, 2, 22 and the wavepacket dynamics on deformed potential energy surface (PES). 20,21 Recently, we carried out an o-2o study on dissociative tunneling ionization of tetrafluoromethane (CF 4 ), which has repulsive potential energy surfaces in the ground and first excited states of CF 4 + .…”