Strong-field ionization of water: Nuclear dynamics revealed by varying the pulse duration

Multi-Particle Three-Dimensional Covariance Imaging: “Coincidence” Insights into the Many-Body Fragmentation of Strong-Field Ionized D2O

“…The results shown in Figure provide a detailed view of the unbending dynamics in strong-field ionized D 2 Ohighlighting the important role of peak laser intensity, complementing previous studies in this area. ,, Even with the longer pulses, for which significant nuclear motion during the pulse is possible, very little evidence of this unbending motion is seen in the low intensity regime, which strongly resembles measurements with much shorter pulses (as can be seen in comparing Figure a to Figure a and b). Likely, this dependence of the fragmentation dynamics on pulse intensity is because for higher intensity pulses, molecules are likely to be ionized earlier in the pulse, and there is a stronger field dressing of states .…”

“…Here, we extend the three-dimensional covariance imaging technique to three-body dissociations, using both 2-fold and 3-fold covariance analysis to gain a kinematically complete view of strong-field doubly ionized D 2 O. Crucially, these results are compared quantitatively to low count rate experiments performed under otherwise identical experimental conditions. − In this case, covariance imaging yields the same ensemble-averaged results as those performed under coincidence conditionswith a substantial decrease in experimental acquisition time of approximately 2 orders of magnitude. This facilitates studies that would otherwise be extremely impractical using traditional techniquesas demonstrated through a survey of the effects of peak laser intensity on the many-body breakup of ionized D 2 O. ,,,,, These results elucidate nuclear dynamics driven during the intense laser pulse, and we expect they will stimulate future theoretical work to unravel the complex coupled nuclear and electron dynamics in the strong laser field. , …”

“…Unravelling this relationship can be a difficult task, particularly when ionization is driven by a strong laser field, which initiates a whole host of exotic phenomena that can influence the ultimate photofragmentation dynamics. These include field-induced distortions of molecular energy levels and nuclear dynamics, geometric and dynamic alignment, multielectron ionization dynamics and electron rescattering. − …”

“…To demonstrate this, we measured the (D + ,D + ) covariance for 30 fs pulses with different intensities. Recent work has compared the observed three-body dissociation dynamics in D 2 O following strong-field ionization by intense 10 and 40 fs pulses. ,, In these studies, D 2 O molecules were found to undergo significant unbending motion during the ionization/fragmentation process for longer laser pulses, characterized by a narrow β distribution in the D + /D + /O channel. One possible contribution to this unbending motion is dynamics in states of the monocation.…”

“…One possible contribution to this unbending motion is dynamics in states of the monocation. This contribution can be understood in terms of the laser field coupling the (bent) D 0 and (linear) D 1 potentials, inducing bond-softening distortions in the D 0 state. ,, Additionally, when ionizing with longer pulses (40 fs), the two D + were preferentially ejected along the polarization axis of the laser, indicative of dynamic alignment, which was absent for the shorter (10 fs) pulses …”