Dynamics of electromagnetically induced water molecule fragmentation

Abstract

The development of intense high-energy radiation sources and the improvement of techniques for detecting charged fragments have made possible experiments on multiple ionization of a molecule with registration of the momentum and charge of dissociation products in coincidence. This technique allows to determine (`fix') a molecular geometry at the time of fragmentation and called fixed-in-space molecule. In this work, the dynamics the water molecule dissociation fragments resulting from interaction with intense X-ray radiation has been studied. The charge distribution of oxygen ions was calculated, Newton diagrams were constructed for fragments - protons and the oxygen ion - for various charge states of the latter, and the released kinetic energy was evaluated. Calculations were performed using the [1]code for parameters close to [2]. The predictions for the different pulse parameters are done.

Figures (10)

• Figure 1: The neutral water geometry; shaded area indicates a region around the equilibrium available due to the vibrational modes: the green arrows schematically indicate the scissors' mode, the red ones --- symmetrical mode, and the blue arrows --- asymmetrical mode.
• Figure 2: PES of water cations as a function of distance between oxygen and hydrogen nuclei ($r_1$ and $r_2$) at the bond angle $\theta=110^{\circ}$. The row (a) presents data for the ground state, the row (b) --- for SCH state. On the right panels, there are sections of the PES with the planes: $r_1=r_2$, one proton is placed at the energy minimum $r_1=r_{min}$, and $r_1=3$ a.u. The 3D plots are shifted for better visualization of the energy minimum.
• Figure 3: The same as in Fig. \ref{['fig:fig2a']} but for a water dication. The row (a) presents data for the ground state, the row (b) --- for SCH, the row (c) --- for DCH state.
• Figure 4: The KER measured experimentally Isinger2019 (crosses) and calculated for the single-Gaussian (\ref{['eq:pulse']}) pulse (dashed line) with FWHM=20 fs and for double-Gaussian (\ref{['eq:pulse2']}) pulse (solid line, see parameters in the text). Color indicates the charge of the oxygen ion.
• Figure 5: The Newton diagram (a,b) and the angular correlation between protons (c,d) calculated (b,d) and measured in Jahnke (a,c). The calculations were performed for the pulse (\ref{['eq:pulse2']}).