Dissociative double ionization of CO in orthogonal two-color laser fields

We experimentally investigate dissociative double ionization of CO by a phase-controlled orthogonal two-color (OTC) laser pulse. Directional breaking of doubly ionized CO as a function of both kinetic energy and emission direction of the nuclear fragments is observed in the polarization plane steered by the laser phase. It is attributed to the dominating sequential double ionization at the maximum strength and nonsequential double ionization at a relatively weak strength of the spatiotemporally shaped oscillating laser field pointing to various directions. Our results are interesting not only for two-dimensional control of directional bond breaking, but also strengthen our understanding of strong-field sequential and nonsequential double ionization of molecules which are spatiotemporally streaked to various directions and kinetic energies by an OTC laser pulse.

Figure 1

Schematic diagram of the experimental apparatus.

Figure 2

(a,b) Sketch map of the spatiotemporal evolution of the electric field of the OTC laser pulse, and (c,d) measured two-dimensional asymmetry patterns of the directional emission of ${\mathrm{C}}^{+}$ from the (${\mathrm{C}}^{+}, {\mathrm{O}}^{+}$) channel in the $(p_y,p_z)$ plane at (a,c) ${\varphi }_{\mathrm{L}}=0$ and (b,d) ${\varphi }_{\mathrm{L}}=\pi$, respectively.

Figure 3

Two-dimensional maps of the retrieved (a) amplitude $A_0$ and (b) phase ${\varphi }_0$ of the asymmetry contrast of the (${\mathrm{C}}^{+}, {\mathrm{O}}^{+}$) channel as a function of ${\varphi }_{\mathrm{C}+}$ and KER of the nuclear fragments. (c,d) Retrieved amplitude $A_0$ and phase ${\varphi }_{\mathrm{A}0}$ as a function ${\varphi }_{\mathrm{C}+}$ for various KER ranges. The solid curves are the fits of the ${\varphi }_{\mathrm{C}+}$-resolved asymmetry amplitude.

Figure 4

(a) Normalized yield of the measured (${\mathrm{C}}^{+}, {\mathrm{O}}^{+}$) channel as a function of KER (or momentum) of the nuclear fragments. (b) Simulated rescattering probability of the electron versus its return energy at the recolliding time. The dashed green line denotes the ionization potential of $\mathrm{C}{\mathrm{O}}^{+}$.