Multielectron ionization in O$_2^+$ driven by intense infrared laser pulses

Abstract

We extend a recently developed three-dimensional semiclassical model [\href{https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.033106}{Phys. Rev. \textbf{A} 109, 033106 (2024)}] to study multielectron ionization and the formation of highly excited Rydberg states in O$_{2}^+$ driven by intense infrared laser pulses. Our model fully accounts for the Coulomb interaction between all particles, except for the Coulomb repulsion between bound electrons which is replaced by effective potentials. This replacement overcomes the hurdle of artificial autoinization. In addition, the multielectron motion is treated on an equal footing with nuclear motion, that is, electrons and nuclei are both allowed to move at the same time. We focus on triple and double ionization as well as frustrated triple and double ionization. For these processes, we identify and explain the main features of the sum of the kinetic energies of the final ion fragments resulting from the break-up of O$_{2}^+$. We also describe a physical mechanism that underlies frustrated triple ionization.

Figures (10)

• Figure 1: Schematic illustration of the main steps involved in the ECBB model.
• Figure 2: The configuration of the diatomic molecule we use to set-up the microcanonical distribution. The origin of the coordinate system is halfway between nuclei 1 and 2.
• Figure 3: Probabilities of the TI, FTI with $n>2$, DI and FDI with $n>2$, for O$_2^+$, for the four intensities and two molecular orientations considered in this work.
• Figure 4: Distribution of the sum of the final kinetic energies of the ions produced in triple ionization (gray solid lines), double ionization (black solid lines), frustrated triple ionization (black dotted lines) and frustrated double ionization (gray dotted lines) for $\mathrm{O_2^+}$ oriented parallel (a),(c),(e),(g) and perpendicular (b),(d),(f),(h) to the electric field. All distributions are normalized to one.
• Figure 5: Distribution of the sum of the final kinetic energies of the ions produced in triple ionization (gray solid lines) and double ionization (black solid lines) at 7 $\mathrm{PW/cm^2}$ averaged over both orientations. We also include experimental distributions from Ref. PhysRevA.79.063414 for triple ionization (gray dotted lines), double ionization (black dotted lines). All distributions are normalized to one.