Multiorbital and excitation effects on dissociative double ionization of CO molecules in strong circularly polarized laser fields

Abstract

We investigate the sequential double-ionization dynamics for the dissociative channel C++O+ of CO molecules in strong circularly polarized laser fields using four-particle coincidence measurements. By combining the fragmentation-pathway-resolved ionic angular distributions with the molecular frame photoelectron angular distributions distinguished for each ionization step, the significant effects of multiorbital ionization and laser-driven excitation are revealed. For the main distribution of ionic fragments in the polarization plane, the participation of the highest-occupied molecular orbitals (HOMO, HOMO-1, and HOMO-2) and the important contribution of postionization excitation are identified for various fragmentation pathways. Comparisons among different intensities further indicate the dependence of the multiorbital ionization on laser intensities. For the substantial emissions of fragments out of the polarization plane, however, the ionization from HOMO-1 (and subsequent excitation) always plays a crucial role. This work demonstrates the feasibility of disentangling the complex dynamics in molecular dissociative double ionization with the angular streaking method.