关键词: alignment, Coulomb-corrected strong-field approximation (CCSFA), photoelectron momentum distribution (PMD), image

Abstract: The alignment-dependent photoelectron spectrum is a valuable tool for mapping out the electronic structure of molecular orbitals. However, this approach may not be applicable to all molecules, such as CO$_{2}$, as the ionization process in a linearly polarized laser field involves contributions from orbitals other than the highest occupied molecular orbital (HOMO). Here, we conducted a theoretical investigation into the ionization process of N$_{2}$ and CO$_{2}$ in near-circularly polarized laser field using the Coulomb-corrected strong-field approximation (CCSFA) method for molecules. In particular, we introduced a generalized dressed state into the CCSFA method in order to account for the impact of the laser field on the molecular initial state. The simulated alignment-dependent photoelectron momentum distribution (PMD) of the two molecules exhibited markedly disparate behaviors, which were in excellent agreement with the previous experimental observations reported in [Phys. Rev. A 102, 013117 (2020)]. Our findings indicate that under a near-circularly polarized laser field, the alignment-dependent PMD of molecules is primarily sourced from the HOMO, in contrast to the situation under a linearly polarized laser field. Moreover, a satisfactory correlation between the alignment-dependent angular distribution and the orbital symmetry was observed, which suggests an effective approach for molecular orbital imaging.

Key words: alignment, Coulomb-corrected strong-field approximation (CCSFA), photoelectron momentum distribution (PMD), image