Images of molecular orbitals in strong-field photoelectron momentum distributions generated by circularly polarized pulses

Abstract

Strong-field photoelectron momentum distributions (PEMDs) generated in the ionization of molecules by circularly polarized laser pulses contain valuable information on the structure of the ionizing molecular orbital. In this paper, we investigate using the adiabatic theory how this information is imprinted in and can be extracted from such PEMDs. The PEMDs have a donutlike shape. The variation of a PEMD along the donut reproduces the orientation dependence of the ionization rate of the ionizing orbital, and hence reflects its nodal structure and shape. The transverse structure of the PEMD in cross sections of the donut corresponding to orientations of the molecule at which the ionizing orbital has a node in the direction opposite to that of the instantaneous laser field reflects the interplay of two competing ionization channels, which provides additional information on the orbital structure. We illustrate these features by the analysis of PEMDs for three states of different symmetries of the hydrogen molecular ion ${\mathrm{H}}_{2}{}^{+}$.