Selection of the magnetic quantum number in resonant ionization of neon using an XUV-IR two-color laser field

A recent experiment (Villeneuveet al2017Science3561150) has shown that two-color photoionization of neon by the combination of an attosecond XUV pulse train and a moderately strong, linearly polarized IR pulse can preferentially produce photoelectrons with orbital angular quantum numberl= 3 (f-wave) and magnetic quantum numberm= 0. This result was rationalized by the occurrence of different Stark shifts ofm= 0 and |m| = 1 sub-levels in the IR laser field. Here we perform 3D time-dependent Schrodinger equation calculations with a neon effective potential to identify the mechanism for the selective excitation and ionization ofm= 0 sub-levels. Calculations of the ionization and excitation yields as a function of the IR intensity and the XUV and IR photon energy reveal that a coupling between two dominant ionization channels involving 3p and 3d intermediate excitations is responsible for the observedm-level selectivity. We compare calculated and measured photoelectron velocity map images and ionization yields over a range of IR intensities and XUV and IR photon energies, and confirm that them= 0 or |m| = 1 channel, and thus a single set of the quantum numbers, (J(ion),l,m), can be selected by an appropriate choice of these parameters.