Interferometric extraction of photoionization-path amplitudes and phases from time-dependent multiconfiguration self-consistent-field simulations

Abstract

Bichromatic extreme-ultraviolet pulses from a seeded free-electron laser enable us to measure photoelectron angular distribution (PAD) as a function of the relative phase between the different wavelength components. The time-dependent multiconfiguration self-consistent-field (TD-MCSCF) methods are powerful multielectron computation methods to accurately simulate such photoionization dynamics from the first principles. Here, we propose a method to evaluate the amplitude and phase of each ionization path, which completely determines the photoionization processes, using TD-MCSCF simulation results. The idea is to exploit the capability of TD-MCSCF to calculate the partial wave amplitudes specified by the azimuthal and magnetic angular momenta (l,m) and the m-resolved PAD. The phases of the ionization paths as well as the amplitudes of the paths resulting in the same (l,m) are obtained through global fitting of the expression of the asymmetry parameters to the calculated m-resolved PAD, which depends on the relative phase of the bichromatic field. We apply the present method to ionization of Ne by combined fundamental and second-harmonic extreme ultraviolet pulses, demonstrating that the extracted amplitudes and phases excellently reproduce the asymmetry parameters.