Anisotropy Parameters for Two-Color Photoionization Phases in Randomly Oriented Molecules: Theory and Experiment in Methane and Deuteromethane

Abstract

We present combined theoretical and experimental work investigating the angle-resolved phases of the photoionization process driven by a two-color field consisting of an attosecond pulse train and an infrared pulse in an ensemble of randomly oriented molecules. We derive a general form for the two-color photoelectron (and time-delay) angular distribution valid also in the case of chiral molecules and when relative polarizations of the photons contributing to the attosecond photoelectron interferometer differ. We show a comparison between the experimental data and theoretical predictions in an ensemble of methane and deuteromethane molecules, discussing the effect of nuclear dynamics on the photoionization phases. Finally, we demonstrate that the oscillating component and the phase of the two-color signal can be fitted by using complex asymmetry parameters, in perfect analogy to the atomic case.

Virtual Special Issue on Attosecond Chemistry

“…They conclude that, even in the absence of autoionizing states and shape resonances, the short-range potentials can drastically affect the measured time delays. Along the same line, Ertel et al report a combined experimental and theoretical study showing the angular dependence of photoemission delays on methane and deuteromethane, and the effect of nuclear motion on such delays . The work of Pranjal et al reports a theoretical study of valence-shell photoionization of the triatomic molecule CO 2 .…”