Influence of nuclear dynamics on molecular attosecond photoelectron interferometry

Abstract

In extreme ultraviolet spectroscopy, the photoionization process occurring in a molecule due to the absorption of a single photon can trigger an ultrafast nuclear motion in the cation. Taking advantage of attosecond photoelectron interferometry, where the absorption of the extreme ultraviolet photon is accompanied by the exchange of an additional infrared quantum of light, one can investigate the influence of nuclear dynamics by monitoring the characteristics of the photoelectron spectra generated by the two-color field. Here, we show that attosecond photoelectron interferometry is sensitive to the nuclear response by measuring the two-color photoionization spectra in a mixture of methane (CH 4 ) and deuteromethane (CD 4 ). The effect of the different nuclear evolution in the two isotopologues manifests itself in the modification of the amplitude and contrast of the oscillations of the photoelectron peaks. Our work indicates that nuclear dynamics can affect the coherence properties of the electronic wave packet emitted by photoionization on a time scale as short as a few femtoseconds.

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

“…The two-photon photoionization matrix elements employed here in applications of the theory were calculated using the molecular R-matrix codes UKRmol+ . The details of the calculations were described previously …”

“…The isotopic dependence of the real and imaginary parts of the asymmetry parameters derived from the simulation is very limited, while the corresponding experimental quantities are compatible within the error bars, except for the imaginary part of β̃ 4 for the SB16. The absence of a significant isotopic effect in the photoionization phases is consistent with the results presented in refs and .…”

“… a The experimental parameters (first lines) were retrieved from the analytical fit of A 2ω (θ) and phase Δφ(θ) according to eqs and . The theory values (second line) are in the center of the CH 4 + /CD 4 + -associated band (Figure ), with the nuclear motion treated as described in ref . Fixed-nuclei results (third lines) are for the single geometry of the ground-state neutral CH 4 molecule and for the effective I p of 13.6 eV. …”

“…25 The details of the calculations were described previously. 26 Photoelectron Angular Distributions in the RABBIT Process. The momentum space two-photon matrix element has the form…”

Probing Photoionization Dynamics in Acetylene with Angle-Resolved Attosecond Interferometry

“…With its first experimental realization in 2010, photoionization time delays in ultrafast light–matter interaction have now become an indispensable tool in studying the photoionization dynamics in various systems, ranging from atoms , and molecules − in the gas phase to solids , and liquids . The measured photoionization time delays were found to be sensitive toward a variety of physical properties such as Fano resonance, , shape resonance, − chirality, collective excitation, effect of the chemical environment, , shape and symmetry of the system, and mass of the target, , just to name a few. One of the interferometric techniques giving access to these time delays is known as the reconstruction of attosecond beating by interference of two-photon transitions, or, RABBITT .…”