Nonadiabatic Dynamics May Be Probed through Electronic Coherence in Time-Resolved Photoelectron Spectroscopy

Area of Science:

• Quantum dynamics
• Spectroscopy
• Theoretical chemistry

Background:

• Time-resolved photoelectron spectroscopy (TRPES) probes ultrafast molecular dynamics.
• Accurately modeling coupled electronic and nuclear motion is crucial for interpreting TRPES signals.
• Existing methods often simplify or neglect key quantum effects.

Purpose of the Study:

• To present a hierarchy of Fermi golden rules (FGRs) for analyzing TRPES signals.
• To incorporate strongly coupled electronic/nuclear dynamics at varying levels of theory.
• To investigate the role of electronic coherences and nuclear motion in photoionization.

Main Methods:

• Developed an exact FGR (eFGR) by expanding in the joint electronic-nuclear eigenbasis.
• Introduced quasistatic FGR (qsFGR) neglecting nuclear motion but including electronic coherences.
• Utilized standard semiclassical FGR (scFGR) as a classical Condon approximation baseline.
• Simulated photoelectron spectra from model systems using the developed FGRs.

Main Results:

• The eFGR and qsFGR capture temporal oscillations due to electronic/vibrational coherences.
• These oscillations arise from nuclear wave packet motion through conical intersections.
• The scFGR misses these crucial oscillatory features.
• Coherence contributions are tunable via the ionizing field's phase profile.

Conclusions:

• The developed FGR hierarchy provides a more accurate description of TRPES signals.
• Oscillations observed in eFGR and qsFGR directly reveal time-evolving electronic state splitting.
• Coherent control of TRPES signals is feasible by manipulating the ionizing field.
• This work enhances the interpretation of spectroscopic data in the curve-crossing regime.