Revealing Deactivation Pathways Hidden in Time-Resolved Photoelectron Spectra

Area of Science:

• Physical Chemistry
• Quantum Mechanics
• Spectroscopy

Background:

• Time-resolved photoelectron spectroscopy monitors molecular excited-state dynamics.
• Complex dynamics can obscure relaxation pathways in experimental signals.

Purpose of the Study:

• To investigate the limitations of time-resolved photoelectron spectroscopy for studying complex molecular dynamics.
• To disentangle relaxation pathways in cytosine tautomers using theoretical methods.

Main Methods:

• Non-adiabatic molecular dynamics simulations.
• Dyson norms calculations to analyze photoionization signals.
• Decomposition of total signal based on electronic state populations and mechanistic pathways.

Main Results:

• Simulations revealed that similar time scales of excited-state processes obscure distinct relaxation pathways in the total photoionization signal.
• The total signal from cytosine keto and enol tautomers could be decomposed into contributions from neutral electronic state populations and mechanistic pathways.
• Lifetimes of these contributions were not experimentally extractable.

Conclusions:

• Current experimental setups are insufficient for resolving intricate non-adiabatic pathways in polyatomic molecules.
• Theoretical approaches are crucial for disentangling complex excited-state dynamics.
• New experimental methodologies are required to fully understand light-induced molecular processes.