Imaging Reversible and Irreversible Structural Evolution in Photoexcited 2,4-Difluoroaniline

Area of Science:

• Physical Chemistry
• Molecular Dynamics
• Spectroscopy

Background:

• Understanding molecular structure dynamics is crucial in chemistry.
• Electronically excited states offer unique pathways for molecular transformations.
• 2,4-difluoroaniline serves as a model system for studying excited-state dynamics.

Purpose of the Study:

• To visualize the reversible and irreversible structural evolution of 2,4-difluoroaniline in electronically excited states.
• To investigate the role of vibrational motions in modulating photoionization.
• To elucidate the pathways of molecular geometry rearrangement.

Main Methods:

• Femtosecond time-resolved photoelectron imaging.
• Ultrafast laser excitation at 299.8 nm and 289.0 nm.
• Analysis of time-dependent photoelectron spectra.

Main Results:

• Coherent out-of-plane vibrational motions were observed, leading to periodic modulation of the photoionization channel.
• Reversible nuclear motion between distinct geometries was detected as reverse beats in spectra.
• Irreversible geometry rearrangement towards a planar minimum was observed upon high vibrational excitation.

Conclusions:

• Femtosecond time-resolved photoelectron imaging is a powerful technique for visualizing ultrafast molecular dynamics.
• 2,4-difluoroaniline exhibits both reversible and irreversible structural changes upon electronic excitation.
• The study provides insights into the interplay between electronic excitation, vibrational motion, and molecular geometry.