Probing Ultrafast Dynamics with Time-resolved Multi-dimensional Coincidence Imaging: Butadiene

TL;DR

This paper presents time-resolved multi-dimensional coincidence imaging data of butadiene's ultrafast excited state dynamics, highlighting the complexity of interpreting photoelectron angular distributions and their potential to reveal detailed electronic evolution.

Contribution

It introduces experimental measurements of ultrafast dynamics in butadiene using advanced coincidence imaging, emphasizing the role of TRPADs in probing electronic evolution.

Findings

Complex temporal behavior observed in TRPADs.

Tentative comparison with ab initio calculations.

Insights into wavepacket dynamics from experimental data.

Abstract

Time-resolved coincidence imaging of photoelectrons and photoions represents the most complete experimental measurement of ultrafast excited state dynamics, a multi-dimensional measurement for a multi-dimensional problem. Here we present the experimental data from recent coincidence imaging experiments, undertaken with the aim of gaining insight into the complex ultrafast excited-state dynamics of 1,3-butadiene initiated by absorption of 200 nm light. We discuss photoion and photoelectron mappings of increasing dimensionality, and focus particularly on the time-resolved photoelectron angular distributions (TRPADs), expected to be a sensitive probe of the electronic evolution of the excited state and to provide significant information beyond the time-resolved photoelectron spectrum (TRPES). Complex temporal behaviour is observed in the TRPADs, revealing their sensitivity to the dynamics while also emphasising the difficulty of interpretation of these complex observables. From the experimental data some details of the wavepacket dynamics are discerned relatively directly, and we make some tentative comparisons with existing ab initio calculations in order to gain deeper insight into the experimental measurements; finally, we sketch out some considerations for taking this comparison further in order to bridge the gap between experiment and theory.