Ultrafast Processes in 1,2-Dichloroethene measured with a Universal XUV probe

TL;DR

This study uses a universal XUV probe to investigate ultrafast isomerisation and photochemistry in 1,2-dichloroethene, revealing rapid excited state decay and product formation within 70 femtoseconds.

Contribution

It demonstrates the application of a 22.3 eV XUV probe for time-resolved photoelectron spectroscopy of isomers, capturing ultrafast dynamics and vibrational mode involvement.

Findings

Excited state returns to ground state in <70 fs

Product channels form on the same ultrafast timescale

Vibrational modes involving C-C-H bends facilitate population transfer

Abstract

The presence of two chlorine atoms in 1,2-dichloroethene allows for isomerisation around the double bond. This isomerisation can lead to rich photochemistry. We present a time-resolved pump-probe photoelectron spectroscopy measurement on both the cis- and trans- isomers of 1,2-dichloroethene. A universal XUV probe of 22.3 eV is used allowing observation of photoelectrons formed anywhere on the potential energy surface, even from the ground-state or dissociation products. Following excitation with a 200 nm probe both ultrafast excited state dynamics and product formation are observed within the time resolution of the experiment. Excited state population begins to return to the ground state on an ultrafast time scale (< 70 fs) and population of products channels is observed on the same timescale. With the aid of ab initio calculations it is found that population transfer from the excited state is facilitated by vibrational modes involving C-C-H bends.