Effects of probe energy and competing pathways on time-resolved photoelectron spectroscopy: the ring-opening of 1,3-cyclohexadiene

The ring-opening dynamics of 1,3-cyclohexadiene (CHD) following UV excitation is studied using a model based on quantum molecular dynamics simulations with the ab initio multiconfigurational Ehrenfest (AI-MCE) method coupled to the Dyson orbital approach for photoionisation cross sections. Time-dependent photoelectron spectra are calculated for probe photon energies in the range 2-15 eV. The calculations demonstrate the value of universal high-energy probes, capable of tracking the dynamics in full, but also the utility of more selective lower-energy probes with a more restricted ionisation range. The predicted signal, especially with the universal probes, becomes highly convoluted due to the contributions from multiple reaction paths, rendering interpretation challenging unless complementary measurements and theoretical comparisons are available.