Measuring a complete reaction coordinate: Windowless observation of the photodissociation dynamics of CS<inf>2</inf>

Abstract

Time resolved photoelectron spectroscopy (TRPES) shows exquisite sensitivity to both the electronic and nuclear dynamics of molecules. TRPES is also, in principle, a windowless technique that can provide a measurement for any molecular structure as all states can be ionised. With the advent of high harmonic generation (HHG) sources, this windowless character is beginning to be realised, as pulses of ultrashort duration and sufficient energies to ionise the important reaction intermediates and products are now available. The limited use of HHG sources so far is due to the relatively low flux attainable from most HHG sources. This means experiments have either had to combine the HHG pulse with a strong field pump, or limit their measurements to relatively simple dynamics in diatomic molecules. The use of strong fields in the pump enhances the excitation probability at the expense of selectivity such that the range of dynamics and systems that can be studied is not ideal. Here we present UV pump-XUV probe TRPES experiment that allows for the unambiguous assignment of the full reaction pathway in a polyatomic molecule. The experiments measure the dissociation dynamics of CS 2 following UV excitation through to the formation of multiple dissociation products.