Spectroscopic Signature of Chemical Bond Dissociation Revealed by Calculated Core-Electron Spectra

The advent of ultrashort soft X-ray pulse sources permits the use of established gas-phase spectroscopy methods to investigate ultrafast photochemistry in isolated molecules with element and site specificity. In the present study, we simulate excited-state wavepacket dynamics of a prototypical process, the ultrafast photodissociation of methyl iodide. Using the simulation, we calculate time-dependent excited-state carbon edge photoelectron and Auger electron spectra. We observe distinct signatures in both types of spectra and show their direct connection to C–I bond dissociation and charge rearrangement processes in the molecule. We demonstrate at the CH 3 I molecule that the observed signatures allow us to map the time-dependent dynamics of ultrafast photoinduced bond breaking with unprecedented detail.