Towards Observing Site Selective Chemistry in Real Time

The possibility of site-selective photochemistry, where element and site selective excitation or ionization using x-ray photons guides the outcome of the dissociation has been an intriguing problem since the advent of high average flux sources at synchrotrons. So far, only limited selectivity has been observed, hinting at efficient charge redistribution before decay processes happen. The ability to probe this process as it happens is now becoming a reality at x-ray free electron lasers, with the ability to produce two pulses commensurate with the core-hole lifetimes, with very different photon energies, and soon high repetition rates. By initiating an inner shell process at one molecular site and probing at another place in the molecule, one will be able to observe the evolution of the electronic properties, starting from the ionization energies of the core excited states. Making sense of the data will require comparison with high accuracy computational predictions, such as using our newly developed scalar-relativistic delta-coupled-cluster method. We will present calculations for a class of fluoro-alkane molecules that will be the focus of a demonstration experiment at LCLS this year.