Simulating time-resolved X-ray absorption spectroscopy of molecules |
|
| Tom Penfold | |
| Paul Scherrer Institute /EPFEL, Swiss FEL | |
| Time-resolved X-ray absorption fine structure (XAFS) spectroscopy offers a direct approach for visualising an evolving molecular structure during the course of a chemical reaction or biological function. Recent technological and methodological improvements, such as high repetition rate lasers, femtosecond slicing and X-ray free electron lasers has led to a significant increase in the quality of the experimental data. In parallel, the need to accurately simulate the resulting fine spectroscopic details, especially in the X-ray absorption near edge structure (XANES) region of the spectrum, has been the driving force for new theoretical methods. Here I will present some of our recent work studying the excited state dynamics of atoms and molecules in solution. These examples emphasise the observables at hand using time-resolved XAFS techniques, which include the density of states, full and even partial changes in oxidation state, and internuclear distances. In addition, in some cases it can be important to include the effect of the solvent during the analysis of the spectra. Finally I will discuss the theoretical challenges which are expected to be encountered during the analysis of ultrafast XAS experiments at Free Electron Lasers. |