Femtosecond x-ray fluorescence

Using few-cycle-driven coherent laser harmonics, K-shell vacancies have been created in light elements, such as boron (E-B = 188 eV) and carbon (E-B = 284 eV), on a time scale of a few femtoseconds for the first time. The capability of detecting x-ray fluorescence excited by few-femtosecond radiation with an accuracy of the order of 1 eV paves the way for probing the evolution of the microscopic environment of selected atoms in chemical and biochemical reactions on previously inaccessible time scales (<100 fs) by tracing the temporal evolution of the "chemical shift" of peaks associated with inner-shell electronic transitions in time-resolved x-ray fluorescence and photoelectron spectra.