Time-resolved two-color x-ray pump / x-ray probe photoelectron spectroscopy at LCLS

X-ray Free Electron Lasers (XFELs) are a new generation of X-ray sources, offering highly coherent, intense x-ray pulses with pulse lengths down to a few femtoseconds. Applications for intense X-ray pulses from XFELS span a broad spectrum from atomic and molecular physics to chemical, materials and biological sciences. Recently, XFELs proved the ability to produce two intense femtosecond X-ray pulses with controlled time delay and color. This opened the possibility of carrying out time-resolved studies of complex X-ray induced phenomena with X-ray pump / X-ray probe schemes.