Strong field Multiphoton processes in the high-frequency limit

Last fall, the Linac Coherent Light Source at SLAC National Accelerator Laboratory has delivered users the world first X-ray free electron laser, allowing studying X-ray matter interaction at unprecedented photon flux. We will present the first attempts at observing multiphoton ionization in the X-ray regime, which have been realized by measuring both electron and ion spectra from the ionization of rare gases in the AMO end station. In addition to gaining insight into this new regime, our experiments also participated towards the characterization of this new light source (intensity, harmonic content{\ldots}).