All X-Ray Four-Wave Mixing on a Gas Phase Sample

Mixed EUV/X-ray - optical four-wave mixing (FWM) has been successfully demonstrated in a transient grating (TG) configuration ([1]–[3] and refs. therein). While all-EUV TG have been demonstrated [2], non-linear all-X-ray wave-mixing spectroscopy has been envisioned and theoretically described, [4] but up to now and to the best of our knowledge, it has not been realized experimentally. In this work, we present all-X-ray-four-wave mixing (XFWM) for the first time. The coherent response from core and inner shell electrons in an atomic gas (Ne) is demonstrated.