Pump-Probe Experiment for Temporal Profile Measurement of Plasma X-Ray Laser

Temporal behavior of a soft x-ray laser pulse is measured by means of a pump-probe spectroscopy (cross correlation). In this scheme, first the innershell electron 4d of Xe atom is photoionized with 13.9 nm x-ray pulse (x-ray pump). Simultaneously, an ir probe laser pulse is irradiated to dress the electrons. By varying the time delay between both pulses, the sideband spectra associated with ir photon absorption/emission processes appear at a separation of the ir photon energy from the photo- and Auger main peaks. By analyzing the sideband intensity, we can evaluate the pulse width of the x-ray laser to be similar to 6.2 ps, which is in excellent agreement with the value measured by an x-ray streak camera