Femtosecond Si-K/spl alpha/ pulses from laser produced plasmas

Summary form only given. In several experiments, K/spl alpha/ radiation was used to monitor ultrafast structural changes in matter. An open question in all of these pump-probe experiments was, however, the exact temporal duration of the probing X-rays. This ultimately determines the temporal resolution of the experiment. The determination of the temporal duration of sub-picosecond X-ray pulses is very challenging. We report on the measurement of the temporal profile of the Si-K/spl alpha/ line emission from a femtosecond laser produced plasma. The measurement is performed by cross-correlating the Si-K/spl alpha/ pulse with the ultrafast response of a laser pumped MBE-grown thin CdTe crystal layer. The pump laser induces an ultrafast change of the CdTe crystal structure and causes a rapid decrease of the X-ray reflectivity. In contrast to InSb bulk measurements, the X-ray penetration depth in this measurement is definitely limited by the thickness of the crystalline layer.