Picosecond time-resolved pump-probe XUV absorption L-edge spectroscopy

We present what we believe to be the first measurements of broadband XUV absorption spectroscopy with picosecond time scale resolution. A 10-Hz, 60 mJ 100-fs laser system is used to create a quasi-continuum of XUV radiation (30 Å < λ < 300 Å) from a gold plasmas to act as a probe source. The temporal duration of the probe is typically on the order of 20 ps but can be made shorter or longer by varying the laser parameters.1 Part of the 100-fs laser beam also provides a delta-function pump beam to heat a sample onto which the XUV probe source is focused by a novel XUV imaging optics. Time-resolved results are gathered by two different methods: 1) a variable delay between the pump laser and the probe XUV source is used to collect spatially-resolved spectra of the sample's absorption at different times during the laser heating and 2) a unique jitter-free x-ray streak camera2 developed at the Center for Ultrafast Optical Science is used to obtain temporally-resolved absorption spectra. This broadband time-resolved absorption spectroscopy technique offers a very interesting and flexible alternative to synchrotrons for experiments such as time-resolved EXAFS, chemical dynamics and ion characterization in laser ablation plumes.