L-shell emission from high-Z solid targets by intense (10/sup 19/ W/cm/sup 2/) irradiation with a 248 nm laser

Summary form only given. Much effort has been expended recently in attempts to develop an efficient coherent X-ray source suitable for high-resolution biological imaging. To this end, many experiments have been performed studying the X-ray emissions from high-Z materials under intense (>10/sup 18/ W/cm/sup 2/) irradiation, with the most promising results coming from the irradiation of Xe clusters with a UV (248 nm) laser at intensities of 10/sup 18/-10/sup 19/ W/cm/sup 2/. We report the production of prompt X-rays with energies in excess of 5 keV with efficiencies on the order of 1% as a result of intense irradiation of BaF/sub 2/ and Gd targets with a terawatt 248 nm laser. The efficiency is attributed to an inner shell-selective collisional electron ejection mechanism in which the previously photoionized electrons are ponderomotively driven into an ion while retaining a portion of their atomic phase and symmetry. This partial coherence of the laser-driven electrons has a pronounced effect on the collisional cross-section for the electron ion interaction.