Observation of Subpicosecond X-Ray Emission from Laser-Cluster Interaction

Abstract

We present the first experimental evidence of the subpicosecond duration of x-ray pulses emitted from laser-irradiated clusters, demonstrating the suitability of such a debris free target for ultrafast x-ray science applications. The $K$-shell emission ($\ensuremath{\sim}3\text{ }\text{ }\mathrm{keV}$) from large Ar clusters ($6\ifmmode\times\else\texttimes\fi{}{10}^{5}$ to $4\ifmmode\times\else\texttimes\fi{}{10}^{6}$ atoms) is time resolved, when irradiated by ultrashort (40 fs to 5 ps) and intense laser pulses (${10}^{15\ensuremath{-}17}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$). The observations are supported by hydrodynamical and collisional-radiative calculations, that reproduce the extremely short x-ray pulse duration.