State selective measurements of HCI produced by strong ultrashort laser clusters interaction

International audienceWe have performed studies of keV x-ray production from (Ar)n , (Kr)n and (Xe)n rare gas clusters (with n between 104 and 106 atoms/cluster) submitted to intense (~10^18 W/cm2) infrared (790 nm) laser pulses. We have determined the photon energies and the absolute photon emission yields as a function of several physical parameters governing the interaction : size and atomic number of the clusters, peak intensity of the laser. Up to 10^6 3 keV photons per pulse at a moderate (10^15/cm3) atomic density have been observed. High resolution spectroscopy studies in the case of (Ar)n clusters have also been performed, giving unambiguous evidence of highly charged (up to heliumlike) ions with K vacancies production. The results obtained indicate that X-rays are emitted before cluster explosion on a subpicosecond time scale, and shed some light on the mechanisms involved in the first stage of the production of the nanoplasma induced from each cluster

Absolute keV photon yields from ultrashort laser-field-induced hot nanoplasmas

International audienceWe study the x-ray L-shell production from large krypton clusters submitted to ultrashort and intense laser pulses. The x-ray photon emission pattern appears to be isotropic and the absolute x-ray photon yields per laser pulse are measured as a function of the laser intensity and of the estimated mean cluster size in the supersonic expansion. In particular, up to 4 x 106 x-ray photons per laser shot are detected at intensities approaching 5 x 1017 W cm-2. This allows us to determine precisely a maximum conversion efficiency of 1.7 x 10-8 between the incoming IR photon and the generated x-ray photon energies. Finally, the x-ray photon emission is understood as the result of highly stripped ion production with L-shell electron-impact ionization and excitation in laser-heated cluster-sized nanoplasmas