High-resolution X-ray spectroscopy of hollow atoms created in plasma heated by subpicosecond laser radiation

The investigations of ultrashort (0.4-0.6 ps) laser pulse radiation interaction with solid targets have been carried out. The Trident subpicosecond laser system was used for plasma creation. The X-ray plasma emission was investigated with the help of high-resolution spectrographs with spherically bent mica crystals. It is shown that when high contrast ultrashot laser pulses were used for plasma heating its emission spectra could not be explained in terms of commonly used theoretical models and transitions in so called ''hollow atoms'' must be taken into account for adequate description of plasma radiation.