Observation of H-like ions within argon clusters irradiated by 35-fs laservia high-resolution x-ray spectroscopy - art. no. 021201

Plasmas have been created with bulk temperatures greater than or equal to 4 00 eV and densities greater than 1 x 10(21) cm(-3) in some regions by irrad iating atomic clusters of argon with a 0.4 TW ultrashort (35 fs) laser puls e. An improved nozzle has been designed so that larger clusters can be form ed, allowing the clusters to maintain high-density cores after the preplasm a is formed due to the laser prepulse. Ar is the element with the highest a tomic number, Z for which the Lyman-alpha resonance line (Ly(alpha)) has be en observed in ultrashort (< 100 fs) pulse laser experiments for any target . The unambiguous spectroscopic evidence, including high-resolution measure ments of the Ar+17 Ly(<alpha>) spectrum, is consistent with a theoretical t wo-temperature collisional-radiative model of irradiated atomic clusters in corporating the effects of highly energetic electrons (similar to5 keV).