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Interaction between high-power ultrashort laser pulse and giant clusters (microdroplets) consisting of 109 to 1010 atoms is considered. The microdroplet size is comparable to the laser wavelength. A model of the evolution of a microdroplet plasma induced by a high-power laser pulse is developed, and the processes taking place after interaction with the pulse are analyzed. It is shown theoretically that the plasma is superheated: its temperature is approximately equal to the ionization potential of an ion having a typical charge. The microdroplet plasma parameters are independent of the pulse shape and duration. The theoretical conclusions are supported by experimental studies of x-ray spectra conducted at JAERI, where a 100-terawatt Ti–sapphire laser system was used to irradiate krypton and xenon microdroplets by laser pulses with pulse widths of 30 to 500 fs and intensities of 6×1016 to 2×1019W/cm2. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The evolution of large atomic clusters exposed to a super-intense ultrashort laser pulse is considered. Cluster excitation results from the interaction of its electron subsystem with the laser field. Multiple inner and outer ionization and X-ray emission followed by explosion in clusters irradiated by a laser field are investigated. An increase of the electron temperature in this process and of the charge of the ionized cluster are discussed. The reabsorption of photons in such a plasma is found to be relatively small. The optimal conditions are analyzed for efficient absorption of laser radiation by large clusters. A review is done of the works devoted to X-ray emission and generation of high harmonics of the incident radiation from a hot ionized cluster. The optical depth of the cluster plasma is found to be relatively small for resonance photons of multiply charged atomic ions produced inside the cluster. Expansion and decay of the cluster during and after the laser pulse are analyzed. Nuclear fusion induced by super-intense ultrashort laser pulses in deuterium clusters and in deuterated compounds is considered in detail. The main attention is devoted to the van der Waals clusters consisting of atoms of rare gases, though their properties in super-intense laser field are identical to the properties of metal clusters due to multiple inner and outer ionization. [Copyright &y& Elsevier]