Theoretical description of ultrafast phenomena in clusters

A theoretical study of different ultrafast nonequilibrium processes taking place during and after ultrashort excitation of clusters is presented. We d iscuss similarities and differences for several processes involving nonequi librium ultrafast motion of atoms and electrons. We study ultrashort relaxa tion of clusters in response to excitations produced by femtosecond laser p ulses of different intensities. We show how different relaxation processes, such as bond breaking, melting, fragmentation, emission of atoms, or Coulo mb explosion, can be induced. depending on the laser intensity and laser pu lse duration. We also discuss processes involving nonequilibrium electron d ynamics, such as intraband Auger decay in clusters and ultrafast electronic motion during collisions between clusters and surfaces. We show that this electron dynamics leads to Stuckelberg-like oscillations of measurable quan tities, such as the electron emission yield.