Resonant energy absorption of rare-gas clusters in strong laser pulses

Abstract

The ionization dynamics of rare-gas clusters in strong femtosecond laser pulses is studied microscopically by means of classical molecular dynamics using a hierarchical tree code. Systematic investigations for laser pulses from 25 to 400 fs duration have shown a transition from field ionization to resonant excitation of a collective motion of the cluster electrons. The latter effect is associated with a strong energy absorption and can be microscopically identified by examining the phase lag of the electron oscillation with respect to the laser field. The optimal conditions depend, via the expansion time, strongly on the cluster size, which was varied from 102 up to 104 atoms.