The high-order multielectron ionization of ${\mathrm{Xe}}_{531},$ ${\mathrm{Xe}}_{1061},$ and ${\mathrm{Xe}}_{2097}$ clusters in a strong laser field is studied using classical dynamics. The simulations are performed in the frozen geometry approximation for fixed ionic charges, so that only the evolution of the electrons, which are unbound to the ions, is examined. The dependence of the ionization efficiency on the laser frequency and cluster radius is manifested by pronounced maxima. The presence of these maxima favors the quasiresonance ionization mechanism, which is related to the motion of the unbound electrons in the entire cluster. The high level of ionization $(q\sim 8–18$ per atom) is realized in the expanded cluster, due to the Coulomb explosion.

• Received 11 January 1999

DOI:https://doi.org/10.1103/PhysRevA.60.2215