High-order harmonic generation in atomic clusters with a two-dimensional model

High-order harmonic generation in atom clusters interacting with an intense linearly polarized laser field is studied by means of numerical simulation s of the time-dependent Schrodinger equation for a two-dimensional model cl uster in the single-active electron approximation. The well-known first and second cutoffs (in the atomic and molecular cases) are not clear in cluste r calculations. In fact, the structure of the spectrum consists of a long p lateau that extends far beyond the I-p + 3.17 U-p limit and a collection of high-order harmonics with decreasing but significant intensities up to ext remely high frequencies. (C) 2001 Optical Society of America.