COMPARISON OF QUASI-CLASSICAL AND QUASI-STATIC QUANTUM APPROACHES TO THE IONIZATION OF HELIUM BY A CIRCULARLY-POLARIZED LASER FIELD

Employing the quasi-classical Fermi molecular dynamics (FMD) method, w e find no evidence for the existence of a nonsequential double-ionizat ion mechanism for helium interacting with a pulse of circularly polari zed, high-intensity laser radiation. This contrasts with our earlier r esearch, for linearly polarized laser light [Phys. Rev. A 49, R12 (199 4)], in which effects of the nonsequential double ionization of helium were noted. We also compute emitted-electron kinetic energy spectra b y FMD and compare these with spectra derived from a quasi-static tunne ling model calculation. In this context we discuss the applicability o f the FMD approach to simulations of the photoionization of multielect ron systems by intense pulsed laser fields. (C) 1996 Optical Society o f America