THE SIGNIFICANCE OF ELECTRON CORRELATION AND OF STATE SYMMETRIES IN THE INTERACTION OF STRONG LASER-PULSES OF 5 EV WITH HE

Through a systematic series of solutions of the time-dependent Schrodi nger equation by the state-specific expansion approach, we have comput ed and interpreted the multiphoton ionization rates and the spectra of harmonic generation, above-threshold ionization and photoelectron ang ular distribution from the response of He to laser pulses of lambda = 248 nm and peak intensity in the range 6 x 10(14)-3.46 x 10(15) W cm(- 2). The results are examined by looking at the significance of the spa ce of state symmetries and of electron correlation plus doubly excited states included in the calculation, as a function of intensity. Such information is also relevant to previously published discussions and c onclusions about the interpretation of the generation of harmonics of high order, which were derived from measurements, calculations and sim ulations.