Two-color photoionization of helium above the N=2 ionization threshold

We study two-color photoionization of helium in the region of the 3s3d D-1 autoionizing state with resonant excitation of the intermediate 2s2p P-1 au toionizing state. We show that the corresponding time-dependent Schrodinger equation may be solved by expanding the total wave function on a few compl ex energy states. Perimetric coordinates are used to describe correlation e ffects accurately. Populations at the end of the interaction as well as pho toionization probabilities are studied as a function of the laser pulse dur ation acid both frequencies. Our calculations show that many continua play a crucial role at high intensities. [S1050-2947(99)06308-8].