2-COLOR ABOVE-THRESHOLD IONIZATION OF ATOMS

A nonperturbative method is used to study the two-color multiphoton io nization of atoms by solving the Schrodinger equation in momentum spac e, which facilitates the extraction of the rapidly varying part of the wave function. Our method generalizes the problem for cases where an arbitrary number of ionization photons are absorbed, and also takes in to account the threshold shifts due to both the high- and low-frequenc y fields. The photoelectron energy spectra of the hydrogen atoms are c alculated and the dependence on the laser field strengths and frequenc ies is discussed.