Multiphoton ionization of atoms using the pseudostate summation technique

An accurate and powerful pseudostate summation technique has been used to s tudy multiphoton ionization of an atom. Results are obtained for three-phot on ionization of hydrogen from the ground state, as well as from the metast able 2s state. We calculate the ionization cross section from these states for both linearly and circularly polarized light, thereby showing the effec t of polarization of incident photons on the ionization cross section. Alth ough our method of calculation is entirely different, the results mirror cl osely those obtained by conventional methods.