Polarization of electrons by resonant two-photon ionization of unpolarized atoms

General expressions are derived and investigated for the degree of polarization of electrons as a result of resonant two-photon ionization of unpolarized atoms having the $S$ state as the ground state. The exciting and ionizing electromagnetic fields have arbitrary degrees of polarization and directions of propagation. It is shown that in cases where the matrix elements of $P\to S$ transitions from the resonant state to the continuum predominante over the matrix elements of $P\to D$ transitions, completely polarized photoelectrons may be obtained. These cases are found for sodium and potassium atoms.