Laser photoionization of polarized Ar atoms produced by excitation with synchrotron radiation

The laser-synchrotron radiation combination technique has recently been inc orporated into an apparatus for two-dimensional photoelectron spectroscopy of atoms and molecules in order to investigate photoionization dynamics of polarized atoms. Ground state Ar atoms are excited with linearly polarized synchrotron radiation to Rydberg states lying below the first ionization po tential. The aligned atoms thus formed are ionized by irradiation of a lase r which is also linearly polarized. Photoelectrons emitted in the direction of the electric vector of the synchrotron radiation are sampled and energy analysed. The photoelectron angular distribution is measured with respect to the electric vector of the laser. Expressions which correlate the asymme tric coefficients for the angular distribution with theoretical dynamic par ameters involving transition dipole matrix elements are derived. The anisot ropy of the present angular distribution can bt reasonably explained, assum ing that the matrix elements and phase shift differences are essentially in dependent of the total angular momentum quantum number of the final state a nd that the spin-orbit interaction in the continuous spectrum is small.