Circular dichroism and photoelectron angular distributions of excited states of cesium and rubidium using resonantly enhanced multiphoton ionization techniques

Resonantly enhanced multiphoton ionization (REMPI) techniques are used to study spin-orbit effects in the photoelectron angular distributions (READ) of excited ns (n = 8-13) states of cesium. The asymmetry parameters are shown to exhibit an energy dependence in the region of the Cooper minimum of the photoionization cross section, supporting predictions made by inclusion of relativistic coupling in the continuum. REMPI is also used to study the photoelectron angular distribution of excited n²P3/2 and n²P1/2 states of cesium and rubidium. The measured asymmetry parameters for the PEADs of n²P3/2 states are found to deviate significantly from theoretical predictions. The difference is attributed to depolarization of the angular momentum polarization due to hyperfine coupling. Circular dichroism effects in the photoelectron angular distributions (CDAD) are used to measure alignment of the excited n²P3/2 states of cesium and rubidium. Angular distributions of the n²P1/2m states are used to show that isotropic states do not exhibit CDAD.