Rotationally resolved photoelectron spectra in (2 + 1) resonance-enhanced multiphoton ionization of NO via the C ^2Π Rydberg state

Results of theoretical studies of rotational branching ratios and photoelectron angular distributions for (2 + 1) resonance-enhanced multiphonon ionization (REMPI) of NO via the Q_(21)(13.5) branch of the C ^2Π(3pπ) Rydberg state are reported and compared with recent measurements. Both calculated and measured spectra reveal that the ΔN=±2 peaks (ee line), which are very weak for the laser polarization parallel to the direction of photoelectron detection, have about 1/4 the intensity of the main ΔN=0 peak when the laser polarizaiton is rotated by 90°. This dependence on laser polarization is due to strong inteference among partial wave components of the photoelectron matrix element. This behavior is very evident in the photoelectron angular distribution. In addition, a Cooper minimum is predicted in the d wave of the 3pπ→Kδ ionization channel.