Measurements of molecular-frame Auger electron angular distributions at the CO C 1s^-1 2π* resonance with high energy resolution

The molecular-frame Auger electron angular distributions (MFAEADs) of resonantly excited CO 1s → π molecules in the gas phase were determined with high energy resolution using a novel experimental approach. We investigated the process of excitation, Auger decay and fragmentation in unprecedented detail. We confirmed theoretical predictions for the different MFAEADs of close lying Auger final states. By examining the dependence of the MFAEADs on the vibrational state of the excitation and on the fragmentation energy we found that the measured MFAEADs can be considered independent of the vibrational excitation and the fragmentation process. The method used to obtain molecular-frame angular distributions of Auger electrons is based on electron-ion coincidence measurements using two high-resolution electron spectrometers with limited acceptance angles mounted at fixed positions.