PCI-Induced Exchange of Angular Momentum

Another possibility is the analysis of ejected electron spectra due to electron impact excitation of autoionizing states via a negative-ion resonance. One example, investigated by van de Water and Heideman, is the excitation of He(2s ) 5 via the negative resonance He (2s2p ) D. Several processes can lead to the same final state  

Energy spectra of autoionization electrons can only be influenced by interferences between the various channels, if both electrons e, and e have the same angular momentum. Reaction path lb will result in scattered electrons with 1 = 2. Interferences with the other reaction paths— which have been observed experimentally—can only occur if those too result in scattered electrons with I = 2. With the assumptions that reaction path la is not important and that reactions 2 and 3 yield electrons with / = 0 only, an interference of channel 1 with channels 2 and 3 can therefore only occur by exchange of angular momentum. However, the assumptions that have to be made are questionable. 

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