In the present experiment, we smash polarized electrons into Ar in its ground state. One possible channel produces an excited ArII ion and a free electron. By measuring the polarization of the light emitted as the ArII ion decays through several specific channels, we can determine the shape of the excited ion accurately.

This assumes that we avoid "cascading" from higher states. The graph at the right illustrated the low count rates below the cascading threshold. We measured the polarization of the following transitions: