Complex expectation values and Lewis structures for resonant states

The definition of a norm for scattering states is reviewed particularly with respect to the method of complex scaling used to determine resonant states. The meaning of complex expectation values which result from this procedure is illustrated with a simple two-channel model. In a further example autoionizing states of helium are analysed in terms of complex expectation values which are shown to provide a sensitive tool to probe details of complicated dynamics. We also demonstrate how Lewis structures for resonances may be defined through complex expectation values. (Author)