Applications in atomic spectra

Wigner s theory is most useful for studying cases of Rydberg series of interacting features in which an intruder appears. There are several distinct effects in the spectra of interacting resonances which result from perturbations, and are readily described by K-matrix theory. We first list them, and then discuss each one in turn. 

The simplest expression for the cross section r(e) in terms of the detuning e for this case is  

Typically, the vanishing particle width occurs at e = —pTlT1/2 which is related to the width of the broad intruder and the strength of the coupling. This relationship, and the associated effects are discussed in section 8.29. 

More generally, one finds many cases where the particle widths of resonances in a Rydberg series, instead of decreasing in proportion to the spacings between successive members, fluctuate dramatically. An example will be given in section 8.33. 

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