Properties of Lu-Fano graphs

The most obvious property of a Lu-Fano graph is its branch structure which, in the case of two series, involves only one avoided crossing. An experimental example with two series is shown in fig. 3.3. 

There are three limiting situations to consider we may have R 2 3 1 (strong mixing), R 2 C 1 (weak mixing) and R 2 = 1 (equal mixing). The physical distinction between these three situations will appear more clearly when we come to consider the associated resonances in the continuum (section 6.10). 

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