Center of gravity rule

To form Pj" s P, for example, we need only nse the valne of z at each vertex to obtain P Hiickel approximation (see Hiickel Theory), but this is simply to provide an idea of the bonding/antibonding character, and some more accurate calculations will be discussed below. (Note that the splitting obeys another center-of-gravity rule.) The normalization is simply 1 /s/l, as overlap between the two a orbitals has been neglected. ... 

The center of gravity rule can be useful for obtaining parameter estimates, locating extra lines, and detecting the presence of an unsuspected second per-turber. When main and extra lines are observed for more than two J-values at... 

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