Biradicaloids weak heterosymmetric

It is interesting to distinguish three cases (1) strong heterosymmetric biradicaloid SAB > 8C, (2) weak heterosymmetric biradicaloid SAB < Sc, and (3) critical heterosymmetric biradicaloid 5AB = Sc. 

Three important situations are of interest. For d < the biradicaloid is weakly heterosymmetric. The lowest singlet. So, similar to that of the perfect... 

First of all, we consider the significance of the presence of C-, +, the coefficient of the in-phase combination of the two hole-pair functions in the So wave function, in Equation 4.12. In the simple model for a perfect biradical, this in-phase combination is exactly equal to the wave function of the Sj state, and it does not enter into those of the So and S, states at all. Thus, in this approximation. So does not spin-orbit couple to the triplet. The same is true in weakly heterosymmetric biradicaloids (0 < 5 < S ), in which the in-phase hole-pair character is shared by S, and Sj, but not Sg, and the former two spin-orbit couple to T, but So does not. In strongly heterosymmetric... 

---