First-Order Spin-Orbit Coupling Selection Rules

First-Order Spin-Orbit Coupling Selection Rules... 

Table 9.3. First-Order Spin-Orbit Coupling Selection Rules D

In the present treatment, we retain essentially all the diagonal matrix elements of X these are the first-order contributions to the effective electronic Hamiltonian. There are many possible off-diagonal matrix elements but we shall consider only those due to the terms in Xrot and X o here since these are the largest and provide readily observable effects. The appropriate part of the rotational Hamiltonian is —2hcB(R)(NxLx + NyLy). The matrix elements of this operator are comparatively sparse because they are subject to the selection rules AA = 1, A,Y=0 and AF=0. The spin-orbit coupling term, on the other hand, has a much more extensive set of matrix elements allowed... 

S)unmetry selection rules for radiationless transitions have also been derived by El-Sayed for nitrogen heterocycUcs (7). He showed that to the first order no spin-orbit coupling occurs between singlet and triplet states of the same configuration, i. e. 

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