Vector addition of orbital and spin

The various term values that are obtained by vector addition of orbital and spin angular momenta are energetically different. A suitable guide for energy level scheme is provided by HuncTs rules as follows ... 

Vector addition of orbital and spin angular momenta. 

Figure 2.8 Vector addition of orbital and spin angular momenta for two valence electrons with /j = 1, /j = 1 in the Russell-Saunders coupling scheme.

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