Dipolar alphabet

In the above expressions /+ = / + ily, =Ix — ily, and z is taken to be the reference direction, coincident with the direction of the applied magnetic field, Bq. 6 is the angle between the inter-nuclear vector and Bq, and 0 is a phase angle perpendicular to Bq. The terms A to F are often referred to as the dipolar alphabet . 

It is sometimes convenient to write the dipolar Hamiltonian as a sum of simpler spin operators, according to so called dipolar alphabet ... 

This leads to the important alphabet expression for the dipolar Hamiltonian... 

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