Spin-flip, definition

In the A -operator formalism the relations (35), (37) and (38) are built in to the excitation operators. A full definition is given by Jensen et al. [38] who introduce the pseudo quantum number Mk to play the role of the non-relativistic Ms quantum number. This number is defined as Mk = (M - M 2 with M and Mp the number of occupied unbarred and barred spinors, respectively. The analogue of the non-relativistic spin-restricted excitation operators are now those that preserve Mk, either by disallowing spin flips... 

The semidione group more nearly fulfills the definition of a spin label when the conformational equilibria of the cycloalkane-1,2-semidiones are considered. Thus, by esr spectroscopy the AH for ring flip of this cyclohexene derivative has been measured as 4 kcal/mole which corresponds to a magnetic coalescence temperature of -85° (ii) This value can be compared with a AF" " of 5.3 kcal/mole observed for... 

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