Symmetric states constant fields

Another type of DOUBLE ENDOR, called special TRIPLE , has been introduced by Dinse et al.90 to study proton hf interactions of free radicals in solution. In a special TRIPLE experiment two rf fields with frequencies vp + Av and vp — Av are swept simultaneously. For systems with Tln < T,i this leads to a considerable signal-to-noise improvement and to TRIPLE line intensities which are directly proportional to the number of nuclei with the same hf coupling constant. It should be remembered, however, that in transition metal complexes in the solid state the resonance frequencies are not, in general, symmetrically placed about the free proton frequency vp and that the condition Tln < Tj,i is not always fulfilled. 

When a nucleus with a quadrupole moment is situated in an inhomogeneous electric field, there is a quadrupole splitting of nuclear energy states directly proportional to the quantity e Qq, the nuclear quadrupole coupling constant. In an axially symmetric field (t) = 0), the energy arising from the quadrupole moment (eQ) in an electric-field gradient (q) is ... 

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