Coupling strength, evaluation

Because H linewidths in many elastomers are of the order of 3 kHz or less, spin-echo and gradient-echo imaging techniques can be applied. Contrast is introduced by suitable filters like Ti and double-quantum filters or by use of the spectroscopic dimension. Parameter images of T2, the double-quantum signal intensity, or the quadrupolar coupling strength are evaluated and rescaled according to theory or experimental calibration data (cf. Section 7.1.6). 

ET rate evaluated from different theories as a function of the coupling strength for a spin-boson model (A = 1 and 0) = 0.1) and the temperature 1. Thick solid line present approach dashed line he Zusman theory dash-dotted line FGR thin solid line interpolation thick dotted line adiabatic Kramers theory thin dotted line adiabatic limit of Zusman theory. 

The evaluation of the matrix elements uses the molecular parameter eqQ for the coupling strength, where e is the elementary Charge, q the electric field gradient of the electron distribution at the nucleus averaged over the electron distribution, and Q the nuclear quadrupole moment. The matrix elements as functions of the quantum numbers of the angular momenta involved ean be found in different references. For Z states with two nuclei of spin / > 1 two different basis sets are in use ... 

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