The reduced CR72 2-site CPMG model

This is the model for 2-site exchange on most times scales (with the constraint that pA > pB), named after Carver and Richards (1972). It is selected by setting the model to `CR72'. It is the same as the full CR72 model described above, but with the simplification that R2A0 = R2B0. This simplifies the equations to

R2eff = R20 + $\displaystyle {\frac{{\textrm{k}_{\textrm{ex}}}}{{2}}}$ - νCPMGcosh-1$\displaystyle \big($D+cosh(η+) - D-cos(η-)$\displaystyle \big)$, (11.27)

where D± and η± are unchanged and

Ψ = kex2 - Δω2, (11.28)
ζ = - 2Δω(pAkex - pBkex). (11.29)

As mentioned in the `CR72 full' model section, this model is not accurate when the motional process is very slow. In that case please use the `TSMFK01' model in Section 11.3.6 on page [*] instead.

More information about the CR72 model is available from:

The relax user manual (PDF), created 2016-10-28.