Figure also shows experimental values for T S at the magnetic field of 9.4 T. Further values of T S at different magnetic fields are shown in figure . Although the correspondence between theory and experiment is qualitative at best, the salient features of the experimental data are reproduced. In particular the two-site model does reproduce the rapid transition from short T S to long T S at a pH value which greatly exceeds the pK a value of the acidbased equilibrium. The analytical curves also predict the decrease in the high-pH limit of T S with increasing magnetic field, which is due to the dominant chemical shift anisotropy relaxation in this regime.