Furthermore, it also follows that the same procedure is feasible even without the calculation of the field dependence, as we can replace it with the experimentally measured one. As shown earlier in this paper, such fixed-field experiments (protocol 1) are straightforward to perform, and the detected field dependence show good agreement with simulations. Thus, a simple interpolation of such data, or their fitting with suitable analytical functions, enables a facile and convenient choice of the optimal profile for magnetic field cycling. Fig. . Simulated field dependence of C polarization for the case of continuous hydrogenation at a fixed ultralow field for allyl pyruvate (a). "Optimal" time variation in an adiabatic passage experiment, obtained through the integration of the simulated field dependence (b). Linear and "optimal" field sweep profile (c). Dependence of C polarization on the duration of field sweep with linear and "optimal" profiles (d).