At the next step, we use experimental protocol 3 (Fig. .d) to study adiabatic PHIP transfer. It is completely analogous to protocol 2, except that after finishing the bubbling we perform a field jump to the near-zero magnetic field (50 nT) with subsequent magnetic field sweep with a time-dependent amplitude. This experimental scheme includes three parameters controlling the transfer, the initial 𝐵 𝑆𝑊,𝑖 and final 𝐵 𝑆𝑊,𝑓 fields of the sweep and its duration 𝜏 𝑆𝑊 . Previous studies have demonstrated that sweeping the field from zero up to 2 uT is reasonable for most spin systems . Thus, to optimize this PHIP transfer protocol we study only the dependence of the resulting C polarization on the sweep duration.