Inspired by the strong, approximately 7-fold, improvement of 𝜀 provided by the pulse applied to protons, we decided to look more closely at the singlet-triplet conversion efficiency. To this end, we have varied the length of the proton pulse and measured as a function of the flip angle of this pulse, see 𝜀 𝜑 Figure . The dependence is a periodic function 𝜀(𝜑) = 𝑎 1 -