The dissolution step was performed immediately after so as to minimize relaxation in the solid state. 5 ml of D 2 O with 30 mM ascorbic acid was loaded into a heating module, pressurized to 6 bar with He gas and subsequently heated to 180 • C corresponding to a pressure of 9 bar. The dissolution step consisted of a series of programmed events triggered by the operator. The pressurized hot solvent was injected onto the sample and pushed with He gas at 9 bar through a KelF capillary to the ZULF spectrometer. The capillary was inside a solenoid maintaining a field of 4 mT along the transfer, from the polarizer to the magnet used for thermal-prepolarization experiments. The flow of He gas was stopped after a transfer time t trans = 2 s.