Hydrogenation at an arbitrary magnetic field was performed using a home-built automated gas-flow system described elsewhere . This allowed us to control the timing of both pH2 bubbling and magnetic field switching from the spectrometer console. The pH2 bubbling pressure was set equal to 3 bar with a 0.1 bar differential between the inlet and outlet of the tube, providing an optimal gas flow rate about 20-40 cm 3 /min. The sample temperature was 25 C o .