Fig. 2: DNP enhancement as a function of temperature.

DNP enhancement as a function of temperature, using optimised chirped inversion pulses on 4-amino TEMPO at 50 mM concentration in DNP juice. The blue lines show a fit to the experimental data points to indicate the trend. A dramatic change in enhancement is seen around 65 K where molecular motion and methyl rotation is expected to become significant. The inset plot shows more data points around this transition temperature, and were acquired during a separate experiment (on the same sample).