Yoon, D., et al., 500-fold enhancement of in situ (13)C liquid state NMR using gyrotron-driven temperature-jump DNP. J Magn Reson, 2016. 270: p. 142-6.
A 550-fold increase in the liquid state (13)C NMR signal of a 50muL sample was obtained by first hyperpolarizing the sample at 20K using a gyrotron (260GHz), then, switching its frequency in order to apply 100W for 1.5s so as to melt the sample, finally, turning off the gyrotron to acquire the (13)C NMR signal. The sample stays in its NMR resonator, so the sequence can be repeated with rapid cooling as the entire cryostat stays cold. DNP and thawing of the sample are performed only by the switchable and tunable gyrotron without external devices. Rapid transition from DNP to thawing in one second time scale was necessary especially in order to enhance liquid (1)H NMR signal.