Improved NMR resonator for diamond anvil cells

A new hairpin resonator efficiently couples to nuclear spins in diamond anvil cell–nuclear magnetic resonance (DAC–NMR) experiments. The hairpin resonator is essentially a single turn coil of copper sheet, resonated with a chip capacitor. A modest tuning range is provided by trimmer capacitors. This resonator has so far been the most satisfactory of the DAC–NMR schemes tried in our laboratory. It is easy to make, robust, and reusable, and is easily cleaned to eliminate contaminant signals. The H1 homogeneity is good; the rf performance is described.