Implementing High Q-Factor HTS Resonators to Enhance Probe Sensitivity in ¹³C NMR Spectroscopy

Nuclear magnetic resonance spectroscopy (NMR) probes using thin-film high temperature superconducting (HTS) resonators provide exceptional mass sensitivity in small-sample NMR experiments for natural products chemistry and metabolomics. We report improvements in sensitivity to our 1.5 mm ¹³C-optimized NMR probe based on HTS resonators. The probe has a sample volume of 35 microliters and operates in a 14.1 T magnet. The probe also features HTS resonators for ¹H transmission and detection and the ²H lock. The probe utilizes a ¹³C resonator design that provides greater efficiency than our previous design. The quality factor of the new resonator in the 14.1 T background field was measured to be 4,300, which is over 3x the value of the previous design. To effectively implement the improved quality factor, we demonstrate the effect of adding a shorted transmission line stub to increase the bandwidth and reduce the rise/fall time of ¹³C irradiation pulses. Initial NMR measurements verify ¹³C NMR sensitivity is significantly improved while preserving detection bandwidth. The probe will be used for applications in metabolomics.