Development of a <sup>1</sup>H-<sup>13</sup>C Dual-Optimized NMR Probe Based on Double-Tuned High Temperature Superconducting Resonators

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is a very powerful technique to study molecular structure and dynamics because of the rich chemical information it can extract. However, low inherent sensitivity is the Achilles' heel of NMR. The use of high temperature superconducting (HTS) resonators as pick-up coils in NMR probes can significantly improve the detection sensitivity of NMR and expand the use of NMR for dilute and mass-limited samples. In previously proposed HTS-based probes, the resonators for the various channels are nested orthogonally around the sample region. With this configuration, optimal sensitivity can be achieved only by the single innermost channel, which has its coils closest to the sample. We report here a new configuration in which the NMR probe has been simultaneously optimized for detection sensitivity of two channels, namely, hydrogen and carbon. The probe employs novel double-tuned HTS resonators that generate strong, uniform, and mutually orthogonal magnetic fields at the hydrogen and carbon NMR frequencies. The resonator is designed for optimal magnetic field homogeneity and minimal electric field in the sample region. Design considerations for the resonators and probe performance in NMR tests are presented.