SensitiveJ-coupling spectroscopy using high-Tcsuperconducting quantum interference devices in magnetic fields as low as microteslas

In this work we present a sensitive J-coupling spectroscopy in one shot using high-Tc superconducting quantum interference devices and a flux transformer in microtesla fields. In the proposed NMR detection scheme the precession of proton spin was inductively coupled to the SQUID magnetometer. We enhanced the SNR signal and the spectral resolution significantly by applying a pre-polarization field of 0.045 T. In microtesla fields where chemical shifts are absent, we demonstrate proton–phosphate coupling J3[H,P] = (10.94 ± 0.08) Hz in trimethyl phosphate. The sensitive NMR spectrometer will be of great interest for diagnosis information of molecular structure and biological applications.