Two-dimensional NMR spectroscopy in Earth's magnetic field

We demonstrate the first two-dimensional correlation NMR (COSY) spectra obtained at ultra low frequencies (ULF) using the Earth's magnetic field. Using a specially developed spectrometer with multiple audio-frequency pulses under controlled pulse phase, we observe magnetisation transfer arising from heteronuclear J-couplings in trifluoroethanol and para-difluoroberizene. The 2D COSY spectra exhibit all diagonal and off-diagonal inultiplets consistent with known J-couplings in these molecules. (c) 2006 Elsevier Inc. All rights reserved.