Nuclear magnetic resonance in the nanoTesla range

At ultralow fields of 40 nT to 4 mu T magnetic flux density, nuclear magnetic resonance spectra of a resolution well below 1 Hz were obtained, which is beyond what usually is achieved in the conventional high-field regime. The spectral resolution of our setup allows for the direct observation of the natural linewidth of distilled water. For heteronuclear systems, this enables pure J-spectroscopy in the absence of a chemical shift, with a resolution that is limited only by the natural width of the resonance lines. (c) 2005 American Institute of Physics.