  Nuclear magnetic resonance (NMR) spectroscopy usually requires high magnetic
fields to create spectral resolution among different proton species. At low
fields, chemical shift dispersion is insufficient to separate the species, and
the spectrum exhibits just a single line. In this work, we demonstrate that
spectra can nevertheless be acquired at low field using a novel pulse sequence
called spin-lock induced crossing (SLIC). This probes energy level crossings
induced by a weak spin-locking pulse and produces a unique J-coupling spectrum
for most organic molecules. Unlike other forms of low-field J-coupling
spectroscopy, our technique does not require the presence of heteronuclei and
can be used for most compounds in their native state. We performed SLIC
spectroscopy on a number of small molecules at 276 kHz and 20.8 MHZ, and we
show that SLIC spectra can be simulated in good agreement with measurements.
