Two-dimensional nuclear magnetic resonance correlation spectroscopy at zero field

Three methods for two-dimensional correlation nuclear magnetic resonance sp ectroscopy at zero field are discussed. All three involve coherence transfe r via longitudinal polarization, double quantum coherence, or both in paral lel. The double quantum pulse sequences exploit the spinor property of spin states. These sequences have been applied to connected Delta m=1 transitio ns, as well as for the indirect detection of forbidden or nearly forbidden Delta m > 1 transitions. (C) 1999 American Institute of Physics. [S0021-960 6(99)00331-1].