nuclear magnetic resonance spectrum two-dimensional nuclear magnetic resonance spectrum 2D NMR spectra 2D NMR spectrum CHMO:0000932 2D-NMR spectra 2D-NMR spectrum A two-dimensional plot of chemical shift vs. intensity for spin-active nuclei obtained by measuring the effect of the absorption of radio frequency radiation on nuclear spin-state transitions in the presence of a magnetic field. Signals are defined in terms of two frequencies; by the chemical shift of a particular nucleus in one dimension and, in the other, by the chemical shift of a correlated nucleus.