Fig. 6.

The two most significant methods of organic structural spectroscopy, nuclear magnetic resonance (NMR) and FTICR mass spectrometry, are based on high-precision frequency measurements. The top panels illustrate NMR and FTICR MS for atomic and molecular processes. The precessions of atomic magnetic moments in molecules are defined by the chemical environment, and this means that NMR yields unsurpassed resolution of short-range molecular order (in noncrystalline materials, for which X-ray crystallography is not available). In FT mass spectrometry, the orbital frequencies of ions depend on their molecular masses. Mid-size molecules (see middle panels) provide information-rich signatures in NMR and only single peaks in mass spectra (under conditions of non-fragmentation), while complex non-repetitive materials (see bottom panels) produce low-resolution signatures in NMR because of extensive peak overlap. High FT mass spectra resolution is retained for complex molecules, however, because of the extensive peak capacity of the technique (see Fig. 5)