NMRexperiment

NMR experiment refers to any measurement that uses nuclear magnetic resonance to obtain information about the structure, dynamics, or environment of molecules. In a typical NMR experiment, a sample containing nuclei with nonzero spin is placed in a strong static magnetic field. Nuclei have characteristic Larmor frequencies that depend on the magnetic field and their gyromagnetic ratio. An applied radiofrequency pulse perturbs the nuclear spins, and the resulting spin precession induces a detectable signal, known as the free induction decay. Fourier transformation converts this time-domain signal into a spectrum that shows resonance frequencies, intensities, and line shapes which reflect the chemical environment of the nuclei.

Commonly studied nuclei include hydrogen-1 (1H), carbon-13 (13C), nitrogen-15 (15N), and phosphorus-31 (31P). Experiments can be one-dimensional, providing a direct spectrum for a single nucleus, or multidimensional, which correlate signals from different nuclei or across different time dimensions. Well-known multidimensional experiments include COSY (correlation spectroscopy), TOCSY (total correlation spectroscopy), NOESY (nuclear Overhauser effect spectroscopy), HSQC (heteronuclear single quantum coherence), and HMBC (heteronuclear multiple-bond correlation). Pulse sequences and relaxation parameters yield information on connectivity, stereochemistry, distances, and molecular dynamics.

Samples are typically in solution, though solid-state NMR is used for materials and immobilized systems. Preparation often involves deuterated solvents and temperature control. Data interpretation focuses on chemical shifts, scalar couplings (J-couplings), NOE-derived distances, and relaxation times (T1, T2). Applications span chemistry, biochemistry, pharmacology, and materials science, including structure elucidation, conformational analysis, reaction monitoring, and dynamics studies. The technique requires specialized, costly instrumentation with strong magnets and dedicated receivers.