NMRsignal

NMRsignal refers to the electromagnetic signal produced by nuclei in a sample during nuclear magnetic resonance experiments. The signal arises when a sample placed in a strong static magnetic field is perturbed by a radiofrequency pulse, causing nuclei with nonzero spin to precess and induce oscillating magnetic fields detectable by a receiver coil.

In a typical experiment, the net magnetization of the sample is aligned with B0; a pulse tips the magnetization into the transverse plane, creating transverse magnetization that precesses at the Larmor frequency ω0 = γB0, where γ is the gyromagnetic ratio. The precessing magnetization generates a time-domain signal known as the free induction decay (FID), which is recorded by the detection coil and digitized.

The FID decays due to spin-spin relaxation (T2) and inhomogeneities, and after Fourier transformation, it yields the NMR spectrum with resonances at frequencies determined by chemical environment (chemical shift) and coupling patterns.

Signal intensity scales with the number of resonant nuclei, concentration, and detection efficiency; factors such as temperature, magnetic field homogeneity, probe design, and relaxation times influence sensitivity and linewidth. Repetition rate is limited by T1 relaxation.

NMR signals underpin structure elucidation, dynamics, and quantitative analysis in chemistry, biochemistry, and materials science. Extensions include multi-nuclear and multidimensional NMR, where complex datasets reveal connectivity via coupling and through-space interactions.