PRINCIPLES OF NMR

Nuclear magnetic resonance (NMR) spectroscopy is an analytical technique based on the magnetic properties of certain atomic nuclei. NMR is similar to other types of spectroscopy in that absorption of electromagnetic energy at characteristic frequencies provides analytical information. NMR differs from other types of spectroscopy because the discrete energy levels between which the transitions take place are created by placing the nuclei in a magnetic field of strength H₀. Although the initial field strength of the applied field is H₀, when the sample is inserted into the magnet, the field strength throughout the sample becomes B₀, defined as follows: B₀ = µ_SH₀    [1]in which µ_S is the magnetic susceptibility of the sample.