Nuclear magnetic resonance spin-flips

If the oriented nuclei are now irradiated with electromagnetic radiation of the proper frequency, energy absorption occurs and the lower-energy state "spin-flips" to the higher-energy state. When this spin-flip occurs, the magnetic nuclei are said to be in resonance with the applied radiation—hence the name nuclear magnetic resonance. 

The pulsed field gradient nuclear magnetic resonance (PFG NMR) technique is experimentally distinct from the radiotracer technique but the principle is very similar. A fraction of the nuclei of each constituent is labelled by flipping their spins and monitoring the diffusion of these species. Both techniques are influenced by the presence of neutral associates unlike the Hittorf/Tubandt method. 

As a result, the spins originally precessing with B0 flip over, and now precess against B(). Absorption of energy AE from B, takes place (nuclear magnetic resonance). 

When a nucleus is subjected to the right combination of magnetic field and electromagnetic radiation to flip its spin, it is said to be in resonance (Figure 13-3), and its absorption of energy is detected by the NMR spectrometer. This is the origin of the term nuclear magnetic resonance. ... 

Nuclear magnetic resonance (NMR) spectroscopy probes the energy required to flip a nuclear spin in the presence of a magnetic field. Computation of this effect... 

Nuclear magnetic resonance Characteristic excitations of an atomic nucleus causing it to flip," or alter, its. spin. state. 

The nuclei are said to be in resonance with the rf radiation, hence the term nuclear magnetic resonance. In this context, resonance refers to the nuclei flipping back and forth between the a- and jS-spin states in response to the rf radiation it has nothing to do with the resonance associated with electron delocalization. 

At resonance there is strong coupling between the nuclear spins and the radiation, and strong absorption occurs as the spins flip from a (low energy) to p (high energy). We refer to these transitions as nuclear magnetic resonance (NMR) transitions. 

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