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Insensitive nuclei enhancement by polarization transfer (INEPT) is a signal enhancement method used in NMR spectroscopy. It involves the transfer of nuclear spin polarization from spins with large Boltzmann population differences to nuclear spins of interest with lower Boltzmann population differences. [ 1 ]
When electron spin polarization deviates from its thermal equilibrium value, polarization transfers between electrons and nuclei can occur spontaneously through electron-nuclear cross relaxation or spin-state mixing among electrons and nuclei. For example, polarization transfer is spontaneous after a homolysis chemical reaction.
Magnetization is then transferred from the proton to the heteronucleus through a one-bond scalar coupling (J-coupling), ensuring that only directly bonded nuclei participate in the transfer. Subsequently, the system evolves during a period called t 1 , and the magnetization is transferred back from the heteronuclear to the proton.
A more specific example of this case is presented in the section Chemical Exchange Magnetization transfer. In either case, magnetization transfer techniques probe the dynamic relationship between two or more distinguishable nuclei populations, in so far as energy exchange between the populations can be induced and measured in an idealized NMR ...
The nuclear Overhauser effect (NOE) is the transfer of nuclear spin polarization from one population of spin-active nuclei (e.g. 1 H, 13 C, 15 N etc.) to another via cross-relaxation.
Although usually observed in liquids, the photo-CIDNP effect has also been detected in solid state, for example on 13 C and 15 N nuclei in photosynthetic reaction centres, where significant nuclear polarization can accumulate as a result of spin selection processes in the electron transfer reactions.
In magnetic resonance imaging, additional gradient pulses are applied by switching magnetic fields that exhibit a space-dependent gradient which can be used to reconstruct spatially resolved images after applying Fourier transforms. [2] The outcome of pulse sequences is often analyzed using the product operator formalism.
Finally, the free induction decay (FID) of the X nuclei is detected, typically with 1 H decoupling. Cross-polarization ( CP ), originally published as nuclear double resonance in the rotating frame by Hartmann and Hahn [ 1 ] is a solid-state nuclear magnetic resonance (ssNMR) technique used to transfer nuclear magnetization from different types ...