Proton enhanced nuclear induction spectroscopy is a nuclear magnetic resonance technique invented by Michael Gibby and Alexander Pines while they were graduate students in the lab of John S. Waugh|Professor John S. Waugh at the Massachusetts Institute of Technology. It was patented in 1972. It was one of the first of Pines' experiments transferring spin orientation from one atomic nucleus to another, which has been one of the running themes throughout his career as a leading pioneer in the applications of NMR to the study of non-liquid samples.
In this technique, the natural spin polarization|polarization of an abundant spin (Hydrogen atom, the "proton" which begins the name of the technique) is exploited to increase the polarization of a rare spin (such as Carbon-13), by irradiating the sample with radio waves at the frequency which corresponds to the difference between the rotation frequencies of the two different spins.
Besides its obvious utility for boosting signals from dilute spins, transferring spin-polarization can also be used by surface-scientists, to selectively enhance the spin-polarization of molecules on a sample's surface over the spins in the bulk, by transferring spin-polarization from a gas to the surface.
- US patent 3792346