Chemically induced dynamic nuclear line intensities

One of the most important phenomenon, chemically induced dynamic nuclear polarization (CIDNP), deserves more detailed consideration, since it forms the basis of one of the most powerful modem methods for the investigation of the structure and reactivity of short-lived (from nano- to microseconds) paramagnetic precursors of the reaction products. CIDNP manifests itself in the form of unusual line intensities and/or phases of NMR signals observed when the radical reaction takes place directly in the probe of the spectrometer. These anomalous NMR signals—enhanced absorption or emission — are observed within the time of nuclear relaxation of the diamagnetic molecule (from several seconds to several minutes). Later on, the NMR spectrum re-acquires its equilibrium form. 

NMR spectra of samples in which free radical reactions are taking place may show strongly perturbed intensities for lines belonging to reaction products. This effect is called chemically induced dynamic nuclear polarization or CIDNP. Over the past ten years CIDNP has become an established method for mechanistic investigations of reactions involving short-lived radical intermediates. Several reviews and a mono-... 

The chemically induced dynamic nuclear polarization (CIDNP) phenomenon, (the occurrence of intense emission and enhanced absorption lines in high-resolution NMR spectra during chemical reactions) has been applied to the study of the photodegradation of poly(methyl isopropenyl ketone) [177]. 

---