The Nuclear Overhauser effect
In contrast to all previous experiments, in which we connected spins through bonds, the nuclear Overhauser effects enables us to connect nuclei through space. This effect is fundamentally different as exchange between the nuclei does not involve scalar coupling. Instead, the direct magnetic coupling (no electrons in between) termed dipolar coupling id involved, which usually does not have an observable effect in solution (in contrast to solid state!). The nOe provides an indirect pathway to obtain information of this dipolar coupling, which in turn can be correlated with internuclear distances and molecular motion. Measurements of these parameters are hard to obtain in solution, making the nOe an extremely useful and important phenomenon.
The experimental observation:
Change of resonance line intensity upon
irradiating another nucleus.