Nuclear magnetic resonance Boltzmann distribution

CIDNP (chemically induced dynamic nuclear polarization) Non-Boltzmann nuclear spin state distribution produced in thermal or photochemical reactions, usually from colligation and diffusion, or disproportionation of radical pairs, and detected by nuclear magnetic resonance spectroscopy by enhanced absorption or emission signals. [Pg.51]

In practice, nuclear magnetic resonance is observed in large populations of identical nuclei (10 —10 per sample). The distribution of identical nuclei of spin 1/2 between the two possible energy rates shown in Figure 1 is defined, under conditions of thermal equilibrium, by the Boltzmann equation ... [Pg.6]

A major limitation for NMR spectroscopy is the intrinsically low sensitivity due to the rather unfavorable Boltzmann distribution for nuclear spins at thermal equilibrium. Thus, considerable effort in magnetic resonance spectroscopy is made towards sensitivity enhancement by hyperpolarization techniques, such as optical polarization, para-hydrogen-induced polarization enhancement, and dynamic nuclear polarization (DNP), a method which exploits the magnetization of unpaired electrons in stable radicals or transition metals to enhance nuclear polarization beyond the Boltzmann limit. In the chapter Dynamic Nuclear Hyperpolarization in Liquids, the fundamental theory for different polarization transfer... [Pg.210]