Pake doublet
Encyclopedia
A Pake Doublet is a characteristic line shape seen in solid-state nuclear magnetic resonance
and Electron paramagnetic resonance
. It was first described by George Pake
.
It arises from dipolar coupling between two spin half nuclei, or from transitions in quadrupolar nuclei such as deuterium. It is the general shape obtained from an orientationally dependent doublet. The "horns" of the Pake doublet correspond to the situation when the principal axis of the coupling interaction (the inter-nuclear vector in the case dipolar coupling and the principal component of the electric field gradient tensor for quadrupolar nuclei) is perpendicular to the magnetic field. This situation is the most probable and the intensity is much higher. The "feet" of the lineshape correspond to the situation when the principal axis of the coupling interaction is parallel to the magnetic field which is much less statistically relevant.
Pake was the first to describe this lineshape and used it to extracted the proton-proton distance from his experiments on a single crystal and powdered hydrates of gypsum
(CaSO4.2H2O). This made it possible to experimentally determine the inter nuclear distance between the hydrogen atoms in water.
Solid-state nuclear magnetic resonance
Solid-state NMR spectroscopy is a kind of nuclear magnetic resonance spectroscopy, characterized by the presence of anisotropic interactions.-Introduction:Basic concepts...
and Electron paramagnetic resonance
Electron paramagnetic resonance
Electron paramagnetic resonance or electron spin resonance spectroscopyis a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic complexes possessing a transition metal ion...
. It was first described by George Pake
George Pake
George Pake was a physicist and research executive primarily known for helping found Xerox PARC. Pake earned his bachelors and masters degrees from the Carnegie Institute of Technology and his doctorate in physics at Harvard University in 1948.A rather serious case of scoliosis kept Pake out of...
.
It arises from dipolar coupling between two spin half nuclei, or from transitions in quadrupolar nuclei such as deuterium. It is the general shape obtained from an orientationally dependent doublet. The "horns" of the Pake doublet correspond to the situation when the principal axis of the coupling interaction (the inter-nuclear vector in the case dipolar coupling and the principal component of the electric field gradient tensor for quadrupolar nuclei) is perpendicular to the magnetic field. This situation is the most probable and the intensity is much higher. The "feet" of the lineshape correspond to the situation when the principal axis of the coupling interaction is parallel to the magnetic field which is much less statistically relevant.
Pake was the first to describe this lineshape and used it to extracted the proton-proton distance from his experiments on a single crystal and powdered hydrates of gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
(CaSO4.2H2O). This made it possible to experimentally determine the inter nuclear distance between the hydrogen atoms in water.