A Pake Doublet (or "Pake Pattern") is a characteristic line shape seen in

solid-state nuclear magnetic resonance Solid-state NMR (ssNMR) spectroscopy is a technique for characterizing atomic level structure in solid materials e.g. powders, single crystals and amorphous samples and tissues using nuclear magnetic resonance (NMR) spectroscopy. The anisotropic pa ...

and

electron paramagnetic resonance Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spi ...

spectroscopy. It was first described by

George Pake George E. Pake (April 1, 1924 – March 4, 2004) was a physicist and research executive primarily known for helping founded Xerox PARC. Early life Pake was raised in Kent, Ohio. His father was an English instructor at Kent State Universi ...

. It arises from

dipolar coupling In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system i ...

between isolated two spin-1/2 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 internuclear 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 extract the proton-proton distance from his experiments on a single crystal and powdered hydrates of

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywal ...

(CaSO₄.2H₂O). This made it possible to experimentally determine the internuclear distance between the hydrogen atoms in water. In solids with vacant positions, dipole coupling is averaged partially due to water diffusion which proceeds according to the symmetry of the solids and the probability distribution of molecules between the vacancies.Diffusion of Water Molecules in Hydrates and NMR Spectra, S.P. Gabuda, A.G. Lundin, JETP ''28'', 555 (1969); http://www.jetp.ras.ru/cgi-bin/dn/e_028_03_0555.pdf In the case the averaged lineshape is used to analyze

crystal symmetry In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns t ...

phase transitions In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states of ...

, and the degree of molecular disorder in crystalline hydrates,

zeolites Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a metal ion or H+. These p ...

clays Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

and biological tissues.

References

Nuclear magnetic resonance {{physics-stub