an object to have different resonance chemists at the State University of New York, Stony Brook. Unlike con- frequencies, magnetic field gradients ventional nuclear magnetic resonance allow one-dimensional spatial informamethods, these techniques allow struc- tion to be obtained. By varying the ditures and processes above the molecu- rection of the gradient, enough data on the location of signal sources can be lar level to be visualized. In ordinary NMR spectroscopy, a ho- obtained to allow the construction of mogeneous magnetic field causes nu- an image in two or three dimensions, clei to be divided among various energy usually with the help of a digital comlevels. Absorption of radiofrequency ra- puter. Because Lauterbur regards this imdiation unique to the nuclei produces signals that indicate transitions among age-forming technique as the coupling of these energy levels and provide infor- two fields by the object under study, mation about the molecular properties he calls it "zeugmatography," from the Greek expression, "that which joins toof the matter. However, Dr. Paul C. Lauterbur and gether." When zeugmatographic techhis associates at Stony Brook, as well niques are combined with high-resoluas workers in Nottingham, England; tion pulsed Fourier transform NMR Aberdeen, Scotland; and Zurich, Swit- spectroscopy, both the chemical comzerland, are using a nonhomogeneous position and spatial distribution of magnetic field to gain additional infor- samples can be determined, Lauterbur mation about the three-dimensional tcld the Division of Physical Chemistry. nature of their samples. The nonhomogeneous magnetic field In experiments for determining the varies smoothly across the sample location of the different chemical conbeing studied and can be pictured by a stituents of a sample, a magnetic field set of parallel, equally spaced planes (a gradient is applied to the sample durlinear field gradient) that cut at differ- ing a radiofrequency pulse, Lauterbur ent geographical locations of the sam- explains. Only the nuclei in one area of ple. Under these circumstances, the the sample develop the transverse signal intensity at each radiofrequency magnetization characteristic of pulsed represents the sum of all the absorbing NMR spectroscopy. When the magnetnuclei of a particular species within ic gradient is removed, decay of the the corresponding magnetic field plane, transverse magnetization may be FouLauterbur explains. rier transformed so that only signals Thus, by causing different parts of from the chemical species near one
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