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X-ray scans for trace elements.



Locating trace elements Trace elements
A group of elements that are present in the human body in very small amounts but are nonetheless important to good health. They include chromium, copper, cobalt, iodine, iron, selenium, and zinc. Trace elements are also called micronutrients.
 within minerals and other materials plays an important role in studies of the origin of rocks, the transport of contaminants in groundwater, and other environmental and industrial processes. Obtaining such data more precisely may now be possible with the use of X-ray standing waves The X-ray standing wave technique
The X-ray standing wave (XSW) technique can be used to study the structure of surfaces and interfaces with high spatial resolution and chemical selectivity. Pioneered by B.W.
 generated inside a crystal. Researchers from the Argonne National Laboratory Argonne National Laboratory, research center, based in Argonne, Ill., 27 mi (43 km) SW of downtown Chicago, with other facilities at the Idaho National Engineering Laboratory, 50 mi (80 km) W of Idaho Falls, Idaho. Founded in 1946 by the U.S.  in Argonne, Ill., and Northwestern University in Evanston, Ill., describe the technique in the Sept. 9 SCIENCE.

Michael J. Bedzyk and his coworkers aim a powerful X-ray beam at a tilted crystal surface. This beam interacts with the X rays diffracted by the crystal's rows of atoms to create a standing wave. By manipulating the beam and the crystal, the researchers obtain data they can use to pinpoint the locations of trace elements within the crystal and on its surface.

In one test of the scheme, the researchers located manganese atoms within a calcite calcite (kăl`sīt), very widely distributed mineral, commonly white or colorless, but appearing in a great variety of colors owing to impurities.  crystal and lead atoms that had adhered to its surface after the crystal was dipped in a dilute solution containing lead. In another test, reported in the Sept. 12 PHYSICAL REVIEW LETTERS Physical Review Letters is one of the most prestigious journals in physics.[1] Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. , Bedzyk and his colleagues used the technique to make the first quantitative, high-resolution measurements of the bond length, orientation, and location of pairs of gallium atoms adhering to a silicon surface.
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Title Annotation:new method used to find trace elements within crystal and on its surface
Publication:Science News
Article Type:Brief Article
Date:Sep 24, 1994
Words:214
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