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Chapter 4: Olympian Feats

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CROSSING THE SWORDS 

The first step in understanding the details of chemical processes was taken at the Laboratory in 1954 when Sheldon Datz and Ellison Taylor invented a technique for studying chemical reactions by crossing a beam of one kind of molecule with that of another. Before Datz and Taylor's pioneering work, scientists had to be content with examining molecules before or after their reactions, not during the transitional phase. 

Sheldon Datz

Understanding the dynamics of elementary physical and chemical processes at the molecular level requires fundamental investigations of the movement of molecules and the results of their encounters—in brief, what happens during a chemical reaction. The reactions occur so incredibly fast, however, that observing and understanding a reaction's transition phase seemed impossible before Datz and Taylor invented their technique. 

Datz and Taylor believed that much could be learned about chemical reactions if two reactants could be brought together as crossed beams, creating a shower of new molecules. Because each new molecule would result from a single collision, this process avoided the complications of accounting for chain reactions and collisions with container walls common to simpler experiments. 

In 1954, they "crossed the swords" of two accelerated, collimated (focused) beams, one composed of potassium atoms and the other of hydrogen bromide molecules. They found that they could measure the products' angular distribution. As a result, they could draw conclusions about the relative effectiveness of the various orientations of the colliding reactants. 

Datz and Taylor's crossed-beam scattering technique energized the science of chemical dynamics when their results were published in 1955. The technique was recognized by the 1986 Nobel Prize in chemistry, which went to three men who refined the Oak Ridge technique. Applying infrared-emission spectroscopy, laser probes, and other modern tools to the crossed-beam scattering technique, modern scientists have begun to understand the dynamic interchange of atoms during chemical reactions. 

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