Better known as the ‘fuel’ in fuel cells, hydrogen has revealed some bizarre quirks on the molecular level.

Researchers at Stanford University and England’s University of Durham have observed hydrogen, the most common element in the universe, engaging in some very uncommon behavior. What made the display especially odd was that it occurred in a chemical reaction that has been observed many times over by scientists: the hydrogen exchange reaction. In this reaction, a single atom of hydrogen collides with the two atoms of a hydrogen molecule, usually sending one of the molecule’s atoms shooting off in the opposite direction. But that’s not what happened this time. On this occasion, the hydrogen atom passed right through the molecule, taking one of its atoms with it.

To draw a better picture of the peculiar reaction, the researchers use the analogy of balls on a pool table. They describe the hydrogen molecule as being a pair of numbered pool balls, the 8 and the 9, nestled closely together. The hydrogen atom that collides with the molecule can be seen as the cue ball being shot against them. Richard Zare, a physical chemist at Stanford University, explains the typical scenario. “The cue ball would go up to the 8 ball, and the cue ball and the 8 ball would stop and stick and the nine ball would go forward,” he says. “That’s the mechanism we all expected to see.” But one out of a thousand times, the cue ball atom will do the seemingly impossible. Instead of creating a collision, it seems to curve around or pass directly through the molecule, taking up one of the atoms (or numbered pool balls) with it as it travels past.

Adding to the abnormality of the event, the scientists have noted a hesitation of 25 millionths of a second before the cue ball and numbered pool ball atoms take off together. “This result is very surprising for a system people had thought is now pretty well understood,” comments Dudley Herschback, a Nobel laureate at Harvard. The researchers attribute the hydrogen atom’s startling behavior to the wiles of quantum mechanics, the laws of science that govern objects on the microscopic level and which often seem to defy logic. A classic example of quantum mechanics is the statement that light behaves as both a particle and a wave.

Not content to simply scratch their heads, the researchers are looking at hydrogen’s strange behavior to explain phenomena in other fields. According to the National Science Foundation’s physical chemistry program director, Frank Wodarczyk, “What we learn from this simpler system can probably be translated to more complex systems that have more practical applications – things going on in the atmosphere, or in combustion, or in an industrial setting.”

Source: Hydrogen Yields Bizarre Chemical Results
Charles Choi
Chemicals Headquarters, March 6, 2002
http://www.chemicalshq.com/