Lasers Control Chemical Reaction

For the first time, chemists have been able to precisely control the course of a chemical reaction, forcing one potential reaction of a starting material to occur to the exclusion of all others. Although the reaction they studied was simple and of no commercial or scientific value, Stanford University scientists believe their success will be the foundation for experiments involving more important chemicals.

Richard Zare and his colleagues used a set of lasers to control the reaction of a hydrogen atom with a water molecule. They used a special form of water in which one of the two hydrogen atoms had been replaced with a heavy hydrogen isotope called deuterium.

Normally, when this water molecule reacts with a hydrogen atom, the product is an equal mixture of two new molecules, one containing two hydrogen atoms and one containing a hydrogen and deuterium atom.

Zare and his colleagues report today in the Journal of Chemical Physics that they used the lasers to selectively break either the hydrogen-oxygen or the deuterium-oxygen bond. When they broke the former bond, 100% of the product molecules contained two hydrogen atoms. When they broke the latter bond, all of the product contained the hybrid atom of deuterium and hydrogen.