Born-Oppenheimer rescued

A key assumption of theoretical chemistry was under threat, but has been brought back from the brink by US scientists. The Born-Oppenheimer approximation states that electrons move so fast compared with atomic nuclei that the motion of each can be treated separately in quantum mechanics. However, researchers in Taiwan provided startling evidence that the approximation fails catastrophically under certain conditions which could have lead to the unraveling of much of theoretical chemistry. Now, Etienne Garand of the University of California, Berkeley, and co-workers have demonstrated that the Born-Oppenheimer approximation holds good for the chlorine-hydrogen system and conventional quantum wisdom is saved.