Breaking a molecule’s mirror image

Physicists have demonstrated how a molecule’s symmetry can be broken.

Reinhard Dörner of Johann-Wolfgang-Goethe University in Frankfurt, Germany, and his colleagues began an experiment with a single, symmetrical molecule made of two hydrogen atoms. They then fired a single photon at the dumbbell-shaped molecule to split it. The photon’s energy caused one of the hydrogen molecule’s two electrons to peel away.

However, the ejected and the stay-at-home electrons maintained a lingering interdependence, as the laws of quantum physics dictate. Accordingly, when the researchers measured the ejected electron’s path, that measurement influenced the behavior of the other electron, they say.

When the molecule subsequently fell apart into a single hydrogen atom and an H+ ion, the process of dissociation wasn’t symmetrical, Dörner’s team reports in the Feb. 2 Science. The paths of the atom and the ion weren’t random with respect to that of the emitted electron.

Comments Andrei Sanov, a chemical physicist at the University of Arizona in Tucson, “Asymmetry came from the act of measurement.”

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