Molecules of hydrogen are difficult to steer with electric fields because of the symmetrical way that charges are distributed within them. But now researchers at ETH Zurich have found a clever technique to get a grip on the molecules. Their findings are reported in Physical Review Letters and highlighted in the September 14 issue of Physics.
Electric fields can easily manipulate electrically asymmetric molecules like water, but electric forces can't overcome thermal motions for highly symmetric molecules like H2. In the 1980s, researchers in search of a way to manipulate non-polar molecules proposed a trick: excite one of H2's two electrons into a high orbit, disrupting the molecule's symmetry. The far-flung electron feels the pull of the electric field and drags the rest of the molecule along, rendering H2 as manageable as a puppet on a string.
Now Stephen Hogan, Christian Seiler, and Frederic Merkt at ETH Zurich have made this idea reality by overcoming a key problem: an electron in an excited orbit usually reverts to its ground state long before researchers can take advantage of the molecule's maneuverability. They studied several excited orbits in detail, found the longest-lasting ones, and used lasers to select these special states from a group of hydrogen molecules. The newly manageable molecules could be slowed down and trapped for 50 microseconds, plenty of time for the team to study them in detail.
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