Laser may twirl molecules to pieces.

Physicists often picture the bonds between atoms as springs. Researchers in Canada are developing a new way to exploit that springiness to stretch selected bonds inside molecules until they break.

The method, proposed in the April 26 PHYSICAL REVIEW LETTERS, would use a whirling electric field created by a laser to spin molecules at up to 10 trillion revolutions per second. At that rate, centrifugal forces should tear pairs of atoms apart.

Because the force on heftier atoms would exceed that on lighter neighbors, the bonds connecting more-massive atoms would break sooner, the developers argue. If the method works, chemists may gain a long-sought ability to tailor molecules and reactions with unprecedented precision.

"We hope to have excellent control over how these molecules are spinning and so to have excellent control over this chemistry," says Misha Ivanov of the National Research Council of Canada in Ottawa.

Computer simulations indicate that such an optical twister should work. By inducing a slight electric polarity in the molecule, the laser's oscillating electric field aligns the molecule. As the field then rotates, slowly at first and then rapidly, its electric force makes the molecule spin along with it.

An equipment glitch has so far foiled laboratory tests, Ivanov says. When polarities are aligned, the laser field should hold a spinning molecule in place, as one's palm cups a marble. However, the field intensity jiggles around. For now, says Ivanov, "the twister is like the hand of a person with a hangover. It shakes like hell" and drops the marble.