Phys. Rev. Lett. 101, 013001 (2008)

In order to watch chemical reactions as they happen, researchers need the constituent molecules lined up just right. Lasers can help to achieve this, but usually disturb the reaction process because they excite the molecules.

Hirofumi Sakai and his colleagues at the University of Tokyo now demonstrate a way to avoid this excitation with carbonyl sulphide molecules. First, they placed the molecules in a weak electrostatic field. Then they zapped the carbonyl suphide with a nanosecond laser pulse shaped like a cresting wave. The pulse's shape nudged the molecules into alignment, where they remained after it was turned off.

The team believes that this technique could be adapted for studies of reaction dynamics and molecular imaging.