Researchers Capture First Images of Atoms Moving in a Molecule

Posted on March 7, 2012

Researchers have captured images of atoms moving in a molecule for the first time using a new ultrafast camera. Details of the experiment are published in this week's issue of Nature. The researchers used the energy of a molecule's own electron as a kind of "flash bulb" to illuminate the molecular motion.

The team from Ohio State University used ultrafast laser pulses to knock one electron out of its natural orbit in a molecule. The electron then fell back toward the molecule scattered off of it, analogous to the way a flash of light scatters around an object, or a water ripple scatters in a pond. In each case, the researchers hit the molecule with laser light pulses of 50 femtoseconds, or quadrillionths of a second. They were able to knock a single electron out of the outer shell of the molecule and detect the scattered signal of the electron as it re-collided with the molecule.

The molecules the researchers chose to study were nitrogen, or N2, and oxygen, or O2. Molecular nitrogen is shown in the image above. The image highlights any changes the molecule went through during the one quadrillionth of a second between laser pulses. The atoms' movement is shown as a measure of increasing angular momentum, on a scale from dark blue to pink, with pink showing the region of greatest momentum.

Principal investigator Louis DiMauro, a professor of physics at Ohio State University said the feat marks a first step toward not only observing chemical reactions, but also controlling them on an atomic scale.

DiMauro says, "Through these experiments, we realized that we can control the quantum trajectory of the electron when it comes back to the molecule, by adjusting the laser that launches it. The next step will be to see if we can steer the electron in just the right way to actually control a chemical reaction."

Ohio State postdoctoral researcher Cosmin Blaga says the key is that the atom has moved during the very brief span of time between when the electron is knocked out of the molecule and when it re-collides. He says the laser induced electron diffraction (LIED) method can capture this movement, "similar to making a movie of the quantum world."

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