Ultrafast X-ray laser sheds new light on fundamental ultrafast dynamics

Jul 17, 2014
An artistic view of the electron transfer inside an iodomethane molecule. After the interaction with an ultrafast X-ray laser, the electrons from the methyl group, on the right, jump to the iodine atom, on the left. Credit: SLAC National Accelerator Laboratory

Ultrafast X-ray laser research led by Kansas State University has provided scientists with a snapshot of a fundamental molecular phenomenon. The finding sheds new light on microscopic electron motion in molecules.

Artem Rudenko, assistant professor of physics and a member of the university's James R. Macdonald Laboratory; Daniel Rolles, currently a junior research group leader at Deutsches Elektronen-Synchrotron in Hamburg, Germany, who will be joining the university's physics department in January 2015; and an international group of collaborators studied how an electron moves between different atoms in an exploding molecule.

Researchers measured at which distances between the two atoms the electron transfer can occur. Charge transfer processes—particularly —are important for photosynthesis in solar cells, and drive many other important reactions in physics, chemistry and biology.

Their observation, "Imaging charge transfer in iodomethane upon x-ray photoabsorption," appears in the journal Science.

"There is a very fundamental question about how far an electron can go to reach the nearby atom in a molecule, and how probable that transition is," Rudenko said. "It has been difficult to capture images of this motion because of the very short times and very small distances that need to be measured."

To find the answer, scientists shot an ultrafast optical laser at iodomethane —molecules made of an iodine atom and a —to break the bond of these two partners.

The molecules were hit with an intense, ultrashort X-ray pulse to strip the electrons from the inner shells of the iodine atom as well as to study the charge transfer between the fragments. The experiment was performed using the Linac Coherent Light Source, the world's most powerful X-ray laser. The laser is at the SLAC National Accelerator Laboratory in California and delivers femtosecond X-ray pulses. One femtosecond is one-millionth of a billionth of a second.

Researchers were able to see electrons jumping over surprisingly long distances—up to 10 times the length of the original, intact molecule.

"Conceptually the study was pretty simple," Rudenko said. "We break up the molecule with the optical laser, use the X-rays to knock a few electrons from the iodine atom, and control the distance to the neighboring methyl group by tuning the timing between the and the X-rays. Then we watch how many electrons move from the methyl side to the iodine side to fill the created holes."

The study recently became possible because of the unique combination of ultrafast optical and X-ray pulses, and researchers' expertise in particle detection.

"In the near future we will be able to perform similar experiments with improved time resolution using ultrafast lasers and tabletop soft X-ray sources at the J.R. Macdonald Lab at Kansas State University," Rudenko said.

Explore further: Scientists use X-rays to look at how DNA protects itself from UV light

More information: "Imaging charge transfer in iodomethane upon x-ray photoabsorption", www.sciencemag.org/lookup/doi/… 1126/science.1253607

add to favorites email to friend print save as pdf

Related Stories

X-rays capture electron 'dance'

Jan 31, 2013

(Phys.org)—The way electrons move within and between molecules, transferring energy as they go, plays an important role in many chemical and biological processes, such as the conversion of sunlight to energy ...

X-ray laser gives buckyballs a big kick

Jun 30, 2014

(Phys.org) —Scientists at SLAC have been blowing up "buckyballs" – soccer-ball-shaped carbon molecules – with an X-ray laser to understand how they fly apart. The results, they say, will aid biological ...

New X-ray tool proves timing is everything

Feb 20, 2013

(Phys.org)—With SLAC's Linac Coherent Light Source X-ray laser, timing is everything. Its pulses are designed to explore atomic-scale processes that are measured in femtoseconds, or quadrillionths of a ...

Recommended for you

50-foot-wide Muon g-2 electromagnet installed at Fermilab

11 hours ago

One year ago, the 50-foot-wide Muon g-2 electromagnet arrived at the U.S. Department of Energy's Fermi National Accelerator Laboratory in Illinois after traveling 3,200 miles over land and sea from Long Island, ...

Spin-based electronics: New material successfully tested

Jul 30, 2014

Spintronics is an emerging field of electronics, where devices work by manipulating the spin of electrons rather than the current generated by their motion. This field can offer significant advantages to computer technology. ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

rah
1 / 5 (1) Jul 17, 2014
This seems like it is going to be a very useful process. It is just amazing to me. Good work!