Over the last decade, improvements in lasers have allowed researchers to study chemical reactions like never before. Now they are about to go one step further as a new X-ray laser has been revealed that will be able to track the motion of electrons in molecules, a process that is so fast it is measured in attoseconds.
As reported in Nature Photonics, the Department of Energy’s SLAC National Accelerator, based at Standford University, has developed a laser that shoots X-ray pulses at a tiny fraction of a second. These pulses are used to “photograph” the motion of electrons and atoms as they shift during a chemical reaction. Opening this window into the quantum world will have important consequences for understanding how molecular processes are initiated in biology, chemistry, material science and more.
The device is called the X-ray laser-enhanced attosecond pulse generation (XLEAP) and it produces laser bursts every 280 attoseconds, about a quarter of a millionth of a billionth of a second. Or to put it another way, the interval between bursts is to one second, what one second is to 113 million years.
“Until now, we could precisely observe the motions of atomic nuclei, but the much faster electron motions that actually drive chemical reactions were blurred out,” SLAC scientist James Cryan, one of the paper’s lead authors, said in an emailed statement. “With this advance, we’ll be able to use an X-ray laser to see how electrons move around and how that sets the stage for the chemistry that follows. It pushes the frontiers of ultrafast science.”
The team managed to create precisely timed pairs of attosecond X-ray pulses that kick-started the electrons into motion and then managed to snap them. As the XLEAP observations are only snapshots of what’s happening they are then put together to create “stop-motion” movies, which can then be used to observe and better understand how these reactions work.
“XLEAP is a truly great advance. Its attosecond X-ray pulses of unprecedented intensity and flexibility are a breakthrough tool to observe and control electron motion at individual atomic sites in complex systems,” Linda Young, an expert in X-ray science at the DOE’s Argonne National Laboratory and the University of Chicago who was not involved in the study, stated.
The team has already obtained some interesting observations but the system is being upgraded to reach even higher energies and potentially shorter time-pulses.