High-speed Electron Camera Clicks Atomic Nuclei in Vibrating Molecules

With the aid of the SLAC’s instrument for extremely fast electron diffraction, scientists were able to monitor the movements of atomic nuclei closely in vibrating molecules for the very first instance. In this study, a laser pulse hit a spray of iodine gas where the augmented iodine molecules, which comprise of two iodine atoms, linked via a chemical bond. The molecules were then thrashed by an electron ray, creating a characteristic diffraction structure on a detector, from which the dispersion of the nuclei can be accurately determined.

Figure 1: High-speed ‘electron camera’ films atomic nuclei

Scientists utilized the UED instrument electron ray to witness at iodine molecules at distinct points in time beyond the laser pulse. By linking the pictures together, they collected a ‘molecular show’ that reveals the molecule vibrating and the link between the two iodine nuclei expanding almost 50 percent from 0.27 to 0.39 millionths of a millimetre, before coming back to its initial stage.

One vibrational cycle took around 400 femtoseconds, one femtosecond, or a millionth or a billionth of a second is the overall time it consumes light to travel a minute fraction of the width of a human hair.

“We have forced the speed limit of the method so that we can now witness nuclear movements in real-time,” says co-investigator Xijie Wang. SLAC’s head researcher for UED, “Such breakthrough opens up novel opportunities for accurate studies of dynamic procedures in biology, material science, and chemistry.

The method of UED has been under development by a range of groups across the world since the 1980s. But, the quality of electron beams has just recently become potential enough to allow femtosecond experiments. The instrument of SLAC is of great benefit from an ultrabright electron; high-energy source primarily developed the femtosecond X-ray laser of the lab, Linac Coherent Light Source.

The Co-principal analyser Martin Centurion from the Nebraska’s University, Lincolin, says, “What is also excellent about our technique is that it functions really well for every molecule. It is different from other techniques that rely on the potential to estimate the nuclear structure from the original data that functions best for tiny molecules; we only required to know the features of our electron beam and overall experimental setup.” Following their initial steps with the use of deliberately simple iodine molecule, the group is now looking forward to expanding their researches to molecules with more than double atoms.

Conclusion – “The development of UED into a method that can boost alterations in internuclear distances of a diluted gas product in real-time is really an immense achievement,” says Jianming Cao, a UED expert from the Florida State of University and a prior member of the Zewail lab at the California Institute of Technology.