High-speed observations of hydrogen ions (protons) moving within a molecule could allow chemists to gain new insights into the fundamental processes that take place in reactions, according to UK scientists writing in the journal Science today.
John Tisch of Imperial College London and his colleagues have captured proton movements on the attosecond scale. (Check out our atto to yocto page for a definition). The research provides new clues as to how molecules behave in chemical and biological processes.
“Slicing up a second into intervals as miniscule as 100 attoseconds, as our new technique enables us to do, is extremely hard to conceptualise,” says Tisch, “It’s like chopping up the 630 million kilometres from here to Jupiter into pieces as wide as a human hair.”
Jon Marangos, Director of the Blackett Laboratory Laser Consortium at Imperial, adds that the new technique means scientists will now be able to measure and control the ultra-fast dynamics of molecules. “Control of this kind underpins an array of future technologies, such as control of chemical reactions, quantum computing and high brightness x-ray light sources for material processing. We now have a much clearer insight into what is happening within molecules and this allows us to carry out more stringent testing of theories of molecular structure and motion. This is likely to lead to improved methods of molecular synthesis and the nano-fabrication of a new generation of materials,” explains Marangos.
To make the breakthrough, the scientists, include lead author Sarah Baker, used a specially built laser system capable of producing extremely brief bursts of light. This pulsed light has an oscillating electrical field that exerts a powerful force on the electrons surrounding the protons, repeatedly tearing them from the molecule and driving them back into it. This process causes the electrons to carry a large amount of energy, which they release as an x-ray photon before returning to their original state. How bright this x-ray is depends on how far the protons move in the time between the electrons’ removal and return. The further the proton moves, the lower the intensity of the x-ray, allowing the team to measure how far a proton has moved during the electron oscillation period.
You can read more about the research in today’s issue of Science