March 6, 2006, London, England--The fastest ever observations of protons moving within a molecule open a new window on fundamental processes in chemistry and biology, researchers report this week in the journal Science.
Their capturing of the movements of the lightest and therefore speediest components of a molecule will allow scientists to study molecular behaviour previously too fast to be detected. It gives a new in-depth understanding of how molecules behave in chemical processes, providing opportunities for greater study and control of molecules, including the organic molecules that are the building blocks of life.
The high speed at which protons can travel during chemical reactions means their motion needs to be measured in units of time called 'attoseconds', with one attosecond equating to one billion-billionth of a second. The team's observation of proton motion with an accuracy of 100 attoseconds in hydrogen and methane molecules is the fastest ever recorded.
"Slicing up a second into intervals as miniscule as 100 attoseconds, as our new technique enables us to do, is extremely hard to conceptualise," said John Tisch of Imperial College London. "It's like chopping up the 630 million kilometers from here to Jupiter into pieces as wide as a human hair."
Jon Marangos, director of the Blackett Laboratory Laser Consortium at Imperial, says this 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," he said. "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."
To make this breakthrough, the research team used a specially built laser system capable of producing extremely brief pulses 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.