Freezing time
In 1878 English photographer, Edward Muybridge published in Scientific American, a series of photographs proving that a galloping horse’s four legs are at some point all in the air. He needed to freeze the action with a shutter speed of milliseconds. Now we have laser technology that can generate light pulses that are 100 billion times faster than Muybridge’s shutter and allow us to see the details of molecules in motion. Scientists at the University of East Anglia (UEA), led by Professor Steve Meech, are using this technology to measure how energy is transferred from molecule to molecule in chemical materials.

Seeing what atoms and molecules are doing in chemical reactions in ‘slow motion’ means working at speeds of femtoseconds. A femtosecond is to a second what a second is to 32 million years. But this is the sort of speed required if chemists want to ‘freeze’ the moment when atoms and molecules come together to form new compounds. The technique, called pump-probe spectroscopy, uses lasers to flash intense pulses of light in femtoseconds, and was pioneered by Nobel Prize-winner, Professor Ahmed Zewail in the late 1980s.

Shedding light on chemical mysteries
The UEA femtochemistry team are using pump-probe spectroscopy to look inside a number of chemical reactions. One example is a protein found in photosynthesis, which responds to blue light. At the molecular level they intend to find out why this particular protein can sense the blue light spectrum and what is happening in that chemical reaction.

They have funding now for new lasers for more energy-related work. As Meech explains, ‘our objective is to look at how molecules efficiently transfer charge or energy from one point to another, which is obviously connected with energy harvesting.’

Exciting collaboration
Making the lasers work used to be the biggest problem. Now the challenge is the experiments themselves. Meech continues, ‘that’s part of the fun. Our group is driven experimentally, we are trying to observe things and then to interpret them. At the interpretation level we have to go and talk to our friends.’

If the outcome of their measurements is improving the efficiency of these molecules to build better energy systems, femtochemistry is not just relatively new, it’s involving the team in a growing international scientific community.