Tracking energy flow in large molecules

June 13, 2018, Ecole Polytechnique Federale de Lausanne

Absorption of light energy by large molecules is what drives nature: photosynthesis, vision, the synthesis of vitamin D and many other critical processes use light energy to perform their functions.

Absorption of light can also have negative effects: overexposure to sunlight damages DNA and can cause melanoma. Nature has developed ways to circumvent such effects. For example, protecting the skin is achieved by efficiently funneling the energy absorbed by DNA back to its initial (or ground) state, in which it was before absorption of light.

This process of , taking place within ultrashort time scales of tens to hundreds of femtoseconds (1 fsec = 10-15 seconds), is universal to all polyatomic molecules. Therefore, identifying the pathways of energy is crucial not only for understanding Nature, but also for a large range of applications.

The flow of energy proceeds through funnels that are called "conical intersections". These are points of the molecule's energy landscape where different electronic energy levels cross. The concept of conical intersections is universally used to explain energy flow in polyatomic molecules. Yet, they have never been observed! Different strategies were proposed to detect them, but at present, none seems experimentally feasible.

A team of scientists from the lab of Majed Chergui at EPFL within the Lausanne Centre for Ultrafast Science, the lab of Albert Stolow (University of Ottawa), and the lab of Michael Schuurman (NRC-Ottawa) have now devised an unambiguous approach to detect conical intersections in polyatomic molecules. The approach uses time-resolved X-ray spectroscopy (pioneered by the group of Majed Chergui) that is capable of detecting electronic structure changes with element selectivity, as the energy flows through the conical .

The scientists carried out computer simulations of flow across the ethylene molecule, a model for a wide class of of biological interest. The simulations revealed a clear and unambiguous fingerprint of the passage through the conical intersections by a change of charge at the Carbon atoms.

"Identifying conical intersections is something photobiologists and photochemists have long dreamed of and it opens up new insights for exciting future developments" says Majed Chergui.

Explore further: Supercomputing more light than heat

More information: Simon P. Neville et al. Ultrafast X-Ray Spectroscopy of Conical Intersections, Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.120.243001

Related Stories

Supercomputing more light than heat

February 6, 2018

Solar cells can't stand the heat. Photovoltaics lose some energy as heat in converting sunlight to electricity. The reverse holds true for lights made with light-emitting diodes (LED), which convert electricity into light. ...

Watching electrons in molecules

October 14, 2011

(PhysOrg.com) -- A research group led by ETH Zurich has now, for the first time, visualized the motion of electrons during a chemical reaction. The new findings in the experiment are of fundamental importance for photochemistry ...

Shedding light on the absorption of light by titanium dioxide

April 13, 2017

Titanium dioxide (TiO2) is one of the most promising materials for photovoltaics and photocatalysis nowadays. This material appears in different crystalline forms, but the most attractive one for applications is called "anatase". ...

Solving electron transfer

July 2, 2013

EPFL scientists have shown how a solvent can interfere with electron transfer by using unprecedented time resolution in ultrafast fluorescence spectroscopy.

Molecules in the spotlight

December 12, 2008

A novel x-ray technique allowing the observation of molecular motion on a time scale never reached before has been developed by a team of researchers from EPFL and the Paul Scherrer Institute (PSI) in Switzerland. Results ...

Recommended for you

Quantum transfer at the push of a button

June 15, 2018

In new quantum information technologies, fragile quantum states have to be transferred between distant quantum bits. Researchers at ETH have now realized such a quantum transmission between two solid-state qubits at the push ...

Biological light sensor filmed in action

June 15, 2018

Using X-ray laser technology, a team led by researchers of the Paul Scherrer Institute PSI has recorded one of the fastest processes in biology. In doing so, they produced a molecular movie that reveals how the light sensor ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.