Measuring electron movements

Measuring electron movements in the liquid in super-slow motion

When they are excited from outside or during a chemical reaction, the electrons have the ability to move within molecules. Now researchers have succeeded in studying the first few dozens of attoseconds (1×10-18 of a second) of this electron motion in liquid for the first time ever.

For years, to study the very first moments of a reaction to understand how chemical reactions begin, chemists used super-slow-motion experiments. Nowadays, it is possible to measure a resolution of a few dozen attoseconds.

Hans Jakob Wörner, professor at the Laboratory of Physical Chemistry at ETH Zurich said that in these first few dozen attoseconds of a reaction, one can observe how electrons move within molecules. Chemical reactions lead to movements of atoms up to and including the breaking of chemical bonds, later, in the course of about 10,000 attoseconds, or 10 femtoseconds.

Electron movements in molecules on the attosecond scale was detected for the first time ever by a professor from ETH. But, due to the fact that they occur in a high-vacuum chamber, such measurements could be executed only on molecules in gaseous type.

Delayed transport of electrons from the liquid

Now, Wörner and his colleagues have succeeded in detecting such movements in liquids, after the development of novel equipment for measuring the movements in liquids. For this, the researchers utilized photoemission in water: Water molecules were irradiated using light, which triggered them to emit electrons, which can be measured. Wörner said that as it is feasible to start it with high temporal precision utilizing laser pulses, they chose to use this process for the experiment.

Likewise, the new measurements took place in a high vacuum, and to discover that electrons are emitted from water molecules in liquid form 50-70 attoseconds later than from water molecules in vapor, Wörner, and his group injected a 25-micrometer-thin water microjet into the measuring chamber. As the molecules in liquid form are surrounded by other water molecules having a measurable delay effect on specific molecules – leads to the time difference.

Vital step

Wörner said that the electron movements are vital events in chemical reactions, that’s why it’s so crucial to measure them on a high-resolution time range. Since a lot of chemical reactions – particularly the ones that are biochemically intriguing take place in liquids, the step from measurements in gasses to measurements in liquids is of specific importance.

Additionally, there are numerous processes, like photoemission in water, are triggered by light radiation – including photosynthesis in plants, damage to DNA brought on by X-rays or other ionizing radiation, and the biochemical processes on our retina that allow us to see. Researchers will gain new insights into these processes in the future with the help of attosecond measurements.


Measuring electron movements in the liquid in super-slow motion

Author: Sruthi S


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