2024-02-16 11:56:00
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16.02.2024 14:56, Gennady Detinich
American scientists have just cut through a window into a new field of experimental physics. They were able to obtain an energetic image of the movement of an electron around a hydrogen atom in a drop of water even before the atom began to move. Until now, scientists did not have the tools to drill down into such detail regarding the processes in matter, which would reveal more details regarding the physics and chemistry of many processes and, especially, regarding the radiation effect on living cells.
Image source: PNNL
In an experiment that looked vaguely like filming a slow-motion video, the scientists isolated the energetic motion of an electron while simultaneously freezing the motion of a much larger atom around which the target electron was orbiting, in a sample of ordinary liquid water. The scientists reported their work in article In the magazine Science. The work was mainly aimed at studying high-energy radiation on living cells, which is needed for space, radiotherapy of tumors and more.
“The radiation-induced chemical reactions we want to study are the result of an electronic response from the target that occurs in attosecond time scale” — explained Linda Young, senior author of the work and distinguished scientist at Argonne National Laboratory. Until now, radiochemists might only detect events on a picosecond time scale, which is a million times slower than an attosecond. It’s like saying “I was born and then died.” Would you like to know what happens in between? This is what we can do now.”
To achieve the result, an interinstitutional team of scientists from several US Department of Energy national laboratories, as well as universities in the US and Germany, combined experiments and theory to reveal in real time the effects of ionizing radiation from an X-ray source on matter. The research was supported by the Interface Energy Research Center for Interfacial Dynamics in Radioactive Environments and Materials (IDREAM), with funding from the U.S. Department of Energy, headquartered at Pacific Northwest National Laboratory (PNNL).
It’s no secret that subatomic particles, such as electrons, move so quickly that recording their actions requires a sensor capable of measuring time in attoseconds. It is so fast (or small) that there are, for example, more attoseconds in each second than there have been seconds in the entire history of the Universe.
The research carried out by the authors is based on the discovery and creation of attosecond X-ray free electron lasers, for which, in particular, the Nobel Prize in Physics was awarded last year. The SLAC National Accelerator Laboratory has a source of such light (LCLS), which the experimenters took advantage of.
An experimental setup that creates a thin film of water regarding 1 cm wide
Ordinary liquid water was chosen as a test sample for the experiment. The first attosecond pulse excited the electrons, and the second measured the response. This allowed the sensors to respond so quickly that the excited state of the electron manifested itself even before the central hydrogen atom in the molecule began to move. Previously, in the process of similar observations using pulses of longer duration, the picture was so blurry that scientists assumed the existence of a number of intermediate states. The attosecond laser showed that there are no intermediate states – these are all mirages or interference.
“We now have a tool with which, in principle, you can follow the movement of electrons and see newly ionized molecules as they form in real time,” — the authors of the study summarized the achievement.
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