Czech scientists were the first in the world to make direct observations by subatomic resolution, thus looking inside the atom. Until now, experts could only observe individual atoms directly – and that too was considered a miracle of technology. However, the observation of small, subatomic structures beyond the resolution of existing imaging methods.
The Czechs are now presenting to the world, through a valuable science journal, a method they once saw inside the atom. As a result, they were able to confirm the existence of an event called the sigma-hole, which was theoretically predicted but not directly observed.
In particular, it is the random distribution of the electron charge around the halogen atom (more in the box at the end of the text).
For the first time, Czech scientists were able to observe these asymmetric electron density distributions directly in individual atoms of halogen elements, especially bromine. It is a toxic and highly reactive element, a strong antioxidant agent.
It is a breakthrough discovery involving three disciplines: the Czech Institute of Research and Advanced Technologies (CADRIN), the Czech Academy of Sciences Institute of Physics, and the Academy of Sciences’ Institute of Organic Chemistry and Biochemistry. Czech Republic.
“Confirming the existence of theoretically predicted sigma-holes is a situation similar to observing black holes, whose existence was predicted by the theory of general relativity in 1915, but it was first observed two years ago at the atomic level.
Photo by scientist Pavel Zelinek: Experiania Foundation / Barbora Miragova
In addition, the Czech was able to dramatically increase the resolution of the so-called scanning microscopy. It was a technology that allowed people to show individual atoms a few years ago. This time, thanks to its transformation, scientists have moved from the level of atoms to subatomic phenomena.
Understanding the interactions between individual atoms and molecules, including chemical reactions, requires accurate knowledge of the electron charge distribution in atoms.
The new imaging system opens the way to improve the material and structural properties of many physical, biological or chemical systems that affect daily life.
Scientist Pavel Hobsa. | Photo: Tom Teštík
“I have been dealing with so-called non-covalent interactions all my life, and it gives me satisfaction that so far we can only observe ‘what we have seen’ in theory, and that the test measurements confirm our theoretical predictions. Explains, “says Pavel Hobsa, a computer chemist at the Institute of Organic Chemistry and Biochemistry, who performed advanced quantum chemistry calculations on supercomputers at the IT4Inovations Center in Ostrava.
“Halogen bonds and non-covalent interactions in general play a dominant role not only in biology but also in the material sciences. This makes our current work in science very important,” says Hobsa.
What is the sigma hole
Photo: Tom Belloň / IOCB
It is the asymmetric distribution of electron density in individual atoms of halogen elements. The characteristic shape of the sigma-hole is formed by a positively charged crown surrounded by a band with a negative electron density. This phenomenon was theoretically predicted thirty years ago and is now firmly established by the direct observation of Czech scientists.
The figure shows a theoretical calculation of the random distribution of electron charge in a bromine halogen atom and a comparison of the results of the experiment. This shows how precise theoretical ideas scientists had about the sigma-hole and how much they agreed with what the Czech inventors saw.