The appearance of quasimolecules from matter and antimatter

US, WASHINGTON (ORDO NEWS) — Physicists have found out what causes the helium atom and antiproton to combine into an exotic long-lived structure similar to a molecule. The fact that such a structure exists, scientists predicted back in 1991.

The calculation results published The European Physical Journal D.

Cosmologists suggest that in the first instants of the existence of the Universe, matter and antimatter were approximately equal in it. All chemical and physical properties of their particles, with the exception of charge, should be the same. So says the Standard Model – a theory that describes most of the interactions of all elementary particles known to science now.

Nevertheless, this contradicts the very existence of reality, since all particles of matter and antimatter should have destroyed each other by colliding and annihilating in the first moments after the Big Bang. Therefore, scientists have been arguing for decades about why they cannot find traces of antimatter in the observable Universe.

Now physicists are trying to find differences in how the particles of matter and antimatter are arranged, as well as how they behave. For this, scientists, in particular, observe the behavior of various exotic structures from matter and antimatter. A striking example of such a structure is the so-called positronium, a very unstable “atom”, which consists of an electron and a positron and in its properties resembles hydrogen.

Riddles of Antimatter

There are more complex forms of such compounds of matter and antimatter – for example, the so-called “atomic molecules” of helium. They represent the nucleus of helium around which an electron moves, as well as an antiproton.

Despite the fact that these particles have a huge difference in mass and other properties, such a design, which has both the properties of an atom and a molecule, remains quite stable for an unusually long time. There are several theoretical models that describe the structure of such “atomic molecules” in different ways.

In particular, according to one of them, antiproton helium arises when an antimatter particle interacts with a neutral atom of a noble gas, “knocks out” the last electron from it and starts circling it at a great distance. Physics proved the existence of such particles during experiments at CERN accelerators.

Russian physicist Evgeny Solovyov from the Joint Institute for Nuclear Research (JINR) in Dubna, as well as his colleague Tasko Grozdanov from the University of Belgrade (Serbia), checked the efficiency of the alternative theory. She admits that such structures can be formed upon the interaction of an antiproton with an excited helium atom.

In this case, the atomicule will have a completely different structure, which does not coincide with what the already studied compounds of helium and antiproton look like. Despite the fact that scientists predicted the existence of this form of antiproton helium almost three decades ago, Soloviev and Grozdanov did not fully understand how such atoms look and what makes the antiproton enter a special energy “well”, which is located at a great distance from the helium core.

To fill this gap, physicists calculated how the excited helium atom will behave when approaching the antiproton and determined its exact internal structure. Scientists have proven that such alternative forms of “atomic molecules” can actually arise, and also were able to explain several possible mechanisms of their appearance and decay scenarios.

As the researchers hope, their results will help experimenters discover the first examples of the existence of such exotic “atomic molecules” in experiments on real particle accelerators, as well as find the first differences in the properties of matter and antimatter.


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