How is an atom split?

In 1938, scientists showed how the uranium nucleus splits into two under the influence of neutrons. Decades later, despite the use of this discovery in our energy, medicine, scientific research and wars, nuclear fission is in no hurry to reveal its secrets, because atoms are a wild storm of quantum activity. Understanding how they behave and how their individual nucleons interact with each other is extremely difficult even for stable and quiescent atoms, let alone those that undergo significant transformations, Channel 24 reported, citing a study published in Physical Review Letters.

To make this easier to understand, theoretical physicists at Los Alamos National Laboratory and the University of Washington divided the fission process into four stages.

• in the top 10^-14 The addition of a slow neutron in seconds (plus or minus) causes the nucleus to swell and rearrange at what is called a saddle point, making the atom look like a tiny peanut shell.
• This is quickly followed by a much more rapid change called “saddle-to-fission”, in which parts of the fission process form. It takes about 5×10^-21 one second
• The third stage occurs even faster and turns into a relative moment – 10^-22 seconds During fission or so-called neck rupture, the nucleus is completely torn apart.
• A lazy 10 field is in the final stage^-18 After a few seconds, the decay fragments take shape and fly apart, releasing neutrons and gamma rays and potentially causing further decay processes after a short delay.

Although in many cases experimental results either contradict fundamental assumptions of physics or do not agree with “microscopic” modeling of the interaction between individuals, a single theory explains the complete migration of subatomic particles “from peanut to Eskimo”. protons and neutrons.

The quantum many-body simulation, based on a concept developed by lead author physicist Aurel Bulgak, is the most accurate representation of what to expect at the moment of fission, when the bridge connecting the two halves of a large atomic nucleus contracts and separates.

Calculations uranium-238, plutonium-240 and California-252 It required extensive use of the U.S. Department of Energy’s Oakridge National Laboratory supercomputer under various initial conditions.

Aurel Bulgak is confident that this is “the most accurate and most carefully derived theoretical explanation of neck fracture, without any assumptions or simplifications.”

We have a very specific prediction that hasn’t happened yet. Previous theories were always based on “let’s assume it happens, if it does happen, it’s likely to happen”. We did not do this. We introduced the equations of motion known for decades in nuclear physics with high precision, plus quantum mechanics and nothing else,
– says Bulgak.

Atomic fission presented in time series / Photo by Ibrahim Abdurrahman/Matthew Kafker/Aurel Bulgak/Ionel Stetsu

The simulation revealed many surprises that contradict scientists’ previous assumptions about the fission process: the absence of quantum randomness where it was expected to be seen, and the difference in fission times between the two types of nucleons as the proton neck completes its breaking. earlier than the neutron neck.

However, the simulation confirmed the controversial assumptions regarding the release of high-energy neutrons in the fission phase; the model went so far as to predict their energy, angular distribution, and even direction of separation.

Most experiments look for them in the direction of motion of the fission fragments, and they could not distinguish the fission neutrons there because most of them were thermal neutrons emitted by the hot fragments.
– says Bulgak.

With the predictions in hand, the next step will be to see whether these latest discoveries about how the atom is split in two can be confirmed by experiments.