Uncovering the Mystery of Carbon-12: Exploring the Foil State in Nuclear Physics

2023-06-17 12:02:04

“Carbon” is an essential element for all living organisms known today, including humans. Carbon is one of the most abundant elements in the universe, but the long history of nuclear physics has revealed that its abundance is a great mystery.

Most of the carbon in the universe is “carbon 12(6 protons, 6 neutrons)”, which is believed to be synthesized by fusing three nuclei of “helium 4 (2 protons, 2 neutrons)”. However, the state in which two helium-4 fuses together is extremely unstable, lasting less than one quadrillionth of a second. The third Helium-4 must collide and fuse in that short amount of time. Also, even if three helium-4 atoms simply collide, most of them will not fuse and will disperse once more.

A simple calculation shows that nuclear fusion reactions rarely occur even if three helium-4 collisions occur, and cannot explain the amount of carbon-12 in the universe. Here, when three helium-4 collides, “foil state」 (※) It is known that nuclear fusion reactions that produce carbon-12 tend to occur through an intermediate state called . However, since it is extremely difficult to experimentally create the foil state, the exact state of the foil state has been largely unknown.

*…In order for carbon-12 to be produced by the collision of helium-4, a high-energy unstable state must exist even momentarily following fusion. It doesn’t necessarily exist because of the limits on the energy states allowed in atomic nuclei, but with “evidence” that carbon-12 is abundant in the universe, astronomer Fred Hoyle suggests that such predicted the presence of high-energy states. This is the foil state.

A research team led by Shihang Shen of the Jurich Research Organization used the supercomputer “JUWELS” to conduct unconstrained lattice Monte Carlo simulations of the nuclear lattice effective field theory in order to investigate the details of the foil state. Originally, there is no limit to the arrangement pattern of protons and neutrons that make up the nucleus, so the calculation time of the simulation increases infinitely. Therefore, the research team aimed to complete the research within a realistic time by placing restrictions on this arrangement. However, even so, there are millions of placement patterns that need to be calculated, so the simulation execution time of JUWELS in this research reached 5 million CPU hours (time spent processing by the CPU).

[▲ Figure 1: Red squares and blue circles are values ​​shown in different simulations. ☆ is the experimentally measured value. It can be seen that both results are in good agreement (Credit: Shihang Shen, et.al.)]

[▲Figure2:InthissimulationitwasfoundthattherearesomerestrictionsonthearrangementofprotonsandneutronsThisresultagreeswellwiththeexperimentalresults(Credit:SerdarElhatisari/UniversitätBonn)】

As a result of verification, it is unlikely that protons and neutrons exist individually in the foil state, and in a state in which two protons and two neutrons are clustered (that is, a state very close to the nucleus of helium 4), an equilateral triangle or a considerable It turns out that it most likely exists in an array of flat isosceles triangles. The predicted nuclear physical state in this state is in good agreement with the experimentally measured results, implying that the simulation assumptions are correct.

The simulation results of this time mean that this simulation method is effective for understanding the unstable state of the nucleus, which is limited in experiments, and various physical states that are limited in experiments. It led to knowing

Since carbon is also essential for the synthesis of heavier elements such as nitrogen and oxygen, the foil state is indirectly related to the presence of other elements. In addition, the fact that carbon becomes other elements through nuclear fusion reactions is also related to stellar evolution theory, such as energy generation in stars heavier than the sun. The result of this research, which was able to simulate the foil state correctly and in detail, may be a driving force for deep understanding of difficult problems in nuclear physics.

Source

• Shihang Shen, et.al. “Emergent geometry and duality in the carbon nucleus”. (Nature Communications)
• Ulf G. meissner “Simulation provides images from the carbon nucleus”. (University of Bonn)

Text: Riri Ayae

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