Researchers reveal structure of carbon's 'Hoyle state'

December 10, 2012

A North Carolina State University researcher has taken a "snapshot" of the way particles combine to form carbon-12, the element that makes all life on Earth possible. And the picture looks like a bent arm.

Carbon-12 can only exist when three alpha particles, or helium-4 nuclei, combine in a very specific way. This combination is known as the Hoyle state. NC State physicist Dean Lee and German colleagues Evgeny Epelbaum, Hermann Krebs and Ulf-G. Meissner had previously confirmed the existence of the Hoyle state using a numerical lattice that allowed the researchers to simulate how the protons and neutrons interact. When the researchers ran their simulations on the lattice, the Hoyle state appeared together with other observed states of carbon-12, proving the theory correct from first principles.

But they also wanted to find out how the nucleons (the protons and neutrons inside the nucleus of an atom) were arranged inside the nucleus of carbon-12. This would enable them to "see" the structure of the Hoyle state. Using the same lattice, the researchers, along with collaborator Timo Laehde, found that carbon-12's six protons and six neutrons formed three "alpha clusters" of four nucleons each. At low energy, the alpha clusters tended to clump together in a compact triangular formation. But for the Hoyle state, which is an excited energy state, the three alpha clusters combined in a "bent arm" formation.

The researchers' findings will appear this month in Physical Review Letters.

"It's interesting that a straight chain seems not to be the preferred configuration for the Hoyle state," Lee says. "A bend in the chain seems necessary. This work leads us to the question of what other nuclei have such alpha cluster shapes. These would be rather exotic structures in nuclear physics and open some really interesting questions regarding shape and stability. For example, can we have longer chains of alpha clusters? We are investigating these possibilities."
-end-
The work was funded by the U.S. Department of Energy; the Deutsche Forschungsgemeinschaft, Helmholtz-Gemeinschaft Deutscher Forschungszentren, and Bundesministerium fuer Bildung und Forschung in Germany; European Union HadronPhysics3 Project and the European Research Council; and the National Natural Science Foundation of China. Computational resources were provided by the Juelich Supercomputing Center. The NC State Department of Physics is part of the College of Physical and Mathematical Sciences.

Note to editors: an abstract of the paper follows.

"Structure and Rotations of the Hoyle State"

Authors: Dean Lee, North Carolina State University; Evgeny Epelbaum and Hermann Krebs, Institut fuer Theoretische Physik II, Ruhr-Universitaet Bochum, Germany; Timo A. Laehde, Forschungszentrum Juelich, Germany; Ulf-G. Meissner, Helmholtz-Institut fuer Strahlen-und Kernphysik and Bethe Center for Theoretical Physics, Universitaet Bonn, Germany.

Published:Physical Review LettersAbstract:

The excited state of the 12C nucleus known as the "Hoyle state" constitutes one of the most interesting, difficult and timely challenges in nuclear physics, as it plays a key role in the production of carbon via fusion of three alpha particles in red giant stars. In this letter, we present ab initio lattice calculations which unravel the structure of the Hoyle state, along with evidence for a low-lying spin-2 rotational excitation. For the 12C ground state and the first excited spin-2 state, we find a compact triangular configuration of alpha clusters. For the Hoyle state and the second excited spin-2 state, we find a "bent-arm" or obtuse triangular configuration of alpha clusters. We also calculate the electromagnetic transition rates between the low-lying states of 12C.

North Carolina State University

Related Nuclear Physics Articles from Brightsurf:

Explosive nuclear astrophysics
An international team has made a key discovery related to 'presolar grains' found in some meteorites.

Improved modelling of nuclear structure in francium aids searches for new physics
Thanks to researchers from The University of Queensland, we now know with much greater certainty the nuclear magnetic moments of francium atoms.

Nuclear medicine and COVID-19: New content from The Journal of Nuclear Medicine
In one of five new COVID-19-related articles and commentaries published in the June issue of The Journal of Nuclear Medicine, Johnese Spisso discusses how the UCLA Hospital System has dealt with the pandemic.

Going nuclear on the moon and Mars
It might sound like science fiction, but scientists are preparing to build colonies on the moon and, eventually, Mars.

Six degrees of nuclear separation
For the first time, Argonne scientists have printed 3D parts that pave the way to recycling up to 97 percent of the waste produced by nuclear reactors.

How to dismantle a nuclear bomb
MIT team successfully tests a new method for verification of weapons reduction.

Nuclear physics -- probing a nuclear clock transition
Physicists have measured the energy associated with the decay of a metastable state of the thorium-229 nucleus.

Milestones on the way to the nuclear clock
For decades, people have been searching for suitable atomic nuclei for building an ultra-precise nuclear clock.

Nuclear winter would threaten nearly everyone on Earth
If the United States and Russia waged an all-out nuclear war, much of the land in the Northern Hemisphere would be below freezing in the summertime, with the growing season slashed by nearly 90 percent in some areas, according to a Rutgers-led study.

Nuclear physics in search of world artifacts
NUST MISIS scientists together with the colleagues from PN Lebedev Physical Institute of the Russian Academy of Sciences of the Russian Academy of Sciences, Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University and Dagestan State University have published the first results of a 'scan' obtained by the method of muon radiography of the underground space in the Derbent fortress of Naryn-Kala.

Read More: Nuclear Physics News and Nuclear Physics Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.