Carbon12 nucleus, without which there would be no life here on Earth, resembles equilateral triangle

[G_j]

http://physicsworld.com/cws/article/news/2014/jul/08/carbon-nucleus-seen-spinning-in-triangular-state

Carbon nucleus seen spinning in triangular state
Jul 8, 2014

Physicists have obtained important new evidence showing that the structure of the carbon-12 nucleus – without which there would be no life here on Earth – resembles that of an equilateral triangle. The evidence was obtained by physicists in the UK, Mexico and the US by measuring a new rapidly spinning rotational state of the nucleus. The finding suggests that the "Hoyle state" of carbon-12, which plays an important role in the creation of carbon in red giant stars, has the same shape too. Recent theoretical predictions, in contrast, had suggested that the Hoyle state is more like an obtuse triangle or "bent arm".

All the carbon in the universe is created in red giant stars by two alpha particles (helium-4 nuclei) fusing to create a short-lived beryllium-8 nucleus, which then captures a third alpha particle to form carbon-12. But exactly how this reaction occurs initially puzzled physicists, whose early understanding of carbon-12 suggested that it would proceed much too slowly to account for the known abundance of carbon in the universe. Then in 1954 the British astronomer Fred Hoyle predicted that carbon-12 had a hitherto unknown excited state – now dubbed the Hoyle state – which boosts the rate of carbon-12 production.

Three years later the Hoyle state was confirmed experimentally by physicists working at Caltech. However, the precise arrangement of the protons and neutrons in the carbon-12 nucleus remains a matter of much debate. While some physicists feel that carbon-12 is best thought of as 12 interacting nucleons, others believe that the nucleus can be modelled as three alpha particles that are bound together. The rational for the latter model is that alpha particles are extremely stable and so are likely to endure within the carbon-12 nucleus.

Molecular inspiration

If carbon-12 is indeed well described as three alpha particles, molecular physics could provide important clues about how those particles are arranged. In 2000 Roelof Bijker of the National Autonomous University of Mexico (UNAM) and Francesco Iachello at Yale University suggested that the three alpha particles could arrange themselves in an equilateral triangle in which the three alpha particles are all in the same plane. Such a structure had already been spotted five years earlier in the triatomic hydrogen molecular ion, H3+.

Now, Bijker has joined forces with Martin Freer and colleagues at the University of Birmingham and Moshe Gai at the University of Connecticut to obtain the best experimental evidence so far that carbon-12 is indeed shaped like an equilateral triangle. The experiment was carried out at Birmingham's cyclotron by firing a beam of alpha particles at a carbon target to produce carbon-12 nuclei that are in high spin states. Indeed, the nuclei, which literally spin like tops, are rotating so fast that they tear apart by emitting alpha particles.

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[Tikki]

1. Ah, symmetry.

Thanks for posting this article...I am always fascinated by new discoveries in our Scientific World.


Tikki

[jimlup]

2. Very cool!

I'm a "Nuclear physicist" by my educational heritage so this is fascinating to me.

(These days we say "Heavy Ion Physics" because it carries less of a frightening and negative connotation.)