Atomic core, shaken not stirred

Jan 05, 2012 By Ashley Yeager
Credit: Geo Martinez,

When struck just right, protons and neutrons ring. The sub-atomic particles don’t jingle like when a hammer hits a bell. But they do jiggle in an odd dance where the protons move in one direction and the neutrons move the other way.

Studying this particular particle movement has been difficult because of other motion within an atom’s . But now, researchers using the High Intensity Gamma Ray Source, or HIGS, located on Duke’s campus, say they have gotten the best look yet at a nucleus as it starts its complex, resonant dance.

In the experiment, the researchers slammed a chunk of bismuth-209, which had 83 and 126 neutrons, with a polarized beam of high-energy photons.

The team then recorded all the gamma rays knocked from the nucleus after the collision. Based on the direction the gamma rays were traveling, the scientists were able to figure out the energy, width and strength of the resonance at which the particles’ rang.

The results, which appear in the Nov. 25 issue of Physical Review Letters, along with future studies on the vibrations of other nuclei planned at the HIGS facility will help theorists write a clear, accurate mathematical description of how protons and neutrons behave and also for the state of matter in black holes, stars and even in star explosions called supernovae.

Explore further: IHEP in China has ambitions for Higgs factory

More information: New Method for Precise Determination of the Isovector Giant Quadrupole Resonances in Nuclei. Henshaw,S., Ahmed, M., Feldman, G., Nathan, A., and Weller, H. PRL 107, 222501 (2011). DOI: 10.1103/PhysRevLett.107.222501

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3.7 / 5 (3) Jan 05, 2012
Many analogies can be drawn. Consider one: the vortices that appear in superfluid helium when excess energy is added to the system, by, for example, rotating the container beyond a critical point. Such vortices are the physical manifestation of the superfluid system shedding the energy that cannot "fit" within the system.

Here, the "hammer" adds excess energy to a complex system, the nucleus. It does not fit. The system sheds the energy--protons doing so in one way, neutrons in another way.

In both cases, the dumped energy is in the form of quantized oscillations. Conversely, the system--superfluid helium, or the nucleus--is also a quantized system comprised of interconnected oscillations that must be just so; new energy must be shed, or the system will collapse. Those are the only two alternatives.
1 / 5 (1) Jan 07, 2012
Such resonances could explain the mechanism of cold fusion at certain cases, especially in connections with similar resonance of electron orbitals. We should realize, at the case of large atoms the binding energy of electrons at the bottom of orbitals becomes comparable to the binding energy of neutrons residing at the outer halo of nuclei, so that they could interact mutually.