a Neutron Halo Around Neutron-Rich Magnesium Nuclei
The most stable nuclei are composed of roughly an equal number of protons and neutrons. With the right equipment, however, physicists can create many additional nuclei with neutrons. These neutron-rich nuclei are short-lived, but represent an important tool for developing a better understanding of how the elements were created in the universe tool.
A joint study conducted by Nobuyuki Kobayashi and Takashi Nakamura of Tokyo Institute of Technology involving researchers RIKEN Nishina Center for Accelerator-Based Science has now revealed that the extra neutrons in a nucleus neutron-rich magnesium halo1 produce neutrons.
The researchers used RIKEN beam Radioactive Isotope factory to produce magnesium-cores 37, which consists of 25 neutrons and 12 protons. To test its properties, the researchers observed what happened when these nuclei were bombarded against a white lead. "We found that the magnesium-37 nuclei easily broken in a core of magnesium-36 and a single neutron" says Kobayashi. "Therefore, we conclude that magnesium-37 has a neutron halo."
Halos of neutrons are neutrons dilute cloud surrounding the neutrons and protons are more compacted than in the center of a core. They have been identified in the past, but predominantly in the nuclei with less than 20 neutrons. Magnesium-37 is so far from the heavier nuclei have been found to have a nuclear halo. Evidence of a halo-shaped structure also means that the magnesium-37 cores are deformed and do not conform to the conventional spherical shape.
The researchers then conducted a similar experiment using a carbon target. While lead target experiments revealed reaction cores electrostatic forces, using a carbon target was used to study the response to 37-magnesium nuclear forces, which are sensitive to rotational movement of the neutrons. Neutrons present in the previously studied halogen light nuclei, in which the core is surrounded by a neutron, lack of rotation and are known as halos waves S. However, Kobayashi and colleagues found that the magnesium-neutron halo 37 had a measurable rotation or angular momentum, called a halo waves P.
The results provide crucial information on the reasons why some nuclei are stable, while others rot. "Our results indicate that the formation of halos may be a universal feature in the neutron-rich nuclei," says Ken-Ichiro Yoneda, one of the researchers who contributed to the RIKEN project. "The reason is that there are, however, is still unclear. Hopefully accumulate more detailed information on other neutron-rich nuclei so that we can better understand the information mechanism of halo formation."
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