2023-11-15 07:00:02
Ejecting protons one after the other, unbound nitrogen-9 decays into carbon-8 and then beryllium-6 before transforming into an alpha particle, a chain of events that physicists liken to nested Russian dolls. Scientists may have observed for the first time an ultra-rare version of nitrogen, called nitrogen-9 (9N). This new isotope would contain five neutrons less than its stable form. Carried out at the National Laboratory of Cyclotron Superconductor from the United States, this research could redefine the limits of stability nuclear.
The existence of nitrogen-9 was suggested in an experiment where beams of oxygen isotopes were projected onto atoms of beryllium. If future experiments confirm its presence, nitrogen-9 would set a new record in matter of number of deficit neutrons in a atomic nucleus, going from four to five. Details of this discovery were published October 27 in the journal Physical Review Letters.
This unstable version of nitrogen decays by successively emitting one or two protons, a process reminiscent of Russian dolls, according to Robert Charity, a nuclear scientist at theUniversité from Washington to St. Louis.
Protons and neutrons within atomic nuclei are held together by the strong force, which in stable atoms surpasses the repulsive force of positively charged protons. However, the decrease in the number of neutrons unbalances this stability, driving the atoms to the boundary of the “stability line”. Beyond this line, atoms become unstable and disintegrate, expelling protons or neutrons.
The first clues to the presence of nitrogen-9 were found in data from an old experiment carried out by the same laboratory. Originally, researchers sought to create another isotope, oxygen-11, by bombarding beryllium with oxygen-13 atoms. But among millions of interactions, they detected a decay signature indicating the brief existence of nitrogen-9, lasting only 10-21 seconds.
To partially confirm this discovery, the researchers modeled the structure of the isotope, revealing a helium nucleus surrounded by five loosely bound protons. These protons decayed after a very short time, escaping from the nucleus by quantum tunneling.
Further experiments will be necessary to definitively confirm this discovery. Lee Sobotka, professor of chemistry and physics at the University of Washington, emphasizes the importance of understanding the structure and reactions producing such nuclei to reconstruct the mechanisms of formation of the elements present in our environment.
Nitrogen-9 and its place in nuclear physics
Nitrogen-9, the central subject of the article, represents a particularly intriguing isotope. An isotope is a form of a chemical element characterized by a specific number of neutrons. All isotopes of an element share the same number of protons, but differ in their number of neutrons. Nitrogen, whose atomic number is 7 (which means it always has 7 protons in its nucleus), can have different isotopes, identified by the sum of its protons and neutrons. Thus, nitrogen-9, with only 2 neutrons in addition to its usual 7 protons, becomes a fascinating subject of study due to its rarity and extreme instability.
The study of such isotopes is crucial for nuclear physics because it provides essential information about the fundamental forces at work in the atomic nucleus and helps to understand the formation of elements in the universe. Research on nitrogen-9 and other exotic isotopes also allows testing and refinement of quantum mechanical models, particularly those relating to open or unbound systems, where particles are not firmly bound to the nucleus .
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