Kyle Brown, Michigan State University (MSU), East Lansing, USA, and colleagues have discovered a new magnesium isotope, magnesium-18. With 12 protons and only six neutrons in its nucleus, it is the lightest isotope of magnesium ever found. It is radically unstable and very short-lived, with a half-life of less than 10–21 seconds.
The researchers accelerated a beam of magnesium-24 nuclei (the most common stable magnesium isotope) to about half the speed of light at MSU’s National Superconducting Cyclotron Laboratory, a circular ultrahigh-energy particle accelerator. Then they fired the high-speed beam of magnesium nuclei at a target made of beryllium. The collision yielded lighter magnesium isotopes, including the unstable isotope magnesium-20, which contains only eight neutrons per nucleus and decays radioactively in a few tenths of a second. The researchers fired the magnesium-20 nuclei at about half the speed of light at a beryllium target. One of the products of the resulting collision was magnesium-18.
The isotope is so short-lived that it decays inside the beryllium target. Therefore, the researchers deduced its presence from the telltale products of its decay: stray protons and the isotopes neon-16 and oxygen-14.
- First Observation of the Four-Proton Unbound Nucleus 18Mg,
Y. Jin, C. Y. Niu, K. W. Brown, Z. H. Li, H. Hua, A. K. Anthony, J. Barney, R. J. Charity, J. Crosby, D. Dell’Aquila, J. M. Elson, J. Estee, M. Ghazali, G. Jhang, J. G. Li, W. G. Lynch, N. Michel, L. G. Sobotka, S. Sweany, F. C. E. Teh, A. Thomas, C. Y. Tsang, M. B. Tsang, S. M. Wang, H. Y. Wu, C. X. Yuan, K. Zhu,
Physical Review Letters 2021.