Writing in the March 16 issue of Physical Review Letters, the researchers report they have created an exotic nucleus that can lose half its radioactivity (decay into other elements) in as little as 450 nanometers. second.
Lutetium (Lu) is a rare earth element, a silvery metal in its natural form, with atomic number 71. Usually, lutetium occurs in the Earth’s crust along with the metallic element ytterbium (Yb). Lutetium-176 is a relatively common radioactive isotope (2.5% of all lutetium isotopes) with a half-life of about 38 billion years and can be used to measure the age of meteorites. Lutetium on Earth consists of two isotopes, lutetium-175 and lutetium-176, of which only lutetium-175 is stable.
In the 1980s, scientists observed the decay of the lutetium isotope, lutetium-151, and discovered that it released a proton from the nucleus in its ground state. The ground state is the state in which the atom is at its lowest energy, when electrons move in orbits closest to the nucleus, which is also the most stable configuration of the atom. Proton emission is very rare, and lutetium-151 is the first isotope observed to emit protons in a stable decaying ground state.
Studying proton decay allows researchers to peer inside atomic nuclei to understand how protons and neutrons bind together. As part of this study, Kale Olanin, a postdoctoral researcher in physics at the University of Jyväskylä, and his colleagues created a new isotope of lutetium, lutetium-149, which has 71 protons in it. nucleus and 78 neutrons.
They found that lutetium-149 is more exotic than lutetium-151. First, the nucleus of lutetium-149 is not a neat sphere, but a squashed ellipsoid that looks a bit like a pumpkin. This phenomenon is known as “mass distortion”, and lutetium-149 is the most distorted nucleus ever measured.
The half-life of lutetium-149 is also significantly shorter than that of lutetium-151’s 80.6 milliseconds. The researchers say they created this new isotope of lutetium by burning nickel-58, an isotope of nickel, and ruthenium-96, an isotope of ruthenium. In the study, lutetium-149 decayed to ytterbium-148, which itself is not long-lived, with a half-life of 250 milliseconds. It is possible in the future to make lutetium-148, the researchers say, which may have a longer lifespan than lutetium-149.