A brand new atomic nucleus has just been discovered, claims new study

Astatine: The elusive element

Astatine is a scarce and radioactive element. Its high radioactivity makes it very unstable, with its most stable isotope, ²¹⁰astatine, having a half-life of just over eight hours. Most of its isotopes have a half-life of a few seconds. 

Within the periodic table, astatine is placed with halogens, which are highly reactive nonmetallic elements. 

Astatine is the second-rarest naturally-occurring element, with just one gram present on Earth at any moment. Most of its properties are unknown and derived from inference as it is short-lived. It generally undergoes alpha decay into a more stable form, such as radon or bismuth. 

Even though very little is known about this element, some studies have shown that it may have anti-cancer properties, being a potential candidate for radiation therapies. Therefore, gaining a better understanding of this element is vital. 

Discovering the new astatine

The study involved a fusion-evaporation reaction taking place in a gas-filled recoil separator. This apparatus is used in nuclear physics experiments to separate and analyze energetic nuclear reaction products by passing them through a gas medium.

Fusion-evaporation reactions involve the collision of heavy ions with a target nucleus, which fuse to create a compound nucleus. This compound nucleus undergoes alpha decay by ejecting alpha particles, which are particles containing two neutrons and two protons (basically a helium atom), to produce a more stable element.

The research team bombarded 84strontium into silver atoms and studied the decay products. They were not looking for ¹⁹⁰At, but that's exactly what they discovered.

The reaction revealed that the alpha particles during the decay of ¹⁹⁰At had an energy of around 7750 keV. This measurement provides important insights into the energetics of the decay process.

Additionally, the researchers determined that the half-life of ¹⁹⁰At was around one millisecond. The short half-life indicates that ¹⁹⁰At is a highly radioactive isotope. These measurements aligned with our predictions from atomic mass models of this isotope.

They further found that the alpha decay of ¹⁹⁰At was energetically unhindered, implying that the decay process occurred immediately without delay. The unhindered decay process is notable as it suggests that the spin and parity remain unchanged during the reaction.

The discovery of ¹⁹⁰astatine expands our knowledge of the element's isotopic composition and provides valuable data for atomic mass models.

The findings of the study were published in the journal Physical Review C on June 20 and can be found here.

Study abstract:

The α decay of a new isotope ¹⁹⁰At has been studied via the ¹⁰⁹Ag(⁸⁴Sr,3n)¹⁹⁰At fusion-evaporation reaction by employing a gas-filled recoil separator. An α-particle energy of 7750(20) keV and a half-life of 1.0^+1.4_−0.4 ms were measured. The measured decay properties correspond to an unhindered α decay, suggesting the same spin and parity of (10⁻) as those of the final state of the decay. The systematics of the nearby nuclei and the predictions of selected atomic mass models were compared with the measured decay properties.