Physicists find new Isotope Actinium-204

It is the lightest actinium isotope so far discovered.

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A research team at the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), with their colleagues, have produced a new isotope, actinium-204. The isotope is the lightest actinium isotope so far discovered and the fourth actinium isotope beyond the proton-drip line.

Physicists synthesized it in the fusion-evaporation reaction. They also identified through it the recoil-α correlation at the gas-filled recoiled separators. This is the 35th nuclide synthesized at IMP.

Its α-particle energy and half-life were calculated to be 7948 keV and 7.4 ms, respectively. They are both in accordance with the theoretical forecast.

The half-life of several isotopes is strictly synced with the energy of -particles in an odd-even fashion. Scientists discovered that actinium-204 and other isotopes with fewer than 119 neutrons do not fall under this criteria.

This occurrence demonstrates the actinium-204 unpaired neutron’s blocking influence on the α-decay process. In other words, the unpaired neutron lowers the likelihood that a cluster would develop close to the actinium-204 nucleus’ surface.

This study provided experimental data about the mass and α-decay of the new isotope actinium-204. It contributed to understanding the unpaired nucleon’s role in the α-decay process.

Journal Reference:

  1. M. H. Huang et al. α decay of the new isotope 204Ac. Physics Letters B. DOI: 10.1016/j.physletb.2022.137484