Study of clustering in ¹⁶O by four α decay

Alpha clustering in nuclei is very important to understand better the structure of nuclei. For example, clustering in the ¹²C Hoyle state is responsible for enhancing the triple-α reaction in stars. Recent experiments have been capable of detecting all of the three α decays from this Hoyle state and demonstrated the sequential decay of this state.

If we add another α and study ¹⁶O, there should be an excited state which has an equivalent structure to the Hoyle state, which should lie just above the 4-α separation energy.

In May 2021, we were able to study this α clustering in ¹⁶O at the NSCL using the ReA6 accelerator, using the Active Target Time Projection Chamber (AT-TPC) instead of conventional methods which allowed us to detect many particles with a higher efficiency. We filled the detector with pure Helium gas to study the excited states populated by the inelastic (α, α’) scattering, above the α separation energy, and to detect events with many-particle decays.