Searching for states analogous to the 12C Hoyle state in heavier nuclei using the thick target inverse kinematics technique

Identification of α-cluster states analogous to the ¹²C Hoyle state in heavier α-conjugate nuclei can provide tests of the existence of α condensates in nuclei. Such states are predicted for ¹⁶O, ²⁰Ne, ²⁴Mg, ²⁸Si, etc., at excitation energies slightly above the multi- α-particle decay threshold but have not yet been experimentally identified. The thick target inverse kinematics (TTIK) technique can be used to study the breakup of excited self-conjugate nuclei into many α particles. The reaction ²⁰Ne+α was studied using a ²⁰Ne beam at 12 MeV/nucleon from the K150 cyclotron at Texas A&M University. The TTIK method was used to study both single α-particle emission and multiple α-particle decays. Events with α multiplicity up to four were analyzed. The analysis of the three α-particle emission data allowed the identification of the Hoyle state and other ¹²C excited states decaying into three α particles. The results are shown and compared with other data available in the literature. Although the statistics for events with α-multiplicity four is low, the data show a structure at about 15.2 MeV that could indicate the existence in ¹⁶O of a state analogous to the ¹²C Hoyle state. Moreover, the reconstructed excitation energy of ²⁴Mg for these events peaks at around 34 MeV, very close to the predicted excitation energy for an excited state analogous to the ¹²C Hoyle state in ²⁴Mg. The structure is further confirmed by the reanalysis of α-multiplicity-four events from a previous experiment performed at 9.7 MeV/nucleon with a similar, but lower granularity, experimental setup.