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

Identification of alpha-cluster states analogous to the C-12 Hoyle state in heavier alpha-conjugate nuclei can provide test of the existence of alpha condensates in nuclei. Such states are predicted for O-160, Ne-20, Mg-24, Si-28, etc., at excitation energies slightly above the multi- alpha-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 a particles. The reaction Ne-20 + alpha was studied using a Ne-20 beam at 12 MeV/nucleon from the K150 cyclotron at Texas A&M University. The TTIK method was used to study both single alpha-particle emission and multiple alpha-particle decays. Events with a multiplicity up to four were analyzed. The analysis of the three alpha-particle emission data allowed the identification of the Hoyle state and other C-12 excited states decaying into three alpha particles. The results are shown and compared with other data available in the literature. Although the statistics for events with alpha-multiplicity four is low, the data show a structure at about 15.2 MeV that could indicate the existence in O-16 of a state analogous to the C-12 Hoyle state. Moreover, the reconstructed excitation energy of Mg-24 for these events peaks at around 34 MeV, very close to the predicted excitation energy for an excited state analogous to the C-12 Hoyle state in Mg-24. The structure is further confirmed by the reanalysis of alpha-multiplicity-four events from a previous experiment performed at 9.7 MeV/nucleon with a similar, but lower granularity, experimental setup.