Searching for states analogous to the C 12 Hoyle state in heavier nuclei using the thick target inverse kinematics technique
Identification of α-cluster states analogous to the C 12 Hoyle state in heavier α-conjugate nuclei can provide tests of the existence of α condensates in nuclei. Such states are predicted for O 16 , Ne 20 , Mg 24 , Si 28 , 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 Ne 20 + α 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 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 C 12 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 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 α-multiplicity-four events from a previous experiment performed at 9.7 MeV/nucleon with a similar, but lower granularity, experimental setup.