Investigating the candidate 5-alpha cluster state in 20Ne at Ex =22.5 MeV with the 22Ne(p,t)20Ne reaction

Abstract

The 20Ne nucleus was investigated experimentally with a proton beam energy of Ep = 80 MeV at zero-degrees scattering angle using the 22Ne(p,t)20Ne reaction. The aim of the project was to investigate if the existence of a state at Ex = 22.5 MeV in 20Ne, previously using the same reaction at Ep = 60 MeV, can be confirmed. Measurements were performed using the K600 magnetic spectrometer of iThemba LABS and a newly developed gas handling system that ensured constant pressure throughout the experiment for the 22Ne gas target. In general, a good correspondence between the 20Ne excitation energy spectrum measured in the present experiment and that at Ep = 60 MeV was found in the region below 22.5 MeV. Several strongly populated states in 20Ne identified for the previous experiment at Ep = 60 MeV were again seen in the present experiment at Ep = 80 MeV, for which cross-sections were extracted. However, with the help of wavelet-based semblance analysis a tentative candidate 5-alpha cluster state at Ex = 22.5 MeV, which lies 3.33 MeV above the 20Ne 5-alpha break-up threshold, was established (at Ex = 22.4 MeV in this study) to be only weakly populated in comparison to the Ep = 60 MeV dataset. The present finding supports the existence of a state at Ex = 22.4 MeV but further experimental work is required to investigate its nature