Continuum spectroscopy of light nuclei studied by high-order correlation experiments

L. G. Sobotka

Departments of Chemistry and Physics

Washington University, St. Louis

Recent technical advances have allowed for high-order correlation experiments to be done.  We have primarily focused on experiments in which the final channels are composed of only alphas and protons. Five cases we have studied are: ⁶Be, ⁸C, ⁸B*(IAS) ¹⁰C ^*, and ¹²C*.  While the first case had been studied before, our work presents very high statistics in the full Jacobi coordinates (the coordinates needed to describe 3-body decay.)  Our study of ¹⁰C excited states provides isolatable examples of: correlated 2p decay, from one state and the decay of another which is unusually highly correlated, a “ménage a quatre”.  ⁸C decay presents the only case of sequential 3-body 2p decay steps (i.e. 2p-2p.) The intermediate in this 2-step process is the first example (⁶Be) mentioned above.  Unlike the well-studied second step (⁶Be decay), the first step in this 2p-2p process provides another example of correlated 2p emission. The decay of ⁸B(IAS), the isobaric analog of ⁸C, also decays overwhelmingly by 2p emission, in this case to ⁶Li(IAS). This IAS-to-IAS 2p decay is one for which decay to the potential 1p intermediates is energetically allowed but isospin forbidden.  This represents an expansion, over that originally envisioned by Goldanski, of the conceivable nuclear territory for 2p decay.

The data from these high-order correlation experiments allowed for an improved fit of the IMME equation for the A = 8 isobar that showed that isospin symmetry is broken in the A = 8 system.  These correlation data also allowed us to demonstrate that the alpha decays of the excited states of ¹²C at 7.65 MeV (Hoyle) and 9.64 are consistent with preceding 100% through ⁸Be_g.s.