Special Nuclear Seminar

A Study of the Fusion Reactions ¹²C + ¹²C Toward the Gamow Energy

Dr. Timothy Spillane
University of Connecticut

Monday, August 13, 2007   9:00 a.m.   NSH 124
(Refreshments served prior to seminar in NSH 124)

The set of fusion reactions ¹²C + ¹²C play a critical role in nuclear astrophysics.  Several processes, including quiescent carbon burning and type Ia supernovae depend intimately on the reaction rate of the ¹²C + ¹²C reactions at energies far below the Coulomb barrier.  In addition to their astrophysical relevance, these reactions play an ongoing role as both catalyst and test case for developments in nuclear structure.  These developments include the theory of quasi-molecular nuclei, the hypothesis of absorption under the barrier, and very recently, the phenomenon of sub-barrier fusion hindrance.  In a recent experiment, the fusion reactions ¹²C + ¹²C have been studied at E_CM = 2.10 to 4.75 MeV by g-ray spectroscopy using a C target of ultra-low hydrogen contamination.  The deduced astrophysical factor exhibits previously unknown resonances at E≤3.0 MeV, in particular a strong narrow resonance at E = 2.14 MeV, which lies at the high-energy tail of the Gamow peak.  The experiment and results are described, and the implications to astrophysics and nuclear structure are surveyed.