THE STRUCTURE OF 12C AND STELLAR HELIUM BURNING

The rate of stellar formation of carbon at high temperatures (T > 3 GK) may increase beyond that which is expected from the Hoyle state at 7.654 MeV due to contributions from higher lying states in C-12. The long sought for second 2(+) state predicted at 9-10 MeV excitation energy in C-12 was predicted to significantly increase the production of C-12. An Optical Readout Time Projection Chamber (O-TPC) operating with the gas mixture of CO2(80%) + N-2(20%) at 100 Torr with gamma beams from the HI gamma S facility of TUNL at Duke was used to study the formation of carbon (and oxygen) during helium burning. Preliminary measurements were carried out at beam energies: E = 9.51, 9.61, 9.72, 10.00, 10.54, 10.84 and 11.14 MeV. Extra attention was paid to separating the carbon dissociation events, C-12(gamma, 3 alpha), from the oxygen dissociation events, O-16(gamma, alpha)C-12. Complete angular distributions were measured giving credence to a newly identified 2(+) state just below 10.0 MeV.