Spin assignments for the sub-Coulomb resonances of theC12+C

The12C+12C reaction at subcoulomb energies (II)

“…The present data as well as those of [-3] obviate the need of the hypothesis of absorption under the barrier at least down to E .... =2.45 MeV and support therefore the standard model of extrapolations [10] to stellar energies. It should be noted, that the absolute S(E)-values for the ~-particle channel are in excellent agreement with the results of Galster et al [9] in the overlapping beam energy range (Ec.m.=4.0-6.3 MeV). The absolute S(E)-values for both charged-particle exit channels are also in good agreement with the values reported by Patterson et al [11].…”

“…These analyses require the measurements of angular distributions of the particles in the exit channels at energies on and off the resonance structures. From the summed cross sections of the ~0 to c% particle groups in the 2~ exit channel, Galster et al [9] Previous J~ assignments [9] have been deduced mainly from the angular distributions of the c%-and %-particle groups. While these two groups lead to unique J~ values [9], other resonant groups in the c~-and p-exit channels allow often a broader range of possible J= values.…”

Gammadecay of quasimolecular resonances in the12C+12C system

“…For the same reason the centroids were kept fixed at 4.88 and 5.00 MeV. The two established 2 + resonances at these energies have a width of 60-80 keV [12] which is slightly less, but still comparable to the present result, A similar agreement can be found for the capture resonances at 5.56 and 6.00 MeV [7] both having rather similar widths and energies as quasimolecular resonances found in particle spectroscopy. It should be noted, that a 2 + resonance at 6,01 MeV was discovered only quite recently [-13] which is obscured by a strong and long since known 4 + resonance near 5.95 MeV; for this reason in the previous study [7] a correlation did only exist for the lower one at 5.65 MeV.…”

“…The targets with thicknesses around 100 keV were too thick to allow a more accurate determination of the excitation energies of the two peaks, on the other hand were thin enough to clearly establish the lowenergy peak. This doubly-peaked structure is correlat- [12,13] again a fairly good correlation is observed. Allowing for slight energy shifts the three resonances between 5.5 and 6.0 MeV indicated by the vertical arrows manifest themselves in at least one of the three y-decay channels.…”

“…It should be noted, that a 2 + resonance at 6,01 MeV was discovered only quite recently [-13] which is obscured by a strong and long since known 4 + resonance near 5.95 MeV; for this reason in the previous study [7] a correlation did only exist for the lower one at 5.65 MeV. Figure 6 summarizes the present findings, where the positions of previous [7] and present capture resonances as well as those of established 2 + resonances [1,12,13] are plotted as a function of CM-energy. Included in this figure as a shaded band is a rather crude image of the high energy tail of the GQR as deduced from the data of Borg et al [26] and a plot of the relative heavy-ion partial width FJF extracted from the present statistical model calculations.…”