Intermediate-structure fusion resonances observed in the radiative capture of 12C by 12C

We have investigated the 12C(12C,γ)24Mg reaction, populating low-lying states of 24Mg, with 12C+12C c.m. energies between 5 and 11 MeV. High energy γ rays were detected in a large volume NaI spectrometer which had sufficient resolution to distinguish clearly the γ0, γ1, and γ/sub 2,3/ transitions. Several resonances were observed in each of the decay channels. In particular, the γ0 excitation function has four narrow resonances at E/sub c.m./ = 5.6, 6.0, 6.8, and 8.0 MeV, which are unambiguously assigned J/sup π/ = 2+. The upper three of these resonances are correlated in all three decay channels but are not correlated either with previously identified 2+ structures in the 12C+12C system or with structure in the distribution of ground-state E2 strength in 24Mg. Furthermore, calculations demonstrate that these resonances have large nonstatistical 12C- and photon-partial widths. We argue that the data are suggestive of a new and unusual form of intermediate structure, namely highly clustered 12C+12C configurations built on the ground-state band of 24Mg