A detailed study of the 12C + 16O fusion reaction at Ecm = 19 to 24 MeV

Abstract

Excitation functions of evaporation residues following the 12C + 16O reaction are investigated at E cm = 19 to 24 MeV. At the resonances which have been previously identified in the 12C( 16O, 8Be) 20Ne two-body channel, an order of magnitude larger resonance cross section is observed in the fusion channel than that in the two-body one and is shared among a few evaporation residues ( 20Ne, 23Na and 24Mg). Here the resonance cross section is defined as the resonance part of the cross section on a resonance in an excitation function. It is found that for each resonance the relative intensity of the resonance cross sections of these residues is fairly well explained by assuming that they are coming from the decay of a compound nuclear resonance. It indiates that these intermediate resonances have a large probability to proceed to the formation of a more complicated configuration prior to its decay into exit channels. However, the resonant enhancement in the fusion channel is found to be weak at three energies ( E cm = 19.7, 22.0 and 22.6 MeV), where prominent resonant structures have been observed in inelastic channels. These distinct situations may be attributed to the magnitude of level density of the compound nucleus.