Fusion-evaporation residue as a dynamical decay process in the 48Ca+249Bk → 297117*reaction

The neutron-evaporation residue cross sections sigma(2n), sigma(3n), and sigma(4n) in the hot fusion reaction Ca-48 + Bk-249 -> (297)117* are calculated at the compound-nucleus (CN) excitation energies E*(CN) = 35.3 and 39.3 MeV, by taking the superheavy-region proton magic Z = 126 and neutron magic N = 184, within the dynamical cluster-decay model. However, the above-stated production cross sections could not be fitted if the incoming nuclei and/or decay fragments were considered to be spherical. On the other hand, with inclusion of deformation effects up to quadrupole deformations beta(2i) and with the optimum orientations theta(opt)(i), the sigma(2n) and sigma(3n) cross sections were fitted nicely, but sigma(4n) were still underestimated by about 25%, indicating the possibility of some other competing evaporation residue, like He-4 decay, contributing to 4n-decay cross sections. Also, a possible contribution of a fusion-fission component is predicted which, together with He-4 decay, needs experimental verification. Other important results are that (i) the angular momentum does not show any significant influence on the fragmentation path of the Z = 117 nucleus formed in this reaction, and (ii) the barrier modification is found to be more important for the lower-angular-momentum states, and for the lightest neutron cluster, independent of the CN excitation energy.