Abstract. We obtain the nuclear proximity potential by using semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), and use it in the extended -summed Wong formula under frozen density approximation. This method has the advantage of allowing the use of different Skyrme forces, giving different barriers. Thus, for a given reaction, we could choose a Skyrme force with proper barrier characteristics, not-requiring extra "barrier lowering" or "barrier narrowing" for a best fit to data. For the 64 Ni+ 100 Mo reaction, the -summed Wong formula, with effects of deformations and orientations of nuclei included, fits the fusion-evaporation cross section data exactly for the force GSkI, requiring additional barrier modifications for forces SIII and SV. However, the same for other similar reactions, like 58,64 Ni+ 58,64 Ni, fit the data best for SIII force. Hence, the barrier modification effects in -summed Wong expression depend on the choice of Skyrme force in semiclassical ETF method.
IntroductionThe unexpected behavior of some fusion-evaporation cross sections at energies far below the Coulomb barrier, has challenged the theoretical models to explain the, so called, fusion hindrance phenomenon in true coupled-channels calculations (ccc) for reactions such as 58 Ni+ 58 Ni, 64 Ni+ 64 Ni, and 64 Ni+ 100 Mo [1]. The ccc could, however, be sensitive to the so far unobserved, hence not-included, high-lying states. Misicu and Esbensen [2] were the first who succeeded in describing the above said three reactions in terms of a density-dependent M3Y interaction, modified by adding a repulsive core potential [3]. The repulsive core changes the shape of the inner part of the potential in terms of a thicker barrier (reduced curvaturehω) and shallower pocket. Here, the nuclei are considered spherical in ground-state and the dynamical quadrupole and octupole deformations (β 2 , β 3 ) are included (only β 2 in the case of 58 Ni+ 58 Ni).The dynamical cluster-decay model (DCM) of preformed clusters by Gupta and collaborators [4,5] is found recently [6,7] to have barrier modification effects as the inbuilt property, where "barrier lowering" at sub-barrier energies arise in a natural way in its fitting of the only parameter of model, the neck-length parameter. The difference of actually-calculated barrier from the actually-used barrier height, corresponding to the neck-length parameter for best-fitted fusionevaporation cross section, gives the "barrier lowering" in DCM, whose values are found to increase as the incident energy decreases to sub-barrier energies. Calculations are based on β 2 deformations and orientation θ i -dependent nuclear proximity potential of Blocki et al. [8].