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The role of the nuclear structure degrees of freedom associated with the colliding nuclei and the energy dependence in the nucleus–nucleus interaction potential in fusion dynamics of various projectiles (16O, 27Al and 37Cl) with the Ge-isotopes (74,76Ge) has been investigated. Fusion cross-sections obtained through energy dependent interaction potential (EDWSP model) and coupled channel theory show quite similar behavior in near and above barrier energy regions. In coupled channel view, the couplings to inelastic surface excitations associated with the fusing nuclei results in large fusion enhancement at sub-barrier energies. The consideration of spherical shape for targets (74,76Ge-isotopes) along with their relevant internal structure degrees of freedom in coupled channel approach is sufficient to get a good description to observed fusion enhancement of the studied reactions. In contrast, the energy dependent interaction potential modifies the barrier profile of interaction barrier and subsequently reduces the effective fusion barrier between the colliding systems, henceforth, predicts substantially large fusion enhancement at below barrier energies in comparison to the expectations of the one dimensional barrier penetration model. Furthermore, χ 2 -analysis and the ratio plots σ T h σ E x p for outcomes of the EDWSP model suggested that the model calculations provide a consistent fit to fusion data within 10%. For the chosen reactions, only at 6 fusion data points out of 75 fusion data points does the deviation exceed 5% while 69 fusion data points lie within 5% and hence, the EDWSP model reasonably explained the above barrier fusion data within 5% with a probability more than 90%.

The impacts of breakup channel on fusion of L 6 i with Z 90 , 96 r -nuclei are investigated within the context of the coupled channel model and the energy dependent Woods-Saxon potential (EDWSP) model. For studied reactions, the complete fusion (CF) cross-sections data at above barrier energies are found to be suppressed with respect to the calculated results. In case of L 6 i + 90 Z r ( L 6 i + 96 Z r ) reaction, the CF data at above barrier energies is found to be less by 34% (25%) with reference to the estimations of the coupled channel approach. However, EDWSP model calculations predict fusion suppression up to 20% (10%) for L 6 i + 90 Z r ( L 6 i + 96 Z r ) reaction. The extracted suppression factor for L 6 i + 90 Z r ( L 6 i + 96 Z r ) reaction is smaller by 14% (15%) than the reported value. Such effects can be accredited to the low threshold of α-breakup channel associated with the weakly bound system and hence may be responsible for incomplete fusion (ICF) products. Therefore, the total fusion (TF) cross-sections that are the sum of complete fusion (CF) and incomplete fusion (ICF) yields, are not expected to reduce in the above barrier regions when compared with no-breakup case. In this regard, the TF cross-sections data are analyzed within the view of the EDWSP model and so obtained calculations have close agreement with the TF cross-sections data. The EDWSP based results appreciably explained CF, ICF and TF cross-sections data over a wide range of energies around the Coulomb barrier. Although, the cluster-transfer or stripping process from the ground state of weakly bound nucleus L 6 i may significantly contribute to ICF yields, therefore, the presence of ICF product is an indication of the partial absorption of projectile by target, henceforth, reduces the CF cross-section data in above barrier regimes.

In the present work, the fusion of symmetric and asymmetric projectile–target combinations are deeply analyzed within the framework of energy dependent Woods–Saxon potential model (EDWSP model) in conjunction with one dimensional Wong formula and the coupled channel code CCFULL. The neutron transfer channels and the inelastic surface excitations of collision partners are dominating mode of couplings and the coupling of relative motion of colliding nuclei to such relevant internal degrees of freedom produces a significant fusion enhancement at sub-barrier energies. It is quite interesting that the effects of dominant intrinsic degrees of freedom such as multi-phonon vibrational states, neutron transfer channels and proton transfer channels can be simulated by introducing the energy dependence in the nucleus–nucleus potential (EDWSP model). In the EDWSP model calculations, a wide range of diffuseness parameter ranging from a = 0.85 fm to a = 0.97 fm , which is much larger than a value ( a = 0.65 fm ) extracted from the elastic scattering data, is needed to reproduce sub-barrier fusion data. However, such diffuseness anomaly, which might be an artifact of some dynamical effects, has been resolved by trajectory fluctuation dissipation (TFD) model wherein the resulting nucleus–nucleus potential possesses normal diffuseness parameter.