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We have proposed an energy-dependent parametrization scheme for determining the diffuseness parameter of Woods–Saxon potential which when used in conjunction with the coupled channel code CCFULL explains very well the fusion excitation function data around the barrier for various systems.

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Abstract.We have investigated the relative importance of the energy dependence of diffuseness parameter and barrier position in the description of the fusion excitation function data of some heavy ion systems in near barrier energy region. The effects of the energy dependent diffuseness parameter are found to be much more prominent in comparison to those of barrier position.The sub-barrier heavy ion fusion reactions provide a very good insight into nuclear structure and nuclear interaction [1][2][3][4]. The interaction potential between heavy ions which consists of Coulomb, centrifugal and nuclear terms plays a very crucial role in the description of fusion dynamics because of the fact that the sum of these terms forms the Coulomb barrier which must be overcome for occurrence of fusion. The Coulomb and centrifugal terms are well understood whereas many ambiguities are associated with the nuclear potential. Since the predictions of fusion excitation functions in sub-barrier energy regions are very sensitive to the shape of nuclear potential, the success of any model for fusion depends strongly on the nuclear potential model employed in the analysis. As a result various potential models ranging from the simple phenomenological to realistic microscopic models have been proposed and used to explain the fusion excitation functions data. Generally, the three parametric Woods-Saxon potential remains the most frequently used potential for the description of compound nuclear reactions. Among the three parameters, depth, range and diffuseness parameter, there exist, large ambiguities in the determination of the accurate value of the diffuseness parameter. It was observed that a wide range of values from 0.65 a fm  to fm a 5 . 1  of diffuseness parameter are required to describe various nuclear phenomena [5][6][7][8][9][10][11][12]. As the value of diffuseness parameter increases beyond 0.65 a fm  , the potential pocket becomes more and more shallow and disappears for large values and the fusion barrier radius decreases rapidly [6,[13][14][15]. Very recently, an energy dependent parameterization scheme to determine the value of diffuseness parameter was successfully used to explain the fusion excitation functions of various systems [16]. Since, the barrier position changes with the change in the shape of the potential, the energy dependent potential induces energy dependence in the barrier position also. ____________________________________________ a Corresponding

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We have studied the effects of the finite range of the interaction between the fragments of the projectile on the fusion and/or breakup of 6 He+ 238 U and 11 Li+ 208 Pb systems at near barrier energies within the framework of dynamic polarization potential approach. It has been found that at near barrier energies the maximum flux is lost to the breakup channel and at energies well above the Coulomb barrier the fusion coupled with the breakup channel opens up, initially with sharp rise and later becoming saturated at energy nearly twice of the Coulomb barrier. Further, it is found that the breakup cross section increases with the increasing range of the interaction between the fragments of the projectile while the fusion coupled with the breakup channel cross section decreases with the increasing range.

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