Recent high precision experimental data for heavy-ion fusion reactions at subbarrier energies systematically show that a surprisingly large surface diffuseness parameter for a Woods-Saxon potential is required in order to fit the data. We point out that experimental data for quasi-elastic scattering at backward angles also favor a similar large value of surface diffuseness parameter. Consequently, a double folding approach fails to reproduce the experimental excitation function of quasielastic scattering for the 16 O + 154 Sm system at energies around the Coulomb barrier. We also show that the deviation of the ratio of the quasielastic to the Rutherford cross sections from unity at deep subbarrier energies offers an unambiguous way to determine the value of the surface diffuseness parameter in the nucleus-nucleus potential.PACS numbers: 25.70. Bc,25.70.Jj,24.10.Eq,27.70.+q The nucleus-nucleus potential is the primary ingredient in nuclear reaction calculations. Its nuclear part has often been parametrized as a Woods-Saxon form [1]. Elastic and inelastic scattering are sensitive mainly to the surface region of the nuclear potential, where the WoodsSaxon parametrization has a simple exponential form. This fact has been exploited to study the surface property of nuclear potential. Usually, the best fit to experimental data for scattering is obtained with a diffuseness of around 0.63 fm [1,2,3,4,5]. This value is consistent with a double folding potential [6,7], and seems to be well accepted [1,8].In marked contrast, recent high precision experimental data for heavy-ion fusion reactions at energies around the Coulomb barrier suggest that a much larger value of diffuseness, ranging from 0.75 to 1.5 fm, is required to fit the data [6,7,9,10,11,12] (See Ref.[13] for a detailed systematic study). The Woods-Saxon potential which fits elastic scattering overestimates fusion cross sections at energies both above and below the Coulomb barrier, having an inconsistent energy dependence to the experimental fusion excitation function. When the height of the Coulomb barrier is fixed, the larger diffuseness parameter leads to the smaller barrier position and the smaller barrier curvature (thus the larger tunneling region). The main effect on the fusion cross sections comes from the barrier position and the tunneling width of the barrier at energies above and below the Coulomb barrier, respectively. A large diffuseness parameter appears to be desirable in both these aspects [6]. The reason for the large discrepancies in diffuseness parameters extracted from scattering and from fusion analyses, however, has not yet been understood.The purpose of this paper is to discuss the dependence of quasielastic excitation function at a large scattering angle on the surface diffuseness parameter in a nucleusnucleus potential. The quasielastic cross section is defined as the sum of the cross sections of elastic, inelastic, and transfer reactions. Its excitation function at backward angles provides complementary information to the fusion proc...

We propose the no-recoil approximation, which is valid for heavy systems, for a double folding nucleus-nucleus potential. With this approximation, the non-local knock-on exchange contribution becomes a local form. We discuss the applicability of this approximation for the elastic scattering of 6 Li + 40 Ca system. We find that, for this system and heavier, the no-recoil approximation works as good as another widely used local approximation which employs a local plane wave for the relative motion between the colliding nuclei. We also compare the results of the no-recoil calculations with those of the zero-range approximation often used to handle the knock-on exchange effect.PACS numbers: 25.70.Bc, The double folding model has been widely used to describe the real part of optical potential for heavy-ion collisions [1,2,3]. The direct part of the double folding potential is constructed by convoluting an effective nucleonnucleon interaction with the ground state density distributions of the projectile and target nuclei. In the double folding model, the exchange contribution originating from the antisymmetrization of the total wave function of the system is customarily taken into account simply through the single nucleon knock-on exchange term. The exchange term leads to a non-local potential. Since it is cumbersome to handle the resultant integro-differential equation, a local approximation has usually been employed. In the past, many calculations have been performed along this line by introducing a pseudo zero-range nucleon-nucleon interaction to mock up the knock-on exchange effect [1,2,4]. The strength of the pseudo interaction has been tuned so as to reproduce exact results of the integro-differential equation for proton scattering from various target nuclei at several incident energies [4]. This approach, in conjunction with the (density dependent) Michigan-three-range Yukawa (M3Y) interaction [5,6], has successfully accounted for observed elastic and inelastic scattering for many colliding systems [1,2].Recently, a more consistent treatment for the exchange term has also been considered [3,7,8,9,10]. This approach obtains a local potential by employing a local approximation to the momentum operator (local momentum approximation) [11,12]. Since the local momentum depends explicitly on the potential itself, there arises the self-consistency problem, which however can be solved iteratively. Since the exchange potential is directly constructed from a given nucleon-nucleon interaction of finite range, this approach is more favorable than the zero range approximation. In fact, the finite range treatment for the exchange term has enjoyed a success in reproducing the experimental angular distributions for light heavy-ion scattering where the zero range approximation fails [7,8,13].Despite its success, however, there is a potential difficulty in this approach. That is, the iterative procedure for the self-consistent problem may not work in the classically forbidden region, where the local momentum is imaginary. Althoug...

Inexpensive, high-performing, and environmentally friendly energy storage devices are required for smart grids that efficiently utilize renewable energy. Energy storage devices consisting of organic active materials are promising because organic materials, especially quinones, are ubiquitous and usually do not require harsh conditions for synthesis, releasing less CO2 during mass production. Although fundamental research-scale aqueous quinone-based organic supercapacitors have shown excellent energy storage performance, no practical research has been conducted. In this study, we aimed to develop a practical-scale aqueous-quinone-based organic supercapacitor. By connecting 12 cells of size 10 cm × 10 cm × 0.5 cm each in series, we fabricated a high-voltage (> 6 V) aqueous organic supercapacitor that can charge a smartphone at a 1 C rate. This is the first step in commercializing aqueous organic supercapacitors that could solve environmental problems, such as high CO2 emissions, air pollution by toxic metals, and limited electricity generation by renewable resources.