Transport coefficients in the Fourier shape parametrization

Abstract

An innovative parametrization of nuclear shapes, based on a Fourier expansion of the square distance from the surface of the nucleus to the symmetry axis is introduced. Surface, curvature and Coulomb energy coefficients of a charged liquid drop, that determine the semiclassical nuclear energy, are evaluated within this shape parametrization, together with the wall-friction and the irrotational-flow mass tensors. These transport coefficients are important ingredients of many nuclear models describing nuclear structure and dynamics. A numerical code allowing for the determination of all these quantities for a huge variety of nuclear shapes is made available to the interested user. Program summaryProgram title: inerfricProgram Files doi:http://dx.doi.org/10.17632/gtvbc8b7sw.1Licensing provisions: GPLv3Programming language: FortranNature of problem: The inertia tensor evaluated in the hydrodynamical model using the Werner–Wheeler approximation generalized to nonaxial shapes is evaluated, together with the friction tensor using the wall formula, and the shape functions that define the liquid-drop energy in terms of surface, curvature, Coulomb and congruence energy. For the description of the fission process, the mass ratio of the nascent fission fragments and their centre-of-mass distance is also evaluated together with the quadrupole moment and the moments of inertia for rotation of the deformed shape.Solution method: All these quantities are evaluated in our new rapidly converging Fourier shape parametrization, able to describe a huge variety of nuclear shapes, simply by reading in the (up to 7) shape parameters determining in an unambiguous way the nuclear deformation and corresponding for the (4) principal parameters to the nuclear elongation, left–right asymmetry, non axiality and neck degree of freedom, the remaining 3 allowing, if necessary, to optimize the evaluation of the asymmetry and neck degrees of freedom.