Fission in a wall-and-window one-body-dissipation model

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Abstract
We calculate the fission of idealized nuclei in a modified liquid-drop model. The potential energy is taken to be a combination of Coulomb energy and nuclear energy obtained by double folding a Yukawa-plus-exponential two-body potential. The collective nuclear kinetic energy is calculated by use of the Werner-Wheeler approximation to incompressible, irrotational flow. The dissipation of collective energy into internal energy is calculated from the one-body wall formula until the neck decreases to a critical size, at which point a transition is made to a combination of the one-body wall formula relative to the centers of mass of the two nascent fragments and the one-body window formula. Experimental fission-fragment kinetic energies for the fission of nuclei throughout the Periodic Table are reproduced optimally when the neck radius at the transition point is 2.5 fm. For the alternative dissipation mechanism of ordinary two-body viscosity, the experimental fission-fragment kinetic energies are reproduced equally well when the viscosity coefficient is 0.015 TP.