NONLINEAR HYDRODYNAMIC THEORY OF ELECTRONIC STOPPING POWER

We have formulated a fully nonlinear hydrodynamic theory of the electr onic stopping power of charged particles in matter. In the zero veloci ty limit, our theory reduces to a Thomas-Fermi-Dirac-von Weiszacker de scription of the electronic screening around an external point charge. With increasing velocity, the dynamic screening charge is obtained fr om a numerical solution of the hydrodynamic equations. We also introdu ce a fluid viscosity which allows one to simulate the single-particle excitations responsible for the low velocity stopping power. A compari son of our results for protons and antiprotons with linear response th eory shows that nonlinearities in the screening are important for all velocities up to the stopping power maximum. In addition, comparison w ith earlier nonlinear quantum-mechanical calculations at low velocitie s shows that the hydrodynamic theory provides a realistic and accurate description of the stopping power phenomenon.