Semiclassical calculation of oscillator-strengths

2014 Because they play a fundamental role in the calculation of bound electron stoppingpowers, photon mean free paths and electron impact-excitation cross-sections, there is a need for a convenient method to calculate oscillator strengths for highly charged ions. In this paper we describe a simple semiclassical approximation for electron matrix-elements and oscillator strengths. The method is tested by detailed comparison with known exact results for the Coulomb potential and proves to be numerically robust and reasonably accurate for all transitions examined. J. Phys. France 50 (1989) 35-44 1°r JANVIER 1989, Classification Physics Abstracts 32.70C 1. Stopping-power and oscillator-strengths. The electronic stopping-power for high-velocity ions, dE/dx, can be calculated from the radiative opacity or photon absorption cross-section of the target medium [1]. This is because the electromagnetic field of the fast ion is approximately equivalent to a group of virtual photons carried along by the fast ion. When the ion penetrates a dense plasma target, some of the virtual photons can be absorbed by electrons of the target material. After being absorbed, the virtual photons are regenerated by the electric current of the fast ion, but the energy required for this regeneration is taken from the center-of-mass motion of the ion and therefore the absorption of virtual photons is equivalent to electronic energy-loss. From this * Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:0198900500103500