PLASMA-SCREENING EFFECTS ON THE ELECTRON-IMPACT EXCITATION OF HYDROGENIC IONS IN DENSE-PLASMAS

Plasma-screening effects are investigated on electron-impact excitatio n of hydrogenic ions in dense plasmas. Scaled cross sections Z4 . sigm a for 1s --> 2s and 1s --> 2p are obtained for a Debye-Huckel model of the screened Coulomb interaction. Ground and excited bound wave funct ions are modified in the screened Coulomb potential (Debye-Huckel mode l) using the Ritz variation method. The resulting atomic wave function s and their eigenenergies agree well with the numerical and high-order perturbation theory calculations for the interesting domain of the De bye length LAMBDA/a(Z) greater-than-or-equal-to 10. The Born approxima tion is used to describe the continuum states of the projectile electr on. Plasma screening effects on the atomic electrons cannot be neglect ed in the high-density cases. Including these effects, the cross secti ons are appreciably increased for 1s --> 2s transitions and decreased for 1s --> 2p transitions.