MINIMA OF THE ORIENTATION PHENOMENA FOR DIRECT S-P ELECTRON-ION EXCITATIONS IN DENSE-PLASMAS

Close-encounter effects on electron-ion s-->p oriented excitations in dense plasmas are investigated using a first-order semiclassical strai ght-line trajectory method. Plasma-screened interaction potential is g iven by the classical nonspherical Debye-Huckel model. Without using t he dipole approximation, the transition probabilities and orientation parameters are obtained, for various Debye lengths and projectile ener gies. Including the plasma-screening effects, the transition probabili ties are increased for 1s-->2p(+1) transitions and decreased for 1s--> 2p(-1) transitions. The close-encounter effects appreciably change the transition probabilities and orientation parameters for small impact parameters. It is found that the 1s-->2p(+1) transition probabilities and orientation parameters have minima that correspond to the complete 1s-->2p(-1) transitions.