EXCITATION CROSS-SECTIONS FOR THE NS S-2-]NP P-2 RESONANCE TRANSITIONS IN MG-ENERGY-LOSS AND MERGED-BEAMS METHODS( (N = 3) AND ZN+ (N = 4) USING ELECTRON)

Electron-excitation cross sections are reported for the 3S 2S-->3p 2P( h,k) resonance transition in Mg+ at energies from threshold (4.43 eV) to approximately 9 times threshold (40.0 eV). The electron-energy-loss merged-beams technique used in these measurements is described in det ail. In addition, the method of separating contributions of the elasti cally scattered (Coulomb) and the inelastically scattered electrons in the present Mg+ case and previously reported Zn+ results [Phys. Rev. Lett. 67, 30 (1991)] is described. Comparisons in the experimental ene rgy range are made for Mg+ with the two five-state close-coupling theo retical calculations carried out herein, and with other published clos e-coupling, distorted-wave, and semiempirical calculations. The presen t Mg+ cross sections and Zn+ cross sections from earlier measurements are tabulated.