Electron collisional broadening of isolated lines from multiply-ionized atoms

Recent experimental and theoretical (both improved semiclassical and fully quantum-mechanical) line broadening calculations for B III and Ne VII Delta n = 0 transitions with n = 2 and 3, respectively, are discussed. The disag reements by about a factor of 2 between the fully quantum-mechanically calc ulated and both measured and semiclassically calculated widths can be expla ined in terms of violations of validity criteria for the semiclassical calc ulations and nonthermal Doppler effects. Only the quantum calculations allo w a clear separation of elastic and inelastic scattering contributions to t he width. For B III, elastic scattering contributes about 30%, for Ne VII i nelastic scattering dominates. This allows rather direct comparisons with b enchmark electron-ion scattering experiments. Additional independent determ inations of line widths for multiply-ionized, nonhydrogenic ions are called for, but meanwhile caution should be exercised in the use of corresponding semiclassically calculated widths, e.g., in opacity calculations or for pl asma density diagnostics. (C) 2000 Elsevier Science Ltd. All rights reserve d.