Direct Double Ionization Research Articles

Electron-impact energy dependence of the sodium K-shell double-ionization cross section: A study of hypersatellite spectra.

The K${\ensuremath{\alpha}}_{2}^{h}$ (${L}^{\mathrm{\ensuremath{-}}n}$; n=0--5) hypersatellite spectrum of sodium has been detected for various electron-impact energies in the range of 15\ensuremath{\le}${E}_{0}$\ensuremath{\le}200 keV. The measured energies of the transitions are in agreement with results of previous experiments at low electron energies and theoretical predictions. For the strongest hypersatellite, which corresponds to a ${K}^{\mathrm{\ensuremath{-}}2}$\ensuremath{\rightarrow}${K}^{\mathrm{\ensuremath{-}}1}$${L}^{\mathrm{\ensuremath{-}}1}$ transition, the natural width has been determined. The natural linewidth was found to be ${\ensuremath{\Gamma}}_{K}^{h}$=2.2\ifmmode\pm\else\textpm\fi{}0.4 eV, which is much larger than predicted. Furthermore, the electron double-ionization cross section of the K shell has been obtained. Within the investigated energy region the cross section decreases by about a factor of 4 with increasing electron-impact energy. This energy dependence suggests the dominance of direct double ionization in comparison to the shake-off process.

Electron impact double ionisation of Ar+and Ar4+ions

Employing an improved crossed-beam technique described in the preceding paper, cross sections sigma q,q+2 for electron impact double ionisation of Arq+ ions (q=1 and q=4) were measured for electron energies from threshold to about 700 eV. The improved experimental accuracy allowed contributions of L-shell ionisation-autoionisation to sigma 1,3 to be identified for Ar+. With increasing q the relative importance of the L-shell contribution to sigma q,q+2 strongly increases. As a result the cross section sigma 4,6 for Ar4+ is by far dominated by the L-shell contribution at energies above 350 eV. Calculations on the basis of semiempirical and semiclassical theories are made to compare the relative strengths of direct double ionisation and inner-shell ionisation with subsequent electron emission.

Intershell correlation in double-electron ejection from the outermost shell of Xe

The optical oscillator strength for the production of Xe2+ ions in the energy region 70-80 eV is analysed in terms of two contributions: (i) direct double ionisation in the n=5 shell and (ii) 4d ionisation followed by Auger decay. The direct contribution shows clear evidence for intershell correlation between the 4d shell and the n=5 shell.

Degradation of Low‐Energy Electrons in Alkali Halides

AbstractThe degradation of low‐energy electrons in alkali halides is calculated using Gryzinski's cross‐section and the Monte Carlo method. The stopping power, the extrapolated range, and the degradation spectrum are obtained in the energy range of 100 to 15000 eV and compared with the results of other theoretical and experimental studies. The yield of double ionization produced by the Auger process and by the direct process is also obtained, and it is shown that the former increases as the energy of the incident electron increases, and the latter decreases as the energy increases above a certain value which is about three times the direct double ionization energy.