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Differential cross sections (DCS's) for excitation of the $2{}^{1}S$ and $3{}^{1}S$ states in helium have been measured at small scattering angles from 0\ifmmode^\circ\else\textdegree\fi{} to 15\ifmmode^\circ\else\textdegree\fi{} for the electron-impact energies from 100 to 500 eV. Measurements were performed with a high angular resolution, better than 1\ifmmode^\circ\else\textdegree\fi{}, and with an accuracy of the angle position of 0.2\ifmmode^\circ\else\textdegree\fi{}. Distinct forward peaking features have been observed at minute scattering angles lower than about 3\ifmmode^\circ\else\textdegree\fi{} for impact energies higher than 200 eV. Experimental DCS's as functions of the scattering angle are compared with theoretical calculations based on various kinds of approximation method. Effective generalized oscillator strengths (GOS's) for the $2{}^{1}S$ and $3{}^{1}S$ excitations were deduced from the DCS's for impact energies 100--500 eV as a function of the squared momentum transfer ${K}^{2}.$ A systematic discrepancy between the measured effective GOS's and the theoretical GOS calculated by the first Born approximation has been displayed at the low limit of ${K}^{2}.$ The effective GOS's appear to approach the theoretical GOS very slowly as the impact energy increases, however, the GOS for low values of ${K}^{2}$ still does not agree with the theoretical GOS up to the impact energy 800 eV for the $2{}^{1}S$ excitation.

Ejected electron spectra from doubly-excited beryllium-like ions produced by collisions of helium-like ions with targets have been measured by using zero-degree Auger electron spectroscopy with a high energy-resolution. The energy of the triplet states of doubly-excited configurations were compared with theoretical ones.

Ejected-electron spectra have been measured for collisions of He-atoms with Na+-ions, whose impact energy ranged from 1.7 to 7.0 keV. The ion impact-energy dependence of the angular-differential cross-section of the ejected electrons has been investigated for an aligned autoionizing state Na**(2p5 3s22P), which has been created by charge transfer from the He-atoms. The alignment of the autoionizing state Na**(2p5 3s22P) is discussed in relation to the scattering angles of the Na+-ions. A complete longitudinal alignment has been observed with respect to the quasimolecular axis.

Partial ionization cross sections for 4 d -electrons in xenon by electron impact have been measured by means of a combination of the electron-energy-loss spectroscopy and the Auger electron spectroscopy in the impact energy region from 70 eV to 4 keV. The cross sections increase with the impact energy rapidly from the threshold and display a sharp maximum, whose value is (17.0 ± 3.5) × 10 -18 cm 2 , around 120 eV impact energy, revealing an existence of a resonance. The cross sections arise again from a minimum at about 200 eV and exhibit a broad maximum of (14.5 ± 3.0) × 10 -18 cm 2 around 500 eV. Absolute scale of the cross section is determined using the generalized oscillator strengths for the 4 d -ionization, which are measured by the electron-energy-loss spectroscopy. Relative cross sections are measured as a function of the impact energy using an Auger line assigned to the N 5 O 2,3 O 2,3 ( 1 S 0 ) line. Experimental results are compared with a previous experimental result given by a different proc...

Ejected electrons from helium-like doubly-excited carbon and boron ions, produced by C6+ and B5+ with He collisions, were measured by the zero-degree electron spectroscopy technique. Electrons from configurations 21nl’ were observed in a wide energy range.

Differential cross sections (DCS) for the 1 {sup 1}{ital S}{minus}2 {sup 3}{ital S} excitation in helium have been measured with a high angular resolution of about 1{degree} as a function of the scattering angle {theta} from 12{degree} to 0{degree} for the incident energies of 200 and 500 eV. For the incident energy of 500 eV, the DCS increases drastically as the angle decreases in the angular range smaller than 4{degree} and reaches a value 0.075 {ital a}{sub 0}{sup 2}/sr at {theta}=0{degree}, the increase being nearly 3 orders of magnitude. The DCS at zero scattering angle for impact energies from 200 to 800 eV have been measured. The DCS's are found to be about 1 order of magnitude greater than those of published measurements by Skerbele, Harshbarger, and Lassettre (J. Chem. Phys. 58, 4285 (1973)) and Klump and Lassettre (J. Chem. Phys. 62, 1838 (1975)).

Ejected electron spectra from the double‐excited helium‐like and beryllium‐like ions produced by the double electron capture collisions of bare or helium‐like ions with targets have been measured by using zero‐degree Auger electron spectroscopy with a high energy resolution. Singlet and triplet states of doubly excited configurations were made by the double electron capture processes, selectively.

Ejected electrons from doubly-excited helium atoms, produced by double electron capture collisions of He2+ with Mg, Ca and Ba atoms at low energies, have been measured using zero-degree electron spectroscopy with high energy resolution. Electrons from the configurations (2lnl') (n ≥ 2) were observed. Electron spectra from the terms of higher angular momenta are dominant in contrast to the case of ion or electron-impact excitation of neutral He.

Ejected electrons from helium-like doubly-excited carbon and boron ions, produced by C6+ and B5+ with He collisions, were measured by the zero-degree electron spectroscopy technique. Electrons from configurations 21nl were observed in a wide energy range.

Post-collision interaction is investigated on the spectra of Ar L 3 M 23 M 23 Auger electrons which are created by electron impact of energies from 257 eV up to 2000 eV. The spectral shape has been analyzed by taking into account the finiteness of the velocities of both the receding and Auger electrons. Disappearance of the post-collision interaction is found at the highest electron-impact energies.

Ejected-electron spectra from doubly excited helium are measured at several ejection angles for lithium ions of impact energies 2, 3, 4 and 5 keV. Violent variations are observed in the ejected-electron profiles with the changes of ejection angle and impact energy. An especially drastic change with angle is observed at 2 keV.

The f 3 Pi g state of molecular fluorine, which is assumed to be the upper level of a VUV F2 laser at 157 nm, has been directly observed for the first time by high-resolution electron energy loss spectroscopy at low impact energies (less than about 30 eV) and large scattering angles. The new transitions consist of several vibrational components at 11.62, 11.75, 11.86 and 11.99 eV, and show every characteristic feature of spin-forbidden transitions.