[en] Published in summary form only

[en] Total cross sections for the production of He⁺(2p) in collisions of H⁺ and e^- with He at energies from 75 to 800 keV and from 0.8 to 7 keV respectively were measured. The ratio of the cross sections for He⁺(2p) production and for single ionization is discussed to investigate the contribution of electron correlations in the two-electron transition leading to He⁺(2p). For the first time the impact of H₂⁺ and H₃⁺ ions in comparison with H⁺ impact has also been studied for the energy range mentioned above. (author)

[en] The electron-hydrogen scattering problem is one of the fundamental problems in atomic physics. Surprisingly, agreement between experiment and even the most sophisticated of theoretical calculations is not good. In this paper, we will discuss our recent attempts at understanding the cause for this disagreement. We have examined the problem both from a perturbation series approach and from the close coupling approach. For the perturbation series method we have calculated exact (no approximations) second order distorted wave amplitudes including second order exchange. For the close coupling method, we have used the optical potential approach and have evaluated the optical potential including the continuum states exactly for the first time. Results will be shown for elastic scattering and for excitation of hydrogen

[en] The application of VUV fluorescence spectroscopy in studies of one- and two-electron processes in the outer shells of the rare gases, induced by photon impact or by fast electron impact, is described. Results for ionization of Ar-3s electrons, for additional 3p-electron ionization and for satellite production are discussed in a comparison with recently published results from photoelectron spectroscopy. Cross sections for electron impact ionization into the Ar⁺⁺-3s3p^51,3P states are compared with cross sections for photoionization. The experiments have been carried out to study electron correlations in connection with external perturbations of atomic systems

[en] Using high resolution projectile electron spectroscopy at zero degrees, we have determined projectile Auger electron spectra from collisions of Li-like O⁵⁺ beams with H₂ targets at energies between 4--32 MeV. The strongest populated Li-Like (1s2s2p) states resulting from 1s→2p excitation and Be-like (1s2s2p²) states resulting from Transfer-Excitation (TE) were resolved. The production of (1s2s2p²)³D states by Resonance Transfer-Excitation was clearly observed and compared to theory. The production of (1s2s2p)⁴P and ²P₊ states above ∼12 MeV was found to increase sharply with projectile energy, indicating the onset of projectile excitation due to an interaction with one of the target electrons

[en] In a crossed-beam experiment the impact-ionization cross section, integrated over all angles and energy partitions but excluding positronium formation, has been measured for positrons as well as electrons in the energy region of 30 to 600 eV. Below 400 eV the positron cross section is larger than the electron one, at 40 eV by about a factor of 2. Absolute cross sections are obtained by comparing the electron data with literature values. Our cross sections for positron-impact ionization lie above all theoretical predictions; within the errors they barely agree with the distorted-wave polarized-orbital calculations of Ghosh et al. for the model in which the scattered positron is described by a plane wave

[en] Stepped ionization with excitation (SIE) in neon in case of electron collision with metastable 3s-atoms of NeI has been studied. The investigation of SIE processes was carried out by the optical method of beam emission in a gas cell with an electron beam. Cross section of ion stepped excitation has been measured for the first time. Like stepped excitation of atom levels it is characterized by a large value of cross section, for ²P⁰_3/2 level it is 2.5x10^-15cm²

[en] A measurement of the doubly differential cross sections of secondary electrons ejected from molecular oxygen by electron impact has been made. A modulated crossed-beam method was used with incident electron energies from 25 to 250 eV. The energy and angular range of secondary electrons covered from 1.0 eV to one-half of the difference between the incident energy and ionization potential and from 12 degree to 156 degree, respectively. The present results have been compared with the previous measurements and considerable discrepancies were found

[en] The results of an experiment on the associative ionization collision between sodium and cesium excited atoms are reported. The atoms are excited by two resonant cw lasers to the 3P_3/2 and 6P_3/2 levels, respectively, and the formation of the NaCs⁺ molecular ion is observed. The rate constant of such process has been measured relative to the known rate constant of sodium associative ionization and its value resulted in K=(5.4±3.2)x10^-11 cm³ s^-1

[en] Rubidium vapor, contained together with a buffer gas in a quartz cell located in a 4.75-T magnetic field, was irradiated with light from a pulsed dye laser producing selective excitation of each 6 ²P Zeeman substate in turn. Collisions of the excited and polarized atoms with the ground-state He, Ne, or Ar atoms and the resulting Zeeman mixing produced a population of the whole Zeeman manifold and resulted in the emission of a Zeeman fluorescence spectrum that was resolved with a scanning Fabry-Perot interferometer and recorded with a photomultiplier and a multichannel scaler. Measurements of the relative intensities of the fluorescence components in relation to the buffer-gas pressures yielded the absolute (thermally averaged) cross sections for Zeeman mixing and cross sections for relaxation of the atomic multipole moments for collisions with He, Ne, and Ar