We report a combined experimental and theoretical study on the electron-impact ionization of water (H 2 O) at the relatively low incident energy of E 0 = 81 eV in which either the 1b 1 or 3a 1 orbitals are ionized leading to the stable H 2 O + cation. The experimental data were measured using a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission over a range of ejection energies. We present experimental data for the scattering angles of 6 • and 10 • for the faster of the two outgoing electrons as function of the detection angle of the secondary electron with energies of 5 eV and 10 eV. The experimental triple-differential cross sections are internormalized across the measured scattering angles and ejected energies. The experimental data are compared to predictions from two molecular three-body distorted-wave approaches. One applying the orientation-averaged molecular orbital (OAMO) approximation and one using a proper-average (PA) over orientation-dependent cross sections. The PA calculations are in better agreement with the experimental data than the OAMO calculations, for both the angular dependence and the relative magnitude of the observed cross section structures.

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We present a combined experimental and theoretical study for electron-impact ionization of carbon dioxide (CO 2 ) for the projectile energy E 0 =100 eV. Experimental triple-differential cross sections (TDCS) are obtained using a multi-particle momentum spectrometer (reaction microscope). For projectile scattering angles between −5°and −20°a large part of the full solid angle is covered for the slow ejected electron with energies between 5 and 15 eV. The experimental data are measured for the ionization of the three outer valence molecular orbitals 1π g , 1π u , and 3σ u which lead to a non-dissociating CO 2 + ion. The measured TDCS summed over all three orbitals are internormalized across the scattering angles and ejected electron energies. They are compared to the theoretical results from the multi-center distorted wave (MCDW) approximation, and from the MCDW-WM approximation which includes post-collision interaction using the Ward-Macek factor (WM). Reasonable good agreement is found between the experiment and the MCDW-WM calculations for the angular dependence and the relative magnitude of the cross sections in the coplanar plane, while for the perpendicular and full perpendicular planes larger discrepancies exist. Since post-collision interaction is not considered the MCDW method shows strong discrepancies with experiment for small mutual angles of the two outgoing electrons in the final state.electron impact, ionization, kinematically complete (e, 2e) experiment, CO 2 , MCDW