We report both experimental and theoretical differential and integral excitation cross sections of atomic oxygen corresponding to the 2s 2 2p 4 3 P → 3s 3 S (130.4 nm), 2s 2 2p 4 3 P → 3d 3 D (102.7 nm), 2s 2 2p 4 3 P → 3s 3 D (98.9 nm) and 2s 2 2p 4 3 P → 3s 3 P (87.8 nm) transitions at 30, 50, and 100 eV electronimpact energies. Experimental measurements have been made in the angular range from 0 • to 25 • with a conventional electrostatic electron energy-loss spectrometer. The atomic O differential cross sections (DCSs) were put on an absolute scale by normalization to the O 2 DCS values of Johnson and Kanik (2001). Extrapolation of the measured results to larger angles was performed using theoretical calculations as a guide, and integral cross sections were derived. Theoretical calculations based on the R-matrix method, along with other available experimental data, have been compared with the current experimental results.

Normalized differential cross sections for elastic (rotationally averaged) electron scattering from gaseous water (H2O) are obtained using the relative flow method against helium with a thin aperture collimating source of gas instead of a tube. This method obviates the use of gas kinetic molecular diameters for helium or water. Our measurements are found to be largely in quantitative disagreement with past differential elastic electron scattering measurements and suggest that present recommended electron scattering total cross sections for water be revised.

Measured and calculated differential cross sections for elastic ͑rotationally unresolved͒ electron scattering from two primary alcohols, methanol ͑CH 3 OH͒ and ethanol ͑C 2 H 5 OH͒, are reported. The measurements are obtained using the relative flow method with helium as the standard gas and a thin aperture as the collimating target gas source. The relative flow method is applied without the restriction imposed by the relative flow pressure conditions on helium and the unknown gas. The experimental data were taken at incident electron energies of 1, 2, 5, 10, 15, 20, 30, 50, and 100 eV and for scattering angles of 5°-130°. There are no previous reports of experimental electron scattering differential cross sections for CH 3 OH and C 2 H 5 OH in the literature. The calculated differential cross sections are obtained using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons. Comparison between theory and experiment shows that theory is able to describe low-energy electron scattering from these polyatomic targets quite well.

[1] Integral cross sections for electron impact excitation out of the ground state (X 1 S g + ) to, a 1 Å g , w 1 D u , and C 3 Å u states in N 2 are reported at incident energies ranging between 10 and 100 eV. These data have been derived by integrating differential cross sections previously reported by this group. New differential cross section measurements for the a 1 Å g state at 200 eV are also presented to extend the range of the reported integral cross sections for this state, which is responsible for the emissions of the Lyman-Birge-Hopfield band system (a 1 Å g ! X 1 S g + ). The present results are compared and critically evaluated against existing cross sections. In general, the present cross sections are smaller than previous results at low impact energies from threshold through the excitation function peak regions. These lower cross sections have potentially significant implications on our understanding of UV emissions in the atmospheres of Earth and Titan.

Relative differential cross sections for electron-impact excitation of the four lowest electronic levels ns[3/2]oJ=2 and 1 ns'[1/2]oJ=0 and 1 were measured for Ne, Ar, Kr and Xe at 30 eV impact energy and for Kr and Xe at 20 eV impact energy for a range of scattering angles from 0 degrees to 134 degrees . The aim of the present work was: to improve the quality of existing data, to extend the measurements to small scattering angles, to determine whether statistical weight (branching) ratios represent the ns[3/2]o2 to ns'[1/2]o DCS ratios (r) and to compare the experimental results with the predictions of non-relativistic and relativistic first-order scattering theories. We found that the experimental ratios r closely correspond to statistical weight ratios for Ne and Ar at all scattering angles, for Kr at most angles, but seriously deviate from statistical weight ratios for Xe at all angles. First-order scattering theories yield good and reasonable predictions for Ne, Ar and Kr, respectively. For Xe theories also predict significant deviations from statistical weight ratios but there is no agreement between experiment and theory. Surprisingly, the DCS ratios (r') obtained for the ns[3/2]o1, and ns'[1/2]o1, levels by experiment and various first-order theories deviate significantly for all rare-gas species. It is also surprising that the fully relativistic first-order theory does not show improved agreement between experiment and theory in the case of Xe.