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Absolute total emission cross sections have been measured for electron-impact excitation of He giving radiation from the 6 '$-2 'P, 5 '$-2 'P, 4 '$-2 'P, and 3 '$-2 'P transitions. Electron energies were 50, 100, 500, 1000, and 2000 eV. Particular care was taken to make the measurements accurate and to make knowledgeable assessments of uncertainties, so that the results serve as reliable benchmarks for calibration of other excitation apparatus as well as for comparison with theory. The most accurate results are for 505+V electron energy, where the mean uncertainty is only 3.5% high confidence level. The measured eaiission cross sections are modified to account for branching and cascade to give level-excitation cross sections, and results are compared with other experimental data and theoretical predictions. At 2000 eV, the measurements average 2.5% below Born-approximation calculations.

A variety of cross-section data for electron-impact ionization of N 2 have been analyzed, including those for total N•-production and for the Meinel and first-negative emissions from excited N•-ions. These results are used to infer the relative production rates of the N•-(X), N•-(A), and N•-(B) product ions during the reactions, yielding branching-ratio fractions of 0.320 _+ 0.147, 0.535 _+ 0.112, and 0.145 _+ 0.019, respectively, for 100-eV electrons. The data are compared with the relative formation rates of these ions recently obtained using electron-energy spectroscopy coincidence measurements. The significant discrepancy between these two procedures is discussed, and the results obtained from our data analysis are recommended for auroral modeling at the present time. N•-(X), N• (A), and N•-(B) states, respectively. This work was an extension of their earlier studies [Doering and Goembel, 1991] in which similar data were presented but for only a single secondary-electron emission angle. These initial results, (fx, f.4, fB) = (0.50, 0.40, 0.10), were compared favorably to the values (0.50, 0.39, 0.11) reported by Rees [1989] from an analysis of various ionization and emission cross-section data made by Lummerzheim [1987]. Unfortunately, the N•(A) data used for this analysis [Holland and Maier, 1972] were later found to be in error [Holland and Maier, 1973]. Using the "corrected" N•-(A) results, Crandall et al. [1974] subsequently estimated the branching ratios to be (0.25, 0.61, 0.14), now yielding a much smaller N•-(X) fraction than that found by Goembel et al. [1994]. In contrast, the (0.60, 0.25, 0.12) values of Nagata et al. [1987] suggest a larger fx branching ratio than found by Goembel et al. [1994], with an even larger fx being given by Kawazumi and Ogawa [1987]. Indeed, such scatter in the available branching-ratio data led Darrach and McConkey [1991] to adopt compromise values of (0.45, 0.45, 0.10) to minimize the disparities. The purpose of this paper is to analyze and evaluate the various ionization and emission cross-section data for electron impact on N 2 used in such branching-ratio determinations. We believe such an effort is justified, for the intense N•-Meinel and first-negative emissions observed during atmospheric aurorae or other airglow phenomena cannot be successfully modeled unless the N•-(A) and N•-(B) production rates are accurately known. Of course, the branching ratios found by Goembel et al. [1994] do not in themselves provide the cross-section magnitudes needed for such modeling work. Rather, they must be combined with an absolute value of the total N• production cross section to assess the contributions from these individual processes. For this reason we begin our study with the available data for total N•-formation. (Unless otherwise noted, the results discussed will be for 100-eV electron energy. This energy is at, or close to, the maxima of such cross sections and is the only energy investigated by Goembel et al. [1994] at this time.) We next consider the measured cross sectio...

Absolute total cross sections for producing H+, H, e, N2+, and 02+ have been measured for H+ N, and H+02 collisions from 50-eV to 3-keV hydrogen-atom energy. The experimental techniques used, when combined with classical differential-scattering calculations, also allowed determinations of the absolute largeangle-scattering differential cross sections for H+ production. The experimental and theoretical procedures are reviewed, and the results are compared, where possible, with the data of other investigators.

Absolute cross sections for producing H+, H−, H+2, He+, and e− have been measured for fast hydrogen atom impact on H2 and He targets. The hydrogen atom energy ranged between 50 eV and 3.0 keV. For the H+H2 reaction, the dominant ion-formation process for hydrogen atom energies below 250 eV was found to be H−+H+2 production. For He targets, production of H+ dominated over the entire hydrogen atom energy range. The results are compared, where possible, with the data of other investigators and are discussed in terms of possible reaction mechanisms.