High-Resolution Electron-Impact Emission Spectrum of H₂. I. Cross Sections and Emission Yields 900-1200 Å

High-resolution (Δλ = 115 mÅ) emission spectra of molecular hydrogen produced by electron-impact excitation at 100 eV have been obtained in the wavelength range 900-1200 Å. The emission spectra can be assigned to transitions between the X¹Σ ground state and the 1sσ_gnpσ_u ¹Σ_u and 1sσ_gnpπ_u ¹Π_u Rydberg states. Synthetic rotational line spectra based on the excitation function of Liu et al. and calculated 2pσ B¹Σ-X¹Σ, 2pπ C¹Π_u-X¹Σ, 3pσ B' ¹Σ-X¹Σ, and 3pπD¹Π_u-X¹Σ transition probabilities of Abgrall et al. are generally found to be in good agreement with the experimental spectra in the regions where emissions from 1sσ_gnpσ_u (n ≥ 4) and 1sσ_gnpπ_u (n ≥ 4) states are negligible. Emission cross sections for D¹Π, D' ¹Π_u, and D'' ¹Π, B' ¹Σ, and B'' ¹Σ states are obtained by measuring the emission intensities from these states relative to those from the B¹Σ,C¹Π_u, and D¹Π states. A high- resolution EUV calibration technique is established. At 100 eV the emission cross sections of the D¹Π_u, D' ¹Π_u, D'' ¹Π_u, B' ¹Σ, and B'' ¹Σ states are measured to be (2.8 ± 0.4) × 10^-18, (6.3 ± 1.3) × 10^-19, (5.9 ± 1.7) × 10^-20, (2.1 ± 0.3) × 10^-18, and (1.6 ± 0.4) × 10^-19 cm², respectively. In addition, the vibrational emission cross sections have been compared to the estimated excitation cross sections to obtain the predissociation yields for selected vibrational levels of the D¹Π, D' ¹Π and D'' ¹Π states. The B' ¹Σ state is inferred to have very significant excitation into the H(1s)+H(2p,2s) dissociative continuum.