High-resolution electron-impact study of the far-ultraviolet emission spectrum of molecular hydrogen

The emission spectrum of molecular hydrogen produced by electron-impact excitation at 100 eV has been measured in the wavelength range 1140 endash 1690 A. High-resolution, optically thin spectra (Δλ=0.136 A) of the far-ultraviolet (FUV) Lyman and Werner band systems have been obtained with a newly constructed 3 m spectrometer. Synthetic spectral intensities based on the transition probabilities calculated by Abgrall et al. are in very good agreement with experimentally observed intensities. Previous modeling that utilized Allison ampersand Dalgarno band transition probabilities with Hoenl-London factors breaks down when the transition moment has significant J dependence or when ro-vibrational coupling is significant. Ro-vibrational perturbation between v=14 of the B1 summation +u state and v=3 of the C1Πu state and the rotational dependence of the transition moment in the (6,12) and (7,13) bands of the Lyman system are examined. Complete high-resolution experimental reference FUV spectra, together with the model synthetic spectra based on the Abgrall transition probabilities, are presented. An improved calibration standard is obtained, and an accurate calibration of the 3 m spectrometer has been achieved. copyright 1995 The American Astronomical Society