ANALYSIS OF ELECTRON-IMPACT EXCITATION AND EMISSION OF THE np sigma (1)Sigma(+)(u) AND np pi (1)Pi(u) RYDBERG SERIES OF H-2

Calculated and recently measured photoabsorption transition probabilities of the H-2 np sigma (1)Sigma(+)(u) and np pi (1)Pi(u) - X-1 Sigma(+)(g) band systems have been examined with high-resolution (Delta lambda = 95 - 115 m angstrom) electron-impact induced emission spectra obtained previously by Jonin et al. and Liu et al. When localized rovibronic coupling is insignificant, transition probabilities calculated with the adiabatic approximation are found to be generally consistent with experiment. However, in the presence of significant coupling, the transition probabilities obtained from a nonadiabatic calculation of B'(1)Sigma(+)(u), D'(1)Pi(+)(u), B(B) over bar (1)Sigma(+)(u), D'(1)Pi(+)(u), and 5p sigma(1)Sigma(+)(u) state coupling give better agreement with the experimental spectra. Emission yields obtained by comparison of the calculated and experimental spectra are also consistent with the measured predissociation and autoionization yields. In addition, more accurate excitation and emission cross sections and nonradiative yields have been obtained for a number of the np sigma(1)Sigma(+)(u) and np pi(1)Pi(u) states. The results obtained in the present investigation lead to a significantly more accurate calibration of the Cassini UVIS instrument and laboratory spectrometers in the range 790 - 920 angstrom. They are also an important step toward an accurate model of extreme ultraviolet H-2 auroral and dayglow emissions in the outer planet atmospheres.