Excitation of continuum radiation in collisions of (1) electrons and (2) metastable argon atoms with H2 and D2

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Abstract
Measurements have been made of the spectral distribution of continuum radiation arising from collisions of low energy electrons and of metastable (3P0,2) argon atoms with hydrogen and deuterium molecules. The electron impact spectra, a(3Σ+g, v’=0) → b(3Σ+u)+hν, are in good agreement with the calculations of James and Coolidge. The spectra originating from Ar*+H2, D2 were obtained using crossed supersonic beams. In both cases, an onset at 0.065 ± 0.009 eV relative collision energy was observed. For deuterium, this onset occurs below the energy required to produce D2(a 3Σ+g) . Calculations of the spectral distributions when compared to experiment showed that, at 0.07 eV, the observed radiation arises from the first two vibrational levels of ArD* in the ratio (v’=0)/(v’=1)=4. For hydrogen at this energy, both product channels are present in the ratio ArH*/H*2=2 . At higher energy, both product channels are found in both systems with D*2 predominating in the case of D2 and ArH* in the case of H2.