Optical emissions in the wavelength region 2000-6000 AA produced by electron impact dissociation of NF₃, CF₄ and SF ₆

Light emissions in the wavelength region 2000-6000 AA produced by dissociative electron impact on CF₄, NF₃ and SF ₆ were studied. A double-onset structure in the cross section of the intense continuous emission from CF₄ was found and might be interpreted as evidence that excited CF₃ ⁺ ₃ fragment ions produced by two different mechanisms rather than CF ₄ ⁺ parent ions are the emitting species. Comparatively weak fluorine 4p to 3 s line emissions resulting from the total fragmentation of the parent NF₃ and SF₆ molecules were also observed. In both cases the ^2.4D to ⁴P multiplet at 3669 AA has the largest emission cross section with 4.4+or-1.2*10^-20 cm ² and 12.9+or-3.3*10^-20 cm² from SF ₆ and NF₃, respectively, at 100 eV. Four F II emissions with comparatively high onset potentials and maximum emission cross sections in the 10^-20 cm² range (at 200 eV) were found in the NF ₃ spectrum but not in the SF₆ spectrum. The break-up of both SF₆ and NF₃ leads to a broad unstructured emission between 2000 and 3200 AA which has not yet been identified.