Optical emissions in the wavelength region 2000-6000 AA produced by electron impact dissociation of NF3, CF4and SF6

Light emissions in the wavelength region 2000-6000 AA produced by dissociative electron impact on CF 4 , NF 3 and SF 6 were studied. A double-onset structure in the cross section of the intense continuous emission from CF 4 was found and might be interpreted as evidence that excited CF 3 + 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 NF 3 and SF 6 molecules were also observed. In both cases the 2.4 D to 4 P 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 cm 2 from SF 6 and NF 3 , respectively, at 100 eV. Four F II emissions with comparatively high onset potentials and maximum emission cross sections in the 10 -20 cm 2 range (at 200 eV) were found in the NF 3 spectrum but not in the SF 6 spectrum. The break-up of both SF 6 and NF 3 leads to a broad unstructured emission between 2000 and 3200 AA which has not yet been identified.