Halogen ultraviolet atomic emission

Energy levels of halogen atoms (F, Cl, Br, I) are so high that they emit ultraviolet radiation below 200 nm. This spectral region is called vacuum ultraviolet because radiation below 200 nm is absorbed by Oz, so spectrometers for the far-ultraviolet were customarily evacuated. Some plasma emission spectrometers are now purged with N2 to exclude air so that the region 130 to 200 nm is accessible and Cl, Br, I, P, and S can be analyzed.14... 

Energy disposal in the reactions of electronically excited inert gas atoms with halogen-containing molecules has been studied by observing the ultraviolet or visible emission spectra of the inert gas halide exciplex products under flow or molecular beam conditions. The experimental information consists of branching ratios for the formation of different electronic states of the inert gas halide, vibrational population distributions (obtained by computer simulation of the bound-free spectrum) and the degree of polarisation of the chemiluminescence emission. The metastable inert gases have ionisation potentials that are very similar... 

Acetone has an absorption band in the near ultraviolet with a maximum near A 2800 A, and the substitution of halogen atoms leads to a shift of the maximum to longer wavelengths with an increase in the extinction coefficient. For continuous photolysis the 3130 A emission line in the merciuy spectrum is most frequently used, and hexafluoroacetone has an absorption maximum near this wavelength . 

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