Fluorine Atom Resonance Absorption and Fluorescence

For reasons already given, resonance fluorescence would be a preferred technique 

Although weak fluorescence in the P— P lines was observed, from a practical standpoint only the P— P lines were found to be intense enough for resonance fluorescence work at low atom concentrations. The fluorescence count rates using the whole of the fully allowed P— P transition of F were typically 2 counts s at [F] = 1 X 10 cm . These data set a lower concentration limit of 1 X 10 cm for the smallest detectable concentration of F P atoms. Similar lower limits for O, Br, and I atoms are appreciably less, and are continually being improved by better attention to collimation and detection. Because of the low count rates observed in the F-atom resonance fluorescence studies, it is a better approach to use resonance absorption with a non-reversed line source (see above). 

The sensitivity of resonance fluorescence by F atoms was, however, sufficient for kinetic studies to be made of the rapid titration reaction of F with Brj, v/z. F + Bri - BrF + Br. It was necessary to make corrections both for nonlinearity of fluorescence intensity with [F] and for deviations from pseudo-first-order kinetic conditions, both due to the relatively high F P atom concentrations used ( 1 X 10 cm ). The final rate constant for the F + Br2 reaction was (1.4 0.5) X 10 ° at 298 K, in fair agreement with results from the (similarly difficult) mass spectrometric study of Appelman and Oyne [A = (3.1 0.9) X 10 ]. 

Measurement of Atom Concentiatioas and Mass Spectrometry.—Electron 

Less effort appears to have bear expended on studies of F, Q, Br, and I atom reactions, although the e.p.r. spectra of the P states of F, Cl, Br, and I have all been described. Spectra of F, Q, and Br in P states have also been desmbed. Mass spectrometric detection of atoms also has bemi reviewed fairly recently. Certain indirect methods, e.g. using detection of OF produced by the reaction of F with O2 to detomine [F], have been described above. Direct detection of atoms, using reduced electron enmgies in electron impact, or using photoionization, A. A. Westcnberg, Progr. Reaction Kinetics, 1973, 7, 23. 

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