Isotope Effect and Quenching in the Fluorescence of Bromine

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Abstract
The fine structure of the resonance spectrum of bromine excited by the green line of the mercury arc has been photographed and a theoretical explanation obtained in terms of the three molecular isotopes present and the values of the rotational and vibrational quantum numbers for the transitions. In addition, the fluorescence intensities in bromine were studied as a function of the pressure, for three spectral regions. The much lower intensities in bromine as compared with iodine are accounted for on the basis of less initial absorption, and of greater quenching, due to the longer mean lifetime of the molecule in the upper state. The fluorescence data are concordant with results obtained in the analysis of bromine's absorption spectrum. The green mercury line did not excite any observable fluorescence in gaseous chlorine. This result is shown to be in accordance with the theoretical predictions.