Isotopically Selective Photochemistry of Bromine

A tunable narrow-frequency laser is used to produce an isotopically selected reaction product of bromine. Natural ${\mathrm{Br}}_2$ (${}_{}{}^{79}{}_{}{}^{}\mathrm{Br}$/${}_{}{}^{81}{}_{}{}^{}\mathrm{Br}$=1) is photopredissociated by selective excitation into the ${}_{}{}^3{}_{}{}^{}\mathrm{II}_{0^{+}\mathrm{u}}^{}{}_{}{}^{}$ state. Bromine atoms enriched in one isotope react with HI before scrambling occurs to produce 80-85% ${\mathrm{H}}^{81}$Br. The method should yield an efficient technique for isotope separation. Spectroscopic requirements and the optimum reaction conditions are discussed. The relative amount of nonselective product from excitation of the ${\mathrm{Br}}_2$ continuum is determined.