Decay-induced bromination via the 76Kr(EC)76Br and 77Kr(β,EC)77Br decay. Pt. 1

Substitution reactions by nucleogenic bromine ions generated in situ via the 76,77Kr(β+, EC)76,77Br decay processes were examined in gaseous fluorobenzene and para-difluorobenzene. In the Kr-moderated systems at atmospheric pressure only small yields (0.2 to 2%) of hydrogen and fluorine substitution can be observed. A small nuclear isotope effect (1.2 to 2) with preference for 77Br substitution products is found independent of the mole fraction of krypton moderator gas present. Fluorine substitution is about two to three times more efficient than H-substitution. From the moderator dependence of the absolute F- and H-substitution yields, the relative isomer distribution, and the primary charge- and energy-distribution of the radiobromine, it is concluded that decay-induced bromination in the moderated gas phase proceeds via bromine cations. (orig./HK)