The ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ decay of ${}_{}{}^{222}{}_{}{}^{}\mathrm{Ra}$ has been reinvestigated, using an 85 MBq activity ${}_{}{}^{230}{}_{}{}^{}\mathrm{U}$ source radiochemically separated, a Si barrier detector, and a superconducting magnetic spectrometer. In a 16 days counting run, 210 ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ events were recorded. The ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ particles energy value 30.930±0.090 MeV was found and an upper limit b≤2×${10}^{\mathrm{-}12}$ was estimated for the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ branching ratio to the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ first excited state; the branching-ratio value to the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ ground state, thus equal to the total branching ratio, was found to be b=${\lambda }_{\mathit{c}}$/${\lambda }_{\mathrm{\alpha }}$=(2.31±0.31)×${10}^{\mathrm{-}10}$.

• Received 4 December 1990

DOI:https://doi.org/10.1103/PhysRevC.43.2599