The intensities of mass-separated radon beams have been improved by means of a new high temperature thorium spallation target. The production yields of the selectively produced radon ions were determined. The new nuclide ${}_{}{}^{198}{}_{}{}^{}\mathrm{Rn}$ was found to have an $\alpha$-decay energy of 7196±10 keV and a half-life of 50±9 ms. Decay energies and half-lives for ${}_{}{}^{199}{}_{}{}^{}\mathrm{Rn}_{}^m{}_{}{}^{}$, ${}_{}{}^{199}{}_{}{}^{}\mathrm{Rn}$, and ${}_{}{}^{200}{}_{}{}^{}\mathrm{Rn}$ were remeasured.

• Received 9 July 1984

DOI:https://doi.org/10.1103/PhysRevC.30.1671