New isotopeRn199and evidence for an isomeric stateRnm199

The nuclide ${}_{}{}^{199}{}_{}{}^{}\mathrm{Rn}$ has been produced in the ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$(${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$,$5n$) ${}_{}{}^{199}{}_{}{}^{}\mathrm{Rn}$ reaction. The recoiling ${}_{}{}^{199}{}_{}{}^{}\mathrm{Rn}$ nuclei were separated from the beam at zero degrees by a recoil-separator arrangement utilizing electric and magnetic fields, and detected by their alpha decay signatures in a surface-barrier detector. Two alpha lines were found with energies 6.990±0.015 MeV and 7.060±0.015 MeV. Alpha decay of the known daughter ${}_{}{}^{195}{}_{}{}^{}\mathrm{Po}$ was also observed.