Correlation of time intervals between two modes of decay has been used to determine unequivocally the atomic and mass numbers of ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$, a nuclide which rapidly decays by spontaneous fission. We measured the time interval between the emission of Fm K x rays, due to electron capture by 60-min ${}_{}{}^{258}{}_{}{}^{}\mathrm{Md}_{}^{\mathrm{m}}{}_{}{}^{}$, and the detection of fission fragments from the spontaneous fission of ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$ to establish a genetic relationship and to determine the mean lifetime of ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$. We obtained a half-life of 360±20 μs, which is in good agreement with our much earlier value of 380±60 μs measured by another method.

• Received 2 July 1986

DOI:https://doi.org/10.1103/PhysRevC.34.1394