First observation of spontaneous fission of ${}^{232}\mathrm{U}$

By using a low-sensitivity glass track detector in planar geometry we measured the decay rate of ${}^{232}\mathrm{U}$ by spontaneous fission to be ${\lambda }_{\mathrm{SF}}=(8.6\mathrm{}\pm 1.8)\times {10}^{-24}{\mathrm{s}}^{\mathrm{-}1},$ corresponding to a half-life $T_{1/2}=(8.1\mathrm{}\pm 1.7)\times {10}^{22}\mathrm{s}.$ The inconsistency and consistency of this result with previous work is discussed, and spontaneous fission half-lives are compared with cluster decay ones for the various uranium isotopes measured up to now.