Fission isomer of Np m 237

The excitation function and lifetime ${T}_{i}=(45\ifmmode\pm\else\textpm\fi{}5)$ ns of a $^{237}\mathrm{Np}$ fission isomer were measured using the $^{238}\mathrm{U}(p,2n)$ reaction and the fission-in-flight method. The analysis of the delayed-to-prompt fission ratio provided an excitation energy of (2.85 \ifmmode\pm\else\textpm\fi{} 0.4) MeV for the isomeric state and a branching ratio of 1.9 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}3}$ between $\ensuremath{\gamma}$ and fission decays.NUCLEAR REACTIONS $^{238}\mathrm{U}(p,2n)$; ${E}_{p}=9.75, 11.6, 12.5$ MeV. Measured $^{237}\mathrm{Np}^{m}$ isomeric decay curve and delayed-to-prompt fission ratios. Deduced partial half-lives ${T}_{\mathrm{if}}$, ${T}_{i\ensuremath{\gamma}}$ and the branching ratio.