Long-Lived Isomer ofNp236

A long-lived isomer of ${\mathrm{Np}}^{236}$, identified by chemical and mass spectrometric means, has been prepared by the ${\mathrm{U}}^{238}(d, 4n)$ reaction. The alpha half-life of this isomer has not been established, but a lower limit of 5000 years has been placed on the beta half-life. The cross section for the ${\mathrm{U}}^{238}(d, 4n){\mathrm{Np}}^{236,236*}$ reaction for 21.6-Mev deuterons has been calculated to be approximately 35 millibarns. A slow-neutron fission cross section of 2800 barns has been determined for the long-lived isomer.