A new radioactivity of Np was discovered by chemical separations from targets of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$ irradiated with 30-160 MeV neutrons. Five $\gamma$ rays were identified with $E_{\gamma },I_{\gamma }:159.1\mathrm{} \mathrm{keV},32;265.1\mathrm{} \mathrm{keV},24;785.7\mathrm{} \mathrm{keV},\left(100\right);944.8\mathrm{} \mathrm{keV},63; \mathrm{and} 1104 \mathrm{keV}, 0.6$. The half-life is 5.5±0.1 min and various cross bombardments established that the mass number is 242. $I^{\pi }$ was assigned $6^{+}$ with the configuration ${\frac{5}{2}}^{+}{\mathrm{}\left[642\right]\mathrm{}}_p$, ${\frac{7}{2}}^{+}{\mathrm{}\left[624\right]\mathrm{}}_n$ and a decay scheme is proposed.

RADIOACTIVITY 5.5-min ${}_{}{}^{242}{}_{}{}^{}\mathrm{Np}$ from ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}\mathrm{}(n,p2n)\mathrm{}$ and ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}\mathrm{}(n,p)\mathrm{}$; radiochemistry, Ge(Li). Measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$; deduced $E_{{\beta }^{-}}$, $log\mathrm{ft}$, partial decay scheme, $I$, $\pi$, Nilsson assignments.

• Received 8 December 1980

DOI:https://doi.org/10.1103/PhysRevC.23.2234