Hyperfine Structure and Nuclear Moments of Americium-242

The hyperfine structure of ${}_{95}{}^{}{}_{}{}^{}\mathrm{Am}_{}^{242}{}_{}{}^{}$($T_{\frac{1}{2}}=16\mathrm{}$ hr) in the $J=\frac{7}{2}$ electronic ground state has been studied by the atomic-beam technique using radioactive detection. The nuclear spin is found to be $I=1\mathrm{}$. The measured values of the magnetic-dipole interaction constant $A$ and the electric-quadrupole interaction constant $B$ are $A=\pm 10.124\left(10\right)\mathrm{}$ Mc/sec and $B=\pm 69.639\left(40\right)\mathrm{}$ Mc/sec, respectively. Combining these measurements with optical spectroscopic and atomic-beam data for ${\mathrm{Am}}^{241}$, we infer the nuclear magnetic-dipole moment to be ${\mu }_I=\pm 0.33$ nm and the nuclear quadrupole moment $Q=\mp 2.76$ barns. These results are discussed in terms of the Bohr-Mottelson nuclear model.