The atomic-beam magnetic-resonance method has been used to measure $g_J=1.\mathrm{}16052\pm 0.00014$ for the atomic ground state of fermium I. An intermediate-coupling calculation with parameters extrapolated from lower actinides, and with corrections for diamagnetic and relativistic effects, yielded the value $g_J=1.\mathrm{}1606$. The agreement between the measured and calculated values of $g_J$ establishes the fermium ground state as the ${}_{}{}^3{}_{}{}^{}H_6^{}{}_{}{}^{}$ level of the $5f^{12}7s^2$ configuration. The neutral fermium atoms were obtained by heating Fm${\mathrm{F}}_3$ and its Ho${\mathrm{F}}_3$ carrier in the presence of ZrC and tungsten.

• Received 5 November 1970

DOI:https://doi.org/10.1103/PhysRevA.4.473