Hyperfine Structure of Seven Low Atomic Levels inCo59, and the Nuclear Electric-Quadrupole Moment

The hyperfine structure of the seven lowest atomic levels in ${\mathrm{Co}}^{59}$ has been examined with the atomic-beam magnetic-resonance technique. Quantitative agreement with earlier measurements is found for those states for which results have been published. All of the results are corrected for the effects of off-diagonal hyperfine interactions, and the effective-operator theory used for the interpretation also takes into account such effects as intermediate coupling, configuration interaction, and relativistic effects. The emphasis is on examining the consistency of the results from state to state. Although a very high degree of agreement between theory and experiment is found, some difficulty is encountered in understanding details of the quadrupole interaction. Values for the quadrupole moment of the ${\mathrm{Co}}^{59}$ nuclear ground state are determined in each of two electron configurations. The difference between the two values found is well outside experimental error and is presumably due to different Sternheimer shielding in the two configurations. The value found for $Q$ is consistent with earlier determinations and with nuclear theory. Values are given for the electronic $g$ factor in each state examined.