Complete-active-space multiconfiguration Dirac-Hartree-Fock calculations of hyperfine-structure constants of the gold atom

The multiconfiguration Dirac-Hartree-Fock model has been employed to calculate the expectation values for the hyperfine splittings of the 5d(9)6s(2) D-2(3/2) and 5d(9)6s(2) D-2(5/2) levels of atomic gold. One-, two-, and three-body electron correlation effects involving all 79 electrons have been included in a systematic manner. The approximation employed in this study is equivalent to a complete-active-space approach. Calculated electric field gradients, together with experimental values of the electric quadrupole hyperfine-structure constants, allow us to extract a nuclear electric quadrupole moment Q(Au-197)=521.5(5.0) mb.