Atomic determination of the nuclear quadrupole moment $\mathrm{Q}(^{209}{\rm Bi})$ using the multi-configuration Dirac-Hartree-Fock method

The multiconfiguration Dirac-Hartree-Fock method implemented in the Grasp2018 package was employed to calculate the magnetic dipole hyperfine interaction constants and electric field gradients of levels in the ground configuration of the neutral bismuth atom. Combining the calculated electric field gradient of the ground state with the measured electric quadrupole hyperfine interaction constant, we extracted the nuclear quadrupole moment for the $^{209}$Bi isotope, $\mathrm{Q}(^{209}\textbf{Bi}) = -422(22)$~mb. This value, together with other results obtained from atomic- and molecular-structure calculations, created the ``world average" nuclear quadrupole moment of this isotope, $\mathrm{Q}(^{209}\textbf{Bi}) = -420(17)$~mb.