Degree of accuracy in determining the nuclear electric quadrupole moment of radium

Abstract

The multiconfiguration Dirac-Hartree-Fock (MCDHF) model has been employed to calculate the atomic expectation values responsible for the hyperfine splittings of the $7s7p\phantom{\rule{0.3em}{0ex}}^{3}P_{1,2}$ and $^{1}P_{1}$ levels of radium. Calculated electric field gradients, together with the experimental electric quadrupole hyperfine structure constants, allow us to extract a nuclear electric quadrupole moment $Q(^{223}\mathrm{Ra})$ of 1.21(0.03) barn. This value is in good agreement with the semiempirical determination based on neutral radium hyperfine and fine structure, but differs from the latest result from an alkali-like radium ion.