The intermediate Hamiltonian coupled cluster method is applied to calculate the nuclear quadrupole moments (NQM) of Pb and La. Large, converged basis sets are used to get the electric field gradients at the relevant nuclei; these make possible the extraction of the NQM from the measured hyperfine coupling constant B. The only Pb NQM listed in Pyykkö's 2008 table (Mol Phys 106:1965, 2008) is for the neutron-rich unstable 209 isotope (halflife 3. 25 h), given as -269(165) mb. This error bound of 60%, the largest in the table, comes from the poor precision of the measured B. More precise B values are now available for the neutron-poor isotopes with atomic weights 191, 193, 195, 197 and their NQMs are calculated herein. The best values obtained for these four isotopes are, respectively, 78(11), 179(9), 281(12), and 347(15) mb. The electric field gradient at the nucleus is the same for all Pb isotopes, so that NQMs of other isotopes may be evaluated when better B values become available for them. The same method is applied to 139La, for which an accurate B value in the b1D2 state has recently become available. The calculated NQM is 206(4) mb, in excellent agreement with the recent molecular value of 200(6) mb.
- Coupled cluster method
- Nuclear quadrupole moments