A calculation of the electric field gradient in the ${}_{}{}^2{}_{}{}^{}P$ ground state of atomic boron implies that the quadrupole moments of the stable boron isotopes, in barns, are $Q\left({\mathrm{B}}^{10}\right)=0.084\mathrm{}72\pm 0.00056$, $Q\left({\mathrm{B}}^{11}\right)=0.040\mathrm{}65\pm 0.00026$.

• Received 27 March 1970

DOI:https://doi.org/10.1103/PhysRevLett.24.1155