Correlation Effects on Hyperfine-Structure Expectation Values for the BoronP2Ground State

Pure correlation effects on the hyperfine structure of atomic boron were investigated and found to be important. A natural spin-orbital expansion of the well-correlated 187-term wave function of Schaefer and Harris was used. Pure correlation effects are those contributions to an expectation value obtained when the wave function is improved beyond the best possible Slater determinant (the best overlap determinant). Our results indicate that the unrestricted Hartree-Fock method yields valuable information about the orbital and spin magnetic dipolar and electric quadrupolar terms, but gives unreliable results for the Fermi contact term. Utilizing both experimental and theoretical results, the Fermi contact term $f$ was estimated as $0.096{a_0}^{-3\mathrm{}}$, and the quadrupolar nuclear-shielding factor $\gamma$ as 0.093.