Knowledge Bank

The electron spin-spin dipole and spin= orbit contributions to the zero-field splitting in the $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma g$- ground state of the oxygen molecule were calculated using the correct microscopic Hamiltonians. Calculations were carried out using double-zeta (DZ) and double-zeta-plus-polarization (DZP) basis sets constructed from contracted Gaussian-lobe functions. Configuration-interaction wave functions were used for the ground state and all states coupling to the ground state via the spin-orbit Hamiltonian. Values of $1.876cm-1$ and $2.028cm-1$ were obtained for the splitting parameter for the DZ and DZP basis respectively, in good agreement with the accurate experimental value of $1.981cm1$.