Knowledge Bank

Selected ionized and excited states of the heteropolar molecules CO and NO were calculated in the Hartree-Fock LCAO MO approximation. The method used for open-shell states was that of different orbitals for different spin with the added restriction of identical MO's for paired electrons. The restricted forms of the secular equations are simpler to solve and result in a pure spin state. It is shown that the results of restricted and unrestricted treatments differ only slightly. The SCF MO's were represented in terms of the orthogonalized 1s, 2s and 2p Slater atomic orbitals on each atom. The states chosen for this study were $X\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +,a\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}II,d\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta$ of $CO;X\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +,A\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}II,B2\Sigma +,C\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +$ of $CO+;X\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}II$ of NO; and $X\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$ of $NO+$. These were reasonably well represented by a single AP function. Calculations for all states of CO and $CO+$ were performed at the equilibrium internuclear distance, 1.1282 {\AA} of the neutral ground state. Similarly, the states of NO and $NO+$ were determined at $r=1.1508$ {\AA}. The ionization and excitation energies found by direct calculation agreed within 1-2 ev. with the observed values and those predicted by Koopmans' theorem.