Electronic Structure of Nitric Oxide

The self-consistent field (SCF) molecular orbitals for nitric oxide have been calculated in the linear-combination-of-atomic-orbitals molecular orbital approximation (LCAO-MO) using 1s, 2s, and 2p Slater atomic functions. Three different calculations have been made. (1) An ``incomplete treatment'' in which mixing between the inner orbitals, which contain only 1s functions, and outer orbitals, which contain orthogonalized 2s and 2p functions, is neglected. (2) A similar calculation, but here the outer orbitals are forced to be orthogonal to the inner orbitals. (3) The ``complete treatment'' in which all orbitals are combinations of 1s, 2s, and 2p functions. The single Slater determinant wave function built from the orbitals calculated from the complete treatment gives a negative binding energy, but a limited configuration interaction calculation accounts for 26% of the observed binding energy. The agreement between the calculated and observed first ionization potential is very good. Certain aspects of the uv spectra seem to be reasonably well explained from this calculation. The dipole moment is calculated to be 0.5 D (N-O+) as compared to an observed value of 0.16 D with undetermined sign. Following Mulliken, atomic and overlap populations have been calculated.