The binding energies and momentum profiles for each of the valence orbitals of CO and H₂S have been measured by high momentum resolution electron momentum spectroscopy. The experimental momentum profiles are compared on a quantitative basis within the Target Hartree-Fock Approximation to theoretical calculations using SCF wavefunctions ranging in quality from minimal basis to Hartree-Fock limit. Calculated momentum distributions for the 5σ orbital of CO are shown to be very basis set dependant while calculated momentum distributions of the CO 3σ, 4σ and 1π orbitals change very little with improvements in the wavefunction beyond the double-zeta level. The CO 1π orbital is not very well described in the low momentum region even at the Hartree-Fock limit with basis set saturation including diffuse functions. While the 4a₁, and 2b₂ momentum profiles of H₂S are well described using even minimal basis calculations, diffuse functions must be included in the basis set to describe the 2b₁, and 5a₁, momentum profiles. The experimental momentum profiles of H₂S are also compared with full ion-neutral overlap calculations incorporating correlation in the ground state and correlation and relaxation in the final ion state. These calculations are very similar to the Hartree-Fock level momentum distributions, indicating that correlation is not very important in describing the momentum profiles of H₂S. The binding energy spectra and momentum profiles of the inner valence region of both CO and H₂S are studied in detail. Peaks in the CO binding energy spectrum at 24.1 and 28.3 eV are assigned as satellites 4σ and 1π main lines respectively while the structure above 30 eV is shown to be predominantly due to satellites of the 3σ orbital. The intense structure in the inner valence region of H₂S is found to arise predominantly from the 4a₁, orbital. The assignments of the inner valence spectra of both molecules is confirmed within experimental uncertainties by the spectroscopic sum rule. / Science, Faculty of / Chemistry, Department of / Graduate