<p> Various low-lying electronic states of formaldehyde and acetone have been investigated, using molecular orbital calculations, to determine their involvement in the photochemical system. The potential energy surfaces of these states were calculated using the CND0/2. </p> <p> The results of this study show that the decomposition of formaldehyde to molecular products H2 and CO (process II) occurs via the ground state; the potential surface of this process was studied using configuration interaction methods. </p> <p> The process leading to radical products in both acetone and formaldehyde (process I) can arise either directly from the singlet and triplet (n,π*) states via a reaction path of no symmetry, or by crossing to the 3 (π,π*) state should Cs symmetry be maintained. The ground state is the only other state correlating with radical products. </p> / Thesis / Master of Science (MSc)