"Understanding the energy transfer processes between oxygen molecules is important for the elucidation of the reactions occurring in the Earth's atmosphere. Even though two interacting oxygen molecules is a relatively small system, each diatomic has two unpaired electrons in antibonding, degenerate molecular orbitals, leading to an open shell system that forms a dense manifold of excited electronic states. This type of situation requires a multireference method. For this reason, progress on theoretical calculations for interacting oxygen molecules has been slow, since the discovery of collision-induced absorption in oxygen gas by Crawford, Welsh and Locke in 1949. In this work, interaction energy curves have been generated using the CASPT2 method, and the aug-cc-pVQZ basis set of Dunning. In addition, electronic properties have been obtained for the oxygen molecule, and are used to obtain the dipole moments using the long-range approximation. Changes in the electric charge distribution during a collision between the oxygen molecules can induce a net dipole and render the molecules infrared active, thus contributing to the absorption and emission in the IR and far-IR spectrum. These dipole moments have also been calculated using ab initio methods, for many orientations of the oxygen molecules, and can be used to model the collision-induced spectra."--Page ii.
Read
