Internal energy relaxation and dissociation of molecular oxygen using direct molecular simulation

In this work we present a molecular level study of non-equilibrium dissociation and vibrational excitation of oxygen due to O₂+ O₂and O₂+ O interactions using the direct molecular simulation method (DMS). The O₂+O₂interactions were modeled using potential energy surfaces (PESs) corresponding to the singlet and quintet spin states and isothermal excitation calculations were carried out over temperatures ranging from 5000K to 20000K to calculate non-equilibrium dissociation rate coefficients and characteristic vibrational excitation times over. Non-equilibrium dissociation rate coefficients obtained from both PESs for the O₂+O₂interactions are in agreement. The characteristic vibrational excitation times calculate calculated showed that the molecules colliding over the quintet surface excite slightly faster than those colliding on the singlet surface. The O₂+O interactions were modeled using the four body PESs and placing an atom at a large distance from the three interacting atoms. While, this particular arrangement does not correspond to a specific state for the three body system it gives us a qualitative idea of the properties associated with O₂+ O interactions. Dissociation rate coefficients and characteristic vibrational excitation times were calculated for the O₂+ O interactions. Although preliminary, it was found that the dissociation rate coefficients obtained using the two PESs were similar and the characteristic vibrational excitation times obtained from the singlet PES were higher than those obtained from the the quintet PES.