A computational evaluation of altitude profiles of the equilibrium monomeric-dimeric CO2 fractions in the atmosphere of Venus

Abstract The equilibrium constant of the gas-phase carbon-dioxide dimerization is evaluated either from the Lennard-Jones potential or from two recent quantum-chemical calculations. The dimerization equilibrium constant is combined with observed height profiles of temperature and pressure in the atmosphere of Venus in order to derive the equilibrium dimeric mole fraction. In all the three treatments it is found that the mole fraction decreases with increasing height. The decrease is interpreted in terms of competition between temperature and pressure effects. The dimeric mole fraction should be at least 4% at the surface of Venus and, thus, is important in the planning of future observations.