A computational evaluation of altitude profile of the equilibrium monomer-dimer H2 mole fraction in the atmosphere of Jupiter

Abstract Populations of the hydrogen molecule dimer in the atmosphere of Jupiter are evaluated from the dimerization equilibrium constant calculated either from the Lennard-Jones potential or from quantum-chemical treatments. The latter calculations are of an ab initio type with the second-order Moller-Plesset (MP2) treatments in the 6-311G and 6-311G ∗∗ basis sets. The computed dimerization equilibrium constant is combined with observed height profiles of temperature and pressure in the Jupiter atmosphere in order to derive the dimeric mole fraction x 2 in the partial thermodynamic equilibrium with the monomer. In all the treatments considered, it is found that the mole fraction decreases with increasing height. Various approximations suggest that the dimeric mole fraction at the Jupiter 1 atm pressure level is between 0.04% and 0.94%.