Partition sums for non-local thermodynamic equilibrium applications

Abstract

Internal partition functions are calculated for nine molecules, which are abundant in the terrestrial atmosphere and are important in non-local thermodynamic equilibrium processes. Calculations are performed for the most abundant isotopomer and for several molecules for lesser abundant isotopomers as well. The temperature range considered in the study is for applications in the terrestrial atmosphere from 100 to 450 K . The resulting rotational and vibrational partition functions are each fit separately to a polynomial expression, which is third order in temperature. The methods of calculation of the partition functions, the convergence, and the quality of the fits for each isotopomer are discussed.