Knowledge Bank

The total internal partition sums have been calculated for the molecules and their isotopic variants on the HITRAN database. The calculations employed near complete sets of energy levels for all relevant rotation-vibration states generated from the molecular constants. All degeneracies were accounted for in the calculations. The calculations were performed over a temperature range of 75K to 400K. The accuracies of the resulting partition sums will be shown. For generalized applications, the internal partition sums have been fitted to the expression $Q(T)=a+b\cdot T+c\cdot T2+d\cdot T3$, where a, b, c and d are constants adjusted by means of a least-squares minimax procedure. The maximum deviation of the fit is on the order of a few tenths of a percent.