Eigenvalues and thermal properties of the A¹Σ _u⁺ state of sodium dimers

We evaluate the accuracy of the Sun potential model in reproducing the interaction potential energy curve for the state A¹ (Formula presented.) of sodium diatomic molecules. The average absolute deviation from the experimental discrete variable representation (DVR) data satisfies the Lippincott criterion. The rovibrational energy levels and the radial wave functions have been calculated and compared with the experimental (DVR) data. With the help of the energy spectra, we propose a straightforward model based on only three experimental parameters to predict with very high accuracy the thermodynamic properties of sodium dimers in a wide range of temperatures. The mean absolute percentage deviations of the predicted values of the molar entropy, the molar enthalpy, and reduced Gibbs free energy from the experimental values taken from the National Institute of Standards and Technology database are 0.75%, 5.68% and 0.66%, respectively.