The second group integral of cesium

The literature data on the interaction of two cesium atoms, obtained by processing the results of spectroscopic experiments and quantum-mechanical calculations, are used to calculate the second group integral of cesium at temperatures from 700 to 3000 K. The contributions made by atoms in the ground $^2S$ and first excited $^2P$ electronic states are taken into account. The contribution by the excited state is negligible at 1000 K, approximately 2 % at 2000 K, and as significant as 20 % at 3000 K. The error of calculation results is estimated to range from 0.3 % at the lowest temperatures to 10 % at the highest temperatures.