The Ideal and Real Gas Heat Capacity of Cesium Atoms at High Temperatures

The Ideal Gas Heat Capacity, C _p , of Cesium Atoms is Calculated to High Temperatures using Statistical Mechanics. There Are a Large Number of Electronic States in the State Sum that Determines the Partition Function: 174 Known Levels for Cesium Atoms Below the First Ionization Potential. Thus, at High Temperatures, C _p Becomes Very Large Unless the Number of Contributing States is Constrained. Two Arguments Are Used to Do This. First, at High Temperatures, the Increased Size of the Atoms Constrains the Sum (Bethe Method). Second, the Existence of Interacting Charged Species at Higher Temperatures, Which Lowers the Ionization Potential, Constrains the Sum (Ionization Potential Lowering Method). If Atoms Constitute a Real Gas Obeying the Virial Equation of State, the Lowest Non-Ideal Contribution to Cp Depends on the Second Derivative of the Second Virial Coefficient, B″(T), Which Depends on the Interaction Potential Energy Curves between Two Atoms. When Two Ground-State ( ² S) Cesium Atoms Interact, They Follow Either of Two Potential Energy Curves. When a ² S Cesium Atom Interacts with a Cesium Atom in the First Electronically Excited ( ² P) State, They Follow Any of Eight Potential Energy Curves. the Values of B″(T) for the Ten States Are Determined, Then Averaged, and Used to Calculate the Lowest Order Non-Ideal Contribution to C _p .