Internal energy I From statistics and quantum mechanics

3 Internal energy I From statistics and quantum mechanics 

Absolute energies are not known, because among other things the first level of each quantum set was arbitrarily taken as zero energy level. Let U be the symbol for the 

From now on the reference energy U° and the constant volume label will be considered implicit and will no longer appear. Then  

The total internal energy is a sum of contributions from translation, rotation and vibration. The translational part of U is given by 

Whenever a great many quantum levels are populated and the energy spectrum merges into a continuum, every quadratic term in molecular energies contributes 1/2RT to the internal 

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