Separability of Energy Components

We have thus reduced the problem from finding the ensemble partition function Q to finding the molecular partition function q. In order to make further progress, we assume that the molecular energy e can be expressed as a separable sum of electronic, translational, rotational, and vibrational terms, i.e., 

Note in Eqs. (10.3) and (10.5), Q always appears as the argument of the natural logarithm function. Using Eqs. (10.7) and (10.8), our assumptions to this point allow us to write 

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