Bigeleisen and Mayer The Reduced Isotopic Partition Function Ratio

4 Bigeleisen and Mayer The Reduced Isotopic Partition Function Ratio 

Bigeleisen and Mayer (Historical Vignettes 4.1 and 4.2), recognizing that the term in Equation 4.78 involving isotopic masses would always cancel in the calculation of 

4 Isotope Effects on Equilibrium Constants of Chemical Reactions 

Equation 4.79a points out the Reduced Isotopic Partition Function Ratio (RPFR) may be considered as the product of three factors the product factor (PF), the excitation factor (EXC), and the zero-point energy factor (ZPE). Note that in terms of RPFR s, the isotope effects corresponding to Equations 4.65, 4.66, and 4.68 can be written 

From Equation 4.79, it is then recognized that the isotope effect is given by a symmetry number factor and terms which depend only on the normal mode vibrational frequencies. There are no terms in the equality that depend explicitly on atomic and molecular masses or on moments of inertia. 

---