Isotope effects on intermolecular interactions and isotopic vapor pressure differences

The isotope effect on the part of the van der Waals interaction resulting from vibrational excitation terms has been discussed in great detail to show that it is a zero-point energy effect. Interaction between rotational, translational, and vibrational motion in the condensed phase has been also discussed in detail in terms of a very simple model. By the use of approximation methods, the order of magnitude of these effects is demonstrated and it is shown that consideration of them is of importance in connection with vapor pressure isotope effects. Some other origins of vapor pressure isotope effects are cursorily discussed