The quantum corrections for the second gasndash;surface virial coefficient are derived and applied to the experimental data for H2, D2, CH4, and CD4in the external field provided by a uniform graphite surface. These corrections cause quite sizable differences in the interaction energies and areas obtained for the hydrogen pair, but the differences are, of course, small in the case of the methanes. Quantum effects have been measured in dilute adsorption systems and found to be of considerable importance. Theoretically, Yaris and Sams have developed the second gasndash;surface virial coefficientBASfrom the Wignerndash;Kirkwood expansion to orderplanck;4and examined three different models for the gasndash;surface interaction potential, using the data of Constabariset al. Due to a misprint in theplanck;4term of Uhlenbeck and Beth, which has been carried through in the calculations of Yaris and Sams, we have recalculated the quantum correctedBASand fitted it to the data mentioned above.
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