Effective pair interaction and the Van der Waals constants for second-layer helium atoms in bilayer films

Abstract

The effects of surface normal vibration on the effective pair interaction for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atoms in the second layer of a bilayer has been calculated. The single-particle potential for atoms in the second layer included pair interactions between the second-layer ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atom and fixed carbon atoms in the graphite plus the pair interaction between the second-layer ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atom and an oscillating first layer. The shift in the pair interaction between the second-layer atoms is about 10-15% of the "bare" interaction. Rough estimates were made of the effect upon the Van der Waals constants for the second-layer imperfect gas and these estimates were compared to empirical values.