The dynamical polarisability and van der Waals dimer potential of mercury

Wolfsohn's parameters for the frequency-dependent polarisability alpha(omega) of mercury are modified to fit the recent interferometric measurements of Goebel and Hohm [J. Phys. Chem. 100, 7710 (1996)]. The resulting alpha(omega) are extended to imaginary frequencies alpha(i omega) and used to calculate the upper and lower bounds of the dipole dispersion coefficient in the long range dimer potential. The new value of C(6) = 392 +/- 4a.u. is much greater than the generally accepted value. With the corresponding changes in the dipole-quadrupole and dipole-octopole interactions, new dispersion coefficients C(8) and C(10) are obtained. Together with the experimentally determined D(e) (well-depth) and R(e) (equilibrium distance), the Tang-Toennies model is used to predict the shape of the entire dimer potential energy curve. The new potential is found to be in excellent agreement with the ab initio calculations of Munro et al. [J. Chem. Phys. 114, 5545 (2001)] and the parameters omega(e) and chi(e)omega(e) agree with the spectroscopic measurements within the small experimental errors.