Improved approximation of water dielectric permittivity for calculation ofHamaker constants

Due to the highly polar nature with a multipeak absorption spectrum of wate r, the contribution of the relaxation in the microwave and infrared regions to the water dielectric spectrum is significant. The old data obtained by the Cauchy plot analysis of the parameters of the single-relaxation represe ntation of water dielectric spectrum produce the discrepancy in the Hamaker constants computed by the complete continuum theory. New data are obtained by the direct fitting of the single-relaxation model to the complete water dielectric spectrum. The Hamaker constants computed using the improved app roximate and the complete spectra for water permittivity are in good agreem ent. The Hamaker function of quartz-water-quartz and quartz-water-air syste ms computed using the improved approximation for water and the Cauchy plot approximation for quartz also agrees with that computed using the complete spectrum for both liquid water and crystalline quartz. The new data are to be used, instead of the old Cauchy plot analysis data, in the calculation o f the van der Waals interaction across water films based on the available s implified expressions, (C) 2000 Academic Press.