  We study the dependence of the heat transfer and the van der Waals friction
between two semi-infinite solids on the dielectric properties of the bodies. We
show that the heat transfer and van der Waals friction at short separation
between the solids may increase by many orders of magnitude when the surfaces
are covered by adsorbates, or can support low-frequency surface plasmons. In
this case the heat transfer and van der Waals friction are determined by
resonant photon tunneling between adsorbate vibrational modes, or surface
plasmon modes. The enhancement of the van der Waals friction is especially
large when in the adsorbed layer there is an acoustic branch for the vibrations
parallel to the surface like in the case of Cs adsorption on Cu(100) surface.
In this case we show that even for separation $d=10$nm, the van der Waals
friction induced by adsorbates can be so large that it can be measured with the
present state-of-art equipment. The van an der Waals friction is characterized
by a strong distance dependence ($\sim 1/d^6$), and at the small distances it
can be much larger than \textit{the electrostatic} friction observed in
\cite{Stipe}. \vskip 0.3cm \textit{Keywords}: non-contact friction, van der
Waals friction, radiative heat transfer, atomic force microscope, adsorbate
vibrational mode
