  It is found out that there are physical effects, typical of small metal
clusters deposited on a non-adsorbing support, that cause a difference between
the adsorption properties of sites at the metal cluster surface and those of
sites at the boundary of metal-support. This difference gives rise to an extra
band in the IR spectra of the adsorbate whose major property is that its
intensity changes with cluster size.
  The migration of chemisorbed molecules (atoms, ions) and molecules (atoms,
ions) in any excited state over adsorption sites of different type results in
changes in the state of the molecule (atom, ion) since the latter adjusts its
state to the set of levels of another type of site. This can be described
figuratively as a transformation of the type of adsorption site. Thus, a single
type of adsorption site, called next surface effective site (SES), is formed.
The energy of desorption from SES site retains an explicit dependence on the
metal cluster size. A simulation of TPD spectra of oxygen desorption from small
Pt clusters deposited on NaX zeolite was carried out. A comparison to
experimental TPD spectra obtained by Jaeger and co-workers for the same system
is made.
