327 research outputs found
Low‐temperature (4.2°K) study of the 2E1u ←2E2g band system in the electronic spectra of various ferricenium compounds
A Monte Carlo study of temperature-programmed desorption spectra with attractive lateral interactions
We present results of a Monte Carlo study of temperature-programmed
desorption in a model system with attractive lateral interactions. It is shown
that even for weak interactions there are large shifts of the peak maximum
temperatures with initial coverage. The system has a transition temperature
below which the desorption has a negative order. An analytical expression for
this temperature is derived. The relation between the model and real systems is
discussed.Comment: Accepted for publication in Phys.Rev.B15, 10 pages (REVTeX), 2
figures (PostScript); discussion about Xe/Pt(111) adde
Modeling Elementary Heterogeneous Chemistry and Electrochemistry in Solid-Oxide Fuel Cells
Study of levitating nanoparticles using ultracold neutrons
Physical adsorption of atoms, molecules and clusters on surface is known. It
is linked to many phenomena in physics, chemistry, and biology. Usually the
studies of adsorption are limited to the particle sizes of up to ~10^2-10^3
atoms. Following a general formalism, we apply it to even larger objects and
discover qualitatively new phenomena. A large particle is bound to surface in a
deep and broad potential well formed by van der Waals/ Casimir-Polder forces.
The well depth is significantly larger than the characteristic thermal energy.
Nanoparticles in high-excited bound states form two-dimensional gas of objects
quasi-freely traveling along surface. A particularly interesting prediction is
small-energy-transfer scattering of UCN on solid/ liquid surfaces covered by
such levitating nanoparticles/ nano-droplets. The change in UCN energy is due
to the Doppler shift induced by UCN collisions with nanoparticles; the energy
change is about as small as the UCN initial energy. We compare theoretical
estimations of our model to all relevant existing data and state that they
agree quite well. As our theoretical formalism provides robust predictions and
the experimental data are rather precise, we conclude that the recently
discovered intriguing phenomenon of small heating of UCN in traps is due to
their collisions with such levitating nanoparticles. Moreover, this new
phenomenon might be relevant to the striking contradiction between results of
the neutron lifetime measurements with smallest reported uncertainties as it
might cause major false effects in these experiments; thus it affects
fundamental conclusions concerning precision checks of unitarity of the
Cabibbo-Kobayashi-Maskawa matrix, cosmology, astrophysics. Dedicated
measurements of UCN up-scattering on specially prepared surfaces and
nanoparticles levitating above them might provide a unique method to study
surface potentials.Comment: 20 pages, 12 figure
Missing dimer defects investigated by adsorption of nitric oxide (NO) on silicon (100) 2 × 1
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