188 research outputs found
Optically-stimulated desorption of 'hot' excimers from pre-irradiated Ar solids
Electronically-induced desorption from solid Ar pre-irradiated by a
low-energy electron beam was investigated by activation spectroscopy methods -
photon-stimulated exoelectron emission and photon-stimulated luminescence in
combination with spectrally-resolved measurements in the VUV range of the
spectrum. Desorption of vibrationally excited argon molecules Ar2^*(v) from the
surface of pre-irradiated solid Ar was observed for the first time. It was
shown that desorption of 'hot' Ar2^*(v) molecules is caused by recombination of
self-trapped holes with electrons released from traps by visible range photons.
The possibility of optical stimulation of the phenomenon is evidenced.Comment: The complete version of the paper will be published in Fiz. Nizk.
Temp. (Low Temp. Phys.
Electron traps in solid Xe
Correlated real-time measurements of thermally stimulated luminescence and exoelectron emission from solid Xe pre-irradiated with an electron beam were performed. The study enabled us to distinguish between surface and bulk traps in solid Xe and to identify a peak related to electronically induced defects. The activation energy corresponding to annihilation of these defects was estimated by the following methods: the method of different heating rates, the initial-rise method, and the curve cleaning technique with fitting of the thermally stimulated luminescence glow curve
Molecular structures and vibrations of neutral and anionic CuOx (x = 1-3,6) clusters
We report equilibrium geometric structures of CuO2, CuO3, CuO6, and CuO
clusters obtained by an all-electron linear combination of atomic orbitals
scheme within the density-functional theory with generalized gradient
approximation to describe the exchange-correlation effects. The vibrational
stability of all clusters is examined on the basis of the vibrational
frequencies. A structure with Cs symmetry is found to be the lowest-energy
structure for CuO2, while a -shaped structure with C2v symmetry is the most
stable structure for CuO3. For the larger CuO6 and CuO clusters, several
competitive structures exist with structures containing ozonide units being
higher in energy than those with O2 units. The infrared and Raman spectra are
calculated for the stable optimal geometries. ~Comment: Uses Revtex4, (Better quality figures can be obtained from authors
Relativistic separable dual-space Gaussian Pseudopotentials from H to Rn
We generalize the concept of separable dual-space Gaussian pseudopotentials
to the relativistic case. This allows us to construct this type of
pseudopotential for the whole periodic table and we present a complete table of
pseudopotential parameters for all the elements from H to Rn. The relativistic
version of this pseudopotential retains all the advantages of its
nonrelativistic version. It is separable by construction, it is optimal for
integration on a real space grid, it is highly accurate and due to its analytic
form it can be specified by a very small number of parameters. The accuracy of
the pseudopotential is illustrated by an extensive series of molecular
calculations
Simulation of thermal conductivity and heat transport in solids
Using molecular dynamics (MD) with classical interaction potentials we
present calculations of thermal conductivity and heat transport in crystals and
glasses. Inducing shock waves and heat pulses into the systems we study the
spreading of energy and temperature over the configurations. Phonon decay is
investigated by exciting single modes in the structures and monitoring the time
evolution of the amplitude using MD in a microcanonical ensemble. As examples,
crystalline and amorphous modifications of Selenium and are
considered.Comment: Revtex, 8 pages, 11 postscript figures, accepted for publication in
PR
Correct quantum chemistry in a minimal basis from effective Hamiltonians
We describe how to create ab-initio effective Hamiltonians that qualitatively
describe correct chemistry even when used with a minimal basis. The
Hamiltonians are obtained by folding correlation down from a large parent basis
into a small, or minimal, target basis, using the machinery of canonical
transformations. We demonstrate the quality of these effective Hamiltonians to
correctly capture a wide range of excited states in water, nitrogen, and
ethylene, and to describe ground and excited state bond-breaking in nitrogen
and the chromium dimer, all in small or minimal basis sets
- …