1,611 research outputs found
Quantum reflection of rare gas atoms and molecules from a grating
Quantum reflection is a universal property of atoms and molecules when
scattered from surfaces in ultracold collisions. Recent experimental work has
documented the quantum reflection and diffraction of He atoms, dimers, trimers
and Neon atoms when reflected from a grating. Conditions for the observation of
emerging beam resonances have been discussed and measured. In this paper, we
provide a theoretical simulation of the quantum reflection in these cases from
a grating. We confirm, as expected the universal dependence on the incident de
Broglie wavelength only of the threshold angles for the observation of emerging
beam resonances. However, the angular dependence of the reflection
efficiencies, that is the ratio of scattered intensity into specific
diffraction channels relative to the total intensity is found to be dependent
on the specifics of the incident particle. The dependence of the reflection
efficiency on the identity of the particle is intimately related to the fact
that the incident energy dependence of quantum reflection depends on the
details of the particle surface interaction.Comment: 18 pages, 5 figures, 2 table
Theoretical study of "trapping sites" in cryogenic rare gas solids doped with β-dicarbonyl molecules
International audienceA deposition model to simulate the growth of doped rare gas crystals is used. The study involves organic molecules with a single intramolecular hydrogen bond such as malonaldehyde, 2chloromalonaldehyde and acetylacetone as impurities. Different trapping sites were obtained depending on the rare gas properties for a given impurity, and depending on the molecular size and shape for a given crystal. Simulations were carried out by using classical molecular dynamics methods including an anharmonic thermal correction, to take into account the zero point movement of the crystal. The results are correlated to spectroscopic data previously achieved for these systems by steady state IR spectroscopy
Effects of trapping site on the spectroscopy of 1P1 excited group 12 metal atoms in rare gas matrices
A molecular dynamics deposition model has been used to simulate the growth of rare gas matrices doped with atoms of the group 12 elements zinc, cadmium and mercury. This study investigates the sites occupied by Zn, Cd and Hg metal atoms when isolated in the solid rare gases. To probe the results, the resonance 1 P 1-1 S 0 transitions of the matrix-isolated metal atoms were calculated and compared with the recorded spectra of the M/RG solids. The theoretical spectroscopy obtained in this work was generated using the molecular dynamics with quantum transitions method. In Ne matrices the metal atoms preferably occupy tetra- and hexa-vacancy sites while in the case of Xe matrices, only the single vacancy site is formed. For Ar and Kr matrices Zn but especially Cd can be trapped in tetra- and hexa-vacancy sites in addition to single-vacancy sites, while Hg atoms show exclusive occupancy in single vacancy sites.Fil: Lara Moreno, M.. Universidad de La Habana; Cuba. Instituto Superior de Tecnologías y Ciencias Aplicadas.; Cuba. Université de Bordeaux; Francia. Centre National de la Recherche Scientifique; FranciaFil: Alvarez Hernández, J.. Universidad de La Habana; Cuba. Instituto Superior de Tecnologías y Ciencias Aplicadas.; Cuba. University of Rochester. Department of Chemistry; Estados UnidosFil: Negrín Yuvero, Lázaro Hassiel. Universidad de La Habana; Cuba. Instituto Superior de Tecnologías y Ciencias Aplicadas.; Cuba. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: McCaffrey, J. G.. National University of Ireland. Maynooth University. Department of Chemistry; IrlandaFil: Rojas Lorenzo, G.. Universidad de La Habana; Cuba. Instituto Superior de Tecnologías y Ciencias Aplicadas.; Cub
A Langevin Canonical Approach to the Study of Quantum Stochastic Resonance in Chiral Molecules
A Langevin canonical framework for a chiral two-level system coupled to a bath of harmonic oscillators is used within a coupling scheme different from the well-known spin-boson model to study the quantum stochastic resonance for chiral molecules. This process refers to the amplification of the response to an external periodic signal at a certain value of the noise strength, being a cooperative effect of friction, noise, and periodic driving occurring in a bistable system. Furthermore, from this stochastic dynamics within the Markovian regime and Ohmic friction, the competing process between tunneling and the parity violating energy difference present in this type of chiral systems plays a fundamental role. This mechanism is finally proposed to observe the so-far elusive parity-violating energy difference in chiral molecules.Helen Clara Peñate-Rodríguez and Germán Rojas-Lorenzo acknowledge a scientific project
from InSTEC. Pedro Bargueño acknowledge the support from the Faculty of Science and Vicerrectoría de
Investigaciones of Universidad de Los Andes, Bogotá, Colombia. Salvador Miret-Artés acknowledges a grant
with Ref. FIS2014-52172-C2-1-P from the Ministerio de Economía y Competitividad (Spain).
We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)
Linear response theory of activated surface diffusion with interacting adsorbates
Activated surface diffusion with interacting adsorbates is analyzed within
the Linear Response Theory framework. The so-called interacting single
adsorbate model is justified by means of a two-bath model, where one harmonic
bath takes into account the interaction with the surface phonons, while the
other one describes the surface coverage, this leading to defining a
collisional friction. Here, the corresponding theory is applied to simple
systems, such as diffusion on flat surfaces and the frustrated translational
motion in a harmonic potential. Classical and quantum closed formulas are
obtained. Furthermore, a more realistic problem, such as atomic Na diffusion on
the corrugated Cu(001) surface, is presented and discussed within the classical
context as well as within the framework of Kramer's theory. Quantum corrections
to the classical results are also analyzed and discussed.Comment: 40 pages, 4 figure
Quantum Zeno and anti-Zeno effects in surface diffusion of interacting adsorbates
Surface diffusion of interacting adsorbates is here analyzed within the
context of two fundamental phenomena of quantum dynamics, namely the quantum
Zeno effect and the anti-Zeno effect. The physical implications of these
effects are introduced here in a rather simple and general manner within the
framework of non-selective measurements and for two (surface) temperature
regimes: high and very low (including zero temperature). The quantum
intermediate scattering function describing the adsorbate diffusion process is
then evaluated for flat surfaces, since it is fully analytical in this case.
Finally, a generalization to corrugated surfaces is also discussed. In this
regard, it is found that, considering a Markovian framework and high surface
temperatures, the anti-Zeno effect has already been observed, though not
recognized as such.Comment: 17 pages, 1 figur
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