2,467 research outputs found
A room temperature CO line list with ab initio computed intensities
Atmospheric carbon dioxide concentrations are being closely monitored by
remote sensing experiments which rely on knowing line intensities with an
uncertainty of 0.5% or better. We report a theoretical study providing
rotation-vibration line intensities substantially within the required accuracy
based on the use of a highly accurate {\it ab initio} dipole moment surface
(DMS). The theoretical model developed is used to compute CO intensities
with uncertainty estimates informed by cross comparing line lists calculated
using pairs of potential energy surfaces (PES) and DMS's of similar high
quality. This yields lines sensitivities which are utilized in reliability
analysis of our results. The final outcome is compared to recent accurate
measurements as well as the HITRAN2012 database. Transition frequencies are
obtained from effective Hamiltonian calculations to produce a comprehensive
line list covering all CO transitions below 8000 cm
and stronger than 10 cm / molecule at ~
Mathematical modelling of thermal and kinetic phenomena in electron-beam technologies
The article presents a scheme for constructing models using kinetic laws for additional parameters. The work describes the example of the model of electro-beam treatment of a material with a coating. The study uses the simple kinetic law for powder layer evolution due to shrinkage. The model takes into account the melting of powder layer and substrate. The numerical solution gives the temperature field, evolution of the molten pool, the heat affected zone and the surface relief for different moments of time. The results depend on the treatment rate and electron beam energy
Coherent population trapping resonances with linearly polarized light for all-optical miniature atomic clocks
We present a joint theoretical and experimental characterization of the
coherent population trapping (CPT) resonance excited on the D1 line of 87Rb
atoms by bichromatic linearly polarized laser light. We observe high-contrast
transmission resonances (up to 25%), which makes this excitation scheme
promising for miniature all-optical atomic clock applications. We also
demonstrate cancellation of the first-order light shift by proper choice of the
frequencies and relative intensities of the two laser field components. Our
theoretical predictions are in good agreement with the experimental results.Comment: 8 pages, 7 figure
The characteristic time of glucose diffusion measured for muscle tissue at optical clearing
The study of agent diffusion in biological tissues is very important to understand and characterize the optical clearing effects and mechanisms involved: tissue dehydration and refractive index matching. From measurements made to study the optical clearing, it is obvious that light scattering is reduced and that the optical properties of the tissue are controlled in the process. On the other hand, optical measurements do not allow direct determination of the diffusion properties of the agent in the tissue and some calculations are necessary to estimate those properties. This fact is imposed by the occurrence of two fluxes at optical clearing: water typically directed out of and agent directed into the tissue. When the water content in the immersion solution is approximately the same as the free water content of the tissue, a balance is established for water and the agent flux dominates. To prove this concept experimentally, we have measured the collimated transmittance of skeletal muscle samples under treatment with aqueous solutions containing different concentrations of glucose. After estimating the mean diffusion time values for each of the treatments we have represented those values as a function of glucose concentration in solution. Such a representation presents a maximum diffusion time for a water content in solution equal to the tissue free water content. Such a maximum represents the real diffusion time of glucose in the muscle and with this value we could calculate the corresponding diffusion coefficient
Multiphoton localization and propagating quantum gap solitons in a frequency gap medium
The many-particle spectrum of an isotropic frequency gap medium doped with
impurity resonance atoms is studied using the Bethe ansatz technique. The
spectrum is shown to contain pairs of quantum correlated ``gap excitations''
and their heavy bound complexes (``gap solitons''), enabling the propagation of
quantum information within the classically forbidden gap. In addition,
multiparticle localization of the radiation and the medium polarization occurs
when such a gap soliton is pinned to the impurity atom.Comment: 8 pages, RevTEX, to appear in Phys. Rev. Let
Complete transfer of populations from a single state to a pre-selected superposition of states using Piecewise Adiabatic Passage
We develop a method for executing robust and selective transfer of
populations between a single level and pre-selected superpositions of energy
eigenstates. Viewed in the frequency domain, our method amounts to executing a
series of simultaneous adiabatic passages into each component of the target
superposition state. Viewed in {the} time domain, the method works by
accumulating the wavefunction of the target wave packet as it revisits the
Franck Condon region, in what amounts to an extension of the Piecewise
Adiabatic Passage technique [ Shapiro et.al., Phys. Rev. Lett. 99, 033002
(2007)] to the multi-state regime. The viability of the method is verified by
performing numerical tests for the Na_2 molecule.Comment: 8 pages, 4 figure
Optical conductivity of metal nanofilms and nanowires: The rectangular-box model
The conductivity tensor is introduced for the low-dimensional electron
systems. Within the particle-in-a-box model and the diagonal response
approximation, components of the conductivity tensor for a quasi-homogeneous
ultrathin metal film and wire are calculated under the assumption (where is the characteristic small dimension of the
system, is the Fermi wavelength for bulk metal). We find the
transmittance of ultrathin films and compare these results with available
experimental data. The analytical estimations for the size dependence of the
Fermi level are presented, and the oscillations of the Fermi energy in
ultrathin films and wires are computed. Our results demonstrate the strong size
and frequency dependences of the real and imaginary parts of the conductivity
components in the infrared range. A sharp distinction of the results for Au and
Pb is observed and explained by the difference in the relaxation time of these
metals.Comment: 13 pages, 8 figure
Ground State Properties of Anderson Impurity in a Gapless Host
Using the Bethe ansatz method, we study the ground state properties of a
Anderson impurity in a ``gapless'' host, where a density of band
states vanishes at the Fermi level as . As
in metals, the impurity spin is proven to be screened at arbitrary parameters
of the system. However, the impurity occupancy as a function of the bare
impurity energy is shown to acquire novel qualitative features which
demonstrate a nonuniversal behavior of the system. The latter explains why the
Kondo screening is absent (or exists only at quite a large electron-impurity
coupling) in earlier studies based on scaling arguments.Comment: 5 pages, no figure, RevTe
The low-frequency response in the surface superconducting state of ZrB single crystal}
The large nonlinear response of a single crystal ZrB to an ac field
(frequency 40 - 2500 Hz) for has been observed. Direct
measurements of the ac wave form and the exact numerical solution of the
Ginzburg-Landau equations, as well as phenomenological relaxation equation,
permit the study of the surface superconducting states dynamics. It is shown,
that the low frequency response is defined by transitions between the
metastable superconducting states under the action of an ac field. The
relaxation rate which determines such transitions dynamics, is found.Comment: 7 pages, 11 figure
- …