622 research outputs found
Post-Prior discrepancies in CDW-EIS calculations for ion impact ionization fully differential cross sections
In this work we present fully differential cross sections (FDCSs)
calculations using post and prior version of CDW--EIS theory for helium single
ionization by 100 MeV C amu and 3.6 MeV amu Au and
Au ions. We performed our calculations for different momentum transfer
and ejected electron energies. The influence of internuclear potential on the
ejected electron spectra is taken into account in all cases. We compare our
calculations with absolute experimental measurements. It is shown that prior
version calculations give better agreement with experiments in almost all
studied cases.Comment: 9 pages, 7 figure
Extension of charge-state-distribution calculations for ion-solid collisions towards low velocities and many-electron ions
Knowledge of the detailed evolution of the whole charge-state distribution of projectile ions colliding with targets is required in several fields of research such as material science and atomic and nuclear physics but also in accelerator physics, and in particular in regard to the several foreseen large-scale facilities. However, there is a lack of data for collisions in the nonperturbative energy domain and that involve many-electron projectiles. Starting from the etacha model we developed [Rozet, Nucl. Instrum. Methods Phys. Res., Sect. B 107, 67 (1996)10.1016/0168-583X(95)00800-4], we present an extension of its validity domain towards lower velocities and larger distortions. Moreover, the system of rate equations is able to take into account ions with up to 60 orbital states of electrons. The computed data from the different new versions of the etacha code are compared to some test collision systems. The improvements made are clearly illustrated by 28.9MeVu-1Pb56+ ions, and laser-generated carbon ion beams of 0.045 to 0.5MeVu-1, passing through carbon or aluminum targets, respectively. Hence, those new developments can efficiently sustain the experimental programs that are currently in progress on the "next-generation" accelerators or laser facilities.Fil: Lamour, E.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Fainstein, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Galassi, Mariel Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Prigent, C.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Ramirez, C. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rozet, J. P.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Trassinelli, M.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Vernhet, D.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; Franci
Uncoupled excitons in semiconductor microcavities detected in resonant Raman scattering
We present an outgoing resonant Raman-scattering study of a GaAs/AlGaAs based microcavity embedded in a p-i-n junction. The p-i-n junction allows the vertical electric field to be varied, permitting control of exciton-photon detuning and quenching of photoluminescence which otherwise obscures the inelastic light scattering signals. Peaks corresponding to the upper and lower polariton branches are observed in the resonant Raman cross sections, along with a third peak at the energy of uncoupled excitons. This third peak, attributed to disorder activated Raman scattering, provides clear evidence for the existence of uncoupled exciton reservoir states in microcavities in the strong-coupling regime
Theory of high-order harmonic generation from molecules by intense laser pulses
We show that high-order harmonics generated from molecules by intense laser
pulses can be expressed as the product of a returning electron wave packet and
the photo-recombination cross section (PRCS) where the electron wave packet can
be obtained from simple strong-field approximation (SFA) or from a companion
atomic target. Using these wave packets but replacing the PRCS obtained from
SFA or from the atomic target by the accurate PRCS from molecules, the
resulting HHG spectra are shown to agree well with the benchmark results from
direct numerical solution of the time-dependent Schr\"odinger equation, for the
case of H in laser fields. The result illustrates that these powerful
theoretical tools can be used for obtaining high-order harmonic spectra from
molecules. More importantly, the results imply that the PRCS extracted from
laser-induced HHG spectra can be used for time-resolved dynamic chemical
imaging of transient molecules with temporal resolutions down to a few
femtoseconds.Comment: 10 pages, 5 figure
Microcavity exciton-polariton mediated Raman scattering: Experiments and theory
We studied the intensity of resonant Raman scattering due to optical phonons
in a planar II-VI-type semiconductor microcavity in the regime of strong
coupling between light and matter. Two different sets of independent
experiments were performed at near outgoing resonance with the middle polariton
(MP)branch of the cavity. In the first, the Stokes-shifted photons were kept at
exact resonance with the MP, varying the photonic or excitonic character of the
polariton. In the second, only the incoming light wavelength was varied, and
the resonant profile of the inelastic scattered intensity was studied when the
system was tuned out of the resonant condition. Taking some matrix elements as
free parameters, both independent experiments are quantitatively described by a
model which incorporates lifetime effects in both excitons and photons, and the
coupling of the cavity photons to the electron-hole continuum. The model is
solved using a Green's function approach which treats the exciton-photon
coupling nonperturbatively.Comment: 10 pages, 6 figure
Structural analysis, magnetic and transport properties of the (Ru1-xCox)Sr2GdCu2O8 system
The effects of Co substitution on structural and superconducting properties
of RuSr2GdCu2O8 compound have been studied. Rietveld refinements of the X-ray
diffraction patterns indicate that the cobalt ion progressively replaces
ruthenium sites. This replacement induces significant changes on the crystal
structure and on the magnetic and superconducting properties. The effects Co
substitution on the superconducting behaviour, and more particulary on the
changes induce by the hole doping mechanism, were investigated in
(Ru1-xCox)Sr2GdCu2O8 by a "bond valence sum" analysis with Co content from x=
0.0 to x = 0.2. The weak ferromagnetic transition at Tm= 138.2 K is shifted to
lower temperature, and suppressed at higher Co content. From the
crystallographic point of view the Ru-O(1)-Cu bond angle, associated to the
rotation of the RuO6 octahedra, around the c-axis remain essetially constant
when Ru is substituted by Co. Furthermore, increasing Co content has the effect
to increase the weak ferromagnetic moment, which may be interpreted as the main
responsible for breaking the delicate balance between magnetic and
superconducting ordering.Comment: 21 pages, 8 figure
Just urban transitions: Toward a research agenda
While there are excellent policy and academic foundations for thinking about and making sense of urban climate action and questions of justice and climate change independently, there is less work that considers their intersection. The nature and dynamics of, and requirements for, a just urban transition (JUT)—the fusion of climate action and justice concerns at the urban scale—are not well understood. In this review article we seek to rectify this by first examining the different strains of justice scholarship (environmental, energy, climate, urban) that are informing and should inform JUT. We then turn to a discussion of just transitions in general, tracing the history of the term and current understandings in the literature. These two explorations provide a foundation for considering both scholarly and policy‐relevant JUT agendas. We identify what is still needed to know in order to recognize, study, and foster JUT.This article is categorized under:The Carbon Economy and Climate Mitigation > Benefits of MitigationClimate, Nature, and Ethics > Climate Change and Global JusticeJust urban transitions research and policy agendas center alternative urban futures: cities where the distribution of environmental risks and benefits do not disproportionately burden marginalized groups; where decision‐making is transparent, engaged, and democratic; and where policies seek to remedy structural inequalities and prior injustices.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154981/1/wcc640_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154981/2/wcc640.pd
R-matrix Floquet theory for laser-assisted electron-atom scattering
A new version of the R-matrix Floquet theory for laser-assisted electron-atom
scattering is presented. The theory is non-perturbative and applicable to a
non-relativistic many-electron atom or ion in a homogeneous linearly polarized
field. It is based on the use of channel functions built from field-dressed
target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.
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