173 research outputs found
Renormalized theory of the ion cyclotron turbulence in magnetic field--aligned plasma shear flow
The analytical treatment of nonlinear evolution of the shear-flow-modified
current driven ion cyclotron instability and shear-flow-driven ion cyclotron
kinetic instabilities of magnetic field--aligned plasma shear flow is
presented. Analysis is performed on the base of the nonlinear dispersion
equation, which accounts for a new combined effect of plasma turbulence and
shear flow. It consists in turbulent scattering of ions across the shear flow
with their convection by shear flow and results in enhanced nonlinear
broadening of ion cyclotron resonances. This effect is found to lead to the
saturation of ion cyclotron instabilities as well as to the development of
nonlinear shear flow driven ion cyclotron instability. 52.35.RaComment: 21 page
Renormalized non-modal theory of the kinetic drift instability of plasma shear flows
The linear and renormalized nonlinear kinetic theory of drift instability of
plasma shear flow across the magnetic field, which has the Kelvin's method of
shearing modes or so-called non-modal approach as its foundation, is developed.
The developed theory proves that the time-dependent effect of the finite ion
Larmor radius is the key effect, which is responsible for the suppression of
drift turbulence in an inhomogeneous electric field. This effect leads to the
non-modal decrease of the frequency and growth rate of the unstable drift
perturbations with time. We find that turbulent scattering of the ion gyrophase
is the dominant effect, which determines extremely rapid suppression of drift
turbulence in shear flow
Ion-kinetic D'Angelo mode
An extension of hydrodynamic D'Angelo mode of inhomogeneous sheared plasma
flow along the magnetic field into the short-wavelength limit, where the
hydrodynamic treatment is not valid, has been considered. We find that D'Angelo
mode in this wavelength range is excited by inverse ion Landau damping and
becomes the shear flow driven ion-kinetic mode.Comment: 9 pages, 1 figur
Cavity ring down spectroscopy of water vapour near 750 nm: a test of the HITRAN2020 and W2020 line lists
Cavity ring down spectroscopy (CRDS) is used to measure with unprecedented sensitivity and accuracy the weak water vapour spectrum in the 13,171–13,417 cm−1 region. A total of more than 1400 water lines are rovibrationally assigned to four isotopologues in natural isotopic abundance (H216O, H218O, H217O and HD16O), leading to the determination of 151 new levels and correction of 160 levels. The review of previous experimental works in the region is discussed. The comparison to the recent HITRAN2020 spectroscopic databases and to the W2020 line lists [Furtenbacher et al. J. Phys. Chem. Ref. Data 49 (2020) 043103; doi:10.1063/5.0030680] shows important discrepancies both for line positions and line intensities. A significant fraction of the W2020 line positions is inaccurate and shows deviations compared to measurements largely exceeding their claimed error bars. Line intensities are poorly predicted by available ab initio calculations in the considered region. A recommended line list mostly based on the present CRDS measurements is proposed. © 2022 Informa UK Limited, trading as Taylor & Francis Group.IAO-TomskCentre National de la Recherche Scientifique, CNRS, (IRP SAMIA)Ministry of Science and Higher Education of the Russian FederationFunding text 1: The support of the CNRS (France) in the frame of International Research Project SAMIA is acknowledged. CRDS measurements and spectrum analysis were performed at IAO-Tomsk and funded by Ministry of Science and High Education of the Russian Federation.Funding text 2: This work was supported by Centre National de la Recherche Scientifique [grant number IRP SAMIA]. The support of the CNRS (France) in the frame of International Research Project SAMIA is acknowledged. CRDS measurements and spectrum analysis were performed at IAO-Tomsk and funded by Ministry of Science and High Education of the Russian Federation
Water Vapor Absorption in the Region of the Oxygen A-Band Near 760 nm
The oxygen A-band near 760 nm is used to determine the air-mass along the line of sight from ground or space borne atmospheric spectra. This band is located in a spectral region of very weak absorption of water vapor. The increased requirements on the determination of the air columns make suitable to accurately characterize water absorption spectrum in the region. In the present work, we use a cavity ring down spectrometer newly developed in Tomsk, to measure with unprecedented sensitivity and accuracy the water spectrum in the 12969 - 13172 cm−1 region. While about fifty transitions were previously detected in the region, a total of about 580 water lines are measured by CRDS and rovibrationally assigned, leading to the determination of 103 new levels and correction of 134 levels of H216O. Spectroscopic line lists available in the region (HITRAN, W2020 and theoretical line lists) show some important deviations compared to observations. In particular, line intensities are poorly predicted by available ab initio calculations for transitions involving a highly bending excitation. © 2021 Elsevier Ltd.The support of the CNRS (France) in the frame of International Research Project SAMIA is acknowledged. CRDS measurements and spectrum analysis were performed at IAO-Tomsk and funded by RFBR project 20-32-70054
Validation Tests of the W2020 Energy Levels of Water Vapor
A decade ago, a task group of the International Union of Pure and Applied Chemistry performed an exhaustive collection and review of measured transitions, applied the MARVEL procedure, and derived recommended empirical energy levels for nine major water isotopologues. Very recently, using an improved methodology, the sets of empirical energy levels of H216O, H218O and H217O were updated, leading to the so-called W2020 energy levels and transition wavenumbers [Furtenbacher et al. J. Phys. Chem. Ref. Data 49 (2020) 043103; 10.1063/5.0030680]. Here we present validation tests of the W2020 line list of H216O against spectra recorded by cavity ring down spectroscopy (CRDS) referenced to a frequency comb (FC), newly obtained in the 8040-8630 cm−1 region. The recorded spectra are found in excellent agreement with previous high-quality studies available in the literature. While these literature sources were all incorporated in the transition database used to derive the W2020 energy levels, the direct superposition of the FC-CRDS spectra to the W2020 line list of H216O shows a number of large disagreements. Cases where deviations largely exceed the W2020 claimed uncertainty on the transition frequencies are noted. In the considered spectral region, the resulting W2020 list is thus less accurate than some of the published original sources used to derive the W2020 energy levels. We conclude that the sophisticated global procedure and algorithm elaborated to identify and adequately weight inaccurate line positions among the large W2020 transition database do not always prevent less accurate data from “spoiling” higher quality data sources. The W2020 list of H216O is also compared to newly recorded CRDS spectra in the 12970–13200 cm−1 region (corresponding to the region of the A-band of O2), where previous observations were very scarce. As in the previous region, substantial position deviations are evidenced, and in many cases, the W2020 error bars appear to be strongly underestimated. © 2021 Elsevier LtdThe support of the CNRS (France) in the frame of International Research Project SAMIA is acknowledged. SNM activity was also partly supported in the frame of the Russian Science Foundation, Grant No. 18-11-00024-Π. CRDS measurements near 760 nm were performed at IAO-Tomsk and funded by RFBR project 20-32-70054
Influence of Gamma-X mixing on optical orientation and alignment of excitons in (In,Al)As/AlAs quantum dots
The effect of Gamma-X mixing on the energy levels fine structure of indirect
in k-space excitons in an ensemble of (In,Al)As/AlAs quantum dots with type I
band alignment was experimentally studied. Using the methods of optical spin
orientation and optical alignment in a magnetic field, an increase in the
anisotropic exchange splitting of excitonic levels (from approximately 0.6 to 5
ueV) due to the Gamma-X mixing was revealed. The extent of direct electronic
states admixing to indirect ones depends on the size of the quantum dot. On the
other hand, the optical and spin properties of excitons change radically with
increasing of the Gamma states admixture to the X states: in the absence of a
magnetic field, the optical orientation of excitons decreases from 18 to 3%,
while the alignment of excitons is restored from 6 to 53%.Comment: 12 page
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