120 research outputs found
Simulations of Time-Resolved X-Ray Diffraction in Laue Geometry
A method of computer simulation of Time-Resolved X-ray Diffraction (TRXD) in
asymmetric Laue (transmission) geometry with an arbitrary propagating strain
perpendicular to the crystal surface is presented. We present two case studies
for possible strain generation by short-pulse laser irradiation: (i) a
thermoelastic-like analytic model; (ii) a numerical model including effects of
electron-hole diffusion, Auger recombination, deformation potential and thermal
diffusion. A comparison with recent experimental results is also presented.Comment: 9 pages, 11 figure
Investigation of M1 transitions of the ground-state configuration of In-like Tungsten
Three visible lines of M1 transitions from In-like W were recorded using the
Shanghai permanent magnet electron beam ion trap. The experimental wavelengths
were measured as 493.84 0.15, 226.97 0.13 and 587.63 0.23 nm
(vacuum wavelengths). These results are in good agreement with theoretical
predictions obtained using large-scale Relativistic Many-Body Perturbation
Theory, in the form of the Flexible Atomic Code.Comment: 7 pages, 3 figure
Atomic Processes in Planetary Nebulae and H II Regions
Spectroscopic studies of Planetary Nebulae (PNe) and H {\sc ii} regions have
driven much development in atomic physics. In the last few years the
combination of a generation of powerful observatories, the development of ever
more sophisticated spectral modeling codes, and large efforts on mass
production of high quality atomic data have led to important progress in our
understanding of the atomic spectra of such astronomical objects. In this paper
I review such progress, including evaluations of atomic data by comparisons
with nebular spectra, detection of spectral lines from most iron-peak elements
and n-capture elements, observations of hyperfine emission lines and analysis
of isotopic abundances, fluorescent processes, and new techniques for
diagnosing physical conditions based on recombination spectra. The review is
directed toward atomic physicists and spectroscopists trying to establish the
current status of the atomic data and models and to know the main standing
issues.Comment: 9 pages, 1 figur
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Production of Very Cold, Highly Charged Ions by Synchrotron Radiation: Comparisons of the ''Scalpel'' and ''Hammer'' Methods
Measurements of kinetic energies of highly charged argon ions produced by inner-shell photoionization and by ion-beam impact have been made using time-of-flight techniques. High-charge-state recoil ions produced by beams of approx..5 - 1 MeV/u Cl/sup +5/ are found to have energies one to two orders of magnitude higher than ions of the same charge produced by vacancy cascades following inner-shell photoionization by synchrotron radiation. The results may have application to the development of a very-cold ion source useful for angle-resolved atomic collision studies
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Ultrafast Coherent Diffraction Imaging with X-ray Free-Electron Lasers
The ultrafast pulses from X-ray free-electron lasers will enable imaging of non-periodic objects at near-atomic resolution [1, Neutze]. These objects could include single molecules, protein complexes, or virus particles. The specimen would be completely destroyed by the pulse in a Coulomb explosion, but that destruction will only happen after the pulse. The scattering from the sample will give structural information about the undamaged object. There are many technical challenges that must be addressed before carrying out such experiments at an XFEL, which we are doing so with experiments at FLASH, the soft-X-ray FEL at DESY
Reinfecção pelo Toxoplasma gondii Nicolle & Manceaux, 1909 em camundongos e gatos: estudo experimental
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Convoy electron production in polycrystalline and monocrystalline targets
The velocity distribution of electrons ejected close to the forward direction by 0.8-2 MeV/A ions traversing various solid targets, including a Au monocrystal, is measured in coincidence with emerging charge-selected ions. The velocity spectrum is observed to be independent of outgoing projectile velocity and charge state for polycrystalline targets. Measurements on the Au crystal under channeling conditions show dependences on final charge state, and are tentatively explained by assuming that the main contribution to the production yield comes from the non-channeled fraction of the ions. A simple model for the creation of the forward-ejected electrons is proposed, which accounts for most of the experimental findings
A CONVENIENT DOPPLER SHIFT METHOD FOR DETERMINING THE VELOCITY OF A FAST ION BEAM
On décrit une méthode de détermination de la vitesse d'un faisceau d'ions qui est basée sur l'effet Doppler. Quelques applications sont présentées.A convenient method for determining the velocity of a light emitting fast ion beam utilizing fore and aft Doppler shifts is described, and applications are presented
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