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Jérôme Deprince Manuel Bautista Stephan Fritzsche Javier García Timothy Kallman Claudio Mendoza Patrick Palmeri Pascal Quinet 《X射线光谱测定》2020,49(1):29-32
In the present work, we report an investigation of plasma environment effects on the atomic parameters associated with the K-vacancy states in highly charged iron ions within the astrophysical context of accretion disks around black holes. More particularly, the sensitivity of K-line X-ray fluorescence parameters (wavelengths, radiative transition probabilities, and Auger rates) in Fe XVII–Fe XXV ions has been estimated for plasma conditions characterized by an electron temperature ranging from 105 to 107 K and an electron density ranging from 1018 to 1022 cm−3. In order to do this, relativistic multiconfiguration Dirac-Fock atomic structure calculations have been carried out by considering a time averaged Debye-Hückel potential for both the electron–nucleus and electron–electron interactions. 相似文献
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D. Stephan 《Crystal Research and Technology》1978,13(2):155-163
The asymmetrical Bragg case of X-ray diffraction on a thick real crystal is theoretically investigated on a layer model containing dynamically diffracting mosaic blocks. By means of this theory the experimental dependence of the integrated reflectivity Ri on the asymmetry angle α deviation from the kinematical formula may be understood as a result of extinction- and absorption processes inside the mosaic crystal. Thus the remarkably thick surface layers or surface protuberances assumed by Mathieson and in previous papers for the interpretation of the experimental Ri(α) become needless or they are considerably thinner. respectively, indeed. – On the base of the represented theory the determination of special (model-dependent) characteristics of the dislocation network is possible via absolute Ri(α)-measuring values. 相似文献
36.
Andreas Schwenke Philipp Wagener Stefan Nolte Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2011,104(1):77-82
The influence of fundamental and second harmonic wavelength on ablation efficiency and nanoparticle properties is studied
during picosecond laser ablation of silver, zinc, and magnesium in polymer-doped tetrahydrofuran. Laser ablation in stationary
liquid involves simultaneously the fabrication of nanoparticles by ablation of the target material and fragmentation of dispersed
nanoparticles by post irradiation. The ratio in which the laser pulse energy contributes to these processes depends on laser
wavelength and colloidal properties. For plasmon absorbers (silver), using the second harmonic wavelength leads to a decrease
of the nanoparticle productivity over process time along with exponential decrease in particle diameter, while using the fundamental
wavelength results in a constant ablation rate and linear decrease in particle diameter. For colloids made of materials without
plasmon absorption (zinc, magnesium), laser scattering is the colloidal property that limits nanoparticle productivity by
Mie-scattering of dispersed nanoparticle clusters. 相似文献
37.
We investigate the excitation of surface plasmon polaritons on silver tubes with finite-difference time-domain simulations. These surface plasmon polaritons exhibit azimuthal whispering gallery modes with quality factors in the hundreds. We show that the high quality factors arise from the coupling of the surface plasmon modes to photonic modes inside the tube. We examine the influence of a gain material on the quality factors and find that for material data of rhodamine 6G, the quality factors are enhanced significantly up to values of 3000. 相似文献
38.
Kummerlöwe G Grage SL Thiele CM Kuprov I Ulrich AS Luy B 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(1):19-30
The successful measurement of anisotropic NMR parameters like residual dipolar couplings (RDCs), residual quadrupolar couplings (RQCs), or residual chemical shift anisotropy (RCSA) involves the partial alignment of solute molecules in an alignment medium. To avoid any influence of the change of environment from the isotropic to the anisotropic sample, the measurement of both datasets with a single sample is highly desirable. Here, we introduce the scaling of alignment for mechanically stretched polymer gels by varying the angle of the director of alignment relative to the static magnetic field, which we call variable angle NMR spectroscopy (VA-NMR). The technique is closely related to variable angle sample spinning NMR spectroscopy (VASS-NMR) of liquid crystalline samples, but due to the mechanical fixation of the director of alignment no sample spinning is necessary. Also, in contrast to VASS-NMR, VA-NMR works for the full range of sample inclinations between 0° and 90°. Isotropic spectra are obtained at the magic angle. As a demonstration of the approach we measure 13C-RCSA values for strychnine in a stretched PDMS/CDCl? gel and show their usefulness for assignment purposes. In this context special care has been taken with respect to the exact calibration of chemical shift data, for which three approaches have been derived and tested. 相似文献
39.
In a previous paper a preconditioning strategy based on overlapping domain decomposition was applied to the Galerkin approximation
of elliptic partial differential equations on the sphere. In this paper the methods are extended to more general pseudodifferential
equations on the sphere, using as before spherical radial basis functions for the approximation space, and again preconditioning
the ill-conditioned linear systems of the Galerkin approximation by the additive Schwarz method. Numerical results are presented
for the case of hypersingular and weakly singular integral operators on the sphere
\mathbbS2{\mathbb{S}^2} . 相似文献
40.
Jrg Lambert Stephan Haiber Helmut Herzog 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,150(2):175
A new two-dimensional pulse sequence for T2* measurement of protons directly coupled to 13C spins is proposed. The sequence measures the tranverse relaxation time of heteronuclear proton single-quantum coherence under conditions of free precession and is therefore well suited to evaluate relaxation losses of proton magnetization during preparation delays of heteronuclear pulse experiments in analytical NMR. The relevant part of the pulse sequence can be inserted as a “building block” into any direct or inverse detecting H,C correlation pulse sequence if proton spin–spin relaxation is to be investigated. In this contribution, the building block is inserted into a HETCOR as well as into a HMQC pulse sequence. Experimental results for the HETCOR-based sequence are given. 相似文献