Results 1 - 10 of 3466
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[en] A code, SIGMA1, has been designed to Doppler broaden evaluated cross sections in the ENDF/B format. The code can only be applied to tabulated data that vary linearly in energy and cross section between tabulated points. This report describes the methods used in the code and serves as a user's guide to the code
[en] One of the biggest difficulties in obtaining an analytical expression for the J(ξ, β) function is its explicit dependence on the Doppler broadening function ψ(x,ξ). The objective of this paper is to present a method for the fast and accurate calculation for the J(ξ, β) function based on the recent advances in the calculation of the Doppler broadening function and on a systematic analysis of its integrand. The methodology proposed uses an analytical formulation for the calculation of ψ(x, ξ) and a representation in series for error functions with complex argument. The results were satisfactory from the accuracy and processing time standpoint and are an option to other calculation methods found in the literature.
[en] Recently Milosavljevic and Poparic [Phys. Rev. E 63, 036404 (2001)] proposed a method for the deconvolution of isolated asymmetric plasma broadened atomic (neutral) spectral lines. The authors claim that their method enables a complete plasma diagnostics by applying this deconvolution on a single experimental line profile. In the present Comment the proposed deconvolution procedure and its application are reexamined
[en] The tomographic equation of the temperature of heavy particles in plasma has been derived using the relation of the velocity distribution with the Doppler broadening of the spectral line. This equation is correct for non-Maxwellian velocity distributions and for arbitrary plasma flow. To invert the temperature it is necessary to use also the tomographic equations of emission and velocity. This method has been tested by inversion of the ion temperature in modelling and plasma centrifuge experiment. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)
[en] It is shown that in analyzing the quantum limit of the error in Doppler measurement of momentum the frequency modulation of the wave packet due to acceleration of the body at the expense of the radiation reaction should be taken into account. According to this method the limit in the error in Measurements of the momentum is (h/2πm/tau)sup(1/2) just as in the measurements of momentum by observing the coordinate of the body (m is the body mass and tau duration of measurement)
[en] An Autler–Townes (AT) spectroscopy based on phase conjugate six-wave mixing (SWM) is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system. It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors. We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that, due the atomic motion, the atomic polarizations acquire different phases for atoms with different velocities as time evolves. The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields. (paper)
[en] At T = 0 a perfect Moessbauer line has natural line width Gamma = h/tausub(n). However, with rising temperature the width increases. The reason of the line broadening is the second order Doppler effect which causes a stochastic frequency modulation of the γ-radiation, reflecting the thermal motion of the Moessbauer atom. Following Josephson in treating the second order Doppler shift as a mass change ΔM = Esub(n)/c2 of the γ-emitting atom caused by the loss of nuclear excitation energy Esub(n), and using the well known relaxation formalism for calculating the γ-frequency spectrum, the line broadening ΔGamma is evaluated within the framework of harmonic lattice theory. (orig./BJ)
[de]Bei T = 0 besitzt eine perfekte Moessbauerlinie die natuerliche Linienbreite Gamma = h/tausub(n). Diese Breite nimmt jedoch mit wachsender Temperatur zu. Der Grund fuer die Linienverbreiterung ist der Dopplereffekt zweiter Ordnung, der eine stochastische Frequenzmodulation der Gamma-Strahlung verursacht, die die thermische Bewegung des Moessbaueratoms wiederspiegelt. Nach der Josephson-Interpretation der Dopplerverschiebung zweiter Ordnung als eine durch den Verlust der Kernanregungsenergie Esub(n) verursachte Massenaenderung ΔM = Esub(n)/c2 des γ-emittierenden Atoms, und unter Verwendung des wohlbekannten Relaxationsformalismus zur Berechnung des γ-Frequenzspektrums, wird die Linienverbreiterung im Rahmen der harmonischen Gitter-Theorie berechnet. (orig./BJ)
[en] Highlights: • An alternative setup for Doppler-free ion imaging is reported for the first time. • Measurement of the entire velocity distributions in each laser pulse. • Acquisition of high quality H photofragment images and action spectra. • Reveals the dynamics in methylamine and expected to be useful in other molecular systems. Hydrogen atom photofragments with high velocities in the laboratory frame lead to strong Doppler broadening of the (2 + 1) resonance-enhanced multiphoton ionization transition. Here, an alternative setup for Doppler-free ion imaging is demonstrated and explored for predissociation of methylamine and probing of H photofragments, at close wavelengths. This approach enables measurement of the entire velocity distributions in each laser pulse, enhances sensitivity and consequently provides acquisition of high quality H images and action spectra. These results shed light on dissociation dynamics and can be foreseen to be useful in revealing the dynamics in other molecular systems.