130 research outputs found
Polarization analysis of CuXX-lines emitted from X-pinch
International audienceSoft x-ray emission from CuXX L-shell lines emitted by a dense X-pinch plasma have been investigated with high-resolution curved Bragg crystals at different angles of orientation. Single shot time integrated spectra show clear evidences of polarization for the Ne-like spectral lines 2s22p6 1S0 → 2s22p53s 1P1 (λ = 12.570 Å), 2s22p6 1S0 → 2s22p53s 3P1 (λ = 12.8277 Å). The variation of the intensity ratio of these two well-separated L-shell lines is discussed in view of its application for suprathermal electron characterization under real experimental conditions of pinch plasmas. We demonstrated that the simultaneous use of two different polarization spectrometers (means 4 Bragg crystals) permitted a high level of confidence for the analysis of the variation of the line ratios due to polarization
Ab initio calculation of the 66 low lying electronic states of HeH: adiabatic and diabatic representations
We present an ab initio study of the HeH molecule. Using the quantum
chemistry package MOLPRO and a large adapted basis set, we have calculated the
adiabatic potential energy curves of the first 20 , 19
, 12 , 9 , 4 and 2 electronic
states of the ion in CASSCF and CI approaches. The results are compared with
previous works. The radial and rotational non-adiabatic coupling matrix
elements as well as the dipole moments are also calculated. The asymptotic
behaviour of the potential energy curves and of the various couplings between
the states is also studied. Using the radial couplings, the diabatic
representation is defined and we present an example of our diabatization
procedure on the states.Comment: v2. Minor text changes. 28 pages, 18 figures. accepted in J. Phys.
XFEL resonant photo-pumping of dense plasmas and dynamic evolution of autoionizing core hole states
Spectral Line Shapes as a Diagnostic Tool in Magnetic Fusion
Spectral line shapes and intensities are used for obtaining information on the various regions of magnetic fusion devices. Emission from low principal quantum numbers of hydrogen isotopes is analyzed for understanding the complex recycling mechanism. Lines emitted from high principal quantum numbers of hydrogen and helium are dominated by Stark effect, allowing an electronic density diagnostic in the divertor. Intensities of lines emitted by impurities are fitted for a better knowledge of ion transport in the confined plasma
X-ray radiation from ions with K-shell vacancies
Abstract New types of space resolved X-ray spectra produced in light matter experiments with high intensity lasers have been investigated experimentally and theoretically. This type of spectra is characterised by the disappearance of distinct resonance line emission and the appearance of very broad emission structures due to the dielectronic satellite transitions associated to the resonance lines. Atomic data calculations have shown, that rather exotic states with K-shell vacancies are involved. For quantitative spectra interpretation we developed a model for dielectronic satellite accumulation (DSA-model) in cold dense optically thick plasmas which are tested by rigorous comparison with space resolved spectra from ns-lasers. In experiments with laser intensities up to 10 19 W/cm 2 focused into nitrogen gas targets, hollow ion configurations are observed by means of soft X-ray spectroscopy. It is shown that transitions in hollow ions can be used for plasma diagnostic. The determination of the electron temperature in the long lasting recombining regime is demonstrated. In Light-matter interaction experiments with extremely high contrast (up to 10 10 ) short pulse (400 fs) lasers electron densities of n e ≈3×10 23 cm −3 at temperatures between kT e =200–300 eV have been determined by means of spectral simulations developed previously for ns-laser produced plasmas. Expansion velocities are determined analysing asymmetric optically thick line emission. Further, the results are checked by observing the spectral windows involving the region about the He α -line and the region from the He β -line to the He-like continuum. Finally, plasmas of solid density are characteristic in experiments with heavy ion beams heating massive targets. We report the first spectroscopic investigations in plasmas of this type with results on solid neon heated by Ar-ions. A spectroscopic method for the determination of the electron temperature in extreme optically thick plasmas is developed
An alternative method to determine atomic radiative emission
We reconsider the standard paradigm that detailed spectral
distributions must be determined by the inclusion of detailed
atomic and ionic level structure in the population kinetics. An
alternative method is proposed which creates detailed spectra from
a reduced description of the level-population kinetics. The method
is based on the introduction of a non-LTE effective
population-density coefficient that corresponds to a
redistribution of the population with respect to the strengths of
various excitation channels. An analytical solution that is based
entirely on the reduced level-population kinetics is derived,
which reduces the computational effort in the standard paradigm by
orders of magnitude. Exact numerical calculations show excellent
agreement, even for non-Maxwellian and non-equilibrium plasmas
A new type of analytical model for complex radiation emission of hollow ions in fusion, laser and heavy-ion-beam-produced plasmas
A new type of model for the determination of spectral
line shapes and intensities originating from complex autoionizing
atomic and ionic levels is proposed. It is based on the
introduction of a generalized line profile function (GLPF) for
the total contour. GLPF removes the separation of population
kinetics and line profile calculations. An analytical solution
unifying low- and high-density limits is derived which permits to
shrink population kinetics by several orders of magnitude without
loss of spectral details when using GLPF. Exact numerical
calculations show that even under extreme conditions such as hot
electrons and transient plasma evolution the generalized line
profile function approach holds true
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