J. Dubau

Autoionization rates for 1s2s22p2, 1s2s2p3, 1s2p4 states of B-like ions (6 < Z < 54) for decay via different channels

Two different calculational methods, MZ and AUTOLSJ, are used to obtain autoionization rates for doubly excited states 1s2s22p2, 1s2s2p3, 1s2p4 of B-like ions in a wide range of nuclear charge Z (6 ≤ Z ≤ 54). Besides the total autoionization rates decayed via channels, so-called partial rates are computed in the intermediate coupling scheme. The Z-dependences of the partial rates are investigated in detail. A comparison shows a good agreement between these two methods. These data can be used to model dielectronic satellite spectra in plasmas. In particular, amplitudes and partial rates of autoionization decay are of importance for detailed atomic kinetic calculations and for the the study of polarization properties of dielectronic satellite spectra.

Effects of hyperfine interaction on the circular polarization of the Sc XX x-ray lines

The x-ray lines emitted from highly charged ions collisionally excited by longitudinally polarized electrons can be strongly circularly polarized for ions with no nuclear spin. In the present work, we have theoretically investigated the effects of hyperfine interaction on the circular polarization of the 1s2l → 1s2 lines of helium-like scandium, for which the nuclear spin is large. The hyperfine splitting of the excited levels and the transition probabilities for the hyperfine-induced E1 decays 23P0 → 11S0 and 23P2 F = 5/2 − 9/2 → 11S0 have been calculated by diagonalizing the complete Hamiltonian including both the spin-orbit interaction and the magneticdipole hyperfine interaction. The collision strengths for transitions to the individual magnetic sublevels of the target ion have been computed in two distorted-wave methods, one semi-relativistic and the other fully relativistic. It is shown that the hyperfine effects result in drastic decreases of the degree of circular polarization for the lines 23P2, 1 → 11S0 (labeled x and y, respectively and 23S1 → 11S0 (labeled z). The interference effects between the E1 and M2 transitions for the line x and those between the hyperfine components F = 5/2, 7/2 and 9/2 of the upper level for the line y are considered.

Energies and autoionization rates for Be-like systems. comparison of two methods: AUTOLSJ and MZ

Energy and autoionization rate for Be-like systems (1s2s22p, 1s2s2p2, 1s2p3) with Z = 6-42 have been calculated with two methods: AUTOLSJ (SUPERSTRUCTURE: including only the configurations of the complexes: 1s2s22p, 1s2p3 and 1s2s2p2) and (MZ) perturbation theory methods. Non-relativistic and relativistic parts of the energy have been considered separately. Relativistic effects have been taken into account by the Breit-Pauli operators. Non-relativistic and relativistic autoionization decay have been compared in the two methods, the contributions of 1s22s and 1s22p decay channels have been investigated.

X-ray line polarization spectroscopy of He-like Si satellite line spectra

Laser-produced plasmas driven by high-intensity, femtosecond-duration pulsed lasers have been recognized as sources of short-duration x-ray line emissions. Electron kinetics simulations of such transient and nonequilibrium plasmas predict non-Maxwellian electron distributions and even the presence of electron beams. X-ray line polarization spectroscopy is a diagnostic that can be used to study the directionality of the electron distribution function and thus test electron kinetics simulation results. To this end, we use a time-dependent, collisional-radiative atomic kinetics model of magnetic sublevels to understand the underlying processes and mechanisms leading to the formation of polarized x-ray line emission in Si plasmas driven by high-intensity, ultrashort duration pulsed lasers. We focus on the polarization properties of the He-like Si satellites of the Lyα line. In the cases under consideration, the relevant line emissions last less than 1 ps during which the plasma undergoes a rapid development. ...

Diagnostics of the anisotropy of the electron distribution from the analysis of x-ray line polarization

X-ray lines are emitted by very hot plasmas such as fusion plasmas (magnetic or inertial confinement) and astrophysical plasmas (solar and stellar flares, galaxies, etc.). The excitation processes of the atomic levels are often anisotropic and the emission lines can be expected to be polarized. The measurements of line polarization could give valuable information on the electron energy and angular distribution. The atomic data required to calculate the polarization being very sensitive to the quality of the theoretical method used, it is important to be able to check their accuracy by comparison with experiments. Recently the development of EBIT sources has allowed it to be done. In these devices, the ions being excited by an electron beam, the x-ray emission is often polarized.

Z-dependences of the energy levels and autoionization rates for 2141′ states of two electron systems

Abstract Three different calculational methods (AUTOLSJ, MZ, MCDF) are used to obtain energy levels and autoionization rates for doubly-excited states 2141′ of two electron systems (10⩽ Z ⩽42). By ordering all the states by energy within each block of a given angular momentum J and parity, it becomes possible to compare energy levels and autoionization rates obtained by the three methods. The Z dependences of the quantities are investigated for each calculational method for 10⩽ Z ⩽42. The final comparison reveals rather good agreement between the results obtained by the three methods.

Fe XXIII-Fe XIX theoretical spectra in two calculational methods

Two different calculational methods are compared for atomic data used to analyse transitions of the type 1s2sk2pn-1s22sk2pn-1. Wavelengths, radiative transitions, autoionisation probabilities and intensity factors are compared. These parameters are needed for diagnostics of low-density plasmas as found in solar flares and tokamak devices.

New modeling of germanium soft-X-ray lasers using extended atomic data

Abstract A collisional radiative model, explicitly including the interaction of the amplifying medium with the X-ray laser beam, is used to calculate the intensity of the 2–1 and 0–1 lines in neon-like germanium, as well as the population densities. The required energy levels and electron-impact collision strengths involve the configurations 1s22s22p6, 1s22s22p53l, and 1s22s2p63l (l=s,p,d). The fine-structure excitation rates coefficients are presented for temperatures in the range 100–700 eV. Well-known numerical codes are used for the atomic structure (SUPERSTRUCTURE) and electron–ion collisions (DISWAV/JAJOM). Finally, we solve the collisional radiative population equations. It is recommended to use excitation rates obtained from the extensive quantum calculations, rather than fit formulae. In this case, the calculated populations and intensities show substantial changes.

Theoretical analysis of solar corona spectra emitted in the 14--19 A wavelength range

The atomic data required to analyse low density coronal plasmas have been calculated and used to interpret some X‐ray spectra observed by the Flat Crystal Spectrometer of the SMM/NASA satellite in the 14–19 A wavelength range. The emission lines correspond mainly to Fe ions (Fe XVI, Fe XVII, Fe XVIII) and some O ions (O VII, O VIII).

Theoretical and experimental investigations of spectral and temporal properties of seeded soft x-ray lasers

We present in this paper theoretical and experimental investigations of temporal and spectral properties of seeded soft x-ray lasers. Bloch-Maxwell simulations of the harmonic pulse propagation in a soft x-ray laser plasma have been performed. Results show a growing wake of coherent radiation formed after the harmonic pulse.We describe the first measurement of the spectral bandwidth of a seeded soft x-ray laser. Using a varying path difference interferometer the spectral profile of a seeded OFI x-ray laser has been experimentally determined, leading to a Fourier-transform pulse duration of 5ps. The measured bandwidth is in good agreement with simulations. Finally we present the progress toward the implementation of a seeded soft x-ray laser at 18.9 nm at the new LASERIX facility.