Large-scale level-by-level calculations were carried out to obtain as accurate autoionization and dielectronic capture (DC) rates of Ni-like Au{sup 51+} and Cu-like Au{sup 50+} as possible by ...including adequate electron correlations. The accuracy is estimated to be better than 20% for strong autoionized levels. Our results of the dielectronic recombination (DR) process through 3d{sup 9}4lnl{sup '} (n=4,5) agree excellently (within 10%) with other theoretical results also obtained by detailed level-by-level calculations reported in the literature. The level-by-level results were transformed to configuration-by-configuration autoionization and DC rates (which are estimated to be better than 30% in accuracy) and used to check the validity of the rate coefficients in collisonal-radiative (CR) models by using an analytical formula. Large discrepancies were found between the detailed calculated rates and those predicted by the analytical formula. The autoionization and DC rates predicted by the analytical formula can be more than two orders of magnitude larger than the detailed calculated rates, in particular for the autoionized configurations whose energy is near the ionization potential (IP). However, for those autoionized configurations whose energy is far above the IP, the autoionization and DC rates predicted by the analytical formula can be nearly one order of magnitude smaller. Differences between different theoretical methods found in this work, when approximate methods are used to calculate the autoionization and DC rates, would result in differences when non-local-thermodynamic-equilibrium (NLTE) models used the less accurate methods to obtain these atomic data.
Ultrafast nonequilibrium ion and electron dynamics of a neon plasma produced in the interaction with an ultra-intense x-ray pulse is investigated theoretically. Electron energy distribution function ...(EEDF) is obtained by solving Fokker–Planck equation, which is implemented self-consistently in a time-dependent rate equation in the framework of detailed-level-accounting approximation. Evolution dynamics of EEDF are presented at a variety of ion density in interaction with x-ray pulses of different laser intensities. Thermalization of free electrons is demonstrated after the x-ray pulses have turned off. The results are compared with two other simplified models, i.e., one is a relaxation model and the second uses the Maxwellian approach. Large discrepancies in the EEDF are found and the effects of detailed treatment of electron dynamics on population distributions are demonstrated and discussed.
The level population and charge state distribution (CSD) of the neon atomic system interacting with x-ray pulses of variant intensities and durations at a central photon energy of 1110 eV are ...investigated by solving the time-dependent rate equations. The laser beam has a circular spot size with a Gaussian intensity pattern and the time history of the intensity is represented by Gaussian distribution in time. As an example, the CSD as a function of time is given at different distances from the spot center for an x-ray beam of intensity 1.5 × 1017 W/cm2 and duration 75 fs (fs) for a spot size of 1 μm (full width at half maximum). The final CSD after averaging over the space and time is compared with a recent experiment and good agreement is found between the theory and experiment. Then systematic investigations are carried out to study the evolution of CSD with a wide range of intensity from 1.0 × 1015 W/cm2 to 1.0 × 1019 W/cm2 and duration from 30 fs to 100 fs. The results show that at intensities lower than 1.0 × 1015 W/cm2, the CSD shows a typical physical picture of weak x-ray photoionization of the neutral atomic neon. At higher intensity, i.e., larger than 5.0 × 1016 W/cm2, the dominant ionization stages are Ne7+ and Ne8+, while the fractions of ions in the Ne3+–Ne6+ stages are low for all laser durations and intensities.
A versatile code DLAYZ based on collisional-radiative model is developed for investigating the population kinetics and radiative properties of plasmas in non-local thermodynamic equilibrium. DLAYZ is ...implemented on the detailed level accounting (DLA) approach and can be extended to detailed configuration accounting (DCA) and hybrid DLA/DCA approaches. The code can treat both steady state and time-dependent problems. The implementation of the main modules of DLAYZ is discussed in detail including atomic data, rates, population distributions and radiative properties modules. The complete set of basic atomic data is obtained using relativistic quantum mechanics. For dense plasmas, the basic atomic data with plasma screening effects can be obtained. The populations are obtained by solving the coupled rate equations, which are used to calculate the radiative properties. A parallelized version is implemented in the code to treat the large-scale rate equations. Two illustrative examples of a steady state case for carbon plasmas and a time-dependent case for the relaxation of a K-shell excited argon are employed to show the main features of the present code.
The 1s−2 Auger hypersatellite spectrum of argon is studied experimentally and theoretically. In total, three transitions to the final states 1s−12p−2(2Se,2De) and 1s−12s−1(1S)2p−1(2Po) are ...experimentally observed. The lifetime broadening of the 1s−2 → 1s−12p−2(2Se,2De) states is determined to be 2.1(4) eV. For the used photon energy of hν = 7500 eV a KK/K ionisation ratio of 2.5(3) × 10−4 is derived. Generally, a good agreement between the experimental and present theoretical energy positions, linewidths, and intensities is obtained.
A study of plasma screening effects using a Debye-Hückel model is presented. The effects on the energy levels, oscillator strengths, ionization potential and photoionization cross sections of ...different ionization stages of carbon and on the radiative opacity of hot dense carbon plasmas are presented. The treatment of the atomic structure and radiative opacity is based on the detailed fine-structure level accounting formalism. For the basic atomic data, we compare our calculated energy levels and oscillator strengths with other theoretical results available in the literature and good agreement is found. The calculated ionization potential depressions of helium-like carbon, C V, are compared with the experimental and other theoretical results for a variety of plasma condition. Since the Saha–Boltzmann equation, which determines the ion stage populations, is dependent on the energy levels and ionization potentials of all ionization stages of carbon, the plasma screening effects on these quantities were included to obtain the population distribution. The screening effects play an important role on the spectrally resolved opacity by affecting the position and intensity of the absorption peaks and the K-shell ionization thresholds. With the decrease of Debye screening length, the number and intensity of the absorption peaks are reduced. In particular, the continuum opacity near the K-edge will be so sufficiently affected by the screening effects as to be experimentally observed. Finally, the plasma screening effects on the Rosseland and Planck mean opacities are investigated.
The radiative opacity of iron plasmas at high temperatures is very important in astrophysics. The spectrally resolved radiative opacity and Rosseland and Planck means were investigated by using the ...detailed-level-accounting (DLA) model for iron plasmas at high temperatures and a variety of density. The accuracy of atomic data such as energy levels and transition probabilities is checked by comparison with data from the National Institute of Standards and Technology. The transmission of iron plasma at a temperature of 156 eV and an electron density of 6.9 x 10(21) cm(-3) is studied in detail and compared with results of a recent experiment Bailey et al., Phys. Rev. Lett. 99, 265002 (2007) and other theoretical results. General good agreement is found between our DLA transmission and the experimental and other theoretical results. By using our developed DLA model, we can deduce valuable information on the physical condition of the plasma created in the experiment. The information includes the fractional distribution of different ion stages and whether the plasma is in local thermodynamic equilibrium or not. Illustrative results are given for three isothermal sequences of 100, 150, and 200 eV with different mass densities and for three isodensity sequences of 0.1, 0.05, and 0.01 g/cm3 with different temperatures. The Rosseland and Planck mean opacities are compared with other theoretical results obtained by the Los Alamos light element detailed configuration opacity code.
A collisional-radiative model based on detailed level approach is developed to investigate the population kinetics of non-local thermodynamic equilibrium (NLTE) carbon plasmas. Present model is used ...to diagnose a recent measurement for average ionization degree of carbon plasmas at 0.2 g/cm3 G. Gregori et al., Phys. Rev. Lett. 101, 045003 (2008). Physical factors which may influence the population kinetics are investigated in detail and it indicates that the high temperature radiative field plays an important role on the ionization balance.
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