Excitation-autoionization cross sections and rate coefficients of Cu-like ions
TL;DR: Detailed level-by-level calculations of the excitation-autoionization (EA) cross sections and rate coefficients were performed using the relativistic distorted-wave method along the Cu isoelectronic sequence for all the elements with 34{le}{ital Z}{le}92.
Abstract: Detailed level-by-level calculations of the excitation-autoionization (EA) cross sections and rate coefficients were performed using the relativistic distorted-wave method along the Zn isoelectronic sequence for all the elements with 34\ensuremath{\leqslant}Z\ensuremath{\leqslant}92. While in a previous work only the 3d-4l inner-shell collisional excitations were taken into account, the present calculations also include excitations to higher configurations: ${3\mathrm{d}}^{9}$${4\mathrm{s}}^{2}$nl (n=4 to 7) and ${3\mathrm{p}}^{5}$${3\mathrm{d}}^{10}$${4\mathrm{s}}^{2}$nl (n=4,5). An extrapolation method is used to evaluate the total contribution for the higher principal quantum numbers. Configuration mixing and secondary autoionization processes following radiative decay from autoionizing levels are also included. The results show that the total EA rate is dominant compared to the direct ionization rate, up to a factor 12 at Z=47. The additional inner-shell excitations for Z59 produce an increase in the EA effect varying from 25% to almost a factor of 2, with respect to the previously predicted EA effect through 3d-4l only. The excitations to the higher configurations are the most significant for heavy elements with Z\ensuremath{\geqslant}61, since they open EA channels, resulting in an EA rate which varies along the sequence from 4 to 1 times the direct-ionization rate.
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TL;DR: H ULLAC as mentioned in this paper, an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes, is based on relativistic quantum mechanical calculations including configuration interaction.
Abstract: We describe H ULLAC , an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes. This code evolved and has been used over the years, but so far, there was no coherent, comprehensive, and in-depth presentation of it. It is based on relativistic quantum mechanical calculations including configuration interaction. The collisional cross sections are calculated in the distorted wave approximation. The theory and code are presented, emphasizing the various novel methods that has been developed to obtain accurate results very efficiently. In particular we describe the parametric potential method used for both bound and free orbitals, the factorization–interpolation method applied in the derivation of collisional rates, the phase amplitude approach for calculating the continuum orbitals and the N JGRAF graphical method used in the calculation of the angular momentum part of the matrix elements. Special effort has been made to insure the simplicity of use, which is demonstrated in an example.
437 citations
TL;DR: In this paper, a quasi-continuum structure at? 5 nm emitted by tungsten ions around W27+ was observed in the same spectral region and also in the range from 12 to 14 nm.
Abstract: Tungsten was injected by means of laser ablation in both ohmic and additionally heated plasmas of the ASDEX Upgrade tokamak experiment. Spectroscopic investigations were performed in the extreme ultraviolet (EUV) wavelength region, 4 to 140 nm. Besides the quasi-continuum structure at ? 5 nm emitted by tungsten ions around W27+, isolated lines of tungsten were observed in the same spectral region and also in the range from 12 to 14 nm. By comparison with calculations from the HULLAC and RELAC codes, these lines could be identified as transitions of bromine to nickel-like tungsten ions. The concentration cW of tungsten after laser ablation was determined from comparisons between the total tungsten radiation PW and the calculated radiation losses. Calibration of the quasi-continuum intensity with the help of the PW measurements allows the tungsten concentration to be determined from spectroscopic observations, which are more sensitive. Both concentration measurements (quasi-continuum, PW) agree well in discharges with laser ablation. From a comparison of the intensity of the isolated lines with code results, cW could be estimated in the central region of hot, additionally heated plasmas. The lower detection limit of the spectroscopic method allows the extraction of cW during the tungsten divertor experiment of ASDEX Upgrade.
112 citations
TL;DR: In this article, the authors developed a non-LTE collisional radiative model which takes into account the overwhelming multiplicity of excited levels of heavy elements in hot and dense plasmas and derived analytical formulae for the average transition rates between superconfigurations for collisional excitation and ionization, radiative transitions, photoionization and autoionization.
Abstract: We have developed a non-LTE collisional radiative model which takes into account the overwhelming multiplicity of excited levels of heavy elements in hot and dense plasmas. The model, ‘SCROLL’ (Super Configuration Radiative cOLLisional), treats superconfigurations as effective levels and reproduces detailed configuration accounting results by an iterative procedure which splits superconfiguration until convergence. The fundamental assumption in the model is that within a superconfiguration levels are populated according to Boltzmann statistics. This assumption is effectively relaxed by the convergence procedure. The populations of the superconfigurations are obtained by solving the set of collisional radiative rate equations. For this purpose we have derived analytical formulae for the average transition rates between superconfigurations for collisional excitation and ionization, radiative transitions, photoionization and autoionization. These analytical formulae are obtained using the ‘Partition Function Algebra’ developed in our previous LTE STA model. The calculation of the average rates are performed in the distorted wave approximation framework. Using the resulting superconfiguration populations we can then calculate charge distribution, opacities and emissivities. The model is applicable to any atom. In the present work it was applied to investigate non-LTE thin plasmas of Al and Au for several temperatures and densities. Comparison with detailed calculations when these are possible gave excellent agreement. Both theory and results are addressed.
44 citations
TL;DR: In this paper, the authors check the validity of the RADIOM model in the optically thin case by comparison with two collisional radiative models, MICCRON (level-bylevel) for C and Al and SCROLL (superconfiguration-by-super-configuration) for Lu and Au.
Abstract: Busquet's RADIOM model for effective ionization temperature Tz is an appealing and simple way to introduce non LTE effects in hydrocodes. We report here checking the validity of RADIOM in the optically thin case by comparison with two collisional radiative models, MICCRON (level-by-level) for C and Al and SCROLL (superconfiguration-by-super-configuration) for Lu and Au. MICCRON is described in detail. The agreement between the average ion charge 〈 Z 〉 and the corresponding Tz obtained from RADIOM on the one hand, and from MICCRON on the other hand for C and Al is excellent. The absorption spectra at Tz agree very well with the one generated by SCROLL near LTE conditions (small β). Farther from LTE (large β) the agreement is still good, but another effective temperature gives an excellent agreement. It is concluded that the model of Busquet is very good in most cases. There is however room for improvement when the departure from LTE is more pronounced for heavy atoms and for emissivity. Improvement appears possible because the concept of ionization temperature seems to hold in a broader range of parameters.
23 citations
TL;DR: In this article, three different theoretical methods were employed to obtain 3l- ( to 10) wavelengths and Einstein coefficients for Ni-like Xenon ions produced by a laser gas puff in the 85-95 and 17-wavelength ranges.
Abstract: Emission spectra of multicharged xenon ions produced by a laser gas puff are observed with high spectral resolution in the 85-95 and 17- wavelength ranges Three different theoretical methods are employed to obtain 3l- ( to 10) wavelengths and Einstein coefficients for Ni-like For the 3d-4p transitions, very good agreement is found between the experimental wavelengths and the various theoretical wavelengths These accurate energy level measurements can be useful for studying the Ni-like xenon x-ray laser scheme On the other hand, several intense spectral lines could not be identified as 3l- lines of Ni-like xenon, despite the very good agreement between the wavelengths and Einstein coefficients calculated for these transitions using the three different methods
19 citations