X-ray emission associated with radiative recombination for Pb$^{82+}$ ions at threshold energies
B. Zhu, A. Gumberidze, T. Over, G. Weber, Z. Andelkovic, A. Bräuning-Demian, R. Chen, D. Dmytriiev, O. Forstner, C. Hahn, F. Herfurth, M. O. Herdrich, P. -M. Hi… 展开作者
B. Zhu, A. Gumberidze, T. Over, G. Weber, Z. Andelkovic, A. Bräuning-Demian, R. Chen, D. Dmytriiev, O. Forstner, C. Hahn, F. Herfurth, M. O. Herdrich, P. -M. Hillenbrand, A. Kalinin, F. M. Kröger, M. Lestinsky, Y. A. Litvinov, E. B. Menz, W. Middents, T. Morgenroth, N. Petridis, Ph. Pfäfflein, M. S. Sanjari, R. S. Sidhu, U. Spillmann, R. Schuch, S. Schippers, S. Trotsenko, L. Varga, G. Vorobyev, Th. Stöhlker
For bare lead ions, decelerated to the low beam energy of 10 MeV/u, the x-ray emission associated with radiative recombination (RR) at "cold collision" conditions has been studied at the electron cooler of CRYRING@ESR at GSI-Darmstadt. Utilizing dedicated x-ray detection chambers installed at 0° and 180° observation geometry, we observed for the very first time for stored ions the full x-ray emission spectrum associated with RR under electron cooling conditions. Most remarkably, no line distortion effects due to delayed emission are present in the well resolved spectra, spanning over a wide range of x-ray energies (from about 5 to 100 keV) which enable to identify fine-structure resolved Lyman, Balmer as well as Paschen x-ray lines along with the RR transitions into the K-, L and M-shell of the ions. To compare with theory, an elaborate theoretical model has been applied. By considering the relativistic atomic structure of Pb$^{81+}$, this model is based on a sophisticated computation of the initial population distribution via RR for all atomic levels up to Rydberg states with principal quantum number $n=$ 165 in combination with cascade calculations based on time-dependent rate equations. Within the statistical accuracy, the experimental x-ray line emission is in very good agreement with the results of the theoretical model applied. Most notably, this comparison sheds light on the contribution of prompt and delayed X-ray emission (up to 70 ns) to the observed X-ray spectra, originating in particular from Yrast transitions into inner shells.
We present a theoretical investigation of the radiative recombination of twisted Bessel electrons with initially hydrogen-like (finally helium-like) heavy ions. In our study, we focus especially on the linear polarization of x-ray photons emitted in the electron capture into the ground $1s^2_{1/2}$ ionic state. Particular emphasis is placed on the question of how this polarization is affected if incident hydrogen-like ions are themselves spin-polarized. To explore such a "polarization transfer" we apply the density matrix theory and derive the Stokes parameters of recombination x-rays for the …
A free electron can form a bound state with an atomic center $A$ upon photo emission (radiative recombination). In the presence of a neighboring atom $B$, such a bound state can, under certain conditions, be also formed via resonant transfer of energy to $B$, with its subsequent relaxation through radiative decay (two-center dielectronic recombination). This two-center process is very efficient in the 'static' case where $A$ and $B$ form a weakly bound system, dominating over single-center radiative recombination up to internuclear distances as large as several nanometers. Here we study its dy…
We survey the results of a long-term study of the process of radiative recombination. A rigorous theory of nonrelativistic electron radiative recombination with a hydrogen-like ion is used to calculate the total cross section of the process, the effective radiation, the recombination rate coefficient, and the emission coefficient in a plasma with a Maxwellian electron distribution. The exact results are compared with the numerous known asymptotic and interpolation formulas. We propose interpolation formulas which ensure a uniform approximation of all mentioned quantities in a wide range of pla…
Suppression of Dielectronic Recombination Due to Finite Density Effects II: Analytical Refinement and Application to Density-dependent Ionization Balances and AGN Broad-line Emission
我们提出了一个理论研究的双电子复合(DR)的Ar类离子,揭示了新的光的速率系数的行为在低温下,这些离子形成的光电离等离子体。我们提供的总的和部分麦克斯韦平均DR率系数从K II -锌XIII离子的初始基态的结果。预计这些新的结果将提高类Ar M壳层离子电离平衡的准确性,并为天体物理相关X射线吸收特征的详细建模铺平道路。我们利用AUTOSTRUCTURE计算程序获得了目标离子的准确的核心激发阈值,并在独立过程、孤立共振、扭曲波(IPIRDW)近似下对DR截面进行了多组态Breit-Pauli(MCBP)计算。我们的研究结果调解完全没有直接DR计算某些类Ar离子和现有的经验速率公式的可靠性,往往推断出在此等电子序列的重整化数据的问题。
Large-scale calculations of atomic structures and radiative properties have been carried out for singly, doubly- and trebly ionized cerium. For this purpose, the purely relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method was used, taking into account the effects of valence-valence and core-valence electronic correlations in detail. The results obtained were then used to calculate the expansion opacities characterizing the kilonovae observed as a result of neutron star mergers. Comparisons with previously published experimental and theoretical studies have shown that the results p…
Theoretical and experimental resonance strengths for KLL dielectronic recombination (DR) into He-, Li-, Be-, and B-like mercury ions are presented, based on state-resolved DR x-ray spectra recorded at the Heidelberg electron beam ion trap. The DR resonance strengths were experimentally extracted by normalizing them to simultaneously recorded radiative recombination signals. The results are compared to state-of-the-art atomic calculations that include relativistic electron-electron correlation and configuration mixing effects. Combining the present data with other existing ones, we derive an im…
The influence of hypothetical new interactions beyond the Standard Model on atomic spectra has attracted recent interest. In the present work, interelectronic photon-exchange corrections and radiative quantum electrodynamic corrections to the hypothetical contribution to the energy levels of few-electron ions from a new interaction are calculated. The $1s$, $2s$ and $2p_{1/2}$ ground states of H-like, Li-like and B-like ions are considered, as motivated by proposals to use isotope shift spectroscopy of few-electron ions in order to set stringent constraints on hypothetical new interactions. It…
In this paper, energy levels, radiative rates and lifetimes are reported for 11 F-like ions with 12 $\le$ Z $\le$ 23. Up to 198 levels (depending on the ion) have been considered which include 113 of the 2s$^2$2p$^5$, 2s2p$^6$, 2s$^2$2p$^4$3$\ell$, 2s2p$^5$3$\ell$, and 2p$^6$3$\ell$ configurations. The general-purpose relativistic atomic structure package ({\sc grasp}) and the flexible atomic code ({\sc fac}) have been adopted for calculating the energy levels, but the {\sc grasp} alone for the remaining parameters. Radiative rates (along with oscillator strengths and line strengths) are liste…
Radiative rates for E1, E2, M1, and M2 transitions in F-like ions with 55 <= Z <= 73
在2s $^2$ 2 p $^5$、2s 2 p $^6$、2s $^2$ 2 p $^4$ 3 $\ell$、2s 2 p $^5$ 3 $\ell$和2 p $^6$ 3 $\ell$构型的113个能级中,报道了55 $\le$ Z $\le$ 73的19个类F离子的能级、辐射率和寿命。计算中采用了通用相对论原子结构软件包(GRASP),列出了所有E1、E2、M1和M2跃迁的辐射率(以及其他相关参数,如振子强度和谱线强度)。与早期可用的理论和实验能量进行了比较,特别是对于Ba~XLVIII。尽管如此,为了进一步的准确性评估,特别是对能级的准确性评估,还使用了灵活的原子代码(FAC)和更大的组态相互作用(高达38~089个能级)进行了计算。
Radiative rates for E1, E2, M1, and M2 transitions in F-like ions with 37 $\le$ Z $\le$ 53
计算的能级,辐射率和寿命的17 F-类离子与37 $\le$ Z $\le$ 53。为简洁起见,仅在2s $^2$ 2 p $^5$、2s 2 p $^6$、2s $^2$ 2 p $^4$ 3 $\ell$、2s 2 p $^5$ 3 $\ell$和2 p $^6$ 3 $\ell$配置的最低113个能级中呈现结果,尽管已对每个离子中高达501个能级进行了计算。计算中采用了通用相对论原子结构软件包(GRASP),列出了所有E1、E2、M1和M2跃迁的辐射率(以及振子强度和谱线强度)。与早期可用的实验和理论能量进行比较,虽然这些仅限于少数几个级别的大多数离子。因此,对于额外的准确度评估,特别是对于能级,已经使用灵活原子代码(FAC)对高达72~259个能级进行了类似的计算。有限的以前的结果可用于辐射率的比较目的,并没有观察到任何过渡和/或离子的大的差异。
We review the study of dissociative recombination and ro-vibrational excitation of diatomic and small polyatomic molecular ions initiating complex organic molecules formation. In particular, we show how Multichannel Quantum Defect Theory (MQDT) and R-matrix methods are used to compute cross sections and rate coefficients for cations in well defined ro-vibrational levels of the ground electronic state, from sub-meV up to few eV collision energies. The most recent MQDT results are compared with either other theoretical data, or with measured data obtained in storage-ring experiments.
Aims. In the context of black-hole accretion disks, the main goal of the present study is to estimate the plasma environment effects on the atomic structure and radiative parameters associated with the K-vacancy states in ions of the oxygen isonuclear sequence. Methods. We use a time-averaged Debye-Huckel potential for both the electron-nucleus and the electron-electron interactions implemented in the fully relativistic multiconfiguration Dirac-Fock (MCDF) method. Results. Modified ionization potentials, K thresholds, Auger widths and radiative transition wavelengths and rates are reported for…
Ab initio calculations of QED radiative corrections to the $^2P_{1/2}$ - $^2P_{3/2}$ fine-structure transition energy are performed for selected F-like ions. These calculations are nonperturbative in $αZ$ and include all first-order and many-electron second-order effects in $α$. When compared to approximate QED computations, a notable discrepancy is found especially for F-like uranium for which the predicted self-energy contributions even differ in sign. Moreover, all deviations between theory and experiment for the $^2P_{1/2}$ - $^2P_{3/2}$ fine-structure energies of F-like ions, reported rec…
Radiative and interelectronic-interaction corrections to the hyperfine splitting in highly charged B-like ions
The ground-state hyperfine splitting values of high-Z boronlike ions are calculated. Calculation of the interelectronic-interaction contribution is based on a combination of the 1/Z perturbation theory and the large-scale configuration-interaction Dirac-Fock-Sturm method. The screened QED corrections are evaluated utilizing an effective screening potential approach. Total hyperfine splitting energies are presented for several B-like ions of particular interest: {}^{45}Sc{}^{16+}, {}^{57}Fe{}^{21+}, {}^{207}Pb{}^{77+}, and {}^{209}Bi{}^{78+}. For lead and bismuth the experimental values of the …
Accurate values of electric dipole (E1) amplitudes along with their uncertainties for a number of transitions among low-lying states of Mg$^+$, Ca$^+$, Sr$^+$, and Ba$^+$ are listed by carrying out calculations using a relativistic all-order many-body method. By combining experimental wavelengths with these amplitudes, we quote transition probabilities, oscillator strengths and lifetimes of many short-lived excited states of the above ions. The uncertainties in these radiative properties are also quoted. We also give electric quadrupole (E2) and magnetic dipole (M1) amplitudes of the metastabl…