This is the final report of a three-paper series on the K-shell photoabsorption and photoionization of trace elements, namely F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn. K lines and edges from such elements are observed in the X-ray spectra of supernova remnants, galaxy clusters and accreting black holes and neutron stars, their diagnostic potential being limited by poor atomic data. We are completing the previously reported radiative datasets with new photoabsorption and photoionization cross sections for isoelectronic sequences with electron number $19\leq N\leq 26$. We are also giving attention to the access, integrity and usability of the whole resulting atomic database. Target representations are obtained with the atomic structure code AUTOSTRUCTURE. Where possible, cross sections for ground-configuration states are computed with the Breit--Pauli $R$-matrix method (BPRM) in either intermediate or $LS$ coupling including damping (radiative and Auger) effects; otherwise and more generally, they are generated in the isolated-resonance approximation with AUTOSTRUCTURE. Cross sections were computed with BPRM only for the K ($N=19$) and Ca ($N=20$) isoelectronic sequences, the latter in $LS$ coupling. For the rest of the sequences ($21\leq N \leq 26$), AUTOSTRUCTURE was run in $LS$-coupling mode taking into account damping effects. Comparisons between these two methods for K-like Zn XII and Ca-like Zn XI show that, to ensure reasonable accuracy, the $LS$ calculations must be performed taking into account the non-fine-structure relativistic corrections.
Experimental and theoretical results are presented for double, triple, and quadruple photoionization of Si$^+$ and Si$^{2+}$ ions and for double photoionization of Si$^{3+}$ ions by a single photon. The experiments employed the photon-ion merged-beams technique at a synchrotron light source. The experimental photon-energy range 1835--1900 eV comprises resonances associated with the excitation of a $1s$ electron to higher subshells and subsequent autoionization. Energies, widths, and strengths of these resonances are extracted from high-resolution photoionization measurements, and the core-hole…
Partial photoionization cross sections from the ^1S ground and the ^3P metastable states of the Be isoelectronic series to different final states including a number of satellite (ionization plus excitation) channels are studied using the R-matrix method. As expected, the ratio of each satellite partial cross section to the dominant partial cross section is found to be a monotonic decreasing function of Z for both the ground and the metastable states. The complicated patterns of these ratios as functions of photon energy are analyzed.
The photoionization of the four-electron beryllium-like isoelectronic series from the neutral to Fe^{+22} has been studied for ground ^1S and metastable ^3P initial states. The wave functions of the final-state (target) ions were built using the CIV3 code. Both nonrelativistic LS-coupling R-matrix and relativistic Breit-Pauli (BP) R-matrix methods were used to calculate the cross sections in the photon-energy range between the first ionization threshold and the 1s^2 4f_{7/2} threshold for each ion. Our total cross sections compare well with experiment which is available for Be, B^+, C^{+2}, N^…
With plasma shielding effects of the Debye-Hückel model, we investigate the relativistic photoionization processes of H, Nb$^{40+}$ and Pb$^{81+}$ plasmas in the H-isoelectronic series. The shielded nuclear potential of Yukawa-type experienced by the electron is parameterized by Debye-length $D$. To account for relativistic effects non- perturbatively, we solve the Dirac equation for the bound as well as continuum wavefunctions. Contributions from multipole fields are calculated for high incident photon energies, while the angular distribution and spin polarization parameters of photoelectrons…
A detailed theoretical analysis of the 1s photoionization of neon is presented. It is found that the most significant many-electron correlation in computing photoionization of inner shells is the rearrangement of the outer shells caused by the inner vacancy. Further noticeable effects are: (i) the polarization of the ion core by the outgoing photoelectron and (ii) the coherent effect of double excitation/ionization. The core polarization increases the photoionization cross section by about 10% at the 1s threshold, and the coherent excitation results in further increases by about 5%. Incoherent…
A theoretical investigation of photoabsorption and photoionization of Fe^{14+} extending beyond an earlier frame transformation R-matrix implementation is performed using a fully-correlated, Breit-Pauli R-matrix formulation including both fine-structure splitting of strongly-bound resonances and radiation damping. The radiation damping of $2p\rightarrow nd$ resonances gives rise to a resonant photoionization cross section that is significantly lower than the total photoabsorption cross section. Furthermore, the radiation-damped photoionization cross section is found to be in good agreement wit…
Recently X-ray photoabsorption in KLL resonances of O VI was predicted [Pradhan, Astrophys.J. Lett. 545, L165 (2000)], and detected by the Chandra X-ray Observatory [Lee et al, Astrophys. J. {\it Lett.}, submitted]. The required resonance oscillator strengths f_r, are evaluated in terms of the differential oscillator strength df/de that relates bound and continuum absorption. We present the f_r values from radiatively damped and undamped photoionization cross sections for Li-like C,O, and Fe calculated using relativistic close coupling Breit-Pauli R-matrix method. The KLL resonances of interes…
Metal cluster ionization potentials are important characteristics of these "artificial atoms," but extracting these quantities from cluster photoabsorption spectra, especially in the presence of thermal smearing, remains a big challenge. Here we demonstrate that the classic Fowler theory of surface photoemission does an excellent job of fitting the photoabsorption profile shapes of neutral In_{n=3-34} clusters [Wucher et al., New J. Phys. 10, 103007 (2008)]. The deduced ionization potentials extrapolate precisely to the bulk work function, and the internal cluster temperatures are in close agr…
Reliable atomic data have been computed for the spectral modeling of the nitrogen K lines, which may lead to useful astrophysical diagnostics. Data sets comprise valence and K-vacancy level energies, wavelengths, Einstein $A$-coefficients, radiative and Auger widths and K-edge photoionization cross sections. An important issue is the lack of measurements which are usually employed to fine-tune calculations so as to attain spectroscopic accuracy. In order to estimate data quality, several atomic structure codes are used and extensive comparisons with previous theoretical data have been carried …
We present $R$-matrix calculations of photoabsorption and photoionization cross sections across the K-edge of Mg, Si, S, Ar, and Ca ions with more than 10 electrons. The calculations include the effects of radiative and Auger damping by means of an optical potential. The wave functions are constructed from single-electron orbital bases obtained using a Thomas--Fermi--Dirac statistical model potential. Configuration interaction is considered among all states up to $n=3$. The damping processes affect the resonances converging to the K-thresholds causing them to display symmetric profiles of cons…
We investigate molecular dynamics of multiple ionization in N2 through multiple core-level photoabsorption and subsequent Auger decay processes induced by intense, short X-ray free electron laser pulses. The timing dynamics of the photoabsorption and dissociation processes is mapped onto the kinetic energy of the fragments. Measurements of the latter allow us to map out the average internuclear separation for every molecular photoionization sequence step and obtain the average time interval between the photoabsorption events. Using multiphoton ionization as a tool of multiple-pulse pump-probe …
Double to tenfold M-shell photoionization of singly charged lanthanum ions
Helmholtz Forschungsakademie Hessen für FAIR (HFHF)（黑森FAIR亥姆霍兹研究学院）；GSI Helmholtzzentrum für Schwerionenforschung（GSI重离子研究中心）；Institut für Experimentalphysik, Universität Hamburg（汉堡大学实验物理研究所）
Absolute cross sections for m-fold photoionization (m=1,...,6) of Fe+ by a single photon were measured employing the photon-ion merged-beams setup PIPE at the PETRA III synchrotron light source, operated by DESY in Hamburg, Germany. Photon energies were in the range 680-920 eV which covers the photoionization resonances associated with 2p and 2s excitation to higher atomic shells as well as the thresholds for 2p and 2s ionization. The corresponding resonance positions were measured with an uncertainty of +- 0.2 eV. The cross section for Fe+ photoabsorption is derived as the sum of the individu…
We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of the Li-like to Ca-like ions stages of Ni. Level-resolved, Breit-Pauli calculations were performed for the Li-like to Na-like stages. Term-resolved calculations, which include the mass-velocity and Darwin relativistic corrections, were performed for the Mg-like to Ca-like ion stages. This data set is extended up to Fe-like Ni using the distorted wave approximation as implemented by AUTOSTRUCTURE. The R-matrix calculations include the effects of radiative and Auger dampings by means of an …
In a joint experimental and theoretical endeavour, photoionization of metastable C4+(1s 2s 3S1) ions via intermediate levels with hollow, double-K-vacancy configurations 2s2p, 2s3p, 2p3s, 2p3d, 2s4p, 2p4s and 2p4d has been investigated. High-resolution photon-ion merged-beams measurements were carried out with the resolving power reaching up to 25,000 which is sufficient to separate the leading fine-structure components of the 2s2p 3P term. Many-body perturbation theory was employed to determine level-to-level cross sections for K-shell excitation with subsequent autoionization. The resonance …
An analytical formula is developed to represent accurately the photoabsorption cross section of O I for all energies of interest in X-ray spectral modeling. In the vicinity of the Kedge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both expe…
We discuss the complicated resonance structure of the endohedral atom photoionization cross section. Very strong enhancement and interference patterns in the photoionization cross-section of the valent and subvalent subshells of noble gas endohedral atoms A@C60 are demonstrated. It is shown also that the atomic Giant resonance can be either completely destroyed or remains almost untouched depending on the velocity of photoelectrons that are emitted in the resonance's decay process. These effects are results of dynamic modification of the incoming beam of radiation due to polarization of the fu…
The photon-ion merged-beams technique has been employed at the new Photon-Ion spectrometer at PETRA III (PIPE) for measuring multiple photoionization of Xe$^{q+}$ (q=1-5) ions. Total ionization cross sections have been obtained on an absolute scale for the dominant ionization reactions of the type hν+ Xe$^{q+}$ $\to$ Xe$^{r+}$ + (q-r) e$^-$ with product charge states q+2 $\le$ r $\le$ q+5. Prominent ionization features are observed in the photon-energy range 650-750 eV, which are associated with excitation or ionization of an inner-shell 3d electron. Single-configuration Dirac-Fock calculation…
R-matrix calculations for opacities: V. Temperature-density dependence of photoabsorption cross sections and opacity spectra of oxygen ions O VI and O VII
We demonstrate the prominent modification of the outer shell photoionization cross-section in noble gas (NG) endohedral atoms NG@F under the action of the fullerene F electron shell. This shell leads to two important effects, namely to strong enhancement of the cross-section due to fullerenes shell polarization under the action of the incoming electromagnetic wave and to prominent oscillation of this cross-section due to the reflection of the photoelectron from NG by the F shell. All but He noble gas atoms are considered. The polarization of the fullerene shell is expressed via the total photo…
We demonstrate strong interference patterns in the photoionization cross-section of the subvalent subshells of noble gas (NG) endohedral atoms NG@F. This interference is a result of common action of three factors: the effect of neighboring atomic subshells, reflection of photoelectron waves by the fullerene F shell and resonance modification of the incoming photon beam by the complex effect under the action of the F electrons. We have considered the outer ns-subshells for Ne, Ar, Kr and Xe noble gas atoms. The polarization of the fullerene shell is expressed via the F total photoabsorption cro…
We present a generalization of the pioneering results obtained for single K-shell photoionization of H-like ions by M. Stobbe [Ann. Phys. 7 (1930) 661] to the case of the helium isoelectronic sequence. The total cross section of the process is calculated, taking into account the correlation corrections to first order of the perturbation theory with respect to the electron-electron interaction. Predictions are made for the entire non-relativistic energy domain. The phenomenon of dynamical suppression of correlation effects in the ionization cross section is discussed.
It is demonstrated that in photoabsorption by endohedral atoms some atomic Giant resonances are almost completely destroyed while the others are totally preserved due to different action on it of the fullerenes shell. As the first example we discuss the 4d10 Giant resonance in Xe@C60 whereas as the second serves the Giant autoionization resonance in Eu@C60. The qualitative difference comes from the fact that photoelectrons from the 4d Giant resonance has small energies (tens of eV) and are strongly reflected by the C60 fullerenes shell. As to the Eu@C60, Giant autoionization leads to fast phot…
