Auger Transition Rates Research Articles

Ab Initio Manganese Kα and Kβ Energy Eigenvalues, Shake-Off Probabilities, Auger Rates, with Convergence Tests.

This work presents ab initio calculations for the Kα spectrum of manganese (Z = 25, [Ar]3d54s2), a highly complex system due to the five open orbitals in the 3d shell. The spectrum is composed of the canonical diagram line [1s]→[2p] and shake-off satellite lines [1snl]→[2pnl] (nl∈{2s,2p,3s,3p,3d,4s}), where square brackets denote a hole state. The multiconfiguration Dirac-Hartree-Fock method with the active set approach provides the initial and final atomic wavefunctions. Results are presented as energy eigenvalue spectra for the diagram and satellite transitions. The calculated wavefunctions include over one hundred million configuration state functions and over 280,000 independent transition energies for the seven sets of spectra considered. Shake-off probabilities and Auger transition rates determine satellite intensities. The number of configuration state functions ensures highly-converged wavefunctions. Several measures of convergence demonstrate convergence in the calculated parameters. We obtain convergence of the transition energies in all eight transitions to within 0.06 eV and shake-off probabilities to within 4.5%.

Мезоатомын гадаад Оже эффектийг бодох нэгэн арга

A method for calculating mesic-atom external Auger transition is proposed. The transition proceed in two stages. In the first stage, the quasi-molecular complex, consisting of the mesic atom and the atom is formed in their collisions and on the second stage, the decay of this complex leads to external Auger effects. At given distance between two atoms of the quasi-molecular system, the partial and total width of external Auger transition are calculated. The average Auger transition rates of pionic helium (Helium gass pressure 59.44 atm, velocity of the pionic atom is v=105 cm/s) are calculated and compared the rates of other competitive processes (Internal Auger and Radiation transitions).

Auger electron spectroscopy of fulminic acid, HCNO: an experimental and theoretical study.

HCNO is a molecule of considerable astrochemical interest as a precursor to prebiotic molecules. It is synthesized by preparative pyrolysis and is unstable at room temperature. Here, we investigate its spectroscopy in the soft X-ray regime at the C 1s, N 1s and O 1s edges. All 1s ionization energies are reported and X-ray absorption spectra reveal the transitions from the 1s to the π* state. Resonant and normal Auger electron spectra for the decay of the core hole states are recorded in a hemispherical analyzer. An assignment of the experimental spectra is provided with the aid of theoretical counterparts. The latter are using a valence configuration interaction representation of the intermediate and final state energies and wavefunctions, the one-center approximation for transition rates and band shapes according to the moment theory. The computed spectra are in very good agreement with the experimental data and most of the relevant bands are assigned. Additionally, we present a simple approach to estimate relative Auger transition rates on the basis of a minimal basis representation of the molecular orbitals. We demonstrate that this provides a qualitatively good and reliable estimate for several signals in the normal and resonant Auger electron spectra which have significantly different intensities in the decay of the three core holes.

Feshbach-Fano approach for calculation of Auger decay rates using equation-of-motion coupled-cluster wave functions. II. Numerical examples and benchmarks.

X-ray photon absorption leads to the creation of highly excited species, which often decay through the Auger process. The theoretical treatment of Auger decay is challenging because of the resonance nature of the initial core-excited or core-ionized states and the continuous nature of the ejected electron. In Paper I [W. Skomorowski and A. I. Krylov, J. Chem. Phys. 154, 084124 (2021)], we have introduced a theoretical framework for computing Auger rates based on the Feshbach-Fano approach and the equation-of-motion coupled-cluster ansätze augmented with core-valence separation. The outgoing Auger electron is described with a continuum orbital. We considered two approximate descriptions-a plane wave and a Coulomb wave with an effective charge. Here, we use the developed methodology to calculate Auger transition rates in core-ionized and core-excited benchmark systems (Ne, H2O, CH4, and CO2). Comparison with the available experimental spectra shows that the proposed computational scheme provides reliable ab initio predictions of the Auger spectra. The reliability, cost efficiency, and robust computational setup of this methodology offer advantages in applications to a large variety of systems.

Auger processes of the Rydberg series for Be-like oxygen ions

The relativistic energies and Auger transition rates for the Rydberg series 1s23lnl′ 1,3F° (n = 3–6) of Be-like oxygen ions are determined by the saddle-point variation and saddle-point complex-rotation methods. Relativistic corrections and mass polarization effects are considered to improve the computational accuracy of the energy. The Auger branching ratios of the 1s22s and 1s22p decay channels for these Rydberg series are calculated. The accurate Auger electron energies are compared with high-resolution electron spectroscopy. The results will provide useful data for the identification of spectral lines arising from the Be-like oxygen ions and experimental studies in future work.

Natural widths, lifetimes, and fluorescence yields for the double [formula omitted]-shell hole states of atoms with 10 [formula omitted] Z [formula omitted] 30

The natural widths, lifetimes, and fluorescence yields for the double K-shell hole states have been calculated for atoms with 10 ≤ Z ≤ 30. The Grasp2018 package was adopted to carry out a systematic computation of the Khα1,2 and Khβ1,3 radiative transition rates and Fac was used to calculate the KK−KLL, KK−KLM, and KK−KMM non-radiative Auger transition rates. The dependence of the radiative and non-radiative rates on the existence of 3s, 3p, 3d, or 4s spectator holes is studied.

Absolute radiative and Auger transition rates of K-shell excited few-electron iron ions

SynopsisThe iron Kα lines are among the most prominent features in the x-ray spectra of many celestial sources. However, transition rates used to model these spectra were only known by theoretical calculations. Here we present an absolute measurement of iron K-shell transition rates for Li-like to C-like iron ions. These ions were created with an electron beam ion trap and excited with x rays from the PETRA III synchrotron source. Measuring x-ray fluorescence and Auger decay simultaneously allows to determine absolute decay rates independent of most experimental parameters.

Energies and the radiative and Auger transition rates of1s2p4resonances of B-like ions

Energy levels and the radiative and Auger transition rates of the 1$s$2${p}^{4}$ ${}^{2,4}L$ ($L=S$, $P$, $D$) resonances in the boron isoelectronic sequence are calculated using the saddle-point variation and saddle-point complex-rotation methods. Large-scale wave functions are used to saturate the functional space. Relativistic and mass polarization corrections are included by the first-order perturbation theory. The Auger branching ratios of the important decay channels for these core-excited states are calculated. The reliable transition wavelengths and Auger electron energies are used to identify available x-ray spectra and Auger electron spectra. Identifications of several unknown experimental lines from 1$s$2${p}^{4}$ resonances are reported. The total radiative rates and total Auger rates of these 1$s$2${p}^{4}$ resonances are also reported and discussed along with the increase of atomic number $Z$. It is found that the total Auger rates are several orders of magnitude greater than the total radiative rates in these low-$Z$ ions.

The Radiative and Auger Decay Properties of K-Shell Ionized Np Ions

The radiative and Auger decay processes of K-shell ionized Np ions are studied theoretically using the flexible atomic code (FAC). Relativistic effects, Breit interaction, QED corrections and nuclear finite mass and volume effects are considered systematically. The resulting calculated K x-rays and Auger spectra of Np are compared with the measured spectra emitted after the electron-capture (EC)-decay of mass-separated 237Pu. The general consistency between theory and experiment is good; the relative intensities and relative positions of the peaks in the measured spectra are reproduced with good accuracy, in spite of the existence of different ways to produce the primary K-shell vacancy, enabling identification of the observed structure in the experimental spectra. We find that most of the radiative transition rates are greater than the Auger transition rates, and the latter decrease rapidly with the transfer of initial vacancies to the outer shell.

Auger spectrum of a water molecule after single and double core ionization

The high intensity of free electron lasers opens up the possibility to perform single-shot molecule scattering experiments. However, even for small molecules, radiation damage induced by absorption of high intense x-ray radiation is not yet fully understood. One of the striking effects which occurs under intense x-ray illumination is the creation of double core ionized molecules in considerable quantity. To provide insight into this process, we have studied the dynamics of water molecules in single and double core ionized states by means of electronic transition rate calculations and ab initio molecular dynamics (MD) simulations. From the MD trajectories, photoionization and Auger transition rates were computed based on electronic continuum wavefunctions obtained by explicit integration of the coupled radial Schrödinger equations. These rates served to solve the master equations for the populations of the relevant electronic states. To account for the nuclear dynamics during the core hole lifetime, the calculated electron emission spectra for different molecular geometries were incoherently accumulated according to the obtained time-dependent populations, thus neglecting possible interference effects between different decay pathways. We find that, in contrast to the single core ionized water molecule, the nuclear dynamics for the double core ionized water molecule during the core hole lifetime leaves a clear fingerprint in the resulting electron emission spectra. The lifetime of the double core ionized water was found to be significantly shorter than half of the single core hole lifetime.

Fluorescence and Auger Decay Properties of the Core-Excited F-Like Ions from Ne to Kr

We systematically study the decay properties of the K-shell excited F-like ions with 10≤Z≤36 based on the multiconfiguration Dirac—Fock method. The Breit interaction, the QED corrections and the nuclear finite mass effects are also considered as perturbation. Auger transition rates, radiative, Auger and natural widths, as well as fluorescence and Auger yields for K-shell excited F-like ions are presented. It is shown by means of concrete figures that the decay properties change significantly with the increase of the atomic number Z; the Auger rate is overtaken at Z = 30 by the radiative decay rate. Several fitting formulae for the radiative and Auger widths and the fluorescence yields have been evaluated which is expected to be useful in plasma analysis and plasma modeling.

Auger Spectrum of a Water Molecule after Single and Double Core-Ionization by Intense X-Ray Radiation

The high intensity of new x-ray sources such as Free Electron Lasers (FEL) offers the possibility to do single-shot molecule diffraction experiments. Even for small molecules, the dynamics induced by the radiation damage in such experiments are not yet fully understood. In particular, double core-ionized molecules are expected to be created in considerable quantity. We have therefore studied the electronic and nuclear dynamics of water molecules in single and double core ionized states by means of electronic transition rates and ab initio molecular dynamics (MD) simulations. From MD trajectories Auger transition rates were computed based on continuum electronic wavefunctions obtained by explicit integration of the coupled radial Schrödinger equations. The calculated spectra for different molecular geometries were accumulated to account for the effects of nuclear dynamics during the core-hole lifetime. In contrast to the single core ionized water molecule, we found that dissociation dynamics of double core-ionized water have strong effect on the resulting electron emission spectra. In addition, we found that the single core hole lifetime is slightly smaller than the value obtained in earlier theoretical works. Finally, we predict that the lifetime of double core ionized states is significantly lower than half of the lifetime of a single core hole.

The decay of autoionizing states in electric field formed during collisions of multiply charged ions with metal surface

When a multicharged ion approaches the metal surface, a strong electric field occurs due to interaction between the ion and the charge induced in the metal. During ion-surface scattering, double excited autoionizing states can be formed, and their decay occurs in the presence of strong electric field. The Auger transition rates for such states are higher than those in the absence of the electric field; this is connected with the increase in the wave functions overlap and also with mixing of states with different orbital momentums. This effect changes our view on the population scheme of states with the lowest principal quantum numbers for the collisions considered.

Calculation of X-ray and Auger transition rates, lifetimes, X-ray wavelengths, and fluorescence yields of variously ionized silicon atoms

X-ray and Auger transition rates, X-ray wavelengths, and fluorescence yields are calculated for variously ionized silicon atoms with configurations 1 s2 s m 2 p n , m=0–2, n=1–6. The calculation has been performed using the Hartree–Fock atomic model. Intermediate coupling and configuration interaction have been taken into account. The energies and widths are found to be strongly affected by configuration mixing. The results from the present calculation have been compared with those available in the literature. The theoretical K α hypersatellite and satellite spectra fall into several well-separated regions, corresponding to each of the possible number of spectator electrons in the 2 s and 2 p shells. The dependence of radiative rates and fluorescence yields on the number of spectator electrons is also investigated.

Role of cascade and Auger effects in the enhanced population of theC3+(1s2s2p4P)states following single-electron capture inC4+(1s2s3S)-He collisions

The population of excited three-electron states in carbon ions after single-electron capture in $0.5\ensuremath{-}1.1$ MeV/amu ${\mathrm{C}}^{4+}(1s2s {}^{3}S)$-He collisions is analyzed theoretically by combining different methods. While the two-center basis generator method is used to calculate capture amplitudes on the single-particle level, all-electron structure calculations for the relevant ${\mathrm{C}}^{3+}$ states and their radiative and Auger transition rates are performed on the multiconfiguration Dirac-Fock level. These data are then combined and fed into a set of classical rate equations for the decay dynamics. Total cross sections for the production of the $1s2s2p {}^{4}P$, $1s2s2p {}^{2}{P}_{\ensuremath{-}}$, and $1s2s2p {}^{2}{P}_{+}$ states are calculated and their ratios compared with recent experimental data and previous calculations [D. Strohschein et al., Phys. Rev. A 77, 022706 (2008)]. It is found that the relative intensities of the $1s2s2p {}^{4}P$ states are considerably larger than expected on the basis of pure spin statistics. The Auger transitions, which were not included in the previous calculations, have a significant effect on the final results in that they reduce the $1s2s2p {}^{2}P$ intensities. Although our extended computations explain a significant part of the production of the $1s2s2p {}^{4}P$ states, the experimentally observed enhancement of these states is still considerably larger than the theoretical one.

Relativistic Energies and Auger Widths of High-Lying Doubly-Excited States 1s23lnl′ 1De in Be-Like O4+ Ions

The saddle-point variational method and restricted variational method are used to calculate energies of doubly-excited singlet states 1s23lnl′ (n = 3–5) 1De in Be-like O4+ ions, including the mass polarization and relativistic corrections. The saddle-point complex-rotation method is used to compute the Auger widths and Auger transition rates. These results are compared with other theoretical and experimental data in the literature.

Z dependence of radiative and Auger transitions rates from doubly excited [formula omitted] states of helium-like ions

X-ray and Auger transition rates, transition energies, fluorescence yields, and nonradiative branching ratios are calculated for doubly excited 3 l 3 l ′ configurations of helilum-like chromium and nickel. The calculation has been performed using Hartree–Fock–Slater atomic model. Intermediate coupling and configuration interaction have been taken into account. The energies and widths are found to be strongly affected by configuration interaction. The Z dependence of transition rates are investigated for ions with atomic number Z = 10 , 14, 18, 20, 22, 24, 26, and 28 using the present theoretical data and the data from some of our previous calculations.

Assignment of the [formula omitted] normal Auger decay spectrum of [formula omitted] by ab initio calculations

Auger decay processes of the Cl 2 p ionized states have been studied in Cl 2 by means of high-resolution electron spectroscopy and ab initio calculations. This led to reassignment of the normal L 2 , 3 VV Auger decay spectrum of Cl 2 . The reliability of this assignment is strongly supported by an independent measurement of the L 2 , 3 VV Auger electron spectrum of Cl 2 which has been obtained after selective Cl 2 p 3 / 2 - 1 photoionization of the chlorine molecule. Partial Auger transition rates for the three nongenerate spin–orbit and molecular-field-split 2 p - 1 states – 2 p 3 / 2 , 3 / 2 - 1 ( 2 Π 3 / 2 ) , 2 p 3 / 2 , 1 / 2 - 1 ( 2 Σ 1 / 2 + ) and 2 p 1 / 2 , 1 / 2 - 1 ( 2 Π 1 / 2 ) – show differences similar to the ones reported in previous works for HCl.

Electron correlation effects of the highly-doubly-excited resonances for He-like ions

The hyperspherical method is used to study the electron correlation energy，radiative transition rate and Auger transition rate of the highly-doubly-excited states of He-like oxygen.All these doubly-excited Rydberg states are designated by quantum numbers K，T，A.The results show that properties such as the energy，radiative and Auger transition rate regularly change along with the quantum numbers K，T，A.

Auger transition rates for Ar-like ions

The Auger transition rates for Ar-like ions have been calculated by the relativistic configuration interaction code and flexible atomic code. The calculations have been carried out for the atomic numbers from 18 to 54, that is, for argon to xenon. The calculated data for argon is shown to be in a good agreement with experimental data and other calculated data.