Configuration Interaction Effects Research Articles

R-matrix calculations for opacities: IV. Convergence, completeness, and comparison of relativistic R-matrix and distorted wave calculations for Fe xvii and Fe xviii

To investigate the completeness of coupled channel (CC) Breit–Pauli R-matrix (BPRM) calculations for opacities we employ the relativistic distorted wave (RDW) method to complement (‘top-up’) and compare the BPRM photoionization cross sections for high- nℓ levels of both Fe xvii and Fe xviii . Good agreement is found with background photoionization cross sections using these two methods, which also ensures the correct matching of bound level cross sections for completeness. In order to top-up the CC-BPRM calculations, bound–bound transitions involving additional bound levels, and a large number of doubly-excited quasi-bound levels corresponding to BPRM autoionizing resonances described in the paper RMOPII are calculated using the RDW method. Photoionization cross sections in the high energy region are also computed and compared up to about 500 Ry, and contributions from higher core level excitations than BPRM are considered. The effect of configuration interaction is investigated, which plays a significant role in correctly reproducing some background cross sections. Due to the fact that the additional RDW levels correspond to high- nℓ bound levels that are negligibly populated according to the Mihalas–Hummer–Däppen equation-of-state (paper I), the effect on opacities is expected to be small.

High Accuracy Ab Initio Potential Energy Curves and Dipole Moment Functions for the X1Σ+ and a3Π Spin States of the CF+ Diatomic Molecule.

Potential energy curves and dipole moment functions constructed using high-accuracy ab initio methods allow for an in-depth examination of the electronic structure of diatomic molecules. Ab initio computations serve as a valuable complement to experimental data, offering insights into the nature of short-lived molecules such as those encountered within the interstellar medium (ISM). While laboratory experiments provide critical groundwork, the ISM's conditions often permit longer lifetimes for lower stability molecules, enabling unique observations. The CF+ diatomic molecule is one such molecule that has been observed spectroscopically in the ISM. Previous experimental and theoretical work have examined different spectroscopic aspects of the CF+ molecule, but the development of newer, more complete potential energy curves and dipole moment functions allows for even greater insight. We constructed both potential energy curves and dipole moment functions for the ground X1Σ+ and first excited a3Π states of CF+ for both the 12C and 13C isotopologues. The potential energy curves were constructed using coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) at the complete basis set limit with corrections from full triple, quadruple, quintuple, and hextuple excitations within a finite-basis coupled cluster wave function as well as corrections from full configuration interaction and relativistic effects. Rovibrational wave functions were calculated using a vibrational Hamiltonian matrix, which moves beyond the harmonic oscillator approximation. The equilibrium bond length, vibrational constant, and rotational constant were reproduced to within 0.00013 Å, 0.28 cm-1, and 0.00045 cm-1, respectively, of experimental values. Experimental transition energies from rovibrational spectra were reproduced with an error of no larger than 0.63 cm-1. The triplet excited state (a3Π) was found to have a longer equilibrium bond length at 1.21069 Å, a vibrational constant of 1611.29 cm-1, and a rotational constant of 1.56376 cm-1. Rovibrational line lists for the 12C and 13C isotopologues for both the X1Σ+ and the excited a3Π states were generated.

Fully relativistic many-body perturbation energies, transition properties, and lifetimes of lithium-like iron Fe XXIV

Employing the advanced relativistic configuration interaction (RCI) combined with the many-body perturbation theory (RMBPT) method, we report energies and lifetime values for the lowest 35 energy levels from the (1s2)nl configurations (where the principal quantum number n = 2–6 and the angular quantum number l = 0,…,n–1) of lithium-like iron Fe XXIV, as well as complete data on the transition wavelengths, radiative rates, absorption oscillator strengths, and line strengths between the levels. Both the allowed (E1) and forbidden (magnetic dipole M1, magnetic quadrupole M2, and electric quadrupole E2) ones are reported. Through detailed comparisons with previous results, we assess the overall accuracies of present RMBPT results to be likely the most precise ones to date. Configuration interaction effects are found to be very important for the energies and radiative properties for the ion. The present RMBPT results are valuable for spectral line identification, plasma modeling, and diagnosing.

Understanding the Origins of Site Selectivity in Hydrogen Atom Transfer Reactions from Carbohydrates to the Quinuclidinium Radical Cation: A Computational Study.

The use of quinuclidine as a hydrogen atom transfer (HAT) mediator, along with a light-absorbing photoredox catalyst, has proved to be a powerful and general approach for achieving site-selective radical formation from carbohydrate substrates. Despite numerous literature reports documenting the scope and limitations of such processes, a general rationale for the origins of site selectivity in the key HAT step has not been advanced. In this study, density functional theory calculations (M06-2X/def2-TZVP/PCM(acetonitrile)) were used to model transition states for HAT to the quinuclidinium radical cation from pyranosides and furanosides having various configurations and substitution patterns. The data set (>120 transition state geometries and energies) has allowed for a detailed examination of the factors that influence the relative rates, augmented by additional analysis using the atoms in molecules (AIM) and distortion/interaction-activation strain frameworks. The trends that have emerged regarding the effects of configuration, conformation, substitution, and noncovalent interactions are consistent with experimental observations and reveal a key role for C-H···O hydrogen bonds in stabilizing transition states for HAT to the quinuclidinium radical cation.

Review-driven configuration scheme evaluation methodology with configuration interaction effects

This study focuses on configuration scheme evaluation (CSE) based on customer perceptions deduced from online reviews. It is noteworthy that customers in different market segments often hold significant differences in their perceptions of the same configuration. Meanwhile, there may exist a potential dependency relationship between configurations referred to as configuration interaction increasing the complexity of CSE. This paper proposes a review-driven interacting CSE methodology fusing with review texts and configuration documents to address these challenges. First, three indexes, namely configuration differentiation, price consistency, and usage scenario similarity, are defined to identify targeted segments. Second, a differentiated calculation strategy is designed to measure configuration performances based on the configuration data and review data in the identified segments. Third, a configuration performance aggregation function that considers configuration interaction is developed based on the Choquet integral. Finally, two CSE problem about car and laptop products is analyzed using the proposed methodology to verify its applicability. Three comparative studies are also conducted to show the effectiveness and stability of the proposals.

Detailed Analysis of Spectra from Ga-like Ions of Heavy Elements Observed in High-Temperature Plasmas

This study has systematically investigated the atomic number (Z) dependence of spectra from gallium-like (Ga-like) ions of heavy elements. We have mainly analyzed the experimental spectra recorded in high-temperature plasmas produced in the Large Helical Device (LHD) for various elements with atomic numbers from 57 onward. The measured wavelengths are compared with theoretical values calculated with a multi-configuration Dirac Fock code. As a result, we have successfully obtained Z-dependent wavelengths of several prominent transitions of Ga-like ions, including a magnetic dipole (M1) transition. Many of them have been experimentally identified for the first time in this study. The present results manifest the significant effects of configuration interaction and spin–orbit interaction for highly charged heavy ions.

Nucleon–nucleon correlations in the extreme oxygen isotopes

There has been an upsurge of interest in two-nucleon decays thanks to the studies of nucleon–nucleon correlations. In our previous work (2021 Phys. Rev. Lett. 126 142501), based on a novel time-dependent three-body approach, we demonstrated that the energy and angular correlations of the emitted nucleons can shed light on the structure of nucleonic pairs formed inside the nucleus. In this work, we apply the new framework to study the decay dynamics and properties of some extreme proton-rich and neutron-rich oxygen isotopes, including two-proton (2p) decays of 11,12O and two-neutron (2n) decay of 26O. Here we show that the low-ℓ components of 11,12O wave functions, which are affected by continuum and configuration-interaction effects, strongly impact decay dynamics and asymptotic correlations. In the calculated wave functions of 11,12O, diproton and cigarlike structures merge together during the tunneling process and the resulting energy and angular correlations are very consistent with the experimental data. The asymptotic correlations of the 2n decay of 26O dramatically change as the 2n decay energy approaches the zero-energy threshold. The small reported value of Q 2n suggests that the 2n decay of this nucleus can be understood in terms of the universal phase-space limit.

Theoretical analysis of atomic parameters of Sm-like and Nd-like W ions in soft x-ray region

We calculated atomic data such as energy levels, transition wavelengths, oscillator strengths and transition rates for Sm-like and Nd-like W ions. We employed flexible atomic code (FAC) in our computations. We computed fine structure levels of configurations 4f125s2, 4f125s5p and 4f135s for Nd-like W and configurations 4f145s2, 4f135s25p and 4f125s25p2 for Sm-like W. We have provided transition data of electric dipole (E1) transitions and magnetic quadrupole (M2) transitions for transition 4f125s2—4f125s5p and magnetic dipole (M1) and electric quadrupole (E2) transition data for transition 4f145s2 − 4f125s25p2. We also found that spectral lines of these transitions in Sm and Nd-like W ion spectra lie in soft x-ray (SXR) region. We compared transition data of Nd-like W and excitation energies of Sm-like W ions with available theoretical and experimental results. We also discussed the effect of configuration interaction on atomic data of Nd-like W and excitation energies of Sm-like W by systematically increasing the number of configurations.

Energy Levels and Radiative Properties of Cu-like Tungsten

We have reported fine structure energies along with radiative data namely, transition wavelengths, transition probabilities, oscillator strengths and line strengths for lowest 120 levels of Cu-like W using Multi-Configuration Dirac-Fock (MCDF) method which may be useful ion for fusion plasma research. We have systematically analysed configuration interaction (CI) effects on Dirac-Coulomb as well as Breit and Quantum electrodynamics (QED) excitation energies and demonstrated that in order to attain accuracy in atomic data inclusions of CI in excitation energies are crucial. We have also discussed the evaluation of results from two independent codes GRASP and FAC. We have predicted some new energy levels and transition data where no other experimental or theoretical results are available. The present set of results should be useful in line identification and the interpretation of spectra, as well as in modeling of fusion plasmas.

Spectroscopic analysis of N-intrashell transitions in Rb-like to Ni-like Yb ions

Extreme ultraviolet spectra of highly-charged ytterbium ions produced in an electron beam ion trap at the National Institute of Standards and Technology were observed with a flat-field grazing incidence spectrometer in the wavelength region of about 4 nm–20 nm. The measured spectra were interpreted through detailed analysis by collisional-radiative modeling of the non-Maxwellian EBIT plasma. Seventy-nine new spectral lines due to intrashell (Δn = 0, n = 4) electric–dipole, magnetic–dipole, and electric–quadrupole transitions were identified in Rb-like Yb33+ through Ni-like Yb42+ ions. The effects of strong configuration interaction within the n = 4 complex on the measured spectra are discussed for a number of ionization stages.

Calculations of transition rates in erbium-like ions Lu IV, Hf V and Ta VI using the Ab initio MCDHF-RCI and semi-empirical HFR methods

In the present paper, the radiative properties of three ions belonging to the erbium isoelectronic sequence, i.e. Lu IV, Hf V and Ta IV, are reported and the effect of configuration interaction on these properties are taken into account for the first time to our knowledge. These heavy elements with Z=71–73 are located near to tungsten (Z=74) in the Periodic Table and are of potential interest in controlled thermonuclear fusion. Indeed, they could be used in plasma-facing materials such as the divertors in tokamaks or/and could be generated by neutron-induced transmutations of divertor’s materials. In this work, two independent theoretical atomic structure computational approaches have been considered, i.e. the semi-empirical Hartree–Fock with relativistic corrections method (HFR) and the ab initio multiconfiguration Dirac–Hartree–Fock with subsequent relativistic configuration interaction method (MCDHF-RCI). The transition probabilities and the oscillator strengths have been calculated for 593, 820 and 1101 E1 transitions in Lu IV, Hf V and Ta VI respectively spanning the spectral range from UV to IR. Finally, this study also underlines the importance of core-valence correlations in these heavy atomic ions.

Measurement and analysis of emission spectrum of laser-produced Ni plasma in the range of 7-14 nm

SynopsisWe measured and analyzed the emission spectrum of laser-produced Ni plasma in the range of 7-14 nm. The dominant transition arrays were identified as 3p63dn−3p63dn−1f and 3p53dn+1−3p53dn4f from Ni6+ to Ni9+ ions with aid of the Hartree-Fock calculations with configuration interaction effects. The plasma parameters have been obtained by comparison of experimental and simulated spectrum based on a steady-state collisional-radiative (CR) model.

A Projective Method for the Calculation of Excited-State Electronic Coupling: Isolating Charge Transfer/Recombination Processes in Organic Photovoltaics.

Electronic coupling between excited states is a vital parameter required to describe ultrafast energy and charge transfer processes that occur in photoresponsive organic materials. In such systems, short-range Coulombic, exchange, overlap, and configuration interaction effects must all be accounted for. Although a number of methods are available, the evaluation of coupling between arbitrary excited states remains challenging. In this contribution, a flexible and scalable method for the calculation of short-range electronic coupling between excited states is developed. Excitation- or charge-localized states are projected onto the adiabatic states of a dimeric molecular system using an efficient wave function overlap algorithm. In addition to correctly treating Coulombic, exchange, and overlap contributions, the inclusion of multistate interactions is inherent in the procedure. The method is then used to disentangle excitation energy transfer, charge transfer, and charge recombination processes in donor/acceptor systems relevant to organic photovoltaics, with a view toward the development of material design principles. Calculations were performed within single-excitation frameworks, but the scheme has the potential to be extended to multireference/higher-order excitation quantum-chemical methods.

Fluorescence yields for doubly excited 2s3s configuration in He-like ions

The wavelengths and rates of single- and double-electron transitions leading to the emission of a single photon between 2s3s and nsn′p (n = 1, 2 and n′ = 2–4) groups in He-like ions with empty K shell have been studied for 15 ions in the range 13 ≤ Z ≤ 54 using fully relativistic multi-configuration Dirac–Fock wavefunctions in the active space approximation. The complete relaxation of atomic orbitals and most important configuration interaction effects have been taken into account. The variations in the admixture of the correlation functions coupled with Breit interaction responsible for the sudden changes in the line intensities of certain transitions from 2s3s have been discussed in detail. The radiative rates of the electric dipole transitions have been evaluated as accurately as possible by taking into account all the non-negligible contributions to the X-ray rates. The Auger rates have been calculated using a scaling procedure on the already existing relativistic radial matrix elements for an initial K hole atom. The present results are compared with other available theoretical data. The computed data can be conveniently used in the analysis of experimental spectra and in the measurements of X-ray fluorescence yields for the doubly excited states under study.

Measurement and analysis of the extreme ultraviolet emission band of laser-produced antimony plasmas

The temporal evolution of extreme ultraviolet (EUV) emission spectra of laser-produced antimony (Sb) plasmas has been measured in the 7–16 nm wavelength region using spatio-temporally resolved lase-produced plasma spectroscopy technique. The spectral profiles involve an intense quasi-continuous band with superimposed intense characteristic radiation and are different with the increase of delay time. The spectral structures were also analyzed according to Hartree–Fock calculations with configuration interaction effects and contributed from 4d–4f, 4d–4p, and 4d–5f unresolved transition arrays of Sb7+–Sb13+. A steady-state collisional-radiative model was used to estimate the electron temperature and density range of Sb plasmas. This work would enrich the spectral data of highly-charged ions and provided a possible selection for developing EUV light sources.

Resonance State Method for Electron Injection in Dye Sensitized Solar Cells

Herein, the ab initio method is applied to examine metastable molecular excited states on a solid surface using resonance state theory and Green's function. A formula for the complex energy correction that determines the decay rate is presented; the configuration interaction effect together with major molecule-surface interactions are considered in more detail as compared to previous studies. Furthermore, the lifetimes of the excited states of Ru-terpyridine dyes adsorbed on an anatase surface are calculated, and the effects of the molecular structure and adsorption mode on the electron injection rate are studied. Also, the adsorption structures and relative stabilities of a series of Ru-terpyridine dyes-including the black dye-are reported. An implicit solvation model is necessary to reliably calculate the alignment between the photoabsorption spectrum and the conduction band density of states, governing the injection rate. Finally, some of the factors that limit the injection ability of dyes are discussed.

Many-body quantum chaos and actinide ions: Testing the predictions of random matrix theory with high-Zions

In this study, we present a statistical analysis of the level structures of four highly charged actinide ions: Bk xii, Cf xii, No xiii, and Md xiv. In these ions, $5f$ wave-function contraction gives rise to a manifold of levels arising from configurations with partially filled $5f$ and $6p$ subshells. The cumulative effects of configuration interaction (CI) between these configurations results in a complete breakdown of the independent particle model used in the labeling of the states and leads to the formation of so-called ``compound'' states. Properties of the calculated level structures have been analyzed using the techniques of random-matrix theory (RMT). Standard statistical measures, such as the repulsion parameter $q$, the covariance of adjacent spacings $\text{cov}({s}_{i},{s}_{i+1})$, and the Dyson-Mehta statistic ${\mathrm{\ensuremath{\Delta}}}_{3}(L)$, have been computed for specific ${J}^{\ensuremath{\pi}}$ interacting sets belonging to the four aforementioned ion stages. In the majority of cases, these calculations are found to be in very good agreement with the RMT-predicted values for these quantities. This study therefore extends previous identifications of RMT-like level fluctuations in the level spectra of lanthanide ions to high-$Z$, moderately charged actinide ions.

Effects of crystal structures and intermolecular interactions on charge transport properties of organic semiconductors

In this study, the effects of the packing configuration and intermolecular interaction on the transport properties are investigated based on density functional theory. Molecular design from the standpoint of a quantum-chemical view is helpful to engender favorable molecular packing motifs. The transfer integral along the orientation with π–π overlap is much larger than other directions without π–π overlap, and the mobility along this orientation is higher than that along other directions. The intermolecular interaction analyses demonstrate that hydrogen bonds play a crucial role with strong electrostatic interactions in charge transfer. There will be a synergistic relationship when the π–π stacking and intermolecular interaction coexist in the same direction. It turns out that intermolecular interactions are responsible for charge transport, while π–π stacking interactions dominate donor–acceptor transport. Incorporating the understanding of the molecular packing motifs and intermolecular interactions into the design of organic semiconductors can assist in the development of novel materials.

Effect of Configuration Interaction of Rare-Earth Ion States on the Intensity of Intermultiplet Transitions

We present the analysis of wave functions and the effect of configuration interaction on the intensity of absorption bands for Pr3+, Tm3+, and Er3+ ions. It is shown that due to the strong spin–orbit interaction the wave functions of rare-earth ions are multicomponent superpositions of ″pure″ 2S+1LJ multiplets with different values of S and L and the same values of the angular momentum J. For this reason, the effect of configurational interaction depends not only on the energy gap up to excited configurations, but also on the presence of high-energy 2S+1LJ components. The presence of such components yields a strong influence on the configuration interaction even at the deep layers. Another consequence of the multicomponent composition of the wave functions is the formation of groups of strongly interrelated states. When the configuration interaction is not fully taken into account, the error in describing the oscillator strengths is distributed among all the states of the group, and the low overall accuracy of the description is not perceived as a contradiction to the theory. To confirm the proposed assumptions, the oscillator strengths of the absorption transitions of laser materials activated by Pr3+, Tm3+, and Er3+ ions are described using the modified Judd–Ofelt theory.

Characterization of hot dense plasma with plasma parameters

Characterization of hot dense plasma (HDP) with its parameters temperature, electron density, skin depth, plasma frequency is demonstrated in this work. The dependence of HDP parameters on temperature and electron density is discussed. The ratio of the intensities of spectral lines within HDP is calculated as a function of electron temperature. The condition of weakly coupled for HDP is verified by calculating coupling constant. Additionally, atomic data such as transition wavelength, excitation energies, line strength, etc. are obtained for Be-like ions on the basis of MCDHF method. In atomic data calculations configuration interaction and relativistic effects QED and Breit corrections are newly included for HDP characterization and this is first result of HDP parameters from extreme ultraviolet (EUV) radiations.