Physical Sciences

Abstract: The Spiral Structure Model (SSM) describes the photon as a helical quantum and the electron as a ℤ₂ topological vortex defect of an elastic covariant medium, but its published account is kinematic: the medium’s dynamics was recorded as an open problem. This companion paper reports a concrete candidate dynamics and four derived results. Canonical quantization of the Goldstone (circulation) sector yields an exactly solvable one-quantum problem whose virial theorems return [x, p] = iħ and the SSM momentum width Δp_x = mc/√2. A phase-locking mechanism between the internal circulation and a ξ-scale core texture supplies the two-scale charge structure of the SSM, reduces the self-energy problem by four orders of magnitude, sharpens the core-size bound to ξ ≲ 1.4×10⁻¹⁹ m, and renders the internal excitation band electromagnetically dark (spectral weight ~ 6×10⁻¹²). The gauge sector of the candidate action is QED at one loop, so Schwinger’s a₁ = α/2π is inherited with a definite core-scale deviation; the defect propagator is assembled to the point where its residual failures are quantitative diagnostics rather than open searches; and the elastic vertex follows from the core current with a profile-independent charge radius r_ch = ξ and, for the texture-gradient profile, a diffraction zero at 0.56–4.0 TeV. Finally, the full constraint set on the locked core leaves a global survival window (a factor 65 in the locking stiffness, with walls set by collider and g−2 bounds) and Lorentz covariance of the one-quantum reduction, the one structural gap, is closed: the retarded self-energy kernel supplies (2/3)E₀ of the texture’s inertia where the instantaneous kernel supplies none, the frame-field stress, fixed by the Derrick identity of the soliton sector as the Poincaré-stress analog, supplies the remaining (1/3)E₀, and the von Laue criterion then gives the exact dispersion E(v) = γE₀. The residual open items, the quantum completion of the internal tower and the interaction vertices, are stated with their exact locus of failure.

Abstract: The Spiral Structure Model (SSM) is a phenomenological model in the tradition of Bohr's early atom: confined to kinematics and geometry, it trades dynamical depth for ontological clarity and experimental exposure. Three postulates suffice. (I) The photon is a pointlike energy quantum in uniform helical motion, with axial and circulation speeds both equal to c; (II) physical space is an elastic, relativistically covariant medium that sustains vortex excitations; (III) the electron is a stable topological vortex defect of that medium. From these postulates, with every step carrying an explicit epistemic label, the model obtains the photon's circulation angular momentum mcrγ = ħ as a consistency theorem and identifies it with the photon spin; logarithmic vortex confinement with no free parameters; the two polarization states and the absence of a longitudinal mode; orbital angular momentum as an ensemble property; the electron's 720-degree periodicity and spin ħ/2 from π₁(SO(3)) = ℤ₂. The same postulates yield the fine-structure constant as a ratio of structural scales and the free radiation field as a retarded ensemble moment satisfying the wave equation exactly. They also yield a phase-coupling account of two-slit interference and a double-helix ontology of entangled pairs that reproduces the CHSH value 2√2. Three falsifiable discriminants are stated with explicit falsification criteria: a wavelength-locked on-axis void in the photon's detection profile, a spin-dependent electron form-factor window near Q = mc, and a circulation-periodic component in entangled-pair coincidence timing.

Abstract: With the detection of the gravitational wave event GW170817 and the astronomical transient (kilonova) AT2017gfo, (binary) neutron star mergers arose as possible sites for heavy element nucleosynthesis via the r-process. Lanthanides are theorised to be produced in such astrophysical environments, although to verify such claim it is necessary to model these events. Modelling kilonovae at the nebular phases (or late epochs) is particularly challenging because collisional processes have to be explicitly taken into consideration. Radiative recombination (RR) is one of the collisional atomic processes relevant in nebular phases. This work presents calculations of RR rate coefficients, for doubly ionised lanthanides (open 4fN configurations), performed with the Flexible Atomic Code, benchmarked against Autostructure in simple cases. Moreover, these RR rate coefficients are compared with the Axelrod (1980) approximation, proposing new parameters, and fitted with the expression adopted by Verner and Ferland (1996) to ensure data replication. The new parameters proposed to the Axelrod approximation show scaling with the atomic number. Additionally to computing RR rate coefficients from the ground state level and all levels belonging to the ground state configuration, we also calculate such parameters for levels from excited configurations that can be populated at the temperatures characteristic of kilonovae, proposing a procedure to account for RR from these excited configurations. This work leaves out dielectronic recombination rate coefficients for a future Part II.

Abstract: A standing-wave closure condition in Delta-c Mechanics has two lowest exact orbital solutions: a closed full-orbit branch and an open half-orbit branch. These define, respectively, the atomic and nuclear kernels and satisfy the reciprocal relation α K_A K_N = 1. The principal result is the existence, within the proposed two-photon dynamics, of a single standing-wave closure condition whose two lowest branches correspond to the atomic and nuclear domains. The particle-mass relations that follow are presented as quantitative tests of this structural correspondence, not as an independent derivation of the mass spectrum; a unique, mass-independent generation rule for all higher harmonic assignments remains an open problem, stated as such in Appendix F. The reflecting interior boundary selects even Fourier modes and half-contour phase-lock conditions; multi-flow kernel products then determine rest-mass ratios through the binding law m_x/m_e = √E_x. The proton defines the three-flow nuclear ground state and is disclosed as the calibration identity for the anomalous nuclear ratio η. Independent tests include the neutron (0.268 ppm raw discrepancy), the charged pion (1.5σ from PDG 2024), the muon (−4.1 ppm raw), the tauon (within present uncertainty with a stated higher-harmonic prediction), and the top quark (within its 0.4 GeV measurement uncertainty). The purpose is not to replace QCD or electroweak theory in this paper, but to test whether one harmonic closure structure displays quantitative consilience from hydrogen spectroscopy to the nuclear mass scale.

Abstract: The Thomas–Fermi Relativistic-Shell-Extended Ionic Closed-Form model (TF-RSE-IonCF) v3.2 is presented as a unified closed-form model returning the total electron binding energy (TBE) for every neutral atom and ion across the periodic table. For each nuclear charge Z = 1–92 and each electron number N = 1 to Z (charge state q = Z–N = 0 to Z–1), a single formula evaluates the TBE in microseconds. The model is built in two layers. The neutral-anchor layer (TF-RSE v2) extends the Thomas–Fermi power law with a Dirac relativistic factor, a trigonometric shell-oscillation factor and a piecewise light-element correction (0.40% mean error on the 92 neutral atoms, degrading smoothly to 3.6% out-of-sample on Z = 93–103). The ionic layer decomposes the ionic TBE into shell-resolved contributions anchored at four reference limits — the point-nucleus Dirac value at N = 1 (finite-nuclear-size and QED corrections neglected; +0.35% from the NIST value for H-like uranium), a screened helium-like value at N = 2, a screened neon-like value at N = 10, and the neutral-anchor value at N = Z — blended by power laws, with three ablation-validated upgrades (effective charge Z_eff(Z, N) in the relativistic factor; electron-number shell-sawtooth S(Z, N); shell-closure bumps at N = 10, 18, 36, 54, 86). Fitted to 4278 NIST reference points with the neutral layer frozen, the core closed form achieves a mean relative error of 0.259% (median 0.151%, maximum 4.63%), with 97.7% of points below 1% and 100% below 5%; the safeguarded v3.2 output retains a mean error of 0.260% (median 0.161%, maximum 4.33%). Version 3.2 retains the v3.1 three-tier physical-consistency safeguard — (i) a hard physical cap E(Z, N) ≤ E_v2(Z) enforcing positive binding of the last electron; (ii) a boundary-layer reconstruction (N > Z–5) with an increasing ionization-energy trend (IP_k = 1.8·IP_{k−1}); and (iii) a minimal-touch projection (0.5 eV floor) for interior oscillation violations — and extends Tier 2 from a pure monotonicity test to a physical-plausibility window (0.5 eV ≤ IP_k ≤ 4·IP_base·1.8^(k−1)), which removes monotone-but-unphysical near-neutral links left by v3.1 (e.g. a raw first ionization energy of +2588 eV for U I). After the extension, every element has strictly positive, monotone and trend-correct boundary ionization energies (first ionization energies Si 8.0, Fe 7.0, U 5.0 eV vs. experiment 8.15, 7.90, 6.19 eV). The safeguard modifies 646 of 4278 points (15.1%); core-grid adjustments remain bounded by 1.14 keV (Lu, N = 63), while adjustments exceeding 1 keV occur only in the disclosed boundary layer of the heaviest actinides (maximum 7.84 keV, U, N = 88); the core-grid statistics are essentially unchanged (mean error 0.230% raw vs. 0.238% safeguarded for N ≤ Z−5) and all 29 fitted parameters are unchanged. The model returns cumulative binding energies: individual ionization potentials near the neutral boundary are positive, monotone, trend-correct estimates only (within a factor of about three in the worst case), and quantitative ionization potentials must be taken from experimental databases or ab initio calculations.

Abstract: We use molecular dynamics simulations to study hydrated Nafion at hydration levels λ=3,9,15 under external electric fields. At zero field, the static dielectric constant of the aqueous subsystem, obtained from water dipole fluctuations, grows with hydration, from ϵ≈2.9 at λ=3 to ϵ≈17.2 at λ=15; because the single-molecule dipole is essentially unchanged, this enhancement is cooperative in origin, reflecting the dipolar correlations that build up as the aqueous domains percolate. Under an applied field the fluctuation formula no longer defines an equilibrium dielectric constant, so we characterize the response through the polarization itself: the collective water dipole orients along the field already at low fields, while its magnitude 〈Mz〉 saturates gradually, on a field scale that grows with hydration. This polarization build-up is accompanied by a reorganization of the first H3O+–SO3(H) coordination shell and by a crossover from diffusive to drift-dominated proton transport. These signatures do not evolve independently but shift together to higher fields as hydration increases, showing that the water polarization and the proton transport are coupled to a common, hydration-controlled field scale: electrostatic screening by the added water simultaneously sets the equilibrium dielectric response and the field required for directed hydronium transport in perfluorinated membranes.

Abstract: Building on our previous Multiconfiguration-Dirac-Hartree-Fock (MCDHF) computational strategies taylored for the hyperfine structure (HFS) of low-lying levels in one-valence electron Sr II and Ba II ions, and in two-valence electrons Ba I atom [Nezosi et al, Atoms 14, 17 (2026). DOI: 10.3390/atoms14030017], we successfully extend these methodologies along the alkaline-earth elements to the lighter Ca II and the heavier Ra I-II ions. MCDHF recommended HFS constants, along with their uncertainty estimates, are reported for the first time and critically discussed. Where applicable, the Bohr-Weisskopf correction is applied to the HFS constants, and its effects are analyzed. This is particularly valuable for cases where no measurement is available such as for the [Rn]\(6d ^2D_{3/2,5/2}\) levels in ^223,225Ra II, for the [Rn]\(7s6d~^3D_{1,2,3}\) and ¹D₂ levels in ²²³Ra I, for the [Rn]\(7s6d ^3D_{2,3}\) and ¹D₂ levels in ²²³Ra I, and for the [Rn]\(7s7p~^3P^o_2\) level in ²²⁵Ra I. In all cases, our MCDHF values agree with the ones found in the literature within our error bars. For the ²D_5/2 levels in Ca II and Ra II, the discrepancies with experiment observed in Sr II and Ba II for the HFS \(A\) constant are not seen.

Abstract: The R-matrix method has long been employed as the most advanced and powerful approach to treat a variety of atomic processes. Its main application has been in spectral analysis and modeling of astrophysical and laboratory sources. We describe the R-matrix methodology, computational codes, and extensions developed for numerical simulations under wide-ranging physical conditions in astronomical objects such as stellar atmospheres in non-local-thermodynamic-equilibrium (NLTE), interstellar medium, black hole environments and active galactic nuclei, and in high-energy-density (HED) environments such as high-intensity lasers, plasma fusion devices and stellar interiors. We present exemplary results for atomic cross sections for photoionization, electron impact excitation and electron-ion recombination, as well as for plasma effects in HED sources. In addition, we illustrate selected applications at different and varying temperatures, densities, and other variables.

Abstract: Calculation of nonbonded interactions has been a bottleneck for molecular simulations (for molecular dynamics (MD) and Monte Carlo (MC) simulations) that are limiting the system size and the time scale in MD up to nanoseconds. To reduce the computation time/load in calculating nonbonded interactions, an efficient sampling techniques were introduced in this study, for calculating total potential acting on individual atoms. Conventional way of calculating nonbonded interaction for a particular atom is by calculating pairwise van Der Waal and Coulomb interactions for all neighboring atoms with in cutoff radius and adding tail correction beyond the cutoff. Here, we introduce Theory of Local Sampling (TLS), where nonbonded interactions will be calculated by using selective local region around the atom (instead of considering all region within cutoff). Basic principle in TLS is that, any effect/change in global region will reflect in selective local region and can be integrated into molecular simulations. This local sampling technique, instead of global sampling, helps in reducing total computation time/load in calculating nonbonded interactions for the system at each step in MD and in MC simulations. Applying TLS in MD simulation for Argon atoms gives reduction in computation time up to 60%. For MC simulation, up to 37% of reduction in computation time was acheived. Energies and radial distribution function (RDF) comparison for Argon liquid system gives good agreement with conventional MC and MD simulations. Another approach presented in reducing computation time in MD simulations is using "Curve Fitting" techniques in predicting force/acceleration acting on individual atoms using previous time steps, giving 24% reduction in computation time. Combining "TLS & Curve Fitting" techniques further reduces computation time up to 67% in MD simulations.

Abstract: In strong-field ionization, complex-time saddle points govern electron ionization instant and quantum-orbit interference patterns. Neverthless, not all solutions to the saddle-point equation carry physical contributions. And saddle coalescence can also invalidate the isolated-saddle approximation. Within the strong-field-approximation framework, we propose a topology-constrained approach to reconstruct photoelectron momentum spectra. A physics-informed neural network is employed to produce candidate roots, which are subsequently refined via a Newton-type iteration. Picard–Lefschetz upward flows are adopted to pick out physically connected saddles, while local coherent continuation for pole-saddle pairs handles saddle-coalescence regions. A topological selector is defined by the non-zero support of intersection numbers to filter unphysical solutions. We test our method on hydrogen atoms subjected to six-cycle elliptically polarized laser fields and compare reconstructed spectra against direct numerical strong-field-approximation results. For 300 nm and 500 nm driving fields, the normalized relative L₂ errors on the linear probability scale reach 3.793% and 3.520%, respectively.The topological selection eliminates disconnected non-physical contributions, and local continuation recovers quantum cancellation effects near saddle coalescence. Our method improves the physical interpretability of saddle-based spectrum reconstruction under strong-field approximation and is promising for other computational-physics problems involving saddle-point equations.

Abstract: We present a theoretical investigation of the attoclock method in laser-assisted photoemission (LAPE) processes. We analyze atomic photoionization driven by a short XUV pulse assisted by a circularly polarized strong infrared (IR) laser under accessible experimentally conditions. We calculate three-dimensional photoelectron momentum distributions (PMDs) in order to extract time delays from their angular information based on the attoclock principle. Furthermore, we explore different XUV parameters to determine the optimal achievable temporal precision for the laser-assisted attoclock (LAAC). The analyses performed within the the strong-field approximation (SFA) are further supported by improved Coulomb methods, including the Coulomb–Volkov approximation (CVA) and numerical solutions of the time-dependent Schrödinger equation (TDSE). Our work lays a theoretical foundation for understanding time-resolved electronic dynamics in cutting-edge ultrafast experiments of photonic collisions.

Abstract: High-precision two-dimensional intermolecular potential energy surfaces (PESs) for Rg–CuF (Rg = Ar, Kr, Xe) were constructed at the coupled-cluster singles and doubles with non-iterative triples [CCSD(T)] level, by employing aug-cc-pVXZ (X = D, T, Q) basis sets and the energies were extrapolated to the complete basis set (CBS) limit. All three complexes exhibit a consistent topological pattern: the global minimum corresponds to a collinear Rg–Cu–F configuration, and the local minimum corresponds to an anti-linear Rg–F–Cu configuration. As the atomic number of noble gas increases, the Rg–Cu equilibrium distance lengthens while the binding strength remarkably enhance. Bound state calculations were performed based on these PESs to yield rotational levels, which can be used derive the intermolecular vibrational frequencies, molecular structures and spectroscopic parameters for all primary isotopologues. The predicted rotational constants B are in excellent with the experimental observations, attaining a sub-MHz accuracy at the AVTZ level for Kr–CuF and at the CBS limit for Ar–CuF and Xe–CuF. Vibrational wavefunction analysis reveals that the intermolecular vibrational modes of Kr–CuF and Xe–CuF are highly localized, consistent with the pronounced molecular rigidity observed experimentally. Isotopic effect analysis reveals a well-defined linear relationship between the changes in the rotational constant B and the intermolecular vibrational frequency in relation to the reduced mass of the complex, which provides a reliable basis for predicting spectroscopic parameters of unobserved isotopologues.

Abstract: Accurate atomic data for heavy ions are required for spectroscopic diagnostics and impurity transport modeling in magnetic-confinement fusion devices, particularly for tungsten and its neutron-induced transmutation products. In the present work, we investigate the ytterbium-like ions Ta IV, W V, Re VI, Os VII, Ir VIII, and Pt IX using complementary pseudo-relativistic Hartree–Fock (HFR) and fully relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) approaches. Semi-empirical calculations were first performed using the HFR method including core polarization corrections (HFR+CPOL). The evolution of correlation effects along the isoelectronic sequence was then analyzed through an alternative HFR(CV) model in which the most important core-excited configurations were introduced explicitly to account for core–valence interactions. Extensive least-squares fits to the available experimental energy levels were carried out for all ions considered. The results reveal that the HFR+CPOL approach provides an adequate description of Ta IV and W V, while explicit treatment of core–valence correlations becomes increasingly important from Re VI onwards owing to the growing interaction between the 5d5f and 5p⁵5d³ configurations. New energy level classifications, level compositions, oscillator strengths, and transition probabilities are reported and critically assessed through comparisons between HFR and MCDHF calculations. The resulting dataset extends previous investigations of rhenium and osmium ions and provides benchmark atomic data for heavy-ion spectroscopy and future fusion-plasma applications.

Abstract: The Bohr radius is normally presented as a non-relativistic length scale. Less widely discussed is that, in the second part of his 1913 trilogy, Bohr briefly indicated how the radius formula could be modified when the orbital velocity is not negligible compared with the speed of light. In this paper, we revisit that overlooked prescription and show that replacing the electron rest mass by the Lorentz-factor-adjusted mass term leads to a relativistic Bohr radius a_(0,r) = a₀ √(1 -α²) = (λ̅_e√(1 -α²))/α for hydrogen, and to a^Z_(0,r) = a₀/Z √(1- Z²α²) for a hydrogen-like one-electron ion. The central result is that this semi-classical expression is not merely an ad hoc relativistic contraction: under the assumptions of a point nucleus, infinite nuclear mass, and a one-electron Coulomb field, it is exactly identical to the most probable radius obtained from the Dirac 1s_1/2 radial probability density. This identification appears to be the first explicit demonstration that Bohr’s historical relativistic prescription selects the Dirac most-probable radius, rather than the Dirac expectation value ⟨r⟩D. We emphasize the important distinction between a most-probable radius and a mean radius: even in the non-relativistic Schrödinger 1s state, the most-probable radius is a₀/Z, whereas the expectation value is 3a₀/(2Z) and is therefore larger by a factor of 3/2. For hydrogen the relativistic correction to the most-probable radius is only 1.40898891811 × 10⁻¹⁵ m, or 0.0026626%, but the result is conceptually significant because it links Bohr’s semi-classical radius, the relativistically contracted reduced Compton wavelength, and the Dirac-Coulomb ground-state probability maximum in one compact formula. We also provide numerical values for hydrogen-like ions and explain why these smooth one-electron Dirac radii should not be confused with expectation values or with empirical radii of neutral many-electron atoms, which can vary non-monotonically across the periodic table.

Abstract: We consider quasi-one-dimensional (Q1D) continuous waves (CWs) in the two-dimensional (2D) optical system with the cubic-quintic nonlinearity and a Q1D potential trough. In the case of a smooth trough profile, we confirm the known modulational instability (MI) of Q1D CWs with the transverse structure corresponding to the 1D ground state (GS) in the potential trough, and demonstrate the MI of CWs with the dipole-mode (DM) transverse structure, corresponding to the lowest 1D excited state in the potential trough. The CWs of both GS and DM types remain nearly stable close to edges of their existence regions. Stable stationary states in the form of periodic chains of 2D solitons, trapped in the potential trough, are produced in a numerical form. The dynamics of the soliton chains excited by a localized kick is studied too. For the potential trough with the singular delta-functional profile, we find two species of exact analytical solutions for CWs, one of which is completely stable.

Abstract: The new approach is develop to determine the hyperfine structure of the rotationally excited 1s_µnℓ_e-states in the three-body helium-muonic ³He µ e and ⁴He µ e atoms. The formulas derived in this study allow one to determine the hyperfine structure splittings for an arbitrary rotationally excited 1s_µnℓ_e-state in the three-body helium-muonic atoms. We also created the new approximate method which can be used for fast numerical evaluations of the hyperfine structure splittings in the both 1s_µnp_e and 1s_µnd_e-states of the 3He µ e and 4He µ e atoms. Similar formulas were never produced in earlier studies.

Abstract: We reformulate matrix mechanics by incrementally heating a single hydrogen atom in order to derive the complete, diagonalized Hamiltonian matrix. The spectral lines and transition probabilities cannot be generated by reversing time thereby demonstrating asymmetry. Experimental evidence in support of the theoretical model is obtained from experiments performed with the simplest quantum system, an electron cyclotron. Wave mechanics is also reformulated by altering the original Schrödinger equation describing a time symmetric, conservative system to a system of two independent equations describing a time asymmetric, non-conservative system.

Abstract: Critical binding of quantum states in Screened Coulomb Potentials such as Yukawa/Debye, Hulthén, and ECSC (Exponential Cosine Screened Coulomb) potentials is of perennial interest and relevance in many fields of science, ranging from nuclear and particle physics; plasma physics, astrophysics, cosmology, and nuclear fusion; physical chemistry, condensed matter, and materials physics; to synthetic nanostructures and nanophotonics. The purpose of this paper is to heuristically explore two related mysteries, one new, the other more than 50 years old. The solutions to these mysteries have implications for a much broader class of potentials, those addressed by Klaus and Simon. In our recent paper [1], we presented numerical calculations using the Phase Method (PM), accurate to 60 digits and to screening lengths D ≤ 10³ au, l = 0–20, of the critical binding parameters for these potentials; an for Yukawa and ECSC, l = 0–12, to D ≤ 10⁵ au, at 30 digits. In doing so, we discovered anomalous period-40 sawtooth structure in the critical parameters of the ECSC potential that is not observed for the Yukawa potential. In this second paper, we quantitatively explain the origin and periodicity of this newly discovered structure. To do so, we use two complementary approaches: a “neoclassical” (NC) variant of conventional semiclassical phase space quantization; and the PM for very precise fullyquantum calculations. The observed period-40 sawtooth structure is quantitatively explained in terms of a novel “tick-tock” mechanism. The periodicity is calculated in terms of the ratio of phase-space integrals for the primary and secondary potential wells. A quartic double-well potential is used as a simple model to further illustrate the tick-tock mechanism. Using NC, an approximate expression is derived to predict the locations of tick-tock glitches from higher order wells; it is confirmed by a PM calculation up to D ≤ 10⁶ au. The second mystery is a strangely linear dependence of the total number of bound states vs screening length for both the Yukawa and ECSC potentials. Using the PM we confirm and extend these empirical relations. We show using the PM that an approximate trivariate linear relation between the square root of the critical screening length √D_c, state number n, and angular momentum l applies to these potentials. This, plus a geometrical state accumulation argument solve the second mystery. We show these properties derive from the scaling relation between screening length and coupling constant, and as such are predicted to be applicable to the whole class of potentials. These results are expected to be of both theoretical interest and experimental relevance when interpreting spectra or calculating thermal properties. The significance of these results, and the applicability of these methods and conclusions to a vast array of related potentials is briefly discussed. Tables of critical screening parameters for Yukawa, Hulthén and ECSC D ≤ 10⁵ and l = 0 − 12 are posted as supplementary data.

Abstract: We present new and improved calculations of Stark-broadened profiles for ionized helium, a key ingredient in the spectroscopic analysis of helium-atmosphere DO white dwarfs. Our approach builds upon the computer simulation framework previously developed for neutral helium, which fully accounts for the dynamical interactions of both ions and electrons with the emitting helium atom. We extend this theoretical formalism by relaxing the assumption of straight-line trajectories for the perturbing particles (electrons and ionized helium) and adopting the hyperbolic trajectories appropriate for their interaction with a charged emitter, thereby accounting for their dynamical influence on the line-broadening process. In this exploratory study, we focus on the He II λ4686 line, the strongest absorption feature observed in the spectra of DO white dwarfs. We present the resulting Stark profiles and perform a detailed comparison with those available in the literature.

Abstract: Electron configurations are known to provide (valuable) insights into the electronic structure and behavior of atoms. They specify which and how the electronic (sub-) shells are occupied, and is thus an essential ingredient for most atomic observables. When combined with the shell model and the successive filling of shells, these configurations help explain the Periodic Table and much of chemical binding. They also establish a qualitative framework for analyzing excitation, ionization and relaxation processes and may facilitate–a wide range of–astrophysical and plasma simulations. — Here, we review the role of electron configurations for understanding atomic behavior in interactions with particles and radiation. In particular, we identify several central requirements for an efficient treatment of configuration lists and define a domain-specific language in order to generate, manipulate and analyze such lists as well as to extract physically relevant information. We also demonstrate the implementation of this language in Jac, the Jena Atomic Calculator. An efficient handling of configurations will refine the coupling of structure codes with the spectral synthesis of plasma radiation, the setup of ionic cascades or even non-LTE plasma simulations. This common framework for dealing with electron configurations therefore improves consistency, reproducibility and scalability of atomic modeling.