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8 pages, 655 KB

Open AccessProceeding Paper

QED Coupling of Image States in Spherical Cavities

by Blake Gerardo Pérez, Renata Della Picca and Juan Martín Randazzo

Phys. Sci. Forum 2026, 13(1), 1; https://doi.org/10.3390/psf2026013001 - 17 Apr 2026

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In this work, we address the study of a confined atom in spherical cavities through the Pauli–Fierz Hamiltonian. In this approximation the spherical transverse modes of the field are considered in the Coulomb gauge and in the second quantization formalism. In the present [...] Read more.

In this work, we address the study of a confined atom in spherical cavities through the Pauli–Fierz Hamiltonian. In this approximation the spherical transverse modes of the field are considered in the Coulomb gauge and in the second quantization formalism. In the present contribution, the longitudinal field is considered through the Hartree potential, an interaction between particles and between the particles and the conductive walls, obtained from the electrostatic energy density and consistent with the boundary conditions imposed to the transversal components. The self-energy states of the coupled system are written in terms of a series of separable field–matter orbitals, in a configuration interaction scheme. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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9 pages, 7600 KB

Open AccessProceeding Paper

Electron-Impact Single Ionization of Molecules: Orientation-Resolved Fully Differential Cross Sections

by Emiliano Acebal and Sebastian Otranto

Phys. Sci. Forum 2026, 13(1), 2; https://doi.org/10.3390/psf2026013002 - 30 Apr 2026

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Abstract

In this work, we study the single ionization of H₂O and C₄H₈O by electron impact. Fully differential cross sections are calculated by means of two distorted wave models which vary in the single-centre approximation applied to the [...] Read more.

In this work, we study the single ionization of H₂O and C₄H₈O by electron impact. Fully differential cross sections are calculated by means of two distorted wave models which vary in the single-centre approximation applied to the interaction of the continuum electrons with the residual molecular ion. Dependence on the molecular target orientation is analyzed before performing an average procedure to benchmark with experimental data. The present results suggest that structures in non-oriented triple differential cross sections do not directly reflect the patterns inferred from a limited set of particular orientations, demanding an extensive averaging procedure. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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8 pages, 1271 KB

Open AccessProceeding Paper

Atomic Energy Level Calculations for Lanthanides with AUTOSTRUCTURE

by Tomás Campante, Ricardo Ferreira da Silva, Luís Leitão, Daniel Garcia, Jorge Miguel Sampaio and José Manuel Pires Marques

Phys. Sci. Forum 2026, 13(1), 3; https://doi.org/10.3390/psf2026013003 - 27 Apr 2026

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Abstract

With the detection of kilonova AT2017gfo, (binary) neutron star mergers emerged as possible astrophysical sites for heavy element nucleosynthesis via r-process. To verify this claim, it is key to identify elements such as lanthanides and actinides in kilonovae spectra. Theoretical calculations arise [...] Read more.

With the detection of kilonova AT2017gfo, (binary) neutron star mergers emerged as possible astrophysical sites for heavy element nucleosynthesis via r-process. To verify this claim, it is key to identify elements such as lanthanides and actinides in kilonovae spectra. Theoretical calculations arise as a solution to fill the scarcity of experimental atomic data to perform this identification. This work presents theoretical calculations with the AUTOSTRUCTURE atomic code for Ho, Er, Tm, Yb and Lu singly and doubly ionised, and benchmarks them against experimental data. The similarity between these theoretical calculations and experimental data was quantified via a mean absolute relative error (MARE), which showed that the calculations yield an average MARE of 58.7% and 56.7% for the singly and doubly ionised species, respectively. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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7 pages, 7513 KB

Open AccessProceeding Paper

State-Selective Charge Exchange in Collisions of Multiply Charged Ions with H₂

by Nelson D. Cariatore and Sebastian Otranto

Phys. Sci. Forum 2026, 13(1), 4; https://doi.org/10.3390/psf2026013004 - 28 Apr 2026

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Abstract

We report an enhanced Classical Trajectory Monte Carlo (CTMC) approach developed to study state-selective charge exchange in collisions between multiply charged ions and H₂ molecules. The model combines two hydrogenic three-body formulations—originally designed to improve the H(

1 s

) radial distribution—within [...] Read more.

We report an enhanced Classical Trajectory Monte Carlo (CTMC) approach developed to study state-selective charge exchange in collisions between multiply charged ions and H₂ molecules. The model combines two hydrogenic three-body formulations—originally designed to improve the H( 1 s ) radial distribution—within the five-body CTMC framework introduced by Wood and Olson. The new schemes, termed E-CTMC and Z-CTMC, extend the electronic density of the target to larger distances, providing a more accurate representation of the molecular system. Calculations for 2 to 100 keV/u Ne⁹⁺ and O⁶⁺ projectiles at low and intermediate impact energies are benchmarked against recent laboratory data and the Multichannel Landau–Zener method. The Z-CTMC approach reproduces the observed energy-dependent shift of the most populated n levels, showing the closest overall agreement with the experiments. Complementary simulations for different projectiles show that discrepancies among the CTMC variants grow with increasing projectile charge and lower impact energies, emphasizing the need for further experimental measurements involving highly charged ions. The present formulation offers a consistent framework for analyzing charge-exchange processes relevant to laboratory and astrophysical plasmas. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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8 pages, 276 KB

Open AccessProceeding Paper

Resonant Excitation in r-Process Collision Strengths for Non-LTE Kilonova Modelling

by Ricardo Ferreira da Silva, Luis Leitão, Andreas Flörs, Tomás Campante, Daniel Garcia, Jorge Sampaio, Gabriel Martínez-Pinedo and José Pires Marques

Phys. Sci. Forum 2026, 13(1), 5; https://doi.org/10.3390/psf2026013005 - 11 May 2026

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Abstract

The modelling of kilonova spectra, particularly in the late-time nebular phase, relies heavily on accurate atomic data. While significant progress has been made regarding energy levels and radiative transition rates for r-process elements, data for collisional processes remains scarce. Current models often [...] Read more.

The modelling of kilonova spectra, particularly in the late-time nebular phase, relies heavily on accurate atomic data. While significant progress has been made regarding energy levels and radiative transition rates for r-process elements, data for collisional processes remains scarce. Current models often rely on the Van Regemorter and Axelrod approximations for effective collision strengths. In this work we present the calculation of electron-impact excitation (EIE) collision strengths for relevant r-process elements. We employ the Independent-Process, Isolated-Resonance Distorted-Wave (IPIRDW) approximation to account for the contribution of resonant excitation, which is crucial at the low temperatures characteristic of kilonovae. We demonstrate the validity of our method by benchmarking against R-Matrix calculations for Te iii, finding good agreement while maintaining a significantly lower computational cost. We focus on the relevant 2.1 μm feature and estimate a mass of 2.6× 10 − 3 M ⊙ using our IPIRDW data for EIE effective collision strengths, compatible with other recent estimations using R-Matrix data. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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10 pages, 420 KB

Open AccessProceeding Paper

Atomic Structure Analysis and Radiative Properties with Einstein Coefficients for Ne-like Se (Se XXV)

by Malvika Singh, Richa Paijwar and Rinku Sharma

Phys. Sci. Forum 2026, 13(1), 6; https://doi.org/10.3390/psf2026013006 - 13 May 2026

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Abstract

We present a detailed study of the atomic structure and radiative properties of highly charged neon-like selenium (Se XXV), motivated by its importance in plasma diagnostics, fusion research, and astrophysical spectroscopy. We calculated excitation energies and radiative parameters for the 50 lowest levels [...] Read more.

We present a detailed study of the atomic structure and radiative properties of highly charged neon-like selenium (Se XXV), motivated by its importance in plasma diagnostics, fusion research, and astrophysical spectroscopy. We calculated excitation energies and radiative parameters for the 50 lowest levels of fine structure using a fully relativistic multiconfiguration Dirac–Fock approach. We calculated transition wavelengths, radiative transition rates, oscillator strengths, and line strengths for electric dipole, magnetic dipole, electric quadrupole, and magnetic quadrupole transitions among the specified levels. We also evaluated Einstein coefficients for spontaneous and stimulated emission, transition dipole moments, and radiative lifetimes of the low-lying states. To validate the results, we performed independent relativistic calculations using an alternative theoretical method and compared the datasets to examine internal consistency. The calculated excitation energies and radiative parameters agree well with values reported in the National Institute of Standards and Technology database (NIST) and other published theoretical results. The agreement between the independent approaches confirms the consistency of the present dataset. These results provide reliable atomic data for spectral line identification and quantitative plasma modeling in laboratory and astrophysical environments and support ongoing experimental and diagnostic studies of highly charged ions. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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5 pages, 801 KB

Open AccessProceeding Paper

Fourier Transform Infrared Emission Spectroscopy of Si ii

by Zaid Mustafa and Haris Kunari

Phys. Sci. Forum 2026, 13(1), 7; https://doi.org/10.3390/psf2026013007 - 29 May 2026

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Abstract

Accurate and precise spectral data for singly ionized silicon (Si ii) are important for numerous applications. In this work, we present high-resolution Fourier transform IR emission spectroscopy of Si ii, using spectra recorded with the 1 m FTS at the Kitt [...] Read more.

Accurate and precise spectral data for singly ionized silicon (Si ii) are important for numerous applications. In this work, we present high-resolution Fourier transform IR emission spectroscopy of Si ii, using spectra recorded with the 1 m FTS at the Kitt Peak National Observatory. A total of 18 lines were measured in the region 780 nm to 4000 nm, and an immediate comparison of our data with the NIST ASD shows that our measurements offer at least a tenfold improvement in precision. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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8 pages, 399 KB

Open AccessProceeding Paper

The Effect of Number-State Filtration on the Collapse and Revival Features of the Jaynes–Cummings Model

by Hashmitha Sugumar and Nilakantha Meher

Phys. Sci. Forum 2026, 13(1), 8; https://doi.org/10.3390/psf2026013008 - 17 Jun 2026

Viewed by 195

Abstract

A two-level atom interacting with a cavity field initialized in a coherent state exhibits the collapse and revival features in its population inversion dynamics under the Jaynes–Cummings interaction. When the cavity field is prepared in a number-state filtered coherent state, obtained by filtering [...] Read more.

A two-level atom interacting with a cavity field initialized in a coherent state exhibits the collapse and revival features in its population inversion dynamics under the Jaynes–Cummings interaction. When the cavity field is prepared in a number-state filtered coherent state, obtained by filtering the number state | m 〉 from a coherent state | α 〉 , we observe micro-Rabi oscillations in the collapse region instead of a perfect collapse. We find that the Rabi frequency of these micro oscillations depends only on the filtered photo-number m, whereas the amplitude depends on both m and α . This dependence enables one to infer the filtered number state from the coherent-state distribution by analyzing the time evolution of the atomic population inversion. Conversely, the amplitude and frequency of the micro-Rabi oscillations can be tuned by filtering an appropriate number state. Furthermore, we investigate the effect of filtering multiple number states from a coherent state on the atomic population inversion dynamics. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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8 pages, 925 KB

Open AccessProceeding Paper

Radiative Recombination of Pm-like Tungsten (W XIV): A Theoretical Benchmark for Kilonova Modelling

by Daniel Garcia, Tomás Campante, Ricardo Ferreira da Silva, Luís Leitão, Jorge Sampaio and José Pires Marques

Phys. Sci. Forum 2026, 13(1), 9; https://doi.org/10.3390/psf2026013009 - 17 Jun 2026

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Abstract

Recombination processes heavily influence the ionization balance and level populations of Non-Local Thermodynamic Equilibrium (Non-LTE) plasmas. This is especially relevant for kilonovae, whose ejecta rapidly evolves into a Non-LTE regime. Collisional-radiative models become necessary, but are limited by the scarcity of data for [...] Read more.

Recombination processes heavily influence the ionization balance and level populations of Non-Local Thermodynamic Equilibrium (Non-LTE) plasmas. This is especially relevant for kilonovae, whose ejecta rapidly evolves into a Non-LTE regime. Collisional-radiative models become necessary, but are limited by the scarcity of data for heavy r-process elements. In this work, we present radiative recombination (RR) rate coefficients for Pm-like tungsten (W XIV) using the Flexible Atomic Code (FAC). W XIV makes a reliable benchmark for two primary reasons: tungsten is one of the heavy elements best characterized across its ionization sequence, providing a wealth of available data for comparison, and this charge state shares the complicated open f-shell structure of key r-process elements, consequently presenting similar challenges that emerge when executing this type of calculation. Validating our approach here provides the foundation for extending this methodology to the lanthanide sequence. The calculations performed in this work show good agreement with previous relevant works. Additionally, an RR calculation with a set of configurations that captured the low-lying energy structure of the recombined ion was performed. The results remain within the same order of magnitude as the standard method across the 10 3 to 10 9 K temperature range. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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7 pages, 984 KB

Open AccessProceeding Paper

A New Representation of the 3C Model in the Quasi-Sturmian Approach to Ionization of Helium by Proton Impact

by Sergey Zaytsev, Lorenzo Ugo Ancarani, Darya Zaytseva, Alexander Zaytsev, Yury Popov and Konstantin Kouzakov

Phys. Sci. Forum 2026, 13(1), 10; https://doi.org/10.3390/psf2026013010 - 8 Jun 2026

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Abstract

We investigate the 75 keV proton impact ionization of helium. The convoluted quasi-Sturmian approach is extended to treat both the direct ionization and the electron capture to the continuum by proposing an ansatz for the Coulomb three-body Green’s function operator, for the kernel [...] Read more.

We investigate the 75 keV proton impact ionization of helium. The convoluted quasi-Sturmian approach is extended to treat both the direct ionization and the electron capture to the continuum by proposing an ansatz for the Coulomb three-body Green’s function operator, for the kernel of which the leading asymptotic form contains the wave function of the 3C model. The resulting 3C-like model is tested numerically. Fully differential cross-sections are calculated for different energy-loss regimes and compared with recent experimental data. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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9 pages, 228 KB

Open AccessProceeding Paper

Energy Levels and Transition Data of Cs XI

by Abid Husain and Haris Kunari

Phys. Sci. Forum 2026, 13(1), 11; https://doi.org/10.3390/psf2026013011 - 18 Jun 2026

Viewed by 192

Abstract

Previously reported atomic data for Cs XI, including spectral lines, wavelengths, energy levels, and transition probabilities, were collected and systematically analyzed. The present theoretical investigation was supported by extensive calculations performed for Cs XI using the pseudo-relativistic Hartree–Fock (HFR) method with configuration interaction, [...] Read more.

Previously reported atomic data for Cs XI, including spectral lines, wavelengths, energy levels, and transition probabilities, were collected and systematically analyzed. The present theoretical investigation was supported by extensive calculations performed for Cs XI using the pseudo-relativistic Hartree–Fock (HFR) method with configuration interaction, as implemented in Cowan’s codes. In this work, all previously reported energy levels and their allowed transition assignments were confirmed. A critically evaluated dataset is presented, including optimized energy levels with their uncertainties, observed and Ritz wavelengths with their corresponding uncertainties, and theoretical transition probabilities with estimated uncertainties. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

13 pages, 1604 KB

Open AccessProceeding Paper

AI for Astrophysical Spectroscopy

by Sultana N. Nahar

Phys. Sci. Forum 2026, 13(1), 12; https://doi.org/10.3390/psf2026013012 - 14 Jul 2026

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Abstract

Artificial intelligence (AI) has become an integral part of our daily lives as a most extraordinary assistant for providing information and carrying out various tasks. We can have an extensive amount of work done by a dedicated AI that we cannot do ourselves [...] Read more.

Artificial intelligence (AI) has become an integral part of our daily lives as a most extraordinary assistant for providing information and carrying out various tasks. We can have an extensive amount of work done by a dedicated AI that we cannot do ourselves due to our easily distracted minds. AI is given vast amounts of information that we have been gathering for a long time. Using that information, it can analyze large amounts of data and sort it into particular topics and narrow down the solutions or choices we are interested in. With highly sophisticated high-resolution ground- and space-based telescopes and observatories, we have been gathering huge amounts of data. The analysis of these data will require both a considerable amount of manpower and time. Both of these factors can be reduced easily if we train dedicated AIs for spectral line identification and plasma modeling for analysis. While high-accuracy atomic data are needed for precise astrophysical plasma modeling, there are many gaps in the data due to computations of these high-accuracy data being complex and numerically challenging and requiring a significant amount of time. These problems can also be tackled to a very good approximation by training AI for simulations of existing high-accuracy data and producing data that are missing. A general algorithm for such predicted data and its implementation in astrophysical applications is presented. A recent application of AI in measuring oxygen abundance in galaxies is also presented. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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8 pages, 7438 KB

Open AccessProceeding Paper

Strong-Field Photoionization: Analysis of Overlapping Above-Threshold Ionization and Laser-Assisted Photoemission Structures

by Candelaria Migliaro, Juan Martín Randazzo and Renata Della Picca

Phys. Sci. Forum 2026, 13(1), 13; https://doi.org/10.3390/psf2026013013 - 15 Jul 2026

Viewed by 172

Abstract

We present a theoretical description of atomic strong-field photoionization. Specifically, we consider an atom driven by a combination of two electromagnetic fields: a high-frequency field assisted by an intense laser of lower frequency. We investigate the photoelectron spectrum (PES) as the sum of [...] Read more.

We present a theoretical description of atomic strong-field photoionization. Specifically, we consider an atom driven by a combination of two electromagnetic fields: a high-frequency field assisted by an intense laser of lower frequency. We investigate the photoelectron spectrum (PES) as the sum of two contributions: direct ionization due to the laser field and the photoionization term associated with the high-frequency field. We identify the contributions of above-threshold ionization (ATI) and laser-assisted photoemission (LAPE) structures in the total spectra, even when they overlap. As a particular case, we investigate the situation where an ATI peak coincides with a sideband. Our theoretical scheme for hydrogen initially in the 1 s quantum state and based on strong field approximation is general enough to be applied to other atomic species and field configurations. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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8 pages, 886 KB

Open AccessProceeding Paper

Photoemission Spectra from Al(111) Surface: Jellium and Band-Structure-Based Potentials

by Martín Barlari, Renata Della Picca, Darío M. Mitnik and Diego G. Arbó

Phys. Sci. Forum 2026, 13(1), 14; https://doi.org/10.3390/psf2026013014 - 17 Jul 2026

Viewed by 207

Abstract

We theoretically compare the photoemission spectra of an Al(111) surface under a short laser pulse using two unidimensional models: jellium and band-structure-based (BSB). We solve the time-dependent Schrödinger equation and project the propagated wave-function onto scattering states via the scattering projection method in [...] Read more.

We theoretically compare the photoemission spectra of an Al(111) surface under a short laser pulse using two unidimensional models: jellium and band-structure-based (BSB). We solve the time-dependent Schrödinger equation and project the propagated wave-function onto scattering states via the scattering projection method in order to get clean spectra, free of spurious oscillations. The main difference between the jellium and BSB results consists of a displacement of the multiphoton peaks of about 5 eV in energy. We find that there is a combined effect of atomic layers and surface–vacuum interface smoothness on the overall structure of the BSB spectra that explains the energy shift in the first multiphoton peak. We also present an energy-band analysis of the photoionization spectra that accounts for their structure within the two surface models. Full article

(This article belongs to the Proceedings of The 1st International Online Conference on Atoms)

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