Introduction

Metallic nanoclusters can be synthesized in a wide range of sizes and stoichiometries by incorporating coinage metals. Among the different sizes of nanoclusters, six atom clusters are of particular interest, as they represent the smallest experimentally realized species in both homo- and bimetallic forms, with or without passivating ligands. 2-(3-Methylureido)acetic acid is selected in this study due to its distinctive charge transfer characteristics.

Methods

All DFT computations were carried out with the Gaussian 16 package, employing B3LYP/ LANL2DZ. For the Ag₆ system, three possible configurations were used: metal cluster near to C=O as D1; near to COOH as D2; and near to NH as D3. Geometry optimizations were validated through harmonic vibrational frequency analyses, confirming the absence of imaginary modes.
Results and Discussion

For the MUA, the most reactive sites are O atoms and H atoms. The adsorption energies are -11.04, -6.73, and -4.70 kcal mol^-1 for configurations D1 to D3. The dipole moments (DMs) are varying in the order D1 (10.85) > D2 (10.30) >D3 (4.83). while that of MUA is 5.40 Debye, and for the D3 configuration, DM is less than that of MUA. The polarizability values of the complexes are significantly greater than that of MUA. The interaction between the Ag₆ cluster and drug is given by the separation distance of Ag to O8 as 2.3619 for D1; Ag to O15 separation of 2.4482 for D2; and Ag to N9 separation of 2.5539 Å for D3.
Conclusions

The interaction of MUA with Ag₆ has been comprehensively analyzed in terms of geometry, spectroscopy, polarization, and energetics. Overall, these results indicate that the MUA-Ag₆ system is a promising candidate for application in electronic devices. The D1 configuration gives the maximum adsorption energy.

Authors and Affiliations

Y.Sheena Mary : sheena@fatimacollege.net

Department of Physics, FMN College, Kollam, University of Kerala, Kerala, India

In Non-Local Thermodynamic Equilibrium (Non-LTE) plasmas, the ionization balance and excited-state populations are heavily determined by radiative (RR) and dielectronic (DR) recombination [1]. Accurate data for these processes are thus fundamental to the interpretation of spectral signatures. For kilonova-relevant ions, however, experimental data remains insufficient for spectral modelling, and therefore requires RR and DR data to be theoretically calculated [1,2].

To establish a reliable methodology, first, we perform a benchmark calculation on Pm-like tungsten (W XIV). Tungsten is extensively studied throughout its ionization sequence, providing a wealth of available data for comparison [3,4]. This particular charge state mimics the complicated open f-shell structure of key r-process elements and, consequently, the challenges that arise while performing this type of calculation [5].

In this work, we present primarily RR and DR rate coefficients for W XIV while including other relevant quantities: RR and photoionization cross-sections and precise DR resonance energies. All calculations were made using the well-established Flexible Atomic Code (FAC) [6], which handles the intricate ion structure at a relatively low computational cost. These results provide high confidence in our method, enabling us to subsequently address the lanthanide sequence.

[1] Singh, S. et al., A&A., 700, A110. 2025

[2] Pognan, Q. et al., MNRAS, 510, 3806. 2022

[3] Trzhaskovskaya, M.B. et al., At. Data Nucl. Data Tables, 139, 101389. 2021

[4] Trzhaskovskaya, M.B. et al., At. Data Nucl. Data Tables, 94, 71. 2008

[5] Preval, S. P. et al., J. Phys. B, 52, 025201. 2019

[6] M.F. Gu, Can. J. Phys., 86, 675. 2008

Electrons' interactions with matter give rise to a variety of atomic phenomena, including ionization, excitation, electron backscattering, and X-ray emission (Kanaya and Okayama 1972). In the present work, an experimental investigation was carried out to measure the bremsstrahlung (BS) yield produced by 10–25 keV electrons incident on a thick (0.1 mm) tungsten (Z = 74) target.

The objective of this study is to examine how the bremsstrahlung yield varies with electron energy, angle of incidence (α), and detection angle (θ). The experiment was conducted using a specially designed setup in which the electron beam and the detector were oriented orthogonally, with the target positioned at the center of the vacuum chamber facing the incident beam (Singh et al. 2018). The angle of incidence (α) was varied from 15° to 75°, measured with respect to the incident electron beam; correspondingly, the detection angle (θ) is described as (90° − α). The emitted X-rays were detected using a Si-PIN detector, and the resulting spectra were analyzed with MCA software to determine the photon yield distributions. The electron current was integrated directly on the target using a current integrator to obtain the total incident charge.

To validate the experimental results, the measured bremsstrahlung yields were normalized and compared with Monte Carlo simulations performed using the PENELOPE code (Salvat,F. 2015; Llovet and Salvat 2017). A comparison with the simulations provides insight into the angular dependence of the bremsstrahlung photon yield and the degree of symmetry or asymmetry with respect to the incidence angle.

The electronic stopping power of charged particles is a key parameter describing their slowing down, energy transfer, and penetration range in matter [1]. It plays a crucial role in diverse fields, including nuclear reactor design, ion beam analysis, ion implantation, radiation damage studies, molecular fragmentation, and hadron therapy. Particularly, the antiproton stopping power provides a stringent test for theoretical models operating under charge conjugation symmetry. The difference between proton and antiproton stopping powers, known as the Barkas effect, remains an active topic of research and discussion [2]. In this work, we present a non-perturbative model to describe the stopping power of transition metals (Ni, Cu, Ag, and Au) for low-energy antiprotons, based on the momentum distribution function of the target’s valence and subvalence electrons, combined with a fully relativistic solution of the electronic wave functions for transition metals with Z > 40. The model’s predictions are compared with available experimental data [3], revealing the expected linear dependence on impact velocity and reproducing the characteristic differences between proton and antiproton interactions.

[1] P. Sigmund, Particle Penetration and Radiation Effects Vol. 1, Springer-Verlag, Berlin, (2006).

[2] G. Massillon-JL et al., Phys. Rev. Lett 134, 076401 (2025).

[3] S. P. Møller et al., Phys. Rev. Lett 88, 193201 (2002).

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(1s) 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 Ne⁹⁺ and O⁶⁺ projectiles at intermediate and low 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.

Work at IFISUR was supported by Grant No. PGI 24/F084 (UNS), Argentina.

Introduction: Accurate laboratory atomic data on spectral lines’ wavelengths, energy levels, and transition probabilities (or oscillator strengths) are inevitably important for several research fields and applications, for example, in the field of astrophysics and plasma physics, and for fundamental and technological applications, in which spectra and their modeling are a part. However, most of the laboratory data (experimental and theoretical) are often present in dissimilar formats, widely dispersed/scattered in the literature, and the literature may contain several values for a quantity that disagree greatly, leading to debate about what is best, most reliable, and final value. Critical evaluations of these data sets play a significant role in such cases.

Methods: Several statistical tools and techniques are available to compare and evaluate data from different sources, including modern-level optimization schemes such as LOPT. For theoretical support, extended HFR calculations were performed using Cowan’s codes. For evaluation of the transition probabilities (TP), multiple comparison schemes are generally carried out based on their dS = (S₁/S₂) as a function of line-strengths for a set of transitions with similar accuracy.

Results and Discussion: This work focuses on comprehensive spectral data analysis and their evaluations, including theoretical TP evaluations on spectra of some selected atoms/ions that we have recently compiled, including C II, Au IV, Cs XI, and Kr VI, and Si II.

Conclusion: In this work, the shortcomings of the existing atomic data are discussed, and, accordingly, the importance of critical evaluation of atomic data is demonstrated with specific examples.

Atomic systems interacting with quantized modes of the electromagnetic field (cavity QED) have been extensively studied in the literature. The set of field–matter states (polaritons) can be described by the Pauli–Fierz (PF) Hamiltonian, which is derived from the minimal coupling scheme in the Coulomb gauge and the second quantization of the transverse components of the electromagnetic field under confinement. The longitudinal field components are accounted for through interaction potentials between charged particles. Despite the significant simplifications involved in its derivation, the PF equation has a broad range of validity, enabling the description of optical, molecular, and condensed matter systems.

After the seminal work of E. Jaynes and F. Cummings, the literature on the subject is rich with analytical models and simple numerical calculations. However, even with exact knowledge of the material (atomic) states and the field states (cavity modes), a rigorous treatment requires a full -or at least a converged- consideration of all possible field-matter configurations. Furthermore, the longitudinal field component describing interactions between material particles must be consistent with the transverse modes, which are affected by the confinement; this interaction is not necessarily the simple Coulomb potential.

In this work, we present a Configuration–Interaction (CI) method for the eigenstates of the Pauli–Fierz Hamiltonian for atomic systems in spherical cavities. The longitudinal field components (matter interactions) are consistent with the field's boundary conditions inside the conductor. In the case of spherical confinement, this results in a substantial modification of the Coulomb interactions doubt to the coupling with surface polarization, as well as an image potential for the interaction between each charge and the surface. For large cavities, the radial components of the material states tend towards well-defined surface image states, and the material dynamics become 2D, restricted to the surface of the sphere.

1. Introduction
The investigation of electronic reactions in collisions between ions and molecules
is relevant to many fields, including plasma physics, astrophysics, medical physics,
and radiobiology. In particular, in plasma-facing applications, beryllium and boron
have emerged as promising candidate materials for plasma—wall interfaces. In the
literature, numerous theoretical studies have computed total cross-sections (TCSs)
for collisions between highly charged bare ions and neutral atoms. The interaction between dressed projectiles and neutral atoms has been investigated by Das et
al. [1] using perturbative methods such as the boundary-corrected continuum intermediate state (BCCIS) approximation, as well as by non-perturbative approaches
(see Ref. [2] for a review).
2. Methods
The present work aims to investigate single-electron capture processes from multi-
electron atoms induced by collisions with multi-charged, dressed projectiles at
intermediate and high energies. This process is studied within the Continuum
Distorted Wave (CDW) formalism, extending the recent development of Quinto
et al. [3]—originally formulated for hydrogen—to multi-electron targets. In this
work, the interaction between the projectile and the active electron is described
by the analytic Green–Sellin–Zachor (GSZ) potential. The electrons bound to
the projectile are treated as frozen during the collision. The final states of the
projectile are described by excited atomic wave functions [4].
3. Results
The results in terms of total cross-sections are compared with both experimental
measurements and available theoretical data over the energy range from 10 keV/u
to 10 MeV/u.
References
[1] Das M. et al. 1998 Phys. Rev. A 57 3573
[2] Hill C. et al. 2023 Nucl. Fusion 63 125001
[3] Quinto M. A. et al. 2025 Atoms 13 84
[4] Novikov N. V. 2015 Wave Function Value Database

In the late 1980s, experimenters observed a new phenomenon in the interaction between intense laser fields and gases, which is now known as high-harmonic generation (HHG).
The discovery of HHG paved the way for using infrared (IR) laser sources to produce femtosecond pulses in the extreme ultraviolet (EUV) and soft X-ray spectral ranges.
This nonlinear process also enables the study of two-color photoionization, where an atom is ionized by a combination of EUV and IR laser pulses rather than by a single pulse. In such experiments, the photoelectron energy spectrum reveals that the dominant contributions arise from processes in which an emitted electron, after absorbing an EUV photon, exchanges n infrared photons (n ≥ 1) with the dressing IR field via stimulated absorption or emission.
This results in the formation of photoelectron sidebands (SB±n) that are symmetrically distributed around the main harmonic peak, corresponding to the direct photoionization of the atom.

In this work, we perform numerical simulations of the nonresonant two-color photoionization of argon, using the combined action of an EUV pulse corresponding to the 13th harmonic of an infrared laser and the fundamental IR field itself.
The time-dependent Schrödinger equation (TDSE) is solved numerically within the single-active-electron (SAE) approximation, and the photoelectron wave packet is extracted using the window-operator technique.
This approach allows us to analyze both the photoelectron angular distributions (PADs) and the behavior predicted by the generalized Fano’s propensity rule in IR-assisted EUV photoionization of argon atoms.

Introduction

Above-Threshold Ionization (ATI) is a fundamental strong-field process, in which photoelectrons exhibit a characteristic multi-peak energy spectrum. While well-studied for isolated atoms, this process is less understood in a screened plasma environment. This work utilizes simulations to investigate how a quantum plasma affects the ATI spectrum, comparing the results with those of a classical plasma.

Methods

The one-dimensional time-dependent Schrödinger equation (TDSE) is solved numerically for a hydrogen atom interacting with an intense laser field, defined by a Gaussian pulse envelope. The TDSE is propagated using a stable, unitary Crank–Nicolson algorithm. To compare the two regimes, classical screening is modeled with a Debye–Hückel (Yukawa) potential, while the quantum environment is modeled using an Exponential Cosine Screened Coulomb (ECSC) potential to capture its characteristic oscillatory nature.

Results

The simulations show a clear contrast between the classical and quantum models. In the classical model, stronger screening causes a uniform blue shift of the ATI peaks to higher energies, corresponding to a reduced electron binding energy. The quantum model reproduces this shift but also introduces new features. The oscillatory component of the ECSC potential alters the spectrum's structure, modulating the relative peak heights and creating new spectral peaks indicating absorption of more photons, features that are entirely absent in the classical Debye model. For low laser intensities, the peak heights are reduced due to plasma screening; however, at higher intensities, plasma screening is insufficient to reduce peak heights.

Conclusion

The systematic blue-shift of the spectral peaks with decreasing Debye lengths provides a direct measure of the binding energy reduction caused by plasma screening. Furthermore, the complex modulations and additional spectral features introduced by the oscillatory component of the potential may serve as a unique way of controlling ATI spectra, distinguishing it from simple monotonic screening.