Ion-atom Interaction Research Articles

Use of Particle Induced X-Ray Emission (PIXE), Particle Induced Gamma–Ray Emission (PIGE), Energy Dispersive X-Ray Analysis (EDXRF) for Detecting Trace Elements in Soil Sample

This review paper provides a comprehensive overview of trace element analysis utilizing ion-atom interaction techniques, focusing on the principles, applications, and recent advancements in the field. Ion- atom interaction techniques, including Particle Induced X- Ray Emission (PIXE), Particle Induced Gamma–Ray Emission (PIGE), Energy Dispersive X-Ray Analysis (EDXRF), Rutherford backscattering spectroscopy (RBS), and ion beam analysis (IBA), offer unique capabilities for trace element analysis with high sensitivity and minimal sample preparation requirements. The paper begins by discussing the fundamental principles underlying ion-atom interaction techniques, such as the interaction of energetic ions with matter and the subsequent detection of emitted X-rays or backscattered particles. It explores the various analytical parameters that influence the sensitivity, resolution, and depth profiling capabilities of these techniques. Furthermore, the review highlights the diverse applications of ion-atom interaction techniques in fields such as environmental monitoring, forensic science, biomedical research, and materials science. It showcases how these techniques have been utilized to address specific analytical challenges, such as the detection of trace contaminants in environmental samples or the characterization of thin films and semiconductor materials.

High-resolution X-ray emission study for Xe^{54+} on Xe collisions

We report on an experiment conducted at the ESR storage ring aiming at the study of the X-ray emission of text {Xe}^{54+} ions colliding with Xe atoms at a beam energy of 50 MeV/u. The radiation resulting from the ion–atom interaction was observed using a high-resolution spectrometer based on metallic–magnetic calorimeter technology. In order to benchmark the capabilities of these detectors for high-precision atomic physics experiments, we identified several transitions from H-like and He-like xenon and determined their energies. Furthermore, the 1s-Lamb shift in text {Xe}^{53+} was estimated using the measured line energies. The results are compared with previous experimental studies and theoretical predictions.Graphicalabstract

Energy deposition and formation of nanostructures in the interaction of highly charged xenon ions with gold nanolayers

The effect of the deposition of kinetic energy and neutralization energy of slow highly charged xenon ions on the process of the nanostructures creation at the surface of gold nanolayers is investigated. The nanolayers of thickness of 100 nm were prepared by e-beam evaporation of gold on crystalline silicon Si(100) substrate. The samples were irradiated at the Kielce EBIS facility of the Jan Kochanowski University (Kielce, Poland), under high vacuum conditions. The irradiations were performed for constant kinetic energy 280 keV and different ions charge states (Xeq+, q = 25, 30, 35, 36 and 40) and for constant charge state Xe35+ and different kinetic energies: 280 keV, 360 keV, 420 keV and 480 keV. The fluence of the ions was on the level of 1010 ions/cm2. Before and after irradiation the nanolayer surfaces were investigated using the atomic force microscope.As the result, well pronounced modifications of the nanolayer surfaces in the form of craters have been observed. A systematic analysis of the crater sizes (diameter on the surface and depth) allowed us to determine the influence of the deposited kinetic and the neutralization energy on the size of the obtained nanostructures. The results are theoretically interpreted within the micro-staircase model based on the quantum two-state vector model of the ionic Rydberg states population. The charge dependent ion–atom interaction potential inside the solid is used for the calculation of the nuclear stopping power. According to the model the formation of the nanostructures is governed by the processes of the ionic neutralization in front of the surface and the kinetic energy loss inside the solid. The interplay of these two types of processes in the surface structure creation is described by the critical velocity. Using the proposed theoretical model, the neutralization energy, deposited kinetic energy and critical velocities were calculated and compared qualitatively with the experimental results. The results are consistent (after normalization) with previous experimental data and molecular dynamics simulations for single ionized Xe and crystalline gold surface.

Charging and ion ejection dynamics of large helium nanodroplets exposed to intense femtosecond soft X-ray pulses

Ion ejection from charged helium nanodroplets exposed to intense femtosecond soft X-ray pulses is studied by single-pulse ion time-of-flight (TOF) spectroscopy in coincidence with small-angle X-ray scattering. Scattering images encode the droplet size and absolute photon flux incident on each droplet, while ion TOF spectra are used to determine the maximum ion kinetic energy, \(E_{\text {kin}}\), of \(\hbox {He}_{j}^{+}\) fragments (j = 1–4). Measurements span \(\hbox {He}_N\) droplet sizes between \(N\sim 10^{7}\) and \(\sim 10^{10}\) (radii \(R_0\) = 78–578 nm), and droplet charges between \(\sim 9\times 10^{-5}\) and \(\sim 3\times 10^{-3}\) e/atom. Conditions encompass a wide range of ionization and expansion regimes, from departure of all photoelectrons from the droplet, leading to pure Coulomb explosion, to substantial electron trapping by the electrostatic potential of the charged droplet, indicating the onset of hydrodynamic expansion. The unique combination of absolute X-ray intensities, droplet sizes, and ion \(E_{\text {kin}}\) on an event-by-event basis reveals a detailed picture of the correlations between the ionization conditions and the ejection dynamics of the ionic fragments. The maximum \(E_{\text {kin}}\) of He\(^{+}\) is found to be governed by Coulomb repulsion from unscreened cations across all expansion regimes. The impact of ion-atom interactions resulting from the relatively low charge densities is increasingly relevant with less electron trapping. The findings are consistent with the emergence of a charged spherical shell around a quasineutral plasma core as the degree of ionization increases. The results demonstrate a complex relationship between measured ion \(E_{\text {kin}}\) and droplet ionization conditions that can only be disentangled through the use of coincident single-pulse TOF and scattering data.

Limitations of perturbative coupled-cluster approximations for highly accurate investigations of Rb2+

We reveal limitations of several standard coupled-cluster (CC) methods with perturbation-theory based noniterative or approximate iterative treatments of triple excitations when applied to the determination of highly accurate potential energy curves (PECs) of ionic dimers, such as the XΣg+2 electronic ground state of Rb2 +. Such computations are of current interest for the understanding of ion-atom interactions in the ultracold regime. We demonstrate that these CC methods lead to an unphysical long-range barrier for the Rb2 + system. The barrier is small but spoils the long-range behavior of the PEC. The effect is also found for other X2 + systems, such as X = Li, Na, and K. Calculations using a flexible framework for obtaining leading perturbative triples corrections derived using an analytic CC singles and doubles energy derivative formulation demonstrate that the origin of this problem lies in the use of T̂3 amplitudes obtained from approximate CC singles, doubles, and triples amplitude equations. It is shown that the unphysical barrier is related to a symmetry instability of the underlying Hartree-Fock mean-field solution, leading to orbitals representing two +0.5-fold charged ions in the limit of separated fragments. This, in turn, leads to a wrong 1/R asymptote of the interaction potential computed by perturbation-based CC approximations. Physically meaningful perturbative corrections in the long-range tail of the PEC may instead be obtained using symmetry-broken reference determinants.

Interactions of Ions and Ultracold Neutral Atom Ensembles in Composite Optical Dipole Traps: Developments and Perspectives

Ion–atom interactions are a comparatively recent field of research that has drawn considerable attention due to its applications in areas including quantum chemistry and quantum simulations. In first experiments, atomic ions and neutral atoms have been successfully overlapped by devising hybrid apparatuses combining established trapping methods, Paul traps for ions and optical or magneto-optical traps for neutral atoms, respectively. Since then, the field has seen considerable progress, but the inherent presence of radiofrequency (rf) fields in such hybrid traps was found to have a limiting impact on the achievable collision energies. Recently, it was shown that suitable combinations of optical dipole traps (ODTs) can be used for trapping both atoms and atomic ions alike, allowing to carry out experiments in absence of any rf fields. Here, we show that the expected cooling in such bichromatic traps is highly sensitive to relative position fluctuations between the two optical trapping beams, suggesting that this is the dominant mechanism limiting the currently observed cooling performance. We discuss strategies for mitigating these effects by using optimized setups featuring adapted ODT configurations. This includes proposed schemes that may mitigate three-body losses expected at very low temperatures, allowing to access the quantum dominated regime of interaction.

Crystal rainbow channeling potential for 〈1 0 0〉 and 〈1 1 1〉 cubic crystallographic crystals

In this work we show a way how the crystal rainbow channeling effect can be applied for obtaining the interaction potential between 2 MeV protons and the cubic crystallographic crystals, in the cases of axial channeling of protons along (001) and (111) crystal directions. The procedure for construction of this potential has been based on our previous work in which the rainbow morphology was crucial for their determination. However, important improvements have been made. As a result, the two axial channeling directions can be treated using the same physical arguments leading to more consistent values of the fitting parameters in the ion-atom interaction potential.

Scattering of Fast Atoms and Ions by a Crystalline Surface: Orientation Effects

The features of the scattering of accelerated neutral atoms upon sliding interactions with crystalline surfaces are discussed. Particular attention is paid to the phenomenon of rainbow scattering of neutral atoms upon their reflection from an oriented crystalline surface. The physical causes of the arising effects and the possibility of reconstructing the two-particle “polarization” and “dynamic” ion–atom interaction potentials from the experimental data are considered.

Measurement of 12Cq+ and 35Clq+ ion induced X-ray production cross sections in V, Zr and Sn metal oxide films at 0.1 MeV/u - 1.0 MeV/u energies

Experimental X-ray production cross sections in matter are key to fundamental ion-atom interaction studies. They also find practical applications such as in the advancement of ion beam materials analysis techniques like Particle Induced X-ray Emission (PIXE) spectroscopy. Experimental work shows that heavy ion probes induce higher X-ray yields in target atoms compared to light ions of the same velocity. This, in principle, implies higher sensitivity for PIXE analyses performed using heavy ions (Heavy Ion PIXE). There is therefore need for substantial experimental data to improve existing theoretical models that describe X-ray production due to heavy ion-atom collisions. This article presents measurements carried out to determine K-shell X-ray production cross sections in vanadium (V) due to 12Cq+ ions, and L-shell X-ray production cross sections in zirconium (Zr) and tin (Sn) due to 12Cq+ (q = 2, 3) and 35Clq+ (q = 3, 5, 6, 7) MeV ion beams within a velocity range of 0.1 MeV/u - 1.0 MeV/u. Measured cross sections are compared with predictions by the modified Plane Wave Born Approximation (PWBA) and the ECPSSR theory. Observed agreements and discrepancies between experiment and theory are discussed in terms of the underlying ionisation mechanisms.

Ion Mobilities for Heaviest Element Identification

Relativistic effects strongly influence the chemical and physical properties of the heaviest elements, which can significantly differ from the periodicity predicted by the periodic table of elements. Former systematic mobility measurements on monoatomic lanthanide ions revealed the dependence of ion-atom interactions on the underlying electronic configuration and helped in studying the aforementioned effects. Presently, the measurements are being extended to the actinides, where larger deviations from periodicity are expected. Our studies will cover ion mobilities of several actinide elements under different conditions of electric fields, buffer-gas pressures and temperatures, which will constitute benchmark data for state-of-the-art ab initio calculations.

Comparison of xenon and gallium sources on the detection and mapping of lithium in Li-containing materials by using ToF-SIMS combined FIB-SEM.

Li can find itself a wide range of applications since it is the lightest metal. However, Li detection by microscopy-based techniques is problematic because of the highly susceptible nature during electron beam irradiation. ToF-SIMS is a versatile technique to detect Li but the detection of light materials is also problematic due to the large ion contaminated zone and low sputtering yield. By combining ToF-SIMS with a recently launched Xe ion source FIB-SEM, which has small ion contamination and high sputtering yield features, can produce more realistic data at near surface and below the surface region especially for the detection of lightweight materials such as Li. In this study, Li detection and mapping capabilities of ToF-SIMS attached to the FIB-SEM with Ga and Xe ion sources were discussed for Al incorporated Li7 La3 Zr2 O12 solid electrolyte sample that contains Li and Al rich regions at triple junctions. In spite of smoother milling from Ga source, Xe performs more precisely in Li mapping. Low ion contaminated zone, high sputtering yield and low straggling obtained from Monte Carlo simulations are the main advantages of Xe ion sources. The Li detection efficiency for Xe is higher than Ga source discriminating the LiAlO2 phase placed at the triple junctions of grains and La2 Zr2 O7 regions placed at the outer side of LLZO neighbouring the LiAlO2 phase. LAY DESCRIPTION: Li can find itself a wide range of applications since it is the lightest metal. However, Li detection by microscopy-based techniques is problematic because of the highly susceptible nature during electron beam irradiation. ToF-SIMS is a versatile technique to detect Li but the detection of light materials is also problematic due to the large ion contaminated zone and low sputtering yield. By combining ToF-SIMS with a recently launched Xe ion source FIB-SEM, which has small ion contamination and high sputtering yield features, can produce more realistic data at near surface and below the surface region especially for the detection of lightweight materials such as Li. In this study, Li detection and mapping capabilities of ToF-SIMS attached to the FIB-SEM with Ga and Xe ion sources were discussed for Al incorporated Li7 La3 Zr2 O12 solid electrolyte sample that contains Li and Al rich regions at triple junctions. In spite of smoother milling from Ga source, Xe performs more precisely in Li mapping. Results were also supported from Monte Carlo simulations of ion-atom interactions. The Li detection resolution of xenon is much higher than gallium source discriminating the LiAlO2 phase placed at the triple junctions of grains and La2 Zr2 O7 regions placed at the outer side of LLZO neighbouring the LiAlO2 phase.

Рассеяние быстрых атомов и ионов кристаллической поверхностью. Ориентационные эффекты О б з о р

The features in the scattering of accelerated neutral atoms during sliding interactions with crystalline surfaces are discussed. Particular attention is paid to the phenomenon of Rainbow Scattering of neutral atoms upon their reection from an oriented crystalline surface. The physical causes of the eects and the possibility of reconstructing from the experimental data the two-particle polarization and dynamic ion-atom interaction potentials are considered.

Design and commissioning of an ion guide system for In-Gas Laser Ionization and Spectroscopy experiments

Radio-frequency (RF) ion guides, also known as Linear Paul Traps, are powerful devices to efficiently transport ion beams from high to low pressure regions while keeping good ion optical properties. A set of ion guides comprising three different RF quadrupole (RFQ) structures has been designed using ion-trajectory simulations to improve the performance of the In-Gas Laser Ionizations and Spectroscopy (IGLIS) technique currently under development at KU Leuven. Results of the commissioning tests for the total transport efficiency and transient time through the ion guides as well as the longitudinal energy spread and transverse emittance are found to be in agreement with ion trajectory simulations considering a realistic ion-atom interaction potential.

Characteristics of Interatomic and the Ion—Atom Interaction in Gases during the Dissociation Process

We consider the problem of the choice of “free” particle interaction potential and the calculation of virial corrections for interatomic and ion–atom interaction in chemical models with dissociation reactions. We perform a critical analysis of the potentials given in the available literature, propose simple formulas to calculate virial corrections with allowance for the limitations of the two-particle phase space, and present recommendations to apply these formulas.

Ionic Impurity in a Bose-Einstein Condensate at Submicrokelvin Temperatures.

Rydberg atoms immersed in a Bose-Einstein condensate interact with the quantum gas via electron-atom and ion-atom interaction. To suppress the typically dominant electron-neutral interaction, Rydberg states with a principal quantum number up to n=190 are excited from a dense and tightly trapped micron-sized condensate. This allows us to explore a regime where the Rydberg orbit exceeds the size of the atomic sample by far. In this case, a detailed line shape analysis of the Rydberg excitation spectrum provides clear evidence for ion-atom interaction at temperatures well below a microkelvin. Our results may open up ways to enter the quantum regime of ion-atom scattering for the exploration of charged quantum impurities and associated polaron physics.

Radiation-induced extreme elastic and inelastic interactions in concentrated solid solutions

One of the biggest challenges in the radiation induced defect science is to understand the complex nature of ion-atom interactions under highly extreme conditions. Here, we report the irradiation induced non-equilibrium defect formation in NiCoCr single phase concentrated solid solution alloy due to (i) the extreme inelastic and (ii) the coupled inelastic and elastic ion-atom interactions. These two conditions are achieved at 5 and 30μm penetration depths along the paths of swift heavy ions (1.542GeV Bi). In general, the irradiation induced damage consists of interstitial-type dislocation loops and vacancy-type stacking fault tetrahedra (SFT). Near the surface (~5μm) where electronic energy loss is dominating (~62.5keVnm−1), the atomic motion primarily results in the formation of SFT. A noticeable increase of dislocation loop formation is observed at 30μm near the maximum energy deposition from elastic interactions (~4.9keVnm−1), as compared to the near surface region (~0.06keVnm−1). Insights on the complex electronic and atomic correlations of extreme energy deposition and dissipation on defect dynamics and structural stability may pave the way for new design principles of radiation–tolerant structural alloys.

{1 0 −1 2} twin nucleation induced by FIB micro-stress in magnesium single crystal

In this study, Mg single crystals (99.99% purity) were subjected to focused ion beam (FIB) bombardment perpendicular and parallel to the c-axis of the hexagonal close packed (HCP) lattice respectively. The research results indicate that the {10−12} twin nucleation induced by FIB micro-stress in magnesium single crystal is dependent on the applied ion current and the crystal orientation. The incident Ga+ ions dose increases with ion current, which would enhance the FIB loading micro-stress. And when the FIB incident direction is parallel to the close-packed (0001) plane, there would be more ion-atom interactions during FIB bombardment. Both processing mechanisms could lead to larger precipitate-matrix misfit area and further microstructure damage, which might eventually facilitate {10−12} twin nucleation.

Dynamics of flexible peptides under the action of an electrostatic field in the gas phase

The Ion Mobility Spectrometry data of flexible peptides have been found to depend on the temperature of the buffer gas. It has been observed that the number of the peaks of the arrival time distribution may vary, while the position of the peaks may shift with temperature. Such changes depend on the emerging conformers at the experimental conditions. The motion and the dynamics of the peptide are reproduced here through a Nonequilibrium Molecular Dynamics Simulation procedure that depends on the structure of the bending macromolecule. A specific molecular model of one bending mode is considered that depends on an angular interaction potential. The observed conformations are introduced through the consideration of local minima in the model potential. As the molecular dynamics simulation proceeds, the population of the metastable structures is changing in time due to energy exchange during the ion-atom interactions. The corresponding angle distributions depend on the temperature and the field strength. We find that the observed motion of the peptide conformers can be reproduced accurately with the use of empirical model potentials and further predict the behavior of the ions at strong electric fields. The procedure can produce mean properties, such as the ion velocity and energy, as well as molecular distributions and dynamic properties, such as velocity correlation functions. We expect the method to apply to similar flexible macromolecules that acquire one bending mode.

Ultracold magnetically tunable interactions without radiative-charge-transfer losses betweenCa+, Sr+, Ba+, andYb+ions and Cr atoms

The Ca$^+$, Sr$^+$, Ba$^+$, and Yb$^+$ ions immersed in an ultracold gas of the Cr atoms are proposed as experimentally feasible heteronuclear systems in which ion-atom interactions at ultralow temperatures can be controlled with magnetically tunable Feshbach resonances without charge transfer and radiative losses. \textit{Ab initio} techniques are applied to investigate electronic-ground-state properties of the (CaCr)$^+$, (SrCr)$^+$, (BaCr)$^+$, and (YbCr)$^+$ molecular ions. The potential energy curves, permanent electric dipole moments, and static electric dipole polarizabilities are computed. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), and the multireference configuration interaction method restricted to single and double excitations, MRCISD, are employed. The scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. The leading long-range induction and dispersion interaction coefficients are also reported. Finally, magnetic Feshbach resonances between the Ca$^+$, Sr$^+$, Ba$^+$, and Yb$^+$ ions interacting with the Cr atoms are analyzed. The present proposal opens the way towards robust quantum simulations and computations with ultracold ion-atom systems free of radiative charge transfer losses.

Angle-differential observation of plasmon electrons in the double-differential cross-section spectra of fast-ion-induced electron ejection fromC60

We report on the measurement of double-differential distribution of soft electron emission from ${\text{C}}_{60}$ fullerene, induced by a fast-moving Coulomb field of 76 MeV energy bare fluorine ions. A broad ``plasmon-electron'' peak, riding on the Coulomb-ionization continuum, is observed due to the deexcitation of the giant dipole plasmon resonance state in ${\text{C}}_{60}$. The angular distribution of the plasmon electrons goes through a dip around ${90}^{\ensuremath{\circ}}$, which is contrary to that observed in ion-atom collisions measured in situ, indicating the alignment of the induced dipole moment along the projectile beam direction. A model based on the photoelectron angular distribution which is modified due to the ion-induced postcollisional interaction provides an excellent agreement with the observed asymmetric distribution. The distribution smoothly changes from a dip at ${90}^{\ensuremath{\circ}}$ to a peak with the variation of ejected electron energy indicating transition from a collective plasmon behavior of the whole system to a single ion-atom interaction. The single-differential cross section was also derived, which preserves the signature of the collective excitation.