Ion Atomic Number Research Articles

NUMERICAL SIMULATION OF DIFFERENT ATOMIC NUMBER IONS IRRADIATION EFFECTS ON BENZOCYLOBUTENE MATERIAL

In this paper, the irradiation effect of different atomic number incident ions on benzocylobutene(BCB) material was investigated by using the Monte Carlo method. The results indicated that the projected range of theof the ions got decreased and the irradiation damage region was moved closer to the surface with the increase of ion atomic number. However, the stopping power was increased with the increase of ion atomic number. Moreover, with the increase of the atomic number, particle distribution, ionization energy loss, vacancies and phonons are more in the irradiation damage zone, the radiation damage mechanism caused by the recoil atoms gradually dominates, and the influence caused by the incident particles is becoming secondary

Theoretical elucidation of rare earth extraction and separation by diglycolamides from crystal structures and DFT simulations

Diglycolamides (DGAs) show excellent application prospects for the extraction and separation of rare earth metals from highly radioactive liquid wastes and rare earth ores. The extraction ability of DGAs for rare earth ions in nitrate or chloride media increases with increasing atomic number of the rare earth metal. To understand the origin of this phenomenon, three binuclear crystals [Ln(TEDGA)3][Ln(NO3)6] of N,N,N′,N′-tetraethyldiglycolamide (TEDGA) with rare earth ions La(III), Pr(III) and Eu(III) were prepared and characterized crystallographically. The three complexes belong to the triclinic crystal system, P-1 space group. The bond lengths of Ln–Oamide are significantly shorter than those of Ln–Oether in the same crystal. The Ln–Oamide and Ln–Oether bond lengths gradually decrease with increasing atomic number of the rare earth ion. The dihedral angle formed by TEDGA and metal ions through the tridentate coordination gradually increases with increasing metal ion atomic number, tending toward the formation of sizeable planar coordination structures for the most massive rare earth ions. The structures of the compounds formed by the extractant and metal ion were optimized by means of DFT simulations. We find that the interaction between TEDGA and the rare earth ion is dominated by electrostatic interaction by analyzing binding energy, WBIs, Mulliken charge, natural electron configurations, and molecular orbital interaction. The covalent component of the Ln–O bonds of the complexes increases with increasing metal atomic number. The observed increase in extraction and separation capacity of diglycolamides for rare earth ions with increasing atomic number might be due to the formation of two five-member rings by one tridentate ligand. The rare earth ions with large atomic numbers tend to form planar structures with large dihedral angles with DGA ligands.

Coupled effects of electronic and nuclear energy deposition on damage accumulation in ion-irradiated SiC

Coupling between electronic and nuclear energy dissipation in ion-irradiated, single crystal 4H-SiC has been investigated using Si, Ti, and Ni ions over a range of energies at 300 K, and irradiation damage accumulation is characterized using Rutherford backscattering spectroscopy in channeling geometry. The damage production rate from nuclear energy loss (Sn) is observed to decrease with increasing electronic energy loss (Se) of the incident ions. A dynamic threshold (Se,th) in electronic energy loss is determined for each ion species, which defines two regions: i) Se > Se,th, where electronic energy dissipation fully suppresses damage production due to nuclear energy loss along incident ion paths, and ii) Se < Se,th, where simultaneous damage recovery due to Se competes with damage production processes. The electronic energy loss threshold (Se,th) increases sublinearly with incident ion atomic number. The assessment of Se,th and how it affects damage accumulation is important to advance the understanding of complex processes occurring under ion-solid interactions, as well as in the design of functional materials for opto-electronics and novel structural materials and devices tolerant to harsh thermal and radiation environments.

Dynamic screening of an ion in a degenerate electron gas within the second-order Born approximation

The dynamic Friedel sum rule (FSR) is derived within the second-order Born (B2) approximation for an ion that moves in a fully degenerate electron gas and for an arbitrary spherically-symmetric electron–ion interaction potential. This results in an implicit equation for the dynamic B2 screening parameter which depends on the ion atomic number Z1 unlike the first-order Born (B1) dynamic screening parameter reported earlier by some authors. Furthermore, for typical metallic densities our analytical results for the Yukawa and hydrogenic potentials are compared, for both positive and negative ions, to the exact screening parameters calculated self-consistently by imposing the exact dynamic FSR requirement to the scattering phase shifts. The B1 and B2 screening parameters agree excellently with the exact values at large velocities, while at moderate and low velocities the B1 approximation deviates from the exact solution whereas the B2 approximation still remains close to it. In addition, a Padé approximant to the Born series yields a further improvement of the perturbative approach, showing an excellent agreement on the whole velocity range in the case of antiprotons.

Fast ignition driven by quasi-monoenergetic ions: Optimal ion type and reduction of ignition energies with an ion beam array

AbstractFast ignition of inertial fusion targets driven by quasi-monoenergetic ion beams is investigated by means of numerical simulations. Light and intermediate ions such as lithium, carbon, aluminum and vanadium have been considered. Simulations show that the minimum ignition energies of an ideal configuration of compressed Deuterium-Tritium are almost independent on the ion atomic number. However, they are obtained for increasing ion energies, which scale, approximately, as Z2, where Z is the ion atomic number. Assuming that the ion beam can be focused into 10 µm spots, a new irradiation scheme is proposed to reduce the ignition energies. The combination of intermediate Z ions, such as 5.5 GeV vanadium, and the new irradiation scheme allows a reduction of the number of ions required for ignition by, roughly, three orders of magnitude when compared with the standard proton fast ignition scheme.

Second-order Born approximation for the scattering phase shifts: Application to the Friedel sum rule

Screening effects are important to understand various aspects of ion–solid interactions and, in particular, play a crucial role in the stopping of ions in solids. In this paper the phase shifts and scattering amplitudes for the quantum-mechanical elastic scattering within up to the second-order Born (B2) approximation are revisited for an arbitrary spherically-symmetric electron–ion interaction potential. The B2 phase shifts and scattering amplitudes are then used to derive the Friedel sum rule (FSR) involving the second-order Born corrections. This results in a simple equation for the B2 perturbative screening parameter of an impurity ion immersed in a fully degenerate electron gas which, as expected, turns out to depend on the ion atomic number Z1 unlike the first-order Born (B1) screening parameter reported earlier by some authors. Furthermore, our analytical results for the Yukawa, hydrogenic, Hulthén, and Mensing potentials are compared, for both positive and negative ions and a wide range of one-electron radii, to the exact screening parameters calculated self-consistently by imposing the FSR requirement. It is shown that the B2 screening parameters agree excellently with the exact values at large and moderate densities of the degenerate electron gas, while at lower densities they progressively deviate from the exact numerical solutions but are nevertheless more accurate than the prediction of the B1 approximation. In addition, a simple Padé approximant to the Born series has been developed that improves the performance of the perturbative FSR for any negative ion as well as for Z1=+1.

Hydrodynamic theory for ion structure and stopping power in quantum plasmas

We present a theory for the dynamical ion structure factor (DISF) and ion stopping power in an unmagnetized collisional quantum plasma with degenerate electron fluids and nondegenerate strongly correlated ion fluids. Our theory is based on the fluctuation dissipation theorem and the quantum plasma dielectric constant that is deduced from a linearized viscoelastic quantum hydrodynamical (LVQHD) model. The latter incorporates the essential physics of quantum forces, which are associated with the quantum statistical pressure, electron-exchange, and electron-correlation effects, the quantum electron recoil effect caused by the dispersion of overlapping electron wave functions that control the dynamics of degenerate electron fluids, and the viscoelastic properties of strongly correlated ion fluids. Both degenerate electrons and nondegenerate strongly correlated ions are coupled with each other via the space charge electric force. Thus, our LVQHD theory is valid for a collisional quantum plasma at atomic scales with a wide range of the ion coupling parameter, the plasma composition, and plasma number densities that are relevant for compressed plasmas in laboratories (inertial confinement fusion schemes) and in astrophysical environments (e.g., warm dense matter and the cores of white dwarf stars). It is found that quantum electron effects and viscoelastic properties of strongly correlated ions significantly affect the features of the DISF and the ion stopping power (ISP). Unlike previous theories, which have studied ion correlations in terms of the ion coupling parameter, by neglecting the essential physics of collective effects that are competing among each other, we have here developed a method to evaluate the dependence of the plasma static and dynamical features in terms of individual parameters, like the Wigner-Seitz radius, the ion atomic number, and the ion temperature. It is found that due to the complex nature of charge screening in quantum plasmas, the ion coupling parameter alone cannot be a good measure for determining ion correlation effects in a collisional quantum plasma, and such a characteristic of a dense quantum plasma should be evaluated against each of the plasma parameters involved. The present investigation thus provides testable predictions for the DISF and ISP and is henceforth applicable to a wide range of compressed plasma categories ranging from laboratory to astrophysical warm dense matter.

Theory for large-amplitude electrostatic ion shocks in quantum plasmas

We present a generalized nonlinear theory for large-amplitude electrostatic (ES) ion shocks in collisional quantum plasmas composed of mildly coupled degenerate electron fluid of arbitrary degeneracy and nondegenerate strongly correlated ion fluid with arbitrary atomic number. For our purposes, we use the inertialess electron momentum equation including the electrostatic force, pressure gradient, and relevant quantum forces, as well as a generalized viscoelastic ion momentum (GVIM) equation for strongly correlated nondegenerate ions. The ion continuity equation, in the quasineutral approximation, then closes our nonlinear system of equations. When the electric field force is eliminated from the GVIM equation by using the inertialess electron momentum equation, we then obtain a GVIM and ion continuity equations, which exhibit nonlinear couplings between the ion number density and the ion fluid velocity. The pair of nonlinear equations is numerically solved to study the dynamics of arbitrarily-large-amplitude planar and nonplanar ES shocks arising from a balance between harmonic generation nonlinearities and the ion fluid viscosity for a wide range of plasma mass densities and ion atomic numbers that are relevant for the cores of giant planets (viz., Jupiter) and compact stars (viz., white dwarfs). Our numerical results reveal that the ES shock density profiles strongly depend on the plasma number density and composition (the atomic-number) parameters. Furthermore, ion density perturbations propagate with Mach numbers which significantly depend on the studied plasma fractional parameters. It is concluded that the dynamics of the ES shocks in the superdense degenerate plasma is quite different in the core of a white dwarf star from that in the lower density crust region.

Effects of Ion Atomic Number on Single-Event Gate Rupture (SEGR) Susceptibility of Power MOSFETs

The relative importance of heavy-ion interaction with the oxide, charge ionized in the epilayer, and charge ionized in the drain substrate, on the bias for SEGR failure in vertical power MOSFETs is experimentally investigated. The results indicate that both the charge ionized in the epilayer and the ion atomic number are important parameters of SEGR failure. Implications on SEGR hardness assurance are discussed.

Coulomb heating behavior of fast light diclusters

In this Brief Report we present data on the Coulomb heating induced by ${\text{B}}_{2}^{+}$ molecular beams channeling along $\text{Si}⟨100⟩$ direction in a large energy interval (800 up to 2200 keV/atom). The simultaneous detection of $\text{Si}\text{ }K\ensuremath{\alpha}$ x rays and backscattered particles established the necessary grounds for the calculation of the Coulomb heating, i.e., the molecular transversal energy due to the Coulomb explosion transferred to the target atoms. By combining the present results with those previously published for ${\text{H}}_{2}^{+}$ at 150 keV/atom and for ${\text{C}}_{2}^{+}$ at energies from 800 up to 2200 keV/atom, we were able to obtain two striking results. First, all the experimental values fall on a straight line when they are plotted as a function of the stored potential energy per ion, suggesting some kind of ``universal behavior.'' Second, the analysis of the whole set of experimental data shows that the Coulomb heating scales with 2/3 of the stored potential energy per ion, regardless the ion atomic number. This result is in agreement with theoretical predictions.

Defect engineering and micromachining of Lithium Niobate by ion implantation

A complete set of semi-empirical equations has been determined to engineer the damage formation in Lithium Niobate (LN) by irradiation with any ion atomic number and energy in the range 0.1–1.0 MeV/amu. Both nuclear and electronic process were taken into account and in particular the complex regime of sub-threshold electronic damage was quantitatively approached. The chemical etching of the processed material in 50 wt% HF at room temperature has been studied and the dependence of the etching rate on the damage concentration has been quantified. Finally, some test processes for surface micromachining of LN were first planned by using the above equations and then experimentally demonstrated.

A complex first-principles study of the L 2,3-edge XANES spectra and crystal field effects for divalent 3d ions in cubic ZnS

A detailed first-principles analysis of the L 2,3 X-ray absorption near edge structure (XANES) spectra, crystal field strength 10 Dq, covalent effects and molecular orbitals (MO) position for all divalent 3d ions from Sc 2+ to Cu 2+ in cubic ZnS is performed in the present paper. The calculations were done in the framework of the first-principles fully relativistic discrete variational multi-electron (DVME) based on numerical solution of the Dirac equation with the local density approximation. As a result of the performed calculations, the L 2,3 XANES spectra for all considered ions were calculated and assigned in terms of the electron configurations involved into the absorption transitions; fairly good agreement with available experimental data for Ti 2+, Mn 2+, Fe 2+, Co 2+ and Ni 2+ is demonstrated. Experimental XANES spectra for Sc 2+, V 2+, Cr 2+, Cu 2+ not reported previously were also calculated for the sake of completeness of the present study to enable a systematic analysis of all calculated results for the whole series considered. It was shown that the L 3 and L 2 bands shift to the higher energies on increasing a 3d ion atomic number. In addition, the separation between the L 3 and L 2 bands, the crystal field strength 10 Dq and mixture between the 3d ion and sulfur wave functions increase along the considered series, from Sc 2+ to Cu 2+. On the other hand, all orbitals of the 3d ions systematically lower down in the same direction. The above formulated trends were confirmed by the experimental data on the crystal field splittings and nephelauxetic effect.

Calculation of energy-loss straggling of C, Al, Si, and Cu for fast H, He, and Li ions

We present theoretical calculations of the energy-loss straggling of C, Al, Si, and Cu targets for H, He, and Li ions in the range of intermediate to high energies $(0.01--10\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕\mathrm{u})$. These calculations have been done by employing the dielectric formalism and by considering the different equilibrium charge states of the swift ion inside the solid as a function of its energy. Two different models are used: the Mermin energy-loss functions combined with generalized oscillator strengths (MELF-GOS) and the shellwise application of the local plasma approximation (SLPA). The MELF-GOS describes the target outer-electron excitations through a fitting to experimental data in the optical limit, employing a linear combination of Mermin-type energy-loss functions; the excitations of the inner-shell electrons are taken into account by means of generalized oscillator strengths. The SLPA employs a free-electron-gas model for the target valence electrons and the local density approximation for each shell of target electrons separately by using Hartree-Fock atomic wave functions. The results of the energy-loss straggling obtained by the two independent models show good agreement with the available experimental data. The calculated energy-loss straggling tends at high energies to the Bohr value and takes values below it at intermediate energies. The Bethe-Livingston shoulder (or overshooting) at intermediate energies does not appear in the present calculations. We find that the energy-loss straggling normalized to ${Z}_{\mathrm{P}}^{2}$ is almost independent of the ion atomic number ${Z}_{\mathrm{P}}$; therefore, the results for H, He, and Li projectiles in each target can be approximated by a universal curve at high energies.

Irradiation of Living Cells with Single Ions at the Ion Microprobe SNAKE

The irradiation setup at the ion microprobe SNAKE is used to irradiate living cells with single energetic ions. The irradiation accuracy of 0.55 μm and respectively 0.40 μm allows to irradiate substructures of the cell nucleus. By the choice of ion atomic number and energy the irradiation can be performed with a damage density adjustable over more than three orders of magnitude. Immunofluorescence detection techniques show the distribution of proteins involved in the repair of DNA double-strand breaks. In one of the first experiments the kinetics of appearance of irradiation-induced foci in living HeLa cells was examined. In other experiments a new effect was detected which concerned the interaction between irradiation events performed at different time points within the same cell nucleus.

Ion–biomolecule interactions and radiation damage

Ionization and fragmentation of DNA and its constituents is a primary step in biological radiation damage. In this paper we investigate the response of nucleobases upon interaction with keV singly and multiply charged ions. The dependence of ionization and fragmentation on ion atomic number Z, charge state q and velocity v is investigated. The effect of the target molecule is discussed as well.

Electronic stopping cross sections in silicon carbide for low-velocity ions with 1⩽Z1⩽15

The mean projected range Rp for a large number of H1, H2, Li7, B11, N14, O16, Al27, and P31 implantations into SiC with ion energies ranging from 0.5 keV to 4 MeV are investigated. From the Rp data the electronic stopping cross sections Se are extracted. A plot of the extracted Se at a fixed velocity—below the Fermi velocity of the target valence electrons—versus the ion atomic number Z1 reveals a local maximum around Z1=7. Furthermore, in this velocity regime a slower than velocity-proportional energy dependence, Se∝E0.30–E0.45, is found for ions with 1⩽Z1⩽8, while Al27 and P31 exhibit an energy dependence just above velocity-proportionality: Se∝E0.52, for both ions. These finding are in good qualitative agreement with the low-velocity electronic stopping behavior previously reported for carbon targets.

Modeling of displacement damage in an ion‐beam‐modified perfluorosulfonate ionomer

AbstractA Monte Carlo simulation has been used to model the effects of medium‐energy ion‐beam modification of Nafion. With typical ion energies of 100–200 keV, the treatment affects the outer 0.5–2‐μm surface layer. An equation has been developed for predicting the expected range of implantation as a function of the ion energy and atomic number. The expected range of displacement damage due to the ion beam can similarly be described over the whole parameter range of interest with a double logarithmic fit. A full characterization of the distributions with their first four statistical moments is also presented. The quantitative description of the profiles obtained is useful for the rational design of an ion‐beam treatment for the preparation of integrally skinned membranes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1343–1350, 2004

Application of CR-39 track detectors for corpuscular diagnostics of high-temperature plasmas

Solid State Nuclear Track Detectors (SSNTDs) have been used for corpuscular diagnostic in numerous high-temperature plasma experiments. This paper presents different applications of the detectors mentioned above, particularly in nuclear fusion investigations. Some new projects and proposals of the use of such detectors in large-scale plasma experiments, e.g. tokamaks, and laser-fusion facilities are demonstrated. To use the SSNTDs in the optimal way and to determine their detection characteristics, detailed calibration studies of the selected plastic detectors (CR-39, PM-355, PM-500, PM-600) have been performed at IPJ for several years. To carry out calibration measurements of these detectors, ion beams from different accelerators were applied. The paper presents detection characteristics, i.e. track dimensions as a function of ion energy, atomic number and etching time.

Impact parameter dependent stopping power for highly charged ions

The binary collisions of fast, heavy ions in the 1s2s electronic configuration with atoms was studied theoretically up to the second order Born approximation within the impact parameter method. The impact parameter dependent electronic excitation probabilities, the excitation cross-sections and the energy loss were calculated as functions of the ion atomic number, the number of electrons, the ion velocity and the mean excitation energy. A computer simulation of the channeling process shows that the stopping power effective charge agrees well with experimental data, provided the electronic structure of the ion was taken into account, without appealing to the second order polarisation effects.

Energy loss effective charge for slow ions in electron gas

Within the linear response theory the electronic energy loss in the degenerate electron gas for the slow excited H- to Be-like ions was calculated. The results were compared with the characteristics for the ions in the ground state and with the experimental data. The ion was described by the Hartree–Fock–Slater formalism and the medium by the Lindhard dielectric function. The ion–electron screening, anti-screening are exchange effects were included in the model. The stopping power and the effective charges Zeff1 were found to depend on the one electron radius rs, on the ion atomic number Zi and on the number of electrons Ni carried by the ion.