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We report a detailed study of the structure and absolute intensities of lines in the X-ray spectra of laser-produced tungsten plasmas. Plasmas are generated by focusing a laser pulse (0.53 μm, 5 J, 2 ns) onto massive solid targets. The spectra are measured by two focusing crystal spectrometers in the wavelength range of λ = 4–8 Å with a spectral resolution of λ/δλ = 600–1500. Plasmas are diagnosed using spectra of [He]-like ions of light elements. Absolute spectral brightness of the source is measured, and the temperature of tungsten plasma electrons in the range of Te = 500–750 eV is estimated using the comparison method. [ABSTRACT FROM AUTHOR]

We use post Hartree–Fock advanced electronic structure computations to investigate the lowest electronic states of the AlO3+ trication. These computations confirm the existence of metastable AlO3+ ions in gas phase. At least three electronic states (13Π, 11Δ, 11Σ+) with potential wells are identified. These potential wells have depths of several hundreds of meV, which are deep enough to support several rovibrational levels where this trication may be found. Besides, we estimate the adiabatic triple ionisation energy of AlO at ∼55 eV. Furthermore, the current confirmation of the meta-stability of AlO3+ in gas phase should motivate the search for this aluminium oxide with Al(+V) in liquids and in solid state, in particular at high-pressure/high-temperature phases of alumina polymorphs and of aluminosilicates. [ABSTRACT FROM AUTHOR]

The possibility to observe the relativistic tunneling effect in ionization of multiply charged ions of heavy atoms in the field of multipetawatt laser beams is discussed. An approximate analytical formula is obtained that makes it possible to estimate the change in the ionization rate of deep levels under the action of a strong quasi-static electromagnetic field under conditions close to saturation. It is shown that the Zeeman level shift and the relativistic twist of the subbarrier electron trajectory in the magnetic field of a laser wave lead to corrections to the ionization probability that are close in magnitude to each other. These corrections become significant only at laser radiation intensities of at least 2 × 1023 W/cm2, which are expected to be achieved at multipetawatt laser facilities, including the XCELS facility. The principal scheme of the experimental observation of the deviation of the ionization rate from the values predicted by the nonrelativistic theory is discussed. [ABSTRACT FROM AUTHOR]

The probability of simultaneous tunneling of two electrons from multiply charged Li-like ions in a high-intensity laser field is estimated. It is shown that for atoms with a nuclear charge Zm 1, the probability per unit time of collective tunneling of a 2s–1s electron pair can be more than an order of magnitude higher than the probability of detachment of a 1s electron. This provides favorable conditions for searching for the collective tunneling effect in the ionization of heavy multiply charged ions. The relative contributions of the sequential and collective ionization channels can be separated using the two-beam experimental scheme. Taking into account that to observe the effect, intensities exceeding 1021 W/cm2 in one of the beams are required, the proposed scheme of the experiment to search for the collective tunneling effect requires the use of laser pulses of extreme power, which is planned to be reached, in particular, at the XCELS facility. [ABSTRACT FROM AUTHOR]

This Tutorial is to provide a summary of parameters useful for successful outcomes of laserspray ionization (LSI) and related methods that employ a laser to ablate a matrix:analyte sample to produce highly charged ions. In these methods the purpose of the laser is to transfer matrix‐analyte clusters into the gas phase. Ions are hypothesized to be produced by a thermal process where emitted matrix:analyte gas‐phase particles/clusters are charged and loss of matrix from the charged particles leads to release of the analyte ions into the gas phase. The thermal energy responsible for the charge‐separation process is relatively low and not necessarily supplied by the laser; a heated inlet tube linking atmospheric pressure with the first vacuum stage of a mass spectrometer is sufficient. The inlet becomes the "ion source", and inter alia, pressure, temperature, and the matrix, which can be a solid, liquid, or combinations, become critical parameters. Injecting matrix:analyte into a heated inlet tube using laser ablation, a shockwave, or simply tapping, all produce the similar mass spectra. Applications are provided that showcase new opportunities in the field of mass spectrometry. [ABSTRACT FROM AUTHOR]

Vacuum arc ion sources are capable of generating pulsed ion beams of any solid-state conducting material and are used as injectors in heavy ion accelerators and technological implanters for surface modification of different materials. Without any special measures to increase the charge states of ions with typical arc discharge parameters, at an arc current amplitude of several hundred amperes and a pulse duration of several tens of microseconds, the charge states of ions in the beam do not exceed 5+, and the average ion charge is in the range from 1+ to 3+, depending on the cathode material. An increase in the charge states of vacuum arc plasma ions makes it possible to increase the ion energy in the extracted beam without a corresponding increase in the accelerating voltage or to form ions with a given energy at a significantly lower accelerating voltage. The charge states can be increased by increasing the amplitude of the discharge current and reducing its pulse duration. This article presents a study of the processes of generating beams of multiply charged heavy metal ions using bismuth ions as an example in a high-current vacuum arc with a kiloampere current amplitude at a submicrosecond pulse duration. By shortening the duration of the arc current pulse, the most probable charge state of ions in the extracted 18+ beam is formed, which is a record for bismuth. [ABSTRACT FROM AUTHOR]

A technique is described for achieving high accuracy (relative error up to ≈0.001%) for measuring the absolute wavelengths of the spectral lines of multiply charged ions with an average (Z = 17–25) by the nuclear charge, the spectra of which can be used for plasma diagnostics in laboratory astrophysics experiments. It is based on irradiation with subnanosecond laser pulses with an intensity of 1015–1016 W/cm2 targets with a multicomponent chemical composition, including atoms with both medium and low Z. The presence of the latter ensures the presence in the emission spectrum of the resulting laser plasma of lines of hydrogen-like ions used as references. An atomic-kinetic code was created, and the intensities of possible reference and investigated spectral lines were calculated. The principles of selecting the target material, the features of the implementation of the technique on the example of a focusing spectrometer with spatial resolution based on spherically curved mica and α-quartz crystals are considered, and specific parameters of spectrometer circuits and types of targets for precision measurement of the wavelengths of spectral lines of helium- and lithium-like ions with nuclear charges are given. Z = 13–25. The results obtained in this work will be used in the planning of fundamental X-ray spectral studies at the ELF laser facility being developed at MEPhI. [ABSTRACT FROM AUTHOR]

Traditional analytical methods for thalassemia screening are needed to process complicated and time-consuming sample pretreatment. In recent decades, ambient mass spectrometry (MS) approaches have been proven to be an effective analytical strategy for direct sample analysis. In this work, we applied ambient MS with wooden-tip electrospray ionization (WT-ESI) for the direct analysis of raw human blood samples that were pre-identified by gene detection. A total of 319 whole blood samples were investigated in this work, including 100 α-thalassemia carriers, 67 β-thalassemia carriers, and 152 control healthy samples. Only one microliter of raw blood sample was directly loaded onto the surface of the wooden tip, and then five microliters of organic solvent and a high voltage of +3.0 kV were applied onto the wooden tip to generate spray ionization. Multiply charged ions of human hemoglobin (Hb) were directly observed by WT-ESI-MS from raw blood samples. The signal ratios of Hb chains were used to characterize two main types of thalassemia (α and β types) and healthy control blood samples. Our results suggested that the ratios of charged ions to Hb chains being at +13 would be an indicator for β-thalassemia screening. [ABSTRACT FROM AUTHOR]

Using ab initio methodology, we studied the IOq+ (q = 2, 3, 4) multi-charged ions. Benchmark computations on the IO(X2Π) neutral species allow validate the current procedure. For IOq+, several potential wells were found on the ground and the electronic excited states potentials with potential barriers with respect to dissociation, where this dication can exist in the gas phase as long-lived metastable molecules. We confirm hence the recent observation of the dication by mass spectrometry. Moreover, we predict the existence of the metastable IO3+ trication, where a shallow potential well along the IO internuclear distance is computed. This potential well supports more than 10 vibrational levels. The IO3+ excited states are repulsive in nature, as well as the computed potentials for the IO4+ tetracation. For the bound states, we give a set of spectroscopic parameters including excitation transition energies, equilibrium distances, harmonic and anharmonic vibrational terms, and rotational constants. At the MRCI + Q/aug-cc-pV5Z(-PP) level, the adiabatic double and triple ionization energies of IO are computed to be ∼28.1 eV and ∼55.0 eV, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this work is the efficient reveal and analysis of hidden information in mass spectrometric data on the structural composition of the studied solutions of biomolecules in their electrospray ionization. This paper describes the algorithm of sequential splitting combined with the decomposition of the measured charge-state distributions of biomolecules while increasing the number of individual components corresponding to the independent presence of charge carriers with the found probabilities of retention for a given number of ionogenic groups of these biomolecules. The article discusses the results of calculations for the two-dimensional and one-dimensional decompositions of the charge distributions of cytochrome c with separation, presumably corresponding to different conformations of proteins. For the first time we developed a method and a software for searching individual components and their contributions to the mass spectra of multiply charged ions when the mass spectra of these components are not known in advance. [ABSTRACT FROM AUTHOR]

We have calculated the electronic energies and optimum geometries of C70q+ and C68q+ fullerenes (q=0–14) by means of density functional theory. The ionization energies for C70 and C68 fullerenes increase more or less linearly as functions of charge, consistent with the previously reported behavior for C60 and C58 [S. Díaz-Tendero et al., J. Chem. Phys. 123, 184306 (2005)]. The dissociation energies corresponding to the C70q+→C68q++C2, C70q+→C68(q-1)++C2+, C70q+→C68(q-2)++C++C+, C70q+→C68(q-3)++C2++C+, and C70q+→C68(q-4)++C2++C2+ decay channels show that C70q+ (like C60q+) is thermodynamically unstable for q>=6. However, the slope of the dissociation energy as a function of charge for a given decay channel is different from that of C60q+ fullerenes. On the basis of these results, we predict q=17 to be the highest charge state for which a fission barrier exists for C70q+. [ABSTRACT FROM AUTHOR]

Cathodic arc plasmas are considered fully ionized and they contain multiply charged ions, yet gaseous and metal neutrals can be present. It is shown that they can cause a significant reduction of the ion charge states as measured far from the cathode spots. Several cathode materials were used to study the evolution of the mean ion charge state as a function of time after arc ignition. The type of cathode material, arc current amplitude, intentionally increased background gas, additional surfaces placed near the plasma flow, and other factors influence the degree of charge state reduction because all of these factors influence the density of neutrals. In all cases, it was found that the mean ion charge state follows an exponential decay of first order, [formula], where A is a parameter describing the importance of the decay, τ is the characteristic decay time, and Qss is a steady-state value approached for continuous arc operation. The extrapolated values Q(t→0) indicate surprisingly high mean charge states as produced at cathode spots and not “skewed” by charge exchange collisions with neutrals. [ABSTRACT FROM AUTHOR]

Charge state and energy distributions of ions generated by a 3 J/30 ns Nd-glass laser were measured at a distance of 3.7 m from the target for seven different elements of the Periodic Table and for two different laser power densities (of the order of 1011 and 1012 W/cm2). Two groups of elements were found: highly charged ions with ionization potentials in the range of 500–1000 eV were registered for all elements between 12C and 56Fe; at the same time, ions with about-one-order-less ionization potentials were registered for elements between 74Ge and 181Ta. The most probable reason for such a big difference is the recombination losses of ions during laser-produced plasma expansion into vacuum. Verification of recombination losses in the case of 181Ta target has shown no losses at distances longer than 32.5 cm from the target, so recombination processes should take place at shorter distances. Current densities, pulse durations, energy ranges, and numbers of ions with different charge states were found for all elements by normalizing charge state distributions to total ion currents. Two different ion groups exist for all elements and laser power densities used in experiments: the faster group has a very weak dependence of energy on ion charge state, and the energies of the slower group are proportional to the charge states with high accuracy. [ABSTRACT FROM AUTHOR]

The work is aimed at developing a numerical method for analysing mass spectra of deutero-substituted multicharged ions of biopolymers to determine contributions of components presumably corresponding to different biomolecule conformations. The two-dimensional decomposition of the H-D exchange mass spectra of two, three and four charged apamin ions with their separation suggests that the reaction of apamin ions with ND3 molecules in the gas phase reveals hypothetically three different structural modifications of apamin ions. Usually for H-D exchange mass spectra, the presence of many resolvable protein structures was determined from measured distributions of peak intensities of ions with the same charge state. The method is new and has no published analogues. [ABSTRACT FROM AUTHOR]

Experimental depth distributions of the concentration of implanted xenon ions depending on their charge state and irradiation energy are presented. Xenon ions in charge states q = 1–20 and energies in the range from 50 to 400 keV are incorporated into single-crystal silicon. Irradiation is performed in the direction not coinciding with the crystallographic axes of the crystal to avoid the channeling effect. The ion fluence varies in the range of 5 × (1014–1015) ion/cm2. The irradiation by singly charged ions and investigation of the samples by Rutherford backscattering spectroscopy is performed using an HVEE acceleration complex at Moscow State University. Multiply charged ions are implanted using a FAMA acceleration complex at the Vinća Institute of Nuclear Sciences. The depth distribution profiles of the incorporated ions are found using Rutherford backscattering spectroscopy. Experimental results are correlated with computer calculations. It is shown that the average projective path of multiply charged ions in most cases is shorter when compared with the average projected path of singly charged ions and the results of computer modeling. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the ion-production mechanism in an indirectly heated Penning (PIG) source. Calculation of the ionization time and gas pressure dependence using the effective electron current density; Assumptions for the model for studying multiply charged ion production in a PIG source; Definition of an effective electron current density.

Studies the effect of impurity ions on the energy distribution of scattered neutrals by making use of already published theoretical results of electron loss as a function of impact parameter. Information on classical-trajectory Monte Carlo model; Collisions of hydrogen with multiply charged ions; Probabilities for one- plus two-electron capture in collisions of helium with some multiply charged ions.

A gas cell apparatus to measure charge exchange cross sections for charge state- and energy-resolved ion beams with neutrals is described. The design features a short well-defined interaction region required for beams of multicharged ions with high cross sections. Our method includes measuring the beam transmission at four different neutral pressures and extracting the cross section from the slope of a beam loss vs pressure plot. The design and procedure were tested for Ar+ interacting with neutral Ar gas over the incident ion energy range of 1.0–5.0 keV. The charge exchange cross sections agree well with previous complementary measurement techniques. [ABSTRACT FROM AUTHOR]

The differences between harmonics and multi-charged peaks in mass spectrometry are often not obvious. This work conducts experiments using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources with Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) to investigate the difference between harmonics and multi-charged peaks for the first time. In particular, organometallic compounds, which were characterized by the isotope distribution in ESI, were investigated in detail. A comparison of the peaks of the three charges with the three frequency doubling results at high-resolution mass spectra demonstrated that these peaks may be clearly differentiated from one another. Fullerene (C60) was characterized using APCI in the negative mode by FTICR MS provided further evidence. In addition, harmonics are unavoidable, but can be relatively weakened. These results are helpful to obtain accurate and comprehensive spectral information from FTICR MS. [ABSTRACT FROM AUTHOR]

The increasing prevalence of functional and motility gastrointestinal (GI) disorders is at odds with bottlenecks in their diagnosis, treatment, and follow-up. Lack of noninvasive approaches means that only specialized centers can perform objective assessment procedures. Abnormal GI muscular activity, which is coordinated by electrical slow-waves, may play a key role in symptoms. As such, the electrogastrogram (EGG), a noninvasive means to continuously monitor gastric electrical activity, can be used to inform diagnoses over broader populations. However, it is seldom used due to technical issues: inconsistent results from single-channel measurements and signal artifacts that make interpretation difficult and limit prolonged monitoring. Here, we overcome these limitations with a wearable multi-channel system and artifact removal signal processing methods. Our approach yields an increase of 0.56 in the mean correlation coefficient between EGG and the clinical “gold standard”, gastric manometry, across 11 subjects (p<0.001). We also demonstrate this system’s usage for ambulatory monitoring, which reveals myoelectric dynamics in response to meals akin to gastric emptying patterns and circadian-related oscillations. Our approach is noninvasive, easy to administer, and has promise to widen the scope of populations with GI disorders for which clinicians can screen patients, diagnose disorders, and refne treatments objectively. [ABSTRACT FROM AUTHOR]

Corrections to polarization losses of the energy of multiply charged ions in condensed media, caused by recharge processes, are considered. Charge fluctuations lead to an additional correlation contribution to the stopping power of an ion. If the mean free path between two recharging events is much greater than the wavelength of the plasma oscillations, the correlation contribution to the total polarization losses of energy can be described by introducing an effective charge that depends on the mean-square fluctuations of the charge. For light ions, the correction to the correlation effects can reach 10%. [ABSTRACT FROM AUTHOR]

Electrospray ionization mass spectra of biomolecules typically consist of a series of multiply charged ions because of the transfer of protons or other charge carriers between ions of biomolecules and the surrounding liquid or gas. The distribution of intensities of ions retained charge carriers contains information about the spatial structure of biomolecules. A new method is developed for the separation and decomposition of multidimensional charge distributions of ions bearing other charge carriers, such as alkali metal ions, along with protons. The proposed method ensures the estimation of the probability of charge carrier retention by separate functional groups for the selected conformations of biomolecules. The paper describes the application of this method to the analysis of a two-dimensional charge distribution of horse heart cytochrome C, resulting in the revelation of at least two its structural forms under the studied conditions. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Physics is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Charge distribution of Kr ions produced under irradiation of neutral atoms by x-ray photons with energy of 1.3 keV is calculated by the Monte Carlo method in the model of the effective atomic potential. The calculated results are in good agreement with recent experimental data and can be used in the development and operation of gas detectors controlling the intensity of free-electron x-ray lasers. [ABSTRACT FROM AUTHOR]

Using a retarding field analyzer, we have measured offsets between the nominal and measured kinetic energy of multicharged ions extracted from an electron beam ion source (EBIS). By varying source parameters, a shift in ion kinetic energy was attributed to the trapping potential produced by the space charge of the electron beam within the EBIS. The space charge of the electron beam depends on its charge density, which in turn depends on the amount of negative charge (electron beam current) and its velocity (electron beam energy). The electron beam current and electron beam energy were both varied to obtain electron beams of varying space charge and these were related to the observed kinetic energy offsets for Ar4+ and Ar8+ ion beams. Knowledge of these offsets is important for studies that seek to utilize slow, i.e., low kinetic energy, multicharged ions to exploit their high potential energies for processes such as surface modification. In addition, we show that these offsets can be utilized to estimate the effective radius of the electron beam inside the trap. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Physics is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The possibility of using the relative intensities of the 1 snp P-1 s S0 transitions with n = 3-6 in He-like multicharged ions to diagnose plasma in a nonstationary ionization state is considered. The calculations performed for F VIII ions show that, at electron temperatures of T = 10-100 eV, the intensity ratios are sensitive to the plasma electron density in the range of N = 10-10 cm. The universal calculated dependences can be used to diagnose various kinds of recombining or ionizing plasmas containing such ions. [ABSTRACT FROM AUTHOR]

The Landau (Fokker-Planck) integral of Coulomb collisions is an integral component of the physical and mathematical models of both laboratory and space plasma, in which the intermediate collisionality regime is important. This paper discusses the method for the direct statistical simulation of the Monte Carlo type for a kinetic equation with a nonlinear operator of the Landau-Fokker-Planck (LFP) Coulomb collisions. This method is based on the approximation of the Landau collision integral by the Boltzmann collision integral. The paper has two main objectives: firstly, to obtain numerical estimates of the order of approximation of the Landau collision integral by the Boltzmann integral and, secondly, to explore the possibilities of optimizing the algorithm for multiply charged ions. The results are illustrated by the calculations of the problem on the relaxation of the initial distribution to equilibrium for one and two components. [ABSTRACT FROM AUTHOR]

A superbright X-ray source with a radiation temperature of ~1.2 keV making it possible to create a solid-state plasma whose kinetics is determined by the radiative processes has been implemented under the impact of a 170-TW pulse of the PEARL femtosecond laser facility on an aluminum target with submicron thickness. The diagnostics of the created plasma is performed by X-ray spectral methods using spectral transitions in hollow multicharged ions. [ABSTRACT FROM AUTHOR]

The transport of a single macroparticle (MP) in the region adjacent to the negatively biased substrate immersed into vacuum arc produced plasma is investigated theoretically. The effect of potential electron emission from the deposition substrate due to bombardment of multiply charged ions on the MP dynamics is studied. It is shown that the substrate biasing can significantly restrict the MP content in films deposited by a titanium vacuum arc. It is obtained that the MPs with a size less than 1.1~\mu \textm cannot reach the substrate biased up to −300 V. [ABSTRACT FROM PUBLISHER]

The dependence of multiply charged ions on laser ellipticity in methyl iodide clusters with 532 nm nanosecond laser was measured using a time-of-flight mass spectrometer. The intensities of multiply charged ions Iq+(q= 2–4) with circularly polarised laser pulse were clearly higher than those with linearly polarised laser pulse but the intensity of single charged ions I+was inverse. And the dependences of ions on the optical polarisation state were investigated and a flower petal and square distribution for single charged ions (I+, C+) and multiply charged ions (I2+, I3+, I4+, C2+) were observed, respectively. A theoretical calculation was also proposed to simulate the distributions of ions and theoretical results fitted well with the experimental ones. It indicated that the high multiphoton ionisation probability in the initial stage would result in the disintegration of big clusters into small ones and suppress the production of multiply charged ions. [ABSTRACT FROM AUTHOR]

The problem of the transition radiation of multicharged ions at the interface between two media and in a thin plate under the charge-exchange conditions has been solved. It has been shown that the processes of pickup (or loss) of electrons by accelerated multicharged ions at the interface between two media significantly increases the yield of transition radiation. [ABSTRACT FROM AUTHOR]

We have implemented a solid-phase extraction based time-of-flight mass spectrometer system in combination with novel informatics to rapidly screen and characterize the covalent binding of different irreversible inhibitors to intact proteins. This high-throughput screening platform can be used to accurately detect and quantitate the extent of formation of different covalent protein-inhibitor adducts between electrophilic inhibitors and nucleophilic residues such as cysteine or lysine. For a representative 19.5 kDa protein, the analysis time is approximately 20 s per sample, including an efficient sample loading and desalting step. Accurate protein masses are measured (±0.5 amu of the theoretical molecular weight; measured precision of ±0.02 amu). The fraction of protein reacted with an electrophilic compound is determined relative to an unmodified protein control. A key element of the workflow is the automated identification and quantitation of the expected masses of covalent protein-inhibitor adducts using a custom routine that obviates the need to manually inspect each individual spectrum. Parallel screens were performed on a library of approximately 1000 acrylamide containing compounds (different structures and reactivities) using the solid-phase extraction mass spectrometry based assay and a fluorescence based thiol-reactive probe assay enabling comparison of false positives and false negatives between these orthogonal screening approaches. [ABSTRACT FROM AUTHOR]

The elastic scattering of two X-ray photons by a multicharged atomic ion has been studied theoretically. A pronounced resonance structure and strong angular anisotropy of differential scattering cross section have been predicted in the energy range of a scattered photon from ℏω-I1s to ℏω+I1s (where is the energy of the incident photon and is the ionization energy threshold of the shell of the ion). The absolute value of the observed cross section has been quantitatively estimated. [ABSTRACT FROM AUTHOR]

A spark discharge is coupled to a laser multicharged ion source to enhance ion generation. The laser plasma triggers a spark discharge with electrodes located in front of the ablated target. For an aluminum target, the spark discharge results in significant enhancement in the generation of multicharged ions along with higher charge states than observed with the laser source alone. When a Nd:YAG laser pulse (wavelength 1064 nm, pulse width 7.4 ns, pulse energy 72 mJ, laser spot area on target 0.0024 cm²) is used, the total multicharged ions detected by a Faraday cup is 1.0 nC with charge state up to Al3+. When the spark amplification stage is used (0.1 µF capacitor charged to 5.0 kV), the total charge measured increases by a factor of ~9 with up to Al6+ charge observed. Using laser pulse energy of 45 mJ, charge amplification by a factor of ~13 was observed for a capacitor voltage of 4.5 kV. The spark discharge increases the multicharged ion generation without increasing target ablation, which solely results from the laser pulse. This allows for increased multicharged ion generation with relatively low laser energy pulses and less damage to the surface of the target. [ABSTRACT FROM AUTHOR]

Within quantum geometry it is presented an Generalized version of an energy approach in scattering theory and its application to electron- collisional excitation of multicharged ions. The reestimated numerical data for electron-collisional excitation cross-sections are presented for barium. [ABSTRACT FROM AUTHOR]

The source of X-ray radiation with the energy of quanta that may vary in the range hν = 1÷12 keV was developed for studies in X-ray interaction with matter and modification of solid surfaces. It was based on a vacuum spark discharge with the laser triggering. It was shown in our experiments that there is a possibility to adjust X-ray radiation spectrum by changing the configuration of the electrode system when the energy stored in the capacitor is varied within the range of 1÷17 J. A comprehensive study of X-ray imaging and quanta energy was carried out. These experiments were carried out for the case of both direct and reverse polarity of the voltage on the electrodes. Additionally, ion composition of plasma created in a laser-triggered vacuum discharge was analyzed. Highly charged ions Zn(+21), Cu(+20) and Fe(+18) were observed. [ABSTRACT FROM AUTHOR]

We describe measurements aimed at tracking the subsurface energy deposition of ionic radiation by encapsulating an irradiated oxide target within multiple, spatially separated metal–oxide–semiconductor (MOS) capacitors. In particular, we look at incident kinetic energy and potential energy effects in the low keV regime for alkali ions (Na+) and multicharged ions (MCIs) of ArQ+ (Q = 1, 4, 8, and 11) incident on the as-grown layers of SiO2 on Si. With the irradiated oxide encapsulated under Al top contacts, we record an electronic signature of the incident ionic radiation through capacitance–voltage (C–V) measurements. Both kinetic and potential energy depositions give rise to shifted C–V signatures that can be directly related to internal electron–hole pair excitations. The MCI data reveal an apparent power law dependence on charge state, which is at odds with some prior thin foil studies obtained at higher incident energies. [ABSTRACT FROM PUBLISHER]

Multiply charged ions and plume characteristics in Hall thruster plasmas are investigated with regard to magnetic field configuration. Differences in the plume shape and the fraction of ions with different charge states are demonstrated by the counter-current and co-current magnetic field configurations, respectively. The significantly larger number of multiply charged and higher charge state ions including Xe4+ are observed in the co-current configuration than in the counter-current configuration. The large fraction of multiply charged ions and high ion currents in this experiment may be related to the strong electron confinement, which is due to the strong magnetic mirror effect in the co-current magnetic field configuration. [ABSTRACT FROM AUTHOR]

RATIONALE Clusters exhibit diverse photochemical behavior as a function of laser parameters, i.e. wavelength, pulse duration and intensity. One such aspect of cluster photochemistry is the generation of energetic multiply charged atomic ions, upon efficient interaction of clusters with intense laser pulses. In the present work, mass spectrometric investigations have been carried out on clusters of tetrahydrofuran (THF, C4H8O) - a saturated cyclic ether - subjected to nanosecond laser pulse (spanning from UV to IR wavelength range) with the aim of shedding light on the complex mechanism of laser-cluster interactions, which is still ambiguous. METHODS THF clusters, generated via supersonic expansion of room-temperature THF vapours seeded in argon, were subjected to gigawatt intensity laser pulses (355, 532 and 1064 nm) obtained from a nanosecond Nd:YAG laser. The ions generated upon laser-cluster interaction were characterized using a time-of-flight mass spectrometer. RESULTS At 355 nm, THF clusters exhibit the usual multiphoton dissociation/ionization behavior while, at 532 nm, observation of multiply charged atomic ions of carbon (up to [C]4+) and oxygen (up to [O]3+) was ascribed to Coulomb explosion of THF clusters. For studies carried out at 1064 nm, multiply charged atomic ions of carbon up to [C]5+ having an ionization energy of ~392 eV were observed, at a laser intensity of 1010 W/cm2. CONCLUSIONS The observation of [C]5+ atomic ions signifies efficient coupling of the laser energy with the cluster medium, using a nanosecond laser pulse. The results have been rationalized on the basis of a three-stage cluster ionization mechanism, suggesting the crucial role of the threshold laser intensity for initiating ionization within the cluster and generation of optimum charge centers for efficient extraction of energy from the laser pulse. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Initially our method of the decomposition of charge state distributions of biopolymer ions was designed to estimate the probabilities of the retention of charges by biopolymer ionogenic groups without distinction of different charge carriers (proton, alkali metal ions, or other ions). The analysis of mass spectra of several peptides and proteins produced by electrospray ionization carried out on this basis made possible some conclusions about their ion structure and behavior inside the ion source. A generalization of the method for the case of multidimensional charge state distributions corresponding to the retention of various charge carriers by ions of biomolecules is described. Hopefully, this will make possible gaining more substantial information concerning the structure and behavior of biomolecule ions in solutions and under electrospray conditions, which can be important for various biological applications. [ABSTRACT FROM AUTHOR]

The formation of dianions in helium nanodroplets is reported for the first time. The fullerene cluster dianions (C60) n2− and (C70) n2− were observed by mass spectrometry for n≥5 when helium droplets containing the appropriate fullerene were subjected to electron impact at approximately 22 eV. A new mechanism for dianion formation is described, which involves a two-electron transfer from the metastable He− ion. As well as the prospect of studying other dianions at low temperature using helium nanodroplets, this work opens up the possibility of a wider investigation of the chemistry of He−, a new electron-donating reagent. [ABSTRACT FROM AUTHOR]