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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]

The paper presents the results of a study of the charge and energy characteristics of multiply charged ions excited on the surface of a single-element and hydrogen-containing multi-component element targets under the influence of laser radiation with a power density (q=108-1012 W/cm2). It has been experimentally shown that, for all used values of q laser radiation, laser-induced plasma from gas-containing targets is characterized by a lower relative yield (dN/dE) of multi-charged ions with a charge number of Z>+3, compared to the plasma produced on the surface of the single element target. Moreover, the tendency to reduce dN/dE of multi-charged ions of the multi-element target, in comparison with the relative yield of ions from the plasma of the single-element target, is more significant and it depends on the charge of the excited ions. The increase in the charge and energy state, duration, and yield of ions of the heavy component, which occurs with an increase in the content of the light component in the target, has been established. This is explained by a decrease in the efficiency of recombination processes caused by an increase in the expansion velocity of a plasma plume due to a decrease in its average mass.

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]

The effect exerted by defocusing of double laser pulses on purposeful formation of the component and charge composition of the laser plasma has been studied using the laser spark spectrometry (LSS-1 laser). It has been shown that there is a possibility to increase the portion of differently charged aluminum ions as well as of AlO and AlN nanoclusters in the laser plasma when a target of D16Т aluminum alloy is subjected to a series of defocused double pulses.

The microchannel-form effect on the formation of AlO and AlN in the laser plasma has been studied when the surface of a target of D16 Т aluminum alloy was subjected to series of sequential focused double laser pulses in air. The possibility to increase the quantities of AlO and AlN as well as of nitrogen, oxygen, and aluminum ions with different charges in the laser plasma has been demonstrated depending on the microchannel form.

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.

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]

Graphical abstract Highlights • Photoionisation of carbon disulfide clusters has been studied in intermediate laser intensity regime (∼1011 W/cm2) where ionisation mechanism is less explored. • A series of cluster ion fragments were observed at 266 nm which is explained based on ion-molecule reactions. • Molecular sulphur ion (S2+) was observed at 266, 355 and 532 nm which is explained based on two competitive ion-molecule reactions. • Multiply charged atomic ions were observed at 355 and 532 nm which is explained based on multiphoton ionisation initiated electron impact ionisation. • Doubly charged molecular ion peak (CS22+) was observed at 532 nm and the formation mechanism is explained based on experimental results. Abstract Gas phase ionisation of carbon disulphide clusters (CS 2) n with different laser wavelengths of terawatt intensity has been studied using time-of-flight mass spectrometry. In the mass spectra, series of singly charged cluster fragments such as C+, S+, CS+, [C(CS)]+, [S(CS)]+, [S 2 (CS)]+, [C(CS 2)]+, [C 2 (CS 2)]+, [C 3 (CS 2)]+, [S(CS 2)]+, S 2 +, S 3 +, [CS(CS 2)]+ etc. were observed at 266 nm photoionisation. Higher cluster fragments formation has been rationalised based on various ion-molecule reactions that occur within the cluster following ionisation. One of the prominent cluster fragment was S 2 + whose formation mechanism has been explained based on two competitive ion-molecule reactions. Photoionisation at 355 nm leads to formation of doubly charged carbon and iodine ion along with singly charged cluster fragments. An increase in charge state of carbon and sulphur ions (up to +4 state) was observed on changing the laser wavelength to 532 nm, indicating efficient interaction of CS 2 clusters at longer wavelength. In order to elucidate the mechanism of formation of multiply charged atomic ions at 355 and 532 nm, energy of electrons released on ionisation of CS 2 cluster at different wavelengths was measured. Based on these experimental results, energisation of electrons within the cluster was observed due to influence of electric field of the laser pulse. The extent of energisation was found to be more at longer wavelength indicating role of electron impact ionisation for generation of multiply charged ions at this laser intensity conditions. Apart from multiply charged atomic ions, doubly charged molecular ion (CS 2 2+) was also observed at 532 nm. Generation of CS 2 2+ is explained based on similar ionisation mechanism as described for atomic multiply charged ions. However, lifetime of the doubly charged ion plays an important role for generation of the ions under our experimental conditions. [ABSTRACT FROM AUTHOR]

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.

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.

A comparison is made of experimental results on the generation of multiply-charged bismuth ions in a vacuum arc plasma with a current pulse of half maximum width 2.5 μs and maximum amplitude 3 kA, and numerical simulation of the generation of multiply-charged bismuth ions in this plasma. Images of the luminous arc plasma were obtained experimentally with nanosecond exposure times at different times throughout the arc current pulse, and simultaneously the ion mass-to-charge composition of the plasma was measured at these times. It is shown that the generation of bismuth ions with charge states of 10+ and higher is associated with compression of the plasma column by its own azimuthal magnetic field, which occurs when the arc pulse current reaches its maximum value. Based on a hybrid hydrodynamic model, the spatial distributions of the arc plasma density, electron temperature, and charge state composition of plasma ions were calculated, which makes it possible to obtain a calculated image of the plasma glow. A comparison of the experimental ion charge-state distributions and photographs of the plasma glow with data obtained from the calculation shows good agreement, which theoretically confirms the generation of high charge state ions during pinching of the arc column. • Generation of multiply charged metal ions in the plasma of a vacuum arc. • Nanosecond exposure time imaging of the vacuum arc plasma. • Time-of-flight diagnostics of ion mass-to-charge composition of the vacuum arc plasma. • A hybrid model of a high-current arc plasma and calculation of the plasma parameters. • Good agreement between the experimentally obtained and theoretically predicted plasma luminosity. [ABSTRACT FROM AUTHOR]

The effect exerted by defocusing of double laser pulses on the formation of the component and charge composition in the surface laser plasma has been studied by the laser spark spectrometry (LSS) method. The possibility to increase the portion of variously charged aluminum ions in the surface laser plasma and also of AlN clusters when the target was subjected to a series of successive double laser pulses has been demonstrated.

The Kendrick mass defect (KMD) analysis of multiply charged polymeric distributions has recently revealed a surprising isotopic split in their KMD plots—namely a 1/z difference between KMDs of isotopes of an oligomer at charge state z. Relying on the KMD analysis of actual and simulated distributions of poly(ethylene oxide) (PEO), the isotopic split is mathematically accounted for and found to go with an isotopic misalignment in certain cases. It is demonstrated that the divisibility (resp. indivisibility) of the nominal mass of the repeating unit (R) by z is the condition for homolog ions to line up horizontally (resp. misaligned obliquely) in a KMD plot. Computing KMDs using a fractional base unit R/z eventually corrects the misalignments for the associated charge state while using the least common multiple of all the charge states as the divisor realigns all the points at once. The isotopic split itself can be removed by using either a new charge-dependent KMD plot compatible with any fractional base unit or the remainders of KM (RKM) recently developed for low-resolution data all found to be linked in a unified theory. These original applications of the fractional base units and the RKM plots are of importance theoretically to satisfy the basics of a mass defect analysis and practically for a correct data handling of single stage and tandem mass spectra of multiply charged homo- and copolymers.ᅟ [ABSTRACT FROM AUTHOR]

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]

In the study of the special properties of molecules, diatomic molecules are vital. Three quantum mechanics methods were used to calculate the optimised structure and total electronic energy of the LiF molecule; namely, the Hartree-Fock (HF), density functional theory (DFT), and coupled cluster singles and doubles (and triples) (CCSD(T)) methods. The optimised structure properties, such as diploe moment, spectroscopic constants, and vibrational frequency, were calculated, as well as the potential energy curves. This study found that the negative LiF molecule is more stable than the neutral LiF molecule, and that the positive LiF molecule is unstable. These results were supported by the values of vibrational frequency and spectroscopic constants of LiF. [ABSTRACT FROM AUTHOR]

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]

The fractionation or rejection of concentrated salts by nanofiltration membrane remains the biggest challenge owning to the charge neutrality and concentration polarization. A tight nanofiltration membrane with ultrathin dually charged nanofilm down to 17±5 nm was synthesized to improve the rejection of highly concentrated salts up to 20 g/L. The ultrathin positive polyethylenimine (PEI) and negative poly(acrylic acid) (PAA) polyelectrolyte nanofilm was assembled on the loose nanofiltration membrane via the aid of bio-glue dopamine. The physicochemical property of dependent nanofilm was characterized by the surface morphology (SEM, AFM), element variation (XPS), surface charge (Zeta potential), molecular weight cut off and stokes radius respectively. The influence of dopamine deposition time and PEI concentration on separation performance was investigated. The optimum membrane exhibited outstanding rejection to diluted multivalent salts (1 g/L, 98.5% MgSO 4 , 98.3% Na 2 SO 4 , 97.2% MgCl 2 ), high removal of heavy metal ions (1 g/L, 93.5% Cd 2+ , 95.2% Cu 2+ , 92.7% Pb 2+ ) as well as high removal of dyes (100% Congo red, 99.93% Victoria blue B, 99.91% Brilliant green, 99.82% Basic red 2, 99.03% Neutral red). Moreover, the resultant membrane showed exceptional rejection to highly concentrated salts (20 g/L, 93.4% Na 2 SO 4 , 92.6% MgCl 2 , 93.5% MgSO 4 ), exceeding the previously reported membranes. Both the multi-charged nanofilms and nano-scaled thickness contributed to the outstanding nanofiltration performance. [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]

The atomic properties and transition parameters of Sb-like Cs4+, Ba5+, La6+, Ce7+, Pr8+, Nd9+, Pm10+, and Sm11+ ions were first calculated using the GRASP2K package. This method is based on the multi-configuration Dirac-Hartree-Fock (MCDHF) method. In this calculation, the contributions of Breit and QED corrections were taken into consideration. By comparison, our results were in good agreement with the NIST values for Cs4+ and Ba5+, which revealed that our calculations are dependable. Meanwhile, it also showed that these ions have high sensitivity to the fine-structure constant α and long-lived metastable states. In particular, Pm10+ and Sm11+ had very long-lived metastable states with transitions within the optical transition. These ions are useful for the research of ultra-accurate atomic clocks and fundamental physics. [ABSTRACT FROM AUTHOR]

Liquid AP-MALDI can produce predominantly multiply charged ESI-like ions and stable durable analyte ion yields with samples allowing good shot-to-shot reproducibility and exhibiting self-healing properties during laser irradiation. In this study, LC-MALDI MS/MS workflows that utilize multiply charged ions are reported for the first time and compared with standard LC-ESI MS/MS for bottom-up proteomic analysis. The proposed method is compatible with trifluoroacetic acid as an LC ion pairing reagent and allows multiple MS/MS acquisitions of the LC-separated samples without substantial sample consumption. In addition, the method facilitates the storage of fully spotted MALDI target plates for months without significant sample degradation. [ABSTRACT FROM AUTHOR]

Conventional matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is characterized by the predominant generation of singly charged analyte ions. Recent studies demonstrated that high charge states of peptides and small proteins can be produced with an atmospheric pressure (AP) MALDI ion source if liquid glycerol-based matrix systems are utilized and the AP-vacuum transfer is realized via a heated ion inlet tube [R. Cramer, A. Pirkl, F. Hillenkamp, K. Dreisewerd, Angew. Chem. Int. Ed. 52 (2013) 2364–2367]. Here, we used this AP ion source and employed an optical parametric oscillator (OPO) laser to study the wavelength dependence of the ion generation between 260 and 1080 nm. Three matrix systems with different optical absorption characteristics were investigated: non-absorbing glycerol mixed with trifluoroacetic acid (TFA) and glycerol mixed with either 2,4- or 2,5-dihydroxybenzoic acids as two classical UV-MALDI matrices. The highest ion yields of multiply charged peptides were consistently obtained at laser wavelengths for which the chromophore-containing matrix systems exhibited the lowest optical absorption. Best sensitivities were even achieved with the transparent glycerol/TFA mixture and by use of a Nd:YAG-laser operated at 1064 nm (or with the OPO laser tuned to a similar wavelength). Experiments with absorbing and transparent sample substrates demonstrated the involvement of substrate absorption. In contrast to the results obtained with the AP ion source, using the same matrix systems in combination with a standard oMALDI2™ ion source, operated at a fine vacuum of ∼1 mbar and without an inlet tube, the inverse wavelength dependence was observed. Or in other words, like in standard UV-MALDI under these conditions the highest analyte ion yields were obtained for laser excitation wavelengths corresponding to a high absorptivity of the matrix. Our findings thus point to completely different desorption/ionization processes with the two ion source geometries and laser excitation regimes. We hypothesize that for the AP case the material ablation comprises low-energy laser spallation and that rapid evaporative ionization of small droplets in the heated transfer capillary is responsible for charge production. From an analytical point of view, the production of multiply-charged peptide and protein ions with charge states that for the tested analytes (ranging by mass from 1 to 17 kDa) almost fully resembled those generated by nano-electrospray ionization (ESI) could facilitate the coupling of laser-based ion sources with mass analyzers, such as orthogonal-extracting time-of-flight (QTOF) instruments or orbitraps which exhibit only limited m / z ranges. [ABSTRACT FROM AUTHOR]

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 components of a transport line for a laser multicharged ion source are described. Aluminum and carbon multicharged ions are generated by a Q-switched, nanosecond Nd:YAG laser (wavelength λ = 1064 nm, pulse width τ = 7.4 ns, and pulse energy up to 82 mJ) ablation of a target in a vacuum chamber. Time-of-flight and a three-grid retarding ion energy analyzers are used to determine the velocity and the charge state of the ions. A three-electrode cylindrical einzel lens is used to focus the ions. At a distance of 30 cm from the center of the focusing electrode of the einzel lens, Al 1+ and Al 2+ have a minimum beam diameter of ∼1.5 mm, while for Al 3+ and Al 4+ the minimum beam diameter is ∼2.5 mm. The simulation of the ion trajectories is done using SIMION 8.1. A high voltage pulse applied to a set of two parallel deflecting plates is used for the pickup of ions with different charge states according to their time-of-flight. An electrostatic cylindrical ion deflector is used for analysis and selection of charges with specific energy-to-charge ratio. The design of these transport line components and their operation are described. [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]