High Energy Electron Impact Research Articles

Surface finishing of 3D-printed Ti–6Al–4 V alloy by electrolyte plasma polishing: Process optimization and microstructure

The electrolyte plasma polishing (EPP) technology is proposed to remove the unmelted powder particles and oxide film for high-quality surface finishing of 3D-printed Ti–6Al–4 V alloy. An orthogonal experiment is conducted to investigate multiple factors that contribute to the surface quality of the alloy during the polishing process. The optimal parameters determined for the EPP process are a voltage of 300 V, a polishing time of 12 min, a polishing depth of 12 cm, and a temperature of 75 °C. Based on the extent of the effect, the factors influencing surface roughness were ranked: voltage > time > depth > temperature. The surface crest and trough area of the alloy is substantially reduced after polishing, while the average roughness experienced a reduction of 76 %. The improvement in surface quality is attributed to the corrosion of the oxide layer by F ions in the electrolytic solution, and the melting of surface protrusions due to the impact of high-energy electrons under high-temperature and high-pressure conditions during plasma discharge. Additionally, the surface hardness of the material decreases slightly, but its corrosion resistance and hydrophobicity are enhanced, and the calibration rate of the EBSD sample can reach 92.51 %, demonstrating that it is an excellent surface finishing technique. Hence, EPP is a promising approach for smoothening 3D-printed metals, especially for alloy parts with complex geometry and porous structure.

Theoretical study of valence excitations in fluoromethanes by high energy electron impact

We report a theoretical study of the electron-impact electronic excitation of fluoromethanes. Generalized oscillator strengths (GOSs) are calculated for the molecules at the equation-of-motion coupled-cluster singles and doubles level. To clarify the influence of nuclear dynamics on the electronic excitations, the effects of internal molecular vibrations are included in the calculation. Comparison with experimental data resolves some inconsistencies in the assignment of the transition bands. Furthermore, it is shown that the lengthening of the CH bond enhances the excitation from the highest occupied orbital to the 3s Rydberg orbital for CHF3, CH2F2, and CH3F, and that the CH stretching vibrations thus have a significant influence, especially at small momentum transfer where electric dipole transitions are dominant. Since the 2 1A1 state of CHF3 dissociates into CF3 + H, the result indicates that the CH stretching vibration causes an increase in the production of CF3 by electron collision and by photoabsorption.

Theoretical Study of Valence Shell Excitation by Electron Impact in CCl4

This paper reports a theoretical study of valence shell excitation in CCl4 by high-energy electron impact. Generalized oscillator strengths are calculated for the molecule at the equation-of-motion coupled-cluster singles and doubles level. To elucidate the influence of nuclear dynamics on electron excitation cross-sections, the effects of molecular vibration are included in the calculation. Based on a comparison with recent experimental data, several reassignments of spectral features are made, and it is found that excitations from the Cl 3p nonbonding orbitals to σ* antibonding orbitals, 7a1 and 8t2, play dominant roles below the excitation energy of ∼9 eV. Furthermore, the calculations reveal that distortion of the molecular structure due to the asymmetric stretching vibration significantly affects the valence excitations at small momentum transfers, where contributions from dipole transitions are dominant. It indicates that vibrational effects have a considerable influence on Cl formation in the photolysis of CCl4.

Fragmentation of tyrosine by high-energy electron impact

Fragmentation of tyrosine by high-energy electron impact

A device for controlling the energy of ionizing electrons in the low-energy range designed to form a complete mass spectrum of negative ions using a quadrupole mass spectrometer

Operation with positive ions formed from the impact of high energy electrons (usually 70 eV, which exceeds the ionization energy of the molecules) is a standard mode for mass spectrometric detectors of most gas chromatography-mass spectrometric complexes (GC/MS) in the basic configuration. At the same time, we have shown that the option of setting the energy of ionizing electrons (maintained in the design of some serial devices) within the pre-ionization region also allows one to obtain mass spectra of negative ions (NI) which, in turn, significantly expands the analytical potential of standard equipment. The formation of NI occurs in the low-energy range of 0 – 15 eV due to resonant capture of electrons by molecules (REC). In contrast to positive ions, the intensity of NI formation sharply (resonantly) depends on the electron energy and this dependence is characteristic of each chemical compound. Both the relative intensity of the mass-peaks and, in general, the ionic composition of the formed mass spectrum of NI significantly depend on the electron energy. The problem of choosing the optimal energy of ionizing electrons providing the same efficiency of mass-spectrometric determination of all components of complex mixtures of dissimilar compounds is also associated with the features of negative ion formation during chromatography-mass spectrometric analysis. To address the problem, we propose a technique providing generation of complete (in NI composition and intensities) mass spectra of NI through repeated variation of the energy of ionizing electrons in a given range of 0 – 10 eV. Technical implementation of the technique [1] was carried out at the Design Bureau «Chromatec «(Yoshkar Ola, Russia) in the form of a special electronic device, which was tested in pilot operation as part of the gas chromatograph complex with a quadrupole mass spectrometer «Chromatec». We describe the principle of operation of the device and present the results of tests.

High-energy ionizing radiation influence on the fragmentation of glutamine

Both experimentally, by using the mass-spectrometric technique, and theoretically, by applying Becke’s three-parameter hybrid density functional approach, the yield of the ionic products of both single- and dissociative ionization of the glutamine molecule (C5H10N2O3) under high-energy (11.5 MeV) electron impact has been studied. The experimental mass spectra measured at different irradiation doses (i.e., 0, 5, 10, and 20 kGy) have been identified and analyzed. It has been shown that high-energy electrons cause irreversible changes in the structure of the molecule under study, accompanied by a transition to the zwitterionic/deprotonated form, which may cause a change in the fragment ion production at the interatomic distance variation. It has been shown that the yield of the low-mass fragments from the zwitterionic glutamine molecular structure may increase due to an increase in the isobaric ion yield.

Gas Phase Activation of Methane Molecule with Lead Benzene Dication Complex Ion, [Pb(Benzene)<sub>2</sub>]<sup>2+</sup>

Motivated by the search for ways of a more efficient usage of the ubiquitous, and unexploited resources of methane, recent progress in the gas-phase activation of methane by metal dication complex ion is discussed. The gas phase theoretical and experimental analysis on [Pb(Benzene)2]2+ was conducted. The [Pb(Benzene)2]2+ complex ions were prepared using a combination of the pick-up technique and high energy electron impact, and then held in a cold ion trap. Excitation with tuneable UV radiation resulted in the formation of [Pb(Benzene)2(H2O)]2+, [Pb(Benzene)2(H2O)2]2+, [Pb(Benzene)]+, Pb+ and Benzene+ ions when the experimental results were analysed. The two optimised geometries of [Pb(Benzene)2]2+ namely the C2V eclipse and C2 staggered were observed. Methane activation of [Pb(Benzene)2]2+ complex ion yielded [Pb(Benzene)2(Me)]2+. [Pb(Benzene)2(H2O)(Me)2]2+, [Pb(Benzene)2(H2O)(Me)]2+, [PbBenzene(Me)3]2+ and [Pb(Benzene)(Me)]2+. The PEC calculated binding energy of methane to lead benzene dication complex ion was approximately 25.45% higher than the value recorded on DFT calculation. This difference was due to the charge differences on the lead metal centre. While the actual calculated charge on the Pb metal in the optimised geometry was 1.68 the charge of +2 on the Pb metal was considered in the PEC calculation.

Ion fragmentations via photoelectron activated radical relays and competed hole oxidization on semiconductor nanoparticles for mass spectrometry

Structural identification is challenging in mass spectrometric imaging because of inadequate sample quantities and limited sampling time in each pixel for tandem mass spectrometry (MS/MS) experiments, which are usually used for the generation of fragment ions. We report herein the observation of a cascade of highly specific chemical bond cleavages via a low-energy photoelectron activated radical relays and a competed hole oxidization on surfaces of (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles irradiated with the 3rd harmonic (355 nm) of the Nd3+: YAG laser. Distinguished from high energy electron impact (EI), this approach generates gaseous radical anions through the exothermic capture of low-energy tunneling electrons that are not able to cause extensive vibrational excitations. It was found not only original radical center but also secondary or even tertiary radical centers cause specific bond cleavages exclusively on α positions. The original radical center directly activates the cleavages of α-positioned chemical bonds that cause the formation of secondary radical centers. Ion fragmentations proceed along the newly formed radical centers that further activate the cleavages of their α-positioned chemical bonds. Using 8 compounds, we have demonstrated various radical reactions involved in desulfonation, cyclization, and ring contraction reactions as well as competed hole oxidization-generated hydroxyl radical substitution reactions. The interpretable fragment ions provide unambiguous experimental evidences for structural elucidation of drug residues and metabolites in mass spectrometric imaging of tissue slices without tandem mass spectrometry (MS/MS).

Pulsed glow discharge enables direct mass spectrometric measurement of fluorine in crystal materials – Fluorine quantification and depth profiling in fluorine doped potassium titanyl phosphate

A pulsed direct current glow discharge time-of-flight mass spectrometry (GD TOF MS) method for the quantification of fluorine in insoluble crystal materials with fluorine doped potassium titanyl phosphate (KTP) KTiOPO4:KF as an example has been proposed. The following parameters were optimized: repelling pulse delay, discharge duration, discharge voltage, and pressure in the discharge cell. Effective ionization of fluorine in the space between sampler and skimmer under short repelling pulse delay, related to the high-energy electron impact at the discharge front, has been demonstrated. A combination of instrumental and mathematical correction approaches was used to cope for the interferences of 38Ar2+ and 1H316O + on 19F+. To maintain surface conductivity in the dielectric KTP crystals and insure its effective sputtering in combined hollow cathode cell, silver suspension applied by the dip-coating method was employed. Fluorine quantification was performed using relative sensitivity factors. The analysis of a reference material and scanning electron microscope-energy dispersive X-ray spectroscopy was used for validation. Fluorine limit of detection by pulsed direct current GD TOF MS was 0.01mass%. Real sample analysis showed that fluorine seems to be inhomogeneously distributed in the crystals. That is why depth profiling of F, K, O, and P was performed to evaluate the crystals' non-stoichiometry. The approaches designed allow for fluorine quantification in insoluble dielectric materials with minimal sample preparation and destructivity as well as performing depth profiling to assess crystal non-stoichiometry.

Fragment and cluster ions from gaseous and condensed pyridine produced under electron impact.

We report on direct measurement of all major ion-fragments and cluster-ions formed during high-energy electron impact of 2 keV on gaseous and condensed-phase pyridine. The ion-fragments of the parent pyridine cation are discussed in groups according to the number of atoms from the aromatic ring. The ion yield distributions within these groups show significant shifts towards higher masses for condensed pyridine compared to gaseous pyridine due to hydrogen migration. A wide spectrum of desorbed hydrogenated fragment-ions and ionic clusters with masses up to 320 u are observed for pyridine. The ion yields for the protonated parent molecule (C5H5NH+), the dehydrogenated dimer (C10H9N2+) and the dehydrogenated trimer (C15H12N3+) depend on the mass of the desorbing ionic clusters. The strongest cluster signals are assigned to binding between the parent cation and subunits of the pyridine molecule. Quantum-chemical calculations reveal that the formation of a bond between the pyridine molecules and a carbenium ion is crucial for the stability of selected cluster ions.

Relative stability of naphthalene, quinoline and isoquinoline under high energy electron impact

Stability of naphthalene and two of its nitrogen containing derivatives namely, quinoline and isoquinoline are investigated under high energy electron impact. Astro-biologically important statistical dissociation channels are probed using the delayed extraction time-of-flight mass spectrometry technique. The experimental configuration was designed to avoid yield variation due to the thermal velocities for 5μs or more after the collision. The statistical decay channels show an increase in the yield of daughter ions as a function of extraction delay in the range of 106s−1. On the other hand, the yields due to fast dissociation channels were observed to decrease as a function of extraction delay. On the basis of projectile beam energy dependence of the yields, the effect of plasmon excitation in quinoline and isoquinoline is shown for the first time. A strong dependence of the statistical dissociation yield on the location of the nitrogen atom in the two molecules is observed. An attempt is made to correlate these observations with the various structure parameters obtained using structure calculations.

Decay dynamics of N2O under the impact of fast electrons

We experimentally investigate the two- and three-body breakup dynamics of N2O () under the impact of fast (5 keV) electrons using a coincidence momentum spectroscopy technique. The kinetic energy release (KER) distributions have been derived from the measured momenta for various breakup channels. The present values are found to be quite different from a previously reported high energy electron impact study. From the measured momentum vectors, the geometry of the precursor molecular ion prior to the fragmentation has been reconstructed. The three-body decay dynamics of N2O3+ has been studied using Dalitz plots and Newton diagrams with a view of concerted and sequential decay mechanisms. It is found that the sequential process is present along with the concerted process for the N2O3+ N+ + NO2+ N+ + N+ + O+ channel.

Unified calculation of generalized oscillator strength of argon ranging from bound to continuum states

The electron and photon scattering data of an atom are crucial for many scientific fields, including plasma physics, astrophysics, and so on. For high enough but nonrelativistic incident energies, the first Born approximation is applicable for calculating these data, in which the key physics quantity is the generalized oscillator strength (GOS). In high-energy electron impact excitation processes, atoms will be excited into various excited states including strongly perturbed Rydberg and adjacent continuum states. How to calculate these quantities of a nontrivial many-electron atom rapidly and accurately is still a great challenge. Based on our eigenchannel $R$-matrix method $R$-eigen, we further extend it to calculate the GOS of a whole channel in an atom, which includes all Rydberg and adjacent continuum states. The ${J}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ states of argon are chosen as an illustrating example. The calculation results are in good agreement with the available benchmark absolute experimental measurements. The calculated eigenchannel GOS matrix elements are smooth functions of the excitation energy and momentum transfer. From such smooth eigenchannel GOS matrix elements, we can obtain the GOS of any specific excited state through multichannel quantum defect theory, e.g., infinite Rydberg (including a strongly perturbed one), autoionization, and continuum states.

Positive ion desorption from frozen N-heterocycles stimulated by high-energy electron impact

SynopsisIon desorption measurements induced by the impact of electrons onto pyridine and pyrimidine ices will be presented. The data reported here is of relevance for chemical evolution models of astrophysical objects.

ENERGY RELEASE AND INITIATION OF A SUNQUAKE IN A C-CLASS FLARE

We present analysis of C7.0 solar flare of Febrary 17, 2013, revealing a strong helioseismic response (sunquake) caused by a very compact impact in the photosphere. This is the weakest known C-class flare generating a sunquake event. To investigate possible mechanisms of this event, and to understand the role of accelerated charged particles and photospheric electric currents, we use data from three space observatories: Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Solar Dynamics Observatory (SDO) and Geostationary Operational Environmental Satellite (GOES). We find that the photospheric flare impact does not spatially correspond to the strongest HXR emission source, but both of these events are parts of the same energy release. Our analysis reveals a close association of the flare energy release with a rapid increase of the electric currents, and suggests that the sunquake initiation is unlikely to be explained by the impact of high-energy electrons but may be associated with a rapid current dissipation or a localized impulsive Lorentz force.

Double ionization of helium by fast electrons with the Generalized Sturmian Functions method

The double ionization of helium by high energy electron impact is studied. The corresponding four-body Schrödinger equation is transformed into a set of driven equations containing successive orders in the projectile–target interaction. The first order driven equation is solved with a generalized Sturmian functions approach. The transition amplitude, extracted from the asymptotic limit of the first order solution, is equivalent to the familiar first Born approximation. Fivefold differential cross sections are calculated for (e, 3e) processes within the high incident energy and small momentum transfer regimes. The results are compared with other numerical methods, and with the only absolute experimental data available. Our cross sections agree in shape and magnitude with those of the convergent close coupling method for the (10+10) eV and (4+4) eV emission energies. To date this had not been achieved by any two different numerical schemes when solving the three–body continuum problem for the fast projectile (e, 3e) process. Though agreement with the experimental data, in particular with respect to the magnitude, is not achieved, our findings partly clarify a long standing puzzle.

Fragmentation ofCO22+in collisions with low-energy electrons

The fragmentation of the ${\mathrm{CO}}_{2}{}^{2+}$ dication following 200 eV electron impact double ionization was studied using a cold target recoil-ion momentum spectroscopy. Both two-body and three-body fragmentation channels were observed with an ion-ion coincidence technique. The slopes of the peaks in the coincidence spectra were extracted and compared with previous results and theoretical predictions. Overall, good agreement between theoretical and experimental results was achieved, while different behaviors were observed for the channel of fragmentation into $\mathrm{C}{}^{+}+\mathrm{O}{}^{+}+\mathrm{O}$ with previous high energy electron impact results. The momentum vectors of ionic fragments were measured, and thus the momentum vector of the neutral particle was deduced and kinetic energy release (KER) distributions for the different fragmentation channels were obtained. KER distribution behavior also shows a different signature from that induced by high energy electron impact. Furthermore, the three-body fragmentation mechanism, i.e., dissociation in one- or two-step processes, was distinguished from their distinct signatures on the Dalitz plots and the slopes of the islands from the covariance mapping spectrum. For example, the fragmentation channel $\mathrm{C}{}^{+}+\mathrm{O}{}^{+}+\mathrm{O}$ was found to be very similar to the 60 eV photon impact result [J. Laksman, E. P. M\aa{}nsson, C. Grunewald, A. Sankari, M. Gisselbrecht, D. C\'eolin, and S. L. Sorensen, J. Chem. Phys. 136, 104303 (2012)], which shows a predominant sequential dissociation process.

Fragmentation and Ion Desorption from Condensed Pyrimidine by Electron Impact: Implications for Cometary and Interstellar Heterocyclic Chemistry

The desorption process induced by photons, electrons, or ions onto icy surfaces is an important mechanism for leading neutral or ionized molecular species to the gas phase in interstellar and circumstellar environments. In this work, we report the results of high energy electron impact onto a condensed pyrimidine ice by means of electron-stimulated ion desorption (ESID). Desorbed cations from the icy surface were analyzed by time-of-flight mass spectrometry (TOF-MS). The most abundant desorbed ions are H+ and H2+, although several other fragments, such as C2H2+, HCN+, C3H3+, CHN2+, C2H2N2H+, and C4H4N2H+, have also been identified. The fragmentation pattern of pyrimidine was found to be characterized by six distinct regions on its desorption spectra, containing ionic fragments bearing one to six members of the original pyrimidine ring. Five-membered fragment ions were observed for the first time in electron impact experiments. Absolute values of desorption yield for several ions were determined. Desorbed ions observed in this experiment are in agreement with observations of the comet Halley coma composition and may act as markers of the presence of pyrimidine in the interstellar medium.

Feasibility of Detecting Spacecraft Charging and Arcing by Remote Sensing

More than 50 years after the dawn of the space age, most spacecraft still do not have sensors onboard capable of detecting whether they are at potentials likely to put them at risk of severe charging and the concomitant arcing, or, indeed, even capable of detecting when or if they undergo arcing. As a result, anomaly resolution has often been hit or miss, and false diagnoses are probably common. In this paper, a few remote sensing techniques that could be applied for remotely detecting spacecraft charging and/or arcing, and their feasibility, are examined: surface glows from high-energy electron impact, x-rays from bremsstrahlung, and radio and optical emission from arcs and after arcing.

Collision problems treated with the Generalized Hyperspherical Sturmian method

An hyperspherical Sturmian approach recently developed for three-body break-up processes is presented. To test several of its features, the method is applied to two simplified models. Excellent agreement is found when compared with the results of an analytically solvable problem. For the Temkin-Poet model of the double ionization of He by high energy electron impact, the present method is compared with the Spherical Sturmian approach, and again excellent agreement is found. Finally, a study of the channels appearing in the break-up three-body wave function is presented.