Direct Ionization Research Articles

Molecular Insights into Radiation Effects and Protective Mechanisms: A Focus on Cellular Damage and Radioprotectors

Ionizing radiation has been a critical tool in various fields, such as medicine, agriculture, and energy production, since its discovery in 1895. While its applications—particularly in cancer treatment and diagnostics—offer significant benefits, ionizing radiation also poses risks due to its potential to cause molecular and cellular damage. This damage can occur through the direct ionization of biological macromolecules, such as deoxyribonucleic acid (DNA), or indirectly through the radiolysis of water, which generates reactive oxygen species (ROS) that further damage cellular components. Radioprotectors, compounds that protect against radiation-induced damage, have been extensively researched since World War II. These agents work by enhancing DNA repair, scavenging free radicals, and boosting antioxidant defenses, thereby protecting healthy tissues. Furthermore, some radioprotective agents also stimulate DNA repair mechanisms even after radiation exposure, aiding in recovery from radiation-induced damage. This article explores the molecular mechanisms of radiation-induced damage, focusing on both direct and indirect effects on DNA, and discusses the role of radioprotectors, their mechanisms of action, and recent advancements in the field. The findings underscore the importance of developing effective radioprotective strategies, particularly in medical and industrial settings, where radiation exposure is prevalent.

Ponderomotive potential effects on strong field two-photon double ionization in neon

Abstract In the context of the recently reported experiment on photoionization in neon atom, we theoretically study the photoionization of neon atom at a comparatively intense laser field. The calculated photoelectron spectrum for a Gaussian laser pulse show an asymmetric double peak line shape at a pulse duration of 14.2 fs and peak intensity of 1x1015 W/cm2. A systematic study clearly indicates that the ponderomotive potential of the photoelectron released during photoionization of neon is instrumental in causing the visible asymmetry. 
 Interestingly, for similar laser parameters asymmetry in the the photoelectron spectrum gets significantly reduced for a Sech2
shaped laser pulse. Time resolved photoelectron spectrum reveals that even for a Sech2 shaped laser pulse the two peak photoelectron spectrum is initially asymmetric and evolves into a symmetric line shape with increase in time. The results clearly indicate that irrespective of laser pulse shape asymmetry shows a non-linear decrease as a function of time. Our study also shows the possibility of controlling the asymmetry by varying the pulse duration. The calculations establishes a correlation between the effects of direct double ionization and ponderomotive potential on the asymmetry of the photoelectron spectrum at different pulse durations.

Detection of Veterinary Drugs in Food Using a Portable Mass Spectrometer Coupled with Solid-Phase Microextraction Arrow.

A portable mass spectrometer (PMS) was combined with a mesoporous silica material (SBA-15) coated solid-phase microextraction (SPME) Arrow to develop a rapid, easy-to-operate and sensitive method for detecting five veterinary drugs-amantadine, thiabendazole, sulfamethazine, clenbuterol, and ractopamine-in milk and chicken samples. Equipped with a pulsed direct current electrospray ionization source and a hyperboloid linear ion trap, the PMS can simultaneously detect all five analytes in approximately 30 s using a one-microliter sample. Unlike traditional large-scale instruments, this method shows great potential for on-site detection with no need for chromatographic pre-separation and minimal sample preparation. The SBA-15-SPME Arrow, fabricated via electrospinning, demonstrated superior extraction efficiency compared to commercially available SPME Arrows. Optimization of the coating preparation conditions and SPME procedures was conducted to enhance the extraction efficiency of the SBA-15-SPME Arrow. The extraction and desorption processes were optimized to require only 15 and 30 min, respectively. The SBA-15-SPME Arrow-PMS method showed high precision and sensitivity, with detection limits and quantitation limits of 2.8-9.3 µg kg-1 and 10-28 µg kg-1, respectively, in milk. The LOD and LOQ ranged from 3.5 to 11.7 µg kg-1 and 12 to 35 µg kg-1, respectively, in chicken. The method sensitivity meets the requirements of domestic and international regulations. This method was successfully applied to detect the five analytes in milk and chicken samples, with recoveries ranging from 85% to 116%. This approach represents a significant advancement in food safety by facilitating rapid, in-field monitoring of veterinary drug residues.

Electron-impact ionization for Ne[formula omitted] and Ne[formula omitted]

Ionization cross sections are studied for energy levels of the ground configurations of the Ne3+ and Ne4+ ions. The distorted wave (DW) approximation is used to analyze experimental data. The scaled DW cross sections are used to explain measurements for the Ne3+ ion. Study includes analysis of contributions from the direct and indirect ionization processes. Convergences of excitation-autoionization (EA) channels are estimated by analyzing excitations up to shells with the principal quantum number n⩽20. This study shows that the EA process provides from ∼10% to 20% for the energy levels of the ground configurations of the Ne3+ and Ne4+ ions.

Positron interactions with vinyl acetate from 0.1 eV to 5 keV

Abstract Scattering cross sections from positron impact on vinyl acetate are explored in the energy region 0.1~eV to a 5~keV, employing a cc-pVTZ basis set. The optimized molecular wavefunction of the target was obtained through a multi-center expansion of Gaussian-type orbitals in the Hartree-Fock self-consistent field framework. The elastic cross sections are computed using the single-centre-expansion formalism. Two distinct models were employed to address the long-range effects associated with the target's polar nature and yielded almost identical corrections. The Born-corrected elastic cross sections align more strongly with the existing experimental corrected data than the results reported from the independent-atom-model approximation. The differential and momentum transfer cross sections after applying Born-correction are also reported. The direct ionization cross sections are obtained using the binary-encounter-Bethe model for positrons. The cross sections obtained by summing elastic and ionization cross sections align closely with `forward angle corrected' experimental total cross sections across a significant energy range. The agreement significantly improves beyond 30 eV, suggesting that the omission of excitation and positronium formation cross sections becomes less significant. A brief analysis of the electron interaction with the target is also made.

Chemical profile of compounds in irrigated arabica coffee by ESI-MS

The use of irrigation in coffee aims productivity increase and better quality of the final product. The impacts of irrigation in productivity and quality are impressive. In this study, ten different varieties of Coffea arabica L., were cultivated with irrigation and no irrigation regimes and these samples were analyzed by direct infusion electrospray ionization mass spectrometry (ESI-MS), in positive mode. The constituents identified were choline; trigonelline; sucrose; βN-arachinoyl-5-hidroxytryptamide; βN-behenoyl-5-hidroxytryptamide; palmitoyl-linoleoyl (PL); dilinoleoyl (LL); dipalmitoyl-linoleoyl (PPL); palmitoyl-dilinoleoyl (PLL) and three new compounds reported in coffee – triacylglycerol (TG 54:6), phosphoethanolamine (PE 40:7) and 1-hexadecyl-2-dodecanoyl-glycero-3-phosphate It was possible to efficiently sort the groups of irrigated and non-irrigated using PLS-DA to obtain all the minimum requirements for evaluation of efficiency of the rating model. Sucrose and the ion m/z 431 (not identified) suffered a negative influence of irrigation. The trigonelline, and the ion m/z 723 (not identified) were influenced positively by irrigation. The cup test showed that the coffees cultivated in not-irrigated regime had slightly larger cupping notes that the ones cultivated under irrigation, probably because they presented higher sucrose content.

Cross sections for electron scattering from atomic gallium

Abstract The relativistic convergent close-coupling method was applied to calculate cross sections for electron scattering on atomic gallium. The integrated and momentum-transfer cross sections for elastic scattering are presented from the 4 s 2 4 p 4P 1 / 2 , 3 / 2 electronic states for incident energies between 0.03 eV and 1000 eV. Integrated excitation cross sections are also presented from these initial states to the 4 s 2 4 [ d , f ] , 4 s 2 5 [ s , p , d ] , 4 s 2 6 [ s , p ] and 4 s 2 7 s manifolds, as well as cross sections for excitation of the 4 s 2 4 p 2P 1 / 2 state to the 4 s 2 4 p 2P 3 / 2 state. Estimates were presented for the total single ionisation cross section and total cross section for scattering on gallium in the 4 s 2 4 p 2P 1 / 2 , 3 / 2 states, including direct ionisation from the 4p, 4s and 3d electrons, and excitation-autoionisation contributions from the 4s and 3d electrons. The estimated total single ionisation cross section was found to agree well with existing experimental data.

Calculations of positron scattering from F, F2, HF, and various fluorocarbons

Abstract Single center convergent close-coupling (CCC) calculations have been completed for positron scattering from atomic fluorine. Total, electron-loss, positronium-formation, direct ionization, momentum transfer, elastic, bound-state excitation, and stopping power cross sections have been determined for energies between threshold and 5000 eV. Past calculations for this scattering system exist only for elastic and momentum-transfer cross sections. For high energies, good agreement is found between current and past results. At low energies, however, large differences are found between the current calculations and previous results. The atomic fluorine results are then used in a modified independent atom approach to calculate cross sections for positron scattering on F2, HF, CF4, C2F6, C3F6, C3F8, and C6F6. The current molecular results are typically higher than previous positron experiments across the calculated energy range, however, these experiments were not corrected for the forward angle scattering effect and likely underestimate the true result. Good agreement is found between the current positron results and previous electron experiments and calculations at high energies.

Electron-impact double ionization cross sections and rate coefficients for Be-like ions: B+ to Ne6+

We report a detailed analysis of the electron-impact double ionization process for Be-like ions, spanning charge states from B+ to Ne6+. We considered both direct and indirect double ionization processes. For direct double ionization, we calculated the cross sections by considering three different processes: ionization-ionization (II), excitation-ionization-ionization (EII), and ionization-excitation-ionization (IEI). Our results show excellent agreement between the measured cross sections for Be-like-B and Be-like-O ions. The agreement is slightly weaker for Be-like-Ne ions when we take the potential of ionized ions in the distorted-wave method. For other ions for which experimental data are not available, our calculations should provide the missing data. We have summarized the trends of electron-impact double ionization cross sections with atomic number for isoelectronic sequences. Finally, we have provided the Maxwellian and non-Maxwellian rate coefficients for these Be-like ions. The data obtained should be useful for both equilibrium and non-equilibrium charge-state distributions in astrophysical research.

Lipid Marker ESI-MS Method for Quantification of Adulteration in Almond-Based Vegetable Beverage

ABSTRACT Almond-based beverages are valued for their functionalities. However, cases of adulteration are found in the literature aiming to reduce costs. In this study, almond (LA) and peanut (LP)-based beverages were used as investigational controls in commercial products analyzed by gas chromatography and direct infusion electrospray ionization mass spectrometry (ESI-MS) combined with principal component analysis (PCA). Thus, characteristic fatty acids were identified in plant-based beverages. The ESI-MS method combined with PCA indicated individualities regarding the disposition of triacylglycerol (TAG) composition, as higher intensities of TAG were found as a lipid marker at m/z 919 [TAG+NH4]+ of ions formed by arachidic (20:0), 8/heptadecenoic (17:1n-9) and oleic (18:1n-9) fatty acids in LP. The technique demonstrated efficiency in the detection of fraud due to its sensitivity, identifying peanut content in three almond-based commercial beverages (4.4–11.58%). This study highlights the importance of robust analytical methods to the authenticity and quality of food products.

Tracking ultrafast non-adiabatic dissociation dynamics of the deuterated water dication molecule.

We applied reaction microscopy to elucidate fast non-adiabatic dissociation dynamics of deuterated water molecules after direct photo-double ionization at 61eV with synchrotron radiation. For the very rare D+ + O+ + D breakup channel, the particle momenta, angular, and energy distributions of electrons and ions, measured in coincidence, reveal distinct electronic dication states and their dissociation pathways via spin-orbit coupling and charge transfer at crossings and seams on the potential energy surfaces. Notably, we could distinguish between direct and fast sequential dissociation scenarios. For the latter case, our measurements reveal the geometry and orientation of the deuterated water molecule with respect to the polarization vector that leads to this rare 3-body molecular breakup channel. Aided by multi-reference configuration-interaction calculations, the dissociation dynamics could be traced on the relevant potential energy surfaces and particularly their crossings and seams. This approach also unraveled the ultrafast time scales governing these processes.

Calculations of Positron Scattering from Boron, BH, BF, BF2, and BF3

The single-center convergent close-coupling (CCC) method is applied to calculate positron scattering from boron. A model potential approach is utilized to extract the positronium formation, direct ionization, and values between the positronium formation and ionization thresholds. We present results for total, electron loss, elastic, momentum transfer, total bound state excitation, positronium formation, direct ionization, stopping power, and mean excitation energy from 10−5 eV to 5000 eV. For boron, there is only one other set of theoretical positron calculations for elastic and momentum transfer above 500 eV, which is in excellent agreement with the current CCC results. Using the current results for boron atoms and previous CCC calculations for hydrogen and fluorine atoms, positron scattering from BF, BF2, BF3, and BH molecules is calculated for energies between 0.1 eV and 5000 eV with a modified independent atom approach.

Rapid analysis of untreated food samples by gel loading tip spray ionization mass spectrometry.

Rapid, efficient, versatile, easy-to-use, and non-expensive analytical approaches are globally demanded for food analysis. Many ambient ionization approaches based on electrospray ionization (ESI) have been developed recently for the rapid molecular characterization of food products. However, those approaches mainly suffer from insufficient signal duration for comprehensive chemical characterization by tandem MS analysis. Here, a commercially available disposable gel loading tip is used as a low-cost emitter for the direct ionization of untreated food samples. The most important advantages of our approach include high stability, and durability of the signal (> 10min), low cost (ca. 0.1 USD per run), low sample and solvent consumption, prevention of tip clogging and discharge, operational simplicity, and potential for automation. Quantitative analysis of sulfapyridine, HMF (hydroxymethylfurfural), and chloramphenicol in real sample shows the limit-of-detection 0.1μgmL-1, 0.005μgmL-1, 0.01μgmL-1; the linearity range 0.1-5μgmL-1, 0.005-0.25μgmL-1, 0.01-1μgmL-1; and the linear fits R2 ≥ 0.980, 0.991, 0.986. Moreover, we show that tip-ESI can also afford sequential molecular ionization of untreated viscous samples, which is difficult to achieve by conventional ESI. We conclude that tip-ESI-MS is a versatile analytical approach for the rapid chemical analysis of untreated food samples.

Electron Impact Single Ionization Cross Sections of Ar+ Ion

Binary encounter approximation has been used for theoretical calculations of electron impact single ionization cross sections of singly ionized Ar atom at ground state in the energy range of 29.1eV to 2495.1 eV/amu. The cross sections for energy transfer given by Vriens’ and quantum mechanical Hartree-Fock velocity distributions for target electron have been used in the calculation. The contributions in total single ionization cross sections from 3p and 3s subshells are observed higher than from 2p, and the contributions from 3p first increases with impact energy and then decreases with increase of impact energy whereas the contribution from 3s decreases with impact energy. About 69% of results have ratio factors ≤ 1.5 and 59% have values 1.25. Major contributions to the total ionization cross sections are from 3p and 3s for direct single ionization.

Excitation Dynamics of the 5p^6 Auger Spectra in Ba + e^– Collisions

The ionization of the 5p6 subshell in Ba atoms has been studied in an electron-impact energy range 23–105 eV by measuring the Auger spectra arising from the decay of the 5p5nln′l′ states. The energy dependences of the ionization cross-section have been obtained for nine states in the 5p55d2, 5p55d6s and 5p56s2 configurations. The analysis of the behavior of the cross-sections made it possible to determine the role of direct and indirect ionization processes involved in the 5p6 ionization of the Ba atom.

Self-consistent calculation of the optical emission spectrum of an argon capacitively coupled plasma based on the coupling of particle simulation with a collisional-radiative model

We report the development of a computational framework for the calculation of the optical emission spectrum of a low-pressure argon capacitively coupled plasma (CCP), which is based on the coupling of a particle-in-cell/Monte Carlo collision simulation code with a diffusion-reaction-radiation code for Ar I excited levels. In this framework, the particle simulation provides the rates of the direct and stepwise electron-impact excitation and electron-impact de-excitation for 30 excited levels, as well as the rates of electron-impact direct and stepwise ionization. These rates are used in the solutions of the diffusion equations of the excited species in the second code, along with the radiative rates for a high number of Ar-I transitions. The calculations also consider pooling ionization, quenching reactions, and radial diffusion losses. The electron energy distribution function and the population densities of the 30 excited atomic levels are computed self-consistently. The calculations then provide the emission intensities that reproduce reasonably well the experimentally measured optical emission spectrum of a symmetric CCP source operated at 13.56 MHz with 300 V peak-to-peak voltage, in the 2–100 Pa pressure range. The accuracy of the approach appears to be limited by the one-dimensional nature of the model, the treatment of the radiation trapping through the use of escape factors, and the effects of radiative cascades from higher excited levels not taken into account in the model.

A Complementary Multitechnique Approach to Assess the Bias in Molecular Weight Determination of Lignin by Derivatization-Free Gel Permeation Chromatography.

The growing interest in lignin valorization in the past decades calls for analytical techniques for lignin characterization, ranging from wet chemistry techniques to highly sophisticated chromatographic and spectroscopic methods. One of the key parameters to consider is the molecular weight profile of lignin, which is routinely determined by size-exclusion chromatography; however, this is by no means straightforward and is prone to being hampered by considerable errors. Our study expands the fundamental understanding of the bias-inducing mechanisms in gel permeation chromatography (GPC), the magnitude of error originating from using polystyrene standards for mass calibration, and an evaluation of the effects of the solvent and type of lignin on the observed bias. The developed partial least-squares (PLS) regression model for lignin-related monomers revealed that lignin is prone to association mainly via hydrogen bonding. This hypothesis was supported by functional group-based analysis of the bias as well as pulse field gradient (pfg) diffusion NMR spectroscopy of model compounds in THF-d8. Furthermore, although the lack of standards hindered drawing conclusions based on functionalities, direct infusion electrospray ionization mass spectrometry indicated that the relative bias decreases considerably for higher molecular weight species. The results from pfg-diffusion NMR spectroscopy on whole lignin samples were comparable when the same solvents were used in both experiments; in addition, the comparison between results obtained by pfg-diffusion NMR in different solvents gives some additional insights into the aggregation.

Electron-Induced Single-Event Effect in 28 nm SRAM-Based FPGA

As the feature size of integrated circuit decreases, the critical charge of single-event effect decreases as well, making nano-scale devices more susceptible to the high-energy charged particles during their application in space. Here, we study the electron-induced single-event effect in 28 nm static random-access memory (SRAM)-based field programmable gate array (FPGA) utilizing high-energy electrons with energy of 1 MeV~5 MeV. The experimental results demonstrate that the 3 MeV electrons can cause single-event functional interrupts (SEFIs) in FPGA, while the electrons with other energies cannot. To further explore the mechanism of electron-induced SEFIs in this nanoscale FPGA, we combined Monte Carlo, Technology Computer-Aided Design (TCAD), and Simulation Program with Integrated Circuit Emphasis (SPICE) simulations. It is revealed that the SEFI was mainly caused by the direct ionization effect of high-energy electrons, and the SEFI was related to the interactions between multiple sensitive nodes.

Revealing Metabolic Dysregulation Induced by Polypropylene Nano- and Microplastics in Nile Tilapia via Noninvasive Probing Epidermal Mucus.

A noninvasive sampling technology was conceived, employing a disposable acupuncture needle in conjunction with high-resolution mass spectrometry (termed as noninvasive direct sampling extractive electrospray ionization mass spectrometry, NIDS-EESI-MS) to scrutinize the epidermal mucus of Nile tilapia for insights into the metabolic dysregulation induced by polypropylene nano- and microplastics. This analytical method initiates with the dispensing of an extraction solvent onto the needles coated with the mucus sample, almost simultaneously applying a high voltage to generate analyte ions. This innovative strategy obliterates the necessitation for laborious sample preparation, thereby simplifying the sampling process. Employing this technique facilitated the delineation of a plethora of metabolites, encompassing, but not confined to, amino acids, peptides, carbohydrates, ketones, fatty acids, and their derivatives. Follow-up pathway enrichment analysis exposed notable alterations within key metabolic pathways, including the biosynthesis of phenylalanine, tyrosine, and tryptophan, lysine degradation, as well as the biosynthesis and metabolism of valine, leucine, and isoleucine pathways in Nile tilapia, consequent to increased concentrations of polypropylene nanoplastics. These metabolic alterations portend potential implications such as immune suppression, among other deleterious outcomes. This trailblazing application of this methodology not only spares aquatic life from sacrifice but also inaugurates an ethical paradigm for conducting longitudinal studies on the same organisms, facilitating detailed investigations into the long-term effects of environmental pollutants. This technique enhances the ability to observe and understand the subtle yet significant impacts of such contaminants over time.

Direct sub-atmospheric pressure ionization mass spectrometry: Evaporation/sublimation-driven ionization is amazing, fundamentally, and practically.

This paper covers direct sub-atmospheric pressure ionization mass spectrometry (MS). The discovery, applications, and mechanistic aspects of novel ionization processes for use in MS that are not based on the high-energy input from voltage, laser, and/or high temperature but on sublimation/evaporation within a region linking a higher to lower pressure and modulated by heat and collisions, are discussed, including how this new reality has guided a series of discoveries, instrument developments, and commercialization. A research focus, inter alia, is on how best to understand, improve, and use these novel ionization processes, which convert volatile and nonvolatile compounds from solids (sublimation) or liquids (evaporation) into gas-phase ions for analysis by MS providing reproducible, accurate, sensitive, and prompt results. Our perception on how these unprecedented versus traditional ionization processes/methods relate to each other, how they can be made to coexist on the same mass spectrometer, and an outlook on new and expanded applications (e.g., clinical, portable, fast, safe, and autonomous) is presented, and is based on ST's Opening lecture presentation at the Nordic Mass spectrometry Conference, Geilo, Norway, January 2023. Focus will be on matrix-assisted ionization (MAI) and solvent-assisted ionization (SAI) MS covering the period from 2010 to 2023; a potential paradigm shift in the making.