Dissociative Electron Attachment Research Articles

Low-energy (0–9 eV) electron interaction with gas phase 1,3-dichlorobenzene: an experimental and theoretical study

Abstract Dichlorobenzene used widely in industry for the synthesis of complex products, such as polymers. The processes using this compound require, as the initial step, the breakage of the C–Cl bond. In this work, we study the interaction of electrons with 1,3 dichlorobenzene molecules not only below 2 eV [M Mahmoodi-Darian et al 2001 J. Phys. Chem. A 113 11923–14929] but also at higher energies, i.e., up to 10 eV. In this investigated energy range, the electron induces the cleavage of the C–Cl bond producing essentially a Cl− anion and the chlorobenzene radical via dissociative electron attachment. The experimental measurements are completed with quantum scattering treatments providing the resonant states and also the integral scattering cross sections. These outcomes may potentially contribute to elaborate synthesis strategies using electrons (i.e., cold plasma, surface plasmon resonance, …).

Theoretical Study on the Dissociation Mechanism of Thiophene in the UV Photoabsorption, Ionization, and Electron Attachment Processes

ABSTRACTA computational study on the intricate mechanism of thiophene ring‐fragmentation (TRF) in the UV photodissociation, dissociative ionization, and dissociative electron attachment process has been performed. The complete fragmentation process is studied using high level G4 composite method for neutral, cationic, and anionic species by elucidating a detailed mechanism for various reaction channels. The study shows that for neutral thiophene, the major pathway is the migration of H atom and subsequent fragmentation through a transition state yielding acetylene (HC≡CH) and H2C=C=S. However, for the thiophene cation, the acetylene (HC≡CH)+H2C=C=S+ channel is a two‐step and barrier less process. The onset of CH3+HC=C=C=S channel has been observed in both the thiophene cation and anion which was absent in the neutral analogue. Similarly, the onset of H2S+HC≡C—C≡CH channel has been found to operate only in the thiophene cation. Others, such as HCS and HS elimination channels have been found in all the species showing similar dissociation mechanism. For the thiophene anion, the TRF process is very much similar to that of thiophene cation. However, the reaction enthalpies of the various elimination channels in the anionic species are lower as compared to that of cationic species. During the study, the ionization energies and electron affinities of various molecules/radicals produced during the fragmentation process of thiophene were also computed.

Production of Nitrogen Dioxide, NO2-, Anion from Dissociative Electron Attachment to Nitromethane below 1 eV and Its Temperature Dependence: Direct vs Dipole Bound Mediated Processes.

Reaction induced by slow electrons is implicated in a large field of research and applications. Below 3-4 eV, dissociative electron attachment efficiently fragments molecules via (1) shape resonance or (2) mediated by the formation of a dipole bound anion. While the temperature dependence of process 1 is well-known, that of 2 is not clearly established. Nitromethane is the prototypical molecule for which the electron attachment leads to the formation of both a dipole bound and a covalent anion. We provide here a comprehensive study of the fragmentation of nitromethane by <1 eV electron and the unusual temperature effects attributed principally to process 2.

High-resolution anionic velocity map imaging apparatus for dissociative electron attachment dynamics study.

Dissociative electron attachment (DEA) of a molecular target XY, e- + XY → XY- → X + Y-, is an important process in plasma, atmosphere, interstellar space, and ionizing radiation. DEA dynamics, i.e., the formation and fragmentation of an electron-molecule resonant complex, can be unveiled by measuring the product Y- with the velocity map imaging (VMI) technique. However, it is still challenging to achieve a high-resolution VMI measurement. Recently, we developed a high-resolution DEA apparatus that combined the VMI technique with a trochoidal electron monochromator. The energy spread (around 500meV) of thermally emitted incident electrons can be reduced remarkably, but the monochromatized electrons become diffuse again in energy when being pulsed with an electric pulse applied on the grid electrode because the electron beam must be pulsed in the VMI measurement. Now this long-standing technical contradiction is settled by introducing a parallel resistance-capacitor circuit to the electrode of an electron gun. A delay-line detector is used for the VMI measurement, which allows the three-dimensional velocity or momentum images of multiple anionic yields to be recorded efficiently. Our high-resolution VMI apparatus works at a pulse frequency of 5kHz and an energy spread of about 120-150meV, and its credible performances are exhibited by the measurements of the DEA processes of CO(a3Π) and NO2.

Investigation in improving the Cs-free negative hydrogen ion production with short-pulse low power in the afterglow of pulse-power-modulated plasma sources

Abstract Pulse plasma ion sources have been shown to be capable of achieving high negative hydrogen ion densities ( n H − ) or currents. The fast cooling of the electrons and reduction in the electron density (n e) provide favorable plasma conditions to improve the H− production, with a high density ratio of negative hydrogen ions to electrons during the pulse-off period. The purpose of this research is to further improve the performance of volume-produced H− ion sources based on the pulse power modulation. In this study, a time-modulated negative hydrogen plasma sustained by 10 kHz pulse power at the typical gas pressure of 0.3 Pa was numerically investigated using a global model. The model is compared with measurements obtained in a pulsed radio frequency ion source and shows a reasonable agreement. A steplike low-high power strategy in the active glow period and a short-pulse low power in part of the afterglow period are employed to mitigate overshoot of the electron temperature (T e) in the initial stage of the pulse period and to optimize H− production in the afterglow, respectively. The model predicts that a small-magnitude, short-duration low power operation in the afterglow increases n H − and decreases n e from the onset of the low power until the beginning of the next high power pulse, due to a modest temporary increase in the T e (less than 2 eV). It facilitates dissociative electron attachments and thus H− formation. The reduction in the n e indicates that positive ions lost to the walls cannot be compensated by weak ionization. H− production with a low number of co-extracted electrons can be optimized by adjusting the magnitude and duration of the low power in the afterglow.

Dissociative electron attachment and Ar+ reaction with chromium hexacarbonyl, 296-400 K.

Dissociative electron attachment rate constants have been measured for Cr(CO)6 under thermal conditions, 296-400K, yielding Cr(CO)5- product. At 296K, 2.92 ± 0.70cm3s-1 was measured and a small decrease with temperature was observed (2.72 ± 0.70cm3s-1 at 400K). We additionally determined the cation products of Ar+ reacting with Cr(CO)6.

Electron-driven processes in enantiomeric forms of glutamic acid initiated by low-energy resonance electron attachment.

Low-energy (0-14eV) resonance electron interaction and fragment species produced by dissociative electron attachment (DEA) for enantiomeric forms of glutamic acid (Glu) are studied under gas-phase conditions by means of DEA spectroscopy and density functional theory calculations. Contrary to a series of amino acids studied earlier employing the DEA technique, the most abundant species are not associated with the elimination of a hydrogen atom from the parent molecular negative ion. Besides this less intense closed-shell [Glu - H]- fragment, only two mass-selected negative ions, [Glu - 19]- and [Glu - 76]-, are detected within the same electron energy region, with the yield maximum observed at around 0.9eV. This value matches well the energy of vertical electron attachment into the lowest normally empty π* COOH molecular orbital of Glu located at 0.88eV according to the present B3LYP/6-31G(d) calculations. Although the detection of asymmetric DEA properties a priori is not accessible under the present experimental conditions, "chirality non-conservation" can be associated with some decay channels. Evidently, the measured spectra for the L- and D-forms are found to be identical, the results, nevertheless, being of interest for the forthcoming experiments utilizing spin-polarized electron beam as a chiral factor in the framework of conventional DEA technique.

Dissoziative Elektronenanlagerungsdynamik eines vielversprechenden Krebsmedikaments zeigt sein Potential als Radiosensitizer

Abstract2‐Bromo‐1‐(3,3‐dinitroazetidin‐1‐yl)ethan‐1‐on (RRx‐001) ist ein Chemotherapeutikum für sauerstoffarme Tumore und zeigte bereits Synergieeffekte in Kombination mit Strahlentherapie. Die Wechselwirkung des Moleküls mit niederenergetischen Sekundärelektronen, die in großer Zahl in der physikalisch‐chemischen Phase der Bestrahlung gebildet werden, könnten für diesen Synergieeffekt verantwortlich sein. Die vorliegende Studie konzentriert sich auf die ersten Schritte in der Wechselwirkung von RRx‐001 mit niederenergetischen Elektronen, in denen das temporäre negative Ion gebildet wird und rasch fragmentiert. Die Kombination von Resultaten zweier Versuchsaufbauten erlaubt es uns, den Zerfall des RRx‐001 Anions auf verschiedenen Zeitskalen zu entflechten. Die alleinige Anwesenheit des eingefangenen Elektrons führt zu einer raschen Abspaltung von NO2 und HNO2, während NO2− und Br− Anionen direkt beziehungsweise über andere Zwischenprodukte gebildet werden. Auf Basis quantenchemischer Rechnungen schlagen wir einen bidirektionalen Wechsel zwischen π*(NO2) und σ*(C−Br) Zuständen vor, welcher die experimentellen Spektren erklärt. Die beobachtete schnelle Dynamik lässt auch Schlussfolgerungen für die Chemie des Anions in der kondensierten Phase zu.

Electron Attachment to the Nucleobase Uracil in Diethylene Glycol: The Signature of a Doorway.

The cellular environment plays a significant role in low energy electron-mediated radiation damage to genetic materials. In this study, we have modeled the effect of the bulk medium on electron attachment to nucleobases in diethylene glycol (DEG) using uracil as a test case, in accordance with recent experimental work on the observation of dissociative quasi-free electron attachment to nucleoside via excited anion radical in solution (in DEG). Our EOM-CCSD-based quantum mechanical/molecular mechanical (QM/MM) simulations indicate that the electron scavenging by uracil in DEG is much slower than that observed in the aqueous medium due to its viscosity. This work also establishes that a doorway mechanism exists in uracil microsolvated and bulk solvated with DEG, with the dipole-bound state and solvent-bound state acting as doorway states, respectively.

Numerical Simulation of the Dynamics of RF Capacitive Discharge in Carbon Dioxide

In this research, the one-dimensional fluid code SIGLO-rf was used to study the internal parameters of RF capacitive discharge in carbon dioxide, focusing mainly on time-averaged and spatio-temporal distributions of discharge parameters. With the help of this code, in the range of distances between electrodes d = 0.04 – 8 cm, RF frequencies f = 3.89 – 67.8 MHz, and values of carbon dioxide pressure p = 0.1 – 9.9 Torr, averaged over the RF period axial profiles of the density of electrons, positive and negative ions were calculated as well as potential and electric field strength. It is shown that the discharge plasma in CO2 contains electrons, positive ions, as well as negative ions. The negative ions of atomic oxygen are formed by the dissociative attachment of electrons to CO2 molecules. Studies of the spatio-temporal dynamics of plasma parameters (electron density, potential and electric field strength, as well as ionization and attachment rates) in RF capacitive discharge in CO2 showed that during half of the RF period, 1 to 3 ionization bursts are usually observed. They correspond to stochastic heating in the near-electrode sheath and the formation of passive and active double layers near the sheath boundaries. The passive double layer appears in the cathode phase and maintains the discharge plasma. The active layer is formed in the anodic phase and ensures a balance of positive and negative charges escaping to the electrode during the RF period. It was found that when the conditions pd = 2 Torr cm and fd = 27.12 MHz cm are met simultaneously, during half of the RF period, 4 intense ionization peaks are observed: resulting from stochastic heating, passive, active, and additional (auxiliary) double layers. The auxiliary double layer helps bring electrons to the surface of the temporary anode and occurs near its surface inside the near-electrode sheath. Using the similarity law, the conditions for the existence of these 4 ionization peaks in a wide range of RF frequencies, carbon dioxide pressures, and distances between electrodes were verified.

Plasmon-driven chemical transformation of a secondary amide probed by surface enhanced Raman scattering

Plasmon-driven chemical conversion is gaining burgeoning interest in the field of heterogeneous catalysis. Herein, we study the reactivity of N-methyl-4-sulfanylbenzamide (NMSB) at nanocavities of gold and silver nanoparticle aggregates under plasmonic excitation to gain understanding of the respective reaction mechanism. NMSB is a secondary amide, which is a frequent binding motive found in peptides and a common coupling product of organic molecules and biomolecules. Surface-enhanced Raman scattering (SERS) is used as a two-in-one in-situ spectroscopic tool to initiate the molecular transformation process and simultaneously monitor and analyze the reaction products. Supported by dissociative electron attachment (DEA) studies with the gas phase molecule, a hot electron-mediated conversion of NMSB to p-mercaptobenzamide and p-mercaptobenzonitrile is proposed at the plasmonic nanocavities. The reaction rate showed negligible dependence on the external temperature, ruling out the dominant role of heat in the chemical transformation at the plasmonic interface. This is reflected in the absence of a superlinear relationship between the reaction rate constant and the laser power density, and DEA and SERS studies indicate a hot-electron mediated pathway. We conclude that the overall reaction rate is limited by the availability of energetic hot electrons to the NMSB molecule.

Binding energies of CD4 and fragment species to Pt(111): Implications for measurements of anion electron stimulated desorption.

We consider the electron stimulated desorption, via dissociative electron attachment, of anionic species from thin condensed CD4 films deposited on a Pt substrate and compare experimentally observed desorption yields with density functional theory calculations of the binding energies of various anionic and neutral moieties to Pt(111). Certain species (which can be considered chemisorbed) exhibit very high binding energies and large charge transfer with the substrate. Other "physisorbed" species have much lower binding energies. Species that chemisorb have lower desorption yields than those that physisorb, especially at 1-2 monolayer coverage of the Pt substrate. The binding energy of D- to Pt is the weakest, and experimentally, the desorption yield is the highest regardless of the thickness of CD4. The calculations show that the formation and desorption of anionic species at a distance of 16Å from the substrate, which is equivalent to the thickness of CD4 films of four monolayers, are not influenced by the short-range interactions between the substrate and the molecule and DEA products.

Glycyrrhetinic acid interaction with solvated and free electrons studied by the CIDNP and dissociative electron attachment techniques.

Electron transfer plays a crucial role in living systems, including the generation of reactive oxygen species (ROS). Oxygen acts as the terminal electron acceptor in the respiratory chains of aerobic organisms as well as in some photoinduced processes followed by the formation of ROS. This is why the participation of exogenous antioxidants in electron transfer processes in living systems is of particular interest. In the present study, using chemically induced dynamic nuclear polarization (CIDNP) and dissociative electron attachment (DEA) techniques, we have elucidated the affinity of solvated and free electrons to glycyrrhetinic acid (GA)-the aglicon of glycyrrhizin (the main active component of Licorice root). CIDNP is a powerful instrument to study the mechanisms of electron transfer reactions in solution, but the DEA technique shows its effectiveness in gas phase processes. For CIDNP experiments, the photoionization of the dianion of 5-sulfosalicylic acid (HSSA2-) was used as a model reaction of solvated electron generation. DEA experiments testify that GA molecules are even better electron acceptors than molecular oxygen, at least under gas-phase conditions. In addition, the effect of the solvent on the energetics of the reactants is discussed.

Variability of Ionospheric Total Electron Content Over Morocco During the Godzilla Sand and Dust Storm of June 2020

During sand and dust storm (SDS) events, atmospheric suspension and transport of sand and dust brings a reasonable amount of electrification in the atmosphere which plays a very important role in the atmosphere-ionosphere coupling. The Godzilla SDS began on 5&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; June 2020 in Algeria following a decrease in pressure and spread to other areas across the Sahara between 6&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; and 28&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; June 2020. Using SDS data from Copernicus Sentinel-5P satellite mission and Vertical Total Electron Content (VTEC) data from four GNSS receiver stations: IFR1 (Ifrane Seismic), MELI (Melilla), TETN (Tetouan) and OUCA (Ouca) over Morocco, we investigate the possible ionospheric TEC variability over the four GNSS receiver stations during the Godzilla SDS event which was tracked using the Sentinel-5P Satellite mission. Solar wind parameters: Horizontal component of Interplanetary Magnetic Field (IMF-Bz), interplanetary Electric Field (IEF-Ey) and solar wind speed (V) and geomagnetic indices: Disturbance Storm Time (Dst) and Planetary K (Kp) indices were examined and showed very minimal geomagnetic influence during the period. We observed major ionospheric disturbances over the four Global Navigation Satellite System (GNSS) receiver stations on 16&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 17&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 18&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 21&amp;lt;sup&amp;gt;st&amp;lt;/sup&amp;gt;, 22&amp;lt;sup&amp;gt;nd&amp;lt;/sup&amp;gt;, 23&amp;lt;sup&amp;gt;rd&amp;lt;/sup&amp;gt; 25&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; and 26&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; June 2020: the period with the Sentinel-5P Aerosol Index (SAI) of more than 4 as recorded by the Sentinel-5P Satellite engine. The daily VTEC values over the four GNSS receiver stations recorded continuous electron density perturbations during these days. Apart from the ionospheric TEC perturbations, significant enhancements and decreases in daily maximum VTEC values over the four GNSS receiver stations were also noted. These were attributed to the changes in the atmospheric electric fields generated by the SDS event. The VTEC plots for each day exhibited similar trends, hence exhibited the same ionospheric dynamics. VTEC depletions of depths 3 to 6 TECU over all the four GNSS receiver stations were noted on 12&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 14&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 17&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 20&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; and 25&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; June 2020. Nighttime VTEC enhancements were also noted and majorly occurred between 20:00 and 21:00 UT on 9&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 13&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 15&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 17&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 19&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt;, 20&amp;lt;sup&amp;gt;th&amp;lt;/sup&amp;gt; and 21&amp;lt;sup&amp;gt;st&amp;lt;/sup&amp;gt; June 2020. This was attributed to the development of the electron avalanche processes including dust and electron absorption or losses and the active conversion to electron dissociative attachment leading to electron excitation. In conclusion, the Godzilla SDS of June 2020 led to the electron density perturbations over Morocco.

Dissociative Electron Attachment Dynamics of a Promising Cancer Drug Indicates Its Radiosensitizing Potential.

2-Bromo-1-(3,3-dinitroazetidin-1-yl)ethan-1-one (RRx-001) is a hypoxic cell chemotherapeutics with already demonstrated synergism in combined chemo-radiation therapy. The interaction of the compound with secondary low-energy electrons formed in large amounts during the physico-chemical phase of the irradiation may lead to these synergistic effects. The present study focuses on the first step of RRx-001 interaction with low-energy electrons in which a transient anion is formed and fragmented. Combination of two experiments allows us to disentangle the decay of the RRx-001 anion on different timescales. Sole presence of the electron initiates rapid dissociation of NO2 and HNO2 neutrals while NO2 - and Br- anions are produced both directly and via intermediate complexes. Based on our quantum chemical calculations, we propose that bidirectional state switching between π*(NO2) and σ*(C-Br) states explains the experimental spectra. The fast dynamics monitored will impact the condensed phase chemistry of the anion as well.

Electron-induced ligand loss from iron tetracarbonyl methyl acrylate.

We probe the separation of ligands from iron tetracarbonyl methyl acrylate (Fe(CO)4(C4H6O2) or Fe(CO)4MA) induced by the interaction with free electrons. The motivation comes from the possible use of this molecule as a nanofabrication precursor and from the corresponding need to understand its elementary reactions fundamental to the electron-induced deposition. We utilize two complementary electron collision setups and support the interpretation of data by quantum chemical calculations. This way, both the dissociative ionization and dissociative electron attachment fragmentation channels are characterized. Considerable differences in the degree of precursor fragmentation in these two channels are observed. Interesting differences also appear when this precursor is compared to structurally similar iron pentacarbonyl. The present findings shed light on the recent electron-induced chemistry of Fe(CO)4MA on a surface under ultrahigh vacuum.

Kinetic insights into ammonia-hydrogen doped ignition and emission assisted by nanosecond pulsed discharge

Non-equilibrium plasma is applied for the first time to ignite the ammonium-hydrogen mixture and reduce the NOx/N2O emission with effect in this work. Gas chromatography (GC) experiments as well as a detailed kinetic model, including neutral molecules, free radicals, charged particles, vibratory excited states, and electron excited states, are integrated to investigate the kinetic process of ammonia-hydrogen doped ignition and NOx/N2O emission facilitated by nanosecond pulsed discharge. The numerical model closely matches the GC-measured values of NH3 consumption, H2 increase, and N2O production. Pathway fluxes of important species and sensitivity analysis of ignition delay time reveal that the addition of non-equilibrium plasma has an obvious promotion effect on ammonia and hydrogen-doped oxidation and ignition. The initial ignition temperature significantly impacts the ignition delay time, with a more pronounced plasma-promotion effect observed at lower temperatures. Conversely, as the hydrogen mixing ratio increases, the ignition delay time decreases, yet the generation of NO and N2O increases. This is attributed to the heightened production of H and NH through elementary reactions such as NH3+HNH2+ H2, H + O2O + OH, and OH + H2H + H2O. Nevertheless, NO and N2O emissions are reduced by 1-2 orders of magnitude with plasma assistance compared to auto-ignition. The reduction in NO emissions can be attributed to increased consumption in the pathway of NO + NH2N2 + H2O and decreased formation in the pathways of HNO + O2HO2 + NO and NH + NON2O + H. Additionally, it was discovered that the electron attachment dissociation reaction e + N2O → O− + N2 predominantly contributes to the reduction of N2O. These research findings significantly contribute to advancing our understanding of the kinetics involved in ammonia-hydrogen doped ignition and emissions, particularly with plasma assistance, for potential engine applications.

Optical and Chemical Measurements of Solvated Electrons Produced in Plasma Electrolysis with a Water Cathode.

It is known that glow discharges with a water anode inject and form solvated electrons at the plasma-liquid interface, driving a wide variety of reduction reactions. However, in systems with a water cathode, the production and role of solvated electrons are less clear. Here, we present evidence for the direct detection of solvated electrons produced at the interface of an argon plasma and a water cathode via absorption spectroscopy. We further quantify their yield using the dissociative electron attachment of chloroacetate, measuring a yield of 1.04 ± 0.59 electrons per incident ion, corresponding to approximately 100% faradaic efficiency. Additionally, we estimate a yield of 2.09 ± 0.93 hydroxyl radicals per incident ion. Comparison of this yield with other findings in the literature supports that these hydroxyl radicals are likely formed directly in the liquid phase rather than by diffusion from the vapor phase.

Simulation of Radiation-Induced DNA Damage and Protection by Histones Using the Code RITRACKS.

(1) Background: DNA damage is of great importance in the understanding of the effects of ionizing radiation. Various types of DNA damage can result from exposure to ionizing radiation, with clustered types considered the most important for radiobiological effects. (2) Methods: The code RITRACKS (Relativistic Ion Tracks), a program that simulates stochastic radiation track structures, was used to simulate DNA damage by photons and ions spanning a broad range of linear energy transfer (LET) values. To perform these simulations, the transport code was modified to include cross sections for the interactions of ions or electrons with DNA and amino acids for ionizations, dissociative electron attachment, and elastic collisions. The radiochemistry simulations were performed using a step-by-step algorithm that follows the evolution of all particles in time, including reactions between radicals and DNA structures and amino acids. Furthermore, detailed DNA damage events, such as base pair positions, DNA fragment lengths, and fragment yields, were recorded. (3) Results: We report simulation results using photons and the ions 1H+, 4He2+, 12C6+, 16O8+, and 56Fe26+ at various energies, covering LET values from 0.3 to 164 keV/µm, and performed a comparison with other codes and experimental results. The results show evidence of DNA protection from damage at its points of contacts with histone proteins. (4) Conclusions: RITRACKS can provide a framework for studying DNA damage from a variety of ionizing radiation sources with detailed representations of DNA at the atomic scale, DNA-associated proteins, and resulting DNA damage events and statistics, enabling a broader range of future comparisons with experiments such as those based on DNA sequencing.

Direct Observation of Anionic Yields from the Liquid-Vapor Interface by Electron Irradiation.

Dissociative electron attachment (DEA) is widely believed to play a high-profile role in ionizing radiation damages of bioorganic molecules, and its fundamentals are mainly learned from the gas-phase studies. However, the DEA process in aqueous solution is still in debate. Here we provide experimental evidence about the DEA processes of liquid methanol by using electron-impact-time-delayed mass spectrometry. In contrast to the gas- and solid-phase DEAs, methoxide ion CH3O- is the predominant product from the liquid interface. Furthermore, this anion can be produced with both the primary low-energy electrons and the inelastically scattered and secondary low-energy electrons. On the contrary, the primary low-energy electrons in the liquid bulk are more likely to be solvated, rather than directly participating in the DEA process. Our study provides new insights into radiation chemistry, particularly of bioorganic relevance.