Transfer Ionization Research Articles

Comparison of the national standards of air kerma between the PTB and the CPHR for selected x-ray qualities used in radiation protection, diagnostic radiology and radiation therapy (COOMET.RI(I)-S4)

The air kerma calibration coefficients of a set of four transfer ionization chambers and the air kerma-length product calibration coefficients for a set of two transfer pencil-type ionization chambers were compared at the PTB, Germany, and the CPHR, Cuba, for 15 selected radiation qualities as used in mammography, general diagnostic radiology, computed tomography, radiation therapy and radiation protection. The CPHR performed its measurements in the period January to September 2017 and the PTB before (November 2016) and after (December 2017) that period. The comparison results for the selected beam qualities expressed as the ratio of calibration coefficients were in the range (0.98-1.01) and mostly (12 out of 18) consistent within the relative standard uncertainty of the comparison which ranged between 0.6 % and 1 %. Five results were within the extended (k=2) standard uncertainty. One result deviated relatively by 1.9%. A possible reason for the larger deviation is discussed. The results are published in the Key Comparison Data Base (KCDB) of the BIPM as supplementary comparison COOMET.RI(I)-S4.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

1s-1s electron transfer in collisions of fast C and O ions with adenine

1s-1s electron transfer and K-shell ionization cross sections of adenine (C5H5N5) molecule have been measured in collisions with C and O ions in the energy range of 2.5–5.3 MeV/u. These cross sections have been measured from the study of KLL Auger electron yields as a function of projectile charge state. The K-ionization cross section data have been compared with the ECUSAR calculations [ECPSSR model with the perturbed stationary state (PSS) effect calculated in a united and separated atom (USA) approximation]. The K-ionization data shows a good agreement with the model whereas the K-K transfer cross section is underestimated by the same model. Energy dependence of the K-K transfer cross section for adenine is found to be flat compared to that for N2 gas molecules. The values of the K-K e− transfer and the K-ionization cross sections are found to be comparable in this energy range.

Data for secondary-electron production from ion precipitation at Jupiter III: Target and projectile processes in H[formula omitted], H, and H[formula omitted] + H[formula omitted] collisions

To extend the range of data required for modeling the secondary-electron production from ion precipitation into the upper atmosphere of Jupiter, inelastic processes for collisions of 1 keV to 25 MeV H+, H, and H− with H2 are considered. As in other work treating the dominant heavy-ion species of magnetospheric origin, O and S ions (Schultz et al., 2017, 2019; Gharibnejad et al., 2019) the classical trajectory Monte Carlo method is employed to describe the secondary-electron-producing channels (single and double ionization, transfer ionization, and single and double stripping) as well as the other inelastic channels (single and double charge transfer and projectile and target excitation) required to model the energy loss and charge state evolution of the precipitating ions in their passage through the atmospheric gas. Data is described and tabulated both as directly obtained from these calculations and normalized to widely accepted recommended values (Hunter et al., 1990) for channels for which recommendations exist. As in the previous work, the overall accuracy and completeness of the data presented is verified by use of a Monte Carlo ion-transport simulation to obtain the stopping power and ion-fraction populations as a function of impact energy in comparison with accepted values. The addition of the present data to models of secondary-electron production in Jupiter’s atmosphere improves such model’s ability to interpret in situ observations of the precipitating ions’ effect by the spacecraft Juno as well as enhancing the physical reality of models of the coupling of the Jovian magnetosphere, ionosphere, and atmosphere.

Anion and cation emission from water molecules after collisions with 6.6-keV 16O+ ions

Anion and cation emission following water dissociation was studied for 6.6-keV $^{16}$O$^{+}$ + H$_{2}$O collisions. Absolute cross sections for the emission of all positively and negatively charged fragments, differential in both energy and observation angle, were measured. The fragments formed in hard, binary collisions appearing in peaks were distinguishable from those created in soft collisions with many-body dynamics that result in a broad energy spectrum. A striking feature is that anions and cations are emitted with similar energy and angular distributions, with a nearly constant ratio of about 1:100 for H$^{-}$ to H$^{+}$. Model calculations were performed at different levels of complexity. Four-body scattering simulations reproduce the measured fragment distributions if adequate kinetic-energy release of the target is taken into account. Providing even further insight into the underlying processes, predictions of a thermodynamic model indicate that transfer ionization at small impact parameters is the dominant mechanism for H$^{+}$ creation. The present findings confirm our earlier observation that in molecular fragmentation induced by slow, singly charged ions, the charge states of the emitted hydrogen fragments follow a simple statistical distribution independent of the way they are formed.

A Simple 3D-Printed Enzyme Reactor Paper Spray Mass Spectrometry Platform for Detecting BuChE Activity in Human Serum.

To achieve personalized healthcare, a quick, accurate, and high-throughput method to detect disease biomarkers is essential. In the traditional practice, mass spectrometry is one of the most powerful tools and is widely studied. However, the test of human serum usually requires complicated sample pretreatment, tedious operations, and precise condition control, especially for the detection of enzymes as biomarkers. As butyrylcholinesterase (BuChE) has an indicative significance in detecting degenerative disease, liver injury, and organophosphate poisoning, the quick quantification of BuChE is of vital importance to the clinic. In this paper, we report the design and fabrication of a portable 3D-printed enzyme reactor paper spray cartridge (3D ER-PS) with integrated functions: temperature control, enzyme reaction, analyte transfer, and paper spray ionization. Coupled with mass spectrometry, quantitative testing of BuChE activity in human serum was realized conveniently and accurately. While it only requires very simple sample preparation, the results from current 3D ER-PS approach are well consistent with those obtained using Ellman's method. This 3D ER-PS platform not only provides a novel solution for the liquid biopsy of BuChE in clinics but also contributes to the development of quick and targeted medical approaches for analyzing other types of serum biomarker molecules in the field of disease diagnosis.

The effects of intraband and interband carrier‐carrier scattering on hot‐carrier solar cells: A theoretical study of spectral hole burning, electron‐hole energy transfer, Auger recombination, and impact ionization generation

AbstractThe effects of carrier‐carrier scattering resulting from the Coulomb‐potential interaction between two electrons on hot‐carrier solar cells are theoretically studied. Theoretical models and explicit formulas for calculating intraband carrier‐carrier scattering rates, electron‐to‐hole energy transfer rates, Auger recombination rates, and impact ionization generation rates are presented and derived. The numerical calculations from these formulas are obtained, and their effects on hot‐carrier solar cells are investigated. Several findings can be concluded from this study: (1) Intraband electron‐electron scattering and hole‐hole scattering are normally fast enough to randomize carrier distribution in the momentum space and thus maintain quasiequilibrium to establish electron and hole temperatures at a steady state; (2) spectral hole burning in hot‐carrier solar cells can be incurred by fast carrier extraction processes through energy‐selective contacts and slow intraband carrier‐carrier scattering; (3) energy transfer between electrons and holes via intraband electron‐hole scattering cannot guarantee that electrons and holes will maintain the same carrier temperature for hot‐carrier solar cells in all cases, especially if the difference between electron and hole temperatures is smaller than 100 K; and (4) materials with a band‐gap energy larger than 1 eV are favorable as conventional solar cells in which Auger recombination is not significant. On the contrary, materials with a band‐gap energy smaller than 0.5 eV are not suitable for conventional solar cells due to the detrimental effects of Auger recombination. However, they are ideal materials for realizing hot‐carrier solar cells due to beneficial effects of impact ionization generation, although these beneficial effects can be undermined by spectral hole burning.

Evaluation of the Radical-Scavenging Properties of Various Flavonols in Ethanol Environment: an ab initio Study

The antioxidant properties of six flavonols -fisetin, galangin, gossipetin, kaempferol, morin and myricetin- have been investigated at HF/6-311G+(d,p) level of theory, using ethanol as solvent. Three known antioxidant mechanisms, namely HAT (hydrogen atom transfer), SET-PT (single electron transfer followed by proton transfer) and SPLET (sequential proton loss electron transfer) have been employed in order to evaluate the radical scavenging abilities of the investigated compounds. Thermodynamic parameters like bond dissociation energy (BDE), proton affinity (PA), electron transfer enthalpy (ETE), ionization potential (IP) and proton dissociation enthalpy (PDE) were calculated and the results were associated with the number and the positions of the hydroxyl groups, the geometry of the parent molecule and of the corresponding radicals, as well as with the electron spin distribution. Also, computations of global reactivity descriptors like HOMO-LUMO gap showed that an increased reactivity is related to the presence of the catechol moiety (gossipetin, myricetin, fisetin). The influence of the catecholic OH groups is also outlined by the HOMO energies, highest electron-donor ability being obtained for gossipetin, the flavonol with two catecholic moieties on rings A and B. According to the HAT mechanism, it has been outlined an enhanced antioxidant character of the 3-OH groups, followed by the hydroxyl groups attached to the phenyl ring B. The calculated values of the condensed Fukui functions, computed for a radical attack, are in good agreement with the above-mentioned results.

Intercomparaciones a nivel de radioprotección con cámara de ionización de transferencia en la calidad de radiación 137Cs

En el presente trabajo se exponen la metodología y los resultados obtenidos de los ejercicios de intercomparación que fueron adelantados por el Laboratorio Secundario de Calibración Dosimétrica (LSCD) del Servicio Geológico Colombiano en los años 2016 y 2017, con el Laboratorio Secundario del Centro de Protección e Higiene de las Radiaciones (CPHR), de Cuba, y el Laboratorio de Dosimetría del Organismo Internacional de Energía Atómica (OIEA), mediante la calibración de cámaras de transferencia en la magnitud tasa de kerma en aire con haz de 137Cs por el método que usualmente sigue cada laboratorio. De dichos ejercicios se obtuvieron resultados satisfactorios con respecto a la metodología de calibración normalizada que es implementada en el LSCD, la cual a su vez brinda confiabilidad en sus resultados y en la trazabilidad de las magnitudes operacionales en las medidas de campo de los instrumentos utilizados en protección radiológica en Colombia.

Data for secondary-electron production from ion precipitation at Jupiter II: Simultaneous and non-simultaneous target and projectile processes in collisions of O[formula omitted] + H[formula omitted] ([formula omitted

To improve the physical completeness of the data previously calculated (Schultz et al., 2017) to enable modeling of the effects of secondary electrons produced by energetic ion precipitation at Jupiter, we extend the treatment to include inelastic processes that occur simultaneously on the projectile (Oq+, q=0–8)) and target (H2). Here, processes considered in the previous work (single and double ionization, transfer ionization, double capture with subsequent autoionization, single and double stripping, single and double charge transfer, and target excitation) reflecting non-simultaneous projectile and target electron transitions, are replaced with processes that include both non-simultaneous and simultaneous electronic transitions on the target and projectile. These include, for example, single ionization, single ionization with simultaneous single projectile excitation, single ionization with double projectile excitation, single ionization with single projectile stripping, and single ionization with double projectile stripping. Using this expanded set of processes, we show, via Monte Carlo ion-transport simulation, that improved representation of the energy deposition, measured by the stopping power, is obtained as compared to accepted recommended values for intermediate energies (100–2000 keV/u) where the stopping power is largest, while maintaining the existing good agreement with these recommended values for low (∼10–100 keV/u) and high (≥2000 keV/u) energies. In addition, the ion-fraction distribution is altered by use of the improved data set. Both of these effects have implications for the energy deposition by oxygen ion precipitation in an H2 atmosphere. Therefore, use of this expanded data set can provide a more physically realistic secondary-electron distribution, and consequently improved atmospheric reaction network, improved description of ion contribution to atmospheric currents, and therefore improved understanding of Jovian ionosphere–atmosphere coupling.

Orientation effect in Ar dimer fragmentation by highly charged ion impact

The fragmentation experiment on doubly and triply ionized Ar dimers is carried out using 1.0 MeV Ne8+ impact, focusing on the angular distribution of Ar+ and Ar2+ ions. For the fragmentation of (Ar2)2+, one-site double ionization and two-site double ionization are distinguished clearly, and different angular distributions are observed for these two channels. This phenomenon is explained qualitatively in simple geometrical considerations. For the fragmentation of (Ar2)3+, we find that the Ar+ ions tend to fly along the projectile direction, while the doubly charged Ar2+ ions tend to fly in the opposite direction. This result suggests that, to form the parent ion (Ar2)3+, transfer ionization is favorable in the first collision step, while single ionization is dominant in the second collision step.

Electron emission from transfer ionization reaction in 30 keV amu−1 He2+ on Ar collision

A model is presented that describes the transfer ionization process in collision at a projectile energy of 30 keV amu−1. It is based on a semiclassical independent-particle close-coupling method that yields a reasonable agreement between calculated and experimental values of the total single-ionization and single-capture cross sections. It is found that the transfer ionization reaction is predominantly carried out through simultaneous capture and ionization, rather than by sequential processes. The transfer-ionization differential cross section in energy that is obtained satisfactorily reproduces the global behavior of the experimental data. Additionally, the probabilities of capture and ionization as function of the impact parameter for and collisions are calculated, as far as we know, for the first time. The results suggest that the model captures essential elements that describe the two-electron transfer ionization process and could be applied to systems and processes of two electrons.

Evaluating the effect of ion source gas (N2, He, and synthetic air) on the ionization of hydrocarbon, condensed aromatic standards, and paraffin fractions by APCI(+)FT-ICR MS

This study aimed to use different types of ion source gases [synthetic air, nitrogen (N2), and helium (He)] to compare the ionization efficiency of linear, branched, and cyclic hydrocarbon (HC) standards (i.e., hexatriacontane, squalene, and 5-α-cholestane, respectively), condensed aromatics (CA) standards (i.e., coronene, benz[a]anthracene, and n,n′-bis(3-pentyl)perylene-3,4,9,10-bis(dicarboximide)), one n-paraffin standard, containing carbon numbers ranging from C5 to C120, and two saturated HC fractions. In all cases, a positive-ion mode atmospheric pressure chemical ionization coupled to a Fourier transform ion cyclotron resonance mass spectrometer was used. Isooctane reagent was used to facilitate the ionization of n-paraffins. Three ionization mechanisms were observed: electron transfer ([M]rad+), proton transfer ([M+H]+), and hydride abstraction ([M−H]+). For the ionization of HC standards, synthetic air and He gases presented better ionization efficiency and produced mass spectra with greater mass accuracy and signal-to-noise rate. Moreover, linear HCs were preferentially ionized through hydride abstraction (production of [M−H]+ ions), whereas the ionization of unsaturated and cyclic HCs mostly occurred through the production of [M+H]+ and [Mrad+] species. The unique exception is related to 5-α-cholestane, which is ionized as [M−H]+ in the presence of synthetic air. For the CA standards, N2 and synthetic air promoted the detection of CA standards mainly by electron transfer mechanism, [M]rad+ species. Conversely, He favored the proton transfer ionization ([M+H]+) with minimal fragmentation or oxidation of the analyte. In all cases, synthetic air provided mass spectra with excellent signal-to-noise ratio. This performance was attributed to the high reactive-ionizing power of O2 gas over the HC and CA molecules. For the n-paraffin samples, synthetic air and He provided better ionization performance through hydride abstraction ([M−H]+). N2 favored the production and ionization of heteroatomic compound classes (Ox and NOx).

Selective ionization by electron-transfer MALDI-MS of vanadyl porphyrins from crude oils

Petroporphyrins are biomarkers derived from chlorophyll, bacteriochlorophyll and the heme group, commonly present in crude oils as vanadyl or nickel complexes. These compounds, which despite of the organic matter maturation process preserve the tetrapyrrolic core of their precursors, show low polydispersity, concentration and are commonly used in geochemistry to assess oil lithology, oxidation-reduction conditions, geothermal maturation, conversion of organic matter, and burial depth. The physicochemical characteristics of petroporphyrins make them excellent analytes for MALDI-MS. Electron transfer (ET) ionization in MALDI, using novel electron transfer matrices based on cyano-phenylenevinylenes (e.g. CNPV-CH3), allows direct observation of labile compounds such as polyaromatics and porphyrin-like compounds, chlorophylls and pigments, as has been previously demonstrated by our group. In this work, we analyze petroporphyrins from two South American heavy oils using CNPV-CH3 as ET MALDI matrix. Petroporphyrins were isolated by Soxhlet extraction, with acetonitrile, followed by fractionation using normal-phase column chromatography. UV–Vis measurements showed a strong absorption band at 408 nm assigned to porphyrin Soret band for some chromatographic fractions. The fractions enriched with petroporphyrins were subjected to ET MALDI analysis. We demonstrate the suitability of the CNPV-CH3 MALDI matrix for the efficient and selective desorption and ionization of vanadyl porphyrins, when compared with a commercial MALDI matrix (DCTB) and LDI conditions.

IAEA-SSDL bilateral comparisons for diagnostic level air kerma measurement standards

Comparisons of national standard of air kerma for conventional and mammographic diagnostic X-ray radiation qualities were conducted by the IAEA. Eleven secondary standards dosimetry laboratories provided calibration data for Exradin A3 and Radcal RC6M transfer ionization chambers circulated. Each comparison result expressed as the ratio of the participant and IAEA calibration coefficient were within the acceptance limit of ±2.5%. From the 67 results of 11 participants and 10 available beam qualities, the comparison result was within its standard uncertainty in 63 cases, and within the expanded (k = 2) uncertainty in four cases. Detailed calibration uncertainty budgets from participant laboratories are presented. The relative standard calibration uncertainty of each participant was in the range of 0.5–1.3%. These results indicate that the calibration related uncertainty component is reasonable low for a clinical measurement. In addition to the calibration coefficient, other corrections should be applied for clinical measurement to achieve the recommended accuracy.

Speciated Monitoring of Gas-Phase Organic Peroxy Radicals by Chemical Ionization Mass Spectrometry: Cross-Reactions between CH3O2, CH3(CO)O2, (CH3)3CO2, and c-C6H11O2.

Organic peroxy radicals ("RO2", with R organic) are key intermediates in most oxygen-rich systems, where organic compounds are oxidized (natural environment, flames, combustion engines, living organisms, etc). But, until recently, techniques able to monitor simultaneously and distinguish between RO2 species ("speciated" detection) have been scarce, which has limited the understanding of complex systems containing these radicals. Mass spectrometry using proton transfer ionization has been shown previously to detect individual gas-phase RO2 separately. In this work, we illustrate its ability to speciate and monitor several RO2 simultaneously by investigating reactions involving CH3O2, CH3C(O)O2, c-C6H11O2, and (CH3)3CO2. The detection sensitivity of each of these radicals was estimated by titration with NO to between 50 and 1000 Hz/ppb, with a factor from 3 to 5 of uncertainties, mostly due to the uncertainties in knowing the amounts of added NO. With this, the RO2 concentration in the reactor was estimated between 1 × 1010 and 1 × 1012 molecules cm-3. When adding a second radical species to the reactor, the kinetics of the cross-reaction could be studied directly from the decay of the first radical. The time-evolution of two and sometimes three different RO2 was followed simultaneously, as the CH3O2 produced in further reaction steps was also detected in some systems. The rate coefficients obtained are (in molecule-1 cm3 s-1): kCH3O2+CH3C(O)O2 = 1.2 × 10-11, kCH3O2+t-butylO2 = 3.0 × 10-15, kc-hexylO2+CH3O2 = 1.2 × 10-13, kt-butylO2+CH3C(O)O2 = 3.7 × 10-14, and kc-hexylO2+t-butylO2 = 1.5 × 10-15. In spite of their good comparison with the literature and good reproducibility, large uncertainties (×5/5) are recommended on these results because of those in the detection sensitivities. This work is a first illustration of the potential applications of this technique for the investigation of organic radicals in laboratory and in more complex systems.

A portable precision ionization chamber: The transfer ionization reference chamber

A portable instrument was developed at the Institute of Radiation Physics (IRA) for on-site radionuclides measurements. It will enable the measurement of short-lived radionuclides in nuclear medicine departments or isotope production centres. The system involves an ionization chamber read directly by an electrometer and it was optimized to ensure a good reproducibility through the selection of an appropriate vial, filling volume and source position in the well chamber, as well as monitoring the external background and performing a detailed uncertainty estimation. The calibration factors were determined using solutions whose activity concentration is traceable to the international reference system using the IRA reference chamber. Currently the transfer ionization chamber is calibrated for F-18, C-11, O-15, N-13, I-131 and Tc-99m. The final instrument is able to measure isotope activities with a relative standard uncertainty not larger than 1%.

Theoretical investigation of the action mechanisms of N,N-di-alkylated diarylamine antioxidants

In this work, a density functional theory-based method was used to study the antioxidant properties and some reaction mechanism involved in the free radical-scavenging reactions of eight N,N-dialkylaminated diarylamines. The analyzed properties are the bond dissociation enthalpies of NH bond, electron transfer enthalpies, ionization potentials, proton affinities and proton dissociation enthalpies. The reaction mechanisms are hydrogen atom transfer, single electron transfer–proton transfer and sequential proton loss electron transfer. Computations were performed in two different solvents: water, and chlorobenzene. The aim of the work was to establish the effect of the progressive addition of nitrogen atoms into the diarylamines aryl rings on the thermodynamic parameters above mentioned, to individuate the preferred action mechanism of these compounds and the influence of media of different polarities. Results we have obtained indicate that the hydrogen atom transfer or more precisely the proton-coupled electron transfer from antioxidant to a particular free radical that was chosen as target, is the most probable action mechanism, that structural change made including nitrogen atoms into aryl rings does not give benefits nor from thermodynamic neither from kinetic point of view and that polarity of solvent has no significant influence.

28Si total body irradiation injures bone marrow hematopoietic stem cells via induction of cellular apoptosis

Long-term space mission exposes astronauts to a radiation environment with potential health hazards. High-energy charged particles (HZE), including 28Si nuclei in space, have deleterious effects on cells due to their characteristics with high linear energy transfer and dense ionization. The influence of 28Si ions contributes more than 10% to the radiation dose equivalent in the space environment. Understanding the biological effects of 28Si irradiation is important to assess the potential health hazards of long-term space missions. The hematopoietic system is highly sensitive to radiation injury and bone marrow (BM) suppression is the primary life‐threatening injuries after exposure to a moderate dose of radiation. Therefore, in the present study we investigated the acute effects of low doses of 28Si irradiation on the hematopoietic system in a mouse model. Specifically, 6-month-old C57BL/6J mice were exposed to 0.3, 0.6 and 0.9Gy 28Si (600MeV) total body irradiation (TBI). The effects of 28Si TBI on BM hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) were examined four weeks after the exposure. The results showed that exposure to 28Si TBI dramatically reduced the frequencies and numbers of HSCs in irradiated mice, compared to non-irradiated controls, in a radiation dose-dependent manner. In contrast, no significant changes were observed in BM HPCs regardless of radiation doses. Furthermore, irradiated HSCs exhibited a significant impairment in clonogenic ability. These acute effects of 28Si irradiation on HSCs may be attributable to radiation-induced apoptosis of HSCs, because HSCs, but not HPCs, from irradiated mice exhibited a significant increase in apoptosis in a radiation dose-dependent manner. However, exposure to low doses of 28Si did not result in an increased production of reactive oxygen species and DNA damage in HSCs and HPCs. These findings indicate that exposure to 28Si irradiation leads to acute HSC damage.

Synthesis, spectral studies and DFT computational analysis of hydrogen bonded-charge transfer complex between chloranilic acid with 2,4-diamino-quinoline-3-carbonitrile in different polar solvents

Abstract New hydrogen bonded charge transfer complex (HBCT) between 2,4-diamino-quinoline-3-carbonitrile (DAQC) and chloranilic acid (CA) is synthesized and characterized experimentally and theoretically. The experimental work included the use of electronic and vibrational spectra to analyze the formed complex. Based on electronic spectra, the molecular composition was determined by Jobs and molar ratio methods in different polar solvents included acetonitrile (AN), methanol (MeOH) and ethanol (EtOH). It was found to be 1:1 (donor:acceptor) in the different solvents. Also, the formation constant of the formed complex was determined using Benesi-Hildebrand equation where it recorded high values suggesting the high stability of the formed HBCT complex. The stability of the investigated complex was further analyzed by determining different spectroscopic parameters as oscillator strength, transition dipole moment, charge transfer energy, ionization potential, dissociation energy and free energy. The solid complex was synthesized and characterized by elemental analyses where 1:1 complex is formed. The infrared spectra revealed the existence of both charge transfer and hydrogen bonding in the formed complex which is responsible for its high stability. In order to complement the experimental work, two DFT methods, B3LYP and CAM-B3LYP were used to predict the stability, molecular structure, electronic and spectroscopic properties of the studied systems. These methods were introduced, for the first time, to study the stability of the expected structures of CA conformers. The one with lower energy (high stability) included two hydrogen bonding between CA hydroxyls and neighboring carbonyl groups. Of the suggested interaction complexes between chloranilic acid (CA) and 2,4-diamino-quinoline-3-carbonitrile (DAQC), the most stable one which has the lowest energy was used to simulate the observed electronic and vibrational spectra of the CA-DACQ complex. The reactivity descriptors indicated that DAQC is the e-donor while CA is e-acceptor. Also, the most reactive electrophilic and nucleophilic sites of CA and DAQC were predicted using the molecular electrostatic potential (MEP) map. Both experimental and theoretical studies confirmed the high stability of the formed complex based on the presence of charge transfer beside proton transfer in the CA-DAQC complex.

Dynamics of transfer ionization inp-He collisions at intermediate energies

We have performed a kinematically complete experiment for transfer ionization, i.e., the capture of one target electron by the projectile accompanied by the ejection of a second electron, for 50--100 keV $p$-He collisions by means of a reaction microscope. It was found that the electron momentum distribution projected onto the scattering plane is consistent with the prediction of an independent two-step mechanism involving a binary encounter. The deviation of the electron momentum distribution from the ideal binary ridge is attributed to binding energy effects and the interaction between the electron and the residual recoil ion. The good agreement between our measurements with the dynamic-screening classical trajectory Monte-Carlo calculations strongly suggests that electron-electron correlations play an important role in this two-electron process.