Simultaneous Electron Capture Research Articles

Dissipation of chlorantraniliprole, chlorpyrifos-methyl and indoxacarb\u2014insecticides used to control codling moth (Cydia Pomonella L.) and leafrollers (Tortricidae) in apples for production of baby food

Dissipations of three insecticides: chlorantraniliprole, chlorpyrifos-methyl and indoxacarb in apples were studied following their foliar application on apples intended for production of baby food. The apples were sprayed with formulations for control of codling moth (Cydia Pomonella L.) and leafrollers (Tortricidae). Six experiments were conducted; each insecticide was applied individually on dessert apples. A validated gas chromatography-based method with simultaneous electron capture and nitrogen–phosphorus detection (GC-ECD/NPD) was used for the residue analysis. The analytical performance of the method was satisfactory, with expanded uncertainties ≤36% (a coverage factor, k = 2, and a confidence level of 95%). The dissipations of insecticides were studied in pseudo-first-order kinetic models (for which the coefficient of determination, R2, ranged between 0.9188 and 0.9897). Residues of studied insecticides were below their maximum residue limits of 0.5 mg/kg at an early stage of growth of the fruit. The half-lives of chlorantraniliprole, chlorpyrifos-methyl and indoxacarb were 16–17, 4–6 and 20–24 days, respectively. The initial residue levels declined gradually and reached the level of 0.01 mg/kg in 1 month for chlorpyrifos-methyl, 2 months for chlorantraniliprole and 2.5 months for indoxacarb. To obtain the insecticide residue levels below 0.01 mg/kg, which is the default MRL for food intended for infants and young children, the application of the studied insecticides should be carried out at recommended doses not later then: 1 month before harvest for chlorpyrifos-methyl, 2 months for chlorantraniliprole and 2.5 months for indoxacarb.

Dissipation of difenoconazole in apples used for production of baby food

ABSTRACTDissipation of fungicide difenoconazole (3-chloro-4-[(2RS,4RS;2RS,4SR)-4-methyl-2-(1H-1,2,4-triazol-1-ylmethyl)-1,3-dioxolan-2-yl]phenyl 4-chlorophenyl ether) was studied following its application on apples intended for production of baby food. The apples (varieties: Jonagold Decosta, Gala and Idared) were sprayed with the formulation to control pathogens causing fungal diseases: powdery mildew (Podosphaera leucotricha ELL et Ev./Salm.) and apple scab (Venturia inaequalis Cooke/Aderh.). A validated gas chromatography-based method with simultaneous electron capture and nitrogen phosphorus detection (GC-ECD/NPD) was used for the residue analysis. The analytical performance of the method was highly satisfactory, with expanded uncertainties ≤ 19% (a coverage factor, k = 2, and a confidence level of 95%). The dissipation of difenoconazole was studied in pseudo-first-order kinetic models (for which the coefficients of determination, R2, ranged between 0.880 and 0.977). The half-life of difenoconazole was 12–21 days in experiments conducted on three apple varieties. In these experiments, the initial residue levels declined gradually and reached the level of 0.01 mg kg−1 in 50–79 days. For the residue levels to remain below 0.01 mg kg−1 (the maximum acceptable concentration for baby foods), difenoconazole must be applied approximately 3 months before harvest, at a dose of 0.2 L ha−1 (50 g of an active ingredient per ha).

First results from the Jordan COLTRIMS imaging system

A Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) apparatus has been constructed and operated cooperatively by the Atomic and Molecular Physics Laboratory in the Physics Department at the Hashemite University, Jordan, and the Atomic and Molecular Physics Group at the 4.75MeV Van de Graaff Accelerator Facility at the University of Jordan. This COLTRIMS imaging system allows the investigation of the dynamics of various ion impact induced atomic and molecular interactions and fragmentations. The performance of the COLTRIMS system was tested by carrying out preliminary studies of two collision systems. In the first study, electron capture processes in the He2+–Ne collision system at 0.25 and 1.0MeV impact energies were investigated. Significant simultaneous electron capture and target excitation has been observed for the 0.25MeV as opposed to the 1.0MeV impact energy. In the other study, projectile single electron loss and simultaneous single target ionization in the O+–He collision system was studied at three different projectile impact energies: 0.6, 1.45 and 2MeV. Enhancement of the electron–electron contribution to projectile electron loss with increasing collision energy has been observed.

Simultaneous determination of 223 pesticides in tobacco by GC with simultaneous electron capture and nitrogen-phosphorous detection and mass spectrometric confirmation

Abstract LSE (liquid-solid extraction), MSPD (matrix solid phase dispersion) and QuEChERS (quick, easy, cheap, effective, rugged and safe) extractions followed by GC-μECD/NPD to determine 223 pesticide residues in tobacco simultaneously were developed and compared. The identities of ten model pesticides were confirmed by GC-MS/MS. The type and amount of dispersant (Florisil, silica gel and alumina), sample mass, cleanup adsorbent, and the eluent (hexane, acetone and acetonitrile) were optimized. Linearity, recovery, LOQ, LOD, and matrix effect were compared. Most recoveries were 71−120% (RSD < 18%). LOD and LOQ were much lower than the CORESTA GRLs. The best method was QuEChERS: acetonitrile extraction and dispersive solid-phase extraction using primary-secondary amine and graphitized carbon.

Resonant electron transfer and L-shell excitation for _{26}Fe^{19+} and _{30}Zn^{23+} ions

Resonant transfer and excitation (RTE) involving simultaneous electron capture and projectile L-shell excitation has been calculated for Fe^{19+} and Zn^{23+} ions, in charge states ranging from nitrogen-like to oxygen-like incident on molecular hydrogen over an energy range 0--250 MeV. By the same way the calculations have been performed with helium over an energy range 0--300 MeV. The calculations are carried out using the angular momentum average (AMA) scheme in the isolated resonance approximation (IRA). This method was previously used to calculate RTE cross sections for N-like P^{8+} and Ca^{13+}, where the results are found to agree with the present calculations. The present calculations are expected to serve as references for future comparison with experimental and theoretical works in different coupling schemes.

Simultaneous electron capture and bound-free pair production in relativistic collisions of heavy nuclei with atoms

We consider a two-step process that may occur in relativistic ion-atom collisions. In this process, within a single ion-atom collision, an atomic electron is captured by the ion via the radiative and/or nonradiative capture channels, while the colliding nuclei of the atom and ion simultaneously produce an electron-positron pair with the electron created in a bound state of the ion. As a result, the ion picks up two electrons and a positron is emitted. We calculate the total cross section for this process in collisions of incident $1--4\text{ }\text{GeV}/\text{u}$ ${\text{U}}^{92+}$ projectiles with various atomic targets and discuss its dependence on the collision energy and target atomic number. We also analyze whether this process can compete with electron recombination proceeding via the excitation of the negative-continuum states, in which an atomic electron incident on a bare nucleus is captured into a bound state of the ion by transferring the energy excess to a negative-continuum electron with the latter undergoing a transition into a bound state. According to our estimates, the electron recombination dominates the two-step process in collisions with light and intermediately heavy atoms $({Z}_{a}\ensuremath{\lesssim}50)$, while in collisions with heavy atoms the latter leads to much larger cross sections.

Comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry and simultaneous electron capture detection/nitrogen phosphorous detection for incense analysis

This study reports comprehensive two-dimensional gas chromatography hyphenated to time-of-flight mass spectrometry detection (GC × GC/TOFMS) for characterisation and identification of components generated by four different types of powdered incense headspace (H/S) and incense smoke. GC × GC/TOFMS allowed simultaneous separation and identification of compounds emitted into the atmosphere as a result of combustion of incense powder. The smoke stream comprised compounds originating from the incense powder, and combustion products such as saturated and unsaturated hydrocarbons, essential oil type compounds, nitromusks, fatty acid methyl esters (FAMEs), polycyclic aromatic hydrocarbons (PAHs, which possibly include oxygenated and nitrated PAH), N-heterocyclics, pyrans and furans, which were detected and tentatively identified by GC × GC/TOFMS. GC × GC-electron capture detector/nitrogen phosphorous detector (ECD/NPD) potentially offers the prospect of providing selective chemical compositional information of incense powder and smoke, such as nitrogen-containing (N-containing) and halogenated compounds. Results of GC×GC-ECD/NPD showed that both incense powder and smoke generated emission of N-containing and halogenated compounds. A significant number of halogenated and N-containing compounds were emitted during the incomplete combustion of incense. However, one further objective of this paper is to demonstrate the capacity of comprehensive two-dimensional gas chromatography coupled to specific and/or selective detectors such as those used in this study (GC × GC-ECD/NPD) for the detection of particular classes of compounds such as N-containing and halogenated compounds at trace level concentrations in complex smoke samples.

Automated determination of pesticide residues in olive oil by on-line reversed-phase liquid chromatography–gas chromatography using the through oven transfer adsorption desorption interface with electron-capture and nitrogen–phosphorus detectors operating simultaneously

A rapid method for the multiresidue analysis of pesticides in olive oil is presented. Pesticides are analyzed by on-line coupling reversed-phase liquid chromatography–gas chromatography using the through oven transfer adsorption desorption (TOTAD) interface with subsequent simultaneous electron-capture and nitrogen–phosphorus detection by post-column splitter. An autosampler is employed and the olive oil is simply filtered before the chromatographic analysis. Organophosphorus, organochlorine and triazine pesticides are determined in one run. The limits of detection are below the required maximum residue levels and calibration curves are linear in the range tested. Repeatabilities (intra-day and inter-days) are good. The method was satisfactory applied to the routine analysis of numerous olive oil samples.

Neutralization of noble gas ions on ionic insulators: Auger neutralization or double-electron capture

The neutralization of noble gas singly charged ions on large band gap ionic insulators may take place through two distinct mechanisms involving two valence band electrons. One is a kinetically assisted Auger neutralization, and the other a simultaneous double electron capture. Both lead to the same final states, that is at grazing incidence angles a scattered neutral projectile connected to a surface excited state (trion) or an ejected electron. So it is virtually impossible to experimentally identify the neutralization process. From comparison to systems whose neutralization mechanism is clearly identified, the incidence angle dependence of the trion population relative to the total neutral fraction appears as a robust parameter for distinguishing the primary capture process.

Many-particle dynamics in atomic and molecular physics investigated with the COLTRIMS-technique: New inside into e-e correlation

A Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) apparatus has been constructed and operated cooperatively by the Atomic and Molecular Physics Laboratory in the Physics Department at the Hashemite University, Jordan, and the Atomic and Molecular Physics Group at the 4.75 MeV Van de Graaff Accelerator Facility at the University of Jordan. This COLTRIMS imaging system allows the investigation of the dynamics of various ion impact induced atomic and molecular interactions and fragmentations. The performance of the COLTRIMS system was tested by carrying out preliminary studies of two collision systems. In the first study, electron capture processes in the He2+–Ne collision system at 0.25 and 1.0 MeV impact energies were investigated. Significant simultaneous electron capture and target excitation has been observed for the 0.25 MeV as opposed to the 1.0 MeV impact energy. In the other study, projectile single electron loss and simultaneous single target ionization in the O+–He collision system was studied at three different projectile impact energies: 0.6, 1.45 and 2 MeV. Enhancement of the electron–electron contribution to projectile electron loss with increasing collision energy has been observed.

Simultaneous transfer ionization of a negative hydrogen ion by positron impact

A model has been proposed to investigate theoretically, the simultaneous electron capture and the ejection of another electron by which a bare hydrogen ion and a positronium atom (Ps) are produced in a single collision between a positron and a negative hydrogen ion $({\mathrm{H}}^{\ensuremath{-}}).$ The angular distributions of the scattered Ps atom as well as of the ejected electron are studied in the intermediate- and high-energy regimes (40--200 eV) with respect to the threshold energy for this particular transfer ionization (TI) process. The electron-electron correlation effect that mainly governs such two-electron transition processes in this energy regime has been taken into account in both the initial and final channels. The long-range Coulomb attraction between the incident positron and the negative hydrogen ion in the initial channel has also been incorporated properly. Signature of the so-called Thomas peak (a double-peak structure) predicted for charge-transfer or transfer-ionization process for heavy-particle projectiles in the high-energy regime has also been noted in the present TI process (for light projectile ${e}^{+})$ and could be attributed to the correlated ${e}^{+}\ensuremath{-}e\ensuremath{-}e$ scattering mechanism. In addition, the fully differential (triple) cross sections for different kinematics reveal some structures unusual for a pure transfer or a pure ionization process which are to be verified by the future experiments.

Electron emission in collisions of highly charged ions with atoms and diatomic molecules

A short review of theoretical models previously used to study single and multiple electron ionization in collisions of bare fast highly charged ions with atomic and diatomic molecular targets is given. Electron emission with simultaneous electron capture by the projectile is also considered. The principal mechanisms producing the different reactions are revisited. It is emphasized that two-center descriptions are necessary for an adequate description of the existing experimental data. The role of electron correlation in the initial bound state and during the collision process is analyzed as well as the presence of effects associated with the two-center character of diatomic molecular targets.

Thermodynamic and kinetic stability with respect to hole trapping. of silanic bonds at the Si-SiO 2 interface

The thermodynamic and kinetic stabilities of the Si–H bonds at the Si–SiO2 interface are studied on the basis of high-level quantum-mechanical calculations in the framework of density-functional theory. In the absence of an applied electric field, the silanic bond is shown to be stable with respect to both hole capture from the top of the silicon valence band and electron loss to the bottom of the silicon conduction band, but unstable with respect to hole capture from the top of the SiO2 conduction band. The positively charged hydrogen does not shift spontaneously to protonate a neighbouring siloxanic bridge unless it contains one adsorbed water molecule at least. The protonated siloxanic site thus formed may restore the original silanic site (via simultaneous electron capture from the conduction band and hydron shift to silicon) but also evolve spontaneously to a hydrogen atom via simple electron capture.

Gain and Threshold of Quantum Dot Lasers: Theory and Comparison to Experiments

A theory for gain and threshold of quantum dot lasers operating with inhomogeneously broadened dot ensembles is developed. Separate vs. simultaneous electron and hole capture and thermal vs. non-thermal carrier distributions and vertically coupled stacks are considered. In realistic lasers thermally distributed carriers allow lower threshold currents than non-thermal ensembles. Stacked quantum dots provide larger maximum gain but have a priori a higher threshold. However, vertical coupling leads to a redistribution of the carrier population and subsequently to similarly low thresholds as for lasers operating with single sheets of dots. Theoretical predictions are compared to experiments on quantum dot lasers operating on self-organized InAs/GaAs quantum dots.

CGC/AED and CGC/ECD/NPD comparison for the determination of acaricides in honey after hexane/acetone extraction

The performance of a gas chromatographic system coupled to an atomic emission detector (GC/AED) is tested by comparison with a two-dimensional gas chromatographic system equipped with capillary columns of different polarity and simultaneous electron capture and nitrogen-phosphorus detection (ECD/NPD), for the determination of the acaricides chlordimeform, bromopropylate, amitraz and coumaphos on spiked honey samples. The acaricides were extracted with ann-hexane/acetone mixture (80∶20, v/v) with a further clean-up step on an octadecylsilane cartridge. The 193 nm carbon emission line is the best choice in terms of sensitivity whereas the ECD/NPD system gives better selectivity.

Observations of doubly excited states in lithiumlike calcium.

We report observations of simultaneous electron excitation and electron capture in ion-atom collisions of 97-MeV ${\mathrm{Ca}}^{18+}$ and ${\mathrm{Ca}}^{19+}$ in an argon gas target. X-ray spectra at energies near 3.9 keV were collected using a high-resolution x-ray spectrometer. We have resolved transitions from doubly excited 1s2l2l' and 1s2l3l' states to singly excited 1${\mathit{s}}^{2}$2l' and 1${\mathit{s}}^{2}$3l' states in lithiumlike calcium. The observed transitions lie at energies close to the 1s2s-1s2p resonance transitions in heliumlike calcium. We compare the experimental wavelengths and intensities with relativistic Hartree-Fock calculations, and discuss the excitation mechanisms.

Simultaneous electron capture and target ion excitation in collisions of C4+ and N5+ on He

Cross sections for simultaneous electron capture and target ion excitation have been measured for impact of slow He-like C4+ and N5+ ions on He. The energy of the primary ion beams has been varied over more than two orders of magnitude: 0.05–7 keV/amu. The results are discussed on basis of a slightly modified version of the “dynamic” classical over-barrier model for multiple electron capture. The differences in the energy dependences of the experimental results of C4+ and N5+ — He can be explained qualitatively by assuming that for N5+ binding energy sharing between the two participating electrons is of importance, particularly at the lower impact energies.

Search for a narrow resonant transfer and excitation resonance of titanium projectiles channeled in a gold crystal.

Transfer and excitation, resulting from simultaneous electron capture and {ital K}-shell excitation in a single collision, has been measured 280--310-MeV Ti{sup 20+} ions channeled in the {l angle}100{r angle} axis of a thin Au single crystal. The 19+ charge-state fraction of the Ti ions exiting the Au crystal was measured as a function of ion energy and showed no narrow peak attributable to resonant transfer and excitation (RTE). The number of Ti {ital K}{alpha} x rays, emitted by the Ti ions due to RTE, in coincidence with Ti{sup 19+} was also measured at two energies, on and off the previously reported narrow resonance, and again no evidence for a narrow resonance was observed.

Electron capture to the continuum and simultaneous target excitation or ionization in He2++He collisions.

A theoretical calculation, based on the first-order Born and boundary-corrected first-order Born approximation, is presented that includes simultaneous electron capture to the continuum of the projectile and target excitation or ionization processes in the He{sup 2+}+He collision system. The results show that the cross sections are dominated by the continuum capture and that the influence of the accompanying target excitation or ionization is negligible. A comparison with the recent measurement of Koever {ital et} {ital al}. (J. Phys. B 19, 1187 (1986)) shows better agreement than do those of the ordinary first-order Born approximation.

Measurements of resonant transfer and excitation cross-sections for U90+ projectiles in H2

Resonant transfer and excitation (RTE), resulting from simultaneous electron capture and K-shell excitation in a single collision, has been measured for 97 to 150 MeV/u U90+ ions in molecular hydrogen. This measurement, the first for a very heavy projectile, provides a test of relativistic dielectronic-recombination (DR) theory.