Decay Of Ions Research Articles

Plasma flux and gravity waves in the midlatitude ionosphere during the solar eclipse of 20 May 2012

AbstractThe solar eclipse effects on the ionosphere are very complex. Except for the ionization decay due to the decrease of the photochemical process, the couplings of matter and energy between the ionosphere and the regions above and below will introduce much more disturbances. Five ionosondes in the Northeast Asia were used to record the midlatitude ionospheric responses to the solar eclipse of 20 May 2012. The latitude dependence of the eclipse lag was studied first. The foF2 response to the eclipse became slower with increased latitude. The response of the ionosphere at the different latitudes with the same eclipse obscuration differed from each other greatly. The plasma flux from the protonsphere was possibly produced by the rapid temperature drop in the lunar shadow to make up the ionization loss. The greater downward plasma flux was generated at higher latitude with larger dip angle and delayed the ionospheric response later. The waves in the foEs and the plasma frequency at the fixed height in the F layer are studied by the time period analytic method. The gravity waves of 43–51 min center period during and after the solar eclipse were found over Jeju and I‐Cheon. The northward group velocity component of the gravity waves was estimated as ~108.7 m/s. The vertical group velocities between 100 and 150 km height over the two stations were calculated as ~5 and ~4.3 m/s upward respectively, indicating that the eclipse‐induced gravity waves propagated from below the ionosphere.

Radioactive decays of highly-charged ions

Access to stored and cooled highly-charged radionuclides offers unprecedented opportunities to perform high-precision investigations of their decays. Since the few-electron ions, e.g. hydrogen- or helium-like ions, are quantum mechanical systems with clear electronic ground state configurations, the decay studies of such ions are performed under well-defined conditions and allow for addressing fundamental aspects of the decay process. Presented here is a compact review of the relevant experiments conducted at the Experimental Storage Ring ESR of GSI. A particular emphasis is given to the investigations of the two-body beta decay, namely the bound-state β-decay and its time-mirrored counterpart, orbital electron-capture.

Theoretical study on radiative electron capture and subsequent radiative decay in collision of Xe54+ with Xe

Based on the multiconfiguration Dirac-Fock method and impulse approximation, the electron capture and following radiation decay of the projectile ion are studied theoretically for Xe atom which is bombarded by Xe54+ ion at 197 MeV/u. The radiative electron capture (REC) cross-sections and the corresponding emitted photon energies have been calculated in detail. Meanwhile, the probabilities of the radiative decay and energies of the REC final states are also calculated; combined with the calculated results in this paper, the X-ray spectra structure of radiative decay from projectile ion is further simulated. It is found that the simulated spectra are in good agreement with the newly measured results at Lanzhou Heavy-Ion Accelerator Device.

Three Rate-Constant Kinetic Model for Permanganate Reactions Autocatalyzed by Colloidal Manganese Dioxide: The Oxidation of L-Phenylalanine.

The reduction of permanganate ion to MnO(2)-Mn(2)O(3) soluble colloidal mixed oxide by l-phenylalanine in aqueous phosphate-buffered neutral solutions has been followed by a spectrophotometric method, monitoring the decay of permanganate ion at 525 nm and the formation of the colloidal oxide at 420 nm. The reaction is autocatalyzed by the manganese product, and three rate constants have been required to fit the experimental absorbance-time kinetic data. The reaction shows base catalysis, and the values of the activation parameters at different pHs have been determined. A mechanism including both the nonautocatalytic and the autocatalytic reaction pathways, and in agreement with the available experimental data, has been proposed. Some key features of this mechanism are the following: (i) of the two predominant forms of the amino acid, the anionic form exhibits a stronger reducing power than the zwitterionic form; (ii) the nonautocatalytic reaction pathway starts with the transfer of the hydrogen atom in the α position of the amino acid to permanganate ion; and (iii) the autocatalytic reaction pathway involves the reduction of Mn(IV) to Mn(II) by the amino acid and the posterior reoxidation of Mn(II) to Mn(IV) by permanganate ion.

Radiosynthesis of [18F]ATPFU: a potential PET ligand for mTOR.

Mammalian target of rapamycin (mTOR) plays a pivotal role in many aspects of cellular proliferation, and recent evidence suggests that an altered mTOR signaling pathway plays a central role in the pathogenesis of aging, tumor progression, neuropsychiatric, and major depressive disorder. Availability of a mTOR-specific PET tracer will facilitate monitoring early response to treatment with mTOR inhibitors that are under clinical development. Towards this we have developed the radiosynthesis of [(18)F]1-(4-(4-(8-oxa-3-azabicyclo[3.2.1]octan-3-yl)-1-(2,2,2-trifluoroethyl)-1H-pyrazolo[3,4-d]pyrimidin-6-yl)phenyl)-3-(2-fluoroethyl)urea [(18)F]ATPFU ([(18)F]1) as an mTOR PET ligand. Synthesis of reference 1 and the precursor for radiolabeling, 4-(4-8-oxa-3-azabicyclo[3.2.1]-octan-3yl)-1-(2,2,2-trifluoroethyl)-1H-pyrazolo[3,4-d]pyrimidin-6yl)aniline (10), were achieved from beta-chloroaldehyde 3 in 4 and 5 steps, respectively, with an overall yield of 25-28%. [(18)F]Fluoroethylamine was prepared by heating N-[2-(toluene-4-sulfonyloxy)ethyl]phthalimide with [(18)F]fluoride ion in acetonitrile. [(18)F]1 was obtained by slow distillation under argon of [(18) F]FCH2CH2NH2 into amine 10 that was pre-treated with triphosgene at 0-5 °C. The total time required for the two-step radiosynthesis including semi-preparative HPLC purification was 90 min, and the overall radiochemical yield of [(18)F]1 for the process was 15 ± 5% based on [(18)F]fluoride ion (decay corrected). At the end of synthesis (EOS), the specific activity was 37-74 GBq/µmol (N = 6).

The bidirectional character of O2 concentration in pulsed dielectric barrier discharges in O2/N2 gas mixtures

This paper presents experimental results on the influence of O2 on the characteristics of dielectric barrier discharges (DBDs) at one and at half atmospheric pressure. Gas mixtures of 0.1–10 vol % O2 in N2 were investigated, as well as in virtually pure N2. Electrical data, simultaneous streak and intensified charge-coupled device images were recorded in pulsed driven dielectric barrier discharges of 0.8 mm gap in a single filament arrangement. The O2 concentration is shown to have a significant impact on the electrical characteristics, the temporal DBD development and its breakdown inception. Higher O2 concentrations (above 0.1 vol %) led to an ignition delay, a shorter discharge duration, increased discharge radius, higher discharge current maxima and larger velocities of the cathode directed streamers. For O2 concentrations below 0.01 vol %—i.e. nearly pure nitrogen—some of these effects were reversed. Moreover, the effects were more pronounced at a pressure of 0.5 bar compared to 1 bar. This result can be explained by the pressure dependent decay and recombination processes of positive nitrogen and oxygen ions.

Firstβ−νcorrelation measurement from the recoil-energy spectrum of Penning trappedAr35ions

We demonstrate a novel method to search for physics beyond the standard model by determining the $\ensuremath{\beta}\ensuremath{-}\ensuremath{\nu}$ angular correlation from the recoil-ion energy distribution after $\ensuremath{\beta}$ decay of ions stored in a Penning trap. This recoil-ion energy distribution is measured with a retardation spectrometer. The unique combination of the spectrometer with a Penning trap provides a number of advantages, e.g., a high recoil-ion count rate and low sensitivity to the initial position and velocity distribution of the ions and completely different sources of systematic errors compared to other state-of-the-art experiments. Results of a first measurement with the isotope $^{35}\mathrm{Ar}$ are presented. Although currently at limited precision, we show that a statistical precision of about 0.5% is achievable with this unique method, thereby opening up the possibility of contributing to state-of-the-art searches for exotic currents in weak interactions.

Suppression of unimolecular decay of laser desorbed peptide and protein ions by entrainment in rarefied supersonic gas jets under weak electric fields

Unimolecular decay of sample ions imposes a limit on the usable laser fluence in matrix-assisted laser desorption/ionization (MALDI) ion sources. Traditionally, some modest degree of collisional sample ion cooling has been achieved by connecting MALDI ion sources directly to gas-filled radio frequency (RF) multipoles. It was also discovered in the early 1990s that gas-filled RF multipoles exhibit increased ion transmission efficiency due to collisional ion focusing effects. This unexpected experimental finding was later supported by elementary Monte Carlo simulations. Both experiments and simulations assumed a resting background gas with typical pressures of the order of 1 Pa. However, considerable additional improvements can be achieved if laser desorbed sample ions are introduced immediately after desorption, still within the ion source, in an axisymmetric rarefied supersonic gas jet with peak pressure of the order of 100 Pa and flow velocities >300 m/s, and under weak electric fields. We describe here the design principle and report performance data of an ion source coined "MALDI-2," which incorporates elements of both rarefied aerodynamics and particle optics. Such a design allows superb suppression of metastable fragmentation due to rapid collisional cooling in <10 μs and nearly perfect injection efficiency into the attached RF ion guide, as numerous experiments have confirmed.

Motion Characteristics of Single Electrons of Atoms of Atomic Gas of Hydrogen and Single Electrons of Hydrogen-Like Ions in Form Gas or Vapour during Decays of Such Atoms and Ions. Emission Line Spectra

For the first time the vector differential equation of central motion of single electron in electric field of an atomic nucleus as in external central electric field is set up and solved. Here the following findings are reported. Each of single electrons of a part of atoms of atomic gas of hydrogen and a part of hydrogen-like ions in the form of a gas or a vapour revolves around corresponding atomic nucleus in a flat spiral which has an interior maximum of turns density. The distance between each of these single electrons and corresponding atomic nucleus increases while a speed of single electron decreases. Such motion of single electrons takes place with no expenditures of external energy and points to decays of foregoing parts of atoms and ions. The electric field strength of the atomic nuclei of atoms of atomic gas of hydrogen and hydrogen-like ions in the form of a gas or a vapour is inversely proportional to the distance between the atomic nucleus and the corresponding single electron by greater than the power of 3. Calculated cyclic frequency (rough value 3.5×1014 s-1) of revolution of the electron around the nucleus of atom of atomic gas of hydrogen (in interior maximum of turns density of the flat spiral), which moves at speed 2.2×106 ms-1, and central cyclic frequency of α-line of Balmer series (4.5×1014 s-1) have the same order of magnitude. This fact and line structure of experimental emission line spectra confirm the formation of all lines of these spectra by continuous slight emission of light front by single electrons. The formation of series of lines of emission line spectra is linked to repeated creations of atoms of atomic gas of hydrogen and hydrogen-like ions in the form of a gas or a vapour.

Photo excitation and laser detachment of C60− anions in a storage ring

We have studied the photo physics of C60(-) anions in the electrostatic storage ring ELISA with ions produced in a plasma source and cooled and bunched in a He filled ion trap. A previous study using delayed electron detachment as a signal of resonance-enhanced multiphoton electron detachment (REMPED) has been repeated both at room temperature and with the trap cooled to liquid nitrogen temperature. However, wavelength dependence of the overlap of the strongly focused laser beam with the ion beam introduces distortions of the absorption spectrum. We have therefore applied a new method, combining the IR light with a slightly delayed, powerful UV pulse (266 nm). After absorption of three UV photons, the ions decay by delayed (thermal) electron emission, and time spectra are recorded for varying wavelength. The fraction of ions heated by absorption of a single IR photon is then extracted from a principal component analysis of these spectra. In good agreement with the earlier REMPED experiment, an origin band for transitions between the two lowest electronic levels of the anion, with t1u and t1g symmetry, is observed at 9380 cm(-1), with strong sidebands from excitation of the two A(g) and eight H(g) vibrations. As before, a hot band is observed at about 9150 cm(-1) and assigned to a transition from an excited vibronic Jahn-Teller state. However, an earlier observed band at higher energy, interpreted as a transition from this excited state to an excited vibronic state in the t1g electronic level, is much weaker in the new measurements and could be an H(g) vibrational sideband. Also earlier studies of direct laser detachment from C60(-) in the storage ring ASTRID have been revisited, with ions cooled by liquid nitrogen in the ion trap. We confirm the previous measurement with a determination of the threshold for s-wave detachment at 2.664 ± 0.005 eV, slightly lower than a recent value of the electron binding, 2.683 ± 0.008 eV, obtained from the energy spectrum of photo electrons. The detachment yield is observed to increase sharply for photon energies above a threshold at 2.78 eV, maybe caused by either Feshbach resonances or a shape resonance due to the presence of a bound electron state in the continuum.

Beta decay of highly charged ions

A brief overview is presented in this paper on some experiments conducted at the Experimental Storage Ring (ESR) of GSI which addressed the β decay of stored and cooled highly charged ions. Special emphasis is placed on the two-body beta decay of bare or few-electron ions: bound-state β− decay (βb) and its time-mirrored counterpart, orbital electron capture. The former decay mode was detected experimentally 20 years ago at the ESR. The latter could be investigated there for the first time in detail for the simplest quantum systems: hydrogen- and helium-like atoms. The main results of these experiments will be presented. Also their impact on stellar nucleosynthesis, in particular the s-process, is discussed.

Thermal determination of the abundances of c and z type fragment ions generated by in-source decay of peptide ions in matrix-assisted laser desorption ionization

In our previous study on the spectral variation in matrix-assisted laser desorption ionization (MALDI) of peptides, we found that quantitatively reproducible spectra could be acquired by selecting those associated with the same early plume temperature, Tearly. The study was limited to the cases in which the in-source decay (ISD) of peptide ions occurred via b–y channels. Study was extended in this work to the cases in which ISD via c–z channels also occurred significantly, taking MALDI of substance P and chromogranin A using 2,5-dihydroxybenzoic acid (DHB) as examples. The observation made for these peptides were the same as in the previous cases, i.e., MALDI spectra became reproducible when those associated with the same Tearly were selected. The result suggests that the MALDI spectrum of a peptide is thermally determined regardless of the mechanism contributing to ISD of the peptide ion. This, in turn, suggests that c–z channels in ISD of peptide ions are not initiated by electron capture. Also, if hydrogen radical capture initiates these channels, these radicals would be generated by the homolytic cleavage of an XH bond in the ground electronic state of a matrix molecule, not by excited state photolysis.

Copper recovery from tin stripping solution: Galvanostatic deposition in a batch-recycle system

Tin stripping is employed widely for the manufacture of printed circuit boards. At the end of stripping process, in general, 2–40g/l of Cu along with 150g/l SnO2 and ferric and nitrate ions remain in solution. The performance of an electrochemical batch recycle reactor for copper recovery from simulated tin stripping waste solutions was examined by galvanostatic plating. Galvanostatic control was achieved by the application of decreasing constant current steps which followed the concentration decay of metal ions in solution. The concentration decay was predicted by a model based on the batch recycle reactor operating under mass transport control. The current required to reduce the copper ions at the mass transfer limit at each time step was predicted from the model. These were matched against copper reclamation experiments from simulated tin stripping waste solutions using a single volumetric mass transfer coefficient as a fitting parameter. The prediction of the concentration decay of copper ions was in good agreement with the experimental data. It was found that the current efficiency for copper deposition was lowered by nitrates and oxygen present in the electrolyte due to their co-reduction at the cathode. Dissolved Fe3+ ions also influenced current efficiency for copper recovery due to the simultaneous reduction of ferric ions. The current efficiency was between 70% and 90% throughout the electrolytic process, which suggests that electrochemical copper reclamation may be a viable process.

Intense intra‐3d luminescence and waveguide properties of single Co‐doped ZnO nanowires

Abstractmagnified imageSuccessful doping of ZnO nanowires with the transition metal cobalt was achieved by ion implantation. Excellent optical activation of the incorporated Co ions was observed from nanowire ensembles after annealing. Efficient excitation of the Co ions occurs either by near resonant absorption or by energy transfer from the ZnO host. The excited Co ions decay radiatively with a lifetime of 8 ns. Intense and homogeneous Co2+ intra‐3d luminescence was observed from single nanowires with different Co concentrations in the range of 0.02– 4 at% and at various excitation powers. Spatially resolved measurements allowed the characterization of the waveguide properties of single doped nanowires. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Perspectives for mass spectrometry at the DESIR facility of SPIRAL2

DESIR (Desintégration, excitation et stockage des ions radioactifs, i.e. decay, excitation and storage of radioactive ions) will form the experimental area exploiting low-energy beams of the next-generation radioactive beam facility SPIRAL2 at GANIL, presently under construction. In addition to beams from the SPIRAL2 production building, DESIR will also receive beams from the separator-spectrometer S3 and from the SPIRAL1 facility. In the following, the DESIR facility and its instrumentation related to Penning trap based mass spectrometry and trap-assisted decay spectroscopy are introduced. The related envisaged experimental program is outlined.

Multiphoton dissociation of macromolecular ions at the single-molecule level

The laser-induced decay of ethylene oxide polymer ions of megadalton size has been studied in the multiphoton IR excitation regime, with fragmentation products of individual ions being monitored over long times by a trapping device. The experiment reveals several fragmentation pathways having distinct signatures at the single-molecule level that would not be accessible from studies based on statistically averaged reaction rates only. The observations are supported by dedicated molecular simulations based on a coarse-grained model, which further highlight the role played by continuous heating in such out-of-equilibrium conditions. In particular, both experiment and modeling indicate that the dissociation kinetics depends nonlinearly on heating rate.

Decaimento de íons cianato e a formação de carbamato de etila

Cyanate ion stability was studied in aqueous/ethanolic solutions, pH = 4.5 (CH3COOH/NaCH3COO), at different temperatures. Following the decay [(OCN)-] versus time, in the presence of excess C2H5OH, the rate constant for this reaction (k1) was calculated as (2.5 ± 0.3) x 10-4 s-1 at 25 oC, for 0 2.0 mol L-1 a decrease in the numerical value of k1 was observed, reaching 5.2 x 10-5 s-1 when [CH3CH2OH] = 13.7 mol L-1. Variations in the kinetic parameter values ΔH1‡, ΔS1‡ and ΔG1‡ for the cyanate ion decay reaction were observed for solutions at different ethanol concentrations.

Fragmentation of OCS3+ formed by 150 keV Ar+ ion impact on OCS

The dissociation of OCS3+ formed in ion impact ionization of OCS has been studied using the technique of multi-ion time of flight mass spectroscopy employing 150 keV Ar+ ions as projectiles. The coincidence plot reveals several fragmentation channels for the decay of this transient molecular ion with different possible decay mechanisms.

Quantum correlations in the two-photon decay of few-electron ions

The photon-photon polarization entanglement in the two-photon decay of metastable ionic states has been analyzed in the framework of the density matrix and second-order perturbation theory. Emphasis is placed especially upon the relativistic and non-dipole effects along the hydrogen- and helium-isoelectronic sequence.

Parametrization of the angular correlation and degree of linear polarization in two-photon decays of hydrogenlike ions

The spontaneous two-photon emission in hydrogenlike ions is investigated within the framework of second-order perturbation theory and Dirac's equation. Special attention is paid to the angular correlation of the emitted photons as well as to the degree of linear polarization of one of the two photons, if the second is just observed under arbitrary angles. Expressions for the angular correlation and the degree of linear polarization are expanded in powers of cosine functions of the two-photon opening angle, whose coefficients depend on the atomic number and the energy sharing of the emitted photons. The effects of including higher (electric and magnetic) multipoles upon the emitted photon pairs beyond the electric-dipole approximation are also discussed. Calculations of the coefficients are performed for the transitions $2{s}_{1/2}\ensuremath{\rightarrow}1{s}_{1/2}$, $3{d}_{3/2}\ensuremath{\rightarrow}1{s}_{1/2}$, and $3{d}_{5/2}\ensuremath{\rightarrow}1{s}_{1/2}$, along the entire hydrogen isoelectronic sequence ($1\ensuremath{\le}Z\ensuremath{\le}100$).