WorldWideScience

Sample records for vicinal hydrogen atoms

  1. Sampling the Hydrogen Atom

    Directory of Open Access Journals (Sweden)

    Graves N.

    2013-01-01

    Full Text Available A model is proposed for the hydrogen atom in which the electron is an objectively real particle orbiting at very near to light speed. The model is based on the postulate that certain velocity terms associated with orbiting bodies can be considered as being af- fected by relativity. This leads to a model for the atom in which the stable electron orbits are associated with orbital velocities where Gamma is n /α , leading to the idea that it is Gamma that is quantized and not angular momentum as in the Bohr and other models. The model provides a mechanism which leads to quantization of energy levels within the atom and also provides a simple mechanical explanation for the Fine Struc- ture Constant. The mechanism is closely associated with the Sampling theorem and the related phenomenon of aliasing developed in the mid-20th century by engineers at Bell labs.

  2. Scattering of muonic hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Mulhauser, F. [Universite de Fribourg (Switzerland); Adamczak, A. [Institute of Nuclear Physics (Poland); Beer, G.A. [University of Victoria (Canada); Bystritsky, V.M. [Joint Institute for Nuclear Research (Russian Federation); Filipowicz, M. [Institute of Physics and Nuclear Techniques (Poland); Fujiwara, M.C. [University of British Columbia (Canada); Huber, T.M. [Gustavus Adolphus College (United States); Jacot-Guillarmod, R. [Universite de Fribourg (Switzerland); Kammel, P. [University of California (United States); Kim, S.K. [Jeonbuk National University (Korea, Republic of); Knowles, P. [Universite de Fribourg (Switzerland); Kunselman, A.R. [University of Wyoming (United States); Maier, M. [University of Victoria (Canada); Markushin, V.E. [Paul Scherrer Institute (Switzerland); Marshall, G.M. [TRIUMF (Canada); Olin, A. [University of Victoria (Canada); Petitjean, C. [Paul Scherrer Institute (Switzerland); Porcelli, T.A. [University of Victoria (Canada); Stolupin, V.A. [Joint Institute for Nuclear Research (Russian Federation); Wozniak, J. [Institute of Physics and Nuclear Techniques (Poland)] (and others)

    1999-06-15

    Our measurement compares the energy dependence of the scattering cross-sections of muonic deuterium and tritium on hydrogen molecules for collisions in the energy range 0.1-45 eV. A time-of-flight method was used to measure the scattering cross-section as a function of the muonic atom beam energy and shows clearly the Ramsauer-Townsend effect. The results are compared with theoretical calculations by using Monte Carlo simulations. The molecular pd{mu} and pt{mu} formation creates background processes. We measure the formation rates in solid hydrogen by detecting the 5.5 MeV (pd{mu}) and 19.8 MeV (pt{mu}) {gamma}-rays emitted during the subsequent nuclear fusion processes.

  3. Precision spectroscopy on atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Parthey, Christian Godehard

    2011-12-15

    This Thesis reports on three measurements involving the 1S-2S transition in atomic hydrogen and deuterium conducted on a 5.8 K atomic beam. The transition is excited Doppler-free via two counter-propagating photons near 243 nm. The H/D isotope shift has been determined as {delta}{integral}{sub exp}=670 994 334 606(15) Hz. Comparing with the theoretical value for the isotope shift, excluding the leading nuclear size effect, {delta}{integral}{sub th}=670 999 566.90(66)(60) kHz we confirm, twice more accurate, the rms charge radius difference of the deuteron and the proton as left angle r{sup 2} right angle {sub d}- left angle r{sup 2} right angle {sub p}=3.82007(65) fm{sup 2} and the deuteron structure radius r{sub str}=1.97507(78) fm. The frequency ratio of the 1S-2S transition in atomic hydrogen to the cesium ground state hyperfine transition provided by the mobile cesium fountain clock FOM is measured to be {integral}{sub 1S-2S}=2 466 061 413 187 035 (10) Hz which presents a fractional frequency uncertainty of 4.2 x 10{sup -15}. The second absolute frequency measurement of the 1S-2S transition in atomic hydrogen presents the first application of a 900 km fiber link between MPQ and Physikalisch- Technische Bundesanstalt (PTB) in Braunschweig which we have used to calibrate the MPQ hydrogen maser with the stationary cesium fountain clock CSF1 at PTB. With the result of {integral}{sub 1S-2S}=2 466 061 413 187 017 (11) Hz we can put a constraint on the electron Lorentz boost violating coefficients 0.95c{sub (TX)}-0.29c{sub (TY)}-0.08 c{sub (TZ)}=(2.2{+-}1.8) x 10{sup -11} within the framework of minimal standard model extensions. We limit a possible drift of the strong coupling constant through the ratio of magnetic moments at a competitive level ({partial_derivative})/({partial_derivative}t)ln ({mu}{sub Cs})/({mu}{sub B})=-(3.0{+-}1.2) x 10{sup -15} yr{sup -1}.

  4. Atomic hydrogen storage method and apparatus

    Science.gov (United States)

    Woollam, J. A. (Inventor)

    1980-01-01

    Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compounds maintained at liquid helium temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

  5. Muonium/muonic hydrogen formation in atomic hydrogen

    Indian Academy of Sciences (India)

    Abstract. The muonium/muonic hydrogen atom formation in µ±–H collisions is in- vestigated, using a two-state approximation in a time dependent formalism. It is found that muonium cross-section results are similar to the cross-section results obtained for positronium formation in e+–H collision. Muonic hydrogen atom ...

  6. Ionisation of atomic hydrogen by positron impact

    Science.gov (United States)

    Spicher, Gottfried; Olsson, Bjorn; Raith, Wilhelm; Sinapius, Guenther; Sperber, Wolfgang

    1990-01-01

    With the crossed beam apparatus the relative impact-ionization cross section of atomic hydrogen by positron impact was measured. A layout of the scattering region is given. The first measurements on the ionization of atomic hydrogen by positron impact are also given.

  7. Studies in Composing Hydrogen Atom Wavefunctions

    DEFF Research Database (Denmark)

    Putnam, Lance Jonathan; Kuchera-Morin, JoAnn; Peliti, Luca

    2015-01-01

    We present our studies in composing elementary wavefunctions of a hydrogen-like atom and identify several relationships between physical phenomena and musical composition that helped guide the process. The hydrogen-like atom accurately describes some of the fundamental quantum mechanical phenomen...

  8. Atomic hydrogen as a launch vehicle propellant

    Science.gov (United States)

    Palaszewski, Bryan A.

    1990-01-01

    An analysis of several atomic hydrogen launch vehicles was conducted. A discussion of the facilities and the technologies that would be needed for these vehicles is also presented. The Gross Liftoff Weights (GLOW) for two systems were estimated; their specific impulses (I sub sp) were 750 and 1500 lb(sub f)/s/lb(sub m). The atomic hydrogen launch vehicles were also compared to the currently planned Advanced Launch System design concepts. Very significant GLOW reductions of 52 to 58 percent are possible over the Advanced Launch System designs. Applying atomic hydrogen propellants to upper stages was also considered. Very high I(sub sp) (greater than 750 lb(sub f)/s/lb(sub m)) is needed to enable a mass savings over advanced oxygen/hydrogen propulsion. Associated with the potential benefits of high I(sub sp) atomic hydrogen are several challenging problems. Very high magnetic fields are required to maintain the atomic hydrogen in a solid hydrogen matrix. The magnetic field strength was estimated to be 30 kilogauss (3 Tesla). Also the storage temperature of the propellant is 4 K. This very low temperature will require a large refrigeration facility for the launch vehicle. The design considerations for a very high recombination rate for the propellant are also discussed. A recombination rate of 210 cm/s is predicted for atomic hydrogen. This high recombination rate can produce very high acceleration for the launch vehicle. Unique insulation or segmentation to inhibit the propellant may be needed to reduce its recombination rate.

  9. On the energy of electric field in hydrogen atom

    OpenAIRE

    Kornyushin, Yuri

    2009-01-01

    It is shown that hydrogen atom is a unique object in physics having negative energy of electric field, which is present in the atom. This refers also to some hydrogen-type atoms: hydrogen anti-atom, atom composed of proton and antiproton, and positronium.

  10. Benchmarking Attosecond Physics with Atomic Hydrogen

    Science.gov (United States)

    2015-05-25

    Final 3. DATES COVERED (From - To) 12 Mar 12 – 11 Mar 15 4. TITLE AND SUBTITLE Benchmarking attosecond physics with atomic hydrogen 5a...AND SUBTITLE Benchmarking attosecond physics with atomic hydrogen 5a. CONTRACT NUMBER FA2386-12-1-4025 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Final Report for AOARD Grant FA2386-12-1-4025 “ Benchmarking

  11. From lattice gauge theories to hydrogen atoms

    Directory of Open Access Journals (Sweden)

    Manu Mathur

    2015-10-01

    Full Text Available We construct canonical transformations to obtain a complete and most economical realization of the physical Hilbert space Hp of pure SU(22+1 lattice gauge theory in terms of Wigner coupled Hilbert spaces of hydrogen atoms. One hydrogen atom is assigned to every plaquette of the lattice. A complete orthonormal description of the Wilson loop basis in Hp is obtained by all possible angular momentum Wigner couplings of hydrogen atom energy eigenstates |n l m〉 describing electric fluxes on the loops. The SU(2 gauge invariance implies that the total angular momenta of all hydrogen atoms vanish. The canonical transformations also enable us to rewrite the Kogut–Susskind Hamiltonian in terms of fundamental Wilson loop operators and their conjugate electric fields. The resulting loop Hamiltonian has a global SU(2 invariance and a simple weak coupling (g2→0 continuum limit. The canonical transformations leading to the loop Hamiltonian are valid for any SU(N. The ideas and techniques can also be extended to higher dimension.

  12. Wave mechanics of the hydrogen atom

    OpenAIRE

    Ogilvie, J. F.

    2016-01-01

    The hydrogen atom is a system amenable to an exact treatment within Schroedinger's formulation of quantum mechanics according to coordinates in four systems -- spherical polar, paraboloidal, ellipsoidal and spheroconical coordinates; the latter solution is reported for the first time. Applications of these solutions include angular momenta, a quantitative calculation of the absorption spectrum and accurate plots of surfaces of amplitude functions. The shape of an amplitude function, and even ...

  13. Semiclassical treatment of laser excitation of the hydrogen atom

    DEFF Research Database (Denmark)

    Billing, Gert D.; Henriksen, Niels Engholm; Leforestier, C.

    1992-01-01

    We present an alternative method for studying excitation of atoms in intense laser fields. In the present paper we focus upon the optical harmonic generation by hydrogen atoms.......We present an alternative method for studying excitation of atoms in intense laser fields. In the present paper we focus upon the optical harmonic generation by hydrogen atoms....

  14. Solid Hydrogen Particles Analyzed for Atomic Fuels

    Science.gov (United States)

    Palaszewski, Bryan A.

    2001-01-01

    Solid hydrogen particles have been selected as a means of storing atomic propellants in future launch vehicles (refs. 1 to 2). In preparation for this, hydrogen particle formation in liquid helium was tested experimentally. These experiments were conducted to visually characterize the particles and to observe their formation and molecular transformations (aging) while in liquid helium. The particle sizes, molecular transformations, and agglomeration times were estimated from video image analyses. The experiments were conducted at the NASA Glenn Research Center in the Supplemental Multilayer Insulation Research Facility (SMIRF, ref. 3). The facility has a vacuum tank, into which the experimental setup was placed. The vacuum tank prevented heat leaks and subsequent boiloff of the liquid helium, and the supporting systems maintained the temperature and pressure of the liquid helium bath where the solid particles were created. As the operation of the apparatus was developed, the hydrogen particles were easily visualized. The figures (ref. 1) show images from the experimental runs. The first image shows the initial particle freezing, and the second image shows the particles after the small particles have agglomerated. The particles finally all clump, but stick together loosely. The solid particles tended to agglomerate within a maximum of 11 min, and the agglomerate was very weak. Because the hydrogen particles are buoyant in the helium, the agglomerate tends to compact itself into a flat pancake on the surface of the helium. This pancake agglomerate is easily broken apart by reducing the pressure above the liquid. The weak agglomerate implies that the particles can be used as a gelling agent for the liquid helium, as well as a storage medium for atomic boron, carbon, or hydrogen. The smallest particle sizes that resulted from the initial freezing experiments were about 1.8 mm. About 50 percent of the particles formed were between 1.8 to 4.6 mm in diameter. These very

  15. Non-thermal hydrogen atoms in the terrestrial upper thermosphere.

    Science.gov (United States)

    Qin, Jianqi; Waldrop, Lara

    2016-12-06

    Model predictions of the distribution and dynamical transport of hydrogen atoms in the terrestrial atmosphere have long-standing discrepancies with ultraviolet remote sensing measurements, indicating likely deficiencies in conventional theories regarding this crucial atmospheric constituent. Here we report the existence of non-thermal hydrogen atoms that are much hotter than the ambient oxygen atoms in the upper thermosphere. Analysis of satellite measurements indicates that the upper thermospheric hydrogen temperature, more precisely the mean kinetic energy of the atomic hydrogen population, increases significantly with declining solar activity, contrary to contemporary understanding of thermospheric behaviour. The existence of hot hydrogen atoms in the upper thermosphere, which is the key to reconciling model predictions and observations, is likely a consequence of low atomic oxygen density leading to incomplete collisional thermalization of the hydrogen population following its kinetic energization through interactions with hot atomic or ionized constituents in the ionosphere, plasmasphere or magnetosphere.

  16. Atomic hydrogen storage. [cryotrapping and magnetic field strength

    Science.gov (United States)

    Woollam, J. A. (Inventor)

    1980-01-01

    Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compound is maintained at liquid temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

  17. Unparticle physics constraints from the hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    Wondrak, Michael Florian; Nicolini, Piero; Bleicher, Marcus [Frankfurt Institute for Advanced Studies (FIAS), Frankfurt am Main (Germany); Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet Frankfurt am Main, Frankfurt am Main (Germany)

    2016-07-01

    Unparticle stuff has been proposed as an extension of the Standard Model of particle physics by including scale invariant fields. In the framework of effective field theory, it describes the low-energy limit of a so-called Banks-Zaks sector which exhibits scale invariance below an energy scale Λ{sub U}. Unparticle fields are characterized by a non-integer canonical scaling dimension d{sub U}, which leads to unusual properties like resembling a fractional number of (un)particles. The existence of unparticle stuff may be detected experimentally through the interaction with conventional matter. After a review on the unparticle theory and the static potential due to virtual unparticle exchange, we focus on its impact on hydrogen atom energy levels. We obtain the energy shift of the ground state by using Rayleigh-Schroedinger perturbation theory and compare it with experimental data. In this way, bounds on the energy scale Λ{sub U} as a function of d{sub U} are derived. Finally, we offer a comparison with existing constraints in literature like the lepton magnetic anomaly. For some parameter regimes, the hydrogen bound provides competitive results.

  18. Hirshfeld atom refinement for modelling strong hydrogen bonds.

    Science.gov (United States)

    Woińska, Magdalena; Jayatilaka, Dylan; Spackman, Mark A; Edwards, Alison J; Dominiak, Paulina M; Woźniak, Krzysztof; Nishibori, Eiji; Sugimoto, Kunihisa; Grabowsky, Simon

    2014-09-01

    High-resolution low-temperature synchrotron X-ray diffraction data of the salt L-phenylalaninium hydrogen maleate are used to test the new automated iterative Hirshfeld atom refinement (HAR) procedure for the modelling of strong hydrogen bonds. The HAR models used present the first examples of Z' > 1 treatments in the framework of wavefunction-based refinement methods. L-Phenylalaninium hydrogen maleate exhibits several hydrogen bonds in its crystal structure, of which the shortest and the most challenging to model is the O-H...O intramolecular hydrogen bond present in the hydrogen maleate anion (O...O distance is about 2.41 Å). In particular, the reconstruction of the electron density in the hydrogen maleate moiety and the determination of hydrogen-atom properties [positions, bond distances and anisotropic displacement parameters (ADPs)] are the focus of the study. For comparison to the HAR results, different spherical (independent atom model, IAM) and aspherical (free multipole model, MM; transferable aspherical atom model, TAAM) X-ray refinement techniques as well as results from a low-temperature neutron-diffraction experiment are employed. Hydrogen-atom ADPs are furthermore compared to those derived from a TLS/rigid-body (SHADE) treatment of the X-ray structures. The reference neutron-diffraction experiment reveals a truly symmetric hydrogen bond in the hydrogen maleate anion. Only with HAR is it possible to freely refine hydrogen-atom positions and ADPs from the X-ray data, which leads to the best electron-density model and the closest agreement with the structural parameters derived from the neutron-diffraction experiment, e.g. the symmetric hydrogen position can be reproduced. The multipole-based refinement techniques (MM and TAAM) yield slightly asymmetric positions, whereas the IAM yields a significantly asymmetric position.

  19. Use of atomic hydrogen source in collision: technological challenges

    Science.gov (United States)

    Hovey, R. T.; Vargas, E. L.; Panchenko, D. I.; Rivas, D. A.; Andrianarijaona, V. M.

    2015-03-01

    Atomic hydrogen was extensively studied in the past due to its obvious fundamental aspect. Also, quite few investigations were dedicated to atomic hydrogen sources because the results of experimental investigations on systems involving H would provide very rigorous tests for theoretical models. But even if atomic hydrogen sources are currently widespread in experimental physics, their uses in experiments on collisions are still very challenging mainly due to threefold problem. First, there is the difficulty to create H in the laboratory in sufficiently large number densities. Second, there is the strain to adjust the velocities of the produced atomic hydrogens. And third, there is the toil to control the internal energies of these atomic hydrogens. We will present an outline of different techniques using atomic hydrogen sources in collisions, which could be found in the literatures, such as merged-beam technique, gas cell technique, and trap, and propose an experiment scheme using a turn-key atomic hydrogen source that experiments such as charge transfer could benefit from. This work is supported by the National Science Foundation under Grant No. PHY-1068877.

  20. Wavepacket dynamics in the scattering of hydrogen anions off vicinally nano-stepped metal surfaces

    Science.gov (United States)

    Shaw, John; Chakraborty, Himadri; Monismith, David

    2017-04-01

    We study the electron dynamics in monocrystalline Cu, Au and Pd surfaces with stepped vicinal structures modeled in a Kronig-Penney scheme. The unoccupied bands of the surface is resonantly excited via the charge transfer interaction of the surface with a moving hydrogen anion. The interaction dynamics are simulated in a quantum mechanical wavepacket propagation approach that used parallel computations. The survival probability of the interacting ion is calculated as well as the electron probability density at all times during the interaction. Animated videos are produced of the electron probability density which show that, when the electron is transferred to the metal, the first two image states are the most likely locations of the electron as it evolves through the superlattice. The survival probability shows peaks at those energies that produce standing waves between the steps on the surface when the electron is in the image state subbands. The work is supported by the XSEDE allocation Grant for high performance computation.

  1. Embedded-atom method potential for modeling hydrogen and hydrogen-defect interaction in tungsten

    Science.gov (United States)

    Wang, Li-Fang; Shu, Xiaolin; Lu, Guang-Hong; Gao, Fei

    2017-11-01

    An embedded-atom method potential has been developed for modeling hydrogen in body-centered-cubic (bcc) tungsten by fitting to an extensive database of density functional theory (DFT) calculations. Comprehensive evaluations of the new potential are conducted by comparing various hydrogen properties with DFT calculations and available experimental data, as well as all the other tungsten–hydrogen potentials. The new potential accurately reproduces the point defect properties of hydrogen, the interaction among hydrogen atoms, the interplay between hydrogen and a monovacancy, and the thermal diffusion of hydrogen in tungsten. The successful validation of the new potential confirms its good reliability and transferability, which enables large-scale atomistic simulations of tungsten–hydrogen system. The new potential is afterward employed to investigate the interplay between hydrogen and other defects, including [1 1 1] self-interstitial atoms (SIAs) and vacancy clusters in tungsten. It is found that both the [1 1 1] SIAs and the vacancy clusters exhibit considerable attraction for hydrogen. Hydrogen solution and diffusion in strained tungsten are also studied using the present potential, which demonstrates that tensile (compressive) stress facilitates (impedes) hydrogen solution, and isotropic tensile (compressive) stress impedes (facilitates) hydrogen diffusion while anisotropic tensile (compressive) stress facilitates (impedes) hydrogen diffusion.

  2. Topics in atomic hydrogen standard research and applications

    Science.gov (United States)

    Peters, H. E.

    1971-01-01

    Hydrogen maser based frequency and time standards have been in continuous use at NASA tracking stations since February 1970, while laboratory work at Goddard has continued in the further development and improvement of hydrogen masers. Concurrently, experimental work has been in progress with a new frequency standard based upon the hydrogen atom using the molecular beam magnetic resonance method. Much of the hydrogen maser technology is directly applicable to the new hydrogen beam standard, and calculations based upon realistic data indicate that the accuracy potential of the hydrogen atomic beam exceeds that of either the cesium beam tube or the hydrogen maser, possibly by several orders of magnitude. In addition, with successful development, the hydrogen beam standard will have several other performance advantages over other devices, particularly exceptional stability and long continuous operating life. Experimental work with a new laboratory hydrogen beam device has recently resulted in the first resonance transition curves, measurements of relative state populations, beam intensities, etc. The most important aspects of both the hydrogen maser and the hydrogen beam work are covered.

  3. Excited states of muonium in atomic hydrogen

    Indian Academy of Sciences (India)

    Muonium formation in excited states in muon-hydrogen charge-exchange collision is investigated using a method developed in a previous paper. Differential cross-section results are found to resemble positronium formation cross-section results of positron-hydrogen charge-exchange problem. Forward differential and ...

  4. Solid Hydrogen Particles and Flow Rates Analyzed for Atomic Fuels

    Science.gov (United States)

    Palaszewski, Bryan A.

    2003-01-01

    The experiments were conducted at Glenn's Small Multipurpose Research Facility (SMIRF, ref. 5). The experimental setup was placed in the facility's vacuum tank to prevent heat leaks and subsequent boiloff of the liquid helium. Supporting systems maintained the temperature and pressure of the liquid helium bath where the solid particles were created. Solid hydrogen particle formation was tested from February 23 to April 2, 2001. Millimeter-sized solid-hydrogen particles were formed in a Dewar of liquid helium as a prelude to creating atomic fuels and propellants for aerospace vehicles. Atomic fuels or propellants are created when atomic boron, carbon, or hydrogen is stored in solid hydrogen particles. The current testing characterized the solid hydrogen particles without the atomic species, as a first step to creating a feed system for the atomic fuels and propellants. This testing did not create atomic species, but only sought to understand the solid hydrogen particle formation and behavior in the liquid helium. In these tests, video images of the solid particle formation were recorded, and the total mass flow rate of the hydrogen was measured. The mass of hydrogen that went into the gaseous phase was also recorded using a commercially available residual gas analyzer. The temperatures, pressures, and flow rates of the liquids and gases in the test apparatus were recorded as well. Testing conducted in 1999 recorded particles as small as 2 to 5 mm in diameter. The current testing extended the testing conditions to a very cold Dewar ullage gas of about 20 to 90 K above the 4 K liquid helium. With the very cold Dewar gas, the hydrogen freezing process took on new dimensions, in some cases creating particles so small that they seemed to be microscopic, appearing as infinitesimally small scintillations on the videotaped images.

  5. Atomic displacements due to interstitial hydrogen in Cu and Pd

    Indian Academy of Sciences (India)

    The density functional theory (DFT) is used to study the atomic interactions in transition metal-based interstitial alloys. The strain field is calculated in the discrete lattice model using Kanzaki method. The total energy and hence atomic forces between interstitial hydrogen and transition metal hosts are calculated using DFT.

  6. Atomic displacements due to interstitial hydrogen in Cu and Pd

    Indian Academy of Sciences (India)

    Abstract. The density functional theory (DFT) is used to study the atomic interac- tions in transition metal-based interstitial alloys. The strain field is calculated in the discrete lattice model using Kanzaki method. The total energy and hence atomic forces between interstitial hydrogen and transition metal hosts are calculated ...

  7. Dynamic nuclear polarization of high-density atomic hydrogen in solid mixtures of molecular hydrogen isotopes.

    Science.gov (United States)

    Sheludiakov, S; Ahokas, J; Järvinen, J; Zvezdov, D; Vainio, O; Lehtonen, L; Vasiliev, S; Mao, S; Khmelenko, V V; Lee, D M

    2014-12-31

    We report on magnetic resonance studies of high-density atomic hydrogen and deuterium in solid hydrogen matrices at temperatures below 1 K. Average concentrations of H atoms ≈3×10(19)  cm(-3) are obtained in chemical tunneling reactions of isotope exchange with D atoms. The products of these reactions are closely located pairs of H atoms near D2 molecules with strong exchange interactions. We discovered a dynamic nuclear polarization effect on H atoms created by pumping the center of the H electron spin resonance spectrum, similar to the Overhauser effect in metals. Our results indicate that H atoms may be arranged inside molecular matrices at separations equivalent to local concentrations of 2.6×10(21)  cm(-3). This opens up a way to build a metallic state of atomic hydrogen at zero pressure.

  8. Characterization of an atomic hydrogen source for charge exchange experiments

    Energy Technology Data Exchange (ETDEWEB)

    Leutenegger, M. A. [NASA Goddard Space Flight Center, Code 662, Greenbelt, Maryland 20771 (United States); CRESST/University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Beiersdorfer, P.; Brown, G. V.; Magee, E. W. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Betancourt-Martinez, G. L. [NASA Goddard Space Flight Center, Code 662, Greenbelt, Maryland 20771 (United States); University of Maryland College Park, College Park, Maryland 20742 (United States); Hell, N. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Dr. Karl-Remeis-Sternwarte and ECAP, FAU Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg (Germany); Kelley, R. L.; Kilbourne, C. A.; Porter, F. S. [NASA Goddard Space Flight Center, Code 662, Greenbelt, Maryland 20771 (United States)

    2016-11-15

    We characterized the dissociation fraction of a thermal dissociation atomic hydrogen source by injecting the mixed atomic and molecular output of the source into an electron beam ion trap containing highly charged ions and recording the x-ray spectrum generated by charge exchange using a high-resolution x-ray calorimeter spectrometer. We exploit the fact that the charge exchange state-selective capture cross sections are very different for atomic and molecular hydrogen incident on the same ions, enabling a clear spectroscopic diagnostic of the neutral species.

  9. Interactions of atomic hydrogen with amorphous SiO2

    Science.gov (United States)

    Yue, Yunliang; Wang, Jianwei; Zhang, Yuqi; Song, Yu; Zuo, Xu

    2018-03-01

    Dozens of models are investigated by the first-principles calculations to simulate the interactions of an atomic hydrogen with a defect-free random network of amorphous SiO2 (a-SiO2) and oxygen vacancies. A wide variety of stable configurations are discovered due to the disorder of a-SiO2, and their structures, charges, magnetic moments, spin densities, and density of states are calculated. The atomic hydrogen interacts with the defect-free a-SiO2 in positively or negatively charged state, and produces the structures absent in crystalline SiO2. It passivates the neutral oxygen vacancies and generates two neutral hydrogenated E‧ centers with different Si dangling bond projections. Electron spin resonance parameters, including Fermi contacts, and g-tensors, are calculated for these centers. The atomic hydrogen interacts with the positive oxygen vacancies in dimer configuration, and generate four different positive hydrogenated defects, two of which are puckered like the Eγ‧ centers. This research helps to understand the interactions between an atomic hydrogen, and defect-free a-SiO2 and oxygen vacancies, which may generate the hydrogen-complexed defects that play a key role in the degeneration of silicon/silica-based microelectronic devices.

  10. Diffusion mobility of the hydrogen atom with allowance for the anharmonic attenuation of migrating atom state

    Energy Technology Data Exchange (ETDEWEB)

    Kashlev, Y.A., E-mail: yakashlev@yandex.ru

    2017-04-15

    Evolution of vibration relaxation of hydrogen atoms in metals with the close-packed lattice at high and medium temperatures is investigated based on non-equilibrium statistical thermodynamics, in that number on using the retarded two-time Green function method. In accordance with main kinetic equation – the generalized Fokker- Plank- Kolmogorov equation, anharmonism of hydrogen atoms vibration in potential wells does not make any contribution to collision effects. It influences the relaxation processes at the expense of interference of fourth order anharmonism with single-phonon scattering on impurity hydrogen atoms. Therefore, the total relaxation time of vibration energy of system metal-hydrogen is written as a product of two factors: relaxation time of system in harmonic approximation and dimensionless anharmonic attenuation of quantum hydrogen state.

  11. Atomic White-Out: Enabling Atomic Circuitry through Mechanically Induced Bonding of Single Hydrogen Atoms to a Silicon Surface.

    Science.gov (United States)

    Huff, Taleana R; Labidi, Hatem; Rashidi, Mohammad; Koleini, Mohammad; Achal, Roshan; Salomons, Mark H; Wolkow, Robert A

    2017-09-26

    We report the mechanically induced formation of a silicon-hydrogen covalent bond and its application in engineering nanoelectronic devices. We show that using the tip of a noncontact atomic force microscope (NC-AFM), a single hydrogen atom could be vertically manipulated. When applying a localized electronic excitation, a single hydrogen atom is desorbed from the hydrogen-passivated surface and can be transferred to the tip apex, as evidenced from a unique signature in frequency shift curves. In the absence of tunnel electrons and electric field in the scanning probe microscope junction at 0 V, the hydrogen atom at the tip apex is brought very close to a silicon dangling bond, inducing the mechanical formation of a silicon-hydrogen covalent bond and the passivation of the dangling bond. The functionalized tip was used to characterize silicon dangling bonds on the hydrogen-silicon surface, which was shown to enhance the scanning tunneling microscope contrast, and allowed NC-AFM imaging with atomic and chemical bond contrasts. Through examples, we show the importance of this atomic-scale mechanical manipulation technique in the engineering of the emerging technology of on-surface dangling bond based nanoelectronic devices.

  12. Excited states of muonium in atomic hydrogen

    Indian Academy of Sciences (India)

    Differential cross-section results are found to resemble positronium formation cross-section results of positron–hydrogen charge-exchange problem. Forward ... using velocity scaling are compared with the results of the present calculation. .... to carry out calculations for e− capture by muon into n = 2 and n = 3 states.

  13. Atomic configuration and charge state of hydrogen at dislocations in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Vysotskii, N. V., E-mail: mrdestroyed@yandex.ru; Loshachenko, A. S., E-mail: a.loshachenko@spbu.ru; Vyvenko, O. F., E-mail: vyvenko@gmail.com [St. Petersburg State University (Russian Federation)

    2017-03-15

    The effect of the introduction of hydrogen upon the vibration spectra and electrical characteristics of samples with dislocation networks at the interface of bonded silicon wafers was studied. In order to improve the sensitivity of measurements and to distinguish the signal from dislocation networks in Raman spectra, thin foils conventionally prepared for transmission electron microscopy were used as the sample under investigation. In the samples with dislocation networks, a Raman peak at 2000 cm{sup –1} was observed. This peak survived after annealing at a temperature of T = 500°C and was not observed in reference samples. Comparison of the experimental data with currently available theoretical calculations allowed one to attribute the observed peak to neutral hydrogen atoms H{sup 0} at the center of Si–Si bonds. The peak is metastable in the ideal lattice, but becomes stable in the vicinity of dislocations.

  14. Atomic hydrogen distribution. [in Titan atmospheric model

    Science.gov (United States)

    Tabarie, N.

    1974-01-01

    Several possible H2 vertical distributions in Titan's atmosphere are considered with the constraint of 5 km-A a total quantity. Approximative calculations show that hydrogen distribution is quite sensitive to two other parameters of Titan's atmosphere: the temperature and the presence of other constituents. The escape fluxes of H and H2 are also estimated as well as the consequent distributions trapped in the Saturnian system.

  15. Relativistic Hydrogen-Like Atom on a Noncommutative Phase Space

    Science.gov (United States)

    Masum, Huseyin; Dulat, Sayipjamal; Tohti, Mutallip

    2017-09-01

    The energy levels of hydrogen-like atom on a noncommutative phase space were studied in the framework of relativistic quantum mechanics. The leading order corrections to energy levels 2 S 1/2, 2 P 1/2 and 2 P 3/2 were obtained by using the 𝜃 and the \\bar θ modified Dirac Hamiltonian of hydrogen-like atom on a noncommutative phase space. The degeneracy of the energy levels 2 P 1/2 and 2 P 3/2 were removed completely by 𝜃-correction. And the \\bar θ -correction shifts these energy levels.

  16. Fast metastable hydrogen atoms from H2 molecules: twin atoms

    Directory of Open Access Journals (Sweden)

    Trimèche A.

    2015-01-01

    Full Text Available It is a difficult task to obtain “twin atoms”, i.e. pairs of massive particles such that one can perform experiments in the same fashion that is routinely done with “twin photons”. One possible route to obtain such pairs is by dissociating homonuclear diatomic molecules. We address this possibility by investigating the production of metastable H(2s atoms coming from the dissociation of cold H2 molecules produced in a Campargue nozzle beam crossing an electron beam from a high intensity pulsed electron gun. Dissociation by electron impact was chosen to avoid limitations of target molecular excited states due to selection rules. Detectors placed several centimeters away from the collision center, and aligned with respect to possible common molecular dissociation channel, analyze the neutral fragments as a function of their time-of-flight (TOF through Lyman-α detection. Evidence for the first time observed coincidence of pairs of H(2s atoms obtained this way is presented.

  17. Variational perturbation treatment of the confined hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, H E Jr, E-mail: ed.montgomery@centre.edu [Chemistry Program, Centre College, 600 West Walnut Street, Danville, KY 40422-1394 (United States)

    2011-09-15

    The Schroedinger equation for the ground state of a hydrogen atom confined at the centre of an impenetrable cavity is treated using variational perturbation theory. Energies calculated from variational perturbation theory are comparable in accuracy to the results from a direct numerical solution. The goal of this exercise is to introduce the student to the effects of confinement on atomic systems using a tractable problem from which insight into variational perturbation theory may be gained.

  18. Quantum-Classical Connection for Hydrogen Atom-Like Systems

    Science.gov (United States)

    Syam, Debapriyo; Roy, Arup

    2011-01-01

    The Bohr-Sommerfeld quantum theory specifies the rules of quantization for circular and elliptical orbits for a one-electron hydrogen atom-like system. This article illustrates how a formula connecting the principal quantum number "n" and the length of the major axis of an elliptical orbit may be arrived at starting from the quantum…

  19. Radial Matrix Elements of Hydrogen Atom and the Correspondence ...

    Indian Academy of Sciences (India)

    Radial dipole matrix elements having astrophysical importance have been computed for highly excited states of hydrogen atom. Computation is based on Heisenberg's form of correspondence principle for Coulomb potential. Particular attention has been paid to the choice of classical analogue (c) of principal quantum ...

  20. Variational Perturbation Treatment of the Confined Hydrogen Atom

    Science.gov (United States)

    Montgomery, H. E., Jr.

    2011-01-01

    The Schrodinger equation for the ground state of a hydrogen atom confined at the centre of an impenetrable cavity is treated using variational perturbation theory. Energies calculated from variational perturbation theory are comparable in accuracy to the results from a direct numerical solution. The goal of this exercise is to introduce the…

  1. Radial Matrix Elements of Hydrogen Atom and the Correspondence ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. Radial dipole matrix elements having astrophysical impor- tance have been computed for highly excited states of hydrogen atom. Computation is based on Heisenberg's form of correspondence principle for Coulomb potential. Particular attention has been paid to the choice of classical analogue (nc) of principal ...

  2. The Confined Hydrogen Atom with a Moving Nucleus

    Science.gov (United States)

    Fernandez, Francisco M.

    2010-01-01

    We study the hydrogen atom confined to a spherical box with impenetrable walls but, unlike earlier pedagogical articles on the subject, we assume that the nucleus also moves. We obtain the ground-state energy approximately by means of first-order perturbation theory and show that it is greater than that for the case in which the nucleus is clamped…

  3. Formation of ground and excited hydrogen atoms in proton ...

    Indian Academy of Sciences (India)

    2016-10-17

    Oct 17, 2016 ... Abstract. The inelastic scattering of proton with a potassium atom is treated for the first time as a three- channel problem within the framework of the improved coupled static approximation by assuming that the ground. (1s state) and the excited (2s state) hydrogen formation channels are open for seven ...

  4. Dirac equation, hydrogen atom spectrum and the Lamb shift in ...

    Indian Academy of Sciences (India)

    2017-04-12

    Apr 12, 2017 ... Abstract. We derive the relativistic Hamiltonian of hydrogen atom in dynamical non-commutative spaces. (DNCS or τ-space). Using this Hamiltonian we calculate the energy shift of the ground state as well the 2P1/2, 2S1/2 levels. In all the cases, the energy shift depends on the dynamical non-commutative ...

  5. Positron impact ionization of atomic hydrogen at low energies

    Indian Academy of Sciences (India)

    energies. K CHAKRABARTI. Department of Mathematics, Scottish Church College, 1 & 3 Urquhart Square, Calcutta 700 006,. India. MS received 26 June 2000. Abstract. Low energy positron impact ionization of atomic hydrogen is studies theoretically using the hyperspherical partial wave method of Das [1] in constant ΘЅѕ, ...

  6. Positron impact ionization of atomic hydrogen at low energies

    Indian Academy of Sciences (India)

    Low energy positron impact ionization of atomic hydrogen is studies theoretically using the hyperspherical partial wave method of Das [1] in constant 12, equal energy sharing geometry. The TDCS reveal considerable differences in physics compared to electron impact ionization under the same geometry.

  7. Schwinger variational calculation of ionization of hydrogen atoms for ...

    Indian Academy of Sciences (India)

    Schwinger variational calculation of ionization of hydrogen atoms for large momentum transfers. K CHAKRABARTI. Department of Mathematics, Scottish Church College, 1 & 3 Urquhart Square,. Kolkata 700 006, India. MS received 7 July 2001; revised 10 October 2001. Abstract. Schwinger variational principle is used here ...

  8. Suprathermal oxygen atoms in the Martian upper atmosphere: Contribution of the proton and hydrogen atom precipitation

    Science.gov (United States)

    Shematovich, V. I.

    2017-07-01

    This is a study of the kinetics and transport of hot oxygen atoms in the transition region (from the thermosphere to the exosphere) of the Martian upper atmosphere. It is assumed that the source of the hot oxygen atoms is the transfer of momentum and energy in elastic collisions between thermal atmospheric oxygen atoms and the high-energy protons and hydrogen atoms precipitating onto the Martian upper atmosphere from the solar-wind plasma. The distribution functions of suprathermal oxygen atoms by the kinetic energy are calculated. It is shown that the exosphere is populated by a large number of suprathermal oxygen atoms with kinetic energies up to the escape energy 2 eV; i.e., a hot oxygen corona is formed around Mars. The transfer of energy from the precipitating solar-wind plasma protons and hydrogen atoms to the thermal oxygen atoms leads to the formation of an additional nonthermal escape flux of atomic oxygen from the Martian atmosphere. The precipitation-induced escape flux of hot oxygen atoms may become dominant under the conditions of extreme solar events, such as solar flares and coronal mass ejections, as shown by recent observations onboard NASA's MAVEN spacecraft (Jakosky et al., 2015).

  9. Concerted hydrogen-atom abstraction in photosynthetic water oxidation.

    Science.gov (United States)

    Westphal, K L; Tommos, C; Cukier, R I; Babcock, G T

    2000-06-01

    Photosystem II evolves oxygen by using water in the unlikely role of a reductant. The absorption of sunlight by chlorophyll produces highly oxidizing equivalents that are filled with electrons stripped from water. This proton-coupled redox chemistry occurs at the oxygen-evolving complex, which contains a tetramanganese cluster, a redox-active tyrosine amino acid hydrogen-bonded to a histidine amino acid, a calcium ion and chloride. Hydrogen-atom abstraction by the tyrosyl radical from water bound to the manganese cluster is now widely held to occur in this process, at least for some of the steps in the catalytic cycle. We discuss kinetic and energetic constraints on the hydrogen-atom abstraction process.

  10. The Rydberg constant and proton size from atomic hydrogen

    Science.gov (United States)

    Beyer, Axel; Maisenbacher, Lothar; Matveev, Arthur; Pohl, Randolf; Khabarova, Ksenia; Grinin, Alexey; Lamour, Tobias; Yost, Dylan C.; Hänsch, Theodor W.; Kolachevsky, Nikolai; Udem, Thomas

    2017-10-01

    At the core of the “proton radius puzzle” is a four–standard deviation discrepancy between the proton root-mean-square charge radii (rp) determined from the regular hydrogen (H) and the muonic hydrogen (µp) atoms. Using a cryogenic beam of H atoms, we measured the 2S-4P transition frequency in H, yielding the values of the Rydberg constant R∞ = 10973731.568076(96) per meterand rp = 0.8335(95) femtometer. Our rp value is 3.3 combined standard deviations smaller than the previous H world data, but in good agreement with the µp value. We motivate an asymmetric fit function, which eliminates line shifts from quantum interference of neighboring atomic resonances.

  11. Reactivity and Catalytic Activity of Hydrogen Atom Chemisorbed Silver Clusters.

    Science.gov (United States)

    Manzoor, Dar; Pal, Sourav

    2015-06-18

    Metal clusters of silver have attracted recent interest of researchers as a result of their potential in different catalytic applications and low cost. However, due to the completely filled d orbital and very high first ionization potential of the silver atom, the silver-based catalysts interact very weakly with the reacting molecules. In the current work, density functional theory calculations were carried out to investigate the effect of hydrogen atom chemisorption on the reactivity and catalytic properties of inert silver clusters. Our results affirm that the hydrogen atom chemisorption leads to enhancement in the binding energy of the adsorbed O2 molecule on the inert silver clusters. The increase in the binding energy is also characterized by the decrease in the Ag-O and increase in the O-O bond lengths in the case of the AgnH silver clusters. Pertinent to the increase in the O-O bond length, a significant red shift in the O-O stretching frequency is also noted in the case of the AgnH silver clusters. Moreover, the hydrogen atom chemisorbed silver clusters show low reaction barriers and high heat of formation of the final products for the environmentally important CO oxidation reaction as compared to the parent catalytically inactive clusters. The obtained results were compared with those of the corresponding gold and hydrogen atom chemisorbed gold clusters obtained at the same level of theory. It is expected the current computational study will provide key insights for future advances in the design of efficient nanosilver-based catalysts through the adsorption of a small atom or a ligand.

  12. Classical-field model of the hydrogen atom

    Science.gov (United States)

    Rashkovskiy, Sergey A.

    2017-06-01

    It is shown that all of the basic properties of the hydrogen atom can be consistently described in terms of classical electrodynamics if instead of considering the electron to be a particle, we consider an electrically charged classical wave field—an "electron wave"—which is held by the electrostatic field of the proton. It is shown that quantum mechanics must be considered not as a theory of particles but as a classical field theory in the spirit of classical electrodynamics. In this case, we are not faced with difficulties in interpreting the results of the theory. In the framework of classical electrodynamics, all of the well-known regularities of the spontaneous emission of the hydrogen atom are obtained, which is usually derived in the framework of quantum electrodynamics. It is shown that there are no discrete states and discrete energy levels of the atom: the energy of the atom and its states change continuously. An explanation of the conventional corpuscular-statistical interpretation of atomic phenomena is given. It is shown that this explanation is only a misinterpretation of continuous deterministic processes. In the framework of classical electrodynamics, the nonlinear Schrödinger equation is obtained, which accounts for the inverse action of self-electromagnetic radiation of the electron wave and completely describes the spontaneous emissions of an atom.

  13. Electron-impact ionization of atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Baertschy, Mark D. [Univ. of California, Davis, CA (United States)

    2000-02-01

    Since the invention of quantum mechanics, even the simplest example of collisional breakup in a system of charged particles, e- + H → H+ + e- + e+, has stood as one of the last unsolved fundamental problems in atomic physics. A complete solution requires calculating the energies and directions for a final state in which three charged particles are moving apart. Advances in the formal description of three-body breakup have yet to lead to a viable computational method. Traditional approaches, based on two-body formalisms, have been unable to produce differential cross sections for the three-body final state. Now, by using a mathematical transformation of the Schrodinger equation that makes the final state tractable, a complete solution has finally been achieved, Under this transformation, the scattering wave function can be calculated without imposing explicit scattering boundary conditions. This approach has produced the first triple differential cross sections that agree on an absolute scale with experiment as well as the first ab initio calculations of the single differential cross section.

  14. Enhancing the hydrogen bond between the bridged hydrogen atom of diborane and ammonia.

    Science.gov (United States)

    Gao, Lei; Zhang, Xueying; Meng, Lingpeng; Zeng, Yanli

    2015-09-01

    The character of the bridged hydrogen atom (Hb) of B2H6 has become a hot issue in recent years. In this work, the complexes B2H6 · · · NH3, B2H2X4 · · · nNH3 (n = 1, 2) and 2HF · · · B2H2X4 · · · 2NH3 (X = Cl, Br, I) were constructed and studied based on the M06-2X calculations to investigate how to enhance the Hb · · · N hydrogen-bonded interaction. When the terminal hydrogen atoms (Ht) of B2H6 were replaced by X (X = Cl, Br, I) atoms, the Hb · · · N hydrogen bond were strengthened. According to the electrostatic potentials in B2H2X4, two HF molecules were added to the interspace of the B-H-B-H four-membered ring of the B2H2X4 · · · 2NH3 complexes, and H · · · X hydrogen bond formed, resulting in further enhancing effect of Hb · · · N hydrogen bond. As a result, the positive cooperative effect of Hb · · · N hydrogen bond and H · · · X hydrogen bond do enhance the interactions of each other. The two measures not only enhance the strength of Hb · · · N hydrogen bond, but also achieve the goal to make the Hb · · · N hydrogen bond perpendicular to B · · · B direction.

  15. Interaction between an icosahedron Li(13) cluster and a graphene layer doped with a hydrogen atom.

    Science.gov (United States)

    Rangel, Eduardo; Vázquez, Gerardo; Magaña, Fernando; Sansores, Enrique

    2012-12-01

    It is known that graphene reacts with atomic hydrogen to form a hydrogenated sheet of graphene. In order to understand the nature of the interaction between hydrogen and lithium in hydrogenated samples, we have carried out first principle calculations. Density functional theory and molecular dynamics were used to study the interaction between an icosahedron Li(13) cluster, and a graphene layer doped with a hydrogen atom. It was found that a hydrogen atom is levitated from the graphene layer and absorbed into the cluster of Li at 300 K and atmospheric pressure, with a binding energy far exceeding that of the adsorption energy of a hydrogen atom on the graphene layer.

  16. An su(1, 1) algebraic method for the hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    MartInez-y-Romero, R P [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Apartado Postal 50-542, Mexico City 04510 DF (Mexico); Nunez-Yepez, H N [Departamento de FIsica, Universidad Autonoma Metropolitana Unidad Iztapalapa, Apartado Postal 55-534, CP 09340, Iztapalapa DF (Germany); Salas-Brito, A L [Laboratorio de Sistemas Dinamicos, Departamento de Ciencias Basicas, Universidad Autonoma Metropolitana Unidad Azcapotzalco, Apartado Postal 21-267, CP 04000, Coyoacan DF (Mexico)

    2005-10-07

    An algebraic solution for the hydrogen atom analogous to the one recently proposed to solve the relativistic version of the system is presented. We add to the usual radial description of the problem an additional angular variable and an associated operator which can be considered as part of an su(1, 1) Lie algebra. The operators of the algebra define radial ladder operator relating the eigenfunctions of the system in unit steps of the principal quantum number. We conclude that the radial bound states of the hydrogen atom in our extended configuration space can be regarded as spanning the minimal M representation of the su(1, 1) Lie algebra. The method can also be extended to solve the s-wave Morse problem and the three-dimensional harmonic oscillator.

  17. Off-diagonal geometric phase of atom-electron coupling in hydrogen atom

    OpenAIRE

    Zhu, Guo-Qiang

    2009-01-01

    In this paper, the off-diagonal geometric phase of thermal state in hydrogen atom under the effects of external magnetic field is considered. Increasing temperature tends to suppress the off-diagonal geometric phase, including 1-order and 2-order cases. On the other hand, the relationship between the geometric phase and external magnetic field is discussed.

  18. Non-Hydrogenic Rydberg Atoms in Magnetic Fields

    OpenAIRE

    P. A., DANDO; T. S., MONTEIRO; W., JANS; W., SCHWEIZER; Department of Mathematics, Royal Holloway, University of London; Lehrstuhl fur Theoretische Astrophysik, University Tubingen

    1994-01-01

    The classical and quantal dynamics of non-hydrogenic Rydberg atoms in magnetic fields are investigated. Previous attempts to infer classical behaviour from quantum properties produced conflicting results: at low scaled energies (ε=-0.5) the nearest-neighbour statistics (NNS) were found to be at the chaotic (Wigner) limit while quantum phase-space distributions suggested a high degree of regularity. Here the classical limit is investigated directly by solving the equations of motion of the Dia...

  19. Dirac equation in noncommutative space for hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, T.C., E-mail: tadorno@nonada.if.usp.b [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, CEP 05508-090 Sao Paulo, SP (Brazil); Baldiotti, M.C., E-mail: baldiott@fma.if.usp.b [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, CEP 05508-090 Sao Paulo, SP (Brazil); Chaichian, M., E-mail: Masud.Chaichian@helsinki.f [Department of Physics, University of Helsinki and Helsinki Institute of Physics, PO Box 64, FIN-00014 Helsinki (Finland); Gitman, D.M., E-mail: gitman@dfn.if.usp.b [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, CEP 05508-090 Sao Paulo, SP (Brazil); Tureanu, A., E-mail: Anca.Tureanu@helsinki.f [Department of Physics, University of Helsinki and Helsinki Institute of Physics, PO Box 64, FIN-00014 Helsinki (Finland)

    2009-11-30

    We consider the energy levels of a hydrogen-like atom in the framework of theta-modified, due to space noncommutativity, Dirac equation with Coulomb field. It is shown that on the noncommutative (NC) space the degeneracy of the levels 2S{sub 1/2}, 2P{sub 1/2} and 2P{sub 3/2} is lifted completely, such that new transition channels are allowed.

  20. Relative Fisher information of hydrogen-like atoms

    Science.gov (United States)

    Yamano, Takuya

    2018-01-01

    The relative Fisher information is a measure of distance between two probability densities. We calculate it for the electron orbitals of hydrogen-like atoms by taking 1s state as the reference orbital. We find that the measure decreases as the principal quantum number increases, indicating that the electron cloud of excited states in radial direction becomes close to the one of 1s orbital.

  1. Metal-Hydrogen Phase Diagrams in the Vicinity of Melting Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Shapovalov, V.I.

    1999-01-06

    Hydrogen-metal interaction phenomena belong to the most exciting challenges of today's physical metallurgy and physics of solids due to the uncommon behavior of hydrogen in condensed media and to the need for understanding hydrogen's strong negative impact on properties of some high-strength steels and.alloys. The paper cites and summarizes research data on fundamental thermodynamic characteristics of hydrogen in some metals that absorb it endothermally at elevated temperatures. For a number of metal-hydrogen systems, information on some phase diagrams previously not available to the English-speaking scientific community is presented.

  2. Ground-state structures of atomic metallic hydrogen.

    Science.gov (United States)

    McMahon, Jeffrey M; Ceperley, David M

    2011-04-22

    Ab initio random structure searching using density functional theory is used to determine the ground-state structures of atomic metallic hydrogen from 500 GPa to 5 TPa. Including proton zero-point motion within the harmonic approximation, we estimate that molecular hydrogen dissociates into a monatomic body-centered tetragonal structure near 500 GPa (r(s)=1.23) that remains stable to 1 TPa (r(s)=1.11). At higher pressures, hydrogen stabilizes in an …ABCABC… planar structure that is similar to the ground state of lithium, but with a different stacking sequence. With increasing pressure, this structure compresses to the face-centered cubic lattice near 3.5 TPa (r(s)=0.92).

  3. The atomic hydrogen cloud in the saturnian system

    Science.gov (United States)

    Tseng, W.-L.; Johnson, R. E.; Ip, W.-H.

    2013-09-01

    The importance of Titan's H torus shaped by solar radiation pressure and of hydrogen atoms flowing out of Saturn's atmosphere in forming the broad hydrogen cloud in Saturn's magnetosphere is still debated. Since the Saturnian system also contains a water product torus which originates from the Enceladus plumes, the icy ring particles, and the inner icy satellites, as well as Titan's H2 torus, we have carried out a global investigation of the atomic hydrogen cloud taking into account all sources. We show that the velocity and angle distributions of the hot H ejected from Saturn's atmosphere following electron-impact dissociation of H2 are modified by collisions with the ambient atmospheric H2 and H. This in turn affects the morphology of the escaping hydrogen from Saturn, as does the morphology of the ionospheric electron distribution. Although an exact agreement with the Cassini observations is not obtained, our simulations show that H directly escaping from Titan is the dominant contributor in the outer magnetosphere. Of the total number of H observed by Cassini from 1 to 5RS, ∼5.7×1034, our simulations suggest ∼20% is from dissociation in the Enceladus torus, ∼5-10% is from dissociation of H2 in the atmosphere of the main rings, and ∼50% is from Titan's H torus, implying that ∼20% comes from Saturn atmosphere.

  4. THE DYNAMICS OF HYDROGEN ATOM ABSTRACTION FROM POLYATOMIC MOLECULES.

    Energy Technology Data Exchange (ETDEWEB)

    LIU,X.; SUITS,A.G.

    2002-11-21

    The hydrogen atom abstraction reaction is an important fundamental process that is extensively involved in atmospheric and combustion chemistry. The practical significance of this type of reaction with polyatomic hydrocarbons is manifest, which has led to many kinetics studies. The detailed understanding of these reactions requires corresponding dynamics studies. However, in comparison to the A + HX {radical} AH + X reactions, the study of the dynamics of A + HR {yields} AH + R reactions is much more difficult, both experimentally and theoretically (here and in the following, A stands for an atom, X stands for a halogen atom, and R stands for a polyatomic hydrocarbon radical). The complication stems from the structured R, in contrast to the structureless X. First of all, there are many internal degrees of freedom in R that can participate in the reaction. In addition, there are different carbon sites from which an H atom can be abstracted, and the dynamics are correspondingly different; there are also multiple identical carbon sites in HR and in the picture of a local reaction, there exist competitions between neighboring H atoms, and so on. Despite this complexity, there have been continuing efforts to obtain insight into the dynamics of these reactions. In this chapter, some examples are presented, including the reactions of ground state H, Cl, and O atoms, with particular focus on our recent work using imaging to obtain the differential cross sections for these reactions.

  5. Reactions of butadiyne. 1: The reaction with hydrogen atoms

    Science.gov (United States)

    Schwanebeck, W.; Warnatz, J.

    1984-01-01

    The reaction of hydrogen (H) atoms with butadiene (C4H2) was studied at room temperature in a pressure range between w mbar and 10 mbar. The primary step was an addition of H to C4H2 which is in its high pressure range at p 1 mbar. Under these conditions the following addition of a second H atom lies in the transition region between low and high pressure range. Vibrationally excited C4H4 can be deactivated to form buten-(1)-yne-(3)(C4H4) or decomposes into two C2H2 molecules. The rate constant at room temperature for primary step is given. The second order rate constant for the consumption of buten-(1)-yne-(3) is an H atom excess at room temperature is given.

  6. Signatures of a quantum diffusion limited hydrogen atom tunneling reaction.

    Science.gov (United States)

    Balabanoff, Morgan E; Ruzi, Mahmut; Anderson, David T

    2017-12-20

    We are studying the details of hydrogen atom (H atom) quantum diffusion in highly enriched parahydrogen (pH 2 ) quantum solids doped with chemical species in an effort to better understand H atom transport and reactivity under these conditions. In this work we present kinetic studies of the 193 nm photo-induced chemistry of methanol (CH 3 OH) isolated in solid pH 2 . Short-term irradiation of CH 3 OH at 1.8 K readily produces CH 2 O and CO which we detect using FTIR spectroscopy. The in situ photochemistry also produces CH 3 O and H atoms which we can infer from the post-photolysis reaction kinetics that display significant CH 2 OH growth. The CH 2 OH growth kinetics indicate at least three separate tunneling reactions contribute; (i) reactions of photoproduced CH 3 O with the pH 2 host, (ii) H atom reactions with the CH 2 O photofragment, and (iii) long-range migration of H atoms and reaction with CH 3 OH. We assign the rapid CH 2 OH growth to the following CH 3 O + H 2 → CH 3 OH + H → CH 2 OH + H 2 two-step sequential tunneling mechanism by conducting analogous kinetic measurements using deuterated methanol (CD 3 OD). By performing photolysis experiments at 1.8 and 4.3 K, we show the post-photolysis reaction kinetics change qualitatively over this small temperature range. We use this qualitative change in the reaction kinetics with temperature to identify reactions that are quantum diffusion limited. While these results are specific to the conditions that exist in pH 2 quantum solids, they have direct implications on the analogous low temperature H atom tunneling reactions that occur on metal surfaces and on interstellar grains.

  7. Identification of new, well-populated amino-acid sidechain rotamers involving hydroxyl-hydrogen atoms and sulfhydryl-hydrogen atoms

    Directory of Open Access Journals (Sweden)

    Agard David A

    2008-10-01

    Full Text Available Abstract Background An important element in homology modeling is the use of rotamers to parameterize the sidechain conformation. Despite the many libraries of sidechain rotamers that have been developed, a number of rotamers have been overlooked, due to the fact that they involve hydrogen atoms. Results We identify new, well-populated rotamers that involve the hydroxyl-hydrogen atoms of Ser, Thr and Tyr, and the sulfhydryl-hydrogen atom of Cys, using high-resolution crystal structures ( Conclusion Knowledge of these new rotamers will improve the evaluation of hydrogen-bonding networks in protein structures.

  8. Magnetic resonance of atomic hydrogen at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, W.N.; Morrow, M.; Jochemsen, R.; Berlinsky, A.J. (British Columbia Univ., Vancouver (Canada). Dept. of Physics)

    1982-07-01

    This article reviews the present state of magnetic resonance studies of atomic hydrogen gas at low temperatures. The various types of resonances that can be exploited are discussed and the paper ends with a review of the existing experimental data. It will be seen that up to the present, essentially all of the results have been derived from pulsed magnetic resonance of the 1420 MHz zero field hyperfine transition, and the many interesting results expected of the high field experiments are yet to appear.

  9. Asymptotics of Rydberg states for the hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, L.E. [Virginia Univ., Charlottesville, VA (United States). Dept. of Mathematics; Villegas-Blas, C. [Universidad Nacional Autonoma de Mexico, Instituto de Matematicas, Unidad Cuernavaca, A. P. 273-3 Admon. 3, Cuernavaca Morelos 62251 (Mexico)

    1997-08-01

    The asymptotics of Rydberg states, i.e., highly excited bound states of the hydrogen atom Hamiltonian, and various expectations involving these states are investigated. We show that suitable linear combinations of these states, appropriately rescaled and regarded as functions either in momentum space or configuration space, are highly concentrated on classical momentum space or configuration space Kepler orbits respectively, for large quantum numbers. Expectations of momentum space or configuration space functions with respect to these states are related to time-averages of these functions over Kepler orbits. (orig.)

  10. Hot hydrogen atom reactions moderated by H2 and He

    Science.gov (United States)

    Aronowitz, S.; Scattergood, T.; Flores, J.; Chang, S.

    1986-01-01

    Photolysis experiments were performed on the H2-CD4-NH3 and He-CD4-NH3 systems. The photolysis (1849 A) involved only NH3. Mixtures of H2:CD4:NH3 included all combinations of the ratios (200,400,800):(10,20,40):4. Two He:CD4:NH3 mixtures were examined where the ratios equalled the combinations 100:(10,20):4. Abstraction of a D from CD4 by the photolytically produced hot hydrogen from ammonia was monitored by mass spectrometric determination of HD. Both experiment and semiempirical hot-atom theory show that H2 is a very poor thermalizer of hot hydrogens with excess kinetic energy of about 2 eV. Applications of the hard-sphere collision model to the H2-CD4-NH3 system resulted in predicted ratios of net HD production to NH3 decomposition that were two orders of magnitude smaller than the experimental ratios. On the other hand, helium is found to be a very efficient thermalizer; here, the classical model yields reasonable agreement with experiments. Application of a semiempirical hot-atom program gave quantitative agreement with experiment for either system.

  11. Selection rule engineering of forbidden transitions of a hydrogen atom near a nanogap

    Science.gov (United States)

    Kim, Hyunyoung Y.; Kim, Daisik S.

    2018-01-01

    We perform an analytical study on the allowance of forbidden transitions for a hydrogen atom placed near line dipole sources, mimicking light emanating from a one-dimensional metallic nanogap. It is shown that the rapid variation of the electric field vector, inevitable in the near zone, completely breaks the selection rule of Δl=±1. While the forbidden transitions between spherically symmetric S states, such as 2S to 1S or 3S to 1S (Δl=0), are rather robust against selection rule breakage, Δl=±2 transitions such as between 3D and 1S or 3D and 2S states are very vulnerable to the spatial variation of the perturbing electric field. Transitions between 2S and 3D states are enhanced by many orders of magnitude, aided by the quadratic nature of both the perturbing Hamiltonian and D wavefunctions. The forbidden dipole moment, which approaches one Bohr radius times the electric charge in the vicinity of the gap, can be written in a simple closed form owing to the one-dimensional nature of our gap. With large enough effective volume together with the symmetric nature of the excited state wavefunctions, our work paves way towards atomic physics application of infinitely long nanogaps.

  12. Selection rule engineering of forbidden transitions of a hydrogen atom near a nanogap

    Directory of Open Access Journals (Sweden)

    Kim Hyunyoung Y.

    2018-01-01

    Full Text Available We perform an analytical study on the allowance of forbidden transitions for a hydrogen atom placed near line dipole sources, mimicking light emanating from a one-dimensional metallic nanogap. It is shown that the rapid variation of the electric field vector, inevitable in the near zone, completely breaks the selection rule of Δl=±1. While the forbidden transitions between spherically symmetric S states, such as 2S to 1S or 3S to 1S (Δl=0, are rather robust against selection rule breakage, Δl=±2 transitions such as between 3D and 1S or 3D and 2S states are very vulnerable to the spatial variation of the perturbing electric field. Transitions between 2S and 3D states are enhanced by many orders of magnitude, aided by the quadratic nature of both the perturbing Hamiltonian and D wavefunctions. The forbidden dipole moment, which approaches one Bohr radius times the electric charge in the vicinity of the gap, can be written in a simple closed form owing to the one-dimensional nature of our gap. With large enough effective volume together with the symmetric nature of the excited state wavefunctions, our work paves way towards atomic physics application of infinitely long nanogaps.

  13. Modeling hydrogen storage in boron-substituted graphene decorated with potassium metal atoms

    CSIR Research Space (South Africa)

    Tokarev, A

    2015-03-01

    Full Text Available Boron-substituted graphene decorated with potassium metal atoms was considered as a novel material for hydrogen storage. Density functional theory calculations were used to model key properties of the material, such as geometry, hydrogen packing...

  14. The ground state properties of spin-aligned atomic hydrogen, deuterium, and tritium

    Science.gov (United States)

    Etters, R. D.; Dugan, J. V., Jr.; Palmer, R. W.

    1975-01-01

    The internal energy, pressure, and compressibility of ground-state, spin-aligned atomic hydrogen, deuterium, and tritium are calculated assuming that all pair interactions occur via the atomic triplet (spin-aligned) potential. The conditions required to obtain atomic hydrogen and its isotopes in bulk are discussed; such a development would be of value in propulsion systems because of the light mass and energetic recombination of atomic hydrogen. Results show that atomic triplet hydrogen and deuterium remain gaseous at 0 K, and that tritium forms a liquid with a binding energy of approximately -0.75 K per atom at a molar volume of 130 cu cm per mole. The pair distribution function for these systems is calculated, and the predicted superfluid behavior of atomic triplet hydrogen and tritium is briefly discussed.

  15. Dirac equation in very special relativity for hydrogen atom

    Directory of Open Access Journals (Sweden)

    R.V. Maluf

    2014-11-01

    Full Text Available In this work, we study the modified Dirac equation in the framework of very special relativity (VSR. The low-energy regime is accessed and the nonrelativistic Hamiltonian is obtained. It turns out that this Hamiltonian is similar to that achieved from the Standard Model Extension (SME via coupling of the spinor field to a Lorentz-violating term, but new features arise inherited from the non-local character of the VSR. In addition, the implications of the VSR-modified Lorentz symmetry on the spectrum of a hydrogen atom are determined by calculating the first-order energy corrections in the context of standard quantum mechanics. Among the results, we highlight that the modified Hamiltonian provides non-vanishing corrections which lift the degeneracy of the energy levels and allow us to find an upper bound upon the VSR-parameter.

  16. Entropy and complexity analysis of hydrogenic Rydberg atoms

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Rosa, S. [Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada, 18071-Granada (Spain); Departamento de Fisica Aplicada II, Universidad de Sevilla, 41012-Sevilla (Spain); Toranzo, I. V.; Dehesa, J. S. [Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada, 18071-Granada (Spain); Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Sanchez-Moreno, P. [Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada, 18071-Granada (Spain); Departamento de Matematica Aplicada, Universidad de Granada, 18071-Granada (Spain)

    2013-05-15

    The internal disorder of hydrogenic Rydberg atoms as contained in their position and momentum probability densities is examined by means of the following information-theoretic spreading quantities: the radial and logarithmic expectation values, the Shannon entropy, and the Fisher information. As well, the complexity measures of Cramer-Rao, Fisher-Shannon, and Lopez Ruiz-Mancini-Calvet types are investigated in both reciprocal spaces. The leading term of these quantities is rigorously calculated by use of the asymptotic properties of the concomitant entropic functionals of the Laguerre and Gegenbauer orthogonal polynomials which control the wavefunctions of the Rydberg states in both position and momentum spaces. The associated generalized Heisenberg-like, logarithmic and entropic uncertainty relations are also given. Finally, application to linear (l= 0), circular (l=n- 1), and quasicircular (l=n- 2) states is explicitly done.

  17. Quantum dynamics of hydrogen atoms on graphene. II. Sticking

    Energy Technology Data Exchange (ETDEWEB)

    Bonfanti, Matteo, E-mail: matteo.bonfanti@unimi.it [Dipartimento di Chimica, Università degli Studi di Milano, v. Golgi 19, 20133 Milano (Italy); Jackson, Bret [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Hughes, Keith H. [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Burghardt, Irene [Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main (Germany); Martinazzo, Rocco, E-mail: rocco.martinazzo@unimi.it [Dipartimento di Chimica, Università degli Studi di Milano, v. Golgi 19, 20133 Milano (Italy); Istituto di Scienze e Tecnologie Molecolari, Consiglio Nazionale delle Richerche, v. Golgi 19, 20133 Milano (Italy)

    2015-09-28

    Following our recent system-bath modeling of the interaction between a hydrogen atom and a graphene surface [Bonfanti et al., J. Chem. Phys. 143, 124703 (2015)], we present the results of converged quantum scattering calculations on the activated sticking dynamics. The focus of this study is the collinear scattering on a surface at zero temperature, which is treated with high-dimensional wavepacket propagations with the multi-configuration time-dependent Hartree method. At low collision energies, barrier-crossing dominates the sticking and any projectile that overcomes the barrier gets trapped in the chemisorption well. However, at high collision energies, energy transfer to the surface is a limiting factor, and fast H atoms hardly dissipate their excess energy and stick on the surface. As a consequence, the sticking coefficient is maximum (∼0.65) at an energy which is about one and half larger than the barrier height. Comparison of the results with classical and quasi-classical calculations shows that quantum fluctuations of the lattice play a primary role in the dynamics. A simple impulsive model describing the collision of a classical projectile with a quantum surface is developed which reproduces the quantum results remarkably well for all but the lowest energies, thereby capturing the essential physics of the activated sticking dynamics investigated.

  18. In situ ellipsometry study of atomic hydrogen etching of extreme ultraviolet induced carbon layers

    NARCIS (Netherlands)

    Chen, J. Q.; E. Louis,; Harmsen, R.; T. Tsarfati,; Wormeester, H.; van Kampen, M.; van Schaik, W.; van de Kruijs, R.; F. Bijkerk,

    2011-01-01

    Atomic hydrogen based etching is generally considered an efficient method for the removal of carbon films resulting from photo-induced hydrocarbon dissociation, as occurs in extreme ultraviolet (EUV) photolithography environments. The etch rate of atomic hydrogen for three different kinds of carbon

  19. Perturbation calculations of the interaction energies between non-bonded hydrogen atoms - Part 2

    NARCIS (Netherlands)

    Laidlaw, W.G.; Lekkerkerker, H.N.W.; Wieser, H.

    1971-01-01

    Calculations of the interaction energy between non-bonded hydrogen atoms in the fragments A—H---H'—A' for selected displacements of the hydrogen atoms enable one to evaluate corrections to the force field due to the non-bonded interactions and to discuss the changes in the stretching vibration

  20. Schrodinger Equation Solutions that Lead to the Solution for the Hydrogen Atom

    Science.gov (United States)

    Newhouse, Paul F.; McGill, K.C.

    2004-01-01

    Two exercises that would provide beginning quantum theory students with an introduction to more advanced quantum mechanical treatments, especially the hydrogen atom are given. The exercises are stepwise in difficulty, leading naturally to the full hydrogen atom development and greatly extend the pedagogy of most multidimensional Cartesian systems…

  1. Convergent close-coupling approach to light and heavy projectile scattering on atomic and molecular hydrogen

    Science.gov (United States)

    Bray, I.; Abdurakhmanov, I. B.; Bailey, J. J.; Bray, A. W.; Fursa, D. V.; Kadyrov, A. S.; Rawlins, C. M.; Savage, J. S.; Stelbovics, A. T.; Zammit, M. C.

    2017-10-01

    The atomic hydrogen target has played a pivotal role in the development of quantum collision theory. The key complexities of computationally managing the countably infinite discrete states and the uncountably infinite continuum were solved by using atomic hydrogen as the prototype atomic target. In the case of positron or proton scattering the extra complexity of charge exchange was also solved using the atomic hydrogen target. Most recently, molecular hydrogen has been used successfully as a prototype molecule for developing the corresponding scattering theory. We concentrate on the convergent close-coupling computational approach to light projectiles, such as electrons and positrons, and heavy projectiles, such as protons and antiprotons, scattering on atomic and molecular hydrogen.

  2. Hydrogenation of acetylene on Si(100)-(2×1) with atomic hydrogen: evidence for quasi Eley Rideal chemistry

    Science.gov (United States)

    Yi, S. I.; Weinberg, W. H.

    1998-10-01

    The adsorption of atomic hydrogen on the Si(100)-(2×1) surface with pre-adsorbed acetylene has been studied. For exposures of atomic hydrogen less than 2 L, the clean Si dimers without coadsorbed acetylene react to form Si monohydride. With an exposure of 5 to 10 L of atomic hydrogen, acetylene-occupied Si dimers as well as the acetylene itself also react to form Si monohydride and ethylene, respectively. At much higher exposures the formation of ethyl and Si dihydride is observed. This sequence of reaction events is discussed within the context of a quasi Eley-Rideal reaction of atomic hydrogen with the surface species, i.e. the radical atomic hydrogen has a finite diffusion length on the surface prior to reaction or desorption. A modified Kisliuk adsorption model has been employed successfully to describe the rates of Si monohydride and ethylene formation at a surface temperature of 150 K as a function of both the initial acetylene coverage and the post-exposure of atomic hydrogen.

  3. Symmetry-resolved spectroscopy by detection of a metastable hydrogen atom for investigating the doubly excited states of molecular hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Odagiri, Takeshi; Kumagai, Yoshiaki; Tanabe, Takehiko; Nakano, Motoyoshi; Kouchi, Noriyuki [Department of Chemistry, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan); Suzuki, Isao H, E-mail: joe@chem.titech.ac.j [Photon Factory, IMSS, KEK, Tsukuba, Ibaraki 305-0801 (Japan)

    2009-11-01

    Symmetry-resolved spectroscopy for investigating the doubly excited states of molecular hydrogen has been newly developed, where a metastable hydrogen atom dissociating in a direction parallel and perpendicular to the electric vector of the linearly polarized incident light is detected.

  4. The EAGLE simulations: atomic hydrogen associated with galaxies

    Science.gov (United States)

    Crain, Robert A.; Bahé, Yannick M.; Lagos, Claudia del P.; Rahmati, Alireza; Schaye, Joop; McCarthy, Ian G.; Marasco, Antonino; Bower, Richard G.; Schaller, Matthieu; Theuns, Tom; van der Hulst, Thijs

    2017-02-01

    We examine the properties of atomic hydrogen (H I) associated with galaxies in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations of galaxy formation. EAGLE's feedback parameters were calibrated to reproduce the stellar mass function and galaxy sizes at z = 0.1, and we assess whether this calibration also yields realistic H I properties. We estimate the self-shielding density with a fitting function calibrated using radiation transport simulations, and correct for molecular hydrogen with empirical or theoretical relations. The `standard-resolution' simulations systematically underestimate H I column densities, leading to an H I deficiency in low-mass (M⋆ EAGLE simulations featuring a factor of 8 (2) better mass (spatial) resolution, within which the H I mass of galaxies evolves more mildly from z = 1 to 0 than in the standard-resolution simulations. The largest volume simulation reproduces the observed clustering of H I systems, and its dependence on H I richness. At fixed M⋆, galaxies acquire more H I in simulations with stronger feedback, as they become associated with more massive haloes and higher infall rates. They acquire less H I in simulations with a greater star formation efficiency, since the star formation and feedback necessary to balance the infall rate is produced by smaller gas reservoirs. The simulations indicate that the H I of present-day galaxies was acquired primarily by the smooth accretion of ionized, intergalactic gas at z ≃ 1, which later self-shields, and that only a small fraction is contributed by the reincorporation of gas previously heated strongly by feedback. H I reservoirs are highly dynamic: over 40 per cent of H I associated with z = 0.1 galaxies is converted to stars or ejected by z = 0.

  5. Molecular dynamics simulation of effect of hydrogen atoms on crack propagation behavior of α-Fe

    Energy Technology Data Exchange (ETDEWEB)

    Song, H.Y., E-mail: gsfshy@sohu.com; Zhang, L.; Xiao, M.X.

    2016-12-16

    The effect of the hydrogen concentration and hydrogen distribution on the mechanical properties of α-Fe with a pre-existing unilateral crack under tensile loading is investigated by molecular dynamics simulation. The results reveal that the models present good ductility when the front region of crack tip has high local hydrogen concentration. The peak stress of α-Fe decreases with increasing hydrogen concentration. The studies also indicate that for the samples with hydrogen atoms, the crack propagation behavior is independent of the model size and boundaries. In addition, the crack propagation behavior is significantly influenced by the distribution of hydrogen atoms. - Highlights: • The distribution of hydrogen plays a critical role in the crack propagation. • The peak stress decrease with the hydrogen concentration increasing. • The crack deformation behavior is disclosed and analyzed.

  6. Emission of fast non-Maxwellian hydrogen atoms in low-density laboratory plasma

    Science.gov (United States)

    Brandt, Christian; Marchuk, Oleksandr; Pospieszczyk, Albrecht; Dickheuer, Sven

    2017-03-01

    The source of strong and broad emission of the Balmer-α line in mixed plasmas of hydrogen (or deuterium) and noble gases in front of metallic surfaces is a subject of controversial discussion of many plasma types. In this work the excitation source of the Balmer lines is investigated by means of optical emission spectroscopy in the plasma device PSI-2. Neutral fast non-Maxwellian hydrogen atoms are produced by acceleration of hydrogen ions towards an electrode immersed into the plasma. By variation of the electrode potential the energy of ions and in turn of reflected fast atoms can be varied in the range of 40-300 eV. The fast atoms in front of the electrode are observed simultaneously by an Echelle spectrometer (0.001 nm/channel) and by an imaging spectrometer (0.01 nm/channel) up to few cm in the plasma. Intense excitation channels of the Balmer lines are observed when hydrogen is mixed with argon or with krypton. Especially in Ar-H and Ar-D mixed plasmas the emission of fast hydrogen atoms is very strong. Intermixing hydrogen with other noble gases (He, Ne or Xe) one observes the same effect however the emission is one order of magnitude less compared to Kr-H or Kr-D plasmas. It is shown, that the key process, impacting this emission, is the binary collision between the fast neutral hydrogen atom and the noble gas atom. Two possible sources of excitation are discussed in details: one is the excitation of hydrogen atoms by argon atoms in the ground state and the second one is the process of the so-called excitation transfer between the metastable states of noble gases and hydrogen. In the latter case the atomic data for excitation of Balmer lines are still not available in literature. Further experimental investigations are required to conclude on the source process of fast atom emission.

  7. Collisions at thermal energy between metastable hydrogen atoms and hydrogen molecules: Total and differential cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Vassilev, G.; Perales, F.; Miniatura, C.; Robert, J.; Reinhardt, J.; Vecchiocattivi, F.; Baudon, J. (Paris-13 Univ., 93 - Villetaneuse (France). Lab. de Physique des Lasers)

    1990-10-01

    A metastable hydrogen (deuterium) atom source in which groundstate atoms produced by a RF discharge dissociator are bombarded by electrons, provides a relatively large amount of slow metastable atoms (velocity 3-5 km/s). Total integral cross sections for H{sup *}(D{sup *})(2s)+H{sub 2}(X{sup 1}{Sigma}{sub g}{sup +}, {nu}=0) collisions have been measured in a wide range of relative velocity (2,5-30 km/s), by using the attenuation method. A significant improvement of accuracy is obtained, with respect to previous measurements, at low relative velocities. Total cross sections for H{sup *} and D{sup *}, as functions of the relative velocity, are different, especially in the low velocity range. H{sup *}+H{sub 2} total differential cross sections have also been measured, with an angular spread of 3.6deg, for two different collision energy distributions, centered respectively at 100 meV and 390 meV. A first attempt of theoretical analysis of the cross sections, by means of an optical potential, is presented. (orig.).

  8. Studying the InAs quantum points on the vicinal surface of a GaAs crystal by the atomic force microscopy

    CERN Document Server

    Evtikhiev, V P; Kotelnikov, E Y; Matveentsev, A V; Titkov, A N; Shkolnik, A S

    2002-01-01

    The methodology for processing the images, obtained through the atomic force microscopy, is proposed. It is shown by the concrete example, how the parameters of the InAs clusters on the vicinal surface of the GaAs crystal are determined. This makes it possible to calculate the energy levels of the electrons and holes in the quantum point with application of the previously developed cluster spherical model

  9. Hydrogen atom addition to the surface of graphene nanoflakes: A density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, Hiroto, E-mail: hiroto@eng.hokudai.ac.jp

    2017-02-28

    Highlights: • The reaction pathway of the hydrogen addition to graphene surface was determined by the DFT method. • Binding energies of atomic hydrogen to graphene surface were determined. • Absorption spectrum of hydrogenated graphene was theoretically predicted. • Hyperfine coupling constant of hydrogenated graphene was theoretically predicted. - Abstract: Polycyclic aromatic hydrocarbons (PAHs) provide a 2-dimensional (2D) reaction surface in 3-dimensional (3D) interstellar space and have been utilized as a model of graphene surfaces. In the present study, the reaction of PAHs with atomic hydrogen was investigated by means of density functional theory (DFT) to systematically elucidate the binding nature of atomic hydrogen to graphene nanoflakes. PAHs with n = 4–37 were chosen, where n indicates the number of benzene rings. Activation energies of hydrogen addition to the graphene surface were calculated to be 5.2–7.0 kcal/mol at the CAM-B3LYP/6-311G(d,p) level, which is almost constant for all PAHs. The binding energies of hydrogen atom were slightly dependent on the size (n): 14.8–28.5 kcal/mol. The absorption spectra showed that a long tail is generated at the low-energy region after hydrogen addition to the graphene surface. The electronic states of hydrogenated graphenes were discussed on the basis of theoretical results.

  10. An atomic hydrogen beam to test ASACUSA's apparatus for antihydrogen spectroscopy

    CERN Document Server

    Diermaier, Martin; Kolbinger, Bernadette; Malbrunot, Chloé; Massiczek, Oswald; Sauerzopf, Clemens; Simon, Martin C.; Wolf, Michael; Zmeskal, Johann; Widmann, Eberhard

    2015-01-01

    The ASACUSA collaboration aims to measure the ground state hyperfine splitting (GS-HFS) of antihydrogen, the antimatter pendant to atomic hydrogen. Comparisons of the corresponding transitions in those two systems will provide sensitive tests of the CPT symmetry, the combination of the three discrete symmetries charge conjugation, parity, and time reversal. For offline tests of the GS-HFS spectroscopy apparatus we constructed a source of cold polarised atomic hydrogen. In these proceedings we report the successful observation of the hyperfine structure transitions of atomic hydrogen with our apparatus in the earth's magnetic field.

  11. Time-of-flight spectroscopy of muonic hydrogen atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, M.C. [Dept. of Physics and Astronomy, Univ. of British Columbia, Vancouver, BC (Canada)]|[Dept. of Physics, Faculty of Science, Univ. of Tokyo (Japan); Adamczak, A. [Inst. of Nuclear Physics, Krakow (Poland); Bailey, J.M. [Chester Technology, Chester (United Kingdom); Beer, G.A.; Mason, G.R. [Dept. of Physics and Astronomy, Univ. of Victoria, BC (Canada); Beveridge, J.L.; Marshall, G.M.; Olin, A. [TRIUMF, Vancouver, BC (Canada); Faifman, M.P. [Russian Research Center, Kurchatov Inst., Moscow (Russian Federation); Huber, T.M. [Dept. of Physics, Gustavus Adolphus Coll., St. Peter, MN (United States); Kammel, P. [Dept. of Physics and Lawrence Berkeley National Lab., Univ. of California, Berkeley, CA (United States); Kim, S.K. [Dept. of Physics, Jeonbuk National Univ., Jeonju City (Korea); Knowles, P.E.; Mulhauser, F. [Inst. of Physics, Univ. of Fribourg (Switzerland); Kunselman, A.R. [Dept. of Physics and Astronomy, Univ. of Wyoming, Laramie, WY (United States); Markushin, V.E.; Petitjean, C. [Paul Scherrer Inst., Villigen (Switzerland); Porcelli, T.A. [Dept. of Physics, Univ. of Northern British Columbia, Prince George, BC (Canada); Zmeskal, J. [Inst. for Medium Energy Physics, Austrian Academy of Sciences, Vienna (Austria)

    2001-07-01

    Studies of muonic hydrogen atoms and molecules have been performed traditionally in bulk targets of gas, liquid or solid. At TRIUMF, Canada's meson facility, we have developed a new type of target system using multilayer thin films of solid hydrogen, which provides a beam of muonic hydrogen atoms in vacuum. Using the time-of-flight of the muonic atoms, the energy-dependent information of muonic reactions are obtained in direct manner.We discuss some unique measurements enabled by the new technique, with emphasis on processes relevant to muon catalyzed fusion.

  12. The role of final-state correlations in recombination of atomic hydrogen

    NARCIS (Netherlands)

    Stoof, H.T.C.; Goey, L.P.H. de; Verhaar, B.J.; Glöckle, W.

    1987-01-01

    We calculate the rate-constant for recombination in the bulk of a spin-polarized atomic hydrogen gas. We use an exact initial state and include the most essential collision aspects of the final state, except for rearrangement.

  13. Influences of atomic hydrogen on porous low-k dielectric for 45-nm node

    Energy Technology Data Exchange (ETDEWEB)

    Tomioka, K. [Semiconductor Leading Edge Technologies, Inc., 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569 (Japan)]. E-mail: tomioka.kazuhiro@selete.co.jp; Soda, E. [Semiconductor Leading Edge Technologies, Inc., 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569 (Japan); Kobayashi, N. [Semiconductor Leading Edge Technologies, Inc., 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569 (Japan); Takata, M. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); Uda, S. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); Ogushi, K. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); Yuba, Y. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); Akasaka, Y. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan)

    2007-04-23

    Atomic hydrogen generated by a heated tungsten catalyzer has been investigated in terms of the damage-less ash and restoration of damaged low-k dielectric. No difference of damaged thickness of low-k dielectric between before and after the ash by HF dip using patterned porous methyl silsesquioxane (MSQ) film was found. Moreover atomic hydrogen exposure slightly reduced capacitance of the micro-structured capacitor with the Cu wire and the CVD porous low-k dielectric.

  14. Transcendental-function representation of Stark-modified hydrogenic states and atomic dipole polarizability

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, A.; Talukdar, B. [Department of Physics, Visva-Bharati University, Santiniketan (India); Banerji, G. [Mathematics Department, BU, Burdwan (India); Roy, U. [Theoretical Physics Department, IACS, Calcutta (India)

    1998-01-30

    A differential equation approach to the perturbation theoretic correction for excited hydrogenic states is introduced. The radial equations for the problem are solved in terms of known transcendental functions and the method to determine the complete primitive is discussed. The constructed perturbative correction to the wavefunction is adapted to evaluate the dipole polarizability of hydrogenic atoms. (author)

  15. Understanding Hydrogen Atom Transfer: from Bond Strengths to Marcus Theory

    Science.gov (United States)

    MAYER, JAMES M.

    2010-01-01

    CONSPECTUS Hydrogen atom transfer (HAT) is one of the most fundamental chemical reactions: A–H + B → A + H–B. It is a key step in a wide range of chemical, environmental, and biological processes. Traditional HAT involves p-block radicals such as tBuO• abstracting H• from organic molecules. More recently, it has been recognized that many transition metal species undergo HAT. This has led to a broader perspective, with HAT viewed as one type of proton-coupled electron transfer (PCET). When transition metal complexes oxidize substrates by removing H• (≡ e– and H+), typically the electron transfers to the metal and the proton transfers to a ligand. Two examples are shown in the Figure: iron-imidazolinate and vanadium-oxo complexes. Although such reagents do not “look like” main group radicals, they have the same pattern of reactivity. For instance, their HAT rate constants parallel the A–H bond strengths within a series of similar reactions. Just like main group radicals, they abstract H• much faster from O–H bonds than from C–H bonds of the same strength. This shows that driving force is not the only determinant of reactivity. We have found that HAT reactivity is well described using a Marcus-theory approach. In the simplest model, the cross relation, kAH/B = (kAH/AkBH/BKeqf)½, predicts the rate constant for AH + B in terms of the self-exchange rate constants (kAH/A for AH + A) and the equilibrium constant. For a variety of transition metal oxidants, kAH/B is predicted within one or two orders of magnitude with only a few exceptions. For 36 organic reactions of oxyl radicals, kAH/B is predicted with an average deviation of a factor of 3.8, and within a factor of 5 for all but six of the reactions. These reactions involve both O–H or C–H bonds, occur either in water or organic solvents, and over a range of 1028 in Keq and 1013 in kAH/B. The treatment of organic reactions of O–H bonds includes the well-established kinetic solvent

  16. A spectroscopic study of hydrogen atom and molecule collision. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kielkopf, John F.

    2002-07-01

    The fundamental processes which occur in low-energy collisions of excited states of the hydrogen atom with other neutral atoms, protons, and electrons in dense plasmas were investigated in this project. Theoretical and experimental results for the Lyman and Balmer series are described here, including references to recent publications resulting from this project.

  17. Resonant Scattering of Muonic Hydrogen Atoms and Dynamics of the Muonic Molecular Complex

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, M. C., E-mail: Makoto.Fujiwara@cern.ch [University of British Columbia (Canada); Adamczak, A. [Institute Nuclear Physics (Poland); Bailey, J. M. [Chester Technology (United Kingdom); Beer, G. A. [University of Victoria (Canada); Beveridge, J. L. [TRIUMF (Canada); Faifman, M. P. [Kurchatov Institute (Russian Federation); Huber, T. M. [Gustavus Adolphus College (United States); Kammel, P. [University of Illinois at Urbana-Champaign (United States); Kim, S. K. [Jeonbuk National University (Korea, Republic of); Knowles, P. E. [Universite de Fribourg (Switzerland); Kunselman, A. R. [University of Wyoming (United States); Markushin, V. E. [Paul Scherrer Institute (Switzerland); Marshal, G. M. [TRIUMF (Canada); Mason, G. R. [University of Victoria (Canada); Mulhauser, F. [Universite de Fribourg (Switzerland); Olin, A. [TRIUMF (Canada); Petitjean, C. [Paul Scherrer Institute (Switzerland); Porcelli, T. A. [University of Northern British Columbia (Canada); Wozniak, J. [Institute Physics and Nuclear Techniques (Poland); Zmeskal, J. [Austrian Academy of Sciences (Austria)

    2001-12-15

    Resonant scattering of muonic hydrogen atoms via back decay of the molecular complex, a key process in the understanding of epithermal muonic molecular formation, is analyzed. The limitations of the effective rate approximation are discussed and the importance of the explicit treatment of the back decay is stressed. An expression of the energy distribution for the back-decayed atoms is given.

  18. Hydrogen atoms can be located accurately and precisely by x-ray crystallography.

    Science.gov (United States)

    Woińska, Magdalena; Grabowsky, Simon; Dominiak, Paulina M; Woźniak, Krzysztof; Jayatilaka, Dylan

    2016-05-01

    Precise and accurate structural information on hydrogen atoms is crucial to the study of energies of interactions important for crystal engineering, materials science, medicine, and pharmacy, and to the estimation of physical and chemical properties in solids. However, hydrogen atoms only scatter x-radiation weakly, so x-rays have not been used routinely to locate them accurately. Textbooks and teaching classes still emphasize that hydrogen atoms cannot be located with x-rays close to heavy elements; instead, neutron diffraction is needed. We show that, contrary to widespread expectation, hydrogen atoms can be located very accurately using x-ray diffraction, yielding bond lengths involving hydrogen atoms (A-H) that are in agreement with results from neutron diffraction mostly within a single standard deviation. The precision of the determination is also comparable between x-ray and neutron diffraction results. This has been achieved at resolutions as low as 0.8 Å using Hirshfeld atom refinement (HAR). We have applied HAR to 81 crystal structures of organic molecules and compared the A-H bond lengths with those from neutron measurements for A-H bonds sorted into bonds of the same class. We further show in a selection of inorganic compounds that hydrogen atoms can be located in bridging positions and close to heavy transition metals accurately and precisely. We anticipate that, in the future, conventional x-radiation sources at in-house diffractometers can be used routinely for locating hydrogen atoms in small molecules accurately instead of large-scale facilities such as spallation sources or nuclear reactors.

  19. Degradation of fast electrons energy and atomic hydrogen generation in an emission plume from atomic power stations

    Science.gov (United States)

    Kolotkov, G. A.; Penin, S. T.; Chistyakova, L. K.

    2006-02-01

    The problem of remote detecting of a radioactivity in emissions from atomic power stations (APS) is devoted. The basic radionuclides contained in emissions of nuclear energy stations with various types of reactors have been analyzed. The total power spectrum of electrons is determined taking into account their multiplication. Physical and chemical reactions reducing to generation of atomic hydrogen are considered. For definition of the radiating volume in the emission from APS, the spatial distribution of atomic hydrogen concentration has been calculated with the use Pasquill- Gifford model. Power radiating by the emission plume from the APS with the BWR (Boiling Water Reactor) is estimated. It has been shown, that for estimation of radiation effect on the atmosphere, it is necessary to take into account many generations of electrons, because they have average energies exceeding considerably the ionization potentials for atoms and molecules of the atmospheric components. The area of the maximum concentration of atomic hydrogen in an emission plume can be determined by modelling the transport processes of admixture. The power radiated at frequency 1420 MHz by the volume 1 km from the APS emissions can amount to ~10 -13 W that allows one to detect the total level of activity confidently. The possible configuration of an emission plume has been calculated for various atmospheric stratification and underlying surfaces.

  20. Trapping of hydrogen atoms inside small beryllium clusters and their ions

    Science.gov (United States)

    Naumkin, F. Y.; Wales, D. J.

    2016-08-01

    Structure, stability and electronic properties are evaluated computationally for small Ben (n = 5-9) cluster cages accommodating atomic H inside and forming core-shell species. These parameters are predicted to vary significantly upon insertion of H, for ionic derivatives, and with the system size. In particular, the energy barrier for H-atom exit from the cage changes significantly for ions compared to the neutral counterparts. The corresponding effects predicted for cage assemblies suggest the possibility of efficient charge-control of hydrogen release. This, together with a high capacity for storing hydrogen in extended such assemblies might indicate a possible way towards feasible hydrogen-storage solutions.

  1. Adsorption Sites of Hydrogen Atom on Pure and Mg-Doped Multi-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    A. A. Al-Ghamdi

    2012-01-01

    Full Text Available Hydrogen adsorption sites on pure multiwalled carbon nanotube (MWCNT and Mg-doped MWCNTs material system have been investigated using molecular dynamics (MD simulations as well as quantum chemical calculations. Through combining MWCNTs with Mg, the hydrogen adsorption sites energy on this Mg-MWCNTs system is found to be larger than that of the pure MWCNTs. Additionally, it was found that, through Mg-doping, new adsorption sites for hydrogen molecules are created in comparison with undoped nanotubes. It is also found that H atom is preferably adsorbed at every place near magnesium atom.

  2. Quantum yield and translational energy of hydrogen atoms

    Indian Academy of Sciences (India)

    TECS

    09) was determined by calibration method in which CH4 photolysis at 121⋅6 nm was used as a reference source of well-defined H atom concentrations. The line shapes of the measured H atom Doppler profiles indicate a Gaussian velocity ...

  3. Insights into the Hydrogen-Atom Transfer of the Blue Aroxyl.

    Science.gov (United States)

    Bächle, Josua; Marković, Marijana; Kelterer, Anne-Marie; Grampp, Günter

    2017-10-19

    An experimental and theoretical study on hydrogen-atom transfer dynamics in the hydrogen-bonded substituted phenol/phenoxyl complex of the blue aroxyl (2,4,6-tri-tert-butylphenoxyl) is presented. The experimental exchange dynamics is determined in different organic solvents from the temperature-dependent alternating line-width effect in the continuous-wave ESR spectrum. From bent Arrhenius plots, effective tunnelling contributions with parallel heavy-atom motion are concluded. To clarify the transfer mechanism, reaction paths for different conformers of the substituted phenol/phenoxyl complex are modelled theoretically. Various DFT and post-Hartree-Fock methods including multireference methods are applied. From the comparison of experimental and theoretical data it is concluded that the system favours concerted hydrogen-atom transfer along a parabolic reaction path caused by heavy-atom motion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Origin of the smaller conductances of Rh, Pb, and Co atomic junctions in hydrogen environment

    Science.gov (United States)

    Li, Xue; Chen, Mingyan; Ye, Xiang; Xie, Yi-qun; Ke, San-huang

    2015-02-01

    We study theoretically the structural and electronic origins of the smaller conductances (one conductance quantum, G0, and smaller) of Rh, Pb, and Co metal atomic junctions (MAJs) in a hydrogen environment, as were measured in recent experiments. For the Rh MAJs, the 1G0 conductance is attributed to a stable contact bridged by a single hydrogen molecule whose antibonding state provides a single transport channel. For the Pb and Co MAJs the 1G0 conductance is, however, ascribed to a linear atomic chain adsorbing two dissociated H atoms, which largely reduces the density of states at the Fermi energy with respect to the pure ones. On the other hand, the small conductances of 0.3G0 (Rh) and 0.2G0 (Co) are due to H-decorated atomic chains connected to electrodes by a H atom.

  5. Origin of the smaller conductances of Rh, Pb, and Co atomic junctions in hydrogen environment

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xue; Chen, Mingyan; Ye, Xiang; Xie, Yi-qun, E-mail: yqxie@shnu.edu.cn [Department of Physics, Shanghai Normal University, 100 Guilin Road, Shanghai 200232 (China); Ke, San-huang, E-mail: shke@tongji.edu.cn [MOE Key Laboratory of Advanced Microstructured Materials, School of Physics Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China)

    2015-02-14

    We study theoretically the structural and electronic origins of the smaller conductances (one conductance quantum, G{sub 0}, and smaller) of Rh, Pb, and Co metal atomic junctions (MAJs) in a hydrogen environment, as were measured in recent experiments. For the Rh MAJs, the 1G{sub 0} conductance is attributed to a stable contact bridged by a single hydrogen molecule whose antibonding state provides a single transport channel. For the Pb and Co MAJs the 1G{sub 0} conductance is, however, ascribed to a linear atomic chain adsorbing two dissociated H atoms, which largely reduces the density of states at the Fermi energy with respect to the pure ones. On the other hand, the small conductances of 0.3G{sub 0} (Rh) and 0.2G{sub 0} (Co) are due to H-decorated atomic chains connected to electrodes by a H atom.

  6. Derived properties from the dipole and generalized oscillator strength distributions of an endohedral confined hydrogen atom

    Science.gov (United States)

    Martínez-Flores, C.; Cabrera-Trujillo, R.

    2018-03-01

    We report the electronic properties of a hydrogen atom confined by a fullerene molecule by obtaining the eigenvalues and eigenfunctions of the time-independent Schrödinger equation by means of a finite-differences approach. The hydrogen atom confinement by a C60 fullerene cavity is accounted for by two model potentials: a square-well and a Woods–Saxon. The Woods–Saxon potential is implemented to study the role of a smooth cavity on the hydrogen atom generalized oscillator strength distribution. Both models characterize the cavity by an inner radius R 0, thickness Δ, and well depth V 0. We use two different values for R 0 and Δ, found in the literature, that characterize H@C60 to analyze the role of the fullerene cage size and width. The electronic properties of the confined hydrogen atom are reported as a function of the well depth V 0, emulating different electronic configurations of the endohedral cavity. We report results for the hyper-fine splitting, nuclear magnetic screening, dipole oscillator strength, the static and dynamic polarizability, mean excitation energy, photo-ionization, and stopping cross section for the confined hydrogen atom. We find that there is a critical potential well depth value around V 0 = 0.7 a.u. for the first set of parameters and around V 0 = 0.9 a.u. for the second set of parameters, which produce a drastic change in the electronic properties of the endohedral hydrogen system. These values correspond to the first avoided crossing on the energy levels. Furthermore, a clear discrepancy is found between the square-well and Woods–Saxon model potential results on the hydrogen atom generalized oscillator strength due to the square-well discontinuity. These differences are reflected in the stopping cross section for protons colliding with H@C60.

  7. The opening of the nationwide movement against atomic and hydrogen bombs in Japan : On the signature campaign against atomic and hydrogen bombs in 1954

    OpenAIRE

    宇吹, 暁

    1982-01-01

    The Signature Campaign against Atomic and Hydrogen bombs in 1954 caused the nationwide movement against A- and H-bombs in Japan. The purpose of this paper is to explicate characteristics of the Japanese movement against A- and H-bombs through the examination of the Signature Campaign. Especially, this paper tries to show the following four points. 1. When the crew of the Daigo-Fukuryumaru received heavy doses of radiation in the hydrogen bomb test conducted by the United states on Bikini Atol...

  8. Hydrogen sulphide in cardiovascular system: A cascade from interaction between sulphur atoms and signalling molecules.

    Science.gov (United States)

    Wang, Ming-Jie; Cai, Wen-Jie; Zhu, Yi-Chun

    2016-05-15

    As a gasotransmitter, hydrogen sulphide exerts its extensive physiological and pathophysiological effects in mammals. The interaction between sulphur atoms and signalling molecules forms a cascade that modulates cellular functions and homeostasis. In this review, we focus on the signalling mechanism underlying the effect of hydrogen sulphide in the cardiovascular system and metabolism as well as the biological relevance to human diseases. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Nucleon polarizabilities: From Compton scattering to hydrogen atom

    OpenAIRE

    Hagelstein, Franziska; Miskimen, Rory; Pascalutsa, Vladimir

    2016-01-01

    We review the current state of knowledge of the nucleon polarizabilities and of their role in nucleon Compton scattering and in hydrogen spectrum. We discuss the basic concepts, the recent lattice QCD calculations and advances in chiral effective-field theory. On the experimental side, we review the ongoing programs aimed to measure the nucleon (scalar and spin) polarizabilities via the Compton scattering processes, with real and virtual photons. A great part of the review is devoted to the g...

  10. Exciting Nucleons in Compton Scattering and Hydrogen-Like Atoms

    OpenAIRE

    Hagelstein, Franziska

    2017-01-01

    This PhD thesis is devoted to the low-energy structure of the nucleon (proton and neutron) as seen through electromagnetic probes, e.g., electron and Compton scattering. The research presented here is based primarily on dispersion theory and chiral effective-field theory. The main motivation is the recent proton radius puzzle, which is the discrepancy between the classic proton charge radius determinations (based on electron-proton scattering and normal hydrogen spectroscopy) and the highly p...

  11. Surface Magnetism of Cobalt Nanoislands Controlled by Atomic Hydrogen.

    Science.gov (United States)

    Park, Jewook; Park, Changwon; Yoon, Mina; Li, An-Ping

    2017-01-11

    Controlling the spin states of the surface and interface is key to spintronic applications of magnetic materials. Here, we report the evolution of surface magnetism of Co nanoislands on Cu(111) upon hydrogen adsorption and desorption with the hope of realizing reversible control of spin-dependent tunneling. Spin-polarized scanning tunneling microscopy reveals three types of hydrogen-induced surface superstructures, 1H-(2 × 2), 2H-(2 × 2), and 6H-(3 × 3), with increasing H coverage. The prominent magnetic surface states of Co, while being preserved at low H coverage, become suppressed as the H coverage level increases, which can then be recovered by H desorption. First-principles calculations reveal the origin of the observed magnetic surface states by capturing the asymmetry between the spin-polarized surface states and identify the role of hydrogen in controlling the magnetic states. Our study offers new insights into the chemical control of magnetism in low-dimensional systems.

  12. An algebraic SU(1,1) solution for the relativistic hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-y-Romero, R.P. [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Apartado Postal 21-267, CP 04000, Coyoacan DF (Mexico)]. E-mail: rmr@hp.fciencias.unam.mx; Nunez-Yepez, H.N. [Departamento de Fisica, Universidad Autonoma Metropolitana, Unidad Iztapalapa, Apartado Postal 55-534, CP 09340, Iztapalapa DF (Mexico)]. E-mail: nyhn@xanum.uam.mx; Salas-Brito, A.L. [Laboratorio de Sistemas Dinamicos, Departamento de Ciencias Basicas, Universidad Autonoma Metropolitana, Unidad Azcapotzalco, Apartado Postal 21-267, CP 04000, Coyoacan DF (Mexico)]. E-mail: asb@correo.azc.uam.mx

    2005-05-23

    The bound eigenfunctions and spectrum of a Dirac hydrogen atom are found taking advantage of the SU(1,1) Lie algebra in which the radial part of the problem can be expressed. For defining the algebra we need to add to the description an additional angular variable playing essentially the role of a phase. The operators spanning the algebra are used for defining ladder operators for the radial eigenfunctions of the relativistic hydrogen atom and for evaluating its energy spectrum. The status of the Johnson-Lippman operator in this algebra is also investigated.

  13. Ground state of the hydrogen atom via Dirac equation in a minimal-length scenario

    Energy Technology Data Exchange (ETDEWEB)

    Antonacci Oakes, T.L.; Francisco, R.O.; Fabris, J.C.; Nogueira, J.A. [Universidade Federal do Espirito Santo, Departamento de Fisica, Vitoria (Brazil)

    2013-07-15

    In this work we calculate the correction to the ground state energy of the hydrogen atom due to contributions arising from the presence of a minimal length. The minimal-length scenario is introduced by means of modifying the Dirac equation through a deformed Heisenberg algebra (Kempf algebra). With the introduction of the Coulomb potential in the new Dirac energy operator, we calculate the energy shift of the ground state of the hydrogen atom in first order of the parameter related to the minimal length via perturbation theory. (orig.)

  14. Hydrogen trapping by solute atoms in Nb-Mo alloys as observed by the channelling method

    Energy Technology Data Exchange (ETDEWEB)

    Yagi, Eiichi; Nakamura, Shiho; Kano, Fumihisa; Kobayashi, Takane (Institute of Physical and Chemical Research, Wako, Saitama (Japan)); Watanabe, Kenyi; Fukai, Yuh (Chuo Univ., Tokyo (Japan). Dept. of Physics); Matsumoto, Takehiko (National Research Inst. for Metals, Tokyo (Japan))

    1989-01-01

    The enhancement of the terminal solubility for hydrogen (TSH) in group Va metals (V, Nb and Ta) on alloying with metal solute atoms has been reported for various alloying elements. To elucidate the mechanism of this enhancement, in the present study the lattice location of hydrogen was investigated by the channeling method using a nuclear reaction {sup 1}H({sup 11}B,{alpha}){alpha}{alpha} on the Nb alloys containing undersized Mo atoms (Nb-3at%Mo alloys). (orig./MM).

  15. The long-range interaction in the scattering of positronium by hydrogen atoms

    Science.gov (United States)

    Meredith, D. G.; Fraser, P. A.

    2018-03-01

    Elastic scattering of positronium by hydrogen atoms is investigated. A method is devised wherein the effects of the long-range van der Waals attraction between the two atoms are accurately incorporated into a trial wave function in the form of a pseudo-state. The properly adjusted trial function yields a van der Waals coefficient that is within 0.03% of the known value. Improved phase shifts in the absence of exchange are reported.

  16. Shared symmetries of the hydrogen atom and the two-bit system

    Science.gov (United States)

    Rau, A. R. P.; Alber, G.

    2017-12-01

    The hydrogen atom is the simplest system of atomic and molecular physics, while a two-qubit system is the simplest of quantum information. Remarkably, they share common symmetry aspects which are described in this paper, based on a correspondence between the four-dimensional unitary group and the six-dimensional rotational group with its non-compact extensions. Both systems involve 15 basic operators. Reductions to Lorentz and Poincare space–time group symmetries of a free particle are also discussed.

  17. Behavior of hydrogen atoms in boron films during H{sub 2} and He glow discharge and thermal desorption

    Energy Technology Data Exchange (ETDEWEB)

    Tsuzuki, K.; Natsir, M.; Inoue, N. [and others

    1995-09-01

    Hydrogen absorption and desorption characteristics in boron films deposited on a graphite liner have been studied. Number of hydrogen atoms absorbed in the films is estimated from a decrease in hydrogen pressure during a hydrogen glow discharge. It was 1.9 x 10{sup 17} atoms/cm{sup 2} in the 1 hour discharge after an evacuation of H atoms contained in the original boron films by thermal desorption. Hydrogen atoms were absorbed continuously without saturation for 3 hours during the discharge. Number of H atoms absorbed reached to 2.6 x 10{sup 17} atoms/cm{sup 2} at 3 hour. A discharge in helium was carried out to investigate H desorption characteristics from hydrogen implanted boron films. It was verified that reactivity for hydrogen absorption was recovered after the He discharge. Hydrogen atoms were accumulated in the films by repetition of alternate He and H{sub 2} discharge. Thermal desorption experiments have been carried out by raising the liner temperature up to 500degC for films after 1 hour, 3 hours hydrogen discharge and 6 times repetition of H{sub 2}/He discharges. Most of H atoms in the films were desorbed for all these cases. The slow absorption process was confirmed through the thermal desorption experiments. (author).

  18. Atomic hydrogen induced defect kinetics in amorphous silicon

    NARCIS (Netherlands)

    Peeters, F. J. J.; Zheng, J.; Aarts, I. M. P.; Pipino, A. C. R.; Kessels, W. M. M.; van de Sanden, M. C. M.

    2017-01-01

    Near-infrared evanescent-wave cavity ring-down spectroscopy (CRDS) has been applied to study the defect evolution in an amorphous silicon (a-Si:H) thin film subjected to a directed beam of atomic H with a flux of (0.4–2) × 1014 cm−2 s−1. To this end, a 42 ± 2 nm a-Si:H film was grown on the total

  19. Methane Formation by Flame-Generated Hydrogen Atoms in the Flame Ionization Detector

    DEFF Research Database (Denmark)

    Holm, Torkil; Madsen, Jørgen Øgaard

    1996-01-01

    The precombustion degradation of organic compounds in the flame ionization detector has been studied (1) by heating the additives in hydrogen in a quartz capillary and analyzing the reaction products by GC and (2) by following the degradation of the additives in a hydrogen flame, by means of a thin......, and conceivably all hydrocarbons are quantitatively converted into methane at temperatures below 600 C, that is, before the proper combustion has started. The splitting of the C-C bonds is preceded by hydrogenation of double and triple bonds and aromatic rings. The reactions, no doubt, are caused by hydrogen...... atoms, which are formed in the burning hydrogen and which diffuse into the inner core of the flame. The quantitative formation of methane appears to explain the "equal per carbon" rule for the detector response of hydrocarbons, since all carbons are "exchanged" for methane molecules....

  20. Sticking probability for hydrogen atoms on the surface of liquid /sup 4/He

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, D.S.; Berlinsky, A.J.

    1983-03-01

    A calculation is presented of the sticking probability for hydrogen atoms colliding with a liquid /sup 4/He surface. The calculation is based on a model potential for the H-liquid /sup 4/He interaction which is used to derive both bound and free atom wave function and the linear H atom-ripplon coupling. Results are presented in terms of the energy and angle dependent sticking probability s(E,THETA) and the thermally averaged probability s(T), and comparison is made to the experimental results s(T)=0.035 +-0.00 for 0.18 < T < 0.27 K.

  1. Low-energy measurements of electron capture by multicharged ions from excited hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Havener, C.C. (Oak Ridge National Laboratory, Oak Ridge, Tennesse 37831-6372 (United States)); Haque, M.A. (Alcorn State University, Lorman, Mississippi 39096 (United States)); Smith, A.C.H. (University College London, WC1E 6BT (United Kingdom)); Urbain, X. (Universite Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve (Belgium)); Zeijlmans van Emmichoven, P.A. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, Tennessee 37831-6374 (United States))

    1993-06-05

    For very low collision energies electron capture from excited hydrogen by multicharged ions is characterized by enormous cross sections, the predicted maximum being comparable to the geometric size of the Rydberg atom. The ion-atom merged-beams technique is being used to study these collisions for the variety of charge states and the wide range of energies (0.1 to 1000 eV/amu) accessible to the apparatus. A neutral D beam containing a Rydberg atom population proportional to 1/n[sup 3] is produced by collisional electron detachment of 8 keV D[sup [minus

  2. Transformation of Tertiary Benzyl Alcohols into the Vicinal Halo-Substituted Derivatives Using N-Halosuccinimides

    Directory of Open Access Journals (Sweden)

    Njomza Ajvazi

    2016-10-01

    Full Text Available The efficiency of direct conversion of tertiary alcohols bearing a β-hydrogen atom to vicinal halohydrins—chlorohydrins and bromohydrins—under green reaction conditions was tested preliminarily on model tertiary benzyl alcohols. Tertiary alcohols were successfully directly halogenated to vicinal halohydrins with N-halosuccinimide in aqueous media. The efficiency of the reaction in water was significantly improved in the presence of sodium dodecyl sulphate as the surfactant.

  3. Learning about Regiochemistry from a Hydrogen-Atom Abstraction Reaction in Water

    Science.gov (United States)

    Sears-Dundes, Christopher; Huon, Yoeup; Hotz, Richard P.; Pinhas, Allan R.

    2011-01-01

    An experiment has been developed in which the hydrogen-atom abstraction and the coupling of propionitrile, using Fenton's reagent, are investigated. Students learn about the regiochemistry of radical formation, the stereochemistry of product formation, and the interpretation of GC-MS data, in a safe reaction that can be easily completed in one…

  4. Quantum dynamics of hydrogen atoms on graphene. I. System-bath modeling

    Energy Technology Data Exchange (ETDEWEB)

    Bonfanti, Matteo, E-mail: matteo.bonfanti@unimi.it [Dipartimento di Chimica, Università degli Studi di Milano, v. Golgi 19, 20133 Milano (Italy); Jackson, Bret [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Hughes, Keith H. [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Burghardt, Irene [Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main (Germany); Martinazzo, Rocco, E-mail: rocco.martinazzo@unimi.it [Dipartimento di Chimica, Università degli Studi di Milano, v. Golgi 19, 20133 Milano (Italy); Istituto di Scienze e Tecnologie Molecolari, Consiglio Nazionale delle Richerche, v. Golgi 19, 20133 Milano (Italy)

    2015-09-28

    An accurate system-bath model to investigate the quantum dynamics of hydrogen atoms chemisorbed on graphene is presented. The system comprises a hydrogen atom and the carbon atom from graphene that forms the covalent bond, and it is described by a previously developed 4D potential energy surface based on density functional theory ab initio data. The bath describes the rest of the carbon lattice and is obtained from an empirical force field through inversion of a classical equilibrium correlation function describing the hydrogen motion. By construction, model building easily accommodates improvements coming from the use of higher level electronic structure theory for the system. Further, it is well suited to a determination of the system-environment coupling by means of ab initio molecular dynamics. This paper details the system-bath modeling and shows its application to the quantum dynamics of vibrational relaxation of a chemisorbed hydrogen atom, which is here investigated at T = 0 K with the help of the multi-configuration time-dependent Hartree method. Paper II deals with the sticking dynamics.

  5. A theoretical perspective of the nature of hydrogen-bond types - the atoms in molecules approach

    Czech Academy of Sciences Publication Activity Database

    Pandiyan, B. V.; Kolandaivel, P.; Deepa, Palanisamy

    2014-01-01

    Roč. 112, č. 12 (2014), s. 1609-1623 ISSN 0026-8976 Institutional support: RVO:61388963 Keywords : hydrogen bond * proton affinity * deprotanation enthalpy * atoms in molecules * chemical shift Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.720, year: 2014

  6. Relativistic Approach to the Hydrogen Atom in a Minimal Length Scenario

    Energy Technology Data Exchange (ETDEWEB)

    Francisco, Ronald Oliveira; Oakes, Thiago Luiz Antonacci; Fabris, Julio Cesar; Nogueira, Jose Alexandre, E-mail: jose.nogueira@ufes.br [Universidade Federal do Espirito Santo (UFES), Vitoria, ES (Brazil). Departamento de Fisica

    2014-07-01

    We show that relativistic contributions to the ground-state energy of the hydrogen atom from a minimal length introduced by a Lorentz-covariant algebra are more important than non-relativistic contributions; the nonrelativistic approach is therefore unsuitable. We compare our result with experimental data to estimate an upper bound of the order 10{sup -20}m for the minimal length. (author)

  7. High-magnetic-field-assisted scattering of electrons with atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Ajoy [Laban Hrad Vidyapith, AD-369, Salt Lake City, Kolkata 700064 (India)

    2007-04-28

    We have investigated quantum mechanically the scattering of electrons off atomic hydrogen in a strong magnetic field. Elastic, inelastic, backward and total scattering cross sections are reported. Near-resonance behaviour of the system is analysed. Results are presented after evaluating and summing all-order Born series under suitable physical conditions.

  8. Pregalactic black hole formation with an atomic hydrogen equation of state

    NARCIS (Netherlands)

    Spaans, Marco; Silk, Joseph

    2006-01-01

    The polytropic equation of state of an atomic hydrogen gas is examined for primordial halos with baryonic masses of M-h similar to 10(7)-10(9) M-circle dot. For roughly isothermal collapse around 10(4) K, we find that line trapping of Ly alpha (H I and He II) photons causes the polytropic exponent

  9. Laboratory Measurements of Charge Transfer on Atomic Hydrogen at Thermal Energies

    Science.gov (United States)

    Havener, C. C.; Vane, C. R.; Krause, H. F.; Stancil, P. C.; Mroczkowski, T.; Savin, D. W.

    2002-01-01

    We describe our ongoing program to measure velocity dependent charge transfer (CT) cross sections for selected ions on atomic hydrogen using the ion-aloin merged-beams apparatus at Oak Ridge Natioiial Laboralory. Our focus is on those ions for which CT plays an important role in determining the ionization structure, line emis sion, and thermal structure of observed cosmic photoionized plasmas.

  10. Determination of the Relative Atomic Masses of Metals by Liberation of Molecular Hydrogen

    Science.gov (United States)

    Waghorne, W. Earle; Rous, Andrew J.

    2009-01-01

    Students determine the relative atomic masses of calcium, magnesium, and aluminum by reaction with hydrochloric acid and measurement of the volume of hydrogen gas liberated. The experiment demonstrates stoichiometry and illustrates clearly that mass of the reagent is not the determinant of the amounts in chemical reactions. The experiment is…

  11. Most Typical 12 Resonant Perturbation of the Hydrogen Atom by Weak Electric and Magnetic Fields

    NARCIS (Netherlands)

    Efstathiou, K.; Lukina, O. V.; Sadovskii, D. A.

    2008-01-01

    We study a perturbation of the hydrogen atom by small homogeneous static electric and magnetic fields in a specific mutual alignment with angle approximately pi/3 which results in the 12 resonance of the linearized Keplerian n-shell approximation. The bifurcation diagram of the classical integrable

  12. Effect of vacuum polarization on the excitation of hydrogen atom by electron impact

    Directory of Open Access Journals (Sweden)

    Sujata Bhattacharyya

    1981-01-01

    for 1S−2S excitation of the hydrogen atom by electron impact. The excitation amplitude calculated field theoretically is found to be lowered by 0.47t2/(t2+93 where t2=4|P−Q|2, P and Q being the momenta of the incident and scattered electrons respectively.

  13. Insights into the Electronic Structure of Ozone and Sulfur Dioxide from Generalized Valence Bond Theory: Addition of Hydrogen Atoms.

    Science.gov (United States)

    Lindquist, Beth A; Takeshita, Tyler Y; Dunning, Thom H

    2016-05-05

    Ozone (O3) and sulfur dioxide (SO2) are valence isoelectronic species, yet their properties and reactivities differ dramatically. In particular, O3 is highly reactive, whereas SO2 is chemically relatively stable. In this paper, we investigate serial addition of hydrogen atoms to both the terminal atoms of O3 and SO2 and to the central atom of these species. It is well-known that the terminal atoms of O3 are much more amenable to bond formation than those of SO2. We show that the differences in the electronic structure of the π systems in the parent triatomic species account for the differences in the addition of hydrogen atoms to the terminal atoms of O3 and SO2. Further, we find that the π system in SO2, which is a recoupled pair bond dyad, facilitates the addition of hydrogen atoms to the sulfur atom, resulting in stable HSO2 and H2SO2 species.

  14. Graphene oxide/metal nanocrystal multilaminates as the atomic limit for safe and selective hydrogen storage.

    Science.gov (United States)

    Cho, Eun Seon; Ruminski, Anne M; Aloni, Shaul; Liu, Yi-Sheng; Guo, Jinghua; Urban, Jeffrey J

    2016-02-23

    Interest in hydrogen fuel is growing for automotive applications; however, safe, dense, solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However, hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new, environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material, protected from oxygen and moisture by the rGO layers, exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin, this approach minimizes inactive mass in the composite, while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.

  15. Electrical and Surface Properties of InAs/InSb Nanowires Cleaned by Atomic Hydrogen.

    Science.gov (United States)

    Webb, James L; Knutsson, Johan; Hjort, Martin; Gorji Ghalamestani, Sepideh; Dick, Kimberly A; Timm, Rainer; Mikkelsen, Anders

    2015-08-12

    We present a study of InAs/InSb heterostructured nanowires by X-ray photoemission spectroscopy (XPS), scanning tunneling microscopy (STM), and in-vacuum electrical measurements. Starting with pristine nanowires covered only by the native oxide formed through exposure to ambient air, we investigate the effect of atomic hydrogen cleaning on the surface chemistry and electrical performance. We find that clean and unreconstructed nanowire surfaces can be obtained simultaneously for both InSb and InAs by heating to 380 ± 20 °C under an H2 pressure 2 × 10(-6) mbar. Through electrical measurement of individual nanowires, we observe an increase in conductivity of 2 orders of magnitude by atomic hydrogen cleaning, which we relate through theoretical simulation to the contact-nanowire junction and nanowire surface Fermi level pinning. Our study demonstrates the significant potential of atomic hydrogen cleaning regarding device fabrication when high quality contacts or complete control of the surface structure is required. As hydrogen cleaning has recently been shown to work for many different types of III-V nanowires, our findings should be applicable far beyond the present materials system.

  16. Controlling residual hydrogen gas in mass spectra during pulsed laser atom probe tomography.

    Science.gov (United States)

    Kolli, R Prakash

    2017-01-01

    Residual hydrogen (H2) gas in the analysis chamber of an atom probe instrument limits the ability to measure H concentration in metals and alloys. Measuring H concentration would permit quantification of important physical phenomena, such as hydrogen embrittlement, corrosion, hydrogen trapping, and grain boundary segregation. Increased insight into the behavior of residual H2 gas on the specimen tip surface in atom probe instruments could help reduce these limitations. The influence of user-selected experimental parameters on the field adsorption and desorption of residual H2 gas on nominally pure copper (Cu) was studied during ultraviolet pulsed laser atom probe tomography. The results indicate that the total residual hydrogen concentration, HTOT, in the mass spectra exhibits a generally decreasing trend with increasing laser pulse energy and increasing laser pulse frequency. Second-order interaction effects are also important. The pulse energy has the greatest influence on the quantity HTOT, which is consistently less than 0.1 at.% at a value of 80 pJ.

  17. Rotating disk atomization of Gd and Gd-Y for hydrogen liquefaction via magnetocaloric cooling

    Energy Technology Data Exchange (ETDEWEB)

    Slinger, Tyler [Iowa State Univ., Ames, IA (United States)

    2016-12-17

    In order to enable liquid hydrogen fuel cell technologies for vehicles the cost of hydrogen liquefaction should be lowered. The current method of hydrogen liquefaction is the Claude cycle that has a figure of merit (FOM) of 0.3-0.35. New magnetocaloric hydrogen liquefaction devices have been proposed with a FOM>0.5, which is a significant improvement. A significant hurdle to realizing these devices is the synthesis of spherical rare earth based alloy powders of 200μm in diameter. In this study a centrifugal atomization method that used a rotating disk with a rotating oil quench bath was developed to make gadolinium and gadolinium-yttrium spheres. The composition of the spherical powders included pure Gd and Gd0.91Y0.09. The effect of atomization parameters, such as superheat, melt properties, disk shape, disk speed, and melt system materials and design, were investigated on the size distribution and morphology of the resulting spheres. The carbon, nitrogen, and oxygen impurity levels also were analyzed and compared with the magnetic performance of the alloys. The magnetic properties of the charge material as well as the resulting powders were measured using a vibrating sample magnetometer. The saturation magnetization and Curie temperature were the target properties for the resulting spheres. These values were compared with measurements taken on the charge material in order to investigate the effect of atomization processing on the alloys.

  18. Theoretical realization of cluster-assembled hydrogen storage materials based on terminated carbon atomic chains.

    Science.gov (United States)

    Liu, Chun-Sheng; An, Hui; Guo, Ling-Ju; Zeng, Zhi; Ju, Xin

    2011-01-14

    The capacity of carbon atomic chains with different terminations for hydrogen storage is studied using first-principles density functional theory calculations. Unlike the physisorption of H(2) on the H-terminated chain, we show that two Li (Na) atoms each capping one end of the odd- or even-numbered carbon chain can hold ten H(2) molecules with optimal binding energies for room temperature storage. The hybridization of the Li 2p states with the H(2)σ orbitals contributes to the H(2) adsorption. However, the binding mechanism of the H(2) molecules on Na arises only from the polarization interaction between the charged Na atom and the H(2). Interestingly, additional H(2) molecules can be bound to the carbon atoms at the chain ends due to the charge transfer between Li 2s2p (Na 3s) and C 2p states. More importantly, dimerization of these isolated metal-capped chains does not affect the hydrogen binding energy significantly. In addition, a single chain can be stabilized effectively by the C(60) fullerenes termination. With a hydrogen uptake of ∼10 wt.% on Li-coated C(60)-C(n)-C(60) (n = 5, 8), the Li(12)C(60)-C(n)-Li(12)C(60) complex, keeping the number of adsorbed H(2) molecules per Li and stabilizing the dispersion of individual Li atoms, can serve as better building blocks of polymers than the (Li(12)C(60))(2) dimer. These findings suggest a new route to design cluster-assembled hydrogen storage materials based on terminated sp carbon chains.

  19. Relativistic spectrum of hydrogen atom in the space-time non-commutativity

    Energy Technology Data Exchange (ETDEWEB)

    Moumni, Mustafa; BenSlama, Achour; Zaim, Slimane [Matter Sciences Department, Faculty of SE and SNV, University of Biskra (Algeria); Laboratoire de Physique Mathematique et Subatomique, Mentouri University, Constantine (Algeria); Matter Sciences Department, Faculty of Sciences, University of Batna (Algeria)

    2012-06-27

    We study space-time non-commutativity applied to the hydrogen atom and its phenomenological effects. We find that it modifies the Coulomb potential in the Hamiltonian and add an r{sup -3} part. By calculating the energies from Dirac equation using perturbation theory, we study the modifications to the hydrogen spectrum. We find that it removes the degeneracy with respect to the total angular momentum quantum number and acts like a Lamb shift. Comparing the results with experimental values from spectroscopy, we get a new bound for the space-time non-commutative parameter.

  20. Dynamics of a Rydberg hydrogen atom near a metal surface in the electron-extraction scheme

    Energy Technology Data Exchange (ETDEWEB)

    Iñarrea, Manuel [Área de Física Aplicada, Universidad de La Rioja, Logroño (Spain); Lanchares, Víctor [Departamento de Matemáticas y Computación, Universidad de La Rioja, Logroño, La Rioja (Spain); Palacián, Jesús [Departamento de Ingeniería Matemática e Informática, Universidad Pública de Navarra, Pamplona (Spain); Pascual, Ana I. [Departamento de Matemáticas y Computación, Universidad de La Rioja, Logroño, La Rioja (Spain); Salas, J. Pablo, E-mail: josepablo.salas@unirioja.es [Área de Física Aplicada, Universidad de La Rioja, Logroño (Spain); Yanguas, Patricia [Departamento de Ingeniería Matemática e Informática, Universidad Pública de Navarra, Pamplona (Spain)

    2015-01-23

    We study the classical dynamics of a Rydberg hydrogen atom near a metal surface in the presence of a constant electric field in the electron-extraction situation [1], e.g., when the field attracts the electron to the vacuum. From a dynamical point of view, this field configuration provides a dynamics richer than in the usual ion-extraction scheme, because, depending on the values of field and the atom–surface distance, the atom can be ionized only towards the metal surface, only to the vacuum or to the both sides. The evolution of the phase space structure as a function of the atom–surface distance is explored in the bound regime of the atom. In the high energy regime, the ionization mechanism is also investigated. We find that the classical results of this work are in good agreement with the results obtained in the wave-packet propagation study carried out by So et al. [1]. - Highlights: • We study a classical hydrogen atom near a metal surface plus a electric field. • We explore the phase space structure as a function of the field strength. • We find most of the electronic orbits are oriented along the field direction. • We study the ionization of the atom for several atom–surface distances. • This classical study is in good agreement with the quantum results.

  1. An Atomistic Tomographic Study of Oxygen and Hydrogen Atoms and their Molecules in CVD Grown Graphene.

    Science.gov (United States)

    Baik, Sung-Il; Ma, Lulu; Kim, Yoon-Jun; Li, Bo; Liu, Mingjie; Isheim, Dieter; Yakobson, Boris I; Ajayan, Pulickel M; Seidman, David N

    2015-11-25

    The properties and growth processes of graphene are greatly influenced by the elemental distributions of impurity atoms and their functional groups within or on the hexagonal carbon lattice. Oxygen and hydrogen atoms and their functional molecules (OH, CO, and CO2 ) positions' and chemical identities are tomographically mapped in three dimensions in a graphene monolayer film grown on a copper substrate, at the atomic part-per-million (atomic ppm) detection level, employing laser assisted atom-probe tomography. The atomistic plan and cross-sectional views of graphene indicate that oxygen, hydrogen, and their co-functionalities, OH, CO, and CO2 , which are locally clustered under or within the graphene lattice. The experimental 3D atomistic portrait of the chemistry is combined with computational density-functional theory (DFT) calculations to enhance the understanding of the surface state of graphene, the positions of the chemical functional groups, their interactions with the underlying Cu substrate, and their influences on the growth of graphene. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A first-principle study on adsorption of atomic hydrogen on the two-dimensional hexagonal boron nitride monolayer

    Science.gov (United States)

    Hao, Ruirui; Shi, Jianzhang; Zhu, Lin; Ji, Linan; Sun, Tianye; Feng, Shujian

    2017-11-01

    The hydrogenation of the two-dimensional hexagonal boron nitride (H: h-BN) monolayer and electronic properties of hydride are studied in details based on dispersion-corrected density function theory (DFT-D). Particular attention has been fixed on the most favorable site, and on aggregation states, as well as the migration barrier for a hydrogen atom hopping on the 2D h-BN surface. In general, chemisorbed hydrogen atoms on the top of boron will stretch the Bsbnd N bonds nearby, but never break them. The migration of a hydrogen atom on the h-BN surface is prefer to be over the honeycomb sites, but it becomes difficult with the increase of adsorbed hydrogen atoms. Furthermore, adsorbed multiple hydrogen atoms are likely to move close to each other, and to form a hydrogen domain. Hence the 2D h-BN monolayers possesses stable and high-density hydrogen storage properties with single side. In additions, a process of hydrogenation is presented.

  3. On the treatment of ℓ-changing proton-hydrogen Rydberg atom collisions

    Science.gov (United States)

    Vrinceanu, D.; Onofrio, R.; Sadeghpour, H. R.

    2017-11-01

    Energy-conserving, angular momentum changing collisions between protons and highly excited Rydberg hydrogen atoms are important for precise understanding of atomic recombination at the photon decoupling era and the elemental abundance after primordial nucleosynthesis. Early approaches to ℓ-changing collisions used perturbation theory only for dipole-allowed (Δℓ = ±1) transitions. An exact non-perturbative quantum mechanical treatment is possible, but it comes at a computational cost for highly excited Rydberg states. In this paper, we show how to obtain a semiclassical limit that is accurate and simple, and develop further physical insights afforded by the non-perturbative quantum mechanical treatment.

  4. Survival of metastable hydrogen atoms passing through crossed electric and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Robert, J.; Miniatura, C.; Perales, F.; Vassilev, G.; Reinhardt, J.; Baudon, J. (Paris-13 Univ., 93 - Villetaneuse (FR)); Bocvarski, V. (Belgrade Univ. (YU) Inst. Za Fiziku); Lorent, V. (Louvain Univ., Louvain-La-Neuve (BE). Inst. de Physique)

    1989-08-01

    In the present experiment, the motional electric field responsible for the quenching (and polarization) of metastable hydrogen atoms passing through a magnetic field, is compensated, for a prescribed atomic velocity, by a static electric field. The resulting continuous velocity selection has been tested over a wide range of velocities ((5/40) km/s). The relative velocity dispersion ranges from 5% at 40 km/s, to 22% at 5 km/s. As is confirmed by a calculation, the resolution is mainly determined by the quality of the matching of the two field profiles.

  5. Observation of nuclear spin waves in spin-polarized atomic hydrogen gas

    Energy Technology Data Exchange (ETDEWEB)

    Johson, B.R.; Denker, J.S.; Bigelow, N.; Levy, L.P.; Freed, J.H.; Lee, D.M.

    1984-04-23

    We have observed narrow, distinct resonances in the NMR spectrum of dilute spin-polarized atomic hydrogen gas (nroughly-equal10/sup 16/ atoms/cm/sup 3/). The dependence of the observed spectra on temperature, density, polarization, and magnetic field gradient is consistent with theoretical predictions for spin-wave excitations damped by diffusion. We have measured the parameter ..mu.., which is a measure of the importance of exchange effects in spin transport processes, and the diffusion coefficient D/sub 0/, both of which are in reasonable agreement with theory.

  6. Palladium-Catalyzed Atom-Transfer Radical Cyclization at Remote Unactivated C(sp3)-H Sites: Hydrogen-Atom Transfer of Hybrid Vinyl Palladium Radical Intermediates.

    Science.gov (United States)

    Ratushnyy, Maxim; Parasram, Marvin; Wang, Yang; Gevorgyan, Vladimir

    2018-03-01

    A novel mild, visible-light-induced palladium-catalyzed hydrogen atom translocation/atom-transfer radical cyclization (HAT/ATRC) cascade has been developed. This protocol involves a 1,5-HAT process of previously unknown hybrid vinyl palladium radical intermediates, thus leading to iodomethyl carbo- and heterocyclic structures. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Interstitial modification of palladium nanoparticles with boron atoms as a green catalyst for selective hydrogenation

    Science.gov (United States)

    Chan, Chun Wong Aaron; Mahadi, Abdul Hanif; Li, Molly Meng-Jung; Corbos, Elena Cristina; Tang, Chiu; Jones, Glenn; Kuo, Winson Chun Hsin; Cookson, James; Brown, Christopher Michael; Bishop, Peter Trenton; Tsang, Shik Chi Edman

    2014-12-01

    Lindlar catalysts comprising of palladium/calcium carbonate modified with lead acetate and quinoline are widely employed industrially for the partial hydrogenation of alkynes. However, their use is restricted, particularly for food, cosmetic and drug manufacture, due to the extremely toxic nature of lead, and the risk of its leaching from catalyst surface. In addition, the catalysts also exhibit poor selectivities in a number of cases. Here we report that a non-surface modification of palladium gives rise to the formation of an ultra-selective nanocatalyst. Boron atoms are found to take residence in palladium interstitial lattice sites with good chemical and thermal stability. This is favoured due to a strong host-guest electronic interaction when supported palladium nanoparticles are treated with a borane tetrahydrofuran solution. The adsorptive properties of palladium are modified by the subsurface boron atoms and display ultra-selectivity in a number of challenging alkyne hydrogenation reactions, which outclass the performance of Lindlar catalysts.

  8. Transport Properties of Spin-Polarized Atomic Hydrogen Using Generalized Scattering Theory

    Science.gov (United States)

    Joudeh, B. R.; Sandouqa, A. S.

    2018-02-01

    Our results for the scattering and thermophysical properties of spin-polarized atomic hydrogen (H{\\downarrow }) have been presented in the temperature range 0.01-10 K using the Galitskii-Migdal-Feynman formalism. These results include the quantum second virial coefficient, the average total and viscosity cross sections, the viscosity, the diffusion coefficient, and the thermal conductivity. The calculations have been undertaken using three triplet-state potentials: Morse-type, Silvera and Born-Oppenheimer potentials. The Morse potential is less attractive and very simple, but less accurate to describe spin-polarized atomic hydrogen. That explains the differences between it and the other two potentials, which are clearly better. From the results of the average total cross sections, it is concluded the H{\\downarrow } remains a gas even at low temperature. The viscosity, the thermal conductivity, and the diffusion coefficients of H{\\downarrow } increase in all cases with increasing temperature.

  9. Optical potential studies on positron scattering by hydrogenic-type atoms

    Energy Technology Data Exchange (ETDEWEB)

    Ratnavelu, Kuru E-mail: kuru@mail.nhu.ou.edu; Kamali, M.Z.M.; Ng, S.Y

    2002-05-01

    In this report, we will present the work that has been done using the coupled-channels-optical method for positron scattering by atomic hydrogen and atomic lithium at low intermediate energies. The method allows the simultaneous treatment of the target channels and the Positronium (Ps) channels in the close-coupling method and the incorporation of the continuum effects via an optical potential method. Our latest calculations using the CCO(6,3) for positron-hydrogen system for energies ranging from 13.8 to 40 eV will be presented. For the positron-lithium system, we will report our initial findings for energies ranging from 6 to 20 eV using the CCO(2,3) model. Ionization, Ps formation, total cross-sections and differential cross-sections are presented.

  10. A tabulation of the bound-state energies of atomic hydrogen

    CERN Document Server

    Horbatsch, M

    2016-01-01

    We present tables for the bound-state energies for atomic hydrogen. The tabulated energies include the hyperfine structure, and thus this work extends the work of Rev. Mod. Phys. {\\bf 84}, 1527 (2012), which excludes hyperfine structure. The tabulation includes corrections of the hyperfine structure due to the anomalous moment of the electron, due to the finite mass of the proton, and due to off-diagonal matrix elements of the hyperfine Hamiltonian. These corrections are treated incorrectly in most other works. Simple formulas valid for all quantum numbers are presented for the hyperfine corrections. The tabulated energies have uncertainties of less than 1 kHz for all states. This accuracy is possible because of the recent precision measurement [Nature, {\\bf 466}, 213 (2010); Science, {\\bf 339}, 417] of the proton radius. The effect of this new radius on the energy levels is also tabulated, and the energies are compared to precision measurements of atomic hydrogen energy intervals.

  11. The reaction of hydrogen atoms with hydrogen peroxide as a function of temperature

    DEFF Research Database (Denmark)

    Lundström, T.; Christensen, H.; Sehested, K.

    2001-01-01

    The temperature dependence for the reaction of H atoms with H2O2 at pH 1 has been determined using pulse radiolysis technique. The reaction was studied in the temperature range 10-120 degreesC. The rate constant at 25 degreesC was found to be 5.1 +/- 0.5 x 10(7) dm(3) mol(-1) s(-1) and the activa...

  12. Direct time-resolved spectroscopic investigation of intramolecular hydrogen atom transfer of deoxyblebbistatin

    Science.gov (United States)

    Li, Ming-De; Zhu, Ruixue; Lee Phillips, David

    2017-09-01

    The photophysics and photochemistry of deoxyblebbistatin was investigated using femtosecond time-resolved transient absorption spectroscopy. An ultrafast intramolecular hydrogen atom transfer (IHAT) appears to take place via the first singlet excited state of deoxyblebbistatin within 8 ps. Absorption and fluorescence photochemical results indicate the IHAT process leads to mainly conversion of deoxyblebbistatin into an enol form final product which was observed and characterized by resonance Raman spectroscopy.

  13. Precision measurement of the 1S-2S transition in atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Parthey, Christian G.; Matveev, Arthur; Alnis, Janis; Beyer, Axel; Kolachevsky, Nikolai; Pohl, Randolf; Udem, Thomas [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Haensch, Theodor W. [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet, 80799 Muenchen (Germany)

    2011-07-01

    Precision spectroscopy of the 1S-2S transition in atomic hydrogen has been used to test quantum electrodynamics (QED), determine the Rydberg constant and the proton charge radius. It can also be used to set limits on possible Lorentz-boost invariance violations. Here we report on a new measurement of the 1S-2S transition pushing the uncertainty to the 10{sup -15} level.

  14. Atomic Hydrogen Properties of AGN Host Galaxies: HI in 16 NUclei of GAlaxies (NUGA) Sources

    OpenAIRE

    S. de Haan; Schinnerer, E.; Mundell, C. G.; Garcia-Burillo, S.; Combes, F.

    2007-01-01

    We present a comprehensive spectroscopic imaging survey of the distribution and kinematics of atomic hydrogen (HI) in 16 nearby spiral galaxies hosting low luminosity AGN, observed with high spectral and spatial resolution (resolution: ~20 arcsec, 5 km/s) using the NRAO Very Large Array (VLA). The sample contains a range of nuclear types, ranging from Seyfert to star-forming nuclei and was originally selected for the NUclei of GAlaxies project (NUGA) - a spectrally and spatially resolved inte...

  15. Chemical structure of descriptors with an active hydrogen atom in certain bioregulators.

    Science.gov (United States)

    Kurchii, B A

    1996-01-01

    The chemical structure of descriptors (D) for some plant growth regulators (PGR), herbicides, pesticides and drugs is described. The presence of an active hydrogen atom in molecules is an essential factor determining biological activity of chemicals. The results obtained from the study of dependence existing between the structure of a certain substance and its biological activity may be used in designing of novel compounds which possess in biological activity.

  16. Regularity and Chaos in the Hydrogen Atom Highly Excited with a Strong Magnetic Field

    Directory of Open Access Journals (Sweden)

    M. Amdouni

    2014-01-01

    Full Text Available The effects of the relativistic corrections on the energy spectra are analyzed. Effective simulations based on manipulations of operators in the Sturmian basis are developed. Discrete and continuous energy spectra of a hydrogen atom with realistic nucleus mass in a strong magnetic field are computed. The transition from regularity to chaos in diamagnetic problem with the effect of the nucleus recoil energy is explored. Anticrossing of energy levels is observed for strong magnetic field.

  17. Proton and hydrogen atom detection efficiency of resistance strip magnetic electron multiplier particle-counting system

    Energy Technology Data Exchange (ETDEWEB)

    Wehrenberg, P.J.; Clark, K.C.

    1976-10-01

    The absolute detection efficiency for protons and for hydrogen atoms in the energy range 5--60 keV is determined for a resistance strip magnetic electron multiplier particle-counting system. Significant history-dependent gain variations are discussed. The detector system is suitable for use in coincidence experiments requiring particle-counting rates to 1.0 MHz and timing accuracies of 3.0 nsec. (AIP)

  18. Thresholds to Chaos and Ionization for the Hydrogen Atom in Rotating Fields

    OpenAIRE

    Chandre, C.; Farrelly, David; Uzer, T.

    2002-01-01

    We analyze the classical phase space of the hydrogen atom in crossed magnetic and circularly polarized microwave fields in the high frequency regime, using the Chirikov resonance overlap criterion and the renormalization map. These methods are used to compute thresholds to large scale chaos and to ionization. The effect of the magnetic field is a strong stabilization of a set of invariant tori which bound the trajectories and prevent stochastic ionization. In order to ionize, larger amplitude...

  19. Chemisorption of hydrogen atoms and hydroxyl groups on stretched graphene: A coupled QM/QM study

    Science.gov (United States)

    Katin, Konstantin P.; Prudkovskiy, Vladimir S.; Maslov, Mikhail M.

    2017-09-01

    Using the density functional theory coupled with the nonorthogonal tight-binding model, we analyze the chemisorption of hydrogen atoms and hydroxyl groups on the unstrained and stretched graphene sheets. Drawback of finite cluster model of graphene for the chemisorption energy calculation in comparison with the QM/QM approach applied is discussed. It is shown that the chemisorption energy for the hydroxyl group is sufficiently lower than for hydrogen at stretching up to 7.5%. The simultaneous paired chemisorption of hydrogen and hydroxyl groups on the same hexagon has also been examined. Adsorption of two radicals in ortho and para positions is found to be more energetically favorable than those in meta position at any stretching considered. In addition the energy difference between adsorbent pairs in ortho and para positions decreases as the stretching rises. It could be concluded that the graphene stretching leads to the loss of preferred mutual arrangement of two radicals on its surface.

  20. THE INFRARED SPECTRA OF POLYCYCLIC AROMATIC HYDROCARBONS WITH SOME OR ALL HYDROGEN ATOMS REMOVED

    Energy Technology Data Exchange (ETDEWEB)

    Bauschlicher, Charles W. Jr. [Entry Systems and Technology Division, Mail Stop 230-3, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Ricca, Alessandra, E-mail: Charles.W.Bauschlicher@nasa.gov, E-mail: Alessandra.Ricca-1@nasa.gov [Carl Sagan Center, SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043 (United States)

    2013-10-20

    The loss of one hydrogen from C{sub 96}H{sub 24} does not significantly affect the infrared spectra of the neutral, cation, or anion. Excluding a very weak C-C stretching band at 5.1 μm, the loss of two adjacent duo hydrogens does not significantly affect the spectra compared with the parent. Removing all of the hydrogen atoms significantly increases the intensity of the new C-C stretching band, and, for the cation, shifts it to a longer (5.2 μm) wavelength. Observations show a feature near 5.25 μm, which has been attributed to overtone and combination bands from polycyclic aromatic hydrocarbons (PAHs). This current work suggests that dehydrogenated PAHs might also contribute to this band, but its weakness implies that fully dehydrogenated cationic or dicationic species are very rare.

  1. On the combination of a low energy hydrogen atom beam with a cold multipole ion trap

    Energy Technology Data Exchange (ETDEWEB)

    Borodi, Gheorghe

    2008-12-09

    The first part of the activities of this thesis was to develop a sophisticated ion storage apparatus dedicated to study chemical processes with atomic hydrogen. The integration of a differentially pumped radical beam source into an existing temperature variable 22- pole trapping machine has required major modifications. Since astrophysical questions have been in the center of our interest, the introduction first gives a short overview of astrophysics and -chemistry. The basics of ion trapping in temperature variable rf traps is well-documented in the literature; therefore, the description of the basic instrument (Chapter 2) is kept rather short. Much effort has been put into the development of an intense and stable source for hydrogen atoms the kinetic energy of which can be changed. Chapter 3 describes this module in detail with emphasis on the integration of magnetic hexapoles for guiding the atoms and special treatments of the surfaces for reducing H-H recombination. Due to the unique sensitivity of the rf ion trapping technique, this instrument allows one to study a variety of reactions of astrochemical and fundamental interest. The results of this work are summarized in Chapter 4. Reactions of CO{sub 2}{sup +} with hydrogen atoms and molecules have been established as calibration standard for in situ determination of H and H{sub 2} densities over the full temperature range of the apparatus (10 K-300 K). For the first time, reactions of H- and D-atoms with the ionic hydrocarbons CH{sup +}, CH{sub 2}{sup +}, and CH{sub 4}{sup +} have been studied at temperatures of interstellar space. A very interesting, not yet fully understood collision system is the interaction of protonated methane with H. The outlook presents some ideas, how to improve the new instrument and a few reaction systems are mentioned which may be studied next. (orig.)

  2. Muon transfer from muonic hydrogen to heavier atoms; Transfert de charge muonique

    Energy Technology Data Exchange (ETDEWEB)

    Dupays, A

    2004-06-01

    This work concerns muon transfer from muonic hydrogen to heavier atoms. Recently, a method of measurement of the hyperfine structure of ground-state muonic hydrogen based on the collision energy dependence of the muon transfer rate to oxygen has been proposed. This proposal is based on measurements which where performed at the Paul Scherrer Institute in the early nineties which indicate that the muon transfer from muonic hydrogen to oxygen increases by a factor of 4 going from thermal to 0.12 eV energies. The motivation of our calculations was to confirm this behaviour. To study the collision energy dependence of the muon transfer rate, we have used a time-independent close-coupling method. We have set up an hyperspherical elliptic formalism valid for nonzero total angular momentum which allows accurate computations of state-to-state reactive and charge exchange processes. We have applied this formalism to muon-transfer process to oxygen and neon. The comparison with experimental results is in both cases excellent. Finally, the neon transfer rate dependence with energy suggests to use neon instead of oxygen to perform a measurement of the hyperfine structure of muonic hydrogen. The results of accurate calculations of the muon transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen and neon are also reported. Very good agreement with measured rates is obtained and for the three systems, the isotopic effect is perfectly reproduced. (author)

  3. Atomic configuration of hydrogenated and clean tantalum(111) surfaces: Bond relaxation, energy entrapment and electron polarization

    Science.gov (United States)

    Bo, Maolin; Li, Lei; Guo, Yongling; Yao, Chuang; Peng, Cheng; Sun, Chang Q.

    2018-01-01

    By studying the tantalum (Ta)(111) surface with X-ray photoemission spectroscopy and density functional theory, we determined binding energy values for the clean Ta(111) (+3.068 eV) and hydrogenated Ta(111) (+3.421 eV) surfaces with an isolated atom level of 18.977 eV. Using the bond-band barrier and zone-selective electron spectroscopy correlation, we investigated the mechanism of hydrogenation adsorption on the Ta(111) surface. We found the local densities of states of the first layer of Ta atoms in the reconstructed structure, which formed on the adsorbent hydrogen of the surface chemical bond contracts and dipole polarization. Moreover, we showed that on the Ta(111) surface, the hydrogen-induced surface core level shifts are dominated by quantum entrapment and are proportional to the calculated hybridized orbitals of the valence band. The latter is therefore correlated to the local surface chemical reactivity and is useful for other adsorbate systems on transition metals.

  4. High-multipole excitations of hydrogen-like atoms by twisted photons near a phase singularity

    Science.gov (United States)

    Afanasev, Andrei; Carlson, Carl E.; Mukherjee, Asmita

    2016-07-01

    We calculate transition amplitudes and cross sections for excitation of hydrogen-like atoms by the twisted photon states, or photon states with angular momentum projection on the direction of propagation exceeding ℏ. If the target atom is located at distances of the order of atomic size near the phase singularity in the vortex center, the transition rates into the states with orbital angular momentum {l}f\\gt 1 become comparable with the rates for electric dipole transitions. It is shown that when the transition rates are normalized to the local photon flux, the resulting cross sections for {l}f\\gt 1 are singular near the optical vortex center. The relation to the ‘quantum core’ concept introduced by Berry and Dennis is discussed.

  5. Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

    Science.gov (United States)

    Chohan, Urslaan K.; Jimenez-Melero, Enrique; Koehler, Sven P. K.

    2016-11-01

    We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber-Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe-H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm-1, for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.

  6. Nanosecond pulsed humid Ar plasma jet in air: shielding, discharge characteristics and atomic hydrogen production

    Science.gov (United States)

    Yatom, Shurik; Luo, Yuchen; Xiong, Qing; Bruggeman, Peter J.

    2017-10-01

    Gas phase non-equilibrium plasmas jets containing water vapor are of growing interest for many applications. In this manuscript, we report a detailed study of an atmospheric pressure nanosecond pulsed Ar  +  0.26% H2O plasma jet. The plasma jet operates in an atmospheric pressure air surrounding but is shielded with a coaxial argon flow to limit the air diffusion into the jet effluent core. The jet impinges on a metal plate electrode and produces a stable plasma filament (transient spark) between the needle electrode in the jet and the metal plate. The stable plasma filament is characterized by spatially and time resolved electrical and optical diagnostics. This includes Rayleigh scattering, Stark broadening of the hydrogen Balmer lines and two-photon absorption laser induced fluorescence (TaLIF) to obtain the gas temperature, the electron density and the atomic hydrogen density respectively. Electron densities and atomic hydrogen densities up to 5 × 1022 m-3 and 2 × 1022 m-3 have been measured. This shows that atomic hydrogen is one of the main species in high density Ar-H2O plasmas. The gas temperature does not exceed 550 K in the core of the plasma. To enable in situ calibration of the H TaLIF at atmospheric pressure a previously published O density calibration scheme is extended to include a correction for the line profiles by including overlap integrals as required by H TaLIF. The line width of H TaLIF, due to collision broadening has the same trend as the neutral density obtained by Rayleigh scattering. This suggests the possibility to use this technique to in situ probe neutral gas densities.

  7. Precise calibration of few-cycle laser pulses with atomic hydrogen

    Science.gov (United States)

    Wallace, W. C.; Kielpinski, D.; Litvinyuk, I. V.; Sang, R. T.

    2017-12-01

    Interaction of atoms and molecules with strong electric fields is a fundamental process in many fields of research, particularly in the emerging field of attosecond science. Therefore, understanding the physics underpinning those interactions is of significant interest to the scientific community. One crucial step in this understanding is accurate knowledge of the few-cycle laser field driving the process. Atomic hydrogen (H), the simplest of all atomic species, plays a key role in benchmarking strong-field processes. Its wide-spread use as a testbed for theoretical calculations allows the comparison of approximate theoretical models against nearly-perfect numerical solutions of the three-dimensional time-dependent Schrödinger equation. Until recently, relatively little experimental data in atomic H was available for comparison to these models, and was due mostly due to the difficulty in the construction and use of atomic H sources. Here, we review our most recent experimental results from atomic H interaction with few-cycle laser pulses and how they have been used to calibrate important laser pulse parameters such as peak intensity and the carrier-envelope phase (CEP). Quantitative agreement between experimental data and theoretical predictions for atomic H has been obtained at the 10% uncertainty level, allowing for accurate laser calibration intensity at the 1% level. Using this calibration in atomic H, both accurate CEP data and an intensity calibration standard have been obtained Ar, Kr, and Xe; such gases are in common use for strong-field experiments. This calibration standard can be used by any laboratory using few-cycle pulses in the 1014 W cm‑2 intensity regime centered at 800 nm wavelength to accurately calibrate their peak laser intensity to within few-percent precision.

  8. The reactions of ground and excited state sodium atoms with hydrogen halide molecules

    Science.gov (United States)

    Weiss, P. S.; Mestdagh, J. M.; Covinsky, M. H.; Balko, B. A.; Lee, Y. T.

    1988-10-01

    The reactions of ground and excited state Na atoms with hydrogen halide (HX) molecules have been studied using the crossed molecular beams method. With both increasing translational and increasing electronic energy, the reactive cross sections increase in the reactions of HCl and HBr. From product angular and velocity distributions detailed center-of-mass information is derived. For the reactions of Na (3 2S 1/2, 3 2P 1/2, 4 2D 5/2, 5 2S 1/2) with HCl, the product NaCl is back-scattered with respect to the incoming Na atom in the center-of-mass frame of reference. The reaction of each Na state studied with HCl is direct and proceeds via collinear and near-collinear Na-Cl-H approach geometries. For the Na (3 2P 3/2) and Na (4 2D 5/2) reactions with HCl the predominant transition state symmetry is 2Σ in a collinear (C ∞ν) Na-Cl-H geometry. This is consistent with the reaction proceeding via electron transfer from the Na atom to the halide atom. Absolute reactive cross sections for each state of Na studied with HCl were determined by comparison with both small and large angle elastic scattering. We were unable to observe Na atoms with over 4 eV of electronic energy react with HF up to collision energies of 13 kcal/mole.

  9. A theoretical study of hydrogen atoms adsorption and diffusion on PuO{sub 2} (110) surface

    Energy Technology Data Exchange (ETDEWEB)

    Yu, H.L., E-mail: yuhuilong2002@126.com; Tang, T.; Zheng, S.T.; Shi, Y.; Qiu, R.Z.; Luo, W.H.; Meng, D.Q.

    2016-05-05

    The mechanisms of adsorption and diffusion of hydrogen atoms on the PuO{sub 2} (110) surface are investigated by density functional theory corrected for onsite Coulombic interactions (GGA + U). In order to find out the energetically more favorable adsorption site and optimum diffusion path, adsorption energy of atomic H on various sites and the diffusion energy barrier are derived and compared. Our results show that both chemisorption and physisorption exist for H atoms adsorption configurations on PuO{sub 2} (110) surface. Two processes for H diffusion are investigated using the climbing nudged-elastic-band (cNEB) approach. We have identified two diffusion mechanisms, leading to migration of atomic H on the surface and diffusion from surface to subsurface. The energy barriers indicate that it is energetically more favorable for H atom to be on the surface. Hydrogen permeation through purity PuO{sub 2} surface is mainly inhibited from hydrogen atom diffusion from surface to subsurface. - Highlights: • H atoms adsorption on PuO{sub 2} (110) surface are investigated by GGA + U. • Both chemisorption and physisorption exist for H atoms adsorption configurations. • H atoms migration into PuO{sub 2} (100) surface are inhibited with the barrier of 2.15 eV. • H atoms diffusion on PuO{sub 2} (110) surface are difficult at room temperature.

  10. Atomic ionization of hydrogen-like ions by twisted photons: angular distribution of emitted electrons

    Science.gov (United States)

    Matula, O.; Hayrapetyan, A. G.; Serbo, V. G.; Surzhykov, A.; Fritzsche, S.

    2013-10-01

    We investigate the angular distribution of electrons that are emitted in the ionization of hydrogen-like ions by twisted photons. Analysis is performed based on the first-order perturbation theory and the non-relativistic Schrödinger equation. Special attention is paid to the dependence of the electron emission pattern on the impact parameter b of the ion with respect to the centre of the twisted wave front. In order to explore such a dependence, detailed calculations were carried out for the photoionization of the 1s ground and 2 py excited states of neutral hydrogen atoms. Based on these calculations, we argue that for relatively small impact parameters, the electron angular distributions may be strongly affected by altering the position of the atom within the wave front. In contrast, if the atom is placed far from the front centre, the emission pattern of the electrons is independent of the impact parameter b and resembles that observed in the photoionization by plane wave photons.

  11. Measuring deuterium enrichment of glucose hydrogen atoms by gas chromatography/mass spectrometry.

    Science.gov (United States)

    Antoniewicz, Maciek R; Kelleher, Joanne K; Stephanopoulos, Gregory

    2011-04-15

    We developed a simple and accurate method for determining deuterium enrichment of glucose hydrogen atoms by electron impact gas chromatography mass spectrometry (GC/MS). First, we prepared 18 derivatives of glucose and screened over 200 glucose fragments to evaluate the accuracy and precision of mass isotopomer data for each fragment. We identified three glucose derivatives that gave six analytically useful ions: (1) glucose aldonitrile pentapropionate (m/z 173 derived from C4-C5 bond cleavage; m/z 259 from C3-C4 cleavage; m/z 284 from C4-C5 cleavage; and m/z 370 from C5-C6 cleavage); (2) glucose 1,2,5,6-di-isopropylidene propionate (m/z 301, no cleavage of glucose carbon atoms); and (3) glucose methyloxime pentapropionate (m/z 145 from C2-C3 cleavage). Deuterium enrichment at each carbon position of glucose was determined by least-squares regression of mass isotopomer distributions. The validity of the approach was tested using labeled glucose standards and carefully prepared mixtures of standards. Our method determines deuterium enrichment of glucose hydrogen atoms with an accuracy of 0.3 mol %, or better, without the use of any calibration curves or correction factors. The analysis requires only 20 μL of plasma, which makes the method applicable for studying gluconeogenesis using deuterated water in cell culture and animal experiments. © 2011 American Chemical Society

  12. Investigating the role of atomic hydrogen on chloroethene reactions with iron using tafel analysis and electrochemical impedance spectroscopy.

    Science.gov (United States)

    Wang, Jiankang; Farrell, James

    2003-09-01

    Metallic iron filings are commonly employed as reducing agents in permeable barriers used for remediating groundwater contaminated by chlorinated solvents. Reactions of trichloroethylene (TCE) and tetrachloroethylene (PCE) with zerovalent iron were investigated to determine the role of atomic hydrogen in their reductive dechlorination. Experiments simultaneously measuring dechlorination and iron corrosion rates were performed to determine the fractions of the total current going toward dechlorination and hydrogen evolution. Corrosion rates were determined using Tafel analysis, and dechlorination rates were determined from rates of byproduct generation. Electrochemical impedance spectroscopy (EIS) was used to determine the number of reactions that controlled the observed rates of chlorocarbon disappearance, as well as the role of atomic hydrogen in TCE and PCE reduction. Comparison of iron corrosion rates with those for TCE reaction showed that TCE reduction occurred almost exclusively via atomic hydrogen at low pH values and via atomic hydrogen and direct electron transfer at neutral pH values. In contrast, reduction of PCE occurred primarily via direct electron transfer at both low and neutral pH values. At low pH values and micromolar concentrations, TCE reaction rates were faster than those for PCE due to more rapid reduction of TCE by atomic hydrogen. At neutral pH values and millimolar concentrations, PCE reaction rates were faster than those for TCE. This shift in relative reaction rates was attributed to a decreasing contribution of the atomic hydrogen reaction mechanism with increasing halocarbon concentrations and pH values. The EIS data showed that all the rate limitations for TCE and PCE dechlorination occurred during the transfer of the first two electrons. Results from this study show that differences in relative reaction rates of TCE and PCE with iron are dependent on the significance of the reduction pathway involving atomic hydrogen.

  13. Hydrogen atom transfer reactions in thiophenol: photogeneration of two new thione isomers.

    Science.gov (United States)

    Reva, Igor; Nowak, Maciej J; Lapinski, Leszek; Fausto, Rui

    2015-02-21

    Photoisomerization reactions of monomeric thiophenol have been investigated for the compound isolated in low-temperature argon matrices. The initial thiophenol population consists exclusively of the thermodynamically most stable thiol form. Phototransformations were induced by irradiation of the matrices with narrowband tunable UV light. Irradiation at λ > 290 nm did not induce any changes in isolated thiophenol molecules. Upon irradiation at 290-285 nm, the initial thiol form of thiophenol converted into its thione isomer, cyclohexa-2,4-diene-1-thione. This conversion occurs by transfer of an H atom from the SH group to a carbon atom at the ortho position of the ring. Subsequent irradiation at longer wavelengths (300-427 nm) demonstrated that this UV-induced hydrogen-atom transfer is photoreversible. Moreover, upon irradiation at 400-425 nm, the cyclohexa-2,4-diene-1-thione product converts, by transfer of a hydrogen atom from the ortho to para position, into another thione isomer, cyclohexa-2,5-diene-1-thione. The latter thione isomer is also photoreactive and is consumed if irradiated at λ atom-transfer isomerization reactions dominate the unimolecular photochemistry of thiophenol confined in a solid argon matrix. A set of low-intensity infrared bands, observed in the spectra of UV irradiated thiophenol, indicates the presence of a phenylthiyl radical with an H- atom detached from the SH group. Alongside the H-atom-transfer and H-atom-detachment processes, the ring-opening photoreaction occurred in cyclohexa-2,4-diene-1-thione by the cleavage of the C-C bond at the alpha position with respect to the thiocarbonyl C[double bond, length as m-dash]S group. The resulting open-ring conjugated thioketene adopts several isomeric forms, differing by orientations around single and double bonds. The species photogenerated upon UV irradiation of thiophenol were identified by comparison of their experimental infrared spectra with the spectra theoretically calculated for

  14. The human sex odds at birth after the atmospheric atomic bomb tests, after Chernobyl, and in the vicinity of nuclear facilities.

    Science.gov (United States)

    Scherb, Hagen; Voigt, Kristina

    2011-06-01

    Ever since the discovery of the mutagenic properties of ionizing radiation, the possibility of birth sex odds shifts in exposed human populations was considered in the scientific community. Positive evidence, however weak, was obtained after the atomic bombing of Japan. We previously investigated trends in the sex odds before and after the Chernobyl Nuclear Power Plant accident. In a pilot study, combined data from the Czech Republic, Denmark, Finland, Germany, Hungary, Norway, Poland, and Sweden between 1982 and 1992 showed a downward trend in the sex odds and a significant jump in 1987, the year immediately after Chernobyl. Moreover, a significant positive association of the sex odds between 1986 and 1991 with Chernobyl fallout at the district level in Germany was observed. Both of these findings, temporality (effect after exposure) and dose response association, yield evidence of causality. The primary aim of this study was to investigate longer time periods (1950-2007) in all of Europe and in the USA with emphasis on the global atmospheric atomic bomb test fallout and on the Chernobyl accident. To obtain further evidence, we also analyze sex odds data near nuclear facilities in Germany and Switzerland. DATA AND STATISTICAL METHODS: National gender-specific annual live births data for 39 European countries from 1975 to 2007 were compiled using the pertinent internet data bases provided by the World Health Organization, United Nations, Council of Europe, and EUROSTAT. For a synoptic re-analysis of the period 1950 to 1990, published data from the USA and from a predominantly western and less Chernobyl-exposed part of Europe were studied additionally. To assess spatial, temporal, as well as spatial-temporal trends in the sex odds and to investigate possible changes in those trends after the atomic bomb tests, after Chernobyl, and in the vicinity of nuclear facilities, we applied ordinary linear logistic regression. Region-specific and eventually changing spatial

  15. Manganese-Oxygen Intermediates in O-O Bond Activation and Hydrogen-Atom Transfer Reactions.

    Science.gov (United States)

    Rice, Derek B; Massie, Allyssa A; Jackson, Timothy A

    2017-11-21

    Biological systems capitalize on the redox versatility of manganese to perform reactions involving dioxygen and its derivatives superoxide, hydrogen peroxide, and water. The reactions of manganese enzymes influence both human health and the global energy cycle. Important examples include the detoxification of reactive oxygen species by manganese superoxide dismutase, biosynthesis by manganese ribonucleotide reductase and manganese lipoxygenase, and water splitting by the oxygen-evolving complex of photosystem II. Although these enzymes perform very different reactions and employ structurally distinct active sites, manganese intermediates with peroxo, hydroxo, and oxo ligation are commonly proposed in catalytic mechanisms. These intermediates are also postulated in mechanisms of synthetic manganese oxidation catalysts, which are of interest due to the earth abundance of manganese. In this Account, we describe our recent efforts toward understanding O-O bond activation pathways of Mn III -peroxo adducts and hydrogen-atom transfer reactivity of Mn IV -oxo and Mn III -hydroxo complexes. In biological and synthetic catalysts, peroxomanganese intermediates are commonly proposed to decay by either Mn-O or O-O cleavage pathways, although it is often unclear how the local coordination environment influences the decay mechanism. To address this matter, we generated a variety of Mn III -peroxo adducts with varied ligand environments. Using parallel-mode EPR and Mn K-edge X-ray absorption techniques, the decay pathway of one Mn III -peroxo complex bearing a bulky macrocylic ligand was investigated. Unlike many Mn III -peroxo model complexes that decay to oxo-bridged-Mn III Mn IV dimers, decay of this Mn III -peroxo adduct yielded mononuclear Mn III -hydroxo and Mn IV -oxo products, potentially resulting from O-O bond activation of the Mn III -peroxo unit. These results highlight the role of ligand sterics in promoting the formation of mononuclear products and mark an important

  16. Analysis of atomic force microscopy phase data to dynamically detect adsorbed hydrogen under ambient conditions.

    Science.gov (United States)

    Young, Matthew J; Pfromm, Peter H; Rezac, Mary E; Law, Bruce M

    2014-10-14

    Characterization of the interactions of hydrogen with catalytic metal surfaces and the mass transfer processes involved in heterogeneous catalysis are important for catalyst development. Although a range of technologies for studying catalytic surfaces exist, much of it relies on high-vacuum conditions that preclude in situ research. In contrast, atomic force microscopy (AFM) provides an opportunity for direct observation of surfaces under or near actual reaction conditions. Tapping-mode AFM was explored here because it expands AFM beyond the usual topographic information toward speciation and other more subtle surface information. This work describes using phase-angle information from tapping-mode AFM to follow the interactions of hydrogen with palladium, polycarbonate, and iron. Real-time AFM phase-angle information allowed for the observation of multiphase mass transfer to and from the surface of palladium at atmospheric pressure and room temperature without the need for complex sample preparation. The AFM observations are quantitatively benchmarked against and confirm mass transfer predictions based on bulk hydrogen diffusion data. Additionally, they support recent studies that demonstrate the existence of multiple hydrogen states during interactions with palladium surfaces.

  17. Atomic-Scale Mechanism of Efficient Hydrogen Evolution at SiC Nanocrystal Electrodes.

    Science.gov (United States)

    Shen, Xiao; Pantelides, Sokrates T

    2013-01-03

    Efficient electrochemical hydrogen evolution at ultrathin 3C-SiC nanocrystal electrodes in acid solutions was recently reported, but the atomic-scale mechanism of the reaction was not identified. Here we report quantum mechanical calculations of pertinent reactions and show that the reaction happens at pre-existing hydrogenated surface Si-H sites through a mechanism that is related to the Volmer-Heyrovsky mechanism that occurs in metals. Here the Heyrovsky reaction occurs as the first step, where an electron from the substrate reacts with a hydronium adsorbed at a Si-H site, creating an H2 molecule and a Si dangling bond. The Volmer reaction follows and regenerates the Si-H. This ordering of reactions is supported by the fact that the hydrogen coverage on SiC electrodes does not depend on the applied voltage, in contrast to the cases of metal electrodes. Moreover, the Volmer reaction, which is a one-step process on metal surface, is a two-step process here. We then show that the rise of the conduction band due to quantum confinement accounts for the fact that only ultrasmall SiC nanocrystals are electrochemically active. We also show that the ability of a Si-H bond to bind a hydronium is essential for the hydrogen evolution to occur at high rate.

  18. Experimental limits on the velocities of sodium atoms sputtered from solid surfaces by hydrogen ions. [Na cloud production around Io

    Science.gov (United States)

    Stoner, J. O., Jr.

    1976-01-01

    Optical emission at 589.0 nm by sodium atoms sputtered from solid targets by hydrogen molecular ions was observed, and no accompanying broadening or shifts of this line could be detected relative to that from a laboratory lamp. This allowed an upper limit of about 500,000 cm/sec on the mean speed of ejected sodium atoms to be calculated. The results are consistent with the hypothesis that the atomic sodium cloud surrounding Io is produced by this mechanism.

  19. Comment on "Entropy and complexity analysis of hydrogenic Rydberg atoms" [J. Math. Phys. 54, 052109 (2013)

    Science.gov (United States)

    Jiao, Li Guang; Zan, Li Rong

    2017-10-01

    In a recent paper [S. López-Rosa et al., J. Math. Phys. 54, 052109 (2013)], the authors made detailed investigations on the information-theoretic quantities for hydrogenic atoms in Rydberg states. Asymptotic forms of different types of complexity measures (Crámer-Rao, Fisher-Shannon, and LMC types) in both position and momentum spaces were obtained for hydrogenic states (n,l,m) with fixed l and increasingly large n. However, the expressions for the Crámer-Rao complexity are incorrect due to the wrong definition of variance. The correct form of this complexity in position space is presented exactly in this work. In momentum space, two different definitions of variance are provided and corresponding Crámer-Rao complexities are discussed separately. In either case, the momentum complexity increases much faster than that in position space when increasing principal quantum number n.

  20. Spin–spin correlations and entanglement in elastic electron scattering from hydrogen atoms

    Science.gov (United States)

    Bartschat, Klaus

    2017-11-01

    In two recent papers, Blum and Lohmann (2016 Phys. Rev. Lett. 116 033201) and Lohmann et al (2016 Phys. Rev. A 94 032331), the possibility of continuously varying the degree of entanglement between an elastically scattered electron and the valence electron of quasi-one electron targets was discussed. Here we present results for elastic electron scattering from atomic hydrogen in the energy regime of 1‑10 eV and the full range of scattering angles 0^\\circ -180^\\circ . We confirm previous calculations at very low energies, which predicted that the hydrogen target is not a promising candidate for Bell correlations through electron collisions. This finding remains unchanged in the near-resonance regime of incident electron energies just below 10 eV. In addition to the spin-correlation parameter P, we present the angle-integrated total cross section, as well as the angle-differential cross section at a few representative collision energies.

  1. Time-resolved X-ray scattering by electronic wave packets: analytic solutions to the hydrogen atom

    DEFF Research Database (Denmark)

    Simmermacher, Mats; Henriksen, Niels Engholm; Møller, Klaus Braagaard

    2017-01-01

    description of time-resolved X-ray scattering by non-stationary electronic wave packets in atomic systems. A consistent application of the Waller-Hartree approximation is discussed and different contributions to the total differential scattering signal are identified and interpreted. Moreover......, it is demonstrated how the scattering signal of wave packets in the hydrogen atom can be expressed analytically. This permits simulations without numerical integration and establishes a benchmark for both efficiency and accuracy. Based on that, scattering patterns of an exemplary wave packet in the hydrogen atom...

  2. Spatial distribution of atomic and ion hydrogen flux and its effect on hydrogen recycling in long duration confined and non-confined plasmas

    Directory of Open Access Journals (Sweden)

    A. Kuzmin

    2017-08-01

    Full Text Available In order to understand the atomic hydrogen distribution in different kinds of plasma and its influence on the recycling, two kinds of plasmas were used: non-confined annular electron cyclotron resonance (ECR and confined long duration plasmas. The permeation probes are used to measure directly the atomic hydrogen flux at several poloidal positions. The permeation through metals due to the ion and atom component of the hydrogen flux to the wall is indistinguishable. To estimate the contribution of the ions directly, Langmuir probes were used. The Гinc profile behind the plasma facing components (PFCs is almost constant, ∼2 ×1018 H/s/m2.

  3. Hyperfine frequency shift of atomic hydrogen in the presence of helium buffer gas

    Energy Technology Data Exchange (ETDEWEB)

    Jochemsen, R.; Berlinsky, A.J. (British Columbia Univ., Vancouver (Canada). Dept. of Physics)

    1982-02-01

    A quantum mechanical thermal average is performed to obtain the temperature dependence of the hyperfine frequency shift (HFS) of hydrogen atoms in the presence of He buffer gas. The calculations are based on existing ab initio calculations of the hyperfine frequency shift as a function of internuclear separation and of the interatomic potential. We find that the HFS changes sign at fairly low temperature and has a small negative value at T = 1 K in agreement with recent measurements. The overall temperature dependence is shown to be quite sensitive to the interatomic potential.

  4. ESR studies of spin-polarized atomic hydrogen using a 114-GHz heterodyne spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Statt, B.W.; Hardy, W.N.; Berlinsky, A.J.; Klein, E.

    1985-12-01

    Spin-polarized atomic hydrogen (Harrow-down) gas has been studied using electron spin resonance (ESR) techniques at low temperatures. The ESR apparatus and consequent data analysis required for accurate quantitative results are described in detail. Crucial to the data analysis is the ability to confine the sample of Harrow-down gas inside a liquid helium-coated microwave cavity where the magnetic field and temperature are constant. Results obtained so far are reported, which include the first detailed study of the one-body surface relaxation rate due to microscopic magnetic impurities in the cell walls.

  5. Atomic and ionic spectrum lines below 2000A: hydrogen through argon

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, R.L.

    1982-10-01

    A critical tabulation of observed spectral lines below 2000 angstroms has been prepared from the published literature up to July 1978. It is intended principally as an aid to those physicists and astronomers who deal with the spectra of highly stripped atoms. This report includes the first 18 elements, from hydrogen (including deuterium) through argon. The tabulation is divided into two main sections: the spectrum lines by spectrum, and a finding list. The entries for each element give the ionization species, ground state term, and ionization potential, as well as the best values of vacuum wavelength, intensity, and classification. A list of the pertinent references is appended at the end.

  6. On the Treatment of l-changing Proton-hydrogen Rydberg Atom Collisions

    Science.gov (United States)

    Vrinceanu, Daniel; Onofrio, Roberto; Sadeghpour, Hossein

    2018-01-01

    Energy-conserving, angular momentum-changing collisions between protons and highly excited Rydberg hydrogen atoms are important for precise understanding of the primordial recombination cascade, and the elemental abundance.Early approaches to l-changing collisions used perturbation theory for only dipole-allowed (Δl = ±1) transitions. An exact non-perturbative quantum mechanical treatment is possible, but it comes at computational cost for highly excited Rydberg states. In this note we show how to obtain a semi-classical limit that is accurate and simple, and develop further physical insights afforded by the non-perturbative quantum mechanical treatment.

  7. Multiphoton resonant ionization of hydrogen atom exposed to two-colour laser pulses

    Institute of Scientific and Technical Information of China (English)

    Wang Pei-Jie; Fang Yan

    2008-01-01

    This paper studies the multiphoton resonant ionization by two-colour laser pulses in the hydrogen atom by solving the time-dependent Schr(o)dinger equation.By fixing the parameters of fundamental laser field and scanning the frequency of second laser field,it finds that the ionization probability shows several resonance peaks and is also much larger than the linear superposition of probabilities by applying two lasers separately.The enhancement of the ionization happens when the system is resonantly pumped to the excited states by absorbing two or more colour photons non-sequentially.

  8. Electron impact ionization of atomic hydrogen from the 1S and 2S states

    Energy Technology Data Exchange (ETDEWEB)

    Bartschat, K.; Bray, I.

    1996-05-01

    We present results from R-Matrix with Pseudo-States (RMPS) and Convergent Close-Coupling (CCC) calculations for electron impact total ionization of the 1S and 2S states of atomic hydrogen in the energy region from threshold to 100 eV. Particular attention is given to the near threshold region. We find the results for energies more than 2 eV above threshold to be in excellent agreement with the available experimental data. (authors). 19 refs., 3 figs.

  9. Interbasis expansion and SO(3) symmetry in the two-dimensional hydrogen atom.

    Energy Technology Data Exchange (ETDEWEB)

    Torres del Castillo, G.F.; Lopez Villanueva, A. [Universidad Autonoma de Puebla, Puebla (Mexico)

    2001-04-01

    Making use of the SO(3) symmetry of the two-dimensional hydrogen atom, each of the bases for the bound states formed by the separable solutions of the Schroedinger equation in polar and parabolic coordinates are expressed in terms of the other. [Spanish] Usando la simetria SO(3) del atomo de hidrogeno en dos dimensiones, cada una de las bases para los estados ligados formadas por las soluciones separables de la ecuacion de Schroedinger en coordenadas polares y parabolicas se expresan en terminos de la otra.

  10. Existence of a ground state for the confined hydrogen atom in non-relativistic QED

    DEFF Research Database (Denmark)

    Amour, Laurent; Faupin, Jeremy

    2008-01-01

    We consider a system of a hydrogen atom interacting with the quantized electromagnetic field. Instead of fixing the nucleus, we assume that the system is confined by its center of mass. This model is used in theoretical physics to explain the Lamb-Dicke effect. After a brief review...... of the literature, we explain how to verify some properly chosen binding conditions which, by [25], lead to the existence of a ground state for our model, and for all values of the fine-structure constant...

  11. The effect of moderators on the reactions of hot hydrogen atoms with methane

    CERN Document Server

    Estrup, Peder J.

    1960-01-01

    The reaction of recoil tritium with methane has been examined in further detail. The previous hypothesis that this system involves a hot displacement reaction of high kinetic energy hydrogen to give CH$_{3}$T, CH$_{2}$T and HT is confirmed. The effect of moderator on this process is studied by the addition of noble gases. As predicted these gases inhibit the hot reaction action, their efficiency in this respect being He > Ne > A > Se. The data are quantitatively in accord with a theory of hot atom kinetics. The mechanism of the hot displacement process is briefly discussed.

  12. Spontaneous light emission by atomic hydrogen: Fermi's golden rule without cheating

    Science.gov (United States)

    Debierre, V.; Durt, T.; Nicolet, A.; Zolla, F.

    2015-10-01

    Focusing on the 2 p- 1 s transition in atomic hydrogen, we investigate through first order perturbation theory the time evolution of the survival probability of an electron initially taken to be in the excited (2 p) state. We examine both the results yielded by the standard dipole approximation for the coupling between the atom and the electromagnetic field - for which we propose a cutoff-independent regularisation - and those yielded by the exact coupling function. In both cases, Fermi's golden rule is shown to be an excellent approximation for the system at hand: we found its maximal deviation from the exact behaviour of the system to be of order 10-8 /10-7. Our treatment also yields a rigorous prescription for the choice of the optimal cutoff frequency in the dipole approximation. With our cutoff, the predictions of the dipole approximation are almost indistinguishable at all times from the exact dynamics of the system.

  13. Hidden momentum in a hydrogen atom and the Lorentz-force law

    Science.gov (United States)

    Filho, J. S. Oliveira; Saldanha, Pablo L.

    2015-11-01

    By using perturbation theory, we show that a hydrogen atom with magnetic moment due to the orbital angular momentum of the electron has so-called hidden momentum in the presence of an external electric field. This means that the atomic electronic cloud has a nonzero linear momentum in its center-of-mass rest frame due to a relativistic effect. This is completely analogous to the hidden momentum that a classical current loop has in the presence of an external electric field. We discuss how this effect is essential for the validity of the Lorentz-force law in quantum systems. We also connect our results to the long-standing Abraham-Minkowski debate about the momentum of light in material media.

  14. Quantum Diffusion-Controlled Chemistry: Reactions of Atomic Hydrogen with Nitric Oxide in Solid Parahydrogen.

    Science.gov (United States)

    Ruzi, Mahmut; Anderson, David T

    2015-12-17

    Our group has been working to develop parahydrogen (pH2) matrix isolation spectroscopy as a method to study low-temperature condensed-phase reactions of atomic hydrogen with various reaction partners. Guided by the well-defined studies of cold atom chemistry in rare-gas solids, the special properties of quantum hosts such as solid pH2 afford new opportunities to study the analogous chemical reactions under quantum diffusion conditions in hopes of discovering new types of chemical reaction mechanisms. In this study, we present Fourier transform infrared spectroscopic studies of the 193 nm photoinduced chemistry of nitric oxide (NO) isolated in solid pH2 over the 1.8 to 4.3 K temperature range. Upon short-term in situ irradiation the NO readily undergoes photolysis to yield HNO, NOH, NH, NH3, H2O, and H atoms. We map the postphotolysis reactions of mobile H atoms with NO and document first-order growth in HNO and NOH reaction products for up to 5 h after photolysis. We perform three experiments at 4.3 K and one at 1.8 K to permit the temperature dependence of the reaction kinetics to be quantified. We observe Arrhenius-type behavior with a pre-exponential factor of A = 0.036(2) min(-1) and Ea = 2.39(1) cm(-1). This is in sharp contrast to previous H atom reactions we have studied in solid pH2 that display definitively non-Arrhenius behavior. The contrasting temperature dependence measured for the H + NO reaction is likely related to the details of H atom quantum diffusion in solid pH2 and deserves further study.

  15. Quantitative analysis of hydrogen in SiO2/SiN/SiO2 stacks using atom probe tomography

    Directory of Open Access Journals (Sweden)

    Yorinobu Kunimune

    2016-04-01

    Full Text Available We have demonstrated that it is possible to reproducibly quantify hydrogen concentration in the SiN layer of a SiO2/SiN/SiO2 (ONO stack structure using ultraviolet laser-assisted atom probe tomography (APT. The concentration of hydrogen atoms detected using APT increased gradually during the analysis, which could be explained by the effect of hydrogen adsorption from residual gas in the vacuum chamber onto the specimen surface. The amount of adsorbed hydrogen in the SiN layer was estimated by analyzing another SiN layer with an extremely low hydrogen concentration (<0.2 at. %. Thus, by subtracting the concentration of adsorbed hydrogen, the actual hydrogen concentration in the SiN layer was quantified as approximately 1.0 at. %. This result was consistent with that obtained by elastic recoil detection analysis (ERDA, which confirmed the accuracy of the APT quantification. The present results indicate that APT enables the imaging of the three-dimensional distribution of hydrogen atoms in actual devices at a sub-nanometer scale.

  16. Significant change of local atomic configurations at surface of reduced activation Eurofer steels induced by hydrogenation treatments

    Energy Technology Data Exchange (ETDEWEB)

    Greculeasa, S.G.; Palade, P.; Schinteie, G. [National Institute for Materials Physics, P.O. Box MG-7, 77125, Bucharest-Magurele (Romania); Kuncser, A.; Stanciu, A. [National Institute for Materials Physics, P.O. Box MG-7, 77125, Bucharest-Magurele (Romania); University of Bucharest, Faculty of Physics, 77125, Bucharest-Magurele (Romania); Lungu, G.A. [National Institute for Materials Physics, P.O. Box MG-7, 77125, Bucharest-Magurele (Romania); Porosnicu, C.; Lungu, C.P. [National Institute for Laser, Plasma and Radiation Physics, 77125, Bucharest-Magurele (Romania); Kuncser, V., E-mail: kuncser@infim.ro [National Institute for Materials Physics, P.O. Box MG-7, 77125, Bucharest-Magurele (Romania)

    2017-04-30

    Highlights: • Engineering of Eurofer slab properties by hydrogenation treatments. • Hydrogenation modifies significantly the local atomic configurations at the surface. • Hydrogenation increases the expulsion of the Cr atoms toward the very surface. • Approaching binomial atomic distribution by hydrogenation in the next surface 100 nm. - Abstract: Reduced-activation steels such as Eurofer alloys are candidates for supporting plasma facing components in tokamak-like nuclear fusion reactors. In order to investigate the impact of hydrogen/deuterium insertion in their crystalline lattice, annealing treatments in hydrogen atmosphere have been applied on Eurofer slabs. The resulting samples have been analyzed with respect to local structure and atomic configuration both before and after successive annealing treatments, by X-ray diffractometry (XRD), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and conversion electron Mössbauer spectroscopy (CEMS). The corroborated data point out for a bcc type structure of the non-hydrogenated alloy, with an average alloy composition approaching Fe{sub 0.9}Cr{sub 0.1} along a depth of about 100 nm. EDS elemental maps do not indicate surface inhomogeneities in concentration whereas the Mössbauer spectra prove significant deviations from a homogeneous alloying. The hydrogenation increases the expulsion of the Cr atoms toward the surface layer and decreases their oxidation, with considerable influence on the surface properties of the steel. The hydrogenation treatment is therefore proposed as a potential alternative for a convenient engineering of the surface of different Fe-Cr based alloys.

  17. Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Chohan, Urslaan K.; Jimenez-Melero, Enrique [School of Materials, The University of Manchester, Manchester M13 9PL (United Kingdom); Dalton Cumbrian Facility, The University of Manchester, Moor Row CA24 3HA (United Kingdom); Koehler, Sven P.K., E-mail: sven.koehler@manchester.ac.uk [Dalton Cumbrian Facility, The University of Manchester, Moor Row CA24 3HA (United Kingdom); School of Chemistry, The University of Manchester, Manchester M13 9PL (United Kingdom); Photon Science Institute, The University of Manchester, Manchester M13 9PL (United Kingdom)

    2016-11-30

    Highlights: • Potential energy surfaces for H diffusion on Fe(110) calculated. • Full vibrational analysis of surface modes performed. • Vibrational analysis establishes lb site as a transition state to the 3f site. • Pronounced buckling observed in the Fe surface layer. - Abstract: We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber–Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe–H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm{sup −1}, for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.

  18. Chemical Kinetics of Hydrogen Atom Abstraction from Allylic Sites by3O2; Implications for Combustion Modeling and Simulation.

    Science.gov (United States)

    Zhou, Chong-Wen; Simmie, John M; Somers, Kieran P; Goldsmith, C Franklin; Curran, Henry J

    2017-03-09

    Hydrogen atom abstraction from allylic C-H bonds by molecular oxygen plays a very important role in determining the reactivity of fuel molecules having allylic hydrogen atoms. Rate constants for hydrogen atom abstraction by molecular oxygen from molecules with allylic sites have been calculated. A series of molecules with primary, secondary, tertiary, and super secondary allylic hydrogen atoms of alkene, furan, and alkylbenzene families are taken into consideration. Those molecules include propene, 2-butene, isobutene, 2-methylfuran, and toluene containing the primary allylic hydrogen atom; 1-butene, 1-pentene, 2-ethylfuran, ethylbenzene, and n-propylbenzene containing the secondary allylic hydrogen atom; 3-methyl-1-butene, 2-isopropylfuran, and isopropylbenzene containing tertiary allylic hydrogen atom; and 1-4-pentadiene containing super allylic secondary hydrogen atoms. The M06-2X/6-311++G(d,p) level of theory was used to optimize the geometries of all of the reactants, transition states, products and also the hinder rotation treatments for lower frequency modes. The G4 level of theory was used to calculate the electronic single point energies for those species to determine the 0 K barriers to reaction. Conventional transition state theory with Eckart tunnelling corrections was used to calculate the rate constants. The comparison between our calculated rate constants with the available experimental results from the literature shows good agreement for the reactions of propene and isobutene with molecular oxygen. The rate constant for toluene with O 2 is about an order magnitude slower than that experimentally derived from a comprehensive model proposed by Oehlschlaeger and coauthors. The results clearly indicate the need for a more detailed investigation of the combustion kinetics of toluene oxidation and its key pyrolysis and oxidation intermediates. Despite this, our computed barriers and rate constants retain an important internal consistency. Rate constants

  19. STEREO Observations of Energetic Neutral Hydrogen Atoms during the 5 December 2006 Solar Flare

    Science.gov (United States)

    Mewaldt, R. A.; Leske, R. A.; Stone, E. C.; Barghouty, A. F.; Labrador, A. W.; Cohen, C. M. S.; Cummings, A. C.; Davis, A. J.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

    2009-01-01

    We report the discovery of energetic neutral hydrogen atoms emitted during the X9 solar event of December 5, 2006. Beginning 1 hour following the onset of this E79 flare, the Low Energy Telescopes (LETs) on both the STEREO A and B spacecraft observed a sudden burst of 1.6 to 15 MeV protons beginning hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within 10 of the Sun, consistent with the measurement resolution. The derived emission profile at the Sun had onset and peak times remarkably similar to the GOES soft X-ray profile and continued for more than an hour. The observed arrival directions and energy spectrum argue strongly that the particle events less than 5 MeV were due to energetic neutral hydrogen atoms (ENAs). To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. Possible origins for the production of ENAs in a large solar event are considered. We conclude that the observed ENAs were most likely produced in the high corona and that charge-transfer reactions between accelerated protons and partially-stripped coronal ions are an important source of ENAs in solar events.

  20. Observations and Interpretations of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event

    Science.gov (United States)

    Mewaldt, R. A.; Leske, R. A.; Shih, A. Y.; Stone, E. C.; Barghouty, A. f.; Cohen, C. M. S.; Cummings, A. c.; Labrador, A. W.; vonRosenvinge, T. T.

    2009-01-01

    We discuss recently reported observations of energetic neutral hydrogen atoms (ENAs) from an X9 solar flare/coronal mass ejection event on 5 December 2006, located at E79. The observations were made by the Low Energy Telescopes (LETs) on STEREO A and B. Prior to the arrival of the main solar energetic particle (SEP) event at Earth, both LETs observed a sudden burst of 1.6 to 15 MeV energetic neutral hydrogen atoms produced by either flare or shock-accelerated protons. RHESSI measurements of the 2.2-MeV gamma-ray line provide an estimate of the number of interacting flare-accelerated protons in this event, which leads to an improved estimate of ENA production by flare-accelerated protons. Taking into account ENA losses, we find that the observed ENAs must have been produced in the high corona at heliocentric distances > or equal to 2 solar radii. Although there are no CME images from this event, it is shown that CME-shock-accelerated protons can, in principle, produce a time-history consistent with the observations.

  1. Precision spectroscopy of the 2S-4P{sub 1/2} transition in atomic hydrogen on a cold thermal beam of optically excited 2S atoms

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Axel; Kolachevsky, Nikolai; Alnis, Janis; Yost, Dylan C.; Matveev, Arthur; Parthey, Christian G.; Pohl, Randolf; Udem, Thomas [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Khabarova, Ksenia [FSUE ' VNIIFTRI' , 141570 Moscow (Russian Federation); Haensch, Theodor W. [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet, 80799 Muenchen (Germany)

    2013-07-01

    The 'proton size puzzle', i.e. the discrepancy between the values for the proton r.m.s. charge radius deduced from precision spectroscopy of atomic hydrogen and electron-proton-scattering on one side and the value deduced from muonic hydrogen spectroscopy on the other side, has been persisting for more than two years now. Although huge efforts have been put into trying to resolve this discrepancy from experimental and theoretical side, no convincing argument could be found so far. In this talk, we report on a unique precision spectroscopy experiment on atomic hydrogen, which is aiming to bring some light to the hydrogen part of the puzzle: In contrast to any previous high resolution experiment probing a transition frequency between the meta-stable 2S state and a higher lying nL state (n=3,4,6,8,12, L=S,P,D), our measurement of the 2S-4P{sub 1/2} transition frequency is the first experiment being performed on a cold thermal beam of hydrogen atoms optically excited to the 2S state. We will discuss how this helps to efficiently suppresses leading systematic effects of previous measurements and present the preliminary results we obtained so far.

  2. Determination of the Kinematics of the Qweak Experiment and Investigation of an Atomic Hydrogen Moller Polarimeter

    Energy Technology Data Exchange (ETDEWEB)

    Gray, Valerie M. [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2018-01-01

    The Qweak experiment has tested the Standard Model through making a precise measurement of the weak charge of the proton (QpW). This was done through measuring the parity-violating asymmetry for polarized electrons scattering off of unpolarized protons. The parity-violating asymmetry measured is directly proportional to the four-momentum transfer (Q^2) from the electron to the proton. The extraction of QpW from the measured asymmetry requires a precise Q^2 determination. The Qweak experiment had a Q^2 = 24.8 ± 0.1 m(GeV^2) which achieved the goal of an uncertainty of <= 0.5%. From the measured asymmetry and Q^2, QpW was determined to be 0.0719 ± 0.0045, which is in good agreement with the Standard Model prediction. This puts a 7.5 TeV lower limit on possible "new physics". This dissertation describes the analysis of Q^2 for the Qweak experiment. Future parity-violating electron scattering experiments similar to the Qweak experiment will measure asymmetries to high precision in order to test the Standard Model. These measurements will require the beam polarization to be measured to sub-0.5% precision. Presently the electron beam polarization is measured through Moller scattering off of a ferromagnetic foil or through using Compton scattering, both of which can have issues reaching this precision. A novel Atomic Hydrogen Moller Polarimeter has been proposed as a non-invasive way to measure the polarization of an electron beam via Moller scattering off of polarized monatomic hydrogen gas. This dissertation describes the development and initial analysis of a Monte Carlo simulation of an Atomic Hydrogen Moller Polarimeter.

  3. Incorporating nitrogen atoms into cobalt nanosheets as a strategy to boost catalytic activity toward CO2 hydrogenation

    Science.gov (United States)

    Wang, Liangbing; Zhang, Wenbo; Zheng, Xusheng; Chen, Yizhen; Wu, Wenlong; Qiu, Jianxiang; Zhao, Xiangchen; Zhao, Xiao; Dai, Yizhou; Zeng, Jie

    2017-11-01

    Hydrogenation of CO2 into fuels and useful chemicals could help to reduce reliance on fossil fuels. Although great progress has been made over the past decades to improve the activity of catalysts for CO2 hydrogenation, more efficient catalysts, especially those based on non-noble metals, are desired. Here we incorporate N atoms into Co nanosheets to boost the catalytic activity toward CO2 hydrogenation. For the hydrogenation of CO2, Co4N nanosheets exhibited a turnover frequency of 25.6 h-1 in a slurry reactor under 32 bar pressure at 150 °C, which was 64 times that of Co nanosheets. The activation energy for Co4N nanosheets was 43.3 kJ mol-1, less than half of that for Co nanosheets. Mechanistic studies revealed that Co4N nanosheets were reconstructed into Co4NHx, wherein the amido-hydrogen atoms directly interacted with the CO2 to form HCOO* intermediates. In addition, the adsorbed H2O* activated amido-hydrogen atoms via the interaction of hydrogen bonds.

  4. Concerted hydrogen atom and electron transfer mechanism for catalysis by lysine-specific demethylase.

    Science.gov (United States)

    Yu, Tao; Higashi, Masahiro; Cembran, Alessandro; Gao, Jiali; Truhlar, Donald G

    2013-07-18

    We calculate the free energy profile for the postulated hydride transfer reaction mechanism for the catalysis of lysine demethylation by lysine-specific demethylase LSD1. The potential energy surface is obtained by using combined electrostatically embedded multiconfiguration molecular mechanics (EE-MCMM) and single-configuration molecular mechanics (MM). We employ a constant valence bond coupling term to obtain analytical energies and gradients of the EE-MCMM subsystem, which contains 45 quantum mechanics (QM) atoms and which is parametrized with density functional calculations employing specific reaction parameters obtained by matching high-level wave function calculations. In the MM region, we employ the Amber ff03 and TIP3P force fields. The free energy of activation at 300 K is calculated by molecular dynamics (MD) umbrella sampling on a system with 102,090 atoms as the maximum of the free energy profile along the reaction coordinate as obtained by the weighted histogram analysis method with 17 umbrella sampling windows. This yields a free energy of activation of only 10 kcal/mol, showing that the previously postulated direct hydride transfer reaction mechanism is plausible, although we find that it is better interpreted as a concerted transfer of a hydrogen atom and an electron.

  5. Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst.

    Science.gov (United States)

    Cao, Xinrui; Fu, Qiang; Luo, Yi

    2014-05-14

    The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu55 nanoparticles have been systemically examined for H2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu55 shell can considerably reduce the activation energy of H2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.

  6. A comprehensive study on atomic layer deposition of molybdenum sulfide for electrochemical hydrogen evolution

    Science.gov (United States)

    Kwon, Do Hyun; Jin, Zhenyu; Shin, Seokhee; Lee, Wook-Seong; Min, Yo-Sep

    2016-03-01

    Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically-active surface area. In addition, the ALD-MoSx/CFP catalysts exhibit excellent catalytic stability due to the strong adhesion of MoSx on the CFP and the mixed phase.Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically

  7. Monolithic Laser Scribed Graphene Scaffold with Atomic Layer Deposited Platinum for Hydrogen Evolution Reaction

    KAUST Repository

    Nayak, Pranati

    2017-09-01

    The use of three-dimensional (3D) electrode architectures as scaffolds for conformal deposition of catalysts is an emerging research area with significant potential for electrocatalytic applications. In this study, we report the fabrication of monolithic, self-standing, 3D graphitic carbon scaffold with conformally deposited Pt by atomic layer deposition (ALD) as a hydrogen evolution reaction catalyst. Laser scribing is employed to transform polyimide into 3D porous graphitic carbon, which possesses good electronic conductivity and numerous edge plane sites. This laser scribed graphene (LSG) architecture makes it possible to fabricate monolithic electrocatalyst support without any binders or conductive additives. The synergistic effect between ALD of Pt on 3D network of LSG provides an avenue for minimal yet effective Pt usage, leading to an enhanced HER activity. This strategy establish a general approach for inexpensive and large scale HER device fabrication with minimum catalyst cost.

  8. Rovibrational excitation of HD in collisions with atomic and molecular hydrogen

    Science.gov (United States)

    Flower, D. R.; Roueff, E.

    1999-11-01

    We have computed cross-sections and rate coefficients for rovibrational transitions in HD, induced by collisions with atomic and molecular hydrogen. We employed fully quantum-mechanical methods and the potential of Boothroyd et al. for H-HD, and that of Schwenke for H2-HD. The rate coefficients for vibrational relaxation v=1->0 of HD are compared with the corresponding values for H2. The influence of vibrationally excited channels on the rate coefficients for rotational transitions within the v=0 vibrational ground state of HD is shown to be small at T=500K, where T is the kinetic temperature. The rate coefficients, for 100http://ccp7.dur.ac.uk/.

  9. Tunable Electrical Properties of Vanadium Oxide by Hydrogen-Plasma-Treated Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Helen Hejin Park

    2017-04-01

    Full Text Available In this study, a plasma-modified process was developed to control the electrical properties of atomic layer deposition (ALD-grown vanadium dioxide (VO2, which is potentially useful for applications such as resistive switching devices, bolometers, and plasmonic metamaterials. By inserting a plasma pulse with varying H2 gas flow into each ALD cycle, the insulator-to-metal transition (IMT temperature of postdeposition-annealed crystalline VO2 films was adjusted from 63 to 78 °C. Film analyses indicate that the tunability may arise from changes in grain boundaries, morphology, and compositional variation despite hydrogen not remaining in the annealed VO2 films. This growth method, which enables a systematic variation of the electronic behavior of VO2, provides capabilities beyond those of the conventional thermal ALD and plasma-enhanced ALD.

  10. The Quantum Black Hole as a Hydrogen Atom: Microstates Without Strings Attached

    CERN Document Server

    Hooft, Gerard t

    2016-01-01

    Applying an expansion in spherical harmonics, turns the black hole with its microstates into something about as transparent as the hydrogen atom was in the early days of quantum mechanics. It enables us to present a concise description of the evolution laws of these microstates, linking them to perturbative quantum field theory, in the background of the Schwarzschild metric. Three pieces of insight are obtained: One, we learn how the gravitational back reaction, whose dominant component can be calculated exactly, turns particles entering the hole, into particles leaving it, by exchanging the momentum- and position operators; two, we find out how this effect removes firewalls, both on the future and the past event horizon, and three, we discover that the presence of region II in the Penrose diagram forces a topological twist in the background metric, culminating in antipodal identification. Although a cut-off is required that effectively replaces the transverse coordinates by a lattice, the effect of such a cu...

  11. High precision X-ray spectroscopy in hydrogen-like fermionic and bosonic atomic systems

    Energy Technology Data Exchange (ETDEWEB)

    Borchert, G.L.; Anagnostopoulos, D.; Augsburger, M.; Belmiloud, D.; Castelli, C.; Chatellard, D.; Daum, M.; Egger, J.P.; El-Khoury, P.; Elble, M.; Frosch, R.; Gorke, H.; Gotta, D.; Hauser, P.; Indelicato, P.; Kirch, K.; Lenz, S.; Nelms, N.; Rashid, K.; Schult, O.W.B. (and others)

    1998-11-15

    Some time after its formation an exotic atom may be considered a hydrogen-like system consisting of a nucleus and an exotic particle in a bound state. In this situation it is an ideal tool to study cascade properties, while for the innermost orbits it can be used to probe the interaction with the nucleus. From an extended series of experiments using high resolution X-ray spectroscopy for both aspects typical examples are reported and preliminary results are given: 1. To determine the complex scattering length in p-barH the 3D{yields}2P hyperfine transitions have been measured. 2. To determine the pion mass the 5 {yields} 4 transitions in {pi}{sup 14}N have been studied. In all cases a major contribution to the uncertainty originates from the calibration. Therefore a new method is proposed that will establish a universal set of high precision calibration lines for pionic, muonic and electronic systems.

  12. The influence hydrogen atom addition has on charge switching during motion of the metal atom in endohedral Ca@C60H4 isomers

    Science.gov (United States)

    Raggi, G.; Besley, E.; Stace, A. J.

    2016-01-01

    Density functional theory has been applied in a study of charge transfer between an endohedral calcium atom and the fullerene cage in Ca@C60H4 and [Ca@C60H4]+ isomers. Previous calculations on Ca@C60 have shown that the motion of calcium within a fullerene is accompanied by large changes in electron density on the carbon cage. Based on this observation, it has been proposed that a tethered endohedral fullerene might form the bases of a nanoswitch. Through the addition of hydrogen atoms to one hemisphere of the cage it is shown that, when compared with Ca@C60, asymmetric and significantly reduced energy barriers can be generated with respect to motion of the calcium atom. It is proposed that hydrogen atom addition to a fullerene might offer a route for creating a bi-stable nanoswitch that can be fine-tuned through the selection of an appropriate isomer and number of atoms attached to the cage of an endohedral fullerene. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’. PMID:27501967

  13. Observation and Interpretation of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Flare

    Science.gov (United States)

    Barghouty, A. F.; Mewaldt, R. A.; Leske, R. A.; Shih, A. Y.; Stone, E. C.; Cohen, C. M. S.; Cummings, A. C.; Labrador, A. W.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

    2009-01-01

    We discuss observations of energetic neutral hydrogen atoms (ENAs) from a solar flare/coronal mass ejection event reported by Mewaldt et al. (2009). The observations were made during the 5 December 2006 X9 solar flare, located at E79, by the Low Energy Telescopes (LETs) on STEREO A and B. Prior to the arrival of the main solar energetic particle (SEP) event at Earth, both LETs observed a sudden burst of 1.6 to 15 MeV particles arriving from the Sun. The derived solar emission profile, arrival directions, and energy spectrum all show that the atoms produced by either flare or shock-accelerated protons. RHESSI measurements of the 2.2-MeV gamma-ray line provide an estimate of the number of interacting flare-accelerated protons in this event, which leads to an improved estimate of ENA production by flare-accelerated protons. CME-driven shock acceleration is also considered. Taking into account ENA losses, we conclude that the observed ENAs must have been produced in the high corona at heliocentric distances .2 solar radii.

  14. Emission of fast hydrogen atoms at a plasma–solid interface in a low density plasma containing noble gases

    Science.gov (United States)

    Marchuk, O.; Brandt, C.; Pospieszczyk, A.; Reinhart, M.; Brezinsek, S.; Unterberg, B.; Dickheuer, S.

    2018-01-01

    The source of the broad radiation of fast hydrogen atoms in plasmas containing noble gases remains one of the most discussed problems relating to plasma–solid interface. In this paper, we present a detailed study of Balmer lines emission generated by fast hydrogen and deuterium atoms in an energy range between 40 and 300 eV in a linear magnetised plasma. The experiments were performed in gas mixtures containing hydrogen or deuterium and one of the noble gases (He, Ne, Ar, Kr or Xe). In the low-pressure regime (0.01–0.1 Pa) of plasma operation emission is detected by using high spectral and spatial resolution spectrometers at different lines-of-sight for different target materials (C, Fe, Rh, Pd, Ag and W). We observed the spatial evolution for H α , H β and H γ lines with a resolution of 50 μm in front of the targets, proving that emission is induced by reflected atoms only. The strongest radiation of fast atoms was observed in the case of Ar–D or Ar–H discharges. It is a factor of five less in Kr–D plasma and an order of magnitude less in other rare gas mixture plasmas. First, the present work shows that the maximum of emission is achieved for the kinetic energy of 70–120 eV/amu of fast atoms. Second, the emission profile depends on the target material as well as surface characteristics such as the particle reflection, e.g. angular and energy distribution, and the photon reflectivity. Finally, the source of emission of fast atoms is narrowed down to two processes: excitation caused by collisions with noble gas atoms in the ground state, and excitation transfer between the metastable levels of argon and the excited levels of hydrogen or deuterium.

  15. Use of a PhET Interactive Simulation in General Chemistry Laboratory: Models of the Hydrogen Atom

    Science.gov (United States)

    Clark, Ted M.; Chamberlain, Julia M.

    2014-01-01

    An activity supporting the PhET interactive simulation, Models of the Hydrogen Atom, has been designed and used in the laboratory portion of a general chemistry course. This article describes the framework used to successfully accomplish implementation on a large scale. The activity guides students through a comparison and analysis of the six…

  16. 20(R- and 20(S-Simarolide Epimers Isolated from Simaba cuneata: Chemical Shifts Assignment of Carbon and Hydrogen Atoms

    Directory of Open Access Journals (Sweden)

    Vieira Ivo José Curcino

    1999-01-01

    Full Text Available The C25-quassinoids 20(R- and 20(S-simarolide were isolated from Simaba cuneata, Simaroubaceae. The structures of these two compounds were characterized by spectral data, including 1D and 2D NMR spectra which were also used for the complete assignment of the carbon and hydrogen atom chemical shifts.

  17. Visualization of a Large Set of Hydrogen Atomic Orbital Contours Using New and Expanded Sets of Parametric Equations

    Science.gov (United States)

    Rhile, Ian J.

    2014-01-01

    Atomic orbitals are a theme throughout the undergraduate chemistry curriculum, and visualizing them has been a theme in this journal. Contour plots as isosurfaces or contour lines in a plane are the most familiar representations of the hydrogen wave functions. In these representations, a surface of a fixed value of the wave function ? is plotted…

  18. Single crystal to single crystal transformation and hydrogen-atom transfer upon oxidation of a cerium coordination compound.

    Science.gov (United States)

    Williams, Ursula J; Mahoney, Brian D; Lewis, Andrew J; DeGregorio, Patrick T; Carroll, Patrick J; Schelter, Eric J

    2013-04-15

    Trivalent and tetravalent cerium compounds of the octamethyltetraazaannulene (H2omtaa) ligand have been synthesized. Electrochemical analysis shows a strong thermodynamic preference for the formal cerium(IV) oxidation state. Oxidation of the cerium(III) congener Ce(Homtaa)(omtaa) occurs by hydrogen-atom transfer that includes a single crystal to single crystal transformation upon exposure to an ambient atmosphere.

  19. Complete classification of qualitatively different perturbations of the hydrogen atom in weak near-orthogonal electric and magnetic fields

    NARCIS (Netherlands)

    Efstathiou, K.; Lukina, O. V.; Sadovskii, D. A.

    2009-01-01

    We consider perturbations of the hydrogen atom by sufficiently small homogeneous static electric and magnetic fields in near-orthogonal configurations. Normalization of the Keplerian symmetry reveals that in the parameter space such systems belong in a 'zone' of systems close to the 1: 1 resonance,

  20. Theoretical investigation of the coupling between hydrogen-atom transfer and stacking interaction in adenine-thymine dimers.

    Science.gov (United States)

    Villani, Giovanni

    2013-04-15

    Three different dimers of the adenine-thymine (A-T) base pair are studied to point out the changes of important properties (structure, atomic charge, energy and so on) induced by coupling between the movement of the atoms in the hydrogen bonds and the stacking interaction. The comparison of these results with those for the A-T monomer system explains the role of the stacking interaction in the hydrogen-atom transfer in this biologically important base pair. The results support the idea that this coupling depends on the exact dimer considered and is different for the N-N and N-O hydrogen bonds. In particular, the correlation between the hydrogen transfer and the stacking interaction is more relevant for the N-N bridge than for the N-O one. Also, the two different mechanisms of two-hydrogen transfer (step by step and concerted) can be modified by the stacking interaction between the base pairs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Repulsive tip tilting as the dominant mechanism for hydrogen bond-like features in atomic force microscopy imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Alex J. [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Sakai, Yuki [Center for Computational Materials, Institution for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas, 78712 (United States); Kim, Minjung [Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States); Chelikowsky, James R. [Center for Computational Materials, Institute for Computational Engineering and Sciences, Departments of Physics and Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2016-05-09

    Experimental atomic force microscopy (AFM) studies have reported distinct features in regions with little electron density for various organic systems. These unexpected features have been proposed to be a direct visualization of intermolecular hydrogen bonding. Here, we apply a computational method using ab initio real-space pseudopotentials along with a scheme to account for tip tilting to simulate AFM images of the 8-hydroxyquinoline dimer and related systems to develop an understanding of the imaging mechanism for hydrogen bonds. We find that contrast for the observed “hydrogen bond” feature comes not from the electrostatic character of the bonds themselves but rather from repulsive tip tilting induced by neighboring electron-rich atoms.

  2. Intermolecular and intramolecular hydrogen bonds involving fluorine atoms: implications for recognition, selectivity, and chemical properties.

    Science.gov (United States)

    Dalvit, Claudio; Vulpetti, Anna

    2012-02-06

    A correlation between 19F NMR isotropic chemical shift and close intermolecular F⋅⋅⋅H-X contacts (with X=N or O) has been identified upon analysis of the X-ray crystal structures of fluorinated molecules listed in the Cambridge Structural Database (CSD). An optimal F⋅⋅⋅X distance involving primary and shielded secondary fluorine atoms in hydrogen-bond formation along with a correlation between F⋅⋅⋅H distance and F⋅⋅⋅H-X angle were also derived from the analysis. The hydrogen bonds involving fluorine are relevant, not only for the recognition mechanism and stabilization of a preferred conformation, but also for improvement in the permeability of the molecules, as shown with examples taken from a proprietary database. Results of an analysis of the small number of fluorine-containing natural products listed in the Protein Data Bank (PDB) appear to strengthen the derived correlation between 19F NMR isotropic chemical shift and interactions involving fluorine (also known as the "rule of shielding") and provides a hypothesis for the recognition mechanism and catalytic activity of specific enzymes. Novel chemical scaffolds, based on the rule of shielding, have been designed for recognizing distinct structural motifs present in proteins. It is envisaged that this approach could find useful applications in drug design for the efficient optimization of chemical fragments or promising compounds by increasing potency and selectivity against the desired biomolecular target. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Hydrogen atom transfer reactions of imido manganese(V) corrole: one reaction with two mechanistic pathways.

    Science.gov (United States)

    Zdilla, Michael J; Dexheimer, Jennifer L; Abu-Omar, Mahdi M

    2007-09-19

    Hydrogen atom transfer (HAT) reactions of (tpfc)MnNTs have been investigated (tpfc = 5,10,15-tris(pentafluorophenyl)corrole and Ts = p-toluenesulfonate). 9,10-Dihydroanthracene and 1,4-dihydrobenzene reduce (tpfc)MnNTs via HAT with second-order rate constants 0.16 +/- 0.03 and 0.17 +/- 0.01 M(-1) s(-1), respectively, at 22 degrees C. The products are the respective arenes, TsNH(2) and (tpfc)Mn(III). Conversion of (tpfc)MnNTs to (tpfc)Mn by reaction with dihydroanthracene exhibits isosbestic behavior, and formation of 9,9',10,10'-tetrahydrobianthracene is not observed, suggesting that the intermediate anthracene radical rebounds in a second fast step without accumulation of a Mn(IV) intermediate. The imido complex (tpfc)Mn(V)NTs abstracts a hydrogen atom from phenols as well. For example, 2,6-di-tert-butyl phenol is oxidized to the corresponding phenoxyl radical with a second-order rate constant of 0.32 +/- 0.02 M(-1) s(-1) at 22 degrees C. The other products from imido manganese(V) are TsNH(2) and the trivalent manganese corrole. Unlike reaction with dihydroarenes, when phenols are used isosbestic behavior is not observed, and formation of (tpfc)Mn(IV)(NHTs) is confirmed by EPR spectroscopy. A Hammett plot for various p-substituted 2,6-di-tert-butyl phenols yields a V-shaped dependence on sigma, with electron-donating substituents exhibiting the expected negative rho while electron-withdrawing substituents fall above the linear fit (i.e., positive rho). Similarly, a bond dissociation enthalpy (BDE) correlation places electron-withdrawing substituents above the well-defined negative slope found for the electron-donating substituents. Thus two mechanisms are established for HAT reactions in this system, namely, concerted proton-electron transfer and proton-gated electron transfer in which proton transfer is followed by electron transfer.

  4. The role of atomic hydrogen in regulating the scatter of the mass-metallicity relation

    Science.gov (United States)

    Brown, Toby; Cortese, Luca; Catinella, Barbara; Kilborn, Virginia

    2018-01-01

    In this paper, we stack neutral atomic hydrogen (H I) spectra for 9720 star-forming galaxies along the mass-metallicity relation. The sample is selected according to stellar mass (109 ≤ M⋆/M⊙ ≤ 1011) and redshift (0.02 ≤ z ≤ 0.05) from the overlap of the Sloan Digital Sky Survey and Arecibo Legacy Fast ALFA survey. We confirm and quantify the strong anticorrelation between H I mass and gas-phase metallicity at fixed stellar mass. Furthermore, we show for the first time that the relationship between gas content and metallicity is consistent between different metallicity estimators, contrary to the weaker trends found with star formation which are known to depend on the observational techniques used to derive oxygen abundances and star formation rates. When interpreted in the context of theoretical work, this result supports a scenario where galaxies exist in an evolving equilibrium between gas, metallicity and star formation. The fact that deviations from this equilibrium are most strongly correlated with gas mass suggests that the scatter in the mass-metallicity relation is primarily driven by fluctuations in gas accretion.

  5. Collisions of electrons with hydrogen atoms I. Package outline and high energy code

    Science.gov (United States)

    Benda, Jakub; Houfek, Karel

    2014-11-01

    Being motivated by the applied researchers' persisting need for accurate scattering data for the collisions of electrons with hydrogen atoms, we developed a computer package-Hex-that is designed to provide trustworthy results for all basic discrete and continuous processes within non-relativistic framework. The package consists of several computational modules that implement different methods, valid for specific energy regimes. Results of the modules are kept in a common database in the unified form of low-level scattering data (partial-wave T-matrices) and accessed by an interface program which is able to produce various derived quantities like e.g. differential and integral cross sections. This article is the first one of a series of articles that are concerned with the implementation and testing of the modules. Here we give an overview of their structure and present (a) the command-line interface program hex-db that can be also easily compiled into a derived code or used as a backend for a web-page form and (b) simple illustrative module specialized for high energies, hex-dwba, that implements distorted and plane wave Born approximation.

  6. Atomic data on inelastic processes in low-energy manganese-hydrogen collisions

    Science.gov (United States)

    Belyaev, Andrey K.; Voronov, Yaroslav V.

    2017-10-01

    Aims: The aim of this paper is to calculate cross sections and rate coefficients for inelastic processes in low-energy Mn + H and Mn+ + H- collisions, especially, for processes with high and moderate rate coefficients. These processes are required for non-local thermodynamic equilibrium (non-LTE) modeling of manganese spectra in cool stellar atmospheres, and in particular, for metal-poor stars. Methods: The calculations of the cross sections and the rate coefficients were performed by means of the quantum model approach within the framework of the Born-Oppenheimer formalism, that is, the asymptotic semi-empirical method for the electronic MnH molecular structure calculation followed by the nonadiabatic nuclear dynamical calculation by means of the multichannel analytic formulas. Results: The cross sections and the rate coefficients for low-energy inelastic processes in manganese-hydrogen collisions are calculated for all transitions between 21 low-lying covalent states and one ionic state. We show that the highest values of the cross sections and the rate coefficients correspond to the mutual neutralization processes into the final atomic states Mn(3d54s(7S)5s e 6S), Mn(3d54s(7S)5p y 8P°), Mn(3d54s(7S)5s e 8S), Mn(3d54s(7S)4d e 8D) [the first group], the processes with the rate coefficients (at temperature T = 6000 K) of the values 4.38 × 10-8, 2.72 × 10-8, 1.98 × 10-8, and 1.59 × 10-8 cm3/ s, respectively, that is, with the rate coefficients exceeding 10-8 cm3/ s. The processes with moderate rate coefficients, that is, with values between 10-10 and 10-8 cm3/ s include many excitation, de-excitation, mutual neutralization and ion-pair formation processes. In addition to other processes involving the atomic states from the first group, the processes from the second group include those involving the following atomic states: Mn(3d5(6S)4s4p (1P°) y 6P°), Mn(3d54s(7S)4d e 6D), Mn(3d54s(7S)5p w 6P°), Mn(3d5(4P)4s4p (3P°) y 6D°), Mn(3d5(4G)4s4p (3P°) y 6F

  7. Temperature-dependent kinetics of charge transfer, hydrogen-atom transfer, and hydrogen-atom expulsion in the reaction of CO+ with CH4 and CD4.

    Science.gov (United States)

    Melko, Joshua J; Ard, Shaun G; Johnson, Ryan S; Shuman, Nicholas S; Guo, Hua; Viggiano, Albert A

    2014-09-18

    We have determined the rate constants and branching ratios for the reactions of CO(+) with CH4 and CD4 in a variable-temperature selected ion flow tube. We find that the rate constants are collisional for all temperatures measured (193-700 K for CH4 and 193-500 K for CD4). For the CH4 reaction, three product channels are identified, which include charge transfer (CH4(+) + CO), H-atom transfer (HCO(+) + CH3), and H-atom expulsion (CH3CO(+) + H). H-atom transfer is slightly preferred to charge transfer at low temperature, with the charge-transfer product increasing in contribution as the temperature is increased (H-atom expulsion is a minor product for all temperatures). Analogous products are identified for the CD4 reaction. Density functional calculations on the CO(+) + CH4 reaction were also conducted, revealing that the relative temperature dependences of the charge-transfer and H-atom transfer pathways are consistent with an initial charge transfer followed by proton transfer.

  8. Two-step high-resolution laser spectroscopy of the Stark substates of the n = 33 level in atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Delsart, C.; Cabaret, L.; Blondel, C.; Champeau, R.J.

    1987-09-28

    Two synchronised pulsed single-mode tunable laser systems are used to excite atomic hydrogen in an atomic beam. A vacuum ultraviolet laser populates first the 2p /sup 2/Psub(3/2) sublevel from the ground 1s/sup 2/Ssub(1/2) state. A second-step UV laser selects substates of the n = 33 manifold in the presence of a weak electric field. Stark patterns of this manifold are recorded for different polarisation configurations of the exciting light beams. The measured relative intensities of the Stark components agree with the theoretical excitation probabilities in the two-step process, calculated to the first order of perturbation theory. Varying the field value of the ionisation field pulse also makes it possible to plot the ionisation threshold against the parabolic quantum number in the n = 33 manifold. The results agree with an asymptotic formula of ionisation probabilities for hydrogen perturbed by an electric field.

  9. Investigation of Atomic Physics and Frequency Stability with a Croygenic Hydrogen Laser

    National Research Council Canada - National Science Library

    Walsworth, Ronald

    1997-01-01

    .... The cryogenic hydrogen maser (CHM) operates at low temperatures, and may provide frequency stability that is one to three orders of magnitude better than a room temperature hydrogen maser because of greatly reduced thermal noise and larger signal power...

  10. Kinetics of reduction of a RuO2(110) film on Ru by atomic hydrogen

    NARCIS (Netherlands)

    Ugur, D.; Storm, A.J.; Verberk, R.; Brouwer, J.C.; Sloof, W.G.

    2013-01-01

    The kinetics and the mechanism of reduction of a RuO2(110) film, grown thermally on a Ru(0001) surface, has been studied in the temperature range of 60-200 °C by using an atomic hydrogen flux of 2 × 1019 at. H m-2 s-1. The reduction kinetics is dominated by the creation of oxygen vacancies at the

  11. Wave-function Visualization of Core-induced Interaction of Non-hydrogenic Rydberg Atom in Electric Field

    CERN Document Server

    Gao, W; Cheng, H; Zhang, S S; Liu, H P

    2015-01-01

    We have investigated the wave-function feature of Rydberg sodium in a uniform electric field and found that the core-induced interaction of non-hydrogenic atom in electric field can be directly visualized in the wave-function. As is well known, the hydrogen atom in electric field can be separated in parabolic coordinates (\\eta, \\xi), whose eigen-function can show a clear pattern towards negative and positive directions corresponding to the so-called red and blue states without ambiguity, respectively. It can be served as a complete orthogonal basis set to study the core-induced interaction of non-hydrogenic atom in electric field. Owing to complete different patterns of the probability distribution for red and blue states, the interaction can be visualized in the wave-function directly via superposition. Moreover, the constructive and destructive interferences between red and blue states are also observed in the wave-function, explicitly explaining the experimental measurement for the spectral oscillator stre...

  12. Hydrogen storage and stability properties of Pd-Pt solid-solution nanoparticles revealed via atomic and electronic structure.

    Science.gov (United States)

    Kumara, Loku Singgappulige Rosantha; Sakata, Osami; Kobayashi, Hirokazu; Song, Chulho; Kohara, Shinji; Ina, Toshiaki; Yoshimoto, Toshiki; Yoshioka, Satoru; Matsumura, Syo; Kitagawa, Hiroshi

    2017-11-06

    Bimetallic Pd1-x Pt x solid-solution nanoparticles (NPs) display charging/discharging of hydrogen gas, which has relevance for fuel cell technologies; however, the constituent elements are immiscible in the bulk phase. We examined these material systems using high-energy synchrotron X-ray diffraction, X-ray absorption fine structure and hard X-ray photoelectron spectroscopy techniques. Recent studies have demonstrated the hydrogen storage properties and catalytic activities of Pd-Pt alloys; however, comprehensive details of their structural and electronic functionality at the atomic scale have yet to be reported. Three-dimensional atomic-scale structure results obtained from the pair distribution function (PDF) and reverse Monte Carlo (RMC) methods suggest the formation of a highly disordered structure with a high cavity-volume-fraction for low-Pt content NPs. The NP conduction band features, as extracted from X-ray absorption near-edge spectra at the Pd and Pt L III -edge, suggest that the Pd conduction band is filled by Pt valence electrons. This behaviour is consistent with observations of the hydrogen storage capacity of these NPs. The broadening of the valence band width and the down-shift of the d-band centre away from the Fermi level upon Pt substitution also provided evidence for enhanced stability of the hydride (ΔH) features of the Pd1-x Pt x solid-solution NPs with a Pt content of 8-21 atomic percent.

  13. Chemical Reactivity Dynamics and Quantum Chaos in Highly Excited Hydrogen Atoms in an External Field: A Quantum Potential Approach

    Directory of Open Access Journals (Sweden)

    B. Maiti

    2002-04-01

    Full Text Available Abstract: Dynamical behavior of chemical reactivity indices like electronegativity, hardness, polarizability, electrophilicity and nucleophilicity indices is studied within a quantum fluid density functional framework for the interactions of a hydrogen atom in its ground electronic state (n = 1 and an excited electronic state (n = 20 with monochromatic and bichromatic laser pulses. Time dependent analogues of various electronic structure principles like the principles of electronegativity equalization, maximum hardness, minimum polarizability and maximum entropy have been found to be operative. Insights into the variation of intensities of the generated higher order harmonics on the color of the external laser field are obtained. The quantum signature of chaos in hydrogen atom has been studied using a quantum theory of motion and quantum fluid dynamics. A hydrogen atom in the electronic ground state (n = 1 and in an excited electronic state ( n = 20 behaves differently when placed in external oscillating monochromatic and bichromatic electric fields. Temporal evolutions of Shannon entropy, quantum Lyapunov exponent and Kolmogorov – Sinai entropy defined in terms of the distance between two initially close Bohmian trajectories for these two cases show marked differences. It appears that a larger uncertainty product and a smaller hardness value signal a chaotic behavior.

  14. Thermodynamics of various F420 coenzyme models as sources of electrons, hydride ions, hydrogen atoms and protons in acetonitrile.

    Science.gov (United States)

    Xia, Ke; Shen, Guang-Bin; Zhu, Xiao-Qing

    2015-06-14

    32 F420 coenzyme models with alkylation of the three different N atoms (N1, N3 and N10) in the core structure (XFH(-)) were designed and synthesized and the thermodynamic driving forces (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the 32 XFH(-) releasing hydride ions, hydrogen atoms and electrons, the thermodynamic driving forces of the 32 XFH˙ releasing protons and hydrogen atoms and the thermodynamic driving forces of XF(-)˙ releasing electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The effects of the methyl group at N1, N3 and N10 and a negative charge on N1 and N10 atoms on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were examined; the results show that seating arrangements of the methyl group and the negative charge have remarkably different effects on the thermodynamic properties of the F420 coenzyme models and their related reaction intermediates. The effects of the substituents at C7 and C8 on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were also examined; the results show that the substituents at C7 and C8 have good Hammett linear free energy relationships with the six thermodynamic parameters. Meanwhile, a reasonable determination of possible reactions between members of the F420 family and NADH family in vivo was given according to a thermodynamic analysis platform constructed using the elementary step thermodynamic parameter of F420 coenzyme model 2FH(-) and NADH model MNAH releasing hydride ions in acetonitrile. The information disclosed in this work can not only fill a gap in the chemical thermodynamics of F420 coenzyme models as a class of very important organic sources of electrons, hydride ions, hydrogen atoms and protons, but also strongly promote the fast development of the chemistry and applications of F420 coenzyme.

  15. Magnetic resonance studies of atomic hydrogen at zero field and low temperature. Recombination and binding on liquid helium

    Energy Technology Data Exchange (ETDEWEB)

    Jochemsen, R.; Morrow, M.; Berlinsky, A.J.; Hardy, W.N. (British Columbia Univ., Vancouver (Canada). Dept. of Physics)

    1982-07-01

    Magnetic resonance studies at zero field are reported for atomic hydrogen gas confined in a closed glass bulb with helium-coated walls for T<1 K in a dilution refrigerator. Low-energy r.f. discharge pulses have been used to produce H atoms at temperatures as low as T=0.06 K. The atom density nsub(H) (10/sup 9/..H/sub 2/+wall. From the temperature dependence of the rate constant K we have determined the binding energy of H on liquid /sup 4/He and /sup 3/He, and also the cross section for recombination on the surface.

  16. Massive stars formed in atomic hydrogen reservoirs: H i observations of gamma-ray burst host galaxies

    DEFF Research Database (Denmark)

    Michałowski, M. J.; Gentile, G.; Hjorth, J.

    2015-01-01

    Long gamma-ray bursts (GRBs), among the most energetic events in the Universe, are explosions of massive and short-lived stars, so they pinpoint locations of recent star formation. However, several GRB host galaxies have recently been found to be deficient in molecular gas (H2), believed to be th......Long gamma-ray bursts (GRBs), among the most energetic events in the Universe, are explosions of massive and short-lived stars, so they pinpoint locations of recent star formation. However, several GRB host galaxies have recently been found to be deficient in molecular gas (H2), believed......, implying high levels of atomic hydrogen (HI), which suggests that the connection between atomic gas and star formation is stronger than previously thought. In this case, it is possible that star formation is directly fuelled by atomic gas (or that the H1-to-H2 conversion is very efficient, which rapidly...

  17. Benchmark Calculation of Radial Expectation Value \\varvec{< r^{-2} \\rangle } for Confined Hydrogen-Like Atoms and Isotropic Harmonic Oscillators

    Science.gov (United States)

    Yu, Rong Mei; Zan, Li Rong; Jiao, Li Guang; Ho, Yew Kam

    2017-09-01

    Spatially confined atoms have been extensively investigated to model atomic systems in extreme pressures. For the simplest hydrogen-like atoms and isotropic harmonic oscillators, numerous physical quantities have been established with very high accuracy. However, the expectation value of which is of practical importance in many applications has significant discrepancies among calculations by different methods. In this work we employed the basis expansion method with cut-off Slater-type orbitals to investigate these two confined systems. Accurate values for several low-lying bound states were obtained by carefully examining the convergence with respect to the size of basis. A scaling law for was derived and it is used to verify the accuracy of numerical results. Comparison with other calculations show that the present results establish benchmark values for this quantity, which may be useful in future studies.

  18. Selection of a Gaussian basis set for calculating the Bethe logarithm for the ground state of the hydrogen atom

    Science.gov (United States)

    Stanke, Monika; Adamowicz, Ludwik; Kedziera, Dariusz

    2013-07-01

    The inclusion of the leading quantum electrodynamic energy correction is unavoidable if one aims for sub 0.01 cm-1 accuracy in the calculations of atomic and molecular spectra. The important part of the calculation of the correction is the determination of the value of the so-called Bethe logarithm (ln k 0). In this work, we examine how to construct Gaussian basis sets for such calculations. While the testing is performed for the ground state of the hydrogen atom, the results allow us to suggest how the construction of appropriate basis sets can be handled in ln k 0 calculations of atoms and molecules with more than one electron performed with explicitly correlated all-electron Gaussian functions.

  19. Adiabatic Variational Theory for Cold Atom-Molecule Collisions: Application to a Metastable Helium Atom Colliding with ortho- and para-Hydrogen Molecules.

    Science.gov (United States)

    Pawlak, Mariusz; Shagam, Yuval; Klein, Ayelet; Narevicius, Edvardas; Moiseyev, Nimrod

    2017-03-16

    We recently developed an adiabatic theory for cold molecular collision experiments. In our previous application of this theory ( Pawlak, M.; et al. J. Chem. Phys. 2015 , 143 , 074114 ), we assumed that during the experiment the collision of an atom with a diatom takes place when the diatom is in the ground rotational state and is located in a plane. In this paper, we present how the variational approach of the adiabatic theory for low-temperature collision experiments can be used for the study a 5D collision between the atom and the diatomic molecule with no limitations on its rotational quantum states and no plane restrictions. Moreover, we show here the dramatic differences in the measured reaction rates of He(23S1) + ortho/para-H2 → He(1s2) + ortho/para-H2+ + e- resulting from the anisotropic long-range interactions in the reaction. In collisions of metastable helium with molecular hydrogen in the ground rotational state, the isotropic potential term dominates the dynamics. When the collision is with molecular hydrogen in the first excited rotational state, the nonisotropic interactions play an important role in the dynamics. The agreement of our results with the latest experimental findings ( Klein , A. ; et al. Nat. Phys. 2017 , 13 , 35 - 38 ) is very good.

  20. Quasi-metallic behavior of ZnO grown by atomic layer deposition: The role of hydrogen

    Science.gov (United States)

    Beh, Holger; Hiller, Daniel; Bruns, Michael; Welle, Alexander; Becker, Hans-Werner; Berghoff, Birger; Sürgers, Christoph; Merz, Rolf; Zacharias, Margit

    2017-07-01

    Zinc oxide (ZnO) fabricated by atomic layer deposition (ALD) is intrinsically well-conductive (˜5 mΩ cm), in contrast to the single-crystalline bulk material or sputtered ZnO thin films. There are generally three groups of candidates for the intrinsic n-type conductivity: intrinsic point defects, elemental impurities other than hydrogen, and incorporated hydrogen itself. In this study, we assess the different candidates concerning their impact on conductivity. In the presence of free electron densities of up to 5 × 1019 cm-3, impurities other than hydrogen are ruled out due to their ultra-low concentrations in the ppm range. Intrinsic point defects are also considered unlikely since the evolution of conductivity with deposition temperature is not reproduced in the Zn/O ratio as measured by Rutherford backscattering spectrometry. Hence, the most promising candidate is hydrogen with a concentration of ˜1 at. %, i.e., more than sufficient to account for the free electron density. In addition, we find a correlation between the deposition-temperature dependence of the carrier concentration and the hydrogen concentration. The formation energy of the conductive, hydrogen-related state is determined to be ˜40 meV. Hall measurements down to liquid helium temperatures revealed that the electron densities are constant over the whole temperature range. This constitutes a quasi-metallic behavior of ALD-ZnO for deposition temperatures of ≥150 °C. We propose that the very high concentration of hydrogen-induced donor states causes a vanishing ionization energy so that the donor band merges energetically with the ZnO conduction band. This model is supported by ultraviolet photoelectron spectroscopy measurements.

  1. Atomic-Level Organization of Vicinal Acid-Base Pairs through the Chemisorption of Aniline and Derivatives onto Mesoporous SBA15

    KAUST Repository

    Basset, Jean-Marie

    2016-06-09

    The design of novel heterogeneous catalysts with multiple adjacent functionalities is of high interest for heterogeneous catalysis. Herein, we report a method to obtain a majority bifunctional acid-base pairs on SBA15. Aniline reacts with SBA15 by opening siloxane bridges leading to N-phenylsilanamine-silanol pairs. In contrast with ammonia treated surfaces, the material is stable under air/moisture. Advanced solid state MAS NMR: 2D ¹H-¹H double-quantum, ¹H-¹³C HETCOR experiments and dynamic nuclear polarization enhanced ²⁹Si and ¹⁵N spectra demonstrate both the close proximity between the two moieties and the formation of a covalent Si-N surface bond and confirm the design of vicinal acid-base pairs. This approach was successfully applied to the design of a series of aniline derivatives bifunctional SBA15. A correlation of the substituents effects on the aromatic ring (Hammet parameters) on the kinetics of the model reaction of Knoevenagel is observed.

  2. Thermally stable single atom Pt/m-Al2O3 for selective hydrogenation and CO oxidation

    KAUST Repository

    Zhang, Zailei

    2017-07-27

    Single-atom metal catalysts offer a promising way to utilize precious noble metal elements more effectively, provided that they are catalytically active and sufficiently stable. Herein, we report a synthetic strategy for Pt single-atom catalysts with outstanding stability in several reactions under demanding conditions. The Pt atoms are firmly anchored in the internal surface of mesoporous Al2O3, likely stabilized by coordinatively unsaturated pentahedral Al3+ centres. The catalyst keeps its structural integrity and excellent performance for the selective hydrogenation of 1,3-butadiene after exposure to a reductive atmosphere at 200 °C for 24 h. Compared to commercial Pt nanoparticle catalyst on Al2O3 and control samples, this system exhibits significantly enhanced stability and performance for n-hexane hydro-reforming at 550 °C for 48 h, although agglomeration of Pt single-atoms into clusters is observed after reaction. In CO oxidation, the Pt single-atom identity was fully maintained after 60 cycles between 100 and 400 °C over a one-month period.

  3. Thermally stable single atom Pt/m-Al2O3 for selective hydrogenation and CO oxidation.

    Science.gov (United States)

    Zhang, Zailei; Zhu, Yihan; Asakura, Hiroyuki; Zhang, Bin; Zhang, Jiaguang; Zhou, Maoxiang; Han, Yu; Tanaka, Tsunehiro; Wang, Aiqin; Zhang, Tao; Yan, Ning

    2017-07-27

    Single-atom metal catalysts offer a promising way to utilize precious noble metal elements more effectively, provided that they are catalytically active and sufficiently stable. Herein, we report a synthetic strategy for Pt single-atom catalysts with outstanding stability in several reactions under demanding conditions. The Pt atoms are firmly anchored in the internal surface of mesoporous Al2O3, likely stabilized by coordinatively unsaturated pentahedral Al(3+) centres. The catalyst keeps its structural integrity and excellent performance for the selective hydrogenation of 1,3-butadiene after exposure to a reductive atmosphere at 200 °C for 24 h. Compared to commercial Pt nanoparticle catalyst on Al2O3 and control samples, this system exhibits significantly enhanced stability and performance for n-hexane hydro-reforming at 550 °C for 48 h, although agglomeration of Pt single-atoms into clusters is observed after reaction. In CO oxidation, the Pt single-atom identity was fully maintained after 60 cycles between 100 and 400 °C over a one-month period.

  4. Determination of thermodynamic affinities of various polar olefins as hydride, hydrogen atom, and electron acceptors in acetonitrile.

    Science.gov (United States)

    Cao, Ying; Zhang, Song-Chen; Zhang, Min; Shen, Guang-Bin; Zhu, Xiao-Qing

    2013-07-19

    A series of 69 polar olefins with various typical structures (X) were synthesized and the thermodynamic affinities (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the polar olefins obtaining hydride anions, hydrogen atoms, and electrons, the thermodynamic affinities of the radical anions of the polar olefins (X(•-)) obtaining protons and hydrogen atoms, and the thermodynamic affinities of the hydrogen adducts of the polar olefins (XH(•)) obtaining electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The pure C═C π-bond heterolytic and homolytic dissociation energies of the polar olefins (X) in acetonitrile and the pure C═C π-bond homolytic dissociation energies of the radical anions of the polar olefins (X(•-)) in acetonitrile were estimated. The remote substituent effects on the six thermodynamic affinities of the polar olefins and their related reaction intermediates were examined using the Hammett linear free-energy relationships; the results show that the Hammett linear free-energy relationships all hold in the six chemical and electrochemical processes. The information disclosed in this work could not only supply a gap of the chemical thermodynamics of olefins as one class of very important organic unsaturated compounds but also strongly promote the fast development of the chemistry and applications of olefins.

  5. Reactivity of hydropersulfides toward the hydroxyl radical unraveled: disulfide bond cleavage, hydrogen atom transfer, and proton-coupled electron transfer.

    Science.gov (United States)

    Anglada, Josep M; Crehuet, Ramon; Adhikari, Sarju; Francisco, Joseph S; Xia, Yu

    2018-02-14

    Hydropersulfides (RSSH) are highly reactive as nucleophiles and hydrogen atom transfer reagents. These chemical properties are believed to be key for them to act as antioxidants in cells. The reaction involving the radical species and the disulfide bond (S-S) in RSSH, a known redox-active group, however, has been scarcely studied, resulting in an incomplete understanding of the chemical nature of RSSH. We have performed a high-level theoretical investigation on the reactions of the hydroxyl radical (˙OH) toward a set of RSSH (R = -H, -CH 3 , -NH 2 , -C(O)OH, -CN, and -NO 2 ). The results show that S-S cleavage and H-atom abstraction are the two competing channels. The electron inductive effect of R induces selective ˙OH substitution at one sulfur atom upon S-S cleavage, forming RSOH and ˙SH for the electron donating groups (EDGs), whereas producing HSOH and ˙SR for the electron withdrawing groups (EWGs). The H-Atom abstraction by ˙OH follows a classical hydrogen atom transfer (hat) mechanism, producing RSS˙ and H 2 O. Surprisingly, a proton-coupled electron transfer (pcet) process also occurs for R being an EDG. Although for RSSH having EWGs hat is the leading channel, S-S cleavage can be competitive or even dominant for the EDGs. The overall reactivity of RSSH toward ˙OH attack is greatly enhanced with the presence of an EDG, with CH 3 SSH being the most reactive species found in this study (overall rate constant: 4.55 × 10 12 M -1 s -1 ). Our results highlight the complexity in RSSH reaction chemistry, the extent of which is closely modulated by the inductive effect of the substituents in the case of the oxidation by hydroxyl radicals.

  6. Adsorption and diffusion characteristics of lithium on hydrogenated α- and β-silicene

    Directory of Open Access Journals (Sweden)

    Fadil Iyikanat

    2017-08-01

    Full Text Available Using first-principles density functional theory calculations, we investigate adsorption properties and the diffusion mechanism of a Li atom on hydrogenated single-layer α- and β-silicene on a Ag(111 surface. It is found that a Li atom binds strongly on the surfaces of both α- and β-silicene, and it forms an ionic bond through the transfer of charge from the adsorbed atom to the surface. The binding energies of a Li atom on these surfaces are very similar. However, the diffusion barrier of a Li atom on H-α-Si is much higher than that on H-β-Si. The energy surface calculations show that a Li atom does not prefer to bind in the vicinity of the hydrogenated upper-Si atoms. Strong interaction between Li atoms and hydrogenated silicene phases and low diffusion barriers show that α- and β-silicene are promising platforms for Li-storage applications.

  7. Theoretical investigation of hydrogen atom transfer in the cytosine-guanine base pair and its coupling with electronic rearrangement. Concerted vs stepwise mechanism.

    Science.gov (United States)

    Villani, Giovanni

    2010-07-29

    The transformation of the DNA base pairs from the Watson-Crick (WC) structures to its tautomers having imino-enol form can be achieved via two types of hydrogen atom transfer processes: (i) concerted, and/or (ii) stepwise (step by step). Here, we have studied and compared these two mechanisms in the cytosine-guanine (C-G) system. In the first mechanism there is the concerted movement of two hydrogen atoms along two of the three H-bridges that bond the bases, one from the cytosine to guanine and the other in the opposite direction. This movement must be coupled to an electronic reorganization, with some bond orders that pass from single to double and vice versa, in order to preserve the neutrality of these new structures. In the stepwise mechanism the movement of the hydrogen atoms and the electronic reorganization are not concerted, and it implicates the movement of a hydrogen atom at a time with the identification of two or more steps in this reaction. There are two possible neutral imino-enol structures in the C-G system, and both have been considered here. The principal result from this paper is that a different behavior is observed if the hydrogen transfer begins with a H of the guanine or of the cytosine and that a concerted (synchronic in the N-N and asynchronic in the N-O) double-hydrogen transfer can be activated only when the first H atom to move is that of the guanine, in particular. This is different from the A-T system(1) studied previously where the movement in a N-N bridge produces a zwitterionic structure and that in the N-O the concerted double-hydrogen transfer. In both cases a general conclusion can be given: the concerted double-hydrogen process begins with a hydrogen atom of a purinic base.

  8. Force spectroscopy of hyaluronan by atomic force microscopy: from hydrogen-bonded networks toward single-chain behavior.

    Science.gov (United States)

    Giannotti, Marina I; Rinaudo, Marguerite; Vancso, G Julius

    2007-09-01

    The conformational behavior of hyaluronan (HA) polysaccharide chains in aqueous NaCl solution was characterized directly at the single-molecule level. This communication reports on one of the first single-chain atomic force microscopy (AFM) experiments performed at variable temperatures, investigating the influence of the temperature on the stability of the HA single-chain conformation. Through AFM single-molecule force spectroscopy, the temperature destabilization of a local structure was proven. This structure involved a hydrogen-bonded network along the polymeric chain, with hydrogen bonds between the polar groups of HA and possibly water, and a change from a nonrandom coil to a random coil behavior was observed when increasing the temperature from 29 +/- 1 to 46 +/- 1 degrees C. As a result of the applied force, this superstructure was found to break progressively at room temperature. The use of a hydrogen-bonding breaker solvent demonstrated the hydrogen-bonded water-bridged nature of the network structure of HA single chains in aqueous NaCl solution.

  9. Atomically Thin Interfacial Suboxide Key to Hydrogen Storage Performance Enhancements of Magnesium Nanoparticles Encapsulated in Reduced Graphene Oxide.

    Science.gov (United States)

    Wan, Liwen F; Liu, Yi-Sheng; Cho, Eun Seon; Forster, Jason D; Jeong, Sohee; Wang, Hsiao-Tsu; Urban, Jeffrey J; Guo, Jinghua; Prendergast, David

    2017-09-13

    As a model system for hydrogen storage, magnesium hydride exhibits high hydrogen storage density, yet its practical usage is hindered by necessarily high temperatures and slow kinetics for hydrogenation-dehydrogenation cycling. Decreasing particle size has been proposed to simultaneously improve the kinetics and decrease the sorption enthalpies. However, the associated increase in surface reactivity due to increased active surface area makes the material more susceptible to surface oxidation or other side reactions, which would hinder the overall hydrogenation-dehydrogenation process and diminish the capacity. Previous work has shown that the chemical stability of Mg nanoparticles can be greatly enhanced by using reduced graphene oxide as a protecting agent. Although no bulklike crystalline MgO layer has been clearly identified in this graphene-encapsulated/Mg nanocomposite, we propose that an atomically thin layer of honeycomb suboxide exists, based on first-principles interpretation of Mg K-edge X-ray absorption spectra. Density functional theory calculations reveal that in contrast to conventional expectations for thick oxides this interfacial oxidation layer permits H2 dissociation to the same degree as pristine Mg metal with the added benefit of enhancing the binding between reduced graphene oxide and the Mg nanoparticle, contributing to improved mechanical and chemical stability of the functioning nanocomposite.

  10. The mechanism of chemisorption of hydrogen atom on graphene: Insights from the reaction force and reaction electronic flux

    Energy Technology Data Exchange (ETDEWEB)

    Cortés-Arriagada, Diego, E-mail: dcortesr@uc.cl; Gutiérrez-Oliva, Soledad; Herrera, Bárbara; Soto, Karla; Toro-Labbé, Alejandro [Nucleus Millennium Chemical Processes and Catalysis, Laboratorio de Química Teórica Computacional (QTC), Departamento de Química-Física, Facultad de Química, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago (Chile)

    2014-10-07

    At the PBE-D3/cc-pVDZ level of theory, the hydrogen chemisorption on graphene was analyzed using the reaction force and reaction electronic flux (REF) theories in combination with electron population analysis. It was found that chemisorption energy barrier is mainly dominated by structural work (∼73%) associated to the substrate reconstruction whereas the electronic work is the greatest contribution of the reverse energy barrier (∼67%) in the desorption process. Moreover, REF shows that hydrogen chemisorption is driven by charge transfer processes through four electronic events taking place as H approaches the adsorbent surface: (a) intramolecular charge transfer in the adsorbent surface; (b) surface reconstruction; (c) substrate magnetization and adsorbent carbon atom develops a sp{sup 3} hybridization to form the σC-H bond; and (d) spontaneous intermolecular charge transfer to reach the final chemisorbed state.

  11. A First Principles study on Boron-doped Graphene decorated by Ni-Ti-Mg atoms for Enhanced Hydrogen Storage Performance

    Science.gov (United States)

    Nachimuthu, Santhanamoorthi; Lai, Po-Jung; Leggesse, Ermias Girma; Jiang, Jyh-Chiang

    2015-01-01

    We proposed a new solid state material for hydrogen storage, which consists of a combination of both transition and alkaline earth metal atoms decorating a boron-doped graphene surface. Hydrogen adsorption and desorption on this material was investigated using density functional theory calculations. We find that the diffusion barriers for H atom migration and desorption energies are lower than for the previously designed mediums and the proposed medium can reach the gravimetric capacity of ~6.5 wt % hydrogen, which is much higher than the DOE target for the year 2015. Molecular Dynamics simulations show that metal atoms are stably adsorbed on the B doped graphene surface without clustering, which will enhance the hydrogen storage capacity. PMID:26577659

  12. Increase the threshold voltage of high voltage GaN transistors by low temperature atomic hydrogen treatment

    Energy Technology Data Exchange (ETDEWEB)

    Erofeev, E. V., E-mail: erofeev@micran.ru [Tomsk State University of Control Systems and Radioelectronics, Research Institute of Electrical-Communication Systems (Russian Federation); Fedin, I. V.; Kutkov, I. V. [Research and Production Company “Micran” (Russian Federation); Yuryev, Yu. N. [National Research Tomsk Polytechnic University, Institute of Physics and Technology (Russian Federation)

    2017-02-15

    High-electron-mobility transistors (HEMTs) based on AlGaN/GaN epitaxial heterostructures are a promising element base for the fabrication of high voltage electronic devices of the next generation. This is caused by both the high mobility of charge carriers in the transistor channel and the high electric strength of the material, which makes it possible to attain high breakdown voltages. For use in high-power switches, normally off-mode GaN transistors operating under enhancement conditions are required. To fabricate normally off GaN transistors, one most frequently uses a subgate region based on magnesium-doped p-GaN. However, optimization of the p-GaN epitaxial-layer thickness and the doping level makes it possible to attain a threshold voltage of GaN transistors close to V{sub th} = +2 V. In this study, it is shown that the use of low temperature treatment in an atomic hydrogen flow for the p-GaN-based subgate region before the deposition of gate-metallization layers makes it possible to increase the transistor threshold voltage to V{sub th} = +3.5 V. The effects under observation can be caused by the formation of a dipole layer on the p-GaN surface induced by the effect of atomic hydrogen. The heat treatment of hydrogen-treated GaN transistors in a nitrogen environment at a temperature of T = 250°C for 12 h reveals no degradation of the transistor’s electrical parameters, which can be caused by the formation of a thermally stable dipole layer at the metal/p-GaN interface as a result of hydrogenation.

  13. Measuring laser carrier-envelope-phase effects in the noble gases with an atomic hydrogen calibration standard

    Science.gov (United States)

    Khurmi, Champak; Wallace, W. C.; Sainadh U, Satya; Ivanov, I. A.; Kheifets, A. S.; Tong, X. M.; Litvinyuk, I. V.; Sang, R. T.; Kielpinski, D.

    2017-07-01

    We present accurate measurements of carrier-envelope-phase effects on ionization of the noble gases with few-cycle laser pulses. The experimental apparatus is calibrated by using atomic hydrogen data to remove any systematic offsets and thereby obtain accurate CEP data on other generally used noble gases such as Ar, Kr, and Xe. Experimental results for H are well supported by exact time-dependent Schrödinger equation theoretical simulations; however, significant differences are observed in the case of the noble gases.

  14. Diffusion cross section for atomic hydrogen in helium gas at low temperature and the H-He potential

    Energy Technology Data Exchange (ETDEWEB)

    Jochemsen, R.; Berlinsky, A.J.; Hardy, W.N. (British Columbia Univ., Vancouver (Canada). Dept. of Physics)

    1984-08-01

    A calculation of the diffusion cross section Q sub(D) of hydrogen atoms in helium gas at low temperature is performed and compared with recent experimental results. The comparison allows an improved determination of the H-He potential. Calculations were done for three different potentials: our own empirical potential based on experimental high-energy scattering results and calculated long-range dispersion terms, which gives good results for Q sub(D) and total collision cross sections; a recently determined semi-empirical potential, and an ab initio calculated potential. All three potentials imply a strong temperature dependence of Q sub(D) for T < 1.5 K.

  15. Theoretical and kinetic study of the hydrogen atom abstraction reactions of unsaturated C6 methyl esters with hydroxyl radical

    Science.gov (United States)

    Wang, Quan-De; Ni, Zhong-Hai

    2016-04-01

    This work reports a systematic ab initio and chemical kinetic study of the rate constants for hydrogen atom abstraction reactions by hydroxyl radical (OH) on typical isomers of unsaturated C6 methyl esters at the CBS/QB3 level of theory. The high-pressure limit rate constants at different reaction sites for all the methyl esters in the temperature range from 500 to 2000 K are calculated via transition-state theory with the Wigner method for quantum tunneling effect and fitted to the modified three parameters Arrhenius expression using least-squares regression. Further, a branching ratio analysis for each reaction site has been performed.

  16. Transverse momentum asymmetry of the extracted electron in field ionization of a Hydrogen Atom with angular momentum

    CERN Document Server

    Artru, Xavier

    2014-01-01

    The tunneling ionization of a hydrogen atom excited in the presence of a static electric field is investigated for the case where, before being extracted, the electron has an orbital angular momentum L perpendicular to the field E. The escaping electron has a nonzero mean transverse velocity in the direction of E cross . This asymmetry is similar to the Collins effect in the fragmentation into hadrons of a transversely polarized quark. In addition, the linear Stark effect make and oscillate in time. The degree of asymmetry is calculated at leading order in E for an initial state of maximum transverse . The conditions for the observation of this asymmetry are discussed.

  17. Toward a unified single-parameter extrapolation scheme for the correlation energy: Systems formed by atoms of hydrogen through neon

    Science.gov (United States)

    Pansini, F. N. N.; Varandas, A. J. C.

    2015-07-01

    A simple scheme is suggested to extrapolate the valence electron correlation to the one-electron complete-basis-set limit in species formed by atoms of hydrogen through neon. The performance of the novel scheme is benchmarked for the correlation energy with a data set of 106 systems and, for the polarizability, with 8 molecules. For the former, the results are excellent, most often better than when extrapolated with the best available two-parameter protocols. For the polarizability, they show an enhancement relative to the raw ab initio values, and good agreement with the experimental ones.

  18. Long-range interactions of hydrogen atoms in excited states. III. n S -1 S interactions for n ≥3

    Science.gov (United States)

    Adhikari, C. M.; Debierre, V.; Jentschura, U. D.

    2017-09-01

    The long-range interaction of excited neutral atoms has a number of interesting and surprising properties such as the prevalence of long-range oscillatory tails and the emergence of numerically large van der Waals C6 coefficients. Furthermore, the energetically quasidegenerate n P states require special attention and lead to mathematical subtleties. Here we analyze the interaction of excited hydrogen atoms in n S states (3 ≤n ≤12 ) with ground-state hydrogen atoms and find that the C6 coefficients roughly grow with the fourth power of the principal quantum number and can reach values in excess of 240 000 (in atomic units) for states with n =12 . The nonretarded van der Waals result is relevant to the distance range R ≪a0/α , where a0 is the Bohr radius and α is the fine-structure constant. The Casimir-Polder range encompasses the interatomic distance range a0/α ≪R ≪ℏ c /L , where L is the Lamb shift energy. In this range, the contribution of quasidegenerate excited n P states remains nonretarded and competes with the 1 /R2 and 1 /R4 tails of the pole terms, which are generated by lower-lying m P states with 2 ≤m ≤n -1 , due to virtual resonant emission. The dominant pole terms are also analyzed in the Lamb shift range R ≫ℏ c /L . The familiar 1 /R7 asymptotics from the usual Casimir-Polder theory is found to be completely irrelevant for the analysis of excited-state interactions. The calculations are carried out to high precision using computer algebra in order to handle a large number of terms in intermediate steps of the calculation for highly excited states.

  19. Structural and medium effects on the reactions of the cumyloxyl radical with intramolecular hydrogen bonded phenols. The interplay between hydrogen-bonding and acid-base interactions on the hydrogen atom transfer reactivity and selectivity.

    Science.gov (United States)

    Salamone, Michela; Amorati, Riccardo; Menichetti, Stefano; Viglianisi, Caterina; Bietti, Massimo

    2014-07-03

    A time-resolved kinetic study on the reactions of the cumyloxyl radical (CumO(•)) with intramolecularly hydrogen bonded 2-(1-piperidinylmethyl)phenol (1) and 4-methoxy-2-(1-piperidinylmethyl)phenol (2) and with 4-methoxy-3-(1-piperidinylmethyl)phenol (3) has been carried out. In acetonitrile, intramolecular hydrogen bonding protects the phenolic O-H of 1 and 2 from attack by CumO(•) and hydrogen atom transfer (HAT) exclusively occurs from the C-H bonds that are α to the piperidine nitrogen (α-C-H bonds). With 3 HAT from both the phenolic O-H and the α-C-H bonds is observed. In the presence of TFA or Mg(ClO4)2, protonation or Mg(2+) complexation of the piperidine nitrogen removes the intramolecular hydrogen bond in 1 and 2 and strongly deactivates the α-C-H bonds of the three substrates. Under these conditions, HAT to CumO(•) exclusively occurs from the phenolic O-H group of 1-3. These results clearly show that in these systems the interplay between intramolecular hydrogen bonding and Brønsted and Lewis acid-base interactions can drastically influence both the HAT reactivity and selectivity. The possible implications of these findings are discussed in the framework of the important role played by tyrosyl radicals in biological systems.

  20. Hydrogen ADPs with Cu Kα data? Invariom and Hirshfeld atom modelling of fluconazole.

    Science.gov (United States)

    Orben, Claudia M; Dittrich, Birger

    2014-06-01

    For the structure of fluconazole [systematic name: 2-(2,4-difluorophenyl)-1,3-bis(1H-1,2,4-triazol-1-yl)propan-2-ol] monohydrate, C13H12F2N6O·H2O, a case study on different model refinements is reported, based on single-crystal X-ray diffraction data measured at 100 K with Cu Kα radiation to a resolution of sin θ/λ of 0.6 Å(-1). The structure, anisotropic displacement parameters (ADPs) and figures of merit from the independent atom model are compared to `invariom' and `Hirshfeld atom' refinements. Changing from a spherical to an aspherical atom model lowers the figures of merit and improves both the accuracy and the precision of the geometrical parameters. Differences between results from the two aspherical-atom refinements are small. However, a refinement of ADPs for H atoms is only possible with the Hirshfeld atom density model. It gives meaningful results even at a resolution of 0.6 Å(-1), but requires good low-order data.

  1. Algebraic tools for dealing with the atomic shell model. I. Wavefunctions and integrals for hydrogen-like ions

    Science.gov (United States)

    Surzhykov, Andrey; Koval, Peter; Fritzsche, Stephan

    2005-01-01

    Today, the 'hydrogen atom model' is known to play its role not only in teaching the basic elements of quantum mechanics but also for building up effective theories in atomic and molecular physics, quantum optics, plasma physics, or even in the design of semiconductor devices. Therefore, the analytical as well as numerical solutions of the hydrogen-like ions are frequently required both, for analyzing experimental data and for carrying out quite advanced theoretical studies. In order to support a fast and consistent access to these (Coulomb-field) solutions, here we present the DIRAC program which has been developed originally for studying the properties and dynamical behavior of the (hydrogen-like) ions. In the present version, a set of MAPLE procedures is provided for the Coulomb wave and Green's functions by applying the (wave) equations from both, the nonrelativistic and relativistic theory. Apart from the interactive access to these functions, moreover, a number of radial integrals are also implemented in the DIRAC program which may help the user to construct transition amplitudes and cross sections as they occur frequently in the theory of ion-atom and ion-photon collisions. Program summaryTitle of program:DIRAC Catalogue number: ADUQ Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUQ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: None Computer for which the program is designed and has been tested: All computers with a license of the computer algebra package MAPLE [1] Program language used: Maple 8 and 9 No. of lines in distributed program, including test data, etc.:2186 No. of bytes in distributed program, including test data, etc.: 162 591 Distribution format: tar gzip file CPC Program Library subprograms required: None Nature of the physical problem: Analytical solutions of the hydrogen atom are widely used in very different fields of physics [2,3]. Despite of the rather simple structure

  2. Electron predators are hydrogen atom traps. Effects of aryl groups on N-C(α) bond dissociations of peptide radicals.

    Science.gov (United States)

    Tureček, František

    2010-11-01

    Effects of substituted aryl groups on dissociations of peptide aminoketyl radicals were studied computationally for model tetrapeptide intermediates GXD(•) G where X was a cysteine residue that was derivatized by S-(3-nitrobenzyl), S-(3-cyanobenzyl), S-(3,5-dicyanobenzyl), S-(2,3,4,5,6-pentafluorobenzyl), and S-benzyl groups. The aminoketyl radical was placed within the Asp amide group. Aminoketyl radicals having the S-(3-nitrobenzyl) group were found to undergo spontaneous and highly exothermic migration of the hydroxyl hydrogen atom onto the nitro group in conformers allowing interaction between these groups. Competing reaction channels were investigated for aminoketyl radicals having the S-(3-cyanobenzyl) and S-(3,5-dicyanobenzyl) groups, e.g. H-atom migration to the C and N atoms of the C≡N group, migration to the C-4 position of the phenyl ring, and dissociation of the radical-activated NC(α) bond between the Asp and Gly residues. RRKM kinetic analysis on the combined B3LYP and ROMP2/6-311++G(2d,p) potential energy surface indicated > 99% H-atom transfer to the C≡N group forming a stable iminyl intermediate. The NC(α) bond dissociation was negligible. In contrast, peptides with the S-(2,3,4,5,6-pentafluorobenzyl) and S-benzyl groups showed preferential NC(α) bond dissociation that outcompeted H-atom migration to the C-4 position and fluorine substituents in the phenyl ring. These computational results are used to suggest an alternative mechanism for the quenching effect on electron-based peptide backbone dissociations of benzyl groups with electron-withdrawing substitutents, as reported recently. Copyright © 2010 John Wiley & Sons, Ltd.

  3. Reactions of atomic hydrogen with formic acid and carbon monoxide in solid parahydrogen I: Anomalous effect of temperature.

    Science.gov (United States)

    Paulson, Leif O; Mutunga, Fredrick M; Follett, Shelby E; Anderson, David T

    2014-09-11

    Low-temperature condensed phase reactions of atomic hydrogen with closed-shell molecules have been studied in rare gas matrices as a way to generate unstable chemical intermediates and to study tunneling-driven chemistry. Although parahydrogen (pH2) matrix isolation spectroscopy allows these reactions to be studied equally well, little is known about the analogous reactions conducted in a pH2 matrix host. In this study, we present Fourier transform infrared (FTIR) spectroscopic studies of the 193 nm photoinduced chemistry of formic acid (HCOOH) isolated in a pH2 matrix over the 1.7 to 4.3 K temperature range. Upon short-term irradiation the HCOOH readily undergoes photolysis to yield CO, CO2, HOCO, HCO and H atoms. Furthermore, after photolysis at 1.9 K tunneling reactions between migrating H atoms and trapped HCOOH and CO continue to produce HOCO and HCO, respectively. A series of postphotolysis kinetic experiments at 1.9 K with varying photolysis conditions and initial HCOOH concentrations show the growth of HOCO consistently follows single exponential (k = 4.9(7)x10(-3) min(-1)) growth kinetics. The HCO growth kinetics is more complex displaying single exponential growth under certain conditions, but also biexponential growth at elevated CO concentrations and longer photolysis exposures. By varying the temperature after photolysis, we show the H atom reaction kinetics qualitatively change at ∼2.7 K; the reaction that produces HOCO stops at higher temperatures and is only observed at low temperature. We rationalize these results using a kinetic mechanism that involves formation of an H···HCOOH prereactive complex. This study clearly identifies anomalous temperature effects in the reaction kinetics of H atoms with HCOOH and CO in solid pH2 that deserve further study and await full quantitative theoretical modeling.

  4. Stark spectroscopy of atomic hydrogen balmer-alpha line for electric field measurement in plasmas by saturation spectroscopy

    Science.gov (United States)

    Nishiyama, S.; Katayama, K.; Nakano, H.; Goto, M.; Sasaki, K.

    2016-09-01

    Detailed structures of electric fields in sheath and pre-sheath regions of various plasmas are interested from the viewpoint of basic plasma physics. Several researchers observed Stark spectra of Doppler-broadened Rydberg states to evaluate electric fields in plasmas; however, these measurements needed high-power, expensive tunable lasers. In this study, we carried out another Stark spectroscopy with a low-cost diode laser system. We applied saturation spectroscopy, which achieves a Doppler-free wavelength resolution, to observe the Stark spectrum of the Balmer-alpha line of atomic hydrogen in the sheath region of a low-pressure hydrogen plasma. The hydrogen plasma was generated in an ICP source which was driven by on-off modulated rf power at 20 kHz. A planar electrode was inserted into the plasma. Weak probe and intense pump laser beams were injected into the plasma from the counter directions in parallel to the electrode surface. The laser beams crossed with a small angle above the electrode. The observed fine-structure spectra showed shifts, deformations, and/or splits when varying the distance between the observation position and the electrode surface. The detection limit for the electric field was estimated to be several tens of V/cm.

  5. The Moments of the Hydrogen Atom by the Method of Brackets

    Science.gov (United States)

    Gonzalez, Ivan; Kohl, Karen T.; Kondrashuk, Igor; Moll, Victor H.; Salinas, Daniel

    2017-01-01

    Expectation values of powers of the radial coordinate in arbitrary hydrogen states are given, in the quantum case, by an integral involving the associated Laguerre function. The method of brackets is used to evaluate the integral in closed-form and to produce an expression for this average value as a finite sum.

  6. Rational Design of Single Molybdenum Atoms Anchored on N-Doped Carbon for Effective Hydrogen Evolution Reaction.

    Science.gov (United States)

    Chen, Wenxing; Pei, Jiajing; He, Chun-Ting; Wan, Jiawei; Ren, Hanlin; Zhu, Youqi; Wang, Yu; Dong, Juncai; Tian, Shubo; Cheong, Weng-Chon; Lu, Siqi; Zheng, Lirong; Zheng, Xusheng; Yan, Wensheng; Zhuang, Zhongbin; Chen, Chen; Peng, Qing; Wang, Dingsheng; Li, Yadong

    2017-12-11

    The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo-SAs) supported on N-doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo-SAs anchored with one nitrogen atom and two carbon atoms (Mo 1 N 1 C 2 ). Importantly, the Mo 1 N 1 C 2 catalyst displayed much more excellent activity compared with Mo 2 C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo 1 N 1 C 2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo-based HER catalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Response to W. Kramer: The human sex odds at birth after the atmospheric atomic bomb tests, after Chernobyl, and in the vicinity of nuclear facilities: comment (doi:10.1007/s11356-011-0644-8).

    Science.gov (United States)

    Scherb, Hagen; Voigt, Kristina

    2012-05-01

    This paper is in response to criticism of our article "The human sex odds at birth after the atmospheric atomic bomb tests, after Chernobyl, and in the vicinity of nuclear facilities" published in Environ Sci Pollut Res 18(5):697-707, 2011. Our findings and methods concerning the disturbed human sex odds at birth have been criticized in this journal for being artifacts of data mining, that the concept of statistical significance was misunderstood, and that confounding factors have not been accounted for. Here, we show that this criticism has no basis. We applied well-established statistical methods to large official data sets, and confounding is less important at the level of secular sex odds trends in aggregated annual figures from countries or continents. Moreover, our results are strengthened by recent findings concerning increased infant death sex odds in Germany and increased Down syndrome prevalence at birth across Europe after Chernobyl. Prompted by our studies, an official investigation in Lower Saxony, Germany, by the "Niedersächsisches Landesgesundheitsamt (NLGA)" confirmed our observation of severely escalated sex odds within 40 km distance from the nuclear storage site in Gorleben, Germany.

  8. Atomic scale simulations of hydrogen implantation defects in hydrogen implanted silicon - smart Cut technology; Simulations a l'echelle atomique des defauts de l'implantation de l'hydrogene en silicium - technologie smart Cut

    Energy Technology Data Exchange (ETDEWEB)

    Bilteanu, L.

    2010-12-15

    The topic of this thesis is related to the implantation step of the SmartCut{sup TM} technology. This technology uses hydrogen in order to transfer silicon layers on insulating substrates. The transfer is performed through a fracture induced by the formation of bidimensional defects well known in literature as 'platelets'. More exactly, we have studied within this thesis work the defects appearing in the post implant state and the evolution of the implantation damage towards a state dominated by platelets. The study is organised into two parts: in the first part we present the results obtained by atomic scale simulations while in the second part we present an infrared spectroscopy study of the evolution of defects concentrations after annealing at different temperatures. The atomic scale simulations have been performed within the density functional theory and they allowed us to compute the formation energies and the migration and recombination barriers. The defects included in our study are: the atomic and diatomic interstitials, the hydrogenated vacancies and multi-vacancies and the several platelets models. The obtained energies allowed us to build a stability hierarchy for these types of defects. This scheme has been confronted with some infrared analysis on hydrogen implanted silicon samples (37 keV) in a sub-dose regime which does not allow usually the formation of platelets during the implantation step. The analysis of the infrared data allowed the detailed description of the defects concentration based on the behaviour of peaks corresponding to the respective defects during annealing. The comparison between these evolutions and the energy scheme obtained previously allowed the validation of an evolution scenario of defects towards the platelet state. (author)

  9. Effect of metal ions on the reactions of the cumyloxyl radical with hydrogen atom donors. Fine control on hydrogen abstraction reactivity determined by Lewis acid-base interactions.

    Science.gov (United States)

    Salamone, Michela; Mangiacapra, Livia; DiLabio, Gino A; Bietti, Massimo

    2013-01-09

    A time-resolved kinetic study on the effect of metal ions (M(n+)) on hydrogen abstraction reactions from C-H donor substrates by the cumyloxyl radical (CumO(•)) was carried out in acetonitrile. Metal salt addition was observed to increase the CumO(•) β-scission rate constant in the order Li(+) > Mg(2+) > Na(+). These effects were explained in terms of the stabilization of the β-scission transition state determined by Lewis acid-base interactions between M(n+) and the radical. When hydrogen abstraction from 1,4-cyclohexadiene was studied in the presence of LiClO(4) and Mg(ClO(4))(2), a slight increase in rate constant (k(H)) was observed indicating that interaction between M(n+) and CumO(•) can also influence, although to a limited extent, the hydrogen abstraction reactivity of alkoxyl radicals. With Lewis basic C-H donors such as THF and tertiary amines, a decrease in k(H) with increasing Lewis acidity of M(n+) was observed (k(H)(MeCN) > k(H)(Li(+)) > k(H)(Mg(2+))). This behavior was explained in terms of the stronger Lewis acid-base interaction of M(n+) with the substrate as compared to the radical. This interaction reduces the degree of overlap between the α-C-H σ* orbital and a heteroatom lone-pair, increasing the C-H BDE and destabilizing the carbon centered radical formed after abstraction. With tertiary amines, a >2-order of magnitude decrease in k(H) was measured after Mg(ClO(4))(2) addition up to a 1.5:1 amine/Mg(ClO(4))(2) ratio. At higher amine concentrations, very similar k(H) values were measured with and without Mg(ClO(4))(2). These results clearly show that with strong Lewis basic substrates variations in the nature and concentration of M(n+) can dramatically influence k(H), allowing for a fine control of the substrate hydrogen atom donor ability, thus providing a convenient method for C-H deactivation. The implications and generality of these findings are discussed.

  10. Lorentz Trial Function for the Hydrogen Atom: A Simple, Elegant Exercise

    Science.gov (United States)

    Sommerfeld, Thomas

    2011-01-01

    The quantum semester of a typical two-semester physical chemistry course is divided into two parts. The initial focus is on quantum mechanics and simple model systems for which the Schrodinger equation can be solved in closed form, but it then shifts in the second half to atoms and molecules, for which no closed solutions exist. The underlying…

  11. The reaction of nitromethane with hydrogen and deuterium atoms in the gas phase. A mechanistic study

    DEFF Research Database (Denmark)

    Lund Thomsen, E.; Nielsen, O.J.; Egsgaard, H.

    1993-01-01

    The mechanism of the reaction between H and CH3NO2, has been studied in a discharge flow system using electron paramagnetic resonance and modulated molecular beam mass spectrometry for the detection of reactants and products. Deuterium atoms have, in addition to CD3NO2, been used to support...

  12. Collisional electron broadening of Stark sublevels of an atom of hydrogen in a plasma

    Energy Technology Data Exchange (ETDEWEB)

    Sholin, G.V.; Demura, A.V.; Lisitsa, V.S.

    1972-12-31

    A theoretical examination was made of the contours of the hydrogen lines in plasma, excited as a result of the static interaction of ions and collisional electrons with consideration of the special characteristics connected with the presence of supplementary degeneration in the Coulomb field. General expressions were obtained for the half-width of the Stark component of every line of the hydrogen spectrum in parabolic coordinates. A subsequent analysis was carried out of the transition from the overlapping of the Stark component to the isolated lines. It was found that such a transition is accompanied by annulment of the nondiagornl matrix elements of the operator of the collisional electron broadening. The form of the interference member in the operator of the collisional electron broadening is corrected with consideration of the perturbation of the upper and lower levels. The calculations carried out made it possible to improve the agreement between theory and experiment for lines with strong central components. (tr-auth)

  13. Hydrogen atom trapping in a self-organized one-dimensional dimer

    Directory of Open Access Journals (Sweden)

    Tsuyoshi Takami

    2014-09-01

    Full Text Available Metal–organic frameworks (MOFs have attracted widespread attention owing to their unusual structure and properties produced by their nanospaces. However, many MOFs possess the similar three-dimensional frameworks, limiting their structural variety and operating capacity for hydrogen storage under ambient conditions. Here we report the synthesis and structural characterization of a single-crystal one-dimensional dimer whose structure, operating capacity, and physical mechanism contrast with those of existing MOFs. The hydrogen storage capacity of 2.6 wt.% is comparable to the highest capacity achieved by existing MOFs at room temperature. This exceptional storage capacity is realized by self-organization during crystal growth using a weak base.

  14. Hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Pier, M.

    1943-02-19

    A transcript is presented of a speech on the history of the development of hydrogenation of coal and tar. Apparently the talk had been accompanied by the showing of photographic slides, but none of the pictures were included with the report. In giving the history, Dr. Pier mentioned the dependence of much of the development of hydrogenation upon previous development in the related areas of ammonia and methanol syntheses, but he also pointed out several ways in which equipment appropriate for hydrogenation differed considerably from that used for ammonia and methanol. Dr. Pier discussed the difficulties encountered with residue processing, design of the reaction ovens, manufacture of ovens and preheaters, heating of reaction mixtures, development of steels, and development of compressor pumps. He described in some detail his own involvement in the development of the process. In addition, he discussed the development of methods of testing gasolines and other fuels. Also he listed some important byproducts of hydrogenation, such as phenols and polycyclic aromatics, and he discussed the formation of iso-octane fuel from the butanes arising from hydrogenation. In connection with several kinds of equipment used in hydrogenation (whose pictures were being shown), Dr. Pier gave some of the design and operating data.

  15. Calculated vibrational frequencies for FeMo-co, the active site of nitrogenase, bearing hydrogen atoms and carbon monoxide.

    Science.gov (United States)

    Dance, Ian

    2011-06-28

    The intramolecular hydrogenation paradigm for the reducing actions of the enzyme nitrogenase postulates that the iron-molybdenum cofactor (FeMo-co, Fe(7)MoS(9)N(homocitrate)) as active site contains H atoms bound to Fe and S during the catalytic cycle, and that these H atoms are the reducing agents. The reduction of N(2) and of all other non-physiological substrates is strongly inhibited by carbon monoxide, except for the formation of H(2) from protons. It has been recently reported that vanadium nitrogenase and modified molybdenum nitrogenase reduce CO to hydrocarbons. Therefore many questions now arise about relationships between CO and H on the nitrogenase cofactors. In order to assist the interpretation of kinetic infrared spectral data, vibrational frequencies and modes have been calculated for a variety of possible structures in which FeMo-co bears H atoms, or CO ligands, or both. Fe-H stretching frequencies occur in the same spectral window as the C-O stretching frequencies, with lesser intensity, and both stretches are strongly coupled in some structures. Symmetrical bridging of CO between two Fe atoms of FeMo-co is destabilised by the presence of other ligands on Fe, and the reason for this is evident. Two results for bound formyl, HCO, are reported. These calculations of reference structures allow some interpretation of existing experimental spectra, but, more significantly, they suggest further kinetic infrared experiments to elucidate the chemical mechanism of catalysis by nitrogenase under normal turnover conditions. This journal is © The Royal Society of Chemistry 2011

  16. Accurate evaluation of pressure effects on the electronic stopping cross section and mean excitation energy of atomic hydrogen beyond the Bethe approximation

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera-Trujillo, R., E-mail: trujillo@fis.unam.mx [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Ap. Postal 48-3, Cuernavaca, Morelos 62251 (Mexico); Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Ap. Postal 55-534, 09340 México, D.F. (Mexico); Cruz, S.A., E-mail: cruz@xanum.uam.mx [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Ap. Postal 55-534, 09340 México, D.F. (Mexico)

    2014-02-01

    Atomic hydrogen is used as a fundamental reference target system to explore pressure effects on the electronic stopping cross section, S{sub e}, of swift bare ions such as protons and α-particles. This is achieved by considering the hydrogen atom under pressure as a padded spherically-confined quantum system. Within this scheme, S{sub e} is calculated rigorously in the first Born approximation taking into account the full target excitation spectrum and momentum transfer distribution for different confinement conditions (pressures) and fixed projectile charge states. Pressure effects on the target mean excitation energy, I, are also formally calculated and compared with corresponding accurate calculations based on the Local Plasma Approximation (LPA). Even though atomic hydrogen is the simplest target system, its accurate treatment to account for the role of pressure in the stopping dynamics is found to provide useful means to understand the behavior of more complex systems under similar conditions. It is found that: (i) the region of projectile velocities for which the Bethe approximation remains valid is shifted towards higher values as pressure increases; (ii) shell corrections are enhanced relative to the free-atom case as pressure increases, and (iii) the LPA seems to underestimate I as pressure is increased. The results of this work for atomic hydrogen may serve as accurate benchmark reference values for studies of pressure effects on S{sub e} and I using different methodologies.

  17. Communication: Hot-atom abstraction dynamics of hydrogen from tungsten surfaces: The role of surface structure

    Science.gov (United States)

    Galparsoro, Oihana; Busnengo, Heriberto Fabio; Juaristi, Joseba Iñaki; Crespos, Cédric; Alducin, Maite; Larregaray, Pascal

    2017-09-01

    Adiabatic and non-adiabatic quasiclassical molecular dynamics simulations are performed to investigate the role of the crystal face on hot-atom abstraction of H adsorbates by H scattering from covered W(100) and W(110). On both cases, hyperthermal diffusion is strongly affected by the energy dissipated into electron-hole pair excitations. As a result, the hot-atom abstraction is highly reduced in favor of adsorption at low incidence energy and low coverages, i.e., when the mean free path of the hyperthermal H is typically larger. Qualitatively, this reduction is rather similar on both surfaces, despite at such initial conditions, the abstraction process involves more subsurface penetration on W(100) than on W(110).

  18. Collisions of electrons with hydrogen atoms II. Low-energy program using the method of the exterior complex scaling

    Science.gov (United States)

    Benda, Jakub; Houfek, Karel

    2014-11-01

    While collisions of electrons with hydrogen atoms pose a well studied and in some sense closed problem, there is still no free computer code ready for ;production use;, that would enable applied researchers to generate necessary data for arbitrary impact energies and scattering transitions directly if absent in on-line scattering databases. This is the second article on the Hex program package, which describes a new computer code that is, with a little setup, capable of solving the scattering equations for energies ranging from a fraction of the ionization threshold to approximately 100 eV or more, depending on the available computational resources. The program implements the exterior complex scaling method in the B-spline basis.

  19. Complete classification of qualitatively different perturbations of the hydrogen atom in weak near-orthogonal electric and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Efstathiou, K; Lukina, O V [Department of Mathematics, University of Groningen, Groningen 9700 AK (Netherlands); SadovskiI, D A [Departement de physique, Universite du Littoral, 59140 Dunkerque (France)], E-mail: K.Efstathiou@rug.nl, E-mail: O.Lukina@math.rug.nl, E-mail: sadovski@univ-littoral.fr

    2009-02-06

    We consider perturbations of the hydrogen atom by sufficiently small homogeneous static electric and magnetic fields in near-orthogonal configurations. Normalization of the Keplerian symmetry reveals that in the parameter space such systems belong in a 'zone' of systems close to the 1:1 resonance, the latter corresponding to the exactly orthogonal configuration. Integrable approximations obtained from second normalization of systems in the 1:1 zone are classified into several different qualitative types, many of which possess nontrivial monodromy. We compute monodromy of the complete three-dimensional energy-momentum map, compare the joint quantum spectrum to classical bifurcation diagrams, and show the effect of second normalization to the joint spectrum.

  20. Hydrogen atom vs electron transfer in catecholase-mimetic oxidations by superoxometal complexes. Deuterium kinetic isotope effects.

    Science.gov (United States)

    Simándi, Tatiana M; May, Zoltán; Szigyártó, Imola Cs; Simándi, László I

    2005-01-21

    Dioximato-cobalt(II), -iron(II) and -manganese(II) complexes (1)-(6), acting as functional catecholase and phenoxazinone synthase models, exhibit a deuterium kinetic isotope effect predicted by theory (k4H/k4D < or = 3) in the catalytic oxidative dehydrogenation of 3,5-di-tert-butylcatechol and 2-aminophenol by O2. KIEs in the range of (k4H/k4D approximately 1.79-3.51) are observed with (1) and (2) as catalysts, pointing to hydrogen atom transfer in the rate-determining step from the substrate hydroxy group to the metal-bound superoxo ligand. Less significant KIEs (1.06-1.20) are exhibited by catalysts systems (3)-(6), indicating that proton-coupled electron transfer is the preferred route in those cases.

  1. Handshake electron transfer from hydrogen Rydberg atoms incident at a series of metallic thin films.

    Science.gov (United States)

    Gibbard, J A; Softley, T P

    2016-06-21

    Thin metallic films have a 1D quantum well along the surface normal direction, which yields particle-in-a-box style electronic quantum states. However the quantum well is not infinitely deep and the wavefunctions of these states penetrate outside the surface where the electron is bound by its own image-charge attraction. Therefore a series of discrete, vacant states reach out from the thin film into the vacuum increasing the probability of electron transfer from an external atom or molecule to the thin film, especially for the resonant case where the quantum well energy matches that of the atom. We show that "handshake" electron transfer from a highly excited Rydberg atom to these thin-film states is experimentally measurable. Thicker films have a wider 1D box, changing the energetic distribution and image-state contribution to the thin film wavefunctions, resulting in more resonances. Calculations successfully predict the number of resonances and the nature of the thin-film wavefunctions for a given film thickness.

  2. REMO: A new protocol to refine full atomic protein models from C-alpha traces by optimizing hydrogen-bonding networks.

    Science.gov (United States)

    Li, Yunqi; Zhang, Yang

    2009-08-15

    Protein structure prediction approaches usually perform modeling simulations based on reduced representation of protein structures. For biological utilizations, it is an important step to construct full atomic models from the reduced structure decoys. Most of the current full atomic model reconstruction procedures have defects which either could not completely remove the steric clashes among backbone atoms or generate final atomic models with worse topology similarity relative to the native structures than the reduced models. In this work, we develop a new protocol, called REMO, to generate full atomic protein models by optimizing the hydrogen-bonding network with basic fragments matched from a newly constructed backbone isomer library of solved protein structures. The algorithm is benchmarked on 230 nonhomologous proteins with reduced structure decoys generated by I-TASSER simulations. The results show that REMO has a significant ability to remove steric clashes, and meanwhile retains good topology of the reduced model. The hydrogen-bonding network of the final models is dramatically improved during the procedure. The REMO algorithm has been exploited in the recent CASP8 experiment which demonstrated significant improvements of the I-TASSER models in both atomic-level structural refinement and hydrogen-bonding network construction. 2009 Wiley-Liss, Inc.

  3. Mechanism and model of atomic hydrogen cleaning for different types of carbon contamination on extreme ultraviolet multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yuan [State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin 130033 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lu, Qipeng, E-mail: Luqipeng51@126.com [State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin 130033 (China); Gong, Xuepeng [State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin 130033 (China)

    2016-08-01

    The use of atomic hydrogen to clean carbon contaminants on multilayers in extreme ultraviolet lithography systems has been extensively investigated. Additional knowledge of the cleaning rate would not only provide a better understanding of the reaction mechanism but would also inform the industry's cleaning process. In this paper, which focuses on the atomic-hydrogen-based carbon contamination cleaning process, a possible mechanism for the associated reactions is studied and a cleaning model is established. The calculated results are in good agreement with the existing experimental data in the literature. The influences of the main factors – such as activation energy and types of contamination – on the cleaning rate are addressed by the model. The model shows that the cleaning rate depends on the type of carbon contamination. The rate for a polymer-like carbon layer is higher than the rate for graphitic and diamond-like carbon layers. At 340 K, the rate for a polymer-like carbon layer is 10 times higher than for graphitic carbon layers. This model could be used effectively to predict and evaluate the cleaning rates for various carbon contamination types. - Highlights: • Mechanism of H{sup 0} cleaning with C contamination on EUV multilayers is given. • Reflectivity of multilayers rely on various types of C contamination is analyzed. • A model of H{sup 0} cleaning various types of C contamination layers is built. • Accurate predicting and evaluating the rate of H{sup 0} cleaning by the mode is proved. • It would be beneficial for improving H{sup 0} cleaning process of carbon layers.

  4. Atomic hydrogen and diatomic titanium-monoxide molecular spectroscopy in laser-induced plasma

    Science.gov (United States)

    Parigger, Christian G.; Woods, Alexander C.

    2017-03-01

    This article gives a brief review of experimental studies of hydrogen Balmer series emission spectra. Ongoing research aims to evaluate early plasma evolution following optical breakdown in laboratory air. Of interest is as well laser ablation of metallic titanium and characterization of plasma evolution. Emission of titanium monoxide is discussed together with modeling of diatomic spectra to infer temperature. The behavior of titanium particles in plasma draws research interests ranging from the modeling of stellar atmospheres to the enhancement of thin film production via pulsed laser deposition.

  5. Electron-spin resonance, nuclear polarization, and spin relaxation of spin-polarized atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Statt, B.W.; Berlinsky, A.J.; Hardy, W.N.

    1985-03-01

    Electron-spin-resonance measurements of spin-polarized hydrogen are presented. Excellent signal-to-noise ratio, previously obtainable only in pressure studies, allows quantitative fits to the separate a and b (proton up and down) decays of the nuclear-spin-polarized samples, yielding separate temperature dependences of the recombination rate constants K/sub a/a and K/sub a/b. Spin relaxation due to magnetic particles in the substrate is studied for different thicknesses of solid H/sub 2/ wall coating, and the results are compared with a new theoretical model.

  6. Hydrogen.

    Science.gov (United States)

    Bockris, John O'M

    2011-11-30

    The idea of a "Hydrogen Economy" is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO₂ in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H₂ from the electrolyzer. Methanol made with CO₂ from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan). Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs) by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech.

  7. Atomic Layer Deposition of Ultrathin Nickel Sulfide Films and Preliminary Assessment of Their Performance as Hydrogen Evolution Catalysts.

    Science.gov (United States)

    Çimen, Yasemin; Peters, Aaron W; Avila, Jason R; Hoffeditz, William L; Goswami, Subhadip; Farha, Omar K; Hupp, Joseph T

    2016-11-22

    Transition metal sulfides show great promise for applications ranging from catalysis to electrocatalysis to photovoltaics due to their high stability and conductivity. Nickel sulfide, particularly known for its ability to electrochemically reduce protons to hydrogen gas nearly as efficiently as expensive noble metals, can be challenging to produce with certain surface site compositions or morphologies, e.g., conformal thin films. To this end, we employed atomic layer deposition (ALD), a preeminent method to fabricate uniform and conformal films, to construct thin films of nickel sulfide (NiSx) using bis(N,N'-di-tert-butylacetamidinato)nickel(II) (Ni(amd)2) vapor and hydrogen sulfide gas. Effects of experimental conditions such as pulse and purge times and temperature on the growth of NiSx were investigated. These revealed a wide temperature range, 125-225 °C, over which self-limiting NiSx growth can be observed. In situ quartz crystal microbalance (QCM) studies revealed conventional linear growth behavior for NiSx films, with a growth rate of 9.3 ng/cm2 per cycle being obtained. The ALD-synthesized films were characterized using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) methods. To assess the electrocatalyitic activity of NiSx for evolution of molecular hydrogen, films were grown on conductive-glass supports. Overpotentials at a current density of 10 mA/cm2 were recorded in both acidic and pH 7 phosphate buffer aqueous reaction media and found to be 440 and 576 mV, respectively, with very low NiSx loading. These results hint at the promise of ALD-grown NiSx materials as water-compatible electrocatalysts.

  8. Development of Two-Photon Pump Polarization Spectroscopy Probe Technique Tpp-Psp for Measurements of Atomic Hydrogen .

    Science.gov (United States)

    Satija, Aman; Lucht, Robert P.

    2015-06-01

    Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam

  9. van der Waals force between positronium and hydrogenic atoms Finite-mass corrections

    Science.gov (United States)

    Au, C. K.; Drachman, R. J.

    1986-01-01

    The Feshbach projection-operator formalism is used to derive the asymptotic effective interaction potential between two atoms. Beyond the usual van der Waals potential, falling like x exp -6, three x exp -8 terms are also obtained: an attractive dipole-quadrupole term (absent in the positronium-positronium case because of symmetry), a repulsive energy-dependent term, and a repulsive mass-dependent but energy-independent one. This last term was not obtained by Manson and Ritchie (1985) using an independent method.

  10. Determining the energetics of vicinal perovskite oxide surfaces

    NARCIS (Netherlands)

    Wessels, W.A.; Bollmann, Tjeerd Rogier Johannes; Koster, Gertjan; Zandvliet, Henricus J.W.; Rijnders, Augustinus J.H.M.

    2017-01-01

    The energetics of vicinal SrTiO3(001) and DyScO3(110), prototypical perovskite vicinal surfaces, has been studied using topographic atomic force microscopy imaging. The kink formation and strain relaxation energies are extracted from a statistical analysis of the step meandering. Both perovskite

  11. Hydrogen Atom Abstraction Thermodynamics of a μ-1,2-Superoxo Dicopper(II) Complex.

    Science.gov (United States)

    Kindermann, Nicole; Günes, Can-Jerome; Dechert, Sebastian; Meyer, Franc

    2017-07-26

    Pyrazolate-based μ-1,2-peroxo dicopper(II) complex 1 undergoes clean 1e- oxidation at low potential (-0.59 V vs Fc/Fc+) to yield the rather stable μ-1,2-superoxo dicopper(II) complex 3, which was characterized by spectroscopic methods (ν̃(O-O) = 1070 cm-1, Δ(18O-16O) = -59 cm-1) and analyzed by DFT calculations. 3 is also formed via H-atom abstraction from the corresponding μ-1,1-hydroperoxo dicopper(II) complex 2, while 3 itself is able to abstract H-atoms from weaker X-H bonds such as TEMPO-H to re-form 2. Kinetic and thermodynamic analyses evidence a concerted proton-electron transfer pathway for these processes. The thermodynamic square scheme reveals a bond dissociation free energy of 71.7 ± 1.1 kcal mol-1 for the hydroperoxo OO-H bond of 2.

  12. Is There a Need to Discuss Atomic Orbital Overlap When Teaching Hydrogen-Halide Bond Strength and Acidity Trends in Organic Chemistry?

    Science.gov (United States)

    Devarajan, Deepa; Gustafson, Samantha J.; Bickelhaupt, F. Matthias; Ess, Daniel H.

    2015-01-01

    Undergraduate organic chemistry textbooks and Internet websites use a variety of approaches for presenting and explaining the impact of halogen atom size on trends in bond strengths and/or acidity of hydrogen halides. In particular, several textbooks and Internet websites explain these trends by invoking decreasing orbital overlap between the…

  13. Synergistic Formation of Radicals by Irradiation with Both Vacuum Ultraviolet and Atomic Hydrogen: A Real-Time In Situ Electron Spin Resonance Study

    CERN Document Server

    Ishikawa, Kenji; Kono, Akihiko; Horibe, Hideo; Takeda, Keigo; Kondo, Hiroki; Sekine, Makoto; Hori, Masaru; 10.1021/jz2002937

    2012-01-01

    We report on the surface modification of polytetrafluoroethylene (PTFE) as an example of soft- and bio-materials that occur under plasma discharge by kinetics analysis of radical formation using in situ real-time electron spin resonance (ESR) measurements. During irradiation with hydrogen plasma, simultaneous measurements of the gas-phase ESR signals of atomic hydrogen and the carbon dangling bond (C-DB) on PTFE were performed. Dynamic changes of the C-DB density were observed in real time, where the rate of density change was accelerated during initial irradiation and then became constant over time. It is noteworthy that C-DBs were formed synergistically by irradiation with both vacuum ultraviolet (VUV) and atomic hydrogen. The in situ real-time ESR technique is useful to elucidate synergistic roles during plasma surface modification.

  14. Hydrogen

    Directory of Open Access Journals (Sweden)

    John O’M. Bockris

    2011-11-01

    Full Text Available The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H2 from the electrolyzer. Methanol made with CO2 from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan. Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech.

  15. Dynamics of the Vacuum and Casimir Analogs to the Hydrogen Atom

    Science.gov (United States)

    White, Harold; Vera, Jerry; Bailey, Paul; March, Paul; Lawrence, Tim; Sylvester, Andre; Brady, David

    2015-01-01

    This paper will discuss the current viewpoint of the vacuum state and explore the idea of a "natural" vacuum as opposed to immutable, non-degradable vacuum. This concept will be explored for all primary quantum numbers to show consistency with observation at the level of Bohr theory. A comparison with the Casimir force per unit area will be made, and an explicit function for the spatial variation of the vacuum density around the atomic nucleus will be derived. This explicit function will be numerically modeled using the industry multi-physics tool, COMSOL(trademark), and the eigenfrequencies for the n = 1 to n = 7 states will be found and compared to expectation.

  16. Neutron diffraction studies on a system with a 4-coordinate hydrogen atom in an yttrium cluster

    Energy Technology Data Exchange (ETDEWEB)

    Yousufuddin, Muhammed [Department of Chemistry, University of Southern California, Los Angeles, CA 90089 (United States); Baldamus, Jens [RIKEN - Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Tardif, Olivier [RIKEN - Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Hou Zhaomin [RIKEN - Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Mason, Sax A. [Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); McIntyre, Garry J. [Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Bau, Robert [Department of Chemistry, University of Southern California, Los Angeles, CA 90089 (United States)]. E-mail: bau@usc.edu

    2006-11-15

    A 4-coordinate H atom has been unambiguously located, by single-crystal neutron diffraction for the first time, in the center of the tetrahedral metal complex Y{sub 4}H{sub 8}(Cp''){sub 4}(THF) [Cp''=C{sub 5}Me{sub 4}(SiMe{sub 3})]. The core of the molecule consists of a tetranuclear cluster with one interstitial, one face-bridging and six edge-bridging hydride ligands. The four individual Y-H distances to the unique interstitial hydride ligand are 2.184(16), 2.189(16), 2.221(13) and 2.168(12) A. Neutron data were collected on a 4-mm{sup 3} crystal at the Quasi-Laue diffractometer VIVALDI at ILL (Grenoble), and the present agreement factor is R=12.2% for 3566 reflections.

  17. Observation and Interpretation of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event

    Science.gov (United States)

    Mewaldt, R. A.; Leske, R. A.; Stone, E. C.; Barghouty, A. F.; Shih, A. Y.; von Rosenvinge, T. T.; Labrador, A. W.; Cohen, C. M. S.; Cummings, A. C.; Cummings, A. C.

    2009-01-01

    We report the first observations of energetic neutral atoms (ENAs) from a solar flare/coronal mass ejection event. The observations were made during the December 5, 2006 X9 solar flare, located at E79, by the Low Energy Telescopes (LETs) on the STEREO A and B spacecraft. Within 1-2 hours of the flare onset, both LETs observed a sudden burst of 1.6 to 15 MeV protons arriving hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within +-10 degrees of the Sun. The derived emission profile at the Sun lasted for more than an hour and had a profile remarkably similar to the GOES soft X-ray profile. The observed arrival directions and energy spectrum argue strongly that the particle events atoms that were stripped of their electrons upon entering the LET sensor. To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. We discuss possible origins for the production of ENAs in solar events, including charge-transfer reactions involving both flare and shock-accelerated protons. Assuming isotropic emission, we find that 2 x 10E28 ENAs escaped from the Sun in the upper hemisphere. Based on the 2.2 MeV gamma-ray emission observed by RHESSI in this event, and using measured and theoretical cross sections, we estimate that 3 x 10E31 ENAs with 1.8 - 5 MeV could be produced by protons accelerated in the flare. CME-driven shock acceleration is also a possible ENA source, but unfortunately there were no CME observations available from this event. Taking into account ENA losses, we conclude that the observed ENAs were most likely produced in the high corona at heliocentric distances 1.6 solar radii.

  18. Competition between Al2O3 atomic layer etching and AlF3 atomic layer deposition using sequential exposures of trimethylaluminum and hydrogen fluoride

    Science.gov (United States)

    DuMont, Jaime W.; George, Steven M.

    2017-02-01

    The thermal atomic layer etching (ALE) of Al2O3 can be performed using sequential and self-limiting reactions with trimethylaluminum (TMA) and hydrogen fluoride (HF) as the reactants. The atomic layer deposition (ALD) of AlF3 can also be accomplished using the same reactants. This paper examined the competition between Al2O3 ALE and AlF3 ALD using in situ Fourier transform infrared (FTIR) vibrational spectroscopy measurements on Al2O3 ALD-coated SiO2 nanoparticles. The FTIR spectra could observe an absorbance loss of the Al-O stretching vibrations during Al2O3 ALE or an absorbance gain of the Al-F stretching vibrations during AlF3 ALD. The transition from AlF3 ALD to Al2O3 ALE occurred versus reaction temperature and was also influenced by the N2 or He background gas pressure. Higher temperatures and lower background gas pressures led to Al2O3 ALE. Lower temperatures and higher background gas pressures led to AlF3 ALD. The FTIR measurements also monitored AlCH3* and HF* species on the surface after the TMA and HF reactant exposures. The loss of AlCH3* and HF* species at higher temperatures is believed to play a vital role in the transition between AlF3 ALD at lower temperatures and Al2O3 ALE at higher temperatures. The change between AlF3 ALD and Al2O3 ALE was defined by the transition temperature. Higher transition temperatures were observed using larger N2 or He background gas pressures. This correlation was associated with variations in the N2 or He gas thermal conductivity versus pressure. The fluorination reaction during Al2O3 ALE is very exothermic and leads to temperature rises in the SiO2 nanoparticles. These temperature transients influence the Al2O3 etching. The higher N2 and He gas thermal conductivities are able to cool the SiO2 nanoparticles more efficiently and minimize the size of the temperature rises. The competition between Al2O3 ALE and AlF3 ALD using TMA and HF illustrates the interplay between etching and growth and the importance of substrate

  19. Quantum dynamics through a wave packet method to study electron-hydrogen and atom-dihydrogen collisions; Dynamique quantique par une methode de paquets d'ondes. Etude des collisions electron-hydrogene et atome-dihydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Mouret, L

    2002-11-01

    The thesis concerns the development and implementation of numerical methods for solving the time-dependent Schroedinger equation. We first considered the case of electron-hydrogen scattering. The originality of our method is the use of a non-uniform radial grid defined by a Schwarz interpolation based on a Coulomb reference function. This grid allows many hydrogen bound states and associated matrix elements of various operators to be reproduced to machine accuracy. The wave function is propagated in time using a Split-Operator method. The efficiency of our method allows the wave function to be propagated out to large distances for all partial waves. We obtain excitation and ionization cross sections in excellent agreement with the best experimental and theoretical data. We subsequently adapted the method and the program package to study reactive atom-dihydrogen scattering. The wave packet is described using product Jacobi coordinates on a regular grid of radial coordinates combined with a basis of Legendre polynomials for the angular part (partial wave S). The wave function is analysed using a time-to-energy Fourier transform, which provides results over the energy range covered by the initial wave packet in one calculation. The method was first tested on the quasi-direct (F,H2) reaction and then applied to the indirect (C(1D),H2)reaction. The state-to-state reaction probabilities are in good agreement with those obtained by a time-independent approach. In particular, the strongly resonant structure of the (C(1D),H2) reaction probabilities is well reproduced. (author)

  20. Direct measurement of interstellar extinction toward young stars using atomic hydrogen Lyα absorption

    Energy Technology Data Exchange (ETDEWEB)

    McJunkin, Matthew; France, Kevin; Brown, Alexander [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Schneider, P. C. [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Herczeg, Gregory J. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Hillenbrand, Lynne [California Institute of Technology, Department of Astrophysics, MC105-24, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Schindhelm, Eric [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States); Edwards, Suzan, E-mail: matthew.mcjunkin@colorado.edu [Five College Astronomy Department, Smith College, Northampton, MA 01063 (United States)

    2014-01-10

    Interstellar reddening corrections are necessary to reconstruct the intrinsic spectral energy distributions (SEDs) of accreting protostellar systems. The stellar SED determines the heating and chemical processes that can occur in circumstellar disks. Measurement of neutral hydrogen absorption against broad Lyα emission profiles in young stars can be used to obtain the total H I column density (N(H I)) along the line of sight. We measure N(H I) with new and archival ultraviolet observations from the Hubble Space Telescope (HST) of 31 classical T Tauri and Herbig Ae/Be stars. The H I column densities range from log{sub 10}(N(H I)) ≈19.6-21.1, with corresponding visual extinctions of A{sub V} =0.02-0.72 mag, assuming an R{sub V} of 3.1. We find that the majority of the H I absorption along the line of sight likely comes from interstellar rather than circumstellar material. Extinctions derived from new HST blue-optical spectral analyses, previous IR and optical measurements, and new X-ray column densities on average overestimate the interstellar extinction toward young stars compared to the N(H I) values by ∼0.6 mag. We discuss possible explanations for this discrepancy in the context of a protoplanetary disk geometry.

  1. Investigation of the Mechanism of Electron Capture and Electron Transfer Dissociation of Peptides with a Covalently Attached Free Radical Hydrogen Atom Scavenger.

    Science.gov (United States)

    Sohn, Chang Ho; Yin, Sheng; Peng, Ivory; Loo, Joseph A; Beauchamp, J L

    2015-11-15

    The mechanisms of electron capture and electron transfer dissociation (ECD and ETD) are investigated by covalently attaching a free-radical hydrogen atom scavenger to a peptide. The 2,2,6,6-tetramethylpiperidin-l-oxyl (TEMPO) radical was chosen as the scavenger due to its high hydrogen atom affinity (ca. 280 kJ/mol) and low electron affinity (ca. 0.45 ev), and was derivatized to the model peptide, FQX TEMPO EEQQQTEDELQDK. The X TEMPO residue represents a cysteinyl residue derivatized with an acetamido-TEMPO group. The acetamide group without TEMPO was also examined as a control. The gas phase proton affinity (882 kJ/mol) of TEMPO is similar to backbone amide carbonyls (889 kJ/mol), minimizing perturbation to internal solvation and sites of protonation of the derivatized peptides. Collision induced dissociation (CID) of the TEMPO tagged peptide dication generated stable odd-electron b and y type ions without indication of any TEMPO radical induced fragmentation initiated by hydrogen abstraction. The type and abundance of fragment ions observed in the CID spectra of the TEMPO and acetamide tagged peptides are very similar. However, ECD of the TEMPO labeled peptide dication yielded no backbone cleavage. We propose that a labile hydrogen atom in the charge reduced radical ions is scavenged by the TEMPO radical moiety, resulting in inhibition of N-C α backbone cleavage processes. Supplemental activation after electron attachment (ETcaD) and CID of the charge-reduced precursor ion generated by electron transfer of the TEMPO tagged peptide dication produced a series of b + H (b H ) and y + H (y H ) ions along with some c ions having suppressed intensities, consistent with stable O-H bond formation at the TEMPO group. In summary, the results indicate that ECD and ETD backbone cleavage processes are inhibited by scavenging of a labile hydrogen atom by the localized TEMPO radical moiety. This observation supports the conjecture that ECD and ETD processes involve long

  2. Hydrogen Atomic Positions of O-H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with ¹H-NMR Chemical Shifts and X-ray Diffraction Methods.

    Science.gov (United States)

    Siskos, Michael G; Choudhary, M Iqbal; Gerothanassis, Ioannis P

    2017-03-07

    The exact knowledge of hydrogen atomic positions of O-H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i) density functional theory (DFT) calculations after a structure has been determined by X-ray from single crystals or from powders; (ii) ¹H-NMR chemical shifts as constraints in DFT calculations, and (iii) use of root-mean-square deviation between experimentally determined and DFT calculated ¹H-NMR chemical shifts considering the great sensitivity of ¹H-NMR shielding to hydrogen bonding properties.

  3. Hydrogen Atomic Positions of O–H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with 1H-NMR Chemical Shifts and X-ray Diffraction Methods

    Directory of Open Access Journals (Sweden)

    Michael G. Siskos

    2017-03-01

    Full Text Available The exact knowledge of hydrogen atomic positions of O–H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i density functional theory (DFT calculations after a structure has been determined by X-ray from single crystals or from powders; (ii 1H-NMR chemical shifts as constraints in DFT calculations, and (iii use of root-mean-square deviation between experimentally determined and DFT calculated 1H-NMR chemical shifts considering the great sensitivity of 1H-NMR shielding to hydrogen bonding properties.

  4. The Reaction between Sodium Hydroxide and Atomic Hydrogen in Atmospheric and Flame Chemistry.

    Science.gov (United States)

    Gómez Martín, J C; Seaton, C; de Miranda, M P; Plane, J M C

    2017-10-12

    We report the first direct kinetic study of the gas-phase reaction NaOH + H → Na + H2O, which is central to the chemistry of sodium in the upper atmosphere and in flames. The reaction was studied in a fast flow tube, where NaOH was observed by multiphoton ionization and time-of-flight mass spectrometry, yielding k(NaOH + H, 230-298 K) = (3.8 ± 0.8) × 10(-11) cm(3) molecule (-1) s(-1) (at 2σ confidence level), showing no significant temperature dependence over the indicated temperature range and essentially in agreement with previous estimates of the rate constant in hydrogen-rich flames. We show, using theoretical trajectory calculations, that the unexpectedly slow, yet T-independent, rate coefficient for NaOH + H is explained by severe constraints in the angle of attack that H can make on NaOH to produce H2O. This reaction is also central to explaining Na-catalyzed flame inhibition, which has been proposed to occur via the sequence Na + OH (+ M) → NaOH followed by NaOH + H → Na + H2O, thereby effectively recombinating H and OH to H2O. RRKM calculations for the recombination of Na and OH yield k(Na + OH + N2, 300-2400 K) = 2.7 × 10(-29) (300/T)(1.2) cm(6) molecule(-2) s(-1), in agreement with a previous flash photolysis measurement at 653 K and Na-seeded flame studies in the 1800-2200 K range. These results therefore provide strong evidence to support the mechanism of flame inhibition by Na.

  5. Hydrogen-atom abstraction reactions by manganese(V)- and manganese(IV)-oxo porphyrin complexes in aqueous solution.

    Science.gov (United States)

    Arunkumar, Chellaiah; Lee, Yong-Min; Lee, Jung Yoon; Fukuzumi, Shunichi; Nam, Wonwoo

    2009-11-02

    High-valent manganese(IV or V)-oxo porphyrins are considered as reactive intermediates in the oxidation of organic substrates by manganese porphyrin catalysts. We have generated Mn(V)- and Mn(IV)-oxo porphyrins in basic aqueous solution and investigated their reactivities in C-H bond activation of hydrocarbons. We now report that Mn(V)- and Mn(IV)-oxo porphyrins are capable of activating C-H bonds of alkylaromatics, with the reactivity order of Mn(V)-oxo>Mn(IV)-oxo; the reactivity of a Mn(V)-oxo complex is 150 times greater than that of a Mn(IV)-oxo complex in the oxidation of xanthene. The C-H bond activation of alkylaromatics by the Mn(V)- and Mn(IV)-oxo porphyrins is proposed to occur through a hydrogen-atom abstraction, based on the observations of a good linear correlation between the reaction rates and the C-H bond dissociation energy (BDE) of substrates and high kinetic isotope effect (KIE) values in the oxidation of xanthene and dihydroanthracene (DHA). We have demonstrated that the disproportionation of Mn(IV)-oxo porphyrins to Mn(V)-oxo and Mn(III) porphyrins is not a feasible pathway in basic aqueous solution and that Mn(IV)-oxo porphyrins are able to abstract hydrogen atoms from alkylaromatics. The C-H bond activation of alkylaromatics by Mn(V)- and Mn(IV)-oxo species proceeds through a one-electron process, in which a Mn(IV)-oxo porphyrin is formed as a product in the C-H bond activation by a Mn(V)-oxo porphyrin, followed by a further reaction of the Mn(IV)-oxo porphyrin with substrates that results in the formation of a Mn(III) porphyrin complex. This result is in contrast to the oxidation of sulfides by the Mn(V)-oxo porphyrin, in which the oxidation of thioanisole by the Mn(V)-oxo complex produces the starting Mn(III) porphyrin and thioanisole oxide. This result indicates that the oxidation of sulfides by the Mn(V)-oxo species occurs by means of a two-electron oxidation process. In contrast, a Mn(IV)-oxo porphyrin complex is not capable of oxidizing

  6. Combined Molecular Dynamics, Atoms in Molecules, and IR Studies of the Bulk Monofluoroethanol and Bulk Ethanol To Understand the Role of Organic Fluorine in the Hydrogen Bond Network.

    Science.gov (United States)

    Biswas, Biswajit; Mondal, Saptarsi; Singh, Prashant Chandra

    2017-02-16

    The presence of the fluorocarbon group in fluorinated alcohols makes them an important class of molecules that have diverse applications in the field of separation techniques, synthetic chemistry, polymer industry, and biology. In this paper, we have performed the density function theory calculation along with atom in molecule analysis, molecular dynamics simulation, and IR measurements of bulk monofluoroethanol (MFE) and compared them with the data for bulk ethanol (ETH) to understand the effect of the fluorocarbon group in the structure and the hydrogen bond network of bulk MFE. It has been found that the intramolecular O-H···F hydrogen bond is almost absent in bulk MFE. Molecular dynamics simulation and density function theory calculation along with atom in molecule analysis clearly depict that in the case of bulk MFE, a significant amount of intermolecular O-H···F and C-H···F hydrogen bonds are present along with the intermolecular O-H···O hydrogen bond. The presence of intermolecular O-H···F and C-H···F hydrogen bonds causes the difference in the IR spectrum of bulk MFE as compared to bulk ETH. This study clearly depicts that the organic fluorine (fluorocarbon) of MFE acts as a hydrogen bond acceptor and plays a significant role in the structure and hydrogen bond network of bulk MFE through the formation of weak O-H···F as well C-H···F hydrogen bonds, which may be one of the important reasons behind the unique behavior of the fluoroethanols.

  7. Kinetic theory of weakly ionized dilute gas of hydrogen-like atoms of the first principles of quantum statistics and dispersion laws of eigenwaves

    Science.gov (United States)

    Slyusarenko, Yurii V.; Sliusarenko, Oleksii Yu.

    2017-11-01

    We develop a microscopic approach to the construction of the kinetic theory of dilute weakly ionized gas of hydrogen-like atoms. The approach is based on the statements of the second quantization method in the presence of bound states of particles. The basis of the derivation of kinetic equations is the method of reduced description of relaxation processes. Within the framework of the proposed approach, a system of common kinetic equations for the Wigner distribution functions of free oppositely charged fermions of two kinds (electrons and cores) and their bound states—hydrogen-like atoms— is obtained. Kinetic equations are used to study the spectra of elementary excitations in the system when all its components are non-degenerate. It is shown that in such a system, in addition to the typical plasma waves, there are longitudinal waves of matter polarization and the transverse ones with a behavior characteristic of plasmon polaritons. The expressions for the dependence of the frequencies and Landau damping coefficients on the wave vector for all branches of the oscillations discovered are obtained. Numerical evaluation of the elementary perturbation parameters in the system on an example of a weakly ionized dilute gas of the 23Na atoms using the D2-line characteristics of the natrium atom is given. We note the possibility of using the results of the developed theory to describe the properties of a Bose condensate of photons in the diluted weakly ionized gas of hydrogen-like atoms.

  8. Hydrogen Atom Transfer (HAT) Processes Promoted by the Quinolinimide-N-oxyl Radical. A Kinetic and Theoretical Study.

    Science.gov (United States)

    DiLabio, Gino A; Franchi, Paola; Lanzalunga, Osvaldo; Lapi, Andrea; Lucarini, Fiorella; Lucarini, Marco; Mazzonna, Marco; Prasad, Viki Kumar; Ticconi, Barbara

    2017-06-16

    A kinetic study of the hydrogen atom transfer (HAT) reactions from a series of organic compounds to the quinolinimide-N-oxyl radical (QINO) was performed in CH3CN. The HAT rate constants are significantly higher than those observed with the phthalimide-N-oxyl radical (PINO) as a result of enthalpic and polar effects due to the presence of the N-heteroaromatic ring in QINO. The relevance of polar effects is supported by theoretical calculations conducted for the reactions of the two N-oxyl radicals with toluene, which indicate that the HAT process is characterized by a significant degree of charge transfer permitted by the π-stacking that occurs between the toluene and the N-oxyl aromatic rings in the transition state structures. An increase in the HAT reactivity of QINO was observed in the presence of 0.15 M HClO4 and 0.15 M Mg(ClO4)2 due to the protonation or complexation with the Lewis acid of the pyridine nitrogen that leads to a further decrease in the electron density in the N-oxyl radical. These results fully support the use of N-hydroxyquinolinimide as a convenient substitute for N-hydroxyphthalimide in the catalytic aerobic oxidations of aliphatic hydrocarbons characterized by relatively high C-H bond dissociation energies.

  9. Fragmentation and plasmid strand breaks in pure and gold-doped DNA irradiated by beams of fast hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Wyer, J A; Latimer, C J; Shah, M B; Currell, F J [Centre for Plasma Physics, IRCEP, Queen' s University Belfast, BT7 1NN (United Kingdom); Butterworth, K T; Hirst, D G [Experimental Therapeutics Research Group, School of Pharmacy, Queen' s University Belfast, BT9 7BL (United Kingdom); Montenegro, E C [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cx. Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil)], E-mail: jeanwyer@phys.au.dk

    2009-08-07

    The results of an investigation into the damage caused to dry plasmid DNA after irradiation by fast (keV) hydrogen atoms are presented. Agarose gel electrophoresis was used to assess single and double strand break yields as a function of dose in dry DNA samples deposited on a mica substrate. Damage levels were observed to increase with beam energy. Strand break yields demonstrated a considerable dependence on sample structure and the method of sample preparation. Additionally, the effect of high-Z nanoparticles on damage levels was investigated by irradiating DNA samples containing controlled amounts of gold nanoparticles. In contrast to previous (photonic) studies, no enhancement of strand break yields was observed with the particles showing a slight radioprotective effect. A model of DNA damage as a function of dose has been constructed in terms of the probability for the creation of single and double strand breaks, per unit ion flux. This model provides quantitative conclusions about the effects of both gold nanoparticles and the different buffers used in performing the assays and, in addition, infers the proportion of multiply damaged fragments.

  10. Integration of atomic layer deposited high-k dielectrics on GaSb via hydrogen plasma exposure

    Directory of Open Access Journals (Sweden)

    Laura B. Ruppalt

    2014-12-01

    Full Text Available In this letter we report the efficacy of a hydrogen plasma pretreatment for integrating atomic layer deposited (ALD high-k dielectric stacks with device-quality p-type GaSb(001 epitaxial layers. Molecular beam eptiaxy-grown GaSb surfaces were subjected to a 30 minute H2/Ar plasma treatment and subsequently removed to air. High-k HfO2 and Al2O3/HfO2 bilayer insulating films were then deposited via ALD and samples were processed into standard metal-oxide-semiconductor (MOS capacitors. The quality of the semiconductor/dielectric interface was probed by current-voltage and variable-frequency admittance measurements. Measurement results indicate that the H2-plamsa pretreatment leads to a low density of interface states nearly independent of the deposited dielectric material, suggesting that pre-deposition H2-plasma exposure, coupled with ALD of high-k dielectrics, may provide an effective means for achieving high-quality GaSb MOS structures for advanced Sb-based digital and analog electronics.

  11. On the Kantorovich approach for calculations of the hydrogen atom states affected by a train of short pulses

    Science.gov (United States)

    Chuluunbaatar, O.; Gusev, A. A.; Derbov, V. L.; Kaschiev, M. S.; Kouzakov, K. A.; Serov, V. V.; Samoylov, V. N.; Tupikova, T. V.; Vinitsky, S. I.

    2006-07-01

    We present theoretical calculations for the evolution of Zeeman states in a train of short electric half-cycle pulses (kicks). For the numerical solution of the corresponding time-dependent Schrodinger equation (TDSE) the high accuracy splitting scheme based on the unitary approximations of the evolution operator is developed. The finite element method is used for determining the spatial form of the solution. The efficiency and stability of the developed computational method is shown for 1D models in the cases of second-, forth-, and sixth-order accuracy with respect to the time step. Numerical calculations for the kicked hydrogen atom in the presence of magnetic field are performed using the scheme of the sixth-order accuracy with respect to a time step and both Galerkin and Kantorovich reductions of the problem with respect to the angular variables. For a particular choice of the electric- and magnetic-field parameters and the initial Zeeman state the corresponding results exhibit a two-state resonance picture.

  12. Atomic Layer Deposition of Pt Nanoparticles within the Cages of MIL-101: A Mild and Recyclable Hydrogenation Catalyst

    Directory of Open Access Journals (Sweden)

    Karen Leus

    2016-03-01

    Full Text Available We present the in situ synthesis of Pt nanoparticles within MIL-101-Cr (MIL = Materials Institute Lavoisier by means of atomic layer deposition (ALD. The obtained Pt@MIL-101 materials were characterized by means of N2 adsorption and X-ray powder diffraction (XRPD measurements, showing that the structure of the metal organic framework was well preserved during the ALD deposition. X-ray fluorescence (XRF and transmission electron microscopy (TEM analysis confirmed the deposition of highly dispersed Pt nanoparticles with sizes determined by the MIL-101-Cr pore sizes and with an increased Pt loading for an increasing number of ALD cycles. The Pt@MIL-101 material was examined as catalyst in the hydrogenation of different linear and cyclic olefins at room temperature, showing full conversion for each substrate. Moreover, even under solvent free conditions, full conversion of the substrate was observed. A high concentration test has been performed showing that the Pt@MIL-101 is stable for a long reaction time without loss of activity, crystallinity and with very low Pt leaching.

  13. Classical trajectory Monte Carlo model calculations for the antiproton-induced ionization of atomic hydrogen at low impact energy

    CERN Document Server

    Sarkadi, L

    2015-01-01

    The three-body dynamics of the ionization of the atomic hydrogen by 30 keV antiproton impact has been investigated by calculation of fully differential cross sections (FDCS) using the classical trajectory Monte Carlo (CTMC) method. The results of the calculations are compared with the predictions of quantum mechanical descriptions: The semi-classical time-dependent close-coupling theory, the fully quantal, time-independent close-coupling theory, and the continuum-distorted-wave-eikonal-initial-state model. In the analysis particular emphasis was put on the role of the nucleus-nucleus (NN) interaction played in the ionization process. For low-energy electron ejection CTMC predicts a large NN interaction effect on FDCS, in agreement with the quantum mechanical descriptions. By examining individual particle trajectories it was found that the relative motion between the electron and the nuclei is coupled very weakly with that between the nuclei, consequently the two motions can be treated independently. A simple ...

  14. Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H2

    Science.gov (United States)

    Joo, Ji Bong; Dillon, Robert; Lee, Ilkeun; Yin, Yadong; Bardeen, Christopher J.; Zaera, Francisco

    2014-01-01

    The production of hydrogen from water with semiconductor photocatalysts can be promoted by adding small amounts of metals to their surfaces. The resulting enhancement in photocatalytic activity is commonly attributed to a fast transfer of the excited electrons generated by photon absorption from the semiconductor to the metal, a step that prevents deexcitation back to the ground electronic state. Here we provide experimental evidence that suggests an alternative pathway that does not involve electron transfer to the metal but requires it to act as a catalyst for the recombination of the hydrogen atoms made via the reduction of protons on the surface of the semiconductor instead. PMID:24843154

  15. Hydride, hydrogen atom, proton, and electron transfer driving forces of various five-membered heterocyclic organic hydrides and their reaction intermediates in acetonitrile.

    Science.gov (United States)

    Zhu, Xiao-Qing; Zhang, Ming-Tian; Yu, Ao; Wang, Chun-Hua; Cheng, Jin-Pei

    2008-02-27

    The enthalpy changes of 47 five-membered heterocyclic compounds (ZH) [33 substituted 2,3-dihydro-2-phenylbenzo[d]imidazoles (1H-5H), 9 substituted 2,3-dihydro-2-phenylbenzo[d]thiazoles (6H), and 5 substituted 2,3-dihydro-2-phenylbenzo[d]oxazoles (7H)] as a class of very important organic hydride donors to release hydride anion were determined by using titration calorimetry. The result shows that the enthalpy change scale of the 47 ZH in acetonitrile ranges from 49.0 to 93.4 kcal/mol. Such a long energy scale evidently shows that the 47 ZH can construct a large and useful library of organic hydride donors, which can provide various organic hydride donors that the hydride-releasing enthalpies are known. The enthalpy changes of the 47 ZH to release hydrogen atom and the 47 ZH+* to release proton and hydrogen atom were also evaluated by using relative thermodynamic cycles according to Hess' law. The results show: (1) the enthalpy change scale of the 47 ZH to release hydrogen atom covers a range from 71.8 to 91.4 kcal/mol, indicating that the 47 ZH all should be weak hydrogen atom donors. (2) The enthalpy change scales of the 47 ZH+* to release proton and to release hydrogen atom range from 17.5 to 25.7 and from 27.2 to 52.4 kcal/mol, respectively, implying that the proton-donating abilities of ZH+* are generally quite larger than the corresponding hydrogen atom-donating abilities. The standard redox potentials of the 47 ZH and the 47 corresponding salts (Z+) were measured by using cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV), the results display that the standard oxidation potential scale of ZH ranges from -0.254 to -0.002 V for 1H-5H and from 0.310 to 0.638 V for 6H-7H, implying that 1H-5H should be strong one-electron reducing agents and 6H-7H should be weak one-electron reducing agents; the standard reduction potential scale of Z+ ranges from -1.832 to -2.200 V for 1+-5+ and from -1.052 to -1.483V for 6+-7+, meaning that 1+-5+ belong to very

  16. Hydrogen atom scrambling in selectively labeled anionic peptides upon collisional activation by MALDI tandem time-of-flight mass spectrometry

    DEFF Research Database (Denmark)

    Bache, Nicolai; Rand, Kasper Dyrberg; Roepstorff, Peter

    2008-01-01

    We have previously shown that peptide amide hydrogens undergo extensive intramolecular migration (i.e., complete hydrogen scrambling) upon collisional activation of protonated peptides (Jørgensen et al. J. Am. Chem. Soc. 2005, 127, 2785-2793). The occurrence of hydrogen scrambling enforces severe...

  17. Effective atomic number of soft tissue, water and air for interaction of various hadrons, leptons and isotopes of hydrogen.

    Science.gov (United States)

    Kurudirek, Murat

    2017-12-01

    Characterization of soft tissue, water and air in terms of effective atomic number (Zeff) with respect to the interactions of hadrons, leptons and isotopes of hydrogen. Mass collision stopping powers (MCSPs) were calculated first using Bethe formula. Then, these values were used to estimate Zeff using linear-logarithmic interpolation. A scale equation was also used to calculate MCSP. Variation in Zeff, over the 0.5-50 MeV energy range considered, is minimum for muon and pion (π meson) interactions (relative difference [RD] ≤ 7%), while maximum variation has been noticed in Zefffor heavy charged particles, i.e. alpha particle (RD ≤ 26%). The highest values of Zeff were obtained for muon particle, the lightest particle while the minimum values of Zeff were obtained for alpha particle interaction. Except for very low kinetic energies, water equivalence of soft tissue is very satisfactory (RD ≤ 3%). The Zeff of water relative to air was found to be almost constant at high energies. The present results should be valid for especially high energies where the Bethe formula can be applied. This applies to relatively higher energies (>2 MeV) for heavier particles such as alpha particles and applies to relatively lower energies (>0.5 MeV) for lighter particles such as protons. In view of the importance of water equivalence in particle therapy, new data on Zeff in soft tissue, water and air for fundamental particle interaction should be important. Results revealed that soft tissue could be considered as water equivalent for interaction of various fundamental particles.

  18. Study and determination of the ratio atoms between hydrogen and manganese in the manganese sulphate bath: procedure and calculation

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Leonardo C. de; Pereira, Walsan W.; Fonseca, Evaldo S. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)]. E-mail: curvello@ird.gov.br; walsan@ird.gov.br; Leite, Sandro P. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia

    2007-07-01

    The Brazilian Neutron Laboratory (LN) is part of the National Laboratory of Ionising Radiation of Metrology (LNMRI/IRD). It operates a system for absolute standardization for the measurement of the neutrons sources fluence. The Manganese Sulphate Bath (MSB) is part of this measurement system and was donated by the Bureau International de Poids et Measures (BIPM) in 1996. Since then at LN has become a fulfilled inquiry and measurements of fluence rate of a neutrons source Q. LN has carried through activities for the maintenance and dissemination of the reference values for this primary standard. Currently LN advances in two work lines: One of them is the study of the bath sensibility of the detection system (e), and the other is the study of f parameter, that measures the fraction of captured neutrons by {sup 55}Mn. In the present work, we dedicate special attention to the measurement of the neutron fraction that depends on the amount of ratio atoms between hydrogen and manganese. A revision of the procedures and the experience involved with the measurement system gave chance to evaluate points for a metrology refinement leading to lower uncertainties and greater reliability degree values. To obtain the cited refinement, the following stages had been fulfilled: Firstly, the development of a tool for confection of standardized crucibles. Secondly, the characterization of the muffle used in the work through the survey of heating slopes. And finally, the study of the volatility with the temperature of manganese sulphate (MnSO4 + H2O) through a thermo-gravimetric analysis in the own muffle conditions used in the work. It was observed that the steady temperature of operation in the quantification of the Manganese in the solution meets above of 350 deg C and this caused a significant improvement over the measurement proceeding. This work demonstrates that the improvements in the proceeding for the determination of the NH/NMn ratio leads to the one of the goals longed for

  19. Hydrogen Atom Collision Processes in Cool Stellar Atmospheres: Effects on Spectral Line Strengths and Measured Chemical Abundances in Old Stars

    Science.gov (United States)

    Barklem, Paul S.

    2012-12-01

    The precise measurement of the chemical composition of stars is a fundamental problem relevant to many areas of astrophysics. State-of-the-art approaches attempt to unite accurate descriptions of microphysics, non-local thermodynamic equilibrium (non-LTE) line formation and 3D hydrodynamical model atmospheres. In this paper I review progress in understanding inelastic collisions of hydrogen atoms with other species and their influence on spectral line formation and derived abundances in stellar atmospheres. These collisions are a major source of uncertainty in non-LTE modelling of spectral lines and abundance determinations, especially for old, metal-poor stars, which are unique tracers of the early evolution of our galaxy. Full quantum scattering calculations of direct excitation processes X(nl) + H leftrightarrow X(n'l') + H and charge transfer processes X(nl) + H leftrightarrow X+ + H- have been done for Li, Na and Mg [1,2,3] based on detailed quantum chemical data, e.g. [4]. Rate coefficients have been calculated and applied to non-LTE modelling of spectral lines in stellar atmospheres [5,6,7,8,9]. In all cases we find that charge transfer processes from the first excited S-state are very important, and the processes affect measured abundances for Li, Na and Mg in some stars by as much as 60%. Effects vary with stellar parameters (e.g. temperature, luminosity, metal content) and so these processes are important not only for accurate absolute abundances, but also for relative abundances among dissimilar stars.

  20. Effects of co-implanted oxygen or aluminum atoms on hydrogen migration and damage structure in multiple-beam irradiated Al sub 2 O sub 3

    CERN Document Server

    Katano, Y; Yamamoto, S; Nakazawa, T; Yamaki, D; Noda, K

    2000-01-01

    Depth profiles of implanted H atoms were measured for single crystalline Al sub 2 O sub 3 samples irradiated at 923 K with dual or triple beams of 0.25 MeV H-, 0.6 MeV He-, 2.4 MeV O-ions or 2.6 MeV Al-ions. The peaks occur at 1.55 and 1.45 mu m in the depth profiles measured for the H + Al dual beam irradiation and H + O dual beam case, respectively. The ratio of the peak areas is over 4, which is much larger than the implanted H atom ratio of 1.1, indicating that implanted Al atoms suppress the mobility of H atoms. However, the ratio becomes almost 1 between the triple beam samples with H + He + O-ions and with H + He + Al-ions at comparable doses. The fact demonstrates that implanted He atoms overwhelm the effects of the implanted self-cation/anion excess atoms on the migration behaviors of implanted hydrogen and radiation produced point defects, with the resulting sluggish cavity growth observed.

  1. Uma introdução à espectroscopia atômica: o átomo de hidrogênio An introduction to atomic spectroscopy: the hydrogen atom

    Directory of Open Access Journals (Sweden)

    Oswaldo Sala

    2007-01-01

    Full Text Available The Balmer equation is obtained from the hydrogen spectrum in an empirical way, using a graphic method; from this equation the energy level terms are derived. Emphasis is given to concepts in order to make clear the meaning of quantum numbers, eigenvalues and eigenfunctions in the Schrödinger equation.

  2. Magnetic resonance lineshape of atomic hydrogen on liquid helium surfaces. The sticking probability of H on /sup 4/He and /sup 3/He

    Energy Technology Data Exchange (ETDEWEB)

    Berlinsky, A.J.; Morrow, M.; Jochemsen, R.; Hardy, W.N. (British Columbia Univ., Vancouver (Canada). Dept. of Physics)

    1982-07-01

    High resolution magnetic resonance studies of the 1420 MHz transition in atomic hydrogen confined in a liquid helium coated container have been performed at temperatures 0.06atoms on the liquid helium surface, by the exchange rate between atoms in the gas and atoms on the surface, and by the hyperfine frequency shift of an H atom in the bound surface state. Using a model with a Poisson distribution for the residency times, it is possible to interpret both the hyperfine frequency shift and the width of the resonance line as a function of temperature for H on /sup 4/He. The analysis gives the binding energy, the frequency in the surface state, and the sticking probability ..cap alpha.. for H on /sup 4/He. We obtain ..cap alpha..=0.035+-0.004. The results for H on /sup 3/He are more complicated, and possible explanations are discussed.

  3. The Star Formation Rate Efficiency of Neutral Atomic-Dominated Hydrogen Gas in the Ooutskirts of Star-Forming Galaxies From z approx. 1 to z approx. 3

    Science.gov (United States)

    Rafelski, Marc; Gardner, Jonathan P.; Fumagalli, Michele; Neeleman, Marcel; Teplitz, Harry I.; Grogin, Norman; Koekemoer, Anton M.; Scarlata, Claudia

    2016-01-01

    Current observational evidence suggests that the star formation rate (SFR)efficiency of neutral atomic hydrogen gas measured in damped Ly(alpha) systems (DLAs) at z approx. 3 is more than 10 times lower than predicted by the Kennicutt-Schmidt (KS)relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galaxy properties, we measure the SFR efficiency of atomic gas at z approx. 1, z approx. 2, and z approx. 3 around star-forming galaxies. We use new robust photometric redshifts in the Hubble Ultra Deep Field to create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies' outskirts. We find that the SFR efficiency of H I gas at z > 1 is approx. 1%-3% of that predicted by the KS relation. Contrary to simulations and models that predict a reduced SFR efficiency with decreasing metallicity and thus with increasing redshift, we find no significant evolution in the SFR efficiency with redshift. Our analysis instead suggests that the reduced SFR efficiency is driven by the low molecular content of this atomic-dominated phase, with metallicity playing a secondary effect in regulating the conversion between atomic and molecular gas. This interpretation is supported by the similarity between the observed SFR efficiency and that observed in local atomic-dominated gas, such as in the outskirts of local spiral galaxies and local dwarf galaxies.

  4. Experimental and theoretical study of hydrogen atom abstraction from n-butane by lanthanum oxide cluster anions.

    Science.gov (United States)

    Xu, Bo; Zhao, Yan-Xia; Li, Xiao-Na; Ding, Xun-Lei; He, Sheng-Gui

    2011-09-22

    Lanthanum oxide cluster anions are prepared by laser ablation and reacted with n-C(4)H(10) in a fast flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. (La(2)O(3))(m=1-3)OH(-) and La(3)O(7)H(-) are observed as products, which suggests the occurrence of hydrogen atom abstraction reactions: (La(2)O(3))(m=1-3)O(-) + n-C(4)H(10) → (La(2)O(3))(m=1-3)OH(-) + C(4)H(9) and La(3)O(7)(-) + n-C(4)H(10) → La(3)O(7)H(-) + C(4)H(9). Density functional theory (DFT) calculations are performed to study the structures and bonding properties of La(2)O(4)(-), La(3)O(7)(-), and La(4)O(7)(-) clusters. The calculated results show that each of La(2)O(4)(-) and La(4)O(7)(-) contains one oxygen-centered radical (O(-•)) which is responsible for the high reactivity toward n-C(4)H(10). La(3)O(7)(-) contains one oxygen-centered radical (O(-•)) and one superoxide unit (O(2)(-•)), and the O(-•) is responsible for its high reactivity toward n-C(4)H(10). The O(-•) and O(2)(-•) can be considered to be generated by the adsorption of an O(2) molecule onto the singlet La(3)O(5)(-) with electron transfer from a terminally bonded oxygen ion (O(2-)) to the O(2). This may help us understand the mechanism of the formation of O(-•) and O(2)(-•) radicals in lanthanum oxide systems. The reaction mechanisms of La(2)O(4)(-) + n-C(4)H(10) and La(3)O(7)(-) + n-C(4)H(10) are also studied by the DFT calculations, and the calculated results are in good agreement with the experimental observations. © 2011 American Chemical Society

  5. Hydrogen atoms in acetylsalicylic acid (Aspirin): the librating methyl group and probing the potential well in the hydrogen-bonded dimer

    Science.gov (United States)

    Wilson, Chick C.

    2001-02-01

    The structure of acetylsalicylic acid (2-(acetoyloxy)benzoic acid; Aspirin) has been studied by variable temperature single crystal neutron diffraction. The usual large torsional librational motion of the terminal methyl group is observed and its temperature dependence analysed using a simple model for the potential, yielding the force constant and barrier height for this motion. In addition, asymmetry of the scattering density of the proton involved in the hydrogen bond forming the carboxylic acid dimer motif is observed at temperatures above 200 K. This asymmetry is discussed in terms of its possible implications for the shape of the hydrogen bonding potential well.

  6. Neutral escape at Mars induced by the precipitation of high-energy protons and hydrogen atoms of the solar wind origin

    Science.gov (United States)

    Shematovich, Valery I.

    2017-04-01

    One of the first surprises of the NASA MAVEN mission was the observation by the SWIA instrument of a tenuous population of protons with solar wind energies travelling anti-sunward near periapsis, at altitudes of 150-250 km (Halekas et al., 2015). While the penetration of solar wind protons to low altitude is not completely unexpected given previous Mars Express results, this population maintains exactly the same velocity as the solar wind observed. From previous studies it was known that some fraction of the solar wind can interact with the extended corona of Mars. By charge exchange with the neutral particles in this corona, some fraction of the incoming solar wind protons can gain an electron and become an energetic neutral hydrogen atom. Once neutral, these particles penetrate through the Martian induced magnetosphere with ease, with free access to the collisional atmosphere/ionosphere. The origin, kinetics and transport of the suprathermal O atoms in the transition region (from thermosphere to exosphere) of the Martian upper atmosphere due to the precipitation of the high-energy protons and hydrogen atoms are discussed. Kinetic energy distribution functions of suprathermal and superthermal (ENA) oxygen atoms formed in the Martian upper atmosphere were calculated using the kinetic Monte Carlo model (Shematovich et al., 2011, Shematovich, 2013) of the high-energy proton and hydrogen atom precipitation into the atmosphere. These functions allowed us: (a) to estimate the non-thermal escape rates of neutral oxygen from the Martian upper atmosphere, and (b) to compare with available MAVEN measurements of oxygen corona. Induced by precipitation the escape of hot oxygen atoms may become dominant under conditions of extreme solar events - solar flares and coronal mass ejections, - as it was shown by recent observations of the NASA MAVEN spacecraft (Jakosky et al., 2015). This work is supported by the RFBR project and by the Basic Research Program of the Praesidium of

  7. NEW INTERPRETATION OF THE ATOMIC SPECTRA OF THE HYDROGEN ATOM: A MIXED MECHANISM OF CLASSICAL LC CIRCUITS AND QUANTUM WAVE-PARTICLE DUALITY NUEVA INTERPRETACIÓN DEL ESPECTRO ATÓMICO DEL ÁTOMO DE HIDRÓGENO: UN MECANISMO MIXTO DE CIRCUITOS LC Y LA DUALIDAD ONDA CUÁNTICA-PARTÍCULA

    OpenAIRE

    Héctor Torres-Silva

    2008-01-01

    In this paper we study the energy conversion laws of the macroscopic harmonic LC oscillator, the electromagnetic wave (photon) and the hydrogen atom. As our analysis indicates, the energies of these apparently different systems obey exactly the same energy conversion law. Based on our results and the wave-particle duality of electrons, we find that the hydrogen atom is, in fact, a natural chiral microscopic LC oscillator. In the framework of classical electromagnetic field theory we analytica...

  8. Observation by conductive-probe atomic force microscopy of strongly inverted surface layers at the hydrogenated amorphous silicon/crystalline silicon heterojunctions

    Science.gov (United States)

    Maslova, O. A.; Alvarez, J.; Gushina, E. V.; Favre, W.; Gueunier-Farret, M. E.; Gudovskikh, A. S.; Ankudinov, A. V.; Terukov, E. I.; Kleider, J. P.

    2010-12-01

    Heterojunctions made of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) are examined by conducting probe atomic force microscopy. Conductive channels at both (n )a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si interfaces are clearly revealed. These are attributed to two-dimension electron and hole gases due to strong inversion layers at the c-Si surface in agreement with previous planar conductance measurements. The presence of a hole gas in (p )a-Si:H/(n)c-Si structures implies a quite large valence band offset (EVc-Si-EVa-Si:H>0.25 eV).

  9. Hydroperoxyl Radicals (HOO(.) ): Vitamin E Regeneration and H-Bond Effects on the Hydrogen Atom Transfer.

    Science.gov (United States)

    Cedrowski, Jakub; Litwinienko, Grzegorz; Baschieri, Andrea; Amorati, Riccardo

    2016-11-07

    Hydroperoxyl (HOO(.) ) and alkylperoxyl (ROO(.) ) radicals show a different behavior in H-atom-transfer processes. Both radicals react with an analogue of α-tocopherol (TOH), but HOO(.) , unlike ROO(.) , is able to regenerate TOH by a fast H-atom transfer: TO(.) +HOO(.) →TOH+O2 . The kinetic solvent effect on the H-atom transfer from TOH to HOO(.) is much stronger than that observed for ROO(.) because noncovalent interactions with polar solvents (Solv⋅⋅⋅HOO(.) ) destabilize the transition state. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Effect of an acetylene bond on hydrogen adsorption in diamond-like carbon allotropes: from first principles to atomic simulation.

    Science.gov (United States)

    Wu, Xuanjun; Li, Lei; Fang, Tiange; Wang, YeTong; Cai, Weiquan; Xiang, Zhonghua

    2017-03-29

    By inserting an acetylene bond into the organic linkers of porous materials, hydrogen storage can be significantly enhanced; however, the mechanism of this enhancement remains elusive. Herein, we developed a new diamond-like carbon allotrope (referred as diamond-like diacetylene a.k.a. DDA) with medium pores constructed by inserting -C[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C- ligands into the -C-C- bonds of diamond. The structural, mechanical, and electrical properties, as well as hydrogen storage capacities were investigated for this novel material using density functional theory and Monte Carlo simulations. The optimized geometry of DDA shows a high surface area and free pore volume of ca. 5498.76 m2 g-1 and 2.0486 m3 g-1, respectively. DDA also exhibits structural stability and special electronic properties. Interestingly, DDA exhibits exceptional gravimetric hydrogen storage capacity as well as volumetric one. The excess gravimetric and volumetric H2 uptakes at 77 K and 2.0 MPa hit a maximum of 14.12 wt% and 603.35 cm3 (STP) cm-3, respectively, which substantially exceeds those previously reported for MOF or PAF materials. Even at 243 K and 12 MPa, the total gravimetric H2 uptake of DDA reaches 5.38 wt%. To the best of our knowledge, DDA is one of porous materials with the maximum physical hydrogen uptake. It is also one of the few materials that can be close to meeting hydrogen storage target of the US department of energy at room temperature. Significantly, DDA shows the deliverable hydrogen storage capacity up to 5.28 wt% at room temperature. Through analyzing the effect of the acetylene position in the DLCAs on their hydrogen storage capacities, we found that the high hydrogen adsorption performance of DDA is mainly attributed to its high surface area, large number of adsorption sites, and appropriate binding energy. In summary, the newly developed DDA is a promising candidate for hydrogen storage and provides a new possibility for

  11. Mechanistic elucidation of the stepwise formation of a tetranuclear manganese pinned butterfly cluster via N-N bond cleavage, hydrogen atom transfer, and cluster rearrangement.

    Science.gov (United States)

    Hamilton, Clifton R; Gau, Michael R; Baglia, Regina A; McWilliams, Sean F; Zdilla, Michael J

    2014-12-31

    A mechanistic pathway for the formation of the structurally characterized manganese-amide-hydrazide pinned butterfly complex, Mn4(μ3-PhN-NPh-κ(3)N,N')2(μ-PhN-NPh-κ(2)-N,N')(μ-NHPh)2L4 (L = THF, py), is proposed and supported by the use of labeling studies, kinetic measurements, kinetic competition experiments, kinetic isotope effects, and hydrogen atom transfer reagent substitution, and via the isolation and characterization of intermediates using X-ray diffraction and electron paramagnetic resonance spectroscopy. The data support a formation mechanism whereby bis[bis(trimethylsilyl)amido]manganese(II) (Mn(NR2)2, where R = SiMe3) reacts with N,N'-diphenylhydrazine (PhNHNHPh) via initial proton transfer, followed by reductive N-N bond cleavage to form a long-lived Mn(IV) imido multinuclear complex. Coordinating solvents activate this cluster for abstraction of hydrogen atoms from an additional equivalent of PhNHNHPh resulting in a Mn(II)phenylamido dimer, Mn2(μ-NHPh)2(NR2)2L2. This dimeric complex further assembles in fast steps with two additional equivalents of PhNHNHPh replacing the terminal silylamido ligands with η(1)-hydrazine ligands to give a dimeric Mn2(μ-NHPh)2(PhN-NHPh)2L4 intermediate, and finally, the addition of two additional equivalents of Mn(NR2)2 and PhNHNHPh gives the pinned butterfly cluster.

  12. UV-Induced Hydrogen-Atom-Transfer Processes in 3-Thio-1,2,4-triazole Isolated in Ar and H2 Low-Temperature Matrixes.

    Science.gov (United States)

    Rostkowska, Hanna; Lapinski, Leszek; Nowak, Maciej J

    2017-09-21

    The UV-induced thione → thiol phototautomeric reaction has been studied for monomeric 3-thio-1,2,4-triazole (3-ST) isolated in low-temperature Ar and n-H2 (normal hydrogen) matrixes. Prior to any UV irradiation, monomers of 3-ST isolated in solid Ar or solid n-H2 adopted mainly the most stable thione tautomeric form, as revealed by the IR spectra. Upon UV (λ > 275 nm) irradiation of 3-ST isolated in Ar matrixes, the IR bands due to this thione form decreased, while a set of initially weak bands increased in intensity. Growing bands indicated generation of a photoproduct, which was identified as the thiol tautomer with labile hydrogen atoms attached to sulfur and N(2) atoms. The UV-induced spectral changes allowed also identification of another minor thiol tautomer of 3-ST, which was present in the matrix prior to any irradiation and did not change its population upon exposure to UV light. The identification of the observed isomeric forms was supported by comparison of their separated experimental IR spectra with the spectra theoretically predicted for the various structures of 3-ST. The thione → thiol phototautomerization that was the main UV-induced process observed for 3-ST in Ar matrixes did not occur for monomers of the compound trapped in solid n-H2.

  13. Fiscal 1997 report on the development of new hydrogen atomic energy demonstrative technology; 1997 nendo kenkyu hokokusho (shinsuiso energy jissho gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-06-01

    In this validation study, phenomena of excess heat which are said to be generated by electrolysis of deuterium using palladium metal, etc. as electrode are taken as `new hydrogen atomic energy,` and to clarify a possibility of using them as a future energy source, the abnormal heating phenomenon was validated and the mechanism was elucidated. The study targeted quantitative control of heat emissions. The study was finished in 1997, the fifth year from the start. The excess heat measurement could partially be reproduced; however, when conducting a confirmation experiment on the excess heat by another more reliable method under the same condition, it was found that the value of excess heat was not an absolute value exceeding measuring sensitivity and errors of the system. If the excess heat of 0.1W order is to be emitted in nuclear reaction, any reactive product should be detected in a substantial quantity. However, the product of a large quantity was not found. A possibility was found out of an increase in nuclear reaction ratio inside solid by low energy deuterium irradiation. From the above, it was concluded that the use of new hydrogen atomic energy was negative. 20 refs., 149 figs., 29 tabs.

  14. Study of the transfer of electrons and hydrogen atoms between substituted p-benzoquinone triplets and diphenylamine by flash-photolysis methods

    Energy Technology Data Exchange (ETDEWEB)

    Levin, P.P.; Kokrashvili, T.A.

    1981-01-01

    The primary and secondary aromatic amines quench the triplet states of carbonyl compounds through processes involving the transfer of charges and hydrogen atoms. The interaction of the benzophenone triplet with primary and secondary aromatic amines involves a one-step transfer of H atoms, and leads to the formation of ketyl and aminyl radicals in both polar and nonpolar solvents. The triplet state of 2,6-diphenyl-1,4-benzoquinone can be quenched through diphenylamine (DPA), a secondary aromatic amine, the quenching mechanism involving a diffusion-limited transfer of both charges and H atoms. The processes of electron and H atom transfer are in competition here, proceeding independently in the collision complex. Neutral radicals and short-lived radical-ion pairs (t approx. 100 nsec) are formed as the result of quenching in low-polarity solvents. Both neutral and charged radicals are formed through quenching in acetonitrile, but only radical-ions are formed through quenching in alcoholic solution. Only charged radicals are formed through quenching of duroquinone by DPA in ethanol-water mixtures. An understanding of the factors determining the mechanism of carbonyl compound triplet state quenching by electron and H atom donors can be obtained through a study of the effect of the structures of the reacting molecules, and the solvent, on the kinetics of the transfer processes. The present work has used flash photolysis methods to study the intermediates formed during the quenching of the triplet states of the p-benzoquinones by DFA in solvents of various polarities.

  15. Re-establishment of the atomic composition and the oxide structure of contaminated titanium surfaces by means of carbon dioxide laser and hydrogen peroxide: an in vitro study.

    Science.gov (United States)

    Mouhyi, J; Sennerby, L; Wennerberg, A; Louette, P; Dourov, N; van Reck, J

    2000-01-01

    In clinical situations with peri-implant bone resorption, re-integration of the exposed implant surface is sometimes preferable, which requires a clean surface. Previous investigations have shown that cleaning of contaminated titanium surfaces using chemical and abrasive methods is difficult. The aim of this investigation was to evaluate the efficacy of different combinations of chemical and physical methods (citric acid, hydrogen peroxide, and carbon dioxide [CO2] laser irradiation) for removal of contaminants and subsequent reconstruction of the surface oxide of intraorally contaminated titanium foils. Commercially pure titanium foils (99.6%, 5 x 5 mm in size) were contaminated by placement on dentures in volunteering patients, simulating a peri-implantitis situation. The contaminated foils and clean control foils were treated by seven and six combinations of citric acid, hydrogen peroxide, and CO2 laser irradiation, respectively. The effect of the cleaning procedures was evaluated by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The initial elemental composition of the contaminated foils was 70% carbon (C), 20% oxygen (O), 10% nitrogen (N), and only traces of titanium (Ti) (titanium. A combination of citric acid, hydrogen peroxide, and CO2 laser irradiation seems to be effective for cleaning and reestablishment of the atomic composition and oxide structure of contaminated titanium surfaces.

  16. TWO REGIMES OF INTERACTION OF A HOT JUPITER’S ESCAPING ATMOSPHERE WITH THE STELLAR WIND AND GENERATION OF ENERGIZED ATOMIC HYDROGEN CORONA

    Energy Technology Data Exchange (ETDEWEB)

    Shaikhislamov, I. F.; Prokopov, P. A.; Berezutsky, A. G.; Zakharov, Yu. P.; Posukh, V. G. [Institute of Laser Physics SB RAS, Novosibirsk (Russian Federation); Khodachenko, M. L.; Lammer, H.; Kislyakova, K. G.; Fossati, L. [Space Research Institute, Austrian Acad. Sci., Graz (Austria); Johnstone, C. P., E-mail: maxim.khodachenko@oeaw.ac.at [Department of Astrophysics, University of Vienna, Vienna (Austria)

    2016-12-01

    The interaction of escaping the upper atmosphere of a hydrogen-rich non-magnetized analog of HD 209458b with a stellar wind (SW) of its host G-type star at different orbital distances is simulated with a 2D axisymmetric multi-fluid hydrodynamic (HD) model. A realistic Sun-like spectrum of X-ray and ultraviolet radiation, which ionizes and heats the planetary atmosphere, together with hydrogen photochemistry, as well as stellar-planetary tidal interaction are taken into account to generate self-consistently an atmospheric HD outflow. Two different regimes of the planetary and SW interaction have been modeled. These are: (1) the “ captured by the star ” regime, when the tidal force and pressure gradient drive the planetary material beyond the Roche lobe toward the star, and (2) the “ blown by the wind ” regime, when sufficiently strong SW confines the escaping planetary atmosphere and channels it into the tail. The model simulates in detail the HD interaction between the planetary atoms, protons and the SW, as well as the production of energetic neutral atoms (ENAs) around the planet due to charge exchange between planetary atoms and stellar protons. The revealed location and shape of the ENA cloud, either as a paraboloid shell between the ionopause and bowshock (for the “ blown by the wind ” regime), or a turbulent layer at the contact boundary between the planetary stream and SW (for the “ captured by the star ” regime) are of importance for the interpretation of Ly α absorption features in exoplanetary transit spectra and characterization of the plasma environments.

  17. Theory of low temperature spin exchange scattering for a physiosorbed two-dimensional gas of hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Morrow, M.; Berlinsky, A.J.

    1983-07-01

    Calculations are presented of the two-dimensional scattering cross sections which are required to evaluate the longitudinal and transverse relaxation times T/sub 1/ and T/sub 2/ and the frequency shift ..delta..v due to spin exchange collision between H atoms physisorbed on a surface. The results are used to interpret the recent measurements by Crampton and co-workers of the relaxation time T/sub 1/ for H atoms in the presence of solid H/sub 2/ walls. New results are also presented for T/sub 1/, due to three-dimensional scattering in the gas, using a more recent triplet H-H potential than the one previously employed by Berlinsky and Shizgal.

  18. Photoluminescence recovery by in-situ exposure of plasma-damaged n-GaN to atomic hydrogen at room temperature

    Directory of Open Access Journals (Sweden)

    Shang Chen

    2012-06-01

    Full Text Available The effect of in-situ exposure of n-GaN damaged by Cl2 plasma to atomic hydrogen (H radicals at room temperature was investigated. We found that the PL intensities of the band-edge emission, which had been drastically reduced by plasma-beam irradiation at a Cl ion dose of 5 × 1016 cm−2, recovered to values close to those of as-grown samples after H radical exposure at a dose of 3.8 × 1017 cm−2. XPS revealed the appearance of a peak at a binding energy of 18.3 eV, which is tentatively assigned to Ga-H, and confirmed the removal of Cl after H radical exposure.

  19. Negative catalytic effect of water on the reactivity of hydrogen abstraction from the C-H bond of dimethyl ether by deuterium atoms through tunneling at low temperatures

    Science.gov (United States)

    Oba, Yasuhiro; Watanabe, Naoki; Kouchi, Akira

    2016-10-01

    We report an experimental study on the catalytic effect of solid water on the reactivity of hydrogen abstraction (H-abstraction) from dimethyl ether (DME) in the low-temperature solid DME-H2O complex. When DME reacted with deuterium atoms on a surface at 15-25 K, it was efficiently deuterated via successive tunneling H-abstraction and deuterium (D)-addition reactions. The 'effective' rate constant for DME-H2O + D was found to be about 20 times smaller than that of pure DME + D. This provides the first evidence that the presence of solid water has a negative catalytic effect on tunneling H-abstraction reactions.

  20. H atom, e{sup -}, and H{sub 6}{sup +} ions produced in irradiated solid hydrogens: An electron spin resonance study

    Energy Technology Data Exchange (ETDEWEB)

    Kumada, Takayuki [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)], E-mail: kumada.takayuki@jaea.go.jp; Shimizu, Yuta; Ushida, Takahiro; Kumagai, Jun [Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan)

    2008-10-15

    We carried out electron spin resonance (ESR) study of irradiated solid H{sub 2} and para-H{sub 2}. H-atom, e{sup -}, and H{sub 6}{sup +} lines were observed. The H-atom radicals diffuse in solid H{sub 2} by the tunneling chemical reaction H+H{sub 2}{yields}H{sub 2}+H below 4 K, and by the thermally activated process above 5 K. These decay via H-H recombination. Yield of trapped electrons e{sup -} produced by the radiolysis of solid para-H{sub 2} increases with increase in the concentration of added isotopic hydrogen, HD or D{sub 2}. These decay via geminate recombination with positive ions with a half-life of 8 h at 4 K. H{sub 6}{sup +} ion is an ionic hydrogen radical whose spectrum has firstly been observed in irradiated solid para-H{sub 2}. H{sub 6}{sup +} ions diffuse in solid H{sub 2} by sequence of H{sub 6}{sup +}+H{sub 2}{yields}H{sub 2}+H{sub 6}{sup +} reactions, and terminate by the isotope-exchange reaction H{sub 6}{sup +}+HD{yields}H{sub 5}D{sup +}+H{sub 2} or H{sub 6}{sup +}+D{sub 2}{yields}H{sub 4}D{sub 2}{sup +}+H{sub 2}. Unlike H{sub 6}{sup +}, isotopically substituted H{sub 5}D{sup +} and H{sub 4}D{sub 2}{sup +} cannot diffuse in solid para-H{sub 2}. Rate-determining step of their decay is charge recombination with e{sup -}.

  1. High-level direct-dynamics variational transition state theory calculations including multidimensional tunneling of the thermal rate constants, branching ratios, and kinetic isotope effects of the hydrogen abstraction reactions from methanol by atomic hydrogen.

    Science.gov (United States)

    Meana-Pañeda, Rubén; Truhlar, Donald G; Fernández-Ramos, Antonio

    2011-03-07

    We report a detailed theoretical study of the hydrogen abstraction reaction from methanol by atomic hydrogen. The study includes the analysis of thermal rate constants, branching ratios, and kinetic isotope effects. Specifically, we have performed high-level computations at the MC3BB level together with direct dynamics calculations by canonical variational transition state theory (CVT) with the microcanonically optimized multidimensional tunneling (μOMT) transmission coefficient (CVT/μOMT) to study both the CH(3)OH+H→CH(2)OH+H(2) (R1) reaction and the CH(3)OH+H→CH(3)O+H(2) (R2) reaction. The CVT/μOMT calculations show that reaction R1 dominates in the whole range 298≤T (K)≤2500 and that anharmonic effects on the torsional mode about the C-O bond are important, mainly at high temperatures. The activation energy for the total reaction sum of R1 and R2 reactions changes substantially with temperature and, therefore, the use of straight-line Arrhenius plots is not valid. We recommend the use of new expressions for the total R1 + R2 reaction and for the R1 and R2 individual reactions. © 2011 American Institute of Physics.

  2. Self-assembled nanostructures on vicinal surfaces

    Science.gov (United States)

    Petrovykh, Dmitri Yourievich

    2000-10-01

    One of the first methods for visualizing crystal planes and atomic steps has been step decoration with gold on alkali-halide surfaces. An impressive body of work has been conducted since then on the role of steps in controlling surface diffusion and adsorption rates, catalytic and chemical activity, and other physical and chemical surface properties. Due to these special characteristics, vicinal surfaces offer an approach for creating self-assembled structures with one or more dimensions on nanometer scale. The storage and communications industries have been revolutionized by applications of two-dimensional electron gas confined in thin films, so an interest in one and zero-dimensional systems is not surprising. This work demonstrates how macroscopic amounts of low-dimensional structures can be produced by self-assembly using stepped surfaces as nanometer-scale templates. High-quality templates of step arrays can be prepared on vicinal Si(111) surfaces. Sub-monolayer CaF2/Si(111) heteroepitaxial growth is examined in a series of experiments. A new growth mode is observed in addition to the ones typical in three dimensions. With increasing coverage, the growth front changes from rough to smooth geometry, driven by the elastic interactions between the multiple growth fronts and the surface steps. The mechanism is thus unique to the two-dimensional growth on stepped surfaces. The possible arrangements of the CaF2 self-assembled nanostructures are arrays of stripes or islands, both interesting as potential masks for silicon nanolithography. Anisotropic surface reconstructions, such as Ca and Au induced 3 x 1 and 5 x 2 on Si(111), are effectively self-assembled one-dimensional atomic chains. Reconstructions are single-domain on vicinal surfaces and with odd electron count a metallic one-dimensional state is expected in both the above examples. However in angular-resolved photoemission both appear as semiconductors, and Au-Si(111)5 x 2 exhibits a continuous one

  3. Measurement and analysis of atomic hydrogen and diatomic molecular AlO, C2, CN, and TiO spectra following laser-induced optical breakdown.

    Science.gov (United States)

    Parigger, Christian G; Woods, Alexander C; Witte, Michael J; Swafford, Lauren D; Surmick, David M

    2014-02-14

    In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement is used. Here we operate a Nd:YAG laser at a frequency of 10 Hz at the fundamental wavelength of 1,064 nm. The 14 nsec pulses with anenergy of 190 mJ/pulse are focused to a 50 µm spot size to generate a plasma from optical breakdown or laser ablation in air. The microplasma is imaged onto the entrance slit of a 0.6 m spectrometer, and spectra are recorded using an 1,800 grooves/mm grating an intensified linear diode array and optical multichannel analyzer (OMA) or an ICCD. Of interest are Stark-broadened atomic lines of the hydrogen Balmer series to infer electron density. We also elaborate on temperature measurements from diatomic emission spectra of aluminum monoxide (AlO), carbon (C2), cyanogen (CN), and titanium monoxide (TiO). The experimental procedures include wavelength and sensitivity calibrations. Analysis of the recorded molecular spectra is accomplished by the fitting of data with tabulated line strengths. Furthermore, Monte-Carlo type simulations are performed to estimate the error margins. Time-resolved measurements are essential for the transient plasma commonly encountered in LIBS.

  4. Hydrogen Embrittlement

    Science.gov (United States)

    Woods, Stephen; Lee, Jonathan A.

    2016-01-01

    Hydrogen embrittlement (HE) is a process resulting in a decrease in the fracture toughness or ductility of a metal due to the presence of atomic hydrogen. In addition to pure hydrogen gas as a direct source for the absorption of atomic hydrogen, the damaging effect can manifest itself from other hydrogen-containing gas species such as hydrogen sulfide (H2S), hydrogen chloride (HCl), and hydrogen bromide (HBr) environments. It has been known that H2S environment may result in a much more severe condition of embrittlement than pure hydrogen gas (H2) for certain types of alloys at similar conditions of stress and gas pressure. The reduction of fracture loads can occur at levels well below the yield strength of the material. Hydrogen embrittlement is usually manifest in terms of singular sharp cracks, in contrast to the extensive branching observed for stress corrosion cracking. The initial crack openings and the local deformation associated with crack propagation may be so small that they are difficult to detect except in special nondestructive examinations. Cracks due to HE can grow rapidly with little macroscopic evidence of mechanical deformation in materials that are normally quite ductile. This Technical Memorandum presents a comprehensive review of experimental data for the effects of gaseous Hydrogen Environment Embrittlement (HEE) for several types of metallic materials. Common material screening methods are used to rate the hydrogen degradation of mechanical properties that occur while the material is under an applied stress and exposed to gaseous hydrogen as compared to air or helium, under slow strain rates (SSR) testing. Due to the simplicity and accelerated nature of these tests, the results expressed in terms of HEE index are not intended to necessarily represent true hydrogen service environment for long-term exposure, but rather to provide a practical approach for material screening, which is a useful concept to qualitatively evaluate the severity of

  5. Ammonia Oxidation by Abstraction of Three Hydrogen Atoms from a Mo–NH 3 Complex

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Papri; Heiden, Zachariah M.; Wiedner, Eric S.; Raugei, Simone; Piro, Nicholas A.; Kassel, W. Scott; Bullock, R. Morris; Mock, Michael T.

    2017-02-15

    We report ammonia oxidation by homolytic cleavage of all three H atoms from a Mo-15NH3 complex using the 2,4,6-tri-tert-butylphenoxyl radical to afford a Mo-alkylimido (Mo=15NR) complex (R = 2,4,6-tri-t-butylcyclohexa-2,5-dien-1-one). Reductive cleavage of Mo=15NR generates a terminal Mo≡N nitride, and a [Mo-15NH]+ complex is formed by protonation. Computational analysis describes the energetic profile for the stepwise removal of three H atoms from the Mo-15NH3 complex and the formation of Mo=15NR. Acknowledgment. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Re-search Center funded by the U.S. Department of Energy (U.S. DOE), Office of Science, Office of Basic Energy Sciences. EPR and mass spectrometry experiments were performed using EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL. The authors thank Dr. Eric D. Walter and Dr. Rosalie Chu for assistance in performing EPR and mass spectroscopy analysis, respectively. Computational resources provided by the National Energy Re-search Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. Pacific North-west National Laboratory is operated by Battelle for the U.S. DOE.

  6. Experimental and theoretical studies of the reactions of ground-state sulfur atoms with hydrogen and deuterium

    Science.gov (United States)

    Thompson, Kristopher M.; Gao, Yide; Marshall, Paul; Wang, Han; Zhou, Linsen; Li, Yongle; Guo, Hua

    2017-10-01

    The gas-phase kinetics of S(3P) atoms with H2 and D2 have been studied via the laser flash photolysis—resonance fluorescence technique. S atoms were generated by pulsed photolysis of CS2 at 193 nm and monitored by time-resolved fluorescence at 181 nm. The rate coefficients for H2 (k1) and D2 (k2), respectively, are summarized as k1(600-1110 K) = 3.0 × 10-9 exp(-1.317/×105-2.703 ×107K /T 8.314 T /K ) cm3 molecule-1 s-1 and k2(770-1110 K) = 2.2 × 10-14 (T/298 K)3.55 exp(-5420 K/T) cm3 molecule-1 s-1. Error limits are discussed in the text. The rate coefficients for formation of SH(SD) + H(D) on a newly developed triplet potential energy surface were characterized via ring polymer molecular dynamics and canonical variational transition-state theory. There is excellent agreement above about 1000 K between theory and experiment. At lower temperatures, the experimental rate coefficient is substantially larger than the results computed for the adiabatic reaction, suggesting a significant role for intersystem crossing to the singlet potential energy surface at lower temperatures.

  7. Imaging correlated three-particle continuum states. Experiment and theory on the non-adiabatic projection of bound triatomic hydrogen into three separated atoms

    Energy Technology Data Exchange (ETDEWEB)

    Fechner, Peer Cornelis

    2015-07-21

    The central topic of this thesis is the experimental observation and the theoretical modeling of non-adiabatic three-body dissociation of H{sub 3} and D{sub 3} neutral triatomic hydrogen molecules. Our goal is to lend a meaning to the observed momentum vector correlation (MVC) of the three emerging ground state hydrogen atoms, for example H{sub 3}→H(1s)+H(1s)+H(1s), in terms of symmetries of the nuclear molecular wave function and of the non-adiabatic coupling which initiates this decay. In many experiments carried out over the years, a wealth of state specific MVCs was collected by different research groups. The MVCs are imaged in form of so-called Dalitz plots which show a rich structure of maxima and nodal lines, depending on the initial state of the triatomic hydrogen neutral. Theory was slow to catch up with experiment and only by this year, 2015, a general agreement was accomplished. Nevertheless, these models lack of an easy understanding of the underlying physics as many numerical calculations are involved. The theoretical model presented in this thesis follows a different approach which is more guided by the imaging character of our experiments. We concentrate on a rather qualitative treatment by limiting ourselves to the essential ingredients only. This proceeding contributes to giving a physical interpretation of the structures in the Dalitz plots in the following form: Three-particle coincident imaging offers a direct view of the emerging spatial continuum wave function of a predissociating triatomic molecule as it evolves from molecular spatial dimensions into the realm of independent free particles. This latter result is discussed in the context of the so-called Imaging Theorem, the second main part of this work. A third major part of this thesis pertains to obtaining molecular momentum wave functions in separated degrees-of-freedom via Fourier transformation. Even for triatomic hydrogen - the most simple polyatomic molecule - this is a challenging

  8. Effectiveness of an Asynchronous Online Module on University Students' Understanding of the Bohr Model of the Hydrogen Atom

    Science.gov (United States)

    Farina, William J.; Bodzin, Alec M.

    2017-12-01

    Web-based learning is a growing field in education, yet empirical research into the design of high quality Web-based university science instruction is scarce. A one-week asynchronous online module on the Bohr Model of the atom was developed and implemented guided by the knowledge integration framework. The unit design aligned with three identified metaprinciples of science learning: making science accessible, making thinking visible, and promoting autonomy. Students in an introductory chemistry course at a large east coast university completed either an online module or traditional classroom instruction. Data from 99 students were analyzed and results showed significant knowledge growth in both online and traditional formats. For the online learning group, findings revealed positive student perceptions of their learning experiences, highly positive feedback for online science learning, and an interest amongst students to learn chemistry within an online environment.

  9. Laser detection of spin-polarized hydrogen from HCl and HBr photodissociation: comparison of H- and halogen-atom polarizations.

    Science.gov (United States)

    Sofikitis, Dimitris; Rubio-Lago, Luis; Bougas, Lykourgos; Alexander, Andrew J; Rakitzis, T Peter

    2008-10-14

    Thermal HCl and HBr molecules were photodissociated using circularly polarized 193 nm light, and the speed-dependent spin polarization of the H-atom photofragments was measured using polarized fluorescence at 121.6 nm. Both polarization components, described by the a(0)(1)(perpendicular) and Re[a(1)(1)(parallel, perpendicular)] parameters which arise from incoherent and coherent dissociation mechanisms, are measured. The values of the a(0)(1)(perpendicular) parameter, for both HCl and HBr photodissociation, are within experimental error of the predictions of both ab initio calculations and of previous measurements of the polarization of the halide cofragments. The experimental and ab initio theoretical values of the Re[a(1)(1)(parallel, perpendicular)] parameter show some disagreement, suggesting that further theoretical investigations are required. Overall, good agreement occurs despite the fact that the current experiments photodissociate molecules at 295 K, whereas previous measurements were conducted at rotational temperatures of about 15 K.

  10. Degeneracy and instability of nanocontacts between conductive tips and hydrogenated nanocrystalline Si surfaces in conductive atomic force microscopy.

    Science.gov (United States)

    Cavalcoli, Daniela; Rossi, Marco; Tomasi, Andrea; Cavallini, Anna

    2009-01-28

    Conductive atomic force microscopy (C-AFM) has been extensively used for making measurements of electrical properties of nanostructures, devices and multiphase materials. Despite its wide use, the mechanical and electrical interactions at the nanoscale between the tip and the sample surface are not yet well understood. These phenomena should be carefully studied and modeled in order to avoid significant measurement artifacts. In the present contribution a study of the interactions occurring between conductive tips and the surface of nanocrystalline silicon thin films that lead to measurement artifacts is presented. A significant deterioration of the tip coating was detected after a few maps, resulting in meaningless maps. The features of the map obtained dramatically depend on the tip coating characteristics and on the load conditions. Moreover, under a constant bias voltage, the electrical current passing through the tip-sample junction degenerates strongly with time. These phenomena were interpreted by considering the effect of strong electric fields present during C-AFM experiments.

  11. Excitation and ionization of hydrogen and helium atoms by femtosecond laser pulses: theoretical approach by Coulomb-Volkov states; Excitation et ionisation des atomes d'hydrogene et d'helium par des impulsions laser femtosecondes: approche theorique par des etats de Coulomb-Volkov

    Energy Technology Data Exchange (ETDEWEB)

    Guichard, R

    2007-12-15

    We present a theoretical approach using Coulomb-Volkov states that appears useful for the study of atomic multi-photonic processes induced by intense XUV femtosecond laser pulses. It predicts hydrogen ionization spectra when it is irradiated by laser pulses in perturbations conditions. Three ways have been investigated. Extension to strong fields when {Dirac_h}{omega} > I{sub p}: it requires to include the hydrogen ground state population, introducing it in standard Coulomb-Volkov amplitude leads to saturated multi-photonic ionization. Extension to multi-photonic transitions with {Dirac_h}{omega} < I{sub p}: new quantum paths are open by the possibility to excite the lower hydrogen bound states. Multiphoton excitation of these states is investigated using a Coulomb-Volkov approach. Extension to helium: two-photon double ionization study shows the influence of electronic correlations in both ground and final state. Huge quantity of information such as angular and energetic distributions as well as total cross sections is available. (author)

  12. Frequency chain to measure the 2S-8S/8D transitions in atomic hydrogen: measurement of the Rydberg constant in frequency unit; Chaine de frequence optique pour mesurer les transitions 2S-8S/8D dans l'atome d'hydrogene: mesure de la constante de Rydberg en unite de frequence

    Energy Technology Data Exchange (ETDEWEB)

    Nez, F

    1993-10-15

    The aim of this thesis is to make a pure measurement of the frequency of the 2S-8S/8D two-photon transition in atomic hydrogen. In that purpose we have built a frequency chain in which hydrogen frequencies are compared with the difference of two optical standards, the methane stabilized He-Ne laser (3.39 {mu}m) and the iodine stabilized He-Ne laser (633 nm). The radiation from a home made Ti-sapphire laser (TS2) at 778 nm is mixed, in a LiIO{sub 3} crystal, with the one of a auxiliary He-Ne laser at 3.39 {mu}m to produce a synthesized radiation at 633 nm. The frequency of the Ti-sapphire (TS1) laser used for the two photon excitation is 89 GHz away from the one of TS2. To compare these two lasers, we have used a Schottky diode. The two lasers and a microwave radiation at 89 GHz, produced by a Gunn diode, are focused on the Schottky diode. The Gunn diode is phase locked on an ultra-stable quartz oscillator. In this way, we have linked an optical frequency of atomic hydrogen to the cesium clock without interferometry. From our measurements, we have deduced a new value of the Rydberg constant: R{sub {infinity}} equals 109737.3156834 (24) cm{sup -1} with an uncertainty of 2.2 10{sup -11}. Our uncertainty is near the one of the Q.E.D calculations giving the theoretical values of the energy levels. This value, which is currently the most precise available, is in good agreement with the recent result obtained from the 1S-2S and 2S-4D transitions. (author)

  13. Hydrogen atom abstraction from C-H bonds of benzylamides by the aminoxyl radical BTNO: a kinetic study.

    Science.gov (United States)

    Coniglio, Alessandra; Galli, Carlo; Gentili, Patrizia; Vadalà, Raffaella

    2009-01-07

    The aminoxyl radical BTNO (benzotriazole-N-oxyl; >N-O*) is generated from HBT (1-hydroxybenzotriazole; >N-OH) by oxidation with a Ce(IV) salt. BTNO presents a broad absorption band with lambda(max) 474 nm that lends itself to investigate the kinetics of H-abstraction from H-donor substrates by spectrophotometry. Thus, rate constants (k(H)) of H-abstraction by BTNO from CH(2)-groups alpha to the nitrogen atom in X-substituted-(N-acetyl)benzylamines (X-C(6)H(4)CH(2)NHCOCH(3)) have been determined in MeCN solution at 25 degrees C. Correlation of the k(H)(X) data with the Hammett sigma(+) parameters gives a small value for rho (-0.65) that is compatible with a radical H-abstraction step. The sizeable value (k(H)/k(D)=8.8) of the kinetic isotope effect from a suitably deuteriated amide substrate further confirms H-abstraction as rate-determining. Evidence is acquired for the relevance of stereoelectronic effects that speed up the H-abstraction whenever the scissile C-H bond is co-linear with either the nitrogen lone-pair of the amide moiety or an adjacent aromatic group. An assessment of the dissociation energy value of the benzylic C-H bond in ArCH(2)NHCOMe is accordingly reported.

  14. Calculation Of Change-Changing Cross Sections Of IONS Or Atoms Colliding With Fast IONS Using The Classical Trajectory Method

    Energy Technology Data Exchange (ETDEWEB)

    Kaganovich, I. D., Shnidman, Ariel, Mebane, Harrison, Davidson, R.C.

    2008-10-10

    Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross section. Shortcomings of the CTMC method for multielectron target atoms are discussed.

  15. Hydrogen analysis in solid samples by utilizing He metastable atoms induced by TEA CO{sub 2} laser plasma in He gas at 1 atm

    Energy Technology Data Exchange (ETDEWEB)

    Ramli, Muliadi [Program of Nuclear Power and Energy Safety Engineering, Graduate School of Engineering, University of Fukui, Fukui 910-8507 (Japan); Idris, Nasrullah [Department of Physics, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh, Aceh 23111 (Indonesia); Fukumoto, Kenichi; Niki, Hideaki [Program of Nuclear Power and Energy Safety Engineering, Graduate School of Engineering, University of Fukui, Fukui 910-8507 (Japan); Sakan, Fujio [Department of Material Science, Faculty of Engineering, University of Fukui, Fukui 910-8507 (Japan); Maruyama, Tadashi [Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuda-cho, Midori-ku Yokohama 226-8503 (Japan); Kurniawan, Koo Hendrik; Lie, Tjung Jie [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Kagawa, Kiichiro [Department of Physics, Faculty of Education and Regional Studies, University of Fukui (Japan)], E-mail: kagawa@edu00.f-edu.fukui-u.ac.jp

    2007-12-15

    A TEA CO{sub 2} laser (350 mJ-1.5 J, 10.6 {mu}m, 200 ns, 10 Hz) was focused onto a metal sub-target under He as host gas at 1 atmospheric pressure with a small amount of impurity gas, such as water and ethanol vapors. It was found that the TEA CO{sub 2} laser with the help of the metal sub-target is favorable for generating a strong, large volume helium gas breakdown plasma at 1 atmospheric pressure, in which the helium metastable-excited state was then produced overwhelmingly. While the metal sub-target itself was never ablated. The helium metastable-excited state produced after the strong helium gas breakdown plasma was considered to play an important role in exciting the atoms. This was confirmed by the specific characteristics of the detected H{alpha} emission, namely the strong intensity with low background, narrow spectral width, and the long lifetime. This technique can be used for gas and solid samples analysis. For nonmetal solid analysis, a metal mesh was introduced in front of the nonmetal sample surface to help initiation of the helium gas breakdown plasma. For metal sample, analysis can be carried out by combining the TEA CO{sub 2} laser and an Nd-YAG laser where the Nd-YAG laser is used to ablate the metal sample. The ablated atoms from the metal sample are then sent into the region of helium gas breakdown plasma induced by the TEA CO{sub 2} laser to be excited through the helium metastable-excited state. This technique can be extended to the analysis of other elements, not limited only to hydrogen, such as halogens.

  16. Atomic force microscopy contrast with CO functionalized tips in hydrogen-bonded molecular layers: Does the real tip charge distribution play a role?

    Science.gov (United States)

    Ellner, Michael; Pou, Pablo; Pérez, Rubén

    2017-08-01

    The interplay of van der Waals (vdW), electrostatic (ES), and short-range (SR) interactions on both the intra- and intermolecular contrast observed in high-resolution atomic force microscopy (HR-AFM) is explored in a hydrogen-bonded monolayer of triazine molecules. Our efficient model to simulate AFM images uses the three-dimensional (3D) charge distribution of both tip and sample to calculate the ES interaction, takes into account the tilting of the CO molecule, and reproduces with high accuracy density functional theory calculations. In spite of triazine's hexagonal structure, the intramolecular contrast has triangular symmetry, reflecting the charge density of the molecule. Stripelike intermolecular features, which join the molecules in the H-bond directions, originate from the overlap of the charge density of the atoms in neighboring molecules and are sharpened by the CO tilt. We demonstrate the existence of different potential energy surface minima for the CO tilt and discuss its influence on imaging. Our results clearly show that the ES interaction maps represent a local 3D average of the ES potential of the sample weighted by the tip's charge density, while the SR interaction resembles a local 3D average of the charge density of the sample. However, the strong cancellation of both contributions results in a net interaction dominated by the ES and vdW far from the molecules, and by the SR at short distance. This cancellation, which essentially removes the dependence on the detailed charge distribution of the tip, explains why AFM images can be reproduced using only sample properties such as the z component of the electric field and the charge density of the molecule, and the success of simple models that only incorporate pairwise, point-charge interactions.

  17. Surveys of the Milky Way and Magellanic System in the λ21-cm line of atomic hydrogen

    Directory of Open Access Journals (Sweden)

    Dickey J.M.

    2012-02-01

    Full Text Available In the next three years, surveys of the Northern and Southern skies using focal plane arrays on aperture synthesis radio telescopes will lead to a breakthrough in our knowledge of the warm and cool atomic phases of the interstellar medium and their relationship with the diffuse molecular gas. The sensitivity and resolution of these surveys will give an order of magnitude or more improvement over existing interstellar medium data. The GASKAP (South and GAMES (North projects together constitute a complete survey of the Milky Way plane and the Magellanic Clouds and Stream in both emission and absorption in the H I 21-cm line and the OH 18-cm lines. The overall goal of this project is to understand the mechanism of galaxy evolution, through a detailed tracing of the astrophysical processes that drive the cycle of star formation in very different environments. Comparison of 21-cm emission and absorption highlights the transition from the warm, diffuse medium to cool clouds. Tracing turbulence in the Magellanic Stream shows how extra-galactic gas makes the difficult passage through the halo to replenish the disk. Finally, high resolution images of OH masers trace outflows from evolved stars that enrich the medium with heavy elements. To understand how the Milky Way was assembled and how it has evolved since, the speed and efficiency of these processes must be measured, as functions of Galactic radius and height above the plane. Observations of similar processes in the Magellanic Clouds show how differently they might have worked in conditions typical of the early universe.

  18. Kinetics of the Hydrogen Atom Abstraction Reactions from 1-Butanol by Hydroxyl Radical: Theory Matches Experiment and More

    Energy Technology Data Exchange (ETDEWEB)

    Seal, Prasenjit; Oyedepo, Gbenga; Truhlar, Donald G.

    2013-01-17

    In the present work, we study the H atom abstraction reactions by hydroxyl radical at all five sites of 1-butanol. Multistructural variational transition state theory (MS-VTST) was employed to estimate the five thermal rate constants. MS-VTST utilizes a multifaceted dividing surface that accounts for the multiple conformational structures of the transition state, and we also include all the structures of the reactant molecule. The vibrational frequencies and minimum energy paths (MEPs) were computed using the M08-HX/MG3S electronic structure method. The required potential energy surfaces were obtained implicitly by direct dynamics employing interpolated variational transition state theory with mapping (IVTST-M) using a variational reaction path algorithm. The M08-HX/MG3S electronic model chemistry was then used to calculate multistructural torsional anharmonicity factors to complete the MS-VTST rate constant calculations. The results indicate that torsional anharmonicity is very important at higher temperatures, and neglecting it would lead to errors of 26 and 32 at 1000 and 1500 K, respectively. Our results for the sums of the site-specific rate constants agree very well with the experimental values of Hanson and co-workers at 896–1269 K and with the experimental results of Campbell et al. at 292 K, but slightly less well with the experiments of Wallington et al., Nelson et al., and Yujing and Mellouki at 253–372 K; nevertheless, the calculated rates are within a factor of 1.61 of all experimental values at all temperatures. Finally, this gives us confidence in the site-specific values, which are currently inaccessible to experiment.

  19. Kinetics of the hydrogen atom abstraction reactions from 1-butanol by hydroxyl radical: theory matches experiment and more.

    Science.gov (United States)

    Seal, Prasenjit; Oyedepo, Gbenga; Truhlar, Donald G

    2013-01-17

    In the present work, we study the H atom abstraction reactions by hydroxyl radical at all five sites of 1-butanol. Multistructural variational transition state theory (MS-VTST) was employed to estimate the five thermal rate constants. MS-VTST utilizes a multifaceted dividing surface that accounts for the multiple conformational structures of the transition state, and we also include all the structures of the reactant molecule. The vibrational frequencies and minimum energy paths (MEPs) were computed using the M08-HX/MG3S electronic structure method. The required potential energy surfaces were obtained implicitly by direct dynamics employing interpolated variational transition state theory with mapping (IVTST-M) using a variational reaction path algorithm. The M08-HX/MG3S electronic model chemistry was then used to calculate multistructural torsional anharmonicity factors to complete the MS-VTST rate constant calculations. The results indicate that torsional anharmonicity is very important at higher temperatures, and neglecting it would lead to errors of 26 and 32 at 1000 and 1500 K, respectively. Our results for the sums of the site-specific rate constants agree very well with the experimental values of Hanson and co-workers at 896-1269 K and with the experimental results of Campbell et al. at 292 K, but slightly less well with the experiments of Wallington et al., Nelson et al., and Yujing and Mellouki at 253-372 K; nevertheless, the calculated rates are within a factor of 1.61 of all experimental values at all temperatures. This gives us confidence in the site-specific values, which are currently inaccessible to experiment.

  20. POTHMF: A program for computing potential curves and matrix elements of the coupled adiabatic radial equations for a hydrogen-like atom in a homogeneous magnetic field

    Science.gov (United States)

    Chuluunbaatar, O.; Gusev, A. A.; Gerdt, V. P.; Rostovtsev, V. A.; Vinitsky, S. I.; Abrashkevich, A. G.; Kaschiev, M. S.; Serov, V. V.

    2008-02-01

    A FORTRAN 77 program is presented which calculates with the relative machine precision potential curves and matrix elements of the coupled adiabatic radial equations for a hydrogen-like atom in a homogeneous magnetic field. The potential curves are eigenvalues corresponding to the angular oblate spheroidal functions that compose adiabatic basis which depends on the radial variable as a parameter. The matrix elements of radial coupling are integrals in angular variables of the following two types: product of angular functions and the first derivative of angular functions in parameter, and product of the first derivatives of angular functions in parameter, respectively. The program calculates also the angular part of the dipole transition matrix elements (in the length form) expressed as integrals in angular variables involving product of a dipole operator and angular functions. Moreover, the program calculates asymptotic regular and irregular matrix solutions of the coupled adiabatic radial equations at the end of interval in radial variable needed for solving a multi-channel scattering problem by the generalized R-matrix method. Potential curves and radial matrix elements computed by the POTHMF program can be used for solving the bound state and multi-channel scattering problems. As a test desk, the program is applied to the calculation of the energy values, a short-range reaction matrix and corresponding wave functions with the help of the KANTBP program. Benchmark calculations for the known photoionization cross-sections are presented. Program summaryProgram title:POTHMF Catalogue identifier:AEAA_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAA_v1_0.html Program obtainable from:CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions:Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.:8123 No. of bytes in distributed program, including test data

  1. Hydrogen-bridge Si(μ-H)3CeH and inserted H3SiCeH molecules: Matrix infrared spectra and DFT calculations for reaction products of silane with Ce atoms

    Science.gov (United States)

    Xu, Bing; Shi, Peipei; Huang, Tengfei; Wang, Xuefeng

    2017-10-01

    Reactions of laser-ablated cerium atoms with silane were investigated by matrix isolation infrared spectroscopy and theoretical calculations. The reaction products, Si(μ-H)3CeH, H3SiCeH, H2Si(μ-H)CeH and HSi(μ-H)2CeH were identified on the basis of the SiD4 isotopic substitutions and DFT frequency calculations. In the solid argon or krypton matrix, the inserted H3SiCeH molecule was observed as initial product on deposition, which rearranged to hydrogen bridge species Si(μ-H)3CeH on follow-up annealing through H2Si(μ-H)CeH and HSi(μ-H)2CeH species. The Sisbnd Hsbnd Ce hydrogen bridge was investigated by NBO and ELF analysis. Calculation suggested that in Si(μ-H)3CeH molecule Ce atom donated one electron to Si atom, resulting in electron-rich SiH3 subunit, which was confirmed by ESP and AIM analysis. The increased basicity of Sisbnd H bond facilitates the formation of hydrogen bridge bond between Si and Ce. For comparison only insertion H3CCeH structure was obtained from the reaction of Ce atoms with CH4.

  2. Ionization of atomic hydrogen by an intense x-ray laser pulse: An ab initio study of the breakdown of the dipole approximation

    Science.gov (United States)

    Moe, Thore Espedal; Førre, Morten

    2018-01-01

    Solving the time-dependent Schrödinger equation numerically within the framework of an ab initio model, the breakdown of the dipole approximation in modeling the ionization and excitation dynamics of a hydrogen atom exposed to an intense 1.36-keV x-ray laser pulse is investigated in some detail. The relative importance of the A2 diamagnetic term in comparison with the A .p contribution to the resulting beyond-dipole (nondipole) light-matter interaction is studied for laser pulse intensities ranging from the weak perturbative to the strong-field regime. It is found that the diamagnetic interaction represents by far the most important correction to the dipole approximation at higher field strengths, while nondipole corrections induced by the A .p operator are generally small and largely independent of the laser intensity. The most profound finding of the present study was the discovery of a forward-backward asymmetry in the underlying electron ejection dynamics: Depending on the electron's kinetic energy in the final state, the photoelectron tends to be emitted in the laser propagation (forward) and/or counterpropagation (backward) directions, for energies corresponding to the low-energy and/or high-energy side of the multiphoton resonances, respectively.

  3. Effect of hydrogen peroxide pretreatment on ZnO-based metal–semiconductor–metal ultraviolet photodetectors deposited using plasma-enhanced atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yu-Chang; Lee, Hsin-Ying, E-mail: hylee@ee.ncku.edu.tw [Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China); Lee, Tsung-Hsin [Metal Industries Research and Development Centre, Kaohsiung 82151, Taiwan (China)

    2016-01-15

    In this study, zinc oxide (ZnO) films were deposited on sapphire substrates using a plasma-enhanced atomic layer deposition system. Prior to deposition, the substrates were treated with hydrogen peroxide (H{sub 2}O{sub 2}) in order to increase nucleation on the initial sapphire surface and, thus, enhance the quality of deposited ZnO films. Furthermore, x-ray diffraction spectroscopy measurements indicated that the crystallinity of ZnO films was considerably enhanced by H{sub 2}O{sub 2} pretreatment, with the strongest (002) diffraction peak occurring for the film pretreated with H{sub 2}O{sub 2} for 60 min. X-ray photoelectron spectroscopy also was used, and the results indicated that a high number of Zn–O bonds was generated in ZnO films pretreated appropriately with H{sub 2}O{sub 2}. The ZnO film deposited on a sapphire substrate with H{sub 2}O{sub 2} pretreatment for 60 min was applied to metal–semiconductor–metal ultraviolet photodetectors (MSM-UPDs) as an active layer. The fabricated ZnO MSM-UPDs showed improvements in dark current and ultraviolet–visible rejection ratios (0.27 μA and 1.06 × 10{sup 3}, respectively) compared to traditional devices.

  4. HYDROGEN VACANCY INTERACTION IN MOLYBDENUM

    NARCIS (Netherlands)

    Abd El Keriem, M.S.; van der Werf, D.P.; Pleiter, F

    1993-01-01

    Vacancy-hydrogen interaction in molybdenum was investigated by means of the perturbed angular correlation technique, using the isotope In-111 as a probe. The complex InV2 turned out to trap up to two hydrogen atoms: trapping of a single hydrogen atom gives rise to a decrease of the quadrupole

  5. Hydrogen-atom transfer in reactions of organic radicals with [Co-II(por)](center dot) (por = porphyrinato) and in subsequent addition of [Co(H)(por)] to olefins

    NARCIS (Netherlands)

    de Bruin, B.; Dzik, W.I.; Li, S.; Wayland, B.B.

    2009-01-01

    The mechanisms for hydrogen-atom transfer from the cyanoisopropyl radical C-center dot(CH3)(2)CN to [Co-II(por)](center dot) (yielding [Co-III(H)(por)] and CH2=C(CH3)(CN); por = porphyrinato) and the insertion of vinyl acetate (CH2=CHOAc) into the Co-H bond of [Co(H)(por)] (giving

  6. THEORETICAL STUDY OF CATALYTIC HYDROGENATION OF ...

    African Journals Online (AJOL)

    Preferred Customer

    Hydrogen. (H2). Figure 1. Drawings of molecules contained in the chemical systems studied. During the hydrogenation process of each molecule, one atom of the hydrogen molecule is turned to the oxygen atom O of the adsorbed molecule. At the beginning of process, the distance of OH between those both atoms was 10 ...

  7. Development of novel and sensitive methods for the determination of sulfide in aqueous samples by hydrogen sulfide generation-inductively coupled plasma-atomic emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Colon, M. [Department of Chemistry, University of Girona, Campus Montilivi, 17071 Girona (Spain); Departamento de Quimica Analitica, Nutricion y Bromatologia, University of Alicante, 03080 Alicante (Spain); Todoli, J.L. [Departamento de Quimica Analitica, Nutricion y Bromatologia, University of Alicante, 03080 Alicante (Spain); Hidalgo, M. [Department of Chemistry, University of Girona, Campus Montilivi, 17071 Girona (Spain); Iglesias, M. [Department of Chemistry, University of Girona, Campus Montilivi, 17071 Girona (Spain)], E-mail: monica.iglesias@udg.es

    2008-02-25

    Two new, simple and accurate methods for the determination of sulfide (S{sup 2-}) at low levels ({mu}g L{sup -1}) in aqueous samples were developed. The generation of hydrogen sulfide (H{sub 2}S) took place in a coil where sulfide reacted with hydrochloric acid. The resulting H{sub 2}S was then introduced as a vapor into an inductively coupled plasma-atomic emission spectrometer (ICP-AES) and sulfur emission intensity was measured at 180.669 nm. In comparison to when aqueous sulfide was introduced, the introduction of sulfur as H{sub 2}S enhanced the sulfur signal emission. By setting a gas separator at the end of the reaction coil, reduced sulfur species in the form of H{sub 2}S were removed from the water matrix, thus, interferences could be avoided. Alternatively, the gas separator was replaced by a nebulizer/spray chamber combination to introduce the sample matrix and reagents into the plasma. This methodology allowed the determination of both sulfide and sulfate in aqueous samples. For both methods the linear response was found to range from 5 {mu}g L{sup -1} to 25 mg L{sup -1} of sulfide. Detection limits of 5 {mu}g L{sup -1} and 6 {mu}g L{sup -1} were obtained with and without the gas separator, respectively. These new methods were evaluated by comparison to the standard potentiometric method and were successfully applied to the analysis of reduced sulfur species in environmental waters.

  8. Are Vicinal Metal Surfaces Stable?

    DEFF Research Database (Denmark)

    Frenken, J. W. M.; Stoltze, Per

    1999-01-01

    We use effective medium theory to demonstrate that the energies of many metal surfaces are lowered when these surfaces are replaced by facets with lower-index orientations. This implies that the low-temperature equilibrium shapes of many metal crystals should be heavily faceted. The predicted ins...... instability of vicinal metal surfaces is at variance with the almost generally observed stability of these surfaces. We argue that the unstable orientations undergo a defaceting transition at relatively low temperatures, driven by the high vibrational entropy of steps....

  9. Effect of pressure on the solution structure and hydrogen bond properties of aqueous N-methylacetamide

    Energy Technology Data Exchange (ETDEWEB)

    Sarma, Rahul [Department of Chemistry, Indian Institute of Technology, Guwahati, Guwahati 781 039, Assam (India); Paul, Sandip, E-mail: sandipp@iitg.ernet.in [Department of Chemistry, Indian Institute of Technology, Guwahati, Guwahati 781 039, Assam (India)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer NMA molecules are associated mostly through their hydrophobic methyl groups. Black-Right-Pointing-Pointer High pressure reduces association propensity causing dispersion of these moieties. Black-Right-Pointing-Pointer Orientational polarization of vicinal water molecules near O and H atoms of NMA. Black-Right-Pointing-Pointer NMA prefers to be a H-bond acceptor rather than a donor in interaction with water. Black-Right-Pointing-Pointer Energy of these hydrogen bonds reduces slightly at high pressure. -- Abstract: Effects of high pressure on hydrophobic and hydrogen bonding interactions are investigated by employing molecular dynamics (MD) simulations of aqueous N-methylacetamide (NMA) solutions. Such systems are of interest mainly because high pressure causes protein denaturation and NMA is a computationally effective model to understand the atomic-level picture of pressure-induced structural transitions of protein. Simulations are performed for five different pressure values ranging from 1 atm to 8000 atm. We find that NMA molecules are associated mostly through their hydrophobic methyl groups and high pressure reduces this association propensity, causing dispersion of these moieties. At high pressure, structural void decreases and the packing efficiency of water molecules around NMA molecules increases. Hydrogen bond properties calculations show favorable NMA-NMA hydrogen bonds as compared to those of NMA-water hydrogen bonds and preference of NMA to be a hydrogen bond acceptor rather than a donor in interaction with water.

  10. High-performance liquid chromatographic method to evaluate the hydrogen atom transfer during reaction between 1,1-diphenyl-2-picryl-hydrazyl radical and antioxidants

    Energy Technology Data Exchange (ETDEWEB)

    Boudier, Ariane; Tournebize, Juliana [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France); Bartosz, Grzegorz [Department of Molecular Biophysics, University of Lodz, Lodz (Poland); El Hani, Safae; Bengueddour, Rachid [Laboratoire de Nutrition et Sante, Biology Department, Faculty of Sciences, Ibn Tofail University, Kenitra (Morocco); Sapin-Minet, Anne [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France); Leroy, Pierre, E-mail: pierre.leroy@pharma.uhp-nancy.fr [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France)

    2012-01-20

    Highlights: Black-Right-Pointing-Pointer Both 1,1-diphenyl-2-picrylhydrazyl radical and its product measurement by HPLC. Black-Right-Pointing-Pointer Lowest limit of detection by monitoring 1,1-diphenyl-2-picryl-hydrazine. Black-Right-Pointing-Pointer Adsorption problem of the radical on HPLC parts have been pointed out. - Abstract: 1,1-Diphenyl-2-picrylhydrazyl (DPPH{center_dot}) is a stable nitrogen centred radical widely used to evaluate direct radical scavenging properties of various synthetic or natural antioxidants (AOs). The bleaching rate of DPPH{center_dot} absorbance at 515 nm is usually monitored for this purpose. In order to avoid the interference of complex coloured natural products used as antioxidant supplements or cosmetics, HPLC systems have been reported as alternative techniques to spectrophotometry. They also rely upon measurement of DPPH{center_dot} quenching rate and none of them permits to identify and measure 1,1-diphenyl-2-picryl-hydrazine (DPPH-H), the reduced product of DPPH{center_dot} resulting from hydrogen atom transfer (HAT), which is the main mechanism of the reaction between DPPH{center_dot} and AOs. We presently report an HPLC method devoted to the simultaneous measurement of DPPH{center_dot} and DPPH-H. Both were fully separated on a C18 column eluted with acetonitrile-10 mM ammonium citrate buffer pH 6.8 (70:30, v/v) and detected at 330 nm. Adsorption process of DPPH{center_dot} onto materials of the HPLC system was pointed out. Consequently, the linearity range observed for DPPH{center_dot} was restricted, thus a much lower limit of detection was obtained for DPPH-H than for DPPH{center_dot} using standards (0.02 and 14 {mu}M, respectively). The method was applied to three commonly used AOs, i.e. Trolox{sup Registered-Sign }, ascorbic acid and GSH, and compared with spectrophotometry. Further application to complex matrices (cell culture media, vegetal extracts) and nanomaterials demonstrated (i) its usefulness because of

  11. Determination of hydrogen sulfide and volatile thiols in air samples by mercury probe derivatization coupled with liquid chromatography-atomic fluorescence spectrometry.

    Science.gov (United States)

    Bramanti, Emilia; D'Ulivo, Lucia; Lomonte, Cristina; Onor, Massimo; Zamboni, Roberto; Raspi, Giorgio; D'Ulivo, Alessandro

    2006-10-02

    A new procedure is proposed for the sampling and storage of hydrogen sulphide (H2S) and volatile thiols (methanethiol or methyl mercaptan, ethanethiol and propanethiol) for their determination by liquid chromatography. The sampling procedure is based on the trapping/pre-concentration of the analytes in alkaline aqueous solution containing an organic mercurial probe p-hydroxymercurybenzoate, HO-Hg-C6H4-COO- (PHMB), where they are derivatized to stable PHMB complexes based on mercury-sulfur covalent bonds. PHMB complexes are separated on a C18 reverse phase column, allowing their determination by liquid chromatography coupled with sequential non-selective UV-vis (DAD) and mercury specific (chemical vapor generation atomic fluorescence spectrometry, CVGAFS) on-line detectors. PHMB complexes, S(PHMB)2CH3S-PHMB, C2H5S-PHMB and C3H7S-PHMB, are stable alt least for 12 h at room temperature and for 3 months if stored frozen (-20 degrees C). The best analytical figures of merits in the optimized conditions were obtained by CVGAFS detection, with detection limits (LODc) of 9.7 microg L(-1) for H2S, 13.7 microg L(-1) for CH(3)SH, 17.7 microg L(-1) for C2H5SH and 21.7 microg L(-1) for C3H7SH in the trapping solution in form of RS-PHMB complexes, the relative standard deviation (R.S.D.) ranging between 1.0 and 1.5%, and a linear dynamic range (LDR) between 10 and 9700 microg L(-1). Conventional UV absorbance detectors tuned at 254 nm can be employed as well with comparable R.S.D. and LDR, but with LODc one order of magnitude higher than AFS detector and lower specificity. The sampling procedure followed by LC-DAD-CVGAFS analysis has been validated, as example, for H2S determination by a certified gas permeation tube as a source of 3.071+/-0.154 microg min(-1) of H2S, giving a recovery of 99.8+/-7% and it has been applied to the determination of sulfur compounds in real gas samples (biogas and the air of a plant for fractional distillation of crude oil).

  12. Topics in atomic physics

    CERN Document Server

    Burkhardt, Charles E

    2006-01-01

    The study of atomic physics propelled us into the quantum age in the early twentieth century and carried us into the twenty-first century with a wealth of new and, in some cases, unexplained phenomena. Topics in Atomic Physics provides a foundation for students to begin research in modern atomic physics. It can also serve as a reference because it contains material that is not easily located in other sources. A distinguishing feature is the thorough exposition of the quantum mechanical hydrogen atom using both the traditional formulation and an alternative treatment not usually found in textbooks. The alternative treatment exploits the preeminent nature of the pure Coulomb potential and places the Lenz vector operator on an equal footing with other operators corresponding to classically conserved quantities. A number of difficult to find proofs and derivations are included as is development of operator formalism that permits facile solution of the Stark effect in hydrogen. Discussion of the classical hydrogen...

  13. Free radical hydrogen atom abstraction from saturated hydrocarbons: A crossed-molecular-beams study of the reaction Cl + C{sub 3}H{sub 8} {yields} HCl + C{sub 3}H{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Blank, D.A.; Hemmi, N.; Suits, A.G.; Lee, Y.T. [Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    The abstraction of hydrogen atoms from saturated hydrocarbons are reactions of fundamental importance in combustion as well as often being the rate limiting step in free radical substitution reactions. The authors have begun studying these reactions under single collision conditions using the crossed molecular beam technique on beamline 9.0.2.1, utilizing VUV undulator radiation to selectively ionize the scattered hydrocarbon free radical products (C{sub x}H{sub 2x+1}). The crossed molecular beam technique involves two reactant molecular beams fixed at 90{degrees}. The molecular beam sources are rotatable in the plane defined by the two beams. The scattered neutral products travel 12.0 cm where they are photoionized using the VUV undulator radiation, mass selected, and counted as a function of time. In the authors initial investigations they are using halogen atoms as protypical free radicals to abstract hydrogen atoms from small alkanes. Their first study has been looking at the reaction of Cl + propane {r_arrow} HCl + propyl radical. In their preliminary efforts the authors have measured the laboratory scattering angular distribution and time of flight spectra for the propyl radical products at collision energies of 9.6 kcal/mol and 14.9 kcal/mol.

  14. Numerical Investigation of the Role of Volumetric Transformation Strain on the Relaxation Stress and the Corresponding Hydrogen Interstitial Concentration in Niobium Matrix

    Directory of Open Access Journals (Sweden)

    Burak Bal

    2017-01-01

    Full Text Available The effects of relaxation stress on the hydrogen concentration in Niobium- (Nb- H media were investigated by iterative numerical modeling approach. To calculate the transformation strain, relaxation stress, and corresponding relaxed hydrogen concentration around an edge dislocation, a new third-order polynomial formulation was utilized in the model. With the aid of this polynomial, hydrogen induced relaxation stress never exceeds the dislocation stress, which indicates that the total stress field never turns to compressive state and diverges the results. The current model calculates the hydrogen concentration not only in the vicinity of an edge dislocation but also far away from the dislocation. Furthermore, the effect of relaxation stress on the interaction energy was also captured in the model. Overall, the current findings shed light on the complicated hydrogen embrittlement mechanisms of metallic materials by demonstrating that hydrogen induced relaxation has a significant effect on the hydrogen atom concentration and the interaction energy between the existing internal stress field and the solute hydrogen atom.

  15. A combined experimental, theoretical, and Van't Hoff model study for identity methyl, proton, hydrogen atom, and hydride exchange reactions. Correlation with three-center four-, three-, and two-electron systems

    Science.gov (United States)

    Buck, Henk M.

    We have studied carbon transfer reactions following an SN2 reaction profile. With ab initio calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff's tetrahedral configuration by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical bond and corresponding tetrahedral bond distances is then nearly 1.333. The relevance of this approach has also been shown for identity proton-(hydrogen atom-, and hydride-) in-line reactions. The use of this geometrical transmission will be demonstrated for the hydrogen bonding distances in e.g., DNA duplexes and other biological (supra) molecular systems.

  16. An Atomic X-ray Absorption Fine Structure Study of the Influence of Hydrogen Chemisorption and Support on the Electronic Structure of Supported Pt Particles

    NARCIS (Netherlands)

    Koningsberger, D.C.; Ramaker, D.E.; Dorssen, G.E. van; Mojet, B.L.

    2000-01-01

    The physical principles of atomic XAFS (AXAFS) are presented along with important details on how to isolate the AXAFS contribution from the experimental XAFS data. Intuitive illustrations are given showing how various interactions of the absorber atom with its neighbours influence the AXAFS

  17. Real-time study of the adiabatic energy loss in an atomic collision with a metal cluster.

    Science.gov (United States)

    Baer, Roi; Siam, Nidal

    2004-10-01

    Gas-phase hydrogen atoms are accelerated towards metallic surfaces in their vicinity. As it approaches the surface, the velocity of an atom increases and this motion excites the metallic electrons, causing energy loss to the atom. This dissipative dynamics is frequently described as atomic motion under friction, where the friction coefficient is obtained from ab initio calculations assuming a weak interaction and slow atom. This paper tests the aforementioned approach by comparing to a real-time Ehrenfest molecular dynamics simulation of such a process. The electrons are treated realistically using standard approximations to time-dependent density functional theory. We find indeed that the electronic excitations produce a friction-like force on the atom. However, the friction coefficient strongly depends on the direction of the motion of the atom: it is large when the atom is moving towards the cluster and much smaller when the atom is moving away. It is concluded that a revision of the model for energy dissipation at metallic surfaces, at least for clusters, may be necessary. (c) 2004 American Institute of Physics

  18. Stark effect in a hydrogenic atom or ion treated by the phase-integral method with adjoined papers by A. Hökback and P. O. Fröman

    CERN Document Server

    Fröman, Nanny

    2008-01-01

    This book treats the Stark effect of a hydrogenic atom or ion in a homogeneous electric field. It begins with a thorough review of previous work in this field since 1926. After the Schrödinger equation has been separated with respect to time dependence, centre of mass motion and internal motion, followed by a discussion of its eigenfunctions, the exact development in time of the probability amplitude for a decaying state is obtained by means of a formula analogous to the Fock-Krylov theorem. From this formula one obtains by means of the phase-integral approximation generated from a particular

  19. Pathways to Metallic Hydrogen

    OpenAIRE

    Silvera, Isaac F.; Deemyad, Shanti

    2008-01-01

    The traditional pathway that researchers have used in the goal of producing atomic metallic hydrogen is to compress samples with megabar pressures at low temperature. A number of phases have been observed in solid hydrogen and its isotopes, but all are in the insulating phase. The results of experiment and theory for this pathway are reviewed. In recent years a new pathway has become the focus of this challenge of producing metallic hydrogen, namely a path along the melting line. It has bee...

  20. Stable hydrogen configurations between graphite layers

    CERN Document Server

    Dino, W A; Nakanishi, H; Kasai, H; Sugimoto, T

    2003-01-01

    Based on the density functional theory, we investigate and discuss what possible stable configurations hydrogen might assume, once found inside/between graphite layers stacked in an AB configuration. Our calculation results show that the reconstruction of the constituent carbon atoms is crucial in determining the final configuration of hydrogen. When a hydrogen atom impinges directly above one of the carbon atoms on the surface, that carbon atom relaxes 0.26-0.33 A towards the incoming hydrogen atom. Similarly, when a hydrogen atom is positioned between two graphite layers such that there are carbon atoms immediately above and below it, one of these two carbon atoms relaxes 0.26-0.33 A towards the hydrogen atom, while the other carbon atom hardly moves. The hydrogen atom finally takes a position 1.11-1.15 A from one of the carbon atoms and 1.87-1.98 A from the other. Note that, without the hydrogen atom, the distance between successive layers is 3.35 A. Our calculation results indicate agreement with the resu...

  1. Hirshfeld atom refinement.

    Science.gov (United States)

    Capelli, Silvia C; Bürgi, Hans-Beat; Dittrich, Birger; Grabowsky, Simon; Jayatilaka, Dylan

    2014-09-01

    Hirshfeld atom refinement (HAR) is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustrated via the example of crystalline ammonia. The new HAR method is then applied to X-ray diffraction data of the dipeptide Gly-l-Ala measured at 12, 50, 100, 150, 220 and 295 K, using Hartree-Fock and BLYP density functional theory electron densities and three different basis sets. All positions and anisotropic displacement parameters (ADPs) are freely refined without constraints or restraints - even those for hydrogen atoms. The results are systematically compared with those from neutron diffraction experiments at the temperatures 12, 50, 150 and 295 K. Although non-hydrogen-atom ADPs differ by up to three combined standard uncertainties (csu's), all other structural parameters agree within less than 2 csu's. Using our best calculations (BLYP/cc-pVTZ, recommended for organic molecules), the accuracy of determining bond lengths involving hydrogen atoms from HAR is better than 0.009 Å for temperatures of 150 K or below; for hydrogen-atom ADPs it is better than 0.006 Å(2) as judged from the mean absolute X-ray minus neutron differences. These results are among the best ever obtained. Remarkably, the precision of determining bond lengths and ADPs for the hydrogen atoms from the HAR procedure is comparable with that from the neutron measurements - an outcome which is obtained with a routinely achievable resolution of the X-ray data of 0.65 Å.

  2. Assessment of pollution trend of heavy metals in soils in the vicinity ...

    African Journals Online (AJOL)

    Topsoil and subsoil obtained in the vicinity of the Nigerian Gas Company were digested and analysed for some selected trace metals using atomic absorption spectrophotometer of model pye unicam SP 2900. The trace metals determined include nickel, copper, iron, barium, lead, cadmium and zinc respectively.

  3. Probing hydrogen spillover in Pd@MIL-101(Cr) with a focus on hydrogen chemisorption

    OpenAIRE

    Szilágyi, P.Á; Callini, E.; Anastasopol, A.; Kwakernaak, C.; Sachdeva, S.; Van de Krol, R.; Geerlings, H; Borgschulte, A.; Züttel, A.; Dam, B.

    2014-01-01

    Palladium nanoparticles can split the dihydrogen bond and produce atomic hydrogen. When the metal nanoparticles are in intimate contact with a hydrogen-atom host, chemisorption of H-atoms by the host has been suggested to occur via the hydrogen spillover mechanism. Metal–organic frameworks were predicted to be able to act as effective chemisorption sites, and increased ambient-temperature hydrogen adsorption was reported on several occasions. The intimate contact was supposedly ensured by the...

  4. Habitat--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the habitat map of the seafloor of the Monterey Canyon and Vicinity map area, California. The vector data file is included in...

  5. Contours--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents bathymetric contours for several seafloor maps of the Monterey Canyon and Vicinity map area, California. The raster data file is...

  6. Formation of noble-gas hydrides and decay of solvated protons revisited: diffusion-controlled reactions and hydrogen atom losses in solid noble gases.

    Science.gov (United States)

    Tanskanen, Hanna; Khriachtchev, Leonid; Lignell, Antti; Räsänen, Markku; Johansson, Susanna; Khyzhniy, Ivan; Savchenko, Elena

    2008-02-07

    UV photolysis and annealing of C2H2/Xe, C2H2/Xe/Kr, and HBr/Xe matrices lead to complicated photochemical processes and reactions. The dominating products in these experiments are noble-gas hydrides with general formula HNgY (Ng = noble-gas atom, Y = electronegative fragment). We concentrate on distinguishing the local and global mobility and losses of H atoms, barriers of the reactions, and the decay of solvated protons. Different deposition temperatures change the amount of lattice imperfections and thus the amount of traps for H atoms. The averaged distance between reacting species influencing the reaction kinetics is controlled by varying the precursor concentration. A number of solid-state processes connected to the formation of noble-gas hydrides and decay of solvated protons are discussed using a simple kinetic model. The most efficient formation of noble-gas hydrides is connected with global (long-range) mobility of H atoms leading to the H + Xe + Y reaction. The highest concentration of noble-gas hydrides was obtained in matrices of highest optical quality, which probably have the lowest concentration of defects and H-atom losses. In matrices with high amount of geometrical imperfections, the product formation is inefficient and dominated by a local (short-range) process. The decay of solvated protons is rather local than a global process, which is different from the formation of noble-gas molecules. However, the present data do not allow distinguishing local proton and electron mobilities. Our previous results indicate that these are electrons which move to positively-charged centers and neutralize them. It is believed that the image obtained here for solid xenon is applicable to solid krypton whereas the case of argon deserves special attention.

  7. [Analysis of optical emission spectra from ICP of Ar in the vicinity of plasma sheath].

    Science.gov (United States)

    Zhao, Wen-Feng; Chen, Jun-Fang; Meng, Ran

    2009-11-01

    In order to control the ion density and energy distribution in the vicinity of plasma sheath independently, the inductively coupled plasma and its glow discharge mechanism in the vicinity of plasma sheath were studied by means of optical emission spectroscopy (OES) under different RF power, different discharge and different substrate DC bias voltage. It was shown that the ion density is higher and the electron temperature is lower in the vicinity of inductively coupled plasma sheath according to the ionic line and atomic line. With changing the discharge pressure and RF power, the spectral characteristics analysis shows that the ion density in the vicinity of plasma sheath linearly increases with the RF power and rises with the pressure under the low pressure. The atomic spectral intensity of low excitation states increases rapidly. The atomic spectral intensity of high excitation states rises slowly and the intensity of ion spectrum increases not obviously. By applying the DC bias voltage to substrate, the intensity of emission spectroscopy was analyzed. The result shows that the intensity of spectra rises with the increase in positive bias voltage, while first reduces then increases with the increase in negative bias voltage, and is the weakest in the case of DC bias at -30 V. This shows that the fast ions and the electrons are the main source of energy for Ar ionization and excitation.

  8. Hydrogen storage methods

    Science.gov (United States)

    Züttel, Andreas

    system mass ratio close to one. The highest volumetric densities of hydrogen are found in metal hydrides. Many metals and alloys are capable of reversibly absorbing large amounts of hydrogen. Charging can be done using molecular hydrogen gas or hydrogen atoms from an electrolyte. The group one, two and three light metals (e.g. Li, Mg, B, Al) can combine with hydrogen to form a large variety of metal-hydrogen complexes. These are especially interesting because of their light weight and because of the number of hydrogen atoms per metal atom, which is two in many cases. Hydrogen can also be stored indirectly in reactive metals such as Li, Na, Al or Zn. These metals easily react with water to the corresponding hydroxide and liberate the hydrogen from the water. Since water is the product of the combustion of hydrogen with either oxygen or air, it can be recycled in a closed loop and react with the metal. Finally, the metal hydroxides can be thermally reduced to metals in a solar furnace. This paper reviews the various storage methods for hydrogen and highlights their potential for improvement and their physical limitations.

  9. Laser stabilisation for velocity-selective atomic absorption

    NARCIS (Netherlands)

    Meijer, H.A.J.; Meulen, H.P. van der; Ditewig, F.; Wisman, C.J.; Morgenstern, R.

    1987-01-01

    A relatively simple method is described for stabilising a dye laser at a frequency ν = ν0 + νc in the vicinity of an atomic resonance frequency ν0. The Doppler effect is exploited by looking for atomic fluorescence when a laser beam is crossed with an atomic beam at certain angles αi. Absolute

  10. Allylammonium hydrogen oxalate hemihydrate

    Directory of Open Access Journals (Sweden)

    Błażej Dziuk

    2014-08-01

    Full Text Available In the title hydrated molecular salt, C3H8N+·C2HO4−·0.5H2O, the water O atom lies on a crystallographic twofold axis. The C=C—C—N torsion angle in the cation is 2.8 (3° and the dihedral angle between the CO2 and CO2H planes in the anion is 1.0 (4°. In the crystal, the hydrogen oxalate ions are linked by O—H...O hydrogen bonds, generating [010] chains. The allylammonium cations bond to the chains through N—H...O and N—H...(O,O hydrogen bonds. The water molecule accepts two N—H...O hydrogen bonds and makes two O—H...O hydrogen bonds. Together, the hydrogen bonds generate (100 sheets.

  11. Intermolecular atom-atom bonds in crystals - a chemical perspective.

    Science.gov (United States)

    Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

    2015-03-01

    Short atom-atom distances between molecules are almost always indicative of specific intermolecular bonding. These distances may be used to assess the significance of all hydrogen bonds, including the C-H⋯O and even weaker C-H⋯F varieties.

  12. Ultraviolet photochemistry of buta-1,3- and buta-1,2-dienes: laser spectroscopic absolute hydrogen atom quantum yield and translational energy distribution measurements.

    Science.gov (United States)

    Hanf, A; Volpp, H-R; Sharma, P; Mittal, J P; Vatsa, R K

    2010-07-14

    Using pulsed H-atom Lyman-alpha laser-induced fluorescence spectroscopy along with a photolytic calibration approach, absolute H-atom product quantum yields of phi(H-b13d) = (0.32+/-0.04) and phi(H-b12d) = (0.36+/-0.04) were measured under collision-free conditions for the 193 nm gas-phase laser flash photolysis of buta-1,3- and buta-1,2-diene at room temperature, which demonstrate that nascent H-atom formation is of comparable importance for both parent molecules. Comparison of the available energy fraction, f(T-b13d) = (0.22+/-0.03) and f(T-b12d) = (0.13+/-0.01), released as H+C(4)H(5) product translational energy with results of impulsive and statistical energy partitioning modeling calculations indicates that for both, buta-1,3- and buta-1,2-diene, H-atom formation is preceded by internal conversion to the respective electronic ground state (S(0)) potential energy surfaces. In addition, values of sigma(b-1,3-d-L alpha) = (3.5+/-0.2)x10(-17) cm(2) and sigma(b-1,2-d-L alpha) = (4.4+/-0.2)x10(-17) cm(2) for the previously unknown Lyman-alpha (121.6 nm) radiation photoabsorption cross sections of buta-1,3- and buta-1,2-diene in the gas-phase were determined.

  13. Genetic algorithm approach to global optimization of the full-dimensional potential energy surface for hydrogen atom at fcc-metal surfaces

    Science.gov (United States)

    Kammler, Marvin; Janke, Svenja M.; Kandratsenka, Alexander; Wodtke, Alec M.

    2017-09-01

    We have developed a genetic algorithm approach for the parametrization of a multi-dimensional potential energy surface based on the analytical expression for energy derived from Effective Medium Theory by fitting it to DFT data. This approach yields consistent results for the H-atom interaction energy with a number of fcc-metal surfaces (Al, Ag, Au, Cu, Ni, Pd, Pt and Rh) and provides reasonable energy values for virtually any system geometry including various facets.

  14. Effect of an in situ Hydrogen Plasma Pre-treatment on the Reduction of GaSb Native oxides Prior to Atomic Layer Deposition

    Science.gov (United States)

    2013-04-12

    transistors ( MOSFETs ) demonstrating excellent electron mobility and high drive currents [4–7]. However, hole mobility in III–V p- channel MOSFETs typically...the resulting surface morphology were performed using an ex situ Digital Instruments Atomic Force Microscope (AFM) (MultiModeTM NanoScope® IV) in...capacitance in arsenide–antimonide quantum-well MOSFETS incorporating nonparabolicity effect, IEEE Transactions on Electron Devices 58 (2011) 1397–1403. [8

  15. Clarifying Atomic Weights: A 2016 Four-Figure Table of Standard and Conventional Atomic Weights

    Science.gov (United States)

    Coplen, Tyler B.; Meyers, Fabienne; Holden, Norman E.

    2017-01-01

    To indicate that atomic weights of many elements are not constants of nature, in 2009 and 2011 the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) replaced single-value standard atomic weight values with atomic weight intervals for 12 elements (hydrogen, lithium, boron,…

  16. Determination of the semi-empiric relationship among the physical density, the concentration and rate between hydrogen and manganese atoms, and a manganese sulfate solution; Determinacao da relacao semi-empirica entre a densidade fisica, concentracao e razao entre atomos de hidrogenio e manganes em uma solucao de sulfato de manganes

    Energy Technology Data Exchange (ETDEWEB)

    Bittencourt, Guilherme Rodrigues [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil). PIBIC; Castro, Leonardo Curvello de; Pereira, Walsan W.; Patrao, Karla C. de Souza; Fonseca, Evaldo S. da; Dantas, Maria Leticia [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI). Lab. de Neutrons

    2009-07-01

    The bath of a manganese sulfate (BMS) is a system for absolute standardization of the neutron sources. This work establishes a functional relationship based on semi-empirical methods for the theoretical prediction of physical density values, concentration and rate between the hydrogen and manganese atoms presents in the solution of the BMS

  17. Effects of External Hydrogen on Hydrogen Transportation and Distribution Around the Fatigue Crack Tip in Type 304 Stainless Steel

    Science.gov (United States)

    Chen, Xingyang; Zhou, Chengshuang; Cai, Xiao; Zheng, Jinyang; Zhang, Lin

    2017-10-01

    The effects of external hydrogen on hydrogen transportation and distribution around the fatigue crack tip in type 304 stainless steel were investigated by using hydrogen microprint technique (HMT) and thermal desorption spectrometry. HMT results show that some silver particles induced by hydrogen release are located near the fatigue crack and more silver particles are concentrated around the crack tip, which indicates that hydrogen accumulates in the vicinity of the crack tip during the crack growth in hydrogen gas environment. Along with the crack propagation, strain-induced α' martensite forms around the crack tip and promotes hydrogen invasion into the matrix, which will cause the crack initiation and propagation at the austenite/ α' martensite interface. In addition, the hydrogen content in the vicinity of the crack tip is higher than that at the crack edge far away from the crack tip, which is related to the stress state and strain-induced α' martensite.

  18. Hirshfeld atom refinement

    Directory of Open Access Journals (Sweden)

    Silvia C. Capelli

    2014-09-01

    Full Text Available Hirshfeld atom refinement (HAR is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustrated via the example of crystalline ammonia. The new HAR method is then applied to X-ray diffraction data of the dipeptide Gly–l-Ala measured at 12, 50, 100, 150, 220 and 295 K, using Hartree–Fock and BLYP density functional theory electron densities and three different basis sets. All positions and anisotropic displacement parameters (ADPs are freely refined without constraints or restraints – even those for hydrogen atoms. The results are systematically compared with those from neutron diffraction experiments at the temperatures 12, 50, 150 and 295 K. Although non-hydrogen-atom ADPs differ by up to three combined standard uncertainties (csu's, all other structural parameters agree within less than 2 csu's. Using our best calculations (BLYP/cc-pVTZ, recommended for organic molecules, the accuracy of determining bond lengths involving hydrogen atoms from HAR is better than 0.009 Å for temperatures of 150 K or below; for hydrogen-atom ADPs it is better than 0.006 Å2 as judged from the mean absolute X-ray minus neutron differences. These results are among the best ever obtained. Remarkably, the precision of determining bond lengths and ADPs for the hydrogen atoms from the HAR procedure is comparable with that from the neutron measurements – an outcome which is obtained with a routinely achievable resolution of the X-ray data of 0.65 Å.

  19. Characterization of polycyclic aromatic hydrocarbon emissions in the particulate and gas phase from smoldering mosquito coils containing various atomic hydrogen/carbon ratios

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Tzu-Ting, E-mail: d89844001@ntu.edu.tw [Department of Environmental Engineering and Health, Yuanpei University, No. 306, Yuanpei St., Hsin Chu 30015, Taiwan (China); Lin, Shaw-Tao [Department of Applied Chemistry, Providence University, No. 200 Chung-Chi Rd., Salu Dist., Taichung City 43301, Taiwan (China); Lin, Tser-Sheng [Department of Safety, Health, and Environmental Engineering, National United University, 2 Lien Da, Maioli 360, Taiwan (China); Chung, Hua-Yi [Department of Environmental Engineering and Health, Yuanpei University, No. 306, Yuanpei St., Hsin Chu 30015, Taiwan (China)

    2015-02-15

    The polycyclic aromatic hydrocarbon emissions in particulate and gas phases generated from smoldering mosquito coils containing various atomic H/C ratios were examined. Five types of mosquito coils were burned in a test chamber with a total airflow rate of 8.0 L/min at a constant relative humidity and temperature. The concentrations of individual PAHs were determined using the GC/MS technique. Among the used mosquito coils, the atomic H/C ratio ranged from 1.23 to 1.57, yielding total mass, gaseous, and particulate PAH emission factors of 28.17–78.72 mg/g, 26,139.80–35,932.98 and 5735.22–13,431.51 ng/g, respectively. The various partitions of PAHs in the gaseous and particulate phases were in the ranges, 70.26–83.70% and 16.30–29.74% for the utilized mosquito coils. The carcinogenic potency of PAH emissions in the particulate phase (203.82–797.76 ng/g) was approximately 6.92–25.08 times higher than that of the gaseous phase (26.27–36.07 ng/g). Based on the analyses of PAH emissions, mosquito coils containing the lowest H/C ratio, a low oxygen level, and additional additives (i.e., CaCO{sub 3}) are recommended for minimizing the production of total PAH emission factors and carcinogenic potency. - Highlights: • PAHs emissions are influenced by mosquito coils containing various atomic H/C ratios. • The PAHs generated by burning mosquito coils mainly occur in the gaseous phase. • Total TEQ emission factors of PAHs mainly consisted of the particulate phase (> 87%). • The BaP and BaA accounted for 71.13–77.28% of the total TEQ emission factors. • Special PAH ratios were regarded as characteristic ratios for burning mosquito coil.

  20. Distance criterion for hydrogen bond

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Distance criterion for hydrogen bond. In a D-H ...A contact, the D...A distance must be less than the sum of van der Waals Radii of the D and A atoms, for it to be a hydrogen bond.

  1. Hydrogen effects in corrosion: discussion

    Science.gov (United States)

    Stopher, Miles A.; Simpson, E. Luke

    2017-06-01

    This session contained talks on the characterization of hydrogen-enhanced corrosion of steels and nickel-based alloys, emphasizing the different observations across length scales, from atomic-scale spectrographic to macro-scale fractographic examinations. This article is part of the themed issue 'The challenges of hydrogen and metals'.

  2. Atomic structure under external confinement: effect of plasma on the spin orbit splitting, relativistic mass correction and Darwin term for hydrogen-like ions

    Science.gov (United States)

    Chaudhuri, Supriya K.; Mukherjee, Prasanta K.; Fricke, Burkhard

    2017-03-01

    The effect of Debye and quantum plasma environment on the structural properties such as spin orbit splitting, relativistic mass correction and Darwin term for a few iso-electronic members of hydrogen viz. C5 +, O7 +, Ne9 +, Mg11 +, Si13 +, S15 +, Ar17 +, Ca19 + and Ti21 + has been analysed systematically for the first time for a range of coupling strengths of the plasma. The Debye plasma environment has been treated under a standard screened Coulomb potential (SCP) while the quantum plasma has been treated under an exponential cosine screened Coulomb potential (ECSCP). Estimation of the spin orbit splitting under SCP and ECSCP plasma is restricted to the lowest two dipole allowed states while for the other two properties, the ground state as well as the first two excited states have been chosen. Calculations have been extended to nuclear charges for which appreciable relativistic corrections are noted. In all cases calculations have been extended up to such screening parameters for which the respective excitation energies tend towards their stability limit determined by the ionisation potential at that screening parameter. Interesting behavior of the respective properties with respect to the plasma coupling strength has been noted.

  3. 129I and 137Cs in groundwater in the vicinity of Fukushima Dai-ichi nuclear power plant

    DEFF Research Database (Denmark)

    Xu, Sheng; Zhang, Luyuan; Freeman, Stewart P.H.T.

    2016-01-01

    This paper reports iodine (127I and 129I) and cesium (137Cs) isotope concentrations in groundwater of confined and unconfined aquifers in the vicinity of the Fukushima Dai-ichi nuclear power plant (FDNPP). 127I and 129I concentrations range from 2–13 μg/L and 5 × 107–8 × 1010 atom/L respectively...

  4. Probing hydrogen spillover in Pd@MIL-101(Cr) with a focus on hydrogen chemisorption.

    Science.gov (United States)

    Szilágyi, P Á; Callini, E; Anastasopol, A; Kwakernaak, C; Sachdeva, S; van de Krol, R; Geerlings, H; Borgschulte, A; Züttel, A; Dam, B

    2014-03-28

    Palladium nanoparticles can split the dihydrogen bond and produce atomic hydrogen. When the metal nanoparticles are in intimate contact with a hydrogen-atom host, chemisorption of H-atoms by the host has been suggested to occur via the hydrogen spillover mechanism. Metal-organic frameworks were predicted to be able to act as effective chemisorption sites, and increased ambient-temperature hydrogen adsorption was reported on several occasions. The intimate contact was supposedly ensured by the use of a carbon bridge. In this work, we show that it is possible to introduce catalyst palladium particles into MOF's pores and simultaneously ensuring good contact, making the employment of the carbon bridge redundant. The addition of Pd nanoparticles indeed increases the ambient-temperature hydrogen uptake of the framework, but this is found to be solely due to palladium hydride formation. In addition, we show that the hydrogen atoms do not chemisorb on the host framework, which excludes the possibility of hydrogen spillover.

  5. Visualization of Hydrogen Diffusion in a Hydrogen-Enhanced Fatigue Crack Growth in Type 304 Stainless Steel

    Science.gov (United States)

    Matsunaga, Hisao; Noda, Hiroshi

    2011-09-01

    To study the influence of hydrogen on the fatigue strength of AISI type 304 metastable austenitic stainless steel, specimens were cathodically charged with hydrogen. Using tension-compression fatigue tests, the behavior of fatigue crack growth from a small drill hole in the hydrogen-charged specimen was compared with that of noncharged specimen. Hydrogen charging led to a marked increase in the crack growth rate. Typical characteristics of hydrogen effect were observed in the slip band morphology and fatigue striation. To elucidate the behavior of hydrogen diffusion microscopically in the fatigue process, the hydrogen emission from the specimens was visualized using the hydrogen microprint technique (HMT). In the hydrogen-charged specimen, hydrogen emissions were mainly observed in the vicinity of the fatigue crack. Comparison between the HMT image and the etched microstructure image revealed that the slip bands worked as a pathway for hydrogen to move preferentially. Hydrogen-charging resulted in a significant change in the phase transformation behavior in the fatigue process. In the noncharged specimen, a massive type α' martensite was observed in the vicinity of the fatigue crack. On the other hand, in the hydrogen-charged specimen, large amounts of ɛ martensite and a smaller amount of α' martensite were observed along the slip bands. The results indicated that solute hydrogen facilitated the ɛ martensitic transformation in the fatigue process. Comparison between the results of HMT and EBSD inferred that martensitic transformations as well as plastic deformation itself can enhance the mobility of hydrogen.

  6. Metallic Hydrogen and Nano-Tube Magnets

    Science.gov (United States)

    Cole, John W.

    2004-01-01

    When hydrogen is subjected to enough pressure the atoms will be pressed into close enough proximity that each electron is no longer bound to a single proton. The research objectives is to find whether metallic hydrogen can be produced and once produced will the metallic hydrogen be metastable and remain in the metallic form when the pressure is released.

  7. Promising monolayer membranes for CO{sub 2}/N{sub 2}/CH{sub 4} separation: Graphdiynes modified respectively with hydrogen, fluorine, and oxygen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Lianming, E-mail: lmzhao@upc.edu.cn; Sang, Pengpeng; Guo, Sheng; Liu, Xiuping; Li, Jing; Zhu, Houyu; Guo, Wenyue, E-mail: wyguo@upc.edu.cn

    2017-05-31

    Graphical abstract: Graphdiyne monolayer membrane modified by fluorine or oxygen can effectively separate CO{sub 2}/N{sub 2}/CH{sub 4} mixtures. - Highlights: • Three graphdiyne-like membranes were designed and their stabilities were confirmed. • The DFT and MD results claimed a tunable gas separation property of the membranes. • Graphdiyne modified with F or O can effectively separate CO{sub 2}/N{sub 2}/CH{sub 4} mixtures. - Abstract: Three graphdiyne-like monolayers were designed by substituting one-third diacetylenic linkages with heteroatoms hydrogen, fluorine, and oxygen (GDY-X, X = H, F, and O), respectively. The CO{sub 2}/N{sub 2}/CH{sub 4} separation performance of the designed graphdiyne-like monolayers was investigated by using both first-principle density functional theory (DFT) and molecular dynamic (MD) simulations. The stabilities of GDY-X monolayers were confirmed by the calculated cohesive energies and phonon dispersion spectra. Both the DFT and MD calculations demonstrated that although the GDY-H membrane has poor selectivity for CO{sub 2}/N{sub 2}/CH{sub 4} gases, the GDY-F and GDY-O membranes can excellently separate CO{sub 2} and N{sub 2} from CH{sub 4} in a wide temperature range. Moreover, the CO{sub 2}/N{sub 2} mixture can be effectively separated by GDY-O at temperatures lower than 300 K. Based on the kinetic theory, extremely high permeances were found for CO{sub 2} and N{sub 2} passing through the GDY-X membranes (10{sup −4}–10{sup −2} mol/m{sup 2} s Pa at 298 K). In addition, the influence of relative concentration on selectivity was also investigated for gases in the binary mixtures. This work provides an effective way to modify graphdiyne for the separation of large molecular gases, which is quite crucial in the gas separation industry.

  8. Hydrogen bonding in oxalic acid and its complexes: A database ...

    Indian Academy of Sciences (India)

    The basic result of carboxylic group that the oxygen atom of the –OH never seems to be a hydrogen bond acceptor is violated in the cases, namely urea oxalic acid and bis urea oxalic acid complexes, where the hydroxyl oxygen atom is an acceptor of a weak N–H... O hydrogen bond. The parameters of this hydrogen bond, ...

  9. Effects of ion concentration on the hydrogen bonded structure of ...

    Indian Academy of Sciences (India)

    Molecular dynamics simulations of dilute and concentrated aqueous NaCl solutions are carried out to investigate the changes of the hydrogen bonded structures in the vicinity of ions for different ion concentrations. An analysis of the hydrogen bond population in the first and second solvation shells of the ions and in the bulk ...

  10. Hydrogen sensor

    Science.gov (United States)

    Duan, Yixiang; Jia, Quanxi; Cao, Wenqing

    2010-11-23

    A hydrogen sensor for detecting/quantitating hydrogen and hydrogen isotopes includes a sampling line and a microplasma generator that excites hydrogen from a gas sample and produces light emission from excited hydrogen. A power supply provides power to the microplasma generator, and a spectrometer generates an emission spectrum from the light emission. A programmable computer is adapted for determining whether or not the gas sample includes hydrogen, and for quantitating the amount of hydrogen and/or hydrogen isotopes are present in the gas sample.

  11. Porphyrin Cobalt(III “Nitrene Radical” Reactivity; Hydrogen Atom Transfer from Ortho-YH Substituents to the Nitrene Moiety of Cobalt-Bound Aryl Nitrene Intermediates (Y = O, NH

    Directory of Open Access Journals (Sweden)

    Monalisa Goswami

    2016-02-01

    Full Text Available In the field of cobalt(II porphyrin-catalyzed metallo-radical reactions, organic azides have emerged as successful nitrene transfer reagents. In the pursuit of employing ortho-YH substituted (Y = O, NH aryl azides in Co(II porphyrin-catalyzed nitrene transfer reactions, unexpected hydrogen atom transfer (HAT from the OH or NH2 group in the ortho-position to the nitrene moiety of the key radical-intermediate was observed. This leads to formation of reactive ortho-iminoquinonoid (Y = O and phenylene diimine (Y = NH species. These intermediates convert to subsequent products in non-catalyzed reactions, as is typical for these free organic compounds. As such, the observed reactions prevent the anticipated cobalt-mediated catalytic radical-type coupling of the nitrene radical intermediates to alkynes or alkenes. Nonetheless, the observed reactions provide valuable insights into the reactivity of transition metal nitrene-radical intermediates, and give access to ortho-iminoquinonoid and phenylene diimine intermediates from ortho-YH substituted aryl azides in a catalytic manner. The latter can be employed as intermediates in one-pot catalytic transformations. From the ortho-hydroxy aryl azide substrates both phenoxizinones and benzoxazines could be synthesized in high yields. From the ortho-amino aryl azide substrates azabenzene compounds were obtained as the main products. Computational studies support these observations, and reveal that HAT from the neighboring OH and NH2 moiety to the nitrene radical moiety has a low energy barrier.

  12. Properties of SBA-15 modified by iron nanoparticles as potential hydrogen adsorbents and sensors

    Science.gov (United States)

    Bouazizi, N.; Ouargli, R.; Nousir, S.; Slama, R. Ben; Azzouz, A.

    2015-02-01

    SBA-15-Fe was synthesized via the incorporation of Fe0 nanoparticles (Fe(0)-Nps) in the mesoporous channels. Electron microscopy and X-ray diffraction showed that dispersion of fine iron NPs occurs mainly inside the channels of SBA-15, producing a slight structure compaction. This was accompanied by a significant improvement of both the affinity towards hydrogen and electrical conductivity, as supported by hydrogen adsorption tests and impedance measurements. CO2 thermal programmed desorption measurements revealed an attenuation of the acid character of the solid surface. This was explained in terms of strong iron interaction with the lattice oxygen atoms that reduces the SiO-H bond polarity. The close vicinity of fine Fe(0)-Nps combined with the large pore size of SBA-15 appear to contribute to a synergistic improvement of the electrical conductivity. The results reported herein open new prospects for SBA-15 as potential adsorbents for hydrogen storage and carriers for hydrogen sensors. The use of iron in lieu of noble metals for designing such materials is a novelty, because such applications of iron-loaded silica have not been envisaged so far due to the high reactivity of iron towards air and water. The development of such technologies, if any, should address this issue.

  13. Poly phenylenediamine and its TiO{sub 2} composite as hydrogen storage material

    Energy Technology Data Exchange (ETDEWEB)

    Rehim, Mona H. Abdel [Packing and Packaging Materials Department, Center of Excellence for Advanced Science, Renewable Energy Group, National Research Center, Cairo (Egypt); Ismail, Nahla, E-mail: nahlaismail24@yohoo.com [Physical Chemistry Department, National Research Center, Center of Excellence for Advanced Science, Renewable Energy Group, National Research Center, El-bohooth St 33, Cairo (Egypt); Badawy, Abd El-Rahman A.A. [Physical Chemistry Department, National Research Center, Center of Excellence for Advanced Science, Renewable Energy Group, National Research Center, El-bohooth St 33, Cairo (Egypt); Turky, Gamal [Microwave Physics and Dielectrics Department, National Research Center, Cairo (Egypt)

    2011-08-15

    Highlights: {yields} A new polymeric material has been prepared and fully characterized. {yields} The composite with TiO{sub 2} showed a change in the morphology. {yields} The mechanism of the reaction of the polymer with TiO{sub 2} is studied. {yields} The conductivity of the new polymer and the composite is studied. {yields} The hydrogen storage capacity of the materials prepared are evaluated. - Abstract: Poly phenylenediamine was synthesized from 1,4-phenylenediamine in presence of potassium persulphate and salicylic acid. The structure of the formed poly phenylenediamine was traced using FTIR and its morphology was examined by transmittance electron microscope (TEM). Gel permeation chromatography (GPC) was used to evaluate the polymer molecular weight which showed that the value of its molar mass is 20,000 g mol{sup -1} and it has polydispersity index of 1.01. Different concentrations of TiO{sub 2} were incorporated in the poly phenylenediamine structure via coordination bond between the oxygen atom of TiO{sub 2} and the hydrogen atom of N-H group of polymer. The prepared composites were characterized using FTIR, TA, TEM and SEM/EDX. The TEM micrographs revealed that the composites have 2-D network structure and its morphology changed from a dendritic structure for the pure polymer to layered structure of the composite. The polymer and its composite are completely insulators. Their hydrogen storage capacity has been estimated at -193 deg. C and the composite reported higher hydrogen uptake values than the pure polymer. The reason is suggested to be due to the layered structure of composite which gives it the privilege to store more hydrogen in its interlayer vicinity.

  14. Effects of xenon insertion into hydrogen bromide. Comparison of the electronic structure of the HBr···CO2 and HXeBr···CO2 complexes using quantum chemical topology methods: electron localization function, atoms in molecules and symmetry adapted perturbation theory.

    Science.gov (United States)

    Makarewicz, Emilia; Gordon, Agnieszka J; Mierzwicki, Krzysztof; Latajka, Zdzislaw; Berski, Slawomir

    2014-06-05

    Quantum chemistry methods have been applied to study the influence of the Xe atom inserted into the hydrogen-bromine bond (HBr → HXeBr), particularly on the nature of atomic interactions in the HBr···CO2 and HXeBr···CO2 complexes. Detailed analysis of the nature of chemical bonds has been carried out using topological analysis of the electron localization function, while topological analysis of electron density was used to gain insight into the nature of weak nonbonding interactions. Symmetry-adapted perturbation theory within the orbital approach was applied for greater understanding of the physical contributions to the total interaction energy.

  15. NEW INTERPRETATION OF THE ATOMIC SPECTRA OF THE HYDROGEN ATOM: A MIXED MECHANISM OF CLASSICAL LC CIRCUITS AND QUANTUM WAVE-PARTICLE DUALITY NUEVA INTERPRETACIÓN DEL ESPECTRO ATÓMICO DEL ÁTOMO DE HIDRÓGENO: UN MECANISMO MIXTO DE CIRCUITOS LC Y LA DUALIDAD ONDA CUÁNTICA-PARTÍCULA

    Directory of Open Access Journals (Sweden)

    Héctor Torres-Silva

    2008-11-01

    Full Text Available In this paper we study the energy conversion laws of the macroscopic harmonic LC oscillator, the electromagnetic wave (photon and the hydrogen atom. As our analysis indicates, the energies of these apparently different systems obey exactly the same energy conversion law. Based on our results and the wave-particle duality of electrons, we find that the hydrogen atom is, in fact, a natural chiral microscopic LC oscillator. In the framework of classical electromagnetic field theory we analytically obtain, for the hydrogen atom, the quantized electron orbit radius , and quantized energy , (n = 1, 2, 3, · · ·, where is the Bohr radius and is the Rydberg constant. Without the adaptation of any other fundamental principles of quantum mechanics, we present a reasonable explanation of the polarization of photon, selection rules and Pauli exclusion principle. Our results also reveal an essential connection between electron spin and the intrinsic helical movement of electrons and indicate that the spin itself is the effect of quantum confinement.En este trabajo se presenta un estudio de las leyes macroscópicas de conversión de energía del oscilador armónico LC, la onda electromagnética (fotones y el átomo de hidrógeno. Como nuestro análisis indica, las energías de estos aparentemente diferentes sistemas obedecen exactamente la misma ley de conversión de la energía. Sobre la base de nuestros resultados y de la dualidad onda-partícula del electrón, nos encontramos con que el átomo de Hidrógeno, de hecho, es un oscilador LC microscópico naturalmente quiral. En el marco de la teoría clásica de campos electromagnéticos se obtiene analíticamente, para el átomo de hidrógeno, el radio cuantizado de la órbita electrónica , y la energía cuantizada , (n=1, 2, 3.., donde es el radio de Bohr, y es la constante de Rydberg. Sin la adaptación de otros principios fundamentales de la mecánica cuántica, se presenta una explicación razonable de

  16. Atomic polarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  17. Atomic Physics

    CERN Document Server

    Foot, Christopher J

    2007-01-01

    This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen

  18. Realization of a frequency standard at 778 nm: absolute frequency measurement of the 2S-8S/D transitions in hydrogen and deuterium and determination of the Rydberg constant; Realisation d'un etalon de frequence a 778 nm: mesure absolue des frequences 2S-8S/D des atomes d'hydrogene et de deuterium et determination de la constante de rydberg

    Energy Technology Data Exchange (ETDEWEB)

    Beauvoir, B. de

    1996-12-15

    The purpose of this work is to design a 778 nm standard laser for performing an absolute measurement of 2S-8S/D frequencies of hydrogen and deuterium atoms. This frequency calibration is based on a 5S-5D two-photon transition of the rubidium atom. Metrological performance of this laser is 10 times as good as that of He-Ne laser calibrated on iodine. It has been shown that the passage of a laser radiation through an optic fiber does not deteriorate its metrological properties. 2S-8S/8D transitions have been excited in an atomic jet by a titanium-sapphire laser. Spurious effects can shift and broaden lines. In order to prevent these effects, a theoretical line has been shaped and adjusted on experimental signals. The frequency comparison between the excitation laser and the standard laser has led to the measurement of the absolute frequency of the line concerned. The value of the Rydberg constant has been deduced: R{sub {infinity}} = 109737.3156859 (10) cm{sup -1}. The comparison of experimental data between deuterium and hydrogen has allowed us to determine the value of the Lamb shift of the 2S state of deuterium: L(2S-2P) = 1059,230 (9) MHz.

  19. Ultracold atoms on atom chips

    DEFF Research Database (Denmark)

    Krüger, Peter; Hofferberth, S.; Haller, E.

    2005-01-01

    Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...

  20. Dichotomous Hydrogen Atom Transfer vs. Proton Coupled Electron Transfer During Activation of X-H Bonds (X = C, N, O) by Nonheme Iron-Oxo Complexes of Variable Basicity

    Science.gov (United States)

    Usharani, Dandamudi; Lacy, David C.; Borovik, A. S.; Shaik, Sason

    2013-01-01

    We describe herein the hydrogen-atom transfer (HAT)/ proton-coupled electron-transfer (PCET) reactivity for FeIV-oxo and FeIII-oxo complexes (1–4) that activate C-H, N-H, and O-H bonds in 9,10 dihydroanthracene (S1), dimethylformamide (S2), 1,2 diphenylhydrazine (S3), p-methoxyphenol (S4), and 1,4-cyclohexadiene (S5). In 1–3, the iron is pentacoordinated by tris[N'-tert-butylureaylato)-N-ethylene]aminato ([H3buea]3−) or its derivatives. These complexes are basic, in the order 3 >> 1 > 2. Oxidant 4, [FeIVN4Py(O)]2+ (N4Py: N,N-bis(2-pyridylmethyl)-bis(2-pyridyl) methylamine), is the least basic oxidant. The DFT results match experimental trends and exhibit a mechanistic spectrum ranging from concerted HAT and PCET reactions to concerted-asynchronous proton transfer (PT) / electron transfer (ET) mechanisms, all the way to PT. The singly occupied orbital along the O---H---X (X= C, N, O) moiety in the TS shows clearly that in the PCET cases, the electron is transferred separately from the proton. The Bell-Evans-Polanyi principle does not account for the observed reactivity pattern, as evidenced by the scatter in the plot of calculated barrier vs. reactions driving forces. However, a plot of the deformation energy in the TS vs. the respective barrier provides a clear signature of the HAT/PCET dichotomy. Thus, in all C-H bond activations, the barrier derives from the deformation energy required to create the TS, whereas in N-H/O-H bond activations, the deformation energy is much larger than the corresponding barrier, indicating the presence of stabilizing interaction between the TS fragments. A valence bond model is used to link the observed results with the basicity/acidity of the reactants. PMID:24124906

  1. Alloying effect on the electronic structures of hydrogen storage compounds

    Energy Technology Data Exchange (ETDEWEB)

    Yukawa, H.; Moringa, M.; Takahashi, Y. [Nagoya Univ. (Japan). Dept. of Mater. Sci. and Eng.

    1997-05-20

    The electronic structures of hydrogenated LaNi{sub 5} containing various 3d transition elements were investigated by the DV-X{alpha} molecular orbital method. The hydrogen atom was found to form a strong chemical bond with the Ni rather than the La atoms. The alloying modified the chemical bond strengths between atoms in a small metal octahedron containing a hydrogen atom at the center, resulting in the change in the hydrogen absorption and desorption characteristics of LaNi{sub 5} with alloying. (orig.) 7 refs.

  2. Cross section measurements of the processes occurring in the fragmentation of H{sub n}{sup +} (3 {<=} n {<=} 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms; Mesure des sections efficaces des differents processus intervenant dans la fragmentation d`agregats d`hydrogene H{sub n}{sup +} (3 {<=} n {<=} 35) induite par collision a haute vitesse (60 keV/u) sur un atome d`helium

    Energy Technology Data Exchange (ETDEWEB)

    Louc, Sandrine [Inst. de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

    1997-09-15

    Different processes involved in the fragmentation of ionised hydrogen clusters H{sub 3} + (H{sub 2}){sub (n-3)/2} (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity ({approx_equal} c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H{sub 3}{sup +} ion. In the same way, the dissociation cross section of the H{sub 3}{sup +} core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H{sub 3}{sup +} core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H{sub 9}{sup +}, H{sub 15}{sup +}, H{sub 19}{sup +} and H{sub 29}{sup +} clusters could be the `core` of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author) 114 refs., 74 figs., 9 tabs.

  3. Hydrogenation of zirconium film by implantation of hydrogen ions

    Science.gov (United States)

    Liu, Yang; Fang, Kaihong; Lv, Huiyi; Liu, Jiwei; Wang, Boyu

    2017-03-01

    In order to understand the drive-in target in a D-D type neutron generator, it is essential to study the mechanism of the interaction between hydrogen ion beams and the hydrogen-absorbing metal film. The present research concerns the nucleation of hydride within zirconium film implanted with hydrogen ions. Doses of 30 keV hydrogen ions ranging from 4.30 × 1017 to 1.43 × 1018 ions cm-2 were loaded into the zirconium film through the ion beam implantation technique. Features of the surface morphology and transformation of phase structures were investigated with scanning electron microscopy, atomic force microscopy and x-ray diffraction. Confirmation of the formation of δ phase zirconium hydride in the implanted samples was first made by x-ray diffraction, and the different stages in the gradual nucleation and growth of zirconium hydride were then observed by atomic force microscope and scanning electron microscopy.

  4. Early hydrogen user centres and corridors as part of the European hydrogen energy roadmap (HyWays)

    Energy Technology Data Exchange (ETDEWEB)

    Stiller, Christoph; Buenger, Ulrich [Ludwig-Boelkow-Systemtechnik GmbH (LBST), Daimlerstrasse 15, D-85521 Ottobrunn (Germany); Seydel, Philipp; Wietschel, Martin [Fraunhofer-Institute for Systems and Innovation Research (ISI), Breslauer Strasse 48, D-76139 Karlsruhe (Germany)

    2008-08-15

    Within the HyWays project, hydrogen user centres and corridors for the early phase of hydrogen commercialisation have been selected for 10 European countries by a large number of stakeholders based on a set of indicators. The purpose is to detect realistic starting points for hydrogen use and facilitate modelling of further deployment of hydrogen use and supply infrastructure. The results reveal that stakeholders anticipate mostly highly populated regions as early hydrogen user centres, as well as corridors linking the regions and enabling commuting in the vicinity. (author)

  5. Binuclear manganese compounds of potential biological significance. Part 2. Mechanistic study of hydrogen peroxide disproportionation by dimanganese complexes: the two oxygen atoms of the peroxide end up in a dioxo intermediate.

    Science.gov (United States)

    Dubois, Lionel; Caspar, Régis; Jacquamet, Lilian; Petit, Pierre-Emmanuel; Charlot, Marie-France; Baffert, Carole; Collomb, Marie-Noëlle; Deronzier, Alain; Latour, Jean-Marc

    2003-08-11

    The dimanganese(II,II) complexes 1a [Mn(2)(L)(OAc)(2)(CH(3)OH)](ClO(4)) and 1b [Mn(2)(L)(OBz)(2)(H(2)O)](ClO(4)), where HL is the unsymmetrical phenol ligand 2-(bis-(2-pyridylmethyl)aminomethyl)-6-((2-pyridylmethyl)(benzyl)aminomethyl)-4-methylphenol, react with hydrogen peroxide in acetonitrile solution. The disproportionation reaction was monitored by electrospray ionization mass spectrometry (ESI-MS) and EPR and UV-visible spectroscopies. Extensive EPR studies have shown that a species (2) exhibiting a 16-line spectrum at g approximately 2 persists during catalysis. ESI-MS experiments conducted similarly during catalysis associate 2a with a peak at 729 (791 for 2b) corresponding to the formula [Mn(III)Mn(IV)(L)(O)(2)(OAc)](+) ([Mn(III)Mn(IV)(L)(O)(2)(OBz)](+) for 2b). At the end of the reaction, it is partly replaced by a species (3) possessing a broad unfeatured signal at g approximately 2. ESI-MS associates 3a with a peak at 713 (775 for 3b) corresponding to the formula [Mn(II)Mn(III)(L)(O)(OAc)](+) ([Mn(II)Mn(III)(L)(O)(OBz)](+) for 3b). In the presence of H(2)(18)O, these two peaks move to 733 and to 715 indicating the presence of two and one oxo ligands, respectively. When H(2)(18)O(2) is used, 2a and 3a are labeled showing that the oxo ligands come from H(2)O(2). Interestingly, when an equimolar mixture of H(2)O(2) and H(2)(18)O(2) is used, only unlabeled and doubly labeled 2a/b are formed, showing that its two oxo ligands come from the same H(2)O(2) molecule. All these experiments lead to attribute the formula [Mn(III)Mn(IV)(L)(O)(2)(OAc)](+) to 2a and to 3a the formula [Mn(II)Mn(III)(L)(O)(OAc)](+). Freeze-quench/EPR experiments revealed that 2a appears at 500 ms and that another species with a 6-line spectrum is formed transiently at ca. 100 ms. 2a was prepared by reaction of 1a with tert-butyl hydroperoxide as shown by EPR and UV-visible spectroscopies and ESI-MS experiments. Its structure was studied by X-ray absorption experiments which revealed the

  6. Storing Renewable Energy in the Hydrogen Cycle.

    Science.gov (United States)

    Züttel, Andreas; Callini, Elsa; Kato, Shunsuke; Atakli, Züleyha Özlem Kocabas

    2015-01-01

    An energy economy based on renewable energy requires massive energy storage, approx. half of the annual energy consumption. Therefore, the production of a synthetic energy carrier, e.g. hydrogen, is necessary. The hydrogen cycle, i.e. production of hydrogen from water by renewable energy, storage and use of hydrogen in fuel cells, combustion engines or turbines is a closed cycle. Electrolysis splits water into hydrogen and oxygen and represents a mature technology in the power range up to 100 kW. However, the major technological challenge is to build electrolyzers in the power range of several MW producing high purity hydrogen with a high efficiency. After the production of hydrogen, large scale and safe hydrogen storage is required. Hydrogen is stored either as a molecule or as an atom in the case of hydrides. The maximum volumetric hydrogen density of a molecular hydrogen storage is limited to the density of liquid hydrogen. In a complex hydride the hydrogen density is limited to 20 mass% and 150 kg/m(3) which corresponds to twice the density of liquid hydrogen. Current research focuses on the investigation of new storage materials based on combinations of complex hydrides with amides and the understanding of the hydrogen sorption mechanism in order to better control the reaction for the hydrogen storage applications.

  7. Simulation of silicon nanoparticles stabilized by hydrogen at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Galashev, Alexander Y., E-mail: galashev@ecko.uran.r [Russian Academy of Sciences, Ural Division, Institute of Industrial Ecology (Russian Federation)

    2010-10-15

    The stability of different silicon nanoparticles are investigated at a high temperature. The temperature dependence of the physicochemical properties of 60- and 73-atom silicon nanoparticles are investigated using the molecular dynamics method. The 73-atom particles have a crystal structure, a random atomic packing, and a packing formed by inserting a 13-atom icosahedron into a 60-atom fullerene. They are surrounded by a 'coat' from 60 atoms of hydrogen. The nanoassembled particle at the presence of a hydrogen 'coat' has the most stable number (close to four) of Si-Si bonds per atom. The structure and kinetic properties of a hollow single-layer fullerene-structured Si{sub 60} cluster are considered in the temperature range 10 K {<=} T {<=} 1760 K. Five series of calculations are conducted, with a simulation of several media inside and outside the Si{sub 60} cluster, specifically, the vacuum and interior spaces filled with 30 and 60 hydrogen atoms with and without the exterior hydrogen environment of 60 atoms. Fullerene surrounded by a hydrogen 'coat' and containing 60 hydrogen atoms in the interior space has a higher stability. Such cluster has smaller self-diffusion coefficients at high temperatures. The fullerene stabilized with hydrogen is stable to the formation of linear atomic chains up to the temperatures 270-280 K.

  8. Tetramethylammonium hydrogen terephthalate

    Directory of Open Access Journals (Sweden)

    Leila Dolatyari

    2012-10-01

    Full Text Available The asymmetric unit of the title salt, C4H12N+·C8H5O4−, contains one half of a tetramethylammonium cation and one half of a hydrogen terephthalate monoanion. The N atom of the ammonium cation lies on a twofold rotation axis and the centre of mass of the terephthalate anion is on a centre of inversion. In the crystal, the centrosymmetric terephthalate ions are linked by a very short symmetric O—H...O hydrogen bond [O...O = 2.4610 (19 Å] into a one-dimensional polymeric chain along [1-12]. The tetramethylammonium cations and terephthalate anions are then connected through a pair of bifurcated acceptor C—H...O hydrogen bonds, generating a three-dimensional supramolecular network. The carboxylate groups at both ends of the terephthalate anion are charge-shared with an equal probability of 0.5.

  9. Hydrogen Generator

    Science.gov (United States)

    1983-01-01

    A unit for producing hydrogen on site is used by a New Jersey Electric Company. The hydrogen is used as a coolant for the station's large generator; on-site production eliminates the need for weekly hydrogen deliveries. High purity hydrogen is generated by water electrolysis. The electrolyte is solid plastic and the control system is electronic. The technology was originally developed for the Gemini spacecraft.

  10. Mechanism of single atom switch on silicon

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Stokbro, Kurt; Thirstrup, C.

    1998-01-01

    We demonstrate single atom switch on silicon which operates by displacement of a hydrogen atom on the silicon (100) surface at room temperature. We find two principal effects by which the switch is controlled: a pronounced maximum of the switching probability as function of sample bias...

  11. Atomic physics

    CERN Document Server

    Born, Max

    1969-01-01

    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  12. Early Atomism

    Indian Academy of Sciences (India)

    http://www.ias.ac.in/article/fulltext/reso/015/10/0905-0925. Keywords. Atomic theory; Avogadro's hypothesis; atomic weights; periodic table; valence; molecular weights; molecular formula; isomerism. Author Affiliations. S Ramasesha1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, ...

  13. Thermodynamic properties of hydrogen-helium plasmas.

    Science.gov (United States)

    Nelson, H. F.

    1972-01-01

    Calculation of the thermodynamic properties of an atomic hydrogen-helium plasma for postulated conditions present in a stagnation shock layer of a spacecraft entering the atmosphere of Jupiter. These properties can be used to evaluate transport properties, to calculate convective heating, and to investigate nonequilibrium behavior. The calculations have been made for temperatures from 10,000 to 100,000 K, densities of 10 to the minus 7th and .00001 g cu cm, and three plasma compositions: pure hydrogen, 50% hydrogen/50% helium, and pure helium. The shock layer plasma consists of electrons, protons, atomic hydrogen, atomic helium, singly ionized helium, and doubly atomized helium. The thermodynamic properties which have been investigated are: pressure, average molecular weight, internal energy, enthalpy, entropy, specific heat, and isentropic speed of sound. A consistent model was used for the reduction of the ionization potential in the calculation of the partition functions.

  14. Atomic data for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, H.T.; Kirkpatrick, M.I.; Alvarez, I.; Cisneros, C.; Phaneuf, R.A. (eds.); Barnett, C.F.

    1990-07-01

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research.

  15. Prospects for hydrogen storage in graphene.

    Science.gov (United States)

    Tozzini, Valentina; Pellegrini, Vittorio

    2013-01-07

    Hydrogen-based fuel cells are promising solutions for the efficient and clean delivery of electricity. Since hydrogen is an energy carrier, a key step for the development of a reliable hydrogen-based technology requires solving the issue of storage and transport of hydrogen. Several proposals based on the design of advanced materials such as metal hydrides and carbon structures have been made to overcome the limitations of the conventional solution of compressing or liquefying hydrogen in tanks. Nevertheless none of these systems are currently offering the required performances in terms of hydrogen storage capacity and control of adsorption/desorption processes. Therefore the problem of hydrogen storage remains so far unsolved and it continues to represent a significant bottleneck to the advancement and proliferation of fuel cell and hydrogen technologies. Recently, however, several studies on graphene, the one-atom-thick membrane of carbon atoms packed in a honeycomb lattice, have highlighted the potentialities of this material for hydrogen storage and raise new hopes for the development of an efficient solid-state hydrogen storage device. Here we review on-going efforts and studies on functionalized and nanostructured graphene for hydrogen storage and suggest possible developments for efficient storage/release of hydrogen under ambient conditions.

  16. Controlled surface functionalization via self-selective metal adsorption and pattern transformation on the vicinal Si(111) surface

    Science.gov (United States)

    Chin, A. L.; Men, F. K.; Liu, Feng

    2010-11-01

    We demonstrate a self-selective metal adsorption and pattern transformation process on vicinal Si(111) surfaces. When Au atoms are deposited onto the self-organized periodic Si(111) surface patterns, the Au atoms self-select to adsorb predominantly onto one of the two distinct domains, the Si(111) terrace or the step-bunched facet at different Au coverage. This leads to a systematic transformation of the surface pattern, whose domain population changes while its periodicity remains intact with the increasing Au coverage. A stress-domain model is used to explain the observed phenomenon. Our findings suggest a unique method for controlled functionalization of surfaces at the nanoscale, as illustrated further by domain-selective self-assembly of uniform CoSi2 nanoclusters on the Au-functionalized vicinal Si(111) surface.

  17. Controlled Surface functionalization via self-selective metal adsorption and pattern transformation on vicinal Si(111) surface

    Science.gov (United States)

    Men, F. K.; Chin, A. L.; Liu, Feng

    2011-03-01

    We demonstrate a self-selective metal adsorption and pattern transformation process on vicinal Si(111) surfaces. When Au atoms are deposited onto the self-organized periodic Si(111) surface patterns, the Au atoms self-select to adsorb predominantly onto one of the two distinct domains, the Si(111) terrace or the step-bunched facet, at different Au coverage. This leads to a systematic transformation of the surface pattern, whose domain population changes while its periodicity remains intact with the increasing Au coverage. A stress-domain model is used to explain the observed phenomenon. Our findings suggest a unique method for controlled functionalization of surfaces at the nanoscale, as illustrated further by domain- selective self-assembly of uniform CoSi 2 nanoclusters on the Au-functionalized vicinal Si(111) surface. Work supported by NSC of Taiwan, ROC (Men) and NSF and DOE-BES of US (Liu).

  18. 4-Chloroanilinium hydrogen oxalate hemihydrate

    Directory of Open Access Journals (Sweden)

    Hajer Rahmouni

    2010-04-01

    Full Text Available In the title hydrated molecular salt, C6H7ClN+·C2HO4−·0.5H2O, the water O atom lies on a crystallographic twofold axis. In the crystal, the anions are linked by O—H...O hydrogen bonds, forming chains propagating along the b axis. These chains are interconnected through O—H...O hydrogen bonds from the water molecules and N—H...O hydrogen bonds from the cations, building layers parallel to the ab plane.

  19. Influence of hydrogen on hydrogenated cadmium telluride optical spectra

    Energy Technology Data Exchange (ETDEWEB)

    Pociask, M.; Polit, J.; Sheregii, E.; Cebulski, J. [Institute of Physics, University of Rzeszow (Poland); Kisiel, A. [Institute of Physics, Jagiellonian University, Krakow (Poland); Mycielski, A. [Institute of Physics, PAS, Warszawa (Poland); Morgiel, J. [Polish Academy of Sciences, Institute of Metallurgy and Materials Sciences, Krakow (Poland); Piccinini, M. [INFN-Laboratori Nazionali di Frascati (Italy); Dipartimento Scienze Geologiche, Universita Roma Tre, Rome (Italy); Marcelli, A.; Robouch, B.; Guidi, M.C. [INFN-Laboratori Nazionali di Frascati (Italy); Savchyn, V. [Ivan Franko Lviv National University (Ukraine); Izhnin, I.I. [Institute for Materials SRC ' ' Carat' ' , Lviv (Ukraine); Zajdel, P. [Institute of Fizyki, University of Silesia, 4 Uniwersytecka Str., 40-007 Katowice (Poland); Nucara, A. [Universita' di Roma La Sapienza, P. le Aldo Moro 1, Rome (Italy)

    2009-09-15

    The presence of oxygen impurity in semiconducting materials affects the electrical properties of crystals and significantly limits their application. To remove oxygen impurity, ultra-pure hydrogen is used while growing Te-containing crystals such as CdTe, CdZnTe, and ZnTe. The hydrogenation of CdTe crystals is a technological process that purifies the basic material from oxygen, mainly cadmium and tellurium oxide compounds incorporated in CdTe crystalline lattice. In the present work we analyses the deformations induced by hydrogen and oxygen atoms in CdTe crystals looking at their influence on the near fundamental band (NFB), middle infrared (MIR) and far infrared (FIR) reflectivity spectra as well as on cathodoluminescence (CL) spectra. Comparison of the hydrogenated CdTe phonon structure profiles confirms the presence of hydrogen atoms bounded inside the lattice. The possible localization of hydrogen and oxygen ions within the tetrahedron coordinated lattice is discussed in the framework of a model that shows a good agreement with recent NFB, MIR and FIR experiments carried out on hydrogenated CdTe crystals. Measured reflection spectra in the wavelength range 190-1400 nm (NFB) indicate the appearance in CdTe(H{sub M}) and CdTe(H{sub L}) of additional maxima at 966 nm related to the electron transitions from level about 0.2 eV above the valence band. The CL spectra confirmed existence of this electron level. We present a possible H{sub 2} alignment similar to the single H model i.e., over the face (at about 0.38 Aa). For this model the angle from the central atom to the H atoms is equal to 64 which is also close to the bonding angle of CdH{sub 2} (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Hydrogen storage in carbon nanotubes.

    Science.gov (United States)

    Hirscher, M; Becher, M

    2003-01-01

    The article gives a comprehensive overview of hydrogen storage in carbon nanostructures, including experimental results and theoretical calculations. Soon after the discovery of carbon nanotubes in 1991, different research groups succeeded in filling carbon nanotubes with some elements, and, therefore, the question arose of filling carbon nanotubes with hydrogen by possibly using new effects such as nano-capillarity. Subsequently, very promising experiments claiming high hydrogen storage capacities in different carbon nanostructures initiated enormous research activity. Hydrogen storage capacities have been reported that exceed the benchmark for automotive application of 6.5 wt% set by the U.S. Department of Energy. However, the experimental data obtained with different methods for various carbon nanostructures show an extreme scatter. Classical calculations based on physisorption of hydrogen molecules could not explain the high storage capacities measured at ambient temperature, and, assuming chemisorption of hydrogen atoms, hydrogen release requires temperatures too high for technical applications. Up to now, only a few calculations and experiments indicate the possibility of an intermediate binding energy. Recently, serious doubt has arisen in relation to several key experiments, causing considerable controversy. Furthermore, high hydrogen storage capacities measured for carbon nanofibers did not survive cross-checking in different laboratories. Therefore, in light of today's knowledge, it is becoming less likely that at moderate pressures around room temperature carbon nanostructures can store the amount of hydrogen required for automotive applications.

  1. Precipitation hardening and hydrogen embrittlement of aluminum ...

    Indian Academy of Sciences (India)

    tate free zone at the grain boundaries may lead to reduced resistance to stress corrosion cracking. Mechanistically, both features play a role in environmental susceptibility. ... cracking of Al alloys (Scamans et al 1987). Mg atoms may localize hydrogen entry, accelerate hydrogen transport and/or provide sites for grain ...

  2. Vibrational characterization of different benzene phases on flat and vicinal Si(100) surfaces.

    Science.gov (United States)

    Naydenov, Borislav; Widdra, Wolf

    2007-10-21

    Based on high-resolution electron energy loss spectroscopy and temperature-programmable desorption, benzene chemisorption on vicinal and nominally flat Si(100) surfaces has been studied for various adsorption, annealing, and site blocking treatments. Three different chemisorbed benzene (C6H6 and C6D6) phases with distinct thermal desorption characteristics and different vibrational spectra have been separated and characterized on both substrates. All three phases are identified as 1,4-cyclohexadiene-like structures with butterfly geometry. Whereas the dominant phase is di-sigma bonded to the two Si atoms of a single Si-Si dimer, the benzene orientation (double bond orientation) in the other phases is rotated. Di-sigma bonding to Si atoms of adjacent Si-Si dimer for the latter cases is most likely. Coverage and temperature dependent conversions between the different phases have been addressed by vibrational spectroscopy.

  3. Sputtering of solid neon by keV hydrogen ions

    DEFF Research Database (Denmark)

    Ellegaard, Ole; Schou, Jørgen; Sørensen, H.

    1986-01-01

    Sputtering of solid Ne with the hydrogen ions H+1, H+2 and H+3 in the energy range 1–10 keV/atom has been studied by means of a quartz microbalance technique. No enhancement in the yield per atom for molecular ions was found. The results for hydrogen ions are compared with data for keV electrons....

  4. Phenazin-5-ium hydrogen sulfate monohydrate

    Directory of Open Access Journals (Sweden)

    Joseph deGeorge

    2013-04-01

    Full Text Available The crystal structure of the title salt, C12H9N2+·HSO4−·H2O, comprises inversion-related pairs of phenazinium ions linked by C—H...N hydrogen bonds. The phenazinium N—H atoms are hydrogen bonded to the bisulfate anions. The bisulfate anions and water molecules are linked by O—H...O hydrogen-bonding interactions into a structural ladder motif parallel to the a axis.

  5. Interaction of hydrogen with metallic nanojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Halbritter, Andras; Csonka, Szabolcs; Makk, Peter; Mihaly, Gyoergy [Electron Transport Research Group of the Hungarian Academy of Sciences and Department of Physics, Budapest University of Technology and Economics, 1111 Budapest (Hungary)

    2007-03-15

    We study the behavior of hydrogen molecules between atomic-sized metallic electrodes using the mechanically controllable break junction technique. We focus on the interaction H{sub 2} with monoatomic gold chains demonstrating the possibility of a hydrogen molecule being incorporated in the chain. We also show that niobium is strongly reactive with hydrogen, which enables molecular transport studies between superconducting electrodes. This opens the possibility for a full characterization of the transmission properties of molecular junctions with superconducting subgap structure measurements.

  6. Why are Hydrogen Bonds Directional?

    Indian Academy of Sciences (India)

    for an interaction to be characterized as a hydro- gen bond but does not provide any rationale for the same. This article reports a rationale for limiting the angle, based on the electron density topology using the quantum theory of atoms in molecules. Electron density topol- ogy for common hydrogen bond donors HF, HCl, ...

  7. From vicinal to rough crystal surfaces

    Science.gov (United States)

    Balibar, S.; Guthmann, C.; Rolley, E.

    1993-06-01

    One generally expects the properties of a vicinal surface to be independent of the existence of steps as soon as these steps overlap, i.e. when their mutual distance is smaller than their width. By using the roughening theory by Nozières and Gallet [1], we show that, at least for surfaces weakly coupled to the lattice, this overlap occurs for distances significantly larger than the commonly defined width. Our prediction is supported by an analysis of the various measurements of the angular variation of the surface stiffness of helium crystals, which were performed by Wolf et al. [2], Andreeva et al. [3] and Babkin et al. [4]. As a consequence, the interaction between crystal steps should be studied on vicinal surfaces with a much smaller tilt angle than previously thought. This article is also an opportunity to return to the relation between the step width and the correlation length on smooth surfaces, as well as to the treatment of the various finite size effects which occur in the problem of roughening. We finally reconsider how the weak coupling hypothesis applies to the case of helium crystals. On s'attend généralement à ce que les propriétés d'une surface vicinale ne soient plus contrôlées par l'existence des marches lorsque celles-ci se recouvrent, donc lorsque leur distance mutuelle devient inférieure à leur largeur. En reprenant la théorie de la transition rugueuse élaborée par Nozières et Gallet [1], nous montrons que, pour des surfaces faiblement couplées au réseau cristallin, ce recouvrement doit se produire pour des distances nettement plus grandes que la largeur (telle qu'elle est habituellement définie). Notre prédiction est confirmée par l'analyse des différentes mesures de la variation angulaire de la rigidité de surface des cristaux d'hélium réalisées par Wolf et al. [2], Andreeva et al. [3] and Babkin et al. [4]. Il s'ensuit que l'étude de l'interaction entre marches cristallines doit être effectuée sur des surfaces

  8. Excited-state hydrogen atom abstraction initiates the photochemistry of β-2′-deoxycytidine† †Electronic supplementary information (ESI) available: Including relevant preliminary results as well as illustrations and geometrical parameters of selected structures. See DOI: 10.1039/c4sc03761h Click here for additional data file.

    Science.gov (United States)

    Campos, Jesús; Šponer, Judit E.; Šponer, Jiří

    2015-01-01

    Understanding the effects of ultraviolet radiation on nucleotides in solution is an important step towards a comprehensive description of the photochemistry of nucleic acids and their constituents. Apart from having implications for mutagenesis and DNA photoprotection mechanisms, the photochemistry of cytidines is a central element in UV-assisted syntheses of pyrimidine nucleotides under prebiotically plausible conditions. In this contribution, we present UV-irradiation experiments of β-2′-deoxycytidine in aqueous solution involving H–D exchange followed by NMR spectroscopic analysis of the photoproducts. We further elucidate the outcome of these experiments by means of high-level quantum chemical calculations. In particular, we show that prolonged UV-irradiation of cytidine may lead to H–C1′ hydrogen atom abstraction by the carbonyl oxygen atom of cytosine. This process may enable photoanomerisation and nucleobase loss, two previously unexplained photoreactions observed in pyrimidine nucleotides. PMID:27182431

  9. Novel developments in hydrogen storage, hydrogen activation and ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Doroodian, Amir

    2010-12-03

    This dissertation is divided into three chapters. Recently, metal-free hydrogen activation using phosphorous compounds has been reported in science magazine. We have investigated the interaction between hydrogen and phosphorous compounds in presence of strong Lewis acids (chapter one). A new generation of metal-free hydrogen activation, using amines and strong Lewis acids with sterically demanding nature, was already developed in our group. Shortage of high storage capacity using large substitution to improve sterical effect led us to explore the amine borane derivatives, which are explained in chapter two. Due to the high storage capacity of hydrogen in aminoborane derivatives, we have explored these materials to extend hydrogen release. These compounds store hydrogen as proton and hydride on adjacent atoms or ions. These investigations resulted in developing hydrogen storage based on ionic liquids containing methyl guanidinium cation. Then we have continued to develop ionic liquids based on methyl guanidinium cation with different anions, such as tetrafluoro borate (chapter three). We have replaced these anions with transition metal anions to investigate hydrogen bonding and catalytic activity of ionic liquids. This chapter illustrates the world of ionic liquid as a green solvent for organic, inorganic and catalytic reactions and combines the concept of catalysts and solvents based on ionic liquids. The catalytic activity is investigated particularly with respect to the interaction with CO{sub 2}. (orig.)

  10. Bis(hydrogen l-glutamato)palladium(II)

    OpenAIRE

    Kurt Merzweiler; Christoph Wagner; Antje Seifert

    2011-01-01

    In the title compound, [Pd(C5H8NO4)2], the Pd(II) atom is coordinated by two O atoms and two N atoms of two N,O-chelating hydrogen l-glutatmate ligands in a square–planar geometry with the N and O atoms in a mutually trans arrangement. The complex units are embedded in a network of N—H...O and O—H...O hydrogen-bonding interactions that stabilize the three-dimensional crystal structure. The strongest hydrogen bonds are formed between the γ-COOH untis of a...

  11. Hydrogen Bibliography

    Energy Technology Data Exchange (ETDEWEB)

    1991-12-01

    The Hydrogen Bibliography is a compilation of research reports that are the result of research funded over the last fifteen years. In addition, other documents have been added. All cited reports are contained in the National Renewable Energy Laboratory (NREL) Hydrogen Program Library.

  12. Compositional changes of Pd-Au bimetallic nanoclusters upon hydrogenation

    NARCIS (Netherlands)

    Di Vece, M.|info:eu-repo/dai/nl/248753355; Bals, S.; Verbeeck, J.; Lievens, P.; Van Tendeloo, G.

    2009-01-01

    Changes in the size distribution and composition of bimetallic Pd-Au nanoclusters have been observed after hydrogen exposure. This effect is caused by hydrogen-induced Ostwald ripening whereby the hydrogen reduces the binding energy of the cluster atoms leading to their detachment from the cluster.

  13. Hydrogen exchange

    DEFF Research Database (Denmark)

    Jensen, Pernille Foged; Rand, Kasper Dyrberg

    2016-01-01

    Hydrogen exchange (HX) monitored by mass spectrometry (MS) is a powerful analytical method for investigation of protein conformation and dynamics. HX-MS monitors isotopic exchange of hydrogen in protein backbone amides and thus serves as a sensitive method for probing protein conformation...... and dynamics along the entire protein backbone. This chapter describes the exchange of backbone amide hydrogen which is highly quenchable as it is strongly dependent on the pH and temperature. The HX rates of backbone amide hydrogen are sensitive and very useful probes of protein conformation......, as they are distributed along the polypeptide backbone and form the fundamental hydrogen-bonding networks of basic secondary structure. The effect of pressure on HX in unstructured polypeptides (poly-dl-lysine and oxidatively unfolded ribonuclease A) and native folded proteins (lysozyme and ribonuclease A) was evaluated...

  14. Atomic theories

    CERN Document Server

    Loring, FH

    2014-01-01

    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  15. Atomic and molecular beams production and collimation

    CERN Document Server

    Lucas, Cyril Bernard

    2013-01-01

    Atomic and molecular beams are employed in physics and chemistry experiments and, to a lesser extent, in the biological sciences. These beams enable atoms to be studied under collision-free conditions and allow the study of their interaction with other atoms, charged particles, radiation, and surfaces. Atomic and Molecular Beams: Production and Collimation explores the latest techniques for producing a beam from any substance as well as from the dissociation of hydrogen, oxygen, nitrogen, and the halogens.The book not only provides the basic expressions essential to beam design but also offers

  16. Graphene hydrogenation by molecular hydrogen in the process of graphene oxide thermal reduction

    Science.gov (United States)

    Mikoushkin, V. M.; Nikonov, S. Yu.; Dideykin, A. T.; Vul', A. Ya.; Sakseev, D. A.; Baidakova, M. V.; Vilkov, O. Yu.; Nelyubov, A. V.

    2013-02-01

    Thermal reduction in molecular hydrogen of the graphene oxide films has been studied by X-ray photoelectron spectroscopy using synchrotron radiation. The restoration process was revealed to be accompanied by hydrogenation due to collisionally induced interaction of molecular hydrogen with carbon atoms. One side hydrogenated graphene films consisting of 20 μm one monolayer flakes were fabricated on SiO2/Si surface with hydrogen concentration as far as 40 at. %, at which the 0.3 eV bandgap opening was observed. It was shown that both H-coverage and bandgap width of the films can be controlled by varying the temperature of the heat treatment.

  17. Faults--Drakes Bay and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data of faults for the geologic and geomorphologic map of the Drakes Bay and Vicinity map area, California. The vector data file is...

  18. BackscatterB [EM300]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  19. BackscatterC [7125]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  20. Folds--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the folds for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  1. Backscatter A [8101]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  2. Backscatter C [7125]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  3. Faults--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the faults for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  4. establishment of background radiation dose rate in the vicinity

    African Journals Online (AJOL)

    nb

    .ac.tz). *Permanent address: Department of Physics, University of Dodoma. P. O. Box 339 Dodoma. ABSTRACT. The absorbed dose rate in air in the vicinity of the proposed Manyoni uranium mining project located in Singida region, Tanzania, ...

  5. Folds--Drakes Bay and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data of folds for the geologic and geomorphologic map of the Drakes Bay and Vicinity map area, California. The vector data file is...

  6. Paleoshorelines--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the paleoshorelines for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is...

  7. Aerial survey of sea otters in the Cordova vicinity

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The movement of significantly large numbers of sea otters into the Cordova vicinity has generated a local storm of protest concerning the ability of sea otters to...

  8. Measurement of barium ion density in the vicinity of fluorescent lamp electrodes

    Science.gov (United States)

    Bhattacharya, A. K.

    1989-06-01

    A laser-induced fluorescence technique for the detection and measurement of ionized barium atoms near the vicinity of an oxide-coated electrode in a low-pressure discharge lamp is presented. Ionized Ba atoms are produced by the ionization of neutral Ba atoms in the electrode fall region of the discharge. Radiation at 455.4 nm obtained from a pulsed dye laser was used to excite Ba ii from the ground state, 62S1/2, to the resonance level, 62P3/2, and the fluorescence radiation at 614.2 nm for the 62P3/2→52D5/2 transition was measured. The number density of Ba ii atoms as determined from the measured intensity of the fluorescence signal (614.2 nm) is dependent on the discharge current, and the polarity of the neighboring electrode. It is found to be larger when it is acting as an anode than when it is a cathode.

  9. Bis(hydrogen l-glutamatopalladium(II

    Directory of Open Access Journals (Sweden)

    Kurt Merzweiler

    2011-10-01

    Full Text Available In the title compound, [Pd(C5H8NO42], the Pd(II atom is coordinated by two O atoms and two N atoms of two N,O-chelating hydrogen l-glutatmate ligands in a square–planar geometry with the N and O atoms in a mutually trans arrangement. The complex units are embedded in a network of N—H...O and O—H...O hydrogen-bonding interactions that stabilize the three-dimensional crystal structure. The strongest hydrogen bonds are formed between the γ-COOH untis of adjacent glutamate ligands, leading to dimers of the type R22(8 with O...O separations of 2.640 (6 Å.

  10. Atomic Power

    African Journals Online (AJOL)

    Atomic Power. By Denis Taylor: Dr. Taylor was formerly Chief UNESCO Advisor at the University. College, Nairobi, Kenya and is now Professor of Electrical Engineering in the Uni- versity of ... method of producing radioactive isotopes, which are materials .... the sealing and the pressure balancing, all can be carried out ...

  11. Boron-Based Hydrogen Storage: Ternary Borides and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Vajo, John J. [HRL Laboratories, LLC, Malibu, CA (United States)

    2016-04-28

    DOE continues to seek reversible solid-state hydrogen materials with hydrogen densities of ≥11 wt% and ≥80 g/L that can deliver hydrogen and be recharged at moderate temperatures (≤100 °C) and pressures (≤100 bar) enabling incorporation into hydrogen storage systems suitable for transportation applications. Boron-based hydrogen storage materials have the potential to meet the density requirements given boron’s low atomic weight, high chemical valance, and versatile chemistry. However, the rates of hydrogen exchange in boron-based compounds are thus far much too slow for practical applications. Although contributing to the high hydrogen densities, the high valance of boron also leads to slow rates of hydrogen exchange due to extensive boron-boron atom rearrangements during hydrogen cycling. This rearrangement often leads to multiple solid phases occurring over hydrogen release and recharge cycles. These phases must nucleate and react with each other across solid-solid phase boundaries leading to energy barriers that slow the rates of hydrogen exchange. This project sought to overcome the slow rates of hydrogen exchange in boron-based hydrogen storage materials by minimizing the number of solid phases and the boron atom rearrangement over a hydrogen release and recharge cycle. Two novel approaches were explored: 1) developing matched pairs of ternary borides and mixed-metal borohydrides that could exchange hydrogen with only one hydrogenated phase (the mixed-metal borohydride) and only one dehydrogenated phase (the ternary boride); and 2) developing boranes that could release hydrogen by being lithiated using lithium hydride with no boron-boron atom rearrangement.

  12. Submesoscale Dispersion in the Vicinity of the Deepwater Horizon Spill

    Science.gov (United States)

    2014-09-02

    RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (Include area code) 11-03-2014 Journal Article Submesoscale dispersion in the vicinity of the Deepwater ...ecosystems, society, and the economy as evidenced by the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 and the Fukushima nuclear plant...vicinity of the Deepwater Horizon spill Andrew C. Pojea, Tamay M. Özgökmenb,1, Bruce L. Lipphardt, Jr.c, Brian K. Hausb, Edward H. Ryanb, Angelique C

  13. Hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Donath, E.

    1942-10-16

    This report mentioned that not very severe demands for purity were made on the hydrogen used in hydrogenation of coal or similar raw materials, because the catalysts were not very sensitive to poisoning. However, the hydrogenation plants tried to remove most impurities anyway by means of oil washes. The report included a table giving the amount of wash oil used up and the amount of hydrogen lost by dissolving into the wash oil used up and the amount of hydrogen lost by dissolving into the wash oil in order to remove 1% of various impurities from 1000 m/sup 3/ of the circulating gas. The amounts of wash oil used up were 1.1 m/sup 3/ for removing 1% nitrogen, 0.3 m/sup 3/ for 1% carbon monoxide, 0.03 m/sup 3/ for 1% methane. The amount of hydrogen lost was 28 m/sup 3/ for 1% nitrogen, 9 m/sup 3/ for 1% methane and ranged from 9 m/sup 3/ to 39 m/sup 3/ for 1% carbon monoxide and 1 m/sup 3/ to 41 m/sup 3/ for carbon dioxide depending on whether the removal was done in liquid phase or vapor phase and with or without reduction of the oxide to methane. Next the report listed and described the major processes used in German hydrogenation plants to produce hydrogen. Most of them produced water gas, which then had its carbon monoxide changed to carbon dioxide, and the carbon oxides washed out with water under pressure and copper hydroxide solution. The methods included the Winkler, Pintsch-Hillebrand, and Schmalfeldt-Wintershall processes, as well as roasting of coke in a rotating generator, splitting of gases formed during hydrogenation, and separation of cokery gas into its components by the Linde process.

  14. Recirculating cryogenic hydrogen maser

    Energy Technology Data Exchange (ETDEWEB)

    Huerlimann, M.D.; Hardy, W.N.; Berlinsky, A.J.; Cline, R.W.

    1986-08-01

    We report on the design and initial testing of a new type of hydrogen maser, operated at dilution refrigerator temperatures, in which H atoms circulate back and forth between a microwave-pumped state selector and the maser cavity. Other novel design features include liquid-/sup 4/He-coated walls, He-cooled electronics, and the use of microscopic magnetic particles to relax the two lowest hyperfine levels in the state selector. Stabilities at least as good as that of a Rb clock and a high-stability quartz oscillator are observed for measuring times between 1 and 300 s.

  15. Deposition and properties of Fe(Se,Te) thin films on vicinal CaF2 substrates

    Science.gov (United States)

    Bryja, Hagen; Hühne, Ruben; Iida, Kazumasa; Molatta, Sebastian; Sala, Alberto; Putti, Marina; Schultz, Ludwig; Nielsch, Kornelius; Hänisch, Jens

    2017-11-01

    We report on the growth of epitaxial Fe1+δ Se0.5Te0.5 thin films on 0°, 5°, 10°, 15° and 20° vicinal cut CaF2 single crystals by pulsed laser deposition. In situ electron and ex situ x-ray diffraction studies reveal a tilted growth of the Fe1+δ Se0.5Te0.5 films, whereby under optimized deposition conditions the c-axis alignment coincides with the substrate [001] tilted axis up to a vicinal angle of 10°. Atomic force microscopy shows a flat island growth for all films. From resistivity measurements in longitudinal and transversal directions, the ab- and c-axis components of resistivity are derived and the mass anisotropy parameter is determined. Analysis of the critical current density indicates that no effective c-axis correlated defects are generated by vicinal growth, and pinning by normal point core defects dominates. However, for H∣∣ab the effective pinning centers change from surface defects to point core defects near the superconducting transition due to the vicinal cut. Furthermore, we show in angular-dependent critical current density data a shift of the ab-planes maxima position with the magnetic field strength.

  16. MAJOR OIL PLAYS IN UTAH AND VICINITY

    Energy Technology Data Exchange (ETDEWEB)

    Thomas C. Chidsey; Craig D. Morgan; Kevin McClure; Grant C. Willis

    2003-09-01

    Arizona. Outcrop analogs are found in the stratigraphically equivalent Navajo Sandstone of southern Utah which displays large-scale dunal cross-strata with excellent reservoir properties and interdunal features such as oases, wadi, and playa lithofacies with poor reservoir properties. Hydrocarbons in the Paradox Formation are stratigraphically trapped in carbonate buildups (or phylloid-algal mounds). Similar carbonate buildups are exposed in the Paradox along the San Juan River of southeastern Utah. Reservoir-quality porosity may develop in the types of facies associated with buildups such as troughs, detrital wedges, and fans, identified from these outcrops. When combined with subsurface geological and production data, these outcrop analogs can improve (1) development drilling and production strategies such as horizontal drilling, (2) reservoir-simulation models, (3) reserve calculations, and (4) design and implementation of secondary/tertiary oil recovery programs and other best practices used in the oil fields of Utah and vicinity. During this quarter, technology transfer activities consisted of exhibiting the project plans, objectives, and products at a booth at the 2003 annual convention of the American Association of Petroleum Geologists. The project home page was updated on the Utah Geological Survey Internet web site.

  17. Electrochemically assisted localized etching of ZnO single crystals in water using a catalytically active Pt-coated atomic force microscopy probe

    Science.gov (United States)

    Shibata, Takayuki; Yamamoto, Kota; Sasano, Junji; Nagai, Moeto

    2017-09-01

    This paper presents a nanofabrication technique based on the electrochemically assisted chemical dissolution of zinc oxide (ZnO) single crystals in water at room temperature using a catalytically active Pt-coated atomic force microscopy (AFM) probe. Fabricated grooves featured depths and widths of several tens and several hundreds of nanometers, respectively. The material removal rate of ZnO was dramatically improved by controlling the formation of hydrogen ions (H+) on the surface of the catalytic Pt-coated probe via oxidation of H2O molecules; this reaction can be enhanced by applying a cathodic potential to an additional Pt-wire working electrode in a three-electrode configuration. Consequently, ZnO can be dissolved chemically in water as a soluble Zn2+ species via a reaction with H+ species present in high concentrations in the immediate vicinity of the AFM tip apex.

  18. Tritium levels in milk in the vicinity of chronic tritium releases.

    Science.gov (United States)

    Le Goff, P; Guétat, Ph; Vichot, L; Leconte, N; Badot, P M; Gaucheron, F; Fromm, M

    2016-01-01

    Tritium is the radioactive isotope of hydrogen. It can be integrated into most biological molecules. Even though its radiotoxicity is weak, the effects of tritium can be increased following concentration in critical compartments of living organisms. For a better understanding of tritium circulation in the environment and to highlight transfer constants between compartments, we studied the tritiation of different agricultural matrices chronically exposed to tritium. Milk is one of the most frequently monitored foodstuffs in the vicinity of points known for chronic release of radionuclides firstly because dairy products find their way into most homes but also because it integrates deposition over large areas at a local scale. It is a food which contains all the main nutrients, especially proteins, carbohydrates and lipids. We thus studied the tritium levels of milk in chronic exposure conditions by comparing the tritiation of the main hydrogenated components of milk, first, component by component, then, sample by sample. Significant correlations were found between the specific activities of drinking water and free water of milk as well as between the tritium levels of cattle feed dry matter and of the main organic components of milk. Our findings stress the importance of the metabolism on the distribution of tritium in the different compartments. Overall, dilution of hydrogen in the environmental compartments was found to play an important role dimming possible isotopic effects even in a food chain chronically exposed to tritium. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Atomic arias

    Science.gov (United States)

    Crease, Robert P.

    2009-01-01

    The American composer John Adams uses opera to dramatize controversial current events. His 1987 work Nixon in China was about the landmark meeting in 1972 between US President Richard Nixon and Chairman Mao Zedong of China; The Death of Klinghoffer (1991) was a musical re-enactment of an incident in 1985 when Palestinian terrorists kidnapped and murdered a wheelchair-bound Jewish tourist on a cruise ship. Adams's latest opera, Doctor Atomic, is also tied to a controversial event: the first atomic-bomb test in Alamogordo, New Mexico, on 16 June 1945. The opera premièred in San Francisco in 2005, had a highly publicized debut at the Metropolitan Opera in New York in 2008, and will have another debut on 25 February - with essentially the same cast - at the English National Opera in London.

  20. Atomic rivals

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmidt, B.

    1990-01-01

    This book is a memoir of rivalries among the Allies over the bomb, by a participant and observer. Nuclear proliferation began in the uneasy wartime collaboration of the United States, England, Canada, and Free France to produce the atom bomb. Through the changes of history, a young French chemist had a role in almost every act of this international drama. This memoir is based on Goldschmidt's own recollections, interviews with other leading figures, and 3,000 pages of newly declassified documents in Allied archives. From his own start as Marie Curie's lab assistant, Goldschmidt's career was closely intertwined with Frances complicated rise to membership in the nuclear club. As a refugee from the Nazis, he became part of the wartime nuclear energy project in Canada and found himself the only French scientist to work (although briefly) on the American atom bomb project.

  1. Monitoring the ordering in biomolecular films on vicinal silicon surfaces by reflectance difference/anisotropy spectroscopy

    Science.gov (United States)

    Silaghi, Simona D.; Zahn, Dietrich R. T.

    2006-05-01

    DNA base molecules, adenine, thymine, guanine, and cytosine may be employed as charge transport molecules in biomolecular electronic devices. Their electronic properties are comparable with those of inorganic wide bandgap materials, e.g. GaN with the absorption onset in the near ultra-violet (UV) range. A recent field effect transistor study based on a modified DNA base revealed that the prototype bio-transistor gives rise to a better voltage gain compared to one based on carbon nanotubes (CNTs) [G. Mauricio, P. Visconti, V. Arima, S. D'Amico, A. Biasco, E. D'Amone, R. Cingolani, R. Rinaldi, Nanoletters 3 (2003) 479]. Here, in situ reflectance difference/anisotropy spectroscopy (RDS/RAS) is employed under ultra-high vacuum (UHV) conditions for monitoring the growth of DNA base molecules on vicinal hydrogen passivated Si(1 1 1) surfaces. Such vicinal substrates consisting of steps and terraces may serves as suitable templates for molecular ordering. Indeed, RDS/RAS measurements reveal information about molecular ordering of DNA bases induced by the density of steps on silicon surfaces. All four molecules, however, behave differently on the vicinal substrates. The first transition dipole moments corresponding to adenine and thymine molecules align mainly perpendicular to the step edge direction while for guanine and cytosine they align parallel to this direction, however, only in very thin layers. The RDS/RAS signal of the guanine and cytosine layers with thicknesses above 20 nm saturates due to a loss of ordering at higher coverages. Additionally, time-resolved RDS/RAS measurements at the silicon E 2 (4.25 eV) critical point (CP) demonstrate the sensitivity to the biomolecular/inorganic interface formation.

  2. NMR study of borohydrides for hydrogen storage applications

    Science.gov (United States)

    Shane, David Timothy

    There is great interest today in developing a hydrogen economy, and hydrogen powered vehicles to replace vehicles powered by fossil fuels. This presents many challenges for researchers, and one of the biggest is developing materials that could be used to store the hydrogen on-vehicle. We used nuclear magnetic resonance to study the atomic motions in many hydrogen storage materials, including sodium magnesium hydride, lithium borohydride, and magnesium borohydride. We also examined the effects of nanoscaffold incorporation on the latter two materials.

  3. Production and detection of cold antihydrogen atoms

    CERN Multimedia

    Amoretti, M; Bonomi, G; Bouchta, A; Bowe, P; Carraro, C; Cesar, C L; Charlton, M; Collier, M; Doser, Michael; Filippini, V; Fine, K S; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Holzscheiter, M H; Jørgensen, L V; Lagomarsino, V; Landua, Rolf; Landua, Rolf; Lindelöf, D; Lodi-Rizzini, E; Macri, M; Madsen, N; Manuzio, G; Marchesotti, M; Montagna, P; Pruys, H S; Regenfus, C; Riedler, P; Rochet, J; Rotondi, A; Rouleau, G; Testera, G; Van der Werf, D P; Variola, A; Watson, T L; CERN. Geneva

    2002-01-01

    A theoretical underpinning of the standard model of fundamental particles and interactions is CPT invariance, which requires that the laws of physics be invariant under the combined discrete operations of charge conjugation, parity and time reversal. Antimatter, the existence of which was predicted by Dirac, can be used to test the CPT theorem experimental investigations involving comparisons of particles with antiparticles are numerous. Cold atoms and anti-atoms, such as hydrogen and anti-hydrogen, could form the basis of a new precise test, as CPT invariance implies that they must have the same spectrum. Observations of antihydrogen in small quantities and at high energies have been reported at the European Organization for Nuclear Research (CERN) and at Fermilab, but were not suited to precision comparison measurements. Here we demonstrate the production of antihydrogen atoms at very low energy by mixing trapped antiprotons and positrons in a cryogenic environment. The neutral anti-atoms have been detected...

  4. Fabrication method for a room temperature hydrogen sensor

    Science.gov (United States)

    Seal, Sudipta (Inventor); Shukla, Satyajit V. (Inventor); Ludwig, Lawrence (Inventor); Cho, Hyoung (Inventor)

    2011-01-01

    A sensor for selectively determining the presence and measuring the amount of hydrogen in the vicinity of the sensor. The sensor comprises a MEMS device coated with a nanostructured thin film of indium oxide doped tin oxide with an over layer of nanostructured barium cerate with platinum catalyst nanoparticles. Initial exposure to a UV light source, at room temperature, causes burning of organic residues present on the sensor surface and provides a clean surface for sensing hydrogen at room temperature. A giant room temperature hydrogen sensitivity is observed after making the UV source off. The hydrogen sensor of the invention can be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently used at room temperature.

  5. Major Oil Plays in Utah and Vicinity

    Energy Technology Data Exchange (ETDEWEB)

    Thomas C. Chidsey; Craig D. Morgan; Kevin McClure; Douglas A. Sprinkel; Roger L. Bon; Hellmut H. Doelling

    2003-12-31

    fractured and sealed by overlying argillaceous and non-fractured units. The best outcrop analogs for Twin Creek reservoirs are found at Devils Slide and near the town of Peoa, Utah, where fractures in dense, homogeneous non-porous limestone beds are in contact with the basal siltstone units (containing sealed fractures) of the overlying units. The shallow marine, Mississippian Leadville Limestone is a major oil and gas reservoir in the Paradox Basin of Utah and Colorado. Hydrocarbons are produced from basement-involved, northwest-trending structural traps with closure on both anticlines and faults. Excellent outcrops of Leadville-equivalent rocks are found along the south flank of the Uinta Mountains, Utah. For example, like the Leadville, the Mississippian Madison Limestone contains zones of solution breccia, fractures, and facies variations. When combined with subsurface geological and production data, these outcrop analogs can improve (1) development drilling and production strategies such as horizontal drilling, (2) reservoir-simulation models, (3) reserve calculations, and (4) design and implementation of secondary/tertiary oil recovery programs and other best practices used in the oil fields of Utah and vicinity. In the southern Green River Formation play of the Uinta Basin, optimal drilling, development, and production practices consist of: (1) owning drilling rigs and frac holding tanks; (2) perforating sandstone beds with more than 8 percent neutron porosity and stimulate with separate fracture treatments; (3) placing completed wells on primary production using artificial lift; (4) converting wells relatively soon to secondary waterflooding maintaining reservoir pressure above the bubble point to maximize oil recovery; (5) developing waterflood units using an alternating injector--producer pattern on 40-acre (16-ha) spacing; and (6) recompleting producing wells by perforating all beds that are productive in the waterflood unit. As part of technology transfer

  6. Hydrogen Storage in Single-Walled Carbon Nanotubes at Room Temperature

    National Research Council Canada - National Science Library

    C. Liu; Y. Y. Fan; M. Liu; H. T. Cong; H. M. Cheng; M. S. Dresselhaus

    1999-01-01

    .... A hydrogen storage capacity of 4.2 weight percent, or a hydrogen to carbon atom ratio of 0.52, was achieved reproducibly at room temperature under a modestly high pressure (about 10 megapascal...

  7. (R,R-Disynephrine ether bis(hydrogen sulfate

    Directory of Open Access Journals (Sweden)

    William Arbuckle

    2009-08-01

    Full Text Available The asymmetric unit of the title compound [systematic name: (R,R-2,4-bis(4-hydroxyphenyl-N,N′-dimethyl-3-oxapentane-1,5-diammonium bis(hydrogen sulfate], C18H26N2O32+·2HSO4−, contains one half-cation and one hydrogen sulfate anion. The cation has crystallographically imposed twofold symmetry with the rotation axis passing through the central ether O atom. Hydrogen bonds between the hydroxy group and amine H atoms of the cation to two hydrogen sulfate anions link the three ions in a ring motif. A three-dimensional network is accomplished by additional O—H...O hydrogen bonds between the anions and by N—H...O hydrogen bonds between the cations. Disorder with equally occupied sites affects the H-atom position in the anion.

  8. Atomic energy levels and Grotrian diagrams

    CERN Document Server

    Bashkin, Stanley

    1975-01-01

    Atomic Energy Levels and Grotrian Diagrams, Volume I: Hydrogen I - Phosphorus XV presents diagrams of various elements that show their energy level and electronic transitions. The book covers the first 15 elements according to their atomic number. The text will be of great use to researchers and practitioners of fields such as astrophysics that requires pictorial representation of the energy levels and electronic transitions of elements.

  9. Hydrogen-based electrochemical energy storage

    Science.gov (United States)

    Simpson, Lin Jay

    2013-08-06

    An energy storage device (100) providing high storage densities via hydrogen storage. The device (100) includes a counter electrode (110), a storage electrode (130), and an ion conducting membrane (120) positioned between the counter electrode (110) and the storage electrode (130). The counter electrode (110) is formed of one or more materials with an affinity for hydrogen and includes an exchange matrix for elements/materials selected from the non-noble materials that have an affinity for hydrogen. The storage electrode (130) is loaded with hydrogen such as atomic or mono-hydrogen that is adsorbed by a hydrogen storage material such that the hydrogen (132, 134) may be stored with low chemical bonding. The hydrogen storage material is typically formed of a lightweight material such as carbon or boron with a network of passage-ways or intercalants for storing and conducting mono-hydrogen, protons, or the like. The hydrogen storage material may store at least ten percent by weight hydrogen (132, 134) at ambient temperature and pressure.

  10. PubChem atom environments.

    Science.gov (United States)

    Hähnke, Volker D; Bolton, Evan E; Bryant, Stephen H

    2015-01-01

    Atom environments and fragments find wide-spread use in chemical information and cheminformatics. They are the basis of prediction models, an integral part in similarity searching, and employed in structure search techniques. Most of these methods were developed and evaluated on the relatively small sets of chemical structures available at the time. An analysis of fragment distributions representative of most known chemical structures was published in the 1970s using the Chemical Abstracts Service data system. More recently, advances in automated synthesis of chemicals allow millions of chemicals to be synthesized by a single organization. In addition, open chemical databases are readily available containing tens of millions of chemical structures from a multitude of data sources, including chemical vendors, patents, and the scientific literature, making it possible for scientists to readily access most known chemical structures. With this availability of information, one can now address interesting questions, such as: what chemical fragments are known today? How do these fragments compare to earlier studies? How unique are chemical fragments found in chemical structures? For our analysis, after hydrogen suppression, atoms were characterized by atomic number, formal charge, implicit hydrogen count, explicit degree (number of neighbors), valence (bond order sum), and aromaticity. Bonds were differentiated as single, double, triple or aromatic bonds. Atom environments were created in a circular manner focused on a central atom with radii from 0 (atom types) up to 3 (representative of ECFP_6 fragments). In total, combining atom types and atom environments that include up to three spheres of nearest neighbors, our investigation identified 28,462,319 unique fragments in the 46 million structures found in the PubChem Compound database as of January 2013. We could identify several factors inflating the number of environments involving transition metals, with many

  11. Generation of the Ultracold Muonic Hydrogen Flux

    Energy Technology Data Exchange (ETDEWEB)

    Bystritsky, V. M. [Joint Institute for Nuclear Research (Russian Federation); Adamczak, A. [Institute of Nuclear Physics (Poland); Beer, G. A. [University of Victoria (Canada); Filipowicz, M. [Institute of Physics and Nuclear Techniques (Poland); Fujiwara, M. C. [University of Tokyo (Japan); Huber, T. M. [Gustavus Adolphus College (United States); Jacot-Guillarmod, R. [Universite de Fribourg (Switzerland); Kammel, P. [University of Illinois at Urbana-Champaign (United States); Kim, S. K. [Jeonbuk National University (Korea, Republic of); Knowles, P. [Universite de Fribourg (Switzerland); Kunselman, A. R. [University of Wyoming (United States); Maier, M. [University of Victoria (Canada); Markushin, V. E. [Paul Scherrer Institute (Switzerland); Marshall, G. M. [TRIUMF (Canada); Mulhauser, F. [Universite de Fribourg (Switzerland); Olin, A. [University of Victoria (Canada); Petitjean, C. [Paul Scherrer Institute (Switzerland); Porcelli, T. A. [University of Northen British Columbia (Canada); Stolupin, V. A. [Joint Institute for Nuclear Research (Russian Federation); Wozniak, J. [Institute of Physics and Nuclear Techniques (Poland)

    2001-12-15

    We present the study of {mu}p atom scattering in solid hydrogen. Anomalously large emission of E{sub p{mu}{<=}1}.9 meV {mu}p's from a solid H{sub 2} layer was observed for the first time. This three times greater {mu}p atom yield is due to non-elastic phonon scattering. As a result, it becomes possible to generate an ultracold flux of {mu}p atoms. The recent calculations of the total and differential cross sections agree with all experimental results of {mu}p atom scattering in solid H{sub 2}.

  12. Hydrogen program overview

    Energy Technology Data Exchange (ETDEWEB)

    Gronich, S. [Dept. of Energy, Washington, DC (United States). Office of Utility Technologies

    1997-12-31

    This paper consists of viewgraphs which summarize the following: Hydrogen program structure; Goals for hydrogen production research; Goals for hydrogen storage and utilization research; Technology validation; DOE technology validation activities supporting hydrogen pathways; Near-term opportunities for hydrogen; Market for hydrogen; and List of solicitation awards. It is concluded that a full transition toward a hydrogen economy can begin in the next decade.

  13. Infrared spectroscopy of one-dimensional metallic nanostructures on silicon vicinal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoang, Chung Vu

    2010-06-23

    Vicinal silicon(111) surfaces are used as templates for the growth of lead nanowires as well as gold and indium atom chains. The morphology of the Au atom chains was studied by use of Scanning Tunneling Microscopy (STM) and Reflection High Energy Electron Diffraction (RHEED). The In chains were investigated by infrared spectroscopy with the electrical field component of the IR light polarized either parallel or perpendicular to the wires. It is shown that at room temperature, In atom-chains display a plasmonic absorption feature along the chain but not in the perpendicular direction. Furthermore, upon cooling down to liquid nitrogen temperature, a metal to insulator transition is observed. A structural distortion is also confirmed by RHEED. As for the result of Pb nanowires, by means of infrared spectroscopy, it is now possible to control the average length of parallel nanowire arrays by monitoring four experimental parameters that influence on the nucleation density; namely: Pb coverage, evaporation rate, substrate temperature and the surface itself. The system shows an enhancement of the absorption at the antenna frequency in the low temperature regime. This scenario is assigned to the reduction of electron-phonon scattering due to low temperature. (orig.)

  14. Group V adsorbate structures on vicinal Ge(001) surfaces determined from the optical spectrum

    Science.gov (United States)

    Banerjee, S.; Patterson, C. H.; McGilp, J. F.

    2017-06-01

    Vicinal Ge(001) is the standard substrate for the fabrication of high-performance solar cells by metal-organic vapour phase epitaxy, where growth of the III-V material on single domain Ge surfaces, with a single dimer orientation, minimizes the formation of anti-phase domain defects. Reflectance anisotropy spectroscopy has proved to be a powerful and sensitive optical probe of such anisotropic surface structures, but moving beyond fingerprinting to atomic structure determination from the optical spectra has been held back by the high computational cost. It is shown that an empirical, local-orbital-based hybrid density functional theory approach produces very good agreement between the theory and the experiment for (2 × 1)-As and (2 × 1)-Sb structures grown on vicinal Ge(001). These results, when taken together with previous work on Si interfaces, show that this computationally efficient approach is likely to prove to be an important general technique for determining the structure of anisotropic semiconductor surfaces and interfaces by comparing the experimental and calculated optical spectrum.

  15. Nanoscale patterning, macroscopic reconstruction, and enhanced surface stress by organic adsorption on vicinal surfaces

    Science.gov (United States)

    Pollinger, Florian; Schmitt, Stefan; Sander, Dirk; Tian, Zhen; Kirschner, Jürgen; Vrdoljak, Pavo; Stadler, Christoph; Maier, Florian; Marchetto, Helder; Schmidt, Thomas; Schöll, Achim; Umbach, Eberhard

    2017-01-01

    Self-organization is a promising method within the framework of bottom-up architectures to generate nanostructures in an efficient way. The present work demonstrates that self-organization on the length scale of a few to several tens of nanometers can be achieved by a proper combination of a large (organic) molecule and a vicinal metal surface if the local bonding of the molecule on steps is significantly stronger than that on low-index surfaces. In this case thermal annealing may lead to large mass transport of the subjacent substrate atoms such that nanometer-wide and micrometer-long molecular stripes or other patterns are being formed on high-index planes. The formation of these patterns can be controlled by the initial surface orientation and adsorbate coverage. The patterns arrange self-organized in regular arrays by repulsive mechanical interactions over long distances accompanied by a significant enhancement of surface stress. We demonstrate this effect using the planar organic molecule PTCDA as adsorbate and Ag(10 8 7) and Ag(775) surfaces as substrate. The patterns are directly observed by STM, the formation of vicinal surfaces is monitored by high-resolution electron diffraction, the microscopic surface morphology changes are followed by spectro-microscopy, and the macroscopic changes of surface stress are measured by a cantilever bending method. The in situ combination of these complementary techniques provides compelling evidence for elastic interaction and a significant stress contribution to long-range order and nanopattern formation.

  16. Scanning Tunneling Microscopy Study of a Vicinal Anatase TiO2 Surface

    Science.gov (United States)

    Li, Shao-Chun; Dulub, Olga; Diebold, Ulrike

    2009-03-01

    Titanium dioxide finds versatile applications in various technical fields including gas sensing, coatings, pigments, heterogeneous catalysis, photocatalytic degradation of pollutants, and solar cells. TiO2 is found in three main crystallographic phases: rutile, anatase and brookite. Rutile is the thermodynamically most stable form and is considered a model system for basic research. However, anatase TiO2 is often considered to be catalytically more active than rutile for reasons not yet completely understood. In this work, using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED), the structure of the anatase TiO2(5 14) surface, ˜10 vicinal to the -- lowest energy -- (101) plane, has been studied. The surface was found to facet into a structure composed of ridges with a uniform width of 5 lattice units. Based on atomically-resolved STM and electron counting rules, it is proposed that the sides of the ridges are parallel to (1 10) and (112) planes. These sides might be reconstructed to stabilize the microfaceted structure. Vapor-deposited gold shows pronounced clustering between the ridges, indicating a one-dimensional template effect of the vicinal surface, which supports denser and more uniformly sized Au clusters, as compared to the flat (101) surface.

  17. Ionization of hydrogen and hydrogenic ions by antiprotons

    Science.gov (United States)

    Schultz, D. R.; Krstić, P. S.; Reinhold, C. O.; Wells, J. C.

    1996-05-01

    Motivated by earlier theoretical studies which utilized simplified models and by a very recent experiment regarding antiproton-impact of hydrogen, we present a description (D.R. Schultz, P.S. Krstić, C.O. Reinhold, and J.C. Wells, Phys. Rev. Lett. (1996) submitted.) of ionization of hydrogen and hydrogenic ions based on very large scale numerical solutions of the time-dependent Schrödinger equation in three spatial dimensions and on analysis of the topology of the electronic eigenenergy surfaces in the plane of complex internuclear distance. It is illustrated how ionization of atomic hydrogen and hydrogenic ions by antiprotons is quite different from that for impact by positively charged particles at low energies. Most significantly, for hydrogen targets, the quasi-molecular electronic eigenenergies approach close to and ultimately merge with the continuum at small distances, leading to a plateau of the low energy ionization cross section. Work supported by US DOE Office of BES through contract No. DE-AC05-84OR21400 managed by Lockheed Martin Energy Research Corp.

  18. Hydrogen usage

    Energy Technology Data Exchange (ETDEWEB)

    1942-10-22

    This short tabular report listed the number of m/sup 3/ of hydrogen required for a (metric) ton of product for various combinations of raw material and product in a hydrogenation procedure. In producing auto gasoline, bituminous coal required 2800 m/sup 3/, brown coal required 2400 m/sup 3/, high-temperature-carbonization tar required 2100 m/sup 3/, bituminous coal distillation tar required 1300 m/sup 3/, brown-coal low-temperature-carbonization tar required 850 m/sup 3/, petroleum residues required 900 m/sup 3/, and gas oil required 500 m/sup 3/. In producing diesel oil, brown coal required 1900 m/sup 3/, whereas petroleum residues required 500 m/sup 3/. In producing diesel oil, lubricants, and paraffin by the TTH (low-temperature-hydrogenation) process, brown-coal low-temperature-carbonization tar required 550 m/sup 3/. 1 table.

  19. Atom Skimmers and Atom Lasers Utilizing Them

    Science.gov (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  20. Nanostructured sapphire vicinal surfaces as templates for the growth of self-organized oxide nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Thune, E., E-mail: elsa.thune@unilim.fr [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France); Boulle, A. [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France); Babonneau, D.; Pailloux, F. [Laboratoire de Physique des Materiaux (PHYMAT), UMR CNRS 6630, Universite de Poitiers, Boulevard Marie et Pierre Curie - Teleport 2, BP 30179, F-86962 Futuroscope - Chasseneuil Cedex (France); Hamd, W.; Guinebretiere, R. [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France)

    2009-11-15

    Vicinal substrates of sapphire with miscut angle of 10 deg. from the (0 0 1) planes towards the [1 1 0] direction have been annealed in air in the range from 1000 to 1500 deg. C. The behaviour of these surfaces has been characterized as a function of the temperature and the thermal treatment time by Atomic Force Microscopy observations. A thermal treatment at 1250 deg. C allows to stabilize a surface made of periodically spaced nanosized step-bunches. Such stepped surfaces were used as template to grow self-patterned epitaxial oxide nanoparticles by thermal annealing of yttria-stabilized zirconia thin films produced by sol-gel dip-coating. Grazing Incidence Small Angle X-ray Scattering and High-Resolution Transmission Electron Microscopy were used to study the morphology of the nanoparticles and their epitaxial relationships with the substrate.