WorldWideScience

Sample records for atomic hydrogen gas

  1. Interaction of gas phase atomic hydrogen with Pt(111): Direct evidence for the formation of bulk hydrogen species

    Institute of Scientific and Technical Information of China (English)

    JIANG ZhiQuan; HUANG WeiXin; BAO XinHe

    2007-01-01

    Employing hot tungsten filament to thermal dissociate molecular hydrogen, we generated gas phase atomic hydrogen under ultra-high vacuum (UHV) conditions and investigated its interaction with Pt(111) surface. Thermal desorption spectroscopy (TDS) results demonstrate that adsorption of molecular hydrogen on Pt(111) forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species. Bulk Had species is more thermal-unstable than surface Had species on Pt(111), suggesting that bulk Had species is more energetic. This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions.

  2. Interaction of gas phase atomic hydrogen with Pt(111):Direct evidence for the formation of bulk hydrogen species

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Employing hot tungsten filament to thermal dissociate molecular hydrogen,we generated gas phase atomic hydrogen under ultra-high vacuum(UHV)conditions and investigated its interaction with Pt(111) surface.Thermal desorption spectroscopy(TDS)results demonstrate that adsorption of molecular hy- drogen on Pt(111)forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species.Bulk Had species is more thermal-unstable than surface Had species on Pt(111),suggesting that bulk Had species is more energetic.This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions.

  3. Catalysis by Single Atoms: Water Gas Shift and Ethylene Hydrogenation

    Science.gov (United States)

    2009-04-20

    This adsorbed oxygen reacts with methane leading to combustion or partial oxidation to syngas at lower temperatures than in the existing commercial...600 Energy (eV) 28 To test the accuracy of reported ZrB2 atomic composition, we analyzed a hot-pressed ZrB2 sample supplied by Ceradyne. Fig. 26(a...specimens. 50um Electron Imaae 1 (a) (b) Figure 26. Analysis of boron-enriched ZrB2 sample supplied by Ceradyne: (a) SEM image (b) EDS counts (c

  4. 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.

  5. Atomic Hydrogen Gas in Dark-Matter Minihalos and the Compact High Velocity Clouds

    CERN Document Server

    Sternberg, A; Wolfire, M G

    2002-01-01

    We calculate the coupled hydrostatic and ionization structures of pressure-supported gas clouds that are confined by gravitationally dominant dark-matter (DM) mini-halos and by an external bounding pressure provided by a hot medium. We focus on clouds that are photoionized and heated by the present-day background metagalactic field and determine the conditions for the formation of warm (WNM), and multi-phased (CNM/WNM) neutral atomic hydrogen (HI) cores in the DM-dominated clouds. We consider LCDM dark-matter halos, and we compute models for a wide range of halo masses, total cloud gas masses, and external bounding pressures. We present models for the pressure-supported HI structures observed in the Local Group dwarf galaxies Leo A and Sag DIG. We then construct minihalo models for the multi-phased (and low-metallicity) compact high-velocity HI clouds (CHVCs). If the CHVCs are drawn from the same family of halos that successfully reproduce the dwarf galaxy observations, then the CHVCs must be "circumgalactic ...

  6. Inside the Hydrogen Atom

    CERN Document Server

    Nowakowski, M; Fierro, D Bedoya; Manjarres, A D Bermudez

    2016-01-01

    We apply the non-linear Euler-Heisenberg theory to calculate the electric field inside the hydrogen atom. We will demonstrate that the electric field calculated in the Euler-Heisenberg theory can be much smaller than the corresponding field emerging from the Maxwellian theory. In the hydrogen atom this happens only at very small distances. This effect reduces the large electric field inside the hydrogen atom calculated from the electromagnetic form-factors via the Maxwell equations. The energy content of the field is below the pair production threshold.

  7. 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.

  8. Einstein's Hydrogen Atom

    CERN Document Server

    Kim, Y S

    2011-01-01

    In 1905, Einstein formulated his special relativity for point particles. For those particles, his Lorentz covariance and energy-momentum relation are by now firmly established. How about the hydrogen atom? It is possible to perform Lorentz boosts on the proton assuming that it is a point particle. Then what happens to the electron orbit? The orbit could go through an elliptic deformation, but it is not possible to understand this problem without quantum mechanics, where the orbit is a standing wave leading to a localized probability distribution. Is this concept consistent with Einstein's Lorentz covariance? Dirac, Wigner, and Feynman contributed important building blocks for understanding this problem. The remaining problem is to assemble those blocks to construct a Lorentz-covariant picture of quantum bound states based on standing waves. It is shown possible to assemble those building blocks using harmonic oscillators.

  9. 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...... the proposed reaction mechanism. The reaction was studied with the atomic reactant in slight excess at 298 K and a total pressure of 2 Torr. Two concurrent reaction channels: (1a) H+CH3NO2-->HONO+.CH3 and (1b) H+CH3NO2-->CH3NO+.OH were observed. The branching ratio, k1a/(k1a+k1b), is 0.7+/-0.2....

  10. Atomic hydrogen interaction with Ru(1010).

    Science.gov (United States)

    Vesselli, E; Comelli, G; Rosei, R

    2004-05-01

    The interaction of atomic hydrogen with clean and deuterium precovered Ru(1010) was studied by means of temperature-programmed desorption (TPD) spectroscopy. Compared to molecular hydrogen experiments, after exposure of the clean surface to gas-phase atomic hydrogen at 90 K, two additional peaks grow in the desorption spectra at 115 and 150 K. The surface saturation coverage, determined by equilibrium between abstraction and adsorption reactions, is 2.5 monolayers. Preadsorbed deuterium abstraction experiments with gas-phase atomic hydrogen show that a pure Eley-Rideal mechanism is not involved in the process, while a hot atom (HA) kinetics describes well the reaction. By least-squares fitting of the experimental data, a simplified HA kinetic model yields an abstraction cross section value of 0.5 +/- 0.2 angstroms2. The atomic hydrogen interaction with an oxygen precovered surface was also studied by means of both TPD and x-ray photoelectron spectroscopy: oxygen hydrogenation and water production take place already at very low temperature (90 K).

  11. The Star Formation Rate Efficiency of Neutral Atomic-dominated Hydrogen Gas in the Outskirts of Star Forming Galaxies from z~1 to z~3

    CERN Document Server

    Rafelski, Marc; 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~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~1, z~2, and z~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 HI gas at z>1 is ~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...

  12. 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}.

  13. Bose-Einstein condensation of atomic hydrogen

    NARCIS (Netherlands)

    Willmann, L

    1999-01-01

    The recent creation of a Bose-Einstein condensate of atomic hydrogen has added a new system to this exciting field, The differences between hydrogen and the alkali metal atoms require other techniques for the initial trapping and cooling of the atoms and the subsequent detection of the condensate. T

  14. Highly regioselective hydride transfer, oxidative dehydrogenation, and hydrogen-atom abstraction in the thermal gas-phase chemistry of [Zn(OH)](+)/C3H8.

    Science.gov (United States)

    Wu, Xiao-Nan; Zhao, Hai-Tao; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2014-12-28

    The thermal reactions of [Zn(OH)](+) with C3H8 have been studied by means of gas-phase experiments and computational investigation. Two types of C-H bond activation are observed in the experiment, and pertinent mechanistic features include inter alia: (i) the metal center of [Zn(OH)](+) serves as active site in the hydride transfer to generate [i-C3H7](+) as major product, (ii) generally, a high regioselectivity is accompanied by remarkable chemoselectivity: for example, the activation of a methyl C-H bond results mainly in the formation of water and [Zn(C3,H7)](+). According to computational work, this ionic product corresponds to [HZn(CH3CH=CH2)](+). Attack of the zinc center at a secondary C-H bond leads preferentially to hydride transfer, thus giving rise to the generation of [i-C3H7](+); (iii) upon oxidative dehydrogenation (ODH), liberation of CH3CH2=CH2 occurs to produce [HZn(H2O)](+). Both, ODH as well as H2O loss proceed through the same intermediate which is characterized by the fact that a methylene hydrogen atom from the substrate is transferred to the zinc and one hydrogen atom from the methyl group to the OH group of [Zn(OH)](+). The combined experimental/computational gas-phase study of C-H bond activation by zinc hydroxide provides mechanistic insight into related zinc-catalyzed large-scale processes and identifies the crucial role that the Lewis-acid character of zinc plays.

  15. 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.

  16. Hydrogen atom temperature measured with wavelength-modulated laser absorption spectroscopy in large scale filament arc negative hydrogen ion source

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, H., E-mail: nakano@nifs.ac.jp; Goto, M.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 5095292 (Japan); Nishiyama, S.; Sasaki, K. [Graduate school of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo 0608628 (Japan)

    2015-04-08

    The velocity distribution function of hydrogen atoms is one of the useful parameters to understand particle dynamics from negative hydrogen production to extraction in a negative hydrogen ion source. Hydrogen atom temperature is one of the indicators of the velocity distribution function. To find a feasibility of hydrogen atom temperature measurement in large scale filament arc negative hydrogen ion source for fusion, a model calculation of wavelength-modulated laser absorption spectroscopy of the hydrogen Balmer alpha line was performed. By utilizing a wide range tunable diode laser, we successfully obtained the hydrogen atom temperature of ∼3000 K in the vicinity of the plasma grid electrode. The hydrogen atom temperature increases as well as the arc power, and becomes constant after decreasing with the filling of hydrogen gas pressure.

  17. 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...

  18. Observation of Atomic Steps on Vicinal Si(111) Annealed in Hydrogen Gas Flow by Scanning Tunneling Microscopy

    Science.gov (United States)

    Kitahara, Kuninori; Ueda, Osamu

    1993-12-01

    The surface of vicinal Si(111) annealed in H2 flow was observed by equipping the chemical vapor deposition chamber with the scanning tunneling microscope. Samples were annealed at 1000°C for 10 min by passing an electric current under the H2 pressure of 7 Torr. Their surface morphology was compared with those annealed in ultrahigh vacuum (UHV) and in N2 flow at the same temperature. We found that the step motion during annealing in H2 was obviously smaller than that for annealing in UHV and N2. The multisteps formed during the annealing in UHV and N2 were not observed for H2 annealing except in the case of heating by direct current in the direction of lower to higher terraces. The mechanism of the interruption of the step motion is discussed from the viewpoint of the interaction between the surface and hydrogen.

  19. Muonium/muonic hydrogen formation in atomic hydrogen

    Indian Academy of Sciences (India)

    V S Kulhar

    2004-09-01

    The muonium/muonic hydrogen atom formation in ± –H collisions is investigated, 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 + –H collision. Muonic hydrogen atom formation cross-sections in - –H collision are found to be significant in a narrow range of energy (5 eV–25 eV).

  20. Solid Hydrogen Formed for Atomic Propellants

    Science.gov (United States)

    Palaszewski, Bryan A.

    2000-01-01

    Several experiments on the formation of solid hydrogen particles in liquid helium were recently conducted at the NASA Glenn Research Center at Lewis Field. The solid hydrogen experiments are the first step toward seeing these particles and determining their shape and size. The particles will ultimately store atoms of boron, carbon, or hydrogen, forming an atomic propellant. Atomic propellants will allow rocket vehicles to carry payloads many times heavier than possible with existing rockets or allow them to be much smaller and lighter. Solid hydrogen particles are preferred for storing atoms. Hydrogen is generally an excellent fuel with a low molecular weight. Very low temperature hydrogen particles (T < 4 K) can prevent the atoms from recombining, making it possible for their lifetime to be controlled. Also, particles that are less than 1 mm in diameter are preferred because they can flow easily into a pipe when suspended in liquid helium. The particles and atoms must remain at this low temperature until the fuel is introduced into the engine combustion (or recombination) chamber. Experiments were, therefore, planned to look at the particles and observe their formation and any changes while in liquid helium.

  1. The Unique Gas-Phase Chemistry of the [AuO](+) /CH4 Couple: Selective Oxygen-Atom Transfer to, Rather than Hydrogen-Atom Abstraction from, Methane.

    Science.gov (United States)

    Zhou, Shaodong; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2016-08-26

    The thermal reaction of [AuO](+) with methane has been explored using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. In contrast to the previously studied congener [CuO](+) , and to [AgO](+) , [AuO](+) reacts with CH4 exclusively via oxygen-atom transfer to form CH3 OH, and a novel mechanistic scenario for this selective oxidation process has been revealed. Also, the origin of the inertness of the [AgO](+) /CH4 couple has been addressed computationally.

  2. Atomic hydrogen as a launch vehicle propellant

    Energy Technology Data Exchange (ETDEWEB)

    Palaszewski, B.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.

  3. 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.

  4. 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.

  5. Atomic hydrogen at high redshift

    NARCIS (Netherlands)

    Briggs, FH; Rickman, H

    2002-01-01

    After the production of the ionizing background by the first generation of stars, neutral gas must be confined to sufficiently high density to be self-shielding and remain neutral. Neutral gas is an identifier of the presence of confining gravitational potentials and a tracer of the kinematics of th

  6. Software for Hydrogenic Atoms and Orbitals Visualization

    Directory of Open Access Journals (Sweden)

    Kowit KITTIWUTTHISAKDI

    2005-06-01

    Full Text Available A program was developed in java for hydrogenic atoms and orbitals visualization. The first 18 atoms in the periodic table were approximated with a hydrogenic wave-function. This simple hydrogenic wave-function allowed quick calculation for real-time interactive visualization. Electron cloud based models were employed and displayed by a ray-tracing technique. One or more orbitals that defined an atom could be selected and displayed. A user could zoom in, zoom out, and rotate the displayed cloud in real time. The approximation method for probability integrals was summation. The intensity of color at each point on the screen directly related to the integrated probability in finding the electron across the viewer%s eye path.

  7. How solvent modulates hydroxyl radical reactivity in hydrogen atom abstractions.

    Science.gov (United States)

    Mitroka, Susan; Zimmeck, Stephanie; Troya, Diego; Tanko, James M

    2010-03-10

    The hydroxyl radical (HO*) is a highly reactive oxygen-centered radical whose bimolecular rate constants for reaction with organic compounds (hydrogen atom abstraction) approach the diffusion-controlled limit in aqueous solution. The results reported herein show that hydroxyl radical is considerably less reactive in dipolar, aprotic solvents such as acetonitrile. This diminished reactivity is explained on the basis of a polarized transition state for hydrogen abstraction, in which the oxygen of the hydroxyl radical becomes highly negative and can serve as a hydrogen bond acceptor. Because acetonitrile cannot participate as a hydrogen bond donor, the transition state cannot be stabilized by hydrogen bonding, and the reaction rate is lower; the opposite is true when water is the solvent. This hypothesis explains hydroxyl radical reactivity both in solution and in the gas phase and may be the basis for a "containment strategy" used by Nature when hydroxyl radical is produced endogenously.

  8. 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

  9. Bose-Einstein Condensation of Atomic Hydrogen

    CERN Document Server

    Kleppner, D; Killian, T C; Fried, D G; Willmann, L; Landhuis, D; Moss, S C; Kleppner, Daniel; Greytak, Thomas J.; Killian, Thomas C.; Fried, Dale G.; Willmann, Lorenz; Landhuis, David; Moss, Stephen C.

    1998-01-01

    We have observed Bose-Einstein condensation (BEC) of trapped atomic hydrogen, and studied it by two-photon spectroscopy of the 1S-2S transition. In these lecture notes we briefly review the history of spin-polarized atomic hydrogen and describe the final steps to BEC. Laser spectroscopy, which probes the difference in mean field energy of the 1S and 2S states, is used to study the condensate, which has a peak density of 4.8e15 cm^-3 and population of 10^9.

  10. Quantum Structures of the Hydrogen Atom

    CERN Document Server

    Jeknic-Dugic, J; Francom, A; Arsenijevic, M

    2012-01-01

    Modern quantum theory introduces quantum structures (decompositions into subsystems) as a new discourse that is not fully comparable with the classical-physics counterpart. To this end, so-called Entanglement Relativity appears as a corollary of the universally valid quantum mechanics that can provide for a deeper and more elaborate description of the composite quantum systems. In this paper we employ this new concept to describe the hydrogen atom. We offer a consistent picture of the hydrogen atom as an open quantum system that naturally answers the following important questions: (a) how do the so called "quantum jumps" in atomic excitation and de-excitation occur? and (b) why does the classically and seemingly artificial "center-of-mass + relative degrees of freedom" structure appear as the primarily operable form in most of the experimental reality of atoms?

  11. Effect of atomization gas pressure variation on gas flow field in supersonic gas atomization

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper, a computational fluid flow model was adopted to investigate the effect of varying atomization gas pressure (P0) on the gas flow field in supersonic gas atomization. The influence of P0 on static pressure and velocity magnitude of the central axis of the flow field was also examined. The numerical results indicate that the maximum gas velocity within the gas field increases with increasing P0. The aspiration pressure (ΔP) is found to decrease as P0 increases at a lower atomization gas pressure. However, at a higher atomization gas pressure increasing P0 causes the opposite: the higher atomization gas pressure, the higher aspiration pressure. The alternation of ΔP is caused by the variations of stagnation point pressure and location of Mach disk, while hardly by the location of stagnation point. A radical pressure gradient is formed along the tip of the delivery tube and increases as P0 increases.

  12. Hydrogen Atom Spectrum in Noncommutative Phase Space

    Institute of Scientific and Technical Information of China (English)

    LI Kang; CHAMOUN Nidal

    2006-01-01

    @@ We study the energy levels of the hydrogen atom in the noncommutative phase space with simultaneous spacespace and momentum-momentum noncommutative relations. We find new terms compared to the case that only noncommutative space-space relations are assumed. We also present some comments on a previous paper [Alavi S A hep-th/0501215].

  13. 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.

  14. Mechanistic aspects of gas-phase hydrogen-atom transfer from methane to [CO](·+) and [SiO](·+) : why do they differ?

    Science.gov (United States)

    Dietl, Nicolas; Troiani, Anna; Schlangen, Maria; Ursini, Ornella; Angelini, Giancarlo; Apeloig, Yitzhak; de Petris, Giulia; Schwarz, Helmut

    2013-05-17

    The reactivity of the two diatomic congeneric systems [CO](·+) and [SiO](·+) towards methane has been investigated by means of mass spectrometry and quantum-chemical calculations. While [CO](·+) gives rise to three different reaction channels, [SiO](·+) reacts only by hydrogen-atom transfer (HAT) from methane under thermal conditions. A theoretical analysis of the respective HAT processes reveals two distinctly different mechanistic pathways for [CO](·+) and [SiO](·+), and a comparison to the higher metal oxides of Group 14 emphasizes the particular role of carbon as a second-row p element.

  15. 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.

  16. Device removes hydrogen gas from enclosed spaces

    Science.gov (United States)

    Carson, W. N.

    1966-01-01

    Hydrogen-oxidant galvanic cell removes small amounts of hydrogen gas continually released from equipment, such as vented silver-zinc batteries, in enclosed compartments where air venting is not feasible. These cells are used in satellite compartments.

  17. Atomic hydrogen behaviour in Heliotron E

    Energy Technology Data Exchange (ETDEWEB)

    Muraoka, K.; Uchino, K.; Kajiwara, T.; Matsuo, K.; Honda, C.; Suehiro, Y.; Yano, N.; Takeda, K.; Hagiwara, H.; Akazaki, M. (Kyushu Univ., Fukuoka (Japan). Dept. of Energy Conversion); Maeda, M.; Okada, T. (Kyushu Univ., Fukuoka (Japan). Dept. of Electrical Engineering); Sudo, S.; Kondo, K.; Mizuuchi, T.; Sano, F.; Sato, M.; Zushi, H.; Obiki, T. (Kyoto Univ., Uji (Japan). Plasma Physics Lab.); Matsuura, H. (Osaka Prefectural Univ., Sakai (Japan). Dept. of Mechanical Engineering)

    1990-12-01

    In order to understand atomic hydrogen behaviour and particle confinement properties in Heliotron E plasmas, techniques of laser induced fluorescence (LIF) have been extensively used, combined with measurements of absolute Balmer alpha emissions and density fluctuations. The results revealed that for an average electron density anti n{sub e}>1.5x10{sup 19} m{sup -3}, H{alpha} fluorescence allowed the measurements of atomic hydrogen densities and yielded the recycled Franck-Condon neutrals ({approx equal} 3 eV) to penetrate into core plasmas, whereas for anti n{sub e}<1.0x10{sup 19} m{sup -3}, such measurements were perturbed by dissociative-excitation of H{sub 2} molecules into the n=2 state. Also, the global confinement times showed a clear correlation with electron density fluctuations. (orig.).

  18. Hydrogen atom in a Laser-Plasma

    CERN Document Server

    Falaye, Babatunde James; Liman, Muhammed S; Oyewumi, K J; Dong, Shi-Hai

    2016-01-01

    We scrutinize the behaviour of hydrogen atom's eigenvalues in a quantum plasma as it interacts with electric field directed along $\\theta=\\pi$ and exposed to linearly polarized intense laser field radiation. Using the Kramers-Henneberger (KH) unitary transformation, which is semiclassical counterpart of the Block-Nordsieck transformation in the quantized field formalism, the squared vector potential that appears in the equation of motion is eliminated and the resultant equation is expressed in KH frame. Within this frame, the resulting potential and the corresponding wavefunction have been expanded in Fourier series and using Ehlotzky's approximation, we obtain a laser-dressed potential to simulate intense laser field. By fitting the exponential-cosine-screened Coulomb potential into the laser-dressed potential, and then expanding it in Taylor series up to $\\mathcal{O}(r^4,\\alpha_0^9)$, we obtain the eigensolution (eigenvalues and wavefunction) of hydrogen atom in laser-plasma encircled by electric field, wit...

  19. Solid Hydrogen Experiments for Atomic Propellants

    Science.gov (United States)

    Palaszewski, Bryan

    2001-01-01

    This paper illustrates experiments that were conducted on the formation of solid hydrogen particles in liquid helium. Solid particles of hydrogen were frozen in liquid helium, and observed with a video camera. The solid hydrogen particle sizes, their molecular structure transitions, and their agglomeration times were estimated. article sizes of 1.8 to 4.6 mm (0.07 to 0. 18 in.) were measured. The particle agglomeration times were 0.5 to 11 min, depending on the loading of particles in the dewar. These experiments are the first step toward visually characterizing these particles, and allow designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  20. 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....

  1. Solid H2 versus solid noble-gas environment: Influence on photoinduced hydrogen-atom transfer in matrix-isolated 4(3H)-pyrimidinone

    Science.gov (United States)

    Lapinski, Leszek; Nowak, Maciej J.; Rostkowska, Hanna

    2017-03-01

    UV-induced transformations have been studied for 4(3H)-pyrimidinone monomers isolated in low-temperature Ar, Ne, n-D2, and n-H2 matrices. The observed photochemical behavior of the compound drastically depended on the solid matrix environment. For 4(3H)-pyrimidinone isolated in solid Ar, the UV-induced phototautomeric transformation was clearly the dominating process, leading to a nearly quantitative conversion of the oxo reactant into the hydroxy product. For solid Ne environment, the oxo → hydroxy transformation was still the major photoprocess, but yielding less of the hydroxy product (ca. 64% of the yield in solid Ar). For 4(3H)-pyrimidinone isolated in solid n-H2, the oxo → hydroxy phototautomeric conversion did not occur (or occurred at a very tiny scale). Also for deuterated 4(3D)-pyrimidinone isolated in solid hydrogen, the analogous oxo → deuteroxy phototransformation was not observed. Finally, for the compound trapped in solid n-D2, the oxo → hydroxy phototautomerism clearly occurred, but the yield of the hydroxy tautomer was small (ca. 18% of the yield in solid Ar). Apart from hydrogen-atom-transfer processes, two other phototransformations: generation of open-ring conjugated ketene and valence Dewar isomer were observed for the compound isolated in Ar, Ne, n-D2, and n-H2 matrices.

  2. Absorption spectrum of very low pressure atomic hydrogen

    CERN Document Server

    Moret-Bailly, Jacques

    2015-01-01

    Spectra of quasars result primarily from interactions of natural light with atomic hydrogen. A visible absorption of a sharp and saturated spectral line in a gas requires a low pressure, so a long path without blushing as a cosmological redshift. Burbidge and Karlsson observed that redshifts of quasars result from fundamental redshifts, written 3K and 4K, that cause a shift of absorbed beta and gamma lines of H to alpha gas line. Thus absorbed spectrum is shifted until an absorbed line overlaps with Lyman alpha line of gas: redshift only occurs if an alpha absorption pumps atoms to 2P state. Thus, space is divided into spherical shells centered on the quasar, containing or not 2P atoms. Neglecting collisional de-excitations in absorbing shells, more and more atoms are excited until amplification of a beam having a long path in a shell, thus perpendicular to the observed ray, is large enough for a superradiant flash at alpha frequency. Energy is provided by atoms and observed ray, absorbing a line at local Lym...

  3. Classical theory of the hydrogen atom

    CERN Document Server

    Rashkovskiy, Sergey

    2016-01-01

    It is shown that all of the basic properties of the hydrogen atom can be consistently described in terms of classical electrodynamics instead of taking the electron to be a particle; we consider an electrically charged classical wave field, an "electron wave", which is held in a limited region of space by the electrostatic field of the proton. It is shown that quantum mechanics must be considered to be not a theory of particles but 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 interpre...

  4. Discrete wave mechanics: The hydrogen atom.

    Science.gov (United States)

    Wall, F T

    1986-08-01

    The quantum mechanical problem of the hydrogen atom is treated by use of a finite difference equation in place of Schrödinger's differential equation. The exact solution leads to a wave vector energy expression that is readily converted to the Bohr-Rydberg formula. (The calculations here reported are limited to spherically symmetric states.) The wave vectors reduce to the familiar solutions of Schrödinger's equation as c --> infinity. The internal consistency and limiting behavior provide support for the view that the equations employed could well constitute an approach to a relativistic formulation of wave mechanics.

  5. Ionization in collisions between metastable hydrogen atoms

    Science.gov (United States)

    Bohr, Alex; Blickle, Andrew; Paolini, Stephen; Ohlinger, Luke; Forrey, Robert

    2012-06-01

    Associative and Penning ionization cross sections are calculated for collisions between metastable hydrogen 2s atoms at thermal energies. Cross sections for deuterium 2s collisions are also reported. The associative ionization cross sections behave as E-1 for collision energy E, in agreement with an existing experiment. The Penning ionization cross sections dominate for all energies and are found to follow the E-2/3 behavior that was predicted in previous work for the total ionization cross section. The magnitudes of our theoretical associative ionization cross sections for H(2s)+H(2s) collisions are between two and four times larger than the experimental data.

  6. ATOMIC HYDROGEN IN A GALACTIC CENTER OUTFLOW

    Energy Technology Data Exchange (ETDEWEB)

    McClure-Griffiths, N. M.; Green, J. A.; Hill, A. S. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Marsfield, NSW 2122 (Australia); Lockman, F. J. [National Radio Astronomy Observatory, Green Bank, WV 24944 (United States); Dickey, J. M. [School of Physics and Mathematics, University of Tasmania, TAS 7001 (Australia); Gaensler, B. M.; Green, A. J., E-mail: naomi.mcclure-griffiths@csiro.au [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia)

    2013-06-10

    We describe a population of small, high-velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic center. The objects have a mean radius of 15 pc, velocity widths of {approx}14 km s{sup -1}, and are observed at |z| heights up to 700 pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic center. We discuss the clouds as entrained material traveling at {approx}200 km s{sup -1} in a Galactic wind.

  7. Which hydrogen atom of toluene protonates PAH molecules in (+)-mode APPI MS analysis?

    Science.gov (United States)

    Ahmed, Arif; Ghosh, Manik Kumer; Choi, Myung Chul; Choi, Cheol Ho; Kim, Sunghwan

    2013-03-01

    A previous study (Ahmed, A. et al., Anal. Chem. 84, 1146-1151( 2012) reported that toluene used as a solvent was the proton source for polyaromatic hydrocarbon compounds (PAHs) that were subjected to (+)-mode atmospheric-pressure photoionization. In the current study, the exact position of the hydrogen atom in the toluene molecule (either a methyl hydrogen or an aromatic ring hydrogen) involved in the formation of protonated PAH ions was investigated. Experimental analyses of benzene and anisole demonstrated that although the aromatic hydrogen atom of toluene did not contribute to the formation of protonated anthracene, it did contribute to the formation of protonated acridine. Thermochemical data and quantum mechanical calculations showed that the protonation of anthracene by an aromatic ring hydrogen atom of toluene is endothermic, while protonation by a methyl hydrogen atom is exothermic. However, protonation of acridine by either an aromatic ring hydrogen or a methyl hydrogen atom of toluene is exothermic. The different behavior of acridine and anthracene was attributed to differences in gas-phase basicity. It was concluded that both types of hydrogen in toluene can be used for protonation of PAH compounds, but a methyl hydrogen atom is preferred, especially for non-basic compounds.

  8. Isotope effects of hydrogen and atom tunnelling

    Science.gov (United States)

    Buchachenko, A. L.; Pliss, E. M.

    2016-06-01

    The abnormally high mass-dependent isotope effects in liquid-phase hydrogen (deuterium) atom transfer reactions, which are customarily regarded as quantum effects, are actually the products of two classical effects, namely, kinetic and thermodynamic ones. The former is determined by the rate constants for atom transfer and the latter is caused by nonbonded (or noncovalent) isotope effects in the solvation of protiated and deuterated reacting molecules. This product can mimic the large isotope effects that are usually attributed to tunnelling. In enzymatic reactions, tunnelling is of particular interest; its existence characterizes an enzyme as a rigid molecular machine in which the residence time of reactants on the reaction coordinate exceeds the waiting time for the tunnelling event. The magnitude of isotope effect becomes a characteristic parameter of the internal dynamics of the enzyme catalytic site. The bibliography includes 61 references.

  9. Wave mechanics of the hydrogen atom

    CERN Document Server

    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 the quantum numbers in a particular set to specify such an individual function, depend on the coordinates in a particular chosen system, and are therefore artefacts of that particular coordinate representation within wave mechanics. All discussion of atomic or molecular properties based on such shapes or quantum numbers therefore lacks general significance

  10. Time-of-Flight Spectroscopy of Muonic Hydrogen Atoms and Molecules

    CERN Document Server

    Fujiwara, M C; Bailey, J M; Beer, G A; Beveridge, J L; Faifman, M P; Huber, T M; Kammel, P; Kim, S K; Knowles, P E; Kunselman, A R; Markushin, V E; Marshall, G M; Mason, G R; Mulhauser, F; Olin, A; Petitjean, C; Porcelli, T A; Zmeskal, J

    2001-01-01

    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.

  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 Hydrogen Atom in Relativistic Motion

    CERN Document Server

    Jarvinen, M

    2004-01-01

    The Lorentz contraction of bound states in field theory is often appealed to in qualitative descriptions of high energy particle collisions. Surprisingly, the contraction has not been demonstrated explicitly even in simple cases such as the Hydrogen atom. It requires a calculation of wave functions evaluated at equal (ordinary) time for bound states in motion. Such wave functions are not obtained by kinematic boosts from the rest frame. Starting from the exact Bethe-Salpeter equation we derive the equal-time wave function of a fermion-antifermion bound state in QED, i.e., positronium or the Hydrogen atom, in any frame to leading order in alpha. We show explicitly that the bound state energy transforms as the fourth component of a vector and that the wave function of the fermion-antifermion Fock state contracts as expected. Transverse photon exchange contributes at leading order to the binding energy of the bound state in motion. We study the general features of the corresponding fermion-antifermion-photon Foc...

  13. 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.

  14. 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.

  15. Static dipole polarizability of shell-confined hydrogen atom

    Science.gov (United States)

    Sen, K. D.; Garza, Jorge; Vargas, Rubicelia; Aquino, Norberto

    2002-04-01

    Using the Sternheimer perturbation-numerical procedure, calculations of static dipole polarizability are reported for the shell-confined hydrogen atom as defined by two impenetrable concentric spherical walls. Unusually high polarizability states are predicted for the hydrogen atom as the inner sphere radius is increased to larger values inside the outer sphere of a constant radius. Implications of this model in mimicking internal compression leading to the metallic behaviour of the shell-confined hydrogen atoms are discussed.

  16. Inflow of atomic gas fuelling star formation

    DEFF Research Database (Denmark)

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

    2016-01-01

    Gamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we show that they have substantial atomic gas reservoirs. This suggests that star formation in these ga......Gamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we show that they have substantial atomic gas reservoirs. This suggests that star formation...... in these galaxies may be fuelled by recent inflow of metal-poor atomic gas. While this process is debated, it can happen in low-metallicity gas near the onset of star formation because gas cooling (necessary for star formation) is faster than the Hi-to-H2 conversion....

  17. Possibility of obtaining atomic metallic hydrogen by electrochemical method

    OpenAIRE

    Galushkin, Nikolay E.; Yazvinskaya, Nataliya N.; Galushkin, Dmitriy N.

    2013-01-01

    In this work we show, that atomic metallic hydrogen (AMH) is formed inside of sintered oxide-nickel electrodes of nickel-cadmium battery over a long period of electrochemical hydrogenation (more than five years). It was established that density AMH is 12 times higher, than the density of liquid molecular hydrogen, the specific energy of hydrogen recombination is 20 times higher than of liquid hydrogen-oxygen fuel. At the room temperature AMH is a good conductor, but not a superconductor.

  18. 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.

  19. The Physical Conditions of Atomic Gas at High Redshift

    Science.gov (United States)

    Neeleman, Marcel

    In this thesis we provide insight into the chemical composition, physical conditions and cosmic distribution of atomic gas at high redshift. We study this gas in absorption against bright background quasars in absorption systems known as Damped Ly-alpha Systems (DLAs). These systems contain the bulk of the atomic gas at high redshift and are the likely progenitors of modern-day galaxies. In Chapter 2, we find that the atomic gas in DLAs obeys a mass-metallicity relationship that is similar to the mass-metallicity relationship seen in star-forming galaxies. The evolution of this relationship is linear with redshift, allowing for a planar equation to accurately describe this evolution, which provides a more stringent constraint on simulations modeling DLAs. Furthermore, the concomitant evolution of the mass-metallicity relationship of atomic gas and star-forming galaxies suggests an intimate link between the two. We next use a novel way to measure the physical conditions of the gas by using fine-structure line ratios of singly ionized carbon and silicon. By measuring the density of the upper and lower level states, we are able to determine the temperature, hydrogen density and electron density of the gas. We find that the conditions present in this high redshift gas are consistent with the conditions we see in the local interstellar medium (ISM). A few absorbers have higher than expected pressure, which suggests that they probe the ISM of star-forming galaxies. Finally in Chapter 4, we measure the cosmic neutral hydrogen density at redshifts below 1.6. Below this redshift, the Ly-alpha line of hydrogen is absorbed by the atmosphere, making detection difficult. Using the archive of the Hubble Space Telescope, we compile a comprehensive list of quasars for a search of DLAs at redshift below 1.6. We find that the incidence rate of DLAs and the cosmic neutral hydrogen density is smaller than previously measured, but consistent with the values both locally and at

  20. Scattering of p$\\mu$ muonic atoms in solid hydrogen

    CERN Document Server

    Wozniak, J; Beer, G A; Bystritsky, V M; Filipowicz, M; Fujiwara, M C; Huber, T M; Huot, O; Jacot-Guillarmod, R; Kammel, P; Knowles, P E; Kunselman, A R; Marshall, G M; Mulhauser, F; Olin, A; Petitjean, C; Porcelli, T A; Schaller, L A; Stolupin, V A; Zmeskal, J

    2002-01-01

    We present the results of experimental and theoretical study of the scattering of low energy p$\\mu$ atoms in solid hydrogen cooled to 3 K. The resulting emission of low energy p$\\mu$ atoms from the hydrogen layer into the adjacent vacuum was much higher than that predicted by calculations which ignored the solid nature of the hydrogen. New differential scattering cross sections have been calculated for the collisions of p$\\mu$ atoms on solid hydrogen to acount for its quantum crystalline nature. Analysis of the experimental data performed using such cross sections shows the important role of the coherent scattering in p$\\mu$ atom diffusion. For p$\\mu$ energies lower than the Bragg cutoff limit (2 meV) the elastic Bragg scattering vanishes which makes the total scattering cross section fall by several orders of magnitude, and thus the hydrogen target becomes transparent allowing the emission of cold p$\\mu$ atoms to occur.

  1. Integrated Mirco-Machined Hydrogen Gas Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Frank DiMeoJr. Ing--shin Chen

    2005-12-15

    The widespread use of hydrogen as both an industrial process gas and an energy storage medium requires fast, selective detection of hydrogen gas. This report discusses the development of a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a MEMS (Micro-Electro-Mechanical System) structure known as a micro-hotplate. In this project, Micro-hotplate structures were overcoated with engineered multilayers that serve as the active hydrogen-sensing layer. The change in electrical resistance of these layers when exposed to hydrogen gas was the measured sensor output. This project focused on achieving the following objectives: (1) Demonstrating the capabilities of micro-machined H2 sensors; (2) Developing an understanding of their performance; (3) Critically evaluating the utility and viability of this technology for life safety and process monitoring applications. In order to efficiently achieve these objectives, the following four tasks were identified: (1) Sensor Design and Fabrication; (2) Short Term Response Testing; (3) Long Term Behavior Investigation; (4) Systems Development. Key findings in the project include: The demonstration of sub-second response times to hydrogen; measured sensitivity to hydrogen concentrations below 200 ppm; a dramatic improvement in the sensor fabrication process and increased understanding of the processing properties and performance relationships of the devices; the development of improved sensing multilayers; and the discovery of a novel strain based hydrogen detection mechanism. The results of this program suggest that this hydrogen sensor technology has exceptional potential to meet the stringent demands of life safety applications as hydrogen utilization and infrastructure becomes more prevalent.

  2. Inert gas atomization of chemical grade silicon

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, D.; Ferreira Neto, J.B.; Salgado, L.; Nogueira, P.F.; Poco, J.G.R. [Metallurgy Div. Cidade Univ., Inst. for Technological Research, Sao Paulo, SP (Brazil)

    2001-07-01

    The use of inert gas atomization to obtain chemical grade silicon particles was investigated. Both cooling rate and chemical composition are very important regarding a tailored microstructure, related with silicon performance during the synthesis of the silanos, an intermediary raw material in the silicone production. Previously refined silicon was used as raw material. Silicon with different aluminum contents were atomized and analyzed. The atomization temperature was set around 1520 C, and it was used a confined atomization nozzle. It was necessary to use a long atomization chamber to allow the cooling of the coarse silicon particles. After atomization, the powder was characterized and classified. The coarse fraction was milled. Two different particle size groups (different cooling rates) and the as atomized particles were investigated. The chemical behavior during the synthesis of the silanos was analyzed in a laboratory reactor. The relationship between cooling rate, aluminum content and silicon performance during the silanos synthesis is discussed. (orig.)

  3. Convergent variational calculation of positronium-hydrogen-atom scattering lengths

    CERN Document Server

    Adhikari, S K; Adhikari, Sadhan K.; Mandal, Puspajit

    2001-01-01

    We present a convergent variational basis-set calculational scheme for elastic scattering of positronium atom by hydrogen atom in S wave. Highly correlated trial functions with appropriate symmetry are needed for achieving convergence. We report convergent results for scattering lengths in atomic units for both singlet ($=3.49\\pm 0.20$) and triplet ($=2.46\\pm 0.10$) states.

  4. 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.

  5. Effect of atomic ordering on environmental embrittlement of (Co, Fe)3V alloy in gaseous hydrogen

    Institute of Scientific and Technical Information of China (English)

    程晓英; 万晓景

    2002-01-01

    The diffusible hydrogen contents in precharged (Co,Fe)3V alloy were measured. It is found that atomic ordering can not promote hydrogen penetration in the (Co,Fe)3V alloy. The ultimate tensile strength (UTS) and ductilities in various condition were also investigated. The results show that the UTS and elongation of disordered alloy are higher than that of ordered one with fixed diffusible hydrogen content and (Co,Fe)3V alloy with ordered structure is highly susceptible to the embrittlement in hydrogen gas. The factor which may affect the susceptibility to the embrittlement of (Co,Fe)3V alloy in h ydrogen gas is mainly due to that the atomic ordering may accelerate the kinetics of the catalytic reaction for the dissociation of molecular hydrogen into atomic hydrogen. However, it can not be roled out that atomic ordering intensifies planar slip and restricts cross-slip at the grain boundaries and enhances the susceptibility of the alloy to hydrogen embrittlement.

  6. Effects of hydrogen atoms on surface conductivity of diamond film

    Directory of Open Access Journals (Sweden)

    Fengbin Liu

    2015-04-01

    Full Text Available To investigate the effects of surface chemisorbed hydrogen atoms and hydrogen atoms in the subsurface region of diamond on surface conductivity, models of hydrogen atoms chemisorbed on diamond with (100 orientation and various concentrations of hydrogen atoms in the subsurface layer of the diamond were built. By using the first-principles method based on density functional theory, the equilibrium geometries and densities of states of the models were studied. The results showed that the surface chemisorbed hydrogen alone could not induce high surface conductivity. In addition, isolated hydrogen atoms in the subsurface layer of the diamond prefer to exist at the bond centre site of the C-C bond. However, such a structure would induce deep localized states, which could not improve the surface conductivity. When the hydrogen concentration increases, the C-H-C-H structure and C-3Hbc-C structure in the subsurface region are more stable than other configurations. The former is not beneficial to the increase of the surface conductivity. However, the latter would induce strong surface states near the Fermi level, which would give rise to high surface conductivity. Thus, a high concentration of subsurface hydrogen atoms in diamond would make significant contributions to surface conductivity.

  7. Bose-Einstein Condensation of Atomic Hydrogen observation for the thesis

    CERN Document Server

    Fried, D G; Willmann, L; Landhuis, D; Moss, S C; Kleppner, D; Greytak, T J; Fried, Dale G.; Killian, Thomas C.; Willmann, Lorenz; Landhuis, David; Moss, Stephen C.; Kleppner, Daniel; Greytak, Thomas J.

    1998-01-01

    We report observation of Bose-Einstein condensation of a trapped, dilute gas of atomic hydrogen. The condensate and normal gas are studied by two-photon spectroscopy of the 1S-2S transition. Interactions among the atoms produce a shift of the resonance frequency proportional to density. The condensate is clearly distinguished by its large frequency shift. The peak condensate density is 4.8 +/- 1.1 \\times 10^{15} cm^{-3}, corresponding to a condensate population of 10^9 atoms. The BEC transition occurs at about T=50 uK and n=1.8 \\times 10^{14} cm^{-3}.

  8. Rapid formation of molecular clouds from turbulent atomic gas

    Science.gov (United States)

    Glover, S. C. O.; Mac Low, M.-M.

    The characteristic lifetimes of molecular clouds remain uncertain and a topic of frequent debate, with arguments having recently been advanced both in support of short-lived clouds, with lifetimes of a few Myr or less (see e.g. Elmegreen 2000; Hartmann et al. 2001) and in support of much longer-lived clouds, with lifetimes of the order of 10 Myr or more (see e.g. Tassis & Mouschovias, 2004; Goldsmith & Li, 2005). An argument that has previously been advanced in favour of longer lived clouds is the apparent difficulty involved in converting sufficient atomic hydrogen to molecular hydrogen within the short timescale required by the rapid cloud formation scenario. However, previous estimates of the time required for this conversion to occur have not taken into account the effects of the supersonic turbulence which is inferred to be present in the atomic gas. In this contribution, we present results from a set of high resolution three-dimensional simulations of turbulence in gravitationally unstable atomic gas. These simulations were performed using a modified version of the ZEUS-MP hydrodynamical code (Norman 2000), and include a detailed treatment of the thermal balance of the gas and of the formation of molecular hydrogen. The effects of photodissociation of H2 by the Galactic UV field are also included, with a simple local approximation used to compute the effects of H2 self-shielding. The results of our simulations demonstrate that H2 formation occurs rapidly in turbulent atomic gas. Starting from purely atomic gas, large quantities of molecular gas can be produced on timescales of less than a Myr, given turbulent velocity dispersions and magnetic field strengths consistent with observations. Moreover, as our simulations underestimate the effectiveness of H2 self-shielding and dust absorption, we can be confident that the molecular fractions which we compute are strong lower limits on the true values. The formation of large quantities of molecular gas on the

  9. Atomic gas in debris discs

    Science.gov (United States)

    Hales, Antonio S.; Barlow, M. J.; Crawford, I. A.; Casassus, S.

    2017-04-01

    We have conducted a search for optical circumstellar absorption lines in the spectra of 16 debris disc host stars. None of the stars in our sample showed signs of emission line activity in either Hα, Ca II or Na I, confirming their more evolved nature. Four stars were found to exhibit narrow absorption features near the cores of the photospheric Ca II and Na I D lines (when Na I D data were available). We analyse the characteristics of these spectral features to determine whether they are of circumstellar or interstellar origins. The strongest evidence for circumstellar gas is seen in the spectrum of HD 110058, which is known to host a debris disc observed close to edge-on. This is consistent with a recent ALMA detection of molecular gas in this debris disc, which shows many similarities to the β Pictoris system.

  10. Stable atomic hydrogen possible application in intense polarized sources

    CERN Document Server

    Niinikoski, T O; Rieubland, Jean Michel

    1982-01-01

    The authors briefly review the status of spin-polarized atomic hydrogen and discuss a possible way of extending the present limit of density. Pulse extraction of stabilized atoms by millimetre wave is proposed as a means of producing polarized atomic beams of uniform velocity and low divergence. It is speculated that these atoms could be used either as jet targets of a conventional type, or as a stored atomic beam target by injecting them into a storage ring intersecting with an accelerator beam. When used in a polarized ion source, the high density of the atomic beam could possibly also improve the ionizer efficiency.

  11. 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 t

  12. 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…

  13. Direct Microscopic Study of Doubly Polarized Atomic-Hydrogen by Electron-Spin Resonance

    NARCIS (Netherlands)

    van Yperen, G.H.; Silvera, I.F.; Walraven, J.T.M.; Berkhout, J.; Brisson, J.G.

    1983-01-01

    By means of ESR in a high magnetic field the hyperfine states of a gas of spin-polarized atomic hydrogen are directly probed. This allows a direct determination of the spin-state populations and nuclear polarization. The unusual ESR line shape is attributed to field inhomogeneities. The temperature

  14. Radial Matrix Elements of Hydrogen Atom and the Correspondence Principle

    Indian Academy of Sciences (India)

    T. N. Chakrabarty

    2004-03-01

    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 number (). The computed radial matrix elements are in good agreement with quantum mechanical results. Further, radial matrix elements for few transitions involving high neighboring states of hydrogen atom are presented.

  15. 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⋆ 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.

  16. The structure, properties, and nature of HArF-benzene complex: redshift and blueshift of Ar-H stretch frequency and rare gas atomic number dependence of hydrogen bonds.

    Science.gov (United States)

    Liu, Xiaofeng; Li, Qingzhong; Li, Ran; Li, Wenzuo; Cheng, Jianbo

    2011-12-15

    Ab initio calculations have been performed for the complexes of benzene with HArF, HKrF, and HXeF. The computed results indicate that the complexes of benzene-HArF exist in different conformations and among them those with π-hydrogen bonds are the more stable than those with C-H···F hydrogen bonds. Interestingly, the Ar-H stretching frequency is redshifted in the more stable isomer and blueshifted in the less stable form. The Ng (Ng=Ar, Kr, and Xe) atomic number dependence of the Ng-H···π and C-H···F hydrogen bonds has been explored. The result indicates that the strength of Ng-H···π and C-H···F hydrogen bonds is weakened with the increase of Ng atomic number. Natural bond orbital analysis has been performed to understand the interaction nature, frequency shift of H-Ng stretch, and dependence of Ng-H···π and C-H···F hydrogen bonds on the Ng atomic number.

  17. Strain field of interstitial hydrogen atom in body-centered cubic iron and its effect on hydrogen-dislocation interaction

    OpenAIRE

    Wang, Shuai; Takahashi, Keisuke; Hashimoto, Naoyuki; Isobe, Shigehito; Ohnuki, Somei

    2013-01-01

    Effect of hydrogen in body-centered cubic iron is explored by using the density function theory. Hydrogen atoms increase the concentration of free electrons in the simulation cell and have bonding interaction with Fe atom. Caused by anisotropic strain components of hydrogen atoms in the tetrahedral sites, elastic interaction for hydrogen with screw dislocation has been found. The dependence of hydrogen-screw dislocation interaction on hydrogen concentration is confirmed by repeated stress rel...

  18. A tale of two condensates: the odd "Bose - Einstein" condensation of atomic Hydrogen

    OpenAIRE

    1998-01-01

    The recent report of the observation of Bose-Einstein condensation in atomic Hydrogen, characterized by an "anomalous" density spectrum, is shown to be in agreement with the prediction of the existence of two condensates for temperatures lower than a well defined temperature (which for Hydrogen is $ 105~ \\mu K $), based on the QED coherent interaction in a gas of ultracold atoms at a density $n > n_0 (n_0=(1/\\lambda)^3, \\lambda$ being the wave-length of the e.m. modes resonantly coupled to th...

  19. First principles study of inert-gas (helium, neon, and argon) interactions with hydrogen in tungsten

    Science.gov (United States)

    Kong, Xiang-Shan; Hou, Jie; Li, Xiang-Yan; Wu, Xuebang; Liu, C. S.; Chen, Jun-Ling; Luo, G.-N.

    2017-04-01

    We have systematically evaluated binding energies of hydrogen with inert-gas (helium, neon, and argon) defects, including interstitial clusters and vacancy-inert-gas complexes, and their stable configurations using first-principles calculations. Our calculations show that these inert-gas defects have large positive binding energies with hydrogen, 0.4-1.1 eV, 0.7-1.0 eV, and 0.6-0.8 eV for helium, neon, and argon, respectively. This indicates that these inert-gas defects can act as traps for hydrogen in tungsten, and impede or interrupt the diffusion of hydrogen in tungsten, which supports the discussion on the influence of inert-gas on hydrogen retention in recent experimental literature. The interaction between these inert-gas defects and hydrogen can be understood by the attractive interaction due to the distortion of the lattice structure induced by inert-gas defects, the intrinsic repulsive interaction between inert-gas atoms and hydrogen, and the hydrogen-hydrogen repelling in tungsten lattice.

  20. Excited states of muonium in atomic hydrogen

    Indian Academy of Sciences (India)

    V S Kulhar

    2006-06-01

    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 integrated cross-sections are computed for muon energy of 2 keV and higher. Total muonium formation cross-sections are computed using Jackson and Schiff scaling rules. Muonium formation cross-section results obtained from proton-hydrogen charge-exchange cross-section results, using velocity scaling are compared with the results of the present calculation.

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

    Science.gov (United States)

    Leutenegger, M. A.; Beiersdorfer, P.; Betancourt-Martinez, G. L.; Brown, G. V.; Hell, N.; Kelley, R. L.; Kilbourne, C. A.; Magee, E. W.; Porter, F. S.

    2016-11-01

    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.

  2. Compressorless Gas Storage and Regenerative Hydrogen Purification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Microwave regenerative sorption media gas storage/delivery techniques are proposed to address both compressed gas management and hydrogen purification requirements...

  3. Diffusion membrane and process for separating hydrogen from gas mixture

    Energy Technology Data Exchange (ETDEWEB)

    Behr, F.; Schulten, R.; Weirich, W.

    1985-01-29

    For separation of hydrogen and its isotopes by diffusion through a membrane virtually impermeable to other gases, a non-porous hydrogen-permeable metallic membrane is provided on the gas access side with a coating of an alloy of palladium with at least 45 atomic % Cu or at least 50 atomic percent Ag or at least 7 atomic % Y, the membrane itself containing Cu, Ag or Y respectively in a concentration at least equilibrated with the coating at operation temperature. Preferably the membrane consists of a metal of niobium and/or tantalum bases especially of an alloy containing from 10 to 30 % Ti, 3 to 10 % V, 0 to 25 % Nb and at least 30 % Ta, all by weight, and preferably it is of a composition of 20 to 25 % Ti, 5 to 7,5 % V, 0 to 25 Nb, and at least 50 % Ta, being saturated with copper and or silver, while a copper and/or silver palladium alloy coating is used. Such inherently oxidation sensitive membranes can be stabilized by provision of an internal intermediate layer in the form of a melt forming or containing an alkaline metal hydride and/or an alkaline earth metal hydride. A melt containing alkaline metal and/or alkaline earth metal which forms a hydride, brought into contact on the secondary side of a membrane in accordance with the invention, provides a hydrogen sink on the secondary side and inhibits internal hydride formation and secondary side oxidation of the membrane.

  4. Quantum Gas Microscope for Fermionic Atoms

    Science.gov (United States)

    Okan, Melih; Cheuk, Lawrence; Nichols, Matthew; Lawrence, Katherine; Zhang, Hao; Zwierlein, Martin

    2016-05-01

    Strongly interacting fermions define the properties of complex matter throughout nature, from atomic nuclei and modern solid state materials to neutron stars. Ultracold atomic Fermi gases have emerged as a pristine platform for the study of many-fermion systems. In this poster we demonstrate the realization of a quantum gas microscope for fermionic 40 K atoms trapped in an optical lattice and the recent experiments which allows one to probe strongly correlated fermions at the single atom level. We combine 3D Raman sideband cooling with high- resolution optics to simultaneously cool and image individual atoms with single lattice site resolution at a detection fidelity above 95%. The imaging process leaves the atoms predominantly in the 3D motional ground state of their respective lattice sites, inviting the implementation of a Maxwell's demon to assemble low-entropy many-body states. Single-site resolved imaging of fermions enables the direct observation of magnetic order, time resolved measurements of the spread of particle correlations, and the detection of many-fermion entanglement. NSF, AFOSR-PECASE, AFOSR-MURI on Exotic Phases of Matter, ARO-MURI on Atomtronics, ONR, a Grant from the Army Research Office with funding from the DARPA OLE program, and the David and Lucile Packard Foundation.

  5. Modeling of hydrogen atom diffusion and response behavior of hydrogen sensors in Pd–Y alloy nanofilm

    Science.gov (United States)

    Liu, Yi; Li, Yanli; Huang, Pengcheng; Song, Han; Zhang, Gang

    2016-11-01

    To detect hydrogen gas leakage rapidly, many types of hydrogen sensors containing palladium alloy film have been proposed and fabricated to date. However, the mechanisms and factors that determine the response rate of such hydrogen sensor have not been established theoretically. The manners in which response time is forecasted and sensitive film is designed are key issues in developing hydrogen sensors with nanometer film. In this paper, a unilateral diffusion model of hydrogen atoms in Pd alloy based on Fick’s second law is proposed to describe the Pd–H reaction process. Model simulation shows that the hydrogen sensor response time with Pd alloy film is dominated by two factors (film thickness and hydrogen diffusion coefficient). Finally, a series of response rate experiments with varying thicknesses of Pd–Y (yttrium) alloy film are implemented to verify model validity. Our proposed model can help researchers in the precise optimization of film thickness to realize a simultaneously speedy and sensitive hydrogen sensor. This study also aids in evaluating the influence of manufacturing errors on performances and comparing the performances of sensors with different thicknesses.

  6. Modeling of hydrogen atom diffusion and response behavior of hydrogen sensors in Pd-Y alloy nanofilm.

    Science.gov (United States)

    Liu, Yi; Li, Yanli; Huang, Pengcheng; Song, Han; Zhang, Gang

    2016-11-15

    To detect hydrogen gas leakage rapidly, many types of hydrogen sensors containing palladium alloy film have been proposed and fabricated to date. However, the mechanisms and factors that determine the response rate of such hydrogen sensor have not been established theoretically. The manners in which response time is forecasted and sensitive film is designed are key issues in developing hydrogen sensors with nanometer film. In this paper, a unilateral diffusion model of hydrogen atoms in Pd alloy based on Fick's second law is proposed to describe the Pd-H reaction process. Model simulation shows that the hydrogen sensor response time with Pd alloy film is dominated by two factors (film thickness and hydrogen diffusion coefficient). Finally, a series of response rate experiments with varying thicknesses of Pd-Y (yttrium) alloy film are implemented to verify model validity. Our proposed model can help researchers in the precise optimization of film thickness to realize a simultaneously speedy and sensitive hydrogen sensor. This study also aids in evaluating the influence of manufacturing errors on performances and comparing the performances of sensors with different thicknesses.

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

    Science.gov (United States)

    Kashlev, Y. A.

    2017-04-01

    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.

  8. Photoionization microscopy of hydrogen atom near a metal surface

    Institute of Scientific and Technical Information of China (English)

    Yang Hai-Feng; Wang Lei; Liu Xiao-Jun; Liu Hong-Ping

    2011-01-01

    We have studied the ionization of Rydberg hydrogen atom near a metal surface with a semiclassical analysis of photoionization microscopy. Interference patterus of the electron radial distribution are calculated at different scaled energies above the classical saddle point and at various atom-surface distances. We find that different types of trajectories contribute predominantly to different manifolds in a certain interference pattern. As the scaled energy increases, the structure of the interference pattern evolves smoothly and more types of trajectories emerge. As the atom approaches the metal surface closer, there are more types of trajectories contributing to the interference pattern as well. When the Rydberg atom comes very close to the metal surface or the scaled energy approaches the zero field ionization energy,the potential induced by the metal surface will make atomic system chaotic. The results also show that atoms near a metal surface exhibit similar properties like the atoms in the parallel electric and magnetic fields.

  9. Positronium collisions with rare-gas atoms

    CERN Document Server

    Gribakin, G F; Wilde, R S; Fabrikant, I I

    2015-01-01

    We calculate elastic scattering of positronium (Ps) by the Xe atom using the recently developed pseudopotential method [Fabrikant I I and Gribakin G F 2014 Phys. Rev. A 90 052717] and review general features of Ps scattering from heavier rare-gas atoms: Ar, Kr and Xe. The total scattering cross section is dominated by two contributions: elastic scattering and Ps ionization (break-up). To calculate the Ps ionization cross sections we use the binary-encounter method for Ps collisions with an atomic target. Our results for the ionization cross section agree well with previous calculations carried out in the impulse approximation. Our total Ps-Xe cross section, when plotted as a function of the projectile velocity, exhibits similarity with the electron-Xe cross section for the collision velocities higher than 0.8 a.u., and agrees very well with the measurements at Ps velocities above 0.5 a.u.

  10. Graviton Emission and Absorption by Atomic Hydrogen

    CERN Document Server

    Rothman, S B T

    2006-01-01

    Graviton absorption cross sections and emission rates for hydrogen are calculated by both semi-classical and field theoretic methods. We point out several mistakes in the literature concerning spontaneous emission of gravitons and related phenomena, some of which are due to a subtle issue concerning gauge invariance of the linearized interaction Hamiltonian.

  11. Sensoring hydrogen gas concentration using electrolyte made of proton

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Yoshikatsu [Kyoto University, Japan; Kolesnikov, Alexander I [ORNL; Koyanaka, Hideki [Kyoto University, Japan

    2011-01-01

    Hydrogen gas promises to be a major clean fuel in the near future. Thus, sensors that can measure the concentrations of hydrogen gas over a wide dynamic range (e.g., 1 99.9%) are in demand for the production, storage, and utilization of hydrogen gas. However, it is difficult to directly measure hydrogen gas concentrations greater than 10% using conventional sensor [1 11]. We report a simple sensor using an electrolyte made of proton conductive manganese dioxide that enables in situmeasurements of hydrogen gas concentration over a wide range of 0.1 99.9% at room temperature.

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

    Indian Academy of Sciences (India)

    Hitesh Sharma; S Prakash

    2007-08-01

    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. The norm-conserving pseudopotentials for H, Cu and Pd are generated self-consistently. The dynamical matrices are evaluated considering interaction up to first nearest neighbors whereas impurity-induced forces are calculated with M32H shell (where M = Cu and Pd). The atomic displacements produced by interstitial hydrogen at the octahedral site in Cu and Pd show displacements of 7.36% and 4.3% of the first nearest neighbors respectively. Both Cu and Pd lattices show lattice expansion due to the presence of hydrogen and the obtained average lattice expansion / = 0.177 for Cu and 0.145 for Pd.

  13. Measurements of atomic splittings in atomic hydrogen and the proton charge radius

    Science.gov (United States)

    Hessels, E. A.

    2016-09-01

    The proton charge radius can be determined from precise measurements of atomic hydrogen spectroscopy. A review of the relevant measurements will be given, including an update on our measurement of the n=2 Lamb shift. The values obtained from hydrogen will be compared to those obtained from muonic hydrogen and from electron-proton elastic scattering measurements. This work is funded by NSERC, CRC and CFI.

  14. The collision between two hydrogen atoms

    CERN Document Server

    Ray, Hasi

    2013-01-01

    The electron-electron correlation term in two-atomic collision is the most important, most difficult term to obtain the effective interatomic potential. Generally the H and H collision is a four center problem. It is extremely difficult to compute the electron-electron correlation term to include the effect of exchange or antisymmetry between two system electrons exactly. All the two-atomic collision related theoretical data differ from each other due to its difference in approximating the electron-electron correlation term. I invent a trick to evaluate the term exactly. Earlier the positronium (Ps) and H system was easily approximated as a three center problem due to the light mass of Ps. My new code for H-H collision using the ab-initio and exact static-exchange model (SEM) can reproduce exactly the same data of Ps and H system just by using the appropriate atomic parameters. The success of the present trick makes the foundation of a big monument in cold and low energy atomic collision physics. The Feshbach...

  15. 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.

  16. Formation and Transport of Atomic Hydrogen in Hot-Filament Chemical Vapor Deposition Reactors

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant ishydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless numbers forheat and mass transfer reveals that thermal conduction and diffusion are the dominant mechanisms for gas-phaseheat and mass transfer, respectively. A simplified model has been established to simulate gas-phase temperature andH concentration distributions between the filament and the substrate. Examination of the relative importance ofhomogeneous and heterogeneous production of H atoms indicates that filament-surface decomposition of molecularhydrogen is the dominant source of H and gas-phase reaction plays a negligible role. The filament-surface dissociationrates of H2 for various filament temperatures were calculated to match H-atom concentrations observed in the liter-ature or derived from power consumption by filaments. Arrhenius plots of the filament-surface hydrogen dissociationrates suggest that dissociation of H2 at refractory filament surface is a catalytic process, which has a rather lowereffective activation energy than homogeneous thermal dissociation. Atomic hydrogen, acting as an important heattransfer medium to heat the substrate, can freely diffuse from the filament to the substrate without recombination.

  17. The photon scattering cross-sections of atomic hydrogen

    OpenAIRE

    2016-01-01

    We present a unified view of the frequency dependence of the various scattering processes involved when a neutral hydrogen atom interacts with a monochromatic, linearly-polarized photon. A computational approach is employed of the atom trapped by a finite-sized-box due to a finite basis-set expansion, which generates a set of transition matrix elements between $E0$ pseudostates. We introduce a general computational methodology that enables the computation of the frequency-dependent dipole tra...

  18. 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.

  19. Hydrogen-related contrast in atomic force microscopy

    Science.gov (United States)

    Schmidt, René; Schwarz, Alexander; Wiesendanger, Roland

    2009-07-01

    We study the effect of hydrogen adsorption on gadolinium islands epitaxially grown on W(110) utilizing atomic force microscopy operated in the non-contact regime. In constant force images, gadolinium islands exhibit two height levels, corresponding to hydrogen covered and clean gadolinium areas, respectively. The experimentally measured height differences are strongly bias dependent, showing that the contrast pattern is dominated by electrostatic tip-sample forces. We interpret our experimental findings in terms of a local reduction of the work function and the presence of localized charges on hydrogen covered areas. Both effects lead to a variation of the contact potential difference between tip and surface areas, which are clean or hydrogen covered gadolinium. After clarifying the electrostatic contrast formation, we can unambiguously identify regions of clean gadolinium on the islands. These results are important for further magnetic exchange force microscopy based studies, because hydrogen also alters the magnetic properties locally.

  20. Cooperative triple-proton/hydrogen atom relay in 7-azaindole(CH3OH)2 in the gas phase: remarkable change in the reaction mechanism from vibrational-mode specific to statistical fashion with increasing internal energy.

    Science.gov (United States)

    Sakota, Kenji; Inoue, Naomi; Komoto, Yusuke; Sekiya, Hiroshi

    2007-05-31

    The 7-azaindole-methanol 1:2 cluster [7AI(CH(3)OH)2] undergoes excited-state triple-proton/hydrogen atom transfer (ESTPT/HT) along the hydrogen-bonded network in the gas phase. The measurements of the resonance-enhanced multiphoton ionization (REMPI) spectra of 7AI(CH(3)OH)2-d(n) (n = 0-3), where subscript n indicates the number of deuterium, and the fluorescence excitation spectrum of 7AI(CH(3)OH)2-d(0) allowed us to investigate the ESTPT/HT dynamics. By comparing the intensity ratios of the vibronic bands between 7AI(CH(3)OH)2-d(0) and 7AI(CH(3)OH)2-d(3) in REMPI spectra, we obtained the lower limit of an acceleration factor (f(a)(low)) of 7AI(CH(3)OH)2-d(0), which is the ratio of the reaction rate for the excitation of a vibronic state to that of the zero-point state in S(1). The f(a)(low) values are 2.7 +/- 0.83 and 4.0 +/- 1.2 for an in-phase intermolecular stretching vibration (sigma(1)) and its overtone (2sigma(1)) observed at 181 cm(-1) and 359 cm(-1) in the excitation spectrum, respectively, while that of the vibration (nu(2)/sigma(1) or nu(3)/sigma(1)) at 228 cm(-1) is 1.1 +/- 0.83. Thus, vibrational-mode-specific ESTPT/HT occurs in the low-energy region (600 cm(-1)). The excitation of an intramolecular ring mode (nu(intra)) of 7AI at 744 cm(-1) substantially enhances the reaction rate (f(a)(low) = 4.4 +/- 0.98), but the increase of f(a)(low) is not prominent for the excitation of v(intra) + sigma(1) at 926 cm(-1) (f(a)(low) = 5.0 +/- 1.6), although the sigma(1) mode is excited. These results suggest that the ESTPT/HT reaction in 7AI(CH(3)OH)2-d(0) directly proceeds from the photoexcited states with the internal energy less than approximately 600 cm(-1), but it occurs from the isoenergetically vibrational-energy redistributed states when the internal energy is large. This shows a remarkable feature of ESTPT/HT in 7AI(CH(3)OH)2; the nature of the reaction mechanism changes from vibrational-mode specific to statistical fashion with increasing the internal

  1. Hydrogen gas storage in fluorinated ultramicroporous tunnel crystal.

    Science.gov (United States)

    Kataoka, Keisuke; Katagiri, Toshimasa

    2012-08-21

    We report hydrogen storage at an ordinary pressure due to a bottle-neck effect of an ultramicroporous crystal. Stored hydrogen was kept at an ordinary pressure below -110 °C. The amounts of stored hydrogen gas linearly correlated with the initial pressures. These phenomena suggested the ultramicroporous tunnels worked as a molecular gas cylinder.

  2. Advanced IGCC/Hydrogen Gas Turbine Development

    Energy Technology Data Exchange (ETDEWEB)

    York, William [General Electric Company, Schenectady, NY (United States); Hughes, Michael [General Electric Company, Schenectady, NY (United States); Berry, Jonathan [General Electric Company, Schenectady, NY (United States); Russell, Tamara [General Electric Company, Schenectady, NY (United States); Lau, Y. C. [General Electric Company, Schenectady, NY (United States); Liu, Shan [General Electric Company, Schenectady, NY (United States); Arnett, Michael [General Electric Company, Schenectady, NY (United States); Peck, Arthur [General Electric Company, Schenectady, NY (United States); Tralshawala, Nilesh [General Electric Company, Schenectady, NY (United States); Weber, Joseph [General Electric Company, Schenectady, NY (United States); Benjamin, Marc [General Electric Company, Schenectady, NY (United States); Iduate, Michelle [General Electric Company, Schenectady, NY (United States); Kittleson, Jacob [General Electric Company, Schenectady, NY (United States); Garcia-Crespo, Andres [General Electric Company, Schenectady, NY (United States); Delvaux, John [General Electric Company, Schenectady, NY (United States); Casanova, Fernando [General Electric Company, Schenectady, NY (United States); Lacy, Ben [General Electric Company, Schenectady, NY (United States); Brzek, Brian [General Electric Company, Schenectady, NY (United States); Wolfe, Chris [General Electric Company, Schenectady, NY (United States); Palafox, Pepe [General Electric Company, Schenectady, NY (United States); Ding, Ben [General Electric Company, Schenectady, NY (United States); Badding, Bruce [General Electric Company, Schenectady, NY (United States); McDuffie, Dwayne [General Electric Company, Schenectady, NY (United States); Zemsky, Christine [General Electric Company, Schenectady, NY (United States)

    2015-07-30

    The objective of this program was to develop the technologies required for a fuel flexible (coal derived hydrogen or syngas) gas turbine for IGCC that met DOE turbine performance goals. The overall DOE Advanced Power System goal was to conduct the research and development (R&D) necessary to produce coal-based IGCC power systems with high efficiency, near-zero emissions, and competitive capital cost. To meet this goal, the DOE Fossil Energy Turbine Program had as an interim objective of 2 to 3 percentage points improvement in combined cycle (CC) efficiency. The final goal is 3 to 5 percentage points improvement in CC efficiency above the state of the art for CC turbines in IGCC applications at the time the program started. The efficiency goals were for NOx emissions of less than 2 ppm NOx (@15 % O2). As a result of the technologies developed under this program, the DOE goals were exceeded with a projected 8 point efficiency improvement. In addition, a new combustion technology was conceived of and developed to overcome the challenges of burning hydrogen and achieving the DOE’s NOx goal. This report also covers the developments under the ARRA-funded portion of the program that include gas turbine technology advancements for improvement in the efficiency, emissions, and cost performance of gas turbines for industrial applications with carbon capture and sequestration. Example applications could be cement plants, chemical plants, refineries, steel and aluminum plants, manufacturing facilities, etc. The DOE’s goal for more than 5 percentage point improvement in efficiency was met with cycle analyses performed for representative IGCC Steel Mill and IGCC Refinery applications. Technologies were developed in this program under the following areas: combustion, larger latter stage buckets, CMC and EBC, advanced materials and coatings, advanced configurations to reduce cooling, sealing and rotor purge flows, turbine aerodynamics, advanced sensors, advancements in first

  3. On the hydrogen atom via Wigner-Heisenberg algebra

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, R. de Lima [Universidade Federal de Campina Grande (UFCG), Cuite, PB (Brazil). Unidade Academica de Educacao]. E-mail: rafael@df.ufcg.edu.br; rafaelr@cbpf.br

    2008-07-01

    We extend the usual Kustaanheimo-Stiefel 4D {yields} 3D mapping to study and discuss a constrained super-Wigner oscillator in four dimensions. We show that the physical hydrogen atom is the system that emerges in the bosonic sector of the mapped super 3D system. (author)

  4. 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…

  5. Hydrogen atom spectrum and the lamb shift in noncommutative QED.

    Science.gov (United States)

    Chaichian, M; Sheikh-Jabbari, M M; Tureanu, A

    2001-03-26

    We have calculated the energy levels of the hydrogen atom as well as the Lamb shift within the noncommutative quantum electrodynamics theory. The results show deviations from the usual QED both on the classical and the quantum levels. On both levels, the deviations depend on the parameter of space/space noncommutativity.

  6. Three-body recombination in spin-polarized atomic hydrogen

    NARCIS (Netherlands)

    Goey, L.P.H. de; Berg, T.H.M. van de; Mulders, N.; Stoof, H.T.C.; Verhaar, B.J.; Glöckle, W.

    1986-01-01

    In view of the failure of the Kagan dipole mechanism to explain the magnetic field dependence of the H+H+H recombination rate in spin-polarized atomic hydrogen, we consider an additional process, the so-called dipole-exchange mechanism. Two simple approaches to estimate its consequences turn out to

  7. Positron impact ionization of atomic hydrogen at low energies

    Indian Academy of Sciences (India)

    K Chakrabarti

    2001-04-01

    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.

  8. Doppler-free two-photon spectroscopy on atomic hydrogen

    CERN Document Server

    Niering, M

    1999-01-01

    In the framework of the present thesis the internal structure of the hydrogen atom is studied by means of optical spectroscopic methods. The main interest is thereby devoted to the transition of the 1S ground-state into the metastable 2S-state.

  9. Experimental ionization of atomic hydrogen with few-cycle pulses

    CERN Document Server

    Pullen, M G; Laban, D E; Palmer, A J; Hanne, G F; Grum-Grzhimailo, A N; Abeln, B; Bartschat, K; Weflen, D; Ivanov, I; Kheifets, A; Quiney, H M; Litvinyuk, I V; Sang, R T; Kielpinski, D

    2011-01-01

    We present the first experimental data on strong-field ionization of atomic hydrogen by few-cycle laser pulses. We obtain quantitative agreement at the 10% level between the data and an {\\it ab initio} simulation over a wide range of laser intensities and electron energies.

  10. 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…

  11. 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…

  12. Higher-order Sternheimer shieldings of the hydrogen atom

    Science.gov (United States)

    Fowler, P. W.; Steiner, E.

    Multiple perturbation theory is used to calculate the response of the electric field gradient at the nucleus of the hydrogen atom to external non-uniform fields. The parallel component of the field gradient at the nucleus in an axial field F with gradient F' and second derivative F'' has the perturbation expansion: [Enlarge Image

  13. Force Density Balance inside the Hydrogen Atom

    CERN Document Server

    Himpsel, F J

    2015-01-01

    Motivated by the long-debated question about the internal stability of the electron, the force densities acting on the charge density of the 1s electron in the H atom are investigated. The problem is mapped onto the canonical formalism for a classical Dirac field coupled to the electric field of an external point charge. An explicit calculation shows that the attractive Coulomb force density is balanced exactly at every point in space by the repulsive confinement force density. The latter requires evaluating the divergence of the stress tensor for the 1s solution of the Dirac equation. Such a local force balance goes beyond the global stability criteria that are usually given for the H atom. This concept is extended to the internal stability of any charged particle by investigating the force densities acting on its surrounding vacuum polarization. At large distances one has to consider only the charge density of virtual electrons and positrons, induced by a point charge in the vacuum of quantum electrodynamic...

  14. Relativistic Transitions in the Hydrogenic Atoms

    CERN Document Server

    Boudet, R

    2009-01-01

    When one approaches the study of the quantal relativistic theory of the electron, one may be surprised by the gap which lies between the frame of the experiments, i.e. the real geometry of the space and time, and the abstraction of the complex matrices and spinors formalism employed in the presentation of the theory. This book uses a theory of the electron, introduced by David Hestenes, in which the mathematical language is the same as the one of the geometry of the space and time. Such a language not only allows one to find again the well known results concerning the one-electron atoms theory but furthermore leads easily to the resolution of problems considered for a long time without solution.

  15. Collisional excitation of water by hydrogen atoms

    CERN Document Server

    Daniel, F; Dagdigian, P J; Dubernet, M -L; lique, F; forêts, G Pineau des

    2014-01-01

    We present quantum dynamical calculations that describe the rotational excitation of H$_2$O due to collisions with H atoms. We used a recent, high accuracy potential energy surface, and solved the collisional dynamics with the close-coupling formalism, for total energies up to 12 000 cm$^{-1}$. From these calculations, we obtained collisional rate coefficients for the first 45 energy levels of both ortho- and para-H$_2$O and for temperatures in the range T = 5-1500 K. These rate coefficients are subsequently compared to the values previously published for the H$_2$O / He and H$_2$O / H$_2$ collisional systems. It is shown that no simple relation exists between the three systems and that specific calculations are thus mandatory.

  16. Production of Excited Atomic Hydrogen from Methane

    Science.gov (United States)

    Machacek, J. R.; Andrianarijaona, V. M.; Furst, J. E.; Gay, T. J.; Kilcoyne, A. L. D.; Landers, A. L.; McLaughlin, K. W.

    2009-05-01

    We have measured the production of Lyα and Hα fluorescence from atomic H for the photodissociation of CH4 by linearly-polarized photons with energies between 20 and 65 eV. Comparison between our Lyα relative cross section and that previously reported [1] show different peak height ratios. This also occurs in the Hα cross section when compared to previous data [2]. We do not observe as significant a drop in either cross section above 35 eV. Our measurements were taken with pressures two orders of magnitude lower than those used in ref. [1]. We present comparisons between data sets and a discussion of possible systematic effects. [1] H. Fukuzawa et al., J. Phys. B. 38, 565 (2005). [2] M. Kato et al., J. Phys. B. 35, 4383 (2002). Support provided by the NSF (Grant PHY-0653379), DOE (LBNL/ALS) and ANSTO (Access to Major Research Facilities Programme).

  17. The selectivity of charged phenyl radicals in hydrogen atom abstraction reactions with isopropanol.

    Science.gov (United States)

    Jing, Linhong; Guler, Leonard P; Pates, George; Kenttämaa, Hilkka I

    2008-10-09

    The vertical electron affinity is demonstrated to be a key factor in controlling the selectivity of charged phenyl radicals in hydrogen atom abstraction from isopropanol in the gas phase. The measurement of the total reaction efficiencies (hydrogen and/or deuterium atom abstraction) for unlabeled and partially deuterium-labeled isopropanol, and the branching ratios of hydrogen and deuterium atom abstraction, by using a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer, allowed the determination of the selectivity for each site in the unlabeled isopropanol. Examination of hydrogen atom abstraction from isopropanol by eight structurally different radicals revealed that the preferred site is the CH group. The selectivity of the charged phenyl radicals correlates with the radical's vertical electron affinity and the reaction efficiency. The smaller the vertical electron affinity of a radical, the lower its reactivity, and the greater the preference for the thermodynamically favored CH group over the CH3 group or the OH group. As the vertical electron affinity increases from 4.87 to 6.28 eV, the primary kinetic isotope effects decrease from 2.9 to 1.3 for the CD group, and the mixture of primary and alpha-secondary kinetic isotopes decreases from 6.0 to 2.4 for the CD3 group.

  18. Classical-field model of the hydrogen atom

    Science.gov (United States)

    Rashkovskiy, Sergey A.

    2017-02-01

    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.

  19. 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.

  20. Hydrogen and muonic-Hydrogen Atomic Spectra in Non-commutative Space-Time

    CERN Document Server

    Haghighat, M

    2014-01-01

    Comparing electronic Hydrogen with muonic Hydrogen shows that the discrepancy in measurement of the Lamb shift in the both systems are relatively of order of $(\\frac{m_\\mu}{m_e})^{4-5}$. We explore the spectrum of Hydrogen atom in noncommutative $QED$ to compare the noncommutative effects on the both bound states. We show that in the Lorentz violating noncommutative QED the ratio of NC-corrections is $(\\frac{m_\\mu}{m_e})^3$ while in the Lorentz conserving NCQED is $(\\frac{m_\\mu}{m_e})^5$. An uncertainty about $1 \\,Hz\\ll 3\\,kHz$ in the Lamb shift of Hydrogen atom leads to an NC correction about $10 \\,MHz$ in the Lorentz violating noncommutative QED and about $400 \\,GHz$ in the Lorentz conserving noncommutative QED.

  1. Cold three-body collisions in hydrogen-hydrogen-alkali atomic system

    CERN Document Server

    Wang, Yujun; Esry, B D

    2010-01-01

    We have studied hydrogen-hydrogen-alkali three-body systems in the adiabatic hyperspherical representation. For the spin-stretched case, there exists a single $X$H molecular state when $X$ is one of the bosonic alkali atoms: $^7$Li, $^{23}$Na, $^{39}$K, $^{87}$Rb and $^{133}$Cs. As a result, the {\\em only} recombination process is the one that leads to formation of $X$H molecules, H+H+$X

  2. NMR properties of hydrogen-bonded glycine cluster in gas phase

    Science.gov (United States)

    Carvalho, Jorge R.; da Silva, Arnaldo Machado; Ghosh, Angsula; Chaudhuri, Puspitapallab

    2016-11-01

    Density Functional Theory (DFT) calculations have been performed to study the effect of the hydrogen bond formation on the Nuclear Magnetic Resonance (NMR) parameters of hydrogen-bonded clusters of glycine molecules in gas-phase. DFT predicted isotropic chemical shifts of H, C, N and O of the isolated glycine with respect to standard reference materials are in reasonable agreement with available experimental data. The variations of isotropic and anisotropic chemical shifts for all atoms constituting these clusters containing up to four glycine molecules have been investigated systematically employing gradient corrected hybrid B3LYP functional with three different types of extended basis sets. The clusters are mainly stabilized by a network of strong hydrogen bonds among the carboxylic (COOH) groups of glycine monomers. The formation of hydrogen bond influences the molecular structure of the clusters significantly which, on the other hand, gets reflected in the variations of NMR properties. The carbon (C) atom of the sbnd COOH group, the bridging hydrogen (H) and the proton-donor oxygen (O) atom of the Osbnd H bond suffer downfield shift due to the formation of hydrogen bond. The hydrogen bond lengths and the structural complexity of the clusters are found to vary with the number of participating monomers. A direct correlation between the hydrogen bond length and isotropic chemical shift of the bridging hydrogen is observed in all cases. The individual variations of the principal axis elements in chemical shift tensor provide additional insight about the different nature of the monomers within the cluster.

  3. Creation of ultracold molecules from a Fermi gas of atoms

    OpenAIRE

    2003-01-01

    Since the realization of Bose-Einstein condensates (BEC) in atomic gases an experimental challenge has been the production of molecular gases in the quantum regime. A promising approach is to create the molecular gas directly from an ultracold atomic gas; for example, atoms in a BEC have been coupled to electronic ground-state molecules through photoassociation as well as through a magnetic-field Feshbach resonance. The availability of atomic Fermi gases provides the exciting prospect of coup...

  4. Conductance of hydrogen-incorporated Fe single-atom junction

    Directory of Open Access Journals (Sweden)

    ZHENG Xiaolong

    2015-08-01

    Full Text Available We study the origin of the 1G0 conductance of the Fe atom contact in hydrogen environment using first-principle calculations combined with nonequilibrium Green′s function theory.The Fe point contact with two H atoms adsorbed symmetrically and vertically to the transport direction gives rise to the 1G0 conductance.The spin-up channels is found to give a larger contribution to the conductance than the spin-down channels,which is understood from the transmission spectrum at the zero bias voltage.

  5. Powder Size and Distribution in Ultrasonic Gas Atomization

    Science.gov (United States)

    Rai, G.; Lavernia, E.; Grant, N. J.

    1985-08-01

    Ultrasonic gas atomization (USGA) produces powder sizes dependent on the ratio of the nozzle jet diameter to the distance of spread dt/R, Powder size distribution is attributed to the spread of atomizing gas jets during travel from the nozzle exit to the metal stream. The spread diminishes at higher gas atomization pressures. In this paper, calculated powder sizes and distribution are compared with experimentally determined values.

  6. Solid Hydrogen Experiments for Atomic Propellants: Image Analyses

    Science.gov (United States)

    Palaszewski, Bryan

    2002-01-01

    This paper presents the results of detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium. Solid particles of hydrogen were frozen in liquid helium, and observed with a video camera. The solid hydrogen particle sizes, their agglomerates, and the total mass of hydrogen particles were estimated. Particle sizes of 1.9 to 8 mm (0.075 to 0.315 in.) were measured. The particle agglomerate sizes and areas were measured, and the total mass of solid hydrogen was computed. A total mass of from 0.22 to 7.9 grams of hydrogen was frozen. Compaction and expansion of the agglomerate implied that the particles remain independent particles, and can be separated and controlled. These experiment image analyses are one of the first steps toward visually characterizing these particles, and allow designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  7. A discrete variable representation for electron-hydrogen atom scattering

    Energy Technology Data Exchange (ETDEWEB)

    Gaucher, L.F.

    1994-08-01

    A discrete variable representation (DVR) suitable for treating the quantum scattering of a low energy electron from a hydrogen atom is presented. The benefits of DVR techniques (e.g. the removal of the requirement of calculating multidimensional potential energy matrix elements and the availability of iterative sparse matrix diagonalization/inversion algorithms) have for many years been applied successfully to studies of quantum molecular scattering. Unfortunately, the presence of a Coulomb singularity at the electrically unshielded center of a hydrogen atom requires high radial grid point densities in this region of the scattering coordinate, while the presence of finite kinetic energy in the asymptotic scattering electron also requires a sufficiently large radial grid point density at moderate distances from the nucleus. The constraints imposed by these two length scales have made application of current DVR methods to this scattering event difficult.

  8. Fluorescence Quenching of Benzaldehyde in Water by Hydrogen Atom Abstraction.

    Science.gov (United States)

    Fletcher, Katharyn; Bunz, Uwe H F; Dreuw, Andreas

    2016-09-01

    We computed the mechanism of fluorescence quenching of benzaldehyde in water through relaxed potential energy surface scans. Time-dependent density functional theory calculations along the protonation coordinate from water to benzaldehyde reveal that photoexcitation to the bright ππ* (S3 ) state is immediately followed by ultrafast decay to the nπ* (S1 ) state. Evolving along this state, benzaldehyde (BA) abstracts a hydrogen atom, resulting in a BAH(.) and OH(.) radical pair. Benzaldehyde does not act as photobase in water, but abstracts a hydrogen atom from a nearby solvent molecule. The system finally decays back to the ground state by non-radiative decay and an electron transfers back to the OH(.) radical. Proton transfer from BAH(+) to OH(-) restores the initial situation, BA in water.

  9. Massive stars formed in atomic hydrogen reservoirs: HI observations of gamma-ray burst host galaxies

    CERN Document Server

    Michałowski, Michał J; Hjorth, J; Krumholz, M R; Tanvir, N R; Kamphuis, P; Burlon, D; Baes, M; Basa, S; Berta, S; Ceron, J M Castro; Crosby, D; D'Elia, V; Elliott, J; Greiner, J; Hunt, L K; Klose, S; Koprowski, M P; Floc'h, E Le; Malesani, D; Murphy, T; Guelbenzu, A Nicuesa; Palazzi, E; Rasmussen, J; Rossi, A; Savaglio, S; Schady, P; Sollerman, J; Postigo, A de Ugarte; Watson, D; van der Werf, P; Vergani, S D; Xu, D

    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 the fuel of star formation. Moreover, optical spectroscopy of GRB afterglows implies that the molecular phase constitutes only a small fraction of the gas along the GRB line-of-sight. Here we report the first ever 21 cm line observations of GRB host galaxies, using the Australia Telescope Compact Array, implying high levels of atomic hydrogen (HI), which suggests that the connection between atomic gas and star formation is stronger than previously thought, with star formation being potentially directly fuelled by atomic gas (or with very efficient HI-to-H2 conversion and rapid exhaustion of molecular gas), as has been theoretically shown to be possible. This can happen in low metallicity gas near the onset of star forma...

  10. Dynamical localization: Hydrogen atoms in magnetic and microwave fields

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, F.; Casati, G. [Dipartimento di Fisica dellUniversita, Via Castelnuovo 7, 22100 Como (Italy); Shepelyansky, D.L. [Laboratoire de Physique Quantique, UMR C5626 du CNRS, Universite Paul Sabatier, 31062, Toulouse (France)

    1997-03-01

    We show that dynamical localization for excited hydrogen atoms in magnetic and microwave fields takes place at quite low microwave frequency ({omega}n{sup 3}{lt}1). Estimates of the localization length are given for different parameter regimes, showing that the quantum delocalization border drops significantly as compared to the case of zero magnetic field. This opens up broad possibilities for laboratory investigations. {copyright} {ital 1997} {ital The American Physical Society}

  11. Dirac Equation in Noncommutative Space for Hydrogen Atom

    CERN Document Server

    Adorno, T C; Chaichian, M; Gitman, D M; Tureanu, A

    2009-01-01

    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 $2S_{1/2}, 2P_{1/2}$ and $ 2P_{3/2}$ is lifted completely, such that new transition channels are allowed.

  12. 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.

  13. 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).

  14. Manufacture and deflagration of an atomic hydrogen propellant

    Science.gov (United States)

    Rosen, G.

    1974-01-01

    It is observed that the use of very low temperatures (in the range from 0.1 to 1.5 K) produced by advanced cryogenic apparatus and the use of very strong magnetic fields (in the range from 50 to 100 kG) produced by superconducting magnets can yield a significant improvement in the atomic hydrogen trapping effectiveness of an H2 matrix. The use of a radioactive beta-ray emiter isotope may yield H-H2 propellants (with a specific impulse of about 740 sec) by secondary electron impact dissociations of H2 in an impregnated matrix maintained below 1 K in a strong magnetic field. Another method for manufacturing an H-H2 propellant involves bombardment of supercooled solid H2 with a cyclotron-produced beam of 10-MeV hydrogen atoms. The matrix-isolated atomic hydrogen must be used directly without prior melting as a solid propellant, and an analysis of the steady deflagration is presented.

  15. Alkane desaturation by concerted double hydrogen atom transfer to benzyne.

    Science.gov (United States)

    Niu, Dawen; Willoughby, Patrick H; Woods, Brian P; Baire, Beeraiah; Hoye, Thomas R

    2013-09-26

    The removal of two vicinal hydrogen atoms from an alkane to produce an alkene is a challenge for synthetic chemists. In nature, desaturases and acetylenases are adept at achieving this essential oxidative functionalization reaction, for example during the biosynthesis of unsaturated fatty acids, eicosanoids, gibberellins and carotenoids. Alkane-to-alkene conversion almost always involves one or more chemical intermediates in a multistep reaction pathway; these may be either isolable species (such as alcohols or alkyl halides) or reactive intermediates (such as carbocations, alkyl radicals, or σ-alkyl-metal species). Here we report a desaturation reaction of simple, unactivated alkanes that is mechanistically unique. We show that benzynes are capable of the concerted removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this exothermic, net redox process was enabled by the simple thermal generation of reactive benzyne intermediates through the hexadehydro-Diels-Alder cycloisomerization reaction of triyne substrates. We are not aware of any single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane. Computational studies indicate a preferred geometry with eclipsed vicinal C-H bonds in the alkane donor.

  16. 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.

  17. Simulation of the Cosmic Evolution of Atomic and Molecular Hydrogen in Galaxies

    CERN Document Server

    Obreschkow, D; De Lucia, G; Khochfar, S; Rawlings, S

    2009-01-01

    We present a simulation of the cosmic evolution of the atomic and molecular phases of the cold hydrogen gas in about 3e7 galaxies, obtained by post-processing the virtual galaxy catalog produced by (De Lucia et al. 2007) on the Millennium Simulation of cosmic structure (Springel et al. 2005). Our method uses a set of physical prescriptions to assign neutral atomic hydrogen (HI) and molecular hydrogen (H2) to galaxies, based on their total cold gas masses and a few additional galaxy properties. These prescriptions are specially designed for large cosmological simulations, where, given current computational limitations, individual galaxies can only be represented by simplistic model-objects with a few global properties. Our recipes allow us to (i) split total cold gas masses between HI, H2, and Helium, (ii) assign realistic sizes to both the HI- and H2-disks, and (iii) evaluate the corresponding velocity profiles and shapes of the characteristic radio emission lines. The results presented in this paper include ...

  18. $K$-series X-rays yield measurement of kaonic hydrogen atoms in gaseous target

    CERN Document Server

    Bazzi, M; Bellotti, G; Berucci, C; Bragadireanu, A M; Bosnar, D; Cargnelli, M; Curceanu, C; Butt, A D; d'Uffizi, A; Fiorini, C; Ghio, F; Guaraldo, C; Hayanao, R S; Iliescu, M; Ishiwatari, T; Iwasaki, M; Sandri, P Levi; Marton, J; Okada, S; Pietreanu, D; Piscicchia, K; Vidal, A Romero; Sbardella, E; Scordo, A; Shi, H; Sirghi, D L; Sirghi, F; Tatsuno, H; Doce, O Vazquez; Widmann, E; Zmeskal, J

    2016-01-01

    We measured the $K$-series X-rays of the $K^{-}p$ exotic atom in the SIDDHARTA experiment with a gaseous hydrogen target of 1.3 g/l, which is about 15 times the $\\rho_{\\rm STP}$ of hydrogen gas. At this density, the absolute yields of kaonic X-rays, when a negatively charged kaon stopped inside the target, were determined to be 0.012$^{+0.004}_{-0.003}$ for $K_{\\alpha}$ and 0.043$^{+0.012}_{-0.011}$ for all the $K$-series transitions $K_{tot}$. These results, together with the KEK E228 experiment results, confirm for the first time a target density dependence of the yield predicted by the cascade models, and provide valuable information to refine the parameters used in the cascade models for the kaonic atoms.

  19. Hydrogen gas storage in fluorinated ultramicroporous tunnel crystal

    Science.gov (United States)

    Kataoka, Keisuke; Katagiri, Toshimasa

    2012-07-01

    We report hydrogen storage at an ordinary pressure due to a bottle-neck effect of an ultramicroporous crystal. Stored hydrogen was kept at an ordinary pressure below -110 °C. The amounts of stored hydrogen gas linearly correlated with the initial pressures. These phenomena suggested the ultramicroporous tunnels worked as a molecular gas cylinder.We report hydrogen storage at an ordinary pressure due to a bottle-neck effect of an ultramicroporous crystal. Stored hydrogen was kept at an ordinary pressure below -110 °C. The amounts of stored hydrogen gas linearly correlated with the initial pressures. These phenomena suggested the ultramicroporous tunnels worked as a molecular gas cylinder. Electronic supplementary information (ESI) available. CCDC 246922. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30940h

  20. 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.

  1. Model study in chemisorption: atomic hydrogen on beryllium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Bauschlicher, C.W. Jr.

    1976-08-01

    The interaction between atomic hydrogen and the (0001) surface of Be metal has been studied by ab initio electronic structure theory. Self-consistent-field (SCF) calculations have been performed using minimum, optimized minimum, double zeta and mixed basis sets for clusters as large as 22 Be atoms. The binding energy and equilibrium geometry (the distance to the surface) were determined for 4 sites. Both spatially restricted (the wavefunction was constrained to transform as one of the irreducible representations of the molecular point group) and unrestricted SCF calculations were performed. Using only the optimized minimum basis set, clusters containing as many as 22 beryllium atoms have been investigated. From a variety of considerations, this cluster is seen to be nearly converged within the model used, providing the most reliable results for chemisorption. The site dependence of the frequency is shown to be a geometrical effect depending on the number and angle of the bonds. The diffusion of atomic hydrogen through a perfect beryllium crystal is predicted to be energetically unfavorable. The cohesive energy, the ionization energy and the singlet-triplet separation were computed for the clusters without hydrogen. These quantities can be seen as a measure of the total amount of edge effects. The chemisorptive properties are not related to the total amount of edge effects, but rather the edge effects felt by the adsorbate bonding berylliums. This lack of correlation with the total edge effects illustrates the local nature of the bonding, further strengthening the cluster model for chemisorption. A detailed discussion of the bonding and electronic structure is included. The remaining edge effects for the Be/sub 22/ cluster are discussed.

  2. Evolution of the atomic and molecular gas content of galaxies

    NARCIS (Netherlands)

    Popping, Gergö; Somerville, Rachel S.; Trager, Scott C.

    2014-01-01

    We study the evolution of atomic and molecular gas in galaxies in semi-analytic models of galaxy formation that include new modelling of the partitioning of cold gas in galactic discs into atomic, molecular, and ionized phases. We adopt two scenarios for the formation of molecules: one pressure base

  3. Allowed and forbidden transitions in artificial hydrogen and helium atoms.

    Science.gov (United States)

    Fujisawa, Toshimasa; Austing, David Guy; Tokura, Yasuhiro; Hirayama, Yoshiro; Tarucha, Seigo

    2002-09-19

    The strength of radiative transitions in atoms is governed by selection rules that depend on the occupation of atomic orbitals with electrons. Experiments have shown similar electron occupation of the quantized energy levels in semiconductor quantum dots--often described as artificial atoms. But unlike real atoms, the confinement potential of quantum dots is anisotropic, and the electrons can easily couple with phonons of the material. Here we report electrical pump-and-probe experiments that probe the allowed and 'forbidden' transitions between energy levels under phonon emission in quantum dots with one or two electrons (artificial hydrogen and helium atoms). The forbidden transitions are in fact allowed by higher-order processes where electrons flip their spin. We find that the relaxation time is about 200 micro s for forbidden transitions, 4 to 5 orders of magnitude longer than for allowed transitions. This indicates that the spin degree of freedom is well separated from the orbital degree of freedom, and that the total spin in the quantum dots is an excellent quantum number. This is an encouraging result for potential applications of quantum dots as basic entities for spin-based quantum information storage.

  4. Plasma screening effects on the energies of hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    Soylu, A. [Department of Physics, Nigde University, 51240 Nigde (Turkey)

    2012-07-15

    A more general exponential cosine screened Coulomb potential is used for the first time to investigate the screening effects on the hydrogen atom in plasmas. This potential is examined for four different cases that correspond to four different type potentials when the different parameters are used in the potential within the framework of the well-known asymptotic iteration method. By solving the corresponding the radial Schroedinger equation with the screened and exponential cosine screened Coulomb potentials and comparing the obtained energy eigenvalues with the results of other studies, the applicability of the method to this kind of plasma physics problem is shown. The energy values of more general exponential cosine screened Coulomb potential are presented for various parameters in the potential. One of the advantages of the present potential is that it exhibits stronger screening effect than that of the exponential cosine screened Coulomb potential and it is also reduced to screened Coulomb and exponential cosine screened Coulomb as well as Coulomb potentials for special values of parameters. The parameters in the potential would be useful to model screening effects which cause an increase or decrease in the energy values of hydrogen atom in both Debye and quantum plasmas and in this manner this potential would be useful for the investigations of the atomic structure and collisions in plasmas.

  5. On-Board Hydrogen Gas Production System For Stirling Engines

    Science.gov (United States)

    Johansson, Lennart N.

    2004-06-29

    A hydrogen production system for use in connection with Stirling engines. The production system generates hydrogen working gas and periodically supplies it to the Stirling engine as its working fluid in instances where loss of such working fluid occurs through usage through operation of the associated Stirling engine. The hydrogen gas may be generated by various techniques including electrolysis and stored by various means including the use of a metal hydride absorbing material. By controlling the temperature of the absorbing material, the stored hydrogen gas may be provided to the Stirling engine as needed. A hydrogen production system for use in connection with Stirling engines. The production system generates hydrogen working gas and periodically supplies it to the Stirling engine as its working fluid in instances where loss of such working fluid occurs through usage through operation of the associated Stirling engine. The hydrogen gas may be generated by various techniques including electrolysis and stored by various means including the use of a metal hydride absorbing material. By controlling the temperature of the absorbing material, the stored hydrogen gas may be provided to the Stirling engine as needed.

  6. 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.

  7. Changes in Work Function and Electrical Resistance of Pt Thin Films in the Presence of Hydrogen Gas

    Science.gov (United States)

    Tsukada, Keiji; Inoue, Hirotsugu; Katayama, Fumiya; Sakai, Kenji; Kiwa, Toshihiko

    2012-01-01

    The changes in the electrical properties, such as work function and resistance, of Pt thin films in the presence of hydrogen gas were studied. They were simultaneously measured with a flow-through cell at different concentrations of hydrogen gas in atmosphere containing gaseous nitrogen and that containing air. The resistance was measured by a four-terminal sensing method and the relative work function changes were measured using a field effect transistor. In both atmospheres, the resistance decreased as the concentration of hydrogen gas increased. This result was repeatable only in air because of the differences in the dynamic mechanism of increased density of electrical carriers inside the Pt film as a result of diffused H atoms. In the nitrogen atmosphere, the diffused H atoms were not easily released because of the surface barrier. On the other hand, oxygen gas reacted with H atoms at the surface and this reaction accelerated atom release into air. The work function showed repeatable responses in both atmospheres, but the response characteristics were different. The equilibrium reaction between the adsorption and desorption of hydrogen occurred at the surface in the nitrogen atmosphere, whereas the equilibrium reaction of hydrogen and oxygen to form water molecules occurred in air. The changes in work function and resistance in the presence of hydrogen were due to changes in dissociated hydrogen intensity in the bulk, as well as to the surface reactions.

  8. Development Of A Centrifugal Hydrogen Pipeline Gas Compressor

    Energy Technology Data Exchange (ETDEWEB)

    Di Bella, Francis A. [Concepts NREC, White River Junction, VY (United States)

    2015-04-16

    Concepts NREC (CN) has completed a Department of Energy (DOE) sponsored project to analyze, design, and fabricate a pipeline capacity hydrogen compressor. The pipeline compressor is a critical component in the DOE strategy to provide sufficient quantities of hydrogen to support the expected shift in transportation fuels from liquid and natural gas to hydrogen. The hydrogen would be generated by renewable energy (solar, wind, and perhaps even tidal or ocean), and would be electrolyzed from water. The hydrogen would then be transported to the population centers in the U.S., where fuel-cell vehicles are expected to become popular and necessary to relieve dependency on fossil fuels. The specifications for the required pipeline hydrogen compressor indicates a need for a small package that is efficient, less costly, and more reliable than what is available in the form of a multi-cylinder, reciprocating (positive displacement) compressor for compressing hydrogen in the gas industry.

  9. The EAGLE simulations: atomic hydrogen associated with galaxies

    CERN Document Server

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

    2016-01-01

    We examine the properties of atomic hydrogen (HI) associated with galaxies in the 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 HI 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 HI column densities, leading to an HI deficiency in low-mass ($M_\\star < 10^{10}M_\\odot$) galaxies and poor reproduction of the observed HI mass function. These shortcomings are largely absent from EAGLE simulations featuring a factor of 8 (2) better mass (spatial) resolution, within which the HI mass of galaxies evolves more mildly from $z=1$ to $0$ than in the standard-resolution simulations. The largest-volume simulation reproduces the observed clus...

  10. Hydrogen Gas Production from Nuclear Power Plant in Relation to Hydrogen Fuel Cell Technologies Nowadays

    Science.gov (United States)

    Yusibani, Elin; Kamil, Insan; Suud, Zaki

    2010-06-01

    Recently, world has been confused by issues of energy resourcing, including fossil fuel use, global warming, and sustainable energy generation. Hydrogen may become the choice for future fuel of combustion engine. Hydrogen is an environmentally clean source of energy to end-users, particularly in transportation applications because without release of pollutants at the point of end use. Hydrogen may be produced from water using the process of electrolysis. One of the GEN-IV reactors nuclear projects (HTGRs, HTR, VHTR) is also can produce hydrogen from the process. In the present study, hydrogen gas production from nuclear power plant is reviewed in relation to commercialization of hydrogen fuel cell technologies nowadays.

  11. The distribution of atomic hydrogen in EAGLE galaxies: morphologies, profiles, and HI holes

    CERN Document Server

    Bahe, Yannick M; Kauffmann, Guinevere; Bower, Richard G; Schaye, Joop; Furlong, Michelle; Lagos, Claudia; Schaller, Matthieu; Trayford, James W; Vecchia, Claudio Dalla; Theuns, Tom

    2015-01-01

    We compare the mass and internal distribution of atomic hydrogen (HI) in 2200 present-day central galaxies with M_star > 10^10 M_Sun from the 100 Mpc EAGLE Reference simulation to observational data. Atomic hydrogen fractions are corrected for self-shielding using a fitting formula from radiative transfer simulations and for the presence of molecular hydrogen using an empirical or a theoretical prescription from the literature. The resulting neutral hydrogen fractions, M_(HI+H2)/M_star, agree with observations to better than 0.1 dex for galaxies with M_star between 10^10 and 10^11 M_Sun. Our fiducial, empirical H2 model based on gas pressure results in galactic HI mass fractions, M_HI/M_star, that agree with observations from the GASS survey to better than 0.3 dex, but the alternative theoretical H2 formula leads to a negative offset in M_HI/M_star of up to 0.5 dex. Visual inspection reveals that most HI disks in simulated HI-rich galaxies are vertically disturbed, plausibly due to recent accretion events. Ma...

  12. The HERMES Polarized Hydrogen and Deuterium Gas Target in the HERA Electron Storage Ring

    CERN Document Server

    Airapetian, A; Akopov, Z; Amarian, M; Ammosov, V V; Andrus, A; Aschenauer, E C; Augustyniak, W; Avakian, R; Avetisian, A; Avetissian, E; Bailey, P; Baturin, V; Baumgarten, C; Beckmann, M; Belostotskii, S; Bernreuther, S; Bianchi, N; Blok, H P; Böttcher, Helmut B; Borisov, A; Bouwhuis, M; Brack, J; Brüll, A; Bryzgalov, V V; Capitani, G P; Chiang, H C; Ciullo, G; Contalbrigo, M; Dalpiaz, P F; De Leo, R; De Nardo, L; De Sanctis, E; Devitsin, E G; Di Nezza, P; Düren, M; Ehrenfried, M; Elalaoui-Moulay, A; Elbakian, G M; Ellinghaus, F; Elschenbroich, U; Ely, J; Fabbri, R; Fantoni, A; Feshchenko, A; Felawka, L; Fox, B; Franz, J; Frullani, S; Gärber, Y; Gapienko, G; Gapienko, V; Garibaldi, F; Garrow, K; Garutti, E; Gaskell, D; Gavrilov, G E; Karibian, V; Graw, G; Grebenyuk, O; Greeniaus, L G; Hafidi, K; Hartig, M; Hasch, D; Heesbeen, D; Henoch, M; Hertenberger, R; Hesselink, W H A; Hillenbrand, A; Hoek, M; Holler, Y; Hommez, B; Iarygin, G; Ivanilov, A; Izotov, A; Jackson, H E; Jgoun, A; Kaiser, R; Kinney, E; Kiselev, A; Königsmann, K C; Kopytin, M; Korotkov, V A; Kozlov, V; Krauss, B; Krivokhizhin, V G; Lagamba, L; Lapikas, L; Laziev, A; Lenisa, P; Liebing, P; Lindemann, T; Lipka, K; Lorenzon, W; Lü, J; Maiheu, B; Makins, N C R; Marianski, B; Marukyan, H O; Masoli, F; Mexner, V; Meyners, N; Miklukho, O; Miller, C A; Miyachi, Y; Muccifora, V; Nagaitsev, A; Nappi, E; Naryshkin, Yu; Nass, A; Negodaev, M A; Nowak, Wolf-Dieter; Oganessyan, K; Ohsuga, H; Orlandi, G; Pickert, N; Potashov, S Yu; Potterveld, D H; Raithel, M; Reggiani, D; Reimer, P E; Reischl, A; Reolon, A R; Riedl, C; Rith, K; Rosner, G; Rostomyan, A; Rubacek, L; Ryckbosch, D; Salomatin, Yu I; Sanjiev, I; Savin, I; Scarlett, C; Schäfer, A; Schill, C; Schnell, G; Schüler, K P; Schwind, A; Seele, J; Seidl, R; Seitz, B; Shanidze, R G; Shearer, C; Shibata, T A; Shutov, V B; Simani, M C; Sinram, K; Stancari, M D; Statera, M; Steffens, E; Steijger, J J M; Stewart, J; Stösslein, U; Tait, P; Tanaka, H; Taroian, S P; Tchuiko, B; Terkulov, A R; Tkabladze, A V; Trzcinski, A; Tytgat, M; Vandenbroucke, A; Van der Nat, P B; van der Steenhoven, G; Vetterli, Martin C; Vikhrov, V; Vincter, M G; Visser, J; Vogel, C; Vogt, M; Volmer, J; Weiskopf, C; Wendland, J; Wilbert, J; Ybeles-Smit, G V; Yen, S; Zihlmann, B; Zohrabyan, H G; Zupranski, P

    2004-01-01

    The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in use since 1996 with the polarized electron beam of HERA at DESY to study the spin structure of the nucleon. Polarized atoms from a Stern-Gerlach Atomic Beam Source are injected into a storage cell internal to the HERA electron ring. Atoms diffusing from the center of the storage cell into a side tube are analyzed to determine the atomic fraction and the atomic polarizations. The atoms have a nuclear polarization, the axis of which is defined by an external magnetic holding field. The holding field was longitudinal during 1996-2000, and was changed to transverse in 2001. The design of the target is described, the method for analyzing the target polarization is outlined, and the performance of the target in the various running periods is presented.

  13. 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.)

  14. Asymmetry of the natural line profile for the hydrogen atom.

    Science.gov (United States)

    Labzowsky, L N; Solovyev, D A; Plunien, G; Soff, G

    2001-10-01

    The asymmetry of the natural line profile for transitions in hydrogenlike atoms is evaluated within a QED framework. For the Lyman- alpha 1s-2p absorption transition in neutral hydrogen this asymmetry results in an additional energy shift of 2.929 856 Hz. For the 2s(1/2)-2p(3/2) transition it amounts to -1.512 674 Hz. As a new feature this correction turns out to be process dependent. The quoted numbers refer to the Compton-scattering process.

  15. Relativistic Ionization of Hydrogen Atoms by Positron Impact

    Directory of Open Access Journals (Sweden)

    Amal Chahboune

    2016-03-01

    Full Text Available Relativistic triple differential cross-sections (TDCS for ionization of hydrogen atoms by positron impact have been calculated in the symmetric coplanar geometry. We have used Dirac wave functions to describe free electron’s and positron’s sates. The relativistic formalism is examined by taking the non relativistic limit. Present results are compared with those for the corresponding electron-impact case. In the first Born approximation, we found that the TDCS for positron impact ionization exceeds that for electron impact for all energies in accordance with the result obtained by several other theories.

  16. Wave mechanics in quantum phase space: hydrogen atom

    Institute of Scientific and Technical Information of China (English)

    LU Jun

    2007-01-01

    The rigorous sohutions of the stationary Schr(o)dinger equation for hydrogen atom are solved with the wave-mechanics method within the framework of the quantum phase-space representation established by Torres-Vega and Frederick. The "Fourier-like"projection transformations of wave function from the phase space to position and momentum spaces are extended to three-dimensional systems. The eigenfunctions in general position and momentum spaces could be obtained through the transformations from eigenfunction in the phase space.

  17. Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

    Science.gov (United States)

    Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.

    1988-01-01

    The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  18. The photon scattering cross-sections of atomic hydrogen

    CERN Document Server

    Grunefeld, Swaantje J; Cheng, Yongjun

    2016-01-01

    We present a unified view of the frequency dependence of the various scattering processes involved when a neutral hydrogen atom interacts with a monochromatic, linearly-polarized photon. A computational approach is employed of the atom trapped by a finite-sized-box due to a finite basis-set expansion, which generates a set of transition matrix elements between $E0$ pseudostates. We introduce a general computational methodology that enables the computation of the frequency-dependent dipole transition polarizability with one real and two different imaginary contributions. These dipole transition polarizabilities are related to the cross-sections of one-photon photoionization, Rayleigh, Raman, and Compton scattering. Our numerical calculations reveal individual Raman scattering cross-sections above threshold that can rapidly vanish and revive. Furthermore, our numerical Compton cross-sections do not overtly suffer from the infra-red divergence problem, and are three orders-of-magnitude higher than previous analy...

  19. Gas lasers applied atomic collision physics, v.3

    CERN Document Server

    McDaniel, E W

    1982-01-01

    Applied Atomic Collision Physics, Volume 3: Gas Lasers describes the applications of atomic collision physics in the development of many types of gas lasers. Topics covered range from negative ion formation in gas lasers to high-pressure ion kinetics and relaxation of molecules exchanging vibrational energy. Ion-ion recombination in high-pressure plasmas is also discussed, along with electron-ion recombination in gas lasers and collision processes in chemical lasers.Comprised of 14 chapters, this volume begins with a historical summary of gas laser developments and an overview of the basic ope

  20. [Raman spectroscopic investigation of hydrogen storage in nitrogen gas hydrates].

    Science.gov (United States)

    Meng, Qing-guo; Liu, Chang-ling; Ye, Yu-guang; Li, Cheng-feng

    2012-08-01

    Recently, hydrogen storage using clathrate hydrate as a medium has become a hotspot of hydrogen storage research In the present paper, the laser Raman spectroscopy was used to study the hydrogen storage in nitrogen hydrate. The synthetic nitrogen hydrate was reacted with hydrogen gas under relatively mild conditions (e.g., 15 MPa, -18 degrees C). The Raman spectra of the reaction products show that the hydrogen molecules have enclathrated the cavities of the nitrogen hydrate, with multiple hydrogen cage occupancies in the clathrate cavities. The reaction time is an important factor affecting the hydrogen storage in nitrogen hydrate. The experimental results suggest that nitrogen hydrates are expected to be an effective media for hydrogen storage.

  1. A molecular dynamics simulation of hydrogen atoms collisions on an H-preadsorbed silica surface

    Science.gov (United States)

    Rutigliano, M.; Gamallo, P.; Sayós, R.; Orlandini, S.; Cacciatore, M.

    2014-08-01

    The interaction of hydrogen atoms and molecules with a silica surface is relevant for many research and technological areas. Here, the dynamics of hydrogen atoms colliding with an H-preadsorbed β-cristobalite (0 0 1) surface has been studied using a semiclassical collisional method in conjunction with a recently developed analytical potential energy surface based on density functional theory (DFT) calculations. The atomic recombination probability via an Eley-Rideal (E-R) mechanism, as well as the probabilities for other competitive surface processes, have been determined in a broad range of collision energies (0.04-3.0 eV) for off-normal (θv = 45°) and normal (θv = 0°) incidence and for two different surface temperatures (TS = 300 and 1000 K). H2,gas molecules form in roto-vibrational excited levels while the energy transferred to the solid surface is below 10% for all simulated conditions. Finally, the global atomic recombination coefficient (γE-R) and vibrational state resolved recombination coefficients (γ(v)) were calculated and compared with the available experimental values. The calculated collisional data are of interest in chemical kinetics studies and fluid dynamics simulations of silica surface processes in H-based low-temperature, low-pressure plasmas.

  2. Adsorption process to recover hydrogen from feed gas mixtures having low hydrogen concentration

    Science.gov (United States)

    Golden, Timothy Christopher; Weist, Jr., Edward Landis; Hufton, Jeffrey Raymond; Novosat, Paul Anthony

    2010-04-13

    A process for selectively separating hydrogen from at least one more strongly adsorbable component in a plurality of adsorption beds to produce a hydrogen-rich product gas from a low hydrogen concentration feed with a high recovery rate. Each of the plurality of adsorption beds subjected to a repetitive cycle. The process comprises an adsorption step for producing the hydrogen-rich product from a feed gas mixture comprising 5% to 50% hydrogen, at least two pressure equalization by void space gas withdrawal steps, a provide purge step resulting in a first pressure decrease, a blowdown step resulting in a second pressure decrease, a purge step, at least two pressure equalization by void space gas introduction steps, and a repressurization step. The second pressure decrease is at least 2 times greater than the first pressure decrease.

  3. Trends in demand for hydrogen gas and gas separation technology

    Energy Technology Data Exchange (ETDEWEB)

    Osumi, Y.

    1983-01-01

    In the 1970s, the total world consumption of hydrogen was 2 x 10/SUP/1/SUP/1 Nm/SUP/3, of which approximately 50% was used for ammonia synthesis. Recently, however, large quantities of hydrogen have been used in the production of semiconductors and optical fibres. Hydrogen can be produced by steam reforming, partial oxidation, coal gasification, electrolysis, petroleum refining and thermochemical cycles. Cooling, adsorption, membranes and metal hydrides are used for separating the hydrogen. (In English)

  4. Dynamics of hydrogen-like atom bounded by maximal acceleration

    CERN Document Server

    Friedman, Yaakov

    2012-01-01

    The existence of a maximal acceleration for massive objects was conjectured by Caianiello 30 years ago based on the Heisenberg uncertainty relations. Many consequences of this hypothesis have been studied, but until now, there has been no evidence that boundedness of the acceleration may lead to quantum behavior. In previous research, we predicted the existence of a universal maximal acceleration and developed a new dynamics for which all admissible solutions have an acceleration bounded by the maximal one. Based on W. K\\"{u}ndig's experiment, as reanalyzed by Kholmetskii et al, we estimated its value to be of the order $10^{19}m/s^2$. We present here a solution of our dynamical equation for a classical hydrogen-like atom and show that this dynamics leads to some aspects of quantum behavior. We show that the position of an electron in a hydrogen-like atom can be described only probabilistically. We also show that in this model, the notion of "center of mass" must be modified. This modification supports the no...

  5. Low cost hydrogen/novel membrane technology for hydrogen separation from synthesis gas

    Energy Technology Data Exchange (ETDEWEB)

    Baker, R.W.; Bell, C.M.; Chow, P.; Louie, J.; Mohr, J.M.; Peinemann, K.V.; Pinnau, I.; Wijmans, J.G.; Gottschlich, D.E.; Roberts, D.L.

    1990-10-01

    The production of hydrogen from synthesis gas made by gasification of coal is expensive. The separation of hydrogen from synthesis gas is a major cost element in the total process. In this report we describe the results of a program aimed at the development of membranes and membrane modules for the separation and purification of hydrogen from synthesis gas. The performance properties of the developed membranes were used in an economic evaluation of membrane gas separation systems in the coal gasification process. Membranes tested were polyetherimide and a polyamide copolymer. The work began with an examination of the chemical separations required to produce hydrogen from synthesis gas, identification of three specific separations where membranes might be applicable. A range of membrane fabrication techniques and module configurations were investigated to optimize the separation properties of the membrane materials. Parametric data obtained were used to develop the economic comparison of processes incorporating membranes with a base-case system without membranes. The computer calculations for the economic analysis were designed and executed. Finally, we briefly investigated alternative methods of performing the three separations in the production of hydrogen from synthesis gas. The three potential opportunities for membranes in the production of hydrogen from synthesis gas are: (1) separation of hydrogen from nitrogen as the final separation in a air-blown or oxygen-enriched air-blown gasification process, (2) separation of hydrogen from carbon dioxide and hydrogen sulfide to reduce or eliminate the conventional ethanolamine acid gas removal unit, and (3) separation of hydrogen and/or carbon dioxide form carbon monoxide prior to the shift reactor to influence the shift reaction. 28 refs., 54 figs., 40 tabs.

  6. Comment on "Wigner phase-space distribution function for the hydrogen atom"

    DEFF Research Database (Denmark)

    Dahl, Jens Peder; Springborg, Michael

    1999-01-01

    We object to the proposal that the mapping of the three-dimensional hydrogen atom into a four-dimensional harmonic oscillator can be readily used to determine the Wigner phase-space distribution function for the hydrogen atom. [S1050-2947(99)07005-5].......We object to the proposal that the mapping of the three-dimensional hydrogen atom into a four-dimensional harmonic oscillator can be readily used to determine the Wigner phase-space distribution function for the hydrogen atom. [S1050-2947(99)07005-5]....

  7. Hydrogen storage materials discovery via high throughput ball milling and gas sorption.

    Science.gov (United States)

    Li, Bin; Kaye, Steven S; Riley, Conor; Greenberg, Doron; Galang, Daniel; Bailey, Mark S

    2012-06-11

    The lack of a high capacity hydrogen storage material is a major barrier to the implementation of the hydrogen economy. To accelerate discovery of such materials, we have developed a high-throughput workflow for screening of hydrogen storage materials in which candidate materials are synthesized and characterized via highly parallel ball mills and volumetric gas sorption instruments, respectively. The workflow was used to identify mixed imides with significantly enhanced absorption rates relative to Li2Mg(NH)2. The most promising material, 2LiNH2:MgH2 + 5 atom % LiBH4 + 0.5 atom % La, exhibits the best balance of absorption rate, capacity, and cycle-life, absorbing >4 wt % H2 in 1 h at 120 °C after 11 absorption-desorption cycles.

  8. Thermo-Gas Dynamics of Hydrogen Combustion and Explosion

    CERN Document Server

    Gelfand, Boris E; Medvedev, Sergey P; Khomik, Sergey V

    2012-01-01

    The potential of hydrogen as an important future energy source has generated fresh interest in the study of hydrogenous gas mixtures. Indeed, both its high caloricity and reactivity are unique properties, the latter underscoring safety considerations when handling such mixtures.   The present monograph is devoted to the various aspects of hydrogen combustion and explosion processes. In addition to theoretical and phenomenological considerations, this work also collates the results of many experiments from less well known sources. The text reviews the literature in this respect, thereby providing valuable information about the thermo-gas-dynamical parameters of combustion processes for selected experimental settings in a range of scientific and industrial applications.

  9. Steam reforming of natural gas with integrated hydrogen separation for hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Oertel, M.; Schmitz, J.; Weirich, W.; Jendryssek-Neumann, D.; Schulten, R.

    1987-08-01

    The development of heat resistant permeation membranes has opened up new possibilities for the conversion of fossil energy resources. In steam reforming of natural gas, such membranes even permit a direct production of hydrogen at high temperatures during the conversion of feed hydrocarbons. Further gas processing, such as required for reformer gas in existing hydrogen production processes, is not necessary. Due to continuous hydrogen discharge directly in the reformer tube, the chemical equilibrium of the occurring reactions becomes displaced towards the products, resulting in more favourable process conditions and, consequently, in improved by 36% utilization of the feed hydrocarbons. At the same time, the hydrogen yield increases by 44%. The heat required, which is provided by a high temperature reactor, is 17% in excess of that in conventional plants. It can be expected that the simplified process design will produce substantial cost advantages over the existing processes for the production of hydrogen.

  10. Hydrogen mitigation Gas Characterization System: System design description

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, T.C.

    1998-07-17

    The Gas Characterization System (GCS) design is described for flammable gas monitoring. Tank 241-SY-101 (SY-101) is known to experience periodic tank level increases and decreases during which hydrogen gas is released. It is believed that the generated gases accumulate in the solids-containing layer near the bottom of the tank. Solids and gases are also present in the crust and may be present in the interstitial liquid layer. The accumulation of gases creates a buoyancy that eventually overcomes the density and bonding strength of the bottom layer. When this happens, the gas from the bottom layer is released upward through the liquid layer to the vapor space above the tank crust. Previous monitoring of the vapor space gases during such an event indicates hydrogen release concentrations greater than the lower flammability limit (LFL) of hydrogen in a partial nitrous oxide atmosphere. Tanks 241-AN-105, 241-AW-101, and 241-SY-103 have been identified as having the potential to behave similar to SY-101. These waste tanks have been placed on the flammable gas watch list (FGWL). All waste tanks on the FGWL will have a standard hydrogen monitoring system (SHMS) installed to measure hydrogen. In the event that hydrogen levels exceed 0.75% by volume, additional characterization will be required. The purpose of this additional vapor space characterization is to determine the actual lower flammability limit of these tanks, accurately measure low baseline gas release concentrations, and to determine potential hazards associated with larger Gas Release Events (GREs). The instruments to be installed in the GCS for vapor monitoring will allow accurate analysis of samples from the tank vapor space. It will be possible to detect a wide range of hydrogen from parts per million to percent by volume, as well as other gas species suspected to be generated in waste tanks.

  11. Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

    Directory of Open Access Journals (Sweden)

    Yongming Hu

    2012-04-01

    Full Text Available Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors.

  12. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: On the bifurcation of the circular polarisation of the fifth and seventh pump-field harmonics generated in the plasma produced by the ionisation of a gas of excited hydrogen-like atoms

    Science.gov (United States)

    Silin, Viktor P.; Silin, Pavel V.

    2006-05-01

    Within the framework of the Bethe ionisation model we considered theoretically the dependences of the degree of circular polarisation of the fifth and seventh pump-field harmonics, which are generated due to bremsstrahlung, on the electric intensity of the pump field, the degree of its circular polarisation, and the principal quantum number of the excited states of hydrogen-like atoms of a gas ionised by the pump field. A bifurcation of the circular polarisation of these harmonics was discovered, which confirms our previous hypothesis that this effect is common for harmonics generated due to the bremsstrahlung in the pump field when the plasma electrons oscillate in this field. We determined how the relationships under consideration are scaled with VEn/VZ, the product of electron oscillation velocity and the principal quantum number of the excited electron divided by the Coulomb velocity.

  13. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

    2005-12-01

    Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

  14. Comparison of induced damage, range, reflection, and sputtering yield between amorphous, bcc crystalline, and bubble-containing tungsten materials under hydrogen isotope and noble gas plasma irradiations

    Science.gov (United States)

    Saito, Seiki; Nakamura, Hiroaki; Tokitani, Masayuki

    2017-01-01

    Binary-collision-approximation simulation of hydrogen isotope (i.e., hydrogen, deuterium, and tritium) and noble gas (i.e., helium, neon, and argon) injections into tungsten materials is performed. Three tungsten structures (i.e., amorphous, bcc crystalline, and helium bubble-containing structures) are prepared as target materials. Then, the trajectories of incident atoms, the distribution of recoil atoms, the penetration depth range of incident atoms, the sputtering yield, and the reflection rate are carefully investigated for these target materials.

  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. Dirac equation in very special relativity for hydrogen atom

    CERN Document Server

    Maluf, R V; Cruz, W T; Almeida, C A S

    2014-01-01

    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 is 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.

  17. Transient absorption spectra of the laser-dressed hydrogen atom

    Science.gov (United States)

    Murakami, Mitsuko; Chu, Shih-I.

    2013-10-01

    We present a theoretical study of transient absorption spectra of laser-dressed hydrogen atoms, based on numerical solutions of the time-dependent Schrödinger equation. The timing of absorption is controlled by the delay between an extreme ultra violet (XUV) pulse and an infrared (IR) laser field. The XUV pulse is isolated and several hundred attoseconds in duration, which acts as a pump to drive the ground-state electron to excited p states. The subsequent interaction with the IR field produces dressed states, which manifest as sidebands between the 1s-np absorption spectra separated by one IR-photon energy. We demonstrate that the population of dressed states is maximized when the timing of the XUV pulse coincides with the zero crossing of the IR field, and that their energies can be manipulated in a subcycle time scale by adding a chirp to the IR field. An alternative perspective to the problem is to think of the XUV pulse as a probe to detect the dynamical ac Stark shifts. Our results indicate that the accidental degeneracy of the hydrogen excited states is removed while they are dressed by the IR field, leading to large ac Stark shifts. Furthermore, we observe the Autler-Townes doublets for the n=2 and 3 levels using the 656 nm dressing field, but their separation does not agree with the prediction by the conventional three-level model that neglects the dynamical ac Stark shifts.

  18. Refined potentials for rare gas atom adsorption on rare gas and alkali-halide surfaces

    Science.gov (United States)

    Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

    1985-01-01

    The utilization of models of interatomic potential for physical interaction to estimate the long range attractive potential for rare gases and ions is discussed. The long range attractive force is calculated in terms of the atomic dispersion properties. A data base of atomic dispersion parameters for rare gas atoms, alkali ion, and halogen ions is applied to the study of the repulsive core; the procedure for evaluating the repulsive core of ion interactions is described. The interaction of rare gas atoms on ideal rare gas solid and alkali-halide surfaces is analyzed; zero coverage absorption potentials are derived.

  19. Gas Atomization of Aluminium Melts: Comparison of Analytical Models

    Directory of Open Access Journals (Sweden)

    Georgios Antipas

    2012-06-01

    Full Text Available A number of analytical models predicting the size distribution of particles during atomization of Al-based alloys by N2, He and Ar gases were compared. Simulations of liquid break up in a close coupled atomizer revealed that the finer particles are located near the center of the spray cone. Increasing gas injection pressures led to an overall reduction of particle diameters and caused a migration of the larger powder particles towards the outer boundary of the flow. At sufficiently high gas pressures the spray became monodisperse. The models also indicated that there is a minimum achievable mean diameter for any melt/gas system.

  20. 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.

  1. Adsorption of hydrogen gas and redox processes in clays.

    Science.gov (United States)

    Didier, Mathilde; Leone, Laura; Greneche, Jean-Marc; Giffaut, Eric; Charlet, Laurent

    2012-03-20

    In order to assess the adsorption properties of hydrogen gas and reactivity of adsorbed hydrogen, we measured H(2)(g) adsorption on Na synthetic montmorillonite-type clays and Callovo-Oxfordian (COx) clayrock using gas chromatography. Synthetic montmorillonites with increasing structural Fe(III) substitution (0 wt %, 3.2 wt %, and 6.4 wt % Fe) were used. Fe in the synthetic montmorillonites is principally present as structural Fe(III) ions. We studied the concomitant reduction of structural Fe(III) in the clays using (57)Fe Mössbauer spectrometry. The COx, which mainly contains smectite/illite and calcite minerals, is also studied together with the pure clay fraction of this clayrock. Experiments were performed with dry clay samples which were reacted with hydrogen gas at 90 and 120 °C for 30 to 45 days at a hydrogen partial pressure close to 0.45 bar. Results indicate that up to 0.11 wt % of hydrogen is adsorbed on the clays at 90 °C under 0.45 bar of relative pressure. (57)Fe Mössbauer spectrometry shows that up to 6% of the total structural Fe(III) initially present in these synthetic clays is reduced upon adsorption of hydrogen gas. No reduction is observed with the COx sample in the present experimental conditions.

  2. Production of hydrogen by thermocatalytic cracking of natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Muradov, N.Z. [Univ. of Central Florida, Cape Canaveral, FL (United States)

    1995-09-01

    It is universally accepted that in the next few decades hydrogen production will continue to rely on fossil fuels (primarily, natural gas). On the other hand, the conventional methods of hydrogen production from natural gas (for example, steam reforming) are complex multi-step processes. These processes also result in the emission of large quantities of CO{sub 2} into the atmosphere that produce adverse ecological effects. One alternative is the one-step thermocatalytic cracking (TCC) (or decomposition) of natural gas into hydrogen and carbon. Preliminary analysis indicates that the cost of hydrogen produced by thermal decomposition of natural gas is somewhat lower than the conventional processes after by-product carbon credit is taken. In the short term, this process can be used for on-site production of hydrogen-methane mixtures in gas-filling stations and for CO{sub x}-free production of hydrogen for fuel cell driven prime movers. The experimental data on the thermocatalytic cracking of methane over various catalysts and supports in a wide range of temperatures (500-900{degrees}C) are presented in this paper. Two types of reactors were designed and built at FSEC: continuous flow and pulse fix bed catalytic reactors. The temperature dependence of the hydrogen production yield using oxide type catalysts was studied. Alumina-supported Ni- and Fe-catalysts demonstrated relatively high efficiency in the methane cracking reaction at moderate temperatures (600-800{degrees}C). Kinetic curves of hydrogen production over metal and metal oxide catalysts at different temperatures are presented in the paper. Fe-catalyst demonstrated good stability (for several hours), whereas alumina-supported Pt-catalyst rapidly lost its catalytic activity.

  3. Photo-Ionization of Hydrogen Atom in a Circularly Polarized Standing Electromagnetic Wave

    Institute of Scientific and Technical Information of China (English)

    LIU Xiang-Tao; ZHANG Qi-Ren; WANG Wan-Zhang

    2004-01-01

    Applying time-independent non-perturbative formalism to the photo-ionization of hydrogen atom immersed in a strong circularly polarized standing electromagnetic wave, we calculate the shift of energy levels and the distortion of wave functions for the hydrogen atom, the ionization cross section induced by the standing wave, and the angular distribution of photoelectrons and obtain some interesting results.

  4. 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…

  5. Explicit expressions and recurrence formulas of radial average value for N-dimensional hydrogen atom

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In this paper, two recurrence formulas for radial average values of N-dimensional hydrogen atom are derived. Explicit results can be applied to discuss average value of centrifugal potential energy and other physical quantities. The relevant results of the usual hydrogen atom are contained in more general conclusion of this paper as special cases.

  6. Improved Hydrogen Gas Getters for TRU Waste -- Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Mark Stone; Michael Benson; Christopher Orme; Thomas Luther; Eric Peterson

    2005-09-01

    Alpha radiolysis of hydrogenous waste and packaging materials generates hydrogen gas in radioactive storage containers. For that reason, the Nuclear Regulatory Commission limits the flammable gas (hydrogen) concentration in the Transuranic Package Transporter-II (TRUPACT-II) containers to 5 vol% of hydrogen in air, which is the lower explosion limit. Consequently, a method is needed to prevent the build up of hydrogen to 5 vol% during the storage and transport of the TRUPACT-II containers (up to 60 days). One promising option is the use of hydrogen getters. These materials scavenge hydrogen from the gas phase and irreversibly bind it in the solid phase. One proven getter is a material called 1,4-bis (phenylethynyl) benzene, or DEB, characterized by the presence of carbon-carbon triple bonds. Carbon may, in the presence of suitable precious metal catalysts such as palladium, irreversibly react with and bind hydrogen. In the presence of oxygen, the precious metal may also eliminate hydrogen by catalyzing the formation of water. This reaction is called catalytic recombination. DEB has the needed binding rate and capacity for hydrogen that potentially could be generated in the TRUPACT II. Phases 1 and 2 of this project showed that uncoated DEB performed satisfactorily in lab scale tests. Based upon these results, Phase 3, the final project phase, included larger scale testing. Test vessels were scaled to replicate the ratio between void space in the inner containment vessel of a TRUPACT-II container and a payload of seven 55-gallon drums. The tests were run with an atmosphere of air for 63.9 days at ambient temperature (15-27°C) and a scaled hydrogen generation rate of 2.60E-07 moles per second (0.35 cc/min). A second type of getter known as VEI, a proprietary polymer hydrogen getter characterized by carbon-carbon double bonds, was also tested in Phase 3. Hydrogen was successfully “gettered” by both getter systems. Hydrogen concentrations remained below 5 vol% (in

  7. 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.

  8. Exchange of carbon-bound hydrogen atoms ortho to the hydroxyl group in tyrosine.

    Science.gov (United States)

    Martin, R B; Morlino, V J

    1965-10-22

    The carbon-bound hydrogen atoms of tyrosine that exchange with solvent protons in strongly acid solutions at about 100 degrees C are not the methylene hydrogen atoms but a pair on the aromatic ring. Of the two pairs of protons on the aromatic ring, observed in the proton magnetic resonance spectra, the pair at higher field undergoes exchange in 2.4N DCI at 100 degrees C. Other hydrogen atoms, attached either to aliphatic or aromatic carbon atoms, exhibit no noticeable exchange under the same conditions. From a chemicalshift analysis the exchanging protons are assigned as those ortho to the hydroxyl group on the aromatic ring.

  9. Fast automated placement of polar hydrogen atoms in protein-ligand complexes

    Directory of Open Access Journals (Sweden)

    Lippert Tobias

    2009-08-01

    Full Text Available Abstract Background Hydrogen bonds play a major role in the stabilization of protein-ligand complexes. The ability of a functional group to form them depends on the position of its hydrogen atoms. An accurate knowledge of the positions of hydrogen atoms in proteins is therefore important to correctly identify hydrogen bonds and their properties. The high mobility of hydrogen atoms introduces several degrees of freedom: Tautomeric states, where a hydrogen atom alters its binding partner, torsional changes where the position of the hydrogen atom is rotated around the last heavy-atom bond in a residue, and protonation states, where the number of hydrogen atoms at a functional group may change. Also, side-chain flips in glutamine and asparagine and histidine residues, which are common crystallographic ambiguities must be identified before structure-based calculations can be conducted. Results We have implemented a method to determine the most probable hydrogen atom positions in a given protein-ligand complex. Optimality of hydrogen bond geometries is determined by an empirical scoring function which is used in molecular docking. This allows to evaluate protein-ligand interactions with an established model. Also, our method allows to resolve common crystallographic ambiguities such as as flipped amide groups and histidine residues. To ensure high speed, we make use of a dynamic programming approach. Conclusion Our results were checked against selected high-resolution structures from an external dataset, for which the positions of the hydrogen atoms have been validated manually. The quality of our results is comparable to that of other programs, with the advantage of being fast enough to be applied on-the-fly for interactive usage or during score evaluation.

  10. High-speed cinematography of gas-metal atomization

    Energy Technology Data Exchange (ETDEWEB)

    Ting, Jason [ALCOA Specialty Metals Division, 100 Technical Drive, Alcoa Center, PA 15069 (United States)]. E-mail: jason.ting@alcoa.com; Connor, Jeffery [Material Science Engineering Department, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Ridder, Stephen [Metallurgical Processing Group, NIST, 100 Bureau Dr. Stop 8556, Gaithersburg, MD 20899 (United States)

    2005-01-15

    A high-speed cinematographic footage of a 304L stainless steel gas atomization, recorded at the National Institute of Standard and Technology (NIST), was analyzed using a discrete Fourier transform (DFT) algorithm. The analysis showed the gas atomization process possesses two prominent frequency ranges of melt oscillation (pulsation). A low-frequency oscillation in the melt flow occurring between 5.41 and 123 Hz, with a dominant frequency at 9.93 Hz, was seen in the recirculation zone adjacent to the melt orifice. A high-frequency melt oscillation range was observed above 123 Hz, and was more prominent one melt-tip-diameter downstream in the melt atomization image than upstream near the melt tip. This high-frequency range may reflect the melt atomization frequency used to produce finely atomized powder. This range also included a prominent high frequency at 1273 Hz, which dominated in the image further away downstream from the melt tip. This discrete high-frequency oscillation is most probably caused by the aeroacoustic ''screech'' phenomenon, intrasound (<20 kHz), a result of the atomizing gas jets undergoing flow resonance. It is hypothesized that this discrete intrinsic aeroacoustic tone may enhance melt breakup in the atomization process with evidence of this fact in the melt images.

  11. Blending Hydrogen into Natural Gas Pipeline Networks. A Review of Key Issues

    Energy Technology Data Exchange (ETDEWEB)

    Melaina, M. W. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Antonia, O. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Penev, M. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2013-03-01

    This study assesses the potential to deliver hydrogen through the existing natural gas pipeline network as a hydrogen and natural gas mixture to defray the cost of building dedicated hydrogen pipelines. Blending hydrogen into the existing natural gas pipeline network has also been proposed as a means of increasing the output of renewable energy systems such as large wind farms.

  12. Hydrogen Gas as a Fuel in Direct Injection Diesel Engine

    Science.gov (United States)

    Dhanasekaran, Chinnathambi; Mohankumar, Gabriael

    2016-04-01

    Hydrogen is expected to be one of the most important fuels in the near future for solving the problem caused by the greenhouse gases, for protecting environment and saving conventional fuels. In this study, a dual fuel engine of hydrogen and diesel was investigated. Hydrogen was conceded through the intake port, and simultaneously air and diesel was pervaded into the cylinder. Using electronic gas injector and electronic control unit, the injection timing and duration varied. In this investigation, a single cylinder, KIRLOSKAR AV1, DI Diesel engine was used. Hydrogen injection timing was fixed at TDC and injection duration was timed for 30°, 60°, and 90° crank angles. The injection timing of diesel was fixed at 23° BTDC. When hydrogen is mixed with inlet air, emanation of HC, CO and CO2 decreased without any emission (exhaustion) of smoke while increasing the brake thermal efficiency.

  13. Metal-Free Hydrogen Atom Transfer from Water: Expeditious Hydrogenation of N-Heterocycles Mediated by Diboronic Acid.

    Science.gov (United States)

    Xia, Yun-Tao; Sun, Xiao-Tao; Zhang, Ling; Luo, Kai; Wu, Lei

    2016-11-21

    A hydrogenation of N-heterocycles mediated by diboronic acid with water as the hydrogen atom source is reported. A variety of N-heterocycles can be hydrogenated with medium to excellent yields within 10 min. Complete deuterium incorporation from stoichiometric D2 O onto substrates further exemplifies the H/D atom sources. Mechanism studies reveal that the reduction proceeds with initial 1,2-addition, in which diboronic acid synergistically activates substrates and water via a six-membered ring transition state.

  14. Ring opening reaction dynamics in the reaction of hydrogen atoms with ethylene oxide

    Science.gov (United States)

    Shin, S. K.; Jarek, R. L.; Böhmer, E.; Wittig, C.

    1994-10-01

    Ethylene oxide, C2H4O, is a three-membered ring with a single oxygen atom bridging the two carbons. Reactions of H and D atoms with ethylene oxide have been studied in the gas phase to provide insight into the dynamics of three-membered ring opening. H atoms were produced by photolyzing HI in the wavelength range 240-266 nm. The channel leading to OH+C2H4 was monitored via laser-induced fluorescence (LIF) of the OH A 2Σ←X 2Π system. The D atom reaction yields OD with no hydrogen scrambling. With an available energy of 23 000 cm-1, the average OH D rotational energy is ˜350 cm-1 for OH(v=0) and OD(v=0) and ˜250 cm-1 for OD(v=1). OH(v=1) was not observed, while the OD(v=1) population was about one-tenth that of OD(v=0). There was no apparent bias in populations between Λ doublets in each of the spin-orbit states for both OH and OD. Doppler broadening of OH(v=0) rotational lines was measured to evaluate the average center-of-mass (c.m.) translational energy, which was found to be ˜2300 cm-1. On average, the ring opening process deposits ˜10% of the available energy into c.m. translation, ˜2% into OH rotation, and ˜88% into ethylene internal energy. Comparison with CH2CH2OH unimolecular dissociation dynamics and theoretical transition state calculations leads to a likely mechanism in which hydrogen abstracts oxygen via sequential C-O bond fission without involving a long-lived CH2CH2OH intermediate.

  15. Toroidal configuration of the orbit of the electron of the hydrogen atom under strong external magnetic fields

    OpenAIRE

    Aringazin, A. K.

    2002-01-01

    In this paper we overview some results on the hydrogen atom in external static uniform magnetic fields. We focus on the case of very strong magnetic field, B>>B_0=2.3x10^9 Gauss, use various approximate models and, particularly, in the adiabatic approximation have calculated exactly the integral defining the effective potential. This potential appears to be finite at z=0. Our consideration of the problem of highly magnetized atoms and molecules is motivated by the recently developed MagneGas ...

  16. Production of bioplastics and hydrogen gas by photosynthetic microorganisms

    Science.gov (United States)

    Yasuo, Asada; Masato, Miyake; Jun, Miyake

    1998-03-01

    Our efforts have been aimed at the technological basis of photosynthetic-microbial production of materials and an energy carrier. We report here accumulation of poly-(3-hydroxybutyrate) (PHB), a raw material of biodegradable plastics and for production of hydrogen gas, and a renewable energy carrier by photosynthetic microorganisms (tentatively defined as cyanobacteria plus photosynthetic bateria, in this report). A thermophilic cyanobacterium, Synechococcus sp. MA19 that accumulates PHB at more than 20% of cell dry wt under nitrogen-starved conditions was isolated and microbiologically identified. The mechanism of PHB accumulation was studied. A mesophilic Synechococcus PCC7942 was transformed with the genes encoding PHB-synthesizing enzymes from Alcaligenes eutrophus. The transformant accumulated PHB under nitrogen-starved conditions. The optimal conditions for PHB accumulation by a photosynthetic bacterium grown on acetate were studied. Hydrogen production by photosynthetic microorganisms was studied. Cyanobacteria can produce hydrogen gas by nitrogenase or hydrogenase. Hydrogen production mediated by native hydrogenase in cyanobacteria was revealed to be in the dark anaerobic degradation of intracellular glycogen. A new system for light-dependent hydrogen production was targeted. In vitro and in vivo coupling of cyanobacterial ferredoxin with a heterologous hydrogenase was shown to produce hydrogen under light conditions. A trial for genetic trasformation of Synechococcus PCC7942 with the hydrogenase gene from Clostridium pasteurianum is going on. The strong hydrogen producers among photosynthetic bacteria were isolated and characterized. Co-culture of Rhodobacter and Clostriumdium was applied to produce hydrogen from glucose. Conversely in the case of cyanobacteria, genetic regulation of photosynthetic proteins was intended to improve conversion efficiency in hydrogen production by the photosynthetic bacterium, Rhodobacter sphaeroides RV. A mutant acquired by

  17. Intense Atomic and Molecular Beams via Neon Buffer Gas Cooling

    CERN Document Server

    Patterson, David; Doyle, John M

    2008-01-01

    We realize a continuous guided beam of cold deuterated ammonia with a flux of 3e11 ND3 molecules/s and a continuous free-space beam of cold potassium with a flux of 1e16 K atoms/s. A novel feature of the buffer gas source used to produce these beams is cold neon, which, due to intermediate Knudsen number beam dynamics, produces a forward velocity and low-energy tail that is comparable to much colder helium-based sources. We expect this source to be trivially generalizable to a very wide range of atomic and molecular species with significant vapor pressure below 1000 K. This source has properties that make it a good starting point for laser cooling of molecules or atoms, cold collision studies, trapping, or nonlinear optics in buffer-gas-cooled atomic or molecular gases.

  18. 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.

  19. Dipolar Rydberg-atom gas prepared by adiabatic passage through an avoided crossing

    CERN Document Server

    Wang, Limei; Zhang, Linjie; Li, Changyong; Yang, Yonggang; Zhao, Jianming; Raithel, Georg; Jia, Suotang

    2015-01-01

    The passage of cold cesium 49S$_{1/2}$ Rydberg atoms through an electric-field-induced multi-level avoided crossing with nearby hydrogen-like Rydberg levels is employed to prepare a cold, dipolar Rydberg atom gas. When the electric field is ramped through the avoided crossing on time scales on the order of 100~ns or slower, the 49S$_{1/2}$ population adiabatically transitions into high-\\emph{l} Rydberg Stark states. The adiabatic state transformation results in a cold gas of Rydberg atoms with large electric dipole moments. After a waiting time of about $1~\\mu$s and at sufficient atom density, the adiabatically transformed highly dipolar atoms become undetectable, enabling us to discern adiabatic from diabatic passage behavior through the avoided crossing. We attribute the state-selectivity to $m$-mixing collisions between the dipolar atoms. The data interpretation is supported by numerical simulations of the passage dynamics and of binary $m$-mixing collisions.

  20. Low cost hydrogen/novel membrane technology for hydrogen separation from synthesis gas

    Energy Technology Data Exchange (ETDEWEB)

    1986-02-01

    To make the coal-to-hydrogen route economically attractive, improvements are being sought in each step of the process: coal gasification, water-carbon monoxide shift reaction, and hydrogen separation. This report addresses the use of membranes in the hydrogen separation step. The separation of hydrogen from synthesis gas is a major cost element in the manufacture of hydrogen from coal. Separation by membranes is an attractive, new, and still largely unexplored approach to the problem. Membrane processes are inherently simple and efficient and often have lower capital and operating costs than conventional processes. In this report current ad future trends in hydrogen production and use are first summarized. Methods of producing hydrogen from coal are then discussed, with particular emphasis on the Texaco entrained flow gasifier and on current methods of separating hydrogen from this gas stream. The potential for membrane separations in the process is then examined. In particular, the use of membranes for H{sub 2}/CO{sub 2}, H{sub 2}/CO, and H{sub 2}/N{sub 2} separations is discussed. 43 refs., 14 figs., 6 tabs.

  1. Evaporation in equilibrium, in vacuum, and in hydrogen gas

    Science.gov (United States)

    Nagahara, Hiroko

    1993-01-01

    Evaporation experiments were conducted for SiO2 in three different conditions: in equilibrium, in vacuum, and in hydrogen gas. Evaporation rate in vacuum is about two orders of magnitude smaller than that in equilibrium, which is consistent with previous works. The rate in hydrogen gas changes depending on hydrogen pressure. The rate at 10 exp -7 bar of hydrogen pressure is as small as that of free evaporation, but at 10 exp -5 bar of hydrogen pressure it is larger than that in equilibrium. In equilibrium and in vacuum, the evaporation rate is limited by decomposition of SiO2 on the crystal surface, but it is limited by a diffusion process for evaporation in hydrogen gas. Therefore, evaporation rate of minerals in the solar nebula can be shown neither by that in equilibrium nor by that in vacuum. The maximum temperature of the solar nebula at the midplane at 2-3 AU where chondrites are believed to have originated is calculated to be as low as 150 K, 1500 K, or in between them. The temperature is, in any case, not high enough for total evaporation of the interstellar materials. Therefore, evaporation of interstellar materials is one of the most important processes for the origin and fractionation of solid materials. The fundamental process of evaporation of minerals has been intensively studied for these several years. Those experiments were carried out either in equilibrium or in vacuum; however, evaporation in the solar nebula is in hydrogen (and much smaller amount of helium) gas. In order to investigate evaporation rate and compositional (including isotopic) fractionation during evaporation, vaporization experiments for various minerals in various conditions are conducted. At first, SiO2 was adopted for a starting material, because thermochemical data and its nature of congruent vaporization are well known. Experiments were carried out in a vacuum furnace system.

  2. Blending Hydrogen into Natural Gas Pipeline Networks: A Review of Key Issues

    Energy Technology Data Exchange (ETDEWEB)

    Melaina, M. W.; Antonia, O.; Penev, M.

    2013-03-01

    The United States has 11 distinct natural gas pipeline corridors: five originate in the Southwest, four deliver natural gas from Canada, and two extend from the Rocky Mountain region. This study assesses the potential to deliver hydrogen through the existing natural gas pipeline network as a hydrogen and natural gas mixture to defray the cost of building dedicated hydrogen pipelines.

  3. Hydrogen-air energy storage gas-turbine system

    Science.gov (United States)

    Schastlivtsev, A. I.; Nazarova, O. V.

    2016-02-01

    A hydrogen-air energy storage gas-turbine unit is considered that can be used in both nuclear and centralized power industries. However, it is the most promising when used for power-generating plants based on renewable energy sources (RES). The basic feature of the energy storage system in question is combination of storing the energy in compressed air and hydrogen and oxygen produced by the water electrolysis. Such a process makes the energy storage more flexible, in particular, when applied to RES-based power-generating plants whose generation of power may considerably vary during the course of a day, and also reduces the specific cost of the system by decreasing the required volume of the reservoir. This will allow construction of such systems in any areas independent of the local topography in contrast to the compressed-air energy storage gas-turbine plants, which require large-sized underground reservoirs. It should be noted that, during the energy recovery, the air that arrives from the reservoir is heated by combustion of hydrogen in oxygen, which results in the gas-turbine exhaust gases practically free of substances hazardous to the health and the environment. The results of analysis of a hydrogen-air energy storage gas-turbine system are presented. Its layout and the principle of its operation are described and the basic parameters are computed. The units of the system are analyzed and their costs are assessed; the recovery factor is estimated at more than 60%. According to the obtained results, almost all main components of the hydrogen-air energy storage gas-turbine system are well known at present; therefore, no considerable R&D costs are required. A new component of the system is the H2-O2 combustion chamber; a difficulty in manufacturing it is the necessity of ensuring the combustion of hydrogen in oxygen as complete as possible and preventing formation of nitric oxides.

  4. Field test of hydrogen in the natural gas grid

    Energy Technology Data Exchange (ETDEWEB)

    Iskov, H.

    2010-08-15

    In order to prepare for a future use of hydrogen as a fuel gas it became evident that very little information existed regarding the compatibility between long-term exposure and transportation of hydrogen in natural gas pipelines. A program was therefore set to study the transportation in a small-scale pilot grid at the research centre in Hoersholm, Denmark. The test program included steel pipes from the Danish gas transmission grid and polymer pipes from the Danish and Swedish gas distribution grid. The test of polymer pipes was devised so that samples of all test pipes were cut out of the grid each year and analysis performed on these pipe samples; in this way any form of influence on the integrity of the polyethylene pipe would be detected. The analytical program for polymer was devised in order to detect any influence on the additivation of the polyethylene as this has an influence on oxidative resistance, as well as checking already encountered possible degradation caused by extrusion of the material. Further tools as rheology and melt flow rate were used for detecting any structural changes on the material. On the mechanical property side the tensile strength and modulus were followed as well as the most important property for the pipe line, namely slow crack growth. The results of the polymer pipe tests show no degradations of any kind related to the continuous hydrogen exposure for more than 4 years. This is a strong indication of the compatibility to hydrogen of the tested polymer materials PE 80 and PE 100. The object of the steel pipe test was to see the effect on fatigue life of existing natural gas transmission lines with hydrogen replacing the natural gas. Full-scale dynamic tests were performed using randomly selected cut-out API 5L X70 pipe sections with a diameter of 20 inches and a wall thickness of 7 millimetres from the Danish natural gas transmission system. The pipe sections contained field girth weld made during the installation of the pipe

  5. Observation of individual tracer atoms in an ultracold dilute gas

    CERN Document Server

    Hohmann, Michael; Lausch, Tobias; Mayer, Daniel; Schmidt, Felix; Lutz, Eric; Widera, Artur

    2016-01-01

    Understanding the motion of a tracer particle in a rarefied gas is of fundamental and practical importance. We report the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the nonequilibrium relaxation of the initial nonthermal state and detect the effect of single collisions which has eluded observation so far. We show that after few collisions, the measured spatial distribution of the light tracer atoms is correctly described by a generalized Langevin equation with a velocity-dependent friction coefficient, over a large range of Knudsen numbers.

  6. A Novel Method of Atomization with Potential Gas Turbine Applications

    Directory of Open Access Journals (Sweden)

    Arthur H. Lefebvre

    1988-10-01

    Full Text Available In conventional airblast or air-assist nozzles the bulk liquid to be atomized is first transformed into a jet or sheet before being exposed to the atomizing air. In the method of atomization dcscribed in this paper, the air is introduced into the bulk liquid at somc point upstream of the nozzle discharge orifice. This injectcd air forms bubbles which'explode' downstream of the injection orifice thereby shattering the liquid into small drops.Experiments carrried out on this atomizer, using water as the working fluid and nitrogen as the driving gas, show that good atomization can be achieved using only small amounts of atomizing gas at injection pressures as low as 173 kPa (25psi. It is found that atomization quality is largely independent of the size of the nozzle discharge orifice. Thus the system appears to have good potential for applications where small holes and passages cannot be employed due to the risk of blockage by contaminants in the fuel.

  7. Power to gas. The final breakthrough for the hydrogen economy?

    Energy Technology Data Exchange (ETDEWEB)

    Winkler-Goldstein, Raphael [Germany Trade and Invest (GTAI), Paris (France); Rastetter, Aline [Alphea Hydrogene, Forbach (France)

    2013-04-01

    In Germany more than 20% of the energy mix is made up of renewable energy and its share is rapidly increasing. The federal government expects renewables to account for 35% of Germany's electricity consumption by 2020, 50% by 2030 and 80% by 2050. According to the German Energy Agency, multi-billion euro investments in energy storage are expected by 2020 in order to reach these goals. The growth of this fluctuating energy supply has created demand for innovative storage options in Germany and it is accelerating the development of technologies in this field. Along with batteries and smart grids, hydrogen is expected to be one of the lead technologies. 2010 a commercialization roadmap for wind hydrogen was set up by the two northern federal states of Hamburg and Schleswig-Holstein with the goal of utilizing surplus wind power for the electrolytic production of hydrogen. With the creation of the 'performing energy initiative', 2011, Brandenburg and Lower Saxony joined this undertaking. The aim of this initiative is to set up demonstration projects in order to develop and optimize wind-hydrogen hybrid systems and prepare their commercialization for the time after 2020. Beside the conversion of hydrogen into electricity and fuel for cars, further markets like raw material for the chemical, petrochemical, metallurgy and food industry are going to be addressed. Considering the fact there are over 40 caves currently used for natural gas storage with a total volume of 23.5 billion cubic meters and 400 000 km gas grid available in Germany, the German Technical and Scientific Association for Gas and Water sees opportunities for hydrogen to be fed into the existing natural gas grid network. The name of this concept is power-to-gas. According to the current DVGW-Standards natural gas in Germany can contain up to 5% hydrogen. The GERG, European Group on the Gas Research sees potential to increase this amount up to 6% to 20%. Power-to-gas could serve both for fuel and for the

  8. General model of depolarization and transfer of polarization of singly ionized atoms by collisions with hydrogen atoms

    CERN Document Server

    Derouich, Moncef

    2016-01-01

    Simulations of the generation of the atomic polarization is necessary for interpreting the second solar spectrum. For this purpose, it is important to rigorously determine the effects of the isotropic collisions with neutral hydrogen on the atomic polarization of the neutral atoms, ionized atoms and molecules. Our aim is to treat in generality the problem of depolarizing isotropic collisions between singly ionized atoms and neutral hydrogen in its ground state. Using our numerical code, we computed the collisional depolarization rates of the $p$-levels of ions for large number of values of the effective principal quantum number $n^{*}$ and the Uns\\"old energy $E_p$. Then, genetic programming has been utilized to fit the available depolarization rates. As a result, strongly non-linear relationships between the collisional depolarization rates, $n^{*}$ and $E_p$ are obtained, and are shown to reproduce the original data with accuracy clearly better than 10\\%. These relationships allow quick calculations of the ...

  9. Enhanced-hydrogen gas production through underground gasification of lignite

    Institute of Scientific and Technical Information of China (English)

    LIU Shu-qin; WANG Yuan-yuan; ZHAO Ke; YANG Ning

    2009-01-01

    Underground coal gasification is one of the clean technologies of in-situ coal utilization. Hydrogen production from underground gasification of lignite was investigated in this study based on simulation experiments. Pyrolysis of lignite, gasification activity, oxygen-steam gasification and the effect of groundwater influx were studied. As well, the advantages of lignite for stable underground gasification were analyzed. The results indicate that lignite has a high activity for gasification. Coal pyrolysis is an important source of hydrogen emission. Under special heating conditions, hydrogen is released from coal seams at temperatures above 350 ℃ and reaches its maximum value between 725 and 825 ℃. Gas with a hydrogen concentration of 40% to 50% can be continuously obtained by oxygen-steam injection at an optimum ratio of steam to oxygen, while lignite properties will ensure stable gasification. Groundwater influx can be utilized for hydrogen preparation under certain geological conditions through pressure control. Therefore, enhanced-hydrogen gas production through underground gasification of lignite has experimentally been proved.

  10. A novel three-electrode solid electrolyte hydrogen gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Min; Yang, Chunling; Zhang, Yan [Harbin Insitute of Technology, Harbin (China). School of Computer Science and Technology; Jia, Zheng [Harbin Insitute of Technology, Harbin (China). School of Chemical Engineering and Technology

    2013-07-01

    A three-electrode solid electrolyte hydrogen gas sensor is explored in this paper. The sensor utilized phosphotungstic acid as the electrolyte material and adopted platinum, nickel and tungsten as the three-electrode materials respectively. In real applications, platinum was used as the measuring electrode, nickel was used as the adjusting electrode and tungsten was used as the reference electrode. In order to compare the performance of the new sensor with that of the traditional two-electrode sensor, the hydrogen concentrations were adjusted so as to detect the output of the two-electrode sensor and the three-electrode sensor. The dynamic range between the measuring electrode and the reference electrode is about 0.65V and the highest detectable limit is 12% for the three-electrode solid hydrogen gas sensor. While the dynamic range is about 0.25V and and the highest detectable limit is 1% for the two-electrode solid electrolyte gas sensor. The results demonstrate that the three-electrode solid hydrogen gas sensor has a higher resolution and detectable limit than the two-electrode sensor. abstract environment.

  11. Hydrogen and Oxygen Gas Monitoring System Design and Operation

    Energy Technology Data Exchange (ETDEWEB)

    Lee C. Cadwallader; Kevin G. DeWall; J. Stephen Herring

    2007-06-01

    This paper describes pertinent design practices of selecting types of monitors, monitor unit placement, setpoint selection, and maintenance considerations for gas monitors. While hydrogen gas monitors and enriched oxygen atmosphere monitors as they would be needed for hydrogen production experiments are the primary focus of this paper, monitors for carbon monoxide and carbon dioxide are also discussed. The experiences of designing, installing, and calibrating gas monitors for a laboratory where experiments in support of the DOE Nuclear Hydrogen Initiative (NHI) are described along with codes, standards, and regulations for these monitors. Information from the literature about best operating practices is also presented. The NHI program has two types of activities. The first, near-term activity is laboratory and pilot-plant experimentation with different processes in the kilogram per day scale to select the most promising types of processes for future applications of hydrogen production. Prudent design calls for indoor gas monitors to sense any hydrogen leaks within these laboratory rooms. The second, longer-term activity is the prototype, or large-scale plants to produce tons of hydrogen per day. These large, outdoor production plants will require area (or “fencepost”) monitoring of hydrogen gas leaks. Some processes will have oxygen production with hydrogen production, and any oxygen releases are also safety concerns since oxygen gas is the strongest oxidizer. Monitoring of these gases is important for personnel safety of both indoor and outdoor experiments. There is some guidance available about proper placement of monitors. The fixed point, stationary monitor can only function if the intruding gas contacts the monitor. Therefore, monitor placement is vital to proper monitoring of the room or area. Factors in sensor location selection include: indoor or outdoor site, the location and nature of potential vapor/gas sources, chemical and physical data of the

  12. Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

    CERN Document Server

    Accolla, Mario; Dulieu, François; Manicò, Giulio; Chaabouni, Henda; Matar, Elie; Mokrane, Hakima; Lemaire, Jean Louis; Pirronello, Valerio

    2010-01-01

    The morphology of water ice in the interstellar medium is still an open question. Although accretion of gaseous water could not be the only possible origin of the observed icy mantles covering dust grains in cold molecular clouds, it is well known that water accreted from the gas phase on surfaces kept at 10 K forms ice films that exhibit a very high porosity. It is also known that in the dark clouds H2 formation occurs on the icy surface of dust grains and that part of the energy (4.48 eV) released when adsorbed atoms react to form H2 is deposited in the ice. The experimental study described in the present work focuses on how relevant changes of the ice morphology result from atomic hydrogen exposure and subsequent recombination. Using the temperature-programmed desorption (TPD) technique and a method of inversion analysis of TPD spectra, we show that there is an exponential decrease in the porosity of the amorphous water ice sample following D-atom irradiation. This decrease is inversely proportional to the...

  13. Tunable Adsorption and Desorption of Hydrogen Atoms on Single-Walled Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    赵明文; 夏日源; 马玉臣; 英敏菊; 刘向东; 梅良模

    2002-01-01

    Chemical adsorption and desorption of hydrogen atoms on single-walled carbon nanotubes (SWNTs) are investi-gated by using molecular dynamics simulations. It is found that the adsorption and desorption energy of hydrogenatoms depend on the hydrogen coverage and the diameter of the SWNTs. Hydrogen-adsorption geometry at thecoverage of 1.0 is more energetically stable. The adsorption energy decreases with the increasing diameter ofthe armchair tubes. The adsorption and desorption energy of hydrogen atoms can be modified reversibly byexternally radial deformation. The averaged C-H bond energy on the high curvature sites of the deformed tubeincreases with increasing radial deformation, while that on the low curvature sites decreases.

  14. Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

    Science.gov (United States)

    Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

    1986-01-01

    The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  15. Highly excited hydrogen in strong d. c. electric fields: atomic engineering

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.

    1988-03-01

    We excite atomic hydrogen from the ground state via a three-photon process to high-lying excited states in the presence of strong d.c. electric fields. The external field is used to manipulate, control, and design specific atomic structures. We can construct nearly 'one-dimensional' atoms whose electronic distributions are highly extended along the field, and which may have enormous electric dipole moments ('giant-dipole atoms').

  16. Production of hydrogen by thermocatalytic cracking of natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Muradov, N. [Florida Solar Energy Center, Cocoa, FL (United States)

    1996-10-01

    The conventional methods of hydrogen production from natural gas (for example, steam reforming and partial oxidation) are complex, multi-step processes that produce large quantities of CO{sub 2}. The main goal of this project is to develop a technologically simple process for hydrogen production from natural gas (NG) and other hydrocarbon fuels via single-step decomposition of hydrocarbons. This approach eliminates or significantly reduces CO{sub 2} emission. Carbon is a valuable by-product of this process, whereas conventional methods of hydrogen production from NG produce no useful by-products. This approach is based on the use of special catalysts that reduce the maximum temperature of the process from 1400-1500{degrees}C (thermal non-catalytic decomposition of methane) to 500-900{degrees}C. Transition metal based catalysts and various forms of carbon are among the candidate catalysts for the process. This approach can advantageously be used for the development of compact NG reformers for on-site production of hydrogen-methane blends at refueling stations and, also, for the production of hydrogen-rich gas for fuel cell applications. The author extended the search for active methane decomposition catalysts to various modifications of Ni-, Fe-, Mo- and Co-based catalysts. Variation in the operational parameters makes it possible to produce H{sub 2}-CH{sub 4} blends with a wide range of hydrogen concentrations that vary from 15 to 98% by volume. The author found that Ni-based catalysts are more effective at temperatures below 750{degrees}C, whereas Fe-based catalysts are effective at temperatures above 800{degrees}C for the production of hydrogen with purity of 95% v. or higher. The catalytic pyrolysis of liquid hydrocarbons (pentane, gasoline) over Fe-based catalyst was conducted. The author observed the production of a hydrogen-rich gas (hydrogen concentration up to 97% by volume) at a rate of approximately 1L/min.mL of hydrocarbon fuel.

  17. Elastic, charge transfer, and related transport cross sections for proton impact of atomic hydrogen for astrophysical and laboratory plasma modeling

    Science.gov (United States)

    Schultz, D. R.; Ovchinnikov, S. Yu; Stancil, P. C.; Zaman, T.

    2016-04-01

    Updating and extending previous work (Krstić and Schultz 1999 J. Phys. B: At. Mol. Opt. Phys. 32 3458 and other references) comprehensive calculations were performed for elastic scattering and charge transfer in proton—atomic hydrogen collisions. The results, obtained for 1301 collision energies in the center-of-mass energy range of 10-4-104 eV, are provided for integral and differential cross sections relevant to transport modeling in astrophysical and other plasma environments, and are made available through a website. Use of the data is demonstrated through a Monte Carlo transport simulation of solar wind proton propagation through atomic hydrogen gas representing a simple model of the solar wind interaction with heliospheric neutrals.

  18. Biomass & Natural Gas Based Hydrogen Fuel For Gas Turbine (Power Generation)

    Science.gov (United States)

    Significant progress has been made by major power generation equipment manufacturers in the development of market applications for hydrogen fuel use in gas turbines in recent years. Development of a new application using gas turbines for significant reduction of power plant CO2 e...

  19. Hydrogen gas sensor based on metal oxide nanoparticles decorated graphene transistor.

    Science.gov (United States)

    Zhang, Zhangyuan; Zou, Xuming; Xu, Lei; Liao, Lei; Liu, Wei; Ho, Johnny; Xiao, Xiangheng; Jiang, Changzhong; Li, Jinchai

    2015-06-14

    In this work, in order to enhance the performance of graphene gas sensors, graphene and metal oxide nanoparticles (NPs) are combined to be utilized for high selectivity and fast response gas detection. Whether at the relatively optimal temperature or even room temperature, our gas sensors based on graphene transistors, decorated with SnO2 NPs, exhibit fast response and short recovery times (∼1 seconds) at 50 °C when the hydrogen concentration is 100 ppm. Specifically, X-ray photoelectron spectroscopy and conductive atomic force microscopy are employed to explore the interface properties between graphene and SnO2 NPs. Through the complimentary characterization, a mechanism based on charge transfer and band alignment is elucidated to explain the physical originality of these graphene gas sensors: high carrier mobility of graphene and small energy barrier between graphene and SnO2 NPs have ensured a fast response and a high sensitivity and selectivity of the devices. Generally, these gas sensors will facilitate the rapid development of next-generation hydrogen gas detection.

  20. Performance of a CVD grown graphene-based planar device for a hydrogen gas sensor

    Science.gov (United States)

    Dutta, D.; Hazra, A.; Hazra, S. K.; Das, J.; Bhattacharyya, S.; Sarkar, C. K.; Basu, S.

    2015-11-01

    A multilayer graphene (MLG) film was grown on thermally oxidized silicon (SiO2/Si) substrate by atmospheric pressure chemical vapor deposition (APCVD). The formation of the MLG and the presence of the oxide on the graphene surface were confirmed by Raman spectroscopy and electron dispersive spectroscopy (EDS), respectively. An energy gap of 0.234 eV was determined by the optical transmission method. The surface morphology of the graphene film was studied by field emission scanning electron microscopy (FESEM) and by atomic force microscopy (AFM). A planar device with lateral Pd metal contacts was used for the hydrogen sensor studies. The sensor performance in the temperature range (110 °C-150 °C) revealed a relatively fast response (~12 s) and recovery (~24 s) for hydrogen sensing. The reproducibility, the selectivity, and the stability of the device were also studied. The sensor was found to be selective for hydrogen relative to methane in the temperature range studied. The gas sensing mechanism has been suggested on the basis of the interaction of palladium with hydrogen, the change in the interface barrier, and the adsorption-desorption processes related to the change in the hydrogen partial pressure and temperature. The AFM study indicates the reorientation of the graphene surface after the sensing operation, most probably due to hydrogen passivation.

  1. Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

    OpenAIRE

    Marschner, K; Musil, S. (Stanislav); Dědina, J. (Jiří)

    2015-01-01

    A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH4 in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were ...

  2. Schwinger variational calculation of ionization of hydrogen atoms for large momentum transfers

    Indian Academy of Sciences (India)

    K Chakrabarti

    2002-03-01

    Schwinger variational principle is used here to study large momentum transfer cases of electron and positron impact ionization of atomic hydrogen from the ground state at intermediate and moderately high energies. The results appear somewhat better compared to other theories.

  3. Bubble growth from clustered hydrogen and helium atoms in tungsten under a fusion environment

    Science.gov (United States)

    You, Yu-Wei; Kong, Xiang-Shan; Wu, Xuebang; Liu, C. S.; Chen, J. L.; Luo, G.-N.

    2017-01-01

    Bubbles seriously degrade the mechanical properties of tungsten and thus threaten the safety of nuclear fusion devices, however, the underlying atomic mechanism of bubble growth from clustered hydrogen and helium atoms is still mysterious. In this work, first-principles calculations are therefore carried out to assess the stability of tungsten atoms around both hydrogen and helium clusters. We find that the closest vacancy-formation energies of interstitial hydrogen and helium clusters are substantially decreased. The first-nearest and second-nearest vacancy-formation energies close to vacancy-hydrogen clusters decrease in a step-like way to  ˜0, while those close to vacancy-helium clusters are reduced almost linearly to  ˜-5.46 eV when atom number reaches 10. The vacancy-formation energies closest to helium clusters are more significantly reduced than those nearest to hydrogen clusters, whatever the clusters are embedded at interstitial sites or vacancies. The reduction of vacancy-formation energies results in instability and thus emission of tungsten atoms close to interstitial helium and vacancy-helium clusters, which illustrates the experimental results, that the tungsten atoms can be emitted from the vicinity of vacancy-helium clusters. In addition, the emission of unstable tungsten atoms close to hydrogen clusters may become possible once they are disturbed by the environment. The emission of tungsten atoms facilitates the growth and evolution of hydrogen and helium clusters and ultimately the bubble formation. The results also explain the bubble formation even if no displacement damage is produced in tungsten exposed to low-energy hydrogen and helium plasma.

  4. Hyperfine splitting in non-relativistic QED: uniqueness of the dressed hydrogen atom ground state

    CERN Document Server

    Amour, Laurent

    2011-01-01

    We consider a free hydrogen atom composed of a spin-1/2 nucleus and a spin-1/2 electron in the standard model of non-relativistic QED. We study the Pauli-Fierz Hamiltonian associated with this system at a fixed total momentum. For small enough values of the fine-structure constant, we prove that the ground state is unique. This result reflects the hyperfine structure of the hydrogen atom ground state.

  5. Does God Play Dice with Universe The Hydrogen Atomic Model of Bohr and de Broglie

    CERN Document Server

    Kamenov, P S

    1999-01-01

    In this paper it is shown that if one accept assumption of de Broglie that "unitary wave-particle" exists simultaneously and this coexistence is real, then one can find the mean life time of the hydrogen atom of Bohr (intensities). Something more, the acceptance of de Broglie's ideas show that a single excited hydrogen atom decays at exactly predictable moment (after excitation). The natural width of excited hydrogen atoms are found using the Bohr's model of this atom and de Broglie's ideas. The mean life time of the excited states is a characteristic only of a statistical ensemble of many atoms and coincide exactly with experimental data and can be used for analytical applications. It is shown also that resonant Mossbauer absorption in time domain provides a qualitative evidence of the existence of "own lifetime" for first excited states of the nuclei.

  6. Hydrogen and Hydrogen/Natural Gas Station and Vehicle Operations - 2006 Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    Francfort; Donald Karner; Roberta Brayer

    2006-09-01

    This report is a summary of the operations and testing of internal combustion engine vehicles that were fueled with 100% hydrogen and various blends of hydrogen and compressed natural gas (HCNG). It summarizes the operations of the Arizona Public Service Alternative Fuel Pilot Plant, which produces, compresses, and dispenses hydrogen fuel. Other testing activities, such as the destructive testing of a CNG storage cylinder that was used for HCNG storage, are also discussed. This report highlights some of the latest technology developments in the use of 100% hydrogen fuels in internal combustion engine vehicles. Reports are referenced and WWW locations noted as a guide for the reader that desires more detailed information. These activities are conducted by Arizona Public Service, Electric Transportation Applications, the Idaho National Laboratory, and the U.S. Department of Energy’s Advanced Vehicle Testing Activity.

  7. 有序度对Ni4Mo合金在氢气中脆性的影响%Effect of Ordering on Embrittlement of Ni4Mo Alloy in Hydrogen Gas

    Institute of Scientific and Technical Information of China (English)

    程晓英; 李慧改

    2005-01-01

    The fracture behavior of disordered and ordered Ni4 Mo alloy was investigated by tensile tests in hydrogen gas or during hydrogen charging. The results show that the ductility of the disordered alloy decreased slightly with the hydrogen pressure increasing, while that of the ordered alloy decreased rapidly with the hydrogen pressure increasing. However, the ductility of both disordered and ordered alloys reduced similarly seriously with the charging current density increasing. Therefore, the mechanism of order-induced embrittlement of Ni4 Mo alloy in hydrogen gas is supposed to be that atomic order accelerates the kinetics of the catalytic reaction for the dissociation of molecular H2 into atomic H.

  8. Fluorescence (TALIF) measurement of atomic hydrogen concentration in a coplanar surface dielectric barrier discharge

    Science.gov (United States)

    Mrkvičková, M.; Ráheľ, J.; Dvořák, P.; Trunec, D.; Morávek, T.

    2016-10-01

    Spatially and temporally resolved measurements of atomic hydrogen concentration above the dielectric of coplanar barrier discharge are presented for atmospheric pressure in 2.2% H2/Ar. The measurements were carried out in the afterglow phase by means of two-photon absorption laser-induced fluorescence (TALIF). The difficulties of employing the TALIF technique in close proximity to the dielectric surface wall were successfully addressed by taking measurements on a suitable convexly curved dielectric barrier, and by proper mathematical treatment of parasitic signals from laser-surface interactions. It was found that the maximum atomic hydrogen concentration is situated closest to the dielectric wall from which it gradually decays. The maximum absolute concentration was more than 1022 m-3. In the afterglow phase, the concentration of atomic hydrogen above the dielectric surface stays constant for a considerable time (10 μs-1 ms), with longer times for areas situated farther from the dielectric surface. The existence of such a temporal plateau was explained by the presented 1D model: the recombination losses of atomic hydrogen farther from the dielectric surface are compensated by the diffusion of atomic hydrogen from regions close to the dielectric surface. The fact that a temporal plateau exists even closest to the dielectric surface suggests that the dielectric surface acts as a source of atomic hydrogen in the afterglow phase.

  9. Atomic-Scale Mechanism for Hydrogenation of o-Cresol on Pt Catalysis

    Science.gov (United States)

    Li, Yaping; Liu, Zhimin; Xue, Wenhua; Crossley, Steven; Jentoft, Friederike; Wang, Sanwu

    Biofuels derived from lignocellulosic biomass have received significant attention lately due to increasing environmental concerns. With first-principles density-functional theory and ab initio molecular dynamic simulations, we investigated the atomic-scale mechanism of o-cresol hydrogenation on the Pt(111) surface. The formation of 2-methyl-cyclohexanone (the intermediate product) was found to involve two steps. The first step is the dehydrogenation, that is, the H atom in the hydroxyl group moves to the Pt surface. The second step is the hydrogenation, that is, the H atoms on Pt react with the carbon atoms in the aromatic ring. The first step involves a smaller barrier, suggesting that dehydrogenation occurs first, followed by hydrogenation of the ring. In particular, tautomerization is found to occur via a two-step process over the catalyst. On the other hand, 2-methyl-cyclohexanol (the final product) is produced through two paths. One is direct hydrogenation of the aromatic ring. Another pathway includes partial hydrogenation of the ring, dehydrogenation of -OH group, finally hydrogenation of remaining C atoms and the O atom. Our theoretical results agree well with the experimental observations. Supported by DOE (DE-SC0004600). This research used the supercomputer resources of NERSC, XSEDE, TACC.

  10. Angular Momentum Regulates Atomic Gas Fractions of Galactic Disks

    CERN Document Server

    Obreschkow, Danail; Kilborn, Virginia; Lutz, Katharina

    2016-01-01

    We show that the mass fraction f_atm = 1.35*MHI/M of neutral atomic gas (HI and He) in isolated local disk galaxies of baryonic mass M is well described by a straightforward stability model for flat exponential disks. In the outer disk parts, where gas at the characteristic dispersion of the Warm Neutral Medium is stable in the sense of Toomre (1964), the disk consists of neutral atomic gas; conversely the inner part where this medium would be Toomre-unstable, is dominated by stars and molecules. Within this model, f_atm only depends on a global stability parameter q=j*sigma/(GM), where j is the baryonic specific angular momentum of the disk and sigma the velocity dispersion of the atomic gas. The analytically derived first-order solution f_atm = min{1,2.5q^1.12} provides a good fit to all plausible rotation curves. This model, with no free parameters, agrees remarkably well (+-0.2 dex) with measurements of f_atm in isolated local disk galaxies, even with galaxies that are extremely HI-rich or HI-poor for the...

  11. Continuum effects on positron scattering of atomic hydrogen at intermediate energies

    Energy Technology Data Exchange (ETDEWEB)

    Ratnavelu, Kuru [Quantum Scattering Theory Group, Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia). E-mail: j2kurun at umcsd.um.edu.my; Rajagopal, Kalai Kumar [Quantum Scattering Theory Group, Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    1999-07-28

    An optical potential method to study the positron-hydrogen atom scattering system within the close-coupling framework that includes both the positron-hydrogen and positronium-proton channels has been implemented. Ionization, positronium formation and total cross sections are reported and are compared to other available theoretical and experimental data. (author00.

  12. 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.

  13. Fracture mechanism of TiAl intermetallics caused by hydride and atomic hydrogen

    Institute of Scientific and Technical Information of China (English)

    高克玮; 王燕斌; 林志; 乔利杰; 褚武扬

    1999-01-01

    Hydrogen embrittlement (HE) of TiAl intermetallics was studied at room temperature. The results showed that there were two forms of HE in TiAl intermetallics, i.e. hydride HE and atomic HE. Most of hydrogen in TiAl intermetallics was transformed into hydrides at room temperature. The hydride exists as (TiAl)Hx for a low hydrogen concentration while it exists in several forms for a higher hydrogen concentration. Stress intensity factor KIC decreased with increase in hydride concentration. KIC decreased further when TiAl intermetallics were charged cathodically with hydrogen in 1 mol/L H2SO4 solution. Stress intensity factor during hydrogen charging KIH was about 50% KIC. 20% of the decrease was caused by hydrides while 30% was caused by atomic hydrogen. Mechanism of HE caused hydrides was the same as any other second phase in nature. Delayed fracture caused by atomic hydrogen resulted from hydrogen induced local plastic deformation.

  14. A Converter for Producing a Hydrogen-Containing Synthesis Gas

    Science.gov (United States)

    Malkov, Yu. P.; Molchanov, O. N.; Britov, B. K.; Fedorov, I. A.

    2016-11-01

    A computational thermodynamic and experimental investigation of the characteristics of a model of a converter for producing a hydrogen-containing synthesis gas from a hydrocarbon fuel (kerosene) with its separate delivery to thermal-oxidative and steam conversions has been carried out. It is shown that the optimum conditions of converter operation correspond to the oxidant excess coefficient in the converter's combustion chamber α > 0.5 at a temperature of the heat-transmitting wall (made from a heat-resistant KhN78T alloy (ÉI 435)) of 1200 K in the case of using a nickel corrugated tape catalyst. The content of hydrogen in the synthesis gas attains in this case 60 vol.%, and there is no release of carbon (soot) in the conversion products as well as no need for water cooling of the converter walls.

  15. 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.

  16. Resonant Scattering of Muonic Hydrogen Atoms and Dynamics of Muonic Molecular Complex

    CERN Document Server

    Fujiwara, M C; Bailey, J M; Beer, G A; Beveridge, J L; Faifman, M P; Huber, T M; Kammel, P; Kim, S K; Knowles, P E; Kunselman, A R; Maier, M; Markushin, V E; Marshall, G M; Martoff, C J; Mason, G R; Mulhauser, F; Olin, A; Petitjean, C; Porcelli, T A; Wozniak, J; Zmeskal, J

    2001-01-01

    Resonant scattering of muonic hydrogen atoms via back decay of 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.

  17. Hydrogen-Atom Attack on Methyl Viologen in Aqueous Solution Studied by Pulse Radiolysis

    DEFF Research Database (Denmark)

    Solar, S.; Solar, W.; Getoff, N.;

    1984-01-01

    Using hydrogen at high pressures of up to 150 bar (0.12 mol dm–3 H2) as an OH scavenger in aqueous MV2+ solutions (pH 1) it is possible to differentiate between two kinds of transient formed simultaneously by H-atom attack on methyl viologen. One of them is assigned to an H adduct on the N atom, ...

  18. Stability of Titanium Nitride and Titanium Carbide When Exposed to Hydrogen Atoms from 298 to 1950 K

    Science.gov (United States)

    Philipp, Warren H.

    1961-01-01

    Titanium nitride and titanium carbide deposited on tungsten wires were exposed to hydrogen atoms (10(exp -4) atm pressure) produced by the action of microwave radiation on molecular hydrogen. The results of these experiments in the temperature range 298 to 1950 K indicate that no appreciable reaction takes place between atomic hydrogen and TiN or TiC. The formation of reaction products (NH3, CH4, C2H2) should be favored at lower temperatures. However, because of the high catalytic activity of Ti for H atom recombination, the rate of such reactions with H atoms is controlled by the rate of evaporation of Ti from the surface, this rate being low at temperatures below 1200 K. In order to interpret the stability of TiN and TiC in H atoms more fully, the stability of TiN and TiC in vacuum and H2 gas was also studied. The thermodynamic computations conform in order of magnitude to the experimentally found rates of decomposition of TiN and TiC in vacuum and are also consistent with the fact that no appreciable reaction is found with these compounds in molecular H2 at a pressure of 10(exp -3) atmosphere in the temperature range 2980 to 2060 K. When TiN or TiC was heated in atomic H or molecular H2, no reaction products other than those obtained from the simple decomposition of the nitride and carbide were observed. The gaseous products were analyzed in a mass spectrometer.

  19. Evolution of the atomic and molecular gas content of galaxies in dark matter haloes

    CERN Document Server

    Popping, G; Peeples, M S

    2014-01-01

    We present a semi-empirical model to infer the atomic and molecular hydrogen content of galaxies as a function of halo mass and time. Our model combines the SFR-halo mass-redshift relation (constrained by galaxy abundances) with inverted SFR-surface density relations to infer galaxy H I and H2 masses. We present gas scaling relations, gas fractions, and mass functions from z = 0 to z = 3 and the gas properties of galaxies as a function of their host halo masses. Predictions of our work include: 1) there is a ~ 0.2 dex decrease in the H I mass of galaxies as a function of their stellar mass since z = 1.5, whereas the H2 mass of galaxies decreases by > 1 dex over the same period. 2) galaxy cold gas fractions and H2 fractions decrease with increasing stellar mass and time. Galaxies with M* > 10^10 Msun are dominated by their stellar content at z < 1, whereas less-massive galaxies only reach these gas fractions at z = 0. We find the strongest evolution in relative gas content at z < 1.5. 3) the SFR to gas m...

  20. Triboelectric Hydrogen Gas Sensor with Pd Functionalized Surface

    Directory of Open Access Journals (Sweden)

    Sung-Ho Shin

    2016-10-01

    Full Text Available Palladium (Pd-based hydrogen (H2 gas sensors have been widely investigated thanks to its fast reaction and high sensitivity to hydrogen. Various sensing mechanisms have been adopted for H2 gas sensors; however, all the sensors must be powered through an external battery. We report here an H2 gas sensor that can detect H2 by measuring the output voltages generated during contact electrification between two friction surfaces. When the H2 sensor, composed of Pd-coated ITO (indium tin oxide and PET (polyethylene Terephthalate film, is exposed to H2, its output voltage is varied in proportion to H2 concentration because the work function (WF of Pd-coated surface changes, altering triboelectric charging behavior. Specifically, the output voltage of the sensor is gradually increased as exposing H2 concentration increases. Reproducible and sensitive sensor response was observed up 1% H2 exposure. The approach introduced here can easily be adopted to development of triboelectric gas sensors detecting other gas species.

  1. Ultrasonic gas alloy atomization under near-zero aspiration pressure

    Science.gov (United States)

    Yan, Pengfei; Wang, Deping; Yan, Biao

    2015-04-01

    In this paper, ultrasonic gas atomization (USGA) of Zn-Al under near-zero aspiration pressure was discussed. The protrusion length of delivery tube was modified to adjust the aspiration pressure. Under near-zero aspiration pressure, melt filming was observed by camera and more fine powders were produced. While under larger subambient aspiration pressure, melt filming was unavailable, corresponding to less fine powders. The results suggest that the position of the wake near the delivery tube can be optimized under near-zero aspiration. Less protrusion of delivery tube reduces the energy loss in gas flow deflection. Both facilitate to produce finer powders.

  2. Technology of separation of hydrogen from coke oven gas

    Energy Technology Data Exchange (ETDEWEB)

    Budner, Z.; Morawiec, B.

    1989-01-01

    A process to beindustrialised at the Zdzieszowice coking plant and Kedzierzyn fertiliser works is described. Coke oven gas is scrubbed with methanol and subjected to pressure-swing adsorption. The hydrogen-rich fraction is converted with steam to reduce its CO content and then subjected again to pressure-swing adsorption. The methane-rich fraction from the first PSA stage is processed to 90% CH{sub 4} and a fraction containing 35% ethylene and 10% ethane.

  3. 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.

  4. The distribution of atomic hydrogen in EAGLE galaxies: morphologies, profiles, and H I holes

    Science.gov (United States)

    Bahé, Yannick M.; Crain, Robert A.; Kauffmann, Guinevere; Bower, Richard G.; Schaye, Joop; Furlong, Michelle; Lagos, Claudia; Schaller, Matthieu; Trayford, James W.; Dalla Vecchia, Claudio; Theuns, Tom

    2016-02-01

    We compare the mass and internal distribution of atomic hydrogen (H I) in 2200 present-day central galaxies with Mstar > 1010 M⊙ from the 100 Mpc EAGLE `Reference' simulation to observational data. Atomic hydrogen fractions are corrected for self-shielding using a fitting formula from radiative transfer simulations and for the presence of molecular hydrogen using an empirical or a theoretical prescription from the literature. The resulting neutral hydrogen fractions, M_{H_I+H_2} / M_star, agree with observations to better than 0.1 dex for galaxies with Mstar between 1010 and 1011 M⊙. Our fiducial, empirical H2 model based on gas pressure results in galactic H I mass fractions, M_{H I/ M_star, that agree with observations from the GASS survey to better than 0.3 dex, but the alternative theoretical H2 formula from high-resolution simulations leads to a negative offset in M_{H I}/ M_star of up to 0.5 dex. Visual inspection of mock H I images reveals that most H I discs in simulated H I-rich galaxies are vertically disturbed, plausibly due to recent accretion events. Many galaxies (up to 80 per cent) contain spuriously large H I holes, which are likely formed as a consequence of the feedback implementation in EAGLE. The H I mass-size relation of all simulated galaxies is close to (but 16 per cent steeper than) observed, and when only galaxies without large holes in the H I disc are considered, the agreement becomes excellent (better than 0.1 dex). The presence of large H I holes also makes the radial H I surface density profiles somewhat too low in the centre, at Σ _{H I} > 1 M_{⊙} pc^{-2} (by a factor of ≲ 2 compared to data from the Bluedisk survey). In the outer region (Σ _{H I} 10^{9.8} M_{⊙}) and control galaxies (10^{9.1} M_{⊙}> M_{H I} > 10^{9.8} M_{⊙}) follow each other closely, as observed.

  5. Improvement of saturation magnetization of Fe nanoparticles by post-annealing in a hydrogen gas atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Kin, Masane, E-mail: masane-kin@denso.co.jp; Tanaka, Masaaki; Hayashi, Yasushi; Hasaegawa, Jun [Research Laboratories, DENSO CORPORATION, 500-1, Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111 (Japan); Kura, Hiroaki; Ogawa, Tomoyuki [Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, 6-6-05 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

    2015-05-07

    Fe nanoparticles (NPs) were synthesized by the thermal decomposition of Fe(CO){sub 5} and then post-annealing in a hydrogen gas atmosphere to produce highly monodisperse Fe NPs with high saturation magnetization (M{sub s}). The as-synthesized pre-anneal Fe NPs had an expanded α-Fe structure and M{sub s} was only 39% of that for bulk Fe because of the low crystallinity and the inclusion of a surfactant. Post-annealing of the Fe NPs in a hydrogen gas atmosphere at 200 °C improved the crystallinity of the Fe NPs from an amorphous-like structure to a body centered cubic (bcc) structure without any lattice expansion. This result indicates that hydrogen gas plays a significant role in improvement of the crystallinity of Fe NPs. Accompanying the improvement in crystallinity, M{sub s} for the Fe NPs increased from 86 to 190 emu/g{sub net} at 300 K, the values of which include the weight of surfactant. This enhanced M{sub s} is almost the same as that of bulk Fe (218 emu/{sub Fe}). It was concluded that the crystallinity has a significant influence on the M{sub s} of the Fe NPs because long-range ordering of the lattice can maintain strong direct exchange interactions between Fe atoms.

  6. Warm Pressurant Gas Effects on the Liquid Hydrogen Bubble Point

    Science.gov (United States)

    Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

    2013-01-01

    This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device. Three fine mesh screen samples (325 x 2300, 450 x 2750, 510 x 3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0 to 90 K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

  7. Synthesis of SnO{sub 2} hollow microspheres from ultrasonic atomization and their role in hydrogen sensing

    Energy Technology Data Exchange (ETDEWEB)

    Patil, L.A., E-mail: plalchand_phy_aml@yahoo.co.in [Nanomaterials Research Lab., Department of Physics, Pratap College, Amalner 425401, Maharashtra (India); Shinde, M.D.; Bari, A.R.; Deo, V.V. [Nanomaterials Research Lab., Department of Physics, Pratap College, Amalner 425401, Maharashtra (India)

    2011-04-25

    Nanostructured SnO{sub 2} hollow microspheres were synthesized using ultrasonic atomization technique. It is interesting that hollow microspheres could be prepared from ultrasonic atomization technique without any aid of template and surfactant. X-ray powder diffraction (XRD) confirmed the material to be SnO{sub 2} having tetragonal structure. Average crystallite size calculated from X-ray diffractogram using Scherer's equation was found to be 8.45 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the microscopic study of fine powder particles. Powder consists of hollow microspheres of average diameter of 0.58 {mu}m as well as nanoparticles of average diameter of 6 nm. The sensors fabricated from such powder show high hydrogen (1000 ppm) response (S = 2379) under the optimized experimental conditions. Sensor performance merits, such as, high hydrogen response, high hydrogen selectivity, short response time (2 s) and quick recovery time (15 s) may be due to both nanocrystallites and hollow microspheres associated in SnO{sub 2} sensing material. The dramatic change in gas response was explained by the rapid diffusion of the target gas through the nano-porous structure of SnO{sub 2} hollow microspheres.

  8. Experimental Study of Gas Explosions in Hydrogen Sulfide-Natural Gas-Air Mixtures

    Directory of Open Access Journals (Sweden)

    André Vagner Gaathaug

    2014-01-01

    Full Text Available An experimental study of turbulent combustion of hydrogen sulfide (H2S and natural gas was performed to provide reference data for verification of CFD codes and direct comparison. Hydrogen sulfide is present in most crude oil sources, and the explosion behaviour of pure H2S and mixtures with natural gas is important to address. The explosion behaviour was studied in a four-meter-long square pipe. The first two meters of the pipe had obstacles while the rest was smooth. Pressure transducers were used to measure the combustion in the pipe. The pure H2S gave slightly lower explosion pressure than pure natural gas for lean-to-stoichiometric mixtures. The rich H2S gave higher pressure than natural gas. Mixtures of H2S and natural gas were also studied and pressure spikes were observed when 5% and 10% H2S were added to natural gas and also when 5% and 10% natural gas were added to H2S. The addition of 5% H2S to natural gas resulted in higher pressure than pure H2S and pure natural gas. The 5% mixture gave much faster combustion than pure natural gas under fuel rich conditions.

  9. Gas turbine combustion performance test of hydrogen and carbon monoxide synthetic gas

    Energy Technology Data Exchange (ETDEWEB)

    Min Chul Lee; Seok Bin Seo; Jae Hwa Chung; Si Moon Kim; Yong Jin Joo; Dal Hong Ahn [Korea Electric Power Corporation, Daejeon (Republic of Korea). Green Growth Laboratory

    2010-07-15

    The development of coal IGCC (Integrated Gasification Combined Cycle) technology has made it possible to exploit electricity generated from coal at a low cost. Furthermore, IGCC is a pre-requisite for the development of CCS (Carbon Capture and Storage) technology and hydrogen generated from coal. To achieve the need to reduce CO{sub 2} emissions, Korea's 300 MW IGCC RDD&D (Research Development, Demonstration and Dissemination) project was launched in December 2006 under the leadership of the Korea Electric Power Corporation (KEPCO), with the support of the Korea Ministry of Knowledge Economy. When a new fuel is adapted to a gas turbine (such as syngas for IGCC), it is necessary to study the gas turbine combustion characteristics of the fuel, because gas turbines are very sensitive to its physical and chemical properties. This experimental study was conducted by investigating the combustion performance of synthetic gas, which is composed chiefly of hydrogen and carbon monoxide. The results of a test on synthetic gas combustion performance were compared with the results of methane combustion, which is a major component of natural gas. The results of the combustion test of both gases were examined in terms of the turbine's inlet temperature, combustion dynamics, emission characteristics, and flame structure. From the results of this experimental study, we were able to understand the combustion characteristics of synthetic gas and anticipate the problems when synthetic gas rather than natural gas is fuelled to a gas turbine. 21 refs., 11 figs., 1 tab.

  10. Signatures of Quantum-Tunneling Diffusion of Hydrogen Atoms on Water Ice at 10 K

    OpenAIRE

    2015-01-01

    Reported here is the first observation of the tunneling surface diffusion of a hydrogen (H) atom on water ice. Photostimulated desorption and resonance-enhanced multiphoton ionization methods were used to determine the diffusion rates at 10 Kon amorphous solid water and polycrystalline ice. H-atom diffusion on polycrystalline ice was 2 orders of magnitude faster than that of deuterium atoms, indicating the occurrence of tunneling diffusion. Whether diffusion is by tunneling or thermal hopping...

  11. EUV tools: hydrogen gas purification and recovery strategies

    Science.gov (United States)

    Landoni, Cristian; Succi, Marco; Applegarth, Chuck; Riddle Vogt, Sarah

    2015-03-01

    The technological challenges that have been overcome to make extreme ultraviolet lithography (EUV) a reality have been enormous1. This vacuum driven technology poses significant purity challenges for the gases employed for purging and cleaning the scanner EUV chamber and source. Hydrogen, nitrogen, argon and ultra-high purity compressed dry air (UHPCDA) are the most common gases utilized at the scanner and source level. Purity requirements are tighter than for previous technology node tools. In addition, specifically for hydrogen, EUV tool users are facing not only gas purity challenges but also the need for safe disposal of the hydrogen at the tool outlet. Recovery, reuse or recycling strategies could mitigate the disposal process and reduce the overall tool cost of operation. This paper will review the types of purification technologies that are currently available to generate high purity hydrogen suitable for EUV applications. Advantages and disadvantages of each purification technology will be presented. Guidelines on how to select the most appropriate technology for each application and experimental conditions will be presented. A discussion of the most common approaches utilized at the facility level to operate EUV tools along with possible hydrogen recovery strategies will also be reported.

  12. Novel atmospheric pressure plasma device releasing atomic hydrogen: reduction of microbial-contaminants and OH radicals in the air

    Science.gov (United States)

    Nojima, Hideo; Park, Rae-Eun; Kwon, Jun-Hyoun; Suh, Inseon; Jeon, Junsang; Ha, Eunju; On, Hyeon-Ki; Kim, Hye-Ryung; Choi, Kyoung Hui; Lee, Kwang-Hee; Seong, Baik-Lin; Jung, Hoon; Kang, Shin Jung; Namba, Shinichi; Takiyama, Ken

    2007-01-01

    A novel atmospheric pressure plasma device releasing atomic hydrogen has been developed. This device has specific properties such as (1) deactivation of airborne microbial-contaminants, (2) neutralization of indoor OH radicals and (3) being harmless to the human body. It consists of a ceramic plate as a positive ion generation electrode and a needle-shaped electrode as an electron emission electrode. Release of atomic hydrogen from the device has been investigated by the spectroscopic method. Optical emission of atomic hydrogen probably due to recombination of positive ions, H+(H2O)n, generated from the ceramic plate electrode and electrons emitted from the needle-shaped electrode have been clearly observed in the He gas (including water vapour) environment. The efficacy of the device to reduce airborne concentrations of influenza virus, bacteria, mould fungi and allergens has been evaluated. 99.6% of airborne influenza virus has been deactivated with the operation of the device compared with the control test in a 1 m3 chamber after 60 min. The neutralization of the OH radical has been investigated by spectroscopic and biological methods. A remarkable reduction of the OH radical in the air by operation of the device has been observed by laser-induced fluorescence spectroscopy. The cell protection effects of the device against OH radicals in the air have been observed. Furthermore, the side effects have been checked by animal experiments. The harmlessness of the device has been confirmed.

  13. Hot-Wire generated atomic hydrogen and its impact on thermal ALD in $TiCl_4/NH_3$ system

    NARCIS (Netherlands)

    Van Bui, H.; Kovalgin, A.Y.; Aarnink, A.A.I.; Wolters, R.A.M.

    2013-01-01

    We present the generation of atomic hydrogen made by the dissociation of molecular hydrogen upon collision with a tungsten (W) filament kept at a high temperature (T ≈ 1600–1900◦C). We demonstrate the ability to create atomic hydrogen and to introduce it in short pulses in experiments on etching of

  14. A compact design for a magnetic synchrotron to store beams of hydrogen atoms

    CERN Document Server

    van der Poel, Aernout P P; Softley, Timothy P; Bethlem, Hendrick L

    2015-01-01

    We present a design for an atomic synchrotron consisting of 40 hybrid magnetic hexapole lenses arranged in a circle. We show that for realistic parameters, hydrogen atoms with a velocity up to 600 m/s can be stored in a 1-meter diameter ring, which implies that the atoms can be injected in the ring directly from a pulsed supersonic beam source. This ring can be used to study collisions between stored hydrogen atoms and molecular beams of many different atoms and molecules. The advantage of using a synchrotron is two-fold: (i) the collision partners move in the same direction as the stored atoms, resulting in a small relative velocity and thus a low collision energy, and (ii) by storing atoms for many round-trips, the sensitivity to collisions is enhanced by a factor of 100-1000. In the proposed ring, the cross-sections for collisions between hydrogen, the most abundant atom in the universe, with any atom or molecule that can be put in a beam, including He, H$_2$, CO, ammonia and OH can be measured at energies...

  15. Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

    Energy Technology Data Exchange (ETDEWEB)

    Marschner, Karel, E-mail: karel.marschner@biomed.cas.cz [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, Albertov 8, 128 43 Prague (Czech Republic); Musil, Stanislav; Dědina, Jiří [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic)

    2015-07-01

    A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH{sub 4} in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were compared. Under optimum conditions sensitivity obtained with flame-in-gas-shield atomizer was approximately twice higher than with miniature diffusion flame. The additional advantage of flame-in-gas-shield atomizer is significantly lower flame emission resulting in a better signal to noise ratio. The resulting arsenic limits of detection for miniature diffusion flame and flame-in-gas-shield atomizer were 3.8 ng l{sup −1} and 1.0 ng l{sup −1}, respectively. - Highlights: • We optimized and compared two hydride atomizers for atomic fluorescence spectrometry. • Miniature diffusion flame and flame-in-gas-shield atomizer were optimized. • The limit of detection for arsenic was 1.0 ng l{sup −1}.

  16. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    Science.gov (United States)

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-02-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel-carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm-2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis.

  17. Formation of Cu, Ag and Au nanofiims under the influence of hydrogen atoms

    Directory of Open Access Journals (Sweden)

    Zhavzharov E. L.

    2015-12-01

    Full Text Available Due to their electrical properties, thin metallic films are widely used in modern micro- and nanoelectronics. These properties allow solving fundamental problems of surface and solid state physics. Up-to-date methods of producing thin films involve high vacuum or multi-stage processes, which calls for complicated equipment. The authors propose an alternative method of producing thin metallic films using atomic hydrogen. Exothermal reaction of atoms recombination in a molecule (about 4.5 eV / recombination act initiated on the solid surface by atomic hydrogen may stimulate local heating, spraying and surface atoms transfer. We investigated the process of atomic hydrogen treatment of Cu, Ag and Au metal films, obtained by thermal vacuum evaporation. There are two methods of obtaining nanofilms using atomic hydrogen treatment: sputtering and vapor-phase epitaxy. In the first method, a film is formed by reducing the thickness of the starting film. This method allows obtaining a film as thick as the monolayer. In the second method, a nanofilm is formed by deposition of metal atoms from the vapor phase. This method allows obtaining a film thickness from monolayer to ~10 nm. These methods allow creating nanofilms with controlled parameters and metal thickness. Such films would be technologically pure and have good adhesion.

  18. Investigation of the gas-phase hydrogen/deuterium exchange behavior of aromatic dicarboxylic acids in a quadrupole ion trap

    Science.gov (United States)

    Chipuk, Joseph E.; Brodbelt, Jennifer S.

    2007-11-01

    Gas-phase hydrogen/deuterium (H/D) exchange reactions of four deprotonated aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid and 2,6-naphthalic acid) with D2O were performed in a quadrupole ion trap mass spectrometer. Experimental results showed significant differences in the rate and extent of exchange when the relative position of the carboxylic acid groups varied. Spontaneous and near complete exchange of one aromatic hydrogen atom occurred when the carboxylic acid groups were in the meta-position, whereas no additional exchange was observed for either the ortho- or para-isomers or for the structurally similar naphthalic acid. Computational investigations support the participation of several possible exchange mechanisms with the contribution of each relying heavily on the relative orientation of the acid moieties. A relay mechanism that bridges the deprotonation site and the labile hydrogen site appears to be responsible for the H/D exchange of not only the labile hydrogen atom of isophthalic acid, but also for the formation of a stable carbanion and corresponding subsequent exchange of one aromatic hydrogen atom. The impact of hydrogen bonding on the relay mechanism is demonstrated by the reaction of phthalic acid as the extent and rate of reaction are greatly retarded by the favorable interaction of the two carboxylic acid groups. Finally, a flip-flop mechanism is likely responsible for the exchange of both terephthalic acid and 2,6-naphthalic acid where the reactive sites are too remote for exchange via relay.

  19. Excitation and charge transfer in low-energy hydrogen atom collisions with neutral atoms: Theory, comparisons, and application to Ca

    CERN Document Server

    Barklem, Paul S

    2016-01-01

    A theoretical method for the estimation of cross sections and rates for excitation and charge transfer processes in low-energy hydrogen atom collisions with neutral atoms, based on an asymptotic two-electron model of ionic-covalent interactions in the neutral atom-hydrogen atom system, is presented. The calculation of potentials and non-adiabatic radial couplings using the method is demonstrated. The potentials are used together with the multi-channel Landau-Zener model to calculate cross sections and rate coefficients. The main feature of the method is that it employs asymptotically exact atomic wavefunctions, which can be determined from known atomic parameters. The method is applied to Li+H, Na+H, and Mg+H collisions, and the results compare well with existing detailed full-quantum calculations. The method is applied to the astrophysically important problem of Ca+H collisions, and rate coefficients are calculated for temperatures in the range 1000-20000 K.

  20. Hydrogen absorption of LaFe_(11.5)Si_(1.5) compound under low hydrogen gas pressure

    Institute of Scientific and Technical Information of China (English)

    Fu Bin; Long Yi; Shi Pu-Ji; Ma Tao; Bao Bo; Yan A-Ru; Chen Ren-Jie

    2009-01-01

    Hydrogen absorptions of LaFe_(11.5)Si_(1.5) compound in 1-atm hydrogen gas at different temperatures are investigated. The hydrogen content in the hydrogenated sample does not increase with the increase of temperature of hydrogen absorption but changes complicatedly. The characteristic offirst-order transition in LaFe_(11.5) Si_(1.5) compound is weakened after hydrogen absorption. It leads the peaks of magnetic entropy to become wider and the hysteresis loss to reduce significantly, but relative cooling power(RCP)is not changed considerably.

  1. 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.

  2. Atomization mechanisms and gas phase reactions in graphite furnace atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Frech, W.; Lindberg, A.O.; Lundberg, E.; Cedergren, A.

    1986-04-01

    The amounts of carbon monoxide as well as the total amounts of hydrocarbons generated in different types of graphite tubes were investigated under various experimental conditions. Depending on whether or not a matrix like 50 ..mu..g of sodium nitrate was added the amount of carbon monoxide formed during atomization at 1,700 K in a pyrocoated tube was in the range 60 to 600 nmoles when using a thermal pretreatment temperature of 1,200 K. The corresponding values for an uncoated tube were 250 to 1,300 nmoles. The effect of carbon monoxide on the atomization behaviour of silver, bismuth, chromium, copper and lead was investigated experimentally and the results were evaluated by means of thermodynamically based models. In accordance with theoretical predications, only lead, bismuth and chromium, which are assumed to be atomized by oxide decomposition, showed substantial shifts in their appearance temperatures in different gas mixtures, and changes in activation energies.

  3. Gas atomization processing of tin and silicon modified LaNi{sub 5} for nickel-metal hydride battery applications

    Energy Technology Data Exchange (ETDEWEB)

    Ting, J.

    1999-02-12

    Numerous researchers have studied the relevant material properties of so-called AB{sub 5} alloys for battery applications. These studies involved LaNi{sub 5} substituted alloys which were prepared using conventional cast and crush alloying techniques. While valuable to the understanding of metal hydride effects, the previous work nearly ignored the potential for alternative direct powder production methods, like high pressure gas atomization (HPGA). Thus, there is a need to understand the relationship between gas atomization processes, powder particle solidification phases, and hydrogen absorption properties of ultra fine (< 25 {micro}m) atomized powders with high surface area for enhanced battery performance. Concurrently, development of a gas atomization nozzle that is more efficient than all current designs is needed to increase the yield of ultrafine AB{sub 5} alloy powder for further processing advantage. Gas atomization processing of the AB{sub 5} alloys was demonstrated to be effective in producing ultrafine spherical powders that were resilient to hydrogen cycling for the benefit of improving corrosion resistance in battery application. These ultrafine powders benefited from the rapid solidification process by having refined solute segregation in the microstructure of the gas atomized powders which enabled a rapid anneal treatment of the powders. The author has demonstrated the ability to produce high yields of ultrafine powder efficiently and cost effectively, using the new HPGA-III technology. Thus, the potential benefits of processing AB{sub 5} alloys using the new HPGA technology could reduce manufacturing cost of nickel-metal hydride powder. In the near future, the manufacture of AB{sub 5} alloy powders could become a continuous and rapid production process. The economic benefit of an improved AB{sub 5} production process may thereby encourage the use of nickel-metal hydride rechargeable batteries in electrical vehicle applications in the foreseeable

  4. Development and industrial application of catalyzer for low-temperature hydrogenation hydrolysis of Claus tail gas

    OpenAIRE

    Honggang Chang; Ronghai Zhu; Zongshe Liu; Jinlong He; Chongrong Wen; Sujuan Zhang; Yang Li

    2015-01-01

    With the implementation of more strict national environmental protection laws, energy conservation, emission reduction and clean production will present higher requirements for sulfur recovery tail gas processing techniques and catalyzers. As for Claus tail gas, conventional hydrogenation catalyzers are gradually being replaced by low-temperature hydrogenation catalyzers. This paper concentrates on the development of technologies for low-temperature hydrogenation hydrolysis catalyzers, prepar...

  5. STM observation of the chemical reaction of atomic hydrogen on the N-adsorbed Cu(001) surface

    Science.gov (United States)

    Hattori, Takuma; Yamada, Masamichi; Komori, Fumio

    2017-01-01

    Chemical reaction of atomic hydrogen with the N-adsorbed Cu(001) surfaces was investigated at room temperature by scanning tunnel microscopy. At the low exposure of atomic hydrogen, it reacted with the N atoms and turned to be the NH species on the surface. The reaction rate is proportional to the amount of the unreacted N atoms. By increasing the exposure of atomic hydrogen from this condition, the amount of nitrogen species on the surface decreased. This is attributed to the formation of ammonia and its desorption from the surface. The NH species on the surface turn to NH3 through the surface NH2 species by atomic hydrogen. Coexistence of the clean Cu surface enhances the rate of ammonia formation owing to atomic hydrogen migrating on the clean surface.

  6. General model of depolarization and transfer of polarization of singly ionized atoms by collisions with hydrogen atoms

    Science.gov (United States)

    Derouich, M.

    2017-02-01

    Simulations of the generation of the atomic polarization is necessary for interpreting the second solar spectrum. For this purpose, it is important to rigorously determine the effects of the isotropic collisions with neutral hydrogen on the atomic polarization of the neutral atoms, ionized atoms and molecules. Our aim is to treat in generality the problem of depolarizing isotropic collisions between singly ionized atoms and neutral hydrogen in its ground state. Using our numerical code, we computed the collisional depolarization rates of the p-levels of ions for large number of values of the effective principal quantum number n* and the Unsöld energy Ep. Then, genetic programming has been utilized to fit the available depolarization rates. As a result, strongly non-linear relationships between the collisional depolarization rates, n* and Ep are obtained, and are shown to reproduce the original data with accuracy clearly better than 10%. These relationships allow quick calculations of the depolarizing collisional rates of any simple ion which is very useful for the solar physics community. In addition, the depolarization rates associated to the complex ions and to the hyperfine levels can be easily derived from our results. In this work we have shown that by using powerful numerical approach and our collisional method, general model giving the depolarization of the ions can be obtained to be exploited for solar applications.

  7. The hydrogen atom confined by one and two hard cones

    Science.gov (United States)

    Sarsa, A.; Alcaraz-Pelegrina, J. M.; Le Sech, C.

    2017-02-01

    The bound states of the H atom in a semi-infinite space limited by one or two conical boundaries are studied. The exact solution when the nucleus is located at the apex of the conical boundaries is obtained. A rapid increase of the energy when the cone angle opens and tends to π / 2 is found. A second situation with the atom separated from the summit of the cone is considered. The changes on the energy and the electronic structure are analyzed. The quantum force is evaluated by calculating the energy derivative versus the distance to the cone vertex. One of the forces exerted on the tip of an Atomic Force Microscope can be modelized by a hard cone probing the electron cloud in the contact mode. Our numerical results show that the quantum force present an important dependence with the cone angle and it vanishes rapidly as the distance increases.

  8. Quantum mechanical study of atomic hydrogen interaction with a fluorinated boron-substituted coronene radical.

    Science.gov (United States)

    Zhang, Hong; Smith, Sean C; Nanbu, Shinkoh; Nakamura, Hiroki

    2009-04-08

    In this work we study the transmission of atomic hydrogen across a fluorinated boron-substituted coronene radical (C(19)H(12)BF(6)) as a model for partially fluorinated and boron-doped nanotubes or fullerenes. Complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) methods are employed to calculate the potential energy surfaces for both ground and excited electronic states, and one-dimensional R-matrix propagation is utilized to investigate the transmission/reflection dynamics of atomic hydrogen, through the central six-member ring of the fluorinated boron-substituted coronene radical. The quantum scattering includes resonance effects as well as non-adiabatic transitions between the ground and excited electronic states. Within the sudden approximation, both centre and off-centre approach trajectories have been investigated. Implications for atomic hydrogen encapsulation by carbon nanotube and fullerene are discussed.

  9. Experimental investigations of electron capture from atomic hydrogen and deuterium by alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Gay, T.J.; Park, J.T.

    1992-01-01

    We report progress made during the period 15 September 1991--14 September 1992 on the project Experimental Investigations of Electron Capture from Atomic Hydrogen and Deuterium by Alpha Particles''. In the past year we have developed reliable, narrow energy spread, high-current sources of He[sup ++] based on direct-current magentron and electron-cyclotron resonance discharges. These sources have been proven on our test bench accelerator which has been upgraded to also allow us to test atomic hydrogen effusive targets. We have thus made substantial progress toward our goal of studying single electron capture from atomic hydrogen by doubly-ionized helium. A research plan for the upcoming year is also presented.

  10. Hydrogen atom wave function and eigen energy in the Rindler space

    Science.gov (United States)

    Dai, De-Chang

    2016-10-01

    We study the hydrogen atom eigenstate energy and wave function in the Rindler space. The probability distribution is tilted because the electric field of the nucleus is no longer spherically symmetric. The hydrogen atom therefore cannot be treated exactly in the same way as what it is in an inertial frame. We also find that if the external force accelerates only the nucleus and then the nucleus accelerates its surrounding electrons through electromagnetic force, the electrons can tunnel through the local energy gap and split the hydrogen atom into an ion. This is similar to what one expects from the Stark effect. However, the critical acceleration is about 3 ×1022 m /s2. It is well beyond the gravitational acceleration on a regular star surface.

  11. Hydrogen atom wave function and eigen energy in the Rindler space

    CERN Document Server

    Dai, De-Chang

    2016-01-01

    We study the hydrogen atom eigenstate energy and wave function in the Rindler space. The probability distribution is tilted because the electric field of the nucleus is no longer spherically symmetric. The hydrogen atom therefore cannot be treated exactly in the same way as what it is in an inertial frame. We also find that if the external force accelerates only the nucleus and then the nucleus accelerates its surrounding electrons through electromagnetic force, the electrons can tunnel through the local energy gap and split the hydrogen atom into an ion. This is similar to what one expects from the Stark effect. However, the critical acceleration is about $3\\times 10^{22} m/s^2$. It is well beyond the gravitational acceleration on a regular star surface.

  12. Semiclassical Szego limit of resonance clusters for the hydrogen atom Stark Hamiltonian

    CERN Document Server

    Hislop, Peter D

    2011-01-01

    We study the weighted averages of resonance clusters for the hydrogen atom with a Stark electric field in the weak field limit. We prove a semiclassical Szego-type theorem for resonance clusters showing that the limiting distribution of the resonance shifts concentrates on the classical energy surface corresponding to a rescaled eigenvalue of the hydrogen atom Hamiltonian. This result extends Szego-type results on eigenvalue clusters to resonance clusters. There are two new features in this work: first, the study of resonance clusters requires the use of non self-adjoint operators, and second, the Stark perturbation is unbounded so control of the perturbation is achieved using localization properties of coherent states corresponding to hydrogen atom eigenvalues.

  13. Selective permeation of hydrogen gas using cellulose nanofibril film.

    Science.gov (United States)

    Fukuzumi, Hayaka; Fujisawa, Shuji; Saito, Tsuguyuki; Isogai, Akira

    2013-05-13

    Biobased membranes that can selectively permeate hydrogen gas have been developed from aqueous dispersions of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCN) prepared from wood cellulose: TOCN-coated plastic films and self-standing TOCN films. Compared with TOCNs with sodium, lithium, potassium, and cesium carboxylate groups, TOCN with free carboxyl groups (TOCN-COOH) had much high and selective H2 gas permeation performance. Because permeabilities of H2, N2, O2, and CO2 gases through the membranes primarily depended on their kinetic diameters, the gas permeation behavior of the various TOCNs can be explained in terms of a diffusion mechanism. Thus, the selective H2 gas permeability for TOCN-COOH was probably due to a larger average size in free volume holes present between nanofibrils in the layer and film than those of other TOCNs with metal carboxylate groups. The obtained results indicate that TOCN-COOH membranes are applicable as biobased H2 gas separation membranes in fuel cell electric power generation systems.

  14. Probing the Physical Conditions of Atomic Gas at High Redshift

    CERN Document Server

    Neeleman, Marcel; Wolfe, Arthur M

    2014-01-01

    A new method is used to measure the physical conditions of the gas in damped Lyman-alpha systems (DLAs). Using high resolution absorption spectra of a sample of 80 DLAs, we are able to measure the ratio of the upper to lower fine-structure levels of the ground state of C II and Si II. These ratios are determined solely by the physical conditions of the gas. We explore the allowed physical parameter space using a Monte Carlo Markov Chain method to constrain simultaneously the temperature, neutral hydrogen density, and electron density of each DLA. The results indicate that at least 5 % of all DLAs have the bulk of their gas in a dense, cold phase with typical densities of ~100 cm-3 and temperatures below 500 K. We further find that the typical pressure of DLAs in our sample is log(P/k) = 3.4 [K cm-3], which is comparable to the pressure of the local interstellar medium (ISM), and that the components containing the bulk of the neutral gas can be quite small with absorption sizes as small as a few parsec. We sho...

  15. Lewis acid-water/alcohol complexes as hydrogen atom donors in radical reactions.

    Science.gov (United States)

    Povie, Guillaume; Renaud, Philippe

    2013-01-01

    Water or low molecular weight alcohols are, due to their availability, low price and low toxicity ideal reagents for organic synthesis. Recently, it was reported that, despite the very strong BDE of the O-H bond, they can be used as hydrogen atom donors in place of expensive and/or toxic group 14 metal hydrides when boron and titanium(III) Lewis acids are present. This finding represents a considerable innovation and uncovers a new perspective on the paradigm of hydrogen atom transfers to radicals. We discuss here the influence of complex formation and other association processes on the efficacy of the hydrogen transfer step. A delicate balance between activation by complex formation and deactivation by further hydrogen bonding is operative.

  16. Gas atomization of cobalt ferrite-phosphate melts

    Science.gov (United States)

    De Guire, Mark R.; O'Handley, R. C.; Kalonji, G.

    1989-01-01

    XRD, Moessbauer spectroscopy, and EDXS have been used to characterize a rapidly-solidified (Co,Fe)3O4 spinel generated in a cobalt-iron-phosphate glass matrix by gas atomization of melts. Of the two compositions tested, that containing 20 mol pct P2O5 exhibited randomly-oriented ferrite crystallization whose growth appears to have been diffusion-controlled. Unlike the ferrite, in which the iron has both tetrahedral and octahedral coordination, the iron in the glassy matrix was primarily of distorted-octahedral coordination. Calculations indicate that the cooling rates obtained with oxide melts vary strongly with droplet size, but less strongly with melt temperature.

  17. Classical stabilization of the hydrogen atom in a monochromatic field

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, F.; Casati, G. (Dipartimento di Fisica dell' Universita, Via Castelnuovo 7, 22100 Como (Italy)); Shepelyansky, D.L. (Laboratoire de Physique Quantique, Universite Paul Sabatier, 31062, Toulouse (France))

    1993-02-01

    We report the results of analytical and numerical investigations on the ionization of a classical atom in a strong, linearly polarized, monochromatic field. We show that the ionization probability decreases with increasing field intensity at field amplitudes much larger than the classical chaos border. This effect should be observable in real laboratory experiments.

  18. Nucleon Polarizabilities: from Compton Scattering to Hydrogen Atom

    CERN Document Server

    Hagelstein, Franziska; Pascalutsa, Vladimir

    2015-01-01

    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 general constraints based on unitarity, causality, discrete and continuous symmetries, which result in model-independent relations involving nucleon polarizabilities. We (re-)derive a variety of such relations and discuss their empirical value. The proton polarizability effects are presently the major sources of uncertainty in the assessment of the muonic hydrogen Lamb shift and hyperfine structure. Recent calculations of these effects are reviewed here in the context of the "proton-radius puzzle". We conclude with summary...

  19. Conformer-specific hydrogen atom tunnelling in trifluoromethylhydroxycarbene

    Science.gov (United States)

    Mardyukov, Artur; Quanz, Henrik; Schreiner, Peter R.

    2017-01-01

    Conformational control of organic reactions is at the heart of the biomolecular sciences. To achieve a particular reactivity, one of many conformers may be selected, for instance, by a (bio)catalyst, as the geometrically most suited and appropriately reactive species. The equilibration of energetically close-lying conformers is typically assumed to be facile and less energetically taxing than the reaction under consideration itself: this is termed the 'Curtin-Hammett principle'. Here, we show that the trans conformer of trifluoromethylhydroxycarbene preferentially rearranges through a facile quantum-mechanical hydrogen tunnelling pathway, while its cis conformer is entirely unreactive. Hence, this presents the first example of a conformer-specific hydrogen tunnelling reaction. The Curtin-Hammett principle is not applicable, due to the high barrier between the two conformers.

  20. Synthesis of hydrogen gas by thermal decomposition of methane gas with carbon sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Castro, A R [Escuela de Quimica, Facultad de Ciencias, Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of); Manrique, C M [Departamento de Ciencia de los Materiales, GPUSB, Universidad Simon BolIvar, Caracas (Venezuela, Bolivarian Republic of); Castell, R; Ruiz, J [Departamento de Fisica, Universidad Simon BolIvar, Caracas (Venezuela, Bolivarian Republic of)

    2008-10-15

    Hydrogen gas synthesis by the thermal decomposition of methane gas in a non-transferred arc thermal plasma reactor is studied. A thermodynamic study was carried out obtaining free energy minimization plots for the C-H-N and C-H-N-Si systems by using the CSIRO thermo package. Nitrogen gas was used as an ionizing gas and metallic silicon fine powder was injected to promote the in fly silicon carbide nucleation. The effect of current intensity on the thermal decomposition of methane was studied. The degree of methane gas decomposition was in the range 84-97%. The fine solid product collected was characterized using the XRD and MEB-EDAX methods. Elemental carbon particles as well as silicon carbide particles in the nanometric range were identified by the last technique.

  1. 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 literat......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...

  2. LAMB SHIFT IN HYDROGEN-LIKE ATOM INDUCED FROM NON-COMMUTATIVE QUANTUM SPACE-TIME

    Directory of Open Access Journals (Sweden)

    S Zaim

    2015-06-01

    Full Text Available In this work we present an important contribution to the non-commutative approach to the hydrogen atom to deal with lamb shift corrections. This can be done by studying the Klein-Gordon equation in a non-commutative space-time as applied to the Hydrogen atom to extract the energy levels, by considering the second-order corrections in the non commutativity parameter and by comparing with the result of the current experimental results on the Lamb shift of the 2P level to extract a bound on the parameter of non-commutativity. Phenomenologically we show that the non-commutativity effects induce lamb shift corrections.

  3. Deformylation Reaction by a Nonheme Manganese(III)-Peroxo Complex via Initial Hydrogen-Atom Abstraction.

    Science.gov (United States)

    Barman, Prasenjit; Upadhyay, Pranav; Faponle, Abayomi S; Kumar, Jitendra; Nag, Sayanta Sekhar; Kumar, Devesh; Sastri, Chivukula V; de Visser, Sam P

    2016-09-05

    Metal-peroxo intermediates are key species in the catalytic cycles of nonheme metalloenzymes, but their chemical properties and reactivity patterns are still poorly understood. The synthesis and characterization of a manganese(III)-peroxo complex with a pentadentate bispidine ligand system and its reactivity with aldehydes was studied. Manganese(III)-peroxo can react through hydrogen-atom abstraction reactions instead of the commonly proposed nucleophilic addition reaction. Evidence of the mechanism comes from experiments which identify a primary kinetic isotope effect of 5.4 for the deformylation reaction. Computational modeling supports the established mechanism and identifies the origin of the reactivity preference of hydrogen-atom abstraction over nucleophilic addition.

  4. Quantum spacetime fluctuations: Lamb Shift and hyperfine structure of the hydrogen atom

    CERN Document Server

    Rivas, Juan Israel; Goeklue, Ertan

    2011-01-01

    We consider the consequences of the presence of metric fluctuations upon the properties of a hydrogen atom. Particularly, we introduce these metric fluctuations in the corresponding effective Schroedinger equation and deduce the modifications that they entail upon the hyperfine structure related to a hydrogen atom. We will find the change that these effects imply for the ground state energy of the system and obtain a bound for its size comparing our theoretical predictions against the experimental uncertainty reported in the literature. In addition, we analyze the corresponding Lamb shift effect emerging from these fluctuations of spacetime. Once again, we will set a bound to these oscillations resorting to the current experimental outcomes

  5. Reduction of uranium hexafluoride to tetrafluoride by using the hydrogen atoms

    Science.gov (United States)

    Aleksandrov, B. P.; Gordon, E. B.; Ivanov, A. V.; Kotov, A. A.; Smirnov, V. E.

    2016-09-01

    We consider the reduction of UF6 to UF4 by chemical reaction with hydrogen atoms originated in the powerful chemical generator. The principal design of such a chemical convertor is described. The results of the mathematical modeling of the thermodynamics and kinetics of the UF6 to UF4 reduction process are analyzed. The few options for the hydrogen atom generator design are proposed. A layout of the experimental setup with the chemical reactor is presented. The high efficiency together with the ability of the process scaling without loss of its efficiency makes this approach to the uranium hexafluoride depletion into tetrafluoride promising for its application in the industry.

  6. 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.

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

    Science.gov (United States)

    Tachikawa, Hiroto

    2017-02-01

    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.

  8. Adsorption of hydrogen atoms onto the exterior wall of carbon nanotubes and their thermodynamics properties

    Energy Technology Data Exchange (ETDEWEB)

    Ng, T.Y.; Ren, Y.X. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Liew, K.M. [Department of Building and Construction, City University of Hong Kong, Tat Chee Avenue, Kowloon (China)

    2010-05-15

    In the present work, we present a systematic analysis of the chemisorption process pathway of hydrogen atoms onto the exterior wall of (5,5) carbon nanotubes using the ONIOM2 (B3LYP(6-31+G(d,p):UFF)) scheme, and we avoid the gross assumption of fixing any of the carbon atoms during the simulation. It is shown that the adsorption of hydrogen atoms onto the sidewall of CNTs are energetically favorable and the most stable state is to form two H-C {sigma}-bonds while the original {sigma}-bond between the carbon atoms is totally severed. In particular, we examined the molecular thermodynamics properties for the reaction at a range of temperatures from 77 K to 1000 K, and the results suggests that the reaction is possible at ambient temperature, but it is less favorable than that at lower temperatures. (author)

  9. Production of vibrationally excited hydrogen molecules by atom recombination on Cu and W materials.

    Science.gov (United States)

    Markelj, Sabina; Čadež, Iztok

    2011-03-28

    We have measured vibrational population of H(2) and D(2) molecules produced by atom (H or D) recombination on tungsten and copper material. The vibrational spectroscopy, based on the properties of dissociative electron attachment to hydrogen molecule, was used. The vibrationally excited molecules were produced by atom recombination in a cell where the studied sample is exposed to hydrogen atoms, from hot tungsten filament. Vibrational populations were obtained for the studied materials, which can be well described by the Boltzmann distribution, with specific vibrational temperatures for each material. The experimentally obtained vibrational populations for copper approximately agree with the theoretical predictions, whereas the experimentally obtained vibrational temperature for tungsten is higher and thus showing a considerable overpopulation of highly excited vibrational states than predicted. We propose that the origin of this higher excitation is related to the existence of high hydrogen surface coverage on tungsten, where hydrogen is occupying binding sites with different desorption energies. In order to obtain an insight into the recombination mechanism with more than one binding site per unit cell, a Monte Carlo simulation was performed, where it was assumed that the main production of molecules proceeds through the hot-atom recombination with an adsorbed atom. The results show that the recombination proceeds mainly through the weak binding sites, once they are occupied.

  10. Evidence for the Heating of Atomic Interstellar Gas by PAHs

    CERN Document Server

    Helou, G; Hollenbach, D J; Dale, D A; Contursi, A; Helou, George; Malhotra, Sangeeta; Hollenbach, David J.; Dale, Daniel A.; Contursi, Alessandra

    2001-01-01

    We report a strong correlation between the [CII] 158 micron cooling line and the mid-infrared flux in the 5-10 micron range in a wide variety of star-forming galaxies. The mid-infrared flux is dominated by Aromatic Feature Emission (AFE), which is thought to arise from large polycyclic aromatic hydrocarbon molecules or `PAHs' and generally associated with the smallest interstellar grains. The [CII] line is the dominant gas coolant in most regions of atomic interstellar gas, and therefore reflects the heating input to the gas. The ratio of these two quantities, [CII]/AFE, remains nearly constant with the ratio of the IRAS 60 micron band flux to the 100 micron band flux, R(60/100). This is in contrast to the drop in the [CII]/FIR ratio with increasing R(60/100), which signal higher dust temperatures and more intense radiation fields. We interpret the stable [CII]/AFE ratio as evidence that gas heating is dominated by the PAHs or small grains which are also AFE carriers over a wide range of conditions. The trend...

  11. Study on the recovery of hydrogen from refinery (hydrogen+methane) gas mixtures using hydrate technology

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A novel technique for separating hydrogen from (H2 + CH4) gas mixtures through hydrate formation/dissociation was proposed. In this work, a systematic experimental study was performed on the separation of hydrogen from (H2 + CH4) feed mixtures with various hydrogen contents (mole fraction x = 40%-90%). The experimental results showed that the hydrogen content could be enriched to as high as ~94% for various feed mixtures using the proposed hydrate technology under a temperature slightly above 0℃ and a pressure below 5.0 MPa. With the addition of a small amount of suitable additives, the rate of hydrate formation could be increased significantly. Anti-agglomeration was used to disperse hydrate particles into the condensate phase. Instead of preventing hydrate growth (as in the kinetic inhibitor tests), hydrates were allowed to form, but only as small dispersed particles. Anti-agglomeration could keep hydrate particles suspended in a range of condensate types at 1℃ and 5 MPa in the water-in-oil emulsion.

  12. Study on the recovery of hydrogen from refinery (hydrogen + methane) gas mixtures using hydrate technology

    Institute of Scientific and Technical Information of China (English)

    WANG XiuLin; CHEN GuangJin; YANG LanYing; ZHANG LinWei

    2008-01-01

    A novel technique for separating hydrogen from (H2 + CH4) gas mixtures through hydrate forma-tion/dissociation was proposed.In this work, a systematic experimental study was performed on the separation of hydrogen from (H2+CH4) feed mixtures with various hydrogen contents (mole fraction x =40%-90%).The experimental results showed that the hydrogen content could be enriched to as high as~94% for various feed mixtures using the proposed hydrate technology under a temperature slightly above 0℃ and a pressure below 5.0 MPa.With the addition of a small amount of suitable additives, the rate of hydrate formation could be increased significantly.Anti-agglomeration was used to disperse hydrate particles into the condensate phase.Instead of preventing hydrate growth (as in the kinetic inhibitor tests), hydrates were allowed to form, but only as small dispersed particles.Anti-agglomera-tion could keep hydrate particles suspended in a range of condensate types at 1℃ and 5 MPa in the water-in-oil emulsion.

  13. Atomic hydrogen adsorption and incipient hydrogenation of the Mg(0001) surface: a density-functional theory study.

    Science.gov (United States)

    Li, Yanfang; Zhang, Ping; Sun, Bo; Yang, Yu; Wei, Yinghui

    2009-07-21

    We investigate the atomic hydrogen adsorption on Mg(0001) by using density-functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics is systematically studied for a wide range of coverage Theta [from 0.11 to 2.0 monolayers (ML)] and adsorption sites. In the coverage range 0 atomic hydrogen as well as the activation barriers for hydrogen penetration from the on-surface to the subsurface sites are also presented at low coverage. At high coverage of 1.0 < Theta < or = 2.0, it is found that the coadsorption configuration with 1.0 monolayer of H residing on the surface fcc sites and the remaining (Theta-1.0) monolayer of H occupying the subsurface tetra-I sites is most energetically favorable. The resultant H-Mg-H sandwich structure for this most stable coadsorption configuration displays similar spectral features to the bulk hydride MgH(2) in the density of states. The other properties of the H/Mg(0001) system including the charge distribution, the lattice relaxation, the work function, and the electronic density of states are also studied and discussed in detail. It is pointed out that the H-Mg chemical bonding during surface hydrogenation displays a mixed ionic/covalent character.

  14. The RESOLVE Survey Atomic Gas Census and Environmental Influences on Galaxy Gas Content

    Science.gov (United States)

    Stark, David; Kannappan, Sheila; Eckert, Kathleen D.; Jonathan, Florez; Hall, Kirsten; Watson, Linda C.; Hoversten, Erik A.; Burchett, Joseph; Guynn, David; Baker, Ashley; Moffett, Amanda J.; Berlind, Andreas A.; Norris, Mark A.; Haynes, Martha P.; Giovanelli, Riccardo; Leroy, Adam K.; Pisano, Daniel J.; Wei, Lisa H.; Gonzalez, Roberto; RESOLVE Team

    2016-01-01

    We present the >93% complete 21cm inventory for the RESOLVE survey, a volume-limited census of ~1500 galaxies spanning diverse environments and probing baryonic masses down to ~109 M⊙. A key strength of the 21cm observational program is its fractional mass limited design, which yields an unbiased inventory of atomic gas mass, with either clean detections or strong upper limits group processes that deplete gas content are active well below the large group/cluster scale. In addition, at fixed halo mass both centrals and satellites in large-scale walls have systematically lower gas fractions than galaxies in filaments or voids, and this trend cannot be fully explained by differing stellar mass distributions within these large-scale environments. Lastly, we show that the abundance of gas-poor (gas-to-stellar mass ratio 1012 M⊙ groups than do more gas-rich but otherwise analogous low halo-mass centrals, suggesting that the gas-poor centrals have lost their gas in flyby interactions with the nearby groups. We discuss how the observed trends may be shaped by a number of physical processes such as gas stripping, starvation, and halo assembly bias. This project has been supported by NSF funding for the RESOLVE survey (AST-0955368), the GBT Student Observing Support program, and a UNC Royster Society of Fellows Dissertation Completion Fellowship.

  15. PROBING THE PHYSICAL CONDITIONS OF ATOMIC GAS AT HIGH REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Neeleman, Marcel; Wolfe, Arthur M. [Department of Physics and Center for Astrophysics and Space Sciences, UCSD, La Jolla, CA 92093 (United States); Prochaska, J. Xavier, E-mail: mneeleman@physics.ucsd.edu [Department of Astronomy and Astrophysics, UCO/Lick Observatory, 1156 High Street, University of California, Santa Cruz, CA 95064 (United States)

    2015-02-10

    A new method is used to measure the physical conditions of the gas in damped Lyα systems (DLAs). Using high-resolution absorption spectra of a sample of 80 DLAs, we are able to measure the ratio of the upper and lower fine-structure levels of the ground state of C{sup +} and Si{sup +}. These ratios are determined solely by the physical conditions of the gas. We explore the allowed physical parameter space using a Monte Carlo Markov chain method to constrain simultaneously the temperature, neutral hydrogen density, and electron density of each DLA. The results indicate that at least 5% of all DLAs have the bulk of their gas in a dense, cold phase with typical densities of ∼100 cm{sup –3} and temperatures below 500 K. We further find that the typical pressure of DLAs in our sample is log (P/k{sub B} ) = 3.4 (K cm{sup –3}), which is comparable to the pressure of the local interstellar medium (ISM), and that the components containing the bulk of the neutral gas can be quite small with absorption sizes as small as a few parsecs. We show that the majority of the systems are consistent with having densities significantly higher than expected for a purely canonical warm neutral medium, indicating that significant quantities of dense gas (i.e., n {sub H} > 0.1 cm{sup –3}) are required to match observations. Finally, we identify eight systems with positive detections of Si II*. These systems have pressures (P/k{sub B} ) in excess of 20,000 K cm{sup –3}, which suggest that these systems tag a highly turbulent ISM in young, star-forming galaxies.

  16. Stability of the hydrogen atom of classical electrodynamics

    CERN Document Server

    De Luca, J

    2004-01-01

    We study the stability of the circular orbits of the electromagnetic two-body problem of classical electrodynamics. We introduce the concept of resonant dissipation, i.e. a motion that radiates the center-of-mass energy while the interparticle distance performs bounded oscillations about a metastable orbit. The stability mechanism is established by the existence of a quartic resonant constant generated by the stiff eigenvalues of the linear stability problem. This constant bounds the particles together during the radiative recoil. The condition of resonant dissipation predicts angular momenta for the metastable orbits in reasonable agreement with the Bohr atom. The principal result is that the emission lines agree with the predictions of quantum electrodynamics (QED) with 1 percent average error even up to the $40^{th}$ line. Our angular momenta depend logarithmically on the mass of the heavy body, such that the deuterium and the muonium atoms have essentially the same angular momenta, in agreement with QED. ...

  17. Atomic and molecular physics in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Toburen, L.H.

    1990-09-01

    The spatial and temporal distributions of energy deposition by high-linear-energy-transfer radiation play an important role in the subsequent chemical and biological processes leading to radiation damage. Because the spatial structures of energy deposition events are of the same dimensions as molecular structures in the mammalian cell, direct measurements of energy deposition distributions appropriate to radiation biology are infeasible. This has led to the development of models of energy transport based on a knowledge of atomic and molecular interactions process that enable one to simulate energy transfer on an atomic scale. Such models require a detailed understanding of the interactions of ions and electrons with biologically relevant material. During the past 20 years there has been a great deal of progress in our understanding of these interactions; much of it coming from studies in the gas phase. These studies provide information on the systematics of interaction cross sections leading to a knowledge of the regions of energy deposition where molecular and phase effects are important and that guide developments in appropriate theory. In this report studies of the doubly differential cross sections, crucial to the development of stochastic energy deposition calculations and track structure simulation, will be reviewed. Areas of understanding are discussed and directions for future work addressed. Particular attention is given to experimental and theoretical findings that have changed the traditional view of secondary electron production for charged particle interactions with atomic and molecular targets.

  18. Entanglement harvesting from the electromagnetic vacuum with hydrogen-like atoms

    CERN Document Server

    Pozas-Kerstjens, Alejandro

    2016-01-01

    We study how two fully-featured hydrogen-like atoms harvest entanglement from the electromagnetic field vacuum, even when the atoms are spacelike separated. We compare the electromagnetic case ---qualitatively and quantitatively--- with previous results that used scalar fields and featureless, idealized atomic models. Our study reveals the new traits that emerge when we relax these idealizations, such as anisotropies in entanglement harvesting and the effect of exchange of angular momentum. We show that, under certain circumstances, relaxing previous idealizations makes vacuum entanglement harvesting more efficient.

  19. Interference Dynamics of Hydrogen Atoms in High-Frequency Dichromatic Laser Fields

    Science.gov (United States)

    Cheng, Tai-Wang; Li, Xiao-Feng; Fu, Pan-Ming; Chen, Shi-Gang

    2002-08-01

    We investigate the ionization and high-order harmonic generation of a hydrogen atom in high-frequency (several atomic units) super strong (up to several tens of atomic units) dichromatic laser fields. An effective iterative method in the framework of high-frequency Floquet theory is used in the calculations. We have considered two kinds of dichromatic laser field, i.e. 1ω-2ω and 1ω-3ω. We find that, in both the cases, the ionization and high-order harmonic generation show evident dependence on the relative phase and strength of the additional harmonic field. The dynamical origin of these interference effects is also discussed.

  20. Interference Dynamics of Hydrogen Atoms in High-Frequency Dichromatic Laser Fields

    Institute of Scientific and Technical Information of China (English)

    程太旺; 李晓峰; 傅盘铭; 陈式刚

    2002-01-01

    We investigate the ionization and high-order harmonic generation of a hydrogen atom in high-frequency (several atomic units) super strong (up to several tens of atomic units) dichromatic laser fields. An effective iterative method in the framework of high-frequency Floquet theory is used in the calculations. We have considered two kinds of dichromatic laser field, i.e. 1ω - 2ω and lω - 3ω. We find that, in both the cases, the ionization and high-order harmonic generation show evident dependence on the relative phase and strength of the additional harmonic field. The dynamical origin of these interference effects is also discussed.

  1. Resonant three-photon ionization of hydrogenic atoms by a non-monochromatic laser field

    NARCIS (Netherlands)

    Yakhontov, V.; Santra, R.; Jungmann, K.

    1999-01-01

    We present ionization probability and lineshape calculations for the two-step three- photon ionization process, 1S (2(h)over-bar-omega)under-right-arrow, 2S ((h)over-bar-omega)under-right-arrow epsilon P, of the ground state of hydrogenic atoms in a non-monochromatic laser field with a time-dependen

  2. Resonant three-photon ionization of hydrogenic atoms by a non-monochromatic laser field

    NARCIS (Netherlands)

    Yakhontov, V.; Santra, R.; Jungmann, K.

    1999-01-01

    We present ionization probability and lineshape calculations for a specifed two-step three-photon ionization process of the ground state of hydrogenic atoms in a non-monochromatic laser field with a time-dependent amplitude. Within the framework of a three-level model, the AC Stark shifts and non-ze

  3. 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.

  4. 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)

  5. 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

  6. 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.

  7. Atomic and molecular hydrogen in the circumstellar envelopes of late-type stars

    Science.gov (United States)

    Glassgold, A. E.; Huggins, P. J.

    1983-01-01

    The distribution of atomic and molecular hydrogen in the expanding circumstellar envelopes of cool evolved stars is discussed. The main concern is to evaluate the effects of photodestruction of H2 by galactic UV radiation, including shielding of the radiation by H2 itself and by dust in the envelope. One of the most important parameters is the H/H2 ratio which is frozen out in the upper atmosphere of the star. For stars with photospheric temperatures greater than about 2500 K, atmospheric models suggest that the outflowing hydrogen is mainly atomic, whereas cooler stars should be substantially molecular. In the latter case, photodissociation of H2 and heavy molecules contribute to the atomic hydrogen content of the outer envelope. The presented estimates indicate that atomic hydrogen is almost at the limit of detection in the C-rich star IRC + 10216, and may be detectable in warmer stars. Failure to detect it would have important implications for the general understanding of circumstellar envelopes.

  8. Schiff theorem and the electric dipole moments of hydrogen-like atoms

    NARCIS (Netherlands)

    Liu, C. -P.; Haxton, W. C.; Ramsey-Musolf, M. J.; Timmermans, R. G. E.; Dieperink, A. E. L.; Barnes, PD; Cooper, MD; Eisenstein, RA; VanHecke, H; Stephenson, GJ

    2006-01-01

    The Schiff theorem is revisited in this work and the residual P- and T-odd electron-nucleus interaction, after the shielding takes effect, is completely specified. An application is made to the electric dipole moments of hydrogen-like atoms, whose qualitative features and systematics have important

  9. Continuous vs. discrete models for the quantum harmonic oscillator and the hydrogen atom

    OpenAIRE

    Lorente, M.

    2004-01-01

    The Kravchuk and Meixner polynomials of discrete variable are introduced for the discrete models of the harmonic oscillator and hydrogen atom. Starting from Rodrigues formula we construct raising and lowering operators, commutation and anticommutation relations. The physical properties of discrete models are figured out through the equivalence with the continuous models obtained by limit process.

  10. 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.

  11. 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.

  12. Continuous vs. discrete models for the quantum harmonic oscillator and the hydrogen atom

    CERN Document Server

    Lorente, M

    2001-01-01

    The Kravchuk and Meixner polynomials of discrete variable are introduced for the discrete models of the harmonic oscillator and hydrogen atom. Starting from Rodrigues formula we construct raising and lowering operators, commutation and anticommutation relations. The physical properties of discrete models are figured out through the equivalence with the continuous models obtained by limit process.

  13. Continuous vs. discrete models for the quantum harmonic oscillator and the hydrogen atom

    Science.gov (United States)

    Lorente, Miguel

    2001-07-01

    The Kravchuk and Meixner polynomials of discrete variable are introduced for the discrete models of the harmonic oscillator and hydrogen atom. Starting from Rodrigues formula we construct raising and lowering operators, commutation and anticommutation relations. The physical properties of discrete models are figured out through the equivalence with the continuous models obtained by limit process.

  14. Triple differential cross sections for the ionization of atomic hydrogen by fast electrons

    Science.gov (United States)

    Byron, F. W.; Joachain, C. J.; Piraux, B.

    1983-12-01

    The triple differential cross section for the ionization of atomic hydrogen by fast electrons is analyzed in the case of a coplanar, asymmetric geometry by using the eikonal Born series theory. Our calculations are in good agreement with recent measurements performed at an incident electron energy of 250 eV.

  15. 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…

  16. Quantum states of hydrogen atom on Pd(1 1 0) surface

    Science.gov (United States)

    Padama, Allan Abraham B.; Nakanishi, Hiroshi; Kasai, Hideaki

    2015-12-01

    The quantum states of adsorbed hydrogen atom on Pd(1 1 0) surface are investigated in this work. From the calculated potential energy surface (PES) of hydrogen atom on Pd(1 1 0), the wave functions and eigenenergies in the ground and few excited states of protium (H) and deuterium (D) are calculated. Localized wave functions of hydrogen atom exist on pseudo-threefold and long bridge sites of Pd(1 1 0). The short bridge site is a local minimum from the result of PES, however, quantum behavior of hydrogen revealed that its vibration would allow it to hop to other pseudo-threefold site (that crosses the short bridge site) than to stay on the short bridge site. Exchange of ordering of the wave functions between H and D is attributed to the difference in their masses. The calculated eigenenergies are found to be in fair agreement with experimental data based from the identified vibrations of hydrogen with component perpendicular to the surface. The activation barriers measured from the eigenenergies are in better agreement with experimental findings in comparison to the data gathered from PES.

  17. Four kinds of raising and lowering operators of n-dimensional hydrogen atom and isotropic harmonic oscillator

    Institute of Scientific and Technical Information of China (English)

    刘宇峰; 曾谨言

    1997-01-01

    The factorization of the radial Schrodinger equation of n-dimensional (n≥2) hydrogen atoms and isotropic harmonic oscillators was investigated and four kinds of raising and lowering operators were derived.The relation between n -dimensional (n≥2) and one-dimensional hydrogen atoms and harmonic oscillators was discussed.

  18. Protective Effects of Hydrogen Gas on Experimental Acute Pancreatitis.

    Directory of Open Access Journals (Sweden)

    Hao-Xin Zhou

    Full Text Available Acute pancreatitis (AP is an inflammatory disease mediated by damage to acinar cells and pancreatic inflammation. In patients with AP, subsequent systemic inflammatory responses and multiple organs dysfunction commonly occur. Interactions between cytokines and oxidative stress greatly contribute to the amplification of uncontrolled inflammatory responses. Molecular hydrogen (H2 is a potent free radical scavenger that not only ameliorates oxidative stress but also lowers cytokine levels. The aim of the present study was to investigate the protective effects of H2 gas on AP both in vitro and in vivo. For the in vitro assessment, AR42J cells were treated with cerulein and then incubated in H2-rich or normal medium for 24 h, and for the in vivo experiment, AP was induced through a retrograde infusion of 5% sodium taurocholate into the pancreatobiliary duct (0.1 mL/100 g body weight. Wistar rats were treated with inhaled air or 2% H2 gas and sacrificed 12 h following the induction of pancreatitis. Specimens were collected and processed to measure the amylase and lipase activity levels; the myeloperoxidase activity and production levels; the cytokine mRNA expression levels; the 8-hydroxydeoxyguanosine, malondialdehyde, and glutathione levels; and the cell survival rate. Histological examinations and immunohistochemical analyses were then conducted. The results revealed significant reductions in inflammation and oxidative stress both in vitro and in vivo. Furthermore, the beneficial effects of H2 gas were associated with reductions in AR42J cell and pancreatic tissue damage. In conclusion, our results suggest that H2 gas is capable of ameliorating damage to the pancreas and AR42J cells and that H2 exerts protective effects both in vitro and in vivo on subjects with AP. Thus, the results obtained indicate that this gas may represent a novel therapy agent in the management of AP.

  19. Infrared absorption on a complex comprising three equivalent hydrogen atoms in ZnO

    Science.gov (United States)

    Herklotz, F.; Hupfer, A.; Johansen, K. M.; Svensson, B. G.; Koch, S. G.; Lavrov, E. V.

    2015-10-01

    A hydrogen-related defect in ZnO which causes two broad IR absorption bands at 3303 and 3321 cm-1 is studied by means of infrared absorption spectroscopy and first-principles theory. In deuterated samples, the defect reveals two sharp absorption lines at 2466 and 2488 cm-1 accompanied by weaker sidebands at 2462 and 2480 cm-1. Isotope substitution experiments with varying concentrations of H and D together with polarization-sensitive measurements strongly suggest that these IR absorption lines are due to stretch local vibrational modes of a defect comprising three equivalent hydrogen atoms. The zinc vacancy decorated by three hydrogen atoms, VZnH3 , and ammonia trapped at the zinc vacancy, (NH3)Zn, are discussed as a possible origin for the complex.

  20. Spontaneous absorption of an accelerated hydrogen atom near a conducting plane in vacuum

    CERN Document Server

    Yu, H; Yu, Hongwei; Zhu, Zhiying

    2006-01-01

    We study, in the multipolar coupling scheme, a uniformly accelerated multilevel hydrogen atom in interaction with the quantum electromagnetic field near a conducting boundary and separately calculate the contributions of the vacuum fluctuation and radiation reaction to the rate of change of the mean atomic energy. It is found that the perfect balance between the contributions of vacuum fluctuations and radiation reaction that ensures the stability of ground-state atoms is disturbed, making spontaneous transition of ground-state atoms to excited states possible in vacuum with a conducting boundary. The boundary-induced contribution is effectively a nonthermal correction, which enhances or weakens the nonthermal effect already present in the unbounded case, thus possibly making the effect easier to observe. An interesting feature worth being noted is that the nonthermal corrections may vanish for atoms on some particular trajectories.

  1. Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, June Key, E-mail: junekey@jnu.ac.kr, E-mail: hskim7@jbnu.ac.kr; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok [Department of Materials Science and Engineering, and Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Ryu, Sang-Wan [Department of Physics and Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Jeong, Tak [Korea Photonics Technology Institute, Gwangju 500-460 (Korea, Republic of); Jung, Eunjin; Kim, Hyunsoo, E-mail: junekey@jnu.ac.kr, E-mail: hskim7@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2015-05-14

    Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by ∼35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region.

  2. Study on Fine Structure of Gas Atomized LaNi5-based Alloys

    Institute of Scientific and Technical Information of China (English)

    Hai JING; Hong GUO; Shuguang ZHANG; Zili MA; Shaoming ZHANG

    2003-01-01

    The fine structure of hydrogen storage alloy powders MINi4.3-xCoxMn0.4Al0.3(x=0.75, 0.45, 0.10; MI: La-rich mischmetal) prepared by rapidly solidifying gas atomization was investigated using a Rietveld analysis method. Two setsof CaCu5-type crystal constants were observed in the studied alloys and one set was larger than the other. Withdecreasing powder radius the solidification rate of powder increased, and so did the percentage of a particle partwith larger crystal constants. The reason why there were two sets of crystal constants might be the difference ofsolidification rate between the outside and inside of a particle.

  3. Production of Excited Atomic Hydrogen and Deuterium from HD Photodissociation

    Science.gov (United States)

    Machacek, J. R.; Bozek, J. D.; Furst, J. E.; Gay, T. J.; Gould, H.; Kilcoyne, A. L. D.; McLaughlin, K. W.

    2008-05-01

    We have measured the production of Lyα, Hα, and Hβ fluorescence from atomic H and D for the photodissociation of HD by linearly-polarized photons with energies between 20 and 66 eV. In this energy range, excited photofragments result primarily from the production of doubly-excited molecular species which promptly autoionize or dissociate into two neutrals. Theoretical calculation are not yet available for HD, but comparison between the relative cross sections for H2, D2 and HD targets and the available theory for H2 and D2 [1] allow for an estimate of the relative strength of each dissociation channel in this energy range. [1] J. D. Bozek et al., J. Phys. B 39, 4871 (2006). Support provided by the NSF (Grant PHY-0653379), DOE (LBNL/ALS) and ANSTO (Access to Major Research Facilities Programme).

  4. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water.

    Science.gov (United States)

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-08-19

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

  5. Stabilizing a Platinum1 Single-Atom Catalyst on Supported Phosphomolybdic Acid without Compromising Hydrogenation Activity.

    Science.gov (United States)

    Zhang, Bin; Asakura, Hiroyuki; Zhang, Jia; Zhang, Jiaguang; De, Sudipta; Yan, Ning

    2016-07-11

    In coordination chemistry, catalytically active metal complexes in a zero- or low-valent state often adopt four-coordinate square-planar or tetrahedral geometry. By applying this principle, we have developed a stable Pt1 single-atom catalyst with a high Pt loading (close to 1 wt %) on phosphomolybdic acid(PMA)-modified active carbon. This was achieved by anchoring Pt on the four-fold hollow sites on PMA. Each Pt atom is stabilized by four oxygen atoms in a distorted square-planar geometry, with Pt slightly protruding from the oxygen planar surface. Pt is positively charged, absorbs hydrogen easily, and exhibits excellent performance in the hydrogenation of nitrobenzene and cyclohexanone. It is likely that the system described here can be extended to a number of stable SACs with superior catalytic activities.

  6. Effect of gas atoms on X-ray optical properties of multilayers

    Institute of Scientific and Technical Information of China (English)

    冯仕猛; 赵海鹰; 范正修; 邵建达; 窦晓鸣

    2003-01-01

    Multilayers always dissolve some gas atoms during sputtering. In this paper, we develop a new method to study the effect of gas atoms on X-ray reflectance of the multilayer. Our theoretical analysis shows that this effect depends not only on the content of gas atom but also on the wavelength and the grazing angle. The shorter the wavelength and the bigger the grazing angle, the stronger this effect of gas atoms. We fabricated Mo/Si multilayers under various sputtering pressures and measured their small angle X-ray diffraction spectra. The measured results coincide with those calculated by our method.

  7. Solid Hydrogen Experiments for Atomic Propellants: Particle Formation, Imaging, Observations, and Analyses

    Science.gov (United States)

    Palaszewski, Bryan

    2005-01-01

    This report presents particle formation observations and detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium. Hydrogen was frozen into particles in liquid helium, and observed with a video camera. The solid hydrogen particle sizes and the total mass of hydrogen particles were estimated. These newly analyzed data are from the test series held on February 28, 2001. Particle sizes from previous testing in 1999 and the testing in 2001 were similar. Though the 2001 testing created similar particles sizes, many new particle formation phenomena were observed: microparticles and delayed particle formation. These experiment image analyses are some of the first steps toward visually characterizing these particles, and they allow designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  8. Solid Hydrogen Experiments for Atomic Propellants: Particle Formation Energy and Imaging Analyses

    Science.gov (United States)

    Palaszewski, Bryan

    2002-01-01

    This paper presents particle formation energy balances and detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium during the Phase II testing in 2001. Solid particles of hydrogen were frozen in liquid helium and observed with a video camera. The solid hydrogen particle sizes and the total mass of hydrogen particles were estimated. The particle formation efficiency is also estimated. Particle sizes from the Phase I testing in 1999 and the Phase II testing in 2001 were similar. Though the 2001 testing created similar particles sizes, many new particle formation phenomena were observed. These experiment image analyses are one of the first steps toward visually characterizing these particles and it allows designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  9. Microsensor Measurements of Hydrogen Gas Dynamics in Cyanobacterial Microbial Mats

    Directory of Open Access Journals (Sweden)

    Michael eNielsen

    2015-07-01

    Full Text Available We used a novel amperometric microsensor for measuring hydrogen gas production and consumption at high spatio-temporal resolution in cyanobacterial biofilms and mats dominated by non-heterocystous filamentous cyanobacteria (Microcoleus chtonoplastes and Oscillatoria spp.. The new microsensor is based on the use of an organic electrolyte and a stable internal reference system and can be equipped with a chemical sulfide trap in the measuring tip; it exhibits very stable and sulfide-insensitive measuring signals and a high sensitivity (1.5-5 pA per µmol L-1 H2. Hydrogen gas measurements were done in combination with microsensor measurements of scalar irradiance, O2, pH, and H2S and showed a pronounced H2 accumulation (of up to 8-10% H2 saturation within the upper mm of cyanobacterial mats after onset of darkness and O2 depletion. The peak concentration of H2 increased with the irradiance level prior to darkening. After an initial build-up over the first 1-2 hours in darkness, H2 was depleted over several hours due to efflux to the overlaying water, and due to biogeochemical processes in the uppermost oxic layers and the anoxic layers of the mats. Depletion could be prevented by addition of molybdate pointing to sulfate reduction as a major sink for H2. Immediately after onset of illumination, a short burst of presumably photo-produced H2 due to direct photobiolysis was observed in the illuminated but anoxic mat layers. As soon as O2 from photosynthesis started to accumulate, the H2 was consumed rapidly and production ceased. Our data give detailed insights into the microscale distribution and dynamics of H2 in cyanobacterial biofilms and mats, and further support that cyanobacterial H2 production can play a significant role in fueling anaerobic processes like e.g. sulfate reduction or anoxygenic photosynthesis in microbial mats.

  10. Microsensor measurements of hydrogen gas dynamics in cyanobacterial microbial mats.

    Science.gov (United States)

    Nielsen, Michael; Revsbech, Niels P; Kühl, Michael

    2015-01-01

    We used a novel amperometric microsensor for measuring hydrogen gas production and consumption at high spatio-temporal resolution in cyanobacterial biofilms and mats dominated by non-heterocystous filamentous cyanobacteria (Microcoleus chtonoplastes and Oscillatoria sp.). The new microsensor is based on the use of an organic electrolyte and a stable internal reference system and can be equipped with a chemical sulfide trap in the measuring tip; it exhibits very stable and sulfide-insensitive measuring signals and a high sensitivity (1.5-5 pA per μmol L(-1) H2). Hydrogen gas measurements were done in combination with microsensor measurements of scalar irradiance, O2, pH, and H2S and showed a pronounced H2 accumulation (of up to 8-10% H2 saturation) within the upper mm of cyanobacterial mats after onset of darkness and O2 depletion. The peak concentration of H2 increased with the irradiance level prior to darkening. After an initial build-up over the first 1-2 h in darkness, H2 was depleted over several hours due to efflux to the overlaying water, and due to biogeochemical processes in the uppermost oxic layers and the anoxic layers of the mats. Depletion could be prevented by addition of molybdate pointing to sulfate reduction as a major sink for H2. Immediately after onset of illumination, a short burst of presumably photo-produced H2 due to direct biophotolysis was observed in the illuminated but anoxic mat layers. As soon as O2 from photosynthesis started to accumulate, the H2 was consumed rapidly and production ceased. Our data give detailed insights into the microscale distribution and dynamics of H2 in cyanobacterial biofilms and mats, and further support that cyanobacterial H2 production can play a significant role in fueling anaerobic processes like e.g., sulfate reduction or anoxygenic photosynthesis in microbial mats.

  11. Tribology in Gaseous Hydrogen

    Science.gov (United States)

    Sawae, Yoshinori; Sugimura, Joich

    Hydrogen is expected as a clean and renewable energy carrier for future environment-friendly society. Many machine elements in hydrogen energy systems should be operating within hydrogen gas and tribological behavior, such as friction and wear, of bearings and seals are affected by the hydrogen environment through some interactions between material surfaces and gaseous hydrogen, i.e., physisorption of hydrogen molecules and following chemisorptions of dissociated atoms on metal surfaces, formation of metal hydride and reduction of metal oxide layer by hydrogen atoms diffused into bulk. Therefore, friction and wear characteristics of tribomaterials in the hydrogen environment should be appropriately understood to establish a design guideline for reliable hydrogen utilizing systems. This paper reviews the current knowledge about the effect of hydrogen on friction and wear of materials, and then describes our recent progress of hydrogen research in the tribology field.

  12. Palladium-decorated hydrogen-gas sensors using periodically aligned graphene nanoribbons.

    Science.gov (United States)

    Pak, Yusin; Kim, Sang-Mook; Jeong, Huisu; Kang, Chang Goo; Park, Jung Su; Song, Hui; Lee, Ryeri; Myoung, NoSoung; Lee, Byoung Hun; Seo, Sunae; Kim, Jin Tae; Jung, Gun-Young

    2014-08-13

    Polymer residue-free graphene nanoribbons (GNRs) of 200 nm width at 1 μm pitch were periodically generated in an area of 1 cm(2) via laser interference lithography using a chromium interlayer prior to photoresist coating. High-quality GNRs were evidenced by atomic force microscopy, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy measurements. Palladium nanoparticles were then deposited on the GNRs as catalysts for sensing hydrogen gases, and the GNR array was utilized as an electrically conductive path with less electrical noise. The palladium-decorated GNR array exhibited a rectangular sensing curve with unprecedented rapid response and recovery properties: 90% response within 60 s at 1000 ppm and 80% recovery within 90 s in nitrogen ambient. In addition, reliable and repeatable sensing behaviors were revealed when the array was exposed to various gas concentrations even at 30 ppm.

  13. Numerical simulation of high pressure release and dispersion of hydrogen into air with real gas model

    Science.gov (United States)

    Khaksarfard, R.; Kameshki, M. R.; Paraschivoiu, M.

    2010-06-01

    Hydrogen is a renewable and clean source of energy, and it is a good replacement for the current fossil fuels. Nevertheless, hydrogen should be stored in high-pressure reservoirs to have sufficient energy. An in-house code is developed to numerically simulate the release of hydrogen from a high-pressure tank into ambient air with more accuracy. Real gas models are used to simulate the flow since high-pressure hydrogen deviates from ideal gas law. Beattie-Bridgeman and Abel Noble equations are applied as real gas equation of state. A transport equation is added to the code to calculate the concentration of the hydrogen-air mixture after release. The uniqueness of the code is to simulate hydrogen in air release with the real gas model. Initial tank pressures of up to 70 MPa are simulated.

  14. Visualization of Atomization Gas Flow and Melt Break-up Effects in Response to Nozzle Design

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Iver; Rieken, Joel; Meyer, John; Byrd, David; Heidloff, Andy

    2011-04-01

    Both powder particle size control and efficient use of gas flow energy are highly prized goals for gas atomization of metal and alloy powder to minimize off-size powder inventory (or 'reverb') and excessive gas consumption. Recent progress in the design of close-coupled gas atomization nozzles and the water model simulation of melt feed tubes were coupled with previous results from several types of gas flow characterization methods, e.g., aspiration measurements and gas flow visualization, to make progress toward these goals. Size distribution analysis and high speed video recordings of gas atomization reaction synthesis (GARS) experiments on special ferritic stainless steel alloy powders with an Ar+O{sub 2} gas mixture were performed to investigate the operating mechanisms and possible advantages of several melt flow tube modifications with one specific gas atomization nozzle. In this study, close-coupled gas atomization under closed wake gas flow conditions was demonstrated to produce large yields of ultrafine (dia.<20 {mu}m) powders (up to 32%) with moderate standard deviations (1.62 to 1.99). The increased yield of fine powders is consistent with the dual atomization mechanisms of closed wake gas flow patterns in the near-field of the melt orifice. Enhanced size control by stabilized pre-filming of the melt with a slotted trumpet bell pour tube was not clearly demonstrated in the current experiments, perhaps confounded by the influence of the melt oxidation reaction that occurred simultaneously with the atomization process. For this GARS variation of close-coupled gas atomization, it may be best to utilize the straight cylindrical pour tube and closed wake operation of an atomization nozzle with higher gas mass flow to promote the maximum yields of ultrafine powders that are preferred for the oxide dispersion strengthened alloys made from these powders.

  15. Precise atomic-scale investigations of material sputtering process by light gas ions in pre-threshold energy region

    CERN Document Server

    Suvorov, A L

    2002-01-01

    Foundation and prospects of the new original technique of the sputtering yield determination of electro-conducting materials and sub-atomic layers on their surface by light gas ions the pre-threshold energy region (from 10 to 500 eV) are considered. The technique allows to identify individual surface vacancies, i.e., to count individual sputtered atoms directly. A short review of the original results obtained by using the developed techniques is given. Data are presented and analyzed concerning energy thresholds of the sputtering onset and energy dependences of sputtering yield in the threshold energy region for beryllium, tungsten, tungsten oxide, alternating tungsten-carbon layers, three carbon materials as well as for sub-atomic carbon layers on surface of certain metals at their bombardment by hydrogen, deuterium and/or helium ions

  16. Application of gas-fluid atomization technology in ultrosonic vibration cutting titanium alloy workpiece

    Science.gov (United States)

    Zhou, Zhimin; Zhang, Yuangliang; Li, Xiaoyan; Sun, Baoyuan

    2009-11-01

    To further improve machined surface quality of diamond cutting titanium workpiece and reduce diamond tool wear, it puts forward a kind of machining technology with mixture of carbon dioxide gas, water and vegetable oil atomized mist as cooling media in the paper. The cooling media is sprayed to cutting area through gas-liquid atomizer device to achieve purpose of cooling, lubricating, and protecting diamond tool. Experiments indicate that carbon dioxide gas can touch cutting surface more adequately through using gas-liquid atomization technology, which makes iron atoms of cutting surface cause a chemical reaction directly with carbon in carbon dioxide gas and reduce graphitizing degree of diamond tool. Thus, this technology of using gas-liquid atomization and ultrasonic vibration together for cutting Titanium Alloy is able to improve machined surface quality of workpiece and slow of diamond tool wear.

  17. Nanochemistry at the atomic scale revealed in hydrogen-induced semiconductor surface metallization

    Science.gov (United States)

    Derycke, Vincent; Soukiassian, Patrick G.; Amy, Fabrice; Chabal, Yves J.; D'Angelo, Marie D.; Enriquez, Hanna B.; Silly, Mathieu G.

    2003-04-01

    Passivation of semiconductor surfaces against chemical attack can be achieved by terminating the surface-dangling bonds with a monovalent atom such as hydrogen. Such passivation invariably leads to the removal of all surface states in the bandgap, and thus to the termination of non-metallic surfaces. Here we report the first observation of semiconductor surface metallization induced by atomic hydrogen. This result, established by using photo-electron and photo-absorption spectroscopies and scanning tunnelling techniques, is achieved on a Si-terminated cubic silicon carbide (SiC) surface. It results from competition between hydrogen termination of surface-dangling bonds and hydrogen-generated steric hindrance below the surface. Understanding the ingredient for hydrogen-stabilized metallization directly impacts the ability to eliminate electronic defects at semiconductor interfaces critical for microelectronics, provides a means to develop electrical contacts on high-bandgap chemically passive materials, particularly for interfacing with biological systems, and gives control of surfaces for lubrication, for example of nanomechanical devices.

  18. Shock-wave proton acceleration from a hydrogen gas jet

    Science.gov (United States)

    Cook, Nathan; Pogorelsky, Igor; Polyanskiy, Mikhail; Babzien, Marcus; Tresca, Olivier; Maharjan, Chakra; Shkolnikov, Peter; Yakimenko, Vitaly

    2013-04-01

    Typical laser acceleration experiments probe the interaction of intense linearly-polarized solid state laser pulses with dense metal targets. This interaction generates strong electric fields via Transverse Normal Sheath Acceleration and can accelerate protons to high peak energies but with a large thermal spectrum. Recently, the advancement of high pressure amplified CO2 laser technology has allowed for the creation of intense (10^16 Wcm^2) pulses at λ˜10 μm. These pulses may interact with reproducible, high rep. rate gas jet targets and still produce plasmas of critical density (nc˜10^19 cm-3), leading to the transference of laser energy via radiation pressure. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. We observe the interaction of an intense CO2 laser pulse with an overdense hydrogen gas jet. Using two pulse optical probing in conjunction with interferometry, we are able to obtain density profiles of the plasma. Proton energy spectra are obtained using a magnetic spectrometer and scintillating screen.

  19. Upgrade to the Cryogenic Hydrogen Gas Target Monitoring System

    Science.gov (United States)

    Slater, Michael; Tribble, Robert

    2013-10-01

    The cryogenic hydrogen gas target at Texas A&M is a vital component for creating a secondary radioactive beam that is then used in experiments in the Momentum Achromat Recoil Spectrometer (MARS). A stable beam from the K500 superconducting cyclotron enters the gas cell and some incident particles are transmuted by a nuclear reaction into a radioactive beam, which are separated from the primary beam and used in MARS experiments. The pressure in the target chamber is monitored so that a predictable isotope production rate can be assured. A ``black box'' received the analog pressure data and sent RS232 serial data through an outdated serial connection to an outdated Visual Basic 6 (VB6) program, which plotted the chamber pressure continuously. The black box has been upgraded to an Arduino UNO microcontroller [Atmel Inc.], which can receive the pressure data and output via USB to a computer. It has been programmed to also accept temperature data for future upgrade. A new computer program, with updated capabilities, has been written in Python. The software can send email alerts, create audible alarms through the Arduino, and plot pressure and temperature. The program has been designed to better fit the needs of the users. Funded by DOE and NSF-REU Program.

  20. Analytical model of neutral gas shielding for hydrogen pellet ablation

    Energy Technology Data Exchange (ETDEWEB)

    Kuteev, Boris V.; Tsendin, Lev D. [State Technical Univ., St. Petersburg (Russian Federation)

    2001-11-01

    A kinetic gasdynamic scaling for hydrogen pellet ablation is obtained in terms of a neural gas shielding model using both numerical and analytical approaches. The scaling on plasma and pellet parameters proposed in the monoenergy approximation by Milora and Foster dR{sub pe}/dt{approx}S{sub n}{sup 2/3}R{sub p}{sup -2/3}q{sub eo}{sup 1/3}m{sub i}{sup -1/3} is confirmed. Here R{sub p} is the pellet radius, S{sub n} is the optical thickness of a cloud, q{sub eo} is the electron energy flux density and m{sub i} is the molecular mass. Only the numeral factor is approximately two times less than that for the monoenergy approach. Due to this effect, the pellet ablation rates, which were obtained by Kuteev on the basis of the Milora scaling, should be reduced by a factor of 1.7. Such a modification provides a reasonable agreement (even at high plasma parameters) between the two-dimensional kinetic model and the one-dimensional monoenergy approximation validated in contemporary tokamak experiments. As the could (in the kinetic approximation) is significantly thicker than that for the monoenergy case as well as the velocities of the gas flow are much slower, the relative effect of plasma and magnetic shielding on the ablation rate is strongly reduced. (author)

  1. 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.

  2. Tensorial depolarization of alkali atoms by isotropic collisions with neutral hydrogen

    CERN Document Server

    Derouich, Moncef

    2012-01-01

    Results. We consider the problem of isotropic collisions between an alkali atom and neutral hydrogen. We calculate the collisional tensorial components of general p and s-states, characterized by their effective principal quantum number $n^{*}$. It is found that the behaviour of the tensorial components obey simple power laws allowing quick calculations of the depolarizing collisional rates. As application, our results should allow a rigorous treatment of the atomic polarization profiles of the D1 -D2 lines of alkali atoms. Conclusions. Close coupling treatments of atomic collisions are needed to decipher the information encoded in the polarized radiation from the Sun. Important problems remain unresolved like the role of collisions in the Paschen-Back conditions.

  3. Adsorption and Diffusion of Hydrogen Atom on Low-index Ag Planes

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The 5-parameter Morse potential (5-MP) of the interaction between H atom and Ag surfaces has been constructed. The adsorption and diffusion of H on Ag low-index surfaces are investigated with 5-MP in detail. The characteristics of critical points are obtained. The theoretical results show that H atom can only adsorb at the three-fold site on Ag(111); the quasi-3-fold site and long-bridge site are stable adsorption sites on Ag(110) surface for the H atom, and at low coverage hydrogen predominantly occupies the quasi-3-fold site. This work predicts that the four-fold hollow site is the most stable adsorption state for H atom on Ag(100). The results of this work are approved by the experimental and theoretical results.

  4. Adiabatic Floquet Picture for Hydrogen Atom in an Intense Laser Field

    CERN Document Server

    Wang, Yujun; Esry, B D

    2010-01-01

    We develop an adiabatic Floquet picture in the length gauge to describe the dynamics of a hydrogen atom in an intense laser field. In this picture, we discuss the roles played by frequency and intensity in terms of adiabatic potentials and the couplings between them, which gives a physical and intuitive picture for quantum systems exposed to a laser field. For simplicity, analyze hydrogen and give the adiabatic potential curves as well as some physical quantities that can be readily calculated for the ground state. Both linearly and circularly polarized laser fields are discussed.

  5. 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.

  6. Hydrogen-enriched natural gas; Bridge to an ultra low carbon world

    Energy Technology Data Exchange (ETDEWEB)

    Samuel, Joshua; Oliver, Mike

    2010-09-15

    Natural gas is recognized as an important part of the solution to climate change, as it has the smallest carbon footprint among fossil fuels and can be used with high efficiency. This alone is not enough. Supplementing natural gas with hydrogen creating hydrogen-enriched natural gas (HENG), where the hydrogen comes from a low- or zero-carbon energy source. HENG, the subject of this paper, can leverage existing natural gas infrastructure to reduce CO2 and NOx, improve the efficiency of end-use equipment, and lower the overall carbon intensity of energy consumption.

  7. Non-porous metal membranes for selective separation of hydrogen from gas mixtures at higher temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Winkelmann, U.; Schulten, R.; Weirich, W.; Kuegler, B.; Luecke, L.; Oertel, M.; Pietsch, M.; Schmitz, J.

    1986-10-01

    Materials for selective separation of hydrogen from gas mixtures by means of a metal membrane must have high permeability for dissolved oxygen, catalytically active surfaces, and mechanical stability in a hydrogen atmosphere. The transition metals Nb, Ta, and V have high hydrogen permeability, but they must be coated with a catalytically active Pd alloy in order to permit hydrogen permeation. The alloy TiNi can be used without a noble metal coating.

  8. Long-range interactions of excited He atoms with ground-state noble-gas atoms

    KAUST Repository

    Zhang, J.-Y.

    2013-10-09

    The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-n expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the C6 coefficients for the systems involving He(131,3S) and He(131,3P) are calculated and found to be in good agreement with directly calculated values.

  9. The dynamical properties of Rydberg hydrogen atom near a metal surface

    Institute of Scientific and Technical Information of China (English)

    GE Meihua; ZHANG Yanhui; WANG Dehua; DU Mengli; LIN Shenglu

    2005-01-01

    The dynamical properties of Rydberg hydrogen atom near a metal surface are presented by using the methods of phase space analysis and closed orbit theory. Transforming the coordinates of the Hamiltonian, we find that the phase space of the system is divided into vibrational and rotational region. Both the Poincaré surface of section and the closed orbit theory verify the same conclusion clearly. In this paper we choose the atomic principal quantum number as n = 20. The dynamical character of the exited hydrogen atom depends sensitively on the atom-surface distance d. When d is sufficiently large, the atom-surface potential can be expressed by the traditional van der Waals force and the system is integrable. When d becomes smaller, there exists a critical value dc. For d > dc, the system is near-integrable and the motion is regular. While chaotic motion appears for d < dc, and the system tends to be non-integrable. The trajectories become unstable and the electron might be captured onto the metal surface.

  10. 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.

  11. Extremely high reflection of solar wind protons as neutral hydrogen atoms from regolith in space

    CERN Document Server

    Wieser, Martin; Futaana, Yoshifumi; Holmström, Mats; Bhardwaj, Anil; Sridharan, R; Dhanya, MB; Wurz, Peter; Schaufelberger, Audrey; Asamura, Kazushi; 10.1016/j.pss.2009.09.012

    2010-01-01

    We report on measurements of extremely high reflection rates of solar wind particles from regolith-covered lunar surfaces. Measurements by the Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft in orbit around the Moon show that up to 20% of the impinging solar wind protons are reflected from the lunar surface back to space as neutral hydrogen atoms. This finding, generally applicable to regolith-covered atmosphereless bodies, invalidates the widely accepted assumption that regolith almost completely absorbs the impinging solar wind.

  12. Angular momentum in non-relativistic QED and photon contribution to spin of hydrogen atom

    Energy Technology Data Exchange (ETDEWEB)

    Chen Panying, E-mail: pychen@umd.ed [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD 20742 (United States); Ji Xiangdong [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD 20742 (United States); Institute of Particle Physics and Cosmology, Department of Physics, Shanghai Jiao Tong University, Shanghai, 200240 (China); Center for High-Energy Physics and Institute of Theoretical Physics, Peking University, Beijing, 100080 (China); Xu Yang [Center for High-Energy Physics and Institute of Theoretical Physics, Peking University, Beijing, 100080 (China); Zhang Yue [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD 20742 (United States); Center for High-Energy Physics and Institute of Theoretical Physics, Peking University, Beijing, 100080 (China)

    2010-04-26

    We study angular momentum in non-relativistic quantum electrodynamics (NRQED). We construct the effective total angular momentum operator by applying Noether's theorem to the NRQED lagrangian. We calculate the NRQED matching for the individual components of the QED angular momentum up to one loop. We illustrate an application of our results by the first calculation of the angular momentum of the ground state hydrogen atom carried in radiative photons, alpha{sub em}{sup 3}/18pi, which might be measurable in future atomic experiments.

  13. Computation for High Excited Stark Levels of hydrogen Atoms in Uniform Electric Fields

    Institute of Scientific and Technical Information of China (English)

    田人和

    2003-01-01

    We present a new method for the numerical calculation of exact complex eigenvalues of Schrodinger equations for a hydrogen atom in a uniform electric field. This method allows a direct calculation for complex eigenvalues without using any auxiliary treatment, such as the Breit-Wigner parametrization and the complex scale transformation,etc. The characteristics of high excited atoms in electric field have attracted extensive interest in experimental aspect, however, the existing theoretical calculation is only up to n = 40. Here we present the computation results ranging from n = 1 to 100. The data for n(<,_ ) 40 are in agreement with the results of other researchers.

  14. Electronic and optical properties of BxNyCz monolayers with adsorption of hydrogen atoms

    Science.gov (United States)

    Leite, L.; Azevedo, S.; de Lima Bernardo, B.

    2017-03-01

    We apply first-principles calculations, using density functional theory, to analyze the electronic and optical properties of monolayers of graphene with a nanodomain of 2D hexagonal boron nitrite (h-BN). It also investigated the effects of the adsorption of hydrogen atoms in different atoms at the edge of the h-BN nanodomain. We calculate the electronic band structure, the complex dielectric function and the optical conductivity. For such systems, the calculations demonstrate that the compounds exhibit a prominent excitement in the visible and near-infrared regions. In this form, the present study provides physical basis for potential applications of the considered materials in optoelectronic devices at the nanoscale.

  15. Low cost hydrogen/novel membrane technology for hydrogen separation from synthesis gas. Task 1, Literature survey

    Energy Technology Data Exchange (ETDEWEB)

    1986-02-01

    To make the coal-to-hydrogen route economically attractive, improvements are being sought in each step of the process: coal gasification, water-carbon monoxide shift reaction, and hydrogen separation. This report addresses the use of membranes in the hydrogen separation step. The separation of hydrogen from synthesis gas is a major cost element in the manufacture of hydrogen from coal. Separation by membranes is an attractive, new, and still largely unexplored approach to the problem. Membrane processes are inherently simple and efficient and often have lower capital and operating costs than conventional processes. In this report current ad future trends in hydrogen production and use are first summarized. Methods of producing hydrogen from coal are then discussed, with particular emphasis on the Texaco entrained flow gasifier and on current methods of separating hydrogen from this gas stream. The potential for membrane separations in the process is then examined. In particular, the use of membranes for H{sub 2}/CO{sub 2}, H{sub 2}/CO, and H{sub 2}/N{sub 2} separations is discussed. 43 refs., 14 figs., 6 tabs.

  16. 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...

  17. Uniform Atomic Layer Deposition of Al2O3 on Graphene by Reversible Hydrogen Plasma Functionalization

    Science.gov (United States)

    2017-01-01

    A novel method to form ultrathin, uniform Al2O3 layers on graphene using reversible hydrogen plasma functionalization followed by atomic layer deposition (ALD) is presented. ALD on pristine graphene is known to be a challenge due to the absence of dangling bonds, leading to nonuniform film coverage. We show that hydrogen plasma functionalization of graphene leads to uniform ALD of closed Al2O3 films down to 8 nm in thickness. Hall measurements and Raman spectroscopy reveal that the hydrogen plasma functionalization is reversible upon Al2O3 ALD and subsequent annealing at 400 °C and in this way does not deteriorate the graphene’s charge carrier mobility. This is in contrast with oxygen plasma functionalization, which can lead to a uniform 5 nm thick closed film, but which is not reversible and leads to a reduction of the charge carrier mobility. Density functional theory (DFT) calculations attribute the uniform growth on both H2 and O2 plasma functionalized graphene to the enhanced adsorption of trimethylaluminum (TMA) on these surfaces. A DFT analysis of the possible reaction pathways for TMA precursor adsorption on hydrogenated graphene predicts a binding mechanism that cleans off the hydrogen functionalities from the surface, which explains the observed reversibility of the hydrogen plasma functionalization upon Al2O3 ALD.

  18. Hydrogen atom in space with a compactified extra dimension and potential defined by Gauss' law

    CERN Document Server

    Bureš, Martin

    2014-01-01

    We investigate the consequences of one extra spatial dimension for the stability and energy spectrum of the non-relativistic hydrogen atom with a potential defined by Gauss' law, i.e. proportional to $1/|x|^2$. The additional spatial dimension is considered to be either infinite or curled-up in a circle of radius $R$. In both cases, the energy spectrum is bounded from below for charges smaller than the same critical value and unbounded from below otherwise. As a consequence of compactification, negative energy eigenstates appear: if $R$ is smaller than a quarter of the Bohr radius, the corresponding Hamiltonian possesses an infinite number of bound states with minimal energy extending at least to the ground state of the hydrogen atom.

  19. Hydrogen atom in space with a compactified extra dimension and potential defined by Gauss' law

    Science.gov (United States)

    Bureš, Martin; Siegl, Petr

    2015-03-01

    We investigate the consequences of one extra spatial dimension for the stability and energy spectrum of the non-relativistic hydrogen atom with a potential defined by Gauss' law, i.e. proportional to 1 /| x | 2. The additional spatial dimension is considered to be either infinite or curled-up in a circle of radius R. In both cases, the energy spectrum is bounded from below for charges smaller than the same critical value and unbounded from below otherwise. As a consequence of compactification, negative energy eigenstates appear: if R is smaller than a quarter of the Bohr radius, the corresponding Hamiltonian possesses an infinite number of bound states with minimal energy extending at least to the ground state of the hydrogen atom.

  20. Hydrogen gas sensor based on palladium and yttrium alloy ultrathin film

    Science.gov (United States)

    Yi, Liu; You-ping, Chen; Han, Song; Gang, Zhang

    2012-12-01

    Compared with the other hydrogen sensors, optical fiber hydrogen sensors based on thin films exhibits inherent safety, small volume, immunity to electromagnetic interference, and distributed remote sensing capability, but slower response characteristics. To improve response and recovery rate of the sensors, a novel reflection-type optical fiber hydrogen gas sensor with a 10 nm palladium and yttrium alloy thin film is fabricated. The alloy thin film shows a good hydrogen sensing property for hydrogen-containing atmosphere and a complete restorability for dry air at room temperature. The variation in response value of the sensor linearly increases with increased natural logarithm of hydrogen concentration (ln[H2]). The shortest response time and recovery response time to 4% hydrogen are 6 and 8 s, respectively. The hydrogen sensors based on Pd0.91Y0.09 alloy ultrathin film have potential applications in hydrogen detection and measurement.

  1. Cascade Annealing of Tungsten Implanted with 5 keV Noble Gas Atoms : A Computer Simulation

    NARCIS (Netherlands)

    Kolk, G.J. van der; Veen, A. van; Caspers, L.M.; Hosson, J.Th.M. De

    1984-01-01

    The trapping of vacancies by implanted atoms is calculated. After low energy implantation (5 keV) of tungsten with heavy noble gas atoms most of the implanted atoms are in substitutional position with one or two vacancies closer than two lattice units. Under the influence of the lattice distortion a

  2. Hydrogen-Like Atom Description in the Framework of Quantum Mechanics with Consequently Probabilistic Interpretation

    CERN Document Server

    Zhidkov, E P

    2000-01-01

    In the paper a research of spectrum of the energy operator of the hydrogen-like atom in quantum mechanics with non-negative quantum function of distribution (QFD) is carried out. As a principle spectral property of the Hamiltonian its essential spectrum has been established. We have not got the theoretical response on questions of the evaluation of numbers and quantities of eigenvalues, which do not belong the essential spectrum. A method of numerical searching to answer these questions has been proposed.

  3. 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.

  4. Hydrogen atom in strong magnetic field: a high accurate calculation in spheroidal coordinates

    Institute of Scientific and Technical Information of China (English)

    LIU Qiang; KANG Shuai; ZHANG Xian-zhou; SHI Ting-yun

    2006-01-01

    A B-spline-type basis set method for the calculation of hydrogen atom in strong magnetic fields in the frame of spheroidal coordinates has been introduced.High accurate energy levels of hydrogen in the magnetic field,with strength ranging from 0 to 1000 a.u.,have been obtained.For the ground state,ls0,energies with at least 11 significant digits have been obtained.For the low-lying excited state,2p-1,energies with at least 9 significant digits are obtained.The method has also been applied to the calculation of hydrogen Rydberg states in laboratory magnetic fields.Energy spectra with at least 10 significant digits are presented.A comparison with other results in the literatures has been performed.Our results are comparable to the most accurate one up to date.A possible extension to the cases of parallel and crossed electric and magnetic fields have been discussed.

  5. Nuclear recoil effect in the Lamb shift of light hydrogen-like atoms

    CERN Document Server

    Yerokhin, V A

    2015-01-01

    We report high-precision calculations of the nuclear recoil effect to the Lamb shift of hydrogen-like atoms to the first order in the electron-nucleus mass ratio and to all orders in the nuclear binding strength parameter $Z\\alpha$. The results are in excellent agreement with the known terms of the $Z\\alpha$ expansion and allow an accurate identification of the nonperturbative higher-order remainder. For hydrogen, the higher-order remainder was found to be much larger than anticipated. This result resolves the long-standing disagreement between the numerical all-order and the analytical $Z\\alpha$-expansion approaches to the recoil effect and completely removes the second-largest theoretical uncertainty in the hydrogen Lamb shift of the $1S$ and $2S$ states.

  6. Silicon carbide-based hydrogen gas sensors for high-temperature applications.

    Science.gov (United States)

    Kim, Seongjeen; Choi, Jehoon; Jung, Minsoo; Joo, Sungjae; Kim, Sangchoel

    2013-10-09

    We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC) was used as a substrate for high-temperature applications. We fabricated Pd/Ta2O5/SiC-based hydrogen gas sensors, and the dependence of their I-V characteristics and capacitance response properties on hydrogen concentrations were analyzed in the temperature range from room temperature to 500 °C. According to the results, our sensor shows promising performance for hydrogen gas detection at high temperatures.

  7. Polarization dependence in inelastic scattering of electrons by hydrogen atoms in a circularly polarized laser field

    Science.gov (United States)

    Buică, Gabriela

    2017-01-01

    We theoretically study the influence of laser polarization in inelastic scattering of electrons by hydrogen atoms in the presence of a circularly polarized laser field in the domain of field strengths below 107 V/cm and high projectile energies. A semi-perturbative approach is used in which the interaction of the projectile electrons with the laser field is described by Gordon-Volkov wave functions, while the interaction of the hydrogen atom with the laser field is described by first-order time-dependent perturbation theory. A closed analytical solution is derived in laser-assisted inelastic electron-hydrogen scattering for the 1 s → nl excitation cross section which is valid for both circular and linear polarizations. For the excitation of the n=2 levels simple analytical expressions of differential cross section are derived for laser-assisted inelastic scattering in the perturbative domain, and the differential cross sections by the circularly and linearly polarized laser fields and their ratios for one- and two-photon absorption are calculated as a function of the scattering angle. Detailed numerical results for the angular dependence and the resonance structure of the differential cross sections are discussed for the 1 s → 4 l excitations of hydrogen in a circularly polarized laser field.

  8. 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)

  9. Excitation of hydrogen atoms in collisions with helium atoms: the role of electron–electron interaction

    Science.gov (United States)

    Frémont, F.; Belyaev, A. K.

    2017-02-01

    Cross sections for producing H(nl) excited state atoms in H(1s) + He(1s2) collisions are calculated using the CTMC method, at impact energies ranging from 20 eV to 100 keV. The role of the electron correlation is studied. In the first step, the interactions between each pair of the three electrons are neglected. This leads to disagreement of the calculated total cross section for producing H(2l) atoms with previous experimental and theoretical results. In a second step, the electron–electron interaction is taken into account in a rigorous way, that is, in the form of the pure Coulomb potential. To make sure that the He target is stable before the collision, phenomenological potentials for the electron–helium-nucleus interactions that simulate the Heisenberg principle are included in addition to the Coulomb potential. The excitation cross section calculated in the frame of this model is in remarkable agreement with previous data in the range between 200 eV and 5 keV. At other energies, discrepancies are revealed, but only by a factor of less than 2 at high energies. The present results show the decisive role of the electron–electron interaction during collisions. In addition, they demonstrate the ability of classical mechanics to take into account the effects of the electron correlation.

  10. 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.)

  11. Improvement of hydrogen uptake in iron and vanadium matrices by doping with 3d atomic impurities

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, N.B. [Laboratoire de Magnetisme de Bretagne, EA 4522 Universite de Bretagne Occidentale, 6 avenue Victor Le Gorgeu, 29285 Brest Cedex (France); Lebon, A., E-mail: alexandre.lebon@univ-brest.fr [Laboratoire de Magnetisme de Bretagne, EA 4522 Universite de Bretagne Occidentale, 6 avenue Victor Le Gorgeu, 29285 Brest Cedex (France); Vega, A. [Laboratoire de Magnetisme de Bretagne, EA 4522 Universite de Bretagne Occidentale, 6 avenue Victor Le Gorgeu, 29285 Brest Cedex (France); Mokrani, A. [Institut des Materiaux Jean Rouxel, UMR CNRS 6502, Universite de Nantes, 2 rue de la Houssiniere, B.P. 44322 Nantes (France)

    2012-12-25

    Highlights: Black-Right-Pointing-Pointer H trapping is easier in V matrix than in Fe matrix whatever the 3d TM impurity. Black-Right-Pointing-Pointer Sc and Ti are the best impurities to trap atomic H in V matrix. Black-Right-Pointing-Pointer Fe or Mn doping in V enhance the density of H storage. - Abstract: The insertion of hydrogen in V and Fe has been investigated by means of pseudopotential DFT calculations with localized basis sets. In Fe and V matrices we have replaced the central atom by a transition metal impurity X = Sc, Ti, Cr, Mn, Fe, Co and Ni to study the capacity of the environment to trap hydrogen. The dissolution energy and structural rearrangement upon H uptake at the different sites close to the doping impurity are calculated. Optimal electronic environments for H trapping are also determined through the calculation of the Fukui function. In the V matrix, the insertion of hydrogen is promoted by doping with the two impurities located at the left of V in the Periodical Table, that is, Ti and Sc. In the iron matrix, among the elements at its left in the Periodic Table, only Mn improves the H uptake, whereas doping with V and Ti worsen the capability of absorbing hydrogen. Finally, the H-H interaction is found to be strongly dependent upon the metal-hydrogen interaction. Elements like Mn or Fe which shorten the H-X distance, exhibit a strong 3d TM state-1s hydrogen state hybridization that seems to wash out the repulsive H-H Coulomb interaction below the 2.0 Angstrom-Sign limit. Addition of a small percentage of Fe or Mn in binary bcc alloys (V-Ti) is suggested to locally enhance the H storage capacity.

  12. 40 CFR 60.648 - Optional procedure for measuring hydrogen sulfide in acid gas-Tutwiler Procedure. 1

    Science.gov (United States)

    2010-07-01

    ... hydrogen sulfide in acid gas-Tutwiler Procedure. 1 60.648 Section 60.648 Protection of Environment... procedure for measuring hydrogen sulfide in acid gas—Tutwiler Procedure. 1 1 Gas Engineers Handbook, Fuel.... In principle, this method consists of titrating hydrogen sulfide in a gas sample directly with...

  13. Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets

    Institute of Scientific and Technical Information of China (English)

    Zhang Yue-Xia; Meng Hui-Yan; Shi Ting-Yun

    2008-01-01

    The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and I/2 of a hydrogen atom in parallel electric and magnetic fields.The method can calculate the ground and higher excited resonances accurately and efficiently.The resonance parameters with accuracies of 10-9 - 10-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones.Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.

  14. Visualizations of Gas fuel Jet and Combustion Flame on Hydrogen Rotary Engine

    OpenAIRE

    田端, 道彦; 香川, 良二

    2011-01-01

    [Abstract] In this paper, it is a purpose to obtain basic information of a hydrogen jet and combustion flame characteristics of the hydrogen rotary engine. The jet characteristics of the hydrogen gas injector were measured by using the high-speed shadowgraph method. As the result, the jet penetration of the low density gas was weak. The mixing of the direction of the jet axis was disturbed for the low jet pressure. Next, the combustion flame propagation of the hydrogen rotary engine was visua...

  15. Removal of Hydrogen Sulfide Gas using Biofiltration - a Review

    Directory of Open Access Journals (Sweden)

    Cheerawit RATTANAPAN

    2012-03-01

    Full Text Available Hydrogen sulfide (H2S is extremely toxic to living organisms and plants. H2S gas contamination may be treated by both chemical and physical methods but they have high capital costs, demand large energy inputs and result in the generation of secondary hazardous wastes. Biofiltration, a biological technique, has significant economic advantages over other air pollution control technologies. Biofiltration is a process by which contaminated gases pass through the biofilter and pollutants are transported into the biofilm where they are utilized by microbes as a carbon source, an energy source. Thiobacillus sp. is the most frequently used microbial species in H2S biofiltration and can degrade H2S for energy and produce sulfate or sulfuric acid. Moreover, media selection for biofiltration (combing both natural and synthetic media is an important step towards the development of a successful biofiltration operation. In addition, the optimization parameters of a biofiltration operation are found. First, optimal moisture content may vary from 20 to 60 wt%. Second, most microbial growths occur near neutral pH and wide deviation from these levels will impact the efficiency of the biofiltration. Third, the optimum temperature of biofiltration is near the optimum temperature for microbial inoculation based on removal efficiency. Finally, because nutrient supply is less critical as H2S removal requires few nutrients, commercial fertilizer or secondary effluent from wastewater treatment plants can be used for humid and nutrient supply. Many biofiltrations are designed for H2S control.Graphical abstract

  16. Chapter 13 Theoretical and Experimental Studies of the Gas-Phase Cl-Atom Initiated Reactions of Benzene and Toluene

    Science.gov (United States)

    Ryzhkov, A.; Ariya, P. A.; Raofie, F.; Niki, H.; Harris, G. W.

    The reactions of benzene (Bz) and toluene (PhMe) with chlorine atoms in the gas phase have been studied using both theoretical and experimental techniques. Energy and geometry of reaction complexes and transition states were calculated in the Cl-atom initiated reaction of benzene and toluene using modern hybrid functional PBE0 method with the aug-pc1 basis set with an additional CCSD(T)/aug-CC-pVDZ energy single point calculation. Three stationary structures have been found for the Bz...Cl complex: hexahapto-complex, [pi]-complex and [sigma]-complex. The first one is a transition state between two opposite [pi]-complexes. PhMe...Cl has additional structures due to ipso-, ortho-, meta- and para-isomerization. The stability of all calculated complexes was determined and compared. Two reaction pathways for benzene and toluene with a Cl atom were evaluated: (a) the hydrogen abstraction of benzene and toluene by Cl atom, which is seemingly barrierless and endothermic, and (b) the hydrogen substitution reaction that in contrast has a relatively high energy of activation. Rate coefficients for these same reactions were measured using ethane, n-butane, and chloro-, dichloro- and trichloromethane, as reference compounds, with gas chromatography equipped with mass detection spectrometry and flame ionization detection (GC-MSD and GC-FID). The reaction rates were estimated as (5.57±0.15)×10-11 and for benzene and toluene, respectively. Chlorinated products of the reactions were analyzed by GS-MS. Chlorobenzene was the only identified product between a reaction of benzene and the Cl atom. The major products of the PhMe + Cl reaction were chloromethylbenzene with ortho- and para-chlorotoluenes.

  17. Atom Probe Analysis of Ex Situ Gas-Charged Stable Hydrides.

    Science.gov (United States)

    Haley, Daniel; Bagot, Paul A J; Moody, Michael P

    2017-01-30

    In this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200-500 kPa (2-5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide-metal interface of a native oxide formed on vanadium. Through these experiments, we demonstrate the feasibility of ex situ hydrogen analysis for hydrides via atom probe tomography, and thus a practical route to three-dimensional imaging of hydrogen in hydrides at the atomic scale.

  18. Experimental study of hydrogen-rich/oxygen-rich gas-gas injectors

    Institute of Scientific and Technical Information of China (English)

    Jin Ping; Li Mao; Cai Guobiao

    2013-01-01

    Five types of coaxial injectors were investigated experimentally using hot hydrogen-rich gas and oxygen-rich gas, which were respectively provided by a GH2/GO2 hydrogen-rich perburner and a GH2/GO2 oxygen-rich preburner. The injectors were the shear coaxial injector, the oxidizer post expansion coaxial injector, the fuel impinging coaxial injector, the central body coaxial injec-tor, and the shear tri-coaxial injector. The characteristic velocity efficiency and the combustor’s wall temperatures were obtained for different design parameters through the experiments. It can be con-cluded that angles of the oxidizer post expansion and the fuel impinging have little influence on the combustion performance and the wall temperatures. The contact area between fuel and oxidizer and the mass flow rate have significant impacts on the combustion performance. The shear tri-coaxial injector has the best combustion performance but also the highest wall temperatures among the five types of injectors.

  19. Revisiting the inelastic electron tunneling spectroscopy of single hydrogen atom adsorbed on the Cu(100) surface.

    Science.gov (United States)

    Jiang, Zhuoling; Wang, Hao; Sanvito, Stefano; Hou, Shimin

    2015-12-21

    Inelastic electron tunneling spectroscopy (IETS) of a single hydrogen atom on the Cu(100) surface in a scanning tunneling microscopy (STM) configuration has been investigated by employing the non-equilibrium Green's function formalism combined with density functional theory. The electron-vibration interaction is treated at the level of lowest order expansion. Our calculations show that the single peak observed in the previous STM-IETS experiments is dominated by the perpendicular mode of the adsorbed H atom, while the parallel one only makes a negligible contribution even when the STM tip is laterally displaced from the top position of the H atom. This propensity of the IETS is deeply rooted in the symmetry of the vibrational modes and the characteristics of the conduction channel of the Cu-H-Cu tunneling junction, which is mainly composed of the 4s and 4pz atomic orbitals of the Cu apex atom and the 1s orbital of the adsorbed H atom. These findings are helpful for deepening our understanding of the propensity rules for IETS and promoting IETS as a more popular spectroscopic tool for molecular devices.

  20. Revisiting the inelastic electron tunneling spectroscopy of single hydrogen atom adsorbed on the Cu(100) surface

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Zhuoling; Wang, Hao [Centre for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871 (China); Sanvito, Stefano [School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2 (Ireland); Hou, Shimin, E-mail: smhou@pku.edu.cn [Centre for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871 (China); Beida Information Research (BIR), Tianjin 300457 (China)

    2015-12-21

    Inelastic electron tunneling spectroscopy (IETS) of a single hydrogen atom on the Cu(100) surface in a scanning tunneling microscopy (STM) configuration has been investigated by employing the non-equilibrium Green’s function formalism combined with density functional theory. The electron-vibration interaction is treated at the level of lowest order expansion. Our calculations show that the single peak observed in the previous STM-IETS experiments is dominated by the perpendicular mode of the adsorbed H atom, while the parallel one only makes a negligible contribution even when the STM tip is laterally displaced from the top position of the H atom. This propensity of the IETS is deeply rooted in the symmetry of the vibrational modes and the characteristics of the conduction channel of the Cu-H-Cu tunneling junction, which is mainly composed of the 4s and 4p{sub z} atomic orbitals of the Cu apex atom and the 1s orbital of the adsorbed H atom. These findings are helpful for deepening our understanding of the propensity rules for IETS and promoting IETS as a more popular spectroscopic tool for molecular devices.

  1. Semiclassical Calculation of Recurrence Spectra of Rydberg Hydrogen Atom Near a Metal Surface

    Institute of Scientific and Technical Information of China (English)

    WANG De-Hua

    2009-01-01

    Using closed orbit theory, we give a clear physical picture description of the Rydberg hydrogen atom near a metal surface and calculate the Fourier transformed recurrence spectra of this system at different scaled energies below ionization threshold.The results show that with the increase of the scaled energy, the number of the closed orbit increases greatly.Some of the orbits are created by the bifurcation of the perpendicular orbit.This case is quite similar to the Rydberg atom in an electric field.When the scaled energy increases furthermore, chaotic orbits appear.This study provides a different perspective on the dynamical behavior of the Rydberg atom near a metal surface.

  2. Atoms and Nanoparticles of Transition Metals as Catalysts for Hydrogen Desorption from Magnesium Hydride

    Directory of Open Access Journals (Sweden)

    N. Bazzanella

    2011-01-01

    Full Text Available The hydrogen desorption kinetics of composite materials made of magnesium hydride with transition metal additives (TM: Nb, Fe, and Zr was studied by several experimental techniques showing that (i a few TM at.% concentrations catalyse the H2 desorption process, (ii the H2 desorption kinetics results stabilized after a few H2 sorption cycles when TM atoms aggregate by forming nanoclusters; (iii the catalytic process occurs also at TM concentration as low as 0.06 at.% when TM atoms clustering is negligible, and (iv mixed Fe and Zr additives produce faster H2 desorption kinetics than single additive. The improved H2 desorption kinetics of the composite materials can be explained by assuming that the interfaces between the MgH2 matrix and the TM nanoclusters act as heterogeneous sites for the nucleation of the Mg phase in the MgH2 matrix and promote the formation of fast diffusion channels for H migrating atoms.

  3. Outflowing atomic and molecular gas at z ~ 0.67 towards 1504 + 377

    Science.gov (United States)

    Kanekar, Nissim; Chengalur, Jayaram N.

    2008-02-01

    We report the detection of OH 1667-MHz and wide HI 21-cm absorption at z ~ 0.67 towards the red quasar 1504 + 377, with the Green Bank Telescope and the Giant Metrewave Radio Telescope. The HI 21-cm absorption extends over a velocity range of ~600kms-1 blueward of the quasar redshift (z = 0.674), with the new OH 1667-MHz absorption component at ~-430kms-1, nearly coincident with earlier detections of millimetre-wave absorption at z ~ 0.6715. The atomic and molecular absorption appear to arise from a fast gas outflow from the quasar, with a mass outflow rate and a molecular hydrogen fraction . The radio structure of 1504 + 377 is consistent with the outflow arising as a result of a jet-cloud interaction, followed by rapid cooling of the cloud material. The observed ratio of HCO+ and OH column densities is ~20 times higher than typical values in Galactic and high-z absorbers. This could arise because of small-scale structure in the outflowing gas on sub-parsec scales, which would also explain the observed variability in the HI 21-cm line.

  4. Carbon and hydrogen isotopic composition and generation pathway of biogenic gas in China

    Institute of Scientific and Technical Information of China (English)

    SHEN Ping; WANG Xiaofeng; XU Yin; SHI Baoguang; XU Yongchang

    2009-01-01

    The carbon and hydrogen isotopic composition of biogenic gas is of great importance for the study of its generation pathway and reservoiring characteristics. In this paper, the formation pathways and reservoiring characteristics of biogenic gas reservoirs in China are described in terms of the carbon and hydrogen isotopic compositions of 31 gas samples from 10 biogenic gas reservoirs. The study shows that the hydrogen isotopic compositions of these biogenic gas reservoirs can be divided into three intervals:δDCH4>-200‰,-250‰<δDCH4<-200‰ and δDCH4<-250‰. The forerunners believed that the main generation pathway of biogenic gas under the condition of continental fresh water is acetic fermentation. Our research results showed that the generation pathway of biogenic gas under the condition of marine facies is typical CO2- reduction, the biogenic gas has heavy hydrogen isotopic composition: its δDCH4 values are higher than -200‰; that the biogenic gas under the condition of continental facies also was generated by the same way, but its hydrogen isotopic composition is lighter than that of biogenetic gas generated under typical marine facies condition: -250‰<δDCH4<-200‰, the δDCH4 values may be related to the salinity of the water medium in ancient lakes. From the relevant data of the Qaidam Basin, it can be seen that the hydrogen isotopic composition of biogenic methane has the same variation trend with increasing salinity of water medium. There are biogenic gas reservoirs formed in transitional regions under the condition of continental facies. These gas reservoirs resulted from both CO2- reduction and acetic fermentation, the formation of which may be related to the non-variant salinity of ancient water medium and the relatively high geothermal gradient, as is the case encountered in the Baoshan Basin. The biogenic gas generating in these regions has light hydrogen isotopic composition: δDCH4<-250‰, and relatively heavy carbon isotopic

  5. Three-dimensional simulation on explosions of hydrogen atomic clusters irradiated by an intense femtosecond laser pulse

    Institute of Scientific and Technical Information of China (English)

    Xia Yong; Liu Jian-Sheng; Ni Guo-Quan; Xu Zhi-Zhan

    2004-01-01

    Using classic particle dynamics simulations, the interaction process between an intense femtosecond laser pulse and icosahedral hydrogen atomic clusters H13, H55 and H147 has been studied. It is revealed that with increasing number of atoms in the cluster, the kinetic energy of ions generated in the Coulomb explosion of the ionized hydrogen clusters increases. The expansion process of the clusters after laser irradiation has also been examined, showing that the expansion scale decreases with increasing cluster size.

  6. Experimental test of higher-order electron-capture processes in collisions of fast protons with atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, H.; Schuch, R.; Justiniano, E.; Schulz, M.; Schwab, W.

    1986-11-03

    We present measurements of the angular distribution of fast hydrogen atoms formed by electron capture of 2.8- and 5.0-MeV protons in atomic hydrogen. In the angular region of the Thomas peak (0.47 mrad) the experimental results obtained with this pure three-body collision system are in reasonable agreement with a strong potential Born calculation and the impulse approximation, but not with other higher-order theories.

  7. All-optical production and trapping of metastable noble gas atoms down to the single atom regime

    CERN Document Server

    Kohler, M; Sahling, P; Sieveke, C; Jerschabek, N; Kalinowski, M B; Becker, C; Sengstock, K

    2014-01-01

    The determination of isotope ratios of noble gas atoms has many applications e.g. in physics, nuclear arms control, and earth sciences. For several applications, the concentration of specific noble gas isotopes (e.g. Kr and Ar) is so low that single atom detection is highly desirable for a precise determination of the concentration. As an important step in this direction, we demonstrate operation of a krypton Atom Trap Trace Analysis (ATTA) setup based on a magneto-optical trap (MOT) for metastable Kr atoms excited by all-optical means. Compared to other state-of-the-art techniques for preparing metastable noble gas atoms, all-optical production is capable of overcoming limitations regarding minimal probe volume and avoiding cross-contamination of the samples. In addition, it allows for a compact and reliable setup. We identify optimal parameters of our experimental setup by employing the most abundant isotope Kr-84, and demonstrate single atom detection within a 3D MOT.

  8. 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-Cα 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

  9. The role of hydrogen atoms in interactions involving imidazolium-based ionic liquids

    Science.gov (United States)

    Kempter, V.; Kirchner, B.

    2010-05-01

    In the first part of this report experimental results are discussed which focus onto the importance of hydrogen atoms in the interaction of imidazolium-based ionic liquids. These include examples for the cation-anion interaction in neat ionic liquids as well as the interactions between ionic liquids and their molecular environment, water in particular. Most of the studies emphasize the importance of the C(2)-H group of the imidazolium ring for the intra- and intermolecular interactions; commonly, the interactions of the type C-H … X (X =: O, halide) are attributed to "hydrogen bonding". In the second part it is analyzed whether these interactions and their consequences fulfill the criteria set by standard definitions of hydrogen bonding. Two cation-anion co-conformations at the C(2)-H group are found. One co-conformer (in-plane) often resembles a hydrogen bond while the other one (on-top) points to a non-hydrogen bonding behavior. Furthermore, the degree of hydrogen bonding for the in-plane structure is very dependent on the anion. Spatial distribution functions show that, in general, both co-conformations are occupied. However, the question of how long a particular co-conformer is populated in the liquid state has yet to be answered. Therefore, it is concluded that the term "hydrogen bond" should, at present, be treated with care to characterize the cation-anion contacts, because of the above-mentioned difficulties. Once more it must be stressed that oversimplifications and generalizations, even for this subclass of ionic liquids have to be avoided, because these liquids are more complicated than it appears from first sight.

  10. Inhalation of hydrogen gas suppresses hepatic injury caused by ischemia/reperfusion through reducing oxidative stress.

    Science.gov (United States)

    Fukuda, Kei-ichi; Asoh, Sadamitsu; Ishikawa, Masahiro; Yamamoto, Yasuhiro; Ohsawa, Ikuroh; Ohta, Shigeo

    2007-09-28

    We have recently showed that molecular hydrogen has great potential for selectively reducing cytotoxic reactive oxygen species, such as hydroxyl radicals, and that inhalation of hydrogen gas decreases cerebral infarction volume by reducing oxidative stress [I. Ohsawa, M. Ishikawa, K. Takahashi, M. Watanabe, K. Nishimaki, K. Yamagata, K.-I. Katsura, Y. Katayama, S. Asoh, S. Ohta, Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals, Nat. Med., 13 (2007) 688-694]. Here we show that the inhalation of hydrogen gas is applicable for hepatic injury caused by ischemia/reperfusion, using mice. The portal triad to the left lobe and the left middle lobe of the liver were completely occluded for 90min, followed by reperfusion for 180min. Inhalation of hydrogen gas (1-4%) during the last 190min suppressed hepatic cell death, and reduced levels of serum alanine aminotransferase and hepatic malondialdehyde. In contrast, helium gas showed no protective effect, suggesting that the protective effect by hydrogen gas is specific. Thus, we propose that inhalation of hydrogen gas is a widely applicable method to reduce oxidative stress.

  11. A dense gas of laser-cooled atoms for hybrid atom-ion trapping

    Science.gov (United States)

    Höltkemeier, Bastian; Glässel, Julian; López-Carrera, Henry; Weidemüller, Matthias

    2017-01-01

    We describe the realization of a dark spontaneous-force trap of rubidium atoms. The atoms are loaded from a beam provided by a two-dimensional magneto-optical trap yielding a capture efficiency of 75%. The dense and cold atomic sample is characterized by saturated absorption imaging. Up to 10^9 atoms are captured with a loading rate of 3× 10^9 atoms/s into a cloud at a temperature of 250 μK with the density exceeding 10^{11} atoms/cm^3. Under steady-state conditions, more than 90% of the atoms can be prepared into the absolute atomic ground state, which provides favorable conditions for the investigation of sympathetic cooling of ions in a hybrid atom-ion trap.

  12. Investigation of accelerated neutral atom beams created from gas cluster ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Kirkpatrick, A., E-mail: akirkpatrick@exogenesis.us [Exogenesis Corporation, 20 Fortune Drive, Billerica, MA 01821 (United States); Kirkpatrick, S.; Walsh, M.; Chau, S.; Mack, M.; Harrison, S.; Svrluga, R.; Khoury, J. [Exogenesis Corporation, 20 Fortune Drive, Billerica, MA 01821 (United States)

    2013-07-15

    A new concept for ultra-shallow processing of surfaces known as accelerated neutral atom beam (ANAB) technique employs conversion of energetic gas cluster ions produced by the gas cluster ion beam (GCIB) method into intense collimated beams of coincident neutral gas atoms having controllable average energies from less than 10 eV per atom to beyond 100 eV per atom. A beam of accelerated gas cluster ions is first produced as is usual in GCIB, but conditions within the source ionizer and extraction regions are adjusted such that immediately after ionization and acceleration the clusters undergo collisions with non-ionized gas atoms. Energy transfer during these collisions causes the energetic cluster ions to release many of their constituent atoms. An electrostatic deflector is then used to eliminate charged species, leaving the released neutral atoms to still travel collectively at the same velocities they had as bonded components of their parent clusters. Upon target impact, the accelerated neutral atom beams produce effects similar to those normally associated with GCIB, but to shallower depths, with less surface damage and with superior subsurface interfaces. The paper discusses generation and characterization of the accelerated neutral atom beams, describes interactions of the beams with target surfaces, and presents examples of ongoing work on applications for biomedical devices.

  13. Zeolite Membrane Reactor for Water Gas Shift Reaction for Hydrogen Production

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jerry Y.S. [Arizona State Univ., Mesa, AZ (United States)

    2013-01-29

    Gasification of biomass or heavy feedstock to produce hydrogen fuel gas using current technology is costly and energy-intensive. The technology includes water gas shift reaction in two or more reactor stages with inter-cooling to maximize conversion for a given catalyst volume. This project is focused on developing a membrane reactor for efficient conversion of water gas shift reaction to produce a hydrogen stream as a fuel and a carbon dioxide stream suitable for sequestration. The project was focused on synthesizing stable, hydrogen perm-selective MFI zeolite membranes for high temperature hydrogen separation; fabricating tubular MFI zeolite membrane reactor and stable water gas shift catalyst for membrane reactor applications, and identifying experimental conditions for water gas shift reaction in the zeolite membrane reactor that will produce a high purity hydrogen stream. The project has improved understanding of zeolite membrane synthesis, high temperature gas diffusion and separation mechanisms for zeolite membranes, synthesis and properties of sulfur resistant catalysts, fabrication and structure optimization of membrane supports, and fundamentals of coupling reaction with separation in zeolite membrane reactor for water gas shift reaction. Through the fundamental study, the research teams have developed MFI zeolite membranes with good perm-selectivity for hydrogen over carbon dioxide, carbon monoxide and water vapor, and high stability for operation in syngas mixture containing 500 part per million hydrogen sulfide at high temperatures around 500°C. The research teams also developed a sulfur resistant catalyst for water gas shift reaction. Modeling and experimental studies on the zeolite membrane reactor for water gas shift reaction have demonstrated the effective use of the zeolite membrane reactor for production of high purity hydrogen stream.

  14. The selective effect of environment on the atomic and molecular gas-to-dust ratio of nearby galaxies in the Herschel Reference Survey

    CERN Document Server

    Cortese, L; Boselli, A; Catinella, B; Ciesla, L; Hughes, T M; Baes, M; Bendo, G J; Boquien, M; de Looze, I; Smith, M W L; Spinoglio, L; Viaene, S

    2016-01-01

    We combine dust, atomic (HI) and molecular (H$_{2}$) hydrogen mass measurements for 176 galaxies in the Herschel Reference Survey to investigate the effect of environment on the gas-to-dust mass ($M_{\\rm gas}/M_{\\rm dust}$) ratio of nearby galaxies. We find that, at fixed stellar mass, the average $M_{\\rm gas}/M_{\\rm dust}$ ratio varies by no more than a factor of $\\sim$2 when moving from field to cluster galaxies, with Virgo galaxies being slightly more dust rich (per unit of gas) than isolated systems. Remarkably, once the molecular and atomic hydrogen phases are investigated separately, we find that \\hi-deficient galaxies have at the same time lower $M_{\\rm HI}/M_{\\rm dust}$ ratio but higher $M_{\\rm H_{2}}/M_{\\rm dust}$ ratio than \\hi-normal systems. In other words, they are poorer in atomic but richer in molecular hydrogen if normalized to their dust content. By comparing our findings with the predictions of theoretical models, we show that the opposite behavior observed in the $M_{\\rm HI}/M_{\\rm dust}$ a...

  15. A Guided-Inquiry Lab for the Analysis of the Balmer Series of the Hydrogen Atomic Spectrum

    Science.gov (United States)

    Bopegedera, A. M. R. P.

    2011-01-01

    A guided-inquiry lab was developed to analyze the Balmer series of the hydrogen atomic spectrum. The emission spectrum of hydrogen was recorded with a homemade benchtop spectrophotometer. By drawing graphs and a trial-and-error approach, students discover the linear relationship presented in the Rydberg formula and connect it with the Bohr model…

  16. Enzymatic production of hydrogen gas from glucose and cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Mattingly, S.M.; Woodward, J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    An enzymatic process has been used to convert glucose to molecular hydrogen with the ultimate goal of converting cellulose to hydrogen. Two enzymes from the Archae, Thermoplasma acidophilium glucose dehydrogenase (GDH) and Pyrococcus furiosus hydrogenase, were used to oxidize glucose and NADPH respectively, resulting in the formation of molecular hydrogen. The stoichiometric yield of hydrogen from glucose was close to the theoretical maximum expected. Further, the molar amount of hydrogen produced was greater than the molar equivalent of NADP{sup +} present in the reaction mixture indicating that this GDH cofactor was regenerated throughout the course of the reaction. Hydrogen was also shown to be produced from cellulose if cellulase was included in the reaction mixture.

  17. Toxicological analysis of 17 autopsy cases of hydrogen sulfide poisoning resulting from the inhalation of intentionally generated hydrogen sulfide gas.

    Science.gov (United States)

    Maebashi, Kyoko; Iwadate, Kimiharu; Sakai, Kentaro; Takatsu, Akihiro; Fukui, Kenji; Aoyagi, Miwako; Ochiai, Eriko; Nagai, Tomonori

    2011-04-15

    Although many cases of fatal hydrogen sulfide poisoning have been reported, in most of these cases, it resulted from the accidental inhalation of hydrogen sulfide gas. In recent years, we experienced 17 autopsy cases of fatal hydrogen sulfide poisoning due to the inhalation of intentionally generated hydrogen sulfide gas. In this study, the concentrations of sulfide and thiosulfate in blood, urine, cerebrospinal fluid and pleural effusion were examined using GC/MS. The sulfide concentrations were blood: 0.11-31.84, urine: 0.01-1.28, cerebrospinal fluid: 0.02-1.59 and pleural effusion: 2.00-8.59 (μg/ml), while the thiosulfate concentrations were blood: 0-0.648, urine: 0-2.669, cerebrospinal fluid: 0.004-0.314 and pleural effusion: 0.019-0.140 (μmol/ml). In previous reports, the blood concentration of thiosulfate was said to be higher than that of sulfide in hydrogen sulfide poisoning cases, although the latter was higher than the former in 8 of the 14 cases examined in this study. These results are believed to be strongly influenced by the atmospheric concentration of hydrogen sulfide the victims were exposed to and the time interval between exposure and death.

  18. Density functional study of manganese atom adsorption on hydrogen-terminated armchair boron nitride nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Abdullahi, Yusuf Zuntu [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Department of Physics, Faculty of Science, Kaduna State University, P.M.B. 2339, Kaduna State (Nigeria); Rahman, Md. Mahmudur, E-mail: mahmudur@upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Shuaibu, Alhassan [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Department of Physics, Faculty of Science, Nigerian Defence Academy, P.M.B 2109 Kaduna (Nigeria); Abubakar, Shamsu [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Department of Physics, Faculty of Science, Yobe State University, P.M.B. 1144, Yobe State (Nigeria); Zainuddin, Hishamuddin [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Institute for Mathematical Research, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Muhida, Rifki [Department of Physics-Energy Engineering, Surya University, Gedung 01 Scientia Business Park, Jl. Boulevard Gading Serpong Blok O/1, Summarecon Serpong, Tangerang 15810, Banten (Indonesia); Setiyanto, Henry [Analytical Chemistry Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10, Bandung 40132 (Indonesia)

    2014-08-15

    In this paper, we have investigated stable structural, electric and magnetic properties of manganese (Mn) atom adsorption on armchair hydrogen edge-terminated boron nitride nanoribbon (A-BNNRs) using first principles method based on density-functional theory with the generalized gradient approximation. Calculation shows that Mn atom situated on the ribbons of A-BNNRs is the most stable configuration, where the bonding is more pronounced. The projected density of states (PDOS) of the favored configuration has also been computed. It has been found that the covalent bonding of boron (B), nitrogen (N) and Mn is mainly contributed by s, d like-orbitals of Mn and partially occupied by the 2p like-orbital of N. The difference in energy between the inner and the edge adsorption sites of A-BNNRs shows that Mn atoms prefer to concentrate at the edge sites. The electronic structures of the various configurations are wide, narrow-gap semiconducting and half-metallic, and the magnetic moment of Mn atoms are well preserved in all considered configurations. This has shown that the boron nitride (BN) sheet covered with Mn atoms demonstrates additional information on its usefulness in future spintronics, molecular magnet and nanoelectronics devices.

  19. Iridium single atom tips fabricated by field assisted reactive gas etching

    Science.gov (United States)

    Wood, John A.; Urban, Radovan; Salomons, Mark; Cloutier, Martin; Wolkow, Robert A.; Pitters, Jason L.

    2016-03-01

    We present a simple, reliable method to fabricate Ir single atom tips (SATs) from polycrystalline wire. An electrochemical etch in CaCl2 solution is followed by a field assisted reactive gas etch in vacuum at room temperature using oxygen as an etching gas and neon as an imaging gas. Once formed, SATs are cooled to liquid nitrogen temperatures and their underlying structure is examined through evaporation of the apex atoms. Furthermore, a method is developed to repair Ir SATs at liquid nitrogen temperatures when apex atoms evaporate. This method may be used to fabricate Ir SAT ion sources.

  20. Gas chromatographic separation of hydrogen isotopes using metal hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Aldridge, F.T.

    1984-05-09

    A study was made of the properties of metal hydrides which may be suitable for use in chromatographic separation of hydrogen isotopes. Sixty-five alloys were measured, with the best having a hydrogen-deuterium separation factor of 1.35 at 60/sup 0/C. Chromatographic columns using these alloys produced deuterium enrichments of up to 3.6 in a single pass, using natural abundance hydrogen as starting material. 25 references, 16 figures, 4 tables.

  1. Inspection of the hydrogen gas pressure with metal shield by cold neutron radiography at CMRR

    Science.gov (United States)

    Li, Hang; Cao, Chao; Huo, Heyong; Wang, Sheng; Wu, Yang; Yin, Wei; Sun, Yong; Liu, Bin; Tang, Bin

    2017-04-01

    The inspection of the process of gas pressure change is important for some applications (e.g. gas tank stockpile or two phase fluid model) which need quantitative and non-touchable measurement. Neutron radiography provides a suitable tool for such investigations with nice resolution. The quantitative cold neutron radiography (CNR) is developed at China Mianyang Research Reactor (CMRR) to measure the hydrogen gas pressure with metal shield. Because of the high sensitivity to hydrogen, even small change of the hydrogen pressure can be inspected by CNR. The dark background and scattering neutron effect are both corrected to promote measurement precision. The results show that CNR can measure the hydrogen gas pressure exactly and the pressure value average relative error between CNR and barometer is almost 1.9%.

  2. Viscosity Measurement of Hydrogen-Methane Mixed Gas for Future Energy Systems

    Science.gov (United States)

    Kobayashi, Yohei; Kurokawa, Akira; Hirata, Masaru

    In order to reduce the CO2 emission, in May 2004, the European Union (EU) started an experimental approach known as the “naturalhy Project” in order to transport hydrogen by mixing it with the existing high-pressure natural gas in the pipelines. Naturalhy represents a mixture of hydrogen and natural gas. In other words, this gas is also known as hythane, which is an abbreviation of hydrogen and methane. The name “hythane” is the registered trademark of Hydrogen Consulting Inc., USA. Why will this gas gain importance? It is generally considered that the sudden realization of a hydrogen energy society cannot take place. It is normally assumed that the present status of methane as an energy carrier gradually changes to a state of hydrogen-methane mixed gas and finally to 100% hydrogen. This is why the authors investigate the properties of this mixture. This study is considered to be the first to measure the temperature dependence of the viscosity of hydrogen-methane mixed gas. In order to measure the viscosity, the authors used a capillary method that measures the pressure drop in the laminar flow through a pipe. It was conducted in an electrically polished, ultra clean and smooth tube and the pressure drop between the upstream and downstream was carefully measured using a capacitance manometer. In order to remove the effect of temperature dependence, the tube was placed in a constant temperature bath, and the temperature fluctuation was maintained within ±0.3°C throughout this experimental study. The authors obtained the viscosity of the hydrogen-methane mixed gas within a temperature range of 20-70°C.

  3. 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.

  4. 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

  5. Solid-gas and electrochemical hydrogenation properties of pseudo-binary (Ti,Zr)Ni intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Guiose, B.; Cuevas, F.; Decamps, B.; Percheron-Guegan, A. [Equipe de Chimie Metallurgique des Terres Rares, ICMPE, UMR7182, CNRS, 2-8 rue Henri Dunant, 94320 Thiais Cedex (France)

    2008-10-15

    Hydrogenation properties of pseudo-binary Ti{sub 1.02-x}Zr{sub x}Ni{sub 0.98} (0 {<=} x {<=} 0.48) intermetallic compounds have been investigated. The substitution of Zr for Ti in TiNi compound leads to a high increase of the storage capacity both in solid-gas reaction (1.4 hydrogen atoms per formula unit, H f.u.{sup -1} for TiNi and 2.6 H f.u.{sup -1} for the substituted compounds) and electrochemical reaction (150 mAhg{sup -1} for TiNi and {proportional_to}350 mAhg{sup -1} for the substituted compounds). The high capacity of the substituted compounds is closely linked to the martensitic transformation that occurs in TiNi-type intermetallic compounds. (author)

  6. Silicon Carbide-Based Hydrogen Gas Sensors for High-Temperature Applications

    OpenAIRE

    Sangchoel Kim; Jehoon Choi; Minsoo Jung; Seongjeen Kim; Sungjae Joo

    2013-01-01

    We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC) was used as a substrate ...

  7. Application of CFRP with High Hydrogen Gas Barrier Characteristics to Fuel Tanks of Space Transportation System

    Science.gov (United States)

    Yonemoto, Koichi; Yamamoto, Yuta; Okuyama, Keiichi; Ebina, Takeo

    In the future, carbon fiber reinforced plastics (CFRPs) with high hydrogen gas barrier performance will find wide applications in all industrial hydrogen tanks that aim at weight reduction; the use of such materials will be preferred to the use of conventional metallic materials such as stainless steel or aluminum. The hydrogen gas barrier performance of CFRP will become an important issue with the introduction of hydrogen-fuel aircraft. It will also play an important role in realizing fully reusable space transportation system that will have high specific tensile CFRP structures. Such materials are also required for the manufacture of high-pressure hydrogen gas vessels for use in the fuel cell systems of automobiles. This paper introduces a new composite concept that can be used to realize CFRPs with high hydrogen gas barrier performance for applications in the cryogenic tanks of fully reusable space transportation system by the incorporation of a nonmetallic crystal layer, which is actually a dense and highly oriented clay crystal laminate. The preliminary test results show that the hydrogen gas barrier characteristics of this material after cryogenic heat shocks and cyclic loads are still better than those of other polymer materials by approximately two orders of magnitude.

  8. Rate constants for 1,5- and 1,6-hydrogen atom transfer reactions of mono-, di-, and tri-aryl-substituted donors, models for hydrogen atom transfers in polyunsaturated fatty acid radicals.

    Science.gov (United States)

    DeZutter, Christopher B; Horner, John H; Newcomb, Martin

    2008-03-06

    Rate constants for 1,5- and 1,6-hydrogen atom transfer reactions in models of polyunsaturated fatty acid radicals were measured via laser flash photolysis methods. Photolyses of PTOC (pyridine-2-thioneoxycarbonyl) ester derivatives of carboxylic acids gave primary alkyl radicals that reacted by 1,5-hydrogen transfer from mono-, di-, and tri-aryl-substituted positions or 1,6-hydrogen transfer from di- and tri-aryl-substituted positions to give UV-detectable products. Rate constants for reactions in acetonitrile at room temperature ranged from 1 x 10(4) to 4 x 10(6) s(-1). The activation energies for a matched pair of 1,5- and 1,6-hydrogen atom transfers giving tri-aryl-substituted radicals were approximately equal, as were the primary kinetic isotope effects, but the 1,5-hydrogen atom transfer reaction was 1 order of magnitude faster at room temperature than the 1,6-hydrogen atom transfer reaction due to a less favorable entropy of activation for the 1,6-transfer reaction. Solvent effects on the rate constants for the 1,5-hydrogen atom transfer reaction of the 2-[2-(diphenylmethyl)phenyl]ethyl radical at ambient temperature were as large as a factor of 2 with the reaction increasing in rate in lower polarity solvents. Hybrid density functional theory computations for the 1,5- and 1,6-hydrogen atom transfers of the tri-aryl-substituted donors were in qualitative agreement with the experimental results.

  9. Atomic capture and transfer of negative pions stopped in binary mixtures of hydrogen with polyatomic gases

    Energy Technology Data Exchange (ETDEWEB)

    Vasilyev, V.A.; Levay, B.; Minkova, A.; Petrukhin, V.I.; Horvath, D.

    1985-12-01

    The atomic capture and transfer of stopped negative pions have been studied in binary gas mixtures of H/sub 2/+M, where M is CCl/sub 2/F/sub 2/, CClF/sub 3/, CBrF/sub 3/ or SF/sub 6/. The ..pi../sup 0/ yield, versus relative atomic concentration Csub(A) of M, goes through a maximum at Csub(A)proportional0.1 and levels off at zero at high concentrations. This phenomenon together with other observed characteristics of the atomic capture and transfer of pions in these systems is interpreted in the frame of a phenomenological model. The average transfer coefficients anti ..lambda..sub(Z) exhibit a weak concentration dependence. The estimated average atomic capture ratios anti A(Z/H) are lower than those found for noble gases, probably because of the mutual screening of the constituent atoms in the molecules. The probability of pion capture in an atomic orbit is not proportional to the stopping power of the components of the mixture. (orig.).

  10. Hydrogen in natural gases. [In natural gas, in methane in coal deposits and in petroleum deposits

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, A.K.

    1983-01-01

    Extensive factual material regarding hydrogen in the most diverse gases is generalized. Especial attention is focused on hydrogen contained in gases of carboniferous basins. Results are presented of studies of hydrogen content of coal gases of the Donets and L'vov-Volynskiy carboniferous basins, and also in gases of the fields of the Dnieper-Donets Basin. Differences were established in gases of the petroleum and coal series according to their content of hydrogen, and also coal beds and surrounding rocks which are dangerous and not dangerous for sudden blowout. Questions are examined of the genesis of hydrogen. Results are presented of experimental studies to reveal the secondary hydrogen in gases. It is indicated that hydrogen can serve as an important criterion in prospecting for a number of minerals and an indicator in predicting sudden blowouts of coal, rock and gas in mines.

  11. Relativistic Spectrum of Hydrogen Atom in Space-Time Non-Commutativity

    CERN Document Server

    Moumni, Mustafa; Zaim, Slimane; 10.1063/1.4715429

    2012-01-01

    We study space-time non-commutativity applied to the hydrogen atom via the Seiberg-Witten map and its phenomenological effects. We find that it modifies the Coulomb potential in the Hamiltonian and add an r-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. N.B: In precedent works (arXiv:0907.1904, arXiv:1003.5732 and arXiv:1006.4590), we have used the Bopp Shift formulation of non-commutativity but here use it \\`a la Seiberg-Witten in the Relativistic case.

  12. Multiply Confined Nickel Nanocatalysts Produced by Atomic Layer Deposition for Hydrogenation Reactions.

    Science.gov (United States)

    Gao, Zhe; Dong, Mei; Wang, Guizhen; Sheng, Pei; Wu, Zhiwei; Yang, Huimin; Zhang, Bin; Wang, Guofu; Wang, Jianguo; Qin, Yong

    2015-07-27

    To design highly efficient catalysts, new concepts for optimizing the metal-support interactions are desirable. Here we introduce a facile and general template approach assisted by atomic layer deposition (ALD), to fabricate a multiply confined Ni-based nanocatalyst. The Ni nanoparticles are not only confined in Al2 O3 nanotubes, but also embedded in the cavities of Al2 O3 interior wall. The cavities create more Ni-Al2 O3 interfacial sites, which facilitate hydrogenation reactions. The nanotubes inhibit the leaching and detachment of Ni nanoparticles. Compared with the Ni-based catalyst supported on the outer surface of Al2 O3 nanotubes, the multiply confined catalyst shows a striking improvement of catalytic activity and stability in hydrogenation reactions. Our ALD-assisted template method is general and can be extended for other multiply confined nanoreactors, which may have potential applications in many heterogeneous reactions.

  13. Interaction of atomic hydrogen with anthracene and polyacene from density functional theory

    Science.gov (United States)

    Ferullo, Ricardo M.; Castellani, Norberto J.; Belelli, Patricia G.

    2016-03-01

    The interaction of atomic hydrogen with two linear polycyclic aromatic hydrocarbons (PAHs), anthracene and polyacene (the polymer of benzene), was studied within the density functional theory (DFT). Using a proper dispersion-corrected method (DFT-D) the preferential physisorption sites were explored. The activation barrier for the bond formation between a peripheral C and the incoming H was calculated to be 58.5 and 34.1 meV with pure DFT on anthracene and polyacene at its antiferromagnetic ground state, respectively. DFT-D, although improves the description of the physisorbed state, tends to underestimate the chemisorption barriers due an artifact arising from the dispersion correction.

  14. 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.

  15. Quantum Spectra of Hydrogen Atoms in Various Magnetic Fields with the Closed Orbit Theory

    Institute of Scientific and Technical Information of China (English)

    彭良友; 张现周; 饶建国

    2002-01-01

    The quantum spectra of hydrogen atoms in various magnetic fields have been calculated with the closed orbit theory. The magnitude of the magnetic field decreases from 5.96 T to 0.56 T with a step of 0. 6 T. We demonstrate schematically that the closed orbits disappear with the decrease of the magnitude of the magnetic field when the corresponding finite resolution of experiment is fixed. This may give us a good way to control the shape and the number of the closed orbits in the system, and thus to control where a peak should exist in the Fourier transformation of the quantum spectra.

  16. Hydrogen Atom Abstraction from Hydrocarbons by a Copper(III)-Hydroxide Complex

    OpenAIRE

    Dhar, Debanjan; Tolman, William B.

    2015-01-01

    With the aim of understanding the basis for the high rate of hydrogen atom abstraction (HAT) from dihydroanthracene (DHA) by the complex LCuOH (1; L = N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide), the bond dissociation enthalpy of the reaction product LCu(H2O) (2) was determined through measurement of its pK a and E 1/2 in THF solution. In so doing, an equilibrium between 2 and LCu(THF) was characterized by UV–vis and EPR spectroscopy and cyclic voltammetry (CV). A high pK a of ...

  17. 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.

  18. 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.

  19. 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.

  20. Exposure of epitaxial graphene on SiC(0001) to atomic hydrogen.

    Science.gov (United States)

    Guisinger, Nathan P; Rutter, Gregory M; Crain, Jason N; First, Phillip N; Stroscio, Joseph A

    2009-04-01

    Graphene films on SiC exhibit coherent transport properties that suggest the potential for novel carbon-based nanoelectronics applications. Recent studies suggest that the role of the interface between single layer graphene and silicon-terminated SiC can strongly influence the electronic properties of the graphene overlayer. In this study, we have exposed the graphitized SiC to atomic hydrogen in an effort to passivate dangling bonds at the interface, while investigating the results utilizing room temperature scanning tunneling microscopy.

  1. Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

    Science.gov (United States)

    Borges, L. H. C.; Barone, F. A.

    2016-02-01

    Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schrödinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector.

  2. On the theory of (e, 2e) reactions in atomic hydrogen and helium

    Science.gov (United States)

    Byron, F. W.; Joachain, C. J.; Piraux, B.

    1984-12-01

    We compare the results of eikonal-Born series calculations which we have performed for the (e, 2e) reaction in atomic hydrogen with recent absolute measurements of triple differential cross sections for that process, carried out in the asymmetric coplanar geometry. We find that second-order effects play a crucial role in understanding both the angular positions and the magnitudes of the binary and recoil peaks. The implications of our analysis for the case of (e, 2e) reactions in helium are also discussed.

  3. Resonant electron transfer in slow collisions of protons with Rydberg hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Janev, R.K.; Joachain, C.J.; Nedeljkovic, N.N.

    1984-05-01

    The resonant charge-transfer reaction of protons on highly excited hydrogen atoms is considered by taking into account both the tunneling (under-barrier) and the over-barrier (classically allowed) electron transitions. It is demonstrated that in a wide range of variation of the reduced ve- locity v = vn, the classical transition mechanism is predominant. Cross-section calculations for principal quantum numbers n between 10 and 50 are presented. The results for 45< or =n< or =50 are compared with the available experimental data and with other theoretical calculations.

  4. Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

    Energy Technology Data Exchange (ETDEWEB)

    Borges, L.H.C. [Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas, Santo Andre, SP (Brazil); Barone, F.A. [IFQ-Universidade Federal de Itajuba, Itajuba, MG (Brazil)

    2016-02-15

    Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schroedinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector. (orig.)

  5. Design and Evaluation of Ultrasonic Atomization Device for Atomizing Hydrogen Peroxide%超声波雾化过氧化氢雾化装置设计及效果评估

    Institute of Scientific and Technical Information of China (English)

    刘艳朝; 梁婷; 王宁

    2012-01-01

    Objective To develop an easy-operated, economical, and efficient ultrasonic atomization device for atomizing hydrogen peroxide, and evaluate its atomization effect. Methods The ultrasonic generator with power 25W and oscillation frequency 1.7MHz was used for providing energy for atomizing hydrogen peroxide, and the oscillator was made of ceramics. A stainless steel fluid reservoir was made to reserve hydrogen peroxide solution. Two holes were designed at the top of the reservoir, one was for inlet gas, and the other was for outlet gas. A back plate was welded for backing the large particle drop in the reservoir department. An interface fitted to the oscillator was designed at the bottom of the reservoir. An air pump helped to lead out the vapor. Spectrophotometry was used for determining the conversion rate of the hydrogen peroxide. Laser granularity measuring instrument was used for determining the size of the atomization particle. Results The ultrasonic atomization device worked well for producing hydrogen peroxide particle. The effective rate of atomization could reach to 53%, and the average size of atomized particle could reach to 22 (jun. Conclusion The atomization effect of the ultrasonic atomization device is satisfactory, and with further improvement, the devise can be used for generating vaporous hydrogen peroxide.[Chinese Medical Equipment Journal,2011,33(3) =39-40,48]%目的:研制一种简单、经济、高效的超声波雾化过氧化氢雾化装置,并对其雾化效果进行实验评估.方法:用市售的超声波发生器提供过氧化氢雾化所需能量,晶振片优选陶瓷材料,功率25 W,电路振荡频率1.7 MHz;加工 不锈钢储液罐储存过氧化氢溶液,其顶部开设进、出气口,内部焊接大雾粒挡板,底部开设与超声波发生器晶振片相吻合的连接接口;用气泵提供导出过氧化氢雾粒所需的动力,用钛盐光度法测定过氧化氢有效雾化率,用激光粒度仪测定过氧化氢平均

  6. Non-dipole effects in multiphoton ionization of hydrogen atom in short superintense laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Jobunga, Eric O. [AG Moderne Optik, Institut fuer Physik, Humboldt-Universitaet zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany); Department of Mathematics and Physics, Technical University of Mombasa, P. O. Box 90420-80100, Mombasa (Kenya); Saenz, Alejandro [AG Moderne Optik, Institut fuer Physik, Humboldt-Universitaet zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany)

    2014-07-01

    The development of novel light sources has enabled the realization of high-precision experiments investigating various non-linear processes in the dynamics of atomic, molecular, and ionic systems interacting with high intense laser pulses. At high intensities or short wavelengths, the analysis of these experiments would definitely require a reliable non-perturbative solution of the time-dependent Schroedinger or Dirac equation. These solutions should consider both the temporal and the spatial intensity variations of the laser pulse.We have solved the non-relativistic time dependent Schroedinger equation for a ground state hydrogen atom interacting with short intense spatially and temporally resolved laser fields corresponding to the multiphoton ATI regime for a monochromatic source with λ= 800 nm. We shall analyse the effects of the A{sup 2} term and the corresponding orders of the multipolar expansion of the transition matrix.

  7. A unified numerical model of collisional depolarization and broadening rates due to hydrogen atom collisions

    CERN Document Server

    Derouich, M; Barklem, P S

    2015-01-01

    Interpretation of solar polarization spectra accounting for partial or complete frequency redistribution requires data on various collisional processes. Data for depolarization and polarization transfer are needed but often missing, while data for collisional broadening are usually more readily available. Recent work by Sahal-Br\\'echot and Bommier concluded that despite underlying similarities in the physics of collisional broadening and depolarization processes, relationships between them are not possible to derive purely analytically. We aim to derive accurate numerical relationships between the collisional broadening rates and the collisional depolarization and polarization transfer rates due to hydrogen atom collisions. Such relationships would enable accurate and efficient estimation of collisional data for solar applications. Using earlier results for broadening and depolarization processes based on general (i.e. not specific to a given atom), semi-classical calculations employing interaction potentials...

  8. 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.

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

    CERN Document Server

    Filho, J S Oliveira

    2015-01-01

    By using perturbation theory, we show that an hydrogen atom with magnetic moment due to the orbital angular momentum of the electron has 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 that this effect is essential for the validity of the Lorentz force law in quantum systems. We also connect our results to the secular Abraham-Minkowski debate about the momentum of light in material media.

  10. Long-Range Atom--Wall Interactions and Mixing Terms: Metastable Hydrogen

    CERN Document Server

    Jentschura, U D

    2015-01-01

    We investigate the interaction of metastable 2S hydrogen atoms with a perfectly conducting wall, including parity-breaking S-P mixing terms (with full account of retardation). The neighboring 2P_1/2 and 2P_3/2 levels are found to have a profound effect on the transition from the short-range, nonrelativistic regime, to the retarded form of the Casimir-Polder interaction. The corresponding P state admixtures to the metastable 2S state are calculated. We find the long-range asymptotics of the retarded Casimir-Polder potentials and mixing amplitudes, for general excited states, including a fully quantum electrodynamic treatment of the dipole-quadrupole mixing term. The decay width of the metastable 2S state is roughly doubled even at a comparatively large distance of 918 atomic units (Bohr radii) from the perfect conductor. The magnitude of the calculated effects is compared to the unexplained Sokolov effect.

  11. On the role of atomic metastability in the production of Balmer line radiation from ‘cold’ atomic hydrogen, deuterium and hydrogenic ion impurities in fusion edge plasmas

    Science.gov (United States)

    Hey, J. D.

    2012-03-01

    Published arguments, which assign an important role to atomic metastability in the production of ‘narrow’ Zeeman component radiation from the boundary region of fusion plasmas, are examined critically in relation to l-redistribution by proton and electron collisions, and mixing of unperturbed atomic states by the ion microfield and microfield gradient. It is concluded that these important processes indeed severely constrain the contribution from ‘metastable’ states to the generation of the hydrogen Balmer spectra, for electron concentrations above 1012 cm-3, as pointed out before by the present author (Hey et al 1999 J. Phys. B: At. Mol. Opt. Phys. 32 3555). The analysis of collision-induced l-redistribution represents an extension of that used previously (Hey et al 1996 Contrib. Plasma Phys. 36 583), applicable up to higher electron densities. For comparison purposes, we also consider the question of metastability of ionized helium in a low-temperature plasma, and that of some common hydrogenic impurities (C5+ and Ne9+) in a hydrogen (deuterium) fusion plasma. While for low nuclear charge Z the metastability of 2s1/2 levels is quenched by the plasma environment, it is much reduced in high-Z ions owing to the rapid increase with Z of the two-photon electric dipole (2E1) and magnetic dipole (M1) spontaneous transition rates to the ground state, whereas the role of the plasma in these cases is less important. The main new principle elaborated in this work is the sensitivity of atomic line strengths, and hence collision strengths, to perturbation by the plasma environment for transitions between fine-structure sublevels of the same principal quantum number. As the plasma microfield strength grows, ‘allowed’ transitions diminish in strength, while ‘forbidden’ transitions grow. However, owing to violation of the parity selection rule, there is an overall loss of collision strength available to transitions, resulting from the appearance of significant

  12. Hydrogen atom abstraction reactions from tertiary amines by benzyloxyl and cumyloxyl radicals: influence of structure on the rate-determining formation of a hydrogen-bonded prereaction complex.

    Science.gov (United States)

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

    2011-08-05

    A time-resolved kinetic study on the hydrogen atom abstraction reactions from a series of tertiary amines by the cumyloxyl (CumO(•)) and benzyloxyl (BnO(•)) radicals was carried out. With the sterically hindered triisobutylamine, comparable hydrogen atom abstraction rate constants (k(H)) were measured for the two radicals (k(H)(BnO(•))/k(H)(CumO(•)) = 2.8), and the reactions were described as direct hydrogen atom abstractions. With the other amines, increases in k(H)(BnO(•))/k(H)(CumO(•)) ratios of 13 to 2027 times were observed. k(H) approaches the diffusion limit in the reactions between BnO(•) and unhindered cyclic and bicyiclic amines, whereas a decrease in reactivity is observed with acyclic amines and with the hindered cyclic amine 1,2,2,6,6-pentamethylpiperidine. These results provide additional support to our hypothesis that the reaction proceeds through the rate-determining formation of a C-H/N hydrogen-bonded prereaction complex between the benzyloxyl α-C-H and the nitrogen lone pair wherein hydrogen atom abstraction occurs, and demonstrate the important role of amine structure on the overall reaction mechanism. Additional mechanistic information in support of this picture is obtained from the study of the reactions of the amines with a deuterated benzyloxyl radical (PhCD(2)O(•), BnO(•)-d(2)) and the 3,5-di-tert-butylbenzyloxyl radical.

  13. Gas atomization processing of tin and silicon modified LaNi5 for nickel-metal hydride battery applications

    Energy Technology Data Exchange (ETDEWEB)

    Ting, Jason [Iowa State Univ., Ames, IA (United States)

    1999-02-12

    Numerous researchers have studied the relevant material properties of so-called AB5 alloys for battery applications. These studies involved LaNi5 substituted alloys which were prepared using conventional cast and crush alloying techniques. While valuable to the understanding of metal hydride effects, the previous work nearly ignored the potential for alternative direct powder production methods, like high pressure gas atomization (HPGA). Thus, there is a need to understand the relationship between gas atomization processes, powder particle solidification phases, and hydrogen absorption properties of ultra fine (< 25 μm) atomized powders with high surface area for enhanced battery performance. Concurrently, development of a gas atomization nozzle that is more efficient than all current designs is needed to increase the yield of ultrafine AB5 alloy powder for further processing advantage. Gas atomization processing of the AB5 alloys was demonstrated to be effective in producing ultrafine spherical powders that were resilient to hydrogen cycling for the benefit of improving corrosion resistance in battery application. These ultrafine powders benefited from the rapid solidification process by having refined solute segregation in the microstructure of the gas atomized powders which enabled a rapid anneal treatment of the powders. The author has demonstrated the ability to produce high yields of ultrafine powder efficiently and cost effectively, using the new HPGA-III technology. Thus, the potential benefits of processing AB5 alloys using the new HPGA technology could reduce manufacturing cost of nickel-metal hydride powder. In the near future, the manufacture of AB5 alloy powders could become a continuous and rapid production process. The economic benefit of an improved AB5 production process may thereby encourage the use of nickel-metal hydride rechargeable batteries in electrical vehicle

  14. Luther-Emery Phase and Atomic-Density Waves in a Trapped Fermion Gas

    Science.gov (United States)

    Xianlong, Gao; Rizzi, M.; Polini, Marco; Fazio, Rosario; Tosi, M. P.; Campo, V. L., Jr.; Capelle, K.

    2007-01-01

    The Luther-Emery liquid is a state of matter that is predicted to occur in one-dimensional systems of interacting fermions and is characterized by a gapless charge spectrum and a gapped spin spectrum. In this Letter we discuss a realization of the Luther-Emery phase in a trapped cold-atom gas. We study by means of the density-matrix renormalization-group technique a two-component atomic Fermi gas with attractive interactions subject to parabolic trapping inside an optical lattice. We demonstrate how this system exhibits compound phases characterized by the coexistence of spin pairing and atomic-density waves. A smooth crossover occurs with increasing magnitude of the atom-atom attraction to a state in which tightly bound spin-singlet dimers occupy the center of the trap. The existence of atomic-density waves could be detected in the elastic contribution to the light-scattering diffraction pattern.

  15. Observing random walks of atoms in buffer gas through resonant light absorption

    CERN Document Server

    Aoki, Kenichiro

    2016-01-01

    Using resonant light absorption, random walk motions of rubidium atoms in nitrogen buffer gas are observed directly. The transmitted light intensity through atomic vapor is measured and its spectrum is obtained, down to orders of magnitude below the shot noise level to detect fluctuations caused by atomic motions. To understand the measured spectra, the spectrum for atoms performing random walks in a gaussian light beam is computed and its analytical form is obtained. The spectrum has $1/f^2$ ($f$: frequency) behavior at higher frequencies, crossing over to a different, but well defined behavior at lower frequencies. The properties of this theoretical spectrum agree excellently with the measured spectrum. This understanding also enables us to obtain the diffusion constant, the photon cross section of atoms in buffer gas and the atomic number density, from a single spectral measurement. We further discuss other possible applications of our experimental method and analysis.

  16. Dynamic Nuclear Polarization and Relaxation of H and D Atoms in Solid Mixtures of Hydrogen Isotopes

    Science.gov (United States)

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

    2016-12-01

    We report on a study of dynamic nuclear polarization and electron and nuclear spin relaxation of atomic hydrogen and deuterium in solid molecular matrices of H2, D2 , and HD mixtures. The electron and nuclear spin relaxation times (T_{1e} and T_{1N} ) were measured within the temperature range 0.15-2.5 K in a magnetic field of 4.6 T, conditions which ensure a high polarization of electron spins. We found that T_{1e} is nearly temperature independent in this temperature range, while T_{1N} decreased by two orders of magnitude upon raising temperature. Such strong temperature dependence is typical for the nuclear Orbach mechanism of relaxation via the electron spins. We found that the nuclear spins of H atoms in solid D2 and D2{:}HD can be efficiently polarized by the Overhauser effect. Pumping the forbidden transitions of H atoms also leads to DNP, with the efficiency strongly dependent on the concentration of D atoms. This behavior indicates the cross effect mechanism of the DNP and nuclear relaxation, which turns out to be well resolved in the conditions of our experiments. Efficient DNP of H atoms was also observed when pumping the middle D line located in the center of the ESR spectrum. This phenomenon can be explained in terms of clusters or pairs of H atoms with a strong exchange interaction. These clusters have partially allowed transitions in the center of the ESR spectrum, and DNP may be created via the resolved cross effect.

  17. Dynamic nuclear polarization and relaxation of H and D atoms in solid mixtures of hydrogen isotopes

    CERN Document Server

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

    2016-01-01

    We report on a study of Dynamic Nuclear Polarization and electron and nuclear spin relaxation of atomic hydrogen and deuterium in solid molecular matrices of H$_{2}$, D$_{2}$, and HD mixtures. The electron and nuclear spin relaxation times ($T_{1e}$ and $T_{1N}$) were measured within the temperature range 0.15-2.5$\\,$K in a magnetic field of 4.6 T, conditions which ensure a high polarization of electron spins. We found that $T_{1e}$ is nearly temperature independent in this temperature range, while $T_{1N}$ decreased by 2 orders of magnitude. Such strong temperature dependence is typical for the nuclear Orbach mechanism of relaxation via the electron spins. We found that the nuclear spins of H atoms in solid D$_{2}$ and D$_{2}:$HD can be efficiently polarized by the Overhauser effect. Pumping the forbidden transitions of H atoms also leads to DNP, with the efficiency strongly dependent on the concentration of D atoms. This behaviour indicates the Cross effect mechanism of the DNP and nuclear relaxation, which...

  18. Hydrogen distribution in CVD diamond films prepared by DC arcjet operating at gas recycling mode

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Hydrogen distribution and content in diamond films deposited by DC arcjet under gas recycling mode was evaluated by nuclear reaction analysis (NRA). The films were characterized using scanning electron microscopy, X-ray diffraction and Raman spectrometry. The NRA results show that the hydrogen content in diamond films was approximately 0.6% (substrate temperature 770℃), and strongly depended on the substrate temperature. It was that the hydrogen content increased with the increase of the substrate temperature. The possibility of hydrogen trapping in the films was also discussed.

  19. Atom-molecule equilibration in a degenerate Fermi gas with resonant interactions

    DEFF Research Database (Denmark)

    Williams, J. E.; Nikuni, T.; Nygaard, Nicolai;

    2004-01-01

    We present a nonequilibrium kinetic theory describing atom-molecule population dynamics in a two-component Fermi gas with a Feshbach resonance. Key collision integrals emerge that govern the relaxation of the atom-molecule mixture to chemical and thermal equilibrium. Our focus is on the pseudogap...

  20. Novel Applications of Buffer-Gas Cooling to Cold Atoms, Diatomic Molecules, and Large Molecules

    OpenAIRE

    Drayna, Garrett Korda

    2016-01-01

    Cold gases of atoms and molecules provide a system for the exploration of a diverse set of physical phenomena. For example, cold gasses of magnetically and electrically polar atoms and molecules are ideal systems for quantum simulation and quantum computation experiments, and cold gasses of large polar molecules allow for novel spectroscopic techniques. Buffer-gas cooling is a robust and widely applicable method for cooling atoms and molecules to temperatures of approximately 1 Kelvin. In thi...

  1. Atomic Interaction Effects on Electromagnetically Induced Transparency and Slow Light in Ultracold Bose Gas

    Institute of Scientific and Technical Information of China (English)

    胡正峰; 杜春光; 李代军; 李师群

    2002-01-01

    We investigate electromagnetically induced transparency and slow group velocity of light in ultracold Bose gas with a two-photon Raman process. The properties of electromagnetically induced transparency and light speed can be changed by controlling the atomic interaction. Atomic interaction can be used as a knob to control the optical properties of atomic media. This can be realized in experiment by using the Feshbach resonance technique.

  2. Hydrogen gas filling into an actual tank at high pressure and optimization of its thermal characteristics

    Science.gov (United States)

    Khan, Md. Tawhidul Islam; Monde, Masanori; Setoguchi, Toshiaki

    2009-09-01

    Gas with high pressure is widely used at present as fuel storage mode for different hydrogen vehicles. Different types of materials are used for constructing these hydrogen pressure vessels. An aluminum lined vessel and typically carbon fiber reinforced plastic (CFRP) materials are commercially used in hydrogen vessels. An aluminum lined vessel is easy to construct and posses high thermal conductivity compared to other commercially available vessels. However, compared to CFRP lined vessel, it has low strength capacity and safety factors. Therefore, nowadays, CFRP lined vessels are becoming more popular in hydrogen vehicles. Moreover, CFRP lined vessel has an advantage of light weight. CFRP, although, has many desirable properties in reducing the weight and in increasing the strength, it is also necessary to keep the material temperature below 85 °C for maintaining stringent safety requirements. While filling process occurs, the temperature can be exceeded due to the compression works of the gas flow. Therefore, it is very important to optimize the hydrogen filling system to avoid the crossing of the critical limit of the temperature rise. Computer-aided simulation has been conducted to characterize the hydrogen filling to optimize the technique. Three types of hydrogen vessels with different volumes have been analyzed for optimizing the charging characteristics of hydrogen to test vessels. Gas temperatures are measured inside representative vessels in the supply reservoirs (H2 storages) and at the inlet to the test tank during filling.

  3. Experimental research of optical fiber hydrogen gas sensing system based on palladium-silver alloy

    Science.gov (United States)

    Cui, Lu-jun; Zhou, Gao-feng; Li, Zheng-feng; Cao, Yan-long

    2016-11-01

    A novel optical fiber hydrogen sensing system based on palladium (Pd) and sliver (Ag) is proposed. By direct current (DC) magnetron process, Pd/Ag alloy ultra-thin films were deposited on the substrate to eliminate the hydrogen embrittlement of sensor based on pure Pd. Several samples with different thin film thicknesses were fabricated at different substrate temperatures and tested in the optical fiber hydrogen sensor setup. We do a series of experiments for obtaining optimum sputtering parameters, such as optimum sputtering temperature and thickness of Pd/Ag alloy film. The humidity effect and reliability experiment for the optical fiber hydrogen gas sensor are reported in detail. The testing results demonstrate the Pd/Ag alloy is a promising material for optical fiber hydrogen gas sensor.

  4. Molecular and atomic gas along and across the main sequence of star-forming galaxies

    Science.gov (United States)

    Saintonge, Amelie; Catinella, Barbara; Cortese, Luca; Genzel, Reinhard; Giovanelli, Riccardo; Haynes, Martha P.; Janowiecki, Steven; Kramer, Carsten; Lutz, Katharina A.; Schiminovich, David; Tacconi, Linda J.; Wuyts, Stijn; Accurso, Gioacchino

    2016-10-01

    We use spectra from the ALFALFA, GASS and COLD GASS surveys to quantify variations in the mean atomic and molecular gas mass fractions throughout the SFR-M* plane and along the main sequence (MS) of star-forming galaxies. Although galaxies well below the MS tend to be undetected in the Arecibo and IRAM observations, reliable mean atomic and molecular gas fractions can be obtained through a spectral stacking technique. We find that the position of galaxies in the SFR-M* plane can be explained mostly by their global cold gas reservoirs as observed in the H I line, with in addition systematic variations in the molecular-to-atomic ratio and star formation efficiency. When looking at galaxies within ±0.4 dex of the MS, we find that as stellar mass increases, both atomic and molecular gas mass fractions decrease, stellar bulges become more prominent, and the mean stellar ages increase. Both star formation efficiency and molecular-to-atomic ratios vary little for massive MS galaxies, indicating that the flattening of the MS is due to the global decrease of the cold gas reservoirs of galaxies rather than to bottlenecks in the process of converting cold atomic gas to stars.

  5. The Influence of Hydrogen Gas on the Measures of Efficiency of Diesel Internal Combustion Engine

    Directory of Open Access Journals (Sweden)

    Jurgis Latakas

    2014-12-01

    Full Text Available In this research paper energy and ecological parameters of diesel engine which works under addition of hydrogen (10, 20, 30 l/ min are presented. A survey of research literature has shown that addition of hydrogen gases improve diesel combustion; increase indicated pressure; decrease concentration of carbon dioxide (CO2, hydrocarbons (HC, particles; decrease fuel consumptions. Results of the experiment revealed that hydrogen gas additive decreased pressure in cylinder in kinetic combustion phase. Concentration of CO2 and nitrous oxides (NOx decreased not significantly, HC – increased. Concentration of particles in engine exhaust gases significantly decreased. In case when hydrogen gas as additive was supplied, the fuel consumptions decreased a little. Using AVL BOOST software combustion process analysis was made. It was determined that in order to optimize engine work process under hydrogen additive usage, it is necessary to adjust diesel injection angle.

  6. 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).

  7. A probable vacuum state containing a large number of hydrogen atom of excited state or ground state K, Rb or Cs atom

    CERN Document Server

    You, Pei-Lin

    2008-01-01

    The linear Stark effect shows that the first excited state of hydrogen atom has large permanent electric dipole moment (EDM), d(H)=3eao (ao is Bohr radius). Using special capacitors our experiments discovered that the ground state K, Rb or Cs atom is polar atom with a large EDM of the order of eao as hydrogen atom of excited state. Their capacitance(C) at different voltage (V) was measured. The C-V curve shows that the saturation polarization of K, Rb or Cs vapor has be observed when the field E more than ten to the fifth power V/m. When the saturation polarization appeared, nearly all K, Rb or Cs atoms(more than 98 percent) turned toward the direction of the field, and C is approximately equal to Co (Co is vacuum capacitance) or their dielectric constant is nearly the same as vacuum! K, Rb or Cs vapor just exist in the lowest energy state, so we see the vacuum state containing a large number of atoms! Due to the saturation polarization of hydrogen vapor of excited state is easily appears, we conjecture that ...

  8. Role of sodium hydroxide in the production of hydrogen gas from the hydrothermal gasification of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Onwudili, Jude A.; Williams, Paul T. [Energy and Resources Research Institute, University of Leeds, Leeds, LS2 9JT (United Kingdom)

    2009-07-15

    The role of sodium hydroxide as a promoter of hydrogen gas production during the hydrothermal gasification of glucose and other biomass samples has been investigated. Experiments were carried out in a batch reactor with glucose and also in the presence of the alkali from 200 C, 2 MPa to 450 C, 34 MPa at constant water loading. Without sodium hydroxide, glucose decomposed to produce mainly carbon dioxide, water, char and tar. Furfural, its derivatives and reaction products dominated the ethyl acetate extract of the water (organic fraction) at lower reaction conditions. This indicated that the dehydration of glucose to yield these products was unfavourable to hydrogen gas production. In the presence of sodium hydroxide however, glucose initially decomposed to form mostly alkylated and hydroxylated carbonyl compounds, whose further decomposition yielded hydrogen gas. It was observed that at 350 C, 21.5 MPa, half of the optimum hydrogen gas yield had formed and at 450 C, 34 MPa, more than 80 volume percent of the gaseous effluent was hydrogen gas, while the balance was hydrocarbon gases, mostly methane ({>=}10 volume percent). Other biomass samples were also comparably reacted at the optimum conditions observed for glucose. The rate of hydrogen production for the biomass samples was in the following order; glucose > cellulose, starch, rice straw > potato > rice husk. (author)

  9. Structural and optical properties of silicon nanoparticles prepared by pulsed laser ablation in hydrogen background gas

    Science.gov (United States)

    Makino, T.; Inada, M.; Yoshida, K.; Umezu, I.; Sugimura, A.

    We studied the structural and optical properties of silicon (Si) nanoparticles (np-Si) prepared by pulsed laser ablation (PLA) in hydrogen (H2) background gas. The mean diameter of the np-Si was estimated to be approximately 5 nm. The infrared absorption corresponding to Si-Hn (n=1,2,3) bonds was observed at around 2100 cm-1, and a Raman scattering peak corresponding to crystalline Si was observed at around 520 cm-1. These results indicate that nanoparticles are not an alloy of Si and hydrogen but Si nanocrystal covered by hydrogen or hydrogenated silicon. This means that surface passivated Si nanoparticles can be prepared by PLA in H2 gas. The band-gap energy of np-Si prepared in H2 gas (1.9 eV) was larger than that of np-Si prepared in He gas (1.6 eV) even though they are almost the same diameter. After decreasing the hydrogen content in np-Si by thermal annealing, the band-gap energy decreased, and reached the same energy level as np-Si prepared in He gas. Thus, the optical properties of np-Si were affected by the hydrogenation of the surface of np-Si.

  10. Direct chlorination process for geothermal power plant off-gas - hydrogen sulfide abatement

    Energy Technology Data Exchange (ETDEWEB)

    Sims, A.V.

    1983-06-01

    The Direct Chlorination Process removes hydrogen sulfide from geothermal off-gases by reacting hydrogen sulfide with chlorine in the gas phase. Hydrogen chloride and elemental sulfur are formed by this reaction. The Direct Chlorination Process has been successfully demonstrated by an on-site operation of a pilot plant at the 3 M We HPG-A geothermal power plant in the Puna District on the island of Hawaii. Over 99.5 percent hydrogen sulfide removal was achieved in a single reaction stage. Chlorine gas did not escape the pilot plant, even when 90 percent excess chlorine gas was used. Because of the higher cost of chemicals and the restricted markets in Hawaii, the economic viability of this process in Hawaii is questionable.

  11. Direct chlorination process for geothermal power plant off-gas - hydrogen sulfide abatement

    Energy Technology Data Exchange (ETDEWEB)

    Sims, A.V.

    1983-06-01

    The Direct Chlorination Process removes hydrogen sulfide from geothermal off-gases by reacting hydrogen sulfide with chlorine in the gas phase. Hydrogen chloride and elemental sulfur are formed by this reaction. The Direct Chlorination Process has been successfully demonstrated by an on-site operation of a pilot plant at the 3 M We HPG-A geothermal power plant in the Puna District on the island of Hawaii. Over 99.5 percent hydrogen sulfide removal was achieved in a single reaction state. Chlorine gas did not escape the pilot plant, even when 90 percent excess chlorine gas was used. A preliminary economic evaluation of the Direct Chlorination Process indicates that it is very competitive with the Stretford Process. Compared to the Stretford Process, the Direct Chlorination Process requires about one-third the initial capital investment and about one-fourth the net daily expenditure.

  12. 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.

  13. Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's Pseudoscalar Coupling $g_P$

    CERN Document Server

    Andreev, V A; Case, T A; Chitwood, D B; Clayton, S M; Crowe, K M; Deutsch, J; Egger, J; Freedman, S J; Ganzha, V A; Gorringe, T; Gray, F E; Hertzog, D W; Hildebrandt, M; Kammel, P; Kiburg, B; Knaack, S; Kravtsov, P A; Krivshich, A G; Lauss, B; Lynch, K L; Maev, E M; Maev, O E; Mulhauser, F; Özben, C S; Petitjean, C; Petrov, G E; Prieels, R; Schapkin, G N; Semenchuk, G G; Soroka, M A; Tishchenko, V; Vasilyev, A A; Vorobyov, A A; Vznuzdaev, M E; Winter, P

    2007-01-01

    The rate of nuclear muon capture by the proton has been measured using a new experimental technique based on a time projection chamber operating in ultra-clean, deuterium-depleted hydrogen gas at 1 MPa pressure. The capture rate was obtained from the difference between the measured $\\mu^-$ disappearance rate in hydrogen and the world average for the $\\mu^+$ decay rate. The target's low gas density of 1% compared to liquid hydrogen is key to avoiding uncertainties that arise from the formation of muonic molecules. The capture rate from the hyperfine singlet ground state of the $\\mu p$ atom is measured to be $\\Lambda_S=725.0 \\pm 17.4 s^{-1}$, from which the induced pseudoscalar coupling of the nucleon, $g_P(q^2=-0.88 m_\\mu^2)=7.3 \\pm 1.1$, is extracted. This result is consistent with theoretical predictions for $g_P$ that are based on the approximate chiral symmetry of QCD.

  14. A simplified Probabilistic Safety Assesment of a Steam-Methane Reforming Hydrogen Production Plant coupled to a High-Temperature Gas Cooled Nuclear Reactor

    OpenAIRE

    Nelson Edelstein, Pamela; Flores Flores, Alain; Francois Lacouture, Juan Luis

    2005-01-01

    A Probabilistic Safety Assessment (PSA) is being developed for a steam-methane reforming hydrogen production plant linked to a High-Temperature Gas Cooled Nuclear Reactor (HTGR). This work is based on the Japan Atomic Energy Research Institute’s (JAERI) High Temperature Test Reactor (HTTR) prototype in Japan. This study has two major objectives: calculate the risk to onsite and offsite individuals, and calculate the frequency of different types of damage to the complex. A simplified HAZOP...

  15. Geochemical modelling of hydrogen gas migration in an unsaturated bentonite buffer

    NARCIS (Netherlands)

    Sedighi, M.; Thomas, H.R.; Al Masum, S.; Vardon, P.J.; Nicholson, D.; Chen, Q.

    2014-01-01

    This paper presents an investigation of the transport and fate of hydrogen gas through compacted bentonite buffer. Various geochemical reactions that may occur in the multiphase and multicomponent system of the unsaturated bentonite buffer are considered. A reactive gas transport model, developed wi

  16. Outflowing atomic and molecular gas at $z \\sim 0.67$ towards 1504+377

    CERN Document Server

    Kanekar, Nissim

    2007-01-01

    We report the detection of OH 1667 MHz and wide HI 21cm absorption at $z \\sim 0.67$ towards the red quasar 1504+377, with the Green Bank Telescope and the Giant Metrewave Radio Telescope. The HI 21cm absorption extends over a velocity range of $\\sim 600$ km/s blueward of the quasar redshift ($z=0.674$), with the new OH 1667 MHz absorption component at $\\sim -430$ \\kms, nearly coincident with earlier detections of mm-wave absorption at $z \\sim 0.6715$. The atomic and molecular absorption appear to arise from a fast gas outflow from the quasar, with a mass outflow rate ${\\dot M} \\sim 12 M_\\odot$ yr$^{-1}$ and a molecular hydrogen fraction $f_{\\rm H_2} \\equiv (N_{\\rm H_2}/N_{\\rm HI}) \\sim 0.2$. The radio structure of 1504+377 is consistent with the outflow arising due to a jet-cloud interaction, followed by rapid cooling of the cloud material. The observed ratio of HCO$^+$ to OH column densities is $\\sim 20$ times higher than typical values in Galactic and high-$z$ absorbers. This could arise due to small-scale ...

  17. Development and industrial application of catalyzer for low-temperature hydrogenation hydrolysis of Claus tail gas

    Directory of Open Access Journals (Sweden)

    Honggang Chang

    2015-10-01

    Full Text Available With the implementation of more strict national environmental protection laws, energy conservation, emission reduction and clean production will present higher requirements for sulfur recovery tail gas processing techniques and catalyzers. As for Claus tail gas, conventional hydrogenation catalyzers are gradually being replaced by low-temperature hydrogenation catalyzers. This paper concentrates on the development of technologies for low-temperature hydrogenation hydrolysis catalyzers, preparation of such catalyzers and their industrial application. In view of the specific features of SO2 hydrogenation and organic sulfur hydrolysis during low-temperature hydrogenation, a new technical process involving joint application of hydrogenation catalyzers and hydrolysis catalyzers was proposed. In addition, low-temperature hydrogenation catalyzers and low-temperature hydrolysis catalyzers suitable for low-temperature conditions were developed. Joint application of these two kinds of catalyzers may reduce the inlet temperatures in the conventional hydrogenation reactors from 280 °C to 220 °C, at the same time, hydrogenation conversion rates of SO2 can be enhanced to over 99%. To further accelerate the hydrolysis rate of organic sulfur, the catalyzers for hydrolysis of low-temperature organic sulfur were developed. In lab tests, the volume ratio of the total sulfur content in tail gas can be as low as 131 × 10−6 when these two kinds of catalyzers were used in a proportion of 5:5 in volumes. Industrial application of these catalyzers was implemented in 17 sulfur recovery tail gas processing facilities of 15 companies. As a result, Sinopec Jinling Petrochemical Company had outstanding application performances with a tail gas discharging rate lower than 77.9 mg/m3 and a total sulfur recovery of 99.97%.

  18. Chemical Kinetics of Hydrogen Atom Abstraction from Allylic Sites by (3)O2; 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 O2 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. Time-resolved Absorption Spectra of the Laser-dressed Hydrogen Atom

    Science.gov (United States)

    Murakami, Mitsuko; Chu, Shih-I.

    2013-05-01

    A theoretical study of the transient absorption spectra for the laser-dressed hydrogen atom based on the accurate numerical solution of the time-dependent Schrödinger equation is presented. The timing of absorption is controlled by the time delay between an isolated extreme ultraviolet (XUV) pulse and a dressing infrared (IR) field. We identify two different kinds of physical processes in the spectra. One is the formation of dressed states, signified by the appearance of sidebands between the XUV absorption lines separated by one IR-photon energy. We show that their population is maximized when the XUV pulse coincides with the zero-crossing of the IR field, and that their energy can be manipulated by using a chirped IR field. The other process is the dynamical AC Stark shift induced by the IR field and probed by the XUV pulse. Our calculations indicate that the accidental degeneracy of the hydrogen atom leads to the multiple splittings of each XUV absorption line whose separations change in response to a slowly-varying IR envelope. Furthermore, we observe the Autler-Townes doublets for the n=2 and 3 states using the 656 nm dressing field, but their separation does not agree with the prediction by the conventional 3-level model that neglects the dynamical AC Stark effects.

  20. Laser-Assisted Semi Relativistic Excitation of Atomic Hydrogen by Electronic Impact

    CERN Document Server

    Taj, S; Idrissi, M El; Oufni, L

    2012-01-01

    The excitation of H ($1s-2s$) by electron impact in the presence and in the absence of the laser field is studied in the framework of the first Born approximation. The angular variation of the laser-assisted differential cross section (DCS) for atomic hydrogen by electronic impact is presented at various kinetic energies for the incident electron. The use of Darwin wave function as a semirelativistic state to represent the atomic hydrogen gives interesting results when the condition $z/c\\ll1$ is fulfilled. A comparison with the non relativistic theory and experimental data gives good agreement. It was observed that beyond (2700 $eV$) which represents the limit between the two approaches, the non relativistic theory does not yield close agreement with our theory and that, over certain ranges of energy, it can be in error by several orders of magnitude. The sum rule given by Bunkin and Fedorov and by Kroll and Watson \\cite{22} has been verified in both nonrelativistic and relativistic regimes.

  1. Ways to improve the removal of hydrogen sulfide from coke-oven gas

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, M.D.; Lyannaya; No. 1, Z.G.; Ignatova, E.P.; Zbykovskii, I.I.; Shukh, Ya.I.; Andreiko, I.M.; Garkushenko, I.Ya.

    1979-01-01

    Our calculations showed that, if the gas temperatures ahead of the scrubbers were reuced to 30/sup 0/C and 300 to 400 liters/h of concentrated ammonia water were added to the circuit, the degree of hydrogen sulfide absorption could be brought to 58 to 65%, i.e., the hydrogen sulfide content in the return gas would be less than 2.5 g/m/sup 3/. All the hydrogen sulfide removed from the gas would enter the concentrated ammonia water, which would be delivered to facilities for production of soda by the ammonia method. The ammonium sulfide formed in the liquor would be a desirable component, acting to inhibit corrosion. This would provide the simplest solution to the problem of utilizing the hydrogen sulfide removed from the gas. Our investigation thus showed that the hydrogen sulfide content of the coke-oven gas can be reduced to a permissible level in the department as it now exists, without substantial remodelling of the scrubber department. Implementation of the proposed measures (installation of an additional gas cooler beyond the blower and introduction of 300 to 400 liters/h of 20% ammonia liquor into the circuit) will make it possible to improve air-pollution conditions in the carbonization department and adjoining areas, reduce the corrosion of the gaslines, utilize that portion of the gas now discharged into the atmosphere, and eliminate the need for construction of an expensive special facility for removal of hydrogen sulfide. Addition of concentrated ammonia liquor into the scrubber-liquor circuit in the amounts indicated above raised the degree of hydrogen sulfide absorption from 31 to 43 to 47%.

  2. Gas-phase hydrogen/deuterium exchange of 5'- and 3'-mononucleotides in a quadrupole ion trap: exploring the role of conformation and system energy.

    Science.gov (United States)

    Chipuk, Joseph E; Brodbelt, Jennifer S

    2007-04-01

    Gas-phase hydrogen/deuterium (H/D) exchange reactions for deprotonated 2'-deoxy-5'-monophosphate and 2'-deoxy-3'-monophosphate nucleotides with D(2)O were performed in a quadrupole ion trap mass spectrometer. To augment these experiments, molecular modeling was also conducted to identify likely deprotonation sites and potential gas-phase conformations of the anions. A majority of the 5'-monophosphates exchanged extensively with several of the compounds completely incorporating deuterium in place of their labile hydrogen atoms. In contrast, most of the 3'-monophosphate isomers exchanged relatively few hydrogen atoms, even though the rate of the first two exchanges was greater than observed for the 5'-monophosphates. Mononucleotides that failed to incorporate more than two deuterium atoms under default reaction conditions were often found to exchange more extensively when reactions were performed under higher energy conditions. Integration of the experimental and theoretical results supports the use of a relay exchange mechanism and suggests that the exchange behavior depends highly on the identity and orientation of the nucleobase and the position and flexibility of the deprotonated phosphate moiety. These observations also highlight the importance of the distance between the various participating groups in addition to their gas-phase acidity and basicity.

  3. The Transition from Atomic to Molecular Hydrogen in Interstellar Clouds: 21cm Signature of the Evolution of Cold Atomic Hydrogen in Dense Clouds

    CERN Document Server

    Goldsmith, P F; Krco, M; Goldsmith, Paul F.; Li, Di; Krco, Marko

    2006-01-01

    We have investigated the time scale for formation of molecular clouds by examining the conversion of HI to H2 using a time-dependent model. H2 formation on dust grains and cosmic ray and photo destruction are included in one-dimensional model slab clouds which incorporate time-independent density and temperature distributions. We calculate 21cm spectral line profiles seen in absorption against a background provided by general Galactic HI emission, and compare the model spectra with HI Narrow Self-Absorption, or HINSA, profiles absorbed in a number of nearby molecular clouds. The time evolution of the HI and H2 densities is dramatic, with the atomic hydrogen disappearing in a wave propagating from the central, denser regions which have a shorter H2 formation time scale, to the edges, where the density is lower and the time scale for H2 formation longer. The model 21cm spectra are characterized by very strong absorption at early times, when the HI column density through the model clouds is extremely large. The ...

  4. Diffuse Atomic and Molecular Gas near IC443

    CERN Document Server

    Hirschauer, A; Wallerstein, George; Means, T

    2009-01-01

    We present an analysis of results on absorption from Ca II, Ca I, K I, and the molecules CH+, CH, C2, and CN that probes gas interacting with the supernova remnant IC443. The eleven directions sample material across the visible nebula and beyond its eastern edge. Most of the neutral material, including the diatomic molecules, is associated with the ambient cloud detected via H I and CO emission. Analysis of excitation and chemistry yields gas densities that are typical of diffuse molecular gas. The low density gas probed by Ca II extends over a large range in velocities, from -120 to +80 km/s in the most extreme cases. This gas is distributed among several velocity components, unlike the situation for the shocked molecular clumps, whose emission occurs over much the same range but as very broad features. The extent of the high-velocity absorption suggests a shock velocity of 100 km/s for the expanding nebula.

  5. Emission of hydrogen energetic neutral atoms from the Martian subsolar magnetosheath

    Science.gov (United States)

    Wang, X.-D.; Alho, M.; Jarvinen, R.; Kallio, E.; Barabash, S.; Futaana, Y.

    2016-01-01

    We have simulated the hydrogen energetic neutral atom (ENA) emissions from the subsolar magnetosheath of Mars using a hybrid model of the proton plasma charge exchanging with the Martian exosphere to study statistical features revealed from the observations of the Neutral Particle Detectors on Mars Express. The simulations reproduce well the observed enhancement of the hydrogen ENA emissions from the dayside magnetosheath in directions perpendicular to the Sun-Mars line. Our results show that the neutralized protons from the shocked solar wind are the dominant ENA population rather than those originating from the pickup planetary ions. The simulation also suggests that the observed stronger ENA emissions in the direction opposite to the solar wind convective electric field result from a stronger proton flux in the same direction at the lower magnetosheath; i.e., the proton fluxes in the magnetosheath are not cylindrically symmetric. We also confirm the observed increasing of the ENA fluxes with the solar wind dynamical pressure in the simulations. This feature is associated with a low altitude of the induced magnetic boundary when the dynamic pressure is high and the magnetosheath protons can reach to a denser exosphere, and thus, the charge exchange rate becomes higher. Overall, the analysis suggests that kinetic effects play an important and pronounced role in the morphology of the hydrogen ENA distribution and the plasma environment at Mars, in general.

  6. Excitation of heavy hydrogen-like ions by light atoms in relativistic collisions with large momentum transfers

    CERN Document Server

    Najjari, B

    2012-01-01

    We present a theory for excitation of heavy hydrogen-like projectile-ions by light target-atoms in collisions where the momentum transfers to the atom are very large on the atomic scale. It is shown that in this process the electrons and the nucleus of the atom behave as (quasi-) free particles with respect to each other and that their motion is governed by the field of the nucleus of the ion. The effect of this field on the atomic particles can be crucial for the contribution to the excitation of the ion caused by the electrons of the atom. Due to comparatively very large nuclear mass, however, this field can be neglected in the calculation of the contribution to the excitation due to the nucleus of the atom.

  7. Flash Atomization: A New Concept to Control Combustion Instability in Water-Injected Gas Turbines

    Directory of Open Access Journals (Sweden)

    Vishwas Iyengar

    2012-01-01

    Full Text Available The objective of this work is to explore methods to reduce combustor rumble in a water-injected gas turbine. Attempts to use water injection as a means to reduce NOX emissions in gas turbines have been largely unsuccessful because of increased combustion instability levels. This pulsation causes chronic fretting, wear, and fatigue that damages combustor components. Of greater concern is that liberated fragments could cause extensive damage to the turbine section. Combustion instability can be tied to the insufficient atomization of injected water; large water droplets evaporate non-uniformly that lead to energy absorption in chaotic pulses. Added pulsation is amplified by the combustion process and acoustic resonance. Effervescent atomization, where gas bubbles are injected, is beneficial by producing finely atomized droplets; the gas bubbles burst as they exit the nozzles creating additional energy to disperse the liquid. A new concept for effervescent atomization dubbed “flash atomization” is presented where water is heated to just below its boiling point in the supply line so that some of it will flash to steam as it leaves the nozzle. An advantage of flash atomization is that available heat energy can be used rather than mechanical energy to compress injection gas for conventional effervescent atomization.

  8. Evolution of the atomic and molecular gas content of galaxies in dark matter haloes

    NARCIS (Netherlands)

    Popping, Gergö; Behroozi, Peter S.; Peeples, Molly S.

    2015-01-01

    We present a semi-empirical model to infer the atomic and molecular hydrogen content of galaxies as a function of halo mass and time. Our model combines the star formation rate (SFR)-halo mass-redshift relation (constrained by galaxy abundances) with inverted SFR-surface density relations to infer g

  9. Techno-economic Analysis of Distributed Hydrogen Production from Natural Gas

    Institute of Scientific and Technical Information of China (English)

    LUK Ho Ting; LEI Ho Man; NG Wai Yee; JU Yihan; LAM Koon Fung

    2012-01-01

    It is well established that hydrogen has the potential to make a significant contribution to the world energy production. In U.S., majority of hydrogen production plants implement steam methane reforming (SMR) for centralized hydrogen production. However, there is a wide lack of agreement on the nascent stage of using hydro- gen as fuel in vehicles industry because of the difficulty in delivery and storage. By performing technological and economic analysis, this work aims to establish the most feasible hydrogen production pathway for automotives in near future. From the evaluation, processes such as thermal cracking of ammonia and centralized hydrogen production followed by bulk delivery are eliminated while on-site steam reforming of methanol and natural gas are the most technologically feasible options. These two processes are further evaluated by comprehensive economic analysis. The results showed that the steam reforming (SR) of natural gas has a shorter payback time and a higher return on investment (ROI) and internal rate of return (IRR). Sensitivity analysis has also been constructed to evaluate the impact of variables like NG feedstock price, capital of investment and operating capacity factor on the overall production cost of hydrogen. Based on this study, natural gas is prompted to be the most economically and technologically available raw material for short-term hydrogen production before the transition to renewable energy source such as solar energy, biomass and wind power.

  10. Life-cycle analysis of greenhouse gas emission and energy efficiency of hydrogen fuel cell scooters

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Jenn Jiang [Department of Greenergy, National University of Taiwan, Tainan (China); Chang, Wei Ru [Department of Landscape Architecture, FuJen Catholic University, Taipei (China)

    2010-11-15

    The well-to-wheels (WTW) analysis of energy conservation and greenhouse gas emission of advanced scooters associated with new transportation fuels is studied in the present work. Focus is placed on fuel cell scooter technologies, while the gasoline-powered scooter equipped with an internal combustion engine (ICE) serves as a reference technology. The effect of various pathways of hydrogen production on the well-to-tank (WTT) efficiency for energy is examined. Both near-term and long-term hydrogen production options are explored, such as purification of coke oven gas (COG), steam reforming of natural gas, water electrolysis by generation mix and renewable electricity, and gasification of herbaceous biomass. Then, the WTW efficiency of fuel cell scooters for various hydrogen production options is compared with that of the conventional ICE scooters and electric scooters. Results showed that the fuel cell scooters fueled with COG-based hydrogen could achieve the highest reduction benefits in energy consumption and GHG emission. Finally, the potential for hydrogen production from COG resulting from the coking process in steelworks is evaluated, which is anticipated as a near-term hydrogen production for helping transition to a hydrogen energy economy in Taiwan. (author)

  11. Hydrogen Energy Storage (HES) and Power-to-Gas Economic Analysis; NREL (National Renewable Energy Laboratory)

    Energy Technology Data Exchange (ETDEWEB)

    Eichman, Joshua

    2015-07-30

    This presentation summarizes opportunities for hydrogen energy storage and power-to-gas and presents the results of a market analysis performed by the National Renewable Energy Laboratory to quantify the value of energy storage. Hydrogen energy storage and power-to-gas systems have the ability to integrate multiple energy sectors including electricity, transportation, and industrial. On account of the flexibility of hydrogen systems, there are a variety of potential system configurations. Each configuration will provide different value to the owner, customers and grid system operator. This presentation provides an economic comparison of hydrogen storage, power-to-gas and conventional storage systems. The total cost is compared to the revenue with participation in a variety of markets to assess the economic competitiveness. It is found that the sale of hydrogen for transportation or industrial use greatly increases competitiveness. Electrolyzers operating as demand response devices (i.e., selling hydrogen and grid services) are economically competitive, while hydrogen storage that inputs electricity and outputs only electricity have an unfavorable business case. Additionally, tighter integration with the grid provides greater revenue (e.g., energy, ancillary service and capacity markets are explored). Lastly, additional hours of storage capacity is not necessarily more competitive in current energy and ancillary service markets and electricity markets will require new mechanisms to appropriately compensate long duration storage devices.

  12. Life cycle greenhouse emissions of compressed natural gas-hydrogen mixtures for transportation in Argentina

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, P. [Instituto de Energia y Desarrollo Sustentable, CNEA, CONICET, Av. del Libertador 8250, Ciudad Autonoma de Buenos Aires (Argentina); Dawidowski, L.; Gomez, D. [Gerencia Quimica, CNEA, Av. Gral. Paz 1499, San Martin (Argentina); Pasquevich, D. [Instituto de Energia y Desarrollo Sustentable, CNEA, CONICET, Av. del Libertador 8250, Ciudad Autonoma de Buenos Aires (Argentina); Centro Atomico Bariloche, CNEA, Av. Bustillo 9500, S.C. de Bariloche (Argentina)

    2010-06-15

    We have developed a model to assess the life cycle greenhouse emissions of compressed natural gas-hydrogen (CNG-H{sub 2}) mixtures used for transportation in Argentina. The overall fuel life cycle is assessed through a well-to-wheel (WTW) analysis for different hydrogen generation and distribution options. The combustion stage in road vehicles is modeled using the COPERT IV model. Hydrogen generation options include classical steam methane reforming (SMR) and water electrolysis (WE) in central plants and distributed facilities at the refueling stations. Centralized hydrogen generation by electrolysis in nuclear plants as well as the use of solar photovoltaic and wind electricity is also considered. Hydrogen distribution options include gas pipeline and refrigerated truck transportation for liquefied hydrogen. A total number of fifteen fuel pathways are studied; in all the cases the natural gas-hydrogen mixture is made at the refueling station. The use of WE using nuclear or wind electricity appears to be less contaminant that the use of pure CNG. (author)

  13. Coupled cluster and density functional theory calculations of atomic hydrogen chemisorption on pyrene and coronene as model systems for graphene hydrogenation.

    Science.gov (United States)

    Wang, Ying; Qian, Hu-Jun; Morokuma, Keiji; Irle, Stephan

    2012-07-05

    Ab initio coupled cluster and density functional theory studies of atomic hydrogen addition to the central region of pyrene and coronene as molecular models for graphene hydrogenation were performed. Fully relaxed potential energy curves (PECs) were computed at the spin-unrestricted B3LYP/cc-pVDZ level of theory for the atomic hydrogen attack of a center carbon atom (site A), the midpoint of a neighboring carbon bond (site B), and the center of a central hexagon (site C). Using the B3LYP/cc-pVDZ PEC geometries, we evaluated energies at the PBE density functional, as well as ab initio restricted open-shell ROMP2, ROCCSD, and ROCCSD(T) levels of theory, employing cc-pVDZ and cc-pVTZ basis sets, and performed a G2MS extrapolation to the ROCCSD(T)/cc-pVTZ level of theory. In agreement with earlier studies, we find that only site A attack leads to chemisorption. The G2MS entrance channel barrier heights, binding energies, and PEC profiles are found to agree well with a recent ab initio multireference wave function theory study (Bonfanti et al. J. Chem. Phys.2011, 135, 164701), indicating that single-reference open-shell methods including B3LYP are sufficient for the theoretical treatment of the interaction of graphene with a single hydrogen atom.

  14. Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing

    Directory of Open Access Journals (Sweden)

    Adisorn Tuantranont

    2010-08-01

    Full Text Available In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT-doped tungsten oxide (WO3 thin films by means of the powder mixing and electron beam (E-beam evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method.

  15. Multi-walled carbon nanotube-doped tungsten oxide thin films for hydrogen gas sensing.

    Science.gov (United States)

    Wongchoosuk, Chatchawal; Wisitsoraat, Anurat; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Kerdcharoen, Teerakiat

    2010-01-01

    In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO(3)) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO(3) thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO(3) hydrogen sensor prepared by the E-beam method.

  16. Low cost hydrogen/novel membrane technology for hydrogen separation from synthesis gas, Phase 1. Quarterly technical progress report for the period ending December 31, 1986

    Energy Technology Data Exchange (ETDEWEB)

    1986-12-31

    During the last quarter several high performance membranes for the separation of hydrogen from nitrogen, carbon monoxide, hydrogen sulfide and carbon dioxide. The heat-resistant resin poly(etherimide) has been selected as the polymer with the most outstanding properties for the separation of hydrogen from nitrogen and carbon monoxide. Flat sheet and hollow fiber poly(etherimide) membranes have been prepared and evaluated with pure gases and gas mixtures at elevated pressures and temperatures. Multilayer composite poly(ether-ester-amide) membranes were also developed. These membranes are useful for the separation of carbon dioxide and hydrogen sulfide hydrogen. They have very high selectivities and extremely high normalized carbon dioxide and hydrogen sulfide fluxes. Separation of carbon dioxide/hydrogen streams is a key problem in hydrogen production from coal. The development of the two membranes now gives us two approaches to separate these gas streams, depending on the stream`s composition. If the stream contains small quantities of hydrogen, the hydrogen- permeable poly(etherimide) membrane would be used to produce a hydrogen-enriched permeate. If the stream contains small quantities of carbon dioxide or hydrogen sulfide, the poly(ether-ester-amide) membrane would be used to produce a carbon dioxide/hydrogen sulfide-free, hydrogen-enriched residue stream. 6 fig., 4 tabs.

  17. Low cost hydrogen/novel membrane technology for hydrogen separation from synthesis gas, Phase 1. [Poly(etherimide) and poly(ether-ester-amide) membranes

    Energy Technology Data Exchange (ETDEWEB)

    1986-01-01

    During the last quarter several high performance membranes for the separation of hydrogen from nitrogen, carbon monoxide, hydrogen sulfide and carbon dioxide. The heat-resistant resin poly(etherimide) has been selected as the polymer with the most outstanding properties for the separation of hydrogen from nitrogen and carbon monoxide. Flat sheet and hollow fiber poly(etherimide) membranes have been prepared and evaluated with pure gases and gas mixtures at elevated pressures and temperatures. Multilayer composite poly(ether-ester-amide) membranes were also developed. These membranes are useful for the separation of carbon dioxide and hydrogen sulfide hydrogen. They have very high selectivities and extremely high normalized carbon dioxide and hydrogen sulfide fluxes. Separation of carbon dioxide/hydrogen streams is a key problem in hydrogen production from coal. The development of the two membranes now gives us two approaches to separate these gas streams, depending on the stream's composition. If the stream contains small quantities of hydrogen, the hydrogen- permeable poly(etherimide) membrane would be used to produce a hydrogen-enriched permeate. If the stream contains small quantities of carbon dioxide or hydrogen sulfide, the poly(ether-ester-amide) membrane would be used to produce a carbon dioxide/hydrogen sulfide-free, hydrogen-enriched residue stream. 6 fig., 4 tabs.

  18. Influence of the atomic mass of the background gas on laser ablation plume propagation

    DEFF Research Database (Denmark)

    Amoruso, Salvatore; Schou, Jørgen; Lunney, James G.

    2008-01-01

    A combination of time-of-flight ion probe measurements and gas dynamical modeling has been used to investigate the propagation of a laser ablation plume in gases of different atomic/molecular weight. The pressure variation of the ion time-of-flight was found to be well described by the gas...... dynamical model of Predtechensky and Mayorov (Appl. Supercond. 1:2011, 1993). In particular, the model describes how the pressure required to stop the plume in a given distance depends on the atomic/molecular weight of the gas, which is a feature that cannot be explained by standard point...

  19. Effects of Carrier Gas Conditions on Concentration of Alcohol Aqueous Solution by Ultrasonic Atomization

    Science.gov (United States)

    Yasuda, Keiji; Tanaka, Naofumi; Rong, Lei; Nakamura, Masaaki; Li, Li; Oda, Akiyoshi; Kawase, Yasuhito

    2003-05-01

    The effects of carrier gas conditions on the concentration of ethanol by ultrasonic atomization are examined. With increasing height from vessel bottom to gas inlet and outlet, the ethanol content in the accompanied liquid increases and the flow rate of alcohol decreases. The ethanol content in the accompanied liquid becomes lower as the gas velocity becomes higher. The attachment of a demister is effective for the increase of the content in the accompanied liquid.

  20. Magnetic-field-driven localization of light in a cold-atom gas

    CERN Document Server

    Skipetrov, S E

    2014-01-01

    We discover a transition from extended to localized quasi-modes for light in a gas of immobile two-level atoms in a magnetic field. The transition takes place either upon increasing the number density of atoms in a strong field or upon increasing the field at a high enough density. It has many characteristic features of a disorder-driven (Anderson) transition but is strongly influenced by near-field interactions between atoms and the anisotropy of the atomic medium induced by the magnetic field.

  1. Interaction of atomic hydrogen with pico- and femtosecond laser pulses. Technical report

    Energy Technology Data Exchange (ETDEWEB)

    Parker, J.S.

    1989-12-01

    This thesis presents a theoretical study of the interaction of atomic hydrogen with coherent laser pulses in the 5 femtosecond to 10 picosecond range, in the weak-field limit, and in intense fields. We approach the problem in the weak-field limit by studying the relationship between the Fourier relation of the laser pulse (Delta omega Delta t) and the (Delta E Delta t) relation of the atomic Rydberg wave packet generated by the laser pulse. A derivation of the wave packet based on the WKB approximation is given, permitting the quantity Delta t to be derived for the quantum state, with the conclusion that under certain circumstances a transform-limited laser pulse (satisfying Delta omega Delta t = 1/2) can generate a transform-limited electron (satisfying Delta E Delta t/h = 1/2). A population-trapping effect is found numerically and modeled theoretically. Despite the high field intensities, population representing the excited electron is recaptured from the ionization continuum by bound states during the excitation. Population returns to the atom with just the right phase to strongly inhibit ionization. A theory is presented that models this effect for a variety of laser pulse shapes, with and without the rotating-wave approximation. The numerical integration reveals that a certain amount of above-threshold ionization (ATI) occurs.

  2. Effect of hydrogen atoms on the structures of trinuclear metal carbonyl clusters: trinuclear manganese carbonyl hydrides.

    Science.gov (United States)

    Liu, Xian-mei; Wang, Chao-yang; Li, Qian-shu; Xie, Yaoming; King, R Bruce; Schaefer, Henry F

    2009-05-18

    The structures of the trinuclear manganese carbonyl hydrides H(3)Mn(3)(CO)(n) (n = 12, 11, 10, 9) have been investigated by density functional theory (DFT). Optimization of H(3)Mn(3)(CO)(12) gives the experimentally known structure in which all carbonyl groups are terminal and each edge of a central Mn(3) equilateral triangle is bridged by a single hydrogen atom. This structure establishes the canonical distance 3.11 A for the Mn-Mn single bond satisfying the 18-electron rule. The central triangular (mu-H)(3)Mn(3) unit is retained in the lowest energy structure of H(3)Mn(3)(CO)(11), which may thus be derived from the H(3)Mn(3)(CO)(12) structure by removal of a carbonyl group with concurrent conversion of one of the remaining carbonyl groups into a semibridging carbonyl group to fill the resulting hole. The potential energy surface of H(3)Mn(3)(CO)(10) is relatively complicated with six singlet and five triplet structures. One of the lower energy H(3)Mn(3)(CO)(10) structures has one of the hydrogen atoms bridging the entire Mn(3) triangle and the other two hydrogen atoms bridging Mn-Mn edges. This H(3)Mn(3)(CO)(10) structure achieves the favored 18-electron configuration with a very short MnMn triple bond of 2.36 A. The other low energy H(3)Mn(3)(CO)(10) structure retains the (mu-H)(3)Mn(3) core of H(3)Mn(3)(CO)(12) but has a unique six-electron donor eta(2)-mu(3) carbonyl group bridging the entire Mn(3) triangle similar to the unique carbonyl group in the known compound Cp(3)Nb(3)(CO)(6)(eta(2)-mu(3)-CO). For H(3)Mn(3)(CO)(9) a structure with a central (mu(3)-H)(2)Mn(3) trigonal bipyramid lies >20 kcal/mol below any of the other structures. Triplet structures were found for the unsaturated H(3)Mn(3)(CO)(n) (n = 11, 10, 9) systems but at significantly higher energies than the lowest lying singlet structures.

  3. A Study of the Critical Nozzle for Flow Rate Measurement of High-Pressure Hydrogen Gas

    Institute of Scientific and Technical Information of China (English)

    H.D.Kim; J.H.Lee; K.A.Park; T.Setoguchi; S.Matsuo

    2007-01-01

    The mass flow rate measurement using a critical nozzle shows the validity of the inviscid theory, indicating that the discharge coefficient increases and approaches unity as the Reynolds number increases under the ideal gas law.However, when the critical nozzle measures the mass flow rate of a real gas such as hydrogen at a pressure of hundreds bar, the discharge coefficient exceeds unity, and the real gas effects should be taken into account. The present study aims at investigating the flow features of the critical nozzle using high-pressured hydrogen gas. The axisymmetric, compressible Navier-Stokes computation is employed to simulate the critical nozzle flow, and a fully implicit finite volume method is used to discretize the governing equation system. The real gas effects are simulated to consider the intermolecular forces, which account for the possibility of liquefying hydrogen gas. The computational results are compared with past experimental data. It has been found that the coefficient of discharge for real gas can be corrected properly below unity adopting the real gas assumption.

  4. The structure of radiative shock waves. III. The model grid for partially ionized hydrogen gas

    CERN Document Server

    Fadeyev, Y A; Fadeyev, Yu. A.

    2001-01-01

    The grid of the models of radiative shock waves propagating through partially ionized hydrogen gas with temperature 3000K <= T_1 <= 8000K and density 10^{-12} gm/cm^3 <= \\rho_1 <= 10^{-9}gm/cm^3 is computed for shock velocities 20 km/s <= U_1 <= 90 km/s. The fraction of the total energy of the shock wave irreversibly lost due to radiation flux ranges from 0.3 to 0.8 for 20 km/s <= U_1 <= 70 km/s. The postshock gas is compressed mostly due to radiative cooling in the hydrogen recombination zone and final compression ratios are within 1 <\\rho_N/\\rho_1 \\lesssim 10^2, depending mostly on the shock velocity U_1. The preshock gas temperature affects the shock wave structure due to the equilibrium ionization of the unperturbed hydrogen gas, since the rates of postshock relaxation processes are very sensitive to the number density of hydrogen ions ahead the discontinuous jump. Both the increase of the preshock gas temperature and the decrease of the preshock gas density lead to lower postsh...

  5. Hyperbaric oxygen therapy for the prevention of arterial gas embolism in food grade hydrogen peroxide ingestion.

    Science.gov (United States)

    Hendriksen, Stephen M; Menth, Nicholas L; Westgard, Bjorn C; Cole, Jon B; Walter, Joseph W; Masters, Thomas C; Logue, Christopher J

    2016-12-14

    Food grade hydrogen peroxide ingestion is a relatively rare presentation to the emergency department. There are no defined guidelines at this time regarding the treatment of such exposures, and providers may not be familiar with the potential complications associated with high concentration hydrogen peroxide ingestions. In this case series, we describe four patients who consumed 35% hydrogen peroxide, presented to the emergency department, and were treated with hyperbaric oxygen therapy. Two of the four patients were critically ill requiring intubation. All four patients had evidence on CT or ultrasound of venous gas emboli and intubated patients were treated as if they had an arterial gas embolism since an exam could not be followed. After hyperbaric oxygen therapy each patient was discharged from the hospital neurologically intact with no other associated organ injuries related to vascular gas emboli. Hyperbaric oxygen therapy is an effective treatment for patients with vascular gas emboli after high concentration hydrogen peroxide ingestion. It is the treatment of choice for any impending, suspected, or diagnosed arterial gas embolism. Further research is needed to determine which patients with portal venous gas emboli should be treated with hyperbaric oxygen therapy.

  6. Novel Applications of Buffer-gas Cooling to Cold Atoms, Diatomic Molecules, and Large Molecules

    Science.gov (United States)

    Drayna, Garrett Korda

    Cold gases of atoms and molecules provide a system for the exploration of a diverse set of physical phenomena. For example, cold gasses of magnetically and electrically polar atoms and molecules are ideal systems for quantum simulation and quantum computation experiments, and cold gasses of large polar molecules allow for novel spectroscopic techniques. Buffer-gas cooling is a robust and widely applicable method for cooling atoms and molecules to temperatures of approximately 1 Kelvin. In this thesis, I present novel applications of buffer-gas cooling to obtaining gases of trapped, ultracold atoms and diatomic molecules, as well as the study of the cooling of large organic molecules. In the first experiment of this thesis, a buffer-gas beam source of atoms is used to directly load a magneto-optical trap. Due to the versatility of the buffer-gas beam source, we obtain trapped, sub-milliKelvin gases of four different lanthanide species using the same experimental apparatus. In the second experiment of this thesis, a buffer-gas beam is used as the initial stage of an experiment to directly laser cool and magneto-optically trap the diatomic molecule CaF. In the third experiment of this thesis, buffer-gas cooling is used to study the cooling of the conformational state of large organic molecules. We directly observe conformational relaxation of gas-phase 1,2-propanediol due to cold collisions with helium gas. Lastly, I present preliminary results on a variety of novel applications of buffer-gas cooling, such as mixture analysis, separation of chiral mixtures, the measurement of parity-violation in chiral molecules, and the cooling and spectroscopy of highly unstable reaction intermediates.

  7. 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.

  8. Microbial electrolysis cells for high yield hydrogen gas production from organic matter.

    Science.gov (United States)

    Logan, Bruce E; Call, Douglas; Cheng, Shaoan; Hamelers, Hubertus V M; Sleutels, Tom H J A; Jeremiasse, Adriaan W; Rozendal, René A

    2008-12-01

    The use of electrochemically active bacteria to break down organic matter, combined with the addition of a small voltage (> 0.2 V in practice) in specially designed microbial electrolysis cells (MECs), can result in a high yield of hydrogen gas. While microbial electrolysis was invented only a few years ago, rapid developments have led to hydrogen yields approaching 100%, energy yields based on electrical energy input many times greater than that possible by water electrolysis, and increased gas production rates. MECs used to make hydrogen gas are similar in design to microbial fuel cells (MFCs) that produce electricity, but there are important differences in architecture and analytical methods used to evaluate performance. We review here the materials, architectures, performance, and energy efficiencies of these MEC systems that show promise as a method for renewable and sustainable energy production, and wastewater treatment.

  9. Self-heated silicon nanowires for high performance hydrogen gas detection

    Science.gov (United States)

    Ahn, Jae-Hyuk; Yun, Jeonghoon; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu

    2015-03-01

    Self-heated silicon nanowire sensors for high-performance, ultralow-power hydrogen detection have been developed. A top-down nanofabrication method based on well-established semiconductor manufacturing technology was utilized to fabricate silicon nanowires in wafer scale with high reproducibility and excellent compatibility with electronic readout circuits. Decoration of palladium nanoparticles onto the silicon nanowires enables sensitive and selective detection of hydrogen gas at room temperature. Self-heating of silicon nanowire sensors allows us to enhance response and recovery performances to hydrogen gas, and to reduce the influence of interfering gases such as water vapor and carbon monoxide. A short-pulsed heating during recovery was found to be effective for additional reduction of operation power as well as recovery characteristics. This self-heated silicon nanowire gas sensor will be suitable for ultralow-power applications such as mobile telecommunication devices and wireless sensing nodes.

  10. Microbial Electrolysis Cells for High Yield Hydrogen Gas Production from Organic Matter

    KAUST Repository

    Logan, Bruce E.

    2008-12-01

    The use of electrochemically active bacteria to break down organic matter, combined with the addition of a small voltage (>0.2 V in practice) in specially designed microbial electrolysis cells (MECs), can result in a high yield of hydrogen gas. While microbial electrolysis was invented only a few years ago, rapid developments have led to hydrogen yields approaching 100%, energy yields based on electrical energy input many times greater than that possible by water electrolysis, and increased gas production rates. MECs used to make hydrogen gas are similar in design to microbial fuel cells (MFCs) that produce electricity, but there are important differences in architecture and analytical methods used to evaluate performance. We review here the materials, architectures, performance, and energy efficiencies of these MEC systems that show promise as a method for renewable and sustainable energy production, and wastewater treatment. © 2008 American Chemical Society.

  11. Steam Reforming of Dimethyl Ether by Gliding Arc Gas Discharge Plasma for Hydrogen Production

    Institute of Scientific and Technical Information of China (English)

    王保伟; 孙启梅; 吕一军; 杨美琳; 闫文娟

    2014-01-01

    Gliding arc gas discharge plasma was used for the generation of hydrogen from steam reforming of di-methyl ether (DME). A systemic procedure was employed to determine the suitable experimental conditions. It was found that DME conversion first increased up to the maximum and then decreased slightly with the increase of added water and air. The increase of total feed gas flow rate resulted in the decrease of DME conversion and hy-drogen yield, but hydrogen energy consumption dropped down to the lowest as total feed gas flow rate increased to 76 ml·min-1. Larger electrode gap and higher discharge voltage were advantageous. Electrode shape had an impor-tant effect on the conversion of DME and production of H2. Among the five electrodes, electrode 2# with valid length of 55 mm and the radian of 34 degrees of the top electrode section was the best option, which enhanced ob-viously the conversion of DME.

  12. Stationary inverted Lyman population formed from incandescently heated hydrogen gas with certain catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Randell L; Ray, Paresh C; Mayo, Robert M [BlackLight Power, Inc., 493 Old Trenton Road, Cranbury, NJ 08512 (United States)

    2003-07-07

    A new chemically generated plasma source is reported. The presence of gaseous Rb{sup +} or K{sup +} ions with thermally dissociated hydrogen formed a low applied temperature, extremely low voltage plasma called a resonant transfer or rt-plasma having strong vacuum ultraviolet emission. We propose an energetic catalytic reaction involving a resonant energy transfer between hydrogen atoms and Rb{sup +} or 2K{sup +} since Rb{sup +} to Rb{sup 2+}, 2K{sup +} to K + K{sup 2+}, and K to K{sup 3+} each provide a reaction with a net enthalpy equal to the potential energy of atomic hydrogen. Remarkably, a stationary inverted Lyman population was observed; thus, these catalytic reactions may pump a cw HI laser as predicted by a collisional radiative model used to determine that the observed overpopulation was above threshold.

  13. Comparison of hydrogen gas embrittlement of austenitic and ferritic stainless steels

    Science.gov (United States)

    Perng, T. P.; Altstetter, C. J.

    1987-01-01

    Hydrogen-induced slow crack growth (SCG) was compared in austenitic and ferritic stainless steels at 0 to 125 °Cand 11 to 216 kPa of hydrogen gas. No SCG was observed for AISI 310, while AISI 301 was more susceptible to hydrogen embrittlement and had higher cracking velocity than AL 29-4-2 under the same test conditions. The kinetics of crack propagation was modeled in terms of the hydrogen transport in these alloys. This is a function of temperature, microstructure, and stress state in the embrittlement region. The relatively high cracking velocity of AISI 301 was shown to be controlled by the fast transport of hydrogen through the stress-induced α' martensite at the crack tip and low escape rate of hydrogen through the γ phase in the surrounding region. Faster accumulation rates of hydrogen in the embrittlement region were expected for AISI 301, which led to higher cracking velocities. The mechanism of hydrogen-induced SCG was discussed based upon the concept of hydrogen-enhanced plasticity.

  14. Galaxy Zoo and ALFALFA: Atomic Gas and the Regulation of Star Formation in Barred Disc Galaxies

    CERN Document Server

    Masters, Karen L; Haynes, Martha P; Keel, William C; Lintott, Chris; Simmons, Brooke; Skibba, Ramin; Bamford, Steven; Giovanelli, Riccardo; Schawinski, Kevin

    2012-01-01

    We study the observed correlation between atomic gas content and the likelihood of hosting a large scale bar in a sample of 2090 disc galaxies. Such a test has never been done before on this scale. We use data on morphologies from the Galaxy Zoo project and information on the galaxies' HI content from the ALFALFA blind HI survey. Our main result is that the bar fraction is significantly lower among gas rich disc galaxies than gas poor ones. This is not explained by known trends for more massive (stellar) and redder disc galaxies to host more bars and have lower gas fractions: we still see at fixed stellar mass a residual correlation between gas content and bar fraction. We discuss three possible causal explanations: (1) bars in disc galaxies cause atomic gas to be used up more quickly, (2) increasing the atomic gas content in a disc galaxy inhibits bar formation, and (3) bar fraction and gas content are both driven by correlation with environmental effects (e.g. tidal triggering of bars, combined with strangu...

  15. Combustion characteristics of natural gas-hydrogen hybrid fuel turbulent diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    El-Ghafour, S.A.A.; El-dein, A.H.E.; Aref, A.A.R. [Mechanical Power Engineering Department, Faculty of Engineering, Suez Canal University, Port-Said (Egypt)

    2010-03-15

    Combustion characteristics of natural gas - hydrogen hybrid fuel were investigated experimentally in a free jet turbulent diffusion flame flowing into a slow co-flowing air stream. Experiments were carried out at a constant jet exit Reynolds number of 4000 and with a wide range of NG-H{sub 2} mixture concentrations, varied from 100%NG to 50%NG-50% H{sub 2} by volume. The effect of hydrogen addition on flame stability, flame length, flame structure, exhaust species concentration and pollutant emissions was conducted. Results showed that, hydrogen addition sustains a progressive improvement in flame stability and reduction in flame length, especially for relatively high hydrogen concentrations. Hydrogen-enriched flames found to have a higher combustion temperatures and reactivity than natural gas flame. Also, it was found that hydrogen addition to natural gas is an ineffective strategy for NO and CO reduction in the studied range, while a significant reduction in the %CO{sub 2} molar concentration by about 30% was achieved. (author)

  16. Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

    Energy Technology Data Exchange (ETDEWEB)

    Dadfarnia, Mohsen (University of Illinois at Urbana-Champaign, Urbana, IL); Nibur, Kevin A.; San Marchi, Christopher W.; Sofronis, Petros (University of Illinois at Urbana-Champaign, Urbana, IL); Somerday, Brian P.; Foulk, James W., III; Hayden, Gary A. (CP Industries, McKeesport, PA)

    2010-07-01

    Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} is the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.

  17. Gasification of oil shale for hydrogen containing gas production

    Energy Technology Data Exchange (ETDEWEB)

    Lapidus, A.L. [I.M. Gubkin Russian State Univ. of Oil and Gas, Moscow (Russian Federation); United Research and Development Center Ltd., Moscow (Russian Federation); Strizhakova, Yu. [Samara State Technical Univ. (Russian Federation); Zhagfarov, F.G.; Usova, T.; Avakyan, T. [I.M. Gubkin Russian State Univ. of Oil and Gas, Moscow (Russian Federation)

    2010-12-30

    Qualified using of combustible shale, peat and wood for production of fuel and chemical products is a very actual problem for our country because of their large resource. It is possible to carry out two principal different ways of their use: thermal processing and gasification with following processing of gas products. Production of synthesis gas with composition CO:H{sub 2}=1:2 (vol) is possible at gasification of combustible shale. This gas is converted into the mixture of hydrocarbons over cobalt catalysts at 170-280 C at 1-3 bar. The hydrocarbons can be used as motor, including diesel, or reactive fuel. We proposed the effective catalysts at which conversion of synthesis gas in liquid products equals 80-90%. (orig.)

  18. Real gas CFD simulations of hydrogen/oxygen supercritical combustion

    Science.gov (United States)

    Pohl, S.; Jarczyk, M.; Pfitzner, M.; Rogg, B.

    2013-03-01

    A comprehensive numerical framework has been established to simulate reacting flows under conditions typically encountered in rocket combustion chambers. The model implemented into the commercial CFD Code ANSYS CFX includes appropriate real gas relations based on the volume-corrected Peng-Robinson (PR) equation of state (EOS) for the flow field and a real gas extension of the laminar flamelet combustion model. The results indicate that the real gas relations have a considerably larger impact on the flow field than on the detailed flame structure. Generally, a realistic flame shape could be achieved for the real gas approach compared to experimental data from the Mascotte test rig V03 operated at ONERA when the differential diffusion processes were only considered within the flame zone.

  19. Gas Phase Fabrication of Pd-Ni Nanoparticle Arrays for Hydrogen Sensor Applications

    Directory of Open Access Journals (Sweden)

    Peng Xing

    2015-01-01

    Full Text Available Pd-Ni nanoparticles have been fabricated by gas aggregation process. The formation of Pd-Ni nano-alloys was confirmed by X-ray photoelectron spectroscopy measurements. By depositing Pd-Ni nanoparticles on the interdigital electrodes, quantum conductance-based hydrogen sensors were fabricated. The Ni content in the nanoparticle showed an obvious effect on the hydrogen response behavior corresponding to the conductance change of the nanoparticle film. Three typical response regions with different conductance-hydrogen pressure correlations were observed. It was found that the α-β phase transition region of palladium hydride moves to significant higher hydrogen pressure with the addition of nickel element, which greatly enhance the hydrogen sensing performance of the nanoparticle film.

  20. Commissioning of the cryogenic hydrogen system in J-PARC: Preliminary operation by helium gas

    CERN Document Server

    Aso, T; Hasegawa, S; Ohtsu, K; Uehara, T; Kawakami, Y; Sakurayama, H; Maekawa, F; Futakawa, M; Ushijima, I

    2009-01-01

    A cryogenic hydrogen circulation system to cool the moderators for the spallation neutron source in J-PARC has been constructed. This system provides supercritical hydrogen at the temperature of 20 K and the pressure of 1.5 MPa to three moderators and absorbs nuclear heating produced in the moderators. The cryogenic hydrogen system commissioning was started. In January 2008, for the first time, we carried out a cryogenic test of the whole system, in which helium gas was used in stead of hydrogen. The cryogenic hydrogen system can be cooled down to 18 K within 30 hours, and be kept to be the rated condition for 36 hours without any problems. We confirmed the soundness of each component such as circulation pump and operation control system.