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.

Polarization measurement of atomic hydrogen beam spin-exchanged with optically oriented sodium atoms

International Nuclear Information System (INIS)

Ueno, Akira; Ogura, Kouichi; Wakuta, Yoshihisa; Kumabe, Isao

1988-01-01

The spin-exchange reaction between hydrogen atoms and optically oriented sodium atoms was used to produce a polarized atomic hydrogen beam. The electron-spin polarization of the atomic hydrogen beam, which underwent the spin-exchange reaction with the optically oriented sodium atoms, was measured. A beam polarization of -(8.0±0.6)% was obtained when the thickness and polarization of the sodium target were (5.78±0.23)x10 13 atoms/cm 2 and -(39.6±1.6)%, respectively. The value of the spin-exchange cross section in the forward scattering direction, whose scattering angle in the laboratory system was less than 1.0 0 , was obtained from the experimental results as Δσ ex =(3.39±0.34)x10 -15 cm 2 . This value is almost seven times larger than the theoretical value calculated from the Na-H potential. The potential was computed quantum mechanically in the space of the appropriate wave functions of the hydrogen and the sodium atoms. (orig./HSI)

Atom probe tomography of a commercial light emitting diode

International Nuclear Information System (INIS)

Larson, D J; Prosa, T J; Olson, D; Lawrence, D; Clifton, P H; Kelly, T F; Lefebvre, W

2013-01-01

The atomic-scale analysis of a commercial light emitting diode device purchased at retail is demonstrated using a local electrode atom probe. Some of the features are correlated with transmission electron microscopy imaging. Subtle details of the structure that are revealed have potential significance for the design and performance of this device

Atomic hydrogen effects on high-Tc superconductors

International Nuclear Information System (INIS)

Frantskevich, N.V.; Ulyashin, A.G.; Alifanov, A.V.; Stepanenko, A.V.; Fedotova, V.V.

1999-01-01

The atomic hydrogen effects on the properties of bulk high-temperature superconductors were investigated. It is shown that the insertion of the atomic hydrogen into the bulk of these materials from a DC plasma leads to the increase of the critical current density J c for YBaCuO(123) as well as for BiSrCaCuO(2223) high-temperature superconductors. It is found that the hydrogenation of the He implanted samples with following annealing leads to the optically detected blistering on the surface. It means that the textured thin subsurface layers of high-temperature superconductors can be formed by this method. The improvement of superconductivity by atomic hydrogen can be explained by the passivation of dangling bonds and defects on grain boundaries of these materials

The CERN polarized atomic hydrogen beam target project

International Nuclear Information System (INIS)

Kubischta, W.; Dick, L.

1990-01-01

The UA6-experiment at the CERN p bar p Colider is at present using an unpolarized hydrogen cluster target with a thickness up to 5.10 14 atoms/cm 2 . It is planned to replace this target by a polarized atomic hydrogen beam target with a thickness up to about 10 13 atoms/cm 2 . This paper discusses basic requirements and results of atom optical calculations

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.

Atomic-scale observation of hydrogen-induced crack growth by atom-probe FIM

International Nuclear Information System (INIS)

Kuk, Y.; Pickering, H.W.; Sakurai, T.

1980-01-01

Formation and propagation of a microcrack due to hydrogen in a Fe-0.29 wt.% Ti alloy was observed at the atomic scale by field ion microscopy. A microcrack (-20 nm in length) formed and became noticeably large when the tip was heated at 950 0 C in the presence of about 1 torr of Hg. Propagation was reported several times by reheating, until a portion of the tip ruptured and became detached from the tip. Compositional analysis, performed in situ using a high performance atom-probe, identified atomic hydrogen in quantity and some hydrogen molecules and FEH in the crack, but not elsewhere on the surface

Atomic hydrogen determination in medium-pressure microwave discharge hydrogen plasmas via emission actinometry

International Nuclear Information System (INIS)

Geng Zicai; Xu Yong; Yang Xuefeng; Wang Weiguo; Zhu Aimin

2005-01-01

Atomic hydrogen plays an important role in the chemical vapour deposition of functional materials, plasma etching and new approaches to the chemical synthesis of hydrogen-containing compounds. This work reports experimental determinations of atomic hydrogen in microwave discharge hydrogen plasmas formed from the TM 01 microwave mode in an ASTeX-type reactor, via optical emission spectroscopy using Ar as an actinometer. The relative intensities of the H atom Balmer lines and Ar-750.4 nm emissions as functions of input power and gas pressure have been investigated. At an input microwave power density of 13.5 W cm -3 , the approximate hydrogen dissociation fractions calculated from electron-impact excitation and quenching cross sections in the literature, decreased from ∼0.08 to ∼0.03 as the gas pressure was increased from 5 to 25 Torr. The influences of the above cross sections, and the electron and gas temperatures of the plasmas on the determination of the hydrogen dissociation fraction data have been discussed

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....

Atlas cross section for scattering of muonic hydrogen atoms on hydrogen isotope molecules

International Nuclear Information System (INIS)

Adamczak, A.; Faifman, M.P.; Ponomarev, L.I.

1996-01-01

The total cross sections of the elastic, spin-flip, and charge-exchange processes for the scattering of muonic hydrogen isotope atoms (pμ, dμ, tμ) in the ground state on the hydrogen isotope molecules (H 2 , D 2 , T 2 , HD, HT, DT) are calculated. The scattering cross sections of muonic hydrogen isotope atoms on hydrogen isotope nuclei obtained earlier in the multichannel adiabatic approach are used in the calculations. Molecular effects (electron screening, rotational and vibrational excitations of target molecules, etc.) are taken into account. The spin effects of the target molecules and of the incident muonic atoms are included. the cross sections are averaged over the Boltzmann distribution of the molecule rotational states and the Maxwellian distribution of the target molecule kinetic energies for temperatures 30, 100, 300, and 1000 K. The cross sections are given for kinetic energies of the incident muonic atoms ranging from 0.001 to 100 eV in the laboratory frame. 45 refs., 6 tabs

Complex operator method of the hydrogen atom

International Nuclear Information System (INIS)

Jiang, X.

1989-01-01

Frequently the hydrogen atom eigenvalue problem is analytically solved by solving a radial wave equation for a particle in a Coulomb field. In this article, complex coordinates are introduced, and an expression for the energy levels of the hydrogen atom is obtained by means of the algebraic solution of operators. The form of this solution is in accord with that of the analytical solution

Interaction of GaN epitaxial layers with atomic hydrogen

Energy Technology Data Exchange (ETDEWEB)

Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S

2004-08-15

GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H{sub 2} plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states.

Interaction of GaN epitaxial layers with atomic hydrogen

International Nuclear Information System (INIS)

Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S.

2004-01-01

GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H 2 plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states

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.

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

International Nuclear Information System (INIS)

Nakano, H.; Goto, M.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Nishiyama, S.; Sasaki, K.

2015-01-01

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

Hydrogen atom model for nucleon and pion

International Nuclear Information System (INIS)

Baiquni, A.

1976-01-01

Discussion on Dion as double charge particle, covering that on semi classical model, proton Dionium model consequence, symmetry group in hydrogen, hydrogen atom dynamic group, and discussion on relativistic dynamic group, covering relativistic equation for hydrogen, operator extension of SO(4, 2), application of SO(4,2)O SO(4,2), and hydrogen complete equation, are given. (author)

Gravitational perturbations of the hydrogen atom

International Nuclear Information System (INIS)

Parker, L.

1983-01-01

The strength of a gravitational field is characterized by the Riemann curvature tensor. It is of interest to know how the curvature of space-time at the position of an atom affects its spectrum. The author gives a brief summary of work on the effects of curvature on the hydrogen atom. The results refer to an arbitrary metric and can be evaluated for particular space-times of interest. The possibility of using the effect of gravitational waves on the electromagnetic spectrum of hydrogen as a means of detecting gravitational waves is also investigated. (Auth.)

Matrix effect on hydrogen-atom tunneling of organic molecules in cryogenic solids

International Nuclear Information System (INIS)

Ichikawa, Tsuneki

2000-01-01

Although the tunneling of atoms through potential energy barriers separating the reactant and reaction systems is not paid much attention in organic reactions, this plays an important role in reactions including the transfer of light atoms. Atomic tunneling is especially important for chemical reactions at low temperatures, since the thermal activation of reactant systems is very slow process in comparison with the tunneling. One of the typical reactions of atomic tunneling is hydrogen-atom abstraction from alkanes in cryogenic solids exposed to high-energy radiation. Irradiation of alkane molecules causes the homolytic cleavage of C-H bonds, which results in the pairwise formation of free hydrogen atoms and organic free radicals. Since the activation energies for the abstraction of hydrogen atoms from alkane molecules by free hydrogen atoms are higher than 5 kcal/mol, the lifetime of free hydrogen atoms at 77 K is estimated from the Arrhenius equation of k=vexp(-E a /RT) to be longer than 10 hrs. However, except for solid methane, free hydrogen atoms immediately convert to alkyl radicals even at 4.2 K by hydrogen-atom tunneling from alkane molecules to the free hydrogen atoms. The rate of hydrogen atom tunneling does not necessary increase with decreasing activation energy or the peak height of the potential energy barrier preventing the tunneling. Although the activation energy is the lowest at the tertiary carbon of alkanes, hydrogen atom tunneling from branched alkanes with tertiary carbon at the antepenultimate position of the carbon skeleton is the fastest at the secondary penultimate carbon. Based on our experimental results, we have proposed that the peculiarity of the hydrogen-atom abstraction in cryogenic solids comes from the steric hindrance by matrix molecules to the deformation of alkane molecules from the initial sp 3 to the final sp 2 configurations. The steric hindrance causes the increase of the height of the potential energy barrier for the

Chemical reduction of refractory oxides by atomic hydrogen

International Nuclear Information System (INIS)

Dooley, D.; Balooch, M.; Olander, D.R.

1978-11-01

The chemical reduction of UO 2 and Al 2 O 3 by atomic hydrogen was studied. Results of the UO 2 /H investigation indicates that reduction of UO 2 by atomic hydrogen proceeds by the production of water vapor and hypostoichiometric urania. Water vapor and aluminum metal are formed in the Al 2 O 3 /H system. The relative ease which UO 2 is reduced by atomic hydrogen compared with Al 2 O 3 is due to two factors. The first is related to the thermochemistry of the reactions. The second factor which favors efficient reduction of UO 2 but not of Al 2 O 3 is the oxygen diffusivity

High efficiency atomic hydrogen source

International Nuclear Information System (INIS)

Lagomarsino, V.; Bassi, D.; Bertok, E.; De Paz, M.; Tommasini, F.

1974-01-01

This work presents preliminary results of research intended to produce a M.W. discharge atomic hydrogen source with good dissociation at pressures larger than 10 torr. Analysis of the recombination process at these pressures shows that the volume recombination by three body collisions may be more important than wall recombination or loss of atoms by diffusion and flow outside the discharge region

Properties of the localized field emitted from degenerate Λ-type atoms in photonic crystals

International Nuclear Information System (INIS)

Foroozani, N.; Golshan, M. M.; Mahjoei, M.

2007-01-01

The spontaneous emission from a degenerate Λ-type three-level atom, embedded in a photonic crystal, is studied. The emitted field, as a function of time and position, is calculated by solving the three coupled differential equations governing the amplitudes. We show that the spontaneously emitted field is characterized by three components (as in the case of two-level and V-type atoms): a localized part, a traveling part, and a t -3/2 decaying part. Our calculations indicate that under specific conditions the atoms do not emit propagating fields, while the localized field, having shorter localization length and time, is intensified. As a consequence, the population of the upper level, after a short period of oscillations, approaches a constant value. It is also shown that this steady value, under the same conditions, is much larger than its counterpart in V-type atoms

About connection between atomic and hydrogen energy power

International Nuclear Information System (INIS)

Avdeeva, M.Zh.; Vecher, A.A.; Pan'kov, V.V.

2008-01-01

Possible interaction between atomic and hydrogen energy power has been discussed. The analysis of the result held shows that the electrical energy produced by the atomic reactor during the of-load hours can be involved into the process of obtaining hydrogen by electrolysis. In order to optimize the transportation and storage of hydrogen it is proposed to convert it into ammonia. The direct uses of ammonia as a fuel into the internal combustion engine and fuel cells are examined. (authors)

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]....

Interactions of atomic hydrogen with amorphous SiO2

Science.gov (United States)

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

2018-03-01

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

Interaction of atomic hydrogen with ethylene adsorbed on nickel films

International Nuclear Information System (INIS)

Korchak, V.N.; Tret'yakov, I.I.; Kislyuk, M.U.

1976-01-01

The reactivity of ethylene adsorbed on the pure films of nickel at various temperatures was studied with respect to hydrogen atoms generated in the gaseous phase. The experiments were conducted in a glass vacuum apparatus enabling one to obtain the highest vacuum up to 2x20 -10 torr. The catalyst, nickel films, was produced by their deposition onto the walls of the glass reactor at a pressure of the residual gas of 10 -9 torr and a temperature of the walls of 25 deg C. Gas purity was analyzed by the mass spectrometric method. The ethylene adsorbed at the temperatures below 173 deg K reacted readily with the hydrogen atoms to yield ethane. The process ran without practically any activation energy involved and was limited by the attachment of the first hydrogen atom to the ethylene molecule. The efficiency of this interaction was 0.02 of the number of the hydrogen atoms collisions against the surface occupied by the ethylene. The adsorption of the ethylene at room and higher temperatures was accompanied by its disproportioning with the release of the hydrogen into the gaseous phase and a serious destruction of the ethylene molecules adsorbed to produce hydrogen residues interacting with neither molecular nor atomic hydrogen [ru

Precision spectroscopy on atomic hydrogen

International Nuclear Information System (INIS)

Parthey, Christian Godehard

2011-01-01

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 Δ∫ exp =670 994 334 606(15) Hz. Comparing with the theoretical value for the isotope shift, excluding the leading nuclear size effect, Δ∫ 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 2 right angle d - left angle r 2 right angle p =3.82007(65) fm 2 and the deuteron structure radius r 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 ∫ 1S-2S =2 466 061 413 187 035 (10) Hz which presents a fractional frequency uncertainty of 4.2 x 10 -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 ∫ 1S-2S =2 466 061 413 187 017 (11) Hz we can put a constraint on the electron Lorentz boost violating coefficients 0.95c (TX) -0.29c (TY) -0.08 c (TZ) =(2.2±1.8) x 10 -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 (∂)/(∂t)ln (μ Cs )/(μ B )=-(3.0±1.2) x 10 -15 yr -1 .

Atomic capture of negative mesons in hydrogen

International Nuclear Information System (INIS)

Leon, M.

1979-01-01

After a brief description of the present state of theoretical understanding of atomic capture of negative mesons, a very simple model calculation of negative muon capture by the simplest atoms, hydrogen is described. Also the possibility of generalizing these results to more complicated atoms and even molecules is noted. 15 references

Production of hyperthermal hydrogen atoms by an arc discharge

International Nuclear Information System (INIS)

Samano, E.C.

1993-01-01

A magnetically confined thermal electric arc gas heater has been designed and built as a suitable source of heat for dissociating hydrogen molecules with energy in the range of a few eV. Specifically, the average beam kinetic energy is determined to be 1.5 eV, the dissociation rate is 0.5 atoms per molecule and the atom beam intensity in the forward direction is 1018 atoms/sr-sec. The working pressure in the arc discharge region is from 15 to 25 torr. This novel atom source has been successfully ignited and operated with pure hydrogen during several hours of continuous performance, maintaining its characteristics. The hyperthermal hydrogen atom beam, which is obtained from this source is analyzed and characterized in a high vacuum system, the characterization of the atom beam is accomplished by two different methods: calorimetry and surface ionization. Calorimetic sensor were used for detecting the atom beam by measuring the delivered power of the impinging atoms on the sensor surface. In the second approach an H-surface production backscattering experiment from a low work function surface was conducted. The validity of these two methods is discussed, and the results are compared. The different collision mechanisms to dissociate and ionize hydrogen molecules in the arch discharge are reviewed, as well as the physics of electric arcs. Finally, a Monte Carlo simulation program is used to calculate the ionization probability of low energy atoms perpendicularly reflected from a surface converter, as a model for atom surface ionization

Spectroscopic studies of hydrogen atom and molecule collisions: Performance report

International Nuclear Information System (INIS)

Kielkopf, J.

1986-01-01

This research is concerned with spectroscopic measurements of collisions in atomic and molecular hydrogen in order to clarify the basic physical processes that take place during radiative collisions and to provide experimental values for systems where the theoretical analysis is tractable. To this end, we proposed to measure from the cores to the far wings the profiles of the spectral lines of atomic hydrogen broadened by molecular hydrogen and noble gases, and to study energy transfer in the atom and molecule

Trapping hydrogen atoms from a neon-gas matrix: a theoretical simulation.

Science.gov (United States)

Bovino, S; Zhang, P; Kharchenko, V; Dalgarno, A

2009-08-07

Hydrogen is of critical importance in atomic and molecular physics and the development of a simple and efficient technique for trapping cold and ultracold hydrogen atoms would be a significant advance. In this study we simulate a recently proposed trap-loading mechanism for trapping hydrogen atoms released from a neon matrix. Accurate ab initio quantum calculations are reported of the neon-hydrogen interaction potential and the energy- and angular-dependent elastic scattering cross sections that control the energy transfer of initially cold atoms are obtained. They are then used to construct the Boltzmann kinetic equation, describing the energy relaxation process. Numerical solutions of the Boltzmann equation predict the time evolution of the hydrogen energy distribution function. Based on the simulations we discuss the prospects of the technique.

Theoretical aspects of the stabilization of atomic hydrogen

International Nuclear Information System (INIS)

Eijnde, J.P.H.W. van den.

1984-01-01

This thesis describes a theoretical study of processes leading to recombination of hydrogen atoms into molecular form. A relaxation process, due to the transition among the lowest two hyperfine levels of atomic hydrogen, turns out to be of fundamental importance for the recombination rate. Models have been formulated to calculate the relaxation rate by means of quantum mechanical scattering theory. For processes in the bulk of the gas the results of an almost exact coupled-channels calculation have been compared with approximate models. In these models first-order approximations are applied, as well as approximations connected with the large distance of closest approach of the colliding hydrogen atoms. The assumptions turned out to be correct to the promille level, except for the so-called high-temperature limit. (Auth.)

Analysis of angular momentum properties of photons emitted in fundamental atomic processes

Science.gov (United States)

Zaytsev, V. A.; Surzhykov, A. S.; Shabaev, V. M.; Stöhlker, Th.

2018-04-01

Many atomic processes result in the emission of photons. Analysis of the properties of emitted photons, such as energy and angular distribution as well as polarization, is regarded as a powerful tool for gaining more insight into the physics of corresponding processes. Another characteristic of light is the projection of its angular momentum upon propagation direction. This property has attracted a special attention over the past decades due to studies of twisted (or vortex) light beams. Measurements being sensitive to this projection may provide valuable information about the role of angular momentum in the fundamental atomic processes. Here we describe a simple theoretical method for determination of the angular momentum properties of the photons emitted in various atomic processes. This method is based on the evaluation of expectation value of the total angular momentum projection operator. To illustrate the method, we apply it to the textbook examples of plane-wave, spherical-wave, and Bessel light. Moreover, we investigate the projection of angular momentum for the photons emitted in the process of the radiative recombination with ionic targets. It is found that the recombination photons do carry a nonzero projection of the orbital angular momentum.

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}.

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.

Laser driven source of spin polarized atomic deuterium and hydrogen

International Nuclear Information System (INIS)

Poelker, M.; Coulter, K.P.; Holt, R.J.

1993-01-01

Optical pumping of potassium atoms in the presence of a high magnetic field followed by spin exchange collisions with deuterium (hydrogen) is shown to yield a high flux of spin polarized atomic deuterium (hydrogen). The performance of the laser driven source has been characterized as a function of deuterium (hydrogen) flow rate, potassium density, pump laser power, and magnetic field. Under appropriate conditions, the authors have observed deuterium atomic polarization as high as 75% at a flow rate 4.2x10 17 atoms/second. Preliminary results suggest that high nuclear polarizations are obtained in the absence of weak field rf transitions as a result of a spin temperature distribution that evolves through frequent H-H (D-D) collisions

Self-consistent collisional-radiative model for hydrogen atoms: Atom–atom interaction and radiation transport

International Nuclear Information System (INIS)

Colonna, G.; Pietanza, L.D.; D’Ammando, G.

2012-01-01

Graphical abstract: Self-consistent coupling between radiation, state-to-state kinetics, electron kinetics and fluid dynamics. Highlight: ► A CR model of shock-wave in hydrogen plasma has been presented. ► All equations have been coupled self-consistently. ► Non-equilibrium electron and level distributions are obtained. ► The results show non-local effects and non-equilibrium radiation. - Abstract: A collisional-radiative model for hydrogen atom, coupled self-consistently with the Boltzmann equation for free electrons, has been applied to model a shock tube. The kinetic model has been completed considering atom–atom collisions and the vibrational kinetics of the ground state of hydrogen molecules. The atomic level kinetics has been also coupled with a radiative transport equation to determine the effective adsorption and emission coefficients and non-local energy transfer.

Inelastic Transitions in Slow Collisions of Anti-Hydrogen with Hydrogen Atoms

Science.gov (United States)

Harrison, Robert; Krstic, Predrag

2007-06-01

We calculate excited adiabatic states and nonadiabatic coupling matrix elements of a quasimolecular system containing hydrogen and anti-hydrogen atoms, for a range of internuclear distances from 0.2 to 20 Bohrs. High accuracy is achieved by exact diagonalization of the molecular Hamiltionian in a large Gaussian basis. Nonadiabatic dynamics was calculated by solving MOCC equations. Positronium states are included in the consideration.

Infrared studies of ortho-para conversion at Cl-atom and H-atom impurity centers in cryogenic solid hydrogen

International Nuclear Information System (INIS)

Raston, P.L.; Kettwich, S.C.; Anderson, D.T.

2010-01-01

We report infrared spectroscopic studies of H 2 ortho-para (o/p) conversion in solid hydrogen doped with Cl-atoms at 2 K while the Cl + H 2 (υ = 1) → HCl + H infrared-induced chemical reaction is occurring. The Cl-atom doped hydrogen crystals are synthesized using 355 nm in situ photodissociation of Cl 2 precursor molecules. For hydrogen solids with high ortho-H 2 fractional concentrations (X o = 0.55), the o/p conversion kinetics is dominated by Cl-atom catalyzed conversion with a catalyzed conversion rate constant K cc = 1.16(11) min -1 and the process is rate-limited by ortho-H 2 quantum diffusion. For hydrogen crystals with low ortho-H2 concentrations (X o = 0.03), single-exponential decay of the ortho-H 2 concentration with time is observed which is attributed to H-atom catalyzed o/p conversion by the H-atoms produced during the infrared-induced Cl + H 2 reaction. The measured H-atom catalyzed o/p conversion kinetics indicates the H-atoms are mobile under these conditions in agreement with previous ESR measurements.

Hydrogen atom as test field of theoretical models

International Nuclear Information System (INIS)

Baiquni, A.

1976-01-01

Semi classical theory, covering Bohr atom theory, Bohr Sommerfeld theory, Sommerfeld relativistic theory, and quantum theory such as particle and complementarity dualism, wave mechanics, approximation method, relativistic quantum mechanics, and hydrogen atom fine structure, are discussed. (SMN)

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.

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

Science.gov (United States)

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

2009-01-01

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

Analytical Absorption Cross-Section for Photon by a Hydrogen 2s Atom

International Nuclear Information System (INIS)

Ndinya, Boniface Otieno; Okeyo, Stephen Onyango

2011-01-01

We calculate the absorption cross-section for photon by a hydrogen 2s atom using the quantum-classical approximation for the total photo cross-section of many electron atoms. With the application of the first-order term of the Baker-Hausdorf expansion, the absorption cross-section for the hydrogen 2s atom decreases to a minimum, the Cooper pair minimum, at low photon energy. Such a minimum is absent in the exact absorption cross-section for photon by a hydrogen 2s atom. We have extended the calculation for the absorption cross-section of the hydrogen 2s atom using the quantum-classical approximation for the total photo cross-section of many electron to include the second-order term of the Baker-Hausdorf expansion and observed a great reduction in the dip associated with the Cooper pair minimum at the zero crossing. (atomic and molecular physics)

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

CERN Document Server

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

2015-01-01

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

Shannon entropy: A study of confined hydrogenic-like atoms

Science.gov (United States)

Nascimento, Wallas S.; Prudente, Frederico V.

2018-01-01

The Shannon entropy in the atomic, molecular and chemical physics context is presented by using as test cases the hydrogenic-like atoms Hc, Hec+ and Lic2 + confined by an impenetrable spherical box. Novel expressions for entropic uncertainty relation and Shannon entropies Sr and Sp are proposed to ensure their physical dimensionless characteristic. The electronic ground state energy and the quantities Sr,Sp and St are calculated for the hydrogenic-like atoms to different confinement radii by using a variational method. The global behavior of these quantities and different conjectures are analyzed. The results are compared, when available, with those previously published.

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

Science.gov (United States)

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

2017-10-19

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

Wave equation of hydrogen atom

International Nuclear Information System (INIS)

Suwito.

1977-01-01

The calculation of the energy levels of the hydrogen atom using Bohr, Schroedinger and Dirac theories is reviewed. The result is compared with that obtained from infinite component wave equations theory which developed recently. The conclusion can be stated that the latter theory is better to describe the composit system than the former. (author)

Quantum yield and translational energy of hydrogen atoms

Indian Academy of Sciences (India)

TECS

erage kinetic energy of H atoms calculated from Doppler profiles was found to be ET(lab) = (50 ± 3) kJ/mol. The ... in this wavelength range H atoms are produced by ... tral hydrogen. 1,9 ... a spectral window of molecular oxygen, solar radia-.

Muon transfer from hot muonic hydrogen atoms to neon

International Nuclear Information System (INIS)

Jacot-Guillarmod, R.; Beer, G.A.; Knowles, P.E.; Mason, G.R.; Olin, A.; Beveridge, J.L.; Marshall, G.M.; Brewer, J.H.; Forster, B.M.; Huber, T.M.; Kammel, P.; Zmeskal, J.; Petitjean, C.

1992-01-01

A negative muon beam has been directed on adjacent solid layers of hydrogen and neon. Three targets differing by their deuterium concentration were investigated. Muonic hydrogen atoms can drift to the neon layer where the muon is immediately transferred. The time structure of the muonic neon X-rays follows the exponential law with a disappearance rate corresponding to the one of μ -p atoms in each target. The rates λ ppμ and λ pd can be extracted

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

International Nuclear Information System (INIS)

Nojima, Hideo; Park, Rae-Eun; Kwon, Jun-Hyoun; Suh, Inseon; Jeon, Junsang; Ha, Eunju; On, Hyeon-Ki; Kim, Hye-Ryung; Choi, KyoungHui; 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 + (H 2 O)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 m 3 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

The hydrogen atom in D = 3 - 2ɛ dimensions

Science.gov (United States)

Adkins, Gregory S.

2018-06-01

The nonrelativistic hydrogen atom in D = 3 - 2 ɛ dimensions is the reference system for perturbative schemes used in dimensionally regularized nonrelativistic effective field theories to describe hydrogen-like atoms. Solutions to the D-dimensional Schrödinger-Coulomb equation are given in the form of a double power series. Energies and normalization integrals are obtained numerically and also perturbatively in terms of ɛ. The utility of the series expansion is demonstrated by the calculation of the divergent expectation value .

On the dynamical supersymmetry of atomic hydrogen

International Nuclear Information System (INIS)

Slepchenko, L.A.

1986-01-01

In the framework of supersymmetric quantum mechanics a dynamical symmetry of the hydrogen atom is considered. New features of spectra for the dynamical supersymmetry of two-dimensional Kepler problem are found

Mechanism of calcium oxide excitation by atom hydrogen

International Nuclear Information System (INIS)

Kharlamov, V.F.

1991-01-01

Heterogeneous recombination of hydrogen atoms on the surface of calcium oxide proceeds according to the Langmuir-Hinshelwood mechanism with participation of atoms in two different states, belonging to adsorption centres of the same type. CaO excitation is broughty about by vibration-electron transitions during associative desorption of H 2 molecules

Detection of atomic and molecular hydrogen in post-discharge by resonant multi-photo-ionisation. Determination of absolute atomic densities

International Nuclear Information System (INIS)

Persuy, Philippe

1990-01-01

Within the frame of studies on devices for physical vapour deposition, and on phenomena leading to these depositions, this research thesis reports the development of a laser-diagnosis based on the phenomenon of resonant multi-photo-ionisation, and an attempt to obtain from it values of the absolute concentration of atomic hydrogen. After some recalls on the diversity of multi-photon phenomena, their theoretical and experimental evolutions, and on the particular role of hydrogen, the author reports experiments performed at 307.7 and 364.7 nm which respectively addressed the post-discharge detection of molecular hydrogen and of atomic hydrogen. A model is presented which addresses the interaction volume, and results of experiments of atom multi-photo-ionisation are reported. One of the results of this model is an assessment of the cross-section of the excitation with three photons of the hydrogen atom. This result is then used to determine the absolute density of atoms in fundamental state for different discharge conditions. Finally, the author presents the calculation software and some curve examples displaying the evolution of the number of ions and of excited states within the interaction volume [fr

The Rydberg constant and proton size from atomic hydrogen

Science.gov (United States)

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

2017-10-01

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

An atomic hydrogen beam to test ASACUSA’s apparatus for antihydrogen spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Diermaier, M., E-mail: martin.diermaier@oeaw.ac.at; Caradonna, P.; Kolbinger, B. [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria); Malbrunot, C. [CERN (Switzerland); Massiczek, O.; Sauerzopf, C.; Simon, M. C.; Wolf, M.; Zmeskal, J.; Widmann, E. [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria)

2015-08-15

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

Exotic atoms: Hadronic and muonic atoms 1969--1997. Technical progress report, February 1, 1996--August 31, 1997

International Nuclear Information System (INIS)

Kunselman, R.

1997-01-01

Since this is a terminal progress-report it is a synopsis over the total time of the grant. The author has utilized exotic hadronic and muonic atoms as tools to access information concerning questions to do with particle, nuclear, and atomic physics. The information has answered fundamental questions about lepton conservations, quark models, tests of the CPT theorem, QED energies, and nuclear structure. The present experiments involve reactions with a variety of hydrogen isotopic mixtures to form solid targets to produce muonic hydrogen isotope atoms. The method relies on muon capture by a proton and transfer of the muon from the proton to a deuteron or a triton. The resulting muonic deuterium or muonic tritium will not immediately thermalize because of the very low elastic cross sections of the Ramsauer-Townsend effect, and are emitted from the surface of the layer and escape into a vacuum region. A second solid hydrogen isotopic target is produced downstream on which the muonic hydrogen atom can react and the time of flight measured

Reactivity and Catalytic Activity of Hydrogen Atom Chemisorbed Silver Clusters.

Science.gov (United States)

Manzoor, Dar; Pal, Sourav

2015-06-18

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

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

Science.gov (United States)

Bonfanti, Matteo; Jackson, Bret; Hughes, Keith H; Burghardt, Irene; Martinazzo, Rocco

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.

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.

Relativistic Hydrogen-Like Atom on a Noncommutative Phase Space

Science.gov (United States)

Masum, Huseyin; Dulat, Sayipjamal; Tohti, Mutallip

2017-09-01

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

Hydrogen-like atom in laser field: Invariant atomic parameters in the ground state

International Nuclear Information System (INIS)

Bondarev, I.V.; Kuten, S.A.

1994-07-01

The invariant atomic parameters (dynamical vector and tensor polarizabilities) of hydrogen-like atom in the ground 1S 1/2 state are calculated analytically by means of the Laplace transform of the radial Schroedinger equation. The obtained analytical expressions have been written in the compact form as a sum of linear and squared combinations of Gauss hypergeometric functions 2 F 1 . The frequency dependence of the invariant atomic parameters is analyzed. (author). 24 refs, 1 fig

Atomic hydrogen and oxygen adsorptions in single-walled zigzag silicon nanotubes

International Nuclear Information System (INIS)

Chen, Haoliang; Ray, Asok K.

2013-01-01

Ab initio calculations have been performed to study the electronic and geometric structure properties of zigzag silicon nanotubes. Full geometry and spin optimizations have been performed without any symmetry constraints with an all electron 3-21G* basis set and the B3LYP hybrid functional. The largest zigzag SiNT studied here, (12, 0), has a binding energy per atom of 3.584 eV. Atomic hydrogen and oxygen adsorptions on (9, 0) and (10, 0) nanotubes have also been studied by optimizing the distances of the adatoms from both inside and outside the tube. The adatom is initially placed in four adsorption sites-parallel bridge (PB), zigzag bridge (ZB), hollow, and on-top site. The on-top site is the most preferred site for hydrogen atom adsorbed on (9, 0), with an adsorption energy of 3.0 eV and an optimized distance of 1.49 Å from the adatom to the nearest silicon atom. For oxygen adsorption on (9, 0), the most preferred site is the ZB site, with an adsorption energy of 5.987 eV and an optimized distance of 1.72 Å. For atomic hydrogen adsorption on (10, 0), the most preferred site is also the on-top site with an adsorption energy of 3.174 eV and an optimized distance of 1.49 Å. For adsorption of atomic oxygen on (10, 0), the most preferred site is PB site, with an adsorption energy of 6.306 eV and an optimized distance of 1.71 Å. The HOMO–LUMO gaps of (9, 0) after adsorptions of hydrogen and oxygen atoms decrease while the HOMO–LUMO gaps of (10, 0) increase after adsorption of hydrogen and oxygen

Two-step photoionization of hydrogen atoms in interplanetary space

International Nuclear Information System (INIS)

Gruntman, M.A.

1990-01-01

Photoionization is one of the key processes which determine the properties of fluxes of neutral atoms in interplanetary space. A new two-step channel (called indirect) of photoionization of hydrogen atoms is proposed. Hydrogen atoms are at first excited to states with principal quantum number n > 2, then decay to metastable H(2S) states, where they can be photoionized. Competing processes due to the interaction with solar wind plasma and solar radiation are considered and the photoionization rate through the proposed indirect channel is calculated. This rate depends on distance from the Sun as ∝ 1/R 4 at large distances (R > 1-2 a.u.) and as ∝ 1/R 2 at close approaches, where it is higher than the rate of direct photoionization. (author)

Charge degeneracy removal in the screened hydrogen atom

International Nuclear Information System (INIS)

Penna, Andre L A; Diniz, Joao B; Oliveira, Fernando A

2009-01-01

We derive an analytical model for the states of the screened hydrogen atom by using a new charge degeneracy removal approach. Starting from the nonzero Thomas-Fermi parameter q, we show that screening effect is due to breaks of the charge degeneracy in each quantum level of the hydrogen atom. The charge degeneracy removal reparametrizes the atomic system through the effective nuclear charge α n,l and the appearance of a dual charge γ n,l for each quantum level. In this approach, we show that the screening of a quantum state depends hierarchically on the screening from all previous quantum states with the same angular quantum numbers. The excited state energies E n,l (q) are analytically found taking into account the contribution of this new charge degeneracy for each quantum level. Finally, we also have estimated accurate critical screening parameters q* n,l for the bound-unbound transition.

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Science.gov (United States)

2010-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this subpart that... section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you must...

Electron capture to the continuum from atomic hydrogen

International Nuclear Information System (INIS)

Glass, G.A.; Engar, P.; Berry, S.D.; Breinig, M.; Deserio, R.; Elston, S.B.; Sellin, I.A.

1984-01-01

The first known measurement of the differential cross section for electron capture to the continuum(ECC) from atomic hydrogen is presented. A 12 MeV beam of C 6+ ions traversed a static target of atomic hydrogen produced by an electron impact heated dissociation oven. The resulting ECC spectrum was obtained with a channel electron multiplier detector mounted at the exit of a 160 0 spherical sector electrostatic spectrometer with an angular acceptance of 2 0 . The ECC spectrum clearly shows the asymmetry generally associated with ECC spectra from gaseous targets. The ratio of the singly differential cross section of H to that of H 2 was found to be 0.80. 16 references, 3 figures

Interaction of atomic hydrogen with charcoal at 77 K

International Nuclear Information System (INIS)

Gorodetsky, A.E.; Vnukov, S.P.; Zalavutdinov, R.Kh.; Zakharov, A.P.; Buryak, A.K.; Ulyanov, A.V.; Federici, G.; Day, Chr.

2005-01-01

Charcoal is a working material of sorption cryopumps in the ITER project. The interaction of thermal hydrogen molecules and atoms with charcoal has been analyzed by TDS (77-300 K) and sorption measurements at 77 K. A stream quartz reactor with an H 2 RF discharge was used for the production of H atoms. The ratio of H and H 2 in the gas mixture in the afterglow zone was ∼10 -4 , hydrogen flow and inlet pressure were 6.9 sccm and 30 Pa, respectively. After exposure in the H/H 2 mixture during 1 hour the marked change in the shape of the TD spectra and decrease of the charcoal sorption capacity for hydrogen and nitrogen were detected. A wide spectrum of hydrocarbon fragments formed at 77 K was registered by mass-spectrometry at charcoal heating up to 700 K. The specific adsorption volume of charcoal, which was measured by N 2 adsorption at 77 K, decreased directly as amount of H atoms passed through the section with charcoal. (author)

Hydrogen Pellet-Rotating Plasma Interaction

DEFF Research Database (Denmark)

Jørgensen, L. W.; Sillesen, Alfred Hegaard; Øster, Flemming

1977-01-01

Spectroscopic measurements on the interaction between solid hydrogen pellets and rotating plasmas are reported. It was found that the light emitted is specific to the pellet material, and that the velocity of the ablated H-atoms is of the order of l0^4 m/s. The investigation was carried out...

Free hydrogen atom collision cross sections of interest in controlled thermonuclear research

Energy Technology Data Exchange (ETDEWEB)

Fite, W L [John Jay Hopkins Laboratory for Pure and Applied Science, General Atomic Division of General Dynamics Corporation, San Diego, CA (United States)

1958-07-01

The present paper summarizes the results of measurements of the cross sections of hydrogen atoms for: (1) ionization, (2) excitation of Lyman alpha radiation on electron impact, and (3) elastic scattering of electrons of energy less than 10 eV; and also describes the approach of measurements now in progress on (4) charge-exchange between deuterons and deuterium atoms and (5) ionization of the hydrogen atom on proton impact.

Experimental study on pion capture by hydrogen bound in molecules

International Nuclear Information System (INIS)

Horvath, D.; Aniol, K.A.; Entezami, F.; Measday, D.F.; Noble, A.J.; Stanislaus, S.; Virtue, C.J.

1988-08-01

An experiment was performed at TRIUMF to study the formation of pionic hydrogen atoms and molecules in solids, particularly in groups of organic molecules of slightly different structure in order to help further clarify the problem. The nuclear capture of pions by hydrogen was measured using the charge exchange of stopped pions. The coincident photons emitted by the decaying π 0 mesons were detected by TRIUMF's two large NaI spectrometers. New experimental results were obtained for the capture probability of stopped π - mesons in the nuclei of hydrogen atoms, chemically bound in molecules of some simple hydrides, acid anhydrides, and sugar isomers. A linear relation was found between pion capture in hydrogen and melting point in sugar isomers. The pion capture probability in acid anhydrides is fairly well described by a simple atomic capture model in which the capture probability on the hydrogen dramatically increases as the hydrogen atom is separated from the strongly electronegative C 2 O 3 group. Both effects are consistent with a correlation between pion capture and electron density on hydrogen atoms. (Author) (38 refs., 4 tabs., 7 figs.)

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…

Collisional destruction of fast hydrogen Rydberg atoms

International Nuclear Information System (INIS)

King, M.R.

1984-01-01

A new modulated electric field technique was developed to study Rydberg atom destruction processes in a fast beam. The process of destruction of a band of Rydberg atom destruction of a band of Rydberg atoms through the combined processes of ionization, excitation, and deexcitation was studied for collisions with gas targets. Rydberg atoms of hydrogen were formed by electron capture, and detected by field ionization. The modulated field technique described proved to be an effective technique for producing a large signal for accurate cross section measurements. The independent particle model for Rydberg atom destruction processes was found to hold well for collisions with molecular nitrogen, argon, and carbon dioxide. The resonances in the cross sections for the free electron scattering with these targets were found to also occur in Rydberg destruction. Suggestions for future investigations of Rydberg atom collision processes in the fast beam regime are given

Precision spectroscopy of the 2S-4P transition in atomic hydrogen

Science.gov (United States)

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

2017-04-01

Precision measurements of atomic hydrogen have long been successfully used to extract fundamental constants and to test bound-state QED. However, both these applications are limited by measurements of hydrogen lines other than the very precisely known 1S-2S transition. Moreover, the proton r.m.s.charge radius rp extracted from electronic hydrogen measurements currently disagrees by 4 σ with the much more precise value extracted from muonic hydrogen spectroscopy. We have measured the 2S-4P transition in atomic hydrogen using a cryogenic beam of hydrogen atoms optically excited to the initial 2S state. The first order Doppler shift of the one-photon 2S-4P transition is suppressed by actively stabilized counter-propagating laser beams and time-of-flight resolved detection. Quantum interference between excitation paths can lead to significant line distortions in our system. We use an experimentally verified, simple line shape model to take these distortions into account. With this, we can extract a new value for rp and the Rydberg constant R∞ with comparable accuracy as the combined previous H world data.

Electron scattering by hydrogen atoms

International Nuclear Information System (INIS)

Fujii, D.H.

1981-02-01

A variational method to calculate the differential cross section of the electron-hydrogen atom scattering process is presented. The second Born approximation is calculated, through a variational calculation using the energy and electronic charge simultaneously as parameters, in order to calculate the differential cross section which is written in a fractional form according to the Schwinger variational principle. Effects due to the electron change are included in the calculations. (L.C.) [pt

A model for the physical adsorption of atomic hydrogen

NARCIS (Netherlands)

Bruch, L.W.; Ruijgrok, Th.W.

1979-01-01

The formation of the holding potential of physical adsorption is studied with a model in which a hydrogen atom interacts with a perfectly imaging substrate bounded by a sharp planar surface; the exclusion of the atomic electron from the substrate is an important boundary condition in the model. The

Exotic atoms

International Nuclear Information System (INIS)

Kunselman, R.

1993-01-01

The experiments use a solid hydrogen layer to form muonic hydrogen isotopes that escape into vacuum. The method relies on transfer of the muon from protium to either a deuteron or a triton. The resulting muonic deuterium or muonic tritium will not immediately thermalize because of the very low elastic cross sections, and may be emitted from the surface of the layer. Measurements which detect decay electrons, muonic x-rays, and fusion products have been used to study the processes. A target has been constructed which exploits muonic atom emission in order to learn more about the energy dependence of transfer and muon molecular formation

Emission of muonic hydrogen isotopes from solid hydrogen layers into vacuum

International Nuclear Information System (INIS)

Marshall, G.M.; Bailey, J.M.; Beer, G.A.

1989-10-01

An attempt was made to create in vacuum free muonic hydrogen atoms, muonic protium and muonic deuterium. The method was based on slowing a beam of μ - in a layer of solid hydrogen in vacuum frozen to a cold gold foil substrate. Muonic hydrogen formed near the surface is emitted from it into the vacuum with an energy spectrum determined by the formation and subsequent scattering processes. For a typical total cross section of 10 -19 cm 2 the interaction probability is 0.43 μm -1 . For emission at an energy of order 1 eV, the muonic atom travels about 10 mm in vacuum prior to decay. No corresponding signal was observed with a deuterium layer of 6 mg/cm 2 . The natural abundance of deuterons in hydrogen leads to transfer of the muon in a mean time of about 500 ns, and because of the reduced mass difference, the m u - d obtains a kinetic energy of 45 eV, from which the atom will scatter and slow until the energy of the Ramsauer-Townsend minimum is reached and the hydrogen film becomes nearly transparent to μ - d. The Ramsauer-Townsend effect is also expected to show up for tritium in protium, which means a source of μ - t in vacuum should be possible

Soil properties and elements other than hydrogen that can affect the ...

African Journals Online (AJOL)

A neutron water meter (NWM) operates on the principle that emitted high-energy neutrons are thermalised by elastic collisions with atomic nuclei present in soil, such as that of the hydrogen atom. Thermalised neutrons, however, are affected by other nuclear-matter interactions such as their capture by soil elements and ...

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.

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-02-28

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

The study of multiphoton ionization processes in hydrogen atoms

International Nuclear Information System (INIS)

Mohammad, M.A.

1981-01-01

In this thesis we investigate theoretically the multiphoton ionization of hydrogen atoms based on perturbation theory.The main problem in the numorical evaluation is the appearance of infinite summation over the matrix element and energy denominators of the intermediate state in the formula for ionization cross section.Our numerical result is in excellent agreement with other workers.In the last part of the thesis we have again calculated the two photon ionization of hydrogen atoms using momentum translation approximation of Reiss.The method in general is in fair agreement with other calculations but dose not show the resonance behaviour.(2 tabs., 1 fig., 45 refs.)

Reaction kinetics of hydrogen atom abstraction from isopentanol by the H atom and HO2˙ radical.

Science.gov (United States)

Parab, Prajakta Rajaram; Heufer, K Alexander; Fernandes, Ravi Xavier

2018-04-25

Isopentanol is a potential next-generation biofuel for future applications to Homogeneous Charge Compression Ignition (HCCI) engine concepts. To provide insights into the combustion behavior of isopentanol, especially to its auto-ignition behavior which is linked both to efficiency and pollutant formation in real combustion systems, detailed quantum chemical studies for crucial reactions are desired. H-Abstraction reaction rates from fuel molecules are key initiation steps for chain branching required for auto-ignition. In this study, rate constants are determined for the hydrogen atom abstraction reactions from isopentanol by the H atom and HO2˙ radical by implementing the CBS-QB3 composite method. For the treatment of the internal rotors, a Pitzer-Gwinn-like approximation is applied. On comparing the computed reaction energies, the highest exothermicity (ΔE = -46 kJ mol-1) is depicted for Hα abstraction by the H atom whereas the lowest endothermicity (ΔE = 29 kJ mol-1) is shown for the abstraction of Hα by the HO2˙ radical. The formation of hydrogen bonding is found to affect the kinetics of the H atom abstraction reactions by the HO2˙ radical. Further above 750 K, the calculated high pressure limit rate constants indicate that the total contribution from delta carbon sites (Cδ) is predominant for hydrogen atom abstraction by the H atom and HO2˙ radical.

Does antimatter emit a new light?

International Nuclear Information System (INIS)

Santilli, Ruggero Maria

1997-01-01

Contemporary theories of antimatter have a number of insufficiencies which stimulated the recent construction of the new isodual theory based on a certain anti-isomorphic map of all (classical and quantum) formulations of matter called isoduality. In this note we show that the isodual theory predicts that antimatter emits a new light, called isodual light, which can be distinguished from the ordinary light emitted by matter via gravitational interactions (only). In particular, the isodual theory predicts that all stable antiparticles such as the isodual photon, the positron and the antiproton experience antigravity in the field of matter (defined as the reversal of the sign of the curvature tensor). The antihydrogen atom is therefore predicted to: experience antigravity in the field of Earth; emit the isodual photon; and have the same spectroscopy of the hydrogen atom, although subjected to an anti-isomorphic isodual map. In this note we also show that the isodual theory predicts that bound states of elementary particles and antiparticles (such as the positronium) experience ordinary gravitation in both fields of matter and antimatter, thus bypassing known objections against antigravity. A number of intriguing and fundamental, open theoretical and experimental problems of 'the new physics of antimatter' are pointed out

Does antimatter emit a new light?

Energy Technology Data Exchange (ETDEWEB)

Santilli, Ruggero Maria [Instituto per la Ricerca di Base (Italy)

1997-08-15

Contemporary theories of antimatter have a number of insufficiencies which stimulated the recent construction of the new isodual theory based on a certain anti-isomorphic map of all (classical and quantum) formulations of matter called isoduality. In this note we show that the isodual theory predicts that antimatter emits a new light, called isodual light, which can be distinguished from the ordinary light emitted by matter via gravitational interactions (only). In particular, the isodual theory predicts that all stable antiparticles such as the isodual photon, the positron and the antiproton experience antigravity in the field of matter (defined as the reversal of the sign of the curvature tensor). The antihydrogen atom is therefore predicted to: experience antigravity in the field of Earth; emit the isodual photon; and have the same spectroscopy of the hydrogen atom, although subjected to an anti-isomorphic isodual map. In this note we also show that the isodual theory predicts that bound states of elementary particles and antiparticles (such as the positronium) experience ordinary gravitation in both fields of matter and antimatter, thus bypassing known objections against antigravity. A number of intriguing and fundamental, open theoretical and experimental problems of 'the new physics of antimatter' are pointed out.

Does antimatter emit a new light?

International Nuclear Information System (INIS)

Santilli, R.M.

1996-01-01

Contemporary theories of antimatter have a number of insufficiencies which stimulated the recent construction of the new isodual theory based on a certain anti-isomorphic map of all (classical and quantum) formulations of matter called isoduality. In this note we show that the isodual theory predicts that antimatter emits a new light, called isodual light, which can be distinguished from the ordinary light emitted by matter via gravitational interactions (only). In particular, the isodual theory predicts that all stable antiparticles such as the isodual photon, the positron and the antiproton experience antigravity in the field of matter (defined as the reversal of the sign of the curvature tensor). The antihydrogen atom is therefore predicted to: experience antigravity in the field of Earth; emit the isodual photon; and have the same spectroscopy of the hydrogen atom, although subjected to an anti-isomorphic isodual map. In this note we also show that the isodual theory predicts that bound states of elementary particle sand antiparticles (such as the positronium) experience ordinary gravitation in both fields of matter and antimatter, thus by passing known objections against antigravity. A number of intriguing and fundamental, open theoretical and experimental problems of 'the new physics of antimatter' are pointed out. 16 refs

Moeller polarimetry with atomic hydrogen targets

International Nuclear Information System (INIS)

Chudakov, E.; Luppov, V.

2005-01-01

A novel proposal of using polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap, as the target for electron beam polarimetry based on Moeller scattering is discussed. Such a target of practically 100% polarized electrons could provide a superb systematic accuracy of about 0.5% for beam polarization measurements. Feasibility studies for the CEBAF electron beam have been performed. (orig.)

Hydrogen atom moving across a magnetic field

International Nuclear Information System (INIS)

Lozovik, Yu.E.; Volkov, S.Yu.

2004-01-01

A hydrogen atom moving across a magnetic field is considered in a wide region of magnitudes of magnetic field and atom momentum. We solve the Schroedinger equation of the system numerically using an imaginary time method and find wave functions of the lowest states of atom. We calculate the energy and the mean electron-nucleus separation as a function of atom momentum and magnetic field. All the results obtained could be summarized as a phase diagram on the 'atom-momentum - magnetic-field' plane. There are transformations of wave-function structure at critical values of atom momentum and magnetic field that result in a specific behavior of dependencies of energy and mean interparticle separation on the atom momentum P. We discuss a transition from the Zeeman regime to the high magnetic field regime. A qualitative analysis of the complicated behavior of wave functions vs P based on the effective potential examination is given. We analyze a sharp transition at the critical momentum from a Coulomb-type state polarized due to atom motion to a strongly decentered (Landau-type) state at low magnetic fields. A crossover occurring at intermediate magnetic fields is also studied

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.

Hydrogen atoms in the presence of a homogeneous magnetic field

International Nuclear Information System (INIS)

Brandi, H.S.; Koiller, B.

1978-01-01

A variational scheme to obtain the spectrum of the hydrogen atom in the presence of an external homogeneous magnetic field is proposed. Two different sets of basis function to diagonalize the Hamiltonian describing the system are used, namely the eigenfunctions of the free hydrogen atom and of the three-dimensional harmonic oscillator; both having their radial coordinates properly scaled by a variational parammeter. Because of its characteristics, the present approach is suitable to describe the ground state as well as an infinite number of excited states also for a wide range of magnetic field strengths [pt

ESR study on hydrogen-atom abstraction in cryogenic organic solids

International Nuclear Information System (INIS)

Ichikawa, Tsuneki

1995-01-01

The present paper summarizes our recent results on the hydrogen-atom abstraction from protiated alkane molecule by deuterium atoms in cryogenic deuterated organic solids, obtained by the X-band ESR and electron spin-echo measurements of the product alkyl radicals at cryogenic temperatures. (J.P.N.)

Electronic dipole moment and tunneling state of hydrogen atom in hydrogen-bond materials revealed by neutron and X-ray structure analyses

International Nuclear Information System (INIS)

Kiyanagi, Ryoji; Noda, Yukio; Mochida, Tomoyuki; Sugawara, Tadashi

2007-01-01

The isolated hydrogen-bonded materials, 5-methyl-9-hydroxyphenalenone (MeHPLN) and 5-bromo-9-hydroxyphenalenone (Br-HPLN), were studied by means of X-ray and neutron diffraction methods. It was found that the position of the nucleus of the hydrogen atom in the hydrogen-bond region does not agree with the center of mass of the electron cloud of the hydrogen atom. This leads to a local electronic dipole moment in the hydrogen-bond region. Using the experimentally obtained dipole moment, phase transition temperatures for MeHPLN and BrHPLN were calculated based on a tunneling model. Result shows good agreement with the ones obtained by a dielectric measurement. (author)

Effects of an electric field on the confined hydrogen atom in a parabolic potential well

International Nuclear Information System (INIS)

Xie Wenfang

2009-01-01

Using the perturbation method, the confined hydrogen atom by a parabolic potential well is investigated. The binding energy of the confined hydrogen atom in a parabolic potential well is calculated as a function of the confined potential radius and as a function of the intensity of an applied electric field. It is shown that the binding energy of the confined hydrogen atom is highly dependent on the confined potential radius and the intensity of an applied electric field.

Two-photon polarization Fourier spectroscopy of metastable atomic hydrogen

International Nuclear Information System (INIS)

Duncan, A.J.; Beyer, H.-J.; Kleinpoppen, H.; Sheikh, Z.A,; B-Z Univ., Multan

1997-01-01

A novel Fourier-transform spectroscopic method using two-photon polarization to determine the spectral distribution of the two photons emitted in the spontaneous decay of metastable atomic hydrogen is described. The method uses birefringent retardation plates and takes advantage of the subtle interplay between the spectral properties and the entangled polarization properties of the radiation emitted in the decay. Assuming the validity of the theoretical spectral distribution, it is shown that the experimental results agree well with theory. On the other hand, success in solving the inverse problem of determining the spectral distribution from the experimental results is limited by the small number of experimental points. However, making reasonable assumptions it is deduced that the observed spectrum is characterized by a broadband signal of width (0.43 ± 0.06) x 10 16 rad s -1 and centre angular frequency (0.77 ± 0.03) x 10 16 rad s -1 in good agreement with the predictions of 0.489 x 10 16 rad s -1 and 0.775 x 10 16 rad s -1 , respectively, obtained from the theoretical spectral distribution modified to take account of the absorption of the two-photon radiation in air. The values of 1.5 fs for the coherence time and 440 nm for the coherence length for single photons of the two-photon pair which are obtained from the measured bandwidth imply that, in the ideal case, these values are determined by the essentially zero lifetime of the virtual intermediate state of the decay process rather than the long lifetime of the metastable state which, it is suggested, determines the coherence time and coherence length appropriate to certain types of fourth-order interference experiments. (Author)

Moller Polarimetry with Atomic Hydrogen Targets

International Nuclear Information System (INIS)

Chudakov, Eugene; Luppov, V.

2012-01-01

A proposal to use polarized atomic hydrogen gas as the target for electron beam polarimetry based on the Moller scattering is described. Such a gas, stored in an ultra-cold magnetic trap, would provide a target of practically 100% polarized electrons. It is conceivable to reach a ∼0.3% systematic accuracy of the beam polarimetry with such a target. Feasibility studies for the CEBAF electron beam have been performed

Self-Regular Black Holes Quantized by means of an Analogue to Hydrogen Atoms

CERN Document Server

Liu, Chang; Wu, Yu-Mei; Zhang, Yu-Hao

2016-01-01

We suggest a proposal of quantization for black holes that is based on an analogy between a black hole and a hydrogen atom. A self-regular Schwarzschild-AdS black hole is investigated, where the mass density of the extreme black hole is given by the probability density of the ground state of hydrogen atoms and the mass densities of non-extreme black holes are chosen to be the probability densities of excited states with no angular momenta. Consequently, it is logical to accept quantization of mean radii of hydrogen atoms as that of black hole horizons. In this way, quantization of total black hole masses is deduced. Furthermore, the quantum hoop conjecture and the Correspondence Principle are discussed.

The probability of heterogeneous recombination of hydrogen atoms in low-temperature hydrogen plasma

International Nuclear Information System (INIS)

Islyaikin, A.; Rybkin, V.; Svetsov, V.

2000-01-01

In the group of the optical methods, the investigations of the process of recombination of the hydrogen atoms were studied mainly by the jet procedure, based on the measurement of the dependence of the intensity of radiation of the discharge on the speed of flow of particles which makes it possible to obtain information on the processes of annihilation of active particles on the surface of the discharge device both in the zone of plasma at outside to the zone (in the post glow region). However, to realise this method, it is necessary to use higher linear speed of the flow of the particles and this creates additional technical difficulties. A similar disadvantage is not found in the calculation methods of technical application with special reference to the examination of the processes of heterogeneous recombination of the atoms in the low-temperature hydrogen plasma is the main task of this work

Structure of the Balmer jump. The isolated hydrogen atom

Science.gov (United States)

Calvo, F.; Belluzzi, L.; Steiner, O.

2018-06-01

Context. The spectrum of the hydrogen atom was explained by Bohr more than one century ago. We revisit here some of the aspects of the underlying quantum structure, with a modern formalism, focusing on the limit of the Balmer series. Aims: We investigate the behaviour of the absorption coefficient of the isolated hydrogen atom in the neighbourhood of the Balmer limit. Methods: We analytically computed the total cross-section arising from bound-bound and bound-free transitions in the isolated hydrogen atom at the Balmer limit, and established a simplified semi-analytical model for the surroundings of that limit. We worked within the framework of the formalism of Landi Degl'Innocenti & Landolfi (2004, Astrophys. Space Sci. Lib., 307), which permits an almost straight-forward generalization of our results to other atoms and molecules, and which is perfectly suitable for including polarization phenomena in the problem. Results: We analytically show that there is no discontinuity at the Balmer limit, even though the concept of a "Balmer jump" is still meaningful. Furthermore, we give a possible definition of the location of the Balmer jump, and we check that this location is dependent on the broadening mechanisms. At the Balmer limit, we compute the cross-section in a fully analytical way. Conclusions: The Balmer jump is produced by a rapid drop of the total Balmer cross-section, yet this variation is smooth and continuous when both bound-bound and bound-free processes are taken into account, and its shape and location is dependent on the broadening mechanisms.

Laser diagnostics of atomic hydrogen and oxygen production in rf and microwave plasma discharges

International Nuclear Information System (INIS)

Preppernau, B.L.

1993-01-01

The research for this thesis involved the application of two-photon allowed laser-induced fluorescence (TALIF) to the study of atomic hydrogen and oxygen production in industrial scale radio-frequency and microwave plasma discharge apparatus. Absolute atomic hydrogen concentration profiles were measured in a Gaseous Electronics Conference Reference Cell installed at Wright-Patterson AFB, Ohio operating with a simple H 2 discharge. Two-dimensional atomic hydrogen concentration profiles were also measured in an ASTEX HPMM microwave plasma diamond deposition reactor during actual diamond growth. In addition absolute atomic oxygen concentrations were measured in the ASTEX system. Particular attention as paid to refining the concentration calibration technique and in determining a correction to account for the collisional quenching of excited state fluorescence in high pressure gases

Hydrogen atom kinetics in capacitively coupled plasmas

Science.gov (United States)

Nunomura, Shota; Katayama, Hirotaka; Yoshida, Isao

2017-05-01

Hydrogen (H) atom kinetics has been investigated in capacitively coupled very high frequency (VHF) discharges at powers of 16-780 mW cm-2 and H2 gas pressures of 0.1-2 Torr. The H atom density has been measured using vacuum ultra violet absorption spectroscopy (VUVAS) with a micro-discharge hollow cathode lamp as a VUV light source. The measurements have been performed in two different electrode configurations of discharges: conventional parallel-plate diode and triode with an intermediate mesh electrode. We find that in the triode configuration, the H atom density is strongly reduced across the mesh electrode. The H atom density varies from ˜1012 cm-3 to ˜1010 cm-3 by crossing the mesh with 0.2 mm in thickness and 36% in aperture ratio. The fluid model simulations for VHF discharge plasmas have been performed to study the H atom generation, diffusion and recombination kinetics. The simulations suggest that H atoms are generated in the bulk plasma, by the electron impact dissociation (e + H2 \\to e + 2H) and the ion-molecule reaction (H2 + + H2 \\to {{{H}}}3+ + H). The diffusion of H atoms is strongly limited by a mesh electrode, and thus the mesh geometry influences the spatial distribution of the H atoms. The loss of H atoms is dominated by the surface recombination.

Two-photon transitions in hydrogen atoms embedded in weakly coupled plasmas

International Nuclear Information System (INIS)

Paul, S.; Ho, Y. K.

2008-01-01

The pseudostate method has been applied to calculate energy eigenvalues and corresponding eigenfunctions of the hydrogen atom in Debye plasma environments. Resonant two-photon transition rates from the ground state of atomic hydrogen to 2s and 3s excited states have been computed as a function of photon frequency in the length and velocity gauges for different Debye lengths. A two-photon transparency is found in correspondence to each resonance for 1s-3s. The transparency frequency and resonance enhancement frequency vary significantly with the Debye length.

Electron-hydrogen atom collisions in the presence of a laser field

International Nuclear Information System (INIS)

Brandi, H.S.; Koiller, B.; Barros, H.G.P.L. de

1978-01-01

The collision of an electron and a hydrogen atom in the presence of a laser field is studied within a previously proposed approximation (based on the space translation approximation) for the bound states of the hydrogen atom. Fhe Green's function formalism is applied to derive an expression for the scattering amplitude associated to multiphoton processes. The Born-Oppenheimer approximation is obtained and numerical calculations are performed for the ls→2s inelastic excitation. It is shown as expected that exchange effects are important only for scattering processes involving low energy electrons [pt

Analytical transition-matrix treatment of electric multipole polarizabilities of hydrogen-like atoms

International Nuclear Information System (INIS)

Kharchenko, V.F.

2015-01-01

The direct transition-matrix approach to the description of the electric polarization of the quantum bound system of particles is used to determine the electric multipole polarizabilities of the hydrogen-like atoms. It is shown that in the case of the bound system formed by the Coulomb interaction the corresponding inhomogeneous integral equation determining an off-shell scattering function, which consistently describes virtual multiple scattering, can be solved exactly analytically for all electric multipole polarizabilities. Our method allows to reproduce the known Dalgarno–Lewis formula for electric multipole polarizabilities of the hydrogen atom in the ground state and can also be applied to determine the polarizability of the atom in excited bound states. - Highlights: • A new description for electric polarization of hydrogen-like atoms. • Expression for multipole polarizabilities in terms of off-shell scattering functions. • Derivation of integral equation determining the off-shell scattering function. • Rigorous analytic solving the integral equations both for ground and excited states. • Study of contributions of virtual multiple scattering to electric polarizabilities

A model for the stabilization of atomic hydrogen centers in borate glasses

International Nuclear Information System (INIS)

Pontuschka, W.M.; Isotani, S.; Furtado, W.W.; Piccini, A.; Rabbani, S.R.

1989-04-01

A model describing the trapping site of the interstitial atomic hydrogen (H sup(0) sub(i) in borate glasses x-irradiated at 77 K is proposed. The hydrogen atom is stabilized at the centers of oxygen polygons belonging to B-O ring structures in the glass network by van der Waals forces. The previously reported H sup(0) sub(i) isothermal decay experimental data are discussed in the light of this microscopic model. A coupled differential equation system describing the possible reactions was numerically solved by means of Runge-Kutta's method. The parameter best fit was found by trial and error. The untrapping parameter provided an activation energy of 0.7 x 10 sup(-19) J, in good agreement with the calculated results for dispersion interactions between the stabilized atomic hydrogen and the neighbouring oxygen atoms at the vertices of hexagonal and heptagonal structures. The retrapping and recombination parameters were found to be correlated to (T sup1/2) - T sup(1/2) sub(0)) where t sub(0)=179 K is a cutoff temperature for the kinetics process. (author)

Exotic atoms. Technical progress report

International Nuclear Information System (INIS)

Kunselman, R.

1994-01-01

The experiments use a variety of hydrogen isotopic mixtures to form solid targets for muons to produce muonic hydrogen isotope atoms that escape into vacuum. The method relies on transfer of the muon from a proton to either a deuteron or a triton. The resulting muonic deuterium or muonic tritium will not immediately thermalize because of the very low elastic cross sections (RT effect), and are emitted from the surface of the layer. A second solid hydrogen isotopic target is produced downstream on which the muonic hydrogen atom can react. Measurements which detect decay electrons, muonic x-rays, and fusion products have been used to study the processes of energy dependence of transfer, production rates, and muon molecular formation. The processes include muon catalyzed fusion of muonic tritium with deuterium which is the most possible candidate for energy production fusion. Our interest is the nuclear physics reaction rates and to use the muonic hydrogen isotopes in vacuum for energy level measurements. The method uses time of flight and is reminiscent of double scattering experiments. Two other experiments are in the development stages. First to measure the energy dependence of the Ramsauer-Townsend cross section in tritium where it has not been measured. The measurements would be compared to deuterium and calculations. Second, kaonic atoms, hypernuclei, and kaon-nucleon scattering at DAPHNE

Solid hydrogen pellet injection into the ORMAK Tokamak

International Nuclear Information System (INIS)

Foster, C.A.; Colchin, R.J.; Milora, S.L.; Kim, K.; Turnbull, R.J.

1977-06-01

Solid hydrogen spheres were injected into the ORMAK tokamak as a test of pellet refueling for tokamak fusion reactors. Pellets 70 μm and 210 μm in diameter were injected with speeds of 91 m/sec and 100 m/sec, respectively. Each of the 210-μm pellets added about 1% to the number of particles contained in the plasma. Excited neutrals, ablated from these hydrogen spheres, emitted light which was monitored either by a photomultiplier or by a high speed framing camera. From these light signals it was possible to measure pellet lifetimes, ablation rates, and the spatial distribution of hydrogen atoms in the ablation clouds. The average measured lifetime of the 70-μm pellets was 422 μsec, and the 210-μm spheres lasted 880 μsec under bombardment by the plasma. These lifetimes and measured ablation rates are in good agreement with a theoretical model which takes into account shielding of plasma electrons by hydrogen atoms ablated from spherical hydrogen ice

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.

Analysis of the elastic scattering of negative muons from atomic hydrogen

International Nuclear Information System (INIS)

Muller, R.J.

1977-01-01

The total elastic cross section and the transport cross section for the scattering of negative muons from the hydrogen atom is determined by making a partial wave analysis of the elastic scattering amplitude. An effective Schrodinger equation for the muon-hydrogen system is obtained, using a static model of the field of the hydrogen atom, and its numerical solution allows the phase shifts for fifty partial waves to be obtained over a wide range of energies. A polarization potential term is then included, and the results of the scattering from the effective potential obtained are compared with the results from the static field. The results show a substantial effect of the polarization in the cross sections at low energy. The analysis of the low energy behavior of the phase shifts indicates that a substantial number of bound states for the muon exist in both the static and the static + polarization fields of hydrogen

Model study in chemisorption: atomic hydrogen on beryllium clusters

International Nuclear Information System (INIS)

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 22 cluster are discussed

Photoionization of Rydberg hydrogen atom in a magnetic field

International Nuclear Information System (INIS)

Wang, Dehua; Cheng, Shaohao; Chen, Zhaohang

2015-01-01

Highlights: • The ionization of Rydberg hydrogen atom in a magnetic field has been studied. • Oscillatory structures appear in the electron probability density distributions. • This study can guide the experimental research on the photoionization microscopy. - Abstract: The ionization of Rydberg hydrogen atom in a magnetic field has been studied on the basis of a semiclassical analysis of photoionization microscopy. The photoionization microscopy interference patterns of the photoelectron probability density distribution on a given detector plane are calculated at different scaled energies. We find that due to the interference effect of different types of electron trajectories arrived at a given point on the detector plane, oscillatory structures appear in the electron probability density distributions. The oscillatory structure of the interference pattern, which contains the spatial component of the electronic wave function, evolves sensitively on the scaled energy, through which we gain a deep understanding on the probability density distribution of the electron wave function. This study provides some reference values for the future experiment research on the photoionization microscopy of the Rydberg atom in the presence of magnetic field

Decay of atomic metastable states in a plasma

International Nuclear Information System (INIS)

Kleiman, E.B.

1985-01-01

This paper discusses the influence of polarization plasma effects on the lifetime of metastable atomic levels. It is shown that plasma effects can also be important in the case when the distance between the metastable level and the closest emitting level exceeds the Langmuir frequency. The lifetime of the 2S level of a hydrogen atom in a rarefied plasma connected with the action of a longitudinal fluctuation field on the atom is estimated. It is found that this mechanism can determine the lifetime of the 2S level in a rarefied cosmic plasma

First-principles calculation for the effect of hydrogen atoms on the mobility of a screw dislocation in BCC iron

International Nuclear Information System (INIS)

Itakura, Mitsuhiro; Kaburaki, Hideo; Yamaguchi, Masatake; Endo, Tatsuro; Higuchi, Kenji; Ogata, Shigenobu; Kimizuka, Hajime

2012-01-01

Effect of hydrogen atoms on the mobility of a screw dislocation in BCC iron has been evaluated using the first-principles calculation. The stable position of a hydrogen atom is found to be near the screw dislocation core and inside the core respectively when the dislocation is at the easy-core or hard-core configuration in BCC iron. The intrinsically unstable hard-core configuration of the screw dislocation is stabilized when a hydrogen atom is trapped inside the core. On the basis of this first-principles result, an elastic string model of a dislocation is developed to predict the kink motion in the presence of a hydrogen atom. It is found that a double-kink formation is facilitated when a hydrogen atom is located near a dislocation line, however, a kink motion is retarded when a hydrogen atom is behind the kink. (author)

Differential cross section of atomic hydrogen photoionization

International Nuclear Information System (INIS)

Kondratovich, V.D.; Ostrovskij, V.N.

1986-01-01

Differential cross-section of atomic hydrogen photoeffect in external electric field was investigated in semiclassical approximation. Interference was described. It occurred due to the fact that infinite number of photoelectron trajectories leads to any point of classically accessible motion region. Interference picture can reach macroscopic sizes. The picture is determined by location of function nodes, describing finite electron motion along one of parabolic coordinates. The squares of external picture rings are determined only by electric field intensity in the general case at rather high energies. Quantum expression for photocurrent density was obtained using Green function in superposition of Coulomb and uniform field as well as semiclassical approximation. Possible applications of macroscopic interference picture to specification of atom ionization potentials, selective detection of atoms or particular molecules, as well as weak magnetic field and observation of Aaronov-Bom effect are discussed

The EAGLE simulations: atomic hydrogen associated with galaxies

NARCIS (Netherlands)

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

2017-01-01

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

Note on path integral quantization of hydrogen atom

International Nuclear Information System (INIS)

Storchak, S.N.

1988-01-01

For path integrals whose integration measures are generated by stochastic processes of a definite form (Stratonovich-type equations are a local form for stochastic differential equations of these processes) it has been shown that under quantization of hydrogen atom the reparametrization and reduction Jacobians are mutually cancelled. 12 refs

On the hydrogen atom via Wigner-Heisenberg algebra

International Nuclear Information System (INIS)

Rodrigues, R. de Lima . Unidade Academica de Educacao.

2008-01-01

We extend the usual Kustaanheimo-Stiefel 4D → 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)

Hydrogen atoms in protein structures: high-resolution X-ray diffraction structure of the DFPase

Science.gov (United States)

2013-01-01

Background Hydrogen atoms represent about half of the total number of atoms in proteins and are often involved in substrate recognition and catalysis. Unfortunately, X-ray protein crystallography at usual resolution fails to access directly their positioning, mainly because light atoms display weak contributions to diffraction. However, sub-Ångstrom diffraction data, careful modeling and a proper refinement strategy can allow the positioning of a significant part of hydrogen atoms. Results A comprehensive study on the X-ray structure of the diisopropyl-fluorophosphatase (DFPase) was performed, and the hydrogen atoms were modeled, including those of solvent molecules. This model was compared to the available neutron structure of DFPase, and differences in the protein and the active site solvation were noticed. Conclusions A further examination of the DFPase X-ray structure provides substantial evidence about the presence of an activated water molecule that may constitute an interesting piece of information as regard to the enzymatic hydrolysis mechanism. PMID:23915572

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

CSIR Research Space (South Africa)

Tokarev, A

2015-03-01

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

Hydrogen atom within spherical boxes with penetrable walls

International Nuclear Information System (INIS)

Ley-Koo, E.; Rubinstein, S.

1979-01-01

We study a model for the hydrogen atom confined within spherical boxes with penetrable walls. The potential consists of the Coulomb potential inside the box and a constant potential outside the box; the Schroedinger equation admits analytical solutions in both regions. The energy eigenvalues and eigenfunctions for the lowest states of the system are determined numerically for boxes of different sizes and penetrabilities. In addition, we also evaluate the hyperfine splitting, nuclear magnetic shielding, polarizability and pressure of the system and investigate the effect of the confinement on these atomic properties

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-12-16

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

Ground state energy of an hydrogen atom confined in carbon nano-structures: a diffusion quantum Monte Carlo study

International Nuclear Information System (INIS)

Molayem, M.; Tayebi-Rad, Gh.; Esmaeli, L.; Namiranian, A.; Fouladvand, M. E.; Neek-Amal, M.

2006-01-01

Using the diffusion quantum monte Carlo method, the ground state energy of an Hydrogen atom confined in a carbon nano tube and a C60 molecule is calculated. For Hydrogen atom confined in small diameter tubes, the ground state energy shows significant deviation from a free Hydrogen atom, while with increasing the diameter this deviation tends to zero.

On the connection between the hydrogen atom and the harmonic oscillator: the zero-energy case

International Nuclear Information System (INIS)

Kibler, M.; Negali, T.

1983-09-01

The connection between the three-dimensional hydrogen atom and a four-dimensional harmonic oscillator obtained in previous works, from an hybridization of the infinitesimal Pauli approach to the hydrogen system with the Schwinger approach to spherical and hyperbolical angular momenta, is worked out in the case of the zero-energy point of the hydrogen atom. This leads to the equivalence of the three-dimensional hydrogen problem with a four-dimensional free-particle problem involving a constraint condition. For completeness, the latter results is also derived by using the Kustaanheimo-Stiefel transformation introduced in celestial mechanics. Finally, it is shown how the Lie algebra of SO(4,2) quite naturally arises for the whole spectrum (discrete + continuum + zero-energy point) of the three-dimensional hydrogen atom from the introduction of the constraint condition into the Lie algebra of Sp(8,R) associated to the four-dimensional harmonic oscillator

Photoionization microscopy of hydrogen atom near a metal surface

International Nuclear Information System (INIS)

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 patterns 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. (atomic and molecular physics)

Positron impact ionization of atomic hydrogen at low energies

Indian Academy of Sciences (India)

The study of low energy ionization of atomic hydrogen has undergone a rapid ... Three distinct theories for describing low energy ionization can now .... clear evidence that the backward peak for ΘЅѕ = 180° is due to positron-nucleus scat-.

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…

Light exotic atoms in liquid and gaseous hydrogen and deuterium. Atom anti pp, theory and experiment

International Nuclear Information System (INIS)

Markushin, V.E.

1980-01-01

Considered are the de-eXcitation, absorption and Stark mixing processes in light exotic atoms formed in liquid and gaseous hydrogen (deuteriUm) and presented is the new method of the cascade calculations. Atom anti pp is studied in detail, calculated are: the populations of atomic levels, the absorption probabilities, and the X-rays yields. The present-day experimental data are discussed and it is concluded that all of them (but one result), can be easily reconciled with each other and with the theory

Hydrogen–Hydrogen Bonding in Planar Biphenyl, Predicted by Atoms-In-Molecules Theory, Does Not Exist

NARCIS (Netherlands)

Poater, J; Sola, M.; Bickelhaupt, F.M.

2006-01-01

Based on an Atoms-in-Molecules (AIM) analysis, Matta et al. (Chem. Eur. J.2003, 9, 1940) recently claimed evidence for the existence of hydrogen–hydrogen bonding between ortho-hydrogen atoms, pointing towards each other from adjacent phenyl groups in planar biphenyl. This AIM result is opposed to

Experimental investigation of the formation of negative hydrogen ions in collisions between positive ions and atomic or molecular targets

International Nuclear Information System (INIS)

Lattouf, Elie

2013-01-01

The formation of the negative hydrogen ion (H - ) in collisions between a positive ion and a neutral atomic or molecular target is studied experimentally at impact energies of a few keV. The doubly-differential cross sections for H - formation are measured as a function of the kinetic energy and emission angle for the collision systems OH + + Ar and O + + H 2 O at 412 eV/a.m.u. These H - ions can be emitted at high energies (keV) in hard quasi-elastic two-body collisions involving a large momentum transfer to the H center. However, H - anions are preferentially emitted at low energy (eV) due to soft many-body (≥ 2) collisions resulting in a low momentum transfer. The formation of H - ions by electron capture follows excitation or ionization of the molecule. The molecular fragmentation dynamics is modeled to simulate the emission of H - ions. The overall good agreement between the simulation and the experiment leads to the understanding of most of the experimental observations. (author) [fr

Molecular beam studies of oxide reduction by atomic hydrogen

International Nuclear Information System (INIS)

Olander, D.R.

1978-01-01

The graphite and oxide internals of a CTR are susceptible to chemical corrosion as well as to physical degradation by high-energy particles. Reactions of thermal atomic hydrogen with oxides are being studied. The hydrogen used is at thermal energy (0.22 eV). Typical data are reported for the H/UO 2 system. The reaction probability is plotted as a function of solid temperature at fixed beam intensity and moculation frequency. The reaction probability increases from low temperature to a high-temperature plateau at about 1300 0 C. Here the reaction rate is limited solely by the sticking probability of H on the surface; about one in seven of the incident atoms is chemisorbed by the surface and ultimately returns to the gas phase as water vapor. A reaction model comprising sticking, recombination to H 2 , solution and diffusion of H in the bulk of the UO 2 , surface reaction of adsorbed H with lattice oxygen atoms to produce the hydroxyl radical, and production of water is constructed. The rate constants for the elementary steps in the mechanism are tabulated. 2 figures, 2 tables

Spectrum of hydrogen atom, Niels Bohr and their impact on contemporary science: a glimpse of modern spectroscopy

International Nuclear Information System (INIS)

Sastry, M.D.

2013-01-01

This contribution reviews developments in the atomic spectroscopy subsequent to Bohr's model. This follows a brief description of Bohr's model of hydrogen atom that accounts for sharp line spectra of hydrogen atom. The developments include the effects of electron and nuclear spins, spectroscopy of multi electron atom which involve electron-electron repulsion and different angular momentum coupling schemes. More recently, Bohr's atom model has found application to processes at nano dimensions of semiconducting materials. It has now become possible to create a hydrogen-like atom, an exciton, with its size comparable or even more than that of the particle it self. This brings in extra quantization and has profound effects on the motion of the particles involved viz electron and hole. (author)

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…

Continuous coherent Lyman-alpha excitation of atomic hydrogen.

NARCIS (Netherlands)

Eikema, K.S.E.; Waltz, J.; Hänsch, T.

2001-01-01

The first near natural linewidth of the 1S-2P transition in atomic hydrogen was reported with a high degree of accuracy. A high yield of continuous Lyman-α radiation based on four wave mixing in mercury was employed. It was shown that laser cooloing and detection with Lyman-α radiation has excellent

Low-energy hydrogen flux measurements at the TORTUR tokamak with negative ion conversion

International Nuclear Information System (INIS)

Toledo, Wiebo van.

1990-01-01

The interaction of a tokamak plasma with the vessel wall is one of the most important subjects in thermonuclear research. The information about this interaction is not complete without direct detection of the outward stream of low-energy, down to a few electronvolts, neutral hydrogen or deuterium atoms. The detection of these atoms is the subject of this thesis. An appropriate method to analyse the atoms which are emitted from the edge plasma is to use a time-of-flight analyser. This kind of apparatus selects particles according to their velocities with-out distinguishing between different masses. If these analysers use the Daly-method the lowest measurable energy of the hydrogen atoms is approximately 25 electronvolts. To increase the detection efficiency a new detection method was developed. This new method uses the conversion of hydrogen atoms into H- ions on a cesiated tungsten surface. By this conversion the lowest measurable energy is decreased down to 5 electron-volt. (author). 93 refs.; 44 figs.; 7 tabs

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

Science.gov (United States)

Vijaya Pandiyan, B.; Kolandaivel, P.; Deepa, P.

2014-06-01

Hydrogen bonds and their strength were analysed based on their X-H proton-donor bond properties and the parameters of the H-Y distance (Y proton acceptor). Strong, moderate and weak interactions in hydrogen-bond types were verified through the proton affinities of bases (PA), deprotanation enthalpies of acids (DPE) and the chemical shift (σ). The aromaticity and anti-aromaticity were analysed by means of the NICS (0) (nucleus-independent chemical shift), NICS (1) and ΔNICS (0), ΔNICS (1) of hydrogen-bonded molecules. The strength of a hydrogen bond depends on the capacity of hydrogen atom engrossing into the electronegative acceptor atom. The correlation between the above parameters and their relations were discussed through curve fitting. Bader's theory of atoms in molecules has been applied to estimate the occurrence of hydrogen bonds through eight criteria reported by Popelier et al. The lengths and potential energy shifts have been found to have a strong negative linear correlation, whereas the lengths and Laplacian shifts have a strong positive linear correlation. This study illustrates the common factors responsible for strong, moderate and weak interactions in hydrogen-bond types.

Hydrogen atom as a quantum-classical hybrid system

International Nuclear Information System (INIS)

Zhan, Fei; Wu, Biao

2013-01-01

Hydrogen atom is studied as a quantum-classical hybrid system, where the proton is treated as a classical object while the electron is regarded as a quantum object. We use a well known mean-field approach to describe this hybrid hydrogen atom; the resulting dynamics for the electron and the proton is compared to their full quantum dynamics. The electron dynamics in the hybrid description is found to be only marginally different from its full quantum counterpart. The situation is very different for the proton: in the hybrid description, the proton behaves like a free particle; in the fully quantum description, the wave packet center of the proton orbits around the center of mass. Furthermore, we find that the failure to describe the proton dynamics properly can be regarded as a manifestation of the fact that there is no conservation of momentum in the mean-field hybrid approach. We expect that such a failure is a common feature for all existing approaches for quantum-classical hybrid systems of Born-Oppenheimer type.

Time profile of harmonics generated by a single atom in a strong electromagnetic field

International Nuclear Information System (INIS)

Antoine, P.; Piraux, B.; Maquet, A.

1995-01-01

We show that the time profile of the harmonics emitted by a single atom exposed to a strong electromagnetic field may be obtained through a wavelet or a Gabor analysis of the acceleration of the atomic dipole. This analysis is extremely sensitive to the details of the dynamics and sheds some light on the competition between the atomic excitation or ionization processes and photon emission. For illustration we study the interaction of atomic hydrogen with an intense laser pulse

A new exact path integral treatment of the hydrogen atom

International Nuclear Information System (INIS)

Pak, N.K.; Sokmen, I.

1983-08-01

Using a recently developed general new-time transformation method, free of operator ordering ambiguities by construction we reconsider the hydrogen atom problem. We solve the problem direcly without any dimension raising trick. (author)

Measurement of atomic-hydrogen spin-exchange parameters at 0.5 K using a cryogenic hydrogen maser

International Nuclear Information System (INIS)

Hayden, M.E.; Huerlimann, M.D.; Hardy, W.N.

1996-01-01

Using a cryogenic hydrogen maser, suitably modified to have electronic control of both the resonance frequency and the quality factor of the external cavity, we have measured a number of spin-exchange parameters for an atomic-hydrogen (H) gas at a temperature of 0.5 K. These results are relevant to the ultimate achievable frequency stability for cryogenic H masers and, when coupled with accurate calculations of the spin-exchange parameters, serve as a sensitive test of the H-H interatomic potentials. We find evidence for a frequency shift not predicted by semiclassical theories of spin exchange. In the context of a fully quantum mechanical hydrogen-atom spin-exchange theory [B. J. Verhaar et al., Phys. Rev. A 35, 3825 (1987) and J. M. V. A. Koelman et al., Phys. Rev. A 38, 3535 (1988)], this frequency shift is attributed to the influence of hyperfine interactions during spin-exchange collisions. Our findings are generally in agreement with these predictions; however, the sign of the hyperfine-induced frequency shift appears to differ from theory. copyright 1996 The American Physical Society

Atomic scale simulations of hydrogen implantation defects in hydrogen implanted silicon - smart Cut technology

International Nuclear Information System (INIS)

Bilteanu, L.

2010-12-01

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

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…

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

Indian Academy of Sciences (India)

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-04-30

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

Hydrogen atom in the phase-space formulation of quantum mechanics

International Nuclear Information System (INIS)

Gracia-Bondia, J.M.

1984-01-01

Using a coordinate transformation which regularizes the classical Kepler problem, we show that the hydrogen-atom case may be analytically solved via the phase-space formulation of nonrelativistic quantum mechanics. The problem is essentially reduced to that of a four-dimensional oscillator whose treatment in the phase-space formulation is developed. Furthermore, the method allows us to calculate the Green's function for the H atom in a surprisingly simple way

Theoretical studies of the reactions of HCN with atomic hydrogen

International Nuclear Information System (INIS)

Bair, R.A.; Dunning, T.H. Jr.

1985-01-01

A comprehensive theoretical study has been made of the energetics of the important pathways involved in the reaction of hydrogen atoms with hydrogen cyanide. For each reaction ab initio GVB-CI calculations were carried out to determine the structures and vibrational frequencies of the reactants, transition states, and products; then POL-CI calculations were carried out to more accurately estimate the electronic contribution to the energetics of the reactions. The hydrogen abstraction reaction is calculated to be endoergic by 24 kcal/mol [expt. ΔH (0 K) = 16--19 kcal/mol] with a barrier of 31 kcal/mol in the forward direction and 6 kcal/mol in the reverse direction. For the hydrogen addition reactions, addition to the carbon atom is calculated to be exoergic by 19 kcal/mol with a barrier of 11 kcal/mol, while addition to the nitrogen center is essentially thermoneutral with a barrier of 17 kcal/mol. Calculations were also carried out on the isomerization reactions of the addition products. The cis→trans isomerization of HCNH has a barrier of only 10 kcal/mol with the trans isomer being more stable by 5 kcal/mol. The (1,2)-hydrogen migration reaction, converting H 2 CN to trans-HCNH, is endoergic by only 14 kcal/mol, but the calculated barrier for the transfer is 52 kcal/mol. The energy of the migration pathway thus lies above that of the dissociation--recombination pathway

A theoretical study of hydrogen atoms adsorption and diffusion on PuO_2 (110) surface

International Nuclear Information System (INIS)

Yu, H.L.; Tang, T.; Zheng, S.T.; Shi, Y.; Qiu, R.Z.; Luo, W.H.; Meng, D.Q.

2016-01-01

The mechanisms of adsorption and diffusion of hydrogen atoms on the PuO_2 (110) surface are investigated by density functional theory corrected for onsite Coulombic interactions (GGA + U). In order to find out the energetically more favorable adsorption site and optimum diffusion path, adsorption energy of atomic H on various sites and the diffusion energy barrier are derived and compared. Our results show that both chemisorption and physisorption exist for H atoms adsorption configurations on PuO_2 (110) surface. Two processes for H diffusion are investigated using the climbing nudged-elastic-band (cNEB) approach. We have identified two diffusion mechanisms, leading to migration of atomic H on the surface and diffusion from surface to subsurface. The energy barriers indicate that it is energetically more favorable for H atom to be on the surface. Hydrogen permeation through purity PuO_2 surface is mainly inhibited from hydrogen atom diffusion from surface to subsurface. - Highlights: • H atoms adsorption on PuO_2 (110) surface are investigated by GGA + U. • Both chemisorption and physisorption exist for H atoms adsorption configurations. • H atoms migration into PuO_2 (100) surface are inhibited with the barrier of 2.15 eV. • H atoms diffusion on PuO_2 (110) surface are difficult at room temperature.

Chaotic scattering from hydrogen atoms in a circularly polarized laser field

International Nuclear Information System (INIS)

Okon, Elias; Parker, William; Chism, Will; Reichl, Linda E.

2002-01-01

We investigate the classical dynamics of a hydrogen atom in a circularly polarized laser beam with finite radius. The spatial cutoff for the laser field allows us to use scattering processes to examine the laser-atom dynamics. We find that for certain field parameters, the delay times, the angular momentum, and the distance of closest approach of the scattered electron exhibit fractal behavior. This fractal behavior is a signature of chaos in the dynamics of the atom-field system

Electron-capture cross sections for low-energy highly charged neon and argon ions from molecular and atomic hydrogen

International Nuclear Information System (INIS)

Can, C.; Gray, T.J.; Varghese, S.L.; Hall, J.M.; Tunnell, L.N.

1985-01-01

Electron-capture cross sections for low-velocity (10 6 --10 7 cm/s) highly charged Ne/sup q/+ (2< or =q< or =7) and Ar/sup q/+ (2< or =q< or =10)= projectiles incident on molecular- and atomic-hydrogen targets have been measured. A recoil-ion source that used the collisions of fast heavy ions (1 MeV/amu) with target gas atoms was utilized to produce slow highly charged ions. Atomic hydrogen was produced by dissociating hydrogen molecules in a high-temperature oven. Measurements and analysis of the data for molecular- and atomic-hydrogen targets are discussed in detail. The measured absolute cross sections are compared with published data and predictions of theoretical models

Molecular dynamics simulation of chemical sputtering of hydrogen atom on layer structured graphite

International Nuclear Information System (INIS)

Ito, A.; Wang, Y.; Irle, S.; Morokuma, K.; Nakamura, H.

2008-10-01

Chemical sputtering of hydrogen atom on graphite was simulated using molecular dynamics. Especially, the layer structure of the graphite was maintained by interlayer intermolecular interaction. Three kinds of graphite surfaces, flat (0 0 0 1) surface, armchair (1 1 2-bar 0) surface and zigzag (1 0 1-bar 0) surface, are dealt with as targets of hydrogen atom bombardment. In the case of the flat surface, graphene layers were peeled off one by one and yielded molecules had chain structures. On the other hand, C 2 H 2 and H 2 are dominant yielded molecules on the armchair and zigzag surfaces, respectively. In addition, the interaction of a single hydrogen isotope on a single graphene is investigated. Adsorption, reflection and penetration rates are obtained as functions of incident energy and explain hydrogen retention on layered graphite. (author)

Photoionization of the hydrogen atom in strong magnetic fields

Science.gov (United States)

Potekhin, Aleksandr IU.; Pavlov, George G.

1993-01-01

The photoionization of the hydrogen atom in magnetic fields B about 10 exp 11 - 10 exp 13 G typical of the surface layers of neutron stars is investigated analytically and numerically. We consider the photoionization from various tightly bound and hydrogen-like states of the atom for photons with arbitrary polarizations and wave-vector directions. It is shown that the length form of the interaction matrix elements is more appropriate in the adiabatic approximation than the velocity form, at least in the most important frequency range omega much less than omega(B), where omega(B) is the electron cyclotron frequency. Use of the length form yields nonzero cross sections for photon polarizations perpendicular to the magnetic field at omega less than omega(B); these cross sections are the ones that most strongly affect the properties of the radiation escaping from an optically thick medium, e.g., from the atmosphere of a neutron star. The results of the numerical calculations are fitted by simple analytical formulas.

Surface Preparation of InAs (110 Using Atomic Hydrogen

Directory of Open Access Journals (Sweden)

T.D. Veal

2002-06-01

Full Text Available Atomic hydrogen cleaning has been used to produce structurally and electronically damage-free InAs(110 surfaces.  X-ray photoelectron spectroscopy (XPS was used to obtain chemical composition and chemical state information about the surface, before and after the removal of the atmospheric contamination. Low energy electron diffraction (LEED and high-resolution electron-energy-loss spectroscopy (HREELS were also used, respectively, to determine the surface reconstruction and degree of surface ordering, and to probe the adsorbed contaminant vibrational modes and the collective excitations of the clean surface. Clean, ordered and stoichiometric  InAs(110-(1×1 surfaces were obtained by exposure to thermally generated atomic hydrogen at a substrate temperature as low as 400ºC.  Semi-classical dielectric theory analysis of HREEL spectra of the phonon and plasmon excitations of the clean surface indicate that no electronic damage or dopant passivation were induced by the surface preparation method.

Calculating Relativistic Transition Matrix Elements for Hydrogenic Atoms Using Monte Carlo Methods

Science.gov (United States)

Alexander, Steven; Coldwell, R. L.

2015-03-01

The nonrelativistic transition matrix elements for hydrogen atoms can be computed exactly and these expressions are given in a number of classic textbooks. The relativistic counterparts of these equations can also be computed exactly but these expressions have been described in only a few places in the literature. In part, this is because the relativistic equations lack the elegant simplicity of the nonrelativistic equations. In this poster I will describe how variational Monte Carlo methods can be used to calculate the energy and properties of relativistic hydrogen atoms and how the wavefunctions for these systems can be used to calculate transition matrix elements.

Atomic displacements due to interstitial hydrogen in Cu and Pd

Indian Academy of Sciences (India)

2015-11-27

Nov 27, 2015 ... Atomic displacements; density functional theory; Kanzaki method. ... pseudopotentials for H, Cu and Pd are generated self-consistently. ... Both Cu and Pd lattices show lattice expansion due to the presence of hydrogen and ...

Concentration of atomic hydrogen in a dielectric barrier discharge measured by two-photon absorption fluorescence

Science.gov (United States)

Dvořák, P.; Talába, M.; Obrusník, A.; Kratzer, J.; Dědina, J.

2017-08-01

Two-photon absorption laser-induced fluorescence (TALIF) was utilized for measuring the concentration of atomic hydrogen in a volume dielectric barrier discharge (DBD) ignited in mixtures of Ar, H2 and O2 at atmospheric pressure. The method was calibrated by TALIF of krypton diluted in argon at atmospheric pressure, proving that three-body collisions had a negligible effect on quenching of excited krypton atoms. The diagnostic study was complemented with a 3D numerical model of the gas flow and a zero-dimensional model of the chemistry in order to better understand the reaction kinetics and identify the key pathways leading to the production and destruction of atomic hydrogen. It was determined that the density of atomic hydrogen in Ar-H2 mixtures was in the order of 1021 m-3 and decreased when oxygen was added into the gas mixture. Spatially resolved measurements and simulations revealed a sharply bordered region with low atomic hydrogen concentration when oxygen was added to the gas mixture. At substoichiometric oxygen/hydrogen ratios, this H-poor region is confined to an area close to the gas inlet and it is shown that the size of this region is not only influenced by the chemistry but also by the gas flow patterns. Experimentally, it was observed that a decrease in H2 concentration in the feeding Ar-H2 mixture led to an increase in H production in the DBD.

Atomic hydrogen in the Orion star-forming region

International Nuclear Information System (INIS)

Chromey, F.R.; Elmegreen, B.G.; Elmegreen, D.M.

1989-01-01

A large-scale survey of atomic hydrogen in Orion reveals low-density material with a total mass comparable to that in dense molecular clouds. The atomic gas is sufficiently dense that it can shield the molecular material from photodissociative radiation and provide a pressure link to the low-density intercloud medium. An excess of H I emission comes from photodissociation fronts near the bright stars and from a giant shell in the Orion Belt region. This shell may have caused the apparent bifurcation between the Orion A and B clouds, and the associated pressures may have induced peculiar motions and star formation in NGC 2023 and 2024. 49 refs

Dirac equation in noncommutative space for hydrogen atom

International Nuclear Information System (INIS)

Adorno, T.C.; Baldiotti, M.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 θ-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.

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

Indian Academy of Sciences (India)

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

Hydrogen excited states—radial matrix element—corres- ... atoms, its availability, production, its spectras, and importance in astrophysics (Dupree ... far away revolving lazily around in a slow orbit like a distant planet in the solar system. As the electron orbit diameter grows rapidly, its energy also decreases rapidly. Currently ...

When hydroquinone meets methoxy radical: Hydrogen abstraction reaction from the viewpoint of interacting quantum atoms.

Science.gov (United States)

Petković, Milena; Nakarada, Đura; Etinski, Mihajlo

2018-05-25

Interacting Quantum Atoms methodology is used for a detailed analysis of hydrogen abstraction reaction from hydroquinone by methoxy radical. Two pathways are analyzed, which differ in the orientation of the reactants at the corresponding transition states. Although the discrepancy between the two barriers amounts to only 2 kJ/mol, which implies that the two pathways are of comparable probability, the extent of intra-atomic and inter-atomic energy changes differs considerably. We thus demonstrated that Interacting Quantum Atoms procedure can be applied to unravel distinct energy transfer routes in seemingly similar mechanisms. Identification of energy components with the greatest contribution to the variation of the overall energy (intra-atomic and inter-atomic terms that involve hydroquinone's oxygen and the carbon atom covalently bound to it, the transferring hydrogen and methoxy radical's oxygen), is performed using the Relative energy gradient method. Additionally, the Interacting Quantum Fragments approach shed light on the nature of dominant interactions among selected fragments: both Coulomb and exchange-correlation contributions are of comparable importance when considering interactions of the transferring hydrogen atom with all other atoms, whereas the exchange-correlation term dominates interaction between methoxy radical's methyl group and hydroquinone's aromatic ring. This study represents one of the first applications of Interacting Quantum Fragments approach on first order saddle points. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

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.

Magnetic resonance studies of atomic hydrogen gas at low temperatures

International Nuclear Information System (INIS)

Hardy, W.N.; Morrow, M.; Jochemsen, R.; Statt, B.W.; Kubik, P.R.; Marsolais, R.M.; Berlinsky, A.J.; Landesman, A.

1980-01-01

Using a pulsed low temperature discharge in a closed cell containing H 2 and 4 He, we have been able to store a low density (approximately 10 12 atoms/cc) gas of atomic hydrogen for periods of order one hour in zero magnetic field and T=1 K. Pulsed magnetic resonance at the 1420 MHz hyperfine transition has been used to study a number of the properties of the gas, including the recombination rate H + H + 4 He→H 2 + 4 He, the hydrogen spin-exchange relaxation rates, the diffusion coefficient of H in 4 He gas and the pressure shift of the hyperfine frequency due to the 4 He buffer gas. Here we discuss the application of hyperfine frequency shifts as a probe of the H-He potential, and as a means for determining the binding energy of H on liquid helium

Tungsten deposition by hydrogen-atom reaction with tungsten hexafluoride

International Nuclear Information System (INIS)

Lee, W.W.

1991-01-01

Using gaseous hydrogen atoms with WF 6 , tungsten atoms can be produced in a gas-phase reaction. The atoms then deposit in a near-room temperature process, which results in the formation of tungsten films. The W atoms (10 10 -10 11 /cm 3 ) were measured in situ by atomic absorption spectroscopy during the CVD process. Deposited W films were characterized by Auger electron spectroscopy, Rutherford backscattering, and X-ray diffraction. The surface morphology of the deposited films and filled holes was studied using scanning electron microscopy. The deposited films were highly adherent to different substrates, such as Si, SiO 2 , Ti/Si, TiN/Si and Teflon. The reaction mechanism and kinetics were studied. The experimental results indicated that this method has three advantages compared to conventional CVD or PECVD: (1) film growth occurs at low temperatures; (2) deposition takes place in a plasma-free environment; and (3) a low level of impurities results in high-quality adherent films

Some comments on the hydrogen atom in a spherical enclosure

International Nuclear Information System (INIS)

Aguilera-Navarro, V.C.; Koo, E.L.; Zimerman, A.H.

1980-01-01

Some properties of the ground state energy solutions for the hydrogen atom in a spherical enclosure are discussed. The application of the many-point Pade approximants to this kind of systems inside a box is consider also. (Author) [pt

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

Indian Academy of Sciences (India)

2016-10-17

Oct 17, 2016 ... DOI 10.1007/s12043-016-1282-y. Formation of ground and excited hydrogen atoms in proton–potassium inelastic scattering. S A ELKILANY1,2. 1Department of Mathematics, Faculty of Science, University of Dammam, Dammam, Kingdom of Saudi Arabia. 2Department of Mathematics, Faculty of Science, ...

The effect of atomic hydrogen adsorption on single-walled carbon nano tubes properties

International Nuclear Information System (INIS)

Jalili, S.; Majidi, R.

2007-01-01

We investigated the adsorption of hydrogen atoms on metallic single-walled carbon nano tubes using ab initio molecular dynamics method. It was found that the geometric structures and the electronic properties of hydrogenated SWNTs can be strongly changed by varying hydrogen coverage. The circular cross sections of the CNTs were changed with different hydrogen coverage. When hydrogen is chemisorbed on the surface of the carbon nano tube, the energy gap will be appeared. This is due to the degree of the Sp 3 hybridization, and the hydrogen coverage can control the band gap of the carbon nano tube

Parity nonconservation in the hydrogen atom

International Nuclear Information System (INIS)

Chupp, T.E.

1983-01-01

The development of experiments to detect parity nonconserving (PNC) mixing of the 2s/sub a/2/ and 2p/sub 1/2/ levels of the hydrogen atom in a 570 Gauss magnetic field is described. The technique involves observation of an asymmetry in the rate of microwave induced transitions at 1608 MHz due to the interference of two amplitudes, one produced by applied microwave and static electric fields and the other produced by an applied microwave field and the 2s/sub 1/2/-2p/sub 1/2/ mixing inducd by a PNC Hamiltonian

Ion-induced emission of charged particles from solid hydrogen and deuterium

International Nuclear Information System (INIS)

Borgesen, P.; Schou, J.; Sorensen, H.

1980-01-01

Measurements have been made of the emission of both positive and negative particles from solid hydrogen and deuterium for normal incidence of H + , H + 2 , H + 3 , D 2 H + , D + 3 and He + ions up to 10 keV. For positive particles the emission coefficient increased with increasing energy of incidence to reach a value of 0.08 per atom for 10 keV H + onto hydrogen. Apparently the positive particles are sputtered ones. The negative particles emitted are predominantly electrons. The emission coefficient per incident atom as a function of the velocity of the incident particle agress fairly well with results published earlier for incidence of hydrogen and deuterium ions. However, systematic differences of up to 10% are now observed between the coefficients for the different types of ions. (orig.)

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.

Forward elastic scattering of electrons by hydrogen atoms

Energy Technology Data Exchange (ETDEWEB)

Garibotti, C.R. (Instituto de Fisica Teorica, R. Pamplona 145, Sao Paulo (Brazil)); Massaro, P.A. (Bari Univ. (Italy). Ist. di Fisica)

1978-01-11

The available theoretical and experimental values for the elastic, inelastic and ionization cross-sections of electrons by hydrogen atoms are used to obtain the total cross-section. The optical theorem and a dispersion relation are used to calculate the forward e-H scattering amplitude for medium and high energies. Using this quantity the reliability of the Born expansion for elastic e-H scattering is tested.

Fiscal 1997 report on the development of new hydrogen atomic energy demonstrative technology; 1997 nendo kenkyu hokokusho (shinsuiso energy jissho gijutsu kaihatsu)

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-06-01

In this validation study, phenomena of excess heat which are said to be generated by electrolysis of deuterium using palladium metal, etc. as electrode are taken as `new hydrogen atomic energy,` and to clarify a possibility of using them as a future energy source, the abnormal heating phenomenon was validated and the mechanism was elucidated. The study targeted quantitative control of heat emissions. The study was finished in 1997, the fifth year from the start. The excess heat measurement could partially be reproduced; however, when conducting a confirmation experiment on the excess heat by another more reliable method under the same condition, it was found that the value of excess heat was not an absolute value exceeding measuring sensitivity and errors of the system. If the excess heat of 0.1W order is to be emitted in nuclear reaction, any reactive product should be detected in a substantial quantity. However, the product of a large quantity was not found. A possibility was found out of an increase in nuclear reaction ratio inside solid by low energy deuterium irradiation. From the above, it was concluded that the use of new hydrogen atomic energy was negative. 20 refs., 149 figs., 29 tabs.

Phase transition of DNA-linked gold nanoparticles: Creation of a high concentration of atomic hydrogen in impurity-helium solids

International Nuclear Information System (INIS)

Kiselev, S.I.; Khmelenko, V.V.; Bernard, E.P.; Lee, C.Y.; Lee, D.M.

2003-01-01

The exchange tunneling reactions D+H 2 →HD+H and D+HD→D 2 +H were used to generate high concentrations of atomic hydrogen in impurity-helium solids. The dependence of atom concentration on the content of hydrogen in the injected gas mixture gave a maximum concentration of 7.5x10 17 cm -3 hydrogen atoms for an initial gas ratio H 2 :D 2 :He=1:4:100

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

Science.gov (United States)

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

2017-11-01

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

Application of laser fluorescence spectroscopy by two-photon excitation into atomic hydrogen density measurement in reactive plasmas

International Nuclear Information System (INIS)

Kajiwara, Toshinori; Takeda, Kazuyuki; Kim, Hee Je; Park, Won Zoo; Muraoka, Katsunori; Akazaki, Masanori; Okada, Tatsuo; Maeda, Mitsuo.

1990-01-01

Density profiles of hydrogen atoms in reactive plasmas of hydrogen and methane gases were measured, for the first time, using the laser fluorescence spectroscopy by two-photon excitation of Lyman beta transition and observation at the Balmer alpha radiation. Absolute density determinations showed atomic densities of around 3 x 10 17 m -3 , or the degree of dissociation to be 10 -4 . Densities along the axis perpendicular to the RF electrode showed peaked profiles, which were due to the balance of atomic hydrogen production by electron impact on molecules against diffusion loss to the walls. (author)

Electron capture in collisions of S4+ with atomic hydrogen

Science.gov (United States)

Stancil, P. C.; Turner, A. R.; Cooper, D. L.; Schultz, D. R.; Rakovic, M. J.; Fritsch, W.; Zygelman, B.

2001-06-01

Charge transfer processes due to collisions of ground state S4+(3s2 1S) ions with atomic hydrogen are investigated for energies between 1 meV u-1 and 10 MeV u-1 using the quantum mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling, classical trajectory Monte Carlo (CTMC) and continuum distorted wave methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. A number of variants of the CTMC approach were explored, including different momentum and radial distributions for the initial state, as well as effective charge and quantum-defect models to determine the corresponding quantum state after capture into final partially stripped S3+ excited classical states. Hydrogen target isotope effects are explored and rate coefficients for temperatures between 100 and 106 K are also presented.

The antiproton-hydrogen atom interaction

International Nuclear Information System (INIS)

Morgan, D.L. Jr.

1994-07-01

The bar p-H interaction is the most important aspect of the bar ppe system. While this interaction is worthy of study in itself, it is also relevant to a number of bar p applications, both practical and in the area of fundamental physics. Theoretical study of p-H commenced more than 20 years ago and has continued with growing interest through the present. Experimental study has been limited, but recently measurements have been made of bar p's slowing in hydrogen at KeV energies, which shed light on their interaction with hydrogen atoms. Theoretical work involving various kinds and levels of approximation has now been carried out for a variety of bar p energy domains. Particular attention has been given to bar p capture at low and sub eV energies, in which a bound bar p-p state is formed, and to H excitation and ionization at KeV energies. Such calculations now extend into the sub Kelvin domain of energies. It is beginning to be possible to make comparisons between experiment and calculation and to compare calculations to one another. These comparisons suggest that theoretical work needs to be carried out in some intermediate energy domains and that some past calculations have to be repeated with more accurate methods

A laser driven source of spin polarized atomic hydrogen and deuterium

International Nuclear Information System (INIS)

Poelker, M.; Coulter, K.P.; Holt, R.J.; Jones, C.E.; Kowalczyk, R.S.; Young, L.; Toporkov, D.

1993-01-01

Recent results from a laser-driven source of polarized hydrogen (H) and deuterium (D) are presented. The performance of the source is described as a function of atomic flow rate and magnetic field. The data suggest that because atomic densities in the source are high, the system can approach spin-temperature equilibrium although applied magnetic fields are much larger than the critical field of the atoms. The authors also observe that potassium contamination in the source emittance can be reduced to a negligible amount using a teflon-lined transport tube

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.

Laser-driven source of spin-polarized atomic hydrogen and deuterium

International Nuclear Information System (INIS)

Poelker, M.

1995-01-01

A laser-driven source of spin-polarized hydrogen (H) and deuterium (D) that relies on the technique of optical pumping spin exchange has been constructed. In this source, H or D atoms and potassium atoms flow continuously through a drifilm-coated spin-exchange cell where potassium atoms are optically pumped with circularly-polarized laser light in a high magnetic field. The H or D atoms become polarized through spin-exchange collisions with polarized potassium atoms. High electron polarization (∼80%) has been measured for H and D atoms at flow rates ∼2x10 17 atoms/s. Lower polarization values are measured for flow rates exceeding 1x10 18 atoms/s. In this paper, we describe the performance of the laser-driven source as a function of H and D atomic flow rate, magnetic field strength, alkali density and pump-laser power. Polarization measurements as a function of flow rate and magnetic field suggest that, despite a high magnetic field, atoms within the optical-pumping spin-exchange apparatus evolve to spin-temperature equilibrium which results in direct polarization of the H and D nuclei. (orig.)

Atomic hydrogen cleaning of GaAs photocathodes

International Nuclear Information System (INIS)

Poelker, M.; Price, J.; Sinclair, C.

1997-01-01

It is well known that surface contaminants on semiconductors can be removed when samples are exposed to atomic hydrogen. Atomic H reacts with oxides and carbides on the surface, forming compounds that are liberated and subsequently pumped away. Experiments at Jefferson lab with bulk GaAs in a low-voltage ultra-high vacuum H cleaning chamber have resulted in the production of photocathodes with high photoelectron yield (i.e., quantum efficiency) and long lifetime. A small, portable H cleaning apparatus also has been constructed to successfully clean GaAs samples that are later removed from the vacuum apparatus, transported through air and installed in a high-voltage laser-driven spin-polarized electron source. These results indicate that this method is a versatile and robust alternative to conventional wet chemical etching procedures usually employed to clean bulk GaAs

Hydrogen atoms in a strong magnetic field

International Nuclear Information System (INIS)

Santos, R.R. dos.

1975-07-01

The energies and wave functions of the 14 lowest states of a Hydrogen atom in a strong magnetic field are calculated, using a variational scheme. The equivalence between the atomic problem and the problems related with excitons and impurities in semiconductors in the presence of a strong magnetic field are shown. The calculations of the energies and wave functions have been divided in two regions: the first, for the magnetic field ranging between zero and 10 9 G; in the second the magnetic field ranges between 10 9 and 10 11 G. The results have been compared with those obtained by previous authors. The computation time necessary for the calculations is small. Therefore this is a convenient scheme to obtain the energies and wave functions for the problem. Transition probabilities, wavelengths and oscillator strengths for some allowed transitions are also calculated. (Author) [pt

On the connection between the hydrogen atom and the harmonic oscillator: the continuum case

International Nuclear Information System (INIS)

Kibler, M.; Negadi, T.

1983-05-01

The connection between a three-dimensional nonrelativistic hydrogen atom with positive energy and a four-dimensional isotropic harmonic oscillator with repulsive potential is established by applying Jordan-Schwinger boson calculus to the algebra of the Laplace-Runge-Lenz-Pauli vector. The spectrum generating group SO(4,2) both for the bound and free states of the three-dimensional hydrogen atom arises as a quotient of the group Sp(8,R) associated to a four-dimensional isotropic harmonic oscillator with constraint

Plasma screening effects on the energies of hydrogen atom

International Nuclear Information System (INIS)

Soylu, A.

2012-01-01

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 Schrödinger 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.

Optical potential study of positron scattering by hydrogenic-type atoms

International Nuclear Information System (INIS)

Kuru Ratnavelu; Nithyanandan Natchimuthu; Kalai Kumar Rajgopal

1999-01-01

An optical potential method based on the close-coupling formalism has been implemented to study positron scattering by hydrogenic-type atoms. The present work will be reviewed in the context of other theories. Preliminary results will be presented and compared with experimental results. (author)

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.

Polarization effects in two-colour ionization of atomic hydrogen with incommensurable frequencies

International Nuclear Information System (INIS)

Cionga, A.

1993-01-01

The angular distribution of ejected electrons for two-colour ionization of atomic hydrogen are studied using an approach which takes into account the radiative corrections to both bound and the continuum states. One considers the ionization process in which one high-frequency photon has enough energy to ionize the atom, meanwhile, one extra-photon is exchanged between atomic system and the low-frequency field. We focus our attention to the case of two incommensurable frequencies. (Author)

Chemical Kinetics of Hydrogen Atom Abstraction from Allylic Sites by 3O2; Implications for Combustion Modeling and Simulation.

Science.gov (United States)

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

2017-03-09

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

On measurement of cross sections for scattering of pμ - and d μ -atoms in hydrogen and deuterium

International Nuclear Information System (INIS)

Bystritskij, V.M.

1993-01-01

The paper is a brief review of all experiments on measurement of cross sections for scattering of pμ - atoms in hydrogen and dμ - atoms in hydrogen and deuterium. The experimental results are analysed and compared both with one another and with calculated results. A program for further investigation of scattering of muonic atoms of hydrogen isotopes is proposed in order to clarify the nature of discrepancies between some experimental results and to get more precise information about the above processes. (author.). 24 refs.; 4 figs.; 3 tabs

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.

Variational approach to excitation of atomic hydrogen atoms by impacts of protons at intermediate velocities

International Nuclear Information System (INIS)

Lasri, B.; Bouamoud, M.; Gayet, R.

2006-01-01

A variational approach to the excitation of atoms by ion impacts at intermediate velocities is re-examined. Contributions from intermediate states of the target continuum, that were ignored in previous applications of this approach, are taken into account. With this improved variational approach, excitation cross sections of hydrogen atoms by intermediate energy protons are calculated and compared to recent experimental data and to previous theoretical cross sections. The influence of the intermediate target continuum is found to be very weak. In addition, the present approach is shown to apply as long as the capture process is negligible

Hydrogen atom in intense magnetic field.

Science.gov (United States)

Canuto, V.; Kelly, D. C.

1972-01-01

The structure of a hydrogen atom situated in an intense magnetic field is investigaged. Three approaches are employed. An elementary Bohr picture establishes a crucial magnetic field strength, H sub a approximately equal to 5 x 10 to the 9th G. Fields in excess of H sub a are intense in that they are able to modify the characteristic atomic scales of length and binding energy. A second approach solves the Schrodinger equation by a combination of variational methods and perturbation theory. It yields analytic expressions for the wave functions and energy eigenvalues. A third approach determines the energy eigenvalues by reducing the Schrodinger equation to a one-dimensional wave equation, which is then solved numerically. Energy eigenvalues are tabulated for field strengths of 2 x 10 to the 10th G and 2 x 10 to the 12th G. It is found that at 2 x 10 to the 12th G the lowest energy eigenvalue is changed from -13.6 to about -180 eV in agreement with previous variational computations.

Numerology, hydrogenic levels, and the ordering of excited states in one-electron atoms

Science.gov (United States)

Armstrong, Lloyd, Jr.

1982-03-01

We show that the observed ordering of Rydberg states of one-electron atoms can be understood by assuming that these states are basically hydrogenic in nature. Much of the confusion concerning this point is shown to arise from the failure to differentiate between hydrogenic ordering as the nuclear charge approaches infinity, and hydrogenic ordering for an effective charge of one. The origin of κ ordering of Rydberg levels suggested by Sternheimer is considered within this picture, and the predictions of κ ordering are compared with those obtained by assuming hydrogenic ordering.

Atomic and molecular excitation mechanisms in the interstellar medium

International Nuclear Information System (INIS)

Sternberg, A.

1986-01-01

The detailed infrared response of dense molecular hydrogen gas to intense ultraviolet radiation fields in photodissociation regions is presented. The thermal and chemical structures of photodissociation regions are analyzed, and the relationship between the emission by molecular hydrogen and trace atomic and molecular species is explored. The ultraviolet spectrum of radiation generated by cosmic rays inside dense molecular clouds is presented, and the resulting rates of photodissociation for a variety of interstellar molecules are calculated. Effects of this radiation on the chemistry of dense molecular clouds are discussed, and it is argued that the cosmic ray induced photons will significantly inhibit the production of complex molecular species. It is argued that the annihilation of electrons and positrons at the galactic center may result in observable infrared line emission by atomic hydrogen. A correlation between the intensity variations of the 511 keV line and the hydrogen infrared lines emitted by the annihilation region is predicted. The observed infrared fluxes from compact infrared sources at the galactic center may be used to constrain theories of pair production there

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

DEFF Research Database (Denmark)

Holm, Torkil; Madsen, Jørgen Øgaard

1996-01-01

, and conceivably all hydrocarbons are quantitatively converted into methane at temperatures below 600 C, that is, before the proper combustion has started. The splitting of the C-C bonds is preceded by hydrogenation of double and triple bonds and aromatic rings. The reactions, no doubt, are caused by hydrogen...... atoms, which are formed in the burning hydrogen and which diffuse into the inner core of the flame. The quantitative formation of methane appears to explain the "equal per carbon" rule for the detector response of hydrocarbons, since all carbons are "exchanged" for methane molecules....

Ion cyclotron resonance study of reactions of ions with hydrogen atoms

International Nuclear Information System (INIS)

Karpas, Z.; Anicich, V.; Huntress, W.T. Jr.

1979-01-01

Reactions of H 2 + , HeH + , and CO 2 + ions with hydrogen atoms, and the reactions of D 2 + , CO 2 + , CO + , N 2 + and HCN + with deuterium atoms, were studied using ion cyclotron resonance techniques. These reactions proceed predominantly via a charge transfer mechanism. The rate constants measured are: 6.4, 9.1, 1.1, 5.0, 0.84, 0.90, 1.2, and 0.37 x 10 -10 cm 3 /sec, respectively. Hydrocarbon ions of the types CH/sub n/ + and C 2 H/sub n/ + , where n=2--4, do not react with H or D atoms

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

Science.gov (United States)

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

2016-05-05

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

Hydrogen atom and the H+2 and HeH++ molecular ions inside prolate spheroidal boxes

International Nuclear Information System (INIS)

Ley-Koo, E.; Cruz, S.A.

1981-01-01

We formulate the exact solution of the Schroedinger equation for systems of one electron in the Coulomb field of one or two fixed nuclei at the foci inside prolate spheroidal boxes. Numerical results are obtained for the energy eigenvalues and eigenfunctions of the lowest states of the hydrogen atom and the H + 2 and HeH ++ molecular ions for boxes of different sizes and eccentricities. We also evaluate the hyperfine splitting of atomic hydrogen and of H + 2

Photoexcitation and ionization of hydrogen atom confined in Debye environment

International Nuclear Information System (INIS)

Lumb, S.; Lumb, S.; Nautiyal, V.

2015-01-01

The dynamics of a hydrogen atom confined in an impenetrable spherical box and under the effect of Debye screening, in the presence of intense short laser pulses of few femtosecond is studied in detail. The energy spectra and wave functions have been calculated using Bernstein polynomial (B-polynomial) method. Variation of transition probabilities for various transitions due to changes in Debye screening length, confinement radius as well as the parameters characterizing applied laser pulse is studied and explained. The results are found to be in good agreement with the results obtained by others. The photoexcitation and ionization of the atom strongly depend on confinement radius and screening parameter. For small confinement radii and for some values of screening parameter the atom is found to be ionized easily. The dynamics of the atom can be easily controlled by varying pulse parameters

Self-Regular Black Holes Quantized by means of an Analogue to Hydrogen Atoms

Directory of Open Access Journals (Sweden)

Chang Liu

2016-01-01

Full Text Available We suggest a quantum black hole model that is based on an analogue to hydrogen atoms. A self-regular Schwarzschild-AdS black hole is investigated, where the mass density of the extreme black hole is given by the probability density of the ground state of hydrogen atoms and the mass densities of nonextreme black holes are given by the probability densities of excited states with no angular momenta. Such an analogue is inclined to adopt quantization of black hole horizons. In this way, the total mass of black holes is quantized. Furthermore, the quantum hoop conjecture and the Correspondence Principle are discussed.

Stabilization of atomic hydrogen and deuterium

International Nuclear Information System (INIS)

Walraven, J.T.M.

1982-01-01

This thesis deals with the first of a series of experiments done at the University of Amsterdam to study the properties of spin polarized atomic hydrogen (spa H) and deuterium (spa D) at very low temperatures (T approximately 0.3 K) and in high magnetic fields (B approximately 10 T). The experiments show that spa H and spa D may be subjected to experimental investigation like any normal (i.e. stable) gas. Chapter 2 deals with the experimental apparatus and in particular the development of a reliable method to cool atomic hydrogen to very low temperatures which turned out to be decisive for the experiments. An account of the first experiments with spa H can be found in chapter 3. These experiments showed that spa H can be stabilized for extended periods of time (at low temperature and in high magnetic fields) by covering all surfaces with a superfluid film of 4 He. The gas was detected by triggering recombination by locally breaking the helium film and measuring the heat of recombination. This method turned out to be very sensitive and easy to implement. In chapter 4 the physical picture of the gas is discussed. This includes a discussion of the density profile and the phenomenon of thermal leakage from the open structured sample cell. The density profile may be used to detect Bose-Einstein condensation. A second series of experiments is discussed in chapter 5. These measurements were aimed at achieving high densities and to study the limiting processes. They demonstrate that spa H behaves as a gas. Recombination measurements with spa D at low temperatures are discussed in chapter 6 and show that recombination predominantly occurs on the surface of the helium film. (Auth.)

Charge transfer between hydrogen(deuterium) ions and atoms in metal vapors

International Nuclear Information System (INIS)

Alvarez T, I.; Cisneros G, C.

1981-01-01

The current state of the experiments on charge transfer between hydrogen (deuterium) ions and atoms in metal vapors are given. Emphasis is given to describing different experimental techniques. The results of calculations if available, are compared with existing experimental data. (author)

One- and two-photon ionization of hydrogen atom embedded in Debye plasmas

International Nuclear Information System (INIS)

Chang, T. N.; Fang, T. K.; Ho, Y. K.

2013-01-01

We present a detailed analysis of the plasma-induced resonance-like atomic structures near the ionization threshold in one- and two-photon ionization of hydrogen atom. Such resonance-like structures result from the migration of the upper bound excited states of bound-bound atomic transitions into the continuum due to the less attractive screened Coulomb potential which simulates the external environmental effect for an atom embedded in Debye plasma. The change from the resonance-like narrow structures into broad continuous spectra as the plasma effect increases could be accounted for by the overlap between the respective wavefunctions of the atomic electron in the initial state and its corresponding outgoing ionized state in the continuum

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

DEFF Research Database (Denmark)

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

2017-01-01

Modern pulsed X-ray sources permit time-dependent measurements of dynamical changes in atoms and molecules via non-resonant scattering. The planning, analysis, and interpretation of such experiments, however, require a firm and elaborated theoretical framework. This paper provides a detailed...... description of time-resolved X-ray scattering by non-stationary electronic wave packets in atomic systems. A consistent application of the Waller-Hartree approximation is discussed and different contributions to the total differential scattering signal are identified and interpreted. Moreover......, it is demonstrated how the scattering signal of wave packets in the hydrogen atom can be expressed analytically. This permits simulations without numerical integration and establishes a benchmark for both efficiency and accuracy. Based on that, scattering patterns of an exemplary wave packet in the hydrogen atom...

Hydrogen atom in phase space

International Nuclear Information System (INIS)

Chetouani, L.; Hammann, T.F.

1987-01-01

The Hamiltonian of the three-dimensional hydrogen atom is reduced, in parabolic coordinates, to the Hamiltonians of two bidimensional harmonic oscillators, by doing several space-time transformations,separating the movement along the three parabolic directions (ξ,eta,phi), and introducing two auxiliary angular variables psi and psi', 0≤psi, psi'≤2π. The Green's function is developed into partial Green's functions, and expressed in terms of two Green's functions that describe the movements along both the ξ and eta axes. Introducing auxiliary Hamiltonians allows one to calculate the Green's function in the configurational space, via the phase-space evolution function of the two-dimensional harmonic oscillator. The auxiliary variables psi and psi' are eliminated by projection. The thus-obtained Green's function, save for a multiplicating factor, coincides with that calculated following the path-integral formalism

Atomic layer deposition of high-mobility hydrogen-doped zinc oxide

NARCIS (Netherlands)

Macco, B.; Knoops, H.C.M.; Verheijen, M.A.; Beyer, W.; Creatore, M.; Kessels, W.M.M.

2017-01-01

In this work, atomic layer deposition (ALD) has been employed to prepare high-mobility H-doped zinc oxide (ZnO:H) films. Hydrogen doping was achieved by interleaving the ZnO ALD cycles with H2 plasma treatments. It has been shown that doping with H2 plasma offers key advantages over traditional

Hydrogen atom spectrum and the Lamb shift in noncommutative QED

International Nuclear Information System (INIS)

Chaichian, M. . Helsinki Institute of Physics, Helsinki; Tureanu, A. . Helsinki Institute of Physics, Helsinki; FI)

2000-10-01

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

Multiple pole in the electron--hydrogen-atom scattering amplitude

International Nuclear Information System (INIS)

Amusia, M.Y.; Kuchiev, M.Y.

1982-01-01

It is demonstrated that the amplitude for electron--hydrogen-atom forward scattering has the third-order pole at the point E = -13.6 eV, E being the energy of the incident electron. The coefficients which characterize the pole are calculated exactly. The invalidity of the Born approximation is proved. The contribution of the pole singularity to the dispersion relation for the scattering amplitude is discussed

Positron scattering by atomic hydrogen including positronium formation

International Nuclear Information System (INIS)

Higgins, K.; Burke, P.G.

1993-01-01

Positron scattering by atomic hydrogen including positronium formation has been formulated using the R-matrix method and a general computer code written. Partial wave elastic and ground state positronium formation cross sections have been calculated for L ≤ 6 using a six-state approximation which includes the ground state and the 2s and 2p pseudostates of both hydrogen and positronium. The elastic scattering results obtained are in good agreement with those derived from a highly accurate calculation based upon the intermediate energy R-matrix approach. As in a previous coupled-channel static calculation, resonance effects are observed at intermediate energies in the S-wave positronium formation cross section. However, in the present results, the dominant resonance arises in the P-wave cross sections at an energy of 2.73 Ryd and with a width of 0.19 Ryd. (author)

Charge transfer to the continuum by heavy ions in atomic hydrogen

International Nuclear Information System (INIS)

Sellin, I.A.

1981-01-01

Design and installation of an atomic hydrogen target for measurements of charge transfer to the continuum by heavy ions are discussed. The design consists of a tungsten gas cell operated at temperatures of 2500 to 2600 0 K. Initial testing is underway

Pt Single Atoms Embedded in the Surface of Ni Nanocrystals as Highly Active Catalysts for Selective Hydrogenation of Nitro Compounds.

Science.gov (United States)

Peng, Yuhan; Geng, Zhigang; Zhao, Songtao; Wang, Liangbing; Li, Hongliang; Wang, Xu; Zheng, Xusheng; Zhu, Junfa; Li, Zhenyu; Si, Rui; Zeng, Jie

2018-06-13

Single-atom catalysts exhibit high selectivity in hydrogenation due to their isolated active sites, which ensure uniform adsorption configurations of substrate molecules. Compared with the achievement in catalytic selectivity, there is still a long way to go in exploiting the catalytic activity of single-atom catalysts. Herein, we developed highly active and selective catalysts in selective hydrogenation by embedding Pt single atoms in the surface of Ni nanocrystals (denoted as Pt 1 /Ni nanocrystals). During the hydrogenation of 3-nitrostyrene, the TOF numbers based on surface Pt atoms of Pt 1 /Ni nanocrystals reached ∼1800 h -1 under 3 atm of H 2 at 40 °C, much higher than that of Pt single atoms supported on active carbon, TiO 2 , SiO 2 , and ZSM-5. Mechanistic studies reveal that the remarkable activity of Pt 1 /Ni nanocrystals derived from sufficient hydrogen supply because of spontaneous dissociation of H 2 on both Pt and Ni atoms as well as facile diffusion of H atoms on Pt 1 /Ni nanocrystals. Moreover, the ensemble composed of the Pt single atom and nearby Ni atoms in Pt 1 /Ni nanocrystals leads to the adsorption configuration of 3-nitrostyrene favorable for the activation of nitro groups, accounting for the high selectivity for 3-vinylaniline.

The 4-particle hydrogen-anti-hydrogen system revisited. Twofold molecular Hamiltonian symmetry and natural atom anti-hydrogen

International Nuclear Information System (INIS)

Van Hooydonk, G.

2005-01-01

The historical importance of the original quantum mechanical bond theory proposed by Heitler and London in 1927 as well as its pitfalls are reviewed. Modern ab initio treatments of H-H-bar systems are inconsistent with the logic behind algebraic Hamiltonians H ± = H 0 ± ΔH for charge-symmetrical and charge-asymmetrical 4 unit charge systems like H 2 and HH-bar. Their eigenvalues are exactly those of 1927 Heitler-London (HL) theory. Since these 2 Hamiltonians are mutually exclusive, only the attractive one can apply for stable natural molecular H 2 . A wrong choice leads to problems with anti-atom H-bar. In line with earlier results on band and line spectra, we now prove that HL chose the wrong Hamiltonian for H 2 . Their theory explains the stability of attractive system H 2 with a repulsive Hamiltonian H 0 + ΔH instead of with the attractive one H 0 - ΔH, representative for charge-asymmetrical system HH-bar. A new second order symmetry effect is detected in this attractive Hamiltonian, which leads to a 3-dimensional structure for the 4-particle system. Repulsive HL Hamiltonian H + applies at long range but at the critical distance, attractive charge-inverted Hamiltonian H - takes over and leads to bond H 2 but in reality, HH-bar, for which we give an analytical proof. This analysis confirms and generalizes an earlier critique of the wrong long range behavior of HL-theory by Bingel, Preuss and Schmidtke and by Herring. Another wrong asymptote choice in the past also applies for atomic anti-hydrogen H-bar, which has hidden the Mexican hat potential for natural hydrogen. This generic solution removes most problems, physicists and chemists experience with atomic H-bar and molecular HH-bar, including the problem with antimatter in the Universe. (author)

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

Indian Academy of Sciences (India)

2017-04-12

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

Role of hydrogen in the chemical vapor deposition growth of MoS2 atomic layers

Science.gov (United States)

Li, Xiao; Li, Xinming; Zang, Xiaobei; Zhu, Miao; He, Yijia; Wang, Kunlin; Xie, Dan; Zhu, Hongwei

2015-04-01

Hydrogen plays a crucial role in the chemical vapor deposition (CVD) growth of graphene. Here, we have revealed the roles of hydrogen in the two-step CVD growth of MoS2. Our study demonstrates that hydrogen acts as the following: (i) an inhibitor of the thermal-induced etching effect in the continuous film growth process; and (ii) a promoter of the desulfurization reaction by decreasing the S/Mo atomic ratio and the oxidation reaction of the obtained MoSx (0 desulfurization reaction by decreasing the S/Mo atomic ratio and the oxidation reaction of the obtained MoSx (0 < x < 2) films. A high hydrogen content of more than 100% in argon forms nano-sized circle-like defects and damages the continuity and uniformity of the film. Continuous MoS2 films with a high crystallinity and a nearly perfect S/Mo atomic ratio were finally obtained after sulfurization annealing with a hydrogen content in the range of 20%-80%. This insightful understanding reveals the crucial roles of hydrogen in the CVD growth of MoS2 and paves the way for the controllable synthesis of two-dimensional materials. Electronic supplementary information (ESI) available: Low-magnification optical images; Raman spectra of 0% and 5% H2 samples; AFM characterization; Schematic of the film before and after sulfurization annealing; Schematic illustrations of two typical Raman-active phonon modes (E12g, A1g); Raman (mapping) spectra for 40% and 80% H2 samples before and after sulfurization annealing; PL spectra. See DOI: 10.1039/c5nr00904a

Hydrogen atom injection into carbon surfaces by comparison between Monte-Carlo, molecular dynamics and ab-initio calculations

International Nuclear Information System (INIS)

Ito, A.; Kenmotsu, T.; Kikuhara, Y.; Inai, K.; Ohya, K.; Wang, Y.; Irle, S.; Morokuma, K.; Nakamura, H.

2009-01-01

Full text: To understand the plasma-wall interaction on divertor plates, we investigate the interaction of hydrogen atoms and carbon materials used in the high heat flux components by the use of the following simulations. Monte-Carlo (MC) method based on binary collision approximation can calculate the sputtering process of hydrogen atoms on the carbon material quickly. Classical molecular dynamics (MD) method employs multi-body potential models and can treat realistic structures of crystal and molecule. The ab-initio method can calculate electron energy in quantum mechanics, which is regarded as realistic potential for atoms. In the present paper, the interaction of the hydrogen and the carbon material is investigated using the multi-scale (MC, MD and ab-initio) methods. The bombardment of hydrogen atoms onto the carbon material is simulated by the ACAT-code of the MC method, which cannot represent the structure of crystal, and the MD method using modified reactive empirical bond order (REBO) potential, which treats single crystal graphite and amorphous carbon. Consequently, we clarify that the sputtering yield and the reflection rate calculated by the ACAT-code agree with those on the amorphous carbon calculated by the MD. Moreover, there are many kinds of REBO potential for the MD. Adsorption, reflection and penetration rates between a hydrogen atom and a graphene surface are calculated by the MD simulations using the two kinds of potential model. For the incident energy of less than 1 eV, the MD simulation using the modified REBO potential, which is based on Brenner's REBO potential in 2002, shows that reflection is dominant, while the most popular Brenner's REBO potential in 1990 shows that adsorption is dominant. This reflection of the low energy injection is caused by a small potential barrier for the hydrogen atom in the modified REBO potential. The small potential barrier is confirmed by the ab-initio calculations, which are hybrid DFT (B3LYP/cc-pVDZ), ab

Hydrogen atom in a uniform electromagnetic field as an anharmonic oscillator

International Nuclear Information System (INIS)

Kibler, M.; Negadi, T.

1984-01-01

This work establishes, by means of the Kustaanheimo-Stiefel transformation, a connection between two branches of theoretical physics which are, in present times, the object of numerous studies: the quantum mechanics of anharmonic oscillators and of the hydrogen atom in a (strong) homogeneous and constant electromagnetic field

Calculation of the 1s-2s two-photon excitation cross-section in atomic hydrogen

Energy Technology Data Exchange (ETDEWEB)

Celik, G.; Celik, E.; Kilic, H.S. [Selcuk Univ., Dept. of Physics, Faculty of Arts and Science (Turkey)

2008-12-15

The two-photon excitation cross-section of atomic hydrogen is calculated using explicit summation over intermediate states within the framework of dipole approximation. The matrix element for two-photon excitation is transformed into finite sums, consisting of the product of a radial and angular part. Nine intermediate states are employed in the calculation of the transition matrix element. The two-photon excitation cross-section obtained for the transition 1s{sup 2}S{sub 1/2}-2s{sup 2}S{sub 1/2} in atomic hydrogen is in good agreement with the literature. (authors)

Calculation of the 1s-2s two-photon excitation cross-section in atomic hydrogen

International Nuclear Information System (INIS)

Celik, G.; Celik, E.; Kilic, H.S.

2008-01-01

The two-photon excitation cross-section of atomic hydrogen is calculated using explicit summation over intermediate states within the framework of dipole approximation. The matrix element for two-photon excitation is transformed into finite sums, consisting of the product of a radial and angular part. Nine intermediate states are employed in the calculation of the transition matrix element. The two-photon excitation cross-section obtained for the transition 1s 2 S 1/2 -2s 2 S 1/2 in atomic hydrogen is in good agreement with the literature. (authors)

Effect of Ge atoms on crystal structure and optoelectronic properties of hydrogenated Si-Ge films

Science.gov (United States)

Li, Tianwei; Zhang, Jianjun; Ma, Ying; Yu, Yunwu; Zhao, Ying

2017-07-01

Optoelectronic and structural properties of hydrogenated microcrystalline silicon-germanium (μc-Si1-xGex:H) alloys prepared by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) were investigated. When the Ge atoms were predominantly incorporated in amorphous matrix, the dark and photo-conductivity decreased due to the reduced crystalline volume fraction of the Si atoms (XSi-Si) and the increased Ge dangling bond density. The photosensitivity decreased monotonously with Ge incorporation under higher hydrogen dilution condition, which was attributed to the increase in both crystallization of Ge and the defect density.

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, ...

Electron capture in collisions of S{sup 4+} with atomic hydrogen

Energy Technology Data Exchange (ETDEWEB)

Stancil, P.C. [Department of Physics and Astronomy, University of Georgia, Athens, GA (United States)]. E-mail: stancil@physast.uga.edu; Turner, A.R. [Department of Chemistry, University of Liverpool, Liverpool (United Kingdom)]. E-mail: art@liv.ac.uk; Cooper, D.L. [Department of Chemistry, University of Liverpool, Liverpool (United Kingdom)]. E-mail: dlc@liv.ac.uk; Schultz, D.R. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)]. E-mail: schultz@mail.phy.ornl.gov; Rakovic, M.J. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)]. E-mail: milun@mail.phy.ornl.gov; Fritsch, W. [Abteilung Theoretische Physik, Hahn-Meitner-Institut Berlin, Berlin (Germany)]. E-mail: fritsch@hmi.de; Zygelman, B. [Department of Physics, University of Nevada, Las Vegas, NV (United States)]. E-mail: bernard@physics.unlv.edu

2001-06-28

Charge transfer processes due to collisions of ground state S{sup 4+}(3s{sup 2} {sup 1}S) ions with atomic hydrogen are investigated for energies between 1 meV u{sup -1} and 10 MeV u{sup -1} using the quantum mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling, classical trajectory Monte Carlo (CTMC) and continuum distorted wave methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. A number of variants of the CTMC approach were explored, including different momentum and radial distributions for the initial state, as well as effective charge and quantum-defect models to determine the corresponding quantum state after capture into final partially stripped S{sup 3+} excited classical states. Hydrogen target isotope effects are explored and rate coefficients for temperatures between 100 and 10{sup 6} K are also presented. (author)

Quark Synthesis String Theory From Dark Matter to Light Emitting Atoms

Science.gov (United States)

Webb, William

2012-10-01

Forefather physicists formulated fusion based on nucleosynthesis. They directed that whole nucleons synthesize. Quark Synthesis String Theory now shows that it's the string-like quarks that do the synthesizing: not whole nucleons. In a dark region, string-like quarks synthesize with other string-like quarks to make rope-like quarks. Quarks structure into threesomes bound only by electrostatic and gravitational forces. Quarks not structuring as threesomes remain dark. Balanced threesomes of string-like quarks become neutrons. Balanced threesomes of rope-like quarks become more massive neutroniumA nuclei. After their formation, neutrons and neutroniumAs quickly begin emitting electrons. This paper develops equations that correctly describe nuclear structures and their electron emissions. Electron emission beta decay is calculated for the 30 least massive neutroniumA nuclei and their subsequent transmutation thru 203 intermediate nuclei on their way to becoming well known nuclei centering the 30 least massive light emitting atoms. This is a perfect 233 for 233 match between calculations of Quark Synthesis String Theory and factual nuclear data. This perfect match provides affirmation that nuclei have no need for the unknown strong or week forces and mediating particles. Nuclear physics succeeds using a string theory that has the quarks doing the synthesizing.

Higher order Stark effect and transition probabilities on hyperfine structure components of hydrogen like atoms

Energy Technology Data Exchange (ETDEWEB)

Pal' chikov, V.G. [National Research Institute for Physical-Technical and Radiotechnical Measurements - VNIIFTRI (Russian Federation)], E-mail: vitpal@mail.ru

2000-08-15

A quantum-electrodynamical (QED) perturbation theory is developed for hydrogen and hydrogen-like atomic systems with interaction between bound electrons and radiative field being treated as the perturbation. The dependence of the perturbed energy of levels on hyperfine structure (hfs) effects and on the higher-order Stark effect is investigated. Numerical results have been obtained for the transition probability between the hfs components of hydrogen-like bismuth.

Jagiellonian University Study of Hadronic Hydrogen-like Atoms in the DIRAC Experiment at PS CERN

CERN Document Server

Afanasyev, L

2017-01-01

Production of hadronic hydrogen-like atoms at high-energy collisions and method of their observation are considered. Main results of the DIRAC experiment on observation and lifetime measurement of atoms formed by pairs of charged pion–pion and pion–kaon are presented.

Atoms in strong laser fields

International Nuclear Information System (INIS)

L'Huillier, A.

2002-01-01

When a high-power laser focuses into a gas of atoms, the electromagnetic field becomes of the same magnitude as the Coulomb field which binds a 1s electron in a hydrogen atom. 3 highly non-linear phenomena can happen: 1) ATI (above threshold ionization): electrons initially in the ground state absorb a large number of photons, many more than the minimum number required for ionization; 2) multiple ionization: many electrons can be emitted one at a time, in a sequential process, or simultaneously in a mechanism called direct or non-sequential; and 3) high order harmonic generation (HHG): efficient photon emission in the extreme ultraviolet range, in the form of high-order harmonics of the fundamental laser field can occur. The theoretical problem consists in solving the time dependent Schroedinger equation (TDSE) that describes the interaction of a many-electron atom with a laser field. A number of methods have been proposed to solve this problem in the case of a hydrogen atom or a single-active electron atom in a strong laser field. A large effort is presently being devoted to go beyond the single-active approximation. The understanding of the physics of the interaction between atoms and strong laser fields has been provided by a very simple model called ''simple man's theory''. A unified view of HHG, ATI, and non-sequential ionization, originating from the simple man's model and the strong field approximation, expressed in terms of electrons trajectories or quantum paths is slowly emerging. (A.C.)

Formation of the low-resistivity compound Cu_3Ge by low-temperature treatment in an atomic hydrogen flux

International Nuclear Information System (INIS)

Erofeev, E. V.; Kazimirov, A. I.; Fedin, I. V.; Kagadei, V. A.

2016-01-01

The systematic features of the formation of the low-resistivity compound Cu_3Ge by low-temperature treatment of a Cu/Ge two-layer system in an atomic hydrogen flux are studied. The Cu/Ge two-layer system is deposited onto an i-GaAs substrate. Treatment of the Cu/Ge/i-GaAs system, in which the layer thicknesses are, correspondingly, 122 and 78 nm, in atomic hydrogen with a flux density of 10"1"5 at cm"2 s"–"1 for 2.5–10 min at room temperature induces the interdiffusion of Cu and Ge, with the formation of a polycrystalline film containing the stoichiometric Cu_3Ge phase. The film consists of vertically oriented grains 100–150 nm in size and exhibits a minimum resistivity of 4.5 µΩ cm. Variations in the time of treatment of the Cu/Ge/i-GaAs samples in atomic hydrogen affect the Cu and Ge depth distribution, the phase composition of the films, and their resistivity. Experimental observation of the synthesis of the Cu_3Ge compound at room temperature suggests that treatment in atomic hydrogen has a stimulating effect on both the diffusion of Cu and Ge and the chemical reaction of Cu_3Ge-compound formation. These processes can be activated by the energy released upon the recombination of hydrogen atoms adsorbed at the surface of the Cu/Ge/i-GaAs sample.

Measurements of recombination coefficient of hydrogen atoms on plasma deposited thin films

International Nuclear Information System (INIS)

Drenik, A.; Vesel, A.; Mozetic, M.

2006-01-01

We have performed experiments in plasma afterglow in order to determine the recombination coefficients of plasma deposited thin films of tungsten and graphite. Plasma deposited films rather than bulk material were used in order to more closely emulate surface structure of plasma-facing material deposits in fusion reactors. We have also determined the recombination coefficient of 85250 borosilicate glass and Teflon. Plasma was created by means of a radio frequency generator in a mixture of argon and hydrogen at the pressures between 60 Pa and 280 Pa. The degree of dissociation of hydrogen molecules was found to be between 0.1 and 1. The H-atom density was measured by Fiber Optic Catalytic Probe. The recombination coefficient was determined by measuring the axial profile of the H-atom density and using Smith's side arm diffusion model. (author)

A classical treatment of the quadratic Zeeman effect in atomic hydrogen

Science.gov (United States)

Al-Laithy, M. A.; Farmer, C. M.; McDowell, M. R. C.

1985-03-01

A description of the non-relativistic classical motion of the electron of a hydrogen atom in the presence of a static magnetic field of arbitrary (non-relativistic) strength is given for arbitrary angular momentum. Applications are given to m = 0 and m = 3 at B = 26.877 kG.

Excitation and charge transfer in low-energy hydrogen atom collisions with neutral iron

Science.gov (United States)

Barklem, P. S.

2018-05-01

Data for inelastic processes due to hydrogen atom collisions with iron are needed for accurate modelling of the iron spectrum in late-type stars. Excitation and charge transfer in low-energy Fe+H collisions is studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multi-channel Landau-Zener model. An extensive calculation including 166 covalent states and 25 ionic states is presented and rate coefficients are calculated for temperatures in the range 1000-20 000 K. The largest rates are found for charge transfer processes to and from two clusters of states around 6.3 and 6.6 eV excitation, corresponding in both cases to active 4d and 5p electrons undergoing transfer. Excitation and de-excitation processes among these two sets of states are also significant. Full Tables and rate coefficient data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A90

Hydrogen atom in a magnetic field: Ghost orbits, catastrophes, and uniform semiclassical approximations

International Nuclear Information System (INIS)

Main, J.; Wunner, G.

1997-01-01

Applying closed-orbit theory to the recurrence spectra of the hydrogen atom in a magnetic field, one can interpret most, but not all, structures semiclassically in terms of closed classical orbits. In particular, conventional closed-orbit theory fails near bifurcations of orbits where semiclassical amplitudes exhibit unphysical divergences. Here we analyze the role of ghost orbits living in complex phase space. The ghosts can explain resonance structures in the spectra of the hydrogen atom in a magnetic field at positions where no real orbits exist. For three different types of catastrophes, viz. fold, cusp, and butterfly catastrophes, we construct uniform semiclassical approximations and demonstrate that these solutions are completely determined by classical parameters of the real orbits and complex ghosts. copyright 1997 The American Physical Society

Variable scaling method and Stark effect in hydrogen atom

International Nuclear Information System (INIS)

Choudhury, R.K.R.; Ghosh, B.

1983-09-01

By relating the Stark effect problem in hydrogen-like atoms to that of the spherical anharmonic oscillator we have found simple formulas for energy eigenvalues for the Stark effect. Matrix elements have been calculated using 0(2,1) algebra technique after Armstrong and then the variable scaling method has been used to find optimal solutions. Our numerical results are compared with those of Hioe and Yoo and also with the results obtained by Lanczos. (author)

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.

ATOMIC HYDROGEN IN A GALACTIC CENTER OUTFLOW

International Nuclear Information System (INIS)

McClure-Griffiths, N. M.; Green, J. A.; Hill, A. S.; Lockman, F. J.; Dickey, J. M.; Gaensler, B. M.; Green, A. J.

2013-01-01

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 ∼14 km s –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 ∼200 km s –1 in a Galactic wind.

Asymptotics of Rydberg states for the hydrogen atom

International Nuclear Information System (INIS)

Thomas, L.E.

1997-01-01

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.)

Ground-state populations of atomic hydrogen and hydrogen-like ions in nonthermal plasmas, and collisional-radiative recombination and ionization coefficients

International Nuclear Information System (INIS)

Drawin, H.W.; Emard, F.

1978-01-01

The populations of atomic hydrogen and hydrogen-like ions have been calculated using a collisional-radiative model. The global collisional-radiative excitation coefficients rsub(j)sup((0)) and rsub(j)sup((1)) valid for homogeneous-stationary and/or quasi-homogeneous quasi-stationary plasmas were published recently. The present paper contains in tabulated form the ground state populations and Saha decrements for the homogeneous stationary state, and the collisional-radiative recombination and ionization coefficients. (Auth.)

Charge transfer between O6+ and atomic hydrogen

Science.gov (United States)

Wu, Y.; Stancil, P. C.; Liebermann, H. P.; Buenker, R. J.; Schultz, D. R.; Hui, Y.

2011-05-01

The charge exchange process has been found to play a dominant role in the production of X-rays and/or EUV photons observed in cometary and planetary atmospheres and from the heliosphere. Charge transfer cross sections, especially state-selective cross sections, are necessary parameters in simulations of X-ray emission. In the present work, charge transfer due to collisions of ground state O6+(1s2 1 S) with atomic hydrogen has been investigated theoretically using the quantum-mechanical molecular-orbital close-coupling method (QMOCC). The multi-reference single- and double-excitation configuration interaction approach (MRDCI) has been applied to compute the adiabatic potential and nonadiabatic couplings, and the atomic basis sets used have been optimized with the method proposed previously to obtain precise potential data. Total and state-selective cross sections are calculated for energies between 10 meV/u and 10 keV/u. The QMOCC results are compared to available experimental and theoretical data as well as to new atomic-orbital close-coupling (AOCC) and classical trajectory Monte Carlo (CTMC) calculations. A recommended set of cross sections, based on the MOCC, AOCC, and CTMC calculations, is deduced which should aid in X-ray modeling studies.

Comment on "Theoretical study of the dynamics of atomic hydrogen adsorbed on graphene multilayers"

Science.gov (United States)

Bonfanti, Matteo; Martinazzo, Rocco

2018-03-01

It is shown that the theoretical prediction of a transient magnetization in bilayer and multilayer graphene (M. Moaied et al., Phys. Rev. B 91, 155419 (2015), 10.1103/PhysRevB.91.155419) relies on an incorrect physical scenario for adsorption, namely, one in which H atoms adsorb barrierless on graphitic substrates and form a random adsorption pattern of monomers. Rather, according to experimental evidence, H atom sticking is an activated process, and adsorption is under kinetic control, largely ruled by a preferential sticking mechanism that leads to stable, nonmagnetic dimers at all but the smallest coverages (Theory and experiments are reconciled by reconsidering the hydrogen atom adsorption energetics with the help of van der Waals-inclusive density functional calculations that properly account for the basis set superposition error. It is shown that today van der Waals-density functional theory predicts a shallow physisorption well that nicely agrees with available experimental data and suggests that the hydrogen atom adsorption barrier in graphene is 180 meV high, within ˜5 meV accuracy.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-12-17

In order to enable liquid hydrogen fuel cell technologies for vehicles the cost of hydrogen liquefaction should be lowered. The current method of hydrogen liquefaction is the Claude cycle that has a figure of merit (FOM) of 0.3-0.35. New magnetocaloric hydrogen liquefaction devices have been proposed with a FOM>0.5, which is a significant improvement. A significant hurdle to realizing these devices is the synthesis of spherical rare earth based alloy powders of 200μm in diameter. In this study a centrifugal atomization method that used a rotating disk with a rotating oil quench bath was developed to make gadolinium and gadolinium-yttrium spheres. The composition of the spherical powders included pure Gd and Gd_0.91Y_0.09. The effect of atomization parameters, such as superheat, melt properties, disk shape, disk speed, and melt system materials and design, were investigated on the size distribution and morphology of the resulting spheres. The carbon, nitrogen, and oxygen impurity levels also were analyzed and compared with the magnetic performance of the alloys. The magnetic properties of the charge material as well as the resulting powders were measured using a vibrating sample magnetometer. The saturation magnetization and Curie temperature were the target properties for the resulting spheres. These values were compared with measurements taken on the charge material in order to investigate the effect of atomization processing on the alloys.

To problem of experimental determination of parameters of μ-atom charge-exchange process of hydrogen isotopes on He nuclei

International Nuclear Information System (INIS)

Bystritskij, V.M.; Stolupin, V.A.

1990-01-01

The kinetics of μ-atomic and μ-molecular processes occuring in hydrogen isotopes-helium mixture is observed. The expressions are obtained to determine the parameters of a process of the muon transition from hydrogen isotope μ atoms to helium nuclei with the use of different experimental methods. 18 refs.; 3 figs.; 1 tab

What we do and not know about electron impact excitation of atomic hydrogen

International Nuclear Information System (INIS)

Callaway, J.

1982-11-01

The present state of knowledge derived from both theoretical and experimental information on electron impact excitation of atomic hydrogen is briefly reviewed. Suggestions are made for further calculations and for additional experiments. (author)

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-07-01

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

The Influence of Gas Composition in Dielectric Barrier Discharges on the Broadening of the Hydrogen Hα Transition

International Nuclear Information System (INIS)

Janus, H. W.

2006-01-01

The distribution of hydrogen atoms responsible for emission of the Balmer Hα line in the region of the dielectric barrier discharges in the helium and hydrogen as well as in the argon and hydrogen mixtures, in the direction perpendicular to the electrode surfaces, has bee determined by the optical emission spectroscopy accounting for the polarization of the emitted light. The procedure of fitting the measured line profiles accounting for the Stark effect has been used for determination of the distribution of the electric field in the discharge region

Spheroidal corrections to the spherical and parabolic bases of the hydrogen atom

International Nuclear Information System (INIS)

Mardyan, L.G.; Pogosyan, G.S.; Sisakyan, A.N.

1986-01-01

This paper introduces the bases of the hydrogen atom and obtains recursion relations that determine the expansion of the spheroidal basis with respect to its parabolic basis. The leading spheroidal corrections to the spherical and parabolic bases are calculated by perturbation theory

Permeability of two-dimensional graphene and hexagonal-boron nitride to hydrogen atom

Science.gov (United States)

Gupta, Varun; Kumar, Ankit; Ray, Nirat

2018-05-01

The permeability of atomic hydrogen in monolayer hexagonal Boron Nitride(h-BN) and graphene has been studied using first-principles density functional theory based simulations. For the specific cases of physisorption and chemisoroption, barrier heights are calculated using the nudged elastic band approach. We find that the barrier potential for physisorption through the ring is lower for graphene than h-BN. In the case of chemisorption, where the H atom passes through by making bonds with the atoms in the ring, the barrier potential for the graphene was found to be higher than that of h-BN. We conclude that the penetration of H atom with notable kinetic energy (graphene as compared to h-BN. Whereas through chemisorption, lower kinetic energy (>3eV) H-atoms have a higher chance to penetrate through h-BN than graphene.

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…

On the proton exchange contribution to electron-hydrogen atom elastic scattering

International Nuclear Information System (INIS)

Mignaco, J.A.; Tort, A.C.

1979-05-01

It is shown that the exchange contribution to the electron-proton potential Born term in elastic electron-hydrogen atom scattering arises as the non relativistic limit from the exchange of a proton between the two participant electrons - calculated from quantum electrodynamics including properly bound states (as solution of Bethe - Salpeter equation). (Author) [pt

Application of the Ursell-Mayer method in the theory of spin-polarized atomic hydrogen

International Nuclear Information System (INIS)

Kilic, S.; Radelja, T.

1981-01-01

Employing the Ursell-Mayer method and Ljolje semi-free gas model analytic relations describing ground state properties (energy, pressure, compressibility, sound velocity, radial distribution function and one-particle density matrix) of spin-polarized atomic hydrogen were derived. The expressions are valid up to density 2 10 26 atoms/m 3 . It was found out that at density of 2 10 26 atoms/m 3 the condensation of particle in momentum space is 88% (at absolute zero). (orig.)

Microwave ionization of hydrogen atoms below the classical chaos border

Energy Technology Data Exchange (ETDEWEB)

Bluemel, R; Smilansky, U

1987-01-01

We present and discuss theoretical predictions for the occurrence of radiation induced ionization of hydrogen atoms in fields which are well below the classical ionization threshold. Strong ionization occurs due to enhanced population of a band of high n states which ionize easily. This enhancement happens only at rather narrowly defined field values, and is explained in terms of avoided crossings of Floquet levels.

Investigation of confined hydrogen atom in spherical cavity, using B-splines basis set

Directory of Open Access Journals (Sweden)

M Barezi

2011-03-01

Full Text Available Studying confined quantum systems (CQS is very important in nano technology. One of the basic CQS is a hydrogen atom confined in spherical cavity. In this article, eigenenergies and eigenfunctions of hydrogen atom in spherical cavity are calculated, using linear variational method. B-splines are used as basis functions, which can easily construct the trial wave functions with appropriate boundary conditions. The main characteristics of B-spline are its high localization and its flexibility. Besides, these functions have numerical stability and are able to spend high volume of calculation with good accuracy. The energy levels as function of cavity radius are analyzed. To check the validity and efficiency of the proposed method, extensive convergence test of eigenenergies in different cavity sizes has been carried out.

The general expression for the transition amplitude of two-photon ionization of atomic hydrogen

Energy Technology Data Exchange (ETDEWEB)

Karule, E [Institute of Atomic Physics and Spectroscopy, University of Latvia, Raina Boulevard 19, Riga, LV-1586 (Latvia); Moine, B [Universite Paris Sud, 91405 Orsay Cedex (France)

2003-05-28

Two-photon ionization of atomic hydrogen with an excess photon is revisited. The non-relativistic dipole approximation and Coulomb Green function (CGF) formalism are applied. Using the CGF Sturmian expansion straightforwardly, one gets the radial transition amplitude in the form of an infinite sum over Gauss hypergeometric functions which are polynomials. It is convergent if all intermediate states are in the discrete spectrum. In the case of two-photon ionization with an excess photon, when photoionization is also possible, intermediate states are in the continuum. We performed the explicit summation over intermediate states and got a simple general expression for the radial transition amplitude in the form of a finite sum over Appell hypergeometric functions, which are not polynomials. An Appell function may be expressed as an infinite sum over Gauss functions. In the case of ionization by an excess photon, Gauss functions are transformed to give a convergent radial transition amplitude for the whole region. The generalized cross sections for two-photon above-threshold ionization of atomic hydrogen in the ground state and excited states calculated by us agree very well with results of previous calculations. Generalized cross sections for two-photon ionization of positronium in the ground state are obtained by scaling those for atomic hydrogen.

Unparticle physics constraints from the hydrogen atom

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-01

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

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)

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

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

Science.gov (United States)

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

2016-01-01

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

The electromagnetic virtual cloud of the ground-state hydrogen atom - a quantum field theory approach

International Nuclear Information System (INIS)

Radozycki, T.

1990-01-01

The properties of the virtual cloud around the hydrogen atom in the ground state are studied with the use of quantum field theory methods. The relativistic expression for the electromagnetic energy density around the atom, with the electron spin taken into account, is obtained. The distribution of the angular momentum contained in the cloud and the self-interaction kernel for the electrons bound in atom are also investigated. (author)

Measurement of intensity-dependent rates of above-threshold ionization (ATI) of atomic hydrogen at 248 nm

International Nuclear Information System (INIS)

Nichols, T.D.

1991-04-01

Measured rates of multiphoton ionization (MPI) from the ground state of atomic hydrogen by a linearly polarized, subpicosecond KrF laser pulse at 248 nm wavelength are compared to predictions of lowest-order perturbation theory, Floquet theory, and Keldysh-Faisal-Reiss (KFR) theory with and without Coulomb correction for peak irradiance of 3 x 10 12 W/cm 2 to 2 x 10 14 W/cm 2 . The Coulomb-corrected Keldysh model falls closest to the measured rates, the others being much higher or much lower. At 5 x 10 13 W/cm 2 , the number of ATI electrons decreased by a factor of approximately 40 with each additional photon absorbed. ATI of the molecular hydrogen background and of atoms from photodissociation of the molecules were also observed. The experiment employed a crossed-beam technique at ultrahigh vacuum with an rf-discharge atomic hydrogen source and a magnetic-bottle type electron time-of-flight spectrometer to count the electrons in the different ATI channels separately. The apparatus was calibrated to allow comparison of absolute as well as relative ionization rates to the theoretical predictions. This calibration involved measuring the distribution of irradiance in a focal volume that moved randomly and changed its size from time to time. A data collection system under computer control divided the time-of-flight spectra into bins according to the energy of each laser pulse. This is the first measurement of absolute rates of ATI in atomic hydrogen, and the first measurement of absolute test of MPI in atomic hydrogen without a large factor to account for multiple modes in the laser field. As such, the results of this work are important to the development of ATI theories, which presently differ by orders of magnitude in their prediction of the ionization rates. They are also important to recent calculations of temperatures in laser-heated plasmas, many of which incorporate KFR theory

Approximate motion integral for a hydrogen atom in a magnetic field

International Nuclear Information System (INIS)

Solov'ev, E.A.

1981-01-01

It is shown that the Schroedinger equation for highly excited states of a hydrogen atom in a magnetic field H allows a separation of variables (within an accuracy of H 4 ) in elliptical-cylindrical coordinates on a sphere in a four-dimensional momentum space. A new classification and approximate selection rules are proposed for these states

Positron scattering by atomic hydrogen at intermediate energies

International Nuclear Information System (INIS)

Higgins, K.; Burke, P.G.; Walters, H.R.J.

1990-01-01

Results of an accurate calculation based upon the intermediate energy R-matrix theory are reported for elastic scattering of positrons by atomic hydrogen. T-matrix elements for both low and intermediate energy scattering are evaluated for the S e , P o , D e and F o partial wave symmetries. The low-energy elastic phaseshifts are found to be in good agreement with previous accurate variational calculations. Using an optical potential approach to include the effect of the higher partial waves, elastic and total cross sections are presented for energies ranging from near threshold to 3.7 Rydbergs. (author)

Plasma screening effects on the energies of hydrogen atom under the influence of velocity-dependent potential

International Nuclear Information System (INIS)

Bahar, M. K.

2014-01-01

In order to examine the plasma screening and velocity-dependent potential effects on the hydrogen atom, the Schrödinger equation including a more general exponential cosine screened Coulomb and velocity-dependent potential is solved numerically in the framework asymptotic iteration method. The more general exponential cosine screened Coulomb potential is used to model Debye and quantum plasma for the specific values of the parameters in its structure. However, in order to examine effects of velocity-dependent potential on energy values of hydrogen atom in Debye and quantum plasma, the isotropic form factor of velocity-dependent potential is given as harmonic oscillator type, ρ(r)=ρ o r 2 . Then, the energies of s and p states are calculated numerically without any approximation. In order to investigate thoroughly plasma screening effects and contribution of velocity-dependent potential on energy values of hydrogen atom, the corresponding calculations are carried out by using different values of parameters of more general exponential cosine screened Coulomb potential and isotropic dependence, results of which are discussed

Oscillator representation method in the theory of a hydrogen atom in an external field

International Nuclear Information System (INIS)

Dinejkhan, M.

1996-01-01

The Wick-ordering method called the Oscillator representation in the non-relativistic Schroedinger equation is proposed to calculate the energy spectrum for spherically symmetric and axially symmetric potentials allowing the existence of a bound state. In particular, the method is applied to calculate the energy spectrum of (2s)-states of a hydrogen atom in a uniform magnetic field of an arbitrary strength. In the perturbation (external field) approximation, the energy spectrum of the so-called quadratic and spherical quadratic Zeeman problem and the problem of a hydrogen atom in a generalized van der Waals potential is calculated analytically. The results of the zeroth approximation of oscillator representation are in good agreement with the exact values. 31 refs., 3 tabs

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

Science.gov (United States)

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

2018-03-01

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

Charge exchange of excited mesic atoms of hydrogen isotopes in triple collisions with molecules

International Nuclear Information System (INIS)

Men'shikov, L.I.; Ponomarev, L.I.

1985-01-01

At high densities of deuterium-tritium mixture the probability for the occurrence of the isotope-exchange reaction (dμ)/sub n/+t → d+(tμ)/sub n/ from the excited states of n mesic atoms of deuterium is high in the triple collisions of mesic atoms with the molecules of hydrogen isotopes. This reaction should be taken into account in describing the kinetics of muon catalysis

Three-dimensional atomic mapping of hydrogenated polymorphous silicon solar cells

Energy Technology Data Exchange (ETDEWEB)

Chen, Wanghua, E-mail: wanghua.chen@polytechnique.edu; Roca i Cabarrocas, Pere [LPICM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau (France); Pareige, Philippe [GPM, CNRS, Université et INSA de Rouen, Normandie Université, 76801 Saint Etienne du Rouvray (France)

2016-06-20

Hydrogenated polymorphous silicon (pm-Si:H) is a nanostructured material consisting of silicon nanocrystals embedded in an amorphous silicon matrix. Its use as the intrinsic layer in thin film p-i-n solar cells has led to good cell properties in terms of stability and efficiency. Here, we have been able to assess directly the concentration and distribution of nanocrystals and impurities (dopants) in p-i-n solar cells, by using femtosecond laser-assisted atom probe tomography (APT). An effective sample preparation method for APT characterization is developed. Based on the difference in atomic density between hydrogenated amorphous and crystalline silicon, we are able to distinguish the nanocrystals from the amorphous matrix by using APT. Moreover, thanks to the three-dimensional reconstruction, we demonstrate that Si nanocrystals are homogeneously distributed in the entire intrinsic layer of the solar cell. The influence of the process pressure on the incorporation of nanocrystals and their distribution is also investigated. Thanks to APT we could determine crystalline fractions as low as 4.2% in the pm-Si:H films, which is very difficult to determine by standard techniques, such as X-ray diffraction, Raman spectroscopy, and spectroscopic ellipsometry. Moreover, we also demonstrate a sharp p/i interface in our solar cells.

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

Science.gov (United States)

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

2017-11-21

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

Light-Emitting Pickles

Science.gov (United States)

Vollmer, M.; Mollmann, K-P.

2015-01-01

We present experiments giving new insights into the classical light-emitting pickle experiment. In particular, measurements of the spectra and temperatures, as well as high-speed recordings, reveal that light emission is connected to the polarity of the electrodes and the presence of hydrogen.

The hydrogen atom in a magnetic field. Spectrum from the Coulomb dynamical group approach

International Nuclear Information System (INIS)

Delande, D.; Gay, J.C.

1986-01-01

Some sample results are presented for the problems of the hydrogen atom in a magnetic field. The energies have been computed for a typical Rydberg situation of atomic physics interest using limited computer facilities. The use of the Coulomb dynamical group allows a complete description of the symmetries and a rational choice of a Sturmian type basis set. Moreover, comparison with Rayleigh-Schrodinger perturbative expansions of the energies is performed. (author)

a Point-Like Picture of the Hydrogen Atom

Science.gov (United States)

Faghihi, F.; Jangjoo, A.; Khani, M.

A point-like picture of the Schrödinger solution for hydrogen atom is worked to emphasize that "point-like particles" may describe as "probability wave function". In each case, the three-dimensional shape of the |Ψnlm(rn, cosθ)|2 is plotted and the paths of the point-like electron (it is better to say reduced mass of the pair particles) are described in each closed shell. Finally, the orbital shape of the molecules are given according to the present simple model. In our opinion, "interpretations of the Correspondence Principle", which is a basic principle in all elementary quantum text, seems to be reviewed again!

Precise optical Lamb shift measurements in atomic hydrogen

International Nuclear Information System (INIS)

Weitz, M.; Schmidt-Kaler, F.; Haensch, T.W.

1992-01-01

The 1S ground-state Lamb shift in atomic hydrogen has been measured to an accuracy of 1.3 parts in 10 5 by directly comparing the optical frequencies of the 1S-2S and the 2S-4S,4D two-photon transitions. The result, 8172.82(11) MHz, agrees with the theoretical prediction of 8172.94(9) MHz and rivals measurements of the 2S Lamb shift as a test of QED for a bound system. A comparison of the 2S-4S and 2S-4D intervals yields a 4S Lamb shift of 131.66(4) MHz

Hydrogen atom in momentum space with a minimal length

International Nuclear Information System (INIS)

Bouaziz, Djamil; Ferkous, Nourredine

2010-01-01

A momentum representation treatment of the hydrogen atom problem with a generalized uncertainty relation, which leads to a minimal length ΔX imin =(ℎ/2π)√(3β+β ' ), is presented. We show that the distance squared operator can be factorized in the case β ' =2β. We analytically solve the s-wave bound-state equation. The leading correction to the energy spectrum caused by the minimal length depends on √(β). An upper bound for the minimal length is found to be about 10 -9 fm.

Calculation of nuclear-spin-relaxation rate for spin-polarized atomic hydrogen

International Nuclear Information System (INIS)

Ahn, R.M.C.; Eijnde, J.P.H.W.V.; Verhaar, B.J.

1983-01-01

Approximations introduced in previous calculations of spin relaxation for spin-polarized atomic hydrogen are investigated by carrying out a more exact coupled-channel calculation. With the exception of the high-temperature approximation, the approximations turn out to be justified up to the 10 -3 level of accuracy. It is shown that at the lowest temperatures for which experimental data are available, the high-temperature limit underestimates relaxation rates by a factor of up to 2. For a comparison with experimental data it is also of interest to pay attention to the expression for the atomic hydrogen relaxation rates in terms of transition amplitudes for two-particle collisions. Discrepancies by a factor of 2 among previous derivations of relaxation rates are pointed out. To shed light on these discrepancies we present two alternative derivations in which special attention is paid to identical-particle aspects. Comparing with experiment, we find our theoretical volume relaxation rate to be in better agreement with measured values than that obtained by other groups. The theoretical surface relaxation rate, however, still shows a discrepancy with experiment by a factor of order 50

A polarized hydrogen/deuterium atomic beam source for internal target experiments

International Nuclear Information System (INIS)

Szczerba, D.; Buuren, L.D. van; Brand, J.F.J. van den; Bulten, H.J.; Ferro-Luzzi, M.; Klous, S.; Kolster, H.; Lang, J.; Mul, F.; Poolman, H.R.; Simani, M.C.

2000-01-01

A high-brightness hydrogen/deuterium atomic beam source is presented. The apparatus, previously used in electron scattering experiments with tensor-polarized deuterium (Ferro-Luzzi et al., Phys. Rev. Lett. 77 (1996) 2630; van den Brand et al., Phys. Rev. Lett. 78 (1997) 1235; Zhou et al., Phys. Rev. Lett. 82 (1998) 687; Bouwhuis et al., Phys. Rev. Lett. 82 (1999) 3755), was configured as a source for internal target experiments to measure single- and double-polarization observables, with either polarized hydrogen or vector/tensor polarized deuterium. The atomic beam intensity was enhanced by a factor of ∼2.5 by optimizing the Stern-Gerlach focusing system using high tip-field (∼1.5 T) rare-earth permanent magnets, and by increasing the pumping speed in the beam-formation chamber. Fluxes of (5.9±0.2)x10 16 1 H/s were measured in a diameter 12 mmx122 mm compression tube with its entrance at a distance of 27 cm from the last focusing element. The total output flux amounted to (7.6±0.2)x10 16 1 H/s

Bremsstrahlung in atom-atom collisions

International Nuclear Information System (INIS)

Amus'ya, M.Y.; Kuchiev, M.Y.; Solov'ev, A.V.

1985-01-01

It is shown that in the collision of a fast atom with a target atom when the frequencies are on the order of the potentials or higher, there arises bremsstrahlung comparable in intensity with the bremsstrahlung emitted by an electron with the same velocity in the field of the target atom. The mechanism by which bremsstrahlung is produced in atom-atom collisions is elucidated. Results of specific calculations of the bremsstrahlung spectra are given for α particles and helium atoms colliding with xenon

Electron capture by Ne3+ ions from atomic hydrogen

International Nuclear Information System (INIS)

Rejoub, R.; Bannister, M.E.; Havener, C.C.; Savin, D.W.; Verzani, C.J.; Wang, J.G.; Stancil, P.C.

2004-01-01

Using the Oak Ridge National Laboratory ion-atom merged-beam apparatus, absolute total electron-capture cross sections have been measured for collisions of Ne 3+ ions with hydrogen (deuterium) atoms at energies between 0.07 and 826 eV/u. Comparison to previous measurements shows large discrepancies between 50 and 400 eV/u. Previously published molecular-orbital close-coupling (MOCC) calculations were performed over limited energy ranges, but show good agreement with the present measurements. Here MOCC calculations are presented for energies between 0.01 and 1000 eV/u for collisions with both H and D. For energies below ∼1 eV/u, an enhancement in the magnitude of both the experimental and theoretical cross sections is observed which is attributed to the ion-induced dipole attraction between the reactants. Below ∼4 eV/u, the present calculations show a significant target isotope effect

Electron capture by Ne3+ ions from atomic hydrogen

Science.gov (United States)

Rejoub, R.; Bannister, M. E.; Havener, C. C.; Savin, D. W.; Verzani, C. J.; Wang, J. G.; Stancil, P. C.

2004-05-01

Using the Oak Ridge National Laboratory ion-atom merged-beam apparatus, absolute total electron-capture cross sections have been measured for collisions of Ne3+ ions with hydrogen (deuterium) atoms at energies between 0.07 and 826 eV/u . Comparison to previous measurements shows large discrepancies between 50 and 400 eV/u . Previously published molecular-orbital close-coupling (MOCC) calculations were performed over limited energy ranges, but show good agreement with the present measurements. Here MOCC calculations are presented for energies between 0.01 and 1000 eV/u for collisions with both H and D. For energies below ˜1 eV/u , an enhancement in the magnitude of both the experimental and theoretical cross sections is observed which is attributed to the ion-induced dipole attraction between the reactants. Below ˜4 eV/u , the present calculations show a significant target isotope effect.

New directions in the theory of spin-polarized atomic hydrogen and deuterium

International Nuclear Information System (INIS)

Koelman, J.M.V.A.

1988-01-01

The three chapters of this thesis dealing with collisions between hydrogen (or deuterium) atoms in their ground state, each treat a different development in the theory of atomic hydrogen or deuterium gas. The decay due to interatomic collisions hindered till now all attempts to reach the low temperature, high-density regime where effects due to degeneracy are expected to show up. In ch. 2 a simple way out is presented for the case of Fermi gases: In spin-polarized Fermi systems at very low temperatures collisions are much effective than in Bose systems. For the Fermi gas, consisting of magnetically confined deuterium atoms, it appears that fast spin-exchange collisions automatically lead to a completely spin-polarized gas for which the spin-relaxation limited lifetime increases dramatically with decreasing temperature. As also the ratio of internal thermalization rate over decay rate increases with decreasing temperature, this gas can be cooled by forced evaporation down to very low temperatures. In ch. 3 it iis shown that the nuclear spin dynamics due to the hyperfine interaction during collisions, strongly limits the improvement in frequency stability attainable by H masers operating at low temperatures. In ch. 4 the phenomenon of spin waves is studied. It is shown that, despite the fact that interactions between two atoms are nuclear-spin independent, the outcome of a scattering event does not depend on the nuclear spins involved due to the particle indistinguishability effects at low collision energies. This effect gives rise to quantum phenomena on a macroscopic scale via the occurrence of spin waves. (author). 185 refs.; 34 figs

Shape of electron lines emitted by a fast particle in atomic collisions. Influence of the acceptance function

International Nuclear Information System (INIS)

Bordenave-Montesquieu, A.; Gleizes, A.; Benoit-Cattin, P.; Boudjema, M.

1980-01-01

In order to explain the large energy broadening of the lines observed in energy spectra of electrons emitted by fast particles, an accurate knowledge of the angular acceptance function of the electron energy analyser is necessary. A simple method is proposed which can give an accurate function for most atomic collisions: the various approximations are discussed. It is also shown that the analyser transmission depends on the acceptance angle. (author)

Eosin Y as a Direct Hydrogen Atom Transfer Photocatalyst for the Functionalization of C-H Bonds.

Science.gov (United States)

Fan, Xuan-Zi; Rong, Jia-Wei; Wu, Hao-Lin; Zhou, Quan; Deng, Hong-Ping; Tan, Jin Da; Xue, Cheng-Wen; Wu, Li-Zhu; Tao, Hai-Rong; Wu, Jie

2018-05-02

Eosin Y, a well-known economical alternative to metal catalysts in visible-light-driven single-electron transfer-based organic transformations, can behave as an effective direct hydrogen atom transfer catalyst for C-H activation. Using the alkylation of C-H bonds with electron-deficient alkenes as a model study revealed an extremely broad substrate scope, enabling easy access to a variety of important synthons. This eosin Y-based photocatalytic hydrogen atom transfer strategy is promising for diverse functionalization of a wide range of native C-H bonds in a green and sustainable manner. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon-hydrogen defects with a neighboring oxygen atom in n-type Si

Science.gov (United States)

Gwozdz, K.; Stübner, R.; Kolkovsky, Vl.; Weber, J.

2017-07-01

We report on the electrical activation of neutral carbon-oxygen complexes in Si by wet-chemical etching at room temperature. Two deep levels, E65 and E75, are observed by deep level transient spectroscopy in n-type Czochralski Si. The activation enthalpies of E65 and E75 are obtained as EC-0.11 eV (E65) and EC-0.13 eV (E75). The electric field dependence of their emission rates relates both levels to single acceptor states. From the analysis of the depth profiles, we conclude that the levels belong to two different defects, which contain only one hydrogen atom. A configuration is proposed, where the CH1BC defect, with hydrogen in the bond-centered position between neighboring C and Si atoms, is disturbed by interstitial oxygen in the second nearest neighbor position to substitutional carbon. The significant reduction of the CH1BC concentration in samples with high oxygen concentrations limits the use of this defect for the determination of low concentrations of substitutional carbon in Si samples.

Energy dependence of the anisotropy of noncharacteristic x-rays emitted in fast ion-atom collisions

International Nuclear Information System (INIS)

Thoe, R.S.; Sellin, I.A.; Brown, M.D.; Forester, J.P.; Griffin, P.M.; Pegg, D.J.; Peterson, R.S.

1974-01-01

The effect of beam velocity and K-shell binding energy on the angular distributions of the noncharacteristic x-radiation emitted for various collision pairs. The results are in general agreement with the calculations of Mueller and Greiner, in that the anisotropy increases rapidly with energy, provided that the ions are still moving slowly, compared to the velocity of the K-shell electrons of the separated atoms. The anisotropy in some cases exceeds the maximum permitted by the Mueller--Greiner model for the zero alignment case, implying that strong alignment phenomena also occur

Charge changing and excitation cross sections for 1-25 KeV hydrogen ions and atoms incident on sodium

International Nuclear Information System (INIS)

Howald, A.M.

1983-01-01

Measurements of charge changing and excitation cross sections for 1-25 keV beams of hydrogen atoms and ions incident on a sodium vapor target are reported. The charge changing cross sections are for reactions in which the incident H ion or atom gains or loses an electron during a collision with a Na atoms to form a hydrogen ion or atom in a different charge state. The six cross sections measured are sigma/sub +0/ and sigma/sub +-/ for incident protons, sigma/sub -0/ and sigma/sub -+/ for incident H - ions, and sigma/sub g-/ and sigma/sub g+/ for incident H(1s) atoms. Measurements are also reported for the negative, neutral, and positve equilibrium fractions for H beams in thick Na targets. The excitation cross sections are for reactions in which the Na target atom is excited to the 3p level by a collision with a H atom or ion. The five cross sections measured are for incident H + , H 2 + , H 3 + , and H - ions, and for H(1s) atoms. These cross sections are measured using a new technique that compares them directly to the known cross section for excitation by electron impact

Photoabsorption of atomic hydrogen in an external DC electric field

International Nuclear Information System (INIS)

Gailitis, Modris; Gailitis, Agris

1996-01-01

An analytical approach is presented which aids the computation of the photoabsorption spectrum of atomic hydrogen in a weak external DC electric field. Separation constants in the parabolic frame and one of the normalization factors are evaluated by the Telnov algorithm. For matrix elements the series expansion after powers of parabolic coordinates is used. An enhanced precision arithmetic is applied to extract the second normalization factor from the power expansion. The results agree with those from the previous calculations and experiment. (Author)

Hydrogen molecules and hydrogen-related defects in crystalline silicon

OpenAIRE

Fukata, N.; Sasak, S.; Murakami, K.; Ishioka, K.; Nakamura, K. G.; Kitajima, M.; Fujimura, S.; Kikuchi, J.; Haneda, H.

1997-01-01

We have found that hydrogen exists in molecular form in crystalline silicon treated with hydrogen atoms in the downstream of a hydrogen plasma. The vibrational Raman line of hydrogen molecules is observed at 4158cm-1 for silicon samples hydrogenated between 180 and 500 °C. The assignment of the Raman line is confirmed by its isotope shift to 2990cm-1 for silicon treated with deuterium atoms. The Raman intensity has a maximum for hydrogenation at 400 °C. The vibrational Raman line of the hydro...

Reaction of hydrogen atoms produced by radiolysis and photolysis in solid phase at 4 and 77 K

International Nuclear Information System (INIS)

Miyazaki, Tetsuo

1991-01-01

The behavior of H atoms in the solid phase has been reviewed with special attention to comparison of H atoms produced by radiolysis with those produced by photolysis. The paper consists of three parts. I -Production of H atoms: (1) the experimental results which indicate H-atom formation in the radiolysis of solid alkane are summarized; (2) ESR saturation behavior of trapped H atoms depends upon the method of H-atom-production, i.e. photolysis or radiolysis, and upon the initial energy of H atoms in the photolysis. II - Diffusion of H atoms: (1) activation energies for thermally-activated diffusion of H atoms are shown; (2) quantum diffusion of H atoms in solid H 2 is explained in terms of repetition of tunneling reaction H 2 + H → H + H 2 . III -Reaction of H atoms: (1) reactions and trapping processes of hot H atoms have been shown in solid methane and argon by use of hot H atoms with specified initial energy; (2) when H atoms are produced by the radiolysis of solvent alkane or by the photolysis of HI in the alkane mixtures at 77 K, the H atoms react very selectively with solute alkane at low concentration. The selective reaction of the H atom has been found in eight matrices; (3) activation energy for a hydrogen-atom-abstraction reaction by thermal H atoms at low temperatures is less than than several kJ mol -1 because of quantum tunneling. The absolute rate constants for H 2 (D 2 , HD) + H(D) tunneling reactions have been determined experimentally in solid hydrogen at 4.2K; (4) theoretical studies for tunneling reactions H 2 (D 2 ,HD) + H(D) at ultralow temperatures were reviewed. The calculated rate constants were compared with the rate constants obtained experimentally. (author)

Precise calibration of few-cycle laser pulses with atomic hydrogen

Science.gov (United States)

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

2017-12-01

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

Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen

Science.gov (United States)

Barklem, P. S.

2018-02-01

Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000-20 000 K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.5So and 4s.3So, are found to have the highest rates. Data are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57. The data are also available at http://https://github.com/barklem/public-data

Vector dark matter detection using the quantum jump of atoms

Science.gov (United States)

Yang, Qiaoli; Di, Haoran

2018-05-01

The hidden sector U(1) vector bosons created from inflationary fluctuations can be a substantial fraction of dark matter if their mass is around 10-5 eV. The creation mechanism makes the vector bosons' energy spectral density ρcdm / ΔE very high. Therefore, the dark electric dipole transition rate in atoms is boosted if the energy gap between atomic states equals the mass of the vector bosons. By using the Zeeman effect, the energy gap between the 2S state and the 2P state in hydrogen atoms or hydrogen like ions can be tuned. The 2S state can be populated with electrons due to its relatively long life, which is about 1/7 s. When the energy gap between the semi-ground 2S state and the 2P state matches the mass of the cosmic vector bosons, induced transitions occur and the 2P state subsequently decays into the 1S state. The 2 P → 1 S decay emitted Lyman-α photons can then be registered. The choices of target atoms depend on the experimental facilities and the mass ranges of the vector bosons. Because the mass of the vector boson is connected to the inflation scale, the proposed experiment may provide a probe to inflation.

Atomic processes in hydrogen and deuterium negative ion discharges

International Nuclear Information System (INIS)

Hiskes, J.R.

1992-01-01

A knowledge of the atomic processes active in a hydrogen negative ion discharge and their respective rates is an essential component of the interpretation, modeling, and enhancement of negative ion systems. The generation of the cross sections and rate processes appropriate to this problem has been a principal activity at several laboratories. In this paper is discussed those collision processes that are of major importance for the destruction of the vibrationally excited molecules generated in the discharge, processes that are essential to the valuation of the optimization procedure that is to be discussed in this paper

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.

Calculation of the positronium formation differential cross section for collision of electron with anti-hydrogen atoms

International Nuclear Information System (INIS)

Ghanbari Adivi, E.; Kanjuri, F.; Bolorizadeh, M.

2006-01-01

The positronium formation differential cross sections in collision of the high-energy but non-relativistic electrons with anti-hydrogen atoms are calculated by using the three-body Faddeev-Watson-Lovelace formalism. In a second-order approximation, the inter-nuclear and nuclear-electronic partial amplitudes therein the Faddeev-Watson series are calculated, analytically, in the range of 0-180 degrees of the scattering angles. The presence of the T homas peak a t 45 d egree i s investigated. The results are discussed for 1 and 10 keV impact energies and for electron transition from anti-hydrogen ground state into the different states therein the K-, L- and M- shells of the positronium atoms.

Ultrafine hydrogen storage powders

Science.gov (United States)

Anderson, Iver E.; Ellis, Timothy W.; Pecharsky, Vitalij K.; Ting, Jason; Terpstra, Robert; Bowman, Robert C.; Witham, Charles K.; Fultz, Brent T.; Bugga, Ratnakumar V.

2000-06-13

A method of making hydrogen storage powder resistant to fracture in service involves forming a melt having the appropriate composition for the hydrogen storage material, such, for example, LaNi.sub.5 and other AB.sub.5 type materials and AB.sub.5+x materials, where x is from about -2.5 to about +2.5, including x=0, and the melt is gas atomized under conditions of melt temperature and atomizing gas pressure to form generally spherical powder particles. The hydrogen storage powder exhibits improved chemcial homogeneity as a result of rapid solidfication from the melt and small particle size that is more resistant to microcracking during hydrogen absorption/desorption cycling. A hydrogen storage component, such as an electrode for a battery or electrochemical fuel cell, made from the gas atomized hydrogen storage material is resistant to hydrogen degradation upon hydrogen absorption/desorption that occurs for example, during charging/discharging of a battery. Such hydrogen storage components can be made by consolidating and optionally sintering the gas atomized hydrogen storage powder or alternately by shaping the gas atomized powder and a suitable binder to a desired configuration in a mold or die.

Role of atom--atom inelastic collisions in two-temperature nonequilibrium plasmas

International Nuclear Information System (INIS)

Kunc, J.A.

1987-01-01

The contribution of inelastic atom--atom collisions to the production of electrons and excited atoms in two-temperature (with electron temperature T/sub e/, atomic temperature T/sub a/, and atomic density N/sub a/), steady-state, nonequilibrium atomic hydrogen plasma is investigated. The results are valid for plasmas having large amounts of atomic hydrogen as one of the plasma components, so that e--H and H--H inelastic collisions and interaction of these atoms with radiation dominate the production of electrons and excited hydrogen atoms. Densities of electrons and excited atoms are calculated in low-temperature plasma, with T/sub e/ and T/sub a/≤8000 K and 10 16 cm -3 ≤N/sub a/≤10 18 cm -3 , and with different degrees of the reabsorption of radiation. The results indicate that inelastic atom--atom collisions are important for production of electrons and excited atoms in partially ionized plasmas with medium and high atomic density and temperatures below 8000 K

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…

Irregular wave functions of a hydrogen atom in a uniform magnetic field

Science.gov (United States)

Wintgen, D.; Hoenig, A.

1989-01-01

The highly excited irregular wave functions of a hydrogen atom in a uniform magnetic field are investigated analytically, with wave function scarring by periodic orbits considered quantitatively. The results obtained confirm that the contributions of closed classical orbits to the spatial wave functions vanish in the semiclassical limit. Their disappearance, however, is slow. This discussion is illustrated by numerical examples.

Membrane pumping technology, helium and hydrogen isotopes separation in the fusion hydrogen

International Nuclear Information System (INIS)

Pigarov, A.Yu.; Pistunovich, V.I.; Busnyuk, A.O.

1994-01-01

A gas pumping system for the ITER, improved by implementation of superpermeable membranes for selective hydrogen isotope exhaust, is considered. The study of the pumping capability of a niobium membrane for a hydrogen-helium mixture has been fulfilled. The membrane superpermeability can be only realized for atomic hydrogen. Helium does not pass through the membrane, and its presence does not affect the hydrogen pumping. A detailed Monte Carlo simulation of gas behavior for the experimental facility has been done. The probability of permeation for a hydrogen atom for one collision with the membrane is ∼0.1; the same probability of molecule permeation is ∼10 -5 . The probability for atomization, i.e. re-emission of an atomizer is ∼0.2; the probability of recombination of an atom is ∼0.2

Electron capture in slow collisions of multicharged ions with hydrogen atoms using merged beams

International Nuclear Information System (INIS)

Havener, C.C.; Nesnidal, M.P.; Porter, M.R.; Phaneuf, R.A.

1991-01-01

Absolute total electron-capture cross-section mesurements are reported for collisions of O 3+ and O 4+ with atomic hydrogen in the energy range 1-1000 eV /amu using merged beams. The data are compared with available coupled-states theoretical calculations. (orig.)

Classical calculation of radiative lifetimes of atomic hydrogen in a homogeneous magnetic field

International Nuclear Information System (INIS)

Horbatsch, M.W.; Hessels, E.A.; Horbatsch, M.

2005-01-01

Radiative lifetimes of hydrogenic atoms in a homogeneous magnetic field of moderate strength are calculated on the basis of classical radiation. The modifications of the Keplerian orbits due to the magnetic field are incorporated by classical perturbation theory. The model is complemented by a classical radiative decay calculation using the radiated Larmor power. A recently derived highly accurate formula for the transition rate of a field-free hydrogenic state is averaged over the angular momentum oscillations caused by the magnetic field. The resulting radiative lifetimes for diamagnetic eigenstates classified by n,m and the diamagnetic energy shift C compare well with quantum results

Atomic scale study of the chemistry of oxygen, hydrogen and water at SiC surfaces

International Nuclear Information System (INIS)

Amy, Fabrice

2007-01-01

Understanding the achievable degree of homogeneity and the effect of surface structure on semiconductor surface chemistry is both academically challenging and of great practical interest to enable fabrication of future generations of devices. In that respect, silicon terminated SiC surfaces such as the cubic 3C-SiC(1 0 0) 3 x 2 and the hexagonal 6H-SiC(0 0 0 1) 3 x 3 are of special interest since they give a unique opportunity to investigate the role of surface morphology on oxygen or hydrogen incorporation into the surface. In contrast to silicon, the subsurface structure plays a major role in the reactivity, leading to unexpected consequences such as the initial oxidation starting several atomic planes below the top surface or the surface metallization by atomic hydrogen. (review article)

Ionisation of hydrogen-like atoms by a multiphoton absorption process

International Nuclear Information System (INIS)

Gontier, Y.; Trahin, M.

1967-01-01

The general expression for the amplitude of the probability of ionisation by a multiphoton absorption process is derived. Its non-relativistic limit is taken and the bipolar approximation is used for calculating the ionisation cross-section of hydrogen-like atoms. This latter involves the summation over intermediate virtual states by means of: a) a recursion relationship concerning angular functions, b) a particular technique which when applied to radial functions makes it possible to solve a system of inhomogeneous first-order differential equations. (authors) [fr

Production and detection of cold anti-hydrogen atoms A first step towards high precision CPT test

CERN Document Server

Variola, A; Bonomi, G; Boutcha, A; Bowe, P; Carraro, C; Cesar, C L; Charlton, M; Doser, Michael; Filippini, V; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Lagomarsino, V; Landua, Rolf; Lindelöf, D; Lodi-Rizzini, E; Macri, M; Madsen, N; Manuzio, G; Montagna, P; Pruys, H S; Regenfus, C; Rotondi, A; Riedler, P; Testera, G; Van der Werf, D P

2003-01-01

Observations of anti-hydrogen in small quantities have been reported at CERN and at FermiLab, but these experiments were not suited to spectroscopy experiments. In 2002 the ATHENA collaboration reported the production and detection of very low energy anti-hydrogen atoms produced in cryogenic environment. This is the first major step in the study of antiatom's internal structure and it can lead to a high precision test of the CPT fundamental symmetry. The method of production and detection of cold anti-hydrogen will be introduced. The absolute rate of anti-hydrogen production and the signal to background ratio in the ATHENA experiment will be discussed. (7 refs) .

Collisional excitation of ArH+ by hydrogen atoms

Science.gov (United States)

Dagdigian, Paul J.

2018-06-01

The rotational excitation of the 36ArH+ ion in collisions with hydrogen atoms is investigated in this work. The potential energy surface (PES) describing the 36ArH+-H interaction, with the ion bond length r fixed at the average of r over the radial v = 0 vibrational state distribution, was obtained with a coupled cluster method that included single, double, and (perturbatively) triple excitations [RCCSD(T)]. A deep minimum (De = 3135 cm-1) in the PES was found in linear H-ArH+ geometry at an ion-atom separation Re = 4.80a0. Energy-dependent cross-sections and rate coefficients as a function of temperature for this collision pair were computed in close-coupling (CC) calculations. Since the PES possesses a deep well, this is a good system to test the performance of the quantum statistical (QS) method developed by Manolopoulos and co-workers as a more efficient method to compute the cross-sections. Good agreement was found between rate coefficients obtained by the CC and QS methods at several temperatures. In a simple application, the excitation of ArH+ is simulated for conditions under which this ion is observed in absorption.

Collision processes of Li3+ with atomic hydrogen: cross section database

International Nuclear Information System (INIS)

Murakami, I.; Janev, R.K.; Kato, T.; Yan, J.; Sato, H.; Kimura, M.

2004-08-01

Using the available experimental and theoretical data, as well as established cross section scaling relationships, a cross section database for excitation, ionization and charge exchange in collisions of Li 3+ ion with ground state and excited hydrogen atoms has been generated. The critically assessed cross sections are represented by analytic fit functions that have correct asymptotic behavior both at low and high collision energies. The derived cross sections are also presented in graphical form. (author)

Invariance Lie algebra and group of the non relativistic hydrogen atom

International Nuclear Information System (INIS)

Decoster, Alain

1970-01-01

The first part of this work contains a general survey of the use of Lie groups and algebras in quantum mechanics, followed by an extensive description of tbe invariance algebra and invariance group of the non-relativistic hydrogen atom; the realization of this group discovered by FOCK is specially examined. The second part is a two-hundred items bibliography on invariance groups and algebras of classical and quantum-mechanical simple systems. (author) [fr

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

International Nuclear Information System (INIS)

Chen Panying; Ji Xiangdong; Xu Yang; Zhang Yue

2010-01-01

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, α em 3 /18π, which might be measurable in future atomic experiments.

Ab initio atomic simulation of hydrogen and iodine effects in zirconium

International Nuclear Information System (INIS)

Domain, Ch.

2002-03-01

In this work we present ab initio atomic simulations concerning the effects of hydrogen and iodine in hexagonal zirconium. We first studied the point defects in the dilute Zr-H (and to a less extend Zr-H-O) systems and concluded that it is better described within the generalised gradient approximation for the exchange and correlation functional. We calculated the hydrogen thermal diffusion coefficient in solid solution that agree very well with the experimental values. The calculated formation energy of different self-interstitial configuration are rather small (around 3 eV) and close to each other indicating the high complexity of these defects. We studied the core structure of the screw dislocation that has a preferential prismatic spreading. We also calculated the gamma surface for different gliding planes. The influence of hydrogen, that induces a significant reduction of the gamma surfaces excess energies, allows to qualitatively explain experimental results regarding some hydrogen effects on hexagonal zirconium plastic deformation. We also discussed the effect of zirconium hydride stoichiometry on gamma surfaces. The results concerning the iodine and oxygen adsorption on zirconium surfaces, inducing the evaluation of the effective surface energy reduction as a function of the iodine partial pressure allow for a better description of iodine induced stress corrosion cracking of zirconium. (author)

Determination of the 1s-2s two-photon excitation cross-section in atomic hydrogen

Energy Technology Data Exchange (ETDEWEB)

Bickel, G.A.; McRae, G.A

2000-07-01

Hydrogen atoms are ablated from zirconium alloys into the gas phase by a pulsed Nd:YAG laser and photo-ionized with three photons at 243 nm via the two-photon 1s {sup 2}S{sub 1/2}-2s {sup 2}S{sub 1/2} resonant transition. A determination of the effective 1s-2s two-photon excitation cross-section is necessary to quantify the hydrogen atom density in the ablation plume. A measurement of the ion signal vs photo-ionization beam energy is fitted to an expression derived from the rate equations. The temporal and spatial properties of the photo-ionization laser beam, transit of the H atoms through the beam, and detector geometry are taken into account. The effective two-photon cross-section for this experimental configuration, derived with the rate equation formalism, is 3.3 {+-} 0.8 X 10{sup -28} cm{sup 4} W{sup -1}. This compares well with the ab initio prediction of 5 {+-} 1 X 10{sup -28} cm{sup 4} W{sup -1} under these experimental conditions. (author)

Determination of the 1s-2s two-photon excitation cross-section in atomic hydrogen

International Nuclear Information System (INIS)

Bickel, G.A.; McRae, G.A.

2000-01-01

Hydrogen atoms are ablated from zirconium alloys into the gas phase by a pulsed Nd:YAG laser and photo-ionized with three photons at 243 nm via the two-photon 1s 2 S 1/2 -2s 2 S 1/2 resonant transition. A determination of the effective 1s-2s two-photon excitation cross-section is necessary to quantify the hydrogen atom density in the ablation plume. A measurement of the ion signal vs photo-ionization beam energy is fitted to an expression derived from the rate equations. The temporal and spatial properties of the photo-ionization laser beam, transit of the H atoms through the beam, and detector geometry are taken into account. The effective two-photon cross-section for this experimental configuration, derived with the rate equation formalism, is 3.3 ± 0.8 X 10 -28 cm 4 W -1 . This compares well with the ab initio prediction of 5 ± 1 X 10 -28 cm 4 W -1 under these experimental conditions. (author)

The energy dependence of selective hydrogen atom abstraction by H(D) atoms in the photolysis of neopentane - ethane mixtures at 77 K

International Nuclear Information System (INIS)

Miyazaki, T.; Fueki, K.

1980-01-01

Selective hydrogen - atom - abstraction reaction by H or D atom has been studied in a neo C 5 H 12 - C 2 H 6 (less than 1 mol %) mixture at 77 K by ESR spectroscopy. The H (or D) atom produced by the photolysis of HI (or DI) reacts with neo - C 2 H 12 and C 2 H 6 to form neo - C 5 H 11 and C 2 H 5 radicals. In order to obtain H atoms with different kinetic energies, the photolysis was performed with different lights of 313, 254 and 229 nm. The selective formation of the C 2 H 5 radical by the reaction of the H (or D) atom with C 2 H 6 becomes more effective with the decrease in the energy of the H (or D) atom. The formation of the neo - C 5 H 11 radical by the reaction of the H (or D) atom with neo - C 2 H 12 becomes more effective with the increase in the energy of the H (or D) atom. (A.R.H.) [pt

The behavior of hydrogen in metals

International Nuclear Information System (INIS)

Hirabayashi, Makoto

1975-01-01

Explanation is made on the equilibrium diagrams of metal-hydrogen systems and the state of hydrogen in metals. Some metals perform exothermic reaction with hydrogen, and the others endothermic reaction. The former form stable hydrides and solid solutions over a wide range of composition. Hydrogen atoms in fcc and bcc metals are present at the interstitial positions of tetrahedron lattice and octahedron lattice. For example, hydrogen atoms in palladium are present at the intersititial positions of octahedron. When the ratio of the composition of hydrogen and palladium is 1:1, the structure becomes NaCl type. Hydrogen atoms in niobium and vanadium and present interstitially in tetrahedron lattice. Metal hydrides with high hydrogen concentration are becoming important recently as the containers of hydrogen. Hydrogen atoms diffuse in metals quite easily. The activation energy of the diffusion of hydrogen atoms in Nb and V is about 2-3 kcal/g.atom. The diffusion coefficient is about 10 -5 cm 2 /sec in alpha phase at room temperature. The number of jumps of a hydrogen atom between neighboring lattice sites is 10 11 --10 12 times per second. This datum is almost the same as that of liquid metals. Discussion is also made on the electronic state of hydrogen in metals. (Fukutomi, T.)

External electric field: An effective way to prevent aggregation of Mg atoms on γ-graphyne for high hydrogen storage capacity

International Nuclear Information System (INIS)

Liu, Ping-Ping; Zhang, Hong; Cheng, Xin-Lu; Tang, Yong-Jian

2016-01-01

Highlights: • Due to large pores in the sheet of γ-graphyne, it should be a potential materials for energy storage applications. Our calculations might motivate active experimental efforts in designing high-efficiency hydrogen storage media. • For the first time, we use an applied external electric field to prevent Mg atoms from clustering using density functional theory (DFT) calculations. • The results demonstrate that, for Mg-G after electric field (F = 0.05 V/nm) treatment, ten H_2 molecules per Mg atom can be adsorbed and the hydrogen storage capacities reach to 10.64 wt%, with the average binding energies of 0.28 eV/H_2. - Abstract: In this article, we investigate the hydrogen storage capacity of Mg-decorated γ-graphyne (Mg-G) based on DFT calculations. Our results indicate that an external electric field can effectively prevent Mg atoms aggregating on γ-graphyne sheet. The Mg-G, after electric field (F = 0.05 V/nm) treatment, can store up to ten H_2 molecules and the hydrogen storage capacity is 10.64 wt%, with the average adsorption energy of 0.28 eV/H_2. Our calculations demonstrate that Mg-G is a potential material for hydrogen storage with high capacity and might motivate active experimental efforts in designing hydrogen storage media.

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.

Signatures of a quantum diffusion limited hydrogen atom tunneling reaction.

Science.gov (United States)

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

2017-12-20

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

Semiclassical calculation of ionisation rate for Rydberg helium atoms in an electric field

International Nuclear Information System (INIS)

Wang De-Hua

2011-01-01

The ionisation of Rydberg helium atoms in an electric field above the classical ionisation threshold has been examined using the semiclassical method, with particular emphasis on discussing the influence of the core scattering on the escape dynamics of electrons. The results show that the Rydberg helium atoms ionise by emitting a train of electron pulses. Unlike the case of the ionisation of Rydberg hydrogen atom in parallel electric and magnetic fields, where the pulses of the electron are caused by the external magnetic field, the pulse trains for Rydberg helium atoms are created through core scattering. Each peak in the ionisation rate corresponds to the contribution of one core-scattered combination trajectory. This fact further illustrates that the ionic core scattering leads to the chaotic property of the Rydberg helium atom in external fields. Our studies provide a simple explanation for the escape dynamics in the ionisation of nonhydrogenic atoms in external fields. (atomic and molecular physics)

Reaction of O+, CO+, and CH+ ions with atomic hydrogen

International Nuclear Information System (INIS)

Federer, W.; Villinger, H.; Howorka, F.; Lindinger, W.; Tosis, P.; Bassi, D.; Ferguson, E.

1984-01-01

Rate coefficients for reactions of the ions O + , CO + , and CH + with atomic hydrogen have been measured for the first time at 300 K. This provides basic data for the ion chemistry of planetary atmospheres, cometary atmospheres, and interstellar molecular clouds. The O + +H measurement supports quantal calculations of this reaction. The CO + +H reaction provides an example of partial spin nonconservation in a charge-transfer reaction occurring in a deep potential well. Reactions of the same ions with H 2 that have been measured elsewhere are also reported

Electron-hydrogen atom inelastic scattering through a correlated wave function

International Nuclear Information System (INIS)

Serpa Vieira, A.E. de.

1984-01-01

The inelastic collision between an electron and a hydrogen atom is studied. A correlated function, used previously to the same system in elastic collisions in which there are two parameters fitted in the energy range studied, is utilized. With this functions an equation is developed for the direct and exchange transition matrix elements to the 15-25 and 15-2 p transitions. The obtained results are compared with Willians experimental measurements, as well the results given by the theoretical treatments of Kingston, Fon and Burke. (L.C.) [pt

Negative meson capture in hydrogen

International Nuclear Information System (INIS)

Baird, T.J.

1977-01-01

The processes of deexcitation and capture of negative mesons and hadrons in atomic hydrogen are investigated. Only slow collisions in which the projectile-atom relative velocity is less than one atomic unit are considered, and the motion of the incident particle is treated classically. For each classical trajectory the probability of ionizing the hydrogen atom is determined, together with the energy spectrum of the emitted electron. Ionization probabilities are calculated using the time-dependent formulation of the perturbed stationary state method. Exact two-center electronic wave functions are used for both bound and continuum states. The total ionization cross section and electron energy spectrum have been calculated for negative muons, kaons and antiprotons at incident relative velocities between 0.04 and 1.0 atomic units. The electron energy spectrum has a sharp peak for electron kinetic energies on the order of 10 -3 Rydbergs. The ionization process thus favors the emission of very slow electrons. The cross section for ionization with capture of the incident particle was calculated for relative kinetic energies greater than 1.0 Rydberg. Since ionization was found to occur with the emission of electrons of nearly zero kinetic energy, the fraction of ionizing collisions which result in capture decreases very rapidly with projectile kinetic energy. The energy distributions of slowed down muons and hadrons were also computed. These distributions were used together with the capture cross section to determine the distribution of kinetic energies at which capture takes place. It was found that most captures occur for kinetic energies slightly less than 1.0 Rydbergs with relatively little capture at thermal energies. The captured particles therefore tend to go into very large and loosely found orbits with binding energies less than 0.1 Rydbergs

Elastic interaction of hydrogen atoms on graphene: A multiscale approach from first principles to continuum elasticity

Science.gov (United States)

Branicio, Paulo S.; Vastola, Guglielmo; Jhon, Mark H.; Sullivan, Michael B.; Shenoy, Vivek B.; Srolovitz, David J.

2016-10-01

The deformation of graphene due to the chemisorption of hydrogen atoms on its surface and the long-range elastic interaction between hydrogen atoms induced by these deformations are investigated using a multiscale approach based on first principles, empirical interactions, and continuum modeling. Focus is given to the intrinsic low-temperature structure and interactions. Therefore, all calculations are performed at T =0 , neglecting possible temperature or thermal fluctuation effects. Results from different methods agree well and consistently describe the local deformation of graphene on multiple length scales reaching 500 Å . The results indicate that the elastic interaction mediated by this deformation is significant and depends on the deformation of the graphene sheet both in and out of plane. Surprisingly, despite the isotropic elasticity of graphene, within the linear elastic regime, atoms elastically attract or repel each other depending on (i) the specific site they are chemisorbed; (ii) the relative position of the sites; (iii) and if they are on the same or on opposite surface sides. The interaction energy sign and power-law decay calculated from molecular statics agree well with theoretical predictions from linear elasticity theory, considering in-plane or out-of-plane deformations as a superposition or in a coupled nonlinear approach. Deviations on the exact power law between molecular statics and the linear elastic analysis are evidence of the importance of nonlinear effects on the elasticity of monolayer graphene. These results have implications for the understanding of the generation of clusters and regular formations of hydrogen and other chemisorbed atoms on graphene.

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

International Nuclear Information System (INIS)

Borodi, Gheorghe

2008-01-01

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 2 + with hydrogen atoms and molecules have been established as calibration standard for in situ determination of H and H 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 + , CH 2 + , and CH 4 + 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.)

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.)

Angular distribution of atoms emitted from a SrZrO3 target by laser ablation under different laser fluences and oxygen pressures

International Nuclear Information System (INIS)

Konomi, I.; Motohiro, T.; Azuma, H.; Asaoka, T.; Nakazato, T.; Sato, E.; Shimizu, T.; Fujioka, S.; Sarukura, N.; Nishimura, H.

2010-01-01

Angular distributions of atoms emitted by laser ablation of perovskite-type oxide SrZrO 3 have been investigated using electron probe microanalysis with wavelength-dispersive spectroscopy and charge-coupled device photography with an interference filter. Each constituent element has been analyzed as a two-modal distribution composed of a broad cos m θ distribution and a narrow cos n θ distribution. The exponent n characterizes the component of laser ablation while the exponent m characterizes that of thermal evaporation, where a larger n or m means a narrower angular distribution. In vacuum, O (n=6) showed a broader distribution than those of Sr (n=16) and Zr (n=17), and Sr + exhibited a spatial distribution similar to that of Sr. As the laser fluence was increased from 1.1 to 4.4 J/cm 2 , the angular distribution of Sr became narrower. In the laser fluence range of 1.1-4.4 J/cm 2 , broadening of the angular distribution of Sr was observed only at the fluence of 1.1 J/cm 2 under the oxygen pressure of 10 Pa. Monte Carlo simulations were performed to estimate approximately the energy of emitted atoms, focusing on the broadening of the angular distribution under the oxygen pressure of 10 Pa. The energies of emitted atoms were estimated to be 1-20 eV for the laser fluence of 1.1 J/cm 2 , and more than 100 eV for 2.2 and 4.4 J/cm 2 .

Hydrogenation of ethene catalyzed by Ir atom deposited on γ-Al2O3(001) surface: From ab initio calculations

International Nuclear Information System (INIS)

Chen, Yongchang; Sun, Zhaolin; Song, Lijuan; Li, Qiang; Xu, Ming

2012-01-01

Ethene hydrogenation reaction, catalyzed by an iridium atom adsorbed on γ-Al 2 O 3 (001) surface, is studied via ab initio calculations based on density functional theory (DFT). The catalyzed reaction process and activation energy are compared with the counterparts of a reaction occurs in vacuum condition. It is found that the activation energy barrier is substantially lowered by the adsorbed Ir atom on the γ-Al 2 O 3 (001). The catalyzed reaction is modeled in two steps: (1) Hydrogen molecular dissolution and then bonded with C 2 H 4 molecular. (2) Desorption of the C 2 H 6 molecular from the surface. -- Highlights: ► The ethene hydrogenation reaction is simulated with nudged elastic band methods. ► The catalytic effect of the Ir atom on γ-Al 2 O 3 (001) surface is modeled. ► Details of the catalytic reaction are exhibited.

SPIRAL STRUCTURE OF M51 - DISTRIBUTION AND KINEMATICS OF THE ATOMIC AND IONIZED HYDROGEN

NARCIS (Netherlands)

TILANUS, RPJ; ALLEN, RJ

The atomic hydrogen (H I) and the H-alpha emission lines in the grand-design spiral galaxy M51 have been observed with the Westerbork Synthesis Radio Telescope and the TAURUS Fabry-Perot imaging spectrometer, respectively. Across the inner spiral arms significant tangential and radial velocity

Atomic and molecular hydrogen gas temperatures in a low-pressure helicon plasma

Science.gov (United States)

Samuell, Cameron M.; Corr, Cormac S.

2015-08-01

Neutral gas temperatures in hydrogen plasmas are important for experimental and modelling efforts in fusion technology, plasma processing, and surface modification applications. To provide values relevant to these application areas, neutral gas temperatures were measured in a low pressure (radiofrequency helicon discharge using spectroscopic techniques. The atomic and molecular species were not found to be in thermal equilibrium with the atomic temperature being mostly larger then the molecular temperature. In low power operation (measurements near a graphite target demonstrated localised cooling near the sample surface. The temporal evolution of the molecular gas temperature during a high power 1.1 ms plasma pulse was also investigated and found to vary considerably as a function of pressure.

Mapping of the atomic hydrogen density in combustion processes at atmospheric pressure by two-photon polarization spectroscopy

International Nuclear Information System (INIS)

Steiger, A.; Gruetzmacher, K.; Steiger, M.; Gonzalo, A.B.; Rosa, M.I. de la

2001-01-01

With laser spectroscopic techniques used so far, quantitative measurements of atomic number densities in flames and other combustion processes at atmospheric pressure yield no satisfying results because high quenching rates remarkably reduce the signal size and the results suffer from large uncertainties. Whereas, two-photon polarization spectroscopy is not limited by quenching, as the polarization signal is a direct measure of the two-photon absorption. This sensitive laser technique with high spatial and temporal resolution has been applied to determine absolute number densities and the kinetic temperatures of atomic hydrogen in flames for the first time. The great potential of this method of measurement comes into its own only in conjunction with laser radiation of highest possible spectral quality, i.e. single-frequency ns-pulses with peak irradiance of up to 1 GW/cm 2 tunable around 243 nm for 1S-2S two-photon transition of atomic hydrogen

High-precision atom localization via controllable spontaneous emission in a cycle-configuration atomic system.

Science.gov (United States)

Ding, Chunling; Li, Jiahua; Yu, Rong; Hao, Xiangying; Wu, Ying

2012-03-26

A scheme for realizing two-dimensional (2D) atom localization is proposed based on controllable spontaneous emission in a coherently driven cycle-configuration atomic system. As the spatial-position-dependent atom-field interaction, the frequency of the spontaneously emitted photon carries the information about the position of the atom. Therefore, by detecting the emitted photon one could obtain the position information available, and then we demonstrate high-precision and high-resolution 2D atom localization induced by the quantum interference between the multiple spontaneous decay channels. Moreover, we can achieve 100% probability of finding the atom at an expected position by choosing appropriate system parameters under certain conditions.

UV light-emitting-diode photochemical mercury vapor generation for atomic fluorescence spectrometry.

Science.gov (United States)

Hou, Xiaoling; Ai, Xi; Jiang, Xiaoming; Deng, Pengchi; Zheng, Chengbin; Lv, Yi

2012-02-07

A new, miniaturized and low power consumption photochemical vapor generation (PVG) technique utilizing an ultraviolet light-emitting diode (UV-LED) lamp is described, and further validated via the determination of trace mercury. In the presence of formic acid, the mercury cold vapor is favourably generated from Hg(2+) solutions by UV-LED irradiation, and then rapidly transported to an atomic fluorescence spectrometer for detection. Optimum conditions for PVG and interferences from concomitant elements were investigated in detail. Under optimum conditions, a limit of detection (LOD) of 0.01 μg L(-1) was obtained, and the precision was better than 3.2% (n = 11, RSD) at 1 μg L(-1) Hg(2+). No obvious interferences from any common ions were evident. The methodology was successfully applied to the determination of mercury in National Research Council Canada DORM-3 fish muscle tissue and several water samples.

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

Czech Academy of Sciences Publication Activity Database

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

2014-01-01

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

Convergent close-coupling calculations of low-energy positron-atomic-hydrogen scattering

International Nuclear Information System (INIS)

Bray, I.; Stelbovics, A.T.

1993-07-01

The convergent close coupling approach developed by the authors is applied to positron scattering from atomic hydrogen below the first excitation threshold. In this approach the multi-channel expansion one-electron states are obtained by diagonalizing the target Hamiltonian in a large Laguerre basis. It is demonstrated that this expansion of the scattering wave function is sufficient to reproduce the very accurate low-energy variational results, provided target states with l≤ 15 are included in the expansions. 10 refs., 1 tab

Destruction of fast H(2S) atoms in collisions with neon, krypton, xenon, and molecular hydrogen

International Nuclear Information System (INIS)

Roussel, F.; Pradel, P.; Spiess, G.

1977-01-01

Measurements are reported for the total quenching of metastable hydrogen atoms by neon, krypton, xenon, and molecular hydrogen, in the energy range 0.052--3 keV. The cross sections are found to be on the order of 5 x 10 -15 cm 2 at the lowest energies, and decrease to approximately 2 x 10 -15 cm 2 at the highest energies. The data at low energy are analyzed using a simple theoretical model

Charge exchange cross sections in slow collisions of Si3+ with Hydrogen atom

Science.gov (United States)

Joseph, Dwayne; Quashie, Edwin; Saha, Bidhan

2011-05-01

In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. Work supported by NSF CREST project (grant #0630370).

Analysis of mechanism of carbon removal from GaAs(1 0 0) surface by atomic hydrogen

International Nuclear Information System (INIS)

Tomkiewicz, P.; Winkler, A.; Krzywiecki, M.; Chasse, Th.; Szuber, J.

2008-01-01

Etching of carbon contaminations from the GaAs(1 0 0) surface by irradiating with atomic hydrogen, which is one of the key reactions to promote high-quality thin films growth by molecular beam epitaxy (MBE), has been investigated by mass spectrometry (MS), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It is shown that during the cleaning process at room temperature a total reduction of the Auger carbon signal, accompanied by desorption of methane as major reaction product, can be observed. The reaction pathways as well as the processes responsible for the observed carbon removal are discussed in detail to give a support for etching and growth quality enhancement not only in thin films epitaxy but in all atomic hydrogen promoted gas-phase III-V semiconductor processes

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...

Entropy and complexity analysis of hydrogenic Rydberg atoms

Energy Technology Data Exchange (ETDEWEB)

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

2013-05-15

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

Study of the selective abstration reaction of the hydrogen atom in the radiolysis and photolysis of alkane mixture at 77 K

International Nuclear Information System (INIS)

Guedes, S.M.L.

1979-01-01

The occurence of the selective abstraction reaction of the solute hydrogen atom by hydrogen atom produced during radiolysis or photolysis of the systems such as neopentane/cyclo-hexane/HI, neopentane/2,3 dimethylbutane, n-pentane/HI/cyclo-hexane and cyclo-hexane/HI/n-pentane, at 77 K is studied. Experiments have been undertaken on the kinetics nature of the active species, the H atom, during radiolysis and photolysis of the neopentane/cyclo-hexane/HI system at 77 K, presenting competitive reactions. Studies have also been made on the occurrence of the selective abstraction reaction in inverted systems, in which the concentrations of the components of a system are so much altered that the solute becomes the solvent and vice-versa, in the other system. By means of photolysis at 77 K, it has been observed that for the two systems constitued by the cyclo-hexane and n-pentane the selective abstraction reaction occurs. However, for radiolysis of that same two systems it has been observed that only the hydrogen atom abstraction reaction corresponding to the solvent occurs. (Author) [pt

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

International Nuclear Information System (INIS)

Bauschlicher, Charles W. Jr.; Ricca, Alessandra

2013-01-01

The loss of one hydrogen from C 96 H 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

State-selective charge transfer cross sections for light ion impact of atomic hydrogen

Energy Technology Data Exchange (ETDEWEB)

Schultz, D. R. [University of North Texas; Stancil, Phillip C. [University of Georgia, Athens; Havener, C. C. [Oak Ridge National Laboratory (ORNL)

2015-01-01

Owing to the utility of diagnosing plasma properties such as impurity concentration and spatial distribution, and plasma temperature and rotation, by detection of photon emission following capture of electrons from atomic hydrogen to excited states of multiply charged ions, new calculations of state-selective charge transfer involving light ions have been carried out using the atomic orbital close-coupling and the classical trajectory Monte Carlo methods. By comparing these with results of other approaches applicable in a lower impact energy regime, and by benchmarking them using key experimental data, knowledge of the cross sections can be made available across the range parameters needed by fusion plasma diagnostics.

Studies on eletron scattering by hydrogen atoms through of a correlationed wave function

International Nuclear Information System (INIS)

Jacchieri, S.G.

1982-01-01

A correlationed wave function dependent of two adjustable parameters ( α e β), aiming describe a system formed by an electron and a hydrogen atom is studied. Some elastic differential cross-sections for several values of α and β parameters, scattering angle of 2 0 to 140 0 and energies of 50 eV and 680 eV are presented. (M.J.C.) [pt

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

Czech Academy of Sciences Publication Activity Database

Bureš, M.; Siegl, Petr

2015-01-01

Roč. 354, MAR (2015), s. 316-327 ISSN 0003-4916 Grant - others:GA ČR(CZ) GD202/08/H072 Institutional support: RVO:61389005 Keywords : extra dimensions * hydrogen atom * quantum stability Subject RIV: BE - Theoretical Physics Impact factor: 2.375, year: 2015

Hydrogen molecules and hydrogen-related defects in crystalline silicon

Science.gov (United States)

Fukata, N.; Sasaki, S.; Murakami, K.; Ishioka, K.; Nakamura, K. G.; Kitajima, M.; Fujimura, S.; Kikuchi, J.; Haneda, H.

1997-09-01

We have found that hydrogen exists in molecular form in crystalline silicon treated with hydrogen atoms in the downstream of a hydrogen plasma. The vibrational Raman line of hydrogen molecules is observed at 4158 cm-1 for silicon samples hydrogenated between 180 and 500 °C. The assignment of the Raman line is confirmed by its isotope shift to 2990 cm-1 for silicon treated with deuterium atoms. The Raman intensity has a maximum for hydrogenation at 400 °C. The vibrational Raman line of the hydrogen molecules is broad and asymmetric. It consists of at least two components, possibly arising from hydrogen molecules in different occupation sites in crystalline silicon. The rotational Raman line of hydrogen molecules is observed at 590 cm-1. The Raman band of Si-H stretching is observed for hydrogenation temperatures between 100 and 500 °C and the intensity has a maximum for hydrogenation at 250 °C.

Differences between Doppler velocities of ions and neutral atoms in a solar prominence

Science.gov (United States)

Anan, T.; Ichimoto, K.; Hillier, A.

2017-05-01

Context. In astrophysical systems with partially ionized plasma, the motion of ions is governed by the magnetic field while the neutral particles can only feel the magnetic field's Lorentz force indirectly through collisions with ions. The drift in the velocity between ionized and neutral species plays a key role in modifying important physical processes such as magnetic reconnection, damping of magnetohydrodynamic waves, transport of angular momentum in plasma through the magnetic field, and heating. Aims: This paper aims to investigate the differences between Doppler velocities of calcium ions and neutral hydrogen in a solar prominence to look for velocity differences between the neutral and ionized species. Methods: We simultaneously observed spectra of a prominence over an active region in H I 397 nm, H I 434 nm, Ca II 397 nm, and Ca II 854 nm using a high dispersion spectrograph of the Domeless Solar Telescope at Hida observatory. We compared the Doppler velocities, derived from the shift of the peak of the spectral lines presumably emitted from optically-thin plasma. Results: There are instances when the difference in velocities between neutral atoms and ions is significant, for example 1433 events ( 3% of sets of compared profiles) with a difference in velocity between neutral hydrogen atoms and calcium ions greater than 3σ of the measurement error. However, we also found significant differences between the Doppler velocities of two spectral lines emitted from the same species, and the probability density functions of velocity difference between the same species is not significantly different from those between neutral atoms and ions. Conclusions: We interpreted the difference of Doppler velocities as being a result of the motions of different components in the prominence along the line of sight, rather than the decoupling of neutral atoms from plasma. The movie attached to Fig. 1 is available at http://www.aanda.org

A new two-photon mechanism of the formation of a continuous spectrum of photons emitted by secondary emission products of atomic particles

International Nuclear Information System (INIS)

Veksler, V.I.

1986-01-01

A two-photon mechanism of the formation of a continuous spectrum of photons emitted by products of metal sputtering is considered. The following process of the two-photon mechanism is considered: the continuous spectrum is formed under quadrupole two-photon transitions in sputtered excited atoms having vacancies at the d level in atoms of transition metals or at the of level in lanthanides found against the filled conduction band. It is shown that the suggested mechanism should play an essential role in the formation of the continuous spectrum of optical radiation

Selected specific rates of reactions of transients from water in aqueous solution. II. Hydrogen atom

International Nuclear Information System (INIS)

Anbar, M.; Farhataziz; Ross, A.B.

1975-05-01

Rates of reactions of hydrogen atoms (from radiolysis of water and other sources) with organic and inorganic molecules, ions, and transients in aqueous solution were tabulated. Directly measured rates obtained by kinetic spectroscopy or conductimetric methods, and relative rates determined by competition kinetics are included. (U.S.)

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.

Entropy and complexity analysis of hydrogenic Rydberg atoms

International Nuclear Information System (INIS)

López-Rosa, S.; Toranzo, I. V.; Dehesa, J. S.; Sánchez-Moreno, P.

2013-01-01

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

Atomic-scale investigation of point defects and hydrogen-solute atmospheres on the edge dislocation mobility in alpha iron

Energy Technology Data Exchange (ETDEWEB)

Bhatia, M. A.; Solanki, K. N., E-mail: kiran.solanki@asu.edu [School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287 (United States); Groh, S. [Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Freiberg 09556 (Germany)

2014-08-14

In this study, we present atomistic mechanisms of 1/2 [111](11{sup ¯}0) edge dislocation interactions with point defects (hydrogen and vacancies) and hydrogen solute atmospheres in body centered cubic (bcc) iron. In metals such as iron, increases in hydrogen concentration can increase dislocation mobility and/or cleavage-type decohesion. Here, we first investigate the dislocation mobility in the presence of various point defects, i.e., change in the frictional stress as the edge dislocation interacts with (a) vacancy, (b) substitutional hydrogen, (c) one substitutional and one interstitial hydrogen, (d) interstitial hydrogen, (e) vacancy and interstitial hydrogen, and (f) two interstitial hydrogen. Second, we examine the role of a hydrogen-solute atmosphere on the rate of local dislocation velocity. The edge dislocation simulation with a vacancy in the compression side of the dislocation and an interstitial hydrogen atom at the tension side exhibit the strongest mechanical response, suggesting a higher potential barrier and hence, the higher frictional stress (i.e., ∼83% higher than the pure iron Peierls stress). In the case of a dislocation interacting with a vacancy on the compressive side, the vacancy binds with the edge dislocation, resulting in an increase in the friction stress of about 28% when compared with the Peierls stress of an edge dislocation in pure iron. Furthermore, as the applied strain increases, the vacancy migrates through a dislocation transportation mechanism by attaining a velocity of the same order as the dislocation velocity. For the case of the edge dislocation interacting with interstitial hydrogen on the tension side, the hydrogen atom jumps through one layer perpendicular to the glide plane during the pinning-unpinning process. Finally, our simulation of dislocation interactions with hydrogen show first an increase in the local dislocation velocity followed by a pinning of the dislocation core in the atmosphere, resulting in

Precision measurement of the 1S Lamb shift in atomic hydrogen

International Nuclear Information System (INIS)

Beausoleil, R.G.; McIntyre, D.H.; Foot, C.J.; Couillaud, B.; Hildum, E.A.; Hansch, T.W.

1987-01-01

The authors used cw Doppler-free two-photon spectroscopy to measure the 1S-2S transition frequency in atomic hydrogen gas with a precision of 6 parts in 10 10 . Their result for the energy level separation is f(1S-2S) = 2 466 061 413.3(1.5) MHz and can be used to extract a value of the 1S Lamb shift. Choosing a value of the Rydberg constant measured independently by high-resolution spectroscopy of the hydrogen Balmer-β transition, the authors obtain a value of Δf/sub Lamb/(1S) = 8 173.3(1.7) MHz, in good agreement with the theoretical prediction of 8 173.06(20) MHz. On the other hand, if they trust the theoretical determination of the 1S Lamb shift, they can interpret our experimental result as a measurement of the Rydberg constant. The authors obtain R∞ = 109 737.315(7) cm -1 , in agreement with recent precise measurements

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

Science.gov (United States)

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

2015-11-15

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

Excited-state positronium formation from positron--atomic-hydrogen collisions

International Nuclear Information System (INIS)

Mandal, C.R.; Mandal, M.; Mukherjee, S.C.

1991-01-01

Positronium formation into ground and n=2 levels has been studied in collisions of positrons with atomic hydrogen in the framework of an approximation called the boundary-corrected continuum-intermediate-state (BCCIS) approximation in the energy range of 0.08--2 keV. The conventional continuum-intermediate-state approximation does not satisfy the correct boundary condition. It has been shown that, with a suitable choice of the distorting potential, the boundary condition may be satisfied with a proper account of the intermediate continuum states. It has also been shown that the BCCIS approximation leads to the same transition amplitude as may be derived using the Vainshtein-Presnyakov-Sobelman approximation. The results obtained here are found to be in good agreement when compared with other theoretical results

On the transferability of atomic contributions to the optical rotatory power of hydrogen peroxide, methyl hydroperoxide and dimethyl peroxide

DEFF Research Database (Denmark)

Sánchez, Marina; Alkorta, Ibon; Elguero, José

2014-01-01

for the hydrogen, oxygen and carbon atoms as well as for the methyl group at the level of time-dependent density functional theory with the B3LYP exchange-correlation functional employing a large Gaussian basis set. We find that the atomic or group contributions are not transferable among these three molecules....

Left-cut contribution to the dispersion relation for the elastic electron - atomic-hydrogen scattering amplitude

International Nuclear Information System (INIS)

Amusia, M.Ya.; Kuchiev, M.Yu.

1979-01-01

The jump in the electron - atomic-hydrogen forward scattering amplitude at the cut extending to the left from E = -0.5 au is calculated as a function of the incident electron energy, E, by using the second Born approximation. The contribution from this singularity to the dispersion relation is determined. (Auth.)

Coherence effects in atomic impact processes

International Nuclear Information System (INIS)

Blum, K.

1980-01-01

The author considers excitation of target atoms by projectile particles and the coincident detection of the scattered projectiles and the photons emitted in the subsequent decay by the target atoms. The observation is restricted to radiation emitted by those atoms only which 'scattered' the projectiles with a given energy in a given direction defined by the particle detector. Thus, a certain subensemble of atoms is selected in the experiment. The author reviews the theoretical scheme used for the description of the excited subensemble with the emphasis on the coherence properties. The author reviews developments of the Fano-Macek theory concerning the description of coherently excited states with different angular momenta and parities. A comprehensive expression for the angular distribution of the emitted radiation, including all possible interference terms is given. (Auth.)

Boltzmann statistical consideration on the excitation mechanism of iron atomic lines emitted from glow discharge plasmas

International Nuclear Information System (INIS)

Zhang Lei; Kashiwakura, Shunsuke; Wagatsuma, Kazuaki

2011-01-01

A Boltzmann plot for many iron atomic lines having excitation energies of 3.3–6.9 eV was investigated in glow discharge plasmas when argon or neon was employed as the plasma gas. The plot did not show a linear relationship over a wide range of the excitation energy, but showed that the emission lines having higher excitation energies largely deviated from a normal Boltzmann distribution whereas those having low excitation energies (3.3–4.3 eV) well followed it. This result would be derived from an overpopulation among the corresponding energy levels. A probable reason for this is that excitations for the high-lying excited levels would be caused predominantly through a Penning-type collision with the metastable atom of argon or neon, followed by recombination with an electron and then stepwise de-excitations which can populate the excited energy levels just below the ionization limit of iron atom. The non-thermal excitation occurred more actively in the argon plasma rather than the neon plasma, because of a difference in the number density between the argon and the neon metastables. The Boltzmann plots yields important information on the reason why lots of Fe I lines assigned to high-lying excited levels can be emitted from glow discharge plasmas. - Highlights: ► This paper shows the excitation mechanism of Fe I lines from a glow discharge plasma. ► A Boltzmann distribution is studied among iron lines of various excitation levels. ► We find an overpopulation of the high-lying energy levels from the normal distribution. ► It is caused through Penning-type collision of iron atom with argon metastable atom.

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

Science.gov (United States)

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

2015-10-01

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

Role of carbon atoms in the remote plasma deposition of hydrogenated amorphous carbon

International Nuclear Information System (INIS)

Benedikt, J.; Wisse, M.; Woen, R.V.; Engeln, R.; Sanden, M.C.M. van de

2003-01-01

The aim of this article is to determine the role of carbon atoms in the growth of hydrogenated amorphous carbon (a-C:H) films by means of an argon/acetylene expanding thermal plasma. Cavity ring down absorption spectroscopy is used to detect metastable carbon atoms by probing the 1s 2 2s 2 2p 3s 1 P 1 2 2s 2 2p 2 1 S 0 electronic transition. In addition to absorption measurements, the emission of the same transition is monitored by means of optical emission spectroscopy. These two measurements provide information about the local production of the C atoms and about their reactivity in the gas phase. It will be shown that under growth conditions in an Ar/C 2 H 2 expanding thermal plasma, the metastable carbon density is also representative for the ground state carbon density. From obtained results it is concluded that the carbon atoms react rapidly with acetylene in the gas phase and therefore their contribution to the growth of hard diamond-like a-C:H films can be neglected. Only at low acetylene flows, the condition when soft polymer-like films are deposited, carbon atoms are detected close to the substrate and can possibly contribute to the film growth

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.

Anomalously deep penetration of hydrogen into niobium under action of pulse high temperature hydrogen plasma

International Nuclear Information System (INIS)

Didyk, A.Yu.

2011-01-01

The method of elastic recoil detection (ERD) has been used for the study of storage and redistribution processes of hydrogen atoms under the influence of pulse high temperature hydrogen plasma obtained using the 'Plasma Focus' PF-4 set-up in three high purity niobium foils. It was established that with an increase of number of PF-4 set-up pulses there occur spreading and transfer of implanted hydrogen atoms to large depths in three Nb-foils which are significantly larger than the projected range of hydrogen ions (with the velocity ∼ 10 8 cm/s). The maximum hydrogen concentration up to 60 at. % is reached in the nearest to Ph-4 surface of the third Nb-foil at 20 impulses of the Ph-4 set-up. The observed phenomenon can be described by transfer of implanted hydrogen atoms under the action of powerful shock waves, created by pulse hydrogen plasma and (or) by accelerating hydrogen atom diffusion under the influence of compression straining wave at the front of the shock wave at redistribution of hydrogen atoms at large depths. Similar behavior was discovered and described also in series of nickel, vanadium, niobium and tantalum foils (two or three foils and more in a series) including series of foils from heterogeneous (different) materials, which were studied, too

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

Science.gov (United States)

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

2016-11-01

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

Incident angle dependence of reactions between graphene and hydrogen atom by molecular dynamics simulation

International Nuclear Information System (INIS)

Saito, Seiki; Nakamura, Hiroaki; Ito, Atsushi

2010-01-01

Incident angle dependence of reactions between graphene and hydrogen atoms are obtained qualitatively by classical molecular dynamics simulation under the NVE condition with modified Brenner reactive empirical bond order (REBO) potential. Chemical reaction depends on two parameters, i.e., polar angle θ and azimuthal angle φ of the incident hydrogen. From the simulation results, it is found that the reaction rates strongly depend on polar angle θ. Reflection rate becomes larger with increasing θ, and the θ dependence of adsorption rate is also found. The θ dependence is caused by three dimensional structure of the small potential barrier which covers adsorption sites. φ dependence of penetration rate is also found for large θ. (author)

Spectroscopic studies of hydrogen collisions

International Nuclear Information System (INIS)

Kielkopf, J.

1991-01-01

Low energy collisions involving neutral excited states of hydrogen are being studied with vacuum ultraviolet spectroscopy. Atomic hydrogen is generated by focusing an energetic pulse of ArF, KrF, or YAG laser light into a cell of molecular hydrogen, where a plasma is created near the focal point. The H 2 molecules in and near this region are dissociated, and the cooling atomic hydrogen gas is examined with laser and dispersive optical spectroscopy. In related experiments, we are also investigating neutral H + O and H + metal - atom collisions in these laser-generated plasmas

Multiphoton ionization of the hydrogen atom by a circularly polarized electromagnetic field

International Nuclear Information System (INIS)

Prepelitsa, O.B.

1999-01-01

This paper examines the multiphoton ionization of the ground state of the hydrogen atom in the field of a circularly polarized intense electromagnetic wave. To describe the states of photoelectrons, quasiclassical wave functions are introduced that partially allow for the effect of an intense electromagnetic wave and that of the Coulomb potential. Expressions are derived for the angular and energy distributions of photoelectrons with energies much lower than the ionization potential of an unperturbed atom. It is found that, due to allowance for the Coulomb potential in the wave function of the final electron states, the transition probability near the ionization threshold tends to a finite value. In addition, the well-known selection rules for multiphoton transitions in a circularly polarized electromagnetic field are derived in a natural way. Finally, the results are compared with those obtained in the Keldysh-Faisal-Reiss approximation

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.

Quantum dynamics of hydrogen atoms on graphene. II. Sticking

Science.gov (United States)

Bonfanti, Matteo; Jackson, Bret; Hughes, Keith H.; Burghardt, Irene; Martinazzo, Rocco

2015-09-01

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.

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

Science.gov (United States)

Bonfanti, Matteo; Jackson, Bret; Hughes, Keith H; Burghardt, Irene; Martinazzo, Rocco

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.

Quantum dynamics of hydrogen atoms on graphene. II. Sticking

International Nuclear Information System (INIS)

Bonfanti, Matteo; Jackson, Bret; Hughes, Keith H.; Burghardt, Irene; Martinazzo, Rocco

2015-01-01

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

Classical-quantal coupling in the capture of muons by hydrogen atoms

International Nuclear Information System (INIS)

Kwong, N.H.; Garcia, J.D.

1989-01-01

We describe a self-consistent semiclassical approach to the problem of muon capture by hydrogen atoms. The dynamics of the heavier muon and proton are treated classically, and the electron quantally, with the potentials for both being self-consistently determined. Our numerical results are compared to classical-trajectory Monte Carlo (CTMC) and adiabatic ionisation (AI) results. Our capture cross sections are larger at low energy but fall more rapidly to zero. Our results provide the corrections to the dynamics beyond the adiabatic picture, which were missing in other approaches; interesting questions concerning the quantal nature of the events are discussed. (author)

Hirshfeld atom refinement.

Science.gov (United States)

Capelli, Silvia C; Bürgi, Hans-Beat; Dittrich, Birger; Grabowsky, Simon; Jayatilaka, Dylan

2014-09-01

Hirshfeld atom refinement (HAR) is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustrated via the example of crystalline ammonia. The new HAR method is then applied to X-ray diffraction data of the dipeptide Gly-l-Ala measured at 12, 50, 100, 150, 220 and 295 K, using Hartree-Fock and BLYP density functional theory electron densities and three different basis sets. All positions and anisotropic displacement parameters (ADPs) are freely refined without constraints or restraints - even those for hydrogen atoms. The results are systematically compared with those from neutron diffraction experiments at the temperatures 12, 50, 150 and 295 K. Although non-hydrogen-atom ADPs differ by up to three combined standard uncertainties (csu's), all other structural parameters agree within less than 2 csu's. Using our best calculations (BLYP/cc-pVTZ, recommended for organic molecules), the accuracy of determining bond lengths involving hydrogen atoms from HAR is better than 0.009 Å for temperatures of 150 K or below; for hydrogen-atom ADPs it is better than 0.006 Å(2) as judged from the mean absolute X-ray minus neutron differences. These results are among the best ever obtained. Remarkably, the precision of determining bond lengths and ADPs for the hydrogen atoms from the HAR procedure is comparable with that from the neutron measurements - an outcome which is obtained with a routinely achievable resolution of the X-ray data of 0.65 Å.

Visualization of hydrogen gas evolution during deformation and fracture in SCM 440 steel with different tempering conditions

International Nuclear Information System (INIS)

Horikawa, Keitaro; Ando, Nobuaki; Kobayashi, Hidetoshi; Urushihara, Wataru

2012-01-01

Highlights: ► We visualize emission sites of hydrogen atoms on the microstructures during deformation. ► Hydrogen atoms are emitted from slip lines and inclusions when deformed. ► We show the sequence of hydrogen gas evolution during deformation. ► Hydrogen evolution amount will increase if the steels with high strength are tested. - Abstract: In the present study, the hydrogen gas evolution behavior was investigated in SCM 440 steel by using a hydrogen microprint technique (HMT) and a testing machine equipped with a quadrupole mass spectrometer (QMS) in a ultrahigh vacuum (UHV) atmosphere. SCM 440 steels prepared by varying the tempering temperature over the range 200–700 °C were evaluated in order to elucidate the relationship between the hydrogen gas evolution and the tempered microstructures in the deformation. Cathodic hydrogen charging was carried out with a current density of 100 A/m 2 for 1 h at room temperature. For comparison, a tensile specimen was prepared without hydrogen charging. The HMT showed that silver particles, which are indicative of the hydrogen emission sites, were present mainly in the matrix as well as on the slip lines after the deformation. It is believed that the silver particles on the slip lines represent the effect of hydrogen transportation due to mobile dislocations. In addition, accumulation of silver particles around non-metallic inclusions such as Al 2 O 3 was also identified. This tendency was observed for different tempering conditions. From the relationship between the stress–strain curves and the hydrogen evolution, determined by using QMS under a UHV atmosphere, it was found that the hydrogen gas evolution behavior varied with the deformation stage.

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.

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.

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.)

Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

International Nuclear Information System (INIS)

Borges, L.H.C.; Barone, F.A.

2016-01-01

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.)

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

Science.gov (United States)

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

2009-01-01

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

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.

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

International Nuclear Information System (INIS)

Abdullahi, Yusuf Zuntu; Rahman, Md. Mahmudur; Shuaibu, Alhassan; Abubakar, Shamsu; Zainuddin, Hishamuddin; Muhida, Rifki; Setiyanto, Henry

2014-01-01

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.

Hydrogen storage property of alkali and alkaline-earth metal atoms decorated C24 fullerene: A DFT study

Science.gov (United States)

Zhang, Yafei; Cheng, Xinlu

2018-04-01

The hydrogen storage behavior of alkali and alkaline-earth metal (AM = Li, Na, K, Mg, Ca) atoms decorated C24 fullerene was investigated by using density functional theory (DFT) study. Our results indicate that the AM atoms prefer to adsorb atop the center of tetragon of C24 fullerene with the largest binding energy than other possible adsorption sites. Moreover, the hydrogen storage gravimetric density of 24H2/6Li/C24, 24H2/6Na/C24 and 36H2/6Ca/C24 configurations reaches up to 12.7 wt%, 10.1 wt% and 12 wt%, higher than the year 2020 target from the US department of energy (DOE). Also, the average adsorption energies of H2 molecules of the 24H2/6Li/C24, 24H2/6Na/C24 and 36H2/6Ca/C24 configurations are -0.198 eV/H2, -0.164 eV/H2 and -0.138 eV/H2, locate the desirable range under the physical adsorption at near ambient conditions. These findings will have important implications on designing new hydrogen storage materials in the future.

Electron beam induced fluorescence measurements of the degree of hydrogen dissociation in hydrogen plasmas

NARCIS (Netherlands)

Smit, C.; Brussaard, G.J.H.; de Beer, E.C.M.; Schram, D.C.; Sanden, van de M.C.M.

2004-01-01

The degree of dissociation of hydrogen in a hydrogen plasma has been measured using electron beam induced fluorescence. A 20 kV, 1 mA electron beam excites both the ground state H atom and H2 molecule into atomic hydrogen in an excited state. From the resulting fluorescence the degree of

A S-matrix-like approximation in the charged particle scattering by the hydrogen atom

International Nuclear Information System (INIS)

Mignaco, J.A.; Tort, A.C.

1979-01-01

The Born approximation for charged particle scattering by the hydrogen atom is unfit at low energies. From a S-matrix-like consideration on the dominance of the neighbour singularities, the calculation of other contributions is suggested. The inclusion of bound states is made, following Eden's and his colaborators' ideas, which are described by their interest and likeness with procedures in the intermediate energy physics. (Author) [pt

Limitations of the strong field approximation in ionization of the hydrogen atom by ultrashort pulses

International Nuclear Information System (INIS)

Arbo, D.G.; Toekesi, K.; Miraglia, J.E.; FCEN, University of Buenos Aires

2008-01-01

Complete text of publication follows. We presented a theoretical study of the ionization of hydrogen atoms as a result of the interaction with an ultrashort external electric field. Doubly-differential momentum distributions and angular momentum distributions of ejected electrons calculated in the framework of the Coulomb-Volkov and strong field approximations, as well as classical calculations are compared with the exact solution of the time dependent Schroedinger equation. We have shown that the Coulomb-Volkov approximation (CVA) describes the quantum atomic ionization probabilities exactly when the external field is described by a sudden momentum transfer [1]. The velocity distribution of emitted electrons right after ionization by a sudden momentum transfer is given through the strong field approximation (SFA) within both the CVA and CTMC methods. In this case, the classical and quantum time dependent evolutions of an atom subject to a sudden momentum transfer are identical. The difference between the classical and quantum final momentum distributions resides in the time evolution of the escaping electron under the subsequent action of the Coulomb field. Furthermore, classical mechanics is incapable of reproducing the quantum angular momentum distribution due to the improper initial radial distribution used in the CTMC calculations, i.e., the microcanonical ensemble. We find that in the limit of high momentum transfer, based on the SFA, there is a direct relation between the cylindrical radial distribution dP/dρ and the final angular momentum distribution dP/dL. This leads to a close analytical expression for the partial wave populations (dP/dL) SFA-Q given by dP SFA-Q / dL = 4Z 3 L 2 / (Δp) 3 K 1 (2ZL/Δp) which, together with the prescription L = l + 1/2, reproduces quite accurately the quantum (CVA) results. Considering the inverse problem, knowing the final angular momentum distribution can lead to the inference of the initial probability distribution

Low temperature removal of surface oxides and hydrocarbons from Ge(100) using atomic hydrogen

Energy Technology Data Exchange (ETDEWEB)

Walker, M., E-mail: m.walker@warwick.ac.uk; Tedder, M.S.; Palmer, J.D.; Mudd, J.J.; McConville, C.F.

2016-08-30

Highlights: • Preparation of a clean, well-ordered Ge(100) surface with atomic hydrogen. • Surface oxide layers removed by AHC at room temperature, but not hydrocarbons. • Increasing surface temperature during AHC dramatically improves efficiency. • AHC with the surface heated to 250 °C led to a near complete removal of contaminants. • (2 × 1) LEED pattern from IBA and AHC indicates asymmetric dimer reconstruction. - Abstract: Germanium is a group IV semiconductor with many current and potential applications in the modern semiconductor industry. Key to expanding the use of Ge is a reliable method for the removal of surface contamination, including oxides which are naturally formed during the exposure of Ge thin films to atmospheric conditions. A process for achieving this task at lower temperatures would be highly advantageous, where the underlying device architecture will not diffuse through the Ge film while also avoiding electronic damage induced by ion irradiation. Atomic hydrogen cleaning (AHC) offers a low-temperature, damage-free alternative to the common ion bombardment and annealing (IBA) technique which is widely employed. In this work, we demonstrate with X-ray photoelectron spectroscopy (XPS) that the AHC method is effective in removing surface oxides and hydrocarbons, yielding an almost completely clean surface when the AHC is conducted at a temperature of 250 °C. We compare the post-AHC cleanliness and (2 × 1) low energy electron diffraction (LEED) pattern to that obtained via IBA, where the sample is annealed at 600 °C. We also demonstrate that the combination of a sample temperature of 250 °C and atomic H dosing is required to clean the surface. Lower temperatures prove less effective in removal of the oxide layer and hydrocarbons, whilst annealing in ultra-high vacuum conditions only removes weakly bound hydrocarbons. Finally, we examine the subsequent H-termination of an IBA-cleaned sample using XPS, LEED and ultraviolet

Analysis of x-ray spectra emitted from highly ionized atoms in the vacuum spark and laser-produced high power plasma sources

International Nuclear Information System (INIS)

Mandelbaum, P.

1987-05-01

The interest in atomic spectroscopy has greatly been reinforced in the last ten years. This gain of interest is directly related to the developments in different fields of research where hot plasmas are created. These fields include in particular controlled thermonuclear fusion research by means of inertial or magnetic confinement approaches and also the most recent efforts to achieve lasers in the XUV region. The present work is based on the specific contribution of the atomic spectroscopy group at the Hebrew University. The recent development of both theoretical and experimental tools allowed us to progress in the understanding of the highly ionized states of heavy elements. In this work the low-inductance vacuum-spark developed at the Hebrew University was used as the hot plasma source. The spectra were recorded in the 7-300 A range by means of a high-resolution extreme-grazing-incidence spectrometer developed at the Racah Institute by Profs. J.L. Schwob and B.S. Fraenkel. To the extend the spectroscopic studies to higher-Z atoms, the laser-produced plasma facility at Soreq Nuclear Center was used. In this work the spectra of the sixth row elements were recorded in the x-rays by means of a crystal spectrometer. All these experimental systems are briefly described in chapter one. Chapter two deals with the theoretical methods used in the present work for the atomic calculations. Chapter three deals with the spectra of elements of the fifth row emitted from the vacuum-spark in the 30-150 A range. These spectra as experimental data were used in order to test ab-initio computations along the NiI sequence 3d-nl transitions. The results of this work are presented in chapter four. Chapter five is devoted to the measurement and analysis of spectra emitted from the vacuum-spark by rare-earth elements. (author)

Glauber amplitudes for transitions from low lying states in hydrogen atom by charged particle impact

Energy Technology Data Exchange (ETDEWEB)

Kumar, S; Srivastava, M K [Roorkee Univ. (India). Dept. of Physics

1977-07-01

The Glauber amplitudes for the general transition nlm ..-->.. n'1'm' in charged particle - hydrogen atom collisions have been obtained in the form of a one-dimensional integral. The final expression involves only a few hypergeometric functions if n is not too large and is particularly suited to study excitation to highly excited states from a low lying state.

Hydrogen storage and generation system

Science.gov (United States)

Dentinger, Paul M.; Crowell, Jeffrey A. W.

2010-08-24

A system for storing and generating hydrogen generally and, in particular, a system for storing and generating hydrogen for use in an H.sub.2/O.sub.2 fuel cell. The hydrogen storage system uses the beta particles from a beta particle emitting material to degrade an organic polymer material to release substantially pure hydrogen. In a preferred embodiment of the invention, beta particles from .sup.63Ni are used to release hydrogen from linear polyethylene.

Absolute atomic hydrogen density distribution in a hollow cathode discharge by two-photon polarization spectroscopy

International Nuclear Information System (INIS)

Gonzalo, A B; Rosa, M I de la; Perez, C; Mar, S; Gruetzmacher, K

2004-01-01

We report on quantitative measurements of ground-state atomic hydrogen densities in a stationary plasma far off thermodynamic equilibrium, generated in a hollow cathode discharge, by two-photon polarization spectroscopy via the 1S-2S transition. Absolute densities are obtained using a well established calibration method based on the non-resonant two-photon polarization signal of xenon gas at room temperature, which serves as the reference at the wavelength of the hydrogen transition. This study is dedicated to demonstrating the capability of two-photon polarization spectroscopy close to the detection limit. Therefore, it requires single-longitudinal mode UV-laser radiation provided by an advanced UV-laser spectrometer

Collision processes of highly excited hydrogen atom, 1

International Nuclear Information System (INIS)

Toshima, Nobuyuki

1977-01-01

The cross sections for the transitions 5S sub(1/2) → 5P sub(1/2), 5S sub(1/2) → 5P sub(3/2), 5P sub(1/2) → 5D sub(3/2), 5S sub(1/2) → 5D sub(3/2) and 5S sub(1/2) → 5D sub(5/2) in the hydrogen atom by proton impact are calculated on the basis of the impact parameter method. Distant collisions are dominant and the couplings among the sub-levels belonging to the same n are important at low energies, but the couplings with the levels belonging to different n's are negligibly small. The Glauber and the Born approximations are also applied to the same problem and the Glauber approximation gives a good agreement with the impact parameter method over a wide energy range down to at least about 100 eV. (auth.)

Elastic interactions between hydrogen atoms in metals. II. Elastic interaction energies

International Nuclear Information System (INIS)

Shirley, A.I.; Hall, C.K.

1986-01-01

The fully harmonic lattice approximation derived in a previous paper is used to calculate the elastic interaction energies in the niobium-hydrogen system. The permanent-direct, permanent-indirect, induced-direct, and induced-indirect forces calculated previously each give rise to a corresponding elastic interaction between hydrogen atoms. The latter three interactions have three- and four-body terms in addition to the usual two-body terms. These quantities are calculated and compared with the corresponding two-body permanent elastic interactions obtained in the harmonic-approximation treatment of Horner and Wagner. The results show that the total induced elastic energy is approximately (1/3) the size of the total permanent elastic energy and opposite to it in sign. The total elastic energy due to three-body interactions is approximately (1/4) the size of the total two-body elastic energy, while the total four-body elastic energy is approximately 5% of the total two-body energy. These additional elastic energies are expected to have a profound effect on the thermodynamic and phase-change behavior of a metal hydride

Boltzmann statistical consideration on the excitation mechanism of iron atomic lines emitted from glow discharge plasmas

Energy Technology Data Exchange (ETDEWEB)

Zhang Lei; Kashiwakura, Shunsuke; Wagatsuma, Kazuaki, E-mail: wagatuma@imr.tohoku.ac.jp

2011-11-15

A Boltzmann plot for many iron atomic lines having excitation energies of 3.3-6.9 eV was investigated in glow discharge plasmas when argon or neon was employed as the plasma gas. The plot did not show a linear relationship over a wide range of the excitation energy, but showed that the emission lines having higher excitation energies largely deviated from a normal Boltzmann distribution whereas those having low excitation energies (3.3-4.3 eV) well followed it. This result would be derived from an overpopulation among the corresponding energy levels. A probable reason for this is that excitations for the high-lying excited levels would be caused predominantly through a Penning-type collision with the metastable atom of argon or neon, followed by recombination with an electron and then stepwise de-excitations which can populate the excited energy levels just below the ionization limit of iron atom. The non-thermal excitation occurred more actively in the argon plasma rather than the neon plasma, because of a difference in the number density between the argon and the neon metastables. The Boltzmann plots yields important information on the reason why lots of Fe I lines assigned to high-lying excited levels can be emitted from glow discharge plasmas. - Highlights: Black-Right-Pointing-Pointer This paper shows the excitation mechanism of Fe I lines from a glow discharge plasma. Black-Right-Pointing-Pointer A Boltzmann distribution is studied among iron lines of various excitation levels. Black-Right-Pointing-Pointer We find an overpopulation of the high-lying energy levels from the normal distribution. Black-Right-Pointing-Pointer It is caused through Penning-type collision of iron atom with argon metastable atom.

HYDROGEN VACANCY INTERACTION IN MOLYBDENUM

NARCIS (Netherlands)

Abd El Keriem, M.S.; van der Werf, D.P.; Pleiter, F

1993-01-01

Vacancy-hydrogen interaction in molybdenum was investigated by means of the perturbed angular correlation technique, using the isotope In-111 as a probe. The complex InV2 turned out to trap up to two hydrogen atoms: trapping of a single hydrogen atom gives rise to a decrease of the quadrupole

On the chemistry of the lightest exotic atoms

International Nuclear Information System (INIS)

Horvath, D.

1980-01-01

The chemical aspects of formation of three hydrogen-like exotic atoms, positronium, muonium and pionic hydrogen are discussed. For positronium two formation mechanisms, the Ore model with hot-atom reactions, and the spur reaction model are set against experimental observations in solutions. The use of pionic hydrogen atoms in obtaining information on the bond properties of hydrogen is illustrated by recent experiments performed in JINR. The use of negative pions in chemistry is demonstrated by electronic structure investigations performed in Dubna. The probability W that in a chemical system containing bound hydrogen atoms a stopped negative pion is captured by a proton reflects the bond properties of hydrogen. Recent results haVe shown that the hydrogen bond formation in liquid water and the coordination of water molecules in aquacomplexes lead to significant decreases in probability W for water. A comparison of the chemical uses of the exotic atoms shows that positronium and muonium inform us on intermolecular level probing a small environment of a few molecules while the pionic hydrogen atoms deliver information on the chemical bond of hydrogen, i.e. on intramolecular level

The behaviour of hydrogen-like atoms in an intense long-wave field

International Nuclear Information System (INIS)

Brodsky, A.M.

1979-01-01

The equations, which permit the calculation by means of regular operations of multiphoton photoionisation cross sections and the dynamic polarisabilities in an intense classical long-wave electromagnetic field, are considered for a hydrogen atom. The calculations have been performed for a circularly polarised field. A quantitative expression has been derived for the Lamb shift analogue, which can be verified experimentally. Within the framework of the problem the interaction at small distances is self-compensated and reduced to a constant potential. This conclusion is of general interest for the theory of strong interactions. (author)

Polarized atomic beams for targets

International Nuclear Information System (INIS)

Grueebler, W.

1984-01-01

The basic principle of the production of polarized atomic hydrogen and deuterium beams are reviewed. The status of the present available polarization, density and intensity are presented. The improvement of atomic beam density by cooling the hydrogen atoms to low velocity is discussed. The possible use of polarized atomic beams as targets in storage rings is shown. It is proposed that polarized atomic beams can be used to produce polarized gas targets with high polarization and greatly improved density

2-Amino-5-bromopyridinium hydrogen succinate

Directory of Open Access Journals (Sweden)

Hoong-Kun Fun

2010-03-01

Full Text Available In the title compound, C5H6BrN2+·C4H5O4−, the pyridine N atom of the 2-amino-5-bromopyridine molecule is protonated. The protonated N atom and the amino group are linked via N—H...O hydrogen bonds to the carboxylate O atoms of the singly deprotonated succinate anion. The hydrogen succinate anions are linked via O—H...O hydrogen bonds. A weak intermolecular C—H...O hydrogen bond is also observed.

An interface between the nuclear physics and the atomic physics; how to measure nuclear times observing atomic transitions

International Nuclear Information System (INIS)

Pinho, A.G. de

1985-01-01

Recent observations are related in which processes resulting from the ionization in ion-atom collisions are observed in coincidence with nuclear processes (where the incidence ion nucleus hits the target atom nucleus). The delay introduced by the nuclear reaction contaminates the results of the atomic collision and manifest itself either in the X rays (positrons) emitted in the joined atom system or in the X rays (Auger electrons) emitted by separeted atoms, after the collision. Both effects serve to obtain information on the reaction times (in general much less then 10 -16 sec). Following this line, other experimental possibilities are discussed. (L.C.) [pt

Reduction in Recombination Current Density in Boron Doped Silicon Using Atomic Hydrogen

Science.gov (United States)

Young, Matthew Garett

The solar industry has grown immensely in recent years and has reached a point where solar energy has now become inexpensive enough that it is starting to emerge as a mainstream electrical generation source. However, recent economic analysis has suggested that for solar to become a truly wide spread source of electricity, the costs still need to plummet by a factor of 8x. This demands new and innovative concepts to help lower such cost. In pursuit of this goal, this dissertation examines the use of atomic hydrogen to lessen the recombination current density in the boron doped region of n-type silicon solar cells. This required the development of a boron diffusion process that maintained the bulk lifetime of n-type silicon such that the recombination current density could be extracted by photoconductance spectroscopy. It is demonstrated that by hydrogenating boron diffusions, the majority carrier concentration can be controlled. By using symmetrically diffused test structures with quinhydrone-methanol surface passivation the recombination current density of a hydrogenated boron profile is shown to be less than that of a standard boron profile, by as much as 30%. This is then applied to a modified industrial silicon solar cell process to demonstrate an efficiency enhancement of 0.4%.

Dirac equation in very special relativity for hydrogen atom

Energy Technology Data Exchange (ETDEWEB)

Maluf, R.V., E-mail: r.v.maluf@fisica.ufc.br [Universidade Federal do Ceará (UFC), Departamento de Física, Campus do Pici, Caixa Postal 6030, 60455-760 Fortaleza, Ceará (Brazil); Silva, J.E.G., E-mail: euclides@fisica.ufc.br [Universidade Federal do Ceará (UFC), Departamento de Física, Campus do Pici, Caixa Postal 6030, 60455-760 Fortaleza, Ceará (Brazil); Cruz, W.T., E-mail: wilamicruz@gmail.com [Instituto Federal de Educação, Ciência e Tecnologia do Ceará (IFCE), Campus Juazeiro do Norte, 63040-000 Juazeiro do Norte, Ceará (Brazil); Almeida, C.A.S., E-mail: carlos@fisica.ufc.br [Universidade Federal do Ceará (UFC), Departamento de Física, Campus do Pici, Caixa Postal 6030, 60455-760 Fortaleza, Ceará (Brazil)

2014-11-10

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.

Analysis of Data on the Cross Sections for Electron-Impact Ionization and Excitation of Electronic States of Atomic Hydrogen (Review)

Science.gov (United States)

Shakhatov, V. A.; Lebedev, Yu. A.

2018-01-01

A review is given of experimental and theoretical data on the cross sections for ionization, excitation, and deexcitation of atomic hydrogen. The set of the cross sections required to calculate the electron energy distribution function and find the level-to-level rate coefficients needed to solve balance equations for the densities of neutral and charged particles in hydrogen plasma is determined.

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

International Nuclear Information System (INIS)

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

Mechanical filter for alkali atoms

CERN Document Server

Toporkov, D K

2000-01-01

A device for separating gases of different mass is discussed. Such a device could be used in a laser-driven spin exchange source of polarized hydrogen atoms to reduce the contamination of alkali atoms. A Monte Carlo simulation has shown that the suggested apparatus based on a commercial turbo pump could reduce by a factor of 10-15 the concentration of the alkali-metal atoms in the hydrogen flow from a laser driven polarized source. This would greatly enhance the effective polarization in hydrogen targets.

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

Science.gov (United States)

Clark, Ted M.; Chamberlain, Julia M.

2014-01-01

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

Benchmark Calculation of Radial Expectation Value for Confined Hydrogen-Like Atoms and Isotropic Harmonic Oscillators

International Nuclear Information System (INIS)

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

2017-01-01

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

Effect of Atomic Hydrogen on Preparation of Highly Moisture-Resistive SiNx Films at Low Substrate Temperatures

Science.gov (United States)

Heya, Akira; Niki, Toshikazu; Takano, Masahiro; Yonezawa, Yasuto; Minamikawa, Toshiharu; Muroi, Susumu; Minami, Shigehira; Izumi, Akira; Masuda, Atsushi; Umemoto, Hironobu; Matsumura, Hideki

2004-12-01

Highly moisture-resistive SiNx films on a Si substrate are obtained at substrate temperatures of 80°C by catalytic chemical vapor deposition (Cat-CVD) using a source gas with H2. Atomic hydrogen effected the selective etching of a weak-bond regions and an increase in atomic density induced by the energy of the surface reaction. It is concluded that Cat-CVD using H2 is a promising candidate for the fabrication of highly moisture-resistive SiNx films at low temperatures.

Physical reason for quantum behaviour of the electron and stability of the main state of the hydrogen atom

International Nuclear Information System (INIS)

Rangelov, J.M.

1986-01-01

An electron model is proposed explaining the physical reasons for its nonrelativistic quantum-mechanical behaviour, the origin of its own mechanical and magnetic momentum and field energy. As an example the main electron state in hydrogen atom is obtained

Charge exchange of hydrogen atoms with multiply charged ions in a hot plasma

International Nuclear Information System (INIS)

Abramov, V.A.; Baryshnikov, F.F.; Lisitsa, V.S.

1980-08-01

The symmetry properties of the hydrogen atom are used to calculate the charge exchange cross-sections sigma of hydrogen with the nuclei of multiply charged ions, allowance being made for the degeneration of final states. If the transitions between these states produced by rotation of the internuclear axis are taken into account, there is a qualitative change in the dependence of sigma on v for low values of v (a gradual decrease in the cross-section instead of the exponential one in the Landau-Zener model) and also a considerable increase in the peak cross-section. The cross-sections are calculated for a wide range of velocities and charge values Z. It is shown that the cross-section may be approximated to within approximately 9 /v).10 -15 cm 2 for Z>=18 (v in cm/s). A detailed comparison with the calculations of various authors is performed. The distribution of final states over orbital angular momenta is found. A calculation is made of variation in the spectral line intensities of the ion O +7 with injection of a neutral hydrogen beam in conditions similar to the experimental conditions on the ORMAK facility. (author)

Visualization of hydrogen gas evolution during deformation and fracture in SCM 440 steel with different tempering conditions

Energy Technology Data Exchange (ETDEWEB)

Horikawa, Keitaro, E-mail: horikawa@me.es.osaka-u.ac.jp [Department of Mechanical Science and Bioengineering, School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); Ando, Nobuaki; Kobayashi, Hidetoshi [Department of Mechanical Science and Bioengineering, School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); Urushihara, Wataru [Surface Design and Corrosion Research Section, Materials Research Laboratory, Kobe Steel, Ltd., Kobe 651-2271 (Japan)

2012-02-01

Highlights: Black-Right-Pointing-Pointer We visualize emission sites of hydrogen atoms on the microstructures during deformation. Black-Right-Pointing-Pointer Hydrogen atoms are emitted from slip lines and inclusions when deformed. Black-Right-Pointing-Pointer We show the sequence of hydrogen gas evolution during deformation. Black-Right-Pointing-Pointer Hydrogen evolution amount will increase if the steels with high strength are tested. - Abstract: In the present study, the hydrogen gas evolution behavior was investigated in SCM 440 steel by using a hydrogen microprint technique (HMT) and a testing machine equipped with a quadrupole mass spectrometer (QMS) in a ultrahigh vacuum (UHV) atmosphere. SCM 440 steels prepared by varying the tempering temperature over the range 200-700 Degree-Sign C were evaluated in order to elucidate the relationship between the hydrogen gas evolution and the tempered microstructures in the deformation. Cathodic hydrogen charging was carried out with a current density of 100 A/m{sup 2} for 1 h at room temperature. For comparison, a tensile specimen was prepared without hydrogen charging. The HMT showed that silver particles, which are indicative of the hydrogen emission sites, were present mainly in the matrix as well as on the slip lines after the deformation. It is believed that the silver particles on the slip lines represent the effect of hydrogen transportation due to mobile dislocations. In addition, accumulation of silver particles around non-metallic inclusions such as Al{sub 2}O{sub 3} was also identified. This tendency was observed for different tempering conditions. From the relationship between the stress-strain curves and the hydrogen evolution, determined by using QMS under a UHV atmosphere, it was found that the hydrogen gas evolution behavior varied with the deformation stage.

Exceptional Optoelectronic Properties of Hydrogenated Bilayer Silicene

Directory of Open Access Journals (Sweden)

Bing Huang

2014-05-01

Full Text Available Silicon is arguably the best electronic material, but it is not a good optoelectronic material. By employing first-principles calculations and the cluster-expansion approach, we discover that hydrogenated bilayer silicene (BS shows promising potential as a new kind of optoelectronic material. Most significantly, hydrogenation converts the intrinsic BS, a strongly indirect semiconductor, into a direct-gap semiconductor with a widely tunable band gap. At low hydrogen concentrations, four ground states of single- and double-sided hydrogenated BS are characterized by dipole-allowed direct (or quasidirect band gaps in the desirable range from 1 to 1.5 eV, suitable for solar applications. At high hydrogen concentrations, three well-ordered double-sided hydrogenated BS structures exhibit direct (or quasidirect band gaps in the color range of red, green, and blue, affording white light-emitting diodes. Our findings open opportunities to search for new silicon-based light-absorption and light-emitting materials for earth-abundant, high-efficiency, optoelectronic applications.

Chemical reactions of recoil atoms and thermal atoms of tritium with haloid benzenes

International Nuclear Information System (INIS)

Simirskij, Yu.N.; Firsova, L.P.

1978-01-01

Radiochemical yields have been determined for the products of substitution of hydrogen atoms and halides in Cl-, Br-, and I-benzenes with tritium atoms obtained during thermal dissociation of T 2 and with recoil atoms T arising in nuclear reaction 6 Li(n, P)T. It is shown that in the series of Cl-, Br-, and I-benzenes yields of the products of substitution of halides atoms with tritium grow, whereas those of hydrogen atom substitution change only little. The correlation nature of the yields of substitution products of halide atoms with tritium remains constant in a wide range of the initial kinetic energies of T atoms for the recoil atoms with E 0 =2.7 MeV and for the completely thermolized atoms during thermal dissociation of T 2

First-principles calculations of the interaction between hydrogen and 3d alloying atom in nickel

Energy Technology Data Exchange (ETDEWEB)

Liu, Wenguan, E-mail: liuwenguan@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Qian, Yuan; Zhang, Dongxun [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Liu, Wei, E-mail: liuwei@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Han, Han [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai 201800 (China)

2015-10-15

Knowledge of the behavior of hydrogen (H) in Ni-based alloy is essential for the prediction of Tritium behavior in Molten Salt Reactor. First-principles calculations were performed to investigate the interaction between H and 3d transition metal (TM) alloying atom in Ni-based alloy. H prefers the octahedral interstitial site to the tetrahedral interstitial site energetically. Most of the 3d TM elements (except Zn) attract H. The attraction to H in the Ni–TM–H system can be mainly attributed to the differences in electronegativity. With the large electronegativity, H and Ni gain electrons from the other TM elements, resulting in the enhanced Ni–H bonds which are the source of the attraction to H in the Ni–TM–H system. The obviously covalent-like Cr–H and Co–H bindings are also beneficial to the attraction to H. On the other hand, the repulsion to H in the Ni–Zn–H system is due to the stable electronic configuration of Zn. We mainly utilize the results calculated in 32-atom supercell which corresponds to the case of a relatively high concentration of hydrogen. Our results are in good agreement with the experimental ones.

A method of calorimetric detection of two-dimensional atomic hydrogen using an induced two-body exchange recombination

International Nuclear Information System (INIS)

Frolov, A.V.; Safonov, A.I.; Vasilyev, S.A.; Lukashevich, I.I.

1994-01-01

We propose a novel method to detect hydrogen atoms in the pure hyperfine state b at the small dense spot of the sample cell surface by injecting in pulses small controlled amounts of atoms in the reactive mixed state a into the cell volume. The total recombination rate inferred from a carbon bolometer overheating will display pronounced peaks due to two-body ab recombination. The relaxation rate of these peaks to the original value of the bolometer signal will be proportional to b-atoms' density at the spot. This method can be applied to measure the surface density of polarized H in the experiments with the field compression and with the cold spot as well. 14 refs., 4 figs

Shape of argon spectral lines emitted from an electric arc (P=760 Torr). Study and application of pressure broadening

International Nuclear Information System (INIS)

Kretzas, Dimitrios.

1978-01-01

We have studied the broadening and shift of argon spectral lines corresponding to 3p 5 5p-3p 5 4s and 3p 5 4p-3p 5 4s transitions emitted from an electric arc burning under atmospheric pressure. We have revealed the broadening due to neutral atoms pressure effect, distinguishing the transitions whose lower level is a metastable one (1s 3 and 1s 5 ) or a level of strong (1s 2 ) or feeble resonance (1s 4 ). In this study we have employed a mixture of argon (98%) and hydrogen (2%); hydrogen's feeble proportion does not perturb much the discharge and is very suitable for the measure of the electronic density. The important departure of L.T.E. has guided us to imagine and apply an original method to measure the temperature and the overpopulation of the neutral atoms in the fondamental state. Our method which is independent of the existence of L.T.E. is based on the different behavior of the spectral lines which are under the influence of the resonance or Van der Waals broadening. The measure of the broadening constants which in the resonance case are independent of the temperature and vary as Tsup(0,3) for V.d.W's broadening, give us a suitable tool to measure the density and the temperature of the neutral atoms [fr

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-02-15

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

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

International Nuclear Information System (INIS)

Erofeev, E. V.; Fedin, I. V.; Kutkov, I. V.; Yuryev, Yu. N.

2017-01-01

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

Symmetric Atom–Atom and Ion–Atom Processes in Stellar Atmospheres

Directory of Open Access Journals (Sweden)

Vladimir A. Srećković

2017-12-01

Full Text Available We present the results of the influence of two groups of collisional processes (atom–atom and ion–atom on the optical and kinetic properties of weakly ionized stellar atmospheres layers. The first type includes radiative processes of the photodissociation/association and radiative charge exchange, the second one the chemi-ionisation/recombination processes with participation of only hydrogen and helium atoms and ions. The quantitative estimation of the rate coefficients of the mentioned processes were made. The effect of the radiative processes is estimated by comparing their intensities with those of the known concurrent processes in application to the solar photosphere and to the photospheres of DB white dwarfs. The investigated chemi-ionisation/recombination processes are considered from the viewpoint of their influence on the populations of the excited states of the hydrogen atom (the Sun and an M-type red dwarf and helium atom (DB white dwarfs. The effect of these processes on the populations of the excited states of the hydrogen atom has been studied using the general stellar atmosphere code, which generates the model. The presented results demonstrate the undoubted influence of the considered radiative and chemi- ionisation/recombination processes on the optical properties and on the kinetics of the weakly ionized layers in stellar atmospheres.

(e,2e) investigation of atomic hydrogen and helium close to threshold

International Nuclear Information System (INIS)

Schlemmer, P.; Rosel, T.; Jung, K.; Ehrhardt, H.

1989-01-01

For the first time triple differential cross sections of the electron impact ionization of atomic hydrogen close to threshold have been measured. The angular correlation of the outgoing electrons have been determined at 4 eV excess energy and are compared with results obtained with helium. A method is proposed allowing to measure the range of the threshold law. The data are analyzed using a partial-wave method. Although the asymptotic states of the two processes are the same---the charge of the ion is Z=1 in both cases---the triple differential cross sections are drastically different

Charge transfer of O3+ ions with atomic hydrogen

International Nuclear Information System (INIS)

Wang, J.G.; Stancil, P.C.; Turner, A.R.; Cooper, D.L.

2003-01-01

Charge transfer processes due to collisions of ground state O 3+ (2s 2 2p 2 P) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with existing experimental and theoretical data shows our results to be in better agreement with the measurements than the previous calculations, although problems with some of the state-selective measurements are noted. Our calculations demonstrate that rotational coupling is not important for the total cross section, but for state-selective cross sections, its relevance increases with energy. For the ratios of triplet to singlet cross sections, significant departures from a statistical value are found, generally in harmony with experiment

Charge transfer of O3+ ions with atomic hydrogen

Science.gov (United States)

Wang, J. G.; Stancil, P. C.; Turner, A. R.; Cooper, D. L.

2003-01-01

Charge transfer processes due to collisions of ground state O3+(2s22p 2P) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with existing experimental and theoretical data shows our results to be in better agreement with the measurements than the previous calculations, although problems with some of the state-selective measurements are noted. Our calculations demonstrate that rotational coupling is not important for the total cross section, but for state-selective cross sections, its relevance increases with energy. For the ratios of triplet to singlet cross sections, significant departures from a statistical value are found, generally in harmony with experiment.

Electron-impact ionization of atomic hydrogen: dynamical variational treatment

Energy Technology Data Exchange (ETDEWEB)

Defrance, P.; Lecointre, J. [Institute of Condensed Matter and Nanosciences, Universite Catholique de Louvain, Louvain-la-Neuve (Belgium); Kereselidze, T.; Machavariani, Z.S. [Department of Exact and Natural Sciences, Tbilissi State University, Tbilissi (Georgia)

2011-10-15

A simple and straightforward calculating scheme is proposed for electron-impact single and multiple ionization of atoms. The method is based on the application of the Hulthen-Kohn dynamical variational principle. An effective charge seen by the scattered electron is determined for a certain type of trial wave functions mathematically in a rigorous way excluding any empirical assumptions. Validity of the elaborated approach is assessed by calculating triply differential cross section (TDCS) for electron-impact ionization of hydrogen. It is shown that, inclusion of the effective charge into the calculation reduces height of a 'binary peak' in comparison with the first Born approximation result. The height of a 'recoil peak' depends on the sign of the effective charge. The calculated TDCS are compared with the available experimental data and with the results of sophisticated theories and agreement is found. (authors)

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

KAUST Repository

Zhang, Zailei

2017-07-27

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

2S-4S spectroscopy in hydrogen atom: The new value for the Rydberg constant and the proton charge radius

Science.gov (United States)

Kolachevsky, N.; Beyer, A.; Maisenbacher, L.; Matveev, A.; Pohl, R.; Khabarova, K.; Grinin, A.; Lamour, T.; Yost, D. C.; Haensch, T. W.; Udem, Th.

2018-02-01

The core of the "proton radius puzzle" is the discrepancy of four standard deviations between the proton root mean square charge radii (rp) determined from regular hydrogen (H), and the muonic hydrogen atom (μp). We have measured the 2S-4P transition frequency in H, utilizing a cryogenic beam of H and directly demonstrate that quantum interference of neighboring atomic resonances can lead to line shifts much larger than the proton radius discrepancy. Using an asymmetric fit function we obtain rp = 0.8335(95) fm and the Rydberg constant R∞ = 10 973 731.568 076 (96) m-1. The new value for rp is 3.3 combined standard deviations smaller than the latest CODATA value, but in good agreement with the value from μp.

Excitation of hydrogen atom by ultrashort laser pulses in optically dense plasma

Energy Technology Data Exchange (ETDEWEB)