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....
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
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, ...
Collisional excitation of ArH+ by hydrogen atoms
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.
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
Continuous coherent Lyman-alpha excitation of atomic hydrogen.
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
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)
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.
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.)
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
International Nuclear Information System (INIS)
Fritsch, W.; Olson, R.E.; Schartner, K.H.; Belkic, D.S.
1989-01-01
This report discusses (i) proton impact excitation, and (ii) excitation by ion collisions (from helium ions to iron ions) of atomic hydrogen, both for H(1s) and H(n>1), where where n = the principal quantum number, in the energy range from 1 keV/amu to 2 MeV/amu and 10 MeV/amu, respectively. For the range of ions considered, a few generic plots are given for the total cross section as a function of E/q, where E is the beam energy, for different values q (ion charge in units of proton charge) and different final principal quantum numbers. 12 refs, 3 figs
Excitation and charge transfer in low-energy hydrogen atom collisions with neutral iron
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
Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen
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
Excitation of hydrogen atom by ultrashort laser pulses in optically dense plasma
Energy Technology Data Exchange (ETDEWEB)
Calisti, A. [Aix Marseille Universite, CNRS, PIIM, Marseille (France); Astapenko, V.A. [Moscow Institute of Physics and Technology, Dolgoprudnyi (Russian Federation); Lisitsa, V.S. [Moscow Institute of Physics and Technology, Dolgoprudnyi (Russian Federation); Russian Research Center ' ' Kurchatov Institute' ' , Moscow (Russian Federation); National Research Nuclear University MEPhI, Moscow (Russian Federation)
2017-10-15
The features of excitation of a hydrogen atom by ultrashort laser pulses (USP) with a Gaussian envelope in optically dense plasma at a Lyman-beta transition are studied theoretically. The problem is of interest for diagnostics of optically dense media. USP have two doubtless advantages over conventional laser excitation: (a) the USP carrier frequency is shifted to the region of short wavelengths allowing exciting atoms from the ground state and (b) the wide spectrum of USP allows them to penetrate into optically dense media to much longer distances as compared with monochromatic radiation. As actual realistic cases, two examples are considered: hot rarefied plasma (the coronal limit) and dense cold plasma (the Boltzmann equilibrium). Universal expressions for the total probability of excitation of the transition under consideration are obtained in view of absorption of radiation in a medium. As initial data for the spectral form of a line, the results of calculations by methods of molecular dynamics are used. The probability of excitation of an atom is analysed for different values of problem parameters: the pulse duration, the optical thickness of a medium, and the detuning of the pulse carrier frequency from the eigenfrequency of an electron transition. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
International Nuclear Information System (INIS)
Yuan Lin; Zhou Ben-Hu; Zhao Yun-Hui; Xu Jun; Hai Wen-Hua
2012-01-01
A variational-integral perturbation method (VIPM) is established by combining the variational perturbation with the integral perturbation. The first-order corrected wave functions are constructed, and the second-order energy corrections for the ground state and several lower excited states are calculated by applying the VIPM to the hydrogen atom in a strong uniform magnetic field. Our calculations demonstrated that the energy calculated by the VIPM only shows a negative value, which indicates that the VIPM method is more accurate than the other methods. Our study indicated that the VIPM can not only increase the accuracy of the results but also keep the convergence of the wave functions
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)
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)
Population densities of excited atomic hydrogen as diagnostic tool to study an RF hydrogen discharge
van den Donker, M.N.; Jedrzejczyk, D.; Klomfass, J.; Hartgers, A.; Kessels, W.M.M.; Sanden, van de M.C.M.; Rech, B.; Veldhuizen, van E.M.
2005-01-01
The at. state distribution function (ASDF) of hydrogen was numerically modeled as a function of electron d., electron temp. and neutral d., by means of a collisional-radiative modeling code. Two limiting cases regarding the hydrogen dissocn. degree were considered, namely 0% and 100% dissocn.
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
Effects of classical resonances on the chaotic microwave ionization of highly excited hydrogen atoms
Energy Technology Data Exchange (ETDEWEB)
Jensen, R V
1987-05-01
Experimental measurements of the microwave ionization of highly excited hydrogen atoms with principal quantum numbers ranging from n = 32 to 90 are well described by a classical treatment of the nonlinear electron dynamics. In particular, the measurements of the threshold field for the onset of significant ionization exhibits a curious dependence on the microwave frequency with distinct peaks at rational values of the scaled frequency, n/sup 3/..cap omega.. = 1, 2/3, 1/2, 2/5, 1/3, 1/4, 1/5, which is in excellent agreement with the predictions for the onset of classical chaos in a one-dimensional model of the experiment. In the classical theory this frequency dependence of the threshold fields is due to the stabilizing effect of nonlinear resonances (''islands'') in the classical phase space which is greatly enhanced when the microwave perturbation is turned on slowly (adiabatically) as in the experiments. Quantum calculations for this one-dimensional model also exhibit this stabilizing effect due to the preferential excitation of localized quasi-energy states.
Electron impact excitation of the n = 2 to n = 3 transition in atomic hydrogen near threshold
Hata, J.; Morgan, L. A.; McDowell, M. R. C.
1980-06-01
Close-coupling calculations of electron impact excitation of the n = 2 to n = 3 transition of atomic hydrogen at energies below the n = 4 threshold are presented. The algebraic variational close-coupling code of Morgan (1980) with an eighteen-state basis was used to obtain cross sections at eight impact energies from 2.04 to 2.45 eV, and calculations in a six-state close-coupling model were compared with the six-state calculations of Burke et al. (1967). The six-state values are found to be in satisfactory agreement with the exception of the singlet contribution to the 2s-3s transition. Near the n = 3 threshold the cross section obtained in the full calculation is found to be almost a factor of 2 lower than that predicted by Johnson (1972), thus explaining in part the discrepancy between Johnson's results and experiments on hydrogen plasmas. Estimates of rate coefficients based on the cross sections and assuming a Maxwellian velocity distribution, however, are shown to remain in disagreement with experiment.
Study of the light emission from hydrogen atoms excited by the beam-foil technique
International Nuclear Information System (INIS)
Broll, Norbert.
1976-01-01
Zero-field and Stark-induced quantum beat measurements have been performed for beam foil excited hydrogen (H + and H 2 + beam). Experimental evidence of coherent excitation of S and P states of Lyman α line has been demonstrated [fr
Numerology, hydrogenic levels, and the ordering of excited states in one-electron atoms
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.
Emmanouilidou, Agapi
2012-06-01
We present a theoretical quasiclassical treatment of the formation, during Coulomb explosion, of highly excited neutral H atoms for strongly-driven hydrogen molecule. This process, where after the laser field is turned off, one electron escapes to the continuum while the other occupies a Rydberg state, was recently reported in an experimental study in Phys. Rev. Lett 102, 113002 (2009). We find that two-electron effects are important in order to correctly account for all pathways leading to highly excited neutral hydrogen formation [1]. We identify two pathways where the electron that escapes to the continuum does so either very quickly or after remaining bound for a few periods of the laser field. These two pathways of highly excited neutral H formation have distinct traces in the probability distribution of the escaping electron momentum components. [4pt] [1] A. Emmanouilidou, C. Lazarou, A. Staudte and U. Eichmann, Phys. Rev. A (Rapid) 85 011402 (2012).
International Nuclear Information System (INIS)
Guichard, R.
2007-12-01
We present a theoretical approach using Coulomb-Volkov states that appears useful for the study of atomic multi-photonic processes induced by intense XUV femtosecond laser pulses. It predicts hydrogen ionization spectra when it is irradiated by laser pulses in perturbations conditions. Three ways have been investigated. Extension to strong fields when ℎω > I p : it requires to include the hydrogen ground state population, introducing it in standard Coulomb-Volkov amplitude leads to saturated multi-photonic ionization. Extension to multi-photonic transitions with ℎω p : new quantum paths are open by the possibility to excite the lower hydrogen bound states. Multiphoton excitation of these states is investigated using a Coulomb-Volkov approach. Extension to helium: two-photon double ionization study shows the influence of electronic correlations in both ground and final state. Huge quantity of information such as angular and energetic distributions as well as total cross sections is available. (author)
International Nuclear Information System (INIS)
Bayfield, J.E.; Luie, S.Y.; Perotti, L.C.; Skrzypkowski, M.P.
1996-01-01
As the peak electric field of the microwave pulse is increased, steps in the classical microwave ionization probability of the highly excited hydrogen atom are produced by phase-space metamorphosis. They arise from new layers of Kolmogorov-Arnold-Moser (KAM) islands being exposed as KAM surfaces are destroyed. Both quantum numerical calculations and laboratory experiments exhibit the ionization steps, showing that such metamorphoses influence pulsed semiclassical systems. copyright 1996 The American Physical Society
Pischel, Uwe; Patra, Digambara; Koner, Apurba L; Nau, Werner M
2006-01-01
The fluorescence quenching of singlet-excited 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by 22 phenols and 12 alkylbenzenes has been investigated. Quenching rate constants in acetonitrile are in the range of 10(8)-10(9) M(-1)s(-1) for phenols and 10(5)-10(6) M(-1)s(-1) for alkylbenzenes. In contrast to the quenching of triplet-excited benzophenone, no exciplexes are involved, so that a pure hydrogen atom transfer is proposed as quenching mechanism. This is supported by (1) pronounced deuterium isotope effects (kH/kD ca 4-6), which were observed for phenols and alkylbenzenes, and (2) a strongly endergonic thermodynamics for charge transfer processes (electron transfer, exciplex formation). In the case of phenols, linear free energy relationships applied, which led to a reaction constant of rho = -0.40, suggesting a lower electrophilicity of singlet-excited DBO than that of triplet-excited ketones and alkoxyl radicals. The reactivity of singlet-excited DBO exposes statistical, steric, polar and stereoelectronic effects on the hydrogen atom abstraction process in the absence of complications because of competitive exciplex formation.
International Nuclear Information System (INIS)
Holthaus, M.
1990-04-01
The study of short-time phenomena in strongly interacting quantum systems requires on the theoretical side the development of methods, which are both non-perturbative and 'dynamical', which thus regard the change of outer parameters in the slope of time. For systems with a periodic, fast and a further slow, parametric time dependence both requirements are fulfilled by the Floquet picture of quantum mechanics. This picture, which starts from the adiabatic evolution on effective quasi-energy surfaces, is presented in the first chapter of the present thesis, whereby especially the term of the adiabaticity for periodically time dependent systems is explained. In the second chapter the Floquet theory is applied to the description of microwave experiments with highly excited hydrogen atoms. Here it is shown that the Floquet picture permits to understand a manifold of experimental observations under a unified point of view. Really these microwave experiments offer an ideal possibility for the test of the Floquet picture: On the one hand there is the strength of the outer field of the same order of magnitude as that of the nuclear field, by which the highly excited electron is bound, on the other hand in the experiment an extremely precise control of amplitude, frequency, and pulse shape is possible, so that the conditions for a detailed comparison of theory and experiment are given. The insights, which model calculations yield in the dynamics of highly excited hydrogen atoms in strong alternating fields, allow a prediction of further effects, for which it is to be looked for in new experiments. In the following third chapter some further aspects of these model calculations are discussed, whereby also common properties of the dynamics of excited atoms in microwave fields and that of atoms under the influence of strong laser pulses are discussed. (orig./HSI) [de
International Nuclear Information System (INIS)
Kleppner, D.; Littman, M.G.; Zimmerman, M.L.
1981-01-01
Highly excited atoms are often called Rydberg atoms. These atoms have a wealth of exotic properties which are discussed. Of special interest, are the effects of electric and magnetic fields on Rydberg atoms. Ordinary atoms are scarcely affected by an applied electric or magnetic field; Rydberg atoms can be strongly distorted and even pulled apart by a relatively weak electric field, and they can be squeezed into unexpected shapes by a magnetic field. Studies of the structure of Rydberg atoms in electric and magnetic fields have revealed dramatic atomic phenomena that had not been observed before
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.
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.
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
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)
Hydrogen atom excitation in intense attosecond laser field: Gauge dependence of dipole approximation
Energy Technology Data Exchange (ETDEWEB)
Aldarmaa, Ch., E-mail: aldaraa2004@yahoo.com, E-mail: l-xemee@yahoo.com; Khenmedekh, L., E-mail: aldaraa2004@yahoo.com, E-mail: l-xemee@yahoo.com [Theoretical Physics and Simulation Group, School of Materials Technology, MUST (Mongolia); Lkhagva, O. [School of Physics and Electronics, NUM (Mongolia)
2014-03-24
It is assumed that, the atomic excitations probability can be calculated using first order perturbation theory and dipole approximations. The validity of the dipole approximations had been examined by comparing the results with the results obtained by exact calculations within the first order perturbation theory[2]. Figure 1 shows the time dependence of the transition probability in the dipole approximation. From these plots it is obvious that, the probabilities obtained in the length gauge are higher than that in the velocity gauge, in the interaction period (−τ/2
International Nuclear Information System (INIS)
Kawakami, Kazuki; Fujimoto, Takasi
2001-01-01
We treat classically the n-, l- and m r -changing transitions and ionization. Excitation cross sections against the final state energy continue smoothly to the 'ionization cross sections'. The steady state populations determined by elastic collisions among the degenerate states in the same n level show higher populations in the m 1 =0 states, suggesting positive polarizations of Lyman lines emitted from plasmas having directional electrons. For ionization, the two outgoing electrons have large relative angles, suggesting reduced three body recombination rates for these plasmas. (author)
International Nuclear Information System (INIS)
Massip de Turville, C.M.D.
1982-01-01
Methods are discussed of generating heat in an atomic hydrogen reactor which involve; the production of atomic hydrogen by an electrical discharge, the capture of nascent neutrons from atomic hydrogen in a number of surrounding steel alloy tubes having a high manganese content to produce 56 Mn, the irradiation of atomic hydrogen by the high energy antineutrinos from the beta decay of 56 Mn to yield nascent neutrons, and the removal of the heat generated by the capture of nascent neutrons by 55 Mn and the beta decay of 56 Mn. (U.K.)
Kinetics of the excited muonic hydrogen in the mixtures of hydrogen isotopes in helium
International Nuclear Information System (INIS)
Bystritskij, V.M.; Kravtsov, A.V.; Popov, N.P.
1989-01-01
De-excitation of the excited muonic hydrogen in the mixture of hydrogen isotopes and helium is considered. The method is proposed which allows one to determine the rates of the muon transfer from the excited muonic hydrogen to helium nuclei, as well as the probability of the direct muon atomic capture by nuclei of hydrogen isotopes. 20 refs.; 4 figs
International Nuclear Information System (INIS)
Thomas, E.W.; Zivitz, M.; Rausch, E.O.; Baird, W.E.; Harris, J.E.
1975-01-01
A study of the excited states of atoms backscattered from metal surfaces is presented. Incident ions were H + , H 2 + , and He + at energies of 10 to 30 keV. Preliminary data are presented for a study of the charge state distribution among atoms backscattered from surfaces. Results of a study of light emission from atoms sputtered off targets by 10 to 30 keV Ar + ions as a way to determine surface contamination are presented. Brief studies of radiation damage by 10 to 30 keV H + and He + ions are discussed. 5 figures
Excitation of the hydrogen atom by fast-electron impact in the presence of a laser field
International Nuclear Information System (INIS)
Bhattacharya, M.; Sinha, C.; Sil, N.C.
1991-01-01
An approach has been developed to study the excitation of a ground-state H atom to the n=2 level under the simultaneous action of fast-electron impact and a monochromatic, linearly polarized, homogeneous laser beam. The laser frequency is assumed to be low (soft-photon limit) so that a stationary-state perturbation theory can be applied as is done in the adiabatic theory. An elegant method has been developed in the present work to construct the dressed excited-state wave functions of the H atom using first-order perturbation theory in the parabolic coordinate representation. By virtue of this method, the problem arising due to the degeneracy of the excited states of the H atom has been successfully overcome. The main advantage of the present approach is that the dressed wave function has been obtained in terms of a finite number of Laguerre polynomials instead of an infinite summation occurring in the usual perturbative treatment. The amplitude for direct excitation (without exchange) has been obtained in closed form. Numerical results for differential cross sections are presented for individual excitations to different Stark manifolds as well as for excitations to the n=2 level at high energies (100 and 200 eV) and for field directions both parallel and perpendicular to the incident electron momentum. Extension to a higher order of perturbation is also possible in the present approach for the construction of the dressed states, and the electron-exchange effect can also be taken into account without any further approximation
Excitation of the hydrogen atom by fast-electron impact in the presence of a laser field
Bhattacharya, Manabesh; Sinha, C.; Sil, N. C.
1991-08-01
An approach has been developed to study the excitation of a ground-state H atom to the n=2 level under the simultaneous action of fast-electron impact and a monochromatic, linearly polarized, homogeneous laser beam. The laser frequency is assumed to be low (soft-photon limit) so that a stationary-state perturbation theory can be applied as is done in the adiabatic theory. An elegant method has been developed in the present work to construct the dressed excited-state wave functions of the H atom using first-order perturbation theory in the parabolic coordinate representation. By virtue of this method, the problem arising due to the degeneracy of the excited states of the H atom has been successfully overcome. The main advantage of the present approach is that the dressed wave function has been obtained in terms of a finite number of Laguerre polynomials instead of an infinite summation occurring in the usual perturbative treatment. The amplitude for direct excitation (without exchange) has been obtained in closed form. Numerical results for differential cross sections are presented for individual excitations to different Stark manifolds as well as for excitations to the n=2 level at high energies (100 and 200 eV) and for field directions both parallel and perpendicular to the incident electron momentum. Extension to a higher order of perturbation is also possible in the present approach for the construction of the dressed states, and the electron-exchange effect can also be taken into account without any further approximation.
Electronic excitation in ion-atom collisions
International Nuclear Information System (INIS)
Rodriguez, V.D.; Miraglia, J.E.
1988-01-01
Theoretical calculations for excitation of hydrogen-like atoms by ion impact at high and intermediate energies, are presented. Impulsive and eikonal wave functions are employed, both normalized. It is studied the dependence on energy and projectil charge (saturation) of cross sections, compared to experimental results. (A.C.A.S.) [pt
International Nuclear Information System (INIS)
Kim, Hee-Je; Kajiwara, Toshinori; Motoyama, Sumio; Muraoka, Katsunori; Akazaki, Masanori; Okada, Tatsuo; Maeda, Mitsuo
1989-01-01
For measurements of atomic hydrogen density in the periphery region of high temperature plasmas, laser fluorescence spectroscopy (LFS) by two-photon excitation (1s-3s, 3d) was developed. Based upon the theoretical estimates for laser source requirements, which indicated the laser energy and spectral width to be more than 10 mJ (assuming the pulse duration of 10 ns) and several tens of picometers around the wavelength of 205.1 nm, respectively, the first Stokes generation in deuterium gas of ArF laser output was adopted and shown to have the necessary performance. Through the LFS experiment employing the laser source, the minimum detectable limit of atomic hydrogen, normalized by a laser power and an observing solid angle, was demonstrated to be 1 x 10 14 [m -3 · MW · sr], which is usually sufficient for the above purpose, and the accuracy of the density determination was shown to be within a factor 2. (author)
Energy dependence of the ionization of highly excited atoms by collisions with excited atoms
International Nuclear Information System (INIS)
Shirai, T.; Nakai, Y.; Nakamura, H.
1979-01-01
Approximate analytical expressions are derived for the ionization cross sections in the high- and low-collision-energy limits using the improved impulse approximation based on the assumption that the electron-atom inelastic-scattering amplitude is a function only of the momentum transfer. Both cases of simultaneous excitation and de-excitation of one of the atoms are discussed. The formulas are applied to the collisions between two excited hydrogen atoms and are found very useful for estimating the cross sections in the wide range of collisions energies
International Nuclear Information System (INIS)
Batty, C.J.
1989-07-01
Experimental studies of antiprotonic-hydrogen atoms have recently made great progress following the commissioning of the low energy antiproton facility (LEAR) at CERN in 1983. At the same time our understanding of the atomic cascade has increased considerably through measurements of the X-ray spectra. The life history of the p-bar-p atom is considered in some detail, from the initial capture of the antiproton when stopping in hydrogen, through the atomic cascade with the emission of X-rays, to the final antiproton annihilation and production of mesons. The experiments carried out at LEAR are described and the results compared with atomic cascade calculations and predictions of strong interaction effects. (author)
International Nuclear Information System (INIS)
Dharma-wardana, M.W.C.; Grimaldi, F.; Lecourt, A.; Pellissier, J.
1980-01-01
The one-particle hydrogenic Green's function has been calculated for a partially ionized plasma consisting of hydrogen atoms, electrons, and protons at high temperatures. The theoretical method extends a previous publication and involves an evaluation of the mass operator in the Dyson equation to include proper self-energy parts to ''all orders'' in the screened interaction. This mass operator characterizes the effective micropotential felt by the atom in the plasma and determines all of the one-particle properties and some two-particle properties associated with the atomic subsystem. The first-order mass operator is nonzero only for exchange scattering, which leads to a frequency-independent exchange shift. This temperature- and density-dependent theory of the exchange shift replaces the usual semiphenomenological schemes based on the Slater-Kohn-Sham type of theory. The exchange-shifted Green's functions are used in evaluating the higher-order contributions. Computer calculations and the resolution of the poles of the Green's function lead to level shifts, widths, and spectral functions. These are calculated within both the second-order and the all-order theory. The second-order theory, which may be valid at sufficiently high densities and in turbulent plasmas, overemphasises the atom-plasmon coupling and shows new structures. The inclusion of contributions beyond second order removes these structures and produces a more ''conventional'' spectral-intensity function. The effects of center-of-mass motion on the level shifts and level profiles are investigated and the onset of plasma instabilities touched upon. These calculations make contact with the work on ''plasma-polarization shifts'' and provide an approach to q,ω-dependent plasma microfields
Scattering of highly excited atoms
International Nuclear Information System (INIS)
Raith, W.
1980-01-01
Experimental methods to excite atomic beams into Rydberg states and the first results of collision experiments with such beams are reported. For further information see hints under relevant topics. (orig.) [de
Atomic collisions research with excited atomic species
International Nuclear Information System (INIS)
Hoogerland, M.D.; Gulley, R.J.; Colla, M.; Lu, W.; Milic, D.; Baldwin, K.G.H.; Buckman, S.J.
1999-01-01
Measurements and calculations of fundamental atomic collision and spectroscopic properties such as collision cross sections, reaction rates, transition probabilities etc. underpin the understanding and operation of many plasma and gas-discharge-based devices and phenomena, for example plasma processing and deposition. In almost all cases the complex series of reactions which sustains the discharge or plasma, or produces the reactive species of interest, has a precursor electron impact excitation, attachment, dissociation or ionisation event. These processes have been extensively studied in a wide range of atomic and molecular species and an impressive data base of collision cross sections and reaction rates now exists. However, most of these measurements are for collisions with stable atomic or molecular species which are initially in their ground electronic state. Relatively little information is available for scattering from excited states or for scattering from unstable molecular radicals. Examples of such species would be metastable excited rare gases, which are often used as buffer gases, or CF 2 radicals formed by electron impact dissociation in a CF 4 plasma processing discharge. We are interested in developing experimental techniques which will enable the quantitative study of such exotic atomic and molecular species. In this talk I would like to outline one such facility which is being used for studies of collisions with metastable He(2 3 S) atoms
Stable atomic hydrogen: Polarized atomic beam source
International Nuclear Information System (INIS)
Niinikoski, T.O.; Penttilae, S.; Rieubland, J.M.; Rijllart, A.
1984-01-01
We have carried out experiments with stable atomic hydrogen with a view to possible applications in polarized targets or polarized atomic beam sources. Recent results from the stabilization apparatus are described. The first stable atomic hydrogen beam source based on the microwave extraction method (which is being tested ) is presented. The effect of the stabilized hydrogen gas density on the properties of the source is discussed. (orig.)
Vibrational excitation in a hydrogen volume source
International Nuclear Information System (INIS)
Eenshuistra, P.J.
1989-01-01
In this thesis the complex of processes which determines the D - or H - density in a volume source, a hydrogen discharge, is studied. D - beams are of interest for driving the current of a fusion plasma in a TOKAMAK. Densities of vibrationally excited molecules, of H atoms, and of metastable hydrogen molecules were determined using Resonance-Enhanced MultiPhoton Ionization (REMPI). An experiment in which vibrationally highly excited molecules are formed by recombination of atoms in a cold metal surface, is described. The production and destruction of vibrationally excited molecules and atoms in the discharge is discussed. The vibrational distribution for 3≤ν≤5 (ν = vibrational quantumnumber) is strongly super-thermal. This effect is more apparent at higher discharge current and lower gas pressure. The analysis with a model based on rate equations, which molecules are predominantly produced by primary electron excitation of hydrogen molecules and deexcited upon one wall collision. The atom production is compatible with dissociation of molecules by primary electrons, dissociation of molecules on the filaments, and collisions between positive ions and electrons. The electrons are predominantly destroyed by recombination on the walls. Finally the production and destruction of H - in the discharge are discussed. The density of H - in the plasma, the electron density and temperature were determined. H - extraction was measured. The ratio of the extracted H - current and the H - density in the plasma gives an indication of the drift velocity of H - in the plasma. This velocity determines the emittance of the extracted beam. It was found that the H - velocity scales with the square root of the electron temperature. The measured H - densities are compatible with a qualitative model in which dissociative attachment of plasma electrons to vibrationally excited molecules is the most important process. (author). 136 refs.; 39 figs.; 10 tabs
Electron excitation of alkali atoms
International Nuclear Information System (INIS)
Ormonde, S.
1979-02-01
The development and testing of a synthesized close-coupling effective model potential ten-channel electron-atom scattering code and some preliminary calculations of resonances in cross sections for the excitation of excited states of potassium by low energy electrons are described. The main results obtained are: identification of 1 S and 1 D structures in excitation cross sections below the 5 2 S threshold of neutral potassium; indications of additional structures - 1 P and 1 D between the 5 2 S and 5 2 D thresholds; and a suggested explanation of anomalously high interstate-electron impact excitation cross sections inferred from experiments on potassium-seeded plasmas. The effective potential model imbedded in the code can be used to simulate any atomic system that can be approximated by a single bound electron outside an ionic core. All that is needed is a set of effective potential parameters--experimental or theoretical. With minor modifications the code could be adapted to calculations of electron scattering by two-electron systems
Coulomb excitation of atoms by fast multicharged ions
International Nuclear Information System (INIS)
Yudin, G.L.
1980-01-01
Investigated is coulomb eXcitation of discrete levels of a hydrogen-like atom by a fast multicharged ion. Obtained are dependences of probabilities of channels 1S→nS and 1S→nP on the sight parameter in the zero order of sudden excitation theory. 1S-2S transition is considered in detail. Carried out are calculations for excitation of the hydrogen atom by the wholy bare carbon atom. It is shown, that at low values of excitation pr.ocess parameter eta excitation probability is a monotonously decreasing function of the impact parameter. With the growth of eta the situation is changed, and at low impact parameters the probability of 1S-2S transition is decreased. At high impact parameters approximation of sudden excitations is unacceptable, here lagging of coulomb interaction is essential
Quenching reactions of electronically excited atoms
International Nuclear Information System (INIS)
Setser, D.W.
2001-01-01
The two-body, thermal quenching reactions of electronically excited atoms are reviewed using excited states of Ar, Kr, and Xe atoms as examples. State-specific interstate relaxation and excitation-transfer reactions with atomic colliders are discussed first. These results then are used to discuss quenching reactions of excited-state atoms with diatomic and polyatomic molecules, the latter have large cross sections, and the reactions can proceed by excitation transfer and by reactive quenching. Excited states of molecules are not considered; however, a table of quenching rate constants is given for six excited-state molecules in an appendix
Experiments with cold hydrogen atoms
International Nuclear Information System (INIS)
Leonas, V.B.
1981-01-01
Numerous investigations of atomic processes in Waseous phase on the surface with participation of ''cold'' hydrogen atoms, made during the last years, are considered. The term ''cold atom'' means the range of relative collision energies E<10 MeV (respectively 'ultracold ' atoms at E< or approximately 1 MeV) which corresponds to the range of temperatures in tens (units) of K degrees. Three main ranges of investigations where extensive experimental programs are realized are considered: study of collisional processes with hydrogen atom participation, hydrogen atoms being of astrophysical interest; study of elastic atom-molecular scattering at superlow energies and studies on the problem of condensed hydrogen. Hydrogen atoms production is realized at dissociation in non-electrode high-frequency or superhigh-frequency discharge. A method of hydrogen quantum generator and of its modifications appeared to be rather an effective means to study collisional changes of spin state of hydrogen atoms. First important results on storage and stabilization of the gas of polarized hydrogen atoms are received
International Nuclear Information System (INIS)
Ree, J.; Yoon, S. H.; Park, K. G.; Kim, Y. H.
2004-01-01
We have calculated the probability of HBr formation and energy disposal of the reaction exothermicity in HBr produced from the reaction of gas-phase bromine with highly covered chemisorbed hydrogen atoms on a Si (001)-(2 x 1) surface. The reaction probability is about 0.20 at gas temperature 1500 K and surface temperature 300 K. Raising the initial vibrational state of the adsorbate(H)-surface(Si) bond from the ground to v = 1, 2 and 3 states causes the vibrational, translational and rotational energies of the product HBr to increase equally. However, the vibrational and translational motions of product HBr share most of the reaction energy. Vibrational population of the HBr molecules produced from the ground state adsorbate-surface bond (vHSi = 0) follows the Boltzmann distribution, but it deviates seriously from the Boltzmann distribution when the initial vibrational energy of the adsorbate-surface bond increases. When the vibration of the adsorbate-surface bond is in the ground state, the amount of energy dissipated into the surface is negative, while it becomes positive as vHSi increases. The energy distributions among the various modes weakly depends on surface temperature in the range of 0-600 K, regardless of the initial vibrational state of H(ad)-Si(s) bond
Energy Technology Data Exchange (ETDEWEB)
Guichard, R
2007-12-15
We present a theoretical approach using Coulomb-Volkov states that appears useful for the study of atomic multi-photonic processes induced by intense XUV femtosecond laser pulses. It predicts hydrogen ionization spectra when it is irradiated by laser pulses in perturbations conditions. Three ways have been investigated. Extension to strong fields when {Dirac_h}{omega} > I{sub p}: it requires to include the hydrogen ground state population, introducing it in standard Coulomb-Volkov amplitude leads to saturated multi-photonic ionization. Extension to multi-photonic transitions with {Dirac_h}{omega} < I{sub p}: new quantum paths are open by the possibility to excite the lower hydrogen bound states. Multiphoton excitation of these states is investigated using a Coulomb-Volkov approach. Extension to helium: two-photon double ionization study shows the influence of electronic correlations in both ground and final state. Huge quantity of information such as angular and energetic distributions as well as total cross sections is available. (author)
Energy Technology Data Exchange (ETDEWEB)
Guichard, R
2007-12-15
We present a theoretical approach using Coulomb-Volkov states that appears useful for the study of atomic multi-photonic processes induced by intense XUV femtosecond laser pulses. It predicts hydrogen ionization spectra when it is irradiated by laser pulses in perturbations conditions. Three ways have been investigated. Extension to strong fields when {Dirac_h}{omega} > I{sub p}: it requires to include the hydrogen ground state population, introducing it in standard Coulomb-Volkov amplitude leads to saturated multi-photonic ionization. Extension to multi-photonic transitions with {Dirac_h}{omega} < I{sub p}: new quantum paths are open by the possibility to excite the lower hydrogen bound states. Multiphoton excitation of these states is investigated using a Coulomb-Volkov approach. Extension to helium: two-photon double ionization study shows the influence of electronic correlations in both ground and final state. Huge quantity of information such as angular and energetic distributions as well as total cross sections is available. (author)
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}.
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 .
Excitation of simple atoms by slow magnetic monopoles
International Nuclear Information System (INIS)
Kroll, N.M.; Parke, S.J.; Ganapathi, V.; Drell, S.D.
1984-01-01
We present a theory of excitation of simple atoms by slow moving massive monopoles. Previously presented results for a monopole of Dirac strength on hydrogen and helium are reviewed. The hydrogen theory is extended to include arbitrary integral multiples of the Dirac pole strength. The excitation of helium by double strength poles and by dyons is also discussed. It is concluded that a helium proportional counter is a reliable and effective detector for monopoles of arbitrary strength, and for negatively charged dyons
Recent experiments involving highly excited atoms
International Nuclear Information System (INIS)
Latimer, C.J.
1979-01-01
Very large and fragile atoms may be produced by exciting normal atoms with light or by collisions with other atomic particles. Atoms as large as 10 -6 m are now routinely produced in the laboratory and their properties studied. In this review some of the simpler experimental methods available for the production and detection of such atoms are described including tunable dye laser-excitation and field ionization. A few recent experiments which illustrate the collision properties and the effects of electric and and magnetic fields are also described. The relevance of highly excited atoms in other areas of research including radioastronomy and isotope separation are discussed. (author)
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
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
Ionization of highly excited atoms by atomic particle impact
International Nuclear Information System (INIS)
Smirnov, B.M.
1976-01-01
The ionization of a highly excited atom by a collision with an atom or molecule is considered. The theory of these processes is presented and compared with experimental data. Cross sections and ionization potential are discussed. 23 refs
Excited-state imaging of cold atoms
Sheludko, D.V.; Bell, S.C.; Vredenbregt, E.J.D.; Scholten, R.E.; Deshmukh, P.C.; Chakraborty, P.; Williams, J.F.
2007-01-01
We have investigated state-selective diffraction contrast imaging (DCI) of cold 85Rb atoms in the first excited (52P3/2) state. Excited-state DCI requires knowledge of the complex refractive index of the atom cloud, which was calculated numerically using a semi-classical model. The Autler-Townes
Energy Technology Data Exchange (ETDEWEB)
Thomas, E.W.; Rausch, E.O.; Harriss, J.E.; Bell, J.T.
1976-11-01
The scattering of energetic hydrogenic ions from surfaces was investigated. Protons at energies 1 to 30 keV are incident on metal surfaces and studies made of the charge state and excited state fractions of the scattered particles; measurements are also made of angular distributions and velocity spectra. The excited state distribution of back-scattered atoms is found to be governed by Auger de-excitation at the surface. Molecular hydrogen ions (H/sup +//sub 2/ and H/sup +//sub 3/) incident on metal surfaces dissociate on impact and the subsequent behavior of the fragments is uncorrelated. Contamination of metal surfaces with oxygen causes an increase in the backscattered flux of excited particles related to changes in the Auger de-excitation rate. A study of charge state distributions and angular distribution of the backscattered flux has disclosed irregularities related to methods of surface preparation. Measured backscattering coefficients have been compared with theoretical calculations of McCracken and Freeman. A limited study was made of the Mossbauer spectra of Fe after H/sup +/ bombardment. Substantial (1 percent) changes to the hyperfine field occur and anneal out after a period of some days at room temperature. It is suggested that the changes to hyperfine field are related to vacancy formation. A list of publications is included.
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)
Dinamical polarizability of highly excited hydrogen-like states
International Nuclear Information System (INIS)
Delone, N.B.; Krajnov, V.P.
1982-01-01
Analytic expressions are derived for the dynamic polarizability of highly excited hydrogen-like atomic states. It is shown that in the composite matrix element which determines the dynamic polarizability there is a strong compensation of the terms as a result of which the resulting magnitude of the dynamic polarizability is quasiclasically small compared to the individual terms of the composite matrix. It is concluded that the resonance behaviour of the dynamic polarizability of highly excited states differs significantly from the resonance behaviour of the polarizability for the ground and low-lying atomic states. The static limit and high-frequency limit of on electromagnetic field are considered
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
Nuclear transitions induced by atomic excitations
International Nuclear Information System (INIS)
Dyer, P.; Bounds, J.A.; Haight, R.C.; Luk, T.S.
1988-01-01
In the two-step pumping scheme for a gamma-ray laser, an essential step is that of exciting the nucleus from a long-lived storage isomer to a nearby short- lived state that then decays to the upper lasing level. An experiment is in progress to induce this transfer by first exciting the atomic electrons with UV photons. The incident photons couple well to the electrons, which then couple via a virtual photon to the nucleus. As a test case, excitation of the 235 U nucleus is being sought, using a high- brightness UV laser. The excited nuclear state, having a 26- minute half-life, decays by internal conversion, resulting in emission of an atomic electron. A pulsed infrared laser produces an atomic beam of 235 U which is then bombarded by the UV laser beam. Ions are collected, and conversion electrons are detected by a channel electron multiplier. In preliminary experiments, an upper limit of 7 x 10 -5 has been obtained for the probability of exciting a 235 U atom in the UV beam for one picosecond at an intensity of about 10 15 W/cm 2 . Experiments with higher sensitivities and at higher UV beam intensities are underway
Excited hydrogen bonds in the molecular mechanism of muscle contraction.
Bespalova, S V; Tolpygo, K B
1991-11-21
The mechanism of muscle contraction is considered. The hydrolysis of an ATP molecule is assumed to produce the excitation of hydrogen bonds A--H...B between electronegative atoms A and B, which are contained in the myosin head and actin filament. This excitation energy epsilon f depends on the interatomic distance AB = R and generates the tractive force f = -delta epsilon f/delta R, that makes atoms AB approach each other. The swing of the myosin head results in macroscopic mutual displacement of actin and myosin polymers. The motion of the actin filament under the action of this force is studied. The conditions under which a considerable portion of the excitation energy converts into the potential tension energy of the actin filament are analysed, and the probability of higher muscle efficiency existence is discussed.
The Mean Excitation Energy of Atomic Ions
DEFF Research Database (Denmark)
Sauer, Stephan; Oddershede, Jens; Sabin, John R.
2015-01-01
A method for calculation of the mean excitation energies of atomic ions is presented, making the calculation of the energy deposition of fast ions to plasmas, warm, dense matter, and complex biological systems possible. Results are reported to all ions of helium, lithium, carbon, neon, aluminum...
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)
Negative ion formation in collisions involving excited alkali atoms
International Nuclear Information System (INIS)
Cheret, M.
1988-01-01
Ion-pair production is considered as the prototype of the crossing problem between potential energy curves. In general an alkali atom is one of the reactants the other being an halogen, hydrogen atom or molecule. Experimental results are generally analyzed in the framework of the Landau-Zener-Stuekelberg theory, ionization potential and electron affinity, being the most important parameters. In order to vary these parameters over a wide range two experimental works have been devoted to systems of excited alkali atoms colliding with ground state alkali atoms. In the first study Rb atoms are excited to various ns or nd states from Rb(5d) to Rb(9s) in a cell. The second study is devoted to the Na(3p)-Na(3s) system, in this study also the possibility of creating excited negative ions (Na - (3s3p)) has been investigated. These results are presented and analyzed. Finally further developments of the subject are suggested. 17 refs.; 8 figs.; 1 table
Atomic hydrogen storage method and apparatus
Woollam, J. A. (Inventor)
1980-01-01
Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compounds maintained at liquid helium temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.
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 ...
Properties of excited xenon atoms in a plasma display panel
International Nuclear Information System (INIS)
Uhm, Han S.; Hong, Byoung H.; Oh, Phil Y.; Choi, Eun H.
2009-01-01
The luminance efficiency of a plasma display panel is directly related to the vacuum ultraviolet (VUV) light that is emitted from excited xenon (Xe) atoms and molecules. It is therefore necessary to investigate the properties of excited xenon atoms. This study presents experimental data associated with the behavior of excited xenon atoms in a PDP discharge cell and compares the data with the theoretical results obtained using an analytical model. The properties of excited xenon atoms in the discharge cells of a plasma display panel are investigated by measuring the excited atom density through the use of laser absorption spectroscopy. The density of the excited xenon atoms increases from zero, reaches its peak, and decreases with time in the discharge cells. The profile of the excited xenon atoms is also studied in terms of the xenon mole fraction. The typical density of the excited xenon atoms in the metastable state is on the order of 10 13 atoms per cubic cm.
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
Muonium/muonic hydrogen formation in atomic hydrogen
Indian Academy of Sciences (India)
The muonium/muonic hydrogen atom formation in ± –H collisions is investigated, using a two-state approximation in a time dependent formalism. It is found that muonium cross-section results are similar to the cross-section results obtained for positronium formation in + –H collision. Muonic hydrogen atom formation ...
Studies in Composing Hydrogen Atom Wavefunctions
DEFF Research Database (Denmark)
Putnam, Lance Jonathan; Kuchera-Morin, JoAnn; Peliti, Luca
2015-01-01
We present our studies in composing elementary wavefunctions of a hydrogen-like atom and identify several relationships between physical phenomena and musical composition that helped guide the process. The hydrogen-like atom accurately describes some of the fundamental quantum mechanical phenomen...
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
The hydrogen atom and Bateman functions
International Nuclear Information System (INIS)
Yaacob, K.B.
1988-01-01
The radial equations for the multi-dimensional hydrogen atom are reexamined using a integral representation of the equations that is found to be connected to the Schrodinger equation for the one-dimensional hydrogen atom. Application of the integral representation solution to the one-dimensional hydrogen atom leads to the conclusive proof that, contrary to current acceptance, the states of the one-dimensional hydrogen atom are non-degenerate. The integral representation was originally developed by Bateman (1931) and was later generalized by several workers. Based on these later works it is possible to apply the method to find the second solutions to the radial equations for the three and two-dimensional hydrogen atoms. The solutions are expressible in terms of the associated Laguerre polynomials and except for the phase factor, are similar to the first solutions. (author)
Electron spectroscopy of collisional excited atoms
International Nuclear Information System (INIS)
Straten, P. van der.
1987-01-01
In this thesis measurements are described in which coincidences are detected between scattered projectiles and emitted electrons. This yields information on two-electron excitation processes. In order to show what can be learnt from coincidence experiments a detailed theoretical analysis is given. The transition amplitudes, which contain all the information, are introduced (ch.2). In ch.3 the experimental set-up is shown. The results for the Li + -He system are shown in ch. 7 and are compared with predictions based on the Molecular-Orbitalmodel which however does not account for two-excitation mechanisms. With the transition amplitudes also the wave function of the excited atom has been completely determined. In ch.8 the shape of the electron cloud, induced by the collision, is derived from the amplitudes. The relation between the oscillatory motion of this cloud after the collision and the correlation between the two electrons of the excited atom is discussed. In ch. 6 it is shown that the broad structures in the non-coincident energy spectra of the Li + -He system are erroneously interpretated as a result of electron emission from the (Li-He) + -quasimolecule. A model is presented which explains, based on the results obtained from the coincidence measurements, these broad structures. In ch. 4 the Post-Collision Interaction process is treated. It is shown that for high-energy collisions, in contrast with general assumptions, PCI is important. In ch. 5 the importance of PCI-processes in photoionization of atoms, followed by Auger decay, are studied. From the formulas derived in ch. 4 simple analytical results are obtained. These are applied to recent experiments and good agreement is achieved. 140 refs.; 55 figs.; 9 tabs
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
Excitation and decay of correlated atomic states
International Nuclear Information System (INIS)
Rau, A.R.P.
1992-01-01
Doubly excited states of atoms and ions in which two electrons are excited from the ground configuration display strong radial and angular electron correlations. They are prototypical examples of quantum-mechanical systems with strong coupling. Two distinguishing characteristics of these states are: (1) their organization into successive families, with only weak coupling between families, and (2) a hierarchical nature of this coupling, with states from one family decaying primarily to those in the next lower family. A view of the pair of electrons as a single entity, with the electron-electron repulsion between them divided into a adiabatic and nonadiabatic piece, accounts for many of the dominant features. The stronger, adiabatic part determines the family structure and the weaker, nonadiabatic part the excitation and decay between successive families. Similar considerations extend to three-electron atomic states, which group into five different classes. They are suggestive of composite models for quarks in elementary particle physics, which exhibit analogous groupings into families with a hierarchical arrangement of masses and electroweak decays. 49 refs., 6 figs., 2 tabs
Cascade Processes in Muonic Hydrogen Atoms
International Nuclear Information System (INIS)
Faifman, M. P.; Men'Shikov, L. I.
2001-01-01
The QCMC scheme created earlier for cascade calculations in heavy hadronic atoms of hydrogen isotopes has been modified and applied to the study of cascade processes in the μp muonic hydrogen atoms. The distribution of μp atoms over kinetic energies has been obtained and the yields of K-series X-rays per one stopped muon have been calculated.Comparison with experimental data indicated directly that for muonic and pionic atoms new types of non-radiative transitions are essential, while they are negligible for heavy (kaonic, antiprotonic, etc.) atoms. These processes have been considered and their probabilities have been estimated.
Inelastic Transitions in Slow Collisions of Anti-Hydrogen with Hydrogen Atoms
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.
Nuclear Excitations by Antiprotons and Antiprotonic Atoms
2002-01-01
The proposal aims at the investigation of nuclear excitations following the absorption and annihilation of stopped antiprotons in heavier nuclei and at the same time at the study of the properties of antiprotonic atoms. The experimental arrangement will consist of a scintillation counter telescope for the low momentum antiproton beam from LEAR, a beam degrader, a pion multiplicity counter, a monoisotopic target and Ge detectors for radiation and charged particles. The data are stored by an on-line computer.\\\\ \\\\ The Ge detectors register antiprotonic x-rays and nuclear @g-rays which are used to identify the residual nucleus and its excitation and spin state. Coincidences between the two detectors will indicate from which quantum state the antiprotons are absorbed and to which nuclear states the various reactions are leading. The measured pion multiplicity characterizes the annihilation process. Ge&hyphn. and Si-telescopes identify charged particles and determine their energies.\\\\ \\\\ The experiment will gi...
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
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
On the Zeeman Effect in highly excited atoms: 2. Three-dimensional case
International Nuclear Information System (INIS)
Baseia, B.; Medeiros e Silva Filho, J.
1984-01-01
A previous result, found in two-dimensional hydrogen-atoms, is extended to the three-dimensional case. A mapping of a four-dimensional space R 4 onto R 3 , that establishes an equivalence between Coulomb and harmonic potentials, is used to show that the exact solution of the Zeeman effect in highly excited atoms, cannot be reached. (Author) [pt
Reaction of hydrogen atoms with acrylaldehyde
International Nuclear Information System (INIS)
Koda, Seiichiro; Nakamura, Kazumoto; Hoshino, Takashi; Hikita, Tsutomu
1978-01-01
The reaction of hydrogen atoms with acrylaldehyde was investigated in a fast flow reactor equipped with a time-of-flight type mass spectrometer under reduced pressure. Main reaction products were carbon monoxide, ethylene, ethane, methane, and propanal. Consideration of the distributions of the reaction products under various reaction conditions showed that hydrogen atoms attacked the C=C double bond, especially its inner carbon side under reduced pressure. Resulting hot radicals caused subsequent reactions. The relative value of the apparent bimolecular rate constant of the reaction against that of trans-2-butene with hydrogen atoms was 1.6+-0.2, which supported the above-mentioned initial reaction. (auth.)
Hydrogen storage in single-wall carbon nano-tubes by means of laser excitation
International Nuclear Information System (INIS)
Oksengorn, B.
2010-01-01
A new mode for hydrogen adsorption and storage in single-wall carbon nano-tubes is used, on the basis of laser excitation. Remember that this method has been useful to obtain, in the case of the fullerene C 60 , many complex C 60 -atoms or C 60 -molecules, where atoms or molecular particles are trapped inside the C 60 -molecules. We think this method might be important to store many hydrogen molecules inside carbon nano-tubes. (author)
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
Electron impact excitation of copper atoms
International Nuclear Information System (INIS)
Stumpf, B.J.
1993-01-01
The optical excitation function method has been used in a crossed atom and electron beam arrangement to measure the electron impact cross section of the copper 4 2 P → 4 2 S resonance lines (324.8, 327.4 nm) from threshold (3.8 eV) to 8 eV. Relative experimental cross section data are normalized at an energy of 1000 eV with respect to first Born theory that includes the 4 2 S → 4 2 P resonance transition with an oscillator strength of 0.652 and cascading from the (3d 10 nd) 2 D states with n = 4, hor-ellipsis 10. The measured Cu 4 2 S 4 → 4 2 P cross section is compared with recent theoretical calculations in close-coupling approximation. Very good agreement is found with the ten-state close-coupling theory of Scheibner
Electron transfer, ionization, and excitation atomic collisions
International Nuclear Information System (INIS)
Winter, T.G.; Alston, S.G.
1990-01-01
Basic atomic-collision processes at intermediate and high energies are being studied theoretically at Penn State by Alston and Winter. In the high velocity regime, single-electron capture is treated using a high order multiple-scattering approach; extensive comparison with experiment and analysis of mechanisms have been made. Fitting the calculated amplitude with a simple analytic form, the asymptotic velocity dependence of the cross section is obtained. The effect on the capture amplitude of altering the inner part of the internuclear potential has also been explored. In the intermediate velocity regime, earlier work on collisions between protons and hydrogenic-ion targets using a coupled-state approach is being extended to the two-electron helium target. 29 refs
Small-angle scattering of ions or atoms by atomic hydrogen
International Nuclear Information System (INIS)
Franco, V.
1982-01-01
A theory for small-angle scattering of arbitrary medium- or high-energy atoms or ions by atomic hydrogen is described. Results are obtained in terms of the known closed-form and easily calculable Glauber-approximation scattering amplitudes for electron-hydrogen collisions and for collisions between the nucleus (treated as one charged particle) of the ion or atom and the hydrogen atom, and in terms of the transition form factor of the arbitrary ion or atom. Applications are made to the angular differential cross sections for the excitation of atomic hydrogen to its n = 2 states by singly charged ground-state helium ions having velocities of roughly between 1/2 and 1 a.u. The differential cross sections are obtained in terms of electron-hydrogen amplitudes and the known He + ground-state form factor. Comparisons are made with other calculations and with recent measurements. The results are in good agreement with the data. It is seen that the effect of the He + electron is to produce significant constructive interference at most energies
High-spin excitations of atomic nuclei
International Nuclear Information System (INIS)
Xu Furong; National Laboratory of Heavy Ion Physics, Lanzhou; Chinese Academy of Sciences, Beijing
2004-01-01
The authors used the cranking shell model to investigate the high-spin motions and structures of atomic nuclei. The authors focus the collective rotations of the A∼50, 80 and 110 nuclei. The A∼50 calculations show complicated g spectroscopy, which can have significant vibration effects. The A≅80 N≅Z nuclei show rich shape coexistence with prolate and oblate rotational bands. The A≅110 nuclei near the r-process path can have well-deformed oblate shapes that become yrast and more stable with increasing rotational frequency. As another important investigation, the authors used the configuration-constrained adiabatic method to calculate the multi-quasiparticle high-K states in the A∼130, 180 and superheavy regions. The calculations show significant shape polarizations due to quasi-particle excitations for soft nuclei, which should be considered in the investigations of high-K states. The authors predicted some important high-K isomers, e.g., the 8 - isomers in the unstable nuclei of 140 Dy and 188 Pb, which have been confirmed in experiments. In superheavy nuclei, our calculations show systematic existence of high-K states. The high-K excitations can increase the productions of synthesis and the survival probabilities of superheavy nuclei. (authors)
Process to produce excited states of atomic nuclei
International Nuclear Information System (INIS)
Morita, M.; Morita, R.
The claims of a patented process which relates to the production of excited states of atomic nuclei are outlined. Among these are (1) production of nuclear excited states by bombarding the atoms with x rays or electrons under given conditions, (2) production of radioactive substances by nuclear excitation with x rays or electrons, (3) separation of specific isotopes from a mixture of isotopes of the same element by means of nuclear excitation followed by chemical treatment. The invention allows production of excited states of atomic nuclei in a relatively simple manner without the need of large apparatus and equipment
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.
International Nuclear Information System (INIS)
Purkait, M
2009-01-01
State selective charge transfer and excitation cross sections for collisions of Ne q+ (q = 1-10) with atomic hydrogen are calculated within the framework of Classical Trajectory Monte Carlo (CTMC) method and Boundary Corrected Continuum Intermediate State (BCCIS) approximation.
Circular states of atomic hydrogen
International Nuclear Information System (INIS)
Lutwak, R.; Holley, J.; Chang, P.P.; Paine, S.; Kleppner, D.; Ducas, T.
1997-01-01
We describe the creation of circular states of hydrogen by adiabatic transfer of a Rydberg state in crossed electric and magnetic fields, and also by adiabatic passage in a rotating microwave field. The latter method permits rapid switching between the two circular states of a given n manifold. The two methods are demonstrated experimentally, and results are presented of an analysis of the field ionization properties of the circular states. An application for the circular states is illustrated by millimeter-wave resonance in hydrogen of the n=29→n=30 transition. copyright 1997 The American Physical Society
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.
Atomic hydrogen cleaning of EUV multilayer optics
Graham, Samuel, Jr.; Steinhaus, Charles A.; Clift, W. Miles; Klebanoff, Leonard E.; Bajt, Sasa
2003-06-01
Recent studies have been conducted to investigate the use of atomic hydrogen as an in-situ contamination removal method for EUV optics. In these experiments, a commercial source was used to produce atomic hydrogen by thermal dissociation of molecular hydrogen using a hot filament. Samples for these experiments consisted of silicon wafers coated with sputtered carbon, Mo/Si optics with EUV-induced carbon, and bare Si-capped and Ru-B4C-capped Mo/Si optics. Samples were exposed to an atomic hydrogen source at a distance of 200 - 500 mm downstream and angles between 0-90° with respect to the source. Carbon removal rates and optic oxidation rates were measured using Auger electron spectroscopy depth profiling. In addition, at-wavelength peak reflectance (13.4 nm) was measured using the EUV reflectometer at the Advanced Light Source. Data from these experiments show carbon removal rates up to 20 Å/hr for sputtered carbon and 40 Å/hr for EUV deposited carbon at a distance of 200 mm downstream. The cleaning rate was also observed to be a strong function of distance and angular position. Experiments have also shown that the carbon etch rate can be increased by a factor of 4 by channeling atomic hydrogen through quartz tubes in order to direct the atomic hydrogen to the optic surface. Atomic hydrogen exposures of bare optic samples show a small risk in reflectivity degradation after extended periods. Extended exposures (up to 20 hours) of bare Si-capped Mo/Si optics show a 1.2% loss (absolute) in reflectivity while the Ru-B4C-capped Mo/Si optics show a loss on the order of 0.5%. In order to investigate the source of this reflectivity degradation, optic samples were exposed to atomic deuterium and analyzed using low energy ion scattering direct recoil spectroscopy to determine any reactions of the hydrogen with the multilayer stack. Overall, the results show that the risk of over-etching with atomic hydrogen is much less than previous studies using RF discharge cleaning
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.)
Core excitation and de-excitation spectroscopies of free atoms and molecules
International Nuclear Information System (INIS)
Ueda, Kiyoshi
2006-01-01
This article provides a review of the current status of core excitation and de-excitation spectroscopy studies of free atoms molecules using a high-resolution soft X-ray monochromator and a high-resolution electron energy analyzer, installed in the soft X-ray photochemistry beam line at SPring-8. Experimental results are discussed for 1s excitation of Ne, O 1s excitation of CO and H 2 O, and F 1s excitation of CF 4 . (author)
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
Electron capture in collisions of S4+ with atomic hydrogen
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.
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.)
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.
Reactive scattering of electronically excited alkali atoms with molecules
International Nuclear Information System (INIS)
Mestdagh, J.M.; Balko, B.A.; Covinsky, M.H.; Weiss, P.S.; Vernon, M.F.; Schmidt, H.; Lee, Y.T.
1987-06-01
Representative families of excited alkali atom reactions have been studied using a crossed beam apparatus. For those alkali-molecule systems in which reactions are also known for ground state alkali and involve an early electron transfer step, no large differences are observed in the reactivity as Na is excited. More interesting are the reactions with hydrogen halides (HCl): it was found that adding electronic energy into Na changes the reaction mechanism. Early electron transfer is responsible of Na(5S, 4D) reactions, but not of Na(3P) reactions. Moreover, the NaCl product scattering is dominated by the HCl - repulsion in Na(5S, 4D) reactions, and by the NaCl-H repulsion in the case of Na(3P). The reaction of Na with O 2 is of particular interest since it was found to be state specific. Only Na(4D) reacts, and the reaction requires restrictive constraints on the impact parameter and the reactants' relative orientation. The reaction with NO 2 is even more complex since Na(4D) leads to the formation of NaO by two different pathways. It must be mentioned however, that the identification of NaO as product in these reactions has yet to be confirmed
Subwavelength Localization of Atomic Excitation Using Electromagnetically Induced Transparency
Directory of Open Access Journals (Sweden)
J. A. Miles
2013-09-01
Full Text Available We report an experiment in which an atomic excitation is localized to a spatial width that is a factor of 8 smaller than the wavelength of the incident light. The experiment utilizes the sensitivity of the dark state of electromagnetically induced transparency (EIT to the intensity of the coupling laser beam. A standing-wave coupling laser with a sinusoidally varying intensity yields tightly confined Raman excitations during the EIT process. The excitations, located near the nodes of the intensity profile, have a width of 100 nm. The experiment is performed using ultracold ^{87}Rb atoms trapped in an optical dipole trap, and atomic localization is achieved with EIT pulses that are approximately 100 ns long. To probe subwavelength atom localization, we have developed a technique that can measure the width of the atomic excitations with nanometer spatial resolution.
Hydrogen atom kinetics in capacitively coupled plasmas
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.
Associative ionization of two laser excited Na atoms
International Nuclear Information System (INIS)
Meijer, H.A.J.
1988-01-01
An investigation into the associative ionization of two sodium atoms excited by polarized laser beams is described. It was possible to excite the Na atoms in a velocity-selective way by exploiting the Doppler effect. The excitation of Na to the 3 2 P 3/2 , F=3 level is discussed on the basis of so-called saturation curves. Experiments with seven different combinations of polarization of the two exciting laser beams are described and the results discussed. 86 refs.; 53 figs.; 6 tabs
Reactions of butadiyne. 1: The reaction with hydrogen atoms
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.
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
International Nuclear Information System (INIS)
Collins, L.A.; Schneider, B.I.
1984-01-01
The linear algebraic, separable potential approach is applied to the electronic excitation of atoms and molecules by electron impact. By representing the exchange and off-diagonal direct terms on a basis, the standard set of coupled inelastic equations is reduced to a set of elastic inhomogeneous equations. The procedure greatly simplifies the formulation by allowing a large portion of the problem to be handled by standard bound-state techniques and by greatly reducing the order of the scattering equations that must be solved. Application is made to the excitation of atomic hydrogen in the three-state close-coupling (1s, 2s, 2p) approximation. (author)
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
Thermal effects on the stability of excited atoms in cavities
International Nuclear Information System (INIS)
Khanna, F. C.; Malbouisson, A. P. C.; Malbouisson, J. M. C.; Santana, A. E.
2010-01-01
An atom, coupled linearly to an environment, is considered in a harmonic approximation in thermal equilibrium inside a cavity. The environment is modeled by an infinite set of harmonic oscillators. We employ the notion of dressed states to investigate the time evolution of the atom initially in the first excited level. In a very large cavity (free space) for a long elapsed time, the atom decays and the value of its occupation number is the physically expected one at a given temperature. For a small cavity the excited atom never completely decays and the stability rate depends on temperature.
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.)
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
Intershell interaction in excited atom and ion photoionization
International Nuclear Information System (INIS)
Amusia, M.Ya.; Avdonina, N.B.
1989-01-01
It is demonstrated, that the photoionization cross section of an excited electron in Cs atom isoelectronic sequence acquire additional structure if the virtual polarization of the core by the incident photon is taken into account. (orig.)
Self-excitation of Rydberg atoms at a metal surface
DEFF Research Database (Denmark)
Bordo, Vladimir
2017-01-01
The novel effect of self-excitation of an atomic beam propagating above a metal surface is predicted and a theory is developed. Its underlying mechanism is positive feedback provided by the reflective surface for the atomic polarization. Under certain conditions the atomic beam flying in the near...... field of the metal surface acts as an active device that supports sustained atomic dipole oscillations, which generate, in their turn, an electromagnetic field. This phenomenon does not exploit stimulated emission and therefore does not require population inversion in atoms. An experiment with Rydberg...... atoms in which this effect should be most pronounced is proposed and the necessary estimates are given....
Dynamics and applications of excited cold atoms
Claessens, B.J.
2006-01-01
In a Magneto-Optical Trap (MOT), realized for the first time in 1987, one can trap and cool neutral atoms to temperatures below a mK. The invention of this device caused a revolution in atomic physics. With an MOT collision and spectroscopy experiments could be performed with unprecedented accuracy.
Atomic excitation and recombination in external fields
International Nuclear Information System (INIS)
Nayfeh, M.H.; Clark, C.W.
1985-01-01
This volume offers a timely look at Rydberg states of atoms in external fields and dielectronic recombination. Each topic provides authoritative coverage, presents a fresh account of a flourishing field of current atomic physics and introduces new opportunities for discovery and development. Topics considered include electron-atom scattering in external fields; observations of regular and irregular motion as exemplified by the quadratic zeeman effect and other systems; Rydberg atoms in external fields and the Coulomb geometry; crossed-field effects in the absorption spectrum of lithium in a magnetic field; precise studies of static electric field ionization; widths and shapes of stark resonances in sodium above the saddle point; studies of electric field effects and barium autoionizing resonances; autoionization and dielectronic recombination in plasma electric microfields; dielectronic recombination measurements on multicharged ions; merged beam studies of dielectronic recombination; Rydberg atoms and dielectronic recombination in astrophysics; and observations on dielectronic recombination
Inner-shell excitation of alkali-metal atoms
International Nuclear Information System (INIS)
Tiwary, S.N.
1987-06-01
Inner-shell excitation of alkali-metal atoms, which leads to auto-ionization, is reviewed. The validity of quantum mechanical approximation is analyzed and the importance of exchange and correlation is demonstrated. Basic difficulties in making accurate calculations for inner-shell excitation process are discussed. Suggestions are made for further study of inner-shell process in atoms and ions. (author). 26 refs, 4 figs, 1 tab
Method of producing excited states of atomic nuclei
International Nuclear Information System (INIS)
Morita, M.; Morita, R.
1976-01-01
A method is claimed of producing excited states of atomic nuclei which comprises bombarding atoms with x rays or electrons, characterized in that (1) in the atoms selected to be produced in the excited state of their nuclei, (a) the difference between the nuclear excitation energy and the difference between the binding energies of adequately selected two electron orbits is small enough to introduce the nuclear excitation by electron transition, and (b) the system of the nucleus and the electrons in the case of ionizing an orbital electron in said atoms should satisfy the spin and parity conservation laws; and (2) the energy of the bombarding x rays or electrons should be larger than the binding energy of one of the said two electron orbits which is located at shorter distance from the atomic nucleus. According to the present invention, atomic nuclei can be excited in a relatively simple manner without requiring the use of large scale apparatus, equipment and production facilities, e.g., factories. It is also possible to produce radioactive substances or separate a particular isotope with an extremely high purity from a mixture of isotopes by utilizing nuclear excitation
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
Coherent excitation of a single atom to a Rydberg state
DEFF Research Database (Denmark)
Miroshnychenko, Yevhen; Gaëtan, Alpha; Evellin, Charles
2010-01-01
We present the coherent excitation of a single Rubidium atom to the Rydberg state 58d3/2 using a two-photon transition. The experimental setup is described in detail, as are experimental techniques and procedures. The coherence of the excitation is revealed by observing Rabi oscillations between...
Laser techniques for spectroscopy of core-excited atomic levels
Harris, S. E.; Young, J. F.; Falcone, R. W.; Rothenberg, J. E.; Willison, J. R.
1982-01-01
We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.
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
One Photon Can Simultaneously Excite Two or More Atoms.
Garziano, Luigi; Macrì, Vincenzo; Stassi, Roberto; Di Stefano, Omar; Nori, Franco; Savasta, Salvatore
2016-07-22
We consider two separate atoms interacting with a single-mode optical or microwave resonator. When the frequency of the resonator field is twice the atomic transition frequency, we show that there exists a resonant coupling between one photon and two atoms, via intermediate virtual states connected by counterrotating processes. If the resonator is prepared in its one-photon state, the photon can be jointly absorbed by the two atoms in their ground state which will both reach their excited state with a probability close to one. Like ordinary quantum Rabi oscillations, this process is coherent and reversible, so that two atoms in their excited state will undergo a downward transition jointly emitting a single cavity photon. This joint absorption and emission process can also occur with three atoms. The parameters used to investigate this process correspond to experimentally demonstrated values in circuit quantum electrodynamics systems.
Fermionic Collective Excitations in a Lattice Gas of Rydberg Atoms
International Nuclear Information System (INIS)
Olmos, B.; Gonzalez-Ferez, R.; Lesanovsky, I.
2009-01-01
We investigate the many-body quantum states of a laser-driven gas of Rydberg atoms confined to a large spacing ring lattice. If the laser driving is much stronger than the van der Waals interaction among the Rydberg atoms, these many-body states are collective fermionic excitations. The first excited state is a spin wave that extends over the entire lattice. We demonstrate that our system permits us to study fermions in the presence of disorder although no external atomic motion takes place. We analyze how this disorder influences the excitation properties of the fermionic states. Our work shows a route towards the creation of complex many-particle states with atoms in lattices.
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.
Hydrogen atom in phase space: the Wigner representation
International Nuclear Information System (INIS)
Praxmeyer, Ludmila; Mostowski, Jan; Wodkiewicz, Krzysztof
2006-01-01
The hydrogen atom is a fundamental exactly soluble system for which the Wigner function, being a quantum analogue of the joint probability distribution of position and momentum, is unknown. In this paper, we present an effective method of calculating the Wigner function, for all bound states of the nonrelativistic hydrogen atom. The formal similarity between the eigenfunctions of the nonrelativistic hydrogen atom in the momentum representation and the Klein-Gordon propagator has allowed the calculation of the Wigner function for an arbitrary bound state of the hydrogen atom, using a simple atomic integral as a generator. These Wigner functions for some low-lying states are depicted and discussed
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.
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
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.
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
Casimir interaction between gas media of excited atoms
International Nuclear Information System (INIS)
Sherkunov, Yury
2007-01-01
The retarded dispersion interaction (Casimir interaction) between two dilute dielectric media at high temperatures is considered. The excited atoms are taken into account. It is shown that the perturbation technique cannot be applied to this problem due to divergence of integrals. A non-perturbative approach based on kinetic Green functions is implemented. We consider the interaction between two atoms (one of them is excited) embedded in an absorbing dielectric medium. We take into account the possible absorption of photons in the medium, which solves the problem of divergence. The force between two plane dilute dielectric media is calculated at pair interaction approximation. We show that the result of quantum electrodynamics differs from the Lifshitz formula for dilute gas media at high temperatures (if the number of excited atoms is significant). According to quantum electrodynamics, the interaction may be either attractive or repulsive depending on the temperature and the density numbers of the media
Resonance charge exchange between excited states in slow proton-hydrogen collisions
International Nuclear Information System (INIS)
Tolstikhina, Inga Yu.; Kato, Daiji
2010-01-01
The theory of resonance charge exchange in slow collisions of a proton with a hydrogen atom in the excited state is developed. It extends the Firsov-Demkov theory of resonance charge exchange to the case of degenerate initial and final states. The theory is illustrated by semiclassical and quantum calculations of charge exchange cross sections between states with n=2 in parabolic and spherical coordinates. The results are compared with existing close-coupling calculations.
Enhancing atom densities in solid hydrogen by isotopic substitution
International Nuclear Information System (INIS)
Collins, G.W.; Souers, P.C.; Mapoles, E.R.; Magnotta, F.
1991-01-01
Atomic hydrogen inside solid H 2 increases the energy density by 200 MegaJoules/m 3 , for each percent mole fraction stored. How many atoms can be stored in solid hydrogen? To answer this, we need to know: (1) how to produce and trap hydrogen atoms in solid hydrogen, (2) how to keep the atoms from recombining into the ground molecular state, and (3) how to measure the atom density in solid hydrogen. Each of these topics will be addressed in this paper. Hydrogen atoms can be trapped in solid hydrogen by co-condensing atoms and molecules, external irradiation of solid H 2 , or introducing a radioactive impurity inside the hydrogen lattice. Tritium, a heavy isotope of hydrogen, is easily condensed as a radioactive isotopic impurity in solid H 2 . Although tritium will probably not be used in future rockets, it provides a way of applying a large, homogenious dose to solid hydrogen. In all of the data presented here, the atoms are produced by the decay of tritium and thus knowing how many atoms are produced from the tritium decay in the solid phase is important. 6 refs., 6 figs
Energy Technology Data Exchange (ETDEWEB)
Dzantiev, B. G.; Shvedchikov, A. P. [Institut Himicheskoj Fiziki AN SSSR, SSSR (Russian Federation)
1965-04-15
the target. Lowering the temperature from 50 Degree-Sign C to -78 Degree-Sign C has little effect on the distribution of labelled products; however, in the transition to heavy ethylene (-196 Degree-Sign C) a phase effect is observed; the HT and C{sub 4}H{sub 9}T yield decreases and the activity of the parent compound C{sub 2}H{sub 3}T increases, In the radiolysis of C{sub 2}H{sub 4} and its mixtures with ammonia the ratio C{sub 2}H{sub 6}/C{sub 4}H{sub 10} is equal to 1.0 {+-} 0.3, which does not agree with the standard scheme for disproportionation and recombination reactions of thermal ethylene radicals (C{sub 2}H{sub 6}/C{sub 4}H{sub 10} = 0.2 {+-} 0.1). On the basis of data on the effect of helium addition and temperature on C{sub 2}H{sub 6} and C{sub 4}H{sub 10}, yield in the radiolysis of C{sub 2}H{sub 4}, and in the photolysis of mixtures of C{sub 2}H{sub 4} and HI, we were able to get an idea of the formation of excited ethylene radicals of C2H* These are obtained as a result of the addition of hot hydrogen atoms (generated radiolytically or photolytically) to ethylene: H* + C{sub 2}H{sub 4} = C{sub 2}H*{sub 5}. It is shown that the C{sub 2}H*{sub 5} radical easily enters into the stripping reaction C{sub 2}H*{sub 5} + RH = C{sub 2}H{sub 6} + R, which accounts for the ''excess'' quantity of ethane formed in the radiolysis of ethylene [French] On sait qu'a la suite des reactions nucleaires Li{sup 6}(n, {alpha})T et He{sup 3}(n, p) T se forment des atomes chauds de tritium. La forte reactivite chimique de ces atomes determine a maints egards les particularites chimiques des effets dus aux transformations nucleaires. Or, les atomes chauds de tritium peuvent jouer un role important, non seulement en chimie nucleaire, mais aussi dans d'autres domaines de la chimie des hautes energies, notamment dans la radiolyse, la photolyse, etc. Dans le memoire, on essaie de comparer le comportement des atomes chauds de tritium obtenus par les moyens suivants: reaction Li{sup 6
Do static atoms outside a Schwarzschild black hole spontaneously excite?
International Nuclear Information System (INIS)
Yu Hongwei; Zhou Wenting
2007-01-01
The spontaneous excitation of a two-level atom held static outside a four dimensional Schwarzschild black hole and in interaction with a massless scalar field in the Boulware, Unruh, and Hartle-Hawking vacuums is investigated, and the contributions of the vacuum fluctuations and radiation reaction to the rate of change of the mean atomic energy are calculated separately. We find that, for the Boulware vacuum, the spontaneous excitation does not occur and the ground-state atoms are stable, while the spontaneous emission rate for excited atoms in the Boulware vacuum, which is well behaved at the event horizon, is not the same as that in the usual Minkowski vacuum. However, for both the Unruh vacuum and the Hartle-Hawking vacuum, our results show that the atom would spontaneously excite, as if there were an outgoing thermal flux of radiation or as if it were in a thermal bath of radiation at a proper temperature which reduces to the Hawking temperature in the spatial asymptotic region, depending on whether the scalar field is in the Unruh or Hartle-Hawking vacuum
Reaction dynamics of electronically excited alkali atoms with simpler molecules
International Nuclear Information System (INIS)
Weiss, P.S.; Mestdagh, J.M.; Schmidt, H.; Vernon, M.F.; Covinsky, M.H.; Balko, B.A.; Lee, Y.T.
1985-05-01
The reactions of electronically excited sodium atoms with simple molecules have been studied in crossed molecular beams experiments. Electronically excited Na(3 2 P/sub 3/2/, 4 2 D/sub 5/2/, and 5 2 S/sub 1/2/) were produced by optical pumping using single frequency dye lasers. The effects of the symmetry, and the orientation and alignment of the excited orbital on the chemical reactivity, and detailed information on the reaction dynamics were derived from measurements of the product angular and velocity distributions. 12 refs., 9 figs
[Electron transfer, ionization and excitation in atomic collisions
International Nuclear Information System (INIS)
1991-01-01
The research being carried out at Penn State by Winter and Alston addresses the fundamental atomic-collision processes of electron transfer, ionization, and excitation. Winter has focussed attention on intermediate and, more recently, higher collision energies -- proton energies of at least about 50 keV -- for which coupled-state approaches are appropriate. Alston has concentrated on perturbative approaches to symmetric ion-ion/atom collisions at high energies and to asymmetric collisions at intermediate to high energies
Development of laser excited atomic fluorescence and ionization methods
International Nuclear Information System (INIS)
Winefordner, J.D.
1991-01-01
Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies
Liquid-Arc/Spark-Excitation Atomic-Emission Spectroscopy
Schlagen, Kenneth J.
1992-01-01
Constituents of solutions identified in situ. Liquid-arc/spark-excitation atomic-emission spectroscopy (LAES) is experimental variant of atomic-emission spectroscopy in which electric arc or spark established in liquid and spectrum of light from arc or spark analyzed to identify chemical elements in liquid. Observations encourage development of LAES equipment for online monitoring of process streams in such industries as metal plating, electronics, and steel, and for online monitoring of streams affecting environment.
Electron-collision excitation cross section of the silver atom
International Nuclear Information System (INIS)
Krasavin, A.Y.; Kuchenev, A.N.; Smirnov, Y.M.
1983-01-01
The cross sections for direct excitation by electron collision were measured for fifteen transitions of the silver atom. For thirteen of these transitions the optical excitation functions were recorded, varying the energy of the exciting electrons from the threshold energy to 250 eV. The operating region of the spectrum was 2000--5500 A. The excitation cross sections of the two principal lines exceeded the excitation cross sections of all the remaining lines by more than an order of magnitude. Reabsorption of the resonance lines was detected from the change in the ratio of intensities of the lines at 3280.68 and 3382.89 A, and so their intensity has been corrected relative to the intensities of the nonreabsorbed lines. All radiative transitions, with the exception of resonance transitions, participate in cascade population of the lowest resonance levels, making it possible to determine the resulting direct excitation cross sections of the 5p 2 P/sub 1/2/ and 5p 2 P/sub 3/2/ levels from the ground state of the silver atom. The part played by cascade population of the resonance levels is not large and is 2 P/sub 3/2/ level, and 10% for the 5p 2 P/sub 1/2/ level, of the excitation cross sections of the corresponding resonance transitions
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
Atomic hydrogen storage. [cryotrapping and magnetic field strength
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.
Electron impact excitation and ionization of laser-excited sodium atoms Na*(7d)
International Nuclear Information System (INIS)
Nienhaus, J.; Dorn, A.; Mehlhorn, W.; Zatsarinny, O.I.
1997-01-01
We have investigated the ejected-electron spectrum following impact excitation and ionization of laser-excited Na * (nl) atoms by 1.5 keV electrons. By means of two-laser excitation 3s → 3p 3/2 → 7d and subsequent cascading transitions about 8% (4%) of the target atoms were in excited states with n > 3 (7d). The experimental ejected-electron spectrum due to the decay of Auger and autoionization states of laser-excited atoms Na * (nl) with n = 4-7 has been fully interpreted by comprehensive calculations of the energies, cross sections and decay probabilities of the corresponding states. The various processes contributing to the ejected-electron spectrum are with decreasing magnitude: 2s ionization leading to 2s2p 6 nl Auger states, 2p → 3s excitation leading to 2p 5 3s( 1 P)nl autoionization states and 2s → 3l' excitation leading to 2s2p 6 3l'( 1 L)nl autoionization states. (Author)
Linear-algebraic approach to electronic excitation of atoms and molecules by electron impact
International Nuclear Information System (INIS)
Collins, L.A.; Schneider, B.I.
1983-01-01
A linear-algebraic method, based on an integral equations formulation, is applied to the excitation of atoms and molecules by electron impact. Various schemes are devised for treating the one-electron terms that sometimes cause instabilities when directly incorporated into the solution matrix. These include introducing Lagrange undetermined multipliers and correlation terms. Good agreement between the method and other computational techniques is obtained for electron scattering for hydrogenic and Li-like atomic ions and for H 2 + in two- to five-state close-coupling calculations
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)
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)
On the dynamics of excited atoms in time dependent electromagnetic fields
International Nuclear Information System (INIS)
Foerre, Morten
2004-06-01
This thesis is composed of seven scientific publications written in the period 2001-2004. The focus has been set on Rydberg atoms of hydrogen and lithium in relatively weak electromagnetic fields. Such atoms have been studied extensively during many years, both experimentally and theoretically, They are relatively easy to handle in the laboratory. Their willingness to react to conventional field sources and their long lifetimes, are two reasons for this. Much new insight into fundamental quantum mechanics has been extracted from such studies. By exciting a non-hydrogenic ground state atom or molecule into a highly excited state, many properties of atomic hydrogen are adopted. In many cases the dynamics of such systems can be accurately described by the hydrogenic theory, or alternatively by some slightly modified version like quantum defect theory. In such theories the Rydberg electron(s) of the non-hydrogenic Rydberg system is treated like it is confined in a modified Coulomb potential, which arises from the non-hydrogenic core. defined by the non-excited electrons and the nucleus. The more heavily bound core electrons are less influenced from external perturbations than the excited electrons, giving rise to the so-called frozen-core approximation. where the total effect of the core electrons is put into a modified Coulomb potential. A major part of this thesis has been allocated to the study of core effects in highly excited states of lithium. In collaboration with time experimental group of Erik Horsdal-Pedersen at Aarhus University, we have considered several hydrogenic and non-hydrogenic aspects of such states, when exposed to weak slowly varying electromagnetic fields. The dynamics was restricted to one principal shell (intrashell). Two general features were observed, either the hydrogenic theory applied or alternatively, in case of massive deviation, the dynamics was accurately described by quantum defect theory, clearly demonstrating the usefulness of such
On the dynamics of excited atoms in time dependent electromagnetic fields
Energy Technology Data Exchange (ETDEWEB)
Foerre, Morten
2004-06-01
This thesis is composed of seven scientific publications written in the period 2001-2004. The focus has been set on Rydberg atoms of hydrogen and lithium in relatively weak electromagnetic fields. Such atoms have been studied extensively during many years, both experimentally and theoretically, They are relatively easy to handle in the laboratory. Their willingness to react to conventional field sources and their long lifetimes, are two reasons for this. Much new insight into fundamental quantum mechanics has been extracted from such studies. By exciting a non-hydrogenic ground state atom or molecule into a highly excited state, many properties of atomic hydrogen are adopted. In many cases the dynamics of such systems can be accurately described by the hydrogenic theory, or alternatively by some slightly modified version like quantum defect theory. In such theories the Rydberg electron(s) of the non-hydrogenic Rydberg system is treated like it is confined in a modified Coulomb potential, which arises from the non-hydrogenic core. defined by the non-excited electrons and the nucleus. The more heavily bound core electrons are less influenced from external perturbations than the excited electrons, giving rise to the so-called frozen-core approximation. where the total effect of the core electrons is put into a modified Coulomb potential. A major part of this thesis has been allocated to the study of core effects in highly excited states of lithium. In collaboration with time experimental group of Erik Horsdal-Pedersen at Aarhus University, we have considered several hydrogenic and non-hydrogenic aspects of such states, when exposed to weak slowly varying electromagnetic fields. The dynamics was restricted to one principal shell (intrashell). Two general features were observed, either the hydrogenic theory applied or alternatively, in case of massive deviation, the dynamics was accurately described by quantum defect theory, clearly demonstrating the usefulness of such
‘Which-way’ collective atomic spin excitation among atomic ensembles by photon indistinguishability
International Nuclear Information System (INIS)
Zhang Guowan; Bian Chenglin; Chen, L Q; Ou, Z Y; Zhang Weiping
2012-01-01
In spontaneous Raman scattering in an atomic ensemble, a collective atomic spin wave is created in correlation with the Stokes field. When the Stokes photons from two or more such atomic ensembles are made indistinguishable, a ‘which-way’ collective atomic spin excitation is generated among the independent atomic ensembles. We demonstrate this phenomenon experimentally by reading out the atomic spin excitations and observing interference between the read-out beams. When a single-photon projective measurement is made on the indistinguishable Stokes photons, this simple scheme can be used to entangle independent atomic ensembles. Compared to other currently used methods, this scheme can be easily scaled up and has greater efficiency. (paper)
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
Irregular wave functions of a hydrogen atom in a uniform magnetic field
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.
Electronic excitation of Na atom by electron impact
International Nuclear Information System (INIS)
Bielschowsky, C.E.; Souza, G.G.B. de; Lucas, C.A.; Nogueira, J.C.
1988-01-01
Electronic excitation of the 3s-3p transition in the Na atom was studied by intermediate energy electron impact spectroscopy. Differential Cross Sections (DCS) and Generalized Oscillator Strenghts (GOS) were determined experimentally for 1 KeV electrons. Theoretical results within the First Born Approximation as well as Glauber theory, were also performed. (A.C.A.S.) [pt
Amplitudes and state parameters from ion- and atom-atom excitation processes
International Nuclear Information System (INIS)
Andersen, T.; Horsdal-Pedersen, E.
1984-01-01
This chapter examines single collisions between two atomic species, one of which is initially in a 1 S state (there is only one initial spin channel). The collisions are characterized by a definite scattering plane and a definite orientation. Topics considered include an angular correlation between scattered particles and autoionization electrons or polarized photons emitted from states excited in atomic collisions (photon emission, electron emission, selectivity excited target atoms), experimental methods for obtaining information on the alignment and orientation parameters of atoms or ions excited in specific collisions, results of experiments and numerical calculations (quasi-oneelectron systems, He + -He collisions, other collision systems), and future aspects and possible applications of the polarizedphoton, scattered-particle coincidence techniques to atomic spectroscopy
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
Chemical reaction between single hydrogen atom and graphene
International Nuclear Information System (INIS)
Ito, Atsushi; Nakamura, Hiroaki; Takayama, Arimichi
2007-04-01
We study chemical reaction between a single hydrogen atom and a graphene, which is the elemental reaction between hydrogen and graphitic carbon materials. In the present work, classical molecular dynamics simulation is used with modified Brenner's empirical bond order potential. The three reactions, that is, absorption reaction, reflection reaction and penetration reaction, are observed in our simulation. Reaction rates depend on the incident energy of the hydrogen atom and the graphene temperature. The dependence can be explained by the following mechanisms: (1) The hydrogen atom receives repulsive force by π-electrons in addition to nuclear repulsion. (2) Absorbing the hydrogen atom, the graphene transforms its structure to the 'overhand' configuration such as sp 3 state. (3) The hexagonal hole of the graphene is expanded during the penetration of the hydrogen atom. (author)
Fast metastable hydrogen atoms from H2 molecules: twin atoms
Directory of Open Access Journals (Sweden)
Trimèche A.
2015-01-01
Full Text Available It is a difficult task to obtain “twin atoms”, i.e. pairs of massive particles such that one can perform experiments in the same fashion that is routinely done with “twin photons”. One possible route to obtain such pairs is by dissociating homonuclear diatomic molecules. We address this possibility by investigating the production of metastable H(2s atoms coming from the dissociation of cold H2 molecules produced in a Campargue nozzle beam crossing an electron beam from a high intensity pulsed electron gun. Dissociation by electron impact was chosen to avoid limitations of target molecular excited states due to selection rules. Detectors placed several centimeters away from the collision center, and aligned with respect to possible common molecular dissociation channel, analyze the neutral fragments as a function of their time-of-flight (TOF through Lyman-α detection. Evidence for the first time observed coincidence of pairs of H(2s atoms obtained this way is presented.
International Nuclear Information System (INIS)
Miyazaki, T.; Kinugawa, K.; Eguchi, M.; Guedes, S.M.L.
1977-01-01
Selective hydrogen atom abstraction reaction by H atoms, has been found in Isobutane, 2,2,3,3-tetramethylbutane(TMB), cyclopropane matrices besides neopentane matrix. The selective hydrogen atom abstraction reaction in neopentane-isobutane mixture is affected by the difference of kinetic energies of H atoms. The reaction occurs more favorably with decreasing the kinetic energy of H atoms. Competitive reaction between c-C 6 H 12 and Hi for H atoms has been studied in the radiolysis and photolysis of neo-C 5 H 12 HI mixture at 77 K. The rate constants of these reactions in neopentane matrix are quite different from these of thermal H atom reaction, but similar to those of hot H atom reaction. Importance of the selective hydrogen atom abstraction reaction by H atoms is pointed out in the radical formation in the radiolysis of pure TMB at 77 K [pt
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.)
Collective excitations in circular atomic configurations and single-photon traps
International Nuclear Information System (INIS)
Hammer, Hanno
2004-01-01
Correlated excitations in a plane circular configuration of identical atoms with parallel dipole moments are investigated. The collective energy eigenstates, which are formally identical to Frenkel excitons, can be computed together with their level shifts and decay rates by decomposing the atomic state space into carrier spaces for the irreducible representations of the symmetry group Z N of the circle. It is shown that the index p of these representations can be used as a quantum number analogously to the orbital angular momentum quantum number l in hydrogenlike systems. Just as the hydrogen s states are the only electronic wave functions which can occupy the central region of the Coulomb potential, the quasiparticle corresponding to a collective excitation of the atoms in the circle can occupy the central atom only for vanishing Z N quantum number p. If a central atom is present, the p=0 state splits into two and shows level crossing at certain radii; in the regions between these radii, damped quantum beats between two 'extreme' p=0 configurations occur. The physical mechanisms behind super- and subradiance at a given radius are discussed. It is shown that, beyond a certain critical number of atoms in the circle, the lifetime of the maximally subradiant state increases exponentially with the number of atoms in the configuration, making the system a natural candidate for a single-photon trap
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.
Analysis of Excitation and Ionization of Atoms and Molecules by Electron Impact
Chaudhry, Afzal
2011-01-01
Analysis of Excitation and Ionization of Atoms and Molecules by Electron Impact, by Afzal Chaudhry and Hans Kleinpoppen, describes in detail the measurements of the partial and total doubly differential cross sections for the multiple-ionization of rare gas atoms by electron impact. These measurements show, among other trends, the role of Auger transitions in the production of multiply ionized atoms in the region where the incident electron energy is sufficient to produce inner shell ionization. Other processes like Coster-Kronig transitions and shake off also contribute towards increasing the charge of the ions. As discussed in the book, an incident electron having energy of 6 keV, for example, in a collision with xenon atom can remove up to nine electrons! The measurements of doubly differential cross sections for the dissociative and non-dissociative ionization of hydrogen, sulfur dioxide and sulfur hexa fluoride molecular gases are also explored. The results of the measurements for the sulfur dioxide mole...
Hydrogen atom in intense magnetic field.
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.
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
Charge transfer between O6+ and atomic hydrogen
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.
Excited, bound and resonant positron-atom systems
Energy Technology Data Exchange (ETDEWEB)
Bromley, M W J [Department of Physics and Computational Science Research Center, San Diego State University, San Diego CA 92182 (United States); Mitroy, J, E-mail: mbromley@physics.sdsu.ed [ARC Centre for Antimatter-Matter Studies and Faculty of Education, Health and Science, Charles Darwin University, Darwin NT 0909 (Australia)
2010-01-01
Calculations have demonstrated that eleven neutral atoms can bind positrons, while many more can bind positronium. This is a short review of recent progress made in understanding some of the underlying mechanisms. The emphasis here being on configuration interaction calculations with excited state configurations. These have demonstrated the existence of a {sup 2}P{sup o} excited state of e{sup +}Ca, which consists predominantly of a positronium cluster orbiting the Ca{sup +} ion in the L = 1 partial wave. Preliminary results are presented of excited state positron binding to a model alkali atom, where the excited {sup 1}P{sup o} states are stable over a limited region. Implications for the unnatural parity, {sup 2,4}S{sup o}, states of PsH, LiPs, NaPs and KPs are also discussed. The e{sup +}Mg, e{sup +}Cu, e{sup +}Zn and e{sup +}Cd systems show a lack of a {sup 2}P{sup o} excited state, each instead possessing a low-energy p-wave shape resonance of varying strength.
Excited, bound and resonant positron-atom systems
International Nuclear Information System (INIS)
Bromley, M W J; Mitroy, J
2010-01-01
Calculations have demonstrated that eleven neutral atoms can bind positrons, while many more can bind positronium. This is a short review of recent progress made in understanding some of the underlying mechanisms. The emphasis here being on configuration interaction calculations with excited state configurations. These have demonstrated the existence of a 2 P o excited state of e + Ca, which consists predominantly of a positronium cluster orbiting the Ca + ion in the L = 1 partial wave. Preliminary results are presented of excited state positron binding to a model alkali atom, where the excited 1 P o states are stable over a limited region. Implications for the unnatural parity, 2,4 S o , states of PsH, LiPs, NaPs and KPs are also discussed. The e + Mg, e + Cu, e + Zn and e + Cd systems show a lack of a 2 P o excited state, each instead possessing a low-energy p-wave shape resonance of varying strength.
ASACUSA: the first beam of anti-hydrogen atoms
International Nuclear Information System (INIS)
2014-01-01
The ASACUSA experiment at CERN has produced for the first time a beam of anti-hydrogen atoms, 80 atoms of anti-hydrogen have been detected at a distance of 2.7 meters away from their production place which is the true achievement of this experiment. The ASACUSA team has developed an innovative device that allows the transfer of the anti-hydrogen atoms in a place where they can be studied in flight, away from the intense magnetic field that was necessary to produce them but affect their spectroscopic properties. Anti-hydrogen atoms are made up of anti-electrons and anti-protons, according to the theory their spectrum must be identical to that of hydrogen atoms and any difference that might be detected by the ASACUSA experiment may shed light on the matter-antimatter asymmetry issue. (A.C.)
Computer simulation of electronic excitation in atomic collision cascades
International Nuclear Information System (INIS)
Duvenbeck, A.
2007-01-01
The impact of an keV atomic particle onto a solid surface initiates a complex sequence of collisions among target atoms in a near-surface region. The temporal and spatial evolution of this atomic collision cascade leads to the emission of particles from the surface - a process usually called sputtering. In modern surface analysis the so called SIMS technology uses the flux of sputtered particles as a source of information on the microscopical stoichiometric structure in the proximity of the bombarded surface spots. By laterally varying the bombarding spot on the surface, the entire target can be scanned and chemically analyzed. However, the particle detection, which bases upon deflection in electric fields, is limited to those species that leave the surface in an ionized state. Due to the fact that the ionized fraction of the total flux of sputtered atoms often only amounts to a few percent or even less, the detection is often hampered by rather low signals. Moreover, it is well known, that the ionization probability of emitted particles does not only depend on the elementary species, but also on the local environment from which a particle leaves the surface. Therefore, the measured signals for different sputtered species do not necessarily represent the stoichiometric composition of the sample. In the literature, this phenomenon is known as the Matrix Effect in SIMS. In order to circumvent this principal shortcoming of SIMS, the present thesis develops an alternative computer simulation concept, which treats the electronic energy losses of all moving atoms as excitation sources feeding energy into the electronic sub-system of the solid. The particle kinetics determining the excitation sources are delivered by classical molecular dynamics. The excitation energy calculations are combined with a diffusive transport model to describe the spread of excitation energy from the initial point of generation. Calculation results yield a space- and time-resolved excitation
Computer simulation of electronic excitation in atomic collision cascades
Energy Technology Data Exchange (ETDEWEB)
Duvenbeck, A.
2007-04-05
The impact of an keV atomic particle onto a solid surface initiates a complex sequence of collisions among target atoms in a near-surface region. The temporal and spatial evolution of this atomic collision cascade leads to the emission of particles from the surface - a process usually called sputtering. In modern surface analysis the so called SIMS technology uses the flux of sputtered particles as a source of information on the microscopical stoichiometric structure in the proximity of the bombarded surface spots. By laterally varying the bombarding spot on the surface, the entire target can be scanned and chemically analyzed. However, the particle detection, which bases upon deflection in electric fields, is limited to those species that leave the surface in an ionized state. Due to the fact that the ionized fraction of the total flux of sputtered atoms often only amounts to a few percent or even less, the detection is often hampered by rather low signals. Moreover, it is well known, that the ionization probability of emitted particles does not only depend on the elementary species, but also on the local environment from which a particle leaves the surface. Therefore, the measured signals for different sputtered species do not necessarily represent the stoichiometric composition of the sample. In the literature, this phenomenon is known as the Matrix Effect in SIMS. In order to circumvent this principal shortcoming of SIMS, the present thesis develops an alternative computer simulation concept, which treats the electronic energy losses of all moving atoms as excitation sources feeding energy into the electronic sub-system of the solid. The particle kinetics determining the excitation sources are delivered by classical molecular dynamics. The excitation energy calculations are combined with a diffusive transport model to describe the spread of excitation energy from the initial point of generation. Calculation results yield a space- and time-resolved excitation
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)
Electron-impact excitation and ionization cross sections for ground state and excited helium atoms
International Nuclear Information System (INIS)
Ralchenko, Yu.; Janev, R.K.; Kato, T.; Fursa, D.V.; Bray, I.; Heer, F.J. de
2008-01-01
Comprehensive and critically assessed cross sections for the electron-impact excitation and ionization of ground state and excited helium atoms are presented. All states (atomic terms) with n≤4 are treated individually, while the states with n≥5 are considered degenerate. For the processes involving transitions to and from n≥5 levels, suitable cross section scaling relations are presented. For a large number of transitions, from both ground and excited states, convergent close coupling calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions, which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in graphical form
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
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.
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.
Atomic excitation and acceleration in strong laser fields
International Nuclear Information System (INIS)
Zimmermann, H; Eichmann, U
2016-01-01
Atomic excitation in the tunneling regime of a strong-field laser–matter interaction has been recently observed. It is conveniently explained by the concept of frustrated tunneling ionization (FTI), which naturally evolves from the well-established tunneling picture followed by classical dynamics of the electron in the combined laser field and Coulomb field of the ionic core. Important predictions of the FTI model such as the n distribution of Rydberg states after strong-field excitation and the dependence on the laser polarization have been confirmed in experiments. The model also establishes a sound basis to understand strong-field acceleration of neutral atoms in strong laser fields. The experimental observation has become possible recently and initiated a variety of experiments such as atomic acceleration in an intense standing wave and the survival of Rydberg states in strong laser fields. Furthermore, the experimental investigations on strong-field dissociation of molecules, where neutral excited fragments after the Coulomb explosion of simple molecules have been observed, can be explained. In this review, we introduce the subject and give an overview over relevant experiments supplemented by new results. (paper)
Hirshfeld atom refinement for modelling strong hydrogen bonds.
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.
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
Precision spectroscopy of the 2S-4P transition in atomic hydrogen
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.
Self-Regular Black Holes Quantized by means of an Analogue to Hydrogen Atoms
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.
Wagner, E P; Smith, B W; Winefordner, J D
1996-09-15
Laser-excited atomic fluorescence has been used to detect lead that was electrothermally atomized from whole blood in a graphite furnace. A 9 kHz repetition rate copper vapor laser pumped dye laser was used to excite the lead at 283.3 nm, and the resulting atomic fluorescence was detected at 405.8 nm. No matrix modification was used other than a 1:21 dilution of the whole blood with high-purity water. Using the atomic fluorescence peak area as the analytical measure and a background correction technique based upon a simultaneous measurement of the transmitted laser intensity, excellent agreement for NIST and CDC certified whole blood reference samples was obtained with aqueous standards. A limit of detection in blood of 10 fg/mL (100 ag absolute) was achieved.
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
Coupled-channels calculations of excitation and ionization in ion-atom collisions
International Nuclear Information System (INIS)
Martir, M.H.
1981-01-01
A numerical method has been used to compute excitation and ionization cross sections for ion-atom collisions. The projectile is treated classically and follows a straight line, constant velocity path (unless indicated otherwise). The wave function that describes the atom is expanded about the target in a truncated Hilbert space. The interaction between the projectile and the target atom is treated as a time dependent perturbation. A unitary time development operator, U, propagates the wave function from a time prior to the collision to a time after the collision in small time steps. Contrary to first-order theories, coupling between states is allowed. This method has been improved so that any number of partial waves can be included in the wave function expansion. This method has been applied to study negatively charged projectiles. Cross sections are obtained for collisions of antiprotons on atomic hydrogen (30 keV to 372 keV) and compared with cross sections of protons on atomic hydrogen to explore the Z/sub P/ dependence. The antiproton-hydrogen results were converted into electron-hydrogen values with E/sub e/ = E/sub P/(m/sub e//m/sub P/) (15 eV to 200 eV) and compared to experimental values. The method is then applied to study vacancy production from the L-shell. The partial wave convergence of the cross sections was carefully studied for s through g waves. Collisions between protons (and alpha-particles) and argon are studied to explore the Z/sub P/ dependence of the cross sections. The cross section ratio sigma(α)/(4sigma(p)) is compared to experiment
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
Penning ionization cross sections of excited rare gas atoms
International Nuclear Information System (INIS)
Ukai, Masatoshi; Hatano, Yoshihiko.
1988-01-01
Electronic energy transfer processes involving excited rare gas atoms play one of the most important roles in ionized gas phenomena. Penning ionization is one of the well known electronic energy transfer processes and has been studied extensively both experimentally and theoretically. The present paper reports the deexcitation (Penning ionization) cross sections of metastable state helium He(2 3 S) and radiative He(2 1 P) atoms in collision with atoms and molecules, which have recently been obtained by the authors' group by using a pulse radiolysis method. Investigation is made of the selected deexcitation cross sections of He(2 3 S) by atoms and molecules in the thermal collisional energy region. Results indicate that the cross sections are strongly dependent on the target molecule. The deexcitation probability of He(2 3 S) per collision increases with the excess electronic energy of He(2 3 S) above the ionization potential of the target atom or molecule. Another investigation, made on the deexcitation of He(2 1 P), suggests that the deexcitation cross section for He(2 1 P) by Ar is determined mainly by the Penning ionization cross section due to a dipole-dipole interaction. Penning ionization due to the dipole-dipole interaction is also important for deexcitation of He(2 1 P) by the target molecules examined. (N.K.)
Resonant excitation of uranium atoms by an argon ion laser
Energy Technology Data Exchange (ETDEWEB)
Maeyama, H; Morikawa, M; Aihara, Y; Mochizuki, T; Yamanaka, C [Osaka Univ. (Japan)
1979-03-01
Photoionization of uranium atoms by UV lines, 3511 A and 3345 A, of an argon ion laser was observed and attributed due to resonant two-photon ionization. The dependence of the photoion currents on laser power was measured in focusing and non-focusing modes of laser beam, which has enabled us to obtain an absorption cross section and an ionization cross section independently. The orders of magnitude of these cross sections averaged over the fine structure were determined to be 10/sup -14/ cm/sup 2/ and 10/sup -17/ cm/sup 2/ respectively from a rate equation model. Resonance between 3511-A laser line and the absorption line of uranium isotopes was also confirmed by the ionization spectra obtained by near-single-frequency operation of the ion laser, which allowed the isotopic selective excitation of the uranium atoms. The maximum value of the enrichment of /sup 235/U was about 14%. The isotope separation of uranium atoms by this resonant excitation has been discussed.
Excited Atoms and Molecules in High Pressure Gas Discharges
International Nuclear Information System (INIS)
Vuskovic, L.; Popovic, S.
2003-01-01
Various types of high-pressure non-thermal discharges are increasingly drawing attention in view of many interesting applications. These, partially ionized media in non-equilibrium state, tend to generate complex effects that are difficult to interpret without a detailed knowledge of elementary processes involved. Electronically excited molecules and atoms may play an important role as intermediate states in a wide range of atomic and molecular processes, many of which are important in high-pressure discharges. They can serve also as reservoirs of energy or as sources of high energy electrons either through the energy pooling or through superelastic collisions. By presenting the analysis of current situation on the processes involving excited atoms and molecules of interest for high-pressure gas discharges, we will attempt to draw attention on the insufficiency of available data. In the same time we will show how to circumvent this situation and still be able to develop accurate models and interpretations of the observed phenomena
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.
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)
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 ...
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
Simultaneous electron capture and excitation in ion-atom collisions
International Nuclear Information System (INIS)
Tanis, J.A.; Bernstein, E.M.; Graham, W.G.; Clark, M.; Shafroth, S.M.; Johnson, B.M.; Jones, K.; Meron, M.
1982-01-01
A review of recent efforts to observe simultaneous electron capture-and-K-shell excitation in ion-atom collisions is presented. This process which has been referred to as resonant-transfer-and-excitation (RTE), is qualitatively analogous to dielectronic recombination (inverse Auger transition) in free-electron-ion collisions, and, hence, is expected to be resonant. Experimentally, events having the correct signature for simultaneous capture-and-excitation are isolated by detecting projectile K x rays in coincidence with ions which capture a single electron. In a recent experiment involving 70-160 MeV S 13+ ions incident on Ar, a maximum was observed in the yield of projectile K x rays associated with electron capture. This maximum is attributed to simultaneous capture - and excitation. The position (120 MeV) and width (60 MeV) of the observed maximum are in good agreement with theoretical calculations. The data indicate that RTE is an important mechanism for inner-shell vacancy production in the energy range studied
The hydrogen atom in D = 3 - 2ɛ dimensions
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 .
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
Coherent captivity of population in gas of excited atoms
International Nuclear Information System (INIS)
Anisimov, P.M.; Akhmedzhanov, R.A.; Zelenskij, I.V.; Kolesov, R.L.; Kuznetsova, E.A.
2003-01-01
The coherent captivity of the population in the gaseous discharge on the transitions between the neon atoms excited levels is studied. The resonances, corresponding to the origination of the population coherent captivity in the Λ- and V-schemes on the Zeeman sublevels of the low and upper working states, were observed in the presence of the longitudinal magnetic field. The effect of the nonlinear rotation of the polarization plane under the conditions of the population coherent captivity was studied. The possibility of applying the results of the work for the diagnostics of the local magnetic fields and other plasma parameters in the gaseous discharges is considered [ru
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
Laser-excited atomic-fluorescence spectrometry with electrothermal tube atomization.
Vera, J A; Leong, M B; Stevenson, C L; Petrucci, G; Winefordner, J D
1989-12-01
The performance of graphite-tube electrothermal atomizers is evaluated for laser-excited atomic-fluorescence spectrometry for several elements. Three pulsed laser systems are used to pump tunable dye lasers which subsequently are used to excite Pb, Ga, In, Fe, Ir, and Tl atoms in the hot graphite tube. The dye laser systems used are pumped by nitrogen, copper vapour and Nd:YAG lasers. Detection limits in the femtogram and subfemtogram range are typically obtained for all elements. A commercial graphite-tube furnace is important for the successful utilization of the laser-based method when the determination of trace elements is intended, especially when complicated matrices may be present.
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-.
A model for the physical adsorption of atomic hydrogen
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
Atomic excitation and molecular dissociation by low energy electron collisions
International Nuclear Information System (INIS)
Weyland, Marvin
2016-01-01
In this work, momentum imaging experiments have been conducted for the electron impact excitation of metastable states in noble gases and for dissociative electron attachment (DEA) in polyatomic molecules. For the electron impact excitation study a new experimental technique has been developed which is able to measure the scattering angle distribution of the electrons by detection of the momentum transfer to the atoms. Momentum transfer images have been recorded for helium and neon at fixed electron impact energy close to the excitation threshold and good agreement with current R-matrix theory calculations was found. A new momentum imaging apparatus for negative ions has been built for the purpose of studying DEA in biologically relevant molecules. During this work, DEA was investigated in the molecules ammonia, water, formic acid, furan, pyridine and in two chlorofluorocarbons. Furthermore, the change of DEA resonance energies when molecules form clusters compared to monomers was investigated in ammonia and formic acid. The experimental results of most studied molecules could be compared to recent theoretical calculations and they support further development in the theoretical description of DEA. The new apparatus built in this work also delivered a superior momentum resolution compared to existing setups. This allows the momentum imaging of heavier fragments and fragments with lower kinetic energy.
Atomic excitation and molecular dissociation by low energy electron collisions
Energy Technology Data Exchange (ETDEWEB)
Weyland, Marvin
2016-11-16
In this work, momentum imaging experiments have been conducted for the electron impact excitation of metastable states in noble gases and for dissociative electron attachment (DEA) in polyatomic molecules. For the electron impact excitation study a new experimental technique has been developed which is able to measure the scattering angle distribution of the electrons by detection of the momentum transfer to the atoms. Momentum transfer images have been recorded for helium and neon at fixed electron impact energy close to the excitation threshold and good agreement with current R-matrix theory calculations was found. A new momentum imaging apparatus for negative ions has been built for the purpose of studying DEA in biologically relevant molecules. During this work, DEA was investigated in the molecules ammonia, water, formic acid, furan, pyridine and in two chlorofluorocarbons. Furthermore, the change of DEA resonance energies when molecules form clusters compared to monomers was investigated in ammonia and formic acid. The experimental results of most studied molecules could be compared to recent theoretical calculations and they support further development in the theoretical description of DEA. The new apparatus built in this work also delivered a superior momentum resolution compared to existing setups. This allows the momentum imaging of heavier fragments and fragments with lower kinetic energy.
Interactions of atomic hydrogen with amorphous SiO2
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.
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
Shannon entropy: A study of confined hydrogenic-like atoms
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.
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
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
Hong-Ou-Mandel Interference between Two Deterministic Collective Excitations in an Atomic Ensemble
Li, Jun; Zhou, Ming-Ti; Jing, Bo; Wang, Xu-Jie; Yang, Sheng-Jun; Jiang, Xiao; Mølmer, Klaus; Bao, Xiao-Hui; Pan, Jian-Wei
2016-10-01
We demonstrate deterministic generation of two distinct collective excitations in one atomic ensemble, and we realize the Hong-Ou-Mandel interference between them. Using Rydberg blockade we create single collective excitations in two different Zeeman levels, and we use stimulated Raman transitions to perform a beam-splitter operation between the excited atomic modes. By converting the atomic excitations into photons, the two-excitation interference is measured by photon coincidence detection with a visibility of 0.89(6). The Hong-Ou-Mandel interference witnesses an entangled NOON state of the collective atomic excitations, and we demonstrate its two times enhanced sensitivity to a magnetic field compared with a single excitation. Our work implements a minimal instance of boson sampling and paves the way for further multimode and multiexcitation studies with collective excitations of atomic ensembles.
Positron impact excitation (n = 2 states) of hydrogen at 20 eV
Energy Technology Data Exchange (ETDEWEB)
Kamali, M. Z. M.; Ratnavelu, K. [University of Malaya, Kuala Lumpur (Malaysia)
2011-10-15
The calculation of accurate differential cross sections (DCS) has always posed a litmus test for theoretical models. Among the positron-atom scattering systems, the positron-hydrogen (e{sup +}-H) atom system is the fundamental prototype. Thus, the present work utilizes 12- and 15-states coupled channel optical method (CCOM) calculations to study the DCS H(2s+2p) excitation, together with the angular correlation parameters ({lambda}(2p)), for the e{sup +}-H system at 20 eV, but up to now, there have been no measurements yet on the DCS for this system. A comparison is done with other theoretical and experimental works, including the electron case.
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
Plasmon excitations in doped square-lattice atomic clusters
Wang, Yaxin; Yu, Ya-Bin
2017-12-01
Employing the tight-binding model, we theoretically study the properties of the plasmon excitations in doped square-lattice atomic clusters. The results show that the dopant atoms would blur the absorption spectra, and give rise to extra plasmon resonant peaks as reported in the literature; however, our calculated external-field induced oscillating charge density shows that no obvious evidences indicate the so-called local mode of plasmon appearing in two-dimensional-doped atomic clusters, but the dopants may change the symmetry of the charge distribution. Furthermore, we show that the disorder of the energy level due to dopant makes the absorption spectrum has a red- or blue-shift, which depends on the position of impurities; disorder of hopping due to dopant makes a blue- or red-shift, a larger (smaller) hopping gives a blue-shift (red-shift); and a larger (smaller) host-dopant and dopant-dopant intersite coulomb repulsion induces a blue-shift (red-shift).
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
Behavior of ro-vibrationally excited H2 molecules and H atoms in a plasma expansion
International Nuclear Information System (INIS)
Vankan, P.; Schram, D.C.; Engeln, R.
2005-01-01
The behavior in a supersonic plasma expansion of H atom and H2 molecules, both ground-state and ro-vibrationally excited, is studied using various laser spectroscopic techniques. The ground-state H2 molecules expand like a normal gas. The behavior of H atoms and H 2 rv molecules, on the other hand, is considerably influenced, and to some extend even determined, by their reactivity. The H atoms diffuse out of the expansion due to surface association at the walls of the vacuum vessel. Moreover, by reducing the surface area of the nozzle by a factor of two, the amount of H atoms leaving the source is increased by one order of magnitude, due to a decreased surface association of H atoms in the nozzle. The evolution of the ro-vibrational distributions along the expansion axis shows the relaxation of the molecular hydrogen from the high temperature in the up-stream region to the low ambient temperature in the down-stream region. Whereas the vibrational distribution resembles a Boltzmann distribution, the rotational distribution is a non-equilibrium one, in which the high rotational levels (J > 7) are much more populated than what is expected from the low rotational levels (J <5). We observed overpopulations of up to seven orders of magnitude. The production of the high rotational levels is very probably connected to the surface association in the nozzle
International Nuclear Information System (INIS)
Gao Xiang; Cheng Cheng; Li Jiaming
2011-01-01
Scientific research fields for future energies such as inertial confinement fusion researches and astrophysics studies especially with satellite observatories advance into stages of precision physics. The relevant atomic data are not only enormous but also of accuracy according to requirements, especially for both energy levels and the collision data. The fine structure of high excited states of atoms and ions can be measured by precision spectroscopy. Such precision measurements can provide not only knowledge about detailed dynamics of electron-ion interactions but also a bench mark examination of the accuracy of electron-ion collision data, especially incorporating theoretical computations. We illustrate that by using theoretical calculation methods which can treat the bound states and the adjacent continua on equal footing. The precision spectroscopic measurements of excited fine structures can be served as stringent tests of electron-ion collision data. (authors)
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.
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
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
Analysis of Atomic Electronic Excitation in Nonequilibrium Air Plasmas
International Nuclear Information System (INIS)
He Xin; Jia Hong-Hui; Yin Hong-Wei; Zhang Hai-Liang; Chang Sheng-Li; Yang Jun-Cai; Dang Wei-Hua
2014-01-01
Electronic excitation of atoms is studied in nonequilibrium air plasmas with the electronic temperature between 8000 K and 20000 K. By using the modified Saha—Boltzmann equation, our simplified method takes into account significant radiative processes and strong self-absorption of the vacuum ultraviolet lines. Calculations are carried out at three trajectory points of the Fire II flight experiment. Good agreement with the detailed collisional-radiative model is obtained, and the performance of this method in applications to highly nonequilibrium conditions is better than Park's quasi-steady-state model and Spradian-9.0. A short discussion on the influence of optical thickness of the vacuum ultraviolet radiation is also given. It costs about 2.9 ms on the average to solve one cell of the shock layer on a low cost computer, which shows that the present method is fast and efficient. (physics of gases, plasmas, and electric discharges)
Electron transfer, ionization, and excitation in atomic collisions
International Nuclear Information System (INIS)
Winter, T.G.; Alston, S.G.
1992-01-01
The research being carried out at Penn State by Winter and Alston addresses the fundamental processes of electron transfer, ionization, and excitation in ion-atom (and ion-ion) collisions. The focus is on intermediate- and higher-energy collisions, corresponding to proton energies of about 25 kilo-electron-volts (keV) or larger. At intermediate energies, where the transition probabilities are not small, many states must be coupled in a large calculation, while at higher energies, perturbative approaches may be used. Several studies have been carried out in the current three-year period; most of these treat systems with only one or two electrons, so that fewer approximations need be made and the basic collisional mechanisms can be more clearly described
[Electron transfer, ionization, and excitation in atomic collisions
International Nuclear Information System (INIS)
1992-01-01
Fundamental processes of electron transfer, ionization, and excitation in ion-atom and ion-ion collisions are studied. Attention is focussed on one- and two-electron systems and, more recently, quasi-one-electron systems whose electron-target-ion core can be accurately modeled by one-electron potentials. The basic computational approaches can then be taken with few, if any, approximations, and the underlying collisional mechanisms can be more clearly revealed. At intermediate collision energies (e.g., proton energies for p-He + collisions on the order of 100 kilo-electron volts), many electronic states are strongly coupled during the collision, a coupled-state approach, such as a coupled-Sturmian-pseudostate approach, is appropriate. At higher collision energies (million electron-volt energies) the coupling is weaker with, however, many more states being coupled together, so that high-order perturbation theory is essential
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)
Electron-impact excitation of complex atoms and ions
International Nuclear Information System (INIS)
Burke, P.G.; Burke, V.M.; Dunseath, K.M.
1994-01-01
A new R-matrix approach for calculating cross sections and rate coefficients for electron-impact excitation of complex atoms and ions is described. This approach, based on an expansion of the total wavefunction in target configurations rather than in individual target states and taking advantage of the special status of the scattered electron in the collisional wavefunction, enables the angular integrals to be performed very much more efficiently than hitherto. It also enables electron correlation effects in the target and in the electron-target collision complex to be treated consistently, eliminating pseudo-resonances which have caused serious difficulties in some earlier work. A major new program package RMATRIX II has been written that implements this approach and, as an example, electron-impact excitation of Fe 2+ is considered where the four target configurations 3d 6 , 3d 5 4s, 3d 5 4p and 3d 5 4d are retained in the expansion of the total wavefunction. RMATRIX II is compared with the standard R-matrix program package and is found to be much more efficient showing that accurate electron scattering calculations involving complex targets, such as the astrophysically important low ionization stages of iron-peak elements, are now possible. (author)
Excited-atom production by electron and ion bombardment of alkali halides
International Nuclear Information System (INIS)
Walkup, R.E.; Avouris, P.; Ghosh, A.P.
1987-01-01
We present experimental results on the production of excited atoms by electron and ion bombardment of alkali halides. For the case of electron bombardment, Doppler shift measurements show that the electronically excited atoms have a thermal velocity distribution in equilibrium with the surface temperature. Measurements of the absolute yield of excited atoms, the distribution of population among the excited states, and the systematic dependence on incident electron current and sample temperature support a model in which the excited atoms are produced by gas-phase collisions between desorbed ground-state atoms and secondary electrons. In contrast, for the case of ion bombardment, the excited atoms are directly sputtered from the surface, with velocity distributions characteristic of a collision cascade, and with typical energies of --10 eV
International Nuclear Information System (INIS)
Aucelio, R.Q.; Smith, B.W.; Winefordner, J.D.
1998-01-01
A dye laser pumped by a high-repetition-rate copper vapor laser was used as the excitation source to determine indium at parts-per-trillion level by electrothermal atomization laser-excited atomic fluorescence spectrometry (ETA-LEAFS). A comparison was made between wall atomization, in pyrolytic and nonpyrolytic graphite tubes, and platform atomization. The influence of several chemical modifiers either in solution or precoated in the graphite tube was evaluated. The influence of several acids and NaOH in the analyte solution was also studied. Optimization of the analytical conditions was carried out to achieve the best signal-to-background ratio and consequently an absolute limit of detection of 1 fg. Some possible interferents of the method were evaluated. The method was evaluated by determining indium in blood, urine, soil, and urban dust samples. Recoveries between 99.17 and 109.17% are reported. A precision of 4.1% at the 10 ng g -1 level in water standards was achieved. copyright 1998 Society for Applied Spectroscopy
Selective excitation of atoms or molecules to high-lying states
International Nuclear Information System (INIS)
Ducas, T.W.
1978-01-01
This specification relates to the selective excitation of atoms or molecules to high lying states and a method of separating different isotopes of the same element by selective excitation of the isotopes. (U.K.)
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.)
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
Relativistic Hydrogen-Like Atom on a Noncommutative Phase Space
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.
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.)
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
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)
The Confined Hydrogen Atom with a Moving Nucleus
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…
Variational Perturbation Treatment of the Confined Hydrogen Atom
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…
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 ...
Quantum-Classical Connection for Hydrogen Atom-Like Systems
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…
The EAGLE simulations: atomic hydrogen associated with galaxies
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
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)
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)
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 ...
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.
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-.
International Nuclear Information System (INIS)
Kawaguchi, Hiroshi
1996-01-01
Studies on inductively coupled plasma (ICP) for atomic emission and mass spectrometry accomplished in our laboratory since 1978 are reviewed. In emission spectrometry, the characteristics of the plasma are studied concerning the spatial profiles of spectral line intensity, axial profiles of gas and excitation temperatures, spectral line widths and matrix effect. The studies are particularly emphasized on the instrumentation such as developments of plasma generator, emission spectrometers, water-cooled torches and sample introduction methods. A slew-scan type spectrometer developed in these works represents a predecessor of the current commercial spectrometers. An ICP mass spectrometer was first developed in Japan in this laboratory in 1984. Non-spectroscopic interference of this method was found to have the correlation with the atomic weight of the matrix element. Plasma gases other than argon such as nitrogen and oxygen were used for the ICP to evaluate their performance in mass spectrometry as for the sensitivity and interferences. (author). 63 refs
Partial radiative recombination cross sections for excited states of hydrogen
International Nuclear Information System (INIS)
Fazio, P.M.
1984-01-01
In calculating the radiative recombination cross sections for interstellar H II regions, usually only the electric dipole term in the expansion of the interaction Hamiltonian is kept. The dipole and quadrupole transition strengths in closed analytical form are calculated here using the Coulomb wave functions because results for any electron energy and for recombination into any angular momentum state of hydrogen are needed. Several interesting effects are found. First, the transition probabilities are maximum for recombination into specific intermediate angular momentum states at low energies (w < 2eV) and where the free state angular momentum is greater than that of the bound state. Further, that specific intermediate angular momentum state depends on the kinetic energy of the free electron. This behavior is in contrast to the normal behavior of the transition strengths where recombination into s states is greatest and decreases with increasing angular momentum. Second, the quadrupole matrix elements vanish for certain velocities of the free electron. This leads to minima in the corresponding quadrupole cross sections when plotted as a function of the free electron's kinetic energy. Finally, the partial cross sections for highly excited states are greater than previously calculated because of the additional effects of the quadrupole transitions
Winters, C.; Eckert, Z.; Yin, Z.; Frederickson, K.; Adamovich, I. V.
2018-01-01
This work presents the results of number density measurements of metastable Ar atoms and ground state H atoms in diluted mixtures of H2 and O2 with Ar, as well as ground state O atoms in diluted H2-O2-Ar, CH4-O2-Ar, C3H8-O2-Ar, and C2H4-O2-Ar mixtures excited by a repetitive nanosecond pulse discharge. The measurements have been made in a nanosecond pulse, double dielectric barrier discharge plasma sustained in a flow reactor between two plane electrodes encapsulated within dielectric material, at an initial temperature of 500 K and pressures ranging from 300 Torr to 700 Torr. Metastable Ar atom number density distribution in the afterglow is measured by tunable diode laser absorption spectroscopy, and used to characterize plasma uniformity. Temperature rise in the reacting flow is measured by Rayleigh scattering. H atom and O atom number densities are measured by two-photon absorption laser induced fluorescence. The results are compared with kinetic model predictions, showing good agreement, with the exception of extremely lean mixtures. O atoms and H atoms in the plasma are produced mainly during quenching of electronically excited Ar atoms generated by electron impact. In H2-Ar and O2-Ar mixtures, the atoms decay by three-body recombination. In H2-O2-Ar, CH4-O2-Ar, and C3H8-O2-Ar mixtures, O atoms decay in a reaction with OH, generated during H atom reaction with HO2, with the latter produced by three-body H atom recombination with O2. The net process of O atom decay is O + H → OH, such that the decay rate is controlled by the amount of H atoms produced in the discharge. In extra lean mixtures of propane and ethylene with O2-Ar the model underpredicts the O atom decay rate. At these conditions, when fuel is completely oxidized by the end of the discharge burst, the net process of O atom decay, O + O → O2, becomes nearly independent of H atom number density. Lack of agreement with the data at these conditions is
The character of resonant charge exchange involving highly excited atoms
International Nuclear Information System (INIS)
Kosarim, A. V.; Smirnov, B. M.; Capitelli, M.; Laricchiuta, A.
2012-01-01
We study the process of resonant charge exchange involving excited helium atoms with the principal quantum number n = 5 colliding with the helium ion in the ground state in the collision energy range from thermal up to 10 eV. This information may be important for the analysis of planet atmospheres containing helium, in particular, for Jupiter’s atmosphere, but our basic interest is the transition from the quantum to classical description of this process, where, due to large cross sections, evaluations of the cross sections are possible. For the chosen process, quantum theory allows determining the cross section as a result of a tunnel electron transition, while classical theory accounts for over-barrier electron transitions. The classical theory additionally requires effective transitions between states with close energies. The analysis of these transitions for helium with n = 5 shows that electron momenta and their projections are mixed for a part of the states, while for other states, the mixing is absent. A simple criterion to separate such states is given. In addition, the main contribution to the cross section of resonant charge exchange follows from tunnel electron transitions. As a result, the quantum theory is better for calculating the cross sections of resonant charge exchange than the classical one and also allows finding the partial cross sections of resonant charge exchange, while the classical approach gives the cross section of resonant charge exchange in a simple manner with the accuracy of 20%.
The Rydberg constant and proton size from atomic hydrogen
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.
Relativistic Transitions in the Hydrogenic Atoms
Boudet, R
2009-01-01
When one approaches the study of the quantal relativistic theory of the electron, one may be surprised by the gap which lies between the frame of the experiments, i.e. the real geometry of the space and time, and the abstraction of the complex matrices and spinors formalism employed in the presentation of the theory. This book uses a theory of the electron, introduced by David Hestenes, in which the mathematical language is the same as the one of the geometry of the space and time. Such a language not only allows one to find again the well known results concerning the one-electron atoms theory but furthermore leads easily to the resolution of problems considered for a long time without solution.
Dissociative excitation of lithium atom in electron collisions with LiBr molecules
International Nuclear Information System (INIS)
Smirnov, Yu.M.
1998-01-01
Effective cross sections of the lithium atom dissociative excitation in electron collisions with the LiBr molecules are measured. The measurement error equals 5-12%. The optical functions of the lithium atom dissociative excitation are calculated on the basis of the data obtained
Reactivity and Catalytic Activity of Hydrogen Atom Chemisorbed Silver Clusters.
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.
Charge transfer and excitation in high-energy ion-atom collisions
International Nuclear Information System (INIS)
Schlachter, A.S.; Berkner, K.H.; McDonald, R.J.
1986-11-01
Coincidence measurements of charge transfer and simultaneous projectile electron excitation provide insight into correlated two-electron processes in energetic ion-atom collisions. Projectile excitation and electron capture can occur simultaneously in a collision of a highly charged ion with a target atom; this process is called resonant transfer and excitation (RTE). The intermediate excited state which is thus formed can subsequently decay by photon emission or by Auger-electron emission. Results are shown for RTE in both the K shell of Ca ions and the L shell of Nb ions, for simultaneous projectile electron loss and excitation, and for the effect of RTE on electron capture
Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm
Herring, G. C.; Dyer, Mark J.; Jusinski, Leonard E.; Bischel, William K.
1988-01-01
Two-photon-excited fluorescence spectroscopy of atomic fluorine is reported. A doubled dye laser at 286-nm is Raman shifted in H2 to 170 nm (sixth anti-Stokes order) to excite ground-state 2P(0)J fluorine atoms to the 2D(0)J level. The fluorine atoms are detected by one of two methods: observing the fluorescence decay to the 2PJ level or observing F(+) production through the absorption of an additional photon by the excited atoms. Relative two-photon absorption cross sections to and the radiative lifetimes of the 2D(0)J states are measured.
Electron-impact ionization of atomic hydrogen
Energy Technology Data Exchange (ETDEWEB)
Baertschy, Mark D. [Univ. of California, Davis, CA (United States)
2000-02-01
Since the invention of quantum mechanics, even the simplest example of collisional breakup in a system of charged particles, e^{-} + H → H^{+} + e^{-} + e^{+}, has stood as one of the last unsolved fundamental problems in atomic physics. A complete solution requires calculating the energies and directions for a final state in which three charged particles are moving apart. Advances in the formal description of three-body breakup have yet to lead to a viable computational method. Traditional approaches, based on two-body formalisms, have been unable to produce differential cross sections for the three-body final state. Now, by using a mathematical transformation of the Schrodinger equation that makes the final state tractable, a complete solution has finally been achieved, Under this transformation, the scattering wave function can be calculated without imposing explicit scattering boundary conditions. This approach has produced the first triple differential cross sections that agree on an absolute scale with experiment as well as the first ab initio calculations of the single differential cross section.
Electron-impact ionization of atomic hydrogen
International Nuclear Information System (INIS)
Baertschy, Mark D.
2000-01-01
Since the invention of quantum mechanics, even the simplest example of collisional breakup in a system of charged particles, e - + H -> H + + e - + e - , has stood as one of the last unsolved fundamental problems in atomic physics. A complete solution requires calculating the energies and directions for a final state in which three charged particles are moving apart. Advances in the formal description of three-body breakup have yet to lead to a viable computational method. Traditional approaches, based on two-body formalisms, have been unable to produce differential cross sections for the three-body final state. Now, by using a mathematical transformation of the Schrodinger equation that makes the final state tractable, a complete solution has finally been achieved, Under this transformation, the scattering wave function can be calculated without imposing explicit scattering boundary conditions. This approach has produced the first triple differential cross sections that agree on an absolute scale with experiment as well as the first ab initio calculations of the single differential cross section
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
International Nuclear Information System (INIS)
Heitmann, U.; Hese, A.; Schoknecht, G.; Gries, W.
1995-01-01
The high sensitivity detection of the trace element selenium is reported. The analytical method applied is Laser Excited Atomic Fluorescence Spectrometry using Electrothermal Atomization within a graphite furnace atomizer. For the production of tunable laser radiation in the VUV spectral region a laser system was developed which consists of two dye lasers pumped by a Nd:YAG laser. The laser radiations are subsequently frequency doubled and sum frequency mixed by nonlinear optical KDP or BBO crystals, respectively. The system works with a repetition rate of 20 Hz and provides output energies of up to 100 μJ in the VUV at a pulse duration of 5 ns. The analytical investigations were focused on the detection of selenium in aqueous solutions and samples of human whole blood. From measurements on aqueous standards detection limits of 1.5 ng/l for selenium were obtained, with corresponding absolute detected masses of only 15 fg. The linear dynamic range spanned six orders of magnitude and good precision was achieved. In case of human whole blood samples the recovery was found to be within the range of 96% to 104%. The determination of the selenium content yielded medians of [119.5 ± 17.3] μg/l for 200 frozen blood samples taken in 1988 and [109.1 ± 15.6] μg/l for 103 fresh blood samples. (author)
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
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
Energy Technology Data Exchange (ETDEWEB)
Ravi Kumar, Venkatraman; Ariese, Freek; Umapathy, Siva, E-mail: umapathy@ipc.iisc.ernet.in [Inorganic and Physical Chemistry Department, Indian Institute of Science, Bangalore 560012 (India)
2016-03-21
The solvent plays a decisive role in the photochemistry and photophysics of aromatic ketones. Xanthone (XT) is one such aromatic ketone and its triplet-triplet (T-T) absorption spectra show intriguing solvatochromic behavior. Also, the reactivity of XT towards H-atom abstraction shows an unprecedented decrease in protic solvents relative to aprotic solvents. Therefore, a comprehensive solvatochromic analysis of the triplet-triplet absorption spectra of XT was carried out in conjunction with time dependent density functional theory using the ad hoc explicit solvent model approach. A detailed solvatochromic analysis of the T-T absorption bands of XT suggests that the hydrogen bonding interactions are different in the corresponding triplet excited states. Furthermore, the contributions of non-specific and hydrogen bonding interactions towards differential solvation of the triplet states in protic solvents were found to be of equal magnitude. The frontier molecular orbital and electron density difference analysis of the T{sub 1} and T{sub 2} states of XT indicates that the charge redistribution in these states leads to intermolecular hydrogen bond strengthening and weakening, respectively, relative to the S{sub 0} state. This is further supported by the vertical excitation energy calculations of the XT-methanol supra-molecular complex. The intermolecular hydrogen bonding potential energy curves obtained for this complex in the S{sub 0}, T{sub 1}, and T{sub 2} states support the model. In summary, we propose that the different hydrogen bonding mechanisms exhibited by the two lowest triplet excited states of XT result in a decreasing role of the nπ{sup ∗} triplet state, and are thus responsible for its reduced reactivity towards H-atom abstraction in protic solvents.
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
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
Systematics in Rydberg state excitations for ion-atom collisions
International Nuclear Information System (INIS)
Andresen, B.; Jensen, K.; Petersen, N.B.; Veje, E.
1976-01-01
Rydberg state excitations in the Ne + , Mg + -He collisions have been studied in the projectile energy range 10-75 keV by means of optical spectrometry in a search for systematic trends. The relative excitation cross sections for levels of a Rydberg term series are found to follow a general (nsup(x))sup(P) behaviour with P < approximately -3 varying with collision energy and particles, regardless of whether the excited state population results from direct excitation, single electron transfer, or double electron transfer. At higher collision energies P is approximately -3 as predicted by theory. Polarization of the emitted line radiation indicates that there is no general rule for the relative excitation of the different magnetic substates of the same level. A statistical distribution of excitation is found for levels within the same term when the fine structure splitting is small. (Auth.)
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
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
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.
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.
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.
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
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)
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)
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.
Population dynamics of excited atoms in non-Markovian environments at zero and finite temperature
International Nuclear Information System (INIS)
Zou Hong-Mei; Fang Mao-Fa
2015-01-01
The population dynamics of a two-atom system, which is in two independent Lorentzian reservoirs or in two independent Ohmic reservoirs respectively, where the reservoirs are at zero temperature or finite temperature, is studied by using the time-convolutionless master-equation method. The influences of the characteristics and temperature of a non-Markovian environment on the population of the excited atoms are analyzed. We find that the population trapping of the excited atoms is related to the characteristics and the temperature of the non-Markovian environment. The results show that, at zero temperature, the two atoms can be effectively trapped in the excited state both in the Lorentzian reservoirs and in the Ohmic reservoirs. At finite temperature, the population of the excited atoms will quickly decay to a nonzero value. (paper)
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)
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
The atomic hydrogen cloud in the saturnian system
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.
Anisotropy of electronic states excited in ion-atom collisions
International Nuclear Information System (INIS)
Boskamp, E.B.
1983-01-01
The author reports coincidence measurements made on the He + + Ne and He + + He systems. The complex population amplitudes for the magnetic sublevels of the investigated excited states, Ne(2p 4 3s 2 ) 1 D and He(2p 2 ) 1 D, were completely determined and possible excitation mechanisms are described. (Auth.)
Near-field excitation exchange between motionless point atoms located near the conductive surface
Kuraptsev, Aleksei S.; Sokolov, Igor M.
2018-04-01
On the basis of quantum microscopic approach we study the excitation dynamics of two motionless point atoms located near the perfectly conducting mirror. We have analyzed the spontaneous decay rate of individual atoms near the mirror as well as the strength of dipole-dipole interaction between different atoms. It is shown that the spontaneous decay rate of an excited atom significantly depends on the distance from this atom to the mirror. In the case when the interatomic separation is less or comparable with the wavelength of resonant radiation, the spontaneous decay dynamics of an excited atom is described by multi-exponential law. It depends both the interatomic separation and the spatial orientation of diatomic quasimolecule.
International Nuclear Information System (INIS)
Seo, M; Shimamura, T; Furutani, T; Hasuo, M; Bahrim, C; Fujimoto, T
2003-01-01
Disalignment of neon excited atoms in the fine-structure 2p i levels (in Paschen notation) of the 2p 5 3p configuration is investigated in a helium-neon glow discharge at temperatures between 15 and 77 K. At several temperatures, we plot the disalignment rate as a function of the helium atom density for Ne* (2p 2 or 2p 7 ) + He(1s 2 ) collisions. The slope of this dependence gives the disalignment rate coefficient. For both collisions, the experimental data for the disalignment rate coefficient show a more rapid decrease with the decrease in temperature below 40 K than our quantum close-coupling calculations based on the model potential of Hennecart and Masnou-Seeuws (1985 J. Phys. B: At. Mol. Phys. 18 657). This finding suggests that the disalignment cross section rapidly decreases below a few millielectronvolts, in disagreement with our theoretical quantum calculations which predict a strong increase below 1 meV. The disagreement suggests that the long-range electrostatic potentials are significantly more repulsive than in the aforementioned model
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.)
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.
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.
The effect of atoms excited by electron beam on metal evaporation
Xie Guo Feng; Ying Chun Tong
2002-01-01
In atomic vapor laser isotope separation (AVLIS), the metal is heated to melt by electron beams. The vapor atoms may be excited by electrons when flying through the electron beam. The excited atoms may be deexcited by inelastic collision during expansion. The electronic energy transfers translational energy. In order to analyse the effect of reaction between atoms and electron beams on vapor physical parameters, such as density, velocity and temperature, direct-simulation Monte Carlo method (DSMC) is used to simulate the 2-D gadolinium evaporation from long and narrow crucible. The simulation results show that the velocity and temperature of vapor increase, and the density decreases
Low-energy scattering of excited helium atoms by rare gases
International Nuclear Information System (INIS)
Peach, G.
1978-01-01
The construction of semi-empirical model potentials for systems composed of helium in an excited state (Hestar) and a rare-gas atom (He or Ne) is described. The model of the atom-atom pair which has been adopted is one in which the excited electron is included explicitly, but the residual He + ion and the rare-gas atom are treated simply as cores which may be polarised. The results obtained are in satisfactory agreement with other calculations where they are available. (author)
Charge-state-distributions of foil-excited heavy Rydberg atoms
International Nuclear Information System (INIS)
Faibis, A.; Kanter, E.P.; Koenig, W.; Zabransky, B.J.
1985-01-01
Studies of foil-excited fast (MeV/amu) heavy ions have demonstrated large yields of high Rydberg atoms formed in such beams. Further experiments have suggested a strong target-thickness dependence of the yields of such atoms. These results have been puzzling in view of the supposed short mean free paths of such atoms in solids. In an effort to better understand these results, the authors have measured the yields of Rydberg atoms (napprox.100-200) in foil-excited 32 S ions at an incident energy of 125 MeV
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
Structure of the Balmer jump. The isolated hydrogen atom
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.
Compilation of excitation cross sections for He atoms by electron impact
International Nuclear Information System (INIS)
Kato, T.; Itikawa, Y.; Sakimoto, K.
1992-03-01
Experimental and theoretical data are compiled on the cross section for the excitation of He atoms by electron impact. The available data are compared graphically. The survey of the literature has been made through the end 1991. (author)
Generalized Bethe-Negele inequalities for excited states in muonic atoms
International Nuclear Information System (INIS)
Klarsfeld, S.
1976-11-01
Rigorous upper and lower bounds are derived for the Bethe logarithms in excited states of muonic atoms. Comparison with previous empirical estimates shows that the latter are inadequate in certain cases
International Nuclear Information System (INIS)
Kimura, M.; Rice Univ., Houston, TX
1990-01-01
The two-electron capture or excitation process resulting from collisions of H + and O 6+ ions with He atoms in the energy range from 0.5 keV/amu to 5 keV/amu is studied within a molecular representation. The collision dynamics for formation of doubly excited O 4+ ions and He** atoms and their (n ell, n'ell ') populations are analyzed in conjunction with electron correlations. Autoionizing states thus formed decay through the Auger process. An experimental study of an ejected electron energy spectrum shows ample structures in addition to two characteristic peaks that are identified by atomic and molecular autoionizations. These structures are attributable to various interferences among electronic states and trajectories. We examine the dominant sources of the interferences. 12 refs., 5 figs
Investigation of dye laser excitation of atomic systems
International Nuclear Information System (INIS)
Abate, J.A.
1977-01-01
A stabilized cw dye laser system and an optical pumping scheme for a sodium atomic beam were developed, and the improvements over previously existing systems are discussed. A method to stabilize both the output intensity and the frequency of the cw dye laser for periods of several hours is described. The fluctuation properties of this laser are investigated by photon counting and two-time correlation measurements. The results show significant departures from the usual single-mode laser theory in the region of threshold and below. The implications of the deviation from accepted theory are discussed. The atomic beam system that was constructed and tested is described. A method of preparing atomic sodium so that it behaves as a simple two-level atom is outlined, and the results of some experiments to study the resonant interaction between the atoms and the dye laser beam are presented
Spontaneous light emission by atomic hydrogen: Fermi's golden rule without cheating
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.
International Nuclear Information System (INIS)
Ho, Yew Kam; Lin, Chien-Hao
2015-01-01
In this work, we study the quantum entanglement for doubly excited resonance states in two-electron atomic systems such as the H - and Ps - ions and the He atom by using highly correlated Hylleraas type functions The resonance states are determined by calculation of density of resonance states with the stabilization method. The spatial (electron-electron orbital) entanglement entropies (linear and von Neumann) for the low-lying doubly excited states are quantified using the Schmidt-Slater decomposition method. (paper)
Anisotropy in the simultaneous excitation of two colliding atoms to various substate combinations
International Nuclear Information System (INIS)
Moorman, L.
1987-01-01
In this thesis double-atom excitation (DAE) processes in atomic collision experiments are studied by measuring the angular correlation of two coincident photons emitted by both excited collision particles. The analytical expression for the angular correlation function is derived which contains as adjustable parameters the various (complex) excitation amplitudes integrated over all scattering angles. The He+He system is investigated, for projectile energies between 0.5 and 3.5 keV, in which both particles are excited simultaneously to the 2 1 P state. The relation between photon correlations and atomic state correlations is investigated and the density matrix elements are calculated for a statistical distribution of the excited atomic substates into which a certain symmetry is incorporated. Collisions between metastable and groundstate He atoms are considered. Single-photon spectra are presented and compared with spectra from the He+He collision system. Coincidence measurements were performed on these collision systems to study possible double-atom excitations. Coincidences between two ultraviolet as well as an ultraviolet and a visible photon were measu0515 Also a measurement is reported of the relative population of the magnetic substates of the 3 1 D state of helium. Coincidence measurements on two ultraviolet photons emitted upon Ne-Ne and He-Ne collisions are described and the double-atom excitations for these systems are studied. For Ne+Ne no coincidence peaks were found. For He+Ne double-atom excitation was observed and from the measured angular correlations the corresponding density matrix elements for some kinetic energies of the projectile. (Auth.)
Interference between radiative emission and autoionization in the decay of excited states of atoms
International Nuclear Information System (INIS)
Armstrong, L. Jr.; Theodosiou, C.E.; Wall, M.J.
1978-01-01
An excited state of an atom which can autoionize can also undergo radiative decay. We consider the interaction between the final states resulting from these two modes of decay, and its effects on such quantities as the fluorescence yield of the excited state, excitation profile of the excited state, and the spectra of the emitted photons and electrons. It is shown that the fraction of decays of the excited state resulting in a photon (fluorescence yield) is particularly sensitive to the details of the final-state interaction. In lowest order in the final-state interaction, the fluorescence yield is increased by a factor (1 + 1/q 2 ) from the traditional value, where q is the Fano q parameter relating to the excited state and the final atomic state
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
Electron-impact excitation of the potassium atom
International Nuclear Information System (INIS)
Phelps, J.O.; Solomon, J.E.; Korff, D.F.; Lin, C.C.; Lee, E.T.P.
1979-01-01
Absolute optical electron-impact excitation functions for 24 transitions of the sharp, principal, diffuse, and fundamental spectral series of potassium have been measured. The determination of the density of the potassium vapor in the collision chamber was made by measuring the degree of transmission, by the vapor, of potassium resonance radiation generated externally in a fluorescence cell. Direct excitation functions were determined for 14 states (5S, 6S, 7S, 8S, 4P, 5P, 6P, 7P, 3D, 5D, 6D, 5F, 6F, and 7F) with the aid of known radiative-transition probabilities. Theoretical calculations of these same 14 excitation functions, as well as 4D and 4F, were carried out by means of the Born approximation. The 4P, 5P, 5S, 3D, and 4D direct excitation functions at intermediate energies (10--25 eV) were also calculated by the method of multistate close coupling, neglecting projectile--target-electron exchange. The high-energy (above 100 eV) Born-approximation cross sections agree with the experimental results for 4P and for all S states, but are lower than experimental results, by 30--40%, for the D and F states. At intermediate energies the close-coupling excitation calculations agree well with the experimental excitation functions for 4P and 5P, but are significantly higher than experimental values for 5S and 3D. The discrepancies between the experimental and theoretical results are probably due to a combination of systematic experimental errors, errors in the available transition-probability values, and errors in the theoretical excitation functions introduced by the use of approximate excited-state wave functions (Hartree-Fock-Slater), by the neglect of projectile--target-electron exchange. The polarization of the 4P-4S and 3D-4P radiation produced by electron impact was measured, and the results were used to determine the direct excitation functions of the separate magnetic sublevels of the 4P state
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
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
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.
International Nuclear Information System (INIS)
Almaliev, A.N.; Batkin, I.S.; Kopytin, I.V.
1987-01-01
The process of exciting atoms and atomic nuclei by relativistic electrons and positrons bound in a one-dimensional potential is investigated theoretically. It is shown that a pole corresponding to the emergence of a virtual photon on a bulk surface occurs in the matrix interaction element under definite kinematic relationships. It is obtained that the probability of the excitation process depends on the lifetime of the level being excited, the virtual photon, and the charged particle in a definite energetic state. An estimate of the magnitude of the excitation section of low-lying nuclear states yields a value exceeding by several orders the section obtained for charged particles in the absence of a binding potential
Z-dependence of Mean Excitation Energies for Second and Third Row Atoms and Their Ions
DEFF Research Database (Denmark)
Sauer, Stephan P. A.; Sabin, John R.; Oddershede, Jens
2018-01-01
All mean excitations energies for second and third row atoms and their ions are calculated in the random‐phase approximation using large basis sets. To a very good approximation it turns out that mean excitation energies within an isoelectronic series is a quadratic function of the nuclear charge...
Excited neutral atomic fragments in the strong-field dissociation of N2 molecules
International Nuclear Information System (INIS)
Nubbemeyer, T; Eichmann, U; Sandner, W
2009-01-01
Excited neutral N* fragments with energies between 3 eV and 15 eV have been observed from the dissociation of N 2 molecules in strong laser fields. The kinetic energy spectrum of the excited neutral atoms corresponds to Coulomb explosion processes involving N + ions. This supports the assumption that the production of excited neutral fragments stems from a process in which one of the participating ions in the Coulomb explosion captures an electron into a Rydberg state.
Signatures of a quantum diffusion limited hydrogen atom tunneling reaction.
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.
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)
International Nuclear Information System (INIS)
Borovik, A; Roman, V; Zatsarinny, O; Bartschat, K
2013-01-01
Electron impact excitation of the (4p 5 5s 2 ) 2 P 3/2,1/2 and (4p 5 4d5s) 4 P 1/2,3/2,5/2 autoionizing states in rubidium atoms was studied experimentally by measuring the ejected-electron excitation functions and theoretically by employing a fully relativistic Dirac B-spline R-matrix (close-coupling) model. The experimental data were collected in an impact energy range from the respective excitation thresholds up to 50 eV with an incident electron energy resolution of 0.2 eV and an observation angle of 54.7°. Absolute values of the excitation cross sections were obtained by normalizing to the theoretical predictions. The observed near-threshold resonance structures were also analysed by comparison with theory. For the 2 P 3/2,1/2 doublet states, a detailed analysis of the R-matrix results reveals that the most intense resonances are related to odd-parity negative-ion states with dominant configurations 4p 5 5s5p 2 and 4p 5 4d5s6s. The measured excitation functions for the 2 P 1/2 and 4 P J states indicate a noticeable cascade population due to the radiative decay from high-lying autoionizing states. A comparative analysis with similar data for other alkali atoms is also presented.
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
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.
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)
How many atoms get excited when they decay?
DEFF Research Database (Denmark)
Blocher, Philip Daniel; Mølmer, Klaus
2017-01-01
We analyse the time evolution of a two-level system prepared in a superposition of its ground state and radiatively unstable excited state. We show that by choosing appropriate means of detection of the radiated field, we can steer the evolution of the emitter and herald its preparation in the fu...
An exciton approach to the excited states of two electron atoms. I Formalism and interpretation
International Nuclear Information System (INIS)
Schipper, P.E.
1985-01-01
The exciton model is formally applied to a description of the excited states of two electron atoms with the explicit inclusion of exchange. The model leads to a conceptually simple framework for the discussion of the electronic properties of the archetypical atomic electron pair
Nonclassical Effects of a Four-Level Excited-Doublet Atom Model
International Nuclear Information System (INIS)
Zhang Jiansong; Xu Jingbo
2006-01-01
We adopt a dynamical algebraic method to study a four-level excited-doublet atom model and obtain the explicit expressions of the time-evolution operator and the density operator for the system. The nonclassical effects of the system, such as collapses and revivals of the atomic inversion and squeezing of the radiation field, are also discussed.
International Nuclear Information System (INIS)
Bourdilot, M.; Paletto, S.; Goutte, R.; Guillaud, C.
1975-01-01
During the bombardment of a solid target by a positive ion beam, an emission of light proceeding of the deexcitation of the neutral atoms which are sputtered in an excited state, is observed. This phenomenon is used in ionoluminescence analysis. By exciting the neutral atoms sputtered with an auxiliary discharge it is seen that: it is possible to increase, under certain experimental conditions, the sensibility of the ionoluminescence method. This post-excitation is particularly efficient with targets having an high sputtering coefficient [fr
Generalized oscillator strengths for some higher valence-shell excitations of krypton atom
Institute of Scientific and Technical Information of China (English)
2007-01-01
The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ← 4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. (Phys. Rev. A 67 022703 (2003)). The differences between the experimental results and theoretical calculations show that more studies are needed.
Electron excitation collision strengths for positive atomic ions: a collection of theoretical data
International Nuclear Information System (INIS)
Merts, A.L.; Mann, J.B.; Robb, W.D.; Magee, N.H. Jr.
1980-03-01
This report contains data on theoretical and experimental cross sections for electron impact excitation of positive atomic ions. It is an updated and corrected version of a preliminary manuscript which was used during an Atomic Data Workshop on Electron Excitation of Ions held at Los Alamos in November 1978. The current status of quantitative knowledge of collisional excitation collision strengths is shown for highly stripped ions where configuration mixing, relativistic and resonance effects may be important. The results show a reasonably satisfactory state for first-row isoelectronic ions and indicate that a considerable amount of work remains to be done for second-row and heavier ions
Behavior of Excited Argon Atoms in Inductively Driven Plasmas
International Nuclear Information System (INIS)
HEBNER, GREGORY A.; MILLER, PAUL A.
1999-01-01
Laser induced fluorescence has been used to measure the spatial distribution of the two lowest energy argon excited states, 1s 5 and 1s 4 , in inductively driven plasmas containing argon, chlorine and boron trichloride. The behavior of the two energy levels with plasma conditions was significantly different, probably because the 1s 5 level is metastable and the 1s 4 level is radiatively coupled to the ground state but is radiation trapped. The argon data is compared with a global model to identify the relative importance of processes such as electron collisional mixing and radiation trapping. The trends in the data suggest that both processes play a major role in determining the excited state density. At lower rfpower and pressure, excited state spatial distributions in pure argon were peaked in the center of the discharge, with an approximately Gaussian profile. However, for the highest rfpowers and pressures investigated, the spatial distributions tended to flatten in the center of the discharge while the density at the edge of the discharge was unaffected. The spatially resolved excited state density measurements were combined with previous line integrated measurements in the same discharge geometry to derive spatially resolved, absolute densities of the 1s 5 and 1s 4 argon excited states and gas temperature spatial distributions. Fluorescence lifetime was a strong fi.mction of the rf power, pressure, argon fraction and spatial location. Increasing the power or pressure resulted in a factor of two decrease in the fluorescence lifetime while adding Cl 2 or BCl 3 increased the fluorescence lifetime. Excited state quenching rates are derived from the data. When Cl 2 or BCl 3 was added to the plasma, the maximum argon metastable density depended on the gas and ratio. When chlorine was added to the argon plasma, the spatial density profiles were independent of chlorine fraction. While it is energetically possible for argon excited states to dissociate some of the
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
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
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.
International Nuclear Information System (INIS)
Cadez, I.; Markelj, S.; Rupnik, Z.; Pelicon, P.
2006-01-01
We are currently conducting a series of different laboratory experimental studies of processes involving vibrationally excited hydrogen molecules that are relevant to fusion edge plasma. A general overview of our activities is presented together with results of studies of hydrogen recombination on surfaces. This includes vibrational spectroscopy of molecules formed by recombination on metal surfaces exposed to the partially dissociated hydrogen gas and recombination after hydrogen permeation through metal membrane. The goal of these studies is to provide numerical parameters needed for edge plasma modelling and better understanding of plasma wall interaction processes. (author)
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
Theoretical studies of atomic and quasiatomic excitations by electron and ion impact
International Nuclear Information System (INIS)
Kam, K.F.
1999-09-01
Electron emission from ion induced excitations of Ca, Sc, Ti and V metal surfaces and from electron impact on transition metal oxides CoO and TiO 2 has been studied in this thesis. Both the autoionising emission from sputtered atoms and the 3p→3d and 3s→3d excitations in the oxides reveal strong atomic features. The work has involved explaining these spectra in an atomic approach, via the use of atomic structure calculations, cross section studies and empirical/semi-empirical analyses. The other aspect of this work involves extension of current theories of electron-atom scattering in the high electron energy impact regime. Overall it is shown that much can be learned about some solid-state spectra by relating them to atomic phenomena. (author)
Theory of collisional excitation transition between Rydberg states of atoms. Non-inertial mechanism
International Nuclear Information System (INIS)
Kaulakys, B.P.
1982-01-01
The transitions between highly states of an atom due to the collision of its core with another atom are considered. The cross sections of the change of highly excited electron angular momentum, in the case of the transitions when the main quantum number is constant, are expressed in terms of transport cross sections of the perturbing atom scattering on the ion of Rydberg atom. It is shown that the cross sections of the momentum mixing at thermal rapidities are lower than the cross sections of the atom-ion elastic scattering
Miles, J. A.; Das, Diptaranjan; Simmons, Z. J.; Yavuz, D. D.
2015-09-01
We experimentally demonstrate the localization of excitation between hyperfine ground states of 87Rb atoms to as small as λ /13 -wide spatial regions. We use ultracold atoms trapped in a dipole trap and utilize electromagnetically induced transparency (EIT) for the atomic excitation. The localization is achieved by combining a spatially varying coupling laser (standing wave) with the intensity dependence of EIT. The excitation is fast (150 ns laser pulses) and the dark-state fidelity can be made higher than 94% throughout the standing wave. Because the width of the localized regions is much smaller than the wavelength of the driving light, traditional optical imaging techniques cannot resolve the localized features. Therefore, to measure the excitation profile, we use an autocorrelation-like method where we perform two EIT sequences separated by a time delay, during which we move the standing wave.
Collective Excitations in Liquid Hydrogen Observed by Coherent Neutron Scattering
DEFF Research Database (Denmark)
da Costa Carneiro, Kim; Nielsen, M.; McTague, J. P.
1973-01-01
Coherent scattering of neutrons by liquid parahydrogen shows the existence of well-defined collective excitations in this liquid. Qualitative similarity with the scattering from liquid helium is found. Furthermore, in the range of observed wave vectors, 0.7 Å-1 ≤κ≤3.1 Å-1, extending from the firs...
Microwave ionization and excitation of Ba Rydberg atoms
International Nuclear Information System (INIS)
Eichmann, U.; Dexter, J.L.; Xu, E.Y.; Gallagher, T.F.
1989-01-01
We have investigated ionization and excitation of the Ba 6sn s 1 S 0 and 6snd 1,3 D 2 series in strong microwave fields. The observed microwave ionization threshold fields, scaling as 0.28 n -5 , and the state mixing fields cannot be completely explained in terms of a single cycle Landau-Zener model. However, by taking into account multiphoton resonant transitions driven by many cycles of the microwave field we have been able to interpret the data. In particular multi-photon transitions have been found to be responsible for apparent resonance structures and for the unexpectedly low mixing fields. Not surprisingly, doubly excited valence states introduce irregularities into both the microwave ionization and the state mixing field values. (orig.)
International Nuclear Information System (INIS)
Zouros, T.J.M.; Lee, D.H.; Sanders, J.M.; Richard, P.
1993-01-01
The effect of electron-electron interactions between projectile and target electrons observed in recent measurements of projectile K-shell excitation and ionization using 0 projectile Auger electron spectroscopy are analysed within the framework of the impulse approximation (IA). The IA formulation is seen to give a good account of the threshold behavior of both ionization and excitation, while providing a remarkably simple intuitive picture of such electron-electron interactions in ion-atom collisions in general. Thus, the applicability of the IA treatment is extended to cover most known processes involving such interactions including resonance transfer excitation, binary encounter electron production, electron-electron excitation and ionization. (orig.)
Behavior of Excited Argon Atoms in Inductively Driven Plasmas
Hebner, G A
1999-01-01
Laser induced fluorescence has been used to measure the spatial distribution of the two lowest energy argon excited states, 1s sub 5 and 1s sub 4 , in inductively driven plasmas containing argon, chlorine and boron trichloride. The behavior of the two energy levels with plasma conditions was significantly different, probably because the 1s sub 5 level is metastable and the 1s sub 4 level is radiatively coupled to the ground state but is radiation trapped. The argon data is compared with a global model to identify the relative importance of processes such as electron collisional mixing and radiation trapping. The trends in the data suggest that both processes play a major role in determining the excited state density. At lower rfpower and pressure, excited state spatial distributions in pure argon were peaked in the center of the discharge, with an approximately Gaussian profile. However, for the highest rfpowers and pressures investigated, the spatial distributions tended to flatten in the center of the disch...
Photoionization of the hydrogen atom in strong magnetic fields
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.
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.
Lifetime measurement of excited atomic and ionic states of some
Indian Academy of Sciences (India)
High-frequency deflection (HFD) technique with a delayed coincidence single photon counting arrangement is an efficient technique for radiative lifetime measurement. An apparatus for measurement of the radiative lifetime of atoms and molecules has been developed in our laboratory and measurements have been ...
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...
Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr
Zhang, J.-Y.; Babb, J. F.; Mitroy, J.; Sadeghpour, H. R.; Schwingenschlö gl, Udo; Yan, Z.-C.
2013-01-01
Dispersion coefficients for the long-range interactions of the first four excited states of He, i.e., He(2 1, 3 S) and He(2 1, 3 P), with the low-lying states of the alkaline earth atoms Mg, Ca, and Sr are calculated by summing over the reduced matrix elements of multipole transition operators.
Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr
Zhang, J.-Y.
2013-04-05
Dispersion coefficients for the long-range interactions of the first four excited states of He, i.e., He(2 1, 3 S) and He(2 1, 3 P), with the low-lying states of the alkaline earth atoms Mg, Ca, and Sr are calculated by summing over the reduced matrix elements of multipole transition operators.
International Nuclear Information System (INIS)
Kimura, M.
1986-01-01
A review of various theoretical treatments which have been used to study electron-capture and excitation processes in two-electron-system ion-atom, atom-atom collisions at low to intermediate energy is presented. Advantages as well as limitations associated with these theoretical models in application to practical many-electron ion-atom, atom-atom collisions are specifically pointed out. Although a rigorous theoretical study of many-electron systems has just begun so that reports of theoretical calculations are scarce to date in comparison to flourishing experimental activities, some theoretical results are of great interest and provide important information for understanding collision dynamics of the system which contains many electrons. Selected examples are given for electron capture in a multiply charged ion-He collision, ion-pair formation in an atom-atom collision and alignment and orientation in a Li + + He collision. (Auth.)
International Nuclear Information System (INIS)
Catalan, G.; Roberts, M.J.
1979-01-01
A form of the off-shell Coulomb T matrix, which has a well defined on-shell limit, is used in the Faddeev-Watson multiple-scattering expansion for a direct three-body collision process. Using the excitation of atomic hydrogen by electron impact as an example, approximations to the second-order terms, which are valid for high momentum transfers of the incident electron, are derived. It is shown how the resulting asymptotic behaviour of the second-order Faddeev-Watson approximation is related to the high momentum transfer limit of the second Born approximation. The results are generalised to the excitation of more complex atoms. The asymptotic forms of the Faddeev-Watson and Born approximations are compared with other theories and with measurements of differential cross sections and angular correlation parameters for the excitation of H(2p) and He(2 1 P). The results indicate that the Faddeev-Watson approximation converges more rapidly at high momentum transfers than does the Born approximation. (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.
Limit on Excitation and Stabilization of Atoms in Intense Optical Laser Fields.
Zimmermann, H; Meise, S; Khujakulov, A; Magaña, A; Saenz, A; Eichmann, U
2018-03-23
Atomic excitation in strong optical laser fields has been found to take place even at intensities exceeding saturation. The concomitant acceleration of the atom in the focused laser field has been considered a strong link to, if not proof of, the existence of the so-called Kramers-Henneberger (KH) atom, a bound atomic system in an intense laser field. Recent findings have moved the importance of the KH atom from being purely of theoretical interest toward real world applications; for instance, in the context of laser filamentation. Considering this increasing importance, we explore the limits of strong-field excitation in optical fields, which are basically imposed by ionization through the spatial field envelope and the field propagation.
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]....
Multi-quantum excitation in optically pumped alkali atom: rare gas mixtures
Galbally-Kinney, K. L.; Rawlins, W. T.; Davis, S. J.
2014-03-01
Diode-pumped alkali laser (DPAL) technology offers a means of achieving high-energy gas laser output through optical pumping of the D-lines of Cs, Rb, and K. The exciplex effect, based on weak attractive forces between alkali atoms and polarizable rare gas atoms (Ar, Kr, Xe), provides an alternative approach via broadband excitation of exciplex precursors (XPAL). In XPAL configurations, we have observed multi-quantum excitation within the alkali manifolds which result in infrared emission lines between 1 and 4 μm. The observed excited states include the 42FJ states of both Cs and Rb, which are well above the two-photon energy of the excitation laser in each case. We have observed fluorescence from multi-quantum states for excitation wavelengths throughout the exciplex absorption bands of Cs-Ar, Cs-Kr, and Cs-Xe. The intensity scaling is roughly first-order or less in both pump power and alkali concentration, suggesting a collisional energy pooling excitation mechanism. Collisional up-pumping appears to present a parasitic loss term for optically pumped atomic systems at high intensities, however there may also be excitation of other lasing transitions at infrared wavelengths.
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
Theoretical Atomic Physics code development II: ACE: Another collisional excitation code
International Nuclear Information System (INIS)
Clark, R.E.H.; Abdallah, J. Jr.; Csanak, G.; Mann, J.B.; Cowan, R.D.
1988-12-01
A new computer code for calculating collisional excitation data (collision strengths or cross sections) using a variety of models is described. The code uses data generated by the Cowan Atomic Structure code or CATS for the atomic structure. Collisional data are placed on a random access file and can be displayed in a variety of formats using the Theoretical Atomic Physics Code or TAPS. All of these codes are part of the Theoretical Atomic Physics code development effort at Los Alamos. 15 refs., 10 figs., 1 tab
Coherence and correlation in doubly excited heliumlike atoms
International Nuclear Information System (INIS)
Burgdoerfer, J.; Morgenstern, R.
1988-01-01
We analyze properties of the density matrix of doubly excited two-electron systems formed in inelastic collisions. Formulas for the two-particle joint angular probability density, the angular correlation function, and the reduced single-particle density are derived. Of particular interest is the interplay between the intrinsic correlations of the stationary two-electron state and collisionally induced coherences. We focus on its effects on the correlated and single-particle motion of the electrons. If one chooses approximate stationary wave functions reflecting the approximate O(4) x O(4)contains(4) dynamical symmetry, a simple quasiclassical interpretation of coherence and correlation in terms of shapes and modes of the relative motion of Kepler orbits can be given. The present description is applied to recent experimental results by Van der Straten and Morgenstern [Comments At. Mol. Phys. 19, 243 (1986)
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)
Radiative and nonradiative lifetimes in excited states of Ar, Kr and Xe atoms in Ne matrix
International Nuclear Information System (INIS)
Hahn, U.; Schwentner, N.
1979-10-01
Synchrotron radiation with its intense continuum and its excellent time structure has been exploited for time resolved luminescence spectroscopy in the solid state. By selective excitation of n = 1, n' = 1 and n = 2 exciton states of Xe, Kr and Ar atoms in Ne matrix we were able to identify the emitting states involved. Lifetimes within the cascade of radiative and radiationless relaxation between excited states as well as the radiative lifetimes for transitions to the ground state have been derived from the decay curves. Energy positions and radiative lifetimes of the emitting states correspond quite well with those of the free atoms. Radiative and radiationless relaxation processes take place within the manifold of excited states of the guest atoms. The rate constants for radiationless decay confirm an energy gap law. The order of the radiationless processes reaches in some cases extremely high values. Selection rules for spin and angular momentum are essential to understand the observed radiationless transition rates. (orig.)
Cross sections for energy transfer in collisions between two excited sodium atoms
International Nuclear Information System (INIS)
Huennekens, J.; Gallagher, A.
1983-01-01
We have measured cross sections, sigma/sub n/L, for the excitation transfer process Na(3P)+Na(3P)→Na(3S)+Na(nL), where nL is the 4D or 5S level. Our results are sigma/sub 4D/ = 23 A 2 +- 35% and sigma/sub 5S/ = 16 A 2 +- 35% at Tapprox.600 K. To obtain these cross sections we have used pulsed excitation and measured the intensities of 4D, 5S, and 3P fluorescence emissions, and the spatial distribution of excited atoms resulting from radiation diffusion, as well as the excited atom density as a function of time. Additionally, we have accounted for (time-dependent) radiation trapping of 3P and nL level radiation and for the resulting anisotropies of these fluorescence emissions. Comparisons of our results with theory have been made, and their relevance to other experiments is discussed
International Nuclear Information System (INIS)
Demkin, V.P.; Pecheritsyn, A.A.
1995-01-01
Equations for the amplitudes and differential cross sections of electronic excitation and ionization of a helium atom are derived in the approximation of a open-quotes frozenclose quotes ion core. The wave functions of the discrete states are chosen in the form of generalized hydrogenlike orbitals. The radial wave functions of the continuous spectrum are determined by solving the equation of motion numerically. The differential excitation cross sections of excitation of the 2p, 3p, and 4p levels and ionization of a helium atom by electrons are calculated in the energy range up to 50 eV. Estimates are obtained for the nonorthogonal wave functions in the amplitudes of the excitation and ionization processes. It is shown that the given method is more compatible with experiment than the Born method
Energy Technology Data Exchange (ETDEWEB)
Uematsu, K.; Yumoto, M.; Sakai, T. [Musashi Institute of Technology, Tokyo (Japan)
1998-06-01
The authors have studied on surface treatment of PTFE by a low pressure discharge. It is deduced that excited nitrogen molecules contribute to introduce polar components on the surface. To confirm the speculation, we tried to change population of metastable nitrogen N2 (A{sup 3}{Sigma}u{sup +}) by quenching precursor N2 (B{sup 3}{pi}g), with hydrogen molecule. The decrease of relaxation time which indicates a change of excited molecule and measured by emission spectroscopy using a time after glow method was obtained. As a result, the relaxation times of N2 (B{sup 3}{pi}g) and N2 (A{sup 3}{Sigma}u{sup +}) decreased to 55% and 20% respectively, when mixing ratio of hydrogen was 3%. It was also deduced that hydrogen atom may take a part in a quenching process of N2 (A{sup 3}{Sigma}u{sup +}). 14 refs., 11 figs., 1 tab.
International Nuclear Information System (INIS)
Jin, Yao; Hu, Jiawei; Yu, Hongwei
2014-01-01
We study, using the formalism proposed by Dalibard, Dupont-Roc and Cohen-Tannoudji, the contributions of the vacuum fluctuation and radiation reaction to the rate of change of the mean atomic energy for a circularly accelerated multilevel atom coupled to vacuum electromagnetic fields in the ultrarelativistic limit. We find that the balance between vacuum fluctuation and radiation reaction is broken, which causes spontaneous excitations of accelerated ground state atoms in vacuum. Unlike for a circularly accelerated atom coupled to vacuum scalar fields, the contribution of radiation reaction is also affected by acceleration, and this term takes the same form as that of a linearly accelerated atom coupled to vacuum electromagnetic fields. For the contribution of vacuum fluctuations, we find that in contrast to the linear acceleration case, terms proportional to the Planckian factor are replaced by those proportional to a non-Planck exponential term, and this indicates that the radiation perceived by a circularly orbiting observer is no longer thermal as is in the linear acceleration case. However, for an ensemble of two-level atoms, an effective temperature can be defined in terms of the atomic transition rates, which is found to be dependent on the transition frequency of the atom. Specifically, we calculate the effective temperature as a function of the transition frequency and find that in contrast to the case of circularly accelerated atoms coupled to the scalar field, the effective temperature in the current case is always larger than the Unruh temperature. -- Highlights: •We study the spontaneous excitation of a circularly accelerated atom. •Contribution of radiation reaction to the excitation is affected by acceleration. •The radiation perceived by a circularly orbiting observer is no longer thermal. •An effective temperature can be defined in terms of atomic transition rates. •Effective temperature is larger than Unruh temperature and frequency-dependent
Cu 4s → 4p atomic like excitations in the Ne matrix.
Hatano, Yasuyo; Tatewaki, Hiroshi; Yamamoto, Shigeyoshi
2013-06-07
The lowest three or four excited states (the triplet or quartet states) of the Cu atom in a neon (Ne) matrix have been studied experimentally, and have been presumed to have the electronic configuration of Cu 4p(1). The origins of the triplet and the quartet are not yet fully clear, although many models have been proposed. It has been argued, for example, that the existence of different trapping sites would give rise to two partly overlapping triplets, leading to spectra having three or four lines or more. Below, the electronic structures of the ground state and lowest excited states of the Cu atom in the neon matrix are clarified by means of ab initio molecular orbital calculations, using the cluster model. It was found that a rather large vacancy (hollow) with residual Ne atoms is vital for explaining the observed spectra having three or more lines; the Cu atom occupies the center of the substitutional site of a face-centered cubic (fcc)-like cluster comprising 66 Ne atoms, in which the first shell composed of 12 Ne atoms is empty. The presence of the residual Ne atoms in the first shell gives rise to more than three excited states, explaining the experimental spectra. Electron-electron interaction (including the crystal field) and spin-orbit interaction are both important in explaining the experimental spectra.
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)
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
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.
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.
a Point-Like Picture of the Hydrogen Atom
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!
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.
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.
Selective vibrational pumping of molecular hydrogen via gas phase atomic recombination.
Esposito, Fabrizio; Capitelli, Mario
2009-12-31
Formation of rovibrational excited molecular hydrogen from atomic recombination has been computationally studied using three body dynamics and orbiting resonance theory. Each of the two methods in the frame of classical mechanics, that has been used for all of the calculations, appear complementary rather than complete, with similar values in the low temperature region, and predominance of three body dynamics for temperatures higher than about 1000 K. The sum of the two contributions appears in fairly good agreement with available data from the literature. Dependence of total recombination on the temperature over pressure ratio is stressed. Detailed recombination toward rovibrational states is presented, with large evidence of importance of rotation in final products. Comparison with gas-surface recombination implying only physiadsorbed molecules shows approximate similarities at T = 5000 K, being on the contrary different at lower temperature.
The solvation reaction field for a hydrogen atom in a dielectric continuum
International Nuclear Information System (INIS)
Chipman, D.M.
1996-01-01
A reaction field exists even for a nonpolar solute embedded in a spherical cavity within a surrounding homogeneous dielectric continuum. This arises from the tail of the electronic wave function that penetrates beyond the cavity boundary into the dielectric region. This effect, which is neglected or treated only in cursory fashion in most reaction field implementations, is examined in detail for the simple case of a ground state hydrogen atom, where very accurate solutions of the relevant equations can be obtained. Properties considered include the penetration of the electron outside the cavity, the electronic density at the nucleus, the electron binding energy, the electrostatic free energy of solvation, the polarizability, and the vertical 1s→2p excitation energy. Also, the effect of the common approximation of neglecting the volume polarization and treating only the surface polarization contribution to the reaction field is critically evaluated. copyright 1996 American Institute of Physics
International Nuclear Information System (INIS)
Li, J.; Yu, R.; Yang, X.
2008-01-01
We study the propagation of two quantized optical fields via considering the collective effects of photonic emissions and excitations of a three-level cyclic-type system (such as atomic ensemble with symmetry broken, or the chiral molecular gases, or manual 'atomic' array with symmetry broken), where the quantum transitions is driven by two quantized fields and a classical one. The results show that the parametric conversion and maximally entangled photon pair generation can be achieved by means of the collective excitation of the two upper energy levels induced by the classic optical field. This investigation may be used for the generated coherent short-wavelength quantum radiation and quantum information processing
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)
Molecular hydrogen line ratios in four regions of shock-excited gas
International Nuclear Information System (INIS)
Burton, M.G.
1989-01-01
Five emission lines of molecular hydrogen, with wavelengths in the ranges of 2.10-2.25 and 3.80-3.85 μm, have been observed in four objects of different type in which the line emission is believed to be excited by shocks. (author)
Study of atomic excitations in sputtering with the use of composite targets
International Nuclear Information System (INIS)
Kierkegaard, K.; Ludvigsen, S.; Petterson, B.; Veje, E.
1985-01-01
Some Li- and Na-compounds have been bombarded with 80 keV Ar + ions, and excitation of sputtered particles has been studied with optical spectrometry. Very strong excitation of Li I and Na I was observed, but essentially no excitation of electronegative elements. For levels in Li I and also in Na I with n 8, the relative level populations fall noticeably above the extrapolation of such power law behaviors. This is discussed and tentatively interpreted in terms of two-step processes. (i) The projectile excites a target electron from the valence band to the conduction band. (ii) Such an excitation is transferred resonantly to the sputtered atom on its way out. (orig.)
The population transfer of high excited states of Rydberg lithium atoms in a microwave field
International Nuclear Information System (INIS)
Jiang Lijuan; Zhang Xianzhou; Ma Huanqiang; Jia Guangrui; Zhang Yonghui; Xia Lihua
2012-01-01
Using the time-dependent multilevel approach (TDMA), the properties of high excited Rydberg lithium atom have been obtained in the microwave field. The population transfer of lithium atom are studied on numerical calculation, quantum states are controlled and manipulated by microwave field. It shows that the population can be completely transferred to the target state by changing the chirped rate and field amplitude. (authors)
Fast Excitation and Photon Emission of a Single-Atom-Cavity System
International Nuclear Information System (INIS)
Bochmann, J.; Muecke, M.; Langfahl-Klabes, G.; Erbel, C.; Weber, B.; Specht, H. P.; Moehring, D. L.; Rempe, G.
2008-01-01
We report on the fast excitation of a single atom coupled to an optical cavity using laser pulses that are much shorter than all other relevant processes. The cavity frequency constitutes a control parameter that allows the creation of single photons in a superposition of two tunable frequencies. Each photon emitted from the cavity thus exhibits a pronounced amplitude modulation determined by the oscillatory energy exchange between the atom and the cavity. Our technique constitutes a versatile tool for future quantum networking experiments
Studies of photoionization processes from ground-state and excited-state atoms and molecules
International Nuclear Information System (INIS)
Ederer, D.L.; Parr, A.C.; West, J.B.
1982-01-01
Recent triply-differential photoelectron spectroscopy experiments designed for the study of correlation effects in atoms and molecules are described. Final-state symmetry of the n=2 state of helium has been determined. The non-Franck-Condon behavior of vibrational branching ratios and large variations of the angular asymmetry parameter has been observed for shape resonances and autoionizing resonances in CO and other molecules. Recent observations of the photoionization of excited sodium atoms are also described
Excitation of the shear horizontal mode in a monolayer by inelastic helium atom scattering
DEFF Research Database (Denmark)
Bruch, L. W.; Hansen, Flemming Yssing
2005-01-01
Inelastic scattering of a low-energy atomic helium beam (HAS) by a physisorbed monolayer is treated in the one-phonon approximation using a time-dependent wave,packet formulation. The calculations show that modes with shear horizontal polarization can be excited near high symmetry azimuths....... The diffraction and inelastic processes arise from a strong coupling of the incident atom to the target and the calculated results show large departures from expectations based on analogies to inelastic thermal neutron scattering....
Quantum dynamics of hydrogen atoms on graphene. II. Sticking
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.
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
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
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
International Nuclear Information System (INIS)
Glushkov, A.V.
1994-01-01
Based on the method of effective potential involving the new polarization interaction potential calculated from polarization diagrams of the perturbation theory in the Thomas-Fermi approximation, the main parameters of the interatomic potentials (equilibrium distances, potential well depth) are evaluated for a system consisting of an alkali atom in the ground and excited states and of a mercury atom. The results of calculations of quasi-molecular terms for the A-Hg system, where A = Na, Cs, Fr, are reported, some of which are obtained for the first time. A comparison is made with available experimental and theoretical data. 29 refs., 2 figs., 1 tab
Which hydrogen atom of toluene protonates PAH molecules in (+)-mode APPI MS analysis?
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.
Schrodinger Equation Solutions that Lead to the Solution for the Hydrogen Atom
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…
Dynamic study of excited state hydrogen-bonded complexes of harmane in cyclohexane-toluene mixtures.
Carmona, Carmen; Balón, Manuel; Galán, Manuel; Guardado, Pilar; Muñoz, María A
2002-09-01
Photoinduced proton transfer reactions of harmane or 1-methyl-9H-pyrido[3,4-b]indole (HN) in the presence of the proton donor hexafluoroisopropanol (HFIP) in cyclohexane-toluene mixtures (CY-TL; 10% vol/vol of TL) have been studied. Three excited state species have been identified: a 1:2 hydrogen-bonded proton transfer complex (PTC), between the pyridinic nitrogen of the substrate and the proton donor, a hydrogen-bonded cation-like exciplex (CL*) with a stoichiometry of at least 1:3 and a zwitterionic exciplex (Z*). Time-resolved fluorescence measurements evidence that upon excitation of ground state PTC, an excited state equilibrium is established between PTC* and the cationlike exciplex, CL*, lambdaem approximately/= 390 nm. This excited state reaction is assisted by another proton donor molecule. Further reaction of CL* with an additional HFIP molecule produces the zwitterionic species, Z*, lambda(em) approximately/= 500 nm. From the analysis of the multiexponential decays, measured at different emission wavelengths and as a function of HFIP concentration, the mechanism of these excited state reactions has been established. Thus, three rate constants and three reciprocal lifetimes have been determined. The simultaneous study of 1,9-dimethyl-9H-pyrido[3,4-b]indole (MHN) under the same experimental conditions has helped to understand the excited state kinetics of these processes.
TRACE ANALYSIS BY LASER-EXCITED ATOMIC FLUORESCENCE WITH ATOMIZATION IN A PULSED PLASMA
Lunyov , O.; Oshemkov , S.; Petrov , A.
1991-01-01
The possibilities of plasma atomization for laser fluorescence trace analysis are discussed. Pulsed hot hollow cathode discharge was used for analysis of solutions and powdered samples. The high voltage spark and laser-induced breakdown (laser spark) were used as atomizers of metal-containing atmospheric aerosols. Detection limits were improved by means of temporal background selection.
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.
ns-ms excitation of alkali atoms in the Glauber approximation
International Nuclear Information System (INIS)
Barros, H.G. de P.L. de
1980-05-01
An expression for the scattering amplitude in the Glauber approximation for ns-ms electronic excitation of alkali atoms is obtained. The interaction potential between the incident electron, the core electrons and N-1 protons is approximated by an appropriate spherical potential. (Author) [pt
International Nuclear Information System (INIS)
Bolshov, M.A.; Boutron, C.F.
1994-01-01
The new laser-excited atomic fluorescence spectrometry technique offers unrivalled sensitivity for the determination of trace metals in a wide variety of samples. This has allowed the direct determination of Pb, Cd and Bi in Antarctic and Greenland snow and ice down to the sub pg/g level. (authors). 11 refs., 2 figs
International Nuclear Information System (INIS)
Zhou Wenting; Yu Hongwei
2012-01-01
We study the spontaneous excitation of a radially polarized static multilevel atom outside a spherically symmetric black hole in multipolar interaction with quantum electromagnetic fluctuations in the Boulware, Unruh and Hartle-Hawking vacuum states. We find that spontaneous excitation does not occur in the Boulware vacuum, and, in contrast to the scalar field case, the spontaneous emission rate is not well behaved at the event horizon as a result of the blow-up of the proper acceleration of the static atom. However, spontaneous excitation can take place both in the Unruh and the Hartle-Hawking vacua as if there were thermal radiation from the black hole. Distinctive features in contrast to the scalar field case are the existence of a term proportional to the proper acceleration squared in the rate of change of the mean atomic energy in the Unruh and the Hartle-Hawking vacua and the structural similarity in the spontaneous excitation rate between the static atoms outside a black hole and uniformly accelerated ones in a flat space with a reflecting boundary, which is particularly dramatic at the event horizon where a complete equivalence exists. (paper)
Test of the neoclassical theory of radiation in a weakly excited atomic system
International Nuclear Information System (INIS)
Brink, G.O.
1975-01-01
The neoclassical theory of radiation predicts that the decay rate of an excited atomic state depends on the population density of the lower state. Experimental evidence is presented here which shows that in the case of 39 K the decay rate is in agreement with the predictions of quantum electrodynamics and definitely in disagreement with the neoclassical theory
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)
Direct excitation in heavy atom collisions: A propensity rule for charge cloud orientation
International Nuclear Information System (INIS)
Andersen, N.; Aarhus Univ.; Nielsen, S.E.; Royal Danish School of Pharmacy, Copenhagen)
1985-01-01
The Massey Criterion prescribes maximum electronic excitation of atoms in heavy particle collisions for collision velocities v where Δε a/ℎv ≅ π. Here Δε is the energy defect and a is the effective interaction length. Experiments with planar symmetry have revealed a preferred way of rotation of the excited charge cloud in this velocity region. We demonstrate by analysis of a simple, yet realistic model why excitation favors states with a specific orientation. A general propensity rule is derived and its validity evaluated for a specific case, the Na-He system. Implications for future experiments are pointed out. In particular, the propensity rule predicts very different collisions behaviors of oppositely oriented atoms, as prepared e.g. by circular polarized laser light. (orig.)
Systematic observation of tunneling field-ionization in highly excited Rb Rydberg atoms
International Nuclear Information System (INIS)
Kishimoto, Y.; Tada, M.; Kominato, K.; Shibata, M.; Yamada, S.; Haseyama, T.; Ogawa, I.; Funahashi, H.; Yamamoto, K.; Matsuki, S.
2002-01-01
Pulsed field ionization of high-n (90≤n≤150) manifold states in Rb Rydberg atoms has been investigated in high slew-rate regime. Two peaks in the field ionization spectra were systematically observed for the investigated n region, where the field values at the lower peak do not almost depend on the excitation energy in the manifold, while those at the higher peak increase with increasing excitation energy. The fraction of the higher peak component to the total ionization signals increases with increasing n, exceeding 80% at n=147. Characteristic behavior of the peak component and the comparison with theoretical predictions indicate that the higher peak component is due to the tunneling process. The obtained results show that the tunneling process plays increasingly the dominant role at such highly excited nonhydrogenic Rydberg atoms
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
Noise squeezing of fields that bichromatically excite atoms in a cavity.
Li, Lingchao; Hu, Xiangming; Rao, Shi; Xu, Jun
2016-11-14
It is well known that bichromatic excitation on one common transition can tune the emission or absorption spectra of atoms due to the modulation frequency dependent non-linearities. However little attention has been focused on the quantum dynamics of fields under bichromatic excitation. Here we present dissipative effects on noise correlations of fields in bichromatic interactions with atoms in cavities. We first consider an ensemble of two-level atoms that interacts with the two cavity fields of different frequencies and considerable amplitudes. By transferring the atom-field nonlinearities to the dressed atoms we separate out the dissipative interactions of Bogoliubov modes with the dressed atoms. The Bogoliubov mode dissipation establishes stable two-photon processes of two involved fields and therefore leads to two-mode squeezing. As a generalization, we then consider an ensemble of three-level Λ atoms for cascade bichromatic interactions. We extract the Bogoliubov-like four-mode interactions, which establish a quadrilateral of the two-photon processes of four involved fields and thus result in four-mode squeezing.
Microwave multiphoton excitation of helium Rydberg atoms: The analogy with atomic collisions
International Nuclear Information System (INIS)
van de Water, W.; van Leeuwen, K.A.H.; Yoakum, S.; Galvez, E.J.; Moorman, L.; Bergeman, T.; Sauer, B.E.; Koch, P.M.
1989-01-01
We study multiphoton transitions in helium Rydberg atoms subjected to a microwave electric field of fixed frequency but varying intensity. For each principal quantum number in the range n=25--32, the n 3 S to n 3 (L>2), n=25--32, transition probability exhibits very sharp structures as a function of the field amplitude. Their positions could be reproduced precisely using a Floquet Hamiltonian for the interaction between atom and field. Their shapes are determined by the transients of field turn-on and turn-off in a way that makes a close analogy with the theory of slow atomic collisions
International Nuclear Information System (INIS)
O'Neill, J.A.; Cai, J.Y.; Flynn, G.W.; Weston, R.E. Jr.
1986-01-01
The 193 nm excimer laser photolysis of D 2 S in D 2 S/CO 2 mixtures produces fast deuterium atoms (E/sub TR/approx.2.2 eV) which vibrationally excite CO 2 molecules via inelastic translation--vibration/rotation (T--V/R) energy exchange processes. A high resolution (10 -3 cm -1 ) cw diode laser probe was used to monitor the excitation of ν 3 (antisymmetric stretch) and ν 2 (bend) vibrations in CO 2 . The present results are compared with previous experiments involving hot hydrogen atom excitation of CO 2 in H 2 S/CO 2 mixtures as well as with theoretical calculations of the excitation probability. The probability for excitation of a ν 3 quantum in CO 2 is about 1%--2% per gas kinetic D/CO 2 collision. Bending (ν 2 ) quanta are produced about eight times more efficiently than antisymmetric stretching (ν 3 ) quanta. The thermalization rate for cooling hot D atoms below the threshold for production of a ν 3 vibrational quantum corresponds to less than 2 D*/D 2 S collisions or 15 D*/CO 2 collisions
The EAGLE simulations: atomic hydrogen associated with galaxies
Crain, Robert A.; Bahé, Yannick M.; Lagos, Claudia del P.; Rahmati, Alireza; Schaye, Joop; McCarthy, Ian G.; Marasco, Antonino; Bower, Richard G.; Schaller, Matthieu; Theuns, Tom; van der Hulst, Thijs
2017-02-01
We examine the properties of atomic hydrogen (H I) associated with galaxies in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations of galaxy formation. EAGLE's feedback parameters were calibrated to reproduce the stellar mass function and galaxy sizes at z = 0.1, and we assess whether this calibration also yields realistic H I properties. We estimate the self-shielding density with a fitting function calibrated using radiation transport simulations, and correct for molecular hydrogen with empirical or theoretical relations. The `standard-resolution' simulations systematically underestimate H I column densities, leading to an H I deficiency in low-mass (M⋆ < 1010 M⊙) galaxies and poor reproduction of the observed H I mass function. These shortcomings are largely absent from EAGLE simulations featuring a factor of 8 (2) better mass (spatial) resolution, within which the H I mass of galaxies evolves more mildly from z = 1 to 0 than in the standard-resolution simulations. The largest volume simulation reproduces the observed clustering of H I systems, and its dependence on H I richness. At fixed M⋆, galaxies acquire more H I in simulations with stronger feedback, as they become associated with more massive haloes and higher infall rates. They acquire less H I in simulations with a greater star formation efficiency, since the star formation and feedback necessary to balance the infall rate is produced by smaller gas reservoirs. The simulations indicate that the H I of present-day galaxies was acquired primarily by the smooth accretion of ionized, intergalactic gas at z ≃ 1, which later self-shields, and that only a small fraction is contributed by the reincorporation of gas previously heated strongly by feedback. H I reservoirs are highly dynamic: over 40 per cent of H I associated with z = 0.1 galaxies is converted to stars or ejected by z = 0.
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.
Laser-excited atomic fluorescence spectrometry in a pressure-controlled electrothermal atomizer.
Lonardo, R F; Yuzefovsky, A I; Irwin, R L; Michel, R G
1996-02-01
A theoretical model was developed to describe the loss of analyte atoms in graphite furnaces during atomization. The model was based on two functions, one that described the supply of analyte by vaporization, and another that described the removal of the analyte by diffusion. Variation in working pressure was shown to affect the competition between these two processes. Optimal atomization efficiency was predicted to occur at a pressure where the supply of the analyte was maximized, and gas phase interactions between the analyte and matrix were minimized. Experiments to test the model included the direct determination of phosphorus and tellurium in nickel alloys and of cobalt in glass. In all cases, reduction in working pressure from atmospheric pressure to 7 Pa decreased sensitivity by 2 orders of magnitude, but improved temporal peak shape. For the atomization of tellurium directly from a solid nickel alloy, and the atomization of cobalt from an aqueous solution, no change in sensitivity was observed as the working pressure was reduced from atmospheric pressure to approximately 70 kPa. If a reduction in working pressure affected only the diffusion of the analyte, poorer sensitivity should have been obtained. Only a commensurate increase in analyte vaporization could account for maintained sensitivity at lower working pressures. Overall, analyte vaporization was not dramatically improved at reduced working pressures, and maximum atomization efficiency was found to occur near atmospheric pressure.
V. S. Lebedev and I. L. Beigman, Physics of Highly Excited Atoms and Ions
Mewe, R.
1999-07-01
This book contains a comprehensive description of the basic principles of the theoretical spectroscopy and experimental spectroscopic diagnostics of Rydberg atoms and ions, i.e., atoms in highly excited states with a very large principal quantum number (n≫1). Rydberg atoms are characterized by a number of peculiar physical properties as compared to atoms in the ground or a low excited state. They have a very small ionization potential (∝1/n2), the highly excited electron has a small orbital velocity (∝1/n), the radius (∝n2) is very large, the excited electron has a long orbital period (∝n3), and the radiation lifetime is very long (∝n3-5). At the same time the R. atom is very sensitive to perturbations from external fields in collisions with charged and neutral targets. In recent years, R. atoms have been observed in laboratory and cosmic conditions for n up to ˜1000, which means that the size amounts to about 0.1 mm, ˜106 times that of an atom in the ground state. The scope of this monograph is to familiarize the reader with today's approaches and methods for describing isolated R. atoms and ions, radiative transitions between highly excited states, and photoionization and photorecombination processes. The authors present a number of efficient methods for describing the structure and properties of R. atoms and calculating processes of collisions with neutral and charged particles as well as spectral-line broadening and shift of Rydberg atomic series in gases, cool and hot plasmas in laboratories and in astrophysical sources. Particular attention is paid to a comparison of theoretical results with available experimental data. The book contains 9 chapters. Chapter 1 gives an introduction to the basic properties of R. atoms (ions), Chapter 2 is devoted to an account of general methods describing an isolated Rydberg atom. Chapter 3 is focussed on the recent achievements in calculations of form factors and dipole matrix elements of different types of
Study of atomic excitations in sputtering with targets partially covered with oxygen
International Nuclear Information System (INIS)
Weng, J.; Veje, E.
1984-01-01
We have bombarded pure, elemental targets of Be, B, Mg, Al, Si, Ti, and Au with 80 keV Ar + ions and studied excitation of sputtered atoms or ions under UHV conditions as well as with oxygen present at the target surface. The measurements on Mg, Al, Si, and Ti have been done at projectile incidence angles from 0 0 to 85 0 . Excitation probabilities for gold were found to be only very little influenced by oxygen, but for Be, B, Mg, Al, Si, and Ti, the excitation probabilities were in many, but not all, cases found to depend strongly on the oxygen pressure as well as on the beam current density. This indicates that the excitation mechanism is strongly dependent on the initial electronic conditions of the solid. (orig.)
Correlated electron capture and inner-shell excitation measurements in ion-atom collisions
International Nuclear Information System (INIS)
Tanis, J.A.; Bernstein, E.M.; Clark, M.W.
1985-01-01
In an ion-atom collision projectile excitation and charge transfer (electron capture) may occur together in a single encounter. If the excitation and capture are correlated, then the process is called resonant transfer and excitation (RTE); if they are uncorrelated, then the process is termed nonresonant transfer and excitation (NTE). Experimental work to date has shown the existence of RTE and provided strong evidence for NTE. Results presented here provide information on the relative magnitudes of RTE and NTE, the charge state dependence of RTE, the effect of the target momentum distribution on RTE, the magnitude of L-shell RTE compared to K-shell RTE, and the target Z dependences of RTE and NTE. 15 refs., 5 figs
Wu, Zhongchen; Jiang, Jie; Li, Na
2015-11-01
A low-temperature microplasma generated in a dielectric barrier discharge (DBD) was used as a radiation source for the excitation of hydrogen sulfide and its determination by molecular emission spectrometry (MES). The excitation/emission chamber was enclosed to eliminate spectral interference from ambient air. The spectral emission lines of hydrogen sulfide were clearly discriminated from the background spectrum, and the emission line at 365.06 nm was selected for parameter optimization and quantitative analysis. The S(2-) ions in aqueous samples were reacted with acid to generate hydrogen sulfide and then determined. The experimental parameters affecting the determination of hydrogen sulfide and S(2-) were optimized. The limits of detection were 1.4 mg m(-3) for H2S and 11.2 mg L(-1) for S(2-). The repeatability of the method was satisfactory, as the RSD values were 2.3% for H2S and 1.8% for S(2-). The enclosed DBD-MES system was demonstrated to be a useful tool for the determination of hydrogen sulfide in gas samples and S(2-) in aqueous samples. Copyright © 2015 Elsevier B.V. All rights reserved.
Neutral molecules in tokamak edge plasma - role of vibrationally excited hydrogen molecules
International Nuclear Information System (INIS)
Cadez, I.; Cercek, M.; Pelicon, P.; Razpet, A.
2003-01-01
The role of neutral molecules in edge plasma is discussed with special emphasis on the vibrationally excited hydrogen. Neutral molecules are formed mostly by surface processes on the walls and then released to the edge plasma where they take part in volumetric reactions with other particles. Typically these molecules are formed in excited states and data are needed for their reactions on the wall and in the volume. Processes in edge plasma determine particle and energy flux what is especially critical issue in tokamak divertor region. Various cross sections and reaction rates are needed for modelling edge plasma and its interaction with walls. (author)
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
Slow Collisions of Si3+ with Atomic Hydrogen
Joseph, D. C.; Gu, J.-P.; Saha, B. C.; Liebermann, H. P.; Funke, P.; Buenker, R. J.
2010-03-01
Low energy electron capture from hydrogen atom by multi-charged ions continues to be of interest and applications include both magnetically confined fusion and astrophysical plasmas. The charge exchange process reported here, Si^3+ + H -> Si^2+ + H^+ is an important destruction mechanism of Si^3+ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si^3+, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the full quantum [1] and semi-classical molecular orbital close coupling (MOCC) [2] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states of and symmetry are calculated wing the MRD-CI package [3]. Details will be presented at the conference. [4pt] [1] L. B. Zhao, D. C. Joseph, B. C. Saha, H. P. Liebermann, P. Funke and R. J. Buenker, Phys. Rev A, 79, 034701 (1009).[0pt] [2] M. Kimura and N. F. Lane, At. Mol. Opt. Phys 26, 79 (1990).[0pt] [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry 1981, Vol 21, edited by R. Carbo (Elsevier, Amsterdam) p 17.
On the Fock quantisation of the hydrogen atom
International Nuclear Information System (INIS)
Cordani, B.
1989-01-01
In a celebrated work, Fock explained the degeneracy of the energy levels of the Kepler problem (or hydrogen atom) (Z. Phys. 98, 145-54, 1935) in terms of the dynamical symmetry group SO(4). Making a stereographic projection in the momentum space and rescaling the momenta with the eigenvalues of the energy, he showed that the problem is equivalent to the geodesic flow on the sphere S 3 . In this way, the 'hidden' symmetry SO(4) is made manifest. The present author has shown that the classical n-dimensional Kepler problem can be better understood by enlarging the phase space of the geodesical motion on S'' and including time and energy as canonical variables: a following symplectomorphism transforms the motion on S'' in the Kepler problem. We want to prove in this paper that the Fock procedure is the implementation at 'quantum' level of the above-mentioned symplectomorphism. The interest is not restricted to the old Kepler problem: more recently two other systems exhibiting the same symmetries have been found. They are the McIntosh-Cisneros-Zwanziger system and the geodesic motion in Euclidean Taub-NUT space. Both have a physical interest: they indeed describe a spinless test particle moving outside the core of a self-dual monopole and the asymptotic scattering of two self-dual monopoles, respectively. (author)
Trapping hydrogen atoms from a neon-gas matrix: a theoretical simulation.
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.
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)
International Nuclear Information System (INIS)
Smirnov, Yu.M.
2006-01-01
The dissociative excitation of the lead atom in e-PbI 2 collisions has been studied experimentally. 27 excitation cross-sections are measured at an exciting-electron energy of 100 eV. Nine optical excitation functions are recorded at the electron energy varying in the 0-100 eV range. The most possible reaction channels at low electron energies along with the relation of the dissociative-excitation cross-sections of the lead atom both in e-PbI 2 and e-PbCl 2 collisions are discussed. (authors)
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.
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.
Pagano, S T; Smith, B W; Winefordner, J D
1994-12-01
A sample digestion procedure was developed which employs microwave heating of soil and sediment in concentrated nitric acid in a high-pressure closed vessel. Complete dissolution of mercury into the sample solution occurs within 5 min at 59 W/vessel without loss of analyte through overpressurization. Laser-excited atomic fluorescence spectrometry with electrothermal atomization (LEAFS-ETA) was used as the detection method. The scheme uses a two-step excitation, with lambda(1) = 253.7 nm and lambda(2) = 435.8 nm. Direct line fluorescence was measured at 546.2 nm. The absolute instrumental limit of detection was 14 fg; 1.4 pg/ml with a 10 mul sample injection. The recoveries of mercury in two spiked samples were 94 and 98%. The SRM 8406 (Mercury in River Sediment) was digested and analyzed for mercury, and the results (58.4 +/- 1.8 ng/g) agreed well with the reference value of 60 ng/g. The results obtained by LEAFS-ETA with microwave sample digestion are in good agreement with those found by cold vapor atomic absorption spectrometry with EPA Series Method 245.5 sample digestion, which is one of the most commonly used methods for the determination of mercury in soil.
Le Bihan, Alain; Cabon, Jean-Yves; Deschamps, Laure; Giamarchi, Philippe
2011-06-15
In this study, direct determination of mercury at the nanogram per liter level in the complex seawater matrix by imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry (ITR-ETA-LEAFS) is described. In the case of mercury, the use of a nonresonant line for fluorescence detection with only one laser excitation is not possible. For measurements at the 253.652 nm resonant line, scattering phenomena have been minimized by eliminating the simultaneous vaporization of salts and by using temporal resolution and the imaging mode of the camera. Electrothermal conditions (0.1 M oxalic acid as matrix modifier, low atomization temperature) have been optimized in order to suppress chemical interferences and to obtain a good separation of specific signal and seawater background signal. For ETA-LEAFS, a specific response has been obtained for Hg with the use of time resolution. Moreover, an important improvement of the detection limit has been obtained by selecting, from the furnace image, pixels collecting the lowest number of scattered photons. Using optimal experimental conditions, a detection limit of 10 ng L(-1) for 10 μL of sample, close to the lowest concentration level of total Hg in the open ocean, has been obtained.
Study of the anti-hydrogen atom and ion formation in the collisions antiproton-positronium
International Nuclear Information System (INIS)
Comini, Pauline
2014-01-01
The future CERN experiment called GBAR intends to measure the gravitational acceleration of antimatter on Earth using cold (neV) anti-hydrogen atoms undergoing a free fall. The experiment scheme first needs to cool anti-hydrogen positive ions, obtained thanks to two consecutive reactions occurring when an antiproton beam collides with a dense positronium cloud.The present thesis studies these two reactions in order to optimise the production of the anti-ions. The total cross sections of both reactions have been computed in the framework of a perturbation theory model (Continuum Distorted Wave - Final State), in the range 0 to 30 keV antiproton kinetic energy; several excited states of positronium have been investigated. These cross sections have then been integrated to a simulation of the interaction zone where antiprotons collide with positronium; the aim is to find the optimal experimental parameters for GBAR. The results suggest that the 2P, 3D or, to a lower extend, 1S states of positronium should be used, respectively with 2, less than 1 or 6 keV antiprotons. The importance of using short pulses of antiprotons has been underlined; the positronium will have to be confined in a tube of 20 mm length and 1 mm diameter. In the prospect of exciting the 1S-3D two-photon transition in positronium at 410 nm, a pulsed laser system had already been designed. It consists in the frequency doubling of an 820 nm pulsed titanium-sapphire laser. The last part of the thesis has been dedicated to the realisation of this laser system, which delivers short pulses (9 ns) of 4 mJ energy at 820 nm. (author) [fr
Long-range interactions of excited He atoms with ground-state noble-gas atoms
Zhang, J.-Y.; Qian, Ying; Schwingenschlö gl, Udo; Yan, Z.-C.
2013-01-01
The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition
Photoionization of excited atoms and ions: recent progress and future prospects
International Nuclear Information System (INIS)
Wuilleumier, F.J.
2004-01-01
Full text: Photoionization of atoms in the ground state using synchrotron radiation (SR) has contributed extensively to a better knowledge of atomic structure and of its dynamical response to photon interaction. Since the st use in 1963 of an SR facility in the ultraviolet to investigate autoionizing states in helium, each improvement in the performance of available SR beams has allowed to go deeper and deeper into the understanding of isolated atomic systems. The study of very dilute targets such as atoms prepared in selected excited states or multiply-charged ions is more challenging. Using dye lasers, the excited state can be prepared with a well defined set of quantum numbers and SR photoionization of this prepared state can be studied as a function of photon energy and emission-angle. For ions, the equivalent ionic densities achievable in a merged-beam experiment do not exceed, usually, 10 6 cm -3 , i.e. they are lower by 5 orders of magnitude than for atoms in the ground state. This explains why the response of ionized matter to photoionizing radiation has been largely unexplored until recently. Theoretical methods, still to be tested by experimental measurements, have been developed to model stellar atmospheres as well as laboratory plasmas. After the pioneering experiments using plasma discharge technology and laser-produced plasmas to measure photoionization in excited states and ions, the use of SR has allowed to dramatically improve experiments for excited- and ionic-species, starting with the first measurements of electron spectra from photoionization of laser-excited sodium atoms, and with the first determination of doubly-charged ion rate resulting from photoionization of singly-charged ions in merged beam experiments. Over the past 5 years, photoionization of singly- and multiply-charged ions using the merged beam technique has been intensively performed at four SR facilities (ASTRID, Spring-8, the Advanced Light Source (ALS), and Super-ACO), all of
Optical excitation cross-sections for electron collisions with atoms and molecules
International Nuclear Information System (INIS)
McConkey, J.W.; Univ. of Windsor, Ontario)
1983-01-01
A brief review of the status of absolute electron-impact excitation cross-section measurements for atoms and molecules is presented. Some of the reasons for the wide discrepancies which exist in the published data are discussed. Tables are presented of recent publications in the field which are not included in the J.I.L.A. compilations. A tabular compilation of the existing data for e-impact on H 2 O is also given and discussed. Some recent experiments of particular interest to the development of the theory of electron-molecule excitation are mentioned. 112 references, 3 figures, 3 tables
Selection rule engineering of forbidden transitions of a hydrogen atom near a nanogap
Kim, Hyunyoung Y.; Kim, Daisik S.
2018-01-01
We perform an analytical study on the allowance of forbidden transitions for a hydrogen atom placed near line dipole sources, mimicking light emanating from a one-dimensional metallic nanogap. It is shown that the rapid variation of the electric field vector, inevitable in the near zone, completely breaks the selection rule of Δl=±1. While the forbidden transitions between spherically symmetric S states, such as 2S to 1S or 3S to 1S (Δl=0), are rather robust against selection rule breakage, Δl=±2 transitions such as between 3D and 1S or 3D and 2S states are very vulnerable to the spatial variation of the perturbing electric field. Transitions between 2S and 3D states are enhanced by many orders of magnitude, aided by the quadratic nature of both the perturbing Hamiltonian and D wavefunctions. The forbidden dipole moment, which approaches one Bohr radius times the electric charge in the vicinity of the gap, can be written in a simple closed form owing to the one-dimensional nature of our gap. With large enough effective volume together with the symmetric nature of the excited state wavefunctions, our work paves way towards atomic physics application of infinitely long nanogaps.
An atomic hydrogen beam to test ASACUSA's apparatus for antihydrogen spectroscopy
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.
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.
International Nuclear Information System (INIS)
Runge, Serge.
1980-12-01
The relative cross-sections of ionizing collisions between He + He and He + Ne atoms, have been studied, the helium being excited in a state (3 1 p) by a laser beam. The results obtained made it possible (a) to reveal in a direct manner the production of molecular ions He 2 + and He Ne + and (b) to determine the relative change in the associative ionizing cross-section in the area (0.035 - 0.17 eV) in the He (3 1 P) + Ne collision, despite the very short life of the He (3 1 P) excited state (1.7 ns). The production of He 2 + ions from an He (3 1 P) + He collision sets an upper limit to the appearance potential of these ions. The experimental study of the associative ionization in the He (3 1 P) + Ne system made it possible to extend the utilization of the GAMMA(R) self ionization model, already tested for the metastable states, to the radiative states. The GAMMA(R) model seems well suited for the description of collisions of the A excited + B type, where the excitation energy of A is greater than the ionization potential of B [fr
Belkic, Dzevad
Inelastic collisions between bare nuclei and hydrogen-like atomic systems are characterized by three main channels: electron capture, excitation, and ionization. Capture dominates at lower energies, whereas excitation and ionization prevail at higher impact energies. At intermediate energies and in the region of resonant scattering near the Massey peak, all three channels become competitive. For dressed or clothed nuclei possessing electrons, such as hydrogen-like ions, several additional channels open up, including electron loss (projectile ionization or stripping). The most important aspect of electron loss is the competition between one- and two-electron processes. Here, in a typical one-electron process, the projectile emits an electron, whereas the target final and initial states are the same. A prototype of double-electron transitions in loss processes is projectile ionization accompanied with an alteration of the target state. In such a two-electron process, the target could be excited or ionized. The relative importance of these loss channels with single- and double-electron transitions involving collisions of dressed projectiles with atomic systems is also strongly dependent on the value of the impact energy. Moreover, impact energies determine which theoretical method is likely to be more appropriate to use for predictions of cross sections. At low energies, an expansion of total scattering wave functions in terms of molecular orbitals is adequate. This is because the projectile spends considerable time in the vicinity of the target, and as a result, a compound system comprised of the projectile and the target can be formed in a metastable molecular state which is prone to decay. At high energies, a perturbation series expansion is more appropriate in terms of powers of interaction potentials. In the intermediate energy region, atomic orbitals are often used with success while expanding the total scattering wave functions. The present work is focused on
K-shell excitation studied for H- and He-like bismuth ions in collisions with low-z target atoms
International Nuclear Information System (INIS)
Stoehlker, T.; Bosch, F.; Geissel, H.; Kozhuharov, C.; Ludziejewski, T.; Mokler, P.H.; Scheidenberger, C.; Stachura, Z.; Warczak, A.
1997-09-01
The formation of excited projectile states via Coulomb excitation is investigated for hydrogen- and helium-like bismuth projectiles (Z=83) in relativistic ion-atom collisions. The excitation process was unambiguously identified by observing the radiative decay of the excited levels to the vacant 1s shell in coincidence with ions that did not undergo charge exchange in the reaction target. In particular, owing to the large fine structure splitting of Bi, the excitation cross-sections to the various L-shell sublevels are determined separately. The results are compared with detailed relativistic calculations, showing that both the relativistic character of the bound-state wave-functions and the magnetic interaction are of considerable importance for the K-shell excitation process in high-Z ions like Bi. The experimental data confirm the result of the complete relativistic calculations, namely that the magnetic part of the Lienard-Wiechert interaction leads to a significant reduction of the K-shell excitation cross-section. (orig.)
Vibrational excitation of hydrogen molecules by two-photon absorption and third-harmonic generation
Miyamoto, Yuki; Hara, Hideaki; Hiraki, Takahiro; Masuda, Takahiko; Sasao, Noboru; Uetake, Satoshi; Yoshimi, Akihiro; Yoshimura, Koji; Yoshimura, Motohiko
2018-01-01
We report the coherent excitation of the vibrational state of hydrogen molecules by two-photon absorption and the resultant third-harmonic generation (THG). Parahydrogen molecules cooled by liquid nitrogen are irradiated by mid-infrared nanosecond pulses at 4.8 μm with a nearly Fourier-transform-limited linewidth. The first excited vibrational state of parahydrogen is populated by two-photon absorption of the mid-infrared photons. Because of the narrow linewidth of the mid-infrared pulses, coherence between the ground and excited states is sufficient to induce higher-order processes. Near-infrared photons from the THG are observed at 1.6 μm. The dependence of the intensity of the near-infrared radiation on mid-infrared pulse energy, target pressure, and cell length is determined. We used a simple formula for THG with consideration of realistic experimental conditions to explain the observed results.
Excited state hydrogen bonding fluorescent probe: Role of structure and environment
Energy Technology Data Exchange (ETDEWEB)
Dey, Debarati, E-mail: debaratidey07@gmail.com [Department of Chemistry, Vidyasagar College, 39 Sankar Ghosh Lane, Kolkata 700006 (India); Sarangi, Manas Kumar [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Ray, Angana; Bhattacharyya, Dhananjay [Computational Science Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Maity, Dilip Kumar [Department of Chemistry, University College of Science and Technology, 92 A.P.C. Road, Kolkata 700009 (India)
2016-05-15
An environment sensitive fluorescent probe, 11-benzoyl-dibenzo[a,c]phenazine (BDBPZ), has been synthesized and characterized that acts via excited state hydrogen bonding (ESHB). On interaction with hydrogen bond donating solvents the fluorescence intensity of BDBPZ increases abruptly with a concomitant bathochromic shift. The extent of fluorescence increment and the red-shift of λ{sub max} depend on hydrogen bond donating ability of the solvent associated. ESHB restricts the free rotation of the benzoyl group and hence blocks the non-radiative deactivation pathway. BDBPZ forms an exciplex with organic amine in nonpolar medium that readily disappears on increasing the polarity of the solvent. In polar environment the fluorescence of both the free molecule and excited state hydrogen bonded species are quenched on addition of amine unlike its parent dibenzo[a,c]phenazine (DBPZ), that remains very much inaccessible towards the solvent as well as quencher molecules due to its structure. This newly synthesized derivative BDBPZ is much more interactive due to the benzoyl group that is flanked outside the skeletal aromatic rings of DBPZ, which helps to sense the environment properly and thus shows better ESHB capacity than DBPZ.
Excitation dependence of resonance line self-broadening at different atomic densities
Li, Hebin; Sautenkov, Vladimir A.; Rostovtsev, Yuri V.; Scully, Marlan O.
2009-01-01
We study the dipole-dipole spectral broadening of a resonance line at high atomic densities when the self-broadening dominates. The selective reflection spectrum of a weak probe beam from the interface of the cell window and rubidium vapor are recorded in the presence of a far-detuned pump beam. The excitation due to the pump reduces the self-broadening. We found that the self-broadening reduction dependence on the pump power is atomic density independent. These results provide experimental e...
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.
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)
Bibliography of atomic and molecular excitation in heavy particle collisions, 1950--1975
International Nuclear Information System (INIS)
Hawthorne, S.W.; Thomas, E.W.; Barnett, C.F.; Crandall, D.H.; Gilbody, H.B.; Kirkpatrick, M.I.; McDaniel, E.W.; Phaneuf, R.A.
1979-02-01
This annotated bibliography lists published work on atomic and molecular excitation in heavy particle collisions for the period 1950 to 1975. Sources include scientific journals, abstract compilations, conference proceedings, books, and reports. The bibliography is arranged alphabetically by author. Each entry indicates whether the work was experimental or theoretical, what energy range was covered, and what reactants were investigated. Following the bibliographical listing are indexes of reactions and authors
Nonradiative excitation of the muonic atom 238U as an inverse conversion process
International Nuclear Information System (INIS)
Karpeshin, F.F.; Nesterenko, V.U.
1982-01-01
The probabilities of nonradiation nuclear excitation are calculated for different muon transitions in the muonic atom 238 U. Microscopic nuclear wave functions, obtained within the quasiparticle-phonon nuclear model and the muonic conversion coefficients have been used. The probability of nonradiation nuclear excitation for the muonic transitions 2p → 1s and 3p → 1s has been found to be equal to 0.3. It is predicted that nonradiative E3 transitions 3d → 2p can take place with the probability 0.08-0.10. The dynamic effect of nuclear structure on the probability of nonradiative nuclear excitation is taken into account. The estimates of 238 U fissility fission branching at nonradiation transitions are also obtained
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
The mechanism of three-body process of energy transfer from excited xenon atoms to molecules
International Nuclear Information System (INIS)
Wojciechowski, K.; Forys, M.
1999-01-01
The mechanism of energy transfer from Xe(6 s[3/2] 1 ) resonance state (E=8.44 eV) and higher excited Xe(6p, 6p', 6 d) atoms produced in pulse radiolysis to molecules have been discussed. The analysis of the kinetic data for these processes shows that in the sensitized photolysis and radiolysis of Xe-M mixtures the excited atoms decay in 'ordinary' two-body reaction: Xe(6s[3/2] 1 0 )+M→products (r.1) and in fast 'accelerated' third order process: Xe(6s[3/2] 1 0 )+M+Xe→products (r.2) The discussion shows that three-body process occurs via reactions: Xe(6s[3/2] 1 0 )+Xe k w ↔ k d Xe 2 ** (r.2a) Xe 2 **+M k q →[Xe 2 M]*→products (r.2b) It was shown that this mechanism concerns also higher excited Xe atoms and can explain a similar process in He-M mixtures and suggests that it is a general mechanism of energy transfer in all irradiated rare gas-molecule systems
Atomic data on inelastic processes in low-energy manganese-hydrogen collisions
Belyaev, Andrey K.; Voronov, Yaroslav V.
2017-10-01
Aims: The aim of this paper is to calculate cross sections and rate coefficients for inelastic processes in low-energy Mn + H and Mn+ + H- collisions, especially, for processes with high and moderate rate coefficients. These processes are required for non-local thermodynamic equilibrium (non-LTE) modeling of manganese spectra in cool stellar atmospheres, and in particular, for metal-poor stars. Methods: The calculations of the cross sections and the rate coefficients were performed by means of the quantum model approach within the framework of the Born-Oppenheimer formalism, that is, the asymptotic semi-empirical method for the electronic MnH molecular structure calculation followed by the nonadiabatic nuclear dynamical calculation by means of the multichannel analytic formulas. Results: The cross sections and the rate coefficients for low-energy inelastic processes in manganese-hydrogen collisions are calculated for all transitions between 21 low-lying covalent states and one ionic state. We show that the highest values of the cross sections and the rate coefficients correspond to the mutual neutralization processes into the final atomic states Mn(3d54s(7S)5s e 6S), Mn(3d54s(7S)5p y 8P°), Mn(3d54s(7S)5s e 8S), Mn(3d54s(7S)4d e 8D) [the first group], the processes with the rate coefficients (at temperature T = 6000 K) of the values 4.38 × 10-8, 2.72 × 10-8, 1.98 × 10-8, and 1.59 × 10-8 cm3/ s, respectively, that is, with the rate coefficients exceeding 10-8 cm3/ s. The processes with moderate rate coefficients, that is, with values between 10-10 and 10-8 cm3/ s include many excitation, de-excitation, mutual neutralization and ion-pair formation processes. In addition to other processes involving the atomic states from the first group, the processes from the second group include those involving the following atomic states: Mn(3d5(6S)4s4p (1P°) y 6P°), Mn(3d54s(7S)4d e 6D), Mn(3d54s(7S)5p w 6P°), Mn(3d5(4P)4s4p (3P°) y 6D°), Mn(3d5(4G)4s4p (3P°) y 6F
Detection of hot muonic hydrogen atoms emitted in vacuum using x-rays
International Nuclear Information System (INIS)
Jacot-Guillarmod, R.; Bailey, J.M.; 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
Negative muons are stopped in solid layers of hydrogen and neon. Muonic hydrogen atoms can drift to the neon layer where the muon is immediately transferred. It was found that the time structure of the muonic neon X-rays follows the exponential law where the rate is the same as the disappearance rate of μ - p atoms. The ppμ-formation rate and the muon transfer rate to deuterium are deduced
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
Swart, D J; Simeonsson, J B
1999-11-01
A procedure for the direct determination of arsenic in diluted serum by electrothermal atomization laser-excited atomic fluorescence spectrometry (ETA-LEAFS) is reported. Laser radiation needed to excite As at 193.696 and 197.197 nm is generated as the second anti-Stokes stimulated Raman scattering output of a frequency-doubled dye laser operating near 230.5 and 235.5 nm, respectively. Two different LEAFS schemes have been utilized and provide limits of detection of 200-300 fg for As in aqueous standards. When measurements of serum samples diluted 1:10 with deionized water are performed, a stable background signal is observed that can be accounted for by taking measurements with the laser tuned off-wavelength. No As is detected in any of the bovine or human serum samples analyzed. Measurements of 100 pg/mL standard additions of As to a diluted bovine serum sample utilizing either inorganic or organic As species demonstrate a linear relationship of the fluorescence signal to As spike concentration, but exhibit a sensitivity of approximately half that observed in pure aqueous standards. The limit of detection for As in 1:10 diluted serum samples is 65 pg/mL or 650 fg absolute mass, which corresponds to 0.65 ng/mL As in undiluted serum. To our knowledge, the ETA-LEAFS procedure is currently the only one capable of directly measuring As in diluted serum at these levels.
Hydrogen atoms in protein structures: high-resolution X-ray diffraction structure of the DFPase
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
Photoionization dynamics of excited Ne, Ar, Kr and Xe atoms near threshold
International Nuclear Information System (INIS)
Sukhorukov, V L; Petrov, I D; Schäfer, M; Merkt, F; Ruf, M-W; Hotop, H
2012-01-01
A review of experimental and theoretical studies of the threshold photoionization of the heavier rare-gas atoms is presented, with particular emphasis on the autoionization resonances in the spectral region between the lowest two ionization thresholds 2 P 3/2 and 2 P 1/2 , accessed from the ground or excited states. Observed trends in the positions, widths and shapes of the autoionization resonances depending on the atomic number, the principal quantum number n, the orbital angular momentum quantum number ℓ and further quantum numbers specifying the fine- and hyperfine-structure levels are summarized and discussed in the light of ab initio and multichannel quantum defect theory calculations. The dependence of the photoionization spectra on the initially prepared neutral state are also discussed, including results on the photoionization cross sections and photoelectron angular distributions of polarized excited states. The effects of various approximations in the theoretical treatment of photoionization in these systems are analysed. The very large diversity of observed phenomena and the numerous anomalies in spectral structures associated with the threshold ionization of the rare-gas atoms can be described in terms of a limited set of interactions and dynamical processes. Examples are provided illustrating characteristic aspects of the photoionization, and sets of recommended parameters describing the energy-level structure and photoionization dynamics of the rare-gas atoms are presented which were extracted in a critical analysis of the very large body of experimental and theoretical data available on these systems in the literature. (topical review)
Collective excitations and supersolid behavior of bosonic atoms inside two crossed optical cavities
Lang, J.; Piazza, F.; Zwerger, W.
2017-12-01
We discuss the nature of symmetry breaking and the associated collective excitations for a system of bosons coupled to the electromagnetic field of two optical cavities. For the specific configuration realized in a recent experiment at ETH [1, 2], we show that, in absence of direct intercavity scattering and for parameters chosen such that the atoms couple symmetrically to both cavities, the system possesses an approximate U(1) symmetry which holds asymptotically for vanishing cavity field intensity. It corresponds to the invariance with respect to redistributing the total intensity I={I}1+{I}2 between the two cavities. The spontaneous breaking of this symmetry gives rise to a broken continuous translation-invariance for the atoms, creating a supersolid-like order in the presence of a Bose-Einstein condensate. In particular, we show that atom-mediated scattering between the two cavities, which favors the state with equal light intensities {I}1={I}2 and reduces the symmetry to {{Z}}2\\otimes {{Z}}2, gives rise to a finite value ˜ \\sqrt{I} of the effective Goldstone mass. For strong atom driving, this low energy mode is clearly separated from an effective Higgs excitation associated with changes of the total intensity I. In addition, we compute the spectral distribution of the cavity light field and show that both the Higgs and Goldstone mode acquire a finite lifetime due to Landau damping at non-zero temperature.
Reactive quenching of two-photon excited xenon atoms by Cl2
International Nuclear Information System (INIS)
Bruce, M.R.; Layne, W.B.; Meyer, E.; Keto, J.W.
1987-01-01
Total binary and tertiary quench rates have been measured for the reaction Xe (5p 5 6p) + Cl 2 at thermal temperatures. Xenon atoms are excited by state-selective, two-photon absorption with a uv laser. The time dependent fluorescence from the excited atom in the IR and from XeCl* (B) product near 308 nm have been measured with subnanosecond time resolution. The decay rates are measured as a function of Cl 2 pressure to 20 Torr and Xe pressure to 400 Torr. The measured reaction rates (k 2 ∼ 10 -9 cm 3 sec -1 ) are consistent with a harpoon model described in a separate paper. We also measure large termolecular reaction rates for collisions with xenon atoms (k 3 ∼ 10 -28 cm 6 sec -1 ). Total product fluorescence has been examined using a gated optical multichannel analyzer. We measure unit branching fractions for high vibrational levels of XeCl* (B) with very little C state fluorescence observed. The measured termolecular rates suggest similar processes will dominate at the high buffer-gas pressures used in XeCl lasers. The effect of these large reactive cross sections for neutral xenon atoms on models of the XeCl laser will be discussed
Reaction kinetics of hydrogen atom abstraction from isopentanol by the H atom and HO2˙ radical.
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.
Energy Technology Data Exchange (ETDEWEB)
Penedo, M., E-mail: mapenedo@imm.cnm.csic.es; Hormeño, S.; Fernández-Martínez, I.; Luna, M.; Briones, F. [IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid (Spain); Raman, A. [Birck Nanotechnology Center and School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47904 (United States)
2014-10-27
Recent developments in dynamic Atomic Force Microscopy where several eigenmodes are simultaneously excited in liquid media are proving to be an excellent tool in biological studies. Despite its relevance, the search for a reliable, efficient, and strong cantilever excitation method is still in progress. Herein, we present a theoretical modeling and experimental results of different actuation methods compatible with the operation of Atomic Force Microscopy in liquid environments: ideal acoustic, homogeneously distributed force, distributed applied torque (MAC Mode™), photothermal and magnetostrictive excitation. From the analysis of the results, it can be concluded that magnetostriction is the strongest and most efficient technique for higher eigenmode excitation when using soft cantilevers in liquid media.
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.
Long-range interactions of excited He atoms with ground-state noble-gas atoms
Zhang, J.-Y.
2013-10-09
The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-n expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the C6 coefficients for the systems involving He(131,3S) and He(131,3P) are calculated and found to be in good agreement with directly calculated values.
Time evolution of cascade processes of muonic atoms in hydrogen-helium mixtures
International Nuclear Information System (INIS)
Bystritskij, V.; Czaplinski, W.; Filipowicz, M.; Gula, E.; Popov, N.
1999-01-01
Time dependence of population of muonic hydrogen states in hydrogen-helium mixtures is calculated for principal quantum number n. Number of muons transferred to helium nuclei is also determined. Dependence of population of the ground state of muonic hydrogen q ls He on time and target density and helium concentration is also considered. The results are in agreement with recent experimental data. The comparison of the calculated yield of K lines of x-ray in pure hydrogen and deuterium with experimental data indicates on essential role of Coulomb de-excitation process. Possible Stark mixing is also analyzed
Nonlinear dynamic analysis of atomic force microscopy under deterministic and random excitation
International Nuclear Information System (INIS)
Pishkenari, Hossein Nejat; Behzad, Mehdi; Meghdari, Ali
2008-01-01
The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. This paper is devoted to the analysis of nonlinear behavior of amplitude modulation (AM) and frequency modulation (FM) modes of atomic force microscopy. For this, the microcantilever (which forms the basis for the operation of AFM) is modeled as a single mode approximation and the interaction between the sample and cantilever is derived from a van der Waals potential. Using perturbation methods such as averaging, and Fourier transform nonlinear equations of motion are analytically solved and the advantageous results are extracted from this nonlinear analysis. The results of the proposed techniques for AM-AFM, clearly depict the existence of two stable and one unstable (saddle) solutions for some of exciting parameters under deterministic vibration. The basin of attraction of two stable solutions is different and dependent on the exciting frequency. From this analysis the range of the frequency which will result in a unique periodic response can be obtained and used in practical experiments. Furthermore the analytical responses determined by perturbation techniques can be used to detect the parameter region where the chaotic motion is avoided. On the other hand for FM-AFM, the relation between frequency shift and the system parameters can be extracted and used for investigation of the system nonlinear behavior. The nonlinear behavior of the oscillating tip can easily explain the observed shift of frequency as a function of tip sample distance. Also in this paper we have investigated the AM-AFM system response under a random excitation. Using two different methods we have obtained the statistical properties of the tip motion. The results show that we can use the mean square value of tip motion to image the sample when the excitation signal is random
Nonlinear dynamic analysis of atomic force microscopy under deterministic and random excitation
Energy Technology Data Exchange (ETDEWEB)
Pishkenari, Hossein Nejat [Center of Excellence in Design, Robotics and Automation (CEDRA), School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Behzad, Mehdi [Center of Excellence in Design, Robotics and Automation (CEDRA), School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)], E-mail: m_behzad@sharif.edu; Meghdari, Ali [Center of Excellence in Design, Robotics and Automation (CEDRA), School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)
2008-08-15
The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. This paper is devoted to the analysis of nonlinear behavior of amplitude modulation (AM) and frequency modulation (FM) modes of atomic force microscopy. For this, the microcantilever (which forms the basis for the operation of AFM) is modeled as a single mode approximation and the interaction between the sample and cantilever is derived from a van der Waals potential. Using perturbation methods such as averaging, and Fourier transform nonlinear equations of motion are analytically solved and the advantageous results are extracted from this nonlinear analysis. The results of the proposed techniques for AM-AFM, clearly depict the existence of two stable and one unstable (saddle) solutions for some of exciting parameters under deterministic vibration. The basin of attraction of two stable solutions is different and dependent on the exciting frequency. From this analysis the range of the frequency which will result in a unique periodic response can be obtained and used in practical experiments. Furthermore the analytical responses determined by perturbation techniques can be used to detect the parameter region where the chaotic motion is avoided. On the other hand for FM-AFM, the relation between frequency shift and the system parameters can be extracted and used for investigation of the system nonlinear behavior. The nonlinear behavior of the oscillating tip can easily explain the observed shift of frequency as a function of tip sample distance. Also in this paper we have investigated the AM-AFM system response under a random excitation. Using two different methods we have obtained the statistical properties of the tip motion. The results show that we can use the mean square value of tip motion to image the sample when the excitation signal is random.
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.
Hydrogen atoms can be located accurately and precisely by x-ray crystallography.
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.
Jagiellonian University Study of Hadronic Hydrogen-like Atoms in the DIRAC Experiment at PS CERN
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.
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.)
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, ...
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.)
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)
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
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)
Resonance effects in projectile-electron loss in relativistic collisions with excited atoms
International Nuclear Information System (INIS)
Voitkiv, A B
2005-01-01
The theory of electron loss from projectile-ions in relativistic ion-atom collisions is extended to the case of collisions with excited atoms. The main feature of such collisions is a resonance which can emerge between electron transitions in the ion and atom. The resonance becomes possible due to the Doppler effect and has a well-defined impact energy threshold. In the resonance case, the ion-atom interaction is transmitted by the radiation field and the range of this interaction becomes extremely long. Because of this the presence of other atoms in the target medium and the size of the space occupied by the medium have to be taken into account and it turns out that microscopic loss cross sections may be strongly dependent on such macroscopic parameters as the target density, temperature and size. We consider both the total and differential loss cross sections and show that the resonance can have a strong impact on the angular and energy distributions of electrons emitted from the projectiles and the total number of electron loss events
Long-range interactions between excited helium and alkali-metal atoms
Zhang, J.-Y.
2012-12-03
The dispersion coefficients for the long-range interaction of the first four excited states of He, i.e., He(2 1,3S) and He(2 1,3P), with the low-lying states of the alkali-metal atoms Li, Na, K, and Rb are calculated by summing over the reduced matrix elements of the multipole transition operators. For the interaction between He and Li the uncertainty of the calculations is 0.1–0.5%. For interactions with other alkali-metal atoms the uncertainty is 1–3% in the coefficient C5, 1–5% in the coefficient C6, and 1–10% in the coefficients C8 and C10. The dispersion coefficients Cn for the interaction of He(2 1,3S) and He(2 1,3P) with the ground-state alkali-metal atoms and for the interaction of He(2 1,3S) with the alkali-metal atoms in their first 2P states are presented in this Brief Report. The coefficients for other pairs of atomic states are listed in the Supplemental Material.
Insights into the Hydrogen-Atom Transfer of the Blue Aroxyl.
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.
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.
Joo, Ji Bong; Dillon, Robert; Lee, Ilkeun; Yin, Yadong; Bardeen, Christopher J; Zaera, Francisco
2014-06-03
The production of hydrogen from water with semiconductor photocatalysts can be promoted by adding small amounts of metals to their surfaces. The resulting enhancement in photocatalytic activity is commonly attributed to a fast transfer of the excited electrons generated by photon absorption from the semiconductor to the metal, a step that prevents deexcitation back to the ground electronic state. Here we provide experimental evidence that suggests an alternative pathway that does not involve electron transfer to the metal but requires it to act as a catalyst for the recombination of the hydrogen atoms made via the reduction of protons on the surface of the semiconductor instead.
Dynamics of the helium atom close to the full fragmentation threshold: Ionization excitation
International Nuclear Information System (INIS)
Bouri, C.; Selles, P.; Malegat, L.; Teuler, J.M.; Njock, M. Kwato; Kazansky, A.K.
2005-01-01
The hyperspherical R-matrix method with semiclassical outgoing waves, designed to provide accurate double-ionization cross sections, is extended to allow for the computation of ionization-excitation data of comparable quality. Accordingly, it appears now as a complete method for treating the correlated dynamics of two-electron atoms, in particular above their full fragmentation threshold. Cross sections σ n and asymmetry parameters β n are obtained for single photoionization of helium with excitation of the residual ion up to as high a level as n=50 at 0.1 eV above the double-ionization threshold. These data are extrapolated to infinite values of n in order to check widespread assumptions regarding this limit. Our data are found consistent with the assumed n -3 dependence of the partial ionization cross sections. However, the β ∞ =-0.636 obtained still lies far from the -1 value expected at the double-ionization threshold
Charge asymmetry in alignment of atoms excited by protons and antiprotons
International Nuclear Information System (INIS)
Balashov, V.V.; Sokolik, A.A.; Stysin, A.V.
2007-01-01
The multichannel diffraction approximation is used to consider excitation of lithium atom by proton and antiproton impact. Calculations are performed for the energy range 100 keV - 1 MeV of incoming proton and anti-proton which should be reliable enough due to the general requirements of the multichannel diffraction approximation. The sign-of-charge effect in the alignment of produced 1s 2 3d excited state and in the linear polarization of the subsequent spontaneous 1s 2 3d → 1s 2 2p radiation is expected to be considerable. The clear sign-of-charge effect in the polarization occurs for projectile energies below 1 MeV and become stronger when going to lower energies and the difference between the proton case and the anti-proton one looks considerable enough for experimental observation
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.
Gong, Zhen-bin; Liang, Feng; Yang, Peng-yuan; Jin, Qin-han; Huang, Ben-li
2002-02-01
A system of atomic and ionic fluorescence spectrometry in microwave plasma torch (MPT) discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL) has been developed. The operation conditions for Ca atomic and ionic fluorescence spectrometry have been optimized. Compared with atomic fluorescence spectrometry (AFS) in argon microwave induced plasma (MIP) and MPT with the excitation of direct current and conventional pulsed HCL, the system with HCMP HCL excitation can improve AFS and ionic fluorescence spectrometry (IFS) detection limits in MPT atomizer and ionizer. Detection limits (3 sigma) with HCMP HCL-MPT-AFS/IFS are 10.1 ng.mL-1 for Ca I 422.7 nm, 14.6 ng.mL-1 for Ca II 393.4 nm, and 37.4 ng.mL-1 for Ca II 396.8 nm, respectively.
Interference spectra induced by a bichromatic field in the excited state of a three-level atom
International Nuclear Information System (INIS)
Mavroyannis, C.
1998-01-01
The interference spectra for the excited state of a three-level atom have been considered, where the strong and the weak atomic transitions leading to an electric dipole allowed excited state and to a metastable excited state are driven by resonant and nonresonant laser fields, respectively. In the low intensity limit of the strong laser field, there are two short lifetime excitations, the spontaneous one described by the weak signal field and the one induced by the strong laser field, both of which appear at the same frequency, and a long lifetime excitation induced by the weak laser field. The maximum intensities (heights) of the two peaks describing the short lifetime excitations take equal positive and negative values and, therefore, cancel each other out completely, while the long lifetime excitation dominates. This indicates the disappearance of the short lifetime excitations describing the strong atomic transition for a period equal to the lifetime of the long lifetime excitation, which is roughly equal to half of the lifetime of the metastable state. The computed spectra have been graphically presented and discussed at resonance and for finite detunings. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)
International Nuclear Information System (INIS)
Meijer, H.A.J.; Pelgrim, T.J.C.; Heideman, H.G.M.; Morgenstern, R.; Andersen, N.
1988-01-01
The associative ionization process in thermal Na(3p)-Na(3p) encounters has been studied in a series of crossed-beam experiments where the light polarization of the two laser beams preparing the excited atoms before collision was varied independently. It is shown how in this way maximum possible information for our geometry is extracted about the dependence of the ion formation process on the shape and spatial orientation of the electron clouds of the two approaching atoms, including all coherence terms. The experimental findings are discussed in the light of recent theoretical results for the states of the Na 2 molecule. It is concluded that just a few of the possible geometrical approaches are favourable for molecular-ion formation. (orig.)
International Nuclear Information System (INIS)
Broderick, Bernadette M.; Lee, Yumin; Doyle, Michael B.; Chernyak, Vladimir Y.; Suits, Arthur G.; Vasyutinskii, Oleg S.
2014-01-01
We have developed a new experimental method allowing direct detection of the velocity dependent spin-polarization of hydrogen atoms produced in photodissociation. The technique, which is a variation on the H atom Rydberg time-of-flight method, employs a double-resonance excitation scheme and experimental geometry that yields the two coherent orientation parameters as a function of recoil speed for scattering perpendicular to the laser propagation direction. The approach, apparatus, and optical layout we employ are described here in detail and demonstrated in application to HBr and DBr photolysis at 213 nm. We also discuss the theoretical foundation for the approach, as well as the resolution and sensitivity we achieve
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)
ESR measurement of the concentration of vibrationally excited hydrogen and deuterium molecules
International Nuclear Information System (INIS)
Gershenzon, Yu.M.; Ivanov, A.V.; Il'in, S.D.; Kucheryavyi, S.I.; Rozenshtein, V.B.
1988-01-01
A method is described for measuring the concentration of vibrationally excited H 2 and D 2 molecules using an ESR microwave spectrometer. The essence of the method is the titration of H 2 (v = 1) and D 2 (v = 1) with D and H atoms and measurement of the concentrations of the titration products H and D, respectively. Stoichiometric titration coefficients were determined in the form of proportionality coefficients between the titration signals Δ[H], Δ[D] and the concentrations of H 2 (v = 1), D 2 (v = 1)
A theoretical perspective of the nature of hydrogen-bond types - the atoms in molecules approach
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.
Atomic displacements due to interstitial hydrogen in Cu and Pd
Indian Academy of Sciences (India)
Total energy calculations and molecular dynamics simulations employing DFT are reliable tools ... as well as predicting equilibrium and non-equilibrium properties. Self-consistent ..... produced by interstitial hydrogen in Cu and Pd. The quantity of central interest .... These numbers are in reasonable qualitative agreement.
The atomic hydrogen flux during microcrystalline silicon solar cell deposition
Sanden, van de M.C.M.; Dingemans, G.; van den Donker, M.N.; Hrunski, D.; Gordijn, A.; Kessels, W.M.M.
2009-01-01
Etch product detection by in situ optical emission spectroscopy is used to detect the phase transition from amorphous to microcrystalline silicon. In this contribution it is demonstrated that a calibrated version of this technique can be used to determine the absolute hydrogen flux under
International Nuclear Information System (INIS)
Jin Shiqi; Gong Shangqing; Li Ruxin; Xu Zhizhan
2004-01-01
Coherent population transfer and superposition of atomic states via a technique of stimulated Raman adiabatic passage in an excited-doublet four-level atomic system have been analyzed. It is shown that the behavior of adiabatic passage in this system depends crucially on the detunings between the laser frequencies and the corresponding atomic transition frequencies. Particularly, if both the fields are tuned to the center of the two upper levels, the four-level system has two degenerate dark states, although one of them contains the contribution from the excited atomic states. The nonadiabatic coupling of the two degenerate dark states is intrinsic, it originates from the energy difference of the two upper levels. An arbitrary superposition of atomic states can be prepared due to such nonadiabatic coupling effect
Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer
Gil, Michał; Kijak, Michał; Piwonski, Hubert Marek; Herbich, Jerzy; Waluk, Jacek
2017-01-01
Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.
Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer
Gil, Michał
2017-02-03
Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.
Energy Technology Data Exchange (ETDEWEB)
Shimamori, H. [Fukui University of Technology, Fukui (Japan)
1997-05-20
Regarding excitation and deexcitation due to collision of electrons and deexcitation due to collision of baryons in nonequilibrium plasma, explanation is made about the general characteristics of the elementary processes involving their formation and disappearance and about the prediction of their sectional areas and velocity constants. As for the process of the formation of excited atoms and molecules by collision of electrons, it may be divided into the direct excitation in the ground state, excitation and light emission toward the resonance state, reexcitation and transformation of excited particles, recombination of electrons and positive atomic ions, and dissociation and recombination of electrons and positive molecular ions. As for the process of the disappearance of excited particles, there exist various courses it may follow, and it is quite complicated because it is dependent on the types of particles involved and the conditions the process proceeds under. Although the skeleton has been built of the theory of derivation of the sectional area of excitation due to collision of electrons and atoms/molecules, yet it is accurate enough only when applied to simple atomic/molecular systems, is far from satisfying in general, and is to be augmented by data from future experiments. 22 refs., 3 figs., 1 tab.
Production of excited nitrogen atoms and ions by electron impact on nitrogen molecules
International Nuclear Information System (INIS)
Rall, D.L.A.; Anderson, L.W.; Lin, C.C.; Sharpton, F.A.
1984-01-01
Emission lines of the N atoms and N ions are produced by electron-beam dissociative excitation of N 2 molecules. The ns→3 /sub p/ (n=5 to 9), np→3s (n=3 to 7), nd→3 /sub p/ (n=4 to 8), nf→3d (n=4,5) transitions of N and the 3 /sub p/ →3s, 3d→3p, 4s→3p, 4p→3d, 4f→3d transitions of N + have been observed and optical emission cross sections at various incident electron energies have been measured. The energy dependence of the cross sections of the N emission lines is similar to that of the N + lines at high incident electron energies, but the low-energy behaviors are quite different. These features are explained by the mechanisms involved in the production of the excited N atoms and N + ions. Absolute optical emission cross sections for the N and N + lines are presented
International Nuclear Information System (INIS)
Miyazaky, T.; Guedes, S.M.L.; Andrade e Silva, L.G. de; Fernandes, L.
1977-01-01
The reaction of H atoms, produced by the photolysis of HI, has been studied in c-C 6 H 12 -n-C 5 H 12 mixtures at 77K. H atoms in c-C 6 H 12 matrix react more effectively with solute n-C 5 H 12 than solvent c-C 6 H 12 , while H atoms in n-C 5 H 12 matrix react more effectively with solute c-C 6 H 12 than solvent n-C 5 H 12 [pt
International Nuclear Information System (INIS)
Mityureva, A.A.; Penkin, N.P.; Smirnov, V.V.
1989-01-01
Excitation of argon atoms by electron collisions from metastable (MS) to high-lying states of inert gases (the so-called step-by-step excitation) is investigated. Formation of MS atoms m and their further step-by-step excitation up to k level is carried out by an electron beam with energy from 1 up to 40 eV. Time distribution of forming metastable and step-by-step electron collisions is used. The method used permits to measure the functions of step-by-step excitation and the absolute values of cross sections. Absolute values of cross-sections and functions of step-by-step excitation of some lines and argon levels are obtained
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
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)
Röttger, Katharina; Marroux, Hugo J B; Grubb, Michael P; Coulter, Philip M; Böhnke, Hendrik; Henderson, Alexander S; Galan, M Carmen; Temps, Friedrich; Orr-Ewing, Andrew J; Roberts, Gareth M
2015-12-01
Ultrafast deactivation pathways bestow photostability on nucleobases and hence preserve the structural integrity of DNA following absorption of ultraviolet (UV) radiation. One controversial recovery mechanism proposed to account for this photostability involves electron-driven proton transfer (EDPT) in Watson-Crick base pairs. The first direct observation is reported of the EDPT process after UV excitation of individual guanine-cytosine (G⋅C) Watson-Crick base pairs by ultrafast time-resolved UV/visible and mid-infrared spectroscopy. The formation of an intermediate biradical species (G[-H]⋅C[+H]) with a lifetime of 2.9 ps was tracked. The majority of these biradicals return to the original G⋅C Watson-Crick pairs, but up to 10% of the initially excited molecules instead form a stable photoproduct G*⋅C* that has undergone double hydrogen-atom transfer. The observation of these sequential EDPT mechanisms across intermolecular hydrogen bonds confirms an important and long debated pathway for the deactivation of photoexcited base pairs, with possible implications for the UV photochemistry of DNA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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
Desulfurization of chalcopyrite and molybdenite by atomic hydrogen
International Nuclear Information System (INIS)
Bagdasaryan, V.R.; Kosoyan, A.Zh.; Niazyan, O.M.
1989-01-01
Molybdenite (MoS 2 ) desulfurization by monatomic hydrogen in 625-800 K range was studied using helium as diluent gas. Desulfurization degree at 680 K equals 9%. Temperature growth elevates sulfur content in molybdenite. The effect of initial molybdenite enrichment with temperature growth up to 800 K is probably caused by removal of reduced molybdenum capable to form oxide in the presence of traces of oxygen contained in inert diluent gas
Surface Magnetism of Cobalt Nanoislands Controlled by Atomic Hydrogen.
Park, Jewook; Park, Changwon; Yoon, Mina; Li, An-Ping
2017-01-11
Controlling the spin states of the surface and interface is key to spintronic applications of magnetic materials. Here, we report the evolution of surface magnetism of Co nanoislands on Cu(111) upon hydrogen adsorption and desorption with the hope of realizing reversible control of spin-dependent tunneling. Spin-polarized scanning tunneling microscopy reveals three types of hydrogen-induced surface superstructures, 1H-(2 × 2), 2H-(2 × 2), and 6H-(3 × 3), with increasing H coverage. The prominent magnetic surface states of Co, while being preserved at low H coverage, become suppressed as the H coverage level increases, which can then be recovered by H desorption. First-principles calculations reveal the origin of the observed magnetic surface states by capturing the asymmetry between the spin-polarized surface states and identify the role of hydrogen in controlling the magnetic states. Our study offers new insights into the chemical control of magnetism in low-dimensional systems.
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
Calculating Relativistic Transition Matrix Elements for Hydrogenic Atoms Using Monte Carlo Methods
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.
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
Effect of Ge atoms on crystal structure and optoelectronic properties of hydrogenated Si-Ge films
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 addition to the surface of graphene nanoflakes: A density functional theory study
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.
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....
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)
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
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.
International Nuclear Information System (INIS)
Degoli, Elena; Bisi, O.; Ossicini, Stefano; Cantele, G.; Ninno, D.; Luppi, Eleonora; Magri, Rita
2004-01-01
Electronic and structural properties of small hydrogenated silicon nanoclusters as a function of dimension are calculated from ab initio technique. The effects induced by the creation of an electron-hole pair are discussed in detail, showing the strong interplay between the structural and optical properties of the system. The distortion induced on the structure after an electronic excitation of the cluster is analyzed together with the role of the symmetry constraint during the relaxation. We point out how the overall effect is that of significantly changing the electronic spectrum if no symmetry constraint is imposed to the system. Such distortion can account for the Stokes shift and provides a possible structural model to be linked to the four-level scheme invoked in the literature to explain recent results for the optical gain in silicon nanoclusters. Finally, formation energies for clusters with increasing dimension are calculated and their relative stability discussed
Babaev, A. A.; Pivovarov, Yu L.
2010-04-01
Resonant coherent excitation (RCE) of relativistic hydrogen-like ions is investigated by computer simulations methods. The suggested theoretical model is applied to the simulations of recent experiments on RCE of 390 MeV/u Ar17+ ions under (220) planar channeling in a Si crystal performed by T.Azuma et al at HIMAC (Tokyo). Theoretical results are in a good agreement with these experimental data and clearly show the appearance of the doublet structure of RCE peaks. The simulations are also extended to greater ion energies in order to predict the new RCE features at the future accelerator facility FAIR OSI and as an example, RCE of II GeV/u U91+ ions is considered in detail.