WorldWideScience

Sample records for excited argon atoms

  1. Two-photon excitation/ionization of the 1s-shell of the argon atom

    CERN Document Server

    Novikov, S A

    2002-01-01

    The absolute values and the shape of the two-photon excitation/ionization cross section of the 1s-shell of the argon atom are calculated with inclusion of the many-particle effects, i.e., the relaxation of the atomic residue in the field of the vacancies created, and the decay of the vacancies into the channels of Auger and (or) radiative types. The wavefunctions of the one-particle states are calculated in non-relativistic approximation. The calculations are performed for both linear and circular polarization of the laser beam.

  2. Room-temperature atomic layer deposition of ZrO{sub 2} using tetrakis(ethylmethylamino)zirconium and plasma-excited humidified argon

    Energy Technology Data Exchange (ETDEWEB)

    Kanomata, K. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Tokoro, K.; Imai, T.; Pansila, P.; Miura, M.; Ahmmad, B.; Kubota, S.; Hirahara, K. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Hirose, F., E-mail: fhirose@yz.yamagata-u.ac.jp [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan)

    2016-11-30

    Highlights: • RT-ALD of ZrO{sub 2} is developed using TEMAZ and plasma-excited humidified argon. • The plasma-excited humidified argon is effective in oxidizing the TEMAZ saturated ZrO{sub 2}. • We discuss the reaction mechanism of the RT-ZrO{sub 2} ALD. - Abstract: Room-temperature atomic layer deposition (ALD) of ZrO{sub 2} is developed with tetrakis(ethylmethylamino)zirconium (TEMAZ) and a plasma-excited humidified argon. A growth per cycle of 0.17 nm/cycle at room temperature is confirmed, and the TEMAZ adsorption and its oxidization on ZrO{sub 2} are characterized by IR absorption spectroscopy with a multiple internal reflection mode. TEMAZ is saturated on a ZrO{sub 2} surface with exposures exceeding ∼2.0 × 10{sup 5} Langmuir (1 Langmuir = 1.0 × 10{sup −6} Torr s) at room temperature, and the plasma-excited humidified argon is effective in oxidizing the TEMAZ-adsorbed ZrO{sub 2} surface. The IR absorption spectroscopy suggests that Zr-OH works as an adsorption site for TEMAZ. The reaction mechanism of room-temperature ZrO{sub 2} ALD is discussed in this paper.

  3. Deviation from Boltzmann distribution in excited energy levels of singly-ionized iron in an argon glow discharge plasma for atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-15

    A Boltzmann plot for many iron ionic lines having excitation energies of 4.7-9.1 eV was investigated in an argon glow discharge plasma when the discharge parameters, such as the voltage/current and the gas pressure, were varied. A Grimm-style radiation source was employed in a DC voltage range of 400-800 V at argon pressures of 400-930 Pa. The plot did not follow a linear relationship over a wide range of the excitation energy, but it yielded a normal Boltzmann distribution in the range of 4.7-5.8 eV and a large overpopulation in higher-lying excitation levels of iron ion. A probable reason for this phenomenon is that excitations for higher excited energy levels of iron ion would be predominantly caused by non-thermal collisions with argon species, the internal energy of which is received by iron atoms for the ionization. Particular intense ionic lines, which gave a maximum peak of the Boltzmann plot, were observed at an excitation energy of ca. 7.7 eV. They were the Fe II 257.297-nm and the Fe II 258.111-nm lines, derived from the 3d{sup 5}4s4p {sup 6}P excited levels. The 3d{sup 5}4s4p {sup 6}P excited levels can be highly populated through a resonance charge transfer from the ground state of argon ion, because of good matching in the excitation energy as well as the conservation of the total spin before and after the collision. An enhancement factor of the emission intensity for various Fe II lines could be obtained from a deviation from the normal Boltzmann plot, which comprised the emission lines of 4.7-5.8 eV. It would roughly correspond to a contribution of the charge transfer excitation to the excited levels of iron ion, suggesting that the charge-transfer collision could elevate the number density of the corresponding excited levels by a factor of ca.10{sup 4}. The Boltzmann plots give important information on the reason why a variety of iron ionic lines can be emitted from glow discharge plasmas.

  4. Trapping cold ground state argon atoms.

    Science.gov (United States)

    Edmunds, P D; Barker, P F

    2014-10-31

    We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable 4s[3/2](2) state to be (7.3±1.1)×10(-39)  C m(2)/V. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be (3.3±0.8)×10(-10)  cm(3) s(-1).

  5. Scattering of Slow Metastable Argon Atoms by Dielectric Nanospheres

    Science.gov (United States)

    Baudon, J.; Hamamda, M.; Grucker, J.; Perales, F.; Dutier, G.; Ducloy, M.; Bocvarski, V.

    2009-11-01

    The elastic scattering at low energy of metastable argon atoms with internal angular momentum J = 0 and 2 by dielectric nanospheres is investigated. The differential cross sections are calculated for both isotropic and anisotropic interactions. A polarization effect is clearly evidenced. The possible use of a metastable atom beam as a probe of an ensemble of nanospheres deposited on a passive substrate is examined.

  6. Spatially resolved modeling and measurements of metastable argon atoms in argon-helium microplasmas

    Science.gov (United States)

    Hoskinson, Alan R.; Gregório, José; Hopwood, Jeffrey; Galbally-Kinney, Kristin L.; Davis, Steven J.; Rawlins, Wilson T.

    2017-04-01

    Microwave-driven plasmas operating near atmospheric pressure have been shown to be a promising technique for producing the high density of argon metastable atoms required for optically pumped rare gas laser systems. Stable microwave-driven plasmas can be generated at high pressures using microstrip-based resonator circuits. We present results from computational modeling and laser absorption measurements of argon metastable densities in such plasmas operating in argon-helium gas mixtures at pressures up to 300 Torr. The model and measurements resolve the plasma characteristics both perpendicular to the substrate surface and along the resonator length. The measurements qualitatively and in many aspects quantitatively confirm the accuracy of the model. The plasmas exhibit distinct behaviors depending on whether the operating gas is mostly argon or mostly helium. In high-argon plasmas, the metastable density has a large peak value but is confined very closely to the electrode surfaces as well as being reduced near the discharge gap itself. In contrast, metastable densities in high helium-fraction mixtures extend through most of the plasma. In all systems, increasing the power extends the region of metastable along the resonator length, while the extent away from the substrate surface remains approximately constant.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-11-15

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

  8. Compilation of electron collision excitation cross sections for neutral argon; Compilacion de resultados de secciones eficaces de excitacion para niveles del Argon neutro

    Energy Technology Data Exchange (ETDEWEB)

    Blanco, F.

    1993-07-01

    The present work presents a compilation and critical analysis of the available data on electron collision excitation cross sections for neutral Argon levels. This study includes: 1.- A detailed description in intermediate coupling for all the levels belonging the 20 configurations 3p5 ns (n=4to 12), np(n=4to8) and nd(n=3to8)of neutral Argon. 2.- Calculation of the electron collision excitation cross sections in Born and Born-Oppenheimer-Ochkur approximations for all the levels in the 14 configurations 3p5 ns (n=4 to 7), np (n=4 to 7) and nd (n=3 to 8). 3.- comparison and discussion of the compiled data. These are the experimental and theoretical values available from the literature, and those from this work. 4.- Analysis of the regularities and systematic behaviors in order to determine which values can be considered more reliable. It is show that the concept of one electron cross section results quite useful for this purpose. In some cases it has been possible to obtain in this way approximate analytical expressions interpolating the experimental data. 5.- All the experimental and theoretical values studied are graphically presented and compared. 6.- The last part of the work includes a listing of several general purpose programs for Atomic Physics calculations developed for this work. (Author) 35 refs.

  9. Autoionization study of the Argon 2p satellites excited near the argon 2s threshold

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H.; Glans, P.; Hemmers, O. [Univ. of Nevada, Las Vegas, NV (United States)] [and others

    1997-04-01

    The dynamics of near-threshold photoionization is a complex phenomenon in which the many-electron character of the wavefunctions plays an important role. According to generalized time-independent resonant scattering theory, the transition matrix element from an initial state to a final state is the summation of the amplitudes of direct photoionization and an indirect term in which intermediate states are involved and the resonant behavior is embedded. Studies of the interference effects of intermediate states have been explored in the cases where the direct term is negligible. In the present work, electron time-of-flight spectra of the Ar 2p satellites were measured at two angles (magic and 0{degrees}) in the dipole plane with the exciting photon energy tuned in the vicinity of the Ar 2s threshold. For excitation far below or above the 2s threshold, the 2p satellites spectrum is dominated by 3p to np shakeup contributions upon the ionization of a 2p electron.

  10. The mean excitation energy of atomic ions

    DEFF Research Database (Denmark)

    Sauer, Stephan P. A.; 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, ...

  11. A calculation of internal kinetic energy and polarizability of compressed argon from the statistical atom model

    NARCIS (Netherlands)

    Seldam, C.A. ten; Groot, S.R. de

    1952-01-01

    From Jensen's and Gombás' modification of the statistical Thomas-Fermi atom model, a theory for compressed atoms is developed by changing the boundary conditions. Internal kinetic energy and polarizability of argon are calculated as functions of pressure. At 1000 atm. an internal kinetic energy of

  12. Modified morphology of graphene sheets by Argon-atom bombardment: molecular dynamics simulations.

    Science.gov (United States)

    Wei, Xiao-Lin; Zhang, Kai-Wang; Wang, Ru-Zhi; Liu, Wen-Liang; Zhong, Jian-Xin

    2011-12-01

    By a molecular dynamics method, we simulated the process of Argon-atom bombardment on a graphene sheet with 2720 carbon atoms. The results show that, the damage of the bombardment on the graphene sheet depends not only on the incident energy but also on the particle flux density of Argon atoms. To compare and analyze the effect of the incident energy and the particle flux density in the Argon-atom bombardment, we defined the impact factor on graphene sheet by calculating the broken-hole area. The results indicate that, there is an exponential accumulated-damage for the impact of both the incident energy and the particle flux density and there is a critical incident energy ranging from 20-30 eV/atom in Argon-atom bombardment. Different configurations, such as sieve-like and circle-like graphene can be formed by controlling of different particle flux density as the incident energy is more than the critical value. Our results supply a feasible method on fabrication of porous graphene-based materials for gas-storages and molecular sieves, and it also helps to understand the damage mechanism of graphene-based electronic devices under high particle radiation.

  13. Behaviour of tunnelling transition rate of argon atom exposed to ...

    Indian Academy of Sciences (India)

    in the strong laser field ionization of atoms and molecules. Tunnel ionization takes place when the electric field changes the atomic potential and electron sees a very small mod- ified potential and can tunnel through it. Keldysh [4] made the first attempt to perform a general analysis of ionization of atoms by laser radiation as ...

  14. Experimental evidence of resonant energy collisional transfers between argon 1s and 2p states and ground state H atoms by laser collisional induced fluorescence

    Science.gov (United States)

    Carbone, Emile; van Dijk, Jan; Kroesen, Gerrit

    2015-04-01

    In this paper, laser collisional induced fluorescence (LCIF) is used to probe resonant excitation transfers in an argon/hydrogen plasma resulting from heavy particle collisions. Different radiative transitions between the 1s and 2p states (in Paschen's notation) of argon are optically pumped by a nanosecond laser pulse. The spontaneous fluorescence and collisional responses of the argon and hydrogen systems are monitored by optical emission spectroscopy. A surfatron plasma source is used to generate an argon plasma with a few per cent hydrogen addition at pressures between 0.65 and 20 mbar. The electron density is measured independently by means of Thomson scattering. The overall response of the plasma due to optical pumping of argon is briefly discussed and an overview of the known heteronuclear excitation transfers in an argon/hydrogen plasma is given. The propagation of the shortcut in the Ar(1s) to H(n = 2) excitation transfer due to the optical pumping of the Ar(1s) states is seen in the atomic hydrogen LCIF responses. For the first time, we give direct experimental evidence of the existence of an efficient excitation transfer: Additionally, measurements are performed in order to estimate the resonant energy transfer between the resonant argon 1s states and hydrogen atoms: for which no previously measured cross sections could be found in the literature. These are extra quenching channels of argon 1s and 2p states that should be included in collisional-radiative modeling of argon-hydrogen discharges. The high repetition rate of the dye laser allows us to obtain a high sensitivity in the measurements. LCIF is shown to be a powerful tool for unraveling electron and also heavy particle excitation channels in situ in the plasma phase. The technique was previously developed for measuring electron or species densities locally in the plasma, but we show that it can be advantageously used to probe collisional transfers between very short-lived species which exist

  15. 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....

  16. Nuclear Excitations by Antiprotons and Antiprotonic Atoms

    CERN Multimedia

    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...

  17. Laser-excitation atomic fluorescence spectroscopy in a helium microwave-induced plasma

    Science.gov (United States)

    Schroeder, Timothy S.

    The focus of this dissertation is to report the first documented coupling of helium microwave induced plasmas (MIPs) to laser excitation atomic fluorescence spectroscopy. The ability to effectively produce intense atomic emission from both metal and nonmetal analytes gives helium microwave induced plasmas a greater flexibility than the more commonly utilized argon inductively coupled plasma (ICP). Originally designed as an element selective detector for non-aqueous chromatography applications at low applied powers (500 W). The helium MIP has been shown to be a very powerful analytical atomic spectroscopy tool. The development of the pulsed dye laser offered an improved method of excitation in the field of atomic fluorescence. The use of laser excitation for atomic fluorescence was a logical successor to the conventional excitation methods involving hollow cathode lamps and continuum sources. The highly intense, directional, and monochromatic nature of laser radiation results in an increased population of atomic species in excited electronic states where atomic fluorescence can occur. The application of laser excitation atomic fluorescence to the analysis of metals in a helium microwave induced plasma with ultrasonic sample nebulization was the initial focus of this work. Experimental conditions and results are included for the aqueous characterization of manganese, lead, thallium, and iron in the helium MIP- LEAFS system. These results are compared to previous laser excitation atomic fluorescence experimentation. The effect of matrix interferences on the analytical fluorescence signal was also investigated for each element. The advantage of helium MIPs over argon ICPs in the determination of nonmetals in solution indicates that the helium MIP is an excellent candidate for laser excitation atomic fluorescence experiments involving nonmetals such as chlorine, bromine, iodine, and sulfur. Preliminary investigations into this area are reported, including documentation

  18. Three-body recombination and dynamics of electrons and excited states in the low-pressure argon afterglow

    Science.gov (United States)

    Tsankov, Tsanko Vaskov; Johnsen, Rainer; Czarnetzki, Uwe

    2016-09-01

    The afterglow phase occurs naturally during the power-off period in pulsed low-pressure plasmas and in atmospheric pressure ns discharges. During that period the electron energy rapidly declines and the charged particles are lost due to diffusion and recombination. In low-pressure discharges the dominant process is three-body recombination (TBR) of Ar+ ions with electrons. It leads to complex dynamics of the excited states, dominated by collisional-radiative cascades that eventually repopulate the metastable states. In this contribution the afterglow dynamics of an argon discharge is analyzed in detail to elucidate the roles played by the various processes. An analytical model for the fast drop of the electron energy by evaporative cooling and electron-ion collisions is combined with a time-dependent collisional radiative model for the atomic excited states that numerically solves the electron energy and density balance equations. By including further gas heating and cooling, the model leads to excellent agreement with experiments utilizing different diagnostic techniques, and hence gives insight into the interplay of the various processes in the afterglow. Work Supported by the DFG (Grant No. TS 307/1-1).

  19. A simple velocity-tunable pulsed atomic source of slow metastable argon

    Science.gov (United States)

    Taillandier-Loize, T.; Aljunid, S. A.; Correia, F.; Fabre, N.; Perales, F.; Tualle, J. M.; Baudon, J.; Ducloy, M.; Dutier, G.

    2016-04-01

    A pulsed beam of metastable argon atoms having a low tunable velocity (10 to 150 m s-1) is produced with a very substantial brightness (9  ×  108Ar* s-1 sr-1). The present original experimental configuration leads to a variable velocity dispersion that can be smaller than the standard Brownian one. This behaviour, analysed using Monte Carlo simulations, exhibits momentum stretching (heating) or narrowing (cooling) entirely due to a subtle combination of Doppler and Zeeman effects.

  20. Electron impact excitation of helium atom

    Science.gov (United States)

    Han, Xiao-Ying; Zeng, De-Ling; Gao, Xiang; Li, Jia-Ming

    2015-08-01

    A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation (FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method, the convergent e-He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB921501 and 2013CB922200), the National Natural Science Foundation of China (Grant Nos. 11274035, 11275029, 11328401, 11371218, 11474031, 11474032, and 11474034), and the Foundation of Development of Science and Technology of Chinese Academy of Engineering Physics (Grant Nos. 2013A0102005 and 2014A0102005).

  1. Photo- excitation of Cd atom by optogalvanic technique monitoring

    Directory of Open Access Journals (Sweden)

    M. H. Mahdieh

    2004-12-01

    Full Text Available   Optogalavanic technique has been used widely in laser spectroscopy. In this paper we have presented the results of an experimental three- step photo- excitation of Gd atom, using optogalvanic technique. Three tunable dye laser pulses were applied to excite the Gd atom in a three-step photo – excitation process. The optogalvanic signal was used to monitor the laser wavelength and efficiency of the excitation process. The results show that the optogalvanic signal is very sensitive to the first photo- excitation step in comparison with those of the second and the third step.

  2. Intermolecular dispersion interactions of normal alkanes with rare gas atoms: van der Waals complexes of n-pentane with helium, neon, and argon

    Energy Technology Data Exchange (ETDEWEB)

    Balabin, Roman M. [Gubkin Russian State University of Oil and Gas, 199991 Moscow (Russian Federation)], E-mail: balabin.r@gubkin.ru

    2008-09-03

    Interaction energies of normal pentane with three rare gas atoms (helium, neon, and argon) were calculated using ab initio methods: the second-order Moller-Plesset (MP2), the fourth-order Moller-Plesset (MP4), and coupled cluster with single and double substitutions with noniterative triple excitation (CCSD(T)) levels of theory. Dunning's correlation consistent basis sets up to aug-cc-pVQZ were applied. Eight profiles (246 points for each rare gas atom) of potential energy surface (PES) of all-trans (anti-anti) conformation of n-pentane were scanned. Optimal distances for complex formation were found. MP2 interaction energies at the basis set limit were evaluated by three different methods (Feller's, Helgaker's, and Martin's). The MP2 interaction energy at the basis set limit for a global minimum of n-pentane complex with argon was more than 400 cm{sup -1}, so formation of a stable complex (at least at low temperature) can be expected. A comparison with previously published data on propane complexes with rare gas atoms (both computational and experimental) was done. The MP4 level of theory was found to be sufficient for a description of C{sub 5}H{sub 12} complexes with helium, neon, and argon.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, R.L.

    1982-10-01

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

  4. 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....

  5. The role of coherent excitation and collisional energy transfer in atomic vapor filters and photon detectors

    Science.gov (United States)

    Correll, Tiffany Lee

    Many optical techniques, including laser Doppler velocimetry, free space optical communications, and chemical imaging, require-or can be enhanced by-high spectral resolution photon detection. Such detection is characterized by spectral discrimination on the order of GHz or MHz i.e., approximately 10-4 nm in the near-infrared region. This spectral resolution has recently been achieved by exploiting the narrow absorption features of gas phase atoms. Absorption of light by alkali vapors is intrinsically selective and can be monitored by detecting the fluorescence resulting from laser excitation coupled to selectively excited atomic states. Imaging can be accomplished by spatially expanding the excitation lasers into two dimensions. Fluorescence photons are only created and detected when the interrogated object is forced to scatter radiation of an energy precisely matching one of the transitions of a pre-determined optimal excitation/fluorescence scheme. Devices based on resonance fluorescence photon detection have recently been described using cesium atoms. In this work, the sensitivity and spectral resolution of cesium-based photon detectors were evaluated and improved. To this end, initial experiments focused on laser induced fluorescence in room temperature cesium vapor. The fluorescence response of the detector was augmented by the use of cesium-induced collisional excitation energy transfer between states involved in the chosen excitation scheme. Additional studies focused on helium and argon-induced collisions in the vapor to increase the signal output while maintaining adequate spatial resolution in imaging mode. The probability or cross section of helium-cesium collisions at the operating temperature of the detector was determined by use of a simplified rate equation model. The spectral response of the detector was improved by the use of coherent optical effects resulting from the interaction of a multi-level atomic system with narrowband radiation. Superior

  6. 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...

  7. Laser techniques for spectroscopy of core-excited atomic levels

    Science.gov (United States)

    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.

  8. One Photon Can Simultaneously Excite Two or More Atoms.

    Science.gov (United States)

    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.

  9. Excited states of muonium in atomic hydrogen

    Indian Academy of Sciences (India)

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

  10. Two-photon excitation of rubidium atoms inside porous glass

    Science.gov (United States)

    Amy, L.; Lenci, L.; Villalba, S.; Failache, H.; Lezama, A.

    2017-10-01

    We study the two-photon laser excitation to the 5 D5 /2 energy level of 85Rb atoms contained in the interstices of a porous material made from sintered ground glass with typical pore dimensions in the 10-100 μ m range. The excitation spectra show unusual flat-top line shapes, which are shown to be the consequence of wave-vector randomization of the laser light in the porous material. For large atomic densities, the spectra are affected by radiation trapping around the D2 transitions. The effect of the transient atomic response limited by the time of flight between pores walls appears to have a minor influence in the excitation spectra. It is however revealed by the shortening of the temporal evolution of the emitted blue light following a sudden switch-off of the laser excitation.

  11. Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath

    Energy Technology Data Exchange (ETDEWEB)

    Rivera-Rivera, Luis A.; Sewell, Thomas D.; Thompson, Donald L. [Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211-7600 (United States); Wagner, Albert F. [Argonne National Laboratory, Chemical Sciences and Engineering Division, Argonne, Illinois 60439 (United States)

    2015-01-07

    Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is ∼100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit with the Lendvay-Schatz function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane “simultaneously” colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed

  12. Pressure Effects on the Relaxation of an Excited Nitromethane Molecule in Argon Bath

    Energy Technology Data Exchange (ETDEWEB)

    Rivera-Rivera, Luis A.; Wagner, Albert F.; Sewell, Thomas D.; Thompson, Donald L.

    2015-01-07

    Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is similar to 100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit with the Lendvay-Schatz function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane "simultaneously" colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed

  13. Laser excitation dynamics of argon metastables generated in atmospheric pressure flows by microwave frequency microplasma arrays

    Science.gov (United States)

    Rawlins, W. T.; Galbally-Kinney, K. L.; Davis, S. J.; Hoskinson, A. R.; Hopwood, J. A.

    2014-03-01

    The optically pumped rare-gas metastable laser is a chemically inert analogue to diode-pumped alkali (DPAL) and alkali-exciplex (XPAL) laser systems. Scaling of these devices requires efficient generation of electronically excited metastable atoms in a continuous-wave electric discharge in flowing gas mixtures at atmospheric pressure. This paper describes initial investigations of the use of linear microwave micro-discharge arrays to generate metastable rare-gas atoms at atmospheric pressure in optical pump-and-probe experiments for laser development. Power requirements to ignite and sustain the plasma at 1 atm are low, 2p9 transition at 811.5 nm and the corresponding laser-induced fluorescence on the 2p10-->1s5 transition at 912.3 nm; the 2p10 state is efficiently populated by collisional energy transfer from 2p9. Using tunable diode laser absorption/gain spectroscopy, we observe small-signal gains of ~1 cm-1 over a 1.9 cm path. We also observe stable, continuous-wave laser oscillation at 912.3 nm, with preliminary optical efficiency ~55%. These results are consistent with efficient collisional coupling within the Ar(4s) manifold.

  14. Saturation Effect of Projectile Excitation in Ion-Atom Collisions

    Science.gov (United States)

    Mukoyama, Takeshi; Lin, Chii-Dong

    Calculations of projectile K-shell electron excitation cross sections for He-like ions during ion-atom collisions have been performed in the distortion approximation by the use of Herman-Skillman wave functions. The calculated results are compared with the experimental data for several targets. The excitation cross sections deviate from the first-Born approximation and show the saturation effect as a function of target atomic number. This effect can be explained as the distortion of the projectile electronic states by the target nucleus.

  15. Liquid-Arc/Spark-Excitation Atomic-Emission Spectroscopy

    Science.gov (United States)

    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.

  16. Plasmon excitations in the dimers formed by atom chains

    Science.gov (United States)

    Xue, Hong-jie; Hao, Da-peng; Zhang, Ming; Wang, Xiao-mei

    2017-02-01

    Based on the linear response theory in the random-phase approximation and the free-electron gas model, we study the plasmon excitations in the dimers formed by atom chains. With the help of energy absorption spectrum and charge distribution, the evolutions of longitudinal and transverse plasmon, and the effect of the system parameters such as size, atomic separation and electron filling on plasmon are obtained. In addition, the dipole, quadrupole, end and central plasmon are observed.

  17. Reaction dynamics of electronically excited alkali atoms with simple molecules

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-09-01

    The reactions of electronically excited sodium atoms with simple molecules have been studied in crossed molecular beams experiments. Electronically excited Na(3/sup 2/P/sub 3/2/,4/sup 2/D/sub 5/2/, and 5/sup 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.

  18. Reaction dynamics of electronically excited alkali atoms with simpler molecules

    Science.gov (United States)

    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.

  19. Plasmon excitations in two-dimensional atomic cluster systems

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Yan-Qin; Yu, Ya-Bin, E-mail: apybyu@hnu.edu.cn; Xue, Hong-Jie; Wang, Ya-Xin; Chen, Jie

    2016-09-01

    Properties of plasmon excitations in two-dimensional (2D) atomic cluster systems are theoretically studied within an extended Hubbard model. The collective oscillation equations of charge, plasmon eigen-equations and the energy-absorption spectrum formula are presented. The calculated results show that different symmetries of plasmons exist in the cluster systems, and the symmetry of charge distribution in the plasmon resonance originate from the intrinsic symmetry of the corresponding eigen-plasmon modes, but not from the symmetry of applied external fields; however, the plasmon excitation with a certain polarization direction should be excited by the field in this direction, the dipole mode of plasmons can be excited by both uniform and non-uniform fields, but multipole ones cannot be excited by an uniform field. In addition, we show that for a given electron density, plasmon spectra are red-shifted with increasing size of the systems.

  20. Rotationally inelastic collisions of excited NaK and NaCs molecules with noble gas and alkali atom perturbers

    Science.gov (United States)

    Jones, J.; Richter, K.; Price, T. J.; Ross, A. J.; Crozet, P.; Faust, C.; Malenda, R. F.; Carlus, S.; Hickman, A. P.; Huennekens, J.

    2017-10-01

    We report measurements of rate coefficients at T ≈ 600 K for rotationally inelastic collisions of NaK molecules in the 2(A)1Σ+ electronic state with helium, argon, and potassium atom perturbers. Several initial rotational levels J between 14 and 44 were investigated. Collisions involving molecules in low-lying vibrational levels (v = 0, 1, and 2) of the 2(A)1Σ+ state were studied using Fourier-transform spectroscopy. Collisions involving molecules in a higher vibrational level, v = 16, were studied using pump/probe, optical-optical double resonance spectroscopy. In addition, polarization spectroscopy measurements were carried out to study the transfer of orientation in these collisions. Many, but not all, of the measurements were carried out in the "single-collision regime" where more than one collision is unlikely to occur within the lifetime of the excited molecule. The analysis of the experimental data, which is described in detail, includes an estimate of effects of multiple collisions on the reported rate coefficients. The most significant result of these experiments is the observation of a strong propensity for ΔJ = even transitions in collisions involving either helium or argon atoms; the propensity is much stronger for helium than for argon. For the initial rotational levels studied experimentally, almost all initial orientation is preserved in collisions of NaK 2(A)1Σ+ molecules with helium. Roughly between 1/3 and 2/3 of the orientation is preserved in collisions with argon, and almost all orientation is destroyed in collisions with potassium atoms. Complementary measurements on rotationally inelastic collisions of NaCs 2(A)1Σ+ with argon do not show a ΔJ = even propensity. The experimental results are compared with new theoretical calculations of collisions of NaK 2(A)1Σ+ with helium and argon. The calculations are in good agreement with the absolute magnitudes of the experimentally determined rate coefficients and accurately reproduce the very

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

    Indian Academy of Sciences (India)

    2016-10-17

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

  2. Two Step Excitation in Hot Atomic Sodium Vapor.

    Science.gov (United States)

    Docters, Bernd; Wrachtrup, Jörg; Gerhardt, Ilja

    2017-09-18

    A two step excitation scheme in hot atomic sodium vapor is experimentally investigated. The observed effects reflect a coupling between the 32S, 32P and the 32D states. We present the relative dependence on detuning of the two utilized lasers around λ = 589 nm and 819 nm. Unlike expected, we achieve a higher detuning dependence of the probe and the coupling laser by a factor of approximately three. The presented work aimed for a Rydberg excitation and quantum light storage. Such schemes are usually implemented with a red laser on the D-line transition and a coupling laser of shorter (typically blue) wavelength. Due to the fact that higher P-Rydberg states are approximately two times higher in energy than the 32D state, a two photon transition from the atomic excited 32P state to a Rydberg P state is feasible. This might circumvent laser frequency doubling whereby only two lasers might mediate a three photon process. The scheme of adding three k-vectors allows for electromagnetically induced transparency experiments in which the resulting k-vector can be effectively reduced to zero. By measurements utilizing electric fields and an analysis of the emission spectrum of the atomic vapor, we can exclude the excitation of the P-P two photon transition.

  3. Two-Photon Excitation of Launched Cold Atoms in Flight

    Science.gov (United States)

    Goodsell, Anne; Gonzalez, Rene; Alejandro, Eduardo; Erwin, Emma

    2017-04-01

    We demonstrate two-photon bi-chromatic excitation of cold rubidium atoms in flight, using the pathway 5S1 / 2 -> 5P3 / 2 -> 5D5 / 2 with two resonant photons. In our experiment, atoms are laser-cooled in a magneto-optical trap and launched upward in discrete clouds with a controllable vertical speed of 7.1 +/-0.6 m/s and a velocity spread that is less than 10% of the launch speed. Outside the cooling beams, as high as 14 mm above the original center of the trap, the launched cold atoms are illuminated simultaneously by spatially-localized horizontal excitation beams at 780 nm (5S1 / 2 -> 5P3 / 2) and 776 nm (5P3 / 2 -> 5D5 / 2). We monitor transmission of the 780-nm beam over a range of intensities of 780-nm and 776-nm light. As the center of the moving cloud passes the excitation beams, we observe as much as 97.9 +/-1.2% transmission when the rate of two-photon absorption is high and the 5S1 / 2 and 5P3 / 2 states are depopulated, compared to 87.6 +/-0.9% transmission if only the 780-nm beam is present. This demonstrates two-photon excitation of a launched cold-atom source with controllable launch velocity and narrow velocity spread, as a foundation for three-photon excitation to Rydberg states. Research supported by Middlebury College Bicentennial Fund, Palen Fund, and Gladstone Award.

  4. Photothermal excitation setup for a modified commercial atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Adam, Holger; Rode, Sebastian; Schreiber, Martin; Kühnle, Angelika, E-mail: kuehnle@uni-mainz.de [Institute of Physical Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55099 Mainz (Germany); Kobayashi, Kei; Yamada, Hirofumi [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan)

    2014-02-15

    High-resolution imaging in liquids using frequency modulation atomic force microscopy is known to suffer from additional peaks in the resonance spectrum that are unrelated to the cantilever resonance. These unwanted peaks are caused by acoustic modes of the liquid and the setup arising from the indirect oscillation excitation by a piezoelectric transducer. Photothermal excitation has been identified as a suitable method for exciting the cantilever in a direct manner. Here, we present a simple design for implementing photothermal excitation in a modified Multimode scan head from Bruker. Our approach is based on adding a few components only to keep the modifications as simple as possible and to maintain the low noise level of the original setup with a typical deflection noise density of about 15 fm/√(Hz) measured in aqueous solution. The success of the modification is illustrated by a comparison of the resonance spectra obtained with piezoelectric and photothermal excitation. The performance of the systems is demonstrated by presenting high-resolution images on bare calcite in liquid as well as organic adsorbates (Alizarin Red S) on calcite with simultaneous atomic resolution of the underlying calcite substrate.

  5. Electron scattering by laser-excited barium atoms

    Science.gov (United States)

    Register, D. F.; Trajmar, S.; Jensen, S. W.; Poe, R. T.

    1978-01-01

    Inelastic and superelastic scattering of 30- and 100-eV electrons by laser-excited 6s 6p 1P and subsequent cascade-populated 6s 6p 3P, 6s 5d 1D, and 6s 5d 3D Ba atoms have been observed. Absolute differential cross sections for the singlet and relative scattering intensities for the triplet species have been determined in the 5 to 20 deg angular region. Under the present conditions excitations dominate over deexcitations.

  6. Two Step Excitation in Hot Atomic Sodium Vapor

    OpenAIRE

    Docters, Bernd; Wrachtrup, J?rg; Gerhardt, Ilja

    2017-01-01

    A two step excitation scheme in hot atomic sodium vapor is experimentally investigated. The observed effects reflect a coupling between the 32S, 32P and the 32D states. We present the relative dependence on detuning of the two utilized lasers around ??=?589?nm and 819?nm. Unlike expected, we achieve a higher detuning dependence of the probe and the coupling laser by a factor of approximately three. The presented work aimed for a Rydberg excitation and quantum light storage. Such schemes are u...

  7. 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

  8. Excited State Atom-Ion Charge-Exchange

    Science.gov (United States)

    Li, Ming; Makrides, Constantinos; Petrov, Alexander; Kotochigova, Svetlana

    2017-04-01

    We theoretically investigate the exothermic charge-exchange reaction between an excited atom and a ground-state positive ion. In particular, we focus on MOT-excited Ca*(4s4p 1P) atoms colliding with ground-state Yb+ ions, which are under active study by the experimental group of E. Hudson at UCLA. Collisions between an excited atom and an ion are guided by two major contributions to the long-range interaction potentials, the induction C4 /R4 and charge-quadrupole C3 /R3 potentials, and their coupling by the electron-exchange interaction. Our model of these forces leads to close-coupling equations for multiple reaction channels. We find several avoided crossings between the potentials that couple to the nearby asymptotic limits of Yb*+Ca+, some of which can possibly provide large charge exchange rate coefficients above 10-10 cm3 / s. We acknowledge support from the US Army Research Office, MURI Grants W911NF-14-1-0378 and the US National Science Foundation, Grant PHY-1619788.

  9. Atomic collisions involving C60 and collective excitation

    Science.gov (United States)

    Tribedi, L. C.; Kelkar, A. H.

    2011-12-01

    Here we review and discuss some of our recent investigations on collective excitation in a free C60 molecule and its influence on the atomic collisions. In particular, emphasis has been given for collisions with fast highly charged ions. It is demonstrated, from the charge-state-dependence studies of recoil-ion spectra, that the plasmon excitation plays a dominant role in the single and double ionization process. The observed linear charge-state-dependence is in contrast to the expected behavior predicted by ion-atom collisions models. This behavior was observed for different projectiles and at different energies. The time-of-flight recoil-ion mass spectroscopy experiments involve 1-5 MeV/u C, O, F and Si ion beams with different charge states, ranging between 4+ and 14+. In addition, the influence of the collective excitation on the electron capture process was also investigated. The wake-field induced Stark-mixing and splitting of sub-levels of projectile-ions following electron capture from C60 carries signature of the collective plasmon excitation. For the electron capture studies X-ray spectroscopic technique was used for collisions with bare and dressed S and Cl ion beams. The results on the TOF data on fullerene target obtained in last few years will be summarized.

  10. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Argon

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Makoto [Gaseous Electronics Institute, Nagoya, Aichi (Japan)

    2003-01-01

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for argon (Ar). About 1,960 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1921 through 2000 for Ar. Finally, author's recommended Ar electron collision cross section set is given in numerical tables. (author)

  11. Anomalous excitation enhancement with Rydberg-dressed atoms

    Science.gov (United States)

    Chai, Xiaoqian; Zhang, Lu; Ma, Dandan; Yan, Luyao; Bao, Huihan; Qian, Jing

    2017-11-01

    We develop the research achievement of recent work [Gärttner et al., Phys. Rev. Lett. 113, 233002 (2014), 10.1103/PhysRevLett.113.233002], in which an anomalous excitation enhancement is observed in a three-level Rydberg-atom ensemble with many-body coherence. In our theoretical analysis, this effect is ascribed to the existence of a quasidark state as well as its avoided crossings to nearby Rydberg-dressed states. Moreover, we show that with an appropriate control of the optical detuning to the intermediate state, the enhancement can evoke a direct facilitation to atom-light coupling that even breaks through the conventional √{N } limit of strong-blockaded ensembles. As a consequence, the intensity of the probe laser for intermediate transition can be reduced considerably, increasing the feasibility of experiments with Rydberg-dressed atoms.

  12. Thermal beam of metastable krypton atoms produced by optical excitation.

    Science.gov (United States)

    Ding, Y; Hu, S M; Bailey, K; Davis, A M; Dunford, R W; Lu, Z T; O'Connor, T P; Young, L

    2007-02-01

    A room-temperature beam of krypton atoms in the metastable 5s[3/2]2 level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p6 1S0 to the 5s[3/2]1 level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]1 to 5s[3/2]2 followed by a spontaneous decay to the 5s[3/2]2 metastable level. A metastable atomic beam with an angular flux density of 3 x 10(14) s(-1) sr(-1) is achieved at the total gas flow rate of 0.01 cm3/s at STP (or 3 x 10(17) at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.

  13. A model for energy transfer in collisions of atoms with highly excited molecules.

    Science.gov (United States)

    Houston, Paul L; Conte, Riccardo; Bowman, Joel M

    2015-05-21

    A model for energy transfer in the collision between an atom and a highly excited target molecule has been developed on the basis of classical mechanics and turning point analysis. The predictions of the model have been tested against the results of trajectory calculations for collisions of five different target molecules with argon or helium under a variety of temperatures, collision energies, and initial rotational levels. The model predicts selected moments of the joint probability distribution, P(Jf,ΔE) with an R(2) ≈ 0.90. The calculation is efficient, in most cases taking less than one CPU-hour. The model provides several insights into the energy transfer process. The joint probability distribution is strongly dependent on rotational energy transfer and conservation laws and less dependent on vibrational energy transfer. There are two mechanisms for rotational excitation, one due to motion normal to the intermolecular potential and one due to motion tangential to it and perpendicular to the line of centers. Energy transfer is found to depend strongly on the intermolecular potential and only weakly on the intramolecular potential. Highly efficient collisions are a natural consequence of the energy transfer and arise due to collisions at "sweet spots" in the space of impact parameter and molecular orientation.

  14. Super-atom molecular orbital excited states of fullerenes.

    Science.gov (United States)

    Johansson, J Olof; Bohl, Elvira; Campbell, Eleanor E B

    2016-09-13

    Super-atom molecular orbitals are orbitals that form diffuse hydrogenic excited electronic states of fullerenes with their electron density centred at the centre of the hollow carbon cage and a significant electron density inside the cage. This is a consequence of the high symmetry and hollow structure of the molecules and distinguishes them from typical low-lying molecular Rydberg states. This review summarizes the current experimental and theoretical studies related to these exotic excited electronic states with emphasis on femtosecond photoelectron spectroscopy experiments on gas-phase fullerenes.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'. © 2016 The Author(s).

  15. Half-Collision Studies of Excited Metal Atom - Molecule Interactions

    Science.gov (United States)

    Kleiber, P. D.; Chen, J.; Wong, T. H.

    1998-05-01

    We report on state-resolved studies of excited state molecular dynamics, including both reactive and nonreactive (energy transfer) processes using half-collision techniques. Scattering state spectroscopy is used to investigate electronic orbital alignment effects on the reactive quenching of excited p-state alkali and alkaline earth metal atoms in collisions with hydrogen and methane. These experiments give information about the shape of the Born-Oppenheimer potential energy surfaces for the collision complex, and about the nonadiabatic interactions that couple the surfaces. Experimental results indicate two distinct reaction mechanisms are operative in the alkali metal-hydrogen quenching system. In complementary experiments, the spectroscopy and dissociation dynamics of weakly bound metal ion-hydrocarbon bimolecular complexes are studied using photofragmentation spectroscopic techniques in a tandem time-of- flight mass spectrometer. Results suggest that the quenching mechanism involves metal ion activation of the hydrocarbon bonds througha bond- stretch insertion process.

  16. Determination of the Excited State Density Distribution within a Nonequilibrium, Freely Expanding Argon Arcjet Plume

    Science.gov (United States)

    1977-03-01

    transport problem for the radially dependent number densi- ties is required. The details of this inversion technique, based upon an " onion peel... chat of the arcJeC. The reference signal from the chopper and the preampllfled photomultlpller cube output signal were input to a PAR ® synchronous...condition for equilibrium with the free electron density and thus shows Chat the four lowest excited states are demonstrably nonequllibrium and lie

  17. 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.

  18. Two-photon excitation of atoms by ultrashort electromagnetic pulses in a discrete spectrum

    CERN Document Server

    Astapenko, Valery

    2015-01-01

    The present work is dedicated to the theoretical analysis of two-photon excitation of atoms in a discrete energy spectrum by ultrashort electromagnetic pulses of femto- and subfemtosecond ranges of durations. As examples, excitation of hydrogen and sodium atoms from the ground state to excited states with a zero orbital moment is considered.

  19. Characteristics of a micro-gap argon barrier discharge excited by a saw-tooth voltage at atmospheric pressure

    Science.gov (United States)

    Li, Xuechen; Zhang, Qi; Jia, Pengying; Chu, Jingdi; Zhang, Panpan; Dong, Lifang

    2017-03-01

    Using two water electrodes, a micro-gap dielectric barrier discharge excited by a saw-tooth voltage is investigated in atmospheric pressure argon. Through electrical and optical measurements, it is found that, at a lower driving frequency, a stepped discharge mode is obtained per half voltage cycle. Moreover, the duration and amplitude of the current plateau increase with the increase in the applied peak voltage. With the increase in the driving frequency, the stepped discharge mode transits into a pulsed one after a multi-peak mode. During this process, a diffuse discharge at a lower frequency transits into a filamentary one at a higher frequency. Temporal evolutions of the discharges are investigated axially based on fast photography. It is found that the stepped mode is in atmospheric pressure Townsend discharge (APTD) regime. However, there is a transition from APTD to atmospheric pressure glow discharge for the pulsed mode. Spectral intensity ratio of 391.4 nm to 337.1 nm is used to determine the averaged electron energy, which decreases with increasing peak voltage or driving frequency.

  20. Deactivation of Highly Vibrationally Excited OH by O Atoms

    Science.gov (United States)

    Copeland, R. A.; Smith, G. P.; Mlynczak, M. M.; Kalogerakis, K. S.

    2006-12-01

    The hydroxyl radical is a key player in the chemistry and energetics of the middle terrestrial atmosphere, and several studies have investigated energy transfer processes between OH(υ) and atmospheric molecules. Nevertheless, a gap exists in our understanding of its interaction with oxygen atoms. Oxygen atoms are present at about 10% of the oxygen molecule concentration at ~95 km and about 1% at 88 km, so if their rate constant is significantly faster than that of O2 and N2, they will strongly influence the intensity and the vibrational distribution extracted from the OH(υ) emission. We report laboratory measurements of the total removal rate constants of OH(υ = 8, 9) by O(3 P) atoms and preliminary measurements on CO2. These measurements are required so that we can quantify the importance of these collisional processes in the modeling of atmospheric OH emissions and evaluate the chemical heating rate from measurements by the SABER instrument aboard the TIMED satellite. In the experiments, we generate O(3P) and OH(υ) by photodissociation of ozone at 250 nm in a mixture of ozone, nitrogen, hydrogen. The highly excited vibrational levels OH(υ = 7-9) are produced in the reaction of H atoms with ozone that has not been photodissociated. We monitor the temporal evolution of the OH(υ = 8 and 9) population by laser excitation via the \\it B3Σ_u- \\textendash \\it X3Σ_g- (0,9) and (0,8) transitions near 237 nm and 226 nm, respectively, and subsequent detection of visible fluorescence emitted from the \\it B3Σ_u^{- } \\textendash \\it A3Σ_u+ band, an approach developed previously in our laboratory [1]. By controlling the initial conditions of the experiments, we can extract the rate coefficient for OH removal by O atoms in the system. For direct analysis of the OH signal rise to yield accurate rate coefficients an extremely good signal-to-noise-ratio is required. However, a preferred approach involves comparison of the OH signal relative intensity changes when

  1. Characterization of a microwave-excited atmospheric-pressure argon plasma jet using two-parallel-wires transmission line resonator

    Science.gov (United States)

    Choi, J.; Eom, I. S.; Kim, S. J.; Kwon, Y. W.; Joh, H. M.; Jeong, B. S.; Chung, T. H.

    2017-09-01

    This paper presents a method to produce a microwave-excited atmospheric-pressure plasma jet (ME-APPJ) with argon. The plasma was generated by a microwave-driven micro-plasma source that uses a two-parallel-wire transmission line resonator (TPWR) operating at around 900 MHz. The TPWR has a simple structure and is easier to fabricate than coaxial transmission line resonator (CTLR) devices. In particular, the TPWR can sustain more stable ME-APPJ than the CTLR can because the gap between the electrodes is narrower than that in the CTLR. In experiments performed with an Ar flow rate from 0.5 to 8.0 L.min-1 and an input power from 1 to 6 W, the rotational temperature was determined by comparing the measured and simulated spectra of rotational lines of the OH band and the electron excitation temperature determined by the Boltzmann plot method. The rotational temperature obtained from OH(A-X) spectra was 700 K to 800 K, whereas the apparent gas temperature of the plasma jet remains lower than ˜325 K, which is compatible with biomedical applications. The electron number density was determined using the method based on the Stark broadening of the hydrogen Hβ line, and the measured electron density ranged from 6.5 × 1014 to 7.6 × 1014 cm-3. TPWR ME-APPJ can be operated at low flows of the working gas and at low power and is very stable and effective for interactions of the plasma with cells.

  2. Three-photon Gaussian–Gaussian–Laguerre–Gaussian excitation of a localized atom to a highly excited Rydberg state

    Science.gov (United States)

    Mashhadi, L.

    2017-12-01

    Optical vortices are currently one of the most intensively studied topics in light–matter interaction. In this work, a three-step axial Doppler- and recoil-free Gaussian–Gaussian-Laguerre–Gaussian (GGLG) excitation of a localized atom to the highly excited Rydberg state is presented. By assuming a large detuning for intermediate states, an effective quadrupole excitation related to the Laguerre–Gaussian (LG) excitation to the highly excited Rydberg state is obtained. This special excitation system radially confines the single highly excited Rydberg atom independently of the trapping system into a sharp potential landscape into the so-called ‘far-off-resonance optical dipole-quadrupole trap’ (FORDQT). The key parameters of the Rydberg excitation to the highly excited state, namely the effective Rabi frequency and the effective detuning including a position-dependent AC Stark shift, are calculated in terms of the basic parameters of the LG beam and of the polarization of the excitation lasers. It is shown that the obtained parameters can be tuned to have a precise excitation of a single atom to the desired Rydberg state as well. The features of transferring the optical orbital and spin angular momentum of the polarized LG beam to the atom via quadrupole Rydberg excitation offer a long-lived and controllable qudit quantum memory. In addition, in contrast to the Gaussian laser beam, the doughnut-shaped LG beam makes it possible to use a high intensity laser beam to increase the signal-to-noise ratio in quadrupole excitation with minimized perturbations coming from stray light broadening in the last Rydberg excitation process.

  3. Reactive scattering of electronically excited alkali atoms with molecules

    Energy Technology Data Exchange (ETDEWEB)

    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/sup -/ repulsion in Na(5S, 4D) reactions, and by the NaCl-H repulsion in the case of Na(3P). The reaction of Na with O/sub 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/sub 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.

  4. Comparative study on contribution of charge-transfer collision to excitations of iron ion between argon radio-frequency inductively-coupled plasma and nitrogen microwave induced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Satoh, Kozue; Wagatsuma, Kazuaki, E-mail: wagatuma@imr.tohoku.ac.jp

    2015-06-01

    This paper describes an ionization/excitation phenomenon of singly-ionized iron occurring in an Okamoto-cavity microwave induced plasma (MIP) as well as an argon radio-frequency inductively-coupled plasma (ICP), by comparing the Boltzmann distribution among iron ionic lines (Fe II) having a wide range of the excitation energy from 4.76 to 9.01 eV. It indicated in both the plasmas that plots of Fe II lines having lower excitation energies (4.76 to 5.88 eV) were fitted on each linear relationship, implying that their excitations were caused by a dominant thermal process such as collision with energetic electron. However, Fe II lines having higher excitation energies (more than 7.55 eV) had a different behavior from each other. In the ICP, Boltzmann plots of Fe II lines assigned to the higher excited levels also followed the normal Boltzmann relationship among the low-lying excited levels, even including a deviation from it in particular excited levels having an excitation energy of ca. 7.8 eV. This deviation can be attributed to a charge-transfer collision with argon ion, which results in the overpopulation of these excited levels, but the contribution is small. On the other hand, the distribution of the high-lying excited levels was non-thermal in the Okamoto-cavity MIP, which did not follow the normal Boltzmann relationship among the low-lying excited levels. A probable reason for the non-thermal characteristics in the MIP is that a charge-transfer collision with nitrogen molecule ion having many vibrational/rotational levels could work for populating the 3d{sup 6}4p (3d{sup 5}4s4p) excited levels of iron ion broadly over an energy range of 7.6–9.0 eV, while collisional excitation by energetic electron would occur insufficiently to excite these high-energy levels. - Highlights: • This paper describes the excitation mechanism of iron ion in Okamoto-cavity MIP in comparison with conventional ICP. • Boltzmann distribution is studied among iron ionic lines of

  5. Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems.

    Science.gov (United States)

    Zhong, Jian-Qiang; Wang, Mengen; Akter, Nusnin; Kestell, John D; Boscoboinik, Alejandro M; Kim, Taejin; Stacchiola, Dario J; Lu, Deyu; Boscoboinik, J Anibal

    2017-07-17

    The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. The atoms remain in the cages upon heating to 400 K. The trapping and release of Ar is studied combining surface science methods and density functional theory calculations. While the frameworks stay intact with the inclusion of Ar atoms, the permeability of gasses (for example, CO) through them is significantly affected, making these structures also interesting candidates for tunable atomic and molecular sieves. These findings enable the study of individually confined noble gas atoms using surface science methods, opening up new opportunities for fundamental research.

  6. Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems

    Science.gov (United States)

    Zhong, Jian-Qiang; Wang, Mengen; Akter, Nusnin; Kestell, John D.; Boscoboinik, Alejandro M.; Kim, Taejin; Stacchiola, Dario J.; Lu, Deyu; Boscoboinik, J. Anibal

    2017-07-01

    The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. The atoms remain in the cages upon heating to 400 K. The trapping and release of Ar is studied combining surface science methods and density functional theory calculations. While the frameworks stay intact with the inclusion of Ar atoms, the permeability of gasses (for example, CO) through them is significantly affected, making these structures also interesting candidates for tunable atomic and molecular sieves. These findings enable the study of individually confined noble gas atoms using surface science methods, opening up new opportunities for fundamental research.

  7. Deterministic single-atom excitation via adiabatic passage and Rydberg blockade

    Science.gov (United States)

    Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A.; Ryabtsev, I. I.; MacCormick, C.; Bergamini, S.

    2011-08-01

    We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number N of the atoms in the traps. Our method overcomes the problem of the N dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitation in the ensembles with unknown N, and can be applied for single-atom loading of dipole traps and optical lattices.

  8. Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm

    Science.gov (United States)

    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.

  9. Deterministic single-atom excitation via adiabatic passage and Rydberg blockade

    Energy Technology Data Exchange (ETDEWEB)

    Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A.; Ryabtsev, I. I.; MacCormick, C.; Bergamini, S. [A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Prospekt Lavrentieva 13, 630090 Novosibirsk (Russian Federation); Open University, Walton Hall, Milton Keynes MK6 7AA (United Kingdom)

    2011-08-15

    We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number N of the atoms in the traps. Our method overcomes the problem of the {radical}(N) dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitation in the ensembles with unknown N, and can be applied for single-atom loading of dipole traps and optical lattices.

  10. Deterministic single-atom excitation via adiabatic passage and Rydberg blockade

    OpenAIRE

    Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A.; Ryabtsev, I. I.; MacCormick, C.; Bergamini, S.

    2011-01-01

    We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number \\textit{N} of the atoms in the traps. Our method overcomes the problem of the $\\sqrt {N} $ dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitat...

  11. Stern Gerlach interferometry with metastable argon atoms: an immaterial mask modulating the profile of a supersonic beam

    Energy Technology Data Exchange (ETDEWEB)

    Viaris de Lesegno, B. [Toulouse-3 Univ., LCAR-IRSAMC, 31 (France); Karam, J.C.; Perales, F.; Mainos, C.; Reinhardt, J.; Baudon, J.; Grancharova, D.; Durt, T.; Robert, J. [Paris-13 Univ., Lab. de Physique des Lasers, 93 - Villetaneuse (France); Boustimi, M. [ENSSAT, Lab. d' Optronique, 22 - Lannion (France); Bocvarski, V. [Institute of Physics, Zumun (Yugoslavia); Dos Santos, F.P. [Laboratoire Kastler-Brossel, 75 - Paris (France); Durt, T. [Brussel Vrije Universiteit, Tena-Tona, Brussel (Belgium); Haberland, H. [Freiburg Univ. (Germany)

    2003-04-01

    A new Stern Gerlach interferometer operating with a nozzle beam of metastable argon atoms Ar* (3p{sup 5} 4s, {sup 3}P{sub 2}) is described. The selection of incoming (polarisation) and outgoing (analysis) Zeeman sublevels is achieved by use of laser induced transitions at two wavelengths, 811.5 nm (closed J 2 {yields} J = 3 transition) and 801.5 nm (open J = 2 {yields} J = 2 transition). Linear superpositions of Zeeman sublevels, just beyond the polarizer and just before the analyser, are prepared by means of two zones where Majorana transitions take place. In between, a controlled magnetic field configuration (the phase object) is produced within a triple {mu}-metal shielding. Standard interference patterns are obtained by scanning the field and detecting the atoms by secondary electron emission from a Faraday cup. When a static radial magnetic gradient is used, the beam profile is modulated by interference. The transverse pattern. which can be translated at will by adding a homogeneous field, is observed for the first time using a multi-channel electron multiplier followed by a phosphor screen and a CCD camera. The results satisfactorily agree with all theoretical predictions. (authors)

  12. Stern Gerlach interferometry with metastable argon atoms: an immaterial mask modulating the profile of a supersonic beam

    CERN Document Server

    Viaris De Lesegno, B; Perales, F; Mainos, C; Reinhardt, J; Baudon, J; Grancharova, D; Durt, T; Robert, J; Boustimi, M; Bocvarski, V; Dos Santos, F P; Durt, T; Haberland, H

    2003-01-01

    A new Stern Gerlach interferometer operating with a nozzle beam of metastable argon atoms Ar* (3p sup 5 4s, sup 3 P sub 2) is described. The selection of incoming (polarisation) and outgoing (analysis) Zeeman sublevels is achieved by use of laser induced transitions at two wavelengths, 811.5 nm (closed J 2 -> J = 3 transition) and 801.5 nm (open J = 2 -> J = 2 transition). Linear superpositions of Zeeman sublevels, just beyond the polarizer and just before the analyser, are prepared by means of two zones where Majorana transitions take place. In between, a controlled magnetic field configuration (the phase object) is produced within a triple mu-metal shielding. Standard interference patterns are obtained by scanning the field and detecting the atoms by secondary electron emission from a Faraday cup. When a static radial magnetic gradient is used, the beam profile is modulated by interference. The transverse pattern. which can be translated at will by adding a homogeneous field, is observed for the first time ...

  13. Direct Monte Carlo simulation of the sympathetic cooling of trapped molecules by ultracold argon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Barletta, P; Tennyson, J; Barker, P F, E-mail: j.tennyson@ucl.ac.u [Department of Physics and Astronomy, University College London, WC1E 6BT (United Kingdom)

    2010-11-15

    We demonstrate that cold molecules (H{sub 2} and benzene) can be created at temperatures below 1 mK by sympathetic cooling with laser-cooled rare gas atoms on timescales of seconds. The thermalization process is studied using the direct simulation Monte Carlo (DSMC) method, which allows a detailed analysis of the atomic and molecular spatial and energy distributions as a function of time. As part of this study, ultracold elastic cross sections for Ar-Ar and Ar-C{sub 6}H{sub 6} are also calculated.

  14. Scattering of hyperthermal argon atoms from clean and D-covered Ru surfaces

    NARCIS (Netherlands)

    Ueta, H.; Gleeson, M. A.; Kleyn, A. W.

    2011-01-01

    Hyperthermal Ar atoms were scattered from a Ru(0001) surface held at temperatures of 180, 400 and 600 K, and from a Ru(0001)-(1x1) D surface held at 114 and 180 K. The resultant angular intensity and energy distributions are complex. The in-plane angular distributions have narrow (FWHM <= 10

  15. Scattering of hyperthermal argon atoms from clean and D-covered Ru surfaces

    NARCIS (Netherlands)

    Ueta, H.; Gleeson, M.A.; Kleyn, A.W.

    2011-01-01

    Hyperthermal Ar atoms were scattered from a Ru(0001) surface held at temperatures of 180, 400 and 600 K, and from a Ru(0001)-(1×1)D surface held at 114 and 180 K. The resultant angular intensity and energy distributions are complex. The in-plane angular distributions have narrow (FWHM ≤ 10°)

  16. Femtosecond photoelectron imaging of transient electronic states and Rydberg atom emission from electronically excited he droplets.

    Science.gov (United States)

    Kornilov, Oleg; Bünermann, Oliver; Haxton, Daniel J; Leone, Stephen R; Neumark, Daniel M; Gessner, Oliver

    2011-07-14

    Ultrafast relaxation of electronically excited pure He droplets is investigated by femtosecond time-resolved photoelectron imaging. Droplets are excited by extreme ultraviolet (EUV) pulses with photon energies below 24 eV. Excited states and relaxation products are probed by ionization with an infrared (IR) pulse with 1.6 eV photon energy. An initially excited droplet state decays on a time scale of 220 fs, leading predominantly to the emission of unaligned 1s3d Rydberg atoms. In a second relaxation channel, electronically aligned 1s4p Rydberg atoms are emitted from the droplet within less than 120 fs. The experimental results are described within a model that approximates electronically excited droplet states by localized, atomic Rydberg states perturbed by the local droplet environment in which the atom is embedded. The model suggests that, below 24 eV, EUV excitation preferentially leads to states that are localized in the surface region of the droplet. Electronically aligned 1s4p Rydberg atoms are expected to originate from excitations in the outermost surface regions, while nonaligned 1s3d Rydberg atoms emerge from a deeper surface region with higher local densities. The model is used to simulate the He droplet EUV absorption spectrum in good agreement with previously reported fluorescence excitation measurements.

  17. Off-axis excitation of hydrogenlike atoms by twisted photons

    Science.gov (United States)

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

    2013-09-01

    We show that the twisted-photon states, or photon states with large (>ℏ) angular momentum projection (mγ) in the direction of motion, can photoexcite atomic levels for a hydrogenlike atom that are novel and distinct and are not restricted by mγ, when the symmetry axis of the twisted-photon beam does not coincide with the center of the atomic target. Selection rules are given and interesting implications and observables for the above process are pointed out.

  18. The effect of atoms excited by electron beam on metal evaporation

    CERN Document Server

    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

  19. 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.

  20. Total (complete) and ionization cross-sections of argon and krypton ...

    Indian Academy of Sciences (India)

    Abstract. Considering interactions and scattering of positrons with argon (Ar) and krypton (Kr) atoms, we have calculated total cross-sections (QT = Qel + Qinel) using complex spherical poten- tials for these systems. In positron–atom scattering it is difficult to bifurcate the ionization and cumulative excitation contained in the ...

  1. Phase-sensitive electric modulation of photoluminescence upon bichromatic excitation of atoms

    NARCIS (Netherlands)

    Astapenko, VA

    2005-01-01

    A new type of modulation of the photoluminescence intensity of atoms excited by a bichromatic laser radiation with the frequency ratio 1 : 2 is proposed and analysed. The modulation is produced by alternating electric field acting on atoms and occurs due to the quantum interference of the amplitudes

  2. 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...

  3. Spontaneous excitation of a circularly accelerated atom coupled with vacuum Dirac field fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing [Institute of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Hu, Jiawei [Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China); Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn [Institute of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China)

    2015-02-15

    We study the spontaneous excitation of a circularly accelerated atom coupled with vacuum Dirac field fluctuations by separately calculating the contribution to the excitation rate of vacuum fluctuations and a cross term which involves both vacuum fluctuations and radiation reaction, and demonstrate that although the spontaneous excitation for the atom in its ground state would occur in vacuum, such atoms in circular motion do not perceive a pure thermal radiation as their counterparts in linear acceleration do since the transition rates of the atom do not contain the Planckian factor characterizing a thermal bath. We also find that the contribution of the cross term that plays the same role as that of radiation reaction in the scalar and electromagnetic fields cases differs for atoms in circular motion from those in linear acceleration. This suggests that the conclusion drawn for atoms coupled with the scalar and electromagnetic fields that the contribution of radiation reaction to the mean rate of change of atomic energy does not vary as the trajectory of the atom changes from linear acceleration to circular motion is not a general trait that applies to the Dirac field where the role of radiation reaction is played by the cross term. - Highlights: • Spontaneous excitation of a circularly accelerated atom is studied. • The atom interacts with the Dirac field through nonlinear coupling. • A cross term involving vacuum fluctuations and radiation reaction contributes. • The atom in circular motion does not perceive pure thermal radiation. • The contribution of the cross term changes as the atomic trajectory varies.

  4. Localization of atomic excitation beyond the diffraction limit using electromagnetically induced transparency

    Science.gov (United States)

    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.

  5. Probing an Excited-State Atomic Transition Using Hyperfine Quantum Beat Spectroscopy

    CERN Document Server

    Wade, Christopher G; Keaveney, James; Adams, Charles S; Weatherill, Kevin J

    2014-01-01

    We describe a method to observe the dynamics of an excited-state transition in a room temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition, and continuous-wave driving of an excited-state transition from the 6P$_{3/2}$ state to the 7S$_{1/2}$ state. We observe quantum beats in the fluorescence from the 6P$_{3/2}$ state which are modified by the driving of the excited-state transition. The Fourier spectrum of the beat signal yields evidence of Autler-Townes splitting of the 6P$_{3/2}$, F = 5 hyperfine level and Rabi oscillations on the excited-state transition. A detailed model provides qualitative agreement with the data, giving insight to the physical processes involved.

  6. Lifetime measurement of excited atomic and ionic states of some ...

    Indian Academy of Sciences (India)

    Abstract. 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 ...

  7. 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 ...

  8. Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr

    KAUST Repository

    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.

  9. Blocking of diffusion transitions of metal atoms at excitation of weakly attenuating plasmons

    CERN Document Server

    Gorelov, B M; Ogenko, V M; Shalyapina, G M

    2001-01-01

    One studies blocking transitions of metal atoms in YBa sub 2 Cu sub 3 O sub 7 high-temperature superconductor at excitation of weakly attenuating acoustic plasmons and at thermodesorption of 01 atoms. Ni and Au atoms were as diffusates. YBa sub 2 Cu sub 3 O sub 7 sub - subdelta specimens were irradiated by 9.4 GHz frequency and 10 sup 4 W power pulsed UHF-field. Temperature dependences of diffusion coefficient of Ni and Au atoms prior and subsequent to UHF irradiation and thermodesorption of 0 atoms are analyzed. It is pointed out that subsequent to UHF irradiation resistance of a specimen increases near transition into superconducting state. One makes a conclusion that blocking of space and surface transitions of Ni and Au atoms results from accumulation a large number of interstitial atoms in the surface layer of crystallites

  10. An experimental setup for studying the core-excited atoms and molecules by electron impact using energy analysed electron-ion coincidence technique

    Science.gov (United States)

    Kumar, S.; Prajapati, S.; Singh, B.; Singh, B. K.; Shanker, R.

    2017-07-01

    Operation and performance of an apparatus for studying the decay dynamics relevant to core-hole decay processes in atoms and molecules excited by energetic electrons using an energy analysed electron-ion coincidence technique are described in some detail. The setup consists of a time- and position sensitive double-field linear TOF mass spectrometer coupled with a dual MCP detector and a single-pass CMA to select the energy of detected electrons. Details of different components involved in the setup are presented and discussed. To demonstrate the performance and capability of the apparatus, we present some typical results extracted from the TOF argon ion-mass spectra observed in coincidence with 18-energy selected electrons emitted from interaction of a continuous beam of 3.5 keV electrons with a dilute gaseous target of argon atoms. Specifically, the variation of relative correlation probability for the final ion-charge states Ar1+ to Ar4+ produced in the considered collision reactions as a function of energy of emitted electrons is determined and discussed.

  11. Differential cross sections for ionization and excitation of laser-aligned atoms by electron impact

    Science.gov (United States)

    Murray, Andrew

    2012-06-01

    Differential cross section measurements will be presented for electron impact ionization and excitation of atoms prepared using high resolution continuous wave laser radiation. In the case of ionization, low energy coplanar asymmetric (e,2e) experiments were performed from laser excited Mg atoms that were aligned using radiation around 285nm. The atoms were subjected to linearly polarized radiation whose polarization vector was varied from in the plane to perpendicular to the scattering plane. Ionization measurements were then conducted from the laser-excited 3P state, and the differential cross section determined. By careful analysis of the laser pumping, these measurements were directly compared to those from the ground state. Such experiments provide valuable information on the ionization of aligned targets. In the second experiment to be described here, a resonant enhancement cavity has been placed around the interaction region and super-elastic scattering measurements have been carried out from laser-excited atoms inside the cavity. This new technique opens up many new targets for study, since the cavity increases the effective intensity of the laser radiation that is exciting the atoms by a factor of up to 50. As such, new ionization and excitation measurements are possible using deep UV radiation where the laser power is only a few mW. Results from calcium will be presented, and progress towards studies from silver, copper and gold will be discussed. We are also advancing this new technique to allow simultaneous excitation from the hyperfine levels of different targets (such as Rb), which will allow the method to be adopted in different fields, such as laser cooling and trapping.

  12. Studies of photoionization processes from ground-state and excited-state atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-06-05

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

  14. Cluster excitation and ionization in high velocity collisions:the atomic approach

    OpenAIRE

    Mezdari, Férid; Wohrer-Béroff, Karine; Chabot, Marin

    2004-01-01

    NIM; The independent atom and electron model [1] is introduced in a quantum context and associated approximations tentatively estimated. Confrontation of the model to measured ionization and excitation cross sections of small ionic carbon clusters Cn+ in collisions with helium at an impact velocity of 2.6 a.u is presented.

  15. Ionization and excitation of some atomic targets and metal oxides by ...

    Indian Academy of Sciences (India)

    We have calculated total inelastic and total ionization cross-sections for collisions of electrons on atomic targets oxygen (O), aluminium (Al) and copper (Cu) and metal oxides AlO and Al2O, at impact energies from near excitation threshold to 2000 eV. A complex (optical) energy-dependent interaction potential is used to ...

  16. Coherent phase control of excitation of atoms by bichromatic laser radiation in an electric field

    NARCIS (Netherlands)

    Astapenko, VA

    A new method for coherent phase control of excitation of atoms in a discrete spectrum under the action of bichromatic laser radiation with the frequency ratio 1 : 2 is analysed. An important feature of this control method is the presence of a electrostatic field, which removes the parity selection

  17. Excited atoms in cavities of liquid He I: long-range interatomic repulsion and broadening of atomic lines

    Science.gov (United States)

    Atrazhev, Vladimir M.; Eloranta, Jussi; Bonifaci, Nelly; van Nguyen, Hai; Aitken, Frederic; von Haeften, Klaus; Vermeulen, G.

    2013-02-01

    A theoretical analysis of the line broadening of localized atomic transitions in liquid helium is presented. It is shown that accurate information can be derived on the long-range part of the He*-He interaction as well as on the local structure near the He* emitters. The analysis confirms that in corona discharges in liquid helium the emitting He* atoms reside in cavities and that for known He*-He interaction the size of the cavities can be deduced from the line profile. The He*-He interaction was calculated using the full configuration interaction (CI) method as implemented in the Molpro package. The widths of atomic lines due to fluorescent transitions between different excited states of helium atoms were calculated as a function of external pressure in the range from 0.1 and 3.5 MPa using the static approximation method, and the input from the results of the CI calculation and cavity diameters calculated using the bubble model. The calculated widths showed excellent agreement with experimental data of liquid helium excited by corona discharges. A second, analytical analysis using a power function to represent the He*-He interaction showed qualitative agreement with the experimental data. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

  18. Noise squeezing of fields that bichromatically excite atoms in a cavity.

    Science.gov (United States)

    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.

  19. Two-dimensional simulation of argon dielectric barrier discharge excited by a Gaussian voltage at atmospheric pressure

    Science.gov (United States)

    Xu, Yonggang; Wang, Jing; Li, Jing; Lei, Bingying; Tang, Jie; Wang, Yishan; Li, Yongfang; Zhao, Wei; Duan, Yixiang

    2017-04-01

    A two-dimensional self-consistent fluid model was employed to investigate the spatiotemporal characteristics of discharges in atmospheric pressure argon (Ar) dielectric barrier discharge driven by a Gaussian voltage. The simulation results show that a discharge with multiple current pulses occurs each half-cycle in the gas gap. A transition from the Townsend mode to the glow mode is observed with the increasing applied voltage each half-cycle at a lower driving frequency (7.5 kHz). It is also found that the glow mode survives all the discharge phases at a higher driving frequency (12.5 kHz and 40 kHz). The change in the discharge mode with the driving frequency mainly lies in the fact that a lot of charged particles created in the discharge gap have no enough time to drift and diffuse around, and then these particles are assembled in the discharge space at higher frequency. Additionally, the spatial distributions of the electron density indicate that a center-advantage discharge is ignited at the driving frequencies of interest, resulting in the radial non-uniformity of discharge because of the edge effects. However, this overall non-uniformity is weakened with the driving frequency increased to 40 kHz, at which concentric ring patterns are observed. These distinct behaviors are mainly attributed to the fact that many charged particles generated are trapped in the gas gap and then accumulated to make the extension along the radial direction due to the charged particles transport and diffusion, and that the effective overlapping of a large number of avalanches induced by the increased "seed" electron density with the driving frequency. Meanwhile, the surface charged particles accumulated on the dielectric barriers are also shown to play a role in the formation of the discharge structure.

  20. High-multipole excitations of atoms by twisted photons near phase singularity (Conference Presentation)

    Science.gov (United States)

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

    2016-09-01

    We calculate transition amplitudes and cross sections for excitation of hydrogen-like atoms by the twisted photon states, or photon states with more than one unit of angular momentum projection along the direction of propagation. If the target atom is located at distances of the order of atomic size near the vortex center, the transitions rates into l_f>1 states become comparable with the rates for standard electric dipole transitions. It is shown that when the transition rates are normalized to the local photon flux, the resulting cross sections for l_f>1 are singular near the optical vortex center, i.e., high-multipole excitations take place in the region of zero field intensity near phase singularity. Relation to the "quantum core" concept introduced by Berry and Dennis is discussed.

  1. Kinetic Energy Distribution of H(2p) Atoms from Dissociative Excitation of H2

    Science.gov (United States)

    Ajello, Joseph M.; Ahmed, Syed M.; Kanik, Isik; Multari, Rosalie

    1995-01-01

    The kinetic energy distribution of H(2p) atoms resulting from electron impact dissociation of H2 has been measured for the first time with uv spectroscopy. A high resolution uv spectrometer was used for the measurement of the H Lyman-alpha emission line profiles at 20 and 100 eV electron impact energies. Analysis of the deconvolved 100 eV line profile reveals the existence of a narrow line peak and a broad pedestal base. Slow H(2p) atoms with peak energy near 80 meV produce the peak profile, which is nearly independent of impact energy. The wings of H Lyman-alpha arise from dissociative excitation of a series of doubly excited Q(sub 1) and Q(sub 2) states, which define the core orbitals. The fast atom energy distribution peaks at 4 eV.

  2. Lunar exospheric argon modeling

    Science.gov (United States)

    Grava, Cesare; Chaufray, J.-Y.; Retherford, K. D.; Gladstone, G. R.; Greathouse, T. K.; Hurley, D. M.; Hodges, R. R.; Bayless, A. J.; Cook, J. C.; Stern, S. A.

    2015-07-01

    Argon is one of the few known constituents of the lunar exosphere. The surface-based mass spectrometer Lunar Atmosphere Composition Experiment (LACE) deployed during the Apollo 17 mission first detected argon, and its study is among the subjects of the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) and Lunar Atmospheric and Dust Environment Explorer (LADEE) mission investigations. We performed a detailed Monte Carlo simulation of neutral atomic argon that we use to better understand its transport and storage across the lunar surface. We took into account several loss processes: ionization by solar photons, charge-exchange with solar protons, and cold trapping as computed by recent LRO/Lunar Orbiter Laser Altimeter (LOLA) mapping of Permanently Shaded Regions (PSRs). Recycling of photo-ions and solar radiation acceleration are also considered. We report that (i) contrary to previous assumptions, charge exchange is a loss process as efficient as photo-ionization, (ii) the PSR cold-trapping flux is comparable to the ionization flux (photo-ionization and charge-exchange), and (iii) solar radiation pressure has negligible effect on the argon density, as expected. We determine that the release of 2.6 × 1028 atoms on top of a pre-existing argon exosphere is required to explain the maximum amount of argon measured by LACE. The total number of atoms (1.0 × 1029) corresponds to ∼6700 kg of argon, 30% of which (∼1900 kg) may be stored in the cold traps after 120 days in the absence of space weathering processes. The required population is consistent with the amount of argon that can be released during a High Frequency Teleseismic (HFT) Event, i.e. a big, rare and localized moonquake, although we show that LACE could not distinguish between a localized and a global event. The density of argon measured at the time of LACE appears to have originated from no less than four such episodic events. Finally, we show that the extent of the PSRs that trap

  3. Pulsed excitation of Rydberg-atom-pair states in an ultracold Cs gas

    CERN Document Server

    Saßmannshausen, Heiner; Deiglmayr, Johannes

    2015-01-01

    Pulsed laser excitation of a dense ultracold Cs vapor has been used to study the pairwise interactions between Cs atoms excited to $n$p$_{3/2}$ Rydberg states of principal quantum numbers in the range $n=22-36$. Molecular resonances were observed that correspond to excitation of Rydberg-atom-pair states correlated not only to the $n$p$_{3/2}+n$p$_{3/2}$ dissociation asymptotes, but also to $n$s$_{1/2}+(n+1)$s$_{1/2}$, $n$s$_{1/2}+n'$f$_{j}$, and $(n-4)$f$_{j}+(n-3)$f$_{j}$ $(j=5/2,7/2)$ dissociation asymptotes. These pair resonances are interpreted as arising from dipole-dipole, and higher long-range-interaction terms between the Rydberg atoms on the basis of i) their spectral positions, ii) their response to static and pulsed electric fields, and iii) millimeter-wave spectra between pair states correlated to different pair-dissociation asymptotes. The Rydberg-atom--pair states were found to spontaneously decay by Penning ionization and the dynamics of the ionization process were investigated during the first...

  4. Analysis of Excitation and Ionization of Atoms and Molecules by Electron Impact

    CERN Document Server

    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...

  5. 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...... experimental trends for relative excitation probability of the shear horizontal and longitudinal acoustic phonon branches. The inelastic scattering at beam energies near 8 meV is exceedingly sensitive to small misalignment between the scattering plane and the high symmetry directions of the monolayer solid...

  6. Electron impact excitation of the D states of Mg, Ca and Sr atoms ...

    Indian Academy of Sciences (India)

    decay of the atom from D → P and then P → S) is required [3,7–9]. ... for the excitation of helium from its ground 1S state to the 3 1D state at 40 eV. We ..... Further, we use for the projectile electron distorted wave function. FDW i(f) the following relativistic form of partial wave expansion: F± ch,µch (kch, r) = 1. (2π)3/2 ∑ κm.

  7. Formation of H-atom in 2s excited state of proton-lithium and proton ...

    Indian Academy of Sciences (India)

    Abstract. The differential and total cross-sections have been investigated in the forma- tion of H-atom in the 2s excited state of proton-lithium and proton-sodium scattering by using the Coulomb projected Born (CPB) approximation in the energy range from 50 to. 10,000 keV. The results thus obtained are compared with the ...

  8. Bibliography of atomic and molecular excitation in heavy particle collisions, 1950--1975

    Energy Technology Data Exchange (ETDEWEB)

    Hawthorne, S.W.; Thomas, E.W.; Barnett, C.F.; Crandall, D.H.; Gilbody, H.B.; Kirkpatrick, M.I.; McDaniel, E.W.; Phaneuf, R.A. (eds.)

    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.

  9. Collective excitations of a laser driven atomic condensate in an optical cavity

    Science.gov (United States)

    Öztop, B.; Müstecaplıoğlu, Ö. E.; Türeci, H. E.

    2013-02-01

    We theoretically examine collective excitations of an optically driven atomic Bose-Einstein condensate, coupled to a high-finesse optical cavity. This open system has been recently used for the experimental demonstration of the Dicke superradiance of cavity photons, which is simultaneously and mutually triggered by spontaneous breaking of translational symmetry of the condensate into a crystalline order. We first develop a Hartree-Fock mean field dynamical model of the physical system. Using this model, we compute the dynamics of the cavity photons, the condensate density profile and the Dicke phase transition diagram. Both the imaginary-time and real-time evolution methods are used in the calculations. Collective excitations are determined by the solving Bogoliubov-de Gennes equations. The spectrum, softening of the modes and energetic hierarchy of excitations are determined.

  10. Effects of oxygen concentration on atmospheric pressure dielectric barrier discharge in Argon-Oxygen Mixture

    Science.gov (United States)

    Li, Xuechun; Li, Dian; Wang, Younian

    2016-09-01

    A dielectric barrier discharge (DBD) can generate a low-temperature plasma easily at atmospheric pressure and has been investigated for applications in trials in cancer therapy, sterilization, air pollution control, etc. It has been confirmed that reactive oxygen species (ROS) play a key role in the processes. In this work, we use a fluid model to simulate the plasma characteristics for DBD in argon-oxygen mixture. The effects of oxygen concentration on the plasma characteristics have been discussed. The evolution mechanism of ROS has been systematically analyzed. It was found that the ground state oxygen atoms and oxygen molecular ions are the dominated oxygen species under the considered oxygen concentrations. With the oxygen concentration increasing, the densities of electrons, argon atomic ions, resonance state argon atoms, metastable state argon atoms and excited state argon atoms all show a trend of decline. The oxygen molecular ions density is high and little influenced by the oxygen concentration. Ground state oxygen atoms density tends to increase before falling. The ozone density increases significantly. Increasing the oxygen concentration, the discharge mode begins to change gradually from the glow discharge mode to Townsend discharge mode. Project supported by the National Natural Science Foundation of China (Grant No. 11175034).

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

    KAUST Repository

    Zhang, J.-Y.

    2013-10-09

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

  12. Collective excitations and supersolid behavior of bosonic atoms inside two crossed optical cavities

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2016-07-01

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

  14. Controlled Rephasing of Single Collective Spin Excitations in a Cold Atomic Quantum Memory.

    Science.gov (United States)

    Albrecht, Boris; Farrera, Pau; Heinze, Georg; Cristiani, Matteo; de Riedmatten, Hugues

    2015-10-16

    We demonstrate active control of inhomogeneous dephasing and rephasing for single collective atomic spin excitations (spin waves) created by spontaneous Raman scattering in a quantum memory based on cold 87Rb atoms. The control is provided by a reversible external magnetic field gradient inducing an inhomogeneous broadening of the atomic hyperfine levels. We demonstrate experimentally that active rephasing preserves the single photon nature of the retrieved photons. Finally, we show that the control of the inhomogeneous dephasing enables the creation of time-separated spin waves in a single ensemble followed by a selective read-out in time. This is an important step towards the implementation of a functional temporally multiplexed quantum repeater node.

  15. Enhanced efficiency in the excitation of higher modes for atomic force microscopy and mechanical sensors operated in liquids

    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.

  16. The reaction dynamics of alkali dimer molecules and electronically excited alkali atoms with simple molecules

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Hongtao [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-12-01

    This dissertation presents the results from the crossed molecular beam studies on the dynamics of bimolecular collisions in the gas phase. The primary subjects include the interactions of alkali dimer molecules with simple molecules, and the inelastic scattering of electronically excited alkali atoms with O2. The reaction of the sodium dimers with oxygen molecules is described in Chapter 2. Two reaction pathways were observed for this four-center molecule-molecule reaction, i.e. the formations of NaO2 + Na and NaO + NaO. NaO2 products exhibit a very anisotropic angular distribution, indicating a direct spectator stripping mechanism for this reaction channel. The NaO formation follows the bond breaking of O2, which is likely a result of a charge transfer from Na2 to the excited state orbital of O2-. The scattering of sodium dimers from ammonium and methanol produced novel molecules, NaNH3 and Na(CH3OH), respectively. These experimental observations, as well as the discussions on the reaction dynamics and the chemical bonding within these molecules, will be presented in Chapter 3. The lower limits for the bond dissociation energies of these molecules are also obtained. Finally, Chapter 4 describes the energy transfer between oxygen molecules and electronically excited sodium atoms.

  17. Efficient enhancement of below-threshold harmonic generation by laser-driven excited states of Cs atom

    Science.gov (United States)

    Guo, Qiao-Ling; Li, Peng-Cheng; Zhou, Xiao-Xin; Chu, Shih-I.

    2018-03-01

    We propose an efficient method for the enhancement of below-threshold harmonic generation (BTHG) by mid-infrared laser-driven excited states of a Cs atom. The BTHG is calculated by solving three-dimensional time-dependent Schrödinger equation accurately and efficiently using the time-dependent generalized pseudospectral method. We adopt an excited state as the initial state of a Cs atom. As a result, the BTHG is significantly enhanced by two orders of magnitude compared with the case of the initial ground state. Furthermore, we find that a single vacuum-ultraviolet pulse can be generated by mid-infrared laser-driven excited states by superposing several below-threshold harmonics of a Cs atom. Our finding suggests that the generation of below-threshold harmonics by laser-driven excited states of an atom can provide a powerful methodology for the production of intense vacuum-ultraviolet pulses.

  18. Long-range interactions between excited helium and alkali-metal atoms

    KAUST Repository

    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.

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

    Science.gov (United States)

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

    1988-10-01

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

  20. Extended Eckart Theorem and New Variation Method for Excited States of Atoms

    CERN Document Server

    Xiong, Zhuang; Bacalis, N C; Zhou, Qin

    2016-01-01

    We extend the Eckart theorem, from the ground state to excited statew, which introduces an energy augmentation to the variation criterion for excited states. It is shown that the energy of a very good excited state trial function can be slightly lower than the exact eigenvalue. Further, the energy calculated by the trial excited state wave function, which is the closest to the exact eigenstate through Gram-Schmidt orthonormalization to a ground state approximant, is lower than the exact eigenvalue as well. In order to avoid the variation restrictions inherent in the upper bound variation theory based on Hylleraas, Undheim, and McDonald [HUM] and Eckart Theorem, we have proposed a new variation functional Omega-n and proved that it has a local minimum at the eigenstates, which allows approaching the eigenstate unlimitedly by variation of the trial wave function. As an example, we calculated the energy and the radial expectation values of Triplet-S(even) Helium atom by the new variation functional, and by HUM a...

  1. Depopulation of lowly excited ns-states of Rb colliding with the He atom

    Energy Technology Data Exchange (ETDEWEB)

    Verma, S.K. [Jagdam College, Chapra (India). Dept. of Physics; Khan, A.A. [ZAI College, Siwan (India). Dept. of Physics; Kumar, V. [Rajendra College, Chapra (India). Dept. of Physics; Kumar, A. [JP University, Chapra (India). Dept. of Physics

    1996-03-28

    A semiclassical impact-parameter method has been used to study the total depopulation of lowly excited ns-states of the Rb atom colliding with ground-state He in the thermal energy region. A fairly large basis set of STO has been used to generate MO states and then a 14-state calculation has been carried out to evaluate the total as well as individual cross sections for quenching. A comparative study with the previously investigated Li-He and Na-He pairs is also presented. (Author).

  2. The interaction of hyperthermal argon atoms with CO-covered Ru: Scattering and collision-induced desorption

    NARCIS (Netherlands)

    Ueta, H.; Gleeson, M. A.; Kleyn, A. W.

    2011-01-01

    Hyperthermal Ar atoms were scattered under grazing incidence (theta(i) = 60 degrees) from a CO-saturated Ru(0001) surface held at 180 K. Collision-induced desorption involving the ejection of fast CO (similar to 1 eV) occurs. The angularly resolved in-plane CO desorption distribution has a peak

  3. 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

  4. Electronic excitation and deexcitation of atoms and molecules in nonequilibrium plasmas; Hiheiko plasma chu no denshi reiki ryushi hanno katei

    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.

  5. Ground and excited states for exotic three-body atomic systems

    Directory of Open Access Journals (Sweden)

    Gasaneo G.

    2010-04-01

    Full Text Available An Angular Correlated Configuration Interaction method is extended and applied to exotic threebody atomic systems with general masses. A recently proposed angularly correlated basis set is used to construct, simultaneously and with a single diagonalization, ground and excited states wave functions which: (i satisfy exactly Kato cusp conditions at the two-body coalescence points; (ii have only linear parameters; (iii show a fast convergency rate for the energy; (iv form an orthogonal set. The efficiency of the construction is illustrated by the study a variety of three-body atomic systems [m1− m2− m3z3+ ] with two negatively charged light particles, with 123 diverse masses m1− and m2−, and a heavy positively charged nucleus m3z3+. The calculated ground 11S and several excited n1,3S state energies are compared with those given in the literature, when available. We also present a short discussion on the critical charge necessary to get a stable three-body system supporting two electrons, an electron and a muon, or two muons.

  6. Shock-tube measurements of excited oxygen atoms using cavity-enhanced absorption spectroscopy.

    Science.gov (United States)

    Nations, Marcel; Wang, Shengkai; Goldenstein, Christopher S; Sun, Kai; Davidson, David F; Jeffries, Jay B; Hanson, Ronald K

    2015-10-10

    We report the use of cavity-enhanced absorption spectroscopy (CEAS) using two distributed feedback diode lasers near 777.2 and 844.6 nm for sensitive, time-resolved, in situ measurements of excited-state populations of atomic oxygen in a shock tube. Here, a 1% O2/Ar mixture was shock-heated to 5400-8000 K behind reflected shock waves. The combined use of a low-finesse cavity, fast wavelength scanning of the lasers, and an off-axis alignment enabled measurements with 10 μs time response and low cavity noise. The CEAS absorption gain factors of 104 and 142 for the P35←S520 (777.2 nm) and P0,1,23←S310 (844.6 nm) atomic oxygen transitions, respectively, significantly improved the detection sensitivity over conventional single-pass measurements. This work demonstrates the potential of using CEAS to improve shock-tube studies of nonequilibrium electronic-excitation processes at high temperatures.

  7. Electron correlation dynamics of strong-field double ionization of atoms below recollision threshold

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yunquan; Gong Qihuang [Department of Physics and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871 (China); Ye Difa; Liu Jie [Center for Applied Physics and Technology, Peking University, 100084 Beijing (China); Rudenko, A; Tschuch, S; Duerr, M; Moshammer, R; Ullrich, J [Max-Planck-Institut fuer Kernphysik, D-69117 Heidelberg (Germany); Siegel, M; Morgner, U, E-mail: yunquan.liu@pku.edu.cn [Leibniz Universitaet Hannover, Welfengarten 1, D-30167 Hannover (Germany)

    2011-02-01

    In recent combined experimental and theoretical study we have explored nonsequential double ionization of neon and argon atoms in the infrared light field (800nm) below the recollision threshold. We find that the two-electron correlation dynamics depends on atomic structure- 'side-by-side emission' (correlation) for Ne and 'back-to-back emission' (anticorrelation) for argon atoms. This can be explained theoretically within our three dimensional classical model calculation including tunnelling effect. The multiple recollisions as well as recollision-induced-excitation-tunnelling (RIET) effect dominate the anticorrelation of argon, whereas the laser-assisted instantaneous recollision dominates the correlation of neon.

  8. Formation of very low energy states crossing the ionization threshold of argon atoms in strong mid-infrared fields

    CERN Document Server

    Wolter, Benjamin; Baudisch, Matthias; Pullen, Michael G; Tong, Xiao-Min; Hemmer, Michaël; Senftleben, Arne; Schröter, Claus Dieter; Ullrich, Joachim; Moshammer, Robert; Biegert, Jens; Burgdörfer, Joachim

    2014-01-01

    Atomic ionization by intense mid-infrared (mid-IR) pulses produces low electron energy features that the strong-field approximation, which is expected to be valid in the tunneling ionization regime characterized by small Keldysh parameters ($\\gamma \\ll 1$), cannot describe. These features include the low-energy structure (LES), the very-low-energy structure (VLES), and the more recently found zero-energy structure (ZES). They result from the interplay between the laser electric field and the atomic Coulomb field which controls the low-energy spectrum also for small $\\gamma$. In the present joint experimental and theoretical study we investigate the vectorial momentum spectrum at very low energies. Using a reaction microscope optimized for the detection of very low energy electrons, we have performed a thorough study of the three-dimensional momentum spectrum well below 1 eV. Our measurements are complemented by quantum and classical simulations, which allow for an interpretation of the LES, VLES and of the ne...

  9. Single-active-electron analysis of laser-polarization effects on atomic/molecular multiphoton excitation.

    Science.gov (United States)

    Kanno, Manabu; Inada, Nobuyoshi; Kono, Hirohiko

    2017-10-21

    We theoretically explore the effects of optical ellipticity on single-active-electron multiphoton excitation in atoms and (nearly) spherical molecules irradiated by intense polarized laser fields. This work was motivated by the experimental and theoretical studies of Hertel et al. [Phys. Rev. Lett. 102, 023003 (2009) and Phys. Rev. A 79, 053414 (2009)], who reported pronounced changes in the near-infrared-induced ion yields of xenon and C60 as a function of ellipticity (in particular, yield reduction for circular polarization) at low light intensities and derived a perturbative cross section formula to describe such polarization effects by assuming that the excited-state energies and radial transition electric dipole moments of the system are independent of the azimuthal quantum number l. First, by reformulating the N-photon absorption cross section of a single active electron, we prove that their assumptions reduce the network of optically allowed transition pathways into what we call the "Pascal triangle" consisting of (N + 1) (N + 2)/2 states only. Next, nonperturbative analytical and numerical solutions of the time-dependent Schrödinger equation for a simple model of two-photon excitation are presented not only in the low-intensity regime but also in the high-intensity regime. The results show that the determining factor of ellipticity-dependent multiphoton excitation probability is transition moment magnitudes and that the detailed energetic structure of the system also becomes important at high intensities. The experimentally observed flattening of the ion yields of xenon and C60 with increasing intensity can be explained without a saturation effect, which was previously deemed to be responsible for it. We also argue the applicability range of the cross section formula by Hertel et al. and the identity of the "doorway state" for ionization of C60.

  10. Single-active-electron analysis of laser-polarization effects on atomic/molecular multiphoton excitation

    Science.gov (United States)

    Kanno, Manabu; Inada, Nobuyoshi; Kono, Hirohiko

    2017-10-01

    We theoretically explore the effects of optical ellipticity on single-active-electron multiphoton excitation in atoms and (nearly) spherical molecules irradiated by intense polarized laser fields. This work was motivated by the experimental and theoretical studies of Hertel et al. [Phys. Rev. Lett. 102, 023003 (2009) and Phys. Rev. A 79, 053414 (2009)], who reported pronounced changes in the near-infrared-induced ion yields of xenon and C60 as a function of ellipticity (in particular, yield reduction for circular polarization) at low light intensities and derived a perturbative cross section formula to describe such polarization effects by assuming that the excited-state energies and radial transition electric dipole moments of the system are independent of the azimuthal quantum number l. First, by reformulating the N-photon absorption cross section of a single active electron, we prove that their assumptions reduce the network of optically allowed transition pathways into what we call the "Pascal triangle" consisting of (N + 1) (N + 2)/2 states only. Next, nonperturbative analytical and numerical solutions of the time-dependent Schrödinger equation for a simple model of two-photon excitation are presented not only in the low-intensity regime but also in the high-intensity regime. The results show that the determining factor of ellipticity-dependent multiphoton excitation probability is transition moment magnitudes and that the detailed energetic structure of the system also becomes important at high intensities. The experimentally observed flattening of the ion yields of xenon and C60 with increasing intensity can be explained without a saturation effect, which was previously deemed to be responsible for it. We also argue the applicability range of the cross section formula by Hertel et al. and the identity of the "doorway state" for ionization of C60.

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

    Science.gov (United States)

    Flower, D. R.; Roueff, E.

    1999-11-01

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

  12. Comment II on ``Topological angular momentum in electron exchange excitation of a single atom''

    Science.gov (United States)

    Bartschat, Klaus; Zatsarinny, Oleg

    2013-01-01

    A recent article by Williams [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.85.022701 85, 022701 (2012)] highlights a discrepancy between experiment and theory for the linear light polarization P2 measured after impact excitation of zinc atoms by a spin-polarized electron beam. The claim is made that current collision theories must be modified by including a geometric (Berry) phase in the calculations in order to reproduce the experimental data for Zn and similar data from the Münster group for Hg. We show that the e-Hg data can be qualitatively reproduced by our fully relativistic B-spline R-matrix approach without any further modification.

  13. Laser-induced fluorescence with an OPO system. Part II: direct determination of lead content in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF).

    Science.gov (United States)

    Le Bihan, A; Lijour, Y; Giamarchi, P; Burel-Deschamps, L; Stephan, L

    2003-03-01

    Fluorescence was induced by coupling a laser with an optical parametric oscillator (OPO) to develop an analytical method for the direct determination of lead content, at ultra-trace level, in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF). The optimization of atomization conditions, laser pulse energy, and mainly temporal parameters allowed us to reach a 3 fg detection limit (0.3 ng L(-1)) despite the low repetition rate of the device. The expected error on predicted concentrations of lead, at trace levels, in seawater was below 15%.

  14. Atomic xenon recombination laser excited by thermal ionizing radiation from a magnetoplasma compressor and discharge

    Science.gov (United States)

    Kamrukov, A. S.; Kozlov, Nicolay P.; Opekan, A. G.; Protasov, Yuri S.; Rudoi, I. G.; Soroka, A. M.

    1991-09-01

    A description is given and the results are reported of the first photoionization-recombination laser using atomic xenon excited by thermal ionizing radiation from a plasma. The pump source was a multichannel plasmadynamic in magnetoplasma compressors, which was ignited in the active medium of the laser. When the composition of the working mixture was optimal (Xe:Ar equals 1:250) and the total pressure was 1 atm, the output energy was approximately 0.5 in the form of pulses of approximately 10 microsecond(s) duration, and maximum specific output energy represented by laser radiation was 1-2 J/l. The unsaturated gain was 27 m. A kinetic laser scheme was proposed and analyzed. It allowed for the processes of photoionization, ion conversion, dissociative recombination, interaction of excited states with electron and buffer gases, etc. An important role played by heating of the active medium during pumping was demonstrated; it explained the observed characteristics of the spatial and temporal structure of the lasing process, particularly bleaching of large volumes of the active medium. The potential output energy of the laser was considered, and specific constructions were proposed to attain a lasing efficiency amounting to a few percent.

  15. LASERS: Atomic xenon recombination laser excited by thermal ionizing radiation from a magnetoplasma compressor and discharge

    Science.gov (United States)

    Kamrukov, A. S.; Kozlov, N. P.; Opekan, A. G.; Protasov, Yu S.; Rudoĭ, I. G.; Soroka, A. M.

    1989-07-01

    A description is given and the results are reported of the first photoionization-recombination laser using atomic xenon excited by thermal ionizing radiation from a plasma. The pump source was a multichannel plasmadynamic discharge in magnetoplasma compressors, which was ignited in the active medium of the laser. When the composition of the working mixture was optimal (Xe:Ar = 1:250) and the total pressure was 1 atm, the output energy was ~ 0.5 J in the form of pulses of ~ 10 μs duration and the maximum specific output energy represented by laser radiation was 1-2 J/liter. The unsaturated gain was 27 m - 1. A kinetic laser scheme was proposed and analyzed. It allowed for the processes of photoionization, ion conversion, dissociative recombination, interaction of excited states with electron and buffer gases, etc. An important role played by heating of the active medium during pumping was demonstrated and it explained the observed characteristics of the spatial and temporal structure of the lasing process, particularly bleaching of large volumes of the active medium. The potential output energy of the laser was considered and specific constructions were proposed to attain a lasing efficiency amounting to a few percent.

  16. Ultrafast atomic-scale visualization of acoustic phonons generated by optically excited quantum dots.

    Science.gov (United States)

    Vanacore, Giovanni M; Hu, Jianbo; Liang, Wenxi; Bietti, Sergio; Sanguinetti, Stefano; Carbone, Fabrizio; Zewail, Ahmed H

    2017-07-01

    Understanding the dynamics of atomic vibrations confined in quasi-zero dimensional systems is crucial from both a fundamental point-of-view and a technological perspective. Using ultrafast electron diffraction, we monitored the lattice dynamics of GaAs quantum dots-grown by Droplet Epitaxy on AlGaAs-with sub-picosecond and sub-picometer resolutions. An ultrafast laser pulse nearly resonantly excites a confined exciton, which efficiently couples to high-energy acoustic phonons through the deformation potential mechanism. The transient behavior of the measured diffraction pattern reveals the nonequilibrium phonon dynamics both within the dots and in the region surrounding them. The experimental results are interpreted within the theoretical framework of a non-Markovian decoherence, according to which the optical excitation creates a localized polaron within the dot and a travelling phonon wavepacket that leaves the dot at the speed of sound. These findings indicate that integration of a phononic emitter in opto-electronic devices based on quantum dots for controlled communication processes can be fundamentally feasible.

  17. Ultrafast atomic-scale visualization of acoustic phonons generated by optically excited quantum dots

    Directory of Open Access Journals (Sweden)

    Giovanni M. Vanacore

    2017-07-01

    Full Text Available Understanding the dynamics of atomic vibrations confined in quasi-zero dimensional systems is crucial from both a fundamental point-of-view and a technological perspective. Using ultrafast electron diffraction, we monitored the lattice dynamics of GaAs quantum dots—grown by Droplet Epitaxy on AlGaAs—with sub-picosecond and sub-picometer resolutions. An ultrafast laser pulse nearly resonantly excites a confined exciton, which efficiently couples to high-energy acoustic phonons through the deformation potential mechanism. The transient behavior of the measured diffraction pattern reveals the nonequilibrium phonon dynamics both within the dots and in the region surrounding them. The experimental results are interpreted within the theoretical framework of a non-Markovian decoherence, according to which the optical excitation creates a localized polaron within the dot and a travelling phonon wavepacket that leaves the dot at the speed of sound. These findings indicate that integration of a phononic emitter in opto-electronic devices based on quantum dots for controlled communication processes can be fundamentally feasible.

  18. Electron impact excitation cross sections and rates from the ground state of atomic calcium

    CERN Document Server

    Samson, A M

    2001-01-01

    New R-matrix calculations are presented for electron excitation of atomic calcium. The target state expansion includes 22 states: 4s sup 2 sup 1 S; 4snl sup 1 sup , sup 3 L, where nl is 3d, 4p, 5s, 5p, 4d and 4f; 3d4p sup 1 sup , sup 3 P,D,F; and 4p sup 2 sup 3 P, sup 1 D, sup 1 S terms. The calculation is in LS coupling, and configuration interaction involving 3p subshell correlation is included. Electron impact excitation cross sections from the 4s sup 2 ground state to the next 10 states are tabulated for low energies, and thermally averaged effective collision strengths are tabulated over a range of electron temperatures from 1000 to 10,000 K. Comparisons are made with previous cross sections calculations for the 4s sup 2 -4s4p sup 3 P deg. transition; excellent agreement is found with experimentally derived rates for 4s sup 2 -4s4p sup 1 P deg

  19. A New Rb Lamp Exciter Circuit for Rb atomic clocks and Studies on Transition from Ring to Red mode

    CERN Document Server

    Singh, Savita; Saxena, G M

    2010-01-01

    In this paper we describe the development of novel RF exciter circuit for electrode less Rb lamp. The lamp exciter circuit is a RF oscillator with a a new configuration operating at 60 to 65 MHz frequency with 3 to 4 watt power. The Rb lamp is used in exciting the ground state hyperfine transitions in Rb atom in a glass cell placed inside a tuned microwave cavity, As the frequency of these hyperfine transitions is very stable it is used in the development of Rb atomic clock by phase locking the oven controlled crystal oscillator (OCXO) to this atomic transition frequency. The details of the Rb lamp exciter are presented in the paper.The Lamp is ideally operated in ring mode as in this mode the linewidth is narrow and there is no self reversal. However, high temperature and RF excitation power may drive the Rb lamp to red mode which gives rise to line broadening and self reversal. It is the experience that mode change from ring to red deteriorates the atomic signal strength and S/N. In this paper the reasons o...

  20. Multiconfiguration Dirac-Hartree-Fock energy levels, oscillator strengths, transition probabilities, hyperfine constants and Landé g-factor of intermediate Rydberg series in neutral argon atom

    Science.gov (United States)

    Salah, Wa'el; Hassouneh, Ola

    2017-04-01

    We computed the energy levels, oscillator strengths f_{ij}, the radiative transition rates A_{ij}, the Landé g -factor, the magnetic dipole moment and the electric quadrupole hyperfine constants of the intermediate Rydberg series ns [k]J ( 4 ≤ n ≤ 6), nd [k]J (3 ≤ n ≤ 4), np [k]J (4 ≤ n ≤ 5) relative to the ground state 3p6 1S0 for neutral argon atom spectra. The values are obtained in the framework of the multiconfiguration Dirac-Hartree-Fock (MCDHF) approach. In this approach, Breit interaction, leading quantum electrodynamics (QED) effects and self-energy correction are taken into account. Moreover, these spectroscopic parameters have been calculated for many levels belonging to the configuration 3p54s, 3p55s, 3p56s, 3p53d, 3p54d, 3p54p, 3p55p as well as for transitions between levels 3p54s-3p54p, 3p54p-3p53d, 3p54p-3p55s, 3p55s-3p55p and 3p55p-3p56s. The large majority of the lines from the 4p-5s and 4p-3d, 5s-5p and 5p-6s transition arrays have been observed and the calculations are consistent with the J -file-sum rule. The obtained theoretical values are compared with previous experimental and theoretical data available in the literature. An overall satisfactory agreement is noticed allowing assessing the reliability of our data.

  1. Comparison of photothermal and piezoacoustic excitation methods for frequency and phase modulation atomic force microscopy in liquid environments

    OpenAIRE

    Labuda, A.; Kobayashi, K; D. Kiracofe; Suzuki, K; P. H. Grütter; Yamada, H

    2011-01-01

    In attempting to perform frequency modulation atomic force microscopy (FM-AFM) in liquids, a non-flat phase transfer function in the self-excitation system prevents proper tracking of the cantilever natural frequency. This results in frequency-and-phase modulation atomic force microscopy (FPM-AFM) which lies in between phase modulation atomic force microscopy (PM-AFM) and FM-AFM. We derive the theory necessary to recover the conservative force and damping in such a situation, where standard F...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-11-01

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

  3. ANISOTROPY EFFECTS IN SINGLE-ELECTRON TRANSFER BETWEEN LASER-EXCITED ATOMS AND HIGHLY-CHARGED IONS

    NARCIS (Netherlands)

    Recent collision experiments are reviewed in which one-electron transfer between laser excited target atoms and (highly charged) keV-ions has been studied. Especially results showing a dependence of the charge exchange on the initial target orbital alignment are discussed. The question to what

  4. Comparison of photothermal and piezoacoustic excitation methods for frequency and phase modulation atomic force microscopy in liquid environments

    Directory of Open Access Journals (Sweden)

    A. Labuda

    2011-06-01

    Full Text Available In attempting to perform frequency modulation atomic force microscopy (FM-AFM in liquids, a non-flat phase transfer function in the self-excitation system prevents proper tracking of the cantilever natural frequency. This results in frequency-and-phase modulation atomic force microscopy (FPM-AFM which lies in between phase modulation atomic force microscopy (PM-AFM and FM-AFM. We derive the theory necessary to recover the conservative force and damping in such a situation, where standard FM-AFM theory no longer applies. Although our recovery procedure applies to all cantilever excitation methods in principle, its practical implementation may be difficult, or even impossible, if the cantilever is driven piezoacoustically. Specifically, we contrast the piezoacoustic excitation method to the photothermal method in the context of force spectroscopy of hydration structures at the mica-water interface. The results clearly demonstrate that photothermal excitation is superior to piezoacoustic excitation, as it allows for accurate quantitative interpretation of the acquired data.

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

    Science.gov (United States)

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

    2017-09-01

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

  6. In situ detection of atomic and molecular iodine using Resonance and Off-Resonance Fluorescence by Lamp Excitation: ROFLEX

    Science.gov (United States)

    Gómez Martín, J. C.; Blahins, J.; Gross, U.; Ingham, T.; Goddard, A.; Mahajan, A. S.; Ubelis, A.; Saiz-Lopez, A.

    2011-01-01

    We demonstrate a new instrument for in situ detection of atmospheric iodine atoms and molecules based on atomic and molecular resonance and off-resonance ultraviolet fluorescence excited by lamp emission. The instrument combines the robustness, light weight, low power consumption and efficient excitation of radio-frequency discharge light sources with the high sensitivity of the photon counting technique. Calibration of I2 fluorescence is achieved via quantitative detection of the molecule by Incoherent Broad Band Cavity-enhanced Absorption Spectroscopy. Atomic iodine fluorescence signal is calibrated by controlled broad band photolysis of known I2 concentrations in the visible spectral range at atmospheric pressure. The instrument has been optimised in laboratory experiments to reach detection limits of 1.2 pptv for I atoms and 13 pptv for I2, for S/N = 1 and 10 min of integration time. The ROFLEX system has been deployed in a field campaign in northern Spain, representing the first concurrent observation of ambient mixing ratios of iodine atoms and molecules in the 1-350 pptv range.

  7. Measurements and kinetic modeling of atomic species in fuel-oxidizer mixtures excited by a repetitive nanosecond pulse discharge

    Science.gov (United States)

    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

  8. Collisional excitation of metastable oxygen O(1D) atoms through the B3Sigma(-) sub u channel of O2

    Science.gov (United States)

    Jamieson, M. J.; Finch, M.; Friedman, R. S.; Dalgarno, A.

    1992-12-01

    Spectroscopic data on the shifts and widths of the energy levels of molecular oxygen have been used in the empirical construction of a diabatic potential matrix that characterizes the interactions of the B3Sigma(-) sub u state with the 5Pi sub u, 2 3Sigma(+) sub u, 3Pi sub u, and 1Pi sub u states. The diabatic potential matrix is used here in a scattering theory formulation to calculate the cross-sections for the excitation of O(1D) atoms in collisions of two O(3P) atoms. Total cross-sections are obtained by adding the excitation from the 3Pi sub g channel. The rate coefficient for quenching of O(1D) by O(3P) is evaluated as a function of temperature. The values conflict with a recent analysis of the emission of the oxygen red line in the upper atmosphere.

  9. Spatial characterization of laser induced Yb plasma in argon using optical emission spectroscopy: Pressure effect

    Energy Technology Data Exchange (ETDEWEB)

    Jazmati, A.K.; Alnama, K., E-mail: pscientific21@aec.org.sy; Alkhawwam, A.

    2014-09-15

    Highlights: • Laser induced Yb plasma at different pressure of Argon is spatially investigated. • O-TOF profiles and excitation temperature are used to characterize the plasma. • At 100 Pa of argon background gas, shock wave begins to be formed. • Drag force expansion describes the plasma propagation at pressures bigger than 1 Pa. • Two components of velocity distribution of the Yb atoms are estimated. - Abstract: Spatial and temporal behavior of laser induced Ytterbium plasma plume is studied using optical emission spectroscopy technique. A third harmonic Nd:YAG nanosecond laser was used to generate Yb plasma plume at different Argon background pressures (1, 10, 10{sup 2}, 10{sup 3} and 10{sup 4} Pa). The plasma dynamics was investigated based on the spatial behavior of the excitation temperature coupled with optical time of flight (O-TOF) profiles of neutral Yb emission line (555.65 nm) along the propagation axe of the plasma plume. Drag force model was appropriate to describe the propagation dynamics at all pressures except of the lowest one (1 Pa) where free expansion model is dominant. The velocity distribution of Yb I atoms were extracted using two terms of Shifted Maxwell–Boltzmann (SMB) distribution. The correlation between the spatial comportment of both excitation temperature and O-TOF profiles is discussed.

  10. Orbital Angular Momentum of Gauge Fields: Excitation of AN Atom by Twisted Photons

    Science.gov (United States)

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

    2014-01-01

    Twisted photon states, or photon states with large (> ℏ) angular momentum projection in the direction of motion, can photoexcite atomic final states of differing quantum numbers. If the photon symmetry axis coincides with the center of an atom, there are known selection rules that require exact matching between the quantum numbers of the photon and the photoexcited states. The more general case of arbitrarily positioned beams relaxes the selection rules but produces a distribution of quantum numbers of the final atomic states that is novel and distinct from final states produced by plane-wave photons. Numerical calculations are presented using a hydrogen atom as an example.

  11. Electron confinement and heating in microwave-sustained argon microplasmas

    Science.gov (United States)

    Hoskinson, Alan R.; Gregório, José; Parsons, Stephen; Hopwood, Jeffrey

    2015-04-01

    We systematically measure and model the behavior of argon microplasmas sustained by a broad range of microwave frequencies. The plasma behavior exhibits two distinct regimes. Up to a transition frequency of approximately 4 GHz, the electron density, directly measured by Stark broadening, increases rapidly with rising frequency. Above the transition frequency, the density remains approximately constant near 5 × 1020 m-3. The electrode voltage falls with rising frequency across both regimes, reaching approximately 5 V at the highest tested frequency. A fluid model of the plasma indicates that the falling electrode voltage reduces the electron temperature and significantly improves particle confinement, which in turn increases the plasma density. Particles are primarily lost to the electrodes at lower frequencies, but dissociative recombination becomes dominant as particle confinement improves. Recombination events produce excited argon atoms which are efficiently re-ionized, resulting in relatively constant ionization rates despite the falling electron temperature. The fast rates of recombination are the result of high densities of electrons and molecular ions in argon microplasmas.

  12. Nonequilibrium Green function theory for excitation and transport in atoms and molecules

    NARCIS (Netherlands)

    Dahlen, Nils Erik; Stan, Adrian

    2006-01-01

    In this work we discuss the application of nonequilibrium Green functions theory to atomic and molecular systems with the aim to study charge and energy transport in these systems. We apply the Kadanoff-Baym equations to atoms and diatomic molecules initially in the ground state. The results

  13. Goldstone mode and pair-breaking excitations in atomic Fermi superfluids

    Science.gov (United States)

    Hoinka, Sascha; Dyke, Paul; Lingham, Marcus G.; Kinnunen, Jami J.; Bruun, Georg M.; Vale, Chris J.

    2017-10-01

    Spontaneous symmetry breaking is a central paradigm of elementary particle physics, magnetism, superfluidity and superconductivity. According to Goldstone's theorem, phase transitions that break continuous symmetries lead to the existence of gapless excitations in the long-wavelength limit. These Goldstone modes can become the dominant low-energy excitation, showing that symmetry breaking has a profound impact on the physical properties of matter. Here, we present a comprehensive study of the elementary excitations in a homogeneous strongly interacting Fermi gas through the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC) of molecules using two-photon Bragg spectroscopy. The spectra exhibit a discrete Goldstone mode, associated with the broken-symmetry superfluid phase, as well as pair-breaking single-particle excitations. Our techniques yield a direct determination of the superfluid pairing gap and speed of sound in close agreement with strong-coupling theories.

  14. Multi-photon excitation and ionization cross sections in atomic oxygen

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, E.J.

    1985-01-01

    Calculations are presented on a variety of multi-photon excitation and ionization cross sections in oxygen. The regimes of cross sections discussed are: (1) 2-photon excitation to the bound (2p)/sup 3/ /sup 4/S (nl) levels; (2) 2-photon excitation to the autoionizing (2p)/sup 3/ /sup 2/D (3p) and (2p)/sup 3/ /sup 2/P (3p) levels; (3) excitation of the (2p)/sup 4/ /sup 1/D and /sup 1/S levels by both 1-photon excitation on forbidden transitions and 2-photon excitations; (4) 1-photon photoionization of the (2p)/sup 3/ /sup 4/S (3s) /sup 3/S and (2p)/sup 3/ /sup 4/S (3p) /sup 3/P levels; and (5) 3-photon nonresonant ionization with the (2p)/sup 3/ /sup 4/S (3p) /sup 3/P level as an intermediate resonance. 5 refs., 3 figs., 2 tabs.

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

    Directory of Open Access Journals (Sweden)

    B. Maiti

    2002-04-01

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

  16. Quantitative force and dissipation measurements in liquids using piezo-excited atomic force microscopy: a unifying theory.

    Science.gov (United States)

    Kiracofe, Daniel; Raman, Arvind

    2011-12-02

    The use of a piezoelectric element (acoustic excitation) to vibrate the base of microcantilevers is a popular method for dynamic atomic force microscopy. In air or vacuum, the base motion is so small (relative to tip motion) that it can be neglected. However, in liquid environments the base motion can be large and cannot be neglected. Yet it cannot be directly observed in most AFMs. Therefore, in liquids, quantitative force and energy dissipation spectroscopy with acoustic AFM relies on theoretical formulae and models to estimate the magnitude of the base motion. However, such formulae can be inaccurate due to several effects. For example, a significant component of the piezo excitation does not mechanically excite the cantilever but rather transmits acoustic waves through the surrounding liquid, which in turn indirectly excites the cantilever. Moreover, resonances of the piezo, chip and holder can obscure the true cantilever dynamics even in well-designed liquid cells. Although some groups have tried to overcome these limitations (either by theory modification or better design of piezos and liquid cells), it is generally accepted that acoustic excitation is unsuitable for quantitative force and dissipation spectroscopy in liquids. In this paper the authors present a careful study of the base motion and excitation forces and propose a method by which quantitative analysis is in fact possible, thus opening this popular method for quantitative force and dissipation spectroscopy using dynamic AFM in liquids. This method is validated by experiments in water on mica using a scanning laser Doppler vibrometer, which can measure the actual base motion. Finally, the method is demonstrated by using small-amplitude dynamic AFM to extract the force gradients and dissipation on solvation shells of octamethylcyclotetrasiloxane (OMCTS) molecules on mica.

  17. Laser excited analytical atomic and ionic fluorescence in flames, furnaces and inductively coupled plasmas—I. General considerations

    Science.gov (United States)

    Omenetto, N.; Human, H. G. C.

    Several important parameters for the analytical use of laser excited fluorescence spectrometry in flames, graphite furnaces and inductively coupled plasmas are discussed in some detail. These parameters include the laser characteristics such as peak power, pulse duration, spectral bandwidth and repetition rate, the choice of the excitation line, the optical arrangement and the detection system, this last one centred on the widespread use of the boxcar averager. It is shown that, if the ultimate sensitivity is the goal to be achieved, then the choice must be the electrothermal atomization. However, even for flames and inductively coupled plasmas, excellent results are possible provided that: (i) the laser system allows complete spectral coverage in the ultraviolet: (ii) saturation of the fluorescence signal can be approached over a large sample volume; and (iii) the gated detection parameters and the laser repetition frequency are optimized with respect to each other so as to reach the maximum signal-to-noise ratio.

  18. Frustrated tunneling ionization during laser-induced D{sub 2} fragmentation: Detection of excited metastable D{sup *} atoms

    Energy Technology Data Exchange (ETDEWEB)

    McKenna, J.; Zeng, S.; Hua, J. J.; Sayler, A. M.; Zohrabi, M.; Johnson, Nora G.; Gaire, B.; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I. [J. R. Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506 (United States)

    2011-10-15

    In a recent Letter, Manschwetus et al.[Phys. Rev. Lett. 102, 113002 (2009)] reported evidence of electron recapture during strong-field fragmentation of H{sub 2}--explained using a frustrated tunneling ionization model. Unusually, the signature of this process was detection of excited H{sup *} atoms. We report here an extensive study of this process in D{sub 2}. Our measurements encompass a study of the pulse duration, intensity, ellipticity, and angular distribution dependence of D{sup *} formation. While we find that the mechanism suggested by Manschwetus et al. is consistent with our experimental data, our theoretical work shows that electron recollision excitation cannot be completely ruled out as an alternative mechanism for D{sup *} production.

  19. Self-sharpening tip integrated on micro cantilevers with self-exciting piezoelectric sensor for parallel atomic force microscopy

    Science.gov (United States)

    Indermühle, P.-F.; Schürmann, G.; Racine, G.-A.; de Rooij, N. F.

    1997-04-01

    Arrays of cantilevers with integrated self-sharpening tips and self-exciting piezoelectric sensors have been fabricated using monocrystalline silicon micromachining. During the fabrication process, tips are first formed with a wet etching technique allowing a good homogeneity of tip shape over a whole wafer and then protected with a local thick silicon dioxide layer. Single cantilevers have been used to achieve atomic force microscopy images of grids with periods of 0.25, 1, and 5 μm and with height differences of 100, 15, and 180 nm, respectively.

  20. Cooper minima in the transitions from low-excited and Rydberg states of alkali-metal atoms

    OpenAIRE

    Beterov, I. I.; Mansell, C. W.; Yakshina, E. A.; Ryabtsev, I. I.; Tretyakov, D. B.; Entin, V. M.; MacCormick, C.; Piotrowicz, M. J.; Kowalczyk, A.; Bergamini, S.

    2012-01-01

    The structure of the Cooper minima in the transition probabilities and photoionization cross-sections for low-excited and Rydberg nS, nP, nD and nF states of alkali-metal atoms has been studied using a Coulomb approximation and a quasiclassical model. The range of applicability of the quasiclassical model has been defined from comparison with available experimental and theoretical data on dipole moments, oscillator strengths, and photoionization cross-sections. A new Cooper minimum for transi...

  1. Interplay between relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics of Xe atoms

    Science.gov (United States)

    Toyota, Koudai; Son, Sang-Kil; Santra, Robin

    2017-04-01

    In this paper, we theoretically study x-ray multiphoton ionization dynamics of heavy atoms taking into account relativistic and resonance effects. When an atom is exposed to an intense x-ray pulse generated by an x-ray free-electron laser (XFEL), it is ionized to a highly charged ion via a sequence of single-photon ionization and accompanying relaxation processes, and its final charge state is limited by the last ionic state that can be ionized by a single-photon ionization. If x-ray multiphoton ionization involves deep inner-shell electrons in heavy atoms, energy shifts by relativistic effects play an important role in ionization dynamics, as pointed out in Phys. Rev. Lett. 110, 173005 (2013), 10.1103/PhysRevLett.110.173005. On the other hand, if the x-ray beam has a broad energy bandwidth, the high-intensity x-ray pulse can drive resonant photoexcitations for a broad range of ionic states and ionize even beyond the direct one-photon ionization limit, as first proposed in Nat. Photon. 6, 858 (2012), 10.1038/nphoton.2012.261. To investigate both relativistic and resonance effects, we extend the xatom toolkit to incorporate relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics calculations. Charge-state distributions are calculated for Xe atoms interacting with intense XFEL pulses at a photon energy of 1.5 keV and 5.5 keV, respectively. For both photon energies, we demonstrate that the role of resonant excitations in ionization dynamics is altered due to significant shifts of orbital energy levels by relativistic effects. Therefore, it is necessary to take into account both effects to accurately simulate multiphoton multiple ionization dynamics at high x-ray intensity.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-01

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

  3. Electron impact excitation of the D states of Mg, Ca and Sr atoms ...

    Indian Academy of Sciences (India)

    We have used non-relativistic and relativistic distorted wave approximation methods to study the excitation of the 1 states of magnesium ( = 3), calcium ( = 4) and strontium ( = 5) from the ground 1 state. Calculations have been performed for the complete set of parameters ( , L ~ ⊥ + , L ~ ⊥ − , ~ + , ~ − ) .

  4. Formation of cold molecules through the photo-association of cold atoms of Cesium. Existence of long range forces between between cold excited atoms of Cesium; Formation de molecules froides par photoassociation d'atomes froids de cesium. Mise en evidence de forces a longue portee entre atomes froids excites de cesium

    Energy Technology Data Exchange (ETDEWEB)

    Comparat, D

    1999-09-01

    This thesis deals with the experimental study and the theoretical interpretation of the processes involved in photo-association and the formation of cold caesium molecules. It also presents a study of the dipolar forces between a pair of cold excited caesium atoms. We present here the first photo-association experiment on cold caesium atoms: two cold atoms absorb a photon to form an excited electronically excited molecules in a rotation-vibration level. The first production of cold molecules which was realised experimentally, after the spontaneous deexcitation of the photo-associated molecules, is described, stressing the role of the potential well of the molecular states O{sub g}{sup -}(6s+6p{sub 3/2}) or 1{sub u} (6s+6p{sub 3/2}) of caesium. The detection of the formed caesium molecules is based on a two-photons resonant ionisation that creates Cs{sub 2}{sup +} ions, afterwards selectively detected. Temperatures around 20-200 {mu}K have been measured. The photo-associative spectroscopy is described on the theoretical point of view: a detailed theoretical study allows to calculate precisely the asymptotic parts of the potential curves. On the experimental point of view, we present the spectroscopy of the extern potential well of the caesium state O{sub g}{sup -}(6s+6p{sub 3/2}) and the construction of an effective potential curve of the RKR type. A unified theory of photo-association in weak field, considered as a collision assisted by laser, is developed. The cold atoms experiments allow to study and control the collision between two atoms whose mutual interaction is of the dipole-dipole type. Two different physical systems are studied: a sample of Rydberg atoms, and the photo-association process which is a laser-assisted collision. A modification of the motion of one pair of atoms makes it possible to control the bipolar forces and to choose the atoms relative speeds. (author)

  5. The interaction of excited atoms and few-cycle laser pulses

    CERN Document Server

    Calvert, J E; Palmer, A J; Glover, R D; Tong, X M; Dolmatov, V K; Kheifets, A S; Bartschat, K; Litvinyuk, I V; Kielpinski, D; Sang, R T

    2016-01-01

    This work describes the first observations of the ionisation of neon in a metastable atomic state utilising a strong-field, few-cycle light pulse. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory and a solution to the time-dependent Schrodinger equation (TDSE). The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and demonstrate that the ionisation rate depends on the spin state of the target atoms and provide physically transparent interpretation of such a spin dependence in the frameworks of the spin-polarised Hartree-Fock and random-phase approximations.

  6. Laser-Excited Atomic Fluorescence and Ionization in a Graphite Furnace for the Determination of Metals and Nonmetals

    Science.gov (United States)

    Butcher, David James

    1990-01-01

    Here is reported novel instrumentation for atomic spectrometry that combined the use of a pulsed laser system as the light source and an electrothermal atomizer as the atom cell. The main goal of the research was to develop instrumentation that was more sensitive for elemental analysis than commercially available instruments and could be used to determine elements in real sample matrices. Laser excited atomic fluorescence spectrometry (LEAFS) in an electrothermal atomizer (ETA) was compared to ETA atomic absorption spectrometry (AAS) for the determination of thallium, manganese, and lead in food and agricultural standard reference materials (SRMs). Compared to ETA AAS, ETA LEAFS has a longer linear dynamic range (LDR) (5-7 orders of magnitude compared to 2-3 orders of magnitude) and higher sensitivity (10 ^{-16} to 10^{ -14} g as compared to 10^{ -13} to 10^{-11} g). Consequently, ETA LEAFS allows elemental analysis to be done over a wider range of concentrations with less dilution steps. Thallium was accurately determined in biological samples by ETA LEAFS at amounts five to one hundred times below the ETA AAS detection limit. ETA AAS and ETA LEAFS were compared for the determination of lead and manganese, and in general, the accuracies and precisions of ETA AAS were the same, with typical precisions between 3% and 6%. Fluorine was determined using laser excited molecular fluorescence spectrometry (LEMOFS) in an ETA. Molecular fluorescence from magnesium fluoride was collected, and the detection limit of 0.3 pg fluorine was two to six orders of magnitude more sensitive than other methods commonly used for the determination of fluorine. Significant interferences from ions were observed, but the sensitivity was high enough that fluorine could be determined in freeze dried urine SRMs by diluting the samples by a factor of one hundred to remove the interferences. Laser enhanced ionization (LEI) in an ETA was used for the determination of metals. For thallium, indium

  7. Dead-zone-free atomic magnetometry with simultaneous excitation of orientation and alignment resonances.

    Science.gov (United States)

    Ben-Kish, A; Romalis, M V

    2010-11-05

    Atomic magnetometers have very high absolute precision and sensitivity to magnetic fields but suffer from a fundamental problem: the vectorial or tensorial interaction of light with atoms leads to "dead zones," certain orientations of the magnetic field where the magnetometer loses its sensitivity. We demonstrate a simple polarization modulation scheme that simultaneously creates coherent population trapping (CPT) in orientation and alignment, thereby eliminating dead zones. Using 87Rb in a 10 Torr buffer gas cell we measure narrow, high-contrast CPT transparency peaks for all orientations and also show the absence of systematic effects associated with nonlinear Zeeman splitting.

  8. Optical oscillator strengths of the valence-shell excitations of atoms and molecules determined by the dipole ( γ,γ) method

    Science.gov (United States)

    Xu, Long-Quan; Liu, Ya-Wei; Xu, Xin; Ni, Dong-Dong; Yang, Ke; Zhu, Lin-Fan

    2017-07-01

    The dipole (γ,γ) method, which is the inelastic X-ray scattering operated at a negligibly small momentum transfer, has been developed to determine the absolute optical oscillator strengths of the valence-shell excitations of atoms and molecules. This new method is free from the line saturation effect, and its Bethe-Born conversion factor varies much more slowly with the excitation energy than that of the dipole (e, e) method. Thus the dipole (γ,γ) method provides a reliable approach to obtain the benchmark optical oscillator strengths of the valence-shell excitations for gaseous atoms and molecules. In this paper, we give a review of the dipole (γ,γ) method and some recent measurements of absolute optical oscillator strengths of gaseous atoms and molecules. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

  9. Optical Bragg, atomic Bragg and cavity QED detections of quantum phases and excitation spectra of ultracold atoms in bipartite and frustrated optical lattices

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Jinwu, E-mail: jy306@ccs.msstate.edu [Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048 (China); Department of Physics and Astronomy, Mississippi State University, Mississippi State, MS 39762 (United States); Zhang, K.Y.; Li, Yan [Department of Physics, East China Normal university, Shanghai, 200062 (China); Chen, Yan [Department of Physics, State Key Laboratory of Surface Physics and Laboratory of Advanced Materials, Fudan University, Shanghai, 200433 (China); Zhang, W.P. [Department of Physics, East China Normal university, Shanghai, 200062 (China)

    2013-01-15

    Ultracold atoms loaded on optical lattices can provide unprecedented experimental systems for the quantum simulations and manipulations of many quantum phases and quantum phase transitions between these phases. However, so far, how to detect these quantum phases and phase transitions effectively remains an outstanding challenge. In this paper, we will develop a systematic and unified theory of using the optical Bragg scattering, atomic Bragg scattering or cavity QED to detect the ground state and the excitation spectrum of many quantum phases of interacting bosons loaded in bipartite and frustrated optical lattices. The physically measurable quantities of the three experiments are the light scattering cross sections, the atom scattered clouds and the cavity leaking photons respectively. We show that the two photon Raman transition processes in the three detection methods not only couple to the density order parameter, but also the valence bond order parameter due to the hopping of the bosons on the lattice. This valence bond order coupling is very sensitive to any superfluid order or any valence bond (VB) order in the quantum phases to be probed. These quantum phases include not only the well-known superfluid and Mott insulating phases, but also other important phases such as various kinds of charge density waves (CDW), valence bond solids (VBS), and CDW-VBS phases with both CDW and VBS orders unique to frustrated lattices, and also various kinds of supersolids. We analyze respectively the experimental conditions of the three detection methods to probe these various quantum phases and their corresponding excitation spectra. We also address the effects of a finite temperature and a harmonic trap. We contrast the three scattering methods with recent in situ measurements inside a harmonic trap and argue that the two kinds of measurements are complementary to each other. The combination of both kinds of detection methods could be used to match the combination of

  10. Localization and Targeted Transfer of Atomic-Scale Nonlinear Excitations: Perspectives for Applications

    Science.gov (United States)

    Kopidakis, G.; Aubry, S.

    We review nonlinearity-induced localization in discrete systems with emphasis on theory and numerical calculations on models used in materials physics to describe interatomic interactions. We discuss how the concept of discrete breather or intrinsic localized mode could become an important tool for understanding nanoscale phenomena in molecules and solids. A particularly attractive field of application for nonlinear localized excitations is the controlled and directed transport of energy. We discuss the recently proposed targeted transfer of localized excitations based on the concept of nonlinear resonance and its potential applications. As an area for such applications, we present directional ultrafast electron transfer at low temperatures using this selective transfer mechanism and we give examples from biological electron transfer. We finally discuss possible applications in nanotechnology and biomolecules.

  11. Correction of the first Born approximation for ion-atom collision in excitation channel by multi-channel eikonal formalism

    Directory of Open Access Journals (Sweden)

    reza fathi

    2017-05-01

    Full Text Available In the present work has been tried to do a generalized formalism of semi-classical method used in ion-atom impact. One of the current method to calculation of the differential and total cross section for ion-atom impact at high energy range is the first Born approximation because of the simplicity of its calculations, but not necessarily sufficiently accurate. In particular this approximation in the excitation channel take into account orthogonality of the initial and the final state wave functions of the bound subsystem and then disappears inter-nuclear effect in the calculations and offers the poor picture for viewing impact process. Also in this approximation the most important coupling has been considered between the initial and the final state. However the close-coupling method because of some restrictions in high impact energies is unusable. Therefore the aim of this work is correction the first Born approximation by implemented the multi-channel eikonal formalism. At last it will be shown that by simplifying this generalized theory it can be achieved a number of current formalism in terms of ion-atom impact.

  12. Reactions of electronically excited boron atoms. Quenching rate constants and the radiative lifetime of the 4p 2P state

    Science.gov (United States)

    Yang, Xuefeng; Dagdigian, Paul J.

    1992-12-01

    Collisional quenching and radiative decay of the 4p 2P level of the boron atom has been studied in a cell experiment, in which B atoms are prepared by 266 nm multiphoton dissociation of BBr 3 and the 4p 2P level is prepared by sequential 2-photon absorption through the 3s 2S level. A radiative lifetime of 360 ± 50 ns is derived for B (4p 2P) by extrapolation of the measured decay rates versus BBr 3 partial pressure in several Torr helium buffer gas. Bimolecular quenching rate constants were also determined for a number of atomic and molecular species from the dependence of the B (4p 2P) decay rate on the quencher gas partial pressure. The quenching rate constants for the molecular species were quite large (≈(1-2)×10 -9 molecule -1 cm 3 s -1), presumably reflecting the small B (4p 2P) ionization potential and the rapid removal of the excited state by chemical reaction.

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

    Directory of Open Access Journals (Sweden)

    M. Amdouni

    2014-01-01

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

  14. Ionization and excitation of some atomic targets and metal oxides by ...

    Indian Academy of Sciences (India)

    The resulting two-parameter expression is then used to obtain the value of R at a high energy Ei = 10Ep, and the same is employed in (6c). We have shown in table 1 the various parameters involved in the present work on O, Al and Cu along with C1, C2 and a evaluated as explained above. In atomic O there are several.

  15. Contribution of the 4f-core-excited states in determination of atomic properties in the promethium isoelectronic sequence

    Science.gov (United States)

    Safronova, U. I.; Safronova, A. S.; Beiersdorfer, P.

    2013-09-01

    The atomic properties of Pm-like ions were comprehensively studied using relativistic atomic codes. Excitation energies of the 4f14nl (with nl=5s, 6s, 5p, 6p, 5d, 6d, and 5f) states in Pm-like ions with nuclear charge Z ranging from 74 to 100 are evaluated within the framework of relativistic many-body theory (RMBPT). First- and second-order Coulomb energies and first- and second-order Breit corrections to the energies are calculated. Two alternative treatments of the Breit interaction are investigated. In the first approach we omit Breit contributions to the Dirac-Fock potential and evaluate Coulomb and Breit-Coulomb corrections through second order perturbatively. In the second approach were included both Coulomb and Breit contributions on the same footing via the Breit-Dirac-Fock potential and then treat the residual Breit and Coulomb interactions perturbatively. The results obtained from the two approaches are compared and discussed. The important question of what is the ground state in Pm-like ions was answered. Properties of the 4f-core-excited states are evaluated using the multiconfiguration relativistic Hebrew University Lawrence Livermore atomic code (hullac code) and the Hartree-Fock-relativistic method (cowan code). We evaluate excitation energies and transition rates in Pm-like ions with nuclear charge Z ranging from 74 to 92. Our large scale calculations include the following set of configurations: 4f145s, 4f145p, 4f135s2, 4f135p2, 4f135s5p, 4f125s25p, 4f125s5p2, and 4f125p3. Trends of excitation energies as function of Z are shown graphically for selected states. Excitation energies, transition rates, and lifetimes in Pm-like tungsten are evaluated with additional inclusion of the 4f115s25p2, 4f115s5p3, 4f105s25p3, and 4f105s5p4 configurations. This represents an unusual example of an atomic system where the even-parity complex [4f145s+4f135s5p+4f125s5p2+4f115s5p3+4f105s5p4] and the odd-parity complex [4f145p+4f135s2+4f125s25p+4f115s25p2+4f105s25p3

  16. Monte Carlo calculation of collisions of directionally-incident electrons on highly excited hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami, Kazuki; Fujimoto, Takasi [Kyoto Univ., Graduate School of Engineering, Kyoto (Japan)

    2001-10-01

    We treat classically the n-, l- and m{sub 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{sub 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)

  17. Attosecond angular flux of partial charges on the carbon atoms of benzene in non-aromatic excited state

    Science.gov (United States)

    Hermann, Gunter; Liu, ChunMei; Manz, Jörn; Paulus, Beate; Pohl, Vincent; Tremblay, Jean Christophe

    2017-09-01

    Recently, it was discovered that excitation of the oriented model benzene from its aromatic electronic ground state S0 (1A1g) to the non-aromatic S0 +S2 (1B1u) superposition state generates negative and positive partial charges on alternating carbon atoms. Subsequently, they vary periodically, due to adiabatic attosecond charge migration AACM. Here, we determine the angular electronic flux that mediates this new type of AACM, by means of quantum dynamics simulations. It is found to be periodic, with period τ bar = 590as , and with a pincer motion type pattern such that a total of 1.2 valence electrons flow concertedly between alternating sources and sinks at the carbon nuclei.

  18. Development of atomic force microscope with wide-band magnetic excitation for study of soft matter dynamics.

    Science.gov (United States)

    Kageshima, Masami; Chikamoto, Takuma; Ogawa, Tatsuya; Hirata, Yoshiki; Inoue, Takahito; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro

    2009-02-01

    In order to probe dynamical properties of mesoscopic soft matter systems such as polymers, structured liquid, etc., a new atomic force microscopy apparatus with a wide-band magnetic cantilever excitation system was developed. Constant-current driving of an electromagnet up to 1 MHz was implemented with a closed-loop driver circuit. Transfer function of a commercial cantilever attached with a magnetic particle was measured in a frequency range of 1-1000 kHz in distilled water. Effects of the laser spot position, distribution of the force exerted on the cantilever, and difference in the detection scheme on the obtained transfer function are discussed in comparison with theoretical predictions by other research groups. A preliminary result of viscoelasticity spectrum measurement of a single dextran chain is shown and is compared with a recent theoretical calculation.

  19. Alternatives to argon for gas stopping volumes in the B194 neutron imager

    Energy Technology Data Exchange (ETDEWEB)

    Bleuel, D. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Anderson, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Caggiano, J. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hall, J. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Johnson, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ratkiewicz, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rusnak, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-05-17

    In a recent experiment at Lawrence Berkeley National Laboratory, the 40Ar(d,p)41Ar excitation function between 3-7 MeV was measured, confirming a previous estimation that there may be an intolerable radiation dose from 41Ar production by slowing to rest 6.74 MeV deuterons in the gas cell of the neutron imaging facility being constructed in B194. Gas alternatives to argon are considered, including helium, nitrogen (N2), neon, sulfur hexafluoride (SF6), krypton, and xenon, as well as high atomic number solid backings such as tantalum.

  20. Treatment surfaces with atomic oxygen excited in dielectric barrier discharge plasma of O2 admixed to N2

    Directory of Open Access Journals (Sweden)

    E. V. Shun'ko

    2012-06-01

    Full Text Available This paper describes the increase in surface energy of substrates by their treatment with gas composition generated in plasmas of DBD (Dielectric Barrier Discharge in O2 admixed with N2. Operating gas dissociation and excitation was occurred in plasmas developed in two types of reactors of capacitively-coupled dielectric barrier configurations: coaxial cylindrical, and flat rectangular. The coaxial cylindrical type comprised an inner cylindrical electrode encapsulated in a ceramic sheath installed coaxially inside a cylindrical ceramic (quartz tube passing through an annular outer electrode. Components of the flat rectangular type were a flat ceramic tube of a narrow rectangular cross section supplied with two flat electrodes mounted against one another outside of the long parallel walls of this tube. The operating gas, mixture of N2 and O2, was flowing in a completely insulated discharge gap formed between insulated electrodes of the devices with an average velocity of gas inlet of about 7 to 9 m/s. Dielectric barrier discharge plasma was excited in the operating gaps with a bipolar pulse voltage of about 6 kV for 2 ms at 50 kHz repetition rate applied to the electrodes of the coaxial device, and of about 14 kV for 7 ms at 30 kHz repetition rate for the flat linear device. A lifetime of excited to the 2s22p4(1S0 state in DBD plasma and streaming to the surfaces with a gas flow atomic oxygen, responsible presumably for treating surfaces, exceeded 10 ms in certain cases, that simplified its separation from DBD plasma and delivery to substrates. As it was found in particular, surfaces of glass and some of polymers revealed significant enhancement in wettability after treatment.

  1. Detection of copper in water using on-line plasma-excited atomic absorption spectroscopy (AAS).

    Science.gov (United States)

    Porento, Mika; Sutinen, Veijo; Julku, Timo; Oikari, Risto

    2011-06-01

    A measurement method and apparatus was developed to measure continuously toxic metal compounds in industrial water samples. The method was demonstrated by using copper as a sample metal. Water was injected into the sample line and subsequently into a nitrogen plasma jet, in which the samples comprising the metal compound dissolved in water were decomposed. The transmitted monochromatic light was detected and the absorbance caused by copper atoms was measured. The absorbance and metal concentration were used to calculate sensitivity and detection limits for the studied metal. The sensitivity, limit of detection, and quantification for copper were 0.45 ± 0.02, 0.25 ± 0.01, and 0.85 ± 0.04 ppm, respectively.

  2. Comparative study of analytical inductively-coupled argon-plasma discharges using different outer gases.

    Science.gov (United States)

    Zaray, G; Broekaert, J A; Böhmer, R G; Leis, F

    1987-07-01

    The analytical capabilities of high power (2-4 kW) ICPs with argon as inner and intermediate gas and different outer gases (argon, nitrogen, oxygen and air) were studied under optimum and compromise operating conditions. Under the optimum conditions, the lowest detection limits for elements with sensitive atom lines (C, B, Zn) or ion lines (Mg, Mn, Fe, Cr, Ti, V) were achieved with argon as outer gas and an observation height of 13 mm. Under compromise conditions (3 kW, aerosol gas gauge-pressure 3 bar) the lowest detection limits for the atom lines were also found with a pure argon plasma at an observation height of 13 mm. For ion lines, however, the argon/oxygen and argon/nitrogen plasmas and an observation height of 8 mm were better. The detection limits were poorer in the presence of an aluminium matrix; under the optimum operating conditions, the relative increase in detection limit was smaller with the argon/oxygen and argon/air ICPs than with the pure argon or argon/nitrogen ICPs. It was found that the interferences arising from an easily ionizable matrix are lower with a diatomic gas than with argon as outer gas. The interferences when the argon/nitrogen, argon/oxygen and argon/air plasmas are used are similar and practically independent of the nebulizer-gas pressure applied.

  3. Exciting interdisciplinary physics quarks and gluons, atomic nuclei, relativity and cosmology, biological systems

    CERN Document Server

    2013-01-01

    Nuclear physics is an exciting, broadly faceted field. It spans a wide range of topics, reaching from nuclear structure physics to high-energy physics, astrophysics and medical physics (heavy ion tumor therapy).  New developments are presented in this volume and the status of research is reviewed. A major focus is put on nuclear structure physics, dealing with superheavy elements and with various forms of exotic nuclei: strange nuclei, very neutron rich nuclei, nuclei of antimatter. Also quantum electrodynamics of strong fields is addressed, which is linked to the occurrence of giant nuclear systems in, e.g., U+U collisions. At high energies nuclear physics joins with elementary particle physics. Various chapters address the theory of elementary matter at high densities and temperature, in particular the quark gluon plasma which is predicted by quantum chromodynamics (QCD) to occur in high-energy heavy ion collisions. In the field of nuclear astrophysics, the properties of neutron stars and quark stars are d...

  4. Spatial-temporal characteristics of a SPER laser using transitions of the Cd,Zn,In atoms. [Segmented-Plasma-Excitation-Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Apollonov, V.V.; Derzhavin, S.I.; Prokhorov, A.M.; Sirotkin, A.A. (Institut Obshchei Fiziki, Moscow (USSR))

    1989-05-01

    An experimental study of a SPER (segmented-plasma-excitation-recombination) laser using transitions of Cd,Zn,In atoms shows that the stretching of the pump pulse trailing edge results in a increased energy output. The recombination pump mechanism in the atomic-transition SPER laser is confirmed. The feasibility of the repetitively pulsed operation of the SPER laser is examined, and it is found that the maximum pulse repetition rate can amount to 10 kHz. 9 refs.

  5. Cold neutral atoms via charge exchange from excited state positronium: a proposal

    CERN Document Server

    Bertsche, W A; Eriksson, S

    2016-01-01

    We present a method for generating cold neutral atoms via charge exchange reactions between trapped ions and Rydberg positronium. The high charge exchange reaction cross section leads to efficient neutralisation of the ions and since the positronium-ion mass ratio is small, the neutrals do not gain appreciable kinetic energy in the process. When the original ions are cold the reaction produces neutrals that can be trapped or further manipulated with electromagnetic fields. Because a wide range of species can be targeted we envisage that our scheme may enable experiments at low temperature that have been hitherto intractable due to a lack of cooling methods. We present an estimate for achievable temperatures, neutral number and density in an experiment where the neutrals are formed at a milli-Kelvin temperature from either directly or sympathetically cooled ions confined on an ion chip. The neutrals may then be confined by their magnetic moment in a co-located magnetic minimum well also formed on the chip. We ...

  6. Cold neutral atoms via charge exchange from excited state positronium: a proposal

    Science.gov (United States)

    Bertsche, W. A.; Charlton, M.; Eriksson, S.

    2017-05-01

    We present a method for generating cold neutral atoms via charge exchange reactions between trapped ions and Rydberg positronium. The high charge exchange reaction cross section leads to efficient neutralisation of the ions and since the positronium-ion mass ratio is small, the neutrals do not gain appreciable kinetic energy in the process. When the original ions are cold the reaction produces neutrals that can be trapped or further manipulated with electromagnetic fields. Because a wide range of species can be targeted we envisage that our scheme may enable experiments at low temperature that have been hitherto intractable due to a lack of cooling methods. We present an estimate for achievable temperatures, neutral number and density in an experiment where the neutrals are formed at a milli-Kelvin temperature from either directly or sympathetically cooled ions confined on an ion chip. The neutrals may then be confined by their magnetic moment in a co-located magnetic minimum well also formed on the chip. We discuss general experimental requirements.

  7. Determination of the Electron Density and Electron Temperature in A Magnetron Discharge Plasma Using Optical Spectroscopy and the Collisional-Radiative Model of Argon

    Science.gov (United States)

    Evdokimov, K. E.; Konishchev, M. E.; Pichugin, V. F.; Pustovalova, A. A.; Ivanova, N. M.; Sun', Ch.

    2017-09-01

    A method for determining the electron temperature and electron density in a plasma is proposed that is based on minimization of the difference between the experimental relative intensities of the spectral argon (Ar) lines and those same intensities calculated with the aid of the collisional-radiative model. The model describes the kinetics of the ground state and 40 excited states of the Ar atom and takes into account the following processes: excitation and deactivation of the states of the atom by electron impact, radiative decay of the excited states, self-absorption of radiation, ionization of excited states by electron impact, and quenching of metastable states as a consequence of collisions with the chamber walls. Using the given method, we have investigated the plasma of a magnetron discharge on a laboratory setup for intermediate-frequency magnetron sputtering for a few selected operating regimes.

  8. Solvation effects on the molecular 3s Rydberg state: AZAB/CYCLO octanes clustered with argon

    Science.gov (United States)

    Shang, Q. Y.; Moreno, P. O.; Li, S.; Bernstein, E. R.

    1993-02-01

    Two color, 1+1, mass resolved excitation spectroscopy (MRES) is used to obtain molecular Rydberg (3s←n) spectra of azabicyclo[2.2.2]octane (ABCO) and diazabicyclo[2.2.2]octane (DABCO) clustered with argon. Nozzle/laser timing delay studies are employed together with time-of-flight mass spectroscopy to identify cluster composition. Population depletion techniques are used to differentiate between clusters with the same mass, but different geometries. A Lennard-Jones 6-12 potential is used to model the intermolecular interactions and predict minimum energy cluster geometries and cluster binding energies. The experimental results are combined with the cluster geometry calculations to assign spectral features to specific cluster geometries. Three different excited state interactions are required to model the experimentally observed line shapes, spectral shifts, and cluster dissociation. The relationship between these model potentials and the cluster binding sites suggests that the form of the cluster intermolecular potential in the Rydberg excited state is dictated by the distance between the argon and chromophore atoms. A comparison of results for ABCO(Ar)1 and DABCO(Ar)1 leads to the conclusion that the nitrogen 3s Rydberg orbital in clusters of DABCO is delocalized.

  9. Penning de-excitation of spin-polarised metastable He atoms on magnetic surfaces: Mg on Fe

    CERN Document Server

    Moroni, R; Mattera, L

    2003-01-01

    Surface magnetic properties of iron films upon Mg deposition have been investigated by means of spin-polarised metastable de-excitation spectroscopy (SPMDS). Deposition of 1 ML of Mg on iron films preserves the magnetic character of the topmost layer but modifies the metastable de-excitation mechanism. The reduction of the surface work function induced by Mg condensation changes the de-excitation mechanism from the one usually observed on 3d metal surfaces (resonant ionisation followed by Auger neutralisation) to Auger de-excitation. The effects induced on SPMDS spectra by the modification of the de-excitation mechanism are discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-02-01

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

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

    Science.gov (United States)

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

    2017-03-01

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

  12. The second Born approximation of electron–argon elastic scattering ...

    Indian Academy of Sciences (India)

    We study the elastic scattering of atomic argon by electron in the presence of a bichromatic laser field in the second Born approximation. The target atom is approximated by a simple screening potential and the continuum states of the impinging and emitting electrons are described as Volkov states. We evaluate the S-matrix ...

  13. Metastable Electronically Excited Atoms and Molecules: Excitation Transfer in Slow Collisions, Probed by Means of a Counter-Rotating Supersonic Jet

    Science.gov (United States)

    2012-08-15

    Acetylene S1 State,’’ J. Phys. Chem. A (feature article) 115, 11921-11943 (2011). 5. S. H. Lipoff and D. R. Herschbach, “Low-Energy Limit for...triplet states) and how these mechanisms may be experimentally characterized. Throughout this project, the spin-orbit interaction of the acetylene S1...Laser Excited Metastables (SEELEM) experiments, largely because we have accumulated an unprecedentedly complete description of the vibrational levels

  14. Thermophysical properties of argon

    Energy Technology Data Exchange (ETDEWEB)

    Jaques, A.

    1988-02-01

    The entire report consists of tables of thermodynamic properties (including sound velocity, thermal conductivity and diffusivity, Prandtl number, density) of argon at 86 to 400/degree/K, in the form of isobars over 0.9 to 100 bars. (DLC)

  15. Argon in action

    CERN Multimedia

    Corinne Pralavorio

    2015-01-01

    Over the past few days, the SPS has been accelerating argon ions, which have started to be sent to the NA61/SHINE experiment. This operating mode, using a new type of ion, required a number of modifications to the accelerator.   Picture 1: a “super-cycle” of the SPS, featuring a proton cycle for the LHC, followed by an argon ion cycle for the North Area. Today, the accelerators are once again juggling particles and even performing completely new tricks. The SPS is supplying beams of argon ions for the first time, at energies never before achieved for this type of beam. They are destined for the NA61/SHINE experiment (see box) located in the North Area, which began receiving the beams on 11 February. Argon ions have a relatively large mass, as they consist of 40 nucleons, so they can be used in a similar way to lead ions. The main difficulty in accelerating them lies in the SPS, where the variation in acceleration frequency is limited. “The SPS was designed for a...

  16. Low-Drift Coherent Population Trapping Clock Based on Laser-Cooled Atoms and High-Coherence Excitation Fields

    Science.gov (United States)

    Liu, Xiaochi; Ivanov, Eugene; Yudin, Valeriy I.; Kitching, John; Donley, Elizabeth A.

    2017-11-01

    A compact cold-atom coherent population trapping clock in which laser-cooled atoms are interrogated with highly coherent coherent population trapping fields under free fall is presented. The system achieves fractional frequency instability at the level of 3 ×10-13 on the time scale of an hour. The clock may lend itself to portable applications since the atoms typically fall only 1.6 mm during the typical interrogation period of 18 ms.

  17. Differential and total excitation cross sections in the collision of protons with He atoms at intermediate and high energies under a three body formalism

    Directory of Open Access Journals (Sweden)

    R Fathi

    2011-09-01

    Full Text Available  A three-body model is devised to study differential and total cross sections for the excitation of helium atom under impact of energetic protons. The actual process is a four body one but in the present model the process is simplified into a three-body one. In this model, an electron of helium atom is assumed to be inactive and only one electron of the atom is active. Therefore, the active electron is assumed to be in an atomic state with a potential of the nucleus, T, being screened by the inactive electron, e, and, thus, an effective charge of Ze. As a result, the ground state, 11S, or the excited states, 21S and 21P, wave function of the active electron is deduced from similar hydrogenic wave functions assuming effective charge, Ze for the combined nucleus (T+e. In this three-body model, the Faddeev-Watson-Lovelace formalism for excitation channel is used to calculate the transition amplitude. In the first order approximation, electronic and nuclear interaction is assumed in the collision to be A(1e= and A(1n=, respectively. Here, A(1, Txy, |i> and |f> are the first order transition amplitude, the transition matrix for the interaction between particles x and y, the initial state and the final state, respectively. The transition matrix for the first order electronic interaction implemented into A(1e is approximated as the corresponding two-body interaction, Vxy. In order to calculate first order nuclear amplitude A(1n, the near-the-shell form of transition matrix TPT is used. Calculations are performed in the energy range of 50 keV up to 1MeV. The results are then compared with those of theoretical and experimental works in the literature.

  18. Comparison of surface vacuum ultraviolet emissions with resonance level number densities. I. Argon plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Boffard, John B., E-mail: jboffard@wisc.edu; Lin, Chun C. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Culver, Cody [Materials Science Program, University of Wisconsin, Madison, WI 53706 (United States); Wang, Shicong; Wendt, Amy E. [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI 53706 (United States); Radovanov, Svetlana; Persing, Harold [Varian Semiconductor Equipment, Applied Materials Inc., Gloucester, MA 01939 (United States)

    2014-03-15

    Vacuum ultraviolet (VUV) photons emitted from excited atomic states are ubiquitous in material processing plasmas. The highly energetic photons can induce surface damage by driving surface reactions, disordering surface regions, and affecting bonds in the bulk material. In argon plasmas, the VUV emissions are due to the decay of the 1s{sub 4} and 1s{sub 2} principal resonance levels with emission wavelengths of 104.8 and 106.7 nm, respectively. The authors have measured the number densities of atoms in the two resonance levels using both white light optical absorption spectroscopy and radiation-trapping induced changes in the 3p{sup 5}4p→3p{sup 5}4s branching fractions measured via visible/near-infrared optical emission spectroscopy in an argon inductively coupled plasma as a function of both pressure and power. An emission model that takes into account radiation trapping was used to calculate the VUV emission rate. The model results were compared to experimental measurements made with a National Institute of Standards and Technology-calibrated VUV photodiode. The photodiode and model results are in generally good accord and reveal a strong dependence on the neutral gas temperature.

  19. ATLAS Liquid Argon Calorimeter Module Zero

    CERN Multimedia

    1993-01-01

    This module was built and tested with beam to validate the ATLAS electromagnetic calorimeter design. One original design feature is the folding. 10 000 lead plates and electrodes are folded into an accordion shape and immersed in liquid argon. As they cross the folds, particles are slowed down by the lead. As they collide with the lead atoms, electrons and photons are ejected. There is a knock-on effect and as they continue on into the argon, a whole shower is produced. The electrodes collect up all the electrons and this signal gives a measurement of the energy of the initial particle. The M0 was fabricated by French institutes (LAL, LAPP, Saclay, Jussieu) in the years 1993-1994. It was tested in the H6/H8 beam lines in 1994, leading to the Technical Design Report in 1996.

  20. Growth kinetics for temperature-controlled atomic layer deposition of GaN using trimethylgallium and remote-plasma-excited NH{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Pansila, P. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Kanomata, K. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Miura, M. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Ahmmad, B.; Kubota, S. [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); CREST, Japan Science and Technology Agency, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); Hirose, F., E-mail: fhirose@yz.yamagata-u.ac.jp [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan); CREST, Japan Science and Technology Agency, 4-3-16 Jonan, Yonezawa 992-8510 (Japan)

    2015-12-01

    Highlights: • We discuss the reaction mechanism of the low temperature GaN ALD. • The plasma-excited NH{sub 3} is effective in the nitridation of the TMG saturated GaN surface with surface temperatures in excess of 100 °C. • The temperature controlled ALD of GaN is examined using RT-TMG adsorption and plasma-excited NH{sub 3} treatment with the temperature of 115 °C. - Abstract: Fundamental surface reactions in the atomic layer deposition of GaN with trimethylgallium (TMG) and plasma-excited NH{sub 3} are investigated by multiple-internal-reflection infrared absorption spectroscopy (MIR-IRAS) at surface temperatures varying from room temperature (RT) to 400 °C. It is found that TMG is saturated at RT on GaN surfaces when the TMG exposure exceeds 8 × 10{sup 4} Langmuir (L), where 1 L corresponds to 1.33 × 10{sup −4} Pa s (or 1.0 × 10{sup −6} Torr s), and its saturation density reaches the maximum value at RT. Nitridation with the plasma-excited NH{sub 3} on the TMG-saturated GaN surface is investigated by X-ray photoelectron spectroscopy (XPS). The nitridation becomes effective at surface temperatures in excess of 100 °C. The reaction models of TMG adsorption and nitridation on the GaN surface are proposed in this paper. Based on the surface analysis, a temperature-controlled ALD process consisting of RT-TMG adsorption and nitridation at 115 °C is examined, where the growth per cycle of 0.045 nm/cycle is confirmed. XPS analysis indicates that all N atoms are bonded as GaN. Atomic force microscopy indicates an average roughness of 0.23 nm. We discuss the reaction mechanism of GaN ALD in the low-temperature region at around 115 °C with TMG and plasma-excited NH{sub 3}.

  1. Red-detuned, high-intensity, short-duration sweet spot for impulsive X-ray Raman excitation in atoms

    CERN Document Server

    Ware, Matthew R; Haxton, Daniel J

    2016-01-01

    Impulsive X-ray Raman excitations of Lithium, Neon, and Sodium are calculated using the Multiconfiguration Time-Dependent Hartree-Fock method. Using linearly polarized laser pulses without chirp, we determine the optimum central frequency, intensity, and duration for maximum population transfer to valence excited states. We demonstrate the existence of two "sweet spots" for optimum population transfer, either of which, depending on the system, may be superior. The "red-detuned hypothesis" is the proposition that population transfer can be maximized by nonresonant Raman transitions, red-detuned below K-edge, because such detuning minimizes core-excited populations and ionization loss. We find that this hypothesis is verified in the case of Neon -- for Neon, the global optimum for population transfer occurs at high intensity (8 $\\times$ 10$^{19}$ W cm$^{-2}$), short duration (82as full-width-at-half-maximum), and 24eV red-detuned from the K-edge.

  2. Role of two-electron processes in the excitation-ionization of lithium atoms by fast ion impact

    CERN Document Server

    Kirchner, T; Gulyás, L

    2015-01-01

    We study excitation and ionization in the 1.5 MeV/amu O$^{8+}$-Li collision system, which was the subject of a recent reaction-microscope-type experiment [Fischer \\textit{et al.}, Phys. Rev. Lett. \\textbf{109}, 113202 (2012)]. Starting from an independent-electron model based on determinantal wave functions and using single-electron basis generator method and continuum distorted-wave with eikonal initial-state calculations we show that pure single ionization of a lithium $K$-shell electron is too weak a process to explain the measured single differential cross section. Rather, our analysis suggests that two-electron excitation-ionization processes occur and have to be taken into account when comparing with the data. Good agreement is obtained only if we replace the independent-electron calculation by an independent-event model for one of the excitation-ionization processes and also take a shake-off process into account.

  3. A semi-empirical formula for calculation of absolute cross sections for ionization and excitation of atoms by electrons

    NARCIS (Netherlands)

    Vriens, L.

    A simple analytical expression for the absolute ionization and (optically allowed) excitation cross sections, as a function of the electron energy, is “derived”. In this expression there are two parameters. The first one is proportional to the optical oscillator strength and the second one is

  4. Electric and spectroscopic properties of argon-hydrogen RF microplasma jets at atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Souza-Correa, J A; Oliveira, C; Amorim, J [Laboratorio Nacional de Ciencia e Tecnologia do Bioetanol-CTBE, Caixa Postal 6170, 13083-970, Campinas, Sao Paulo (Brazil); Gomes, M P, E-mail: jorge.correa@bioetanol.org.b, E-mail: carlos.filho@bioetanol.org.b, E-mail: gomesmp@ita.b, E-mail: jayr.amorim@bioetanol.org.b [Departamento de Fisica, Instituto Tecnologico de Aeronautica-ITA, Praca Marechal Eduardo Gomes 50, 12.228-900, Sao Jose dos Campos, Sao Paulo (Brazil)

    2010-10-06

    Microplasma jets of argon-hydrogen (Ar-H{sub 2}) gas mixture were generated by 144.0 MHz radio-frequency (RF) waves at powers of 5 W, 10 W, 20 W and 50 W. The experimental setup employed creates stable microplasmas at atmospheric pressure from 5.0 mm up to 20.0 mm visual glow lengths. We have determined the rms voltages, the rms electric currents and the power absorptions of these microplasma jets. By making use of optical spectroscopy, the emission spectra of Ar-H{sub 2} microplasma jets were recorded in the range 3060-8200 A, in order to estimate the axial distribution profiles of electron density, rotational temperature, excitation temperature and hydrogen atomic temperature.

  5. Development Of Beam Position And Profile Monitor Based On Light Radiation Of Atoms Excited By The Beam Particles

    CERN Document Server

    Balalykin, N I; Brovko, O I; Bykovsky, V F; Dietrich, J; Kamerdzhiev, V; Meshkov, I N; Mohos, I; Parfenov, A N

    2004-01-01

    Particle beam position and profile monitor based on registration of the light radiated by residual gas atoms is being developed by collaboration JINR-Forschungszentrum Jülich. Proposed device and first experiments have been performed at Nuclotron (JINR) and COSY (FZJ) accelerators are presented in this report.

  6. Interband electronic excitation-assisted atomic-scale restructuring of metal surfaces by nanosecond pulsed laser light

    Science.gov (United States)

    Ernst; Charra; Douillard

    1998-01-30

    Interaction of high-power laser light with materials often causes irreversible damage of the near-surface region. It is shown that copper single-crystal surfaces can be patterned by laser light. Irradiation with green light produced adatoms and vacancies, which self-organized into nanoscale pyramids. This restructuring can be removed by annealing. In contrast to green light, infrared laser irradiation at equivalent absorbed energy density did not produce any structural change. This, for metallic systems, unforeseen spectral difference in laser light action points to a concerted process as the source for structural modification, which involves long-lived primary excitation of localized d-electrons through interband transition together with phonon excitation.

  7. The influence of higher spatial harmonics of atomic polarization on the saturated absorption resonance upon excitation of open dipole transitions by a field of counterpropagating waves

    Science.gov (United States)

    Brazhnikov, D. V.; Novokreshchenov, A. S.

    2017-04-01

    The effect of a double structure of saturated absorption resonance in the field of counterpropagating light waves interacting with an atomic gas is studied. The experimental observation of this effect was first reported in 2011 in a work by our colleagues at the P.N. Lebedev Physical Institute of the Russian Academy of Sciences (Laboratory of Frequency Standards). The essence of the effect lies in the fact that, on exciting an open dipole transition, another, narrower, resonance of an opposite sign can be observed at the center of the ordinary saturated absorption resonance. A theoretical analysis of this effect has also been performed in this work in terms of a simple spectroscopic model of an atom with two nondegenerate energy levels without taking into account higher spatial harmonics of atomic polarization and polarizations of light waves (scalar model). The present work is devoted to the development of a theory of the formation of a central narrow resonance for the example of a real F g = 1 → F e = 1 atomic transition and to the study of its main characteristics (amplitude, width, contrast, and amplitude-to-width ratio). In addition, the theoretical results obtained without taking into account the influence of higher spatial harmonics and with inclusion of the influence of first higher harmonics are compared. This comparison shows that their influence on the parameters of the new nonlinear resonance is strong even in moderately intense light fields ( R γ, where R is the Rabi frequency). The results of this study can be of interest for quantum metrology, as well as for many experiments in which the laser-radiation frequency is stabilized by the saturated absorption resonance on open dipole transitions in atoms and molecules.

  8. Role of two-electron excitation-ionization processes in the ionization of lithium atoms by fast ion impact

    Science.gov (United States)

    Kirchner, T.; Khazai, N.; Gulyás, L.

    2014-06-01

    We study excitation and ionization in the 1.5-MeV/amu O8+-Li collision system, which was the subject of a recent reaction-microscope-type experiment [D. Fischer et al., Phys. Rev. Lett. 109, 113202 (2012), 10.1103/PhysRevLett.109.113202]. Starting from an independent-electron model based on determinantal wave functions and using a single-electron basis generator method calculation and a single-electron continuum distorted-wave with eikonal initial-state calculation, we show that pure single ionization of a lithium K-shell electron is too weak a process to explain the measured electron-energy-differential cross section. Rather, our analysis suggests that two-electron excitation-ionization processes occur and have to be taken into account when comparing with the data. Good agreement is obtained only if we replace the independent-electron calculation by an independent-event model for one of the excitation-ionization processes and also take a shake-off process into account.

  9. Enhanced high-order harmonic generation from Argon-clusters

    NARCIS (Netherlands)

    Tao, Yin; Hagmeijer, Rob; Bastiaens, Hubertus M.J.; Goh, S.J.; van der Slot, P.J.M.; Biedron, S.; Milton, S.; Boller, Klaus J.

    2017-01-01

    High-order harmonic generation (HHG) in clusters is of high promise because clusters appear to offer an increased optical nonlinearity. We experimentally investigate HHG from Argon clusters in a supersonic gas jet that can generate monomer-cluster mixtures with varying atomic number density and

  10. Argon solubility in liquid steel

    NARCIS (Netherlands)

    Boom, R; Dankert, O; Van Veen, A; Kamperman, AA

    2000-01-01

    Experiments have been performed to establish the solubility of argon in liquid interstitial-free steel. The solubility appears to be lower than 0.1 at ppb, The results are in line with argon solubilities reported in the literature on liquid iron. Semiempirical theories and calculations based on the

  11. Study of fluid mechanical helium argon ion laser

    Science.gov (United States)

    1972-01-01

    An approach to an argon ion laser based on gasdynamic techniques is presented. Improvement in efficiency and power output are achieved by eliminating high heat rejection problems and plasma confinement of the seal-off conventional lasers. The process of producing population inversion between the same energy levels, as in the conventional argon ion laser, has been divided into two phases by separating each other from the processes of ionization and subsequent excitation. Line drawings and graphs are included to amplify the theoretical presentation.

  12. Testing Noncollinear Spin-Flip, Collinear Spin-Flip, and Conventional Time-Dependent Density Functional Theory for Predicting Electronic Excitation Energies of Closed-Shell Atoms.

    Science.gov (United States)

    Xu, Xuefei; Yang, Ke R; Truhlar, Donald G

    2014-05-13

    Conventional time-dependent density functional theory (TDDFT) is based on a closed-shell Kohn-Sham (KS) singlet ground state with the adiabatic approximation, using either linear response (KS-LR) or the Tamm-Dancoff approximation (KS-TDA); these methods can only directly predict singly excited states. This deficiency can be overcome by using a triplet state as the reference in the KS-TDA approximation and "exciting" the singlet by a spin flip (SF) from the triplet; this is the method suggested by Krylov and co-workers, and we abbreviate this procedure as SF-KS-TDA. SF-KS-TDA can be applied either with the original collinear kernel of Krylov and co-workers or with a noncollinear kernel, as suggested by Wang and Ziegler. The SF-KS-TDA method does bring some new practical difficulties into play, but it can at least formally model doubly excited states and states with double-excitation character, so it might be more useful than conventional TDDFT (both KS-LR and KS-TDA) for photochemistry if these additional difficulties can be surmounted and if it is accurate with existing approximate exchange-correlation functionals. In the present work, we carried out calculations specifically designed to understand better the accuracy and limitations of the conventional TDDFT and SF-KS-TDA methods; we did this by studying closed-shell atoms and closed-shell monatomic cations because they provide a simple but challenging testing ground for what we might expect in studying the photochemistry of molecules with closed-shell ground states. To test their accuracy, we applied conventional KS-LR and KS-TDA and 18 versions of SF-KS-TDA (nine collinear and nine noncollinear) to the same set of vertical excitation energies (including both Rydberg and valence excitations) of Be, B(+), Ne, Na(+), Mg, and Al(+). We did this for 10 exchange-correlation functionals of various types, both local and nonlocal. We found that the GVWN5 and M06 functionals with nonlocal kernels in spin-flip calculations

  13. Role of two-electron processes in the excitation-ionization of lithium atoms by fast ion impact

    OpenAIRE

    Kirchner, T.; Khazai, N.; Gulyás, L.

    2015-01-01

    We study excitation and ionization in the 1.5 MeV/amu O$^{8+}$-Li collision system, which was the subject of a recent reaction-microscope-type experiment [Fischer \\textit{et al.}, Phys. Rev. Lett. \\textbf{109}, 113202 (2012)]. Starting from an independent-electron model based on determinantal wave functions and using single-electron basis generator method and continuum distorted-wave with eikonal initial-state calculations we show that pure single ionization of a lithium $K$-shell electron is...

  14. Plasma diagnostics of the SIMPA Ecr ion source by X-ray spectroscopy, Collisions of H-like Neon ions with Argon clusters; Diagnostic du plasma de la source d'ions ECR SIMPA par spectroscopie X, Collision d'ions neon hydrogenoides avec des agregats d'argon

    Energy Technology Data Exchange (ETDEWEB)

    Adrouche, N

    2006-09-15

    The first part of this thesis is devoted to the SIMPA ECR ion source characterization, first, I explored the ion source's capacities on the point of view of extracted currents for three elements, argon, krypton and neon. By analyzing the Bremsstrahlung spectra, I determined the electronic temperature in the plasma and the electronic and ionic densities. In a second time, I recorded high resolution X-spectra of argon and krypton plasma's. By taking into account the principal mechanisms of production of a K hole in the ions inside the plasma, I determined the ionic densities of the high charge states of argon. Lastly, I highlighted a correlation between the ions charge states densities with the intensities of extracted currents. The second part of the thesis is devoted to Ne{sup 9+-} argon clusters collisions. First, I presented simple and effective theoretical models allowing to describe the phenomena occurring during a collision, from the point of view of the projectile. I carried out a simulation for a collision of an ion Ne{sup 9+} with an argon cluster of a given size, which has enabled us to know the energy levels populated during the electronic capture and to follow the number of electrons in each projectile shell. Lastly, I presented the first results of a collision between a Ne{sup 9+} beam and argon clusters. These results, have enabled me by using projectile X-ray spectroscopy during the ions-clusters collision, to evidence a strong clustering of targets atoms and to highlight an electronic multi-capture in the projectile ion excited states. (author)

  15. Time-resolved fine structure mixing of cesium {8}^{2}D induced by helium and argon

    Science.gov (United States)

    Davila, Ricardo C.; Perram, Glen P.; Eshel, Ben

    2017-11-01

    The rates for fine structure mixing and quenching of the moderately excited 8{}2{D}5/2 and 8{}2{D}3/2 states of cesium under collision with argon and the more impulsive helium have been measured, using two-photon pulsed excitation and time-resolved fluorescence techniques. The pressure dependence of the eigenvalues of the rate matrix yields very rapid rate coefficients of 2.6+/- 0.2× {10}-9 {{cm}}3/({{atom}} s) for He and 5.2+/- 0.4× {10}-10 {{cm}}3/({{atom}} s) for Ar, about two–three times faster than for the Cs 7{}2{D}5/2\\rightleftharpoons 7{}2{D}3/2 relaxation. The quenching rates are also rapid, 1.07+/- 0.04× {10}-10 {{cm}}3/({{atom}} s) and 9.5+/- 0.7× {10}-11 {{cm}}3/({{atom}} s) for He and Ar respectively. The rapid fine structure rates are explained by the highly impulsive nature of the collisions, and the large average distance of the valence electron from the nucleus. Quenching rates (intra-multiplet transfer) are likely enhanced by the closely spaced, 9{}2P levels. The observed rates are compared with the predictions from time-dependent perturbation theory.

  16. Depleted argon from underground sources

    Energy Technology Data Exchange (ETDEWEB)

    Back, H.O.; /Princeton U.; Alton, A.; /Augustana U. Coll.; Calaprice, F.; Galbiati, C.; Goretti, A.; /Princeton U.; Kendziora, C.; /Fermilab; Loer, B.; /Princeton U.; Montanari, D.; /Fermilab; Mosteiro, P.; /Princeton U.; Pordes, S.; /Fermilab

    2011-09-01

    Argon is a powerful scintillator and an excellent medium for detection of ionization. Its high discrimination power against minimum ionization tracks, in favor of selection of nuclear recoils, makes it an attractive medium for direct detection of WIMP dark matter. However, cosmogenic {sup 39}Ar contamination in atmospheric argon limits the size of liquid argon dark matter detectors due to pile-up. The cosmic ray shielding by the earth means that Argon from deep underground is depleted in {sup 39}Ar. In Cortez Colorado a CO{sub 2} well has been discovered to contain approximately 500ppm of argon as a contamination in the CO{sub 2}. In order to produce argon for dark matter detectors we first concentrate the argon locally to 3-5% in an Ar, N{sub 2}, and He mixture, from the CO{sub 2} through chromatographic gas separation. The N{sub 2} and He will be removed by continuous cryogenic distillation in the Cryogenic Distillation Column recently built at Fermilab. In this talk we will discuss the entire extraction and purification process; with emphasis on the recent commissioning and initial performance of the cryogenic distillation column purification.

  17. Mathematical identification of homogenisation processes in argon stirred ladle

    Directory of Open Access Journals (Sweden)

    K. Michalek

    2009-10-01

    Full Text Available Mathematical models processed results of experimental investigation obtained during ladle gas argon bubbling realized by stir elements situated in the ladle bottom. Exact theoretical description of processes occurring at argon bubbling into steel would be very complex and it would lead to a system of non-linear partial differential equations describing transfer of momentum, heat, components, and with excitation function in the form of equation of so called deterministic chaos (argon bubbling. On the basis of pouring ladle model diagram and concentrations courses, the simplified linear physically adequate model was proposed, which described behavior of steel concentration in pouring ladle during its bubbling. The analysed process was understood in the form of a cybernetic model.

  18. Argon metastable production in argon-helium microplasmas

    Science.gov (United States)

    Hoskinson, Alan R.; Gregorío, José; Hopwood, Jeffrey; Galbally-Kinney, Kristin; Davis, Steven J.; Rawlins, Wilson T.

    2016-06-01

    Microwave resonator-driven microplasmas are a promising technology for generating the high density of rare-gas metastable states required for optically pumped rare gas laser systems. We measure the density of argon 1s5 states (Paschen notation) in argon-helium plasmas between 100 Torr and atmospheric pressure using diode laser absorption. The metastable state density is observed to rise with helium mole fraction at lower pressures but to instead fall slightly when tested near atmospheric pressure. A 0-D model of the discharge suggests that these distinct behaviors result from the discharge being diffusion-controlled at lower pressures, but with losses occurring primarily through dissociative recombination at high pressures. In all cases, the argon metastable density falls sharply when the neutral argon gas fraction is reduced below approximately 2%.

  19. Metal clusters on supported argon layers; Metallcluster auf dielektrischen Substraten

    Energy Technology Data Exchange (ETDEWEB)

    Faber, Bernhard

    2011-10-21

    The deposition of small sodium clusters on supported Ar(001)-surfaces is simulated. Theoretical description is achieved by a hierarchical model consisting of time-dependent DFT and molecular dynamics. The valence electrons of the sodium atoms are considered by Kohn-Sham-Scheme with self interaction correction. The interaction of argon atoms and sodium ions is described by atom-atom potentials whereas the coupling to the QM electrons is done by local pseudo-potentials. A decisive part of the model is the dynamical polarizability of the rare-gas atoms. The optional metal support is considered by the method of image charges. The influence of the forces caused by image charges and the influence of the number of argon monolayers on structure, optical response and deposition dynamics of Na{sub 6} and Na{sub 8} is investigated. There is very little influence on cluster structure and only a small shift of the cluster perpendicular to the surface. Concerning optical response the position of the Mie plasmon peak stays robust whereas the details of spectral fragmentation react very sensitively to changes. The forces caused by image charges of the metal support play only a little role with the dynamics of deposition while the thickness of the argon surface strongly influences the dissipation. (orig.)

  20. The Liquid Argon Purity Demonstrator

    Energy Technology Data Exchange (ETDEWEB)

    Adamowski, M.; Carls, B.; Dvorak, E.; Hahn, A.; Jaskierny, W.; Johnson, C.; Jostlein, H.; Kendziora, C.; Lockwitz, S.; Pahlka, B.; Plunkett, R.; Pordes, S.; Rebel, B.; Schmitt, R.; Stancari, M.; Tope, T.; Voirin, E.; Yang, T.

    2014-07-01

    The Liquid Argon Purity Demonstrator was an R&D test stand designed to determine if electron drift lifetimes adequate for large neutrino detectors could be achieved without first evacuating the cryostat. We describe here the cryogenic system, its operations, and the apparatus used to determine the contaminant levels in the argon and to measure the electron drift lifetime. The liquid purity obtained by this system was facilitated by a gaseous argon purge. Additionally, gaseous impurities from the ullage were prevented from entering the liquid at the gas-liquid interface by condensing the gas and filtering the resulting liquid before returning to the cryostat. The measured electron drift lifetime in this test was greater than 6 ms, sustained over several periods of many weeks. Measurements of the temperature profile in the argon, to assess convective flow and boiling, were also made and are compared to simulation.

  1. UV and 532 nm Photo-Dissociation of 2-Nitrotoluene: Observation of Electronically-Excited NO; Emission from Carbon (I); N2-NO Energy Transfer; and Stabilization of 2-Nitrotoluene-Ar Clusters

    Science.gov (United States)

    Diez-y-Riega, H.; Eilers, H.

    2012-07-01

    2-nitrotoluene is a taggant used in explosive compounds and also often used as a simulant for nitro-based high explosives. Various spectroscopic techniques focus on the detection of vibrationally excited NO as an indicator for the presence of explosives. We report on the photo-dissociation of 2-nitrotoluene using UV and 532 nm wavelengths. We not only observe vibrationally excited NO in its electronic ground state, but also vibrationally excited NO in its electronic excited state. The photo-dissociation of 2-nitrotoluene leads to the formation of atomic carbon and its emission, overlapping the NO emission, is observed. Energy transfer from laser-excited nitrogen to NO leads to NO emission with long lifetimes. Argon atoms stabilize 2-nitrotoluene molecules and delay their photo-dissociation.

  2. Calculating constants of the rates of the reactions of excitation, ionization, and atomic exchange: A model of a shock oscillator with a change of the Hamiltonian of the system

    Science.gov (United States)

    Tsyganov, D. L.

    2017-11-01

    A new model for calculating the rates of reactions of excitation, ionization, and atomic exchange is proposed. Diatomic molecule AB is an unstructured particle M upon the exchange of elastic-vibrational (VT) energy, i.e., a model of a shock forceful oscillator with a change in Hamiltonian (SFOH). The SFOH model is based on the quantum theory of strong perturbations. The SFOH model allows generalization in simulating the rates of the reactions of excitation, ionization, and atomic exchange in the vibrational-vibrational (VV) energy exchange of diatomic molecules, and the exchange of VV- and VT-energy of polyatomic molecules. The rate constants of the excitation of metastables A 3Σ u +, B 3Π g , W 3Δ u , B'3Σ u -, a'3Σ u -, and the ionization of a nitrogen molecules from ground state X2Σ g + upon a collision with a heavy structureless particle (a nitrogen molecule), are found as examples.

  3. Surface treatment of para-aramid fiber by argon dielectric barrier discharge plasma at atmospheric pressure

    Science.gov (United States)

    Gu, Ruxi; Yu, Junrong; Hu, Chengcheng; Chen, Lei; Zhu, Jing; Hu, Zuming

    2012-10-01

    This paper is focused on influence of argon dielectric barrier discharge (DBD) plasma on the adhesive performance and wettability of para-aramid fibers and three parameters including treated power, exposure time and argon flux were detected. The interfacial shear strength (IFSS) was greatly increased by 28% with 300 W, 60 s, 2 L min-1 argon flux plasma treatment. The content of oxygen atom and oxygen-containing polar functional groups were enhanced after the argon plasma treated, so as the surface roughness, which contributed to the improvement of surface wettability and the decrease of contact angle with water. However, long-time exposure, exorbitant power or overlarge argon flux could partly destroy the prior effects of the treatment and damage the mechanical properties of fibers to some degree.

  4. Atom trap loss, elastic collisions, and technology

    Science.gov (United States)

    Booth, James

    2012-10-01

    The study of collisions and scattering has been one of the most productive approaches for modern physics, illuminating the fundamental structure of crystals, surfaces, atoms, and sub-atomic particles. In the field of cold atoms, this is no less true: studies of cold atom collisions were essential to the production of quantum degenerate matter, the formation of cold molecules, and so on. Over the past few years it has been my delight to investigate elastic collisions between cold atoms trapped in either a magneto-optical trap (MOT) or a magnetic trap with hot, background gas in the vacuum environment through the measurement of the loss of atoms from the trap. Motivated by the goal of creating cold atom-based technology, we are deciphering what the trapped atoms are communicating about their environment through the observed loss rate. These measurements have the advantages of being straightforward to implement and they provide information about the underlying, fundamental inter-atomic processes. In this talk I will present some of our recent work, including the observation of the trap depth dependence on loss rate for argon-rubidium collisions. The data follow the computed loss rate curve based on the long-range Van der Waals interaction between the two species. The implications of these findings are exciting: trap depths can be determined from the trap loss measurement under controlled background density conditions; observation of trap loss rate in comparison to models for elastic, inelastic, and chemical processes can lead to improved understanding and characterization of these fundamental interactions; finally the marriage of cold atoms with collision modeling offers the promise of creating a novel pressure sensor and pressure standard for the high and ultra-high vacuum regime.

  5. Resonant coupling in the Van der Waals interaction between an excited alkali atom and a dielectric surface: an experimental study via stepwise selective reflection spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Failache, H.; Saltiel, S.; Fichet, M.; Bloch, D.; Ducloy, M. [Paris-13 Univ., Lab. de Physique des Lasers, UMR 7538 du CNRS, 93 - Villetaneuse (France)

    2003-05-01

    We present a detailed experimental study of the evaluation of the van der Waals (vW) atom-surface interaction for high-lying excited states of alkali-metal atoms (Cs and Rb), notably R-hen they couple resonantly with a surface-polariton mode of the neighbouring dielectric surface. This report extends our initial observation [Phys. Rev. Lett. 83, 5467 (1999)) of a vW repulsion between Cs(6D{sub 3/2}) and a sapphire surface. The experiment is based upon FM selective reflection spectroscopy, on a transition reaching a high-lying state from a resonance level, that has been thermally pumped by an initial one-photon step. Along with a strong vW repulsion fitted with a blue line-shift, -160 {+-} 25 kHz {mu}m{sup 3} for Cs(6D{sub 3/2}) in front of a sapphire surface (with a perpendicular c-axis), we demonstrate a weaker vW repulsion (-32{+-}5 kHz {mu}m{sup 3}) for Cs(6D{sub 3/2}) in front of a YAG surface, as due to a similar resonant coupling at 12 {mu}m between a virtual atomic emission (6D{sub 3/2}-7P{sub 1/2}) and the surface polariton modes. A resonant behaviour of Rb(6D{sub 5/2}) in front of a sapphire surface exists also because of analogous decay channels in the 12 {mu}m range. Finally. one demonstrates that fused silica. nonresonant for a virtual transition in the 12 {mu}m range and hence weakly attracting for Cs(6D{sub 3/2}), exhibits a resonant behaviour for Cs(9S{sub 1/2}) as due to its surface polariton resonance in the 8-9 {mu}m range. The limiting factors that affect both the accuracy of the theoretical prediction, and that of the fitting method applied to the experimental data. are discussed in the conclusion. (authors)

  6. Structure dynamics of excited atoms

    Science.gov (United States)

    Gallagher, T. F.

    1988-03-01

    The instrumentation grant was used to acquire three types of equipment. First we have purchased a high repetition rate Lambda-Physik eximer laser which we are using to pump several dye lasers. The eximer laser is particularly attractive as a pump laser for blue dye lasers. The eximer laser has been in constant use since June 1987, and we are now trying to improve our dye lasers to allow them to run at the 100 Hz repetition rate of the eximer laser. The second major category of equipment we have purchased is radio frequency and microwave equipment. We have acquired a new Hewlett Packard (HP) sweep oscillator to replace our existing oscillator which is now 15 years old. Specifically we have purchased and HP 8350 mainframe and plug-in units to cover the ranges 2 to 8, 8 to 18, and 18 to 25 GHz. These are entirely solid state devices which can, if need be, be phase locked to an external crystal controlled counter. The third kind of equipment is signal acquisition and averaging equipment. Specifically we have bought a fast 350 MHz Tektronix oscilloscope for diagnosing fast signals, especially photoelectron signals, and a 150 MHz digitizing, averaging oscilloscope which enables us to record time resolved data in a particularly efficient fashion. One can record the entire time resolved signal after each laser shot, raising the effective data collection efficiency by a factor of fifty relative to using a boxcar averager as we now do.

  7. Excitation and ionization of hydrogen and helium atoms by femtosecond laser pulses: theoretical approach by Coulomb-Volkov states; Excitation et ionisation des atomes d'hydrogene et d'helium par des impulsions laser femtosecondes: approche theorique par des etats de Coulomb-Volkov

    Energy Technology Data Exchange (ETDEWEB)

    Guichard, R

    2007-12-15

    We present a theoretical approach using Coulomb-Volkov states that appears useful for the study of atomic multi-photonic processes induced by intense XUV femtosecond laser pulses. It predicts hydrogen ionization spectra when it is irradiated by laser pulses in perturbations conditions. Three ways have been investigated. Extension to strong fields when {Dirac_h}{omega} > I{sub p}: it requires to include the hydrogen ground state population, introducing it in standard Coulomb-Volkov amplitude leads to saturated multi-photonic ionization. Extension to multi-photonic transitions with {Dirac_h}{omega} < I{sub p}: new quantum paths are open by the possibility to excite the lower hydrogen bound states. Multiphoton excitation of these states is investigated using a Coulomb-Volkov approach. Extension to helium: two-photon double ionization study shows the influence of electronic correlations in both ground and final state. Huge quantity of information such as angular and energetic distributions as well as total cross sections is available. (author)

  8. Experimental study on the kinetically induced electronic excitation in atomic collisional cascades; Experimentelle Untersuchung zur kinetisch induzierten elektronischen Anregung in atomaren Stosskaskaden

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, S.

    2006-08-15

    the present thesis deals with the ion-collision-induced electronic excitation of metallic solids. For this for the first time metal-insulator-metal layer systems are used for the detection of this electronic excitation. The here applied aluminium/aluminium oxide/silver layer sytems have barrier heights of 2.4 eV on the aluminium respectively 3.3 eV on the silver side. With the results it could uniquely be shown that the electronic excitation is generated by kinetic processes, this excitation dependenc on the kinetic energy of the colliding particles, and the excitation dependes on the charge state of the projectile.

  9. Experimental evaluation of analyte excitation mechanisms in the inductively coupled plasma

    Science.gov (United States)

    Lehn, Scott A.; Hieftje, Gary M.

    2003-10-01

    The inductively coupled plasma (ICP) is a justifiably popular source for atomic emission spectrometry. However, despite its popularity, the ICP is still only partially understood. Even the mechanisms of analyte excitation remain unclear; some energy levels are quite clearly populated by charge transfer while others might be populated by electron-ion recombination, by electron impact, or by Penning processes. Distinguishing among these alternatives is possible by means of a steady-state kinetics approach that examines correlations between the emission of a selected atom, ion, or level and the local number densities of species assumed to produce the excitation. In an earlier investigation, strong correlations were found between either calcium atom or ion emission and selected combinations of calcium atom or ion number densities and electron number densities in the plasma. However, all radially resolved data employed in the earlier study were produced from Abel inversion and from measurements that were crude by today's standards. Now, by means of tomographic imaging, laser-saturated atomic fluorescence, and Thomson and Rayleigh scattering, it is possible to measure the required radially resolved data without Abel inversion and with far greater fidelity. The correlations previously studied for calcium have been investigated with these more reliable data. Ion-electron recombination, either radiative or with argon as a third body, was determined to be the most likely excitation mechanism for calcium atom, while electron impact appeared to be the most important process to produce excite-state calcium ions. These results were consistent with the previous study. However, the present study suggests that collisional deactivation, rather than radiative decay, is the most likely mode of returning both calcium atoms and ions to the ground state.

  10. Argon solvent effects on optical properties of silver metal clusters.

    Science.gov (United States)

    Christen, W; Radcliffe, P; Przystawik, A; Diederich, Th; Tiggesbäumker, J

    2011-08-18

    Argon gas at a high pressure (∼80 bar) has been expanded using a miniaturized pulsed valve at room temperature, producing a supersonic beam of cold, large argon droplets. Atoms of silver are subsequently embedded into the droplet using the pick-up technique. The resulting Ag(n)Ar(droplet) distribution was analyzed using multiphoton laser ionization time-of-flight mass spectrometry. Besides bare metal clusters, snowballs of silver monomers and dimers encapsulated in up to 50 argon atoms have been observed. The influence of the solvent on the optical absorption of the solute was studied for embedded Ag(8) using resonant two-photon ionization in the ultraviolet. A redshift and broadening of the Ag(8)Ar(droplet) optical spectrum compared to that measured in pure [Federmann et al., Eur. Phys. J. D 1999, 9, 11] and Ar-doped helium droplets [Diederich et al., J. Chem. Phys.2002, 116, 3263] was observed, which is attributed to the interaction with the larger Ar matrix environment. © 2011 American Chemical Society

  11. Liquid Argon Barrel Cryostat Arrived

    CERN Multimedia

    Pailler, P

    Last week the first of three cryostats for the ATLAS liquid argon calorimeter arrived at CERN. It had travelled for 46 days over several thousand kilometers from Japan to CERN. During three years it has been fabricated by Kawasaki Heavy Industries Ltd. at Harima, close to Kobe, under contract from Brookhaven National Laboratory (BNL) of the U.S.. This cryostat consists of two concentric cylinders made of aluminium: the outer vacuum vessel with a diameter of 5.5 m and a length of 7 m, and the inner cold vessel which will contain the electromagnetic barrel calorimeter immersed in liquid argon. The total weight will be 270 tons including the detectors and the liquid argon. The cryostat is now located in building 180 where it will be equipped with 64 feed-throughs which serve for the passage of 122,880 electrical lines which will carry the signals of the calorimeter. After integration of the calorimeter, the solenoidal magnet of ATLAS will be integrated in the vacuum vessel. A final cold test of the cryostat inc...

  12. Diamond growth by microwave plasma enhanced chemical vapour deposition: Optical emission characterisation and effect argon addition

    Science.gov (United States)

    Mortet, V.; Hubicka, Z.; Vorlicek, V.; Jurek, K.; Rosa, J.; Vanecek, M.

    2004-09-01

    Diamond thin films were grown in an ellipsoidal 6 kWatt microwave plasma chemical vapour deposition reactor [1, 2] in a pressure range of 150 to 250 mbar. Effect of total pressure, methane concentration and argon concentration on diamond growth on mechanically seeded silicon substrates and on plasma characteristics were investigated. Optically good thick diamond films were obtained with high growth rate (4.5 m/h) at high-pressure. The argon concentration affects strongly the deposition rate, the surface morphology and the grain size. The microwave plasma was characterized by optical emission spectroscopy (OES) during deposition. Diamond films were characterized by Raman Spectroscopy and Scanning Electron Microscopy (SEM). The temperatures of the excited CH and C2 species, as well as the excitation temperature were determined from the OES measurements. The plasma composition is sensitive to the methane concentration and especially to the argon concentration in the discharge.

  13. Separation of seven arsenic compounds by high performance liquid chromatography with on-line detection by hydrogen-argon flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Hansen, S. H.; Larsen, Erik Huusfeldt; Pritzl, G.

    1992-01-01

    the HPLC column to the nebulizer of the atomic absorption spectrometer. Arsenite, arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) were separated from each other and from the co-injected cationic arsenic compounds, arsenobetaine (AsB), arsenocholine (AsC) and the tetramethylarsonium ion (TMAs...... of mixtures of arsenic standards into the HPLC system were: arsenite, As(III) 1.1; arsenate, As(V) 1.4; MMA 1.4; DMA 0.7; AsB 0.3; AsC 0.5; and the TMAs 0.4. The HPLC-AAS system was used for the analysis of arsenic species in aqueous extracts of soil samples from a polluted land site. Only arsenate was found...

  14. Separation of seven arsenic compounds by high-performance liquid chromatography with on-line detection by hydrogen–argon flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Hansen, S. H.; Larsen, E. H.; Pritzl, G.

    1992-01-01

    the HPLC column to the nebulizer of the atomic absorption spectrometer. Arsenite, arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) were separated from each other and from the co-injected cationic arsenic compounds, arsenobetaine (AsB), arsenocholine (AsC) and the tetramethylarsonium ion (TMAs...... of mixtures of arsenic standards into the HPLC system were: arsenite, As(III) 1.1; arsenate, As(V) 1.4; MMA 1.4; DMA 0.7; AsB 0.3; AsC 0.5; and the TMAs 0.4. The HPLC-AAS system was used for the analysis of arsenic species in aqueous extracts of soil samples from a polluted land site. Only arsenate was found...

  15. Excited states 2

    CERN Document Server

    Lim, Edward C

    2013-01-01

    Excited States, Volume 2 is a collection of papers that deals with molecules in the excited states. The book describes the geometries of molecules in the excited electronic states. One paper describes the geometries of a diatomic molecule and of polyatomic molecules; it also discusses the determination of the many excited state geometries of molecules with two, three, or four atoms by techniques similar to diatomic spectroscopy. Another paper introduces an ordered theory related to excitons in pure and mixed molecular crystals. This paper also presents some experimental data such as those invo

  16. Covalent and Noncovalent Interactions Between Boron and Argon: AN Infrared Photodissociation Spectroscopic Study of Argon-Boron Oxide Cation Complexes

    Science.gov (United States)

    Jin, Jiaye; Li, Wei; Wang, Guanjun; Zhou, Mingfei

    2017-06-01

    Although a wide range of compounds of the heavy rare-gas elements are experimentally known, very few chemically bound molecules have been experimentally observed for the lighter noble gases. Here we report a combined infrared photodissociation spectroscopic and theoretical study on a series of argon-boron oxide cation complexes prepared via a laser vaporization supersonic ion source in the gas phase. Infrared spectroscopic combined with state-of-the-art quantum chemical calculations indicate that the [ArB_3O_{4,5}]^+, [ArB_4O_{5-7}]^+ and [ArB_5O_7]^+ cation complexes have planar structures each involving an aromatic boroxol ring and an argon-boron covalent bond formed between the in-plane 2p atomic orbitals of Ar and boron. In contrast, the [ArB_3O_4]^+ cation complex is characterized to be a weakly bound complex with a BO chain structure.

  17. Penning transfer in argon-based gas mixtures

    CERN Document Server

    Sahin, O; Tapan, I; Ozmutlu, E N

    2010-01-01

    Penning transfers, a group of processes by which excitation energy is used to ionise the gas, increase the gas gain in some detectors. Both the probability that such transfers occur and the mechanism by which the transfer takes place, vary with the gas composition and pressure. With a view to developing a microscopic electron transport model that takes Penning transfers into account, we use this dependence to identify the transfer mechanisms at play. We do this for a number of argon-based gas mixtures, using gain curves from the literature.

  18. Rotational study on the van der Waals complex 1-chloro-1,1-difluoroethane-argon.

    Science.gov (United States)

    Wang, Juan; Chen, Junhua; Feng, Gang; Xia, Zhining; Gou, Qian

    2018-03-15

    The rotational spectrum of the van der Waals complex formed between 1-chloro-1,1-difluoroethane and argon has been investigated by using a pulsed jet Fourier transform microwave spectrometer. Only one set of rotational transitions belonging to the lowest energy conformer has been observed and assigned, although theoretical calculations suggest six stable conformers that might be observed. The observed conformer, according to the experimental evidence from two isotopologues ( 35 Cl and 37 Cl), adopts a configuration in which the argon atom is located, close to the CF 2 Cl top, between the CCF and CCCl planes (the dihedral angle ∠ArCCCl is 65.2°). The distance between argon atom and the center of mass of CH 3 CF 2 Cl is 3.949(2) Å. The dissociation energy, with pseudo diatomic approximation, is evaluated to be 2.4kJmol -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Influence of easily ionised elements on the delayed responses of the emission intensities of an analyte in a power modulated U-shaped argon stabilised DC arc plasma with an aerosol supply

    Directory of Open Access Journals (Sweden)

    MIROSLAV KUZMANOVIC

    2005-09-01

    Full Text Available The current of a U-shaped argon stabilised DC arc was square modulated with a 40 Hz repetition frequency between 6 and 3 A. The delayed line intensity responses to the modulation of the arc current were investigated using calcium as a representative analyte. The intensities of both the atomic and ionic lines were monitored at different distances from the arc axis in the presence of various concentrations of the easily ionised element. Temporal evolutions were monitored on a millisecond time scale. It was found that the responses of the line intesity to the arc current change strongly depended on the observed radial position, especially in the vicinity of the arc axis. The obtained results showed a significant influence of even small amounts of the easily ionised element on the excitation and transport of the analyte and indicated a way of possibly improving the analytical capabilities of the excitation source.

  20. Neutral depletion and ion acceleration in an argon helicon plasma

    Science.gov (United States)

    Denning, C. Mark

    The effects of neutral depletion in an argon helicon plasma are investigated. High radiofrequency (RF) power is used (up to 3 kW) to produce helicon plasmas in a static magnetic field that can be configured in a flat or nozzle profile, with magnetic field strengths up to 1.04 kG in the antenna source region with a 1.5 kG nozzle peak. Microwave (105 GHz) interferometry is used to determine the line-averaged electron density (ne). The comparison of excited state populations of Ar I and Ar II with two different collisional-radiative (CR) models provides a non-invasive technique to measure the line-averaged electron temperature (Te) and neutral density (nn). Te is determined using the Atomic Data and Analysis Structure CR model, while n n is determined using a CR model originally developed by J. Vlcek. Measurement of the strong 488 nm Ar II line provides an indication of the plasma density np where interferometer access is limited. The axial ion velocity and temperature is measured through tunable diode laser-induced fluorescence (LIF). Observations indicate a collisional region of weak neutral depletion upstream of the antenna where increasing RF power leads to increased electron density (up to ne = 1.6 x 1013 cm-3) while Te remains essentially constant and low (1.7 to 2.0 eV). The collisionless downstream region exhibits profound neutral depletion (maximum 92% line-averaged ionization), where Te rises linearly with increasing RF power (4.9 eV at 3 kW) and ne remains constrained (below 6.5 x 1012 cm-3). The closed upstream region exhibits a uniform pressure profile along the axis of the experiment, indicating a pressure balance between the plasma source and a weakly-ionized region dominated by neutral particles. In contrast, a pressure gradient is observed in the downstream region extending to the downstream turbopump. The spatial extent of the pressure gradient region extends farther upstream as depletion levels rise. Plasma flow is accelerated (up to Mach 0.24) due

  1. Mean excitation energies for molecular ions

    DEFF Research Database (Denmark)

    Jensen, Phillip W. K.; Sauer, Stephan P. A.; Oddershede, Jens

    2017-01-01

    The essential material constant that determines the bulk of the stopping power of high energy projectiles, the mean excitation energy, is calculated for a range of smaller molecular ions using the RPA method. It is demonstrated that the mean excitation energy of both molecules and atoms increase...... with ionic charge. However, while the mean excitation energies of atoms also increase with atomic number, the opposite is the case for mean excitation energies for molecules and molecular ions. The origin of these effects is explained by considering the spectral representation of the excited state...... contributing to the mean excitation energy....

  2. Mean excitation energies for molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Phillip W.K.; Sauer, Stephan P.A. [Department of Chemistry, University of Copenhagen, Copenhagen (Denmark); Oddershede, Jens [Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Odense (Denmark); Quantum Theory Project, Departments of Physics and Chemistry, University of Florida, Gainesville, FL (United States); Sabin, John R., E-mail: sabin@qtp.ufl.edu [Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Odense (Denmark); Quantum Theory Project, Departments of Physics and Chemistry, University of Florida, Gainesville, FL (United States)

    2017-03-01

    The essential material constant that determines the bulk of the stopping power of high energy projectiles, the mean excitation energy, is calculated for a range of smaller molecular ions using the RPA method. It is demonstrated that the mean excitation energy of both molecules and atoms increase with ionic charge. However, while the mean excitation energies of atoms also increase with atomic number, the opposite is the case for mean excitation energies for molecules and molecular ions. The origin of these effects is explained by considering the spectral representation of the excited state contributing to the mean excitation energy.

  3. Time-resolved microplasma excitation temperature in a pulsed microwave discharge

    Science.gov (United States)

    Hopwood, Jeffrey; Monfared, Shabnam; Hoskinson, Alan

    2013-09-01

    Microwave-driven microplasmas are usually operated in a steady-state mode such that the electron temperature is constant in time. Transient measurements of excitation temperature and helium emission lines, however, suggest that short microwave pulses can be used to raise the electron energy by 20-30% for approximately 100 ns. Time-resolved optical emission spectrometry reveals an initial burst of light emission from the igniting microplasma. This emission overshoot is also correlated with a measured increase in excitation temperature. Excimer emission lags atomic emission, however, and does not overshoot. A simple model demonstrates that an increase in electron temperature is responsible for the overshoot of atomic optical emission at the beginning of each microwave pulse. The formation of dimers and subsequent excimer emission requires slower three-body collisions with the excited rare gas atom; this is why excimer emission does not overshoot the steady state value. Similar experimental and modeling results are observed in argon gas. The overshoot in electron temperature may be used to manipulate the collisional production of species in microplasmas using short, low-duty cycle microwave pulses. This material is based upon work supported by the USAF and Physical Sciences Inc., under contract No. FA8650-C-12-C-2312. Additional support was provided by the DARPA MPD program under award FA9550-12-1-0006.

  4. The Stair-Step Atom.

    Science.gov (United States)

    Jordan, Thomas M.; And Others

    1992-01-01

    Presents a model of a generic atom that is used to represent the movement of electrons from lower to higher levels and vice-versa due to excitation and de-excitation of the atom. As the process of de-excitation takes place, photons represented by colored ping-pong balls are emitted, indicating the emission of light. (MDH)

  5. Dissociation rate of bromine diatomics in an argon heat bath

    Science.gov (United States)

    Razner, R.; Hopkins, D.

    1973-01-01

    The evolution of a collection of 300 K bromine diatomics embedded in a heat bath of argon atoms at 1800 K was studied by computer, and a dissociation-rate constant for the reaction Br2 + BR + Ar yields Br + Ar was determined. Previously published probability distributions for energy and angular momentum transfers in classical three-dimensional Br2-Ar collisions were used in conjunction with a newly developed Monte Carlo scheme for this purpose. Results are compared with experimental shock-tube data and the predictions of several other theoretical models. A departure from equilibrium is obtained which is significantly greater than that predicted by any of these other theories.

  6. Timeresolved investigation of atomic order in tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) monocrystals after excitation with ultrashort light pulses; Zeitaufgeloeste Untersuchung atomarer Ordnung in Tetrathiafulvalen-Tetracyanochinodimethan (TTF-TCNQ)-Einkristallen nach Anregung mit ultrakurzen Lichtpulsen

    Energy Technology Data Exchange (ETDEWEB)

    Sager, Christian

    2011-02-15

    This thesis describes time-resolved investigations of the atomic structure of one-dimensional organic molecular crystals after laser excitation of the photo-induced phase transition. There is a neutral to ionic phase transition in tetrathiafulvalene-chloranil-crystals (TTF-CA-crystals). At this phase transition a Peierls distortion occurs. A new model is introduced, that can explain the photo-induced phase transition in TTF-CY-crystals. This model is called charge density wave model of photo induced structural phase transition. There is a structural phase transition in tetrathiafulvalene-tetracyanochinodimethane-crystals (TTF-TCNQ-crystals). At this phase transition the one-dimensional metal TTF-TCNQ is transformed to an insulator. The phase transition is driven by the Peierls distortion. The charge density wave model is appropriate for description of the processes in TTF-TCNQ-crystals after laser excitation. The results of time-resolved measurements of the structure of TTF-TCNQ-crystals after excitation of the photo-induced phase transition can be anticipated with the charge density wave model. In the basis of these anticipated results, a time-resolved measurement for investigation of the atomic structure of TTF-TCNQ after excitation of the photo-induced phase transition is proposed. The time-resolved measurement should be performed at a beamline of a third generation synchrotron by the optical pump X-ray probe technique. The time-resolved measurement is prepared by an optical characterization and by static X-ray diffraction measurements. The results of the optical characterization and the static X-ray diffraction measurements are presented and analyzed. (orig.)

  7. Impact of keV-energy argon clusters on diamond and graphite

    DEFF Research Database (Denmark)

    Popok, Vladimir; Samela, Juha; Nordlund, Kai

    2012-01-01

    the graphene planes, significant radiation damage is already introduced by impact of clusters with low kinetic energies (a few tens of eV/atom). However, collisions of the argon clusters cause very elastic response of the graphene planes that leads to efficient closure of the craters which could be formed...

  8. Surface treatment of para-aramid fiber by argon dielectric barrier discharge plasma at atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Gu Ruxi [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Shanghai 201620 (China); Yu Junrong, E-mail: yjr@dhu.edu.cn [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Shanghai 201620 (China); Hu Chengcheng; Chen Lei; Zhu Jing [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Shanghai 201620 (China); Hu Zuming [Key Laboratory of High-performance Fibers and Products, Ministry of Education, Donghua University, Shanghai 201620 (China)

    2012-10-01

    Highlights: Black-Right-Pointing-Pointer We use DBD technique to modify the surface of Kelvar29 fibers. Black-Right-Pointing-Pointer The changed parameters include treated power, time and argon flux. Black-Right-Pointing-Pointer There exists an optimum experimental condition of plasma treatment. Black-Right-Pointing-Pointer Adhesion and wettability properties of fibers are improved through plasma treatment. - Abstract: This paper is focused on influence of argon dielectric barrier discharge (DBD) plasma on the adhesive performance and wettability of para-aramid fibers and three parameters including treated power, exposure time and argon flux were detected. The interfacial shear strength (IFSS) was greatly increased by 28% with 300 W, 60 s, 2 L min{sup -1} argon flux plasma treatment. The content of oxygen atom and oxygen-containing polar functional groups were enhanced after the argon plasma treated, so as the surface roughness, which contributed to the improvement of surface wettability and the decrease of contact angle with water. However, long-time exposure, exorbitant power or overlarge argon flux could partly destroy the prior effects of the treatment and damage the mechanical properties of fibers to some degree.

  9. Coupled cluster calculations of mean excitation energies of the noble gas atoms He, Ne and Ar and of the H2 molecule

    Science.gov (United States)

    Sauer, Stephan P. A.; Haq, Inam Ul; Sabin, John R.; Oddershede, Jens; Christiansen, Ove; Coriani, Sonia

    2014-03-01

    Using an asymmetric Lanczos chain algorithm for the calculation of the coupled cluster linear response functions at the coupled cluster singles and doubles (CCSD) and coupled cluster singles and approximate iterative doubles (CC2) levels of approximation, we have calculated the mean excitation energies of the noble gases He, Ne and Ar, and of the hydrogen molecule (H2). Convergence with respect to the one-electron basis set was investigated in detail for families of correlation-consistent basis sets including both augmentation and core-valence functions. We find that the electron correlation effects at the CCSD level change the mean excitation energies obtained at the uncorrelated Hartree-Fock level by about 1%. For the two-electron systems He and H2, our CCSD results (for a Lanczos chain length equal to the full excitation space), I0 = 42.28 eV (helium) and I0 = 19.62 eV (H2), correspond to full configuration interaction results and are therefore the exact, non-relativistic theoretical values for the mean excitation energy of these two systems within the Bethe theory for the chosen basis set and, in the case of H2, at the experimental equilibrium geometry.

  10. Following electron impact excitations of Rn, Ra, Th, U and Pu single atom L sub-shells ionization cross section calculations by using Lotz’s equation

    Energy Technology Data Exchange (ETDEWEB)

    Ayinol, M., E-mail: aydinolm@dicle.edu.tr [Dicle University, Faculty of Science, Department of Physics, Diyarbakir, 21280 Turkey (Turkey); Aydeniz, D., E-mail: daydeniz@hotmail.com [Artuklu University, At Rectorate of Artuklu University, Mardin (Turkey)

    2016-03-25

    L shell ionization cross section and L{sub i} subshells ionization cross sections of Rn, Ra, Th, U, Pu atoms calculated. For each of atoms, ten different electron impact energy values (E{sub o}) are used. Calculations carried out by using Lotz equation in Matlab. First, calculations done for non-relativistic case by using non-relativistic Lotz equation then repeated with relativistic Lotz equation. σ{sub L} total and σ{sub Li}(i = 1,2,3) subshells ionisation cross section values obtained for E{sub o} values in the energy range of E{sub Li} atom. Starting almost from E{sub o} = E{sub Li} values of the each sub shell ionization threshold energy, σ{sub L} total and σ{sub Li} (i = 1,2,3) are increasing rapidly with E{sub o}. For a fixed E{sub o} = 3.E{sub Li}), while Z increases from 86atom impact studies.

  11. Summaries of Papers Presented at the Multiple Excitations of Atoms Topical Meeting Held in Seattle, Washington on October 20-22, 1986

    Science.gov (United States)

    1986-10-22

    Nucleaires de Saclay, France. Forma- smaller terms. The applicability of the theory to other atoms tion of multiply charged ions and energy spectrum of...Universite Canada Peter P. Lambropoulos University of Southern California Joseph Macek University of Nebraska Gerard Mainfray Centre d’Etudes Nucleaires

  12. Coupled cluster calculations of mean excitation energies of the noble gas atoms He, Ne and Ar and of the H2 molecule

    DEFF Research Database (Denmark)

    Sauer, Stephan P. A.; Ul Haq, Inam; Sabin, John R.

    2014-01-01

    Using an asymmetric-Lanczos-chain algorithm for the calculation of the coupled cluster linear response functions at the CCSD and CC2 levels of approximation, we have calculated the mean excitation energies of the noble gases He, Ne and Ar, and of the hydrogen molecule H2. Convergence with respect...... by about 1%. For the two-electron systems He and H2, our CCSD results (for a Lanczos chain length equal to the full excitation space), I0 = 42:28 eV (Helium) and I0 = 19:62 eV (H2), correspond to full conguration interaction results and are therefore the exact, non-relativistic theoretical values...

  13. Relaxation channels of multi-photon excited xenon clusters.

    Science.gov (United States)

    Serdobintsev, P Yu; Rakcheeva, L P; Murashov, S V; Melnikov, A S; Lyubchik, S; Timofeev, N A; Pastor, A A; Khodorkovskii, M A

    2015-09-21

    The relaxation processes of the xenon clusters subjected to multi-photon excitation by laser radiation with quantum energies significantly lower than the thresholds of excitation of atoms and ionization of clusters were studied. Results obtained by means of the photoelectron spectroscopy method showed that desorption processes of excited atoms play a significant role in the decay of two-photon excited xenon clusters. A number of excited states of xenon atoms formed during this process were discovered and identified.

  14. Spatial and temporal evolution of argon sparks

    OpenAIRE

    Harilal, S.S.

    2004-01-01

    Optical emission spectroscopic studies of laser-created argon sparks are carried out. Pulses of 532 nm and 8 ns from a frequency-doubled Nd:YAG laser are used to create an argon spark at 1 atm. Gated photography of 2 ns is used to investigate spark evolution at early times. Electron temperature and density measurements are made from the spectral data. The Stark broadening of emission lines is used to determine the electron density, and the Boltzmann plot of the singly ionized argon-line inten...

  15. Clinical periodontics with the argon laser

    Science.gov (United States)

    Finkbeiner, R. L.

    1995-04-01

    The argon laser has proven to be a valuable tool for the thermodynamic debridement of the periodontal lesion, incisions and tissue fusion. Illustrations of clinical applications and discussion of laser parameters will be provided.

  16. Broadband Ftmw Spectroscopy of the Urea-Argon and Thiourea-Argon Complexes

    Science.gov (United States)

    Medcraft, Chris; Bittner, Dror M.; Cooper, Graham A.; Mullaney, John C.; Walker, Nick

    2017-06-01

    The rotational spectra complexes of argon-urea, argon-thiourea and water-thiourea have been measured by chirped-pulse Fourier transform microwave spectroscopy from 2-18.5 GHz. The sample was produced via laser vaporisation of a rod containing copper and the organic sample as a stream of argon was passed over the surface and subsequently expanded into the vacuum chamber cooling the sample. Argon was found to bind to π system of the carbonyl bond for both the urea and thiourea complexes.

  17. Transition rate diagrams — A new approach to the study of selective excitation processes: The spectrum of manganese in a Grimm-type glow discharge

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Zdeněk [LECO Instrumente Plzeň spol. s r.o., Plaská 66, 323 25 Plzeň (Czech Republic); Steers, Edward B.M. [London Metropolitan University, 166-220 Holloway Road, London N7 8DB (United Kingdom); Pickering, Juliet C. [Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Mushtaq, Sohail [London Metropolitan University, 166-220 Holloway Road, London N7 8DB (United Kingdom)

    2014-02-01

    The emission spectra of manganese observed using a Grimm-type glow discharge in pure argon, argon with 0.3% v/v hydrogen and pure neon were studied in order to identify major excitation and ionization processes of manganese in the plasma. A new procedure is proposed, in which each observed emission line is associated with the corresponding transition between different states of the Mn atom or Mn ion, and, by considering all the observed transitions from and into a specific state, a measure of the total rate is determined at which this state is radiatively populated and depopulated. These resulting population/depopulation rates are then plotted as function of level energy. Such plots, called here “transition rate diagrams”, show the role of individual states in the formation of the observed spectrum and can be used to identify possible selective excitation processes. Also, cascade excitation by radiative decay of higher excited states can be conveniently evaluated in this way. A detailed description of the observed Mn I and Mn II spectra is given for Ar, Ar–H{sub 2} and Ne plasmas and relevant excitation/ionization mechanisms are discussed. Matrix effects in analysis of manganese by glow discharge spectroscopy are discussed. A list of important Mn I and Mn II lines excited in the glow discharge plasma is given. - Highlights: • We measured GD-OES spectra of Mn in Ar, Ar(H) and Ne discharges. • We determined transition rate diagrams of Mn I and Mn II in these discharges. • Using those diagrams, we identified major excitation processes involved.

  18. Evidence for a Localized Source of the Argon in the Lunar Exosphere

    Science.gov (United States)

    Kegerreis, Jacob A.; Eke, Vincent R.; Massey, Richard J.; Beaumont, Simon K.; Elphic, Rick C.; Teodoro, Luís. F.

    2017-10-01

    We perform the first tests of various proposed explanations for observed features of the Moon's argon exosphere, including models of the following: spatially varying surface interactions; a source that reflects the lunar near-surface potassium distribution; and temporally varying cold trap areas. Measurements from the Lunar Atmosphere and Dust Environment Explorer (LADEE) and the Lunar Atmosphere Composition Experiment (LACE) are used to test whether these models can reproduce the data. The spatially varying surface interactions hypothesized in previous work cannot reproduce the persistent argon enhancement observed over the western maria. They also fail to match the observed local time of the near-sunrise peak in argon density, which is the same for the highland and mare regions and is well reproduced by simple surface interactions with a ubiquitous desorption energy of 28 kJ mol-1. A localized source can explain the observations, with a trade-off between an unexpectedly localized source or an unexpectedly brief lifetime of argon atoms in the exosphere. To match the observations, a point-like source requires source and loss rates of ˜1.9 × 1021 atoms s-1. A more diffuse source, weighted by the near-surface potassium, requires much higher rates of ˜1.1 × 1022 atoms s-1, corresponding to a mean lifetime of just 1.4 lunar days. We do not address the mechanism for producing a localized source, but demonstrate that this appears to be the only model that can reproduce the observations. Large, seasonally varying cold traps could explain the long-term fluctuation in the global argon density observed by LADEE, but not that by LACE.

  19. Excitation energies, singlet-triplet energy gaps, spin-orbit matrix elements and heavy atom effects in BOIMPYs as possible photosensitizers for photodynamic therapy: a computational investigation.

    Science.gov (United States)

    De Simone, Bruna Clara; Mazzone, Gloria; Russo, Nino; Sicilia, Emilia; Toscano, Marirosa

    2018-01-24

    Bis(borondifluoride)-8-imidazodipyrromethene (BOIMPY) based molecules show interesting photophysical properties. We have undertaken a computational study at DFT and TDDFT levels of theory with the aim of verifying if the non-fluorescent BOIMPYs meet those properties necessary to be proposed as potential photosensitizers for photodynamic therapy (PDT). In particular, we have computed the absorption wavelengths, the singlet-triplet energy gaps and the spin-orbit matrix elements. The effect of halogen atom substitution (Br, I), in different amounts and positions in the BOIMPY skeleton, on the photophysical properties, has been elucidated. Some possible pathways for the population of the lowest triplet state have been examined and rationalized on the basis of Kasha rules. The results indicate that many of the studied systems can be indicated as potential photosensitizers for photodynamic therapy.

  20. Effect of argon during diamond deposition

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, D.C.; Mengui, U.A.; Contin, A.; Trava-Airoldi, V.J.; Baldan, M.R.; Corat, E.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Laboratorio Associado de Sensores e Materiais

    2014-07-01

    The effect of argon content upon the growth rate and the properties of diamond thin films grown with different grains sizes is explored. An argon-free and argon-rich gas mixture of methane and hydrogen is used in a hot filament chemical vapor deposition reactor. Characterization of the films is accomplished by scanning electron microscopy, Raman spectroscopy and high-resolution x-ray diffraction. An extensive comparison of the growth rate values obtained in this study with those found in the literature suggests that there are distinct common trends for microcrystalline and nanocrystalline diamond growth, despite a large variation in the gas mixture composition. Included is a discussion of the possible reasons for these observations. (author)

  1. Spatial and temporal evolution of argon sparks.

    Science.gov (United States)

    Harilal, Sivanandan S

    2004-07-01

    Optical emission spectroscopic studies of laser-created argon sparks are carried out. Pulses of 532 nm and 8 ns from a frequency-doubled Nd:YAG laser are used to create an argon spark at 1 atm. Gated photography of 2 ns is used to investigate spark evolution at early times. Electron temperature and density measurements are made from the spectral data. The Stark broadening of emission lines is used to determine the electron density, and the Boltzmann plot of the singly ionized argon-line intensities is exploited for determination of the electron temperature. The dependence on electron temperature and density on different experimental parameters, such as distance from the focal point, delay time after the initiation of the spark, and laser energy, are discussed.

  2. Silane activation by laser-ablated Be atoms: Formation of HBeSiH3 and HBe(μ-H)3Si molecules

    Science.gov (United States)

    Zhao, Jie; Yu, Wenjie; Xu, Bing; Huang, Tengfei; Wang, Xuefeng

    2017-03-01

    Laser-ablated beryllium atoms have been reacted with silane molecules during condensation in excess neon and argon at 4 K. Absorptions due to HBeSiH3 and HBe(μ-H)3Si were observed and identified on the basis of isotopic IR spectroscopy, deuterium substitution with SiD4, and quantum chemical frequency calculations. The observed results show excited Be atom (1P1:2s12p1) can insert into Sisbnd H bond spontaneously and the insertion product rearranges to HBe(μ-H)3Si upon photolysis. The electron localization function (ELF) analysis suggests that 3c-2e hydrogen bridge bond (Besbnd Hsbnd Si) was formed by the donation of electrons for Sisbnd H σ bond to the empty p orbital of Be atom for HBe(μ-H)3Si molecule, which shows much difference from Csbnd H bond complexes.

  3. High Power Argon, Nitrogen Plasma Torches

    Science.gov (United States)

    Hakki, A.; Kashapov, N.; Sadikov, K.

    2017-11-01

    The paper describes a high power supply for Argon and Nitrogen plasma torches. A high frequency was used in order to drive the pulse width modulation circuit. The average output current consumption (AOCC) was modified from 20A up to 80A by increasing the pulse width from 2μsec up to 3μsec for Argon gas plasma torches. The (AOCC) was reduced from 70A down to 25A by increasing the pulse width from 6μsec up to 8μsec in the case of Nitrogen gas plasma torches.

  4. Rotational spectrum of the pentafluoroethane-argon van der Waals complex

    Science.gov (United States)

    Zheng, Yang; Li, Xiaolong; Feng, Gang; Xia, Zhining; Gou, Qian

    2018-01-01

    Rotational spectra of the van der Waals complex of pentafluoroethane-argon and its two 13C isotopes in nature abundance have been investigated by puled jet Fourier transform microwave spectroscopy. The Ar atom lies in the symmetry plane of pentafluoroethane, with a distance of 4.05 Å from its center of mass. The dissociation energy has been estimated to be 3.2 kJ/mol with a pseudodiatomic approximation.

  5. A G/NARRLI Effort. Measuring the Ionization Yield of Low-Energy Nuclear Recoils in Liquid Argon

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Tenzing Henry Yatish [Univ. of California, Berkeley, CA (United States)

    2014-01-01

    Liquid argon has long been used for particle detection due to its attractive drift properties, ample abundance, and reasonable density. The response of liquid argon to lowenergy O(102 -1044 eV) interactions is, however, largely unexplored. Weakly interacting massive particles such as neutrinos and hypothetical dark-matter particles (WIMPs) are predicted to coherently scatter on atomic nuclei, leaving only an isolated low-energy nuclear recoil as evidence. The response of liquid argon to low-energy nuclear recoils must be studied to determine the sensitivity of liquid argon based detectors to these unobserved interactions. Detectors sensitive to coherent neutrino-nucleus scattering may be used to monitor nuclear reactors from a distance, to detect neutrinos from supernova, and to test the predicted behavior of neutrinos. Additionally, direct detection of hypothetical weakly interacting dark matter would be a large step toward understanding the substance that accounts for nearly 27% of the universe. In this dissertation I discuss a small dual-phase (liquid-gas) argon proportional scintillation counter built to study the low-energy regime and several novel calibration and characterization techniques developed to study the response of liquid argon to low-energy O(102 -104 eV) interactions.

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

    Science.gov (United States)

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

    2018-01-01

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

  7. Behavior of the 398.4nm Hg II Spectral Line in the Helium and Argon Plasmas

    Science.gov (United States)

    Skocic, M.; Burger, M.; Gavrilov, M.; Bukvic, S.; Djenize, S.

    2012-12-01

    The astrophysically important 398.4 nm Hg II spectral line was investigated in the laboratory helium and argon plasmas. The mercury atoms were sputtered from the amalgamated gold cylindrical plates located in the homogenous part of the pulsed discharge. We have found that strong intensity of the 398.4 nm Hg II line is due to excessively high density of the helium metastable atoms.

  8. Thermal decomposition of barium valerate in argon

    DEFF Research Database (Denmark)

    Torres, P.; Norby, Poul; Grivel, Jean-Claude

    2015-01-01

    The thermal decomposition of barium valerate (Ba(C4H9CO2)(2)/Ba-pentanoate) was studied in argon by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray diffraction and hot-stage optical microscopy. Melting takes place in two different steps, at 200 degrees C and 280...

  9. Argon-ion contamination of the plasmasphere

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, Y.T.; Cornwall, J.M.; Luhmann, J.G.; Schulz, M.

    1979-07-15

    This paper applies present observational and analytic knowledge on effects of plasma beam interaction wth the magnetosphere to the plasmasphere contamination problem of the argon ion engine exhaust expected to be deposited in the magnetosphere during the construction phase of the Satellite Power System. Effects of plasmasphere, ionosphere, and radiation belt modifications are discussed.

  10. Positive and negative pulsed corona in argon

    NARCIS (Netherlands)

    E.M. van Veldhuizen; W.R. Rutgers; U. Ebert (Ute)

    2002-01-01

    htmlabstractPhotographs are obtained of corona discharges in argon at atmospheric pressure using a high resolution, intensified CCD camera. Positive and negative polarity is applied at the curved electrode in a point-plane gap and a plane-plane gap with a protruding point. Branching is observed in

  11. Antiapoptotic activity of argon and xenon

    Science.gov (United States)

    Spaggiari, Sabrina; Kepp, Oliver; Rello-Varona, Santiago; Chaba, Kariman; Adjemian, Sandy; Pype, Jan; Galluzzi, Lorenzo; Lemaire, Marc; Kroemer, Guido

    2013-01-01

    Although chemically non-reactive, inert noble gases may influence multiple physiological and pathological processes via hitherto uncharacterized physical effects. Here we report a cell-based detection system for assessing the effects of pre-defined gas mixtures on the induction of apoptotic cell death. In this setting, the conventional atmosphere for cell culture was substituted with gas combinations, including the same amount of oxygen (20%) and carbon dioxide (5%) but 75% helium, neon, argon, krypton, or xenon instead of nitrogen. The replacement of nitrogen with noble gases per se had no effects on the viability of cultured human osteosarcoma cells in vitro. Conversely, argon and xenon (but not helium, neon, and krypton) significantly limited cell loss induced by the broad-spectrum tyrosine kinase inhibitor staurosporine, the DNA-damaging agent mitoxantrone and several mitochondrial toxins. Such cytoprotective effects were coupled to the maintenance of mitochondrial integrity, as demonstrated by means of a mitochondrial transmembrane potential-sensitive dye and by assessing the release of cytochrome c into the cytosol. In line with this notion, argon and xenon inhibited the apoptotic activation of caspase-3, as determined by immunofluorescence microscopy coupled to automated image analysis. The antiapoptotic activity of argon and xenon may explain their clinically relevant cytoprotective effects. PMID:23907115

  12. Laser Excited Fluorescence For Forensic Diagnostics

    Science.gov (United States)

    McKinney, Robert E.

    1986-07-01

    The application of laser excited fluorescence to the detection and identification of latent fingerprints was first accomplished ten years ago. The development of the technology has progressed rapidly with the introduction of commercial equipment by several manufacturers. Systems based on Argon-ion, Copper-vapor, and frequency-doubled Nd:YAG lasers are compared. The theoretical basis of detection by fluorescence is discussed along with the more useful techniques of dye staining. Other applications of the laser excited fluorescence in forensic investigation include gunshot residue analysis, serology, collection of trace evidence, and document examination.

  13. 46 CFR 151.50-36 - Argon or nitrogen.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Argon or nitrogen. 151.50-36 Section 151.50-36 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-36 Argon or nitrogen. (a) A cargo tank that contains argon or nitrogen and that has a maximum allowable working pressure of 172 kPa (25...

  14. Excited states

    CERN Document Server

    Lim, Edward C

    1974-01-01

    Excited States, Volume I reviews radiationless transitions, phosphorescence microwave double resonance through optical spectra in molecular solids, dipole moments in excited states, luminescence of polar molecules, and the problem of interstate interaction in aromatic carbonyl compounds. The book discusses the molecular electronic radiationless transitions; the double resonance techniques and the relaxation mechanisms involving the lowest triplet state of aromatic compounds; as well as the optical spectra and relaxation in molecular solids. The text also describes dipole moments and polarizab

  15. Ion acoustic wave studies near the presheath/sheath boundary in a weakly collisional argon/xenon plasma

    Science.gov (United States)

    Oksuz, Lutfi; Lee, Dongsoo; Hershkowitz, Noah

    2008-02-01

    Ion acoustic wave (IAW) phase velocities are measured near the sheath/presheath boundary in a weakly collisional argon/xenon plasma. Wave profiles versus position are measured using a boxcar averager with a gate width of 30 ns and CW excitation at 50 or 75 kHz. Variable gate delays allow measurement of details of the wave close to the boundary. It is shown that the phase velocity at the presheath/sheath boundary is approximately twice the phase velocity in the bulk plasma for both argon and argon/xenon plasmas, in agreement with a recent calculation (Lee D et al 2007 Phys. Rev. Lett. 99 155004). This result indicates each ion's drift velocity at the boundary is equal to the IAW phase velocity in the bulk plasma.

  16. Observation of two-dimensional compositional ordering of a carbon monoxide and argon monolayer mixture physisorbed on graphite

    Energy Technology Data Exchange (ETDEWEB)

    You, H.; Fain, S.C. Jr.; Satija, S.; Passell, L.

    1986-01-20

    Commensurate monolayers of a mixture of 70% carbon monoxide and 30% argon on graphite are studied by neutron and low-energy-electron diffraction. A 2 x 2 superstructure due to 3:1 compositional ordering is observed below 25 K. The compositional ordering is most likely due to molecular-axis ordering of carbon monoxide molecules into a pinwheel pattern with argon atoms at the central sites of each pinwheel. Such a pinwheel structure has been predicted by Harris, Mouritsen, and Berlinsky for planar rotors with anisotropic interactions on a triangular lattice with vacancies.

  17. Nuclear effects in atomic transitions

    CERN Document Server

    Pálffy, Adriana

    2011-01-01

    Atomic electrons are sensitive to the properties of the nucleus they are bound to, such as nuclear mass, charge distribution, spin, magnetization distribution, or even excited level scheme. These nuclear parameters are reflected in the atomic transition energies. A very precise determination of atomic spectra may thus reveal information about the nucleus, otherwise hardly accessible via nuclear physics experiments. This work reviews theoretical and experimental aspects of the nuclear effects that can be identified in atomic structure data. An introduction to the theory of isotope shifts and hyperfine splitting of atomic spectra is given, together with an overview of the typical experimental techniques used in high-precision atomic spectroscopy. More exotic effects at the borderline between atomic and nuclear physics, such as parity violation in atomic transitions due to the weak interaction, or nuclear polarization and nuclear excitation by electron capture, are also addressed.

  18. Influence of nanoparticle formation on the time and the space resolved metastable density in argon-acetylene plasmas

    Science.gov (United States)

    Stefanović, I.; Sadeghi, N.; Winter, J.; Sikimić, B.

    2017-06-01

    Different diagnostic techniques are used to monitor the dynamics of electrons and Ar*(1s5) metastable atoms in the active plasma phase and in the afterglow of a capacitively coupled radio-frequency (RF) discharge operated in different gas mixtures and at different input powers. Diode laser absorption at 772.38 nm is used to measure the time resolved density of Ar*(1s5) atoms in either continuous-wave mode or pulsed RF discharges with 100 Hz pulsing frequency. Simultaneously, microwave interferometry recorded the time dependence of the electron density. Different plasma conditions, namely: (1) pure argon, (2) argon +5.9% acetylene before nanoparticle formation, (3) argon +5.9% acetylene after dust particles have been formed and (4) argon with dust particles remaining in the plasma volume but without acetylene are studied. The measured steady-state Ar*(1s5) density in the middle of the reactor is several times larger in the dusty argon plasma than in the pure argon discharge for the same discharge powers. At the same time, the electron density is several times less in the dusty plasma. These changes are caused by dust formation: the electric field in the bulk plasma is enhanced and thus consequently the electron temperature increases. Laser induced fluorescence (LIF) is used to measure the time and space resolved Ar*(1s5) axial distribution. In the pure argon discharge, the axial Ar*(1s5) metastable distribution has a characteristic saddle-like shape with maxima in the region of the sheaths. With dust particles inside, the axial distribution changes dramatically with the maximum at the discharge mid-plane, revealing an α-γ‧ transition. The spatial distribution and absolute density of metastable atoms are influenced by the formation of a void in the cloud of nanoparticles. Depending on the size of the void, the Ar*(1s5) density reduction inside the void is between 30% and 50%. The high Ar*(1s5) metastable density in the dusty plasma afterglow strongly influences

  19. Argon gas flow through glass nanopipette

    Science.gov (United States)

    Takami, Tomohide; Nishimoto, Kiwamu; Goto, Tadahiko; Ogawa, Shuichi; Iwata, Futoshi; Takakuwa, Yuji

    2016-12-01

    We have observed the flow of argon gas through a glass nanopipette in vacuum. A glass nanopipette with an inner diameter of 100 nm and a shank length of 3 mm was set between vacuum chambers, and argon gas was introduced from the top of the nanopipette to the bottom. The exit pressure was monitored with an increase in entrance pressure in the range of 50-170 kPa. Knudsen flow was observed at an entrance pressure lower than 100 kPa, and Poiseuille flow was observed at an entrance pressure higher than 120 kPa. The proposed pressure-dependent gas flow method provides a means of evaluating the glass nanopipette before using it for various applications including nanodeposition to surfaces and femtoinjection to living cells.

  20. Argon laser irradiation of the otolithic organ

    Energy Technology Data Exchange (ETDEWEB)

    Okuno, T.; Nomura, Y.; Young, Y.H.; Hara, M. (Univ. of Tokyo (Japan))

    1990-12-01

    An argon laser was used to irradiate the otolithic organs of guinea pigs and cynomolgus monkeys. After stapedectomy, the argon laser (1.5 W x 0.5 sec/shot) irradiated the utricle or saccule without touching the sensory organs. The stapes was replaced over the oval window after irradiation. The animals used for acute observation were killed immediately for morphologic studies; those used for long-term observation were kept alive for 2, 4, or 10 weeks. Acute observation revealed that sensory and supporting cells were elevated from the basement membrane only in the irradiated area. No rupture of the membranous labyrinth was observed. Long-term observation revealed that the otolith of the macula utriculi had disappeared in 2-week specimens. The entire macula utricili had disappeared in 10-week specimens. No morphologic changes were observed in cochlea, semicircular canals, or membranous labyrinth. The saccule showed similar changes.

  1. ATLAS liquid argon calorimeter back end electronics

    CERN Document Server

    Bán, J; Bellachia, F; Blondel, A; Böttcher, S; Clark, A; Colas, Jacques; Díaz-Gómez, M; Dinkespiler, B; Efthymiopoulos, I; Escalier, M; Fayard, Lo; Gara, A; He, Y; Henry-Coüannier, F; Hubaut, F; Ionescu, G; Karev, A; Kurchaninov, L; Lafaye, R; Laforge, B; La Marra, D; Laplace, S; Le Dortz, O; Léger, A; Liu, T; Martin, D; Matricon, P; Moneta, L; Monnier, E; Oberlack, H; Parsons, J A; Pernecker, S; Perrot, G; Poggioli, L; Prast, J; Przysiezniak, H; Repetti, B; Rosselet, L; Riu, I; Schwemling, P; Simion, S; Sippach, W; Strässner, A; Stroynowski, R; Tisserant, S; Unal, G; Wilkens, H; Wingerter-Seez, I; Xiang, A; Yang, J; Ye, J

    2007-01-01

    The Liquid Argon calorimeters play a central role in the ATLAS (A Toroidal LHC Apparatus) experiment. The environment at the Large Hadron Collider (LHC) imposes strong constraints on the detectors readout systems. In order to achieve very high precision measurements, the detector signals are processed at various stages before reaching the Data Acquisition system (DAQ). Signals from the calorimeter cells are received by on-detector Front End Boards (FEB), which sample the incoming pulse every 25ns and digitize it at a trigger rate of up to 75~kHz. Off-detector Read Out Driver (ROD) boards further process the data and send reconstructed quantities to the DAQ while also monitoring the data quality. In this paper, the ATLAS Liquid Argon electronics chain is described first, followed by a detailed description of the off-detector readout system. Finally, the tests performed on the system are summarized.

  2. Abnormal epidermal changes after argon laser treatment

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, R.A.; Knobler, R.M.; Aberer, E.; Klein, W.; Kocsis, F.; Ott, E. (Univ. of Vienna (Austria))

    1991-02-01

    A 26-year-old woman with a congenital port-wine stain on the forehead was treated three times at 2-month intervals with an argon laser. Six months after the last treatment, moderate blanching and mild scaling confined to the treated area was observed. A biopsy specimen of the treated area revealed a significant decrease in ectatic vessels. However, epidermal changes similar to those of actinic keratosis with disorganized cell layers and marked cytologic abnormalities were seen. Analysis of peripheral blood lymphocytes for a defect in DNA repair was negative. Multiple, argon laser-induced photothermal effects may be responsible for the changes observed in our case and may lead to premalignant epidermal transformation.

  3. Liquid argon imaging a novel detection technology

    CERN Document Server

    Rubbia, Carlo

    2002-01-01

    Ionisation electrons may drift over large distances (meters) in a volume of highly purified liquid argon (O2 equivalent less than 0.1 ppb!) under the action of an electric field. With an appropriate readout system (i.e. a set of fine pitch wire grids) we have realised a massive, continuously sensitive 'bubble chamber' with multiple readouts of the same, small charge (a minimum ionising track segment, 2 mm long, yields • 10000 electrons). We have developed this technology since 1987, initially with small laboratory devices and later with progressively larger and more sophisticated detectors, the latest being the T600 module (740 ton of liquid Argon), which has been operated in Pavia, as a step toward the ICARUS programme in the Gran Sasso Laboratory (LNGS). With cloning of T600 we aim at a 3000 ton detector by 2005. Argon is a medium with density 1.4 g/cm3, similar in characteristics to the heavy freon used in the famous Gargamelle. With wire pitches of 2-3 mm, it provides an extremely high spatial re...

  4. Excited states of muonium in atomic hydrogen

    Indian Academy of Sciences (India)

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

  5. Fourier-Transform Microwave Spectroscopy of the Argon-Diacetylene van der Waals Complex

    Science.gov (United States)

    Matsumura; Ohshima; Endo

    1997-09-01

    The rotational spectrum of the argon-diacetylene van der Waals complex, produced in a supersonic molecular beam at 1 K, has been observed with a Fourier-transform microwave spectrometer. We observed 22 a-type rotational transitions with Ka up to 3. Three rotational constants, five centrifugal distortion constants, and one higher-order centrifugal distortion constant were determined precisely by least-squares analysis. The complex is shown to have a planer T-shaped structure with C2v symmetry. The structural analysis provides that the Ar atom is located 3.68 A from the center of mass of diacetylene. Force constants for the van der Waals vibrations were determined from the centrifugal distortion constants. It has been found that this complex has a much steeper and more harmonic intermolecular potential than the argon-acetylene complex. Copyright 1997 Academic Press. Copyright 1997Academic Press

  6. Nanometer-scale sharpening and surface roughening of ZnO nanorods by argon ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, Shyamal, E-mail: shyamal@iitbbs.ac.in [School of Basic Sciences, Indian Institute of Technology, Bhubaneswar 751013 (India); Behera, Akshaya K. [School of Basic Sciences, Indian Institute of Technology, Bhubaneswar 751013 (India); Banerjee, Amarabha; Tribedi, Lokesh C. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Som, Tapobrata [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Ayyub, Pushan, E-mail: pushan@tifr.res.in [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

    2012-07-01

    We report the effects of exposing a hydrothermally grown, single crystalline ZnO nanorod array to a beam of 50 keV argon ions at room temperature. High resolution electron microscopy reveals that the ion bombardment results in a nanometer-scale roughening of the nanorod sidewalls, which were almost atomically flat in the pristine sample. Ion bombardment further causes the flat, Almost-Equal-To 100 nm diameter nanorod tips to get sharpened to ultrafine points less than 10 nm across. While tip sharpening is attributed to preferential sputtering, the formation of crystalline surface protuberances can be ascribed to surface instability due to curvature dependent sputtering and surface diffusion under argon-ion bombardment. Both the nanoscale roughening as well as the tip sharpening are expected to favorably impact a wide variety of applications, such as those involving catalysis, gas sensing, solar cells, field emission and gas discharge.

  7. Photochemistry of the ozone-water complex in cryogenic neon, argon, and krypton matrixes.

    Science.gov (United States)

    Tsuge, Masashi; Tsuji, Kazuhide; Kawai, Akio; Shibuya, Kazuhiko

    2013-12-12

    The photochemistry of ozone-water complexes and the wavelength dependence of the reactions were studied by matrix isolation FTIR spectrometry in neon, argon, and krypton matrixes. Hydrogen peroxide was formed upon the irradiation of UV light below 355 nm. Quantitative analyses of the reactant and product were performed to evaluate the matrix cage effect of the photoreaction. In argon and krypton matrixes, a bimolecular O((1)D) + H2O → H2O2 reaction was found to occur to form hydrogen peroxide, where the O((1)D) atom generated by the photolysis of ozone diffused in the cryogenic solids to encounter water. In a neon matrix, hydrogen peroxide was generated through intracage photoreaction of the ozone-water complex, indicating that a neon matrix medium is most appropriate to study the photochemistry of the ozone-water complex.

  8. Effects of argon ion irradiation on nucleation and growth of silver nanoparticles in a soda-glass matrix

    Directory of Open Access Journals (Sweden)

    P. Gangopadhyay

    2011-09-01

    Full Text Available The present article explores an experimental study for nucleation and non-equilibrium growth of silver nanoparticles in a soda-glass matrix. Ion-irradiation induced recoiling of silver atoms with argon ions (at energy 100 keV facilitates nucleation as well as growth of the silver nanoparticles in the soda-glass matrix. Small growth of the silver nanoparticles in the soda-glass matrix has been experimentally observed after the irradiation with higher fluences of the argon ions. Role of the argon ions for the evolution of the silver nanoparticles in the soda-glass matrix has been elucidated in the present report. With increase of the argon-ion fluences, while slight athermal growth of the silver nanoparticles has been estimated, drastic increase in the optical responses and Rutherford backscattering (RBS yields of the silver nanoparticles have been observed in the sample with the maximum fluences. Possible correlations of increase of argon-ion fluences and the observed experimental results (optical and RBS, in particular have been explained in this article. Although it has been demonstrated using the silver metal film on a soda-glass substrate as a model example, the non-equilibrium approach of nucleation and ion-beam controlled growth of metal nanoparticles in a matrix should be applicable to other immiscible systems as well.

  9. FORMATION OF CARBON NANOSTRUCTURES USING ACETYLENE, ARGON-ACETYLENE AND ARGON-HYDROGEN-ACETYLENE PLASMAS

    OpenAIRE

    Marcinauskas, Liutauras; Grigonis, Alfonsas; Valincius, Vitas

    2013-01-01

    The amorphous carbon films were deposited on silicon-metal substrates by plasma jet chemical vapor deposition (PJCVD) and plasma enchanted CVD (PECVD). PJCVD carbon films have been prepared at atmospheric pressure in argon-acetylene and argon-hydrogen-acetylene plasma mixtures. The films deposited in Ar-C2H2 plasma are attributed to graphite-like carbon films. The formation of the nanocrystalline graphite was obtained in Ar-H2-C2H2 plasma. Addition of the hydrogen gas lead to the ...

  10. Generation of 275.4-nm UV output from a large-frame argon-ion laser for fluorescence detection in capillary electrophoresis.

    NARCIS (Netherlands)

    Kok, S.J.; de Ridder, T.; Brinkman, U.A.T.; Velthorst, N.H.; Gooijer, C.; Hoornweg, G.Ph.

    1998-01-01

    A standard, relatively old, large-frame argon-ion laser, which is available in many laboratories, was modified to produce output in the deep- UV (275-306 nm) region by installing a set of inexpensive, commercially available laser mirrors. The deep-UV output is generally applicable as excitation

  11. Infrared spectra and electronic structure calculations for NN complexes with U, UN, and NUN in solid argon, neon, and nitrogen.

    Science.gov (United States)

    Andrews, Lester; Wang, Xuefeng; Gong, Yu; Kushto, Gary P; Vlaisavljevich, Bess; Gagliardi, Laura

    2014-07-17

    Reactions of laser-ablated U atoms with N2 molecules upon codeposition in excess argon or neon at 4 K gave intense NUN and weak UN absorptions. Annealing produced progressions of new absorptions for the UN2(N2)1,2,3,4,5 and UN(N2)1,2,3,4,5,6 complexes. The neon-to-argon matrix shift decreases with increasing NN ligation and therefore the number of noble gas atoms left in the primary coordination sphere around the NUN molecule. Small matrix shifts are observed when the secondary coordination layers around the primary UN2(N2)1,2,3,4,5 and UN(N2)1,2,3,4,5,6 complexes are changed from neon-to-argon to nitrogen. Electronic structure, energy, and frequency calculations provide support for the identification of these complexes and the characterization of the N≡U≡N and U≡N core molecules as terminal uranium nitrides. Codeposition of U with pure nitrogen produced the saturated U(NN)7 complex, which UV irradiation converted to the NUN(NN)5 complex with slightly lower frequencies than found in solid argon.

  12. Ionization of Water Clusters is Mediated by Exciton Energy Transfer from Argon Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Golan, Amir; Ahmed, Musahid

    2012-01-25

    The exciton energy deposited in an argon cluster, (Arn ,< n=20>) using VUV radiation is transferred to softly ionize doped water clusters, ((H2O)n, n=1-9) leading to the formation of non-fragmented clusters. Following the initial excitation, electronic energy is channeled to ionize the doped water cluster while evaporating the Ar shell, allowing identification of fragmented and complete water cluster ions. Examination of the photoionization efficiency curve shows that cluster evaporation from excitons located above 12.6 eV are not enough to cool the energized water cluster ion, and leads to their dissociation to (H2O)n-2H+ (protonated) clusters.

  13. Excited Delirium

    Directory of Open Access Journals (Sweden)

    Takeuchi, Asia

    2011-02-01

    Full Text Available Excited (or agitated delirium is characterized by agitation, aggression, acute distress and sudden death, often in the pre-hospital care setting. It is typically associated with the use of drugs that alter dopamine processing, hyperthermia, and, most notably, sometimes with death of the affected person in the custody of law enforcement. Subjects typically die from cardiopulmonary arrest, although the cause is debated. Unfortunately an adequate treatment plan has yet to be established, in part due to the fact that most patients die before hospital arrival. While there is still much to be discovered about the pathophysiology and treatment, it is hoped that this extensive review will provide both police and medical personnel with the information necessary to recognize and respond appropriately to excited delirium. [West J Emerg Med. 2011;12(1:77-83.

  14. Modeling Neutral-Current Neutrino Interactions in Liquid Argon

    Science.gov (United States)

    Nunez, Cynthia; Scholberg, Kate; Conley, Erin; Deep Underground Neutrino Experiment Collaboration

    2017-09-01

    Studies of supernova neutrinos provide knowledge of neutrino oscillations and supernova physics. The Deep Underground Neutrino Experiment (DUNE) will enable exploration of the three-flavor model of neutrino physics and solve questions in regards to the dynamics of supernova, the stability of matter, and matter-antimatter asymmetry. DUNE will use a Liquid Argon Time-Projection Chamber (LArTPC) which will be able to detect charged-current, neutral-current, and elastic-scattering interactions. The neutral current ν-40 Ar interaction leaves an excited 40 Ar nucleus that releases a 9.8 MeV gamma which is analyzed for the LArTPC. This project creates a smearing file for SNOwGLoBES, an event rate calculator, that corresponds to the DUNE detector simulation for this interaction. The expected number of neutral current supernova neutrino events in liquid 40 Ar is determined and the observable energy distribution is examined. NSF REU Program (NSF-PHY-1461204).

  15. Diode Laser Based LIF Diagnostics for Argon and Helium Plasmas.

    Science.gov (United States)

    Stolzenberg, E.; Boivin, R. F.; Compton, C.; Hardin, R.; Keesee, A.; Kline, J. L.; Scime, E. E.

    2002-11-01

    A diode laser based Laser Induced Fluorescence (LIF) diagnostic that uses an inexpensive diode laser system is presented. The same diode laser is used to pump Ar II and He I transitions to obtain the ion and the neutral temperature of the respective species. The 1 MHz bandwidth diode laser has a Littrow external cavity with a mode-hop free tuning range up to 15 GHz and with a total power output of about 10 mWatt. The wavelength is measured by a wavemeter and frequent monitoring prevent wavelength drift. For the argon ion population, the laser tuned at 668.61 nm, is used to pump the 3d4F7/2 Ar II metastable level to the 4p4D5/2 excited level. The fluorescence radiation between the 4p4D5/2 and the 4s4P3/2 levels (442.6 nm) is monitored by a photomultiplier detector. For neutral helium, the laser is tuned at 667.82 nm to pump a fraction of the electron population from the 21P state to the 31D upper level. Although the 21P level is not a metastable state, the close proximity of 21S metastable level makes this new He I LIF possible in collisional plasmas. Some electrons of this 31D level undergo collisional excitation transfer (optically allowed transition) to the 31P. In turn, this state decay to the metastable 21S by emitting 501.6 nm fluorescence photons. The new LIF diagnostic has been developed at West Virginia University (WVU) and tested on the Hot hELIcon eXperiment (HELIX) plasma device. Ion and neutral temperatures obtained using this new LIF diagnostic are presented and compared to previous measurements performed with a more expensive and elaborate ring dye laser system.

  16. Argon generation in fusion reactor materials

    Energy Technology Data Exchange (ETDEWEB)

    Khripunov, Vladimir, E-mail: Khripunov_VI@NRCKI.ru

    2015-10-15

    Highlights: • A relatively long-lived Ar-39 (T{sub 1/2} = 269 yr) may appear in fusion reactor materials. • Ar-39 activities may become apparent after tritium removal. • Initial impurity control of K is definitely recommended. • A substantiation of the effective dose rates for exposure to inert argon is urgent. - Abstract: Different candidate plasma facing materials (as tungsten, beryllium), the low activation structure materials (as vanadium alloys, silicon carbides), liquid breeders (lithium and lithium-lead) and some others have been suggested for future fusion power reactor cores as corresponding to maintenance, recycling and for waste disposal acceptance after 50 and 100 years of cooling. It is shown by the neutron activation analysis that a relatively short-lived Ar-41 (T{sub 1/2} = 1.85 h), Ar-37 (T{sub 1/2} = 35 days) and rather long lived Ar-39 (T{sub 1/2} = 269 yr) may appear in these materials under the fusion neutron irradiation conditions. While argon production is essentially less than helium production in irradiated materials, at other times its impact, e.g., in the inhalation dose, becomes significant. In some cases the Ar-39 activity is comparable or even exceeds the C-14 activity and may become apparent after tritium removal from plasma exhaust and dust, from the liquid breeders, during plasma-facing and structural component recycling and waste management. The main source terms of argon-39 activity for these materials are identified and the specific production rates are evaluated relative to radiation conditions of a power or DEMO fusion reactor and to electric power production.

  17. Resonant coherent excitation of channeled ions

    Energy Technology Data Exchange (ETDEWEB)

    Datz, S.; Moak, C.D.; Crawford, O.H.; Krause, H.F.; Dittner, P.F.; Gomez del Campo, J.; Biggerstaff, J.A.; Miller, P.D.; Hvelplund, P.; Knudsen, H.

    1978-03-27

    We have observed resonant excitation of swift channeled hydrogenlike ions (Z = 5 to Z = 9) and heliumlike F/sup 7 +/ which arises from a coherent periodic perturbation by the atoms in the bounding crystal rows. The resonance excitation was seen through the reduction in the transmission of fixed-charge-state ions through channels in thin crystals of Au and Ag.

  18. POLARIS: Portable Liquid Argon Imaging Scintillator

    Science.gov (United States)

    Jia, Yanyu; Kovacs, Benjamin; Kamp, Nicholas; Aidala, Christine; Polaris Team

    2017-09-01

    Liquefied noble gas detectors have become widely used in nuclear and particle physics, in particular for detecting neutrinos and in dark matter searches. However, their potential for neutron detection in low-energy nuclear physics has not yet been realized. The University of Michigan has been constructing a hybrid scintillating time projection chamber for detection of neutrons in the 200 keV 10 MeV range. The scintillation material is argon, and various dopants to improve detector efficiency are being explored. With collection of both scintillation light and ionization charge, improved energy resolution for neutrons is expected compared to existing measurement techniques.

  19. Near-infrared scintillation of liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, T. [Fermilab; Escobar, C. O. [Campinas State U.; Lippincott, W. H. [Fermilab; Rubinov, P. [Fermilab

    2016-03-03

    Since the 1970s it has been known that noble gases scintillate in the near infrared (NIR) region of the spectrum (0.7 $\\mu$m < $\\lambda$; < 1.5$\\mu$m). More controversial has been the question of the NIR light yield for condensed noble gases. We first present the motivation for using the NIR scintillation in liquid argon detectors, then briefly review early as well as more recent efforts and finally show encouraging preliminary results of a test performed at Fermilab.

  20. Magnetism of a single atom

    NARCIS (Netherlands)

    Otte, Alexander Ferdinand

    2008-01-01

    A low-temperature scanning tunneling microscope is used to perform spin-excitations on individual magnetic transition metal atoms when placed onto a crystal surface. By following these excitations while applying external magnetic fields the precise influence of the anisotropic crystal field on the

  1. Study of low-energy resonant metastability exchange in argon by a pulsed merging beam technique

    Energy Technology Data Exchange (ETDEWEB)

    Grucker, J [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13, Av. J.B. Clement, 93430-Villetaneuse (France); Baudon, J [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13, Av. J.B. Clement, 93430-Villetaneuse (France); Perales, F [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13, Av. J.B. Clement, 93430-Villetaneuse (France); Dutier, G [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13, Av. J.B. Clement, 93430-Villetaneuse (France); Vassilev, G [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13, Av. J.B. Clement, 93430-Villetaneuse (France); Bocvarski, V [Institute of Physics, Belgrade, Pregrevica 118, 11080, Zemun (Serbia); Ducloy, M [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13, Av. J.B. Clement, 93430-Villetaneuse (France)

    2008-01-28

    The resonant metastability exchange process in low-energy collinear collisions between metastable argon atoms (Ar* {sup 3}P{sub 2}) polarized in spin (M +2) and ground-state Ar atoms from a nozzle beam is studied by means of a time-of-flight technique. A wide range of metastable atom velocities in the laboratory frame (275 m s{sup -1} down to 50 m s{sup -1}) is obtained by use of a Zeeman slower, the counter-propagating laser beam of which is locked in frequency onto the {sup 3}P{sub 2}-{sup 3}D{sub 3} closed transition ({lambda} = 811.5 nm). The accessible centre-of-mass energy range (8-27 meV) has not been explored so far, to our knowledge. Calculations based upon existing interatomic potentials of 2{sub g} and 2{sub u} symmetries are in reasonable agreement with experiment. (fast track communication)

  2. Method and apparatus for transport, introduction, atomization and excitation of emission spectrum for quantitative analysis of high temperature gas sample streams containing vapor and particulates without degradation of sample stream temperature

    Science.gov (United States)

    Eckels, David E.; Hass, William J.

    1989-05-30

    A sample transport, sample introduction, and flame excitation system for spectrometric analysis of high temperature gas streams which eliminates degradation of the sample stream by condensation losses.

  3. FAC: Flexible Atomic Code

    Science.gov (United States)

    Gu, Ming Feng

    2018-02-01

    FAC calculates various atomic radiative and collisional processes, including radiative transition rates, collisional excitation and ionization by electron impact, energy levels, photoionization, and autoionization, and their inverse processes radiative recombination and dielectronic capture. The package also includes a collisional radiative model to construct synthetic spectra for plasmas under different physical conditions.

  4. Argon purification studies and a novel liquid argon re-circulation system

    Science.gov (United States)

    Mavrokoridis, K.; Calland, R. G.; Coleman, J.; Lightfoot, P. K.; McCauley, N.; McCormick, K. J.; Touramanis, C.

    2011-08-01

    Future giant liquid argon (LAr) time projection chambers (TPCs) require a purity of better than 0.1 parts per billion (ppb) to allow the ionised electrons to drift without significant capture by any electronegative impurities. We present a comprehensive study of the effects of electronegative impurity on gaseous and liquid argon scintillation light, an analysis of the efficiency of various purification chemicals, as well as the Liverpool LAr setup, which utilises a novel re-circulation purification system. Of the impurities tested - Air, O2, H2O, N2 and CO2 in the range of between 0.01 ppm to 1000 ppm - H2O was found to have the most profound effect on gaseous argon scintillation light, and N2 was found to have the least. Additionally, a correlation between the slow component decay time and the total energy deposited with 0.01 ppm - 100 ppm O2 contamination levels in liquid argon has been established. The superiority of molecular sieves over anhydrous complexes at absorbing Ar gas, N2 gas and H2O vapour has been quantified using BET isotherm analysis. The efficiency of Cu and P2O5 at removing O2 and H2O impurities from 1 bar N6 argon gas at both room temperature and -130 °C was investigated and found to be high. A novel, highly scalable LAr re-circulation system has been developed. The complete system, consisting of a motorised bellows pump operating in liquid and a purification cartridge, were designed and built in-house. The system was operated successfully over many days and achieved a re-circulation rate of 27 litres/hour and high purity.

  5. Temperature dependence of the intensity of the vibration-rotational absorption band ν2 of H2O trapped in an argon matrix

    Science.gov (United States)

    Pitsevich, G.; Doroshenko, I.; Malevich, A..; Shalamberidze, E.; Sapeshko, V.; Pogorelov, V.; Pettersson, L. G. M.

    2017-02-01

    Using two sets of effective rotational constants for the ground (000) and the excited bending (010) vibrational states the calculation of frequencies and intensities of vibration-rotational transitions for J″ = 0 - 2; and J‧ = 0 - 3; was carried out in frame of the model of a rigid asymmetric top for temperatures from 0 to 40 K. The calculation of the intensities of vibration-rotational absorption bands of H2O in an Ar matrix was carried out both for thermodynamic equilibrium and for the case of non-equilibrium population of para- and ortho-states. For the analysis of possible interaction of vibration-rotational and translational motions of a water molecule in an Ar matrix by 3D Schrödinger equation solving using discrete variable representation (DVR) method, calculations of translational frequencies of H2O in a cage formed after one argon atom deleting were carried out. The results of theoretical calculations were compared to experimental data taken from literature.

  6. Commissioning of the ATLAS Liquid Argon Calorimeter

    CERN Document Server

    Gibson, A; The ATLAS collaboration

    2009-01-01

    The Liquid Argon calorimeter (LAr) is one of the main sub-detectors in the ATLAS experiment at the LHC. It provides precision measurements of electrons, photons, jets and missing transverse energy produced in the LHC pp collisions. The LAr calorimeter has been installed in the ATLAS cavern and filled with liquid argon since 2006. The electronic calibration of the readout system, a critical system for precision measurements, has been continuously exercised in the commissioning phase, resulting in a fully commissioned calorimeter with its readout and a small number of problematic channels. A total of only 0.02% of the read out channels are dead beyond repair and 0.4% need special treatment for calibration. Throughout the last two years a large amount of calibration data has been collected. Cosmic muon data, first triggered via specially developed trigger boards on the LVL1 output of the Tile calorimeter and later with the standard ATLAS LVL1 calorimeter trigger, have been recorded at various stages of commissio...

  7. Darkside: A Depleted Argon Dark Matter Search

    Energy Technology Data Exchange (ETDEWEB)

    Alton, Drew; Durben, Dan; Keeter, Kara; Zehfus, Michael; Brice, Steve; Chou, Aaron; Hall, Jeter; Jostlein, Hans; Pordes, Stephen; Sonnenschein, Andrew; Brodsky, Jason [et al.

    2009-10-01

    The existence of dark matter is known from gravitational effects, but its nature remains a deep mystery. One possibility motivated by other considerations in elementary particle physics is that dark matter consists of undiscovered elementary particles. Axions and Weakly Interacting Massive Particles (WIMPs) are two possibilities. Evidence for new particles that could constitute WIMP dark matter may come from upcoming experiments at the Large Hadron Collider at CERN or from sensitive astronomical instruments that detect radiation produced by WIMP-WIMP annihilations in galaxy halos. The thermal motion of the WIMPS comprising the dark matter halo surrounding the galaxy and the earth should result in WIMP-nuclear collisions of sufficient energy to be observable by sensitive laboratory apparatus. The goal of this proposal is to develop and deploy a liquid argon detector that has high sensitivity for direct detection of WIMP collisions. Liquid argon is a promising medium for WIMP detection due to its efficient conversion of energy from WIMP induced nuclear recoils into both ionization and scintillation. In a Time Projection Chamber (TPC), scintillation and ionization can be independently detected and spatially resolved through large volumes of liquid. The relative size and time dependence of these signals permits discrimination of nuclear recoils from background events.

  8. Electron scattering and transport in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, G. J.; Cocks, D. G.; White, R. D. [College of Science, Technology and Engineering, James Cook University, Townsville 4810 (Australia); McEachran, R. P. [Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia)

    2015-04-21

    The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann’s equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.

  9. Pollution of liquid argon after neutron irradiation

    CERN Document Server

    Andrieux, M L; Collot, J; de Saintignon, P; Ferrari, A; Hostachy, J Y; Hoummada, A; Martin, P; Merkel, B; Puzo, P; Sauvage, D; Wielers, M

    2001-01-01

    The purpose of the neutron facility installed at SARA is to investigate the behavior of various materials to be used in the ATLAS liquid argon calorimeter, when submitted to fast neutron radiation. The samples are placed in a liquid argon cryostat a few cm away from the neutron source. Various pieces of the electromagnetic calorimeter have been tested in order to evaluate the rate of pollution of the liquid and consequently the possible signal loss in energy measurements. The average fluence was equivalent to the maximum expected in the calorimeter in about 10 years. The most striking feature of the results is that the pollution is not due to oxygen, at least for most of it. Using a particular value of the absorption length derived from these data, a simulation was carried out and the energy signal loss in the calorimeter could be predicted. Within the limits of our present knowledge, the conclusion is that damages due to this pollution will not be a problem. (17 refs).

  10. Impact of Argon gas on optical and electrical properties of Carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Usman, Arslan, E-mail: arslan.usman@gmail.com [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan); Rafique, M.S. [Department of Physics, University of Engineering & Technology, Lahore 54890 (Pakistan); Shaukat, S.F. [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan); Siraj, Khurram [Department of Physics, University of Engineering & Technology, Lahore 54890 (Pakistan); Ashfaq, Afshan [Institute of Nuclear Medicine and Oncology Lahore (INMOL), 54000 Pakistan (Pakistan); Anjum, Safia [Department of Physics, Lahore College for Women University (Pakistan); Imran, Muhammad; Sattar, Abdul [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan)

    2016-12-15

    Nanostructured thin films of carbon were synthesized and investigated for their electrical, optical, structural and surface properties. Pulsed Laser Deposition (PLD) technique was used for the preparation of these films under Argon gas environment. A KrF Laser (λ=248 nm) was used as source of ablation and plasma formation. It was observed that the carbon ions and the background gas environment has deep impact on the morphology as well as on the microstructure of the films. Time of Flight (TOF) method was used to determine the energies of the ablated carbon ions. The morphology of film surfaces deposited at various argon pressure was analysed using an atomic force microscope. The Raman spectroscopic measurement reveal that there is shift in phase from sp{sup 3} to sp{sup 2} and a decrease in FWHM of G band, which is a clear indication of enhanced graphitic clusters. The electrical resistivity was also reduced from 85.3×10{sup −1} to 2.57×10{sup −1} Ω-cm. There is an exponential decrease in band gap E{sub g} of the deposited films from 1.99 to 1.37 eV as a function of argon gas pressure.

  11. Role of atoms in atomic gravitational-wave detectors

    Science.gov (United States)

    Norcia, Matthew A.; Cline, Julia R. K.; Thompson, James K.

    2017-10-01

    Recently, it has been proposed that space-based atomic sensors may be used to detect gravitational waves. These proposals describe the sensors either as clocks or as atom interferometers. Here, we seek to explore the fundamental similarities and differences between the two types of proposals. We present a framework in which the fundamental mechanism for sensitivity is identical for clock and atom interferometer proposals, with the key difference being whether or not the atoms are tightly confined by an external potential. With this interpretation in mind, we propose two major enhancements to detectors using confined atoms, which allow for an enhanced sensitivity analogous to large momentum transfer used in atom interferometry (though with no transfer of momentum to the atoms), and a way to extend the useful coherence time of the sensor beyond the atom's excited-state lifetime.

  12. Improved installation prototype for measurement of low argon-37 activity

    Science.gov (United States)

    Pakhomov, Sergei; Dubasov, Yuri

    2015-04-01

    On-site Inspection (OSI) is a key element of verification of State Parties' compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). An on-site inspection is launched to establish whether or not a nuclear explosion has been carried out. One of the most significant evidence of n underground nuclear explosion (UNE) is detection above background concentrations of argon-37 in near surface air. Argon-37 is formed in large amounts at interaction of neutrons of UNE with the potassium which is a part of the majority of rocks. Its estimated contents for the 100th days after explosion with a energy of 1000 t of TNT near a surface can vary from 1 to 1000 mBq/m3. The background concentrations of argon-37 in subsoil air vary 1 do100 mBq/m3. Traditionally, for argon-37 activity measurement the gas-proportional counters are used. But at Khlopin Radium institute the developments of the new type of highly sensitive and low-background installation capable to provide the required range of measurements of the argon-37 concentration are conducted. The liquid scintillation method of the registration of the low-energetic argon-37 electrons is the basic installation principle and as scintillator, the itself condensed air argon sample is used. Registration of scintillations of liquid argon is made by means of system from 3 PMT which cathodes are cooled near to the temperature of liquid nitrogen together with the measuring chamber in which placed the quartz glass ampule, containing the measured sample of the liquefied argon. For converse the short wavelength photons (λ = 127 nm) of liquid argon scintillations to more long-wave, corresponding to the range of PMT sensitivity, the polymer film with tetra-phenyl-butadiene (TPB) is provided. Even the insignificant impurities of nitrogen, oxygen and others gaseous in the liquid argon samples can to cause the quenching of scintillation, especially their slow components. To account this effect and it influence on change of registration

  13. EPR-Spin Trapping and Flow Cytometric Studies of Free Radicals Generated Using Cold Atmospheric Argon Plasma and X-Ray Irradiation in Aqueous Solutions and Intracellular Milieu.

    Science.gov (United States)

    Uchiyama, Hidefumi; Zhao, Qing-Li; Hassan, Mariame Ali; Andocs, Gabor; Nojima, Nobuyuki; Takeda, Keigo; Ishikawa, Kenji; Hori, Masaru; Kondo, Takashi

    2015-01-01

    Electron paramagnetic resonance (EPR)-spin trapping and flow cytometry were used to identify free radicals generated using argon-cold atmospheric plasma (Ar-CAP) in aqueous solutions and intracellularly in comparison with those generated by X-irradiation. Ar-CAP was generated using a high-voltage power supply unit with low-frequency excitation. The characteristics of Ar-CAP were estimated by vacuum UV absorption and emission spectra measurements. Hydroxyl (·OH) radicals and hydrogen (H) atoms in aqueous solutions were identified with the spin traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO), and phenyl N-t-butylnitrone (PBN). The occurrence of Ar-CAP-induced pyrolysis was evaluated using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) in aqueous solutions of DNA constituents, sodium acetate, and L-alanine. Human lymphoma U937 cells were used to study intracellular oxidative stress using five fluorescent probes with different affinities to a number of reactive species. The analysis and quantification of EPR spectra revealed the formation of enormous amounts of ·OH radicals using Ar-CAP compared with that by X-irradiation. Very small amounts of H atoms were detected whereas nitric oxide was not found. The formation of ·OH radicals depended on the type of rare gas used and the yield correlated inversely with ionization energy in the order of krypton > argon = neon > helium. No pyrolysis radicals were detected in aqueous solutions exposed to Ar-CAP. Intracellularly, ·OH, H2O2, which is the recombination product of ·OH, and OCl- were the most likely formed reactive oxygen species after exposure to Ar-CAP. Intracellularly, there was no practical evidence for the formation of NO whereas very small amounts of superoxides were formed. Despite the superiority of Ar-CAP in forming ·OH radicals, the exposure to X-rays proved more lethal. The mechanism of free radical formation in aqueous solutions and an

  14. EPR-Spin Trapping and Flow Cytometric Studies of Free Radicals Generated Using Cold Atmospheric Argon Plasma and X-Ray Irradiation in Aqueous Solutions and Intracellular Milieu.

    Directory of Open Access Journals (Sweden)

    Hidefumi Uchiyama

    Full Text Available Electron paramagnetic resonance (EPR-spin trapping and flow cytometry were used to identify free radicals generated using argon-cold atmospheric plasma (Ar-CAP in aqueous solutions and intracellularly in comparison with those generated by X-irradiation. Ar-CAP was generated using a high-voltage power supply unit with low-frequency excitation. The characteristics of Ar-CAP were estimated by vacuum UV absorption and emission spectra measurements. Hydroxyl (·OH radicals and hydrogen (H atoms in aqueous solutions were identified with the spin traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO, 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO, and phenyl N-t-butylnitrone (PBN. The occurrence of Ar-CAP-induced pyrolysis was evaluated using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS in aqueous solutions of DNA constituents, sodium acetate, and L-alanine. Human lymphoma U937 cells were used to study intracellular oxidative stress using five fluorescent probes with different affinities to a number of reactive species. The analysis and quantification of EPR spectra revealed the formation of enormous amounts of ·OH radicals using Ar-CAP compared with that by X-irradiation. Very small amounts of H atoms were detected whereas nitric oxide was not found. The formation of ·OH radicals depended on the type of rare gas used and the yield correlated inversely with ionization energy in the order of krypton > argon = neon > helium. No pyrolysis radicals were detected in aqueous solutions exposed to Ar-CAP. Intracellularly, ·OH, H2O2, which is the recombination product of ·OH, and OCl- were the most likely formed reactive oxygen species after exposure to Ar-CAP. Intracellularly, there was no practical evidence for the formation of NO whereas very small amounts of superoxides were formed. Despite the superiority of Ar-CAP in forming ·OH radicals, the exposure to X-rays proved more lethal. The mechanism of free radical formation in aqueous solutions and

  15. Autoresonant Excitation of Antiproton Plasmas

    CERN Document Server

    Andresen, Gorm B; Baquero-Ruiz, Marcelo; Bertsche, William; Bowe, Paul D; Butler, Eoin; Carpenter, P T; Cesar, Claudio L; Chapman, Steven; Charlton, Michael; Fajans, Joel; Friesen, Tim; Fujiwara, Makoto C; Gill, David R; Hangst, Jeffrey S; Hardy, Walter N; Hayden, Michael E; Humphries, Andrew J; Hurt, J L; Hydomako, Richard; Jonsell, Svante; Madsen, Niels; Menary, Scott; Nolan, Paul; Olchanski, Konstantin; Olin, Art; Povilus, Alexander; Pusa, Petteri; Robicheaux, Francis; Sarid, Eli; Silveira, Daniel M; So, Chukman; Storey, James W; Thompson, Robert I; van der Werf, Dirk P; Wurtele, Jonathan S; Yamazaki, Yasunori

    2011-01-01

    We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.

  16. ArgonCube: a Modular Approach for Liquid Argon TPC Neutrino Detectors for Near Detector Environments

    CERN Document Server

    Auger, M; Sinclair, JR

    2017-01-01

    Liquid Argon Time Projection Chambers (LAr TPCs) are an ideal detector candidate for future neutrino oscillation physics experiments, underground neutrino observatories and proton decay searches. A large international project based on this technology is currently under consideration at the future LBNF/DUNE facility in the United States. That particular endeavor would be on the very large mass scale of 40~kt. Following diverse and long standing R\\&D work conducted over several years, with contributions from international collaborators, we propose a novel LAr TPC based on a fully-modular, innovative design, ArgonCube. ArgonCube will demonstrate that LAr TPCs are a viable detector technology for high-energy and high-multiplicity environments, such as the DUNE near detector. Necessary R\\&D work is proceeding along two main pathways; the first, aimed at the demonstration of modular detector design and the second, at the exploration of new signal readout methods. This two-pronged approach has provided a hig...

  17. Formation of non-excited and excited hydrogen in proton–lithium inelastic scattering

    National Research Council Canada - National Science Library

    Elkilany, S.A; Al-Dhawi, A.A

    The collisions of a proton with a lithium atom are treated for the first time as a three-channel problem under the assumption that the elastic and hydrogen formation in non-excited, H(1s), and excited, H(2s), channels are open...

  18. Elementary excitations of ferromagnetic metal nanoparticles

    Science.gov (United States)

    Cehovin, A.; Canali, C.; MacDonald, A.

    2003-07-01

    We present a theory of the elementary spin excitations in transition-metal ferromagnet nanoparticles which achieves a unified and consistent quantum description of both collective and quasiparticle physics. The theory starts by recognizing the essential role played by spin-orbit interactions in determining the energies of ferromagnetic resonances in the collective excitation spectrum and the strength of their coupling to low-energy particle-hole excitations. We argue that a crossover between Landau-damped ferromagnetic resonance and pure-state collective magnetic excitations occurs as the number of atoms in typical transition-metal ferromagnet nanoparticles drops below approximately 104, about where the single-particle level spacing, δ, becomes larger than (α)Eres, where Eres is the ferromagnetic resonance frequency and α is the Gilbert damping parameter. We illustrate our ideas by studying the properties of semirealistic model Hamiltonians, which we solve numerically for nanoparticles containing several hundred atoms. For small nanoparticles, we find one isolated ferromagnetic resonance collective mode below the lowest particle-hole excitation energy, at Eres≈0.1 meV. The spectral weight of this pure excitation nearly exhausts the transverse dynamical susceptibility spectral weight. As δ approaches (α)Eres, the ferromagnetic collective excitation is more likely to couple strongly with discrete particle-hole excitations. In this regime the distinction between the two types of excitations blurs. We discuss the significance of this picture for the interpretation of recent single-electron tunneling experiments.

  19. Laser Control of Atoms and Molecules

    CERN Document Server

    Letkhov, V S

    2007-01-01

    This text treats laser light as a universal tool to control matter at the atomic and molecular level, one of the most exciting applications of lasers. Lasers can heat matter, cool atoms to ultra-low temperatures where they show quantum collective behaviour, and can act selectively on specific atoms and molecules for their detection and separation.

  20. Effect of argon gas flow rate on properties of film electrodes prepared by thermal vacuum evaporation from synthesized Cu{sub 2}SnSe{sub 3} source

    Energy Technology Data Exchange (ETDEWEB)

    Sabli, Nordin; Talib, Zainal Abidin; Yunus, Wan Mahmood Mat [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang (Malaysia); Zainal, Zulkarnain [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang (Malaysia); Hilal, Hikmat S. [SSERL, Department of Chemistry An-Najah N. University, PO Box 7, Nablus, West Bank (Country Unknown); Fujii, Masatoshi [Department of Molecular Science, School of Medicine, Shimane University, Izumo, Shimane, 693-8501 (Japan)

    2014-03-05

    This work describes a new technique to enhance photoresponse of metal chalcogenide-based semiconductor film electrodes deposited by thermal vacuum evaporation under argon gas flow from synthesized Cu{sub 2}SnSe{sub 3} sources. SnSe formation with Cu-doped was obtained under higher argon gas flow rate (V{sub A} = 25 cm{sup 3}/min). Higher value of photoresponse was observed for films deposited under V{sub A} = 25 cm{sup 3}/min which was 9.1%. This finding indicates that Cu atoms inside the SnSe film were important to increase carrier concentrations that promote higher photoresponse.

  1. Size dependent ionization dynamics of argon clusters in intense x-ray pulses

    Science.gov (United States)

    Schorb, Sebastian; Rupp, D.; Swiggers, M.; Coffee, R. N.; Messerschmidt, M.; Williams, G.; Bozek, J. D.; Wada, S.-I.; Möller, T.; Bostedt, C.

    2012-06-01

    Free Electron Lasers open the door for novel experiments in many science areas ranging from ultrafast chemical dynamics to single shot imaging of molecules. For the success of virtually all experiments with free electron lasers a detailed understanding of the light - matter interaction in the x-ray regime is pivotal. The Linac Coherent Light Source (LCLS) free electron laser in Stanford allows for the first time to study innershell ionization dynamics of intense x-ray pulses on a femtosecond time scale. We performed experiments on the ionization dynamics of Argon clusters at different pulse length using the slotted spoiler foil in the second LCLS bunch compressor [1]. The Auger rate of argon clusters is predicted to be size dependent and lower than in atoms due to delocalization of the valence electrons [2]. We observe a dependence of the ionization dynamics on pulse length and cluster size. The results are discussed and also compared to recent atomic and molecular data from LCLS.[4pt] [1] P. Emma et al. PRL 92, 074801 (2004)[0pt] [2] U. Saalmann, JM Rost PRL 89, 14 (2002)

  2. Femtosecond laser excitation of mixed Ar/Kr clusters: peculiarities of K-line x-ray production from nanoplasma under varied fraction of initial gas components

    Science.gov (United States)

    Zhvaniya, I. A.; Dzhidzhoev, M. S.; Gordienko, V. M.

    2017-09-01

    For the first time, we defined the range of krypton fraction (C Kr) in an initial binary Ar-Kr gas mixture that provides the production of large (N ~ 106 atoms/cluster) mixed Ar/Kr clusters under co-expansion of the mixture at room temperature and the stagnant pressure of 25 bar. Mixed Ar/Kr clusters exist at the krypton fraction of 3-15%. The presence of mixed clusters is detected by the simultaneous generation of both x-ray Kα lines of argon (E  =  3.1 keV) and krypton (E  =  12.7 keV) from nanoplasma originating as a result of femtosecond nonlinear laser excitation with intensity about 5 · 1017 W cm-2. It was shown that the amplitude of lines in dual-energy x-ray spectrum can be controlled by proper selection of the fraction of initial gas mixture components. Maximal laser energy conversion efficiency to krypton x-ray line is achieved for pure krypton clusters (i.e. C Kr  =  100%) and reaches 2 · 10-7 at laser intensity of 5 · 1017 W cm-2. The laser energy conversion efficiency to argon x-ray line reaches the maximal value of 3 · 10-6 at C kr  =  0%.

  3. Cavity QED with atomic mirrors

    Science.gov (United States)

    Chang, D. E.; Jiang, L.; Gorshkov, A. V.; Kimble, H. J.

    2012-06-01

    A promising approach to merge atomic systems with scalable photonics has emerged recently, which consists of trapping cold atoms near tapered nanofibers. Here, we describe a novel technique to achieve strong, coherent coupling between a single atom and photon in such a system. Our approach makes use of collective enhancement effects, which allow a lattice of atoms to form a high-finesse cavity within the fiber. We show that a specially designated ‘impurity’ atom within the cavity can experience strongly enhanced interactions with single photons in the fiber. Under realistic conditions, a ‘strong coupling’ regime can be reached, wherein it becomes feasible to observe vacuum Rabi oscillations between the excited impurity atom and a single cavity quantum. This technique can form the basis for a scalable quantum information network using atom-nanofiber systems.

  4. Pressure broadening of acetylene rotational Raman lines by argon

    NARCIS (Netherlands)

    Ceruti, M.; Frenkel, D.; McTaque, J.P.

    1980-01-01

    The anisotropic interaction between acetylene and argon has been studied by observing the density dependence of the acetylene pure rotational Raman line broadening. The observed cross sections are approximately twice that predicted from the known polarizabilities and acetylene molecular quadrupole

  5. Characterising argon-bomb balloons for high-speed photography

    CSIR Research Space (South Africa)

    Olivier, M

    2013-08-01

    Full Text Available -1 SABO 2013 TME Workshop Alkantpan Characterising Argon-bomb balloons for High-speed Photography M Olivier and FJ Mostert Landward Sciences, Defence Peace Safety and Security, CSIR, Meiring Naude Road, Pretoria, RSA. Abstract A...

  6. Quenching of the OH and nitrogen molecular emission by methane addition in an Ar capacitively coupled plasma to remove spectral interference in lead determination by atomic fluorescence spectrometry

    Science.gov (United States)

    Frentiu, T.; Ponta, M.; Mihaltan, A. I.; Darvasi, E.; Frentiu, M.; Cordos, E.

    2010-07-01

    A new method is proposed to remove the spectral interference on elements in atomic fluorescence spectrometry by quenching of the molecular emission of the OH radical (A 2Σ + → X 2Π) and N 2 second positive system (C 3Π u → B 3Σ g) in the background spectrum of medium power Ar plasmas. The experiments were carried out in a radiofrequency capacitively coupled plasma (275 W, 27.12 MHz) by CH 4 addition. The quenching is the result of the high affinity of OH radical for a hydrogen atom from the CH 4 molecule and the collisions of the second kind between nitrogen excited molecules and CH 4, respectively. The decrease of the emission of N 2 second positive system in the presence of CH 4 is also the result of the deactivation of the metastable argon atoms that could excite the nitrogen molecules. For flow rates of 0.7 l min - 1 Ar with addition of 7.5 ml min - 1 CH 4, the molecular emission of OH and N 2 was completely removed from the plasma jet spectrum at viewing heights above 60 mm. The molecular emission associated to CH and CH 2 species was not observed in the emission spectrum of Ar/CH 4 plasma in the ultraviolet range. The method was experimented for the determination of Pb at 283.31 nm by atomic fluorescence spectrometry with electrodeless discharge lamp and a multichannel microspectrometer. The detection limit was 35 ng ml - 1 , 2-3 times better than in atomic emission spectrometry using the same plasma source, and similar to that in hollow cathode lamp microwave plasma torch atomic fluorescence spectrometry.

  7. Determination of thicknesses of oxide films grown on titanium under argon irradiation by spectroscopic ellipsometry

    Science.gov (United States)

    Do, Ngoc-Long; Garcia-Caurel, Enric; Bérerd, Nicolas; Moncoffre, Nathalie; Gorse-Pomonti, Dominique

    2014-04-01

    In this article we present a study of the oxidation of pure titanium bulk samples under argon ion irradiation at 500 °C under rarefied air. In particular we follow the dependence of the oxide thickness as a function of the energy of argon ions. The novelty of this study consists in the range of ion energy explored, from 1 to 9 MeV. Until very recently it was commonly accepted that metal surfaces were transparent to ion beams in this low energy range (few MeV), and no surface modifications were expected. In a previous paper by the authors of this work, the formation of shallow craters in the surface of titanium was reported as a result of argon ion bombardment with energies of 2, 4 and 9 MeV under the same environmental conditions. We show here that around 3 MeV the oxide growth is unexpectedly enhanced. We think that an interplay of electronic excitations and nuclear ballistic collisions could possibly explain this enhanced oxide growth. We have used spectroscopic visible ultraviolet ellipsometry and XPS to determine the thickness of the oxide layers and characterize their optical properties. From the optical properties of the oxides we observed that for ion energies below 3-4 MeV the oxides show a dielectric-like behavior, whereas for ion energies above 3-4 MeV the oxides show a metal-like behavior. These findings indicate also that ion bombardment in this energy range may change substantially the oxygen-to-titanium ratio in the oxide films grown under irradiation leading to the formation of titanium sub-oxides.

  8. Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

    Energy Technology Data Exchange (ETDEWEB)

    Basak, Ganesh C. [Rubber Technology Centre, Indian Institute of Technology, Kharagpur 721302 (India); Bandyopadhyay, Abhijit [Department of Polymer Science and Technology, University of Calcutta, Calcutta 700 009 (India); Neogi, Sudarsan [Department of Chemical Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Bhowmick, Anil K., E-mail: anilkb@rtc.iitkgp.ernet.in [Rubber Technology Centre, Indian Institute of Technology, Kharagpur 721302 (India)

    2011-01-15

    Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -C=O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

  9. Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

    Science.gov (United States)

    Basak, Ganesh C.; Bandyopadhyay, Abhijit; Neogi, Sudarsan; Bhowmick, Anil K.

    2011-01-01

    Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -Cdbnd O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

  10. Wigner’s phase-space function and atomic structure: II. Ground states for closed-shell atoms

    DEFF Research Database (Denmark)

    Springborg, Michael; Dahl, Jens Peder

    1987-01-01

    display and analyze the function for the closed-shell atoms helium, beryllium, neon, argon, and zinc in the Hartree-Fock approximation. The quantum-mechanical exact results are compared with those obtained with the approximate Thomas-Fermi description of electron densities in phase space....

  11. Influence of annealing in oxygen and argon on the superconducting properties of Li-doped YBCO single-grain bulks

    Science.gov (United States)

    Antal, V.; Volochová, D.; Kavečanský, V.; Kováč, J.; Diko, P.

    2017-10-01

    YBa2(Cu1-xLix)3O7-δ single-grain bulk superconductors with different Li concentrations were grown using the top-seeded melt growth process. Structural analysis of the samples and magnetisation measurements showed that substitution of the Cu atoms by the Li atoms took place in the YBa2Cu3O7-δ crystal lattice. This substitution was accompanied by the formation of effective pinning centres, which improved the pinning properties of the samples and increased the critical current density. Additional annealing and reannealing in oxygen and argon showed that the superconducting transition temperature displays substantially more suppression, when the Li-doped YBa2Cu3O7-δ samples were annealed in argon, that was associated with different distribution of the Li atoms between the CuO chains and the CuO2 planes in comparison to annealing in oxygen. Investigation of the critical current densities showed that the pinning properties of YBa2(Cu1-xLix)3O7-δ single-grain bulk superconductors did not depend on the arrangement of the Li atoms in the YBa2Cu3O7-δ crystal lattice. It was also observed that the crystal lattice parameters and the mean diameter of the non-superconducting Y2BaCuO5 particles systematically change with Li concentration.

  12. Optimization of effective atom centered potentials for london dispersion forces in density functional theory.

    Science.gov (United States)

    von Lilienfeld, O Anatole; Tavernelli, Ivano; Rothlisberger, Ursula; Sebastiani, Daniel

    2004-10-08

    We add an effective atom-centered nonlocal term to the exchange-correlation potential in order to cure the lack of London dispersion forces in standard density functional theory. Calibration of this long-range correction is performed using density functional perturbation theory and an arbitrary reference. Without any prior assignment of types and structures of molecular fragments, our corrected generalized gradient approximation density functional theory calculations yield correct equilibrium geometries and dissociation energies of argon-argon, benzene-benzene, graphite-graphite, and argon-benzene complexes.

  13. Measurements of atomic state distribution functions of the Philips QL-lamp

    Energy Technology Data Exchange (ETDEWEB)

    Jonkers, J.; Bakker, M.; Mullen, J.A.M. van der [Eindhoven Univ. of Technology (Netherlands). Dept. of Applied Physics

    1996-12-31

    In 1992 Philips Lighting introduced the QL-lamp, an inductively coupled low pressure RF discharge containing a mixture of argon and mercury. Its main advantage is the absence of electrodes, which benefits the life-time. In order to improve the knowledge of this kind of plasmas a model has been developed and measurements have been performed. In every plasma the free electrons are an important species: they control the energy transfer from the electromagnetic field to the heavy particles. Therefore, it is important to know the spatial distribution of the electron temperature and of the electron density. These parameters can be obtained from the Atomic State Distribution Function (ASDF), since the levels close the ionization limit are in partial Local Saha Equilibrium (pLSE). The densities of the excited states are obtained from absolute line intensity measurements. However, it appears that the highly excited, measurable, states are not in pLSE, indicating that the QL plasma is far from Saha equilibrium. In order to obtain the electron densities and temperatures the ASDF has to be combined with either measurements of continuum radiation or a Collisional Radiative Model (CRM). The results of both methods will be presented and compared with a third technique to obtain the electron density and temperature: Thomson scattering.

  14. Polydiagnostic calibration performed on a low pressure surface wave sustained argon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Vries, N de; Iordanova, E I; Van Veldhuizen, E M; Mullen, J J A M van der [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Palomares, J M [Departamento de Fisica, Universidad de Cordoba, Campus de Rabanales, ed. C-2, 14071 Cordoba (Spain)], E-mail: j.j.a.m.v.d.Mullen@tue.nl

    2008-10-21

    The electron density and electron temperature of a low pressure surface wave sustained argon plasma have been determined using passive and active (laser) spectroscopic methods simultaneously. In this way the validity of the various techniques is established while the plasma properties are determined more precisely. The electron density, n{sub e}, is determined with Thomson scattering (TS), absolute continuum measurements, Stark broadening and an extrapolation of the atomic state distribution function (ASDF). The electron temperature, T{sub e}, is obtained using TS and absolute line intensity (ALI) measurements combined with a collisional-radiative (CR) model for argon. At an argon pressure of 15 mbar, the n{sub e} values obtained with TS and Stark broadening agree with each other within the error bars and are equal to (4 {+-} 0.5) x 10{sup 19} m{sup -3}, whereas the n{sub e} value (2 {+-} 0.5) x 10{sup 19} m{sup -3} obtained from the continuum is about 30% lower. This suggests that the used formula and cross-section values for the continuum method have to be reconsidered. The electron density determined by means of extrapolation of the ASDF to the continuum is too high ({approx}10{sup 20} m{sup -3}). This is most probably related to the fact that the plasma is strongly ionizing so that the extrapolation method is not justified. At 15 mbar, the T{sub e} values obtained with TS are equal to 13 400 {+-} 1100 K while the ALI/CR-model yields an electron temperature that is about 10% lower. It can be concluded that the passive results are in good or fair agreement with the active results. Therefore, the calibrated passive methods can be applied to other plasmas in a similar regime for which active diagnostic techniques cannot be used.

  15. Pressure Effects on the Relaxation of an Excited Nitromethane Molecule in an Argon Bath

    Science.gov (United States)

    2015-01-05

    Xe. Kiefer et al.12 reported shock-tube laser-Schlieren measurements of the high-tempera- ture pyrolysis of ethane and CF3CH3 in which they observed...science.energy.gov/∼/media/bes/ pdf /reports/files/ctf_rpt.pdf, 2006, pp. 95–101. 2J. R. Barker and D. M. Golden, Chem. Rev. 103, 4577 (2003). 3D. M. Golden, Chem

  16. Relativistic dynamical spin excitations of magnetic adatoms

    Science.gov (United States)

    dos Santos Dias, M.; Schweflinghaus, B.; Blügel, S.; Lounis, S.

    2015-02-01

    We present a first-principles theory of dynamical spin excitations in the presence of spin-orbit coupling. The broken global spin rotational invariance leads to a new sum rule. We explore the competition between the magnetic anisotropy energy and the external magnetic field, as well as the role of electron-hole excitations, through calculations for 3 d -metal adatoms on the Cu(111) surface. The spin excitation resonance energy and lifetime display nontrivial behavior, establishing the strong impact of relativistic effects. We legitimate the use of the Landau-Lifshitz-Gilbert equation down to the atomic limit, but with parameters that differ from a stationary theory.

  17. Quantum Phase Transition of Polaritonic Excitations in a Multi-Excitation Coupled Array

    Science.gov (United States)

    Shen, Lituo; Chen, Rongxin; Wu, Huaizhi; Yang, Zhenbiao; Irish, E. K.; Zheng, Shibiao

    2017-11-01

    We analyze the quantum phase transition-like behavior in the lowest energy state of a two-site coupled atom-cavity system, where each cavity contains one atom but the total excitation number is not limited to two. Under the large-detuning condition, we identify an interesting coexisting phase involving characteristics of both photonic superfluid and atomic insulator, which has not been previously revealed. For small hopping, we find that the signature of the photonic superfluid state becomes more pronounced with the increase in total excitation number, and that the boundaries of the various phases shift with respect to the case of two excitations. In the limit of small atom-field interaction, the polaritonic superfluid region becomes broader as the total excitation number increases. We use alternative order parameters to characterize the nonclassical property in the lowest-energy state, and find that the entanglement of photons in the photonic superfluid state has an approximately quadratic-like dependence on the total excitation number within the large-detuning limits. The second-order cross-correlation function is demonstrated to become inversely proportional to the total excitation number in the large detuning limits.

  18. Production of a 'natural' metastable nozzle beam: Van der Waals-Zeeman atomic levels near a metal surface

    Energy Technology Data Exchange (ETDEWEB)

    Karam, J-C [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Grucker, J [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Boustimi, M [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Bocvarski, V [Institute of Physics, Pregrevica, Zemun, Belgrade (Serbia and Montenegro); Vassilev, G [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Reinhardt, J [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Mainos, C [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Perales, F [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Baudon, J [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Robert, J [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France); Ducloy, Martial [Laboratoire de Physique des Lasers (UMR-CNRS 7538), Universite Paris 13 99, Av. J.B. Clement, 93430-Villetaneuse (France)

    2005-01-01

    A method for obtaining a metastable atom beam with properties near to those of a ground state supersonic beam is demonstrated. Calculations on m sublevels of metastable argon near a metal surface are then presented.

  19. Characterization of atmospheric pressure microplasma produced from argon and a mixture of argon–ethylenediamine

    Energy Technology Data Exchange (ETDEWEB)

    Bashir, M., E-mail: ranabashir77@gmail.com [Department of Chemical and Biological Engineering and Kroto Research Institute, University of Sheffield, Sheffield S1 3JD (United Kingdom); Rees, Julia M.; Bashir, S. [School of Mathematics and Statistics, Hicks Building, Hounsfield Road, University of Sheffield, Sheffield S3 7RH (United Kingdom); Zimmerman, William B. [Department of Chemical and Biological Engineering and Kroto Research Institute, University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2014-06-27

    A non-thermal atmospheric pressure microplasma generated from pure argon (Ar) and a mixture of argon–ethylenediamine vapors (Ar/EDA) has been characterized in this study. A sinusoidal power supply operating at 30 kHz was used to excite microplasma in a rectangular borosilicate glass capillary (4×0.4 mm{sup 2}). The monomer EDA was mixed with Ar in order to perform plasma polymerization inside the microchannel. The analyses were made by measuring spectroscopic and electrical parameters of the discharge. The effects of EDA mixing on plasma parameters such as electron, excitation and rotational temperatures during the process of surface coating of the microchannel were investigated. These parameters play an important role in the deposition process. The plasma temperatures estimated through spectroscopic measurement were found in the sequence T{sub e}>T{sub exc}>T{sub vib}>T{sub rot}, which indicated the non-thermal characteristics of the proposed DBD microplasma. The parameters of the Ar discharge were also numerically computed using plasma simulations. The numerical predictions of electron temperature (2D simulations) and electron density (3D simulations) were found to be in close agreement to those estimated through experiments. - Highlights: • An atmospheric pressure microplasma was generated in a borosilicate glass capillary. • A pure argon and a mixture of argon–ethylenediamine plasmas were characterized. • Characterization was performed by emission spectrometry and electrical measurements. • Plasma parameters were also predicted by numerical simulations. • The sequence of estimated plasma temperatures indicated its non-thermal behaviour.

  20. Design considerations for teleoperation systems operating in gas-tight argon cells

    Directory of Open Access Journals (Sweden)

    Seungnam Yu

    2017-12-01

    Full Text Available In the nuclear industry, mechanical engineers spend a significant portion of their time designing equipment such as manipulators, bogies, mechanical grippers, and so on. Some customized designs can be considered as standard mechanical equipment in this area, although it is not unusual to find that an existing design cannot simply be copied from one project to another. Varied performance requirements can dictate that redesign, often quite extensive redesign, is required. However, if something similar has been done before, engineers could use that as a starting point for the new project. In this regard, this study presents several guidelines inspired by previous design knowledge for similar development cases. Moreover, this study presents more detailed suggestions such as design guidelines for an argon-based hot cell atmosphere and design experience for a large-scale practical hot cell facility. Design considerations and case studies dealt with in this study are dedicated to teleoperation manipulators that are used at a large-scale argon cell facility for pyroprocess integrated inactive demonstration (PRIDE, at the Korea Atomic Energy Research Institute. In particular, for case studies to support the suggested recommendations, a fabricated telemanipulator system for PRIDE is introduced, and several kinds of experimental results associated with it are presented.

  1. Characterization of CdZnTe after argon ion beam bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Bensalah, H., E-mail: hakima.bensalah@uam.es [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Hortelano, V. [GdS-Optronlab Group, Departamento Fisica Materia Condensada, Universidad de Valladolid, Edificio I-D, Paseo de Belen 1, 47011 Valladolid (Spain); Plaza, J.L. [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Martinez, O. [GdS-Optronlab Group, Departamento Fisica Materia Condensada, Universidad de Valladolid, Edificio I-D, Paseo de Belen 1, 47011 Valladolid (Spain); Crocco, J.; Zheng, Q.; Carcelen, V.; Dieguez, E. [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2012-12-05

    Highlights: Black-Right-Pointing-Pointer After argon irradiation using low fluence, the defects on surface were removed. Black-Right-Pointing-Pointer The PL intensity increases after irradiation. This increase should be related to the improved quality of the CdZnTe surfaces. Black-Right-Pointing-Pointer Irradiation process lead to an elimination of Te precipitates from the surfaces of the CdZnTe samples. - Abstract: The objective of this work is to analyze the effects of argon ion irradiation process on the structure and distribution of Te inclusions in Cd{sub 1-x}Zn{sub x}Te crystals. The samples were treated with different ion fluences ranging from 2 to 8 Multiplication-Sign 10{sup 17} cm{sup -2}. The state of the samples before and after irradiation were studied by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Cathodoluminescence, Photoluminescence, and micro-Raman spectroscopy. The effect of the irradiation on the surface of the samples was clearly observed by SEM or AFM. Even for small fluences a removal of polishing scratches on the sample surfaces was observed. Likely correlated to this effect, an important enhancement in the luminescence intensity of the irradiated samples was observed. An aggregation effect of the Te inclusions seems to occur due to the Ar bombardment, which are also eliminated from the surfaces for the highest ion fluences used.

  2. Electronic structure of nitrogen-containing carbon nanotubes irradiated with argon ions: XPS and XANES studies

    Science.gov (United States)

    Nesov, S. N.; Korusenko, P. M.; Bolotov, V. V.; Povoroznyuk, S. N.; Smirnov, D. A.

    2017-10-01

    Using the methods of X-ray photoelectron (XPS) and X-ray absorption near edge structure (XANES) spectroscopies with synchrotron radiation, data on changes in the electronic structure and chemical composition of nitrogen-containing multiwalled carbon nanotubes (N-MWCNTs) upon their exposure to the radiation of argon ions with an energy of 5 keV are obtained. It is found that the exposure leads to an increase in the degree of defectiveness of the N-MWCNTs structure and to the carbon oxidation with formation of various oxygen-containing groups (C-OH, C=O/COOH, C-O-C/O-C-O, and CO3). The presence of carbon-oxygen bonds on the surface of carbon nanotubes is associated with the formation of radiation defects. It is shown that an increase in the fraction of nitrogen atoms present in the substituting configuration in the N-MWCNTs wall structure due to the irradiation does not give rise to an increase in the density of the occupied states near the Fermi level against the background of an increase in the degree of structure defectiveness, carbon oxidation, and a decrease in the total nitrogen concentration. The obtained results show that the irradiation of N-MWCNTs with argon ions allows one to successfully functionalize their surface.

  3. Atomic polarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  4. Atomic Physics

    CERN Document Server

    Foot, Christopher J

    2007-01-01

    This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen

  5. Characteristics of Knock in Hydrogen-Oxygen-Argon SI Engine

    Energy Technology Data Exchange (ETDEWEB)

    Killingsworth, N; Rapp, V; Flowers, D; Aceves, S; Chen, J; Dibble, R

    2010-02-23

    A promising approach for improving the efficiency of internal combustion engines is to employ a working fluid with a high specific heat ratio such as the noble gas argon. Moreover, all harmful emissions are eliminated when the intake charge is composed of oxygen, nonreactive argon, and hydrogen fuel. Previous research demonstrated indicated thermal efficiencies greater than 45% at 5.5 compression ratio in engines operating with hydrogen, oxygen, and argon. However, knock limits spark advance and increasing the efficiency further. Conditions under which knock occurs in such engines differs from typical gasoline fueled engines. In-cylinder temperatures using hydrogen-oxygen-argon are higher due to the high specific heat ratio and pressures are lower because of the low compression ratio. Better understanding of knock under these conditions can lead to operating strategies that inhibit knock and allow operation closer to the knock limit. In this work we compare knock with a hydrogen, oxygen, and argon mixture to that of air-gasoline mixtures in a variable compression ratio cooperative fuels research (CFR) engine. The focus is on stability of knocking phenomena, as well as, amplitude and frequency of the resulting pressure waves.

  6. FAST TRACK COMMUNICATION: Study of low-energy resonant metastability exchange in argon by a pulsed merging beam technique

    Science.gov (United States)

    Grucker, J.; Baudon, J.; Perales, F.; Dutier, G.; Vassilev, G.; Bocvarski, V.; Ducloy, M.

    2008-01-01

    The resonant metastability exchange process in low-energy collinear collisions between metastable argon atoms (Ar* 3P2) polarized in spin (M = +2) and ground-state Ar atoms from a nozzle beam is studied by means of a time-of-flight technique. A wide range of metastable atom velocities in the laboratory frame (275 m s-1 down to 50 m s-1) is obtained by use of a Zeeman slower, the counter-propagating laser beam of which is locked in frequency onto the 3P2-3D3 closed transition (λ = 811.5 nm). The accessible centre-of-mass energy range (8-27 meV) has not been explored so far, to our knowledge. Calculations based upon existing interatomic potentials of 2g and 2u symmetries are in reasonable agreement with experiment.

  7. Ultracold atoms on atom chips

    DEFF Research Database (Denmark)

    Krüger, Peter; Hofferberth, S.; Haller, E.

    2005-01-01

    Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...

  8. Trace determination of Hg together with As, Sb, Se by miniaturized optical emission spectrometry integrated with chemical vapor generation and capacitively coupled argon microwave miniplasma discharge

    Science.gov (United States)

    Matusiewicz, Henryk; Ślachciński, Mariusz

    2017-07-01

    A miniaturized optical emission spectrometer (OES) with capacitively coupled argon microwave microplasma (μCMP) as and excitation source and chemical vapor generation (CVG) for sample introduction was constructed for the determination of trace Hg, As, Sb and Se. The applied method enabled simultaneous determination of hydride-forming elements (As, Sb, Se) and volatile Hg. Mercury cold vapor and the hydride volatile species of As, Sb and Se were generated when standard or sample solutions were separated from the liquid phase for transport to the capacitively coupled microwave microplasma and detection of their atomic emission. A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. The experimental concentration detection limits (LODs) for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were 3.0, 1.4, 1.5 and 3.8 ng mL- 1 for Hg, As, Sb and Se, respectively. The method was validated by the analysis of three Certified Reference Materials (NIST 2711, NRCC DOLT-2, NIST 1643e) of different matrix composition and by the standard addition technique. The method offers relatively good precision (RSD ranged from 5% to 8%) for microsampling (200 μL) analysis. The measured of contents of elements in certified reference materials were in good agreement with the certified values (Hg 1.99-6.25 μg g- 1, As 16.6-105 μg g- 1, Sb 19.4-56.88 μg g- 1, Se 1.52-11.68 μg g- 1), according to the Student t-test, for a confidence level of 95%.

  9. The spectra of the multicharged argon hollow ions: Observation, modeling and using for diagnostics of the early stage of the heating of clusters by a super high contrast femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Pikuz, T. A.; Faenov, A. Ya.; Skobelev, I. Yu.; Fortov, V. E.; Boldarev, A. S.; Gasilov, V. A.; Chen, L. M.; Zhang, L.; Yan, W. C.; Yuan, D. W.; Mao, J. Y.; Wang, Z. H.; Colgan, J.; Abdallah, J. Jr.; Fukuda, Y.; Hayashi, Y.; Pirozhkov, A.; Kawase, K.; Shimomura, T.; Kiriyama, H. [Joint Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13 bld.2, Moscow, 125412 (Russian Federation) and Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7 Umemidai Kizugawa, Kyoto 619-0215 (Japan); Joint Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13 bld.2, Moscow, 125412 (Russian Federation); Institute of Mathematical Modeling, Russian Academy of Sciences, Miusskaya pl. 4a, Moscow, 125047 (Russian Federation); Institute of Physics, Chinese Academy of Sciences, Beijing, 100190 (China); Los Alamos National Laboratory, NM 87545 Los Alamos (United States); Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7 Umemidai Kizugawa, Kyoto 619-0215 (Japan); Graduate School for the Creation of New Photonics Industries, Hamamatsu, Shizuoka 431-1202 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7 Umemidai Kizugawa, Kyoto 619-0215 (Japan); and others

    2012-07-11

    A study is made of the ultra-short laser pulse irradiation of Ar cluster targets. Experiments have been performed with large cluster sizes and using very high laser contrasts, which have allowed clear and unambiguous observation of exotic inner-shell transitions in near-neutral Ar ions. The interaction of the main laser pulse with the unperturbed target is a necessary requirement for observing these lines. Our measurements are supported by kinetics calculations in which a very detailed atomic model is used. The calculations predict all of the spectral features found experimentally, and support the notion that the X-ray emission arises from many ion stages of the Ar plasma, from near-neutral through He-like ions, and from a range of plasma temperatures and densities. Differences between X-ray argon clusters excited at the laser-cluster and laser-droplet interactions have been analyzed. X-ray spectral methods have been proposed to determine the parameters of the plasma formed at the early stages of its evolution. It has been shown that the spectra of hollow ions are the most informative in the first moments of the heating of a cluster, whereas the diagnostics of the late stages can be performed using the conventional lines of multicharged ions.

  10. Liquid Argon Calorimetry with LHC-Performance Specifications

    CERN Multimedia

    2002-01-01

    % RD-3 Liquid Argon Calorimetry with LHC-Performance Specifications \\\\ \\\\Good electromagnetic and hadronic calorimetry will play a central role in an LHC detector. Among the techniques used so far, or under development, the liquid argon sampling calorimetry offers high radiation resistence, good energy resolution (electromagnetic and hadronic), excellent calibration stability and response uniformity. Its rate capabilities, however, do not yet match the requirements for LHC. \\\\ \\\\The aim of this proposal is to improve the technique in such a way that high granularity, good hermiticity and adequate rate capabilities are obtained, without compromising the above mentioned properties. To reach this goal, we propose to use a novel structure, the $^{\\prime\\prime}$accordion$^{\\prime\\prime}$, coupled to fast preamplifiers working at liquid argon temperature. Converter and readout electrodes are no longer planar and perpendicular to particles, as usual, but instead they are wiggled around a plane containing particles. ...

  11. Developing Detectors for Scintillation Light in Liquid Argon for DUNE

    Energy Technology Data Exchange (ETDEWEB)

    Howard, Bruce [Fermilab

    2016-12-22

    The Deep Underground Neutrino experiment will conduct a broad program of physics research by studying a beam of neutrinos from Fermilab, atmospheric neutrinos, neutrinos from potential supernovae, and potential nucleon decay events. In pursuit of these studies, the experiment will deploy four 10kt fiducial mass liquid argon time projection chambers underground in Lead, South Dakota. Liquid argon time projection chambers allow high-resolution tracking and energy measurements. A precise timing signal is needed to provide the necessary time stamp to localize events in the drift direction. As liquid argon is a natural scintillator, a photon detection system will be deployed to provide such a signal, especially for non-beam events. In the baseline design for the single-phase time projection chamber, the detectors are contained within the anode plane assemblies. The design of two prototypes utilizing wavelength shifters and light guides are presented, and aspects of the research and development program are discussed.

  12. The Simulation of the ATLAS Liquid Argon Calorimetry

    CERN Document Server

    Archambault, J P; Carli, T; Costanzo, D; Dell'Acqua, A; Djama, F; Gallas, M; Fincke-Keeler, M; Khakzad, M; Kiryunin, A; Krieger, P; Leltchouk, M; Loch, P; Ma, H; Menke, S; Monnier, E; Nairz, A; Niess, V; Oakham, G; Oram, C; Pospelov, G; Rajagopalan, S; Rimoldi, A; Rousseau, D; Rutherfoord, J; Seligman, W; Soukharev, A; Strízenec, P; Tóth, J; Tsukerman, I; Tsulaia, V; Unal, G; Grahn, K J

    2008-01-01

    In ATLAS, all of the electromagnetic calorimetry and part of the hadronic calorimetry is performed by a calorimeter system using liquid argon as the active material, together with various types of absorbers. The liquid argon calorimeter consists of four subsystems: the electromagnetic barrel and endcap accordion calorimeters; the hadronic endcap calorimeters, and the forward calorimeters. A very accurate geometrical description of these calorimeters is used as input to the Geant 4-based ATLAS simulation, and a careful modelling of the signal development is applied in the generation of hits. Certain types of Monte Carlo truth information ("Calibration Hits") may, additionally, be recorded for calorimeter cells as well as for dead material. This note is a comprehensive reference describing the simulation of the four liquid argon calorimeteter components.

  13. Laser excitation of Antihydrogen in ALPHA

    CERN Multimedia

    2016-01-01

    Animation of how a trapped antihydrogen atom is excited by two photons from the 1S to the 2S state in antihydrogen, and further photo-ionised by a third foton. The first part of the movie shows how antihydrogen is made and captured in a magnetic minimum trap.

  14. Application of argon atmospheric cold plasma for indium tin oxide (ITO) based diodes

    Science.gov (United States)

    Akbari Nia, S.; Jalili, Y. Seyed; Salar Elahi, A.

    2017-09-01

    Transparent Conductive Oxide (TCO) layers due to transparency, high conductivity and hole injection capability have attracted a lot of attention. One of these layers is Indium Tin Oxide (ITO). ITO due to low resistance, transparency in the visible spectrum and its proper work function is widely used in the manufacture of organic light emitting diodes and solar cells. One way for improving the ITO surface is plasma treatment. In this paper, changes in surface morphology, by applying argon atmospheric pressure cold plasma, was studied through Atomic Force Microscopic (AFM) image analysis and Fourier Transform Infrared Spectroscopy (FTIR) analysis. FTIR analysis showed functional groups were not added or removed, but chemical bond angle and bonds strength on the surface were changed and also AFM images showed that surface roughness was increased. These factors lead to the production of diodes with enhanced Ohmic contact and injection mechanism which are more appropriate in industrial applications.

  15. Mass Measurements Demonstrate a Strong N =28 Shell Gap in Argon

    CERN Document Server

    Meisel, Z; Ahn, S; Browne, J; Bazin, D; Brown, B A; Carpino, J F; Chung, H; Cyburt, R H; Estradé, A; Famiano, M; Gade, A; Langer, C; Matoš, M; Mittig, W; Montes, F; Morrissey, D J; Pereira, J; Schatz, H; Schatz, J; Scott, M; Shapira, D; Smith, K; Stevens, J; Tan, W; Tarasov, O; Towers, S; Wimmer, K; Winkelbauer, J R; Yurkon, J; Zegers, R G T

    2015-01-01

    We present results from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. We report the first mass measurements of 48Ar and 49Ar and find atomic mass excesses of -22.28(31) MeV and -17.8(1.1) MeV, respectively. These masses provide strong evidence for the closed shell nature of neutron number N=28 in argon, which is therefore the lowest even-Z element exhibiting the N=28 closed shell. The resulting trend in binding-energy differences, which probes the strength of the N=28 shell, compares favorably with shellmodel calculations in the sd-pf shell using SDPF-U and SDPF-MU Hamiltonians.

  16. The evolution of dielectric properties of sodium, silicon and argon clusters

    Science.gov (United States)

    Jackson, Koblar; Yang, Mingli; Ma, Li; Jellinek, Julius

    2012-02-01

    We used a computational scheme based on site-specific polarizabilities to study the evolution of the dielectric properties of sodium, silicon and argon clusters. In this approach, the total cluster polarizability is decomposed into local dipole (LD) and charge-transfer (CT) parts. The local dipole part measures the redistribution of charge within an atomic volume, while the CT part describes the movement of charge between volumes. We find distinct differences in the relative contributions of the LD and CT components to the total polarizability as a function of cluster size for the different cluster types and relate this to the development of metallic behavior. The method also directly probes the extent of electrostatic screening of the cluster interior to an applied electric field.

  17. Time-resolved characterization of a filamentary argon discharge at atmospheric pressure in a capillary using emission and absorption spectroscopy

    Science.gov (United States)

    Schröter, Sandra; Pothiraja, Ramasamy; Awakowicz, Peter; Bibinov, Nikita; Böke, Marc; Niermann, Benedikt; Winter, Jörg

    2013-11-01

    An argon/nitrogen (0.999/0.001) filamentary pulsed discharge operated at atmospheric pressure in a quartz tube is characterized using voltage-current measurements, microphotography, optical emission spectroscopy (OES) and absorption spectroscopy. Nitrogen is applied as a sensor gas for the purpose of OES diagnostic. The density of argon metastable atoms Ar(3P2) is determined using tunable diode laser absorption spectroscopy (TDLAS). Using a plasma chemical model the measured OES data are applied for the characterization of the plasma conditions. Between intense positive pulses the discharge current oscillates with a damped amplitude. It is established that an electric current flows in this discharge not only through a thin plasma filament that is observed in the discharge image but also through the whole cross section of the quartz tube. A diffuse plasma fills the quartz tube during a time between intense current pulses. Ionization waves are propagating in this plasma between the spike and the grounded area of the tube producing thin plasma channels. The diameter of these channels increases during the pause between the propagation of ionization waves probably because of thermal expansion and diffusion. Inside the channels electron densities of ˜2 × 1013 cm-3, argon metastable densities ˜1014 cm-3 and a reduced electric field about 10 Td are determined.

  18. Temporally resolved diagnosis of an atmospheric-pressure pulse-modulated argon surface wave plasma by optical emission spectroscopy

    Science.gov (United States)

    Chen, Chuan-Jie; Li, Shou-Zhe; Zhang, Jialiang; Liu, Dongping

    2018-01-01

    A pulse-modulated argon surface wave plasma generated at atmospheric pressure is characterized by means of temporally resolved optical emission spectroscopy (OES). The temporal evolution of the gas temperature, the electron temperature and density, the radiative species of atomic Ar, and the molecular band of OH(A) and N2(C) are investigated experimentally by altering the instantaneous power, pulse repetitive frequency, and duty ratio. We focused on the physical phenomena occurring at the onset of the time-on period and after the power interruption at the start of the time-off period. Meanwhile, the results are discussed qualitatively for an in-depth insight of its dynamic evolution.

  19. The effect of repeating full-circumference argon laser trabeculoplasty.

    Science.gov (United States)

    Starita, R J; Fellman, R L; Spaeth, G L; Poryzees, E

    1984-01-01

    Seventeen eyes of 16 patients who were classified as treatment failures following 360 degrees of argon laser trabeculoplasty underwent repeat treatment of the meshwork with the argon laser. Average intraocular pressure was significantly reduced from 22.5 +/- 6.8 to 19.3 +/- 6.1 mm Hg (P less than 0.05). Fifty-three percent of cases had a reduction and 12% had an increase in intraocular pressure of greater than or equal to 3 mm Hg at an average follow-up of 12 weeks. Visual function was not stabilized in 41% of the cases with 29% requiring further glaucoma surgery.

  20. The Adsorption of Argon and Oxygen on Silver Mordenite

    Science.gov (United States)

    1990-01-01

    argon and oxygen using 5A or 13X zeolites . Silver mordenite was studied as an alternative to the conventional adsorbents. Silver mordenite was...the history and development of PSA, see Yang [3] or Collins [4]). In the case of oxygen production using zeolite 5A or 13X , for example [5], air is...difficulty in separating argon and oy, ’gPn using 5A or 13X zeulites. Silver mordenitc was studied as an alternative to the conventional adsorbents. Silver

  1. Nanoscale control of phonon excitations in graphene

    Science.gov (United States)

    Kim, Hyo Won; Ko, Wonhee; Ku, Jiyeon; Ryu, Seunghwa; Hwang, Sung Woo

    Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities. In particular, phonons in graphene interact strongly with electrons; however, unlike in usual metals, these interactions between phonons and massless Dirac fermions appear to mirror the rather complicated physics of those between light and relativistic electrons. Therefore, a fundamental understanding of the underlying physics through systematic studies of phonon interactions and excitations in graphene is crucial for realizing graphene-based devices. In this study, we demonstrate that the local phonon properties of graphene can be controlled at the nanoscale by tuning the interaction strength between graphene and an underlying Pt substrate. Using scanning probe methods, we determine that the reduced interaction due to embedded Ar atoms facilitates electron-phonon excitations, further influencing phonon-assisted inelastic electron tunneling.

  2. Advanced analysis tool for X-ray photoelectron spectroscopy profiling: Cleaning of perovskite SrTiO{sub 3} oxide surface using argon cluster ion source

    Energy Technology Data Exchange (ETDEWEB)

    Aureau, D., E-mail: damien.aureau@uvsq.fr [Institut Lavoisier de Versailles, (UMR 8180) Université de Versailles-Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Ridier, K. [Institut Lavoisier de Versailles, (UMR 8180) Université de Versailles-Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Groupe d' Étude de la Matière Condensée (UMR 8635) Université de Versailles Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Bérini, B.; Dumont, Y.; Keller, N. [Groupe d' Étude de la Matière Condensée (UMR 8635) Université de Versailles Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Vigneron, J.; Bouttemy, M.; Etcheberry, A. [Institut Lavoisier de Versailles, (UMR 8180) Université de Versailles-Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France); Fouchet, A. [Groupe d' Étude de la Matière Condensée (UMR 8635) Université de Versailles Saint-Quentin-en-Yvelines–CNRS, 45 Av. des États-Unis, 78035 Versailles (France)

    2016-02-29

    This article shows the comparison between three different ionic bombardments during X-ray photoelectron spectroscopy (XPS) studies of single crystalline SrTiO{sub 3} (STO) substrates. The abrasion using a “cluster argon ion source” is compared with the standard “monoatomic Ar”. The influence of the energy of the monoatomic ions used is clearly demonstrated. While the chemically adsorbed species on the STO surface are removed, such bombardment strongly modifies the surface. A reduction of part of the titanium atoms and the appearance of a different chemical environment for surface strontium atoms are observed. Implantation of argon ions is also detected. Cluster ion etching is used on oxide surface and, in this case only, due to a much lower kinetic energy per atom compared to monoatomic ions, the possibility to remove surface contaminants at the surface without modification of the XP spectra is clearly demonstrated, ensuring that the stoichiometry of the surface is preserved. Such result is crucial for everybody working with oxide surfaces to obtain a non-modified XPS analysis. The progressive effect of this powerful tool allows the monitoring of the removal of surface contamination in the first steps of the bombardment which was not achievable with usual guns. - Highlights: • The effects of three argon etchings are studied as a function of time on SrTiO3 oxide. • A method for obtaining non-modified chemical analysis of oxides is presented. • The soft removal of adsorbed species thanks to argon cluster is demonstrated. • The damages induced on SrTiO3 surface by ionic bombardment are shown. • The influence of the kinetic energy of incoming Ar atoms is examined.

  3. Charge exchange recombination in X-ray spectra of He-like argon measured at the tokamak TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Schlummer, Tobias

    2014-06-16

    Charge exchange recombination between ions and atomic hydrogen is an important atomic process in magnetically confined fusion plasmas. Besides radiative cooling of the plasma edge, charge exchange causes modifications of the ionization balance and the population densities of excited ion states. The central goal of this work is to investigate the influence of charge exchange on X-ray spectra measured at the tokamak TEXTOR. A new 2D X-ray spectrometer developed for future use at the stellarator W7-X was recently installed at TEXTOR. The spectrometer is optimized for measuring the K{sub α}-spectrum of He-like argon (1s2l - 1s{sup 2}) at wavelengths close to 4 Aa. K{sub α}-spectroscopy on He-like impurity ions is an established diagnostic for electron and ion temperature measurements in fusion plasmas. Still, up to now the observed intensity ratios of the K{sub α}-lines and their associated satellites are not fully understood. They show significant deviations from the predictions made by basic corona models. In the past charge exchange with the neutral particle background and radial impurity transport have been discussed as likely explanations. Yet a detailed description of the experimental spectra still has not been achieved. To reconstruct the 2D K{sub α}-spectra measured at TEXTOR the radial argon ion distribution is modeled using an impurity transport code. The model accounts for charge exchange and transport on basis of given radial profiles of the neutral particle density n{sub 0}(r) and the diffusion coefficient D {sub perpendicular} {sub to} (r). The theoretical spectrum is then constructed based on the processes relevant for line emission. Within an iterative procedure n{sub 0}(r) and D {sub perpendicular} {sub to} (r) are varied until consistency between the theoretical and the experimental spectra is achieved. It is shown that the 2D K{sub α}-spectra allow a clear distinction of charge exchange and transport effects, ensuring unique solutions for n

  4. A molecular dynamics study of thermal transport in nanoparticle doped Argon like solid

    Energy Technology Data Exchange (ETDEWEB)

    Shahadat, Muhammad Rubayat Bin, E-mail: rubayat37@gmail.com; Ahmed, Shafkat; Morshed, A. K. M. M. [Department of Mechanical Engineering Bangladesh University of Engineering and Technology (BUET) Dhaka (Bangladesh)

    2016-07-12

    Interfacial phenomena such as mass and type of the interstitial atom, nano scale material defect influence heat transfer and the effect become very significant with the reduction of the material size. Non Equilibrium Molecular Dynamics (NEMD) simulation was carried out in this study to investigate the effect of the interfacial phenomena on solid. Argon like solid was considered in this study and LJ potential was used for atomic interaction. Nanoparticles of different masses and different molecular defects were inserted inside the solid. From the molecular simulation, it was observed that a large interfacial mismatch due to change in mass in the homogenous solid causes distortion of the phonon frequency causing increase in thermal resistance. Position of the doped nanoparticles have more profound effect on the thermal conductivity of the solid whereas influence of the mass ratio is not very significant. Interstitial atom positioned perpendicular to the heat flow causes sharp reduction in thermal conductivity. Structural defect caused by the molecular defect (void) also observed to significantly affect the thermal conductivity of the solid.

  5. Spatial Imaging of Strongly Interacting Rydberg Atoms

    Science.gov (United States)

    Thaicharoen, Nithiwadee

    The strong interactions between Rydberg excitations can result in spatial correlations between the excitations. The ability to control the interaction strength and the correlations between Rydberg atoms is applicable in future technological implementations of quantum computation. In this thesis, I investigates how both the character of the Rydberg-Rydberg interactions and the details of the excitation process affect the nature of the spatial correlations and the evolution of those correlations in time. I first describes the experimental apparatus and methods used to perform high-magnification Rydberg-atom imaging, as well as three experiments in which these methods play an important role. The obtained Rydberg-atom positions reveal the correlations in the many-body Rydberg-atom system and their time dependence with sub-micron spatial resolution. In the first experiment, atoms are excited to a Rydberg state that experiences a repulsive van der Waals interaction. The Rydberg excitations are prepared with a well-defined initial separation, and the effect of van der Waals forces is observed by tracking the interatomic distance between the Rydberg atoms. The atom trajectories and thereby the interaction coefficient C6 are extracted from the pair correlation functions of the Rydberg atom positions. In the second experiment, the Rydberg atoms are prepared in a highly dipolar state by using adiabatic state transformation. The atom-pair kinetics that follow from the strong dipole-dipole interactions are observed. The pair correlation results provide the first direct visualization of the electric-dipole interaction and clearly exhibit its anisotropic nature. In both the first and the second experiment, results of semi-classical simulations of the atom-pair trajectories agree well with the experimental data. In the analysis, I use energy conservation and measurements of the initial positions and the terminal velocities of the atom pairs to extract the C6 and C 3 interaction

  6. Electron-Atom Collisions in Gases

    Science.gov (United States)

    Kraftmakher, Yaakov

    2013-01-01

    Electron-atom collisions in gases are an aspect of atomic physics. Three experiments in this field employing a thyratron are described: (i) the Ramsauer-Townsend effect, (ii) the excitation and ionization potentials of xenon and (iii) the ion-electron recombination after interrupting the electric discharge.

  7. Argon plasma coagulation for open surgical and endoscopic applications: state of the art

    Energy Technology Data Exchange (ETDEWEB)

    Raiser, J; Zenker, M [ERBE Elektromedizin GmbH, Waldhoernlestrasse 17, 72072 Tuebingen (Germany)

    2006-08-21

    Argon plasma coagulation is an application of gas discharges in argon in electrosurgery, which is increasingly being used especially in endoscopy. This review describes the underlying physics and technology, gives some application examples, and discusses new developments.

  8. Directional emission of single photons from small atomic samples

    DEFF Research Database (Denmark)

    Miroshnychenko, Yevhen; V. Poulsen, Uffe; Mølmer, Klaus

    2013-01-01

    We provide a formalism to describe deterministic emission of single photons with tailored spatial and temporal profiles from a regular array of multi-level atoms. We assume that a single collective excitation is initially shared by all the atoms in a metastable atomic state, and that this state i...... is coupled by a classical laser field to an optically excited state which rapidly decays to the ground atomic state. Our model accounts for the different field polarization components via re-absorption and emission of light by the Zeeman manifold of optically excited states....

  9. Atomic physics

    CERN Document Server

    Born, Max

    1969-01-01

    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  10. Early Atomism

    Indian Academy of Sciences (India)

    http://www.ias.ac.in/article/fulltext/reso/015/10/0905-0925. Keywords. Atomic theory; Avogadro's hypothesis; atomic weights; periodic table; valence; molecular weights; molecular formula; isomerism. Author Affiliations. S Ramasesha1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, ...

  11. Attosecond-correlated dynamics of two electrons in argon

    Indian Academy of Sciences (India)

    2014-01-11

    correlated dynamics of two electrons in argon. V Sharma N Camus B Fischer M Kremer A Rudenko B Bergues M Kuebel N G Johnson M F Kling T Pfeifer J Ullrich R Moshammer. Invited Talks Volume 82 Issue 1 January 2014 ...

  12. ATLAS Liquid Argon Calorimeter at dawn of LHC Run-2

    CERN Document Server

    Camincher, Clement; The ATLAS collaboration

    2015-01-01

    At the start of the LHC Run-2 here is an overview of the Liquid Argon Calorimeter of ATLAS. It is described the main modifications done during the long shutdown (2013-2015). The first LAr-related results with 2015 data are also highlighted. Finally a short description present the foreseen Phase-I upgrade of the L1 Calo trigger.

  13. LArGe. A liquid argon scintillation veto for GERDA

    Energy Technology Data Exchange (ETDEWEB)

    Heisel, Mark

    2011-04-13

    LArGe is a GERDA low-background test facility to study novel background suppression methods in a low-background environment, for possible applications in the GERDA experiment. GERDA searches for the neutrinoless double-beta decay in {sup 76}Ge, by operating naked germanium detectors submersed into 65 m{sup 3} of liquid argon. Similarly, LArGe runs Ge-detectors in 1 m{sup 3} (1.4 tons) of liquid argon, which in addition is instrumented with photomultipliers to detect argon scintillation light. The light is used in anti-coincidence with the germanium detectors, to effectively suppress background events that deposit energy in the liquid argon. This work adresses the design, construction, and commissioning of LArGe. The background suppression efficiency has been studied in combination with a pulse shape discrimination (PSD) technique for various sources, which represent characteristic backgrounds to GERDA. Suppression factors of a few times 10{sup 3} have been achieved. First background data of LArGe (without PSD) yield a background index of (0.12-4.6).10{sup -2} cts/(keV.kg.y) (90% c.l.), which is at the level of the Gerda phase I design goal. Furthermore, for the first time we measure the natural {sup 42}Ar abundance (in parallel to Gerda), and have indication for the 2{nu}{beta}{beta}-decay in natural germanium. (orig.)

  14. Experimental and numerical study of high intensity argon cluster beams

    Energy Technology Data Exchange (ETDEWEB)

    Korobeishchikov, N. G.; Kalyada, V. V.; Shmakov, A. A.; Zarvin, A. E. [Department of Applied Physics, Novosibirsk State University, 2, Pirogova str., Novosibirsk, 630090 (Russian Federation); Skovorodko, P. A. [Department of Applied Physics, Novosibirsk State University, 2, Pirogova str., Novosibirsk, 630090, Russia and Kutateladze Institute of Thermophysics SB RAS,1, Lavrentyev Ave., Novosibirsk, 630090 (Russian Federation)

    2014-12-09

    Experimental and numerical investigations of expansion of argon with homogeneous condensation in supersonic conical nozzle and in free jet behind it were carried out. Optimal parameters (stagnation pressure, nozzle-skimmer distance) for the formation of cluster beam with maximum intensity were determined. Two available models for nonequilibrium nucleation were tested. The numerical results are in satisfactory agreement with the measured data.

  15. Study of Liquid Argon Dopants for LHC Hadron Calorimetry

    CERN Multimedia

    2002-01-01

    Hadron calorimetry based on the Liquid Argon Ionisation Chamber technique is one of the choice techniques for LHC-experimentation. A systematic study of the effect of selected dopants on Liquid Argon (LAr) will be carried out with the aim to achieve an improvement on: \\item (i)~``Fast Liquid Argon'' search and study of dopants to increase the drift velocity. It has been already shown that CH&sub4. added at a fraction of one percent increases the drift velocity by a factor of two or more. \\item (ii)~``Compensated Liquid Argon'' search and study of dopants to increase the response to densely ionising particles, resulting in improved compensation, such as photosensitive dopants. \\end{enumerate}\\\\ \\\\ Monitoring of the parameters involved in understanding the response of a calorimeter is essential. In case of doped LAr, the charge yield, the non-saturated drift velocity and the electron lifetime in the liquid should be precisely and simultaneously monitored as they all vary with the level of dopant concentrati...

  16. Radiative Properties of Argon Gas-Puff Implosions on COBRA

    Science.gov (United States)

    Ouart, Nicholas; Qi, Niansheng; de Grouchy, Phil; Shelkovenko, Tatiana; Pikuz, Sergei; Giuliani, John; Dasgupta, Arati; Apruzese, John; Clark, Robert; Hammer, David; Kusse, Bruce

    2015-11-01

    Gas-puff Z-pinch experiments were performed on the 1 MA COBRA pulsed power generator at Cornell University. The gas puffs were injected into the load region from a triple nozzle. The load region had an anode-cathode gap of 2.5 cm. The standard diagnostics on COBRA include time-integrated pinhole cameras, a time-integrated axially resolved x-ray spectrometer, filtered photo-conducting detectors, and time-gated XUV cameras. We will focus mainly on results from pinhole images and x-ray spectra from argon gas puffs including some with a SO2 dopant. The x-ray time-integrated pinhole images feature a tight axially uniform plasma column with a diameter of approximately 1 mm for argon gas implosion. The x-ray spectrometer used mica crystals (2d =19.84 Å) and captured the argon K-shell radiation from different crystal reflections. A 1-D multi-zone argon and sulfur non-LTE kinetics code with radiation transport is used to model the K-shell emission for the purpose of inferring the plasma conditions and the interaction of gas from the inner annulus with the central jet. This work is supported by DOE/NNSA.

  17. Thermal decomposition of yttrium(III) hexanoate in argon

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Suarez Guevara, Maria Josefina; Attique, Fahmida

    2015-01-01

    The thermal decomposition of yttrium(III) hexanoate (Y(C5H11CO2)3)·xH2O in argon was studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray diffraction at a laboratory Cu-tube source and in-situ experiments at a synchrotron radiation source as well as hot...

  18. Laser-induced vibrational dynamics of ozone in solid argon

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Amstrup, B.; Henriksen, Niels Engholm

    1997-01-01

    We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18 and compare the dynamics in the gas phase and in solid ar on. not perturbed by argon on a time-scale of a few picoseconds and selective...

  19. Experience with argon laser trabeculoplasty in Nigerians | Olawoye ...

    African Journals Online (AJOL)

    Aim: To report the safety and efficacy of Argon Laser Trabeculoplasty (ALT) in reducing intraocular pressure (IOP). Settings and Design: This was a retrospective study performed on 25 eyes of 25 patients. Methods and Materials: Consecutive patients who met the inclusion criteria for ALT were recruited from the ophthalmic ...

  20. Thermophysical properties of multi-shock compressed dense argon

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Q. F., E-mail: chenqf01@gmail.com; Zheng, J.; Gu, Y. J.; Chen, Y. L.; Cai, L. C. [National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P. O. Box 919-102, Mianyang, Sichuan (China); Shen, Z. J. [Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, P. O. Box 8009-26, Beijing 10086 (China)

    2014-02-21

    In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ∼6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models.

  1. Thermophysical properties of multi-shock compressed dense argon

    Science.gov (United States)

    Chen, Q. F.; Zheng, J.; Gu, Y. J.; Chen, Y. L.; Cai, L. C.; Shen, Z. J.

    2014-02-01

    In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ˜6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models.

  2. The Erosion of Frozen Argon by Swift Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; Bøttiger, Jørgen; Graversen, O.

    1981-01-01

    The temperature, energy, and thickness dependence of the erosion rates of frozen argon films when irradiated with 0.1–3 MeV helium ions have been measured. The erosion yields Y are much too high to be explained by the concentional collisional cascade-sputtering theory and are furthermore...

  3. Stopping Power of Solid Argon for Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; Bøttiger, Jørgen; Grauersen, O.

    1981-01-01

    studied. This proves that the gas/solid difference for argon predicted in recent stopping-power tabulations is significantly overestimated. With high-order Z1 correction terms included in the theoretical description, calculated shell corrections based on the Lindhard-Scharff model are in good agreement...

  4. Readiness of the ATLAS liquid argon calorimeter for LHC collisions

    NARCIS (Netherlands)

    Aad, G.; et al., [Unknown; Bentvelsen, S.; Colijn, A.P.; de Jong, P.; Doxiadis, A.; Garitaonandia, H.; Gosselink, M.; Kayl, M.S.; Koffeman, E.; Lee, H.; Mechnich, J.; Mussche, I.; Ottersbach, J.P.; Rijpstra, M.; Ruckstuhl, N.; Tsiakiris, M.; van der Kraaij, E.; van der Poel, E.; van Kesteren, Z.; van Vulpen, I.; Vermeulen, J.C.; Vreeswijk, M.

    2010-01-01

    The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an

  5. Generation of uniform atmospheric pressure argon glow plasma by ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 80; Issue 3. Generation of uniform atmospheric pressure argon glow plasma by dielectric barrier discharge. Raju Bhai Tyata Deepak Prasad Subedi Rajendra Shrestha Chiow San Wong. Research Articles Volume 80 Issue 3 March 2013 pp 507-517 ...

  6. Theoretical Calculations of Atomic Data for Spectroscopy

    Science.gov (United States)

    Bautista, Manuel A.

    2000-01-01

    Several different approximations and techniques have been developed for the calculation of atomic structure, ionization, and excitation of atoms and ions. These techniques have been used to compute large amounts of spectroscopic data of various levels of accuracy. This paper presents a review of these theoretical methods to help non-experts in atomic physics to better understand the qualities and limitations of various data sources and assess how reliable are spectral models based on those data.

  7. Quantum gates between superconducting and atomic qubits

    Science.gov (United States)

    Saffman, Mark; Wilhelm, Frank; McDermott, Robert

    2009-05-01

    We propose methods for performing entangling gate operations between superconducting phase qubits and neutral atom hyperfine qubits. The gate is mediated by mapping the superconducting qubit onto a microwave excitation of a coplanar waveguide resonator (CPW). The large transition dipole moments of atomic Rydberg states at microwave frequencies enable bidirectional entanglement between a single atom and a single CPW photon. Specific gate protocols and fidelity calculations are presented for experimentally realistic geometries.

  8. Chameleon Induced Atomic Afterglow

    CERN Document Server

    Brax, Philippe

    2010-01-01

    The chameleon is a scalar field whose mass depends on the density of its environment. Chameleons are necessarily coupled to matter particles and will excite transitions between atomic energy levels in an analogous manner to photons. When created inside an optical cavity by passing a laser beam through a constant magnetic field, chameleons are trapped between the cavity walls and form a standing wave. This effect will lead to an afterglow phenomenon even when the laser beam and the magnetic field have been turned off, and could be used to probe the interactions of the chameleon field with matter.

  9. Atomic data for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, H.T.; Kirkpatrick, M.I.; Alvarez, I.; Cisneros, C.; Phaneuf, R.A. (eds.); Barnett, C.F.

    1990-07-01

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research.

  10. Isovector monopole excitation energies

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, J.D.; Lipparini, E.; Stringary, S.

    1987-11-05

    Using a hydrodynamical model whose parameters have been adjusted to fit the polarizability and excitation energy of the giant dipole nuclear resonance we predict excitation energies of the isovector monopole resonance. The predicted values are in good agreement with experimental data. The mass dependence of the excitation energy is strongly influenced by nuclear geometry.

  11. 21 CFR 874.4490 - Argon laser for otology, rhinology, and laryngology.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Argon laser for otology, rhinology, and laryngology. 874.4490 Section 874.4490 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND... Argon laser for otology, rhinology, and laryngology. (a) Identification. The argon laser device for use...

  12. Combination of the ionic-to-atomic line intensity ratios from two test elements for the diagnostic of plasma temperature and electron number density in Inductively Coupled Plasma Atomic Emission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tognoni, E. [Istituto per i Processi Chimico-Fisici, Area della Ricerca del Consiglio Nazionale delle Ricerche Via Moruzzi 1, 56124 Pisa (Italy)], E-mail: tognoni@ipcf.cnr.it; Hidalgo, M.; Canals, A. [Departamento de Quimica Analitica, Nutricion y Bromatologia. Universidad de Alicante. Apdo. 99, 03080, Alicante (Spain); Cristoforetti, G.; Legnaioli, S.; Salvetti, A.; Palleschi, V. [Istituto per i Processi Chimico-Fisici, Area della Ricerca del Consiglio Nazionale delle Ricerche Via Moruzzi 1, 56124 Pisa (Italy)

    2007-05-15

    In Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) spectrochemical analysis, the MgII(280.270 nm)/MgI(285.213 nm) ionic to atomic line intensity ratio is commonly used as a monitor of the robustness of operating conditions. This approach is based on the univocal relationship existing between intensity ratio and plasma temperature, for a pure argon atmospheric ICP in thermodynamic equilibrium. In a multi-elemental plasma in the lower temperature range, the measurement of the intensity ratio may not be sufficient to characterize temperature and electron density. In such a range, the correct relationship between intensity ratio and plasma temperature can be calculated only when the complete plasma composition is known. We propose the combination of the line intensity ratios of two test elements (double ratio) as an effective diagnostic tool for a multi-elemental low temperature LTE plasma of unknown composition. In particular, the variation of the double ratio allows us discriminating changes in the plasma temperature from changes in the electron density. Thus, the effects on plasma excitation and ionization possibly caused by introduction of different samples and matrices in non-robust conditions can be more accurately interpreted. The method is illustrated by the measurement of plasma temperature and electron density in a specific analytic case.

  13. Multi-frequency excitation

    KAUST Repository

    Younis, Mohammad I.

    2016-03-10

    Embodiments of multi-frequency excitation are described. In various embodiments, a natural frequency of a device may be determined. In turn, a first voltage amplitude and first fixed frequency of a first source of excitation can be selected for the device based on the natural frequency. Additionally, a second voltage amplitude of a second source of excitation can be selected for the device, and the first and second sources of excitation can be applied to the device. After applying the first and second sources of excitation, a frequency of the second source of excitation can be swept. Using the methods of multi- frequency excitation described herein, new operating frequencies, operating frequency ranges, resonance frequencies, resonance frequency ranges, and/or resonance responses can be achieved for devices and systems.

  14. Influence of residual ion polarization on the coplanar symmetric (e, 2e) cross sections for calcium and argon

    Science.gov (United States)

    Hu, Xiao-Qing; Chen, Zhan-Bin; Wang, Yang; Wang, Kai

    2017-03-01

    Detailed calculations using a modified distorted wave Born approximation (DWBA) are carried out for the triple differential cross section (TDCS) in the coplanar symmetric single ionization of calcium and argon atoms. The effects of residual ion polarization on the TDCS are investigated systematically. Our results show that the residual ion polarization, arising from the interaction between the target ion and the two outgoing electrons in the final state, may lead to a considerable change in the TDCS with a more pronounced effect in the large scattering angle region at intermediate energies. The present attempt significantly improves the agreement between theoretical and experimental results. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

  15. Positronium-alkali atom scattering at medium energies

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Ajoy [Laban Hrad Vidyapith, AD-369, Salt Lake City, Kolkata 700 064 (India); Basu, Arindam [Department of Physics, Maheshtala College, Chandannagar, South 24 Parganas, Kolkata 700 140 (India); Sarkar, Nirmal K [Sodepur Chandrachur Vidyapith, 1, Desh Bandhu Nagar, Sodepur, 743 174 (India); Sinha, Prabal K [Department of Physics, Bangabasi College, 19, Raj Kumar Chakravorty Sarani, Kolkata 700 009 (India)

    2004-04-28

    We investigate the scattering of orthopositronium (o-Ps) atom off different atomic alkali targets (Na to Cs) at low and medium energies (up to 120 eV). Projectile-elastic and target-elastic close-coupling models have been employed to investigate the systems in addition to the static-exchange model. Elastic, excitation and total cross sections have been reported for all four systems. The magnitude of the alkali excitation cross section increases with increasing atomic number of the target atom while the position of the peak value shifts towards lower incident energies. The magnitudes of the Ps excitation and ionization cross sections increase steadily with atomic number with no change in the peak position. The reported results show regular behaviour with increasing atomic number of the target atom. Scattering parameters for the Ps-Rb and Ps-Cs systems are being reported for the first time.

  16. nuclear and atomic methods applied in the determination of some ...

    African Journals Online (AJOL)

    free atoms in vapour state and a beam of electromagnetic radiation emitted from excited lead atoms is passed through the vaporized sample. Some of the radiation is absorbed by the lead atoms in the sample. Sample Collection and Preparation. Soil samples were collected from Bompai, Kofar Ruwa, Challawa and.

  17. Atom-by-Atom Construction of a Quantum Device.

    Science.gov (United States)

    Petta, Jason R

    2017-03-28

    Scanning tunneling microscopes (STMs) are conventionally used to probe surfaces with atomic resolution. Recent advances in STM include tunneling from spin-polarized and superconducting tips, time-domain spectroscopy, and the fabrication of atomically precise Si nanoelectronics. In this issue of ACS Nano, Tettamanzi et al. probe a single-atom transistor in silicon, fabricated using the precision of a STM, at microwave frequencies. While previous studies have probed such devices in the MHz regime, Tettamanzi et al. probe a STM-fabricated device at GHz frequencies, which enables excited-state spectroscopy and measurements of the excited-state lifetime. The success of this experiment will enable future work on quantum control, where the wave function must be controlled on a time scale that is much shorter than the decoherence time. We review two major approaches that are being pursued to develop spin-based quantum computers and highlight some recent progress in the atom-by-atom fabrication of donor-based devices in silicon. Recent advances in STM lithography may enable practical bottom-up construction of large-scale quantum devices.

  18. Numerical Modeling of an RF Argon-Silane Plasma with Dust Particle Nucleation and Growth

    Science.gov (United States)

    Girshick, Steven; Agarwal, Pulkit

    2012-10-01

    We have developed a 1-D numerical model of an RF argon-silane plasma in which dust particles nucleate and grow. This model self-consistently couples a plasma module, a chemistry module and an aerosol module. The plasma module solves population balance equations for electrons and ions, the electron energy equation under the assumption of a Maxwellian velocity distribution, and Poisson's equation for the electric field. The chemistry module treats silane dissociation and reactions of silicon hydrides containing up to two silicon atoms. The aerosol module uses a sectional method to model particle size and charge distributions. The nucleation rate is equated to the rates of formation of anions containing two Si atoms, and a heterogeneous reaction model is used to model particle surface growth. Aerosol effects considered include particle charging, coagulation, and particle transport by neutral drag, ion drag, electric force, gravity and Brownian diffusion. Simulation results are shown for the case of a 13.56 MHz plasma at a pressure of 13 Pa and applied RF voltage of 100 V (amplitude), with flow through a showerhead electrode. These results show the strong coupling between the plasma and the spatiotemporal evolution of the nanoparticle cloud.

  19. Crane system with remote actuation mechanism for use in argon compartment in ACPF hot cell

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Kwang, E-mail: leejk@kaeri.re.kr; Park, Byung-Suk; Yu, Seung-Nam; Kim, Kiho; Cho, Il-je

    2016-10-15

    Highlights: • Novel crane system with a remote actuation mechanism for feasible maintenance under limited space conditions is proposed. • Linear drive systems are implemented for accurate positioning. • Modular design concepts for easy maintenance are introduced. • The motion controller and the off-the-shelf camera controller are integrated to provide more efficient operation. - Abstract: The Advanced spent fuel Conditioning Process Facility (ACPF) at the Korea Atomic Energy Research Institute (KAERI) has recently been successfully renovated. One of the highlights of this renovation project was the installation of a small argon compartment within the atmospheric hot cell of the facility. Even though a crane system was considered necessary for the remote handling of the processing equipment inside the argon compartment, no suitable commercial cranes were available. This was because a limited amount of space had been reserved for the installation of the crane. Moreover, a master-slave manipulator (MSM), the only available means of maintenance of the crane, was unable to reach it in the limited workspace. To address the difficulties in the design of this crane, in this study, a remote actuation mechanism is devised where the mechanical and electrical parts of the crane system are separated, positioned far away from each other, and connected through power transmission shafts. This approach has two main advantages. First, the electrical parts can be placed inside the workspace of the MSM, hence allowing for remote maintenance. Second, the space occupied by the electrical parts and their cables, which are separate from the crane in the proposed design, can be considered and exploited in designing the mechanical parts of the crane. This enables the construction of a short, special crane in order to maximize the workspace. Furthermore, the mechanical parts for the MSM located outside the workspace are designed to possess a high safety margin to ensure durability

  20. Readiness of the ATLAS Liquid Argon Calorimeter for LHC Collisions

    CERN Document Server

    Aad, G.; Abdallah, J.; Abdelalim, A.A.; Abdesselam, A.; Abdinov, O.; Abi, B.; Abolins, M.; Abramowicz, H.; Abreu, H.; Acharya, B.S.; Adams, D.L.; Addy, T.N.; Adelman, J.; Adorisio, C.; Adragna, P.; Adye, T.; Aefsky, S.; Aguilar-Saavedra, J.A.; Aharrouche, M.; Ahlen, S.P.; Ahles, F.; Ahmad, A.; Ahmed, H.; Ahsan, M.; Aielli, G.; Akdogan, T.; Akesson, T.P.A.; Akimoto, G.; Akimov, A.V.; Aktas, A.; Alam, M.S.; Alam, M.A.; Albert, J.; Albrand, S.; Aleksa, M.; Aleksandrov, I.N.; Alessandria, F.; Alexa, C.; Alexander, G.; Alexandre, G.; Alexopoulos, T.; Alhroob, M.; Aliev, M.; Alimonti, G.; Alison, J.; Aliyev, M.; Allport, P.P.; Allwood-Spiers, S.E.; Almond, J.; Aloisio, A.; Alon, R.; Alonso, A.; Alviggi, M.G.; Amako, K.; Amelung, C.; Ammosov, V.V.; Amorim, A.; Amorós, G.; Amram, N.; Anastopoulos, C.; Andeen, T.; Anders, C.F.; Anderson, K.J.; Andreazza, A.; Andrei, V.; Anduaga, X.S.; Angerami, A.; Anghinolfi, F.; Anjos, N.; Antonaki, A.; Antonelli, M.; Antonelli, S.; Antunovic, B.; Anulli, F.; Aoun, S.; Arabidze, G.; Aracena, I.; Arai, Y.; Arce, A.T.H.; Archambault, J.P.; Arfaoui, S.; Arguin, J-F; Argyropoulos, T.; Arik, E.; Arik, M.; Armbruster, A.J.; Arnaez, O.; Arnault, C.; Artamonov, A.; Arutinov, D.; Asai, M.; Asai, S.; Asfandiyarov, R.; Ask, S.; Asman, B.; Asner, D.; Asquith, L.; Assamagan, K.; Astbury, A.; Astvatsatourov, A.; Atoian, G.; Auerbach, B.; Auge, E.; Augsten, K.; Aurousseau, M.; Austin, N.; Avolio, G.; Avramidou, R.; Axen, D.; Ay, C.; Azuelos, G.; Azuma, Y.; Baak, M.A.; Baccaglioni, G.; Bacci, C.; Bach, A.; Bachacou, H.; Bachas, K.; Backes, M.; Badescu, E.; Bagnaia, P.; Bai, Y.; Bailey, D.C.; Bain, T.; Baines, J.T.; Baker, O.K.; Baker, M.D.; Baltasar Dos Santos Pedrosa, F; Banas, E.; Banerjee, P.; Banerjee, S.; Banfi, D.; Bangert, A.; Bansal, V.; Baranov, S.P.; Baranov, S.; Barashkou, A.; Barber, T.; Barberio, E.L.; Barberis, D.; Barbero, M.; Bardin, D.Y.; Barillari, T.; Barisonzi, M.; Barklow, T.; Barlow, N.; Barnett, B.M.; Barnett, R.M.; Baron, S.; Baroncelli, A.; Barr, A.J.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Barrillon, P.; Barros, N.; Bartoldus, R.; Bartsch, D.; Bastos, J.; Bates, R.L.; Bathe, S.; Batkova, L.; Batley, J.R.; Battaglia, A.; Battistin, M.; Bauer, F.; Bawa, H.S.; Bazalova, M.; Beare, B.; Beau, T.; Beauchemin, P.H.; Beccherle, R.; Becerici, N.; Bechtle, P.; Beck, G.A.; Beck, H.P.; Beckingham, M.; Becks, K.H.; Bedajanek, I.; Beddall, A.J.; Beddall, A.; Bednár, P.; Bednyakov, V.A.; Bee, C.; Begel, M.; Behar Harpaz, S; Behera, P.K.; Beimforde, M.; Belanger-Champagne, C.; Bell, P.J.; Bell, W.H.; Bella, G.; Bellagamba, L.; Bellina, F.; Bellomo, M.; Belloni, A.; Belotskiy, K.; Beltramello, O.; Ben Ami, S; Benary, O.; Benchekroun, D.; Bendel, M.; Benedict, B.H.; Benekos, N.; Benhammou, Y.; Benincasa, G.P.; Benjamin, D.P.; Benoit, M.; Bensinger, J.R.; Benslama, K.; Bentvelsen, S.; Beretta, M.; Berge, D.; Bergeaas Kuutmann, E; Berger, N.; Berghaus, F.; Berglund, E.; Beringer, J.; Bernardet, K.; Bernat, P.; Bernhard, R.; Bernius, C.; Berry, T.; Bertin, A.; Besson, N.; Bethke, S.; Bianchi, R.M.; Bianco, M.; Biebel, O.; Biesiada, J.; Biglietti, M.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Biscarat, C.; Bitenc, U.; Black, K.M.; Blair, R.E.; Blanchard, J-B; Blanchot, G.; Blocker, C.; Blocki, J.; Blondel, A.; Blum, W.; Blumenschein, U.; Bobbink, G.J.; Bocci, A.; Boehler, M.; Boek, J.; Boelaert, N.; Böser, S.; Bogaerts, J.A.; Bogouch, A.; Bohm, C.; Bohm, J.; Boisvert, V.; Bold, T.; Boldea, V.; Boldyrev, A.; Bondarenko, V.G.; Bondioli, M.; Boonekamp, M.; Booth, J.R.A.; Bordoni, S.; Borer, C.; Borisov, A.; Borissov, G.; Borjanovic, I.; Borroni, S.; Bos, K.; Boscherini, D.; Bosman, M.; Bosteels, M.; Boterenbrood, H.; Bouchami, J.; Boudreau, J.; Bouhova-Thacker, E.V.; Boulahouache, C.; Bourdarios, C.; Boyd, J.; Boyko, I.R.; Bozovic-Jelisavcic, I.; Bracinik, J.; Braem, A.; Branchini, P.; Brandenburg, G.W.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J.E.; Braun, H.M.; Brelier, B.; Bremer, J.; Brenner, R.; Bressler, S.; Breton, D.; Brett, N.D.; Britton, D.; Brochu, F.M.; Brock, I.; Brock, R.; Brodbeck, T.J.; Brodet, E.; Broggi, F.; Bromberg, C.; Brooijmans, G.; Brooks, W.K.; Brown, G.; Brubaker, E.; Bruckman de Renstrom, P A; Bruncko, D.; Bruneliere, R.; Brunet, S.; Bruni, A.; Bruni, G.; Bruschi, M.; Buanes, T.; Bucci, F.; Buchanan, J.; Buchholz, P.; Buckley, A.G.; Budagov, I.A.; Budick, B.; Büscher, V.; Bugge, L.; Bulekov, O.; Bunse, M.; Buran, T.; Burckhart, H.; Burdin, S.; Burgess, T.; Burke, S.; Busato, E.; Bussey, P.; Buszello, C.P.; Butin, F.; Butler, B.; Butler, J.M.; Buttar, C.M.; Butterworth, J.M.; Byatt, T.; Caballero, J.; Cabrera Urbán, S; Caforio, D.; Cakir, O.; Calafiura, P.; Calderini, G.; Calfayan, P.; Calkins, R.; Caloba, L.P.; Caloi, R.; Calvet, D.; Camarri, P.; Cambiaghi, M.; Cameron, D.; Campabadal-Segura, F.; Campana, S.; Campanelli, M.; Canale, V.; Canelli, F.; Canepa, A.; Cantero, J.; Capasso, L.; Capeans-Garrido, M.D.M.; Caprini, I.; Caprini, M.; Capua, M.; 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Twomey, M.S.; Tylmad, M.; Tyndel, M.; Tzanakos, G.; Uchida, K.; Ueda, I.; Uhlenbrock, M.; Uhrmacher, M.; Ukegawa, F.; Unal, G.; Underwood, D.G.; Undrus, A.; Unel, G.; Unno, Y.; Urbaniec, D.; Urkovsky, E.; Urquijo, P.; Urrejola, P.; Usai, G.; Uslenghi, M.; Vacavant, L.; Vacek, V.; Vachon, B.; Vahsen, S.; Valenta, J.; Valente, P.; Valentinetti, S.; Valkar, S.; Valladolid Gallego, E; Vallecorsa, S.; Valls Ferrer, J A; Van Berg, R; van der Graaf, H; van der Kraaij, E; van der Poel, E; Van Der Ster, D; van Eldik, N; van Gemmeren, P; van Kesteren, Z; van Vulpen, I; Vandelli, W.; Vandoni, G.; Vaniachine, A.; Vankov, P.; Vannucci, F.; Varela Rodriguez, F; Vari, R.; Varnes, E.W.; Varouchas, D.; Vartapetian, A.; Varvell, K.E.; Vasilyeva, L.; Vassilakopoulos, V.I.; Vazeille, F.; Vegni, G.; Veillet, J.J.; Vellidis, C.; Veloso, F.; Veness, R.; Veneziano, S.; Ventura, A.; Ventura, D.; Venturi, M.; Venturi, N.; Vercesi, V.; Verducci, M.; Verkerke, W.; Vermeulen, J.C.; Vetterli, M.C.; Vichou, I.; Vickey, T.; Viehhauser, G.H.A.; Villa, M.; Villani, E.G.; Villaplana Perez, M; Villate, J.; Vilucchi, E.; Vincter, M.G.; Vinek, E.; Vinogradov, V.B.; Viret, S.; Virzi, J.; Vitale, A.; Vitells, O.V.; Vivarelli, I.; Vives Vaques, F; Vlachos, S.; Vlasak, M.; Vlasov, N.; Vogt, H.; Vokac, P.; Volpi, M.; Volpini, G.; von der Schmitt, H; von Loeben, J; von Radziewski, H; von Toerne, E; Vorobel, V.; Vorobiev, A.P.; Vorwerk, V.; Vos, M.; Voss, R.; Voss, T.T.; Vossebeld, J.H.; Vranjes, N.; Vranjes Milosavljevic, M; Vrba, V.; Vreeswijk, M.; Vu Anh, T; Vudragovic, D.; Vuillermet, R.; Vukotic, I.; Wagner, P.; Wahlen, H.; Walbersloh, J.; Walder, J.; Walker, R.; Walkowiak, W.; Wall, R.; Wang, C.; Wang, H.; Wang, J.; Wang, J.C.; Wang, S.M.; Ward, C.P.; Warsinsky, M.; Wastie, R.; Watkins, P.M.; Watson, A.T.; Watson, M.F.; Watts, G.; Watts, S.; Waugh, A.T.; Waugh, B.M.; Webel, M.; Weber, J.; Weber, M.D.; Weber, M.; Weber, M.S.; Weber, P.; Weidberg, A.R.; Weingarten, J.; Weiser, C.; Wellenstein, H.; Wells, P.S.; Wen, M.; Wenaus, T.; Wendler, S.; Wengler, T.; Wenig, S.; Wermes, N.; Werner, M.; Werner, P.; Werth, M.; Werthenbach, U.; Wessels, M.; Whalen, K.; Wheeler-Ellis, S.J.; Whitaker, S.P.; White, A.; White, M.J.; White, S.; Whiteson, D.; Whittington, D.; Wicek, F.; Wicke, D.; Wickens, F.J.; Wiedenmann, W.; Wielers, M.; Wienemann, P.; Wiglesworth, C.; Wiik, L.A.M.; Wildauer, A.; Wildt, M.A.; Wilhelm, I.; Wilkens, H.G.; Williams, E.; Williams, H.H.; Willis, W.; Willocq, S.; Wilson, J.A.; Wilson, M.G.; Wilson, A.; Wingerter-Seez, I.; Winklmeier, F.; Wittgen, M.; Wolter, M.W.; Wolters, H.; Wosiek, B.K.; Wotschack, J.; Woudstra, M.J.; Wraight, K.; Wright, C.; Wright, D.; Wrona, B.; Wu, S.L.; Wu, X.; Wulf, E.; Xella, S.; Xie, S.; Xie, Y.; Xu, D.; Xu, N.; Yamada, M.; Yamamoto, A.; Yamamoto, S.; Yamamura, T.; Yamanaka, K.; Yamaoka, J.; Yamazaki, T.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, U.K.; Yang, Y.; Yang, Z.; Yao, W-M; Yao, Y.; Yasu, Y.; Ye, J.; Ye, S.; Yilmaz, M.; Yoosoofmiya, R.; Yorita, K.; Yoshida, R.; Young, C.; Youssef, S.P.; Yu, D.; Yu, J.; Yu, M.; Yu, X.; Yuan, J.; Yuan, L.; Yurkewicz, A.; Zaidan, R.; Zaitsev, A.M.; Zajacova, Z.; Zambrano, V.; Zanello, L.; Zarzhitsky, P.; Zaytsev, A.; Zeitnitz, C.; Zeller, M.; Zema, P.F.; Zemla, A.; Zendler, C.; Zenin, O.; Zenis, T.; Zenonos, Z.; Zenz, S.; Zerwas, D.; Zevi della Porta, G; Zhan, Z.; Zhang, H.; Zhang, J.; Zhang, Q.; Zhang, X.; Zhao, L.; Zhao, T.; Zhao, Z.; Zhemchugov, A.; Zheng, S.; Zhong, J.; Zhou, B.; Zhou, N.; Zhou, Y.; Zhu, C.G.; Zhu, H.; Zhu, Y.; Zhuang, X.; Zhuravlov, V.; Zilka, B.; Zimmermann, R.; Zimmermann, S.; Zimmermann, S.; Ziolkowski, M.; Zitoun, R.; Zivkovic, L.; Zmouchko, V.V.; Zobernig, G.; Zoccoli, A.; zur Nedden, M; Zutshi, V.

    2010-01-01

    The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing performance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along eta (averaged over phi) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained u...

  1. Development of cryogenic installations for large liquid argon neutrino detectors

    CERN Document Server

    Adamowski, M; Geynisman, M; Hentschel, S; Montanari, D; Nessi, M; Norris, B

    2015-01-01

    A proposal for a very large liquid argon (68,000 kg) based neutrino detector is being studied. To validate the design principles and the detector technology, and to gain experience in the development of the cryostats and the cryogenic systems needed for such large experiments, several smaller scale installations will be developed and implemented, at Fermilab and CERN. The cryogenic systems for these installations will be developed, constructed, installed and commissioned by an international engineering team. These installations shall bring the required cooling power under specific conditions to the experiments for the initial cool-down and the long term operation, and shall also guarantee the correct distribution of the cooling power within the cryostats to ensure a homogeneous temperature distribution within the cryostat itself. The cryogenic systems shall also include gaseous and liquid phase argon purification devices to be used to reach and maintain the very stringent purity requirements needed for these...

  2. Measurement of longitudinal electron diffusion in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yichen, E-mail: yichen@bnl.gov [Physics Department, Brookhaven National Laboratory, 20 Pennsylvania St., Building 510E, Upton, NY 11973 (United States); Tsang, Thomas [Instrumentation Division, Brookhaven National Laboratory, 20 N. Technology St., Building 535B, Upton, NY 11973 (United States); Thorn, Craig; Qian, Xin; Diwan, Milind; Joshi, Jyoti; Kettell, Steve; Morse, William [Physics Department, Brookhaven National Laboratory, 20 Pennsylvania St., Building 510E, Upton, NY 11973 (United States); Rao, Triveni [Instrumentation Division, Brookhaven National Laboratory, 20 N. Technology St., Building 535B, Upton, NY 11973 (United States); Stewart, James; Tang, Wei; Viren, Brett [Physics Department, Brookhaven National Laboratory, 20 Pennsylvania St., Building 510E, Upton, NY 11973 (United States)

    2016-04-21

    We report the measurement of longitudinal electron diffusion coefficients in liquid argon for electric fields between 100 and 2000 V/cm with a gold photocathode as a bright electron source. The measurement principle, apparatus, and data analysis are described. In the region between 100 and 350 V/cm, our results show a discrepancy with the previous measurement [1]. In the region between 350 and 2000 V/cm, our results represent the world's best measurement. Over the entire measured electric field range, our results are systematically higher than the calculation of Atrazhev‐Timoshkin [2]. The quantum efficiency of the gold photocathode, the drift velocity and longitudinal diffusion coefficients in gas argon are also presented.

  3. Breakdown voltage of metal-oxide resistors in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Bagby, L. F. [Fermilab; Gollapinni, S. [Kansas State U.; James, C. C. [Fermilab; Jones, B. J.P. [MIT; Jostlein, H. [Fermilab; Lockwitz, S. [Fermilab; Naples, D. [Pittsburgh U.; Raaf, J. L. [Fermilab; Rameika, R. [Fermilab; Schukraft, A. [Fermilab; Strauss, T. [Bern U., LHEP; Weber, M. S. [Bern U., LHEP; Wolbers, S. A. [Fermilab

    2014-11-07

    We characterized a sample of metal-oxide resistors and measured their breakdown voltage in liquid argon by applying high voltage (HV) pulses over a 3 second period. This test mimics the situation in a HV-divider chain when a breakdown occurs and the voltage across resistors rapidly rise from the static value to much higher values. All resistors had higher breakdown voltages in liquid argon than their vendor ratings in air at room temperature. Failure modes range from full destruction to coating damage. In cases where breakdown was not catastrophic, subsequent breakdown voltages were lower in subsequent measuring runs. One resistor type withstands 131 kV pulses, the limit of the test setup.

  4. A pressurized argon gas TPC as DUNE near detector

    Science.gov (United States)

    Martín-Albo, J.; DUNE Collaboration

    2017-09-01

    DUNE is a new international experiment for neutrino physics and nucleon decay searches. It will consist of two detectors, about 1300 km apart, exposed to a multi-megawatt neutrino beam that will be built at Fermilab. One of the two detectors will be installed several hundred meters downstream of the neutrino production point with the primary role of characterising the energy spectrum and composition of the beam as well as performing precision measurements of neutrino cross sections. For the design of this so-called near detector, the DUNE Collaboration is considering, among other technologies, a pressurized argon gas time projection chamber. Such a detector, thanks to its low density and low detection thresholds, would allow the detailed measurement in argon of nuclear effects at the neutrino interaction vertex, which are considered at present one of the most important sources of systematic uncertainty for neutrino oscillation measurements.

  5. Detection of Cherenkov light emission in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Antonello, M.; Arneodo, F.; Badertscher, A.; Baiboussinov, B.; Baldo Ceolin, M.; Battistoni, G.; Bekman, B.; Benetti, P.; Bernardini, E.; Bischofberger, M.; Borio di Tigliole, A.; Brunetti, R.; Bueno, A.; Calligarich, E.; Campanelli, M.; Carpanese, C.; Cavalli, D.; Cavanna, F. E-mail: flavio.cavanna@aquila.infn.it; Cennini, P.; Centro, S.; Cesana, A.; Chen, C.; Chen, D.; Chen, D.B.; Chen, Y.; Cieslik, C.; Cline, D.; Dai, Z.; De Vecchi, C.; Dabrowska, A.; Dolfini, R.; Felcini, M.; Ferrari, A.; Ferri, F.; Ge, Y.; Gibin, D.; Gigli Berzolari, A.; Gil-Botella, I.; Graczyk, K.; Grandi, L.; Guglielmi, A.; He, K.; Holeczek, J.; Huang, X.; Juszczak, C.; Kielczewska, D.; Kisiel, J.; Kozlowski, T.; Laffranchi, M.; Lagoda, J.; Li, Z.; Lu, F.; Ma, J.; Markiewicz, M.; Matthey, C.; Mauri, F.; Mazza, D.; Meng, G.; Messina, M.; Montanari, C.; Muraro, S.; Navas-Concha, S.; Nurzia, G.; Otwinowski, S.; Ouyang, Q.; Palamara, O.; Pascoli, D.; Periale, L.; Piano Mortari, G.B.; Piazzoli, A.; Picchi, P.; Pietropaolo, F.; Polchlopek, W.; Rancati, T.; Rappoldi, A.; Raselli, G.L.; Rico, J.; Rondio, E.; Rossella, M.; Rubbia, A.; Rubbia, C.; Sala, P.; Scannicchio, D.; Segreto, E.; Seo, Y.; Sergiampietri, F.; Sobczyk, J.; Stepaniak, J.; Szarska, M.; Szeptycka, M.; Terrani, M.; Ventura, S.; Vignoli, C.; Wang, H.; Woo, J.; Xu, G.; Xu, Z.; Zalewska, A.; Zalipska, J.; Zhang, C.; Zhang, Q.; Zhen, S.; Zipper, W

    2004-01-11

    Detection of Cherenkov light emission in liquid argon has been obtained with an ICARUS prototype, during a dedicated test run at the Gran Sasso Laboratory external facility. Ionizing tracks from cosmic ray muons crossing the detector active volume have been collected in coincidence with visible light signals from a photo-multiplier (PMT) immersed in liquid argon. A 3D reconstruction of the tracks has been performed exploiting the ICARUS imaging capability. The angular distributions of the tracks triggered by the PMT signals show an evident directionality. By means of a detailed Monte Carlo simulation we show that the geometrical characteristics of the events are compatible with the hypothesis of Cherenkov light emission as the main source of the PMT signals.

  6. Dynamics Resonances in Atomic States of Astrophysical Relevance

    CERN Document Server

    Arefieff, K N; Bezuglov, N N; Dimitrijevic, M S; Klyucharev, A N; Mihajlov, A A; Sreckovic, V A

    2016-01-01

    Ionized geocosmic media parameters in a thermal and a subthermal range of energy have a number of unique features. The photoresonance plasma that is formed by optical excitation of the lowest excited (resonance) atomic states is one example of conversion of radiation energy into electrical one. Since spontaneous fluorescence of excited atoms is probabilistic, the description of the radiating quantized system evolution along with photons energy transfer in a cold atoms medium, should include elements of stochastic dynamics. Finally, the chaotic dynamics of a weakly bound Rydberg electron over a grid of the energy levels diagram of a quasi-molecular Rydberg complex provides an excitation migration of the electron forward to the ionization continuum. This work aims at discussing the specific features of the dynamic resonances formalism in the description of processes involving Rydberg states of an excited atom, including features in the fluorescence spectrum partially caused by the quantum defect control due to ...

  7. Thermal decomposition of lanthanum(III) butyrate in argon atmosphere

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Yue, Zhao; Xiao, Tang

    2013-01-01

    The thermal decomposition of La(C3H7CO2)3·xH2O (x≈0.82) was studied in argon during heating at 5K/min. After the loss of bound H2O, the anhydrous butyrate presents at 135°C a phase transition to a mesophase, which turns to an isotropic liquid at 180°C. The decomposition of the anhydrous butyrate ...

  8. Collective excitations of a Bose-Einstein condensate in a magnetic trap

    NARCIS (Netherlands)

    Mewes, M.O.; Andrews, M.R.; van Druten, N.J.; Kurn, D.M.; Durfee, D.S.; Townsend, C.G.; Ketterle, W.

    1996-01-01

    Collective excitations of a dilute Bose condensate have been observed. These excitations are analogous to phonons in superfluid helium. Bose condensates were created by evaporatively cooling magnetically trapped sodium atoms. Excitations were induced by a modulation of the trapping potential, and

  9. Cryogenic Tests of the Atlas Liquid Argon Calorimeter

    CERN Document Server

    Fabre, C; Chalifour, M; Gonidec, A; Passardi, Giorgio

    2006-01-01

    The ATLAS liquid argon calorimeter consists of the barrel and two end-cap detectors housed in three independent cryostats filled with a total volume of 78 m3 of liquid argon. During cool-down the temperature differences in the composite structure of the detectors must be kept within strict limits to avoid excessive mechanical stresses and relative displacements. During normal operation the formation of gas bubbles, which are detrimental to the functioning of the detector, must be prevented and temperature gradients of less than 0.7 K across the argon bath are mandatory due to the temperature dependence of the energy measurements. Between April 2004 and May 2005 the barrel (120 t) and one end-cap (219 t) underwent qualification tests at the operating temperature of 87.3 K using a dedicated test facility at ground level. These tests provided a validation of the cooling methods to be adopted in the final underground configuration. In total 6.9 GJ and 15.7 GJ were extracted from the calorimeters and a temperature...

  10. Status of the ATLAS Liquid Argon Calorimeter and its Performance

    CERN Document Server

    Barillari, T; The ATLAS collaboration

    2011-01-01

    The ATLAS experiment is designed to study the proton-proton collisions produced at the LHC with a centre-of-mass energy of 14 TeV. Liquid argon (LAr) sampling calorimeters are used in ATLAS for all electromagnetic calorimetry covering the pseudorapidity region |eta|<3.2, as well as for hadronic calorimetry from |eta|=1.4 to |eta|=4.8. The calorimeter system consists of an electromagnetic barrel calorimeter and two endcaps with electromagnetic (EMEC), hadronic (HEC) and forward (FCAL) calorimeters. The lead-liquid argon sampling technique with an accordion geometry was chosen for the barrel electromagnetic calorimeter (EMB) and adapted to the endcap (EMEC). This geometry allows a uniform acceptance over the whole azimuthal range without any gap. The hadronic endcap calorimeter (HEC) uses a copper-liquid argon sampling technique with plate geometry and is subdivided into two wheels in depth per end-cap. Finally, the forward calorimeter (FCAL) is composed of three modules featuring cylindrical electrodes ...

  11. Relativistic atomic beam spectroscopy II

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1989-12-31

    The negative ion of H is one of the simplest 3-body atomic systems. The techniques we have developed for experimental study of atoms moving near speed of light have been productive. This proposal request continuing support for experimental studies of the H{sup -} system, principally at the 800 MeV linear accelerator (LAMPF) at Los Alamos. Four experiments are currently planned: photodetachment of H{sup -} near threshold in electric field, interaction of relativistic H{sup -} ions with matter, high excitations and double charge escape in H{sup -}, and multiphoton detachment of electrons from H{sup -}.

  12. Condensate of excitations in moving superfluids

    CERN Document Server

    Kolomeitsev, E E

    2016-01-01

    A possibility of the condensation of excitations with a non-zero momentum in rectilinearly moving and rotating superfluid bosonic and fermionic (with Cooper pairing) media is considered in terms of a phenomenological order-parameter functional at zero and non-zero temperature. The results might be applicable to the description of bosonic systems like superfluid $^4$He, ultracold atomic Bose gases, charged pion and kaon condensates in rotating neutron stars, and various superconducting fermionic systems with pairing, like proton and color-superconducting components in compact stars, metallic superconductors, and neutral fermionic systems with pairing, like the neutron component in compact stars and ultracold atomic Fermi gases. Order parameters of the "mother" condensate in the superfluid and the new condensate of excitations, corresponding energy gains, critical temperatures and critical velocities are found.

  13. Atomic theories

    CERN Document Server

    Loring, FH

    2014-01-01

    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  14. Enhancing ion yields in time-of-flight-secondary ion mass spectrometry: a comparative study of argon and water cluster primary beams.

    Science.gov (United States)

    Sheraz née Rabbani, Sadia; Razo, Irma Berrueta; Kohn, Taylor; Lockyer, Nicholas P; Vickerman, John C

    2015-02-17

    Following from our previous Letter on this topic, this Article reports a detailed study of time-of-flight-secondary ion mass spectrometry (TOF-SIMS) positive ion spectra generated from a set of model biocompounds (arginine, trehalose, DPPC, and angiotensin II) by water cluster primary ion beams in comparison to argon cluster beams over a range of cluster sizes and energies. Sputter yield studies using argon and water beams on arginine and Irganox 1010 have confirmed that the sputter yields using water cluster beams lie on the same universal sputtering curve derived by Seah for argon cluster beams. Thus, increased ion yield using water cluster beams must arise from increased ionization. The spectra and positive ion signals observed using cluster beams in the size range from 1,000 to 10,000 and the energy range 5-20 keV are reported. It is confirmed that water cluster beams enhance proton related ionization over against argon beams to a significant degree such that enhanced detection sensitivities from 1 μm(2) in the region of 100 to 1,000 times relative to static SIMS analysis with Ar2000 cluster beams appear to be accessible. These new studies show that there is an unexpected complexity in the ionization enhancement phenomenon. Whereas optimum ion yields under argon cluster bombardment occur in the region of E/n ≥ 10 eV (where E is the beam energy and n the number of argon atoms in the cluster) and fall rapidly when E/n beams, ion yields increase significantly in this E/n regime (where n is the number of water molecules in the cluster) and peak for 20 keV beams at a cluster size of 7,000 or E/n ∼3 eV. This important result is explored further using D2O cluster beams that confirm that in this low E/n regime protonation does originate to a large extent from the water molecules. The results, encouraging in themselves, suggest that for both argon and water cluster beams, higher energy beams, e.g., 40 and 80 keV, would enable larger cluster sizes to be exploited

  15. Matrix photochemistry of small molecules: Influencing reaction dynamics on electronically excited hypersurfaces

    Energy Technology Data Exchange (ETDEWEB)

    Laursen, S.L.

    1990-01-01

    Investigations of chemical reactions on electronically excited reaction surfaces are presented. The role of excited-surface multiplicity is of particular interest, as are chemical reactivity and energy transfer in systems in which photochemistry is initiated through a metal atom sensitizer.'' Two approaches are employed: A heavy-atom matrix affords access to forbidden triplet reaction surfaces, eliminating the need for a potentially reactive sensitizer. Later, the role of the metal atom in the photosensitization process is examined directly.

  16. Resonance broadening of argon lines in a micro-scaled atmospheric pressure plasma jet (argon μAPPJ)

    Science.gov (United States)

    Pipa, A. V.; Ionikh, Yu. Z.; Chekishev, V. M.; Dünnbier, M.; Reuter, S.

    2015-06-01

    Optical emission from atmospheric pressure micro-jet operating with pure argon (argon μAPPJ) flow has been detected with a moderate resolution spectrometer. Large broadening of the several argon (Ar) lines has been observed in the near infrared spectral region. This effect was attributed to resonance broadening of the s2 (Paschen notation) level in 3p54s configuration. In the present work, corresponding line profiles are suggested for plasma diagnostics. For this, a general case of resonance broadening coefficient of noble gases is discussed. As broadening reflects the Ar density, and the static gas pressure of the jet is in equilibrium with the ambient, the local gas temperature can be inferred. An estimation of gas temperature from the width of the 750 nm Ar line is in agreement with rotational temperature of OH radicals determined from the A2Σ+ → X2Π (0, 0) band. At low temperatures (300-600 K) and at partial Ar pressure near atmospheric, the resonance width of the suggested lines is very sensitive to small temperature variations. High temperature sensitivity and large width make the resonance broadened lines very attractive for diagnostics of low temperature discharges at elevated pressure, e.g., as they are used in plasma-medicine.

  17. Correlation effects of excited charge carriers in semiconductor nanostructures on the example of InGaAs quantum dots and atomic MoS{sub 2} monolayers; Korrelationseffekte angeregter Ladungstraeger in Halbleiter-Nanostrukturen am Beispiel von InGaAs-Quantenpunkten und atomaren MoS{sub 2}-Monolagen

    Energy Technology Data Exchange (ETDEWEB)

    Steinhoff, Alexander

    2014-11-10

    Semiconductor nanostructures are applied in various electronic and optoelectronic devices. As miniaturization of these devices progresses, a microscopic treatment of correlations between excited carriers is essential for understanding and describing the governing physics. We investigate two different types of semiconductor nanostructures, which have each received considerable attention over the last years. These are self-assembled InGaAs quantum dots (QDs) on the one hand and atomic monolayers of MoS{sub 2} on the other hand. Self-assembled semiconductor QDs are used as active material in conventional lasers and as efficient non-classical light sources with applications in quantum information. As they can confine a small number of carriers in localized stats with discrete energies, it is questionable to neglect correlations between the carriers when describing their dynamics. We analyze the influence of carrier correlations in a single QD on Coulomb scattering processes, which are due to the contact with a quasi-continuum of wetting-layer (WL) states. Results obtained from a Boltzmann equation are compared with the fully correlated dynamics governed by a von-Neumann-Lindblad equation. In a first step, we take into account correlations generated by the exact treatment of Pauli blocking due to the contributing QD carrier configurations. Subsequently, we include correlations generated by energy renormalizations due to Coulomb interaction between the QD carriers. It is shown that at low WL carrier densities, neither Pauli correlations nor Coulomb correlations can be safely neglected, if the dynamics of single-particle states in the QD are to be predicted qualitatively and quantitatively. In the high-density regime, both types of correlations play a lesser role and thus a description of carrier dynamics by a Boltzmann equation becomes reliable. Furthermore, the efficiency of WL-assisted scattering processes as well as scattering-induced dephasing rates depending on the

  18. Atomic Power

    African Journals Online (AJOL)

    Atomic Power. By Denis Taylor: Dr. Taylor was formerly Chief UNESCO Advisor at the University. College, Nairobi, Kenya and is now Professor of Electrical Engineering in the Uni- versity of ... method of producing radioactive isotopes, which are materials .... the sealing and the pressure balancing, all can be carried out ...

  19. Quantum Spin Lenses in Atomic Arrays

    Directory of Open Access Journals (Sweden)

    A. W. Glaetzle

    2017-09-01

    Full Text Available We propose and discuss quantum spin lenses, where quantum states of delocalized spin excitations in an atomic medium are focused in space in a coherent quantum process down to (essentially single atoms. These can be employed to create controlled interactions in a quantum light-matter interface, where photonic qubits stored in an atomic ensemble are mapped to a quantum register represented by single atoms. We propose Hamiltonians for quantum spin lenses as inhomogeneous spin models on lattices, which can be realized with Rydberg atoms in 1D, 2D, and 3D, and with strings of trapped ions. We discuss both linear and nonlinear quantum spin lenses: in a nonlinear lens, repulsive spin-spin interactions lead to focusing dynamics conditional to the number of spin excitations. This allows the mapping of quantum superpositions of delocalized spin excitations to superpositions of spatial spin patterns, which can be addressed by light fields and manipulated. Finally, we propose multifocal quantum spin lenses as a way to generate and distribute entanglement between distant atoms in an atomic lattice array.

  20. Investigation of local thermodynamic equilibrium of laser induced Al2O3–TiC plasma in argon by spatially resolved optical emission spectroscopy

    Directory of Open Access Journals (Sweden)

    K. Alnama

    2016-06-01

    Full Text Available Plasma plume of Al2O3–TiC is generated by third harmonic Q-switched Nd:YAG nanosecond laser. It is characterized using Optical Emission Spectroscopy (OES at different argon background gas pressures 10, 102, 103, 104 and 105 Pa. Spatial evolution of excitation and ionic temperatures is deduced from spectral data analysis. Temporal evolution of Ti I emission originated from different energy states is probed. The correlation between the temporal behavior and the spatial temperature evolution are investigated under LTE condition for the possibility to use the temporal profile of Ti I emission as an indicator for LTE validity in the plasma.

  1. Livermore experience: contributions of J. H. Eberly to laser excitation theory

    Energy Technology Data Exchange (ETDEWEB)

    Shore, B W; Kulander, K; Davis, J I

    2000-10-12

    This article summarizes the developing understanding of coherent atomic excitation, as gained through a collaboration of J. H. Eberly with the Laser Isotope Separation Program of the Lawrence Livermore National Laboratory, particularly aspects of coherence, population trapping, multilevel multiphoton excitation sequences, analytic solutions to multistate excitation chains, the quasicontinuum, pulse propagation, and noise. In addition to the discovery of several curious and unexpected properties of coherent excitation, mentioned here, the collaboration provided an excellent example of unexpected benefits from investment into basic research.

  2. Reactions of pulsed-laser evaporated lithium atoms with O 2 and N 2O

    Science.gov (United States)

    Andrews, Lester; Saffell, Wendy; Yustein, Jason T.

    1994-12-01

    Pulsed laser evaporated Li atoms were codeposited with O 2 in excess argon at 12 K. The same LiO 2 and LiO 2Li products were observed that were formed with thermal Li atoms. However, with N 2O the LiO product was observed in contrast to thermal Li atom reactions. Excess kinetic energy in the laser evaporated Li atoms provided activation energy for the abstraction reaction. In addition the extremely large yield of O 4- observed in O 2 experiments provides evidence for photoelectron emission from the lithium metal surface.

  3. Recent updates on the ArDM project: A Liquid Argon TPC for Dark Matter Detection

    OpenAIRE

    Boccone, Vittorio

    2008-01-01

    ArDM is a new-generation WIMP detector which will measure simultaneously light and charge from scintillation and ionization of liquid argon. Our goal is to construct, characterize and operate a 1 ton liquid argon underground detector. The project relies on the possibility to extract the electrons produced by ionization from the liquid into the gas phase of the detector, to amplify and read out with Large Electron Multipliers detectors. Argon VUV scintillation light has to be converted with wa...

  4. The ArDM project: A liquid argon TPC for dark matter detection

    OpenAIRE

    Boccone, V.

    2009-01-01

    ArDM is a new-generation WIMP detector which will measure simultaneously light and charge from scintillation and ionization of liquid argon. Our goal is to construct, characterize and operate a 1 ton liquid argon underground detector. The project relies on the possibility to extract the electrons produced by ionization from the liquid into the gas phase of the detector, to amplify and read out with Large Electron Multipliers detectors. Argon VUV scintillation light has to be converted with wa...

  5. Composition of the atmosphere at the surface of Mars - Detection of argon-36 and preliminary analysis

    Science.gov (United States)

    Owen, T.; Biemann, K.

    1976-01-01

    The composition of the Martian atmosphere was determined by the mass spectrometer in the molecular analysis experiment. The presence of argon and nitrogen was confirmed and a value of 1 to 2750 plus or minus 500 for the ratio of argon-36 to argon-40 was established. A preliminary interpretation of these results suggests that Mars had a slightly more massive atmosphere in the past, but that much less total outgassing has occurred on Mars than on earth.

  6. Excited states 4

    CERN Document Server

    Lim, Edward C

    2013-01-01

    Excited States, Volume 4 is a collection of papers that deals with the excited states of molecular activity. One paper investigates the resonance Raman spectroscopy as the key to vibrational-electronic coupling. This paper reviews the basic theory of Raman scattering; it also explains the derivation of the Raman spectra, excitation profiles, and depolarization ratios for simple resonance systems. Another paper reviews the magnetic properties of triplet states, including the zero-field resonance techniques, the high-field experiments, and the spin Hamiltonian. This paper focuses on the magnetic

  7. Nuclear expansion with excitation

    Energy Technology Data Exchange (ETDEWEB)

    De, J.N. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Departament d' Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona (Spain); Samaddar, S.K. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Vinas, X. [Departament d' Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona (Spain); Centelles, M. [Departament d' Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona (Spain)]. E-mail: mario@ecm.ub.es

    2006-07-06

    The expansion of an isolated hot spherical nucleus with excitation energy and its caloric curve are studied in a thermodynamic model with the SkM{sup *} force as the nuclear effective two-body interaction. The calted results are shown to compare well with the recent experimental data from energetic nuclear collisions. The fluctuations in temperature and density are also studied. They are seen to build up very rapidly beyond an excitation energy of {approx}9 MeV/u. Volume-conserving quadrupole deformation in addition to expansion indicates, however, nuclear disassembly above an excitation energy of {approx}4 MeV/u.

  8. Physical and chemical properties of low-pressure argon-chlorine dielectric barrier discharge

    Science.gov (United States)

    Barjasteh, Azadeh; Eslami, Esmaeil

    2016-03-01

    The influence of adding chlorine on the characteristics of a dielectric barrier discharge in Argon is investigated on the basis of a one-dimensional fluid model. The spatio-temporal characteristics of the discharge are obtained by applying a sinusoidal voltage with a frequency and amplitude of 7 kHz and 350 V, respectively. The study shows that the discharge has a homogeneous feature across the electrodes and has only one current pulse per half cycle of the applied voltage. The calculated electric field and electric potential as well as species number densities indicated that the discharge is in glow mode, and adding chlorine as electronegative gas up to 50% does not change its mode. It is observed that the most abundant negative species are C l - ions even in low additive chlorine. As a result, the maximum of plasma electronegativity takes place at 30% amounts of chlorine additive. The study of plasma radiations on the discharge gap shows that the main spontaneous emissions are observed at the wavelengths of 128.5 nm and 258 nm due to de-excitation of A r C l * and C l2 * molecules, respectively. Between different Ar/Cl2 mixtures, 0.99 A r - 0.01 C l 2 has the nearly uniform radiation in the positive column region.

  9. Effect of Cryogenic Cooling for Gallium Nitride Film Placed in Argon Plasma

    Science.gov (United States)

    Ogawa, Daisuke; Nakano, Yoshitaka; Nakamura, Keiji

    2014-10-01

    There is no doubt for a gallium nitride (GaN) film to have plasma-induced damage (PID) when exposed in a plasma discharge. Our technique to make in-situ monitoring on a GaN film exposed in argon plasma is valuable toward to reveal the evolution of the damage. We evaluated the PID with photoluminescence (PL) that is excited with a ultra-violet light source. Our preliminary result showed that the PL intensity at the blue luminescence band (BL: 400--480 nm) increased while the intensity at yellow luminescence (YL: 480--700 nm) decreased as the plasma exposure time increased. Chen et al. previously found that PL spectrum changes due to both PID and substrate temperature. However, BL intensity is independent from the substrate temperature, while BL intensity is dependent on the degree of PID. In this experiment, we performed the plasma exposure to a GaN film under the situation when the substrate temperature was cooled with liquid nitrogen. The substrate temperature is set at -110 degC and exposed plasma in 15 minutes. In this condition, our BL stayed almost constant. This is an indication that we might be able to avoid the damage in the wavelength shorter than 480 nm. We will show more details from this results and further progresses in this presentation.

  10. An atom in a multi-frequency laser emission field

    Energy Technology Data Exchange (ETDEWEB)

    Delone, N.B.; Kovarskii, V.A.; Masalov, A.V.; Perelman, N.F.

    1980-01-01

    An analysis of the features of the interaction between a nonmonochromatic multi-frequency laser emission field and an isolated atom is given. The multi-photon excitation and non-linear ionization of the atom during the excitation of the atomic levels by the laser emission field are examined. Specific cases of the interaction between the atom and the field are examined in detail: the case of a broad laser emission laser spectrum (rapid field fluctuations) and the case of a narrow spectrum (slow fluctuation). The available experimental data relating to these problems are analyzed.

  11. The exponential laws for emission and decaying of entangled atoms

    Science.gov (United States)

    Sancho, Pedro

    2017-08-01

    The first photon emission and the disentanglement of a pair of identical bosonic atoms in excited entangled states follow an exponential law. We extend the theory to distinguishable and identical fermionic two-atom systems. As a byproduct of the analysis we determine the symmetries of the fermionic wave function. We also derive the emission distributions of excited atoms in product states, which must take into account the presence of simultaneous detections. Comparing both distributions reveals a direct manifestation of the modifications induced by entanglement on the atomic emission properties.

  12. Collisional-radiative nonequilibrium in partially ionized atomic nitrogen

    Science.gov (United States)

    Kunc, J. A.; Soon, W. H.

    1989-01-01

    A nonlinear collisional-radiative model for determination of nonequilibrium production of electrons, excited atoms, and bound-bound, dielectronic and continuum line intensities in stationary partially ionized atomic nitrogen is presented. Populations of 14 atomic levels and line intensities are calculated in plasma with T(e) = 8000-15,000 K and N(t) = 10 to the 12th - 10 to the 18th/cu cm. Transport of radiation is included by coupling the rate equations of production of the electrons and excited atoms with the radiation escape factors, which are not constant but depend on plasma conditions.

  13. Atomic arias

    Science.gov (United States)

    Crease, Robert P.

    2009-01-01

    The American composer John Adams uses opera to dramatize controversial current events. His 1987 work Nixon in China was about the landmark meeting in 1972 between US President Richard Nixon and Chairman Mao Zedong of China; The Death of Klinghoffer (1991) was a musical re-enactment of an incident in 1985 when Palestinian terrorists kidnapped and murdered a wheelchair-bound Jewish tourist on a cruise ship. Adams's latest opera, Doctor Atomic, is also tied to a controversial event: the first atomic-bomb test in Alamogordo, New Mexico, on 16 June 1945. The opera premièred in San Francisco in 2005, had a highly publicized debut at the Metropolitan Opera in New York in 2008, and will have another debut on 25 February - with essentially the same cast - at the English National Opera in London.

  14. Atomic rivals

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmidt, B.

    1990-01-01

    This book is a memoir of rivalries among the Allies over the bomb, by a participant and observer. Nuclear proliferation began in the uneasy wartime collaboration of the United States, England, Canada, and Free France to produce the atom bomb. Through the changes of history, a young French chemist had a role in almost every act of this international drama. This memoir is based on Goldschmidt's own recollections, interviews with other leading figures, and 3,000 pages of newly declassified documents in Allied archives. From his own start as Marie Curie's lab assistant, Goldschmidt's career was closely intertwined with Frances complicated rise to membership in the nuclear club. As a refugee from the Nazis, he became part of the wartime nuclear energy project in Canada and found himself the only French scientist to work (although briefly) on the American atom bomb project.

  15. Rydberg Atom Quantum Hybrid Systems

    Science.gov (United States)

    Chao, Yuanxi; Sheng, Jiteng; Kumar, Santosh; Bigelow, Nicholas P.; Shaffer, James P.

    2017-04-01

    We report on our recent experimental and theoretical work with Rydberg atom-cavity and Rydberg atom-surface hybrid quantum systems. In the atom-cavity system, Rb contained in a dipole trap is transported into a high-finesse optical cavity using a focus-tunable lens. Cavity assisted Rydberg EIT is observed in the cavity transmission and used to characterize the electric fields in the cavity. The electric fields are attributed to surface adsorbates adhering to the cavity mirrors. We also investigate the coupling of a Rydberg atom ensemble to surface phonon polaritons (SPhPs) propagating on piezoelectric superlattices made from thin film ferroelectric materials. Strong coupling between the atomic and surface excitations can be achieved, due to the large Rydberg transition dipole moments and the local field enhancement of the SPhP modes. The system has many advantages for information transport since the atoms need only be placed at distances on the order of mms from the surface and the SPhPs do not couple to free space electro-magnetic fields. Experimental progress will be discussed, including the fabrication of submicron-period periodically poled Lithium Niobate using the direct e-beam writing technique. This work is supported by AFOSR.

  16. Quantum dynamics and topological excitations in interacting dipolar particles

    Science.gov (United States)

    Rey, Ana

    2016-05-01

    Dipole-dipole interactions, long-range and anisotropic interactions that arise due to the virtual exchange of photons, are of fundamental importance in optical physics, and are enabling a range of new quantum technologies including quantum networks and optical lattice atomic clocks. In this talk I will first discuss how arrays of dipolar particles with a simple J = 0- J = 1 internal level structure can naturally host topological and chiral excitations including Weyl quasi-particles. Weyl fermions were first predicted to exist in the context of high energy physics but only recently have been observed in solid state systems. I will discuss a proposal of using Mott insulators of Sr atoms to observe and probe the Weyl excitation spectrum and its non-trivial chirality. Finally I will report on a recent experiment done at JILA which validates the underlying microscopic model that predicts the existence of these excitations. The experiment measured the collective emission from a coherently driven gas of ultracold 88 Sr atoms and observed a highly directional and anisotropic emission intensity and a substantial broadening of the atomic spectral lines. All of the measurements are well reproduced by the theoretical model. These investigations open the door for the exploration of novel quantum many-body systems involving strongly interacting atoms and photons, and are useful guides for further developments of optical atomic clocks and other applications involving dense atomic ensembles. AFOSR, MURI-AFOSR, ARO,NSF-PHY-1521080, JILA-NSF-PFC-1125844.

  17. Study of a Novel Concept for a Liquid Argon Calorimeter \

    CERN Multimedia

    2002-01-01

    % RD33 \\\\ \\\\ The development of a fast, highly granular and compact electromagnetic liquid argon calorimeter prototype is proposed as a generic R\\&D project for a novel concept of calorimetry in proton-proton and electron-positron collider detectors: the $^{\\prime$Thin Gap Turbine$^{\\prime}$ (TGT). The TGT calorimeter has a modular construction, is flexible in its longitudinal and transverse granularity, and offers a uniform energy response and resolution, independent of the production angle of incident particles. An important aspect of the project is the development of fast, radiation-hard front-end electronics which is operating in the cold.

  18. Liquid Argon TPC Signal Formation, Signal Processing and Hit Reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Baller, Bruce [Fermilab

    2017-03-11

    This document describes the early stage of the reconstruction chain that was developed for the ArgoNeuT and MicroBooNE experiments at Fermilab. These experiments study accelerator neutrino interactions that occur in a Liquid Argon Time Projection Chamber. Reconstructing the properties of particles produced in these interactions requires knowledge of the micro-physics processes that affect the creation and transport of ionization electrons to the readout system. A wire signal deconvolution technique was developed to convert wire signals to a standard form for hit reconstruction, to remove artifacts in the electronics chain and to remove coherent noise.

  19. Electron transport in argon in crossed electric and magnetic fields

    Science.gov (United States)

    Ness; Makabe

    2000-09-01

    An investigation of electron transport in argon in the presence of crossed electric and magnetic fields is carried out over a wide range of values of electric and magnetic field strengths. Values of mean energy, ionization rate, drift velocity, and diffusion tensor are reported here. Two unexpected phenomena arise; for certain values of electric and magnetic field we find regions where the swarm mean energy decreases with increasing electric fields for a fixed magnetic field and regions where swarm mean energy increases with increasing magnetic field for a fixed electric field.

  20. Rydberg atoms in low-frequency fields : fundamental aspects and applications

    NARCIS (Netherlands)

    Gürtler, Andreas Stefan

    2003-01-01

    In this thesis we investigate highly excited atoms, so-called Rydberg atoms, in oscillating fields with frequencies from the megahertz to the terahertz domain. The strong interaction of Rydberg atoms with external fields is used to establish a connection between the ionization of Rydberg atoms by

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

    OpenAIRE

    Hagelstein, Franziska

    2017-01-01

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

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

    Indian Academy of Sciences (India)

    Author Affiliations. S A ELKILANY1 2. Department of Mathematics, Faculty of Science, University of Dammam, Dammam, Kingdom of Saudi Arabia; Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafrelsheikh, Egypt ...

  3. Quenching of excited rubidium (52P) atoms in flames

    NARCIS (Netherlands)

    Hooymayers, H.P.; Nienhuis, G.

    An alternating current photoelectric device (compare the work of Boers,(1) Hooymayers et al(2-4) and Hooymayers(5)) has been used for determining the yield factor p of resonance fluorescence for the infrared rubidium doublet (7800/7947 Å). From the p-values measured in five different hydrogen flames

  4. Transient Development of Excited State Densities in Atomic Helium Plasmas

    Science.gov (United States)

    1976-03-01

    n s t i t u e n t s caus ing a t . ransfer to bound e l e c t r o n s b e t w e e n the l o w - l y i n g s t a t e s and u p p e r s t a t...r y and t h e s e a r e d i s c u s s e d in de ta i l . 4.1 ENERGY LEVELS The h e l i u m e n e r g y l e v e l s u s e d in th i s s...e t h e n d e t e r m i n e d f r o m t h e s e v a l u e s . 4] AEDC-TR-76-5 Table 1. Helium Energy Lwel$ State g E (i/cm) State g E (i

  5. Simulations of an Argon Z-pinch Implosion with time-dependent non-LTE kinetics

    Science.gov (United States)

    Ouart, N.; Dasgupta, A.; Giuliani, J.; Jones, B.; Ampleford, D.; Harvey-Thompson, A.; Jennings, C.; Tangri, V.; Clark, R.

    2017-10-01

    Three argon gas-puff implosions were performed on the Z-machine at SNL. These three loads had the same density profile from an 8cm dia. nozzle, a 1mg/cm mass, and a 2.5cm length. The experiments produced similar radiative powers and yields. Simulations with the 2D MHD code Mach2-TCRE reproduced the experimental K-shell powers, yields, and emission region. It was also shown that the ratio of the Ly α to He α + IC lines from the simulation had good agreement to measurements after peak K-power; however, the simulation's line ratio was higher prior to the peak power. The authors attribute the difference to 3D effects or on the implicit assumption of steady-state population kinetics. This presentation will illustrate the effect of time-dependent level populations on the radiation from simulations using the NRL DZAPP code. DZAPP is a coupled 1D MHD, detailed non-LTE atomic physics with radiation transport, incorporating a transmission line circuit. The line ratios and K-powers from the steady-state and time-dependent populations will be presented and compared with experiment. This work supported by DOE/NNSA. SNL is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the US DOE/NNSA under contract DE-NA-0003525.

  6. Interaction of the Helium, Hydrogen, Air, Argon, and Nitrogen Bubbles with Graphite Surface in Water.

    Science.gov (United States)

    Bartali, Ruben; Otyepka, Michal; Pykal, Martin; Lazar, Petr; Micheli, Victor; Gottardi, Gloria; Laidani, Nadhira

    2017-05-24

    The interaction of the confined gas with solid surface immersed in water is a common theme of many important fields such as self-cleaning surface, gas storage, and sensing. For that reason, we investigated the gas-graphite interaction in the water medium. The graphite surface was prepared by mechanical exfoliation of highly oriented pyrolytic graphite (HOPG). The surface chemistry and morphology were studied by X-ray photoelectron spectroscopy, profilometry, and atomic force microscopy. The surface energy of HOPG was estimated by contact angle measurements using the Owens-Wendt method. The interaction of gases (Ar, He, H2, N2, and air) with graphite was studied by a captive bubble method, in which the gas bubble was in contact with the exfoliated graphite surface in water media. The experimental data were corroborated by molecular dynamics simulations and density functional theory calculations. The surface energy of HOPG equaled to 52.8 mJ/m2 and more of 95% of the surface energy was attributed to dispersion interactions. The results on gas-surface interaction indicated that HOPG surface had gasphilic behavior for helium and hydrogen, while gasphobic behavior for argon and nitrogen. The results showed that the variation of the gas contact angle was related to the balance between the gas-surface and gas-gas interaction potentials. For helium and hydrogen the gas-surface interaction was particularly high compared to gas-gas interaction and this promoted the favorable interaction with graphite surface.

  7. Infrared absorption spectroscopy of diacetylene ions trapped in solid argon.

    Science.gov (United States)

    Szczepanski, Jan; Wang, Haiyan; Jones, Brittnee; Arrington, Caleb A; Vala, Martin T

    2005-03-07

    The C4H2+ diacetylene radical cation has been generated in a pulsed jet electrical discharge through both a diacetylene/argon mixture and an acetylene/argon mixture. The product mixture was trapped on a 12 K cryostat window and studied via Fourier transform infrared absorption spectroscopy. The diacetylene cation was also produced via low energy electron bombardment of an effusive C4H2/Ar beam. Two new infrared bands at 3201.6 and 1827.9 cm(-1) have been identified as vibrations of the diacetylene cation, viz the v4 (sigmau) (C-H stretching) and the v5(sigmau) (C[triple bond]C stretching) modes, respectively. Geometry optimization and harmonic frequency calculations, carried out at various spin unrestricted levels (B3LYP, CCSD(T)) for spin doublet structures, indicate that, in its electronic ground state X2pi(g), the C4H2+ cation is linear. Three additional new bands at 2957.5, 1693.8 and 594.5 cm(-1) have been tentatively assigned to the C-H stretching, C[triple bond]C stretching and C[triple bond]C-H (in-plane) bending modes, respectively, of the nonlinear diacetylene anion (C4H2-, X2B(u)).

  8. Prediction of Underground Argon Content for Dark Matter Experiments

    CERN Document Server

    Mei, D -M; Spaans, J; Koppang, M; Hime, A; Keller, C; Gehman, C M

    2009-01-01

    In this paper, we demonstrate the use of physical models to evaluate the production of $^{39}$Ar and $^{40}$Ar underground. Considering both cosmogenic $^{39}$Ar production and radiogenic $^{40}$Ar production in situ and from external sources, we can derive the ratio of $^{39}$Ar to $^{40}$Ar in underground sources. We show for the first time that the $^{39}$Ar production underground is dominated by stopping negative muon capture on $^{39}$K and ($\\alpha,n)$ induced subsequent $^{39}$K(n,p)$^{39}$Ar reactions. The production of $^{39}$Ar is shown as a function of depth. We demonstrate that argon depleted in $^{39}$Ar can be obtained only if the depth of the underground resources is greater than 500 m.w.e. below the surface. The depletion factor depends strongly on both radioactivity level and potassium content in the rock. We measure the radioactivity concentration and potassium concentration in the rock for a potential site of an underground argon source in South Dakota. Depending on the probability of $^{39...

  9. LArIAT: Liquid Argon TPC in a Test Beam

    Energy Technology Data Exchange (ETDEWEB)

    Adamson, Phil [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2013-02-28

    This is a technical scope of work (TSW) between the Fermi National Accelerator Laboratory (Fermilab) and the experimenters of the LArIAT collaboration who have committed to participate in beam tests to be carried out starting during the 2013 Fermilab Test Beam Facility program. The TSW is intended primarily for the purpose of recording expectations for budget estimates and work allocation for Fermilab, the funding agencies and the participating institutions. It reflects an arrangement that currently is satisfactory to the parties; however, it is recognized and anticipated that changing circumstances of the evolving research program will necessitate revisions. The parties agree to modify this TSW to reflect such required adjustments. Actual contractual obligations will be set forth in separate documents. This TSW fulfills Article 1 (facilities and scope of work) of the User Agreements signed (or still to be signed) by an authorized representative of each institution collaborating on this experiment. Precision neutrino physics has entered a new era both with pressing questions to be addressed at short and long baselines, and with increasing interest and development of Liquid Argon Time Projection Chambers (LArTPCs). These open volume liquid argon TPCs drift ionization electrons from passing charged particles to readout wire chamber planes at the edge of the detector. The Signals are then combined to form 2D and 3D pho-quality like millimeter scale images of the charged particles tracks and to provide calorimetric measurements of the deposited energy in the detector.

  10. Argon ion sputtering of niobium and niobium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, Peter Francis [Univ. of Illinois, Urbana-Champaign, IL (United States)

    1978-01-01

    Polycrystalline niobium was irradiated by a beam of 15-keV argon ions, and the effect of certain metallurgical and environmental conditions was studied. Macroscopic sputtering yields were measured for well-annealed niobium and also for Nb--V and Nb--O alloys, cold-worked and recovered niobium and for sputtering conducted in an oxygen atmosphere. In all cases, the resulting surface topography was characterized by scanning electron microscopy. Selected area electron channeling patterns were used to determine the texture of the annealed niobium and to correlate sputter-induced surface features with grain orientations. The surface chemistry of sputtered targets was checked with a scanning Auger microprobe. Results indicate that ion channeling and surface mobility are important in the 15-keV argon sputtering of niobium. The sputtering yield for annealed niobium was accurately described by modifying a sputtering theory for amorphous solids through use of a correction factor based on ion channeling which was calculated from the experimentally determined texture. The sputter topography was varied and, at times, complex. Surface features were dependent on crystallography, background pressure, temperature and the metallurgical conditions of cold work, recovery, annealing, interstitial solute and precipitation structure. The sputtering yield was also determined to be a function of the metallurgical conditions, the crystallography, and pressure. 62 figures, 10 tables.

  11. Surface nanostructuring of CuIn1-x Ga x Se2 films using argon plasma treatment

    Science.gov (United States)

    Zimin, S. P.; Gorlachev, E. S.; Mokrov, D. A.; Amirov, I. I.; Naumov, V. V.; Gremenok, V. F.; Juskenas, R.; Skapas, M.; Kim, W. Y.; Bente, K.; Chung, Y.-D.

    2017-07-01

    In this work we report a phenomenon of the self-formation of nanostructure arrays during low-energy inductively coupled argon plasma treatment of the surface of copper indium gallium diselenide films grown by different methods on glass substrates. Selenization, pulsed laser deposition and multistage co-evaporation technological methods were used for the growth of polycrystalline CuIn1-x Ga x Se2 (0.04 ≤ x ≤ 0.45) films. The plasma treatment of the surface of the films grown by all three methods resulted in the plasma-assisted self-formation of arrays of uniform cylindrical or conical nanostructures with the surface density of (0.8-1.8) × 1011 cm-2. Using scanning electron microscopy, transmission electron microscopy and atomic force microscopy, we describe the morphological parameters and chemical composition of the fabricated nanostructures and discuss possible physical mechanisms of the observed plasma-assisted nanostructuring.

  12. Effect of voltage shape of electrical power supply on radiation and density of a cold atmospheric argon plasma jet

    Directory of Open Access Journals (Sweden)

    F Sohbatzadeh

    2017-02-01

    Full Text Available In this work, we investigated generating argon cold plasma jet at atmospheric pressure based on dielectric barrier discharge configuration using three electrical power supplies of sinusoidal, pulsed and saw tooth high voltage shapes at 8 KHZ. At first; we describe the electronic circuit features for generating high voltage (HV wave forms including saw tooth, sinusoidal and pulsed forms. Then, we consider the effect of voltage shape on the electrical breakdown. Relative concentrations of chemical reactive species such as Oxygen, atomic Nitrogen and OH were measured using optical emission spectroscopy. Using a simple numerical model, we showed a HV with less rise time increases electron density, therefore a cold plasma jet can be produced with a minimal consumption electrical power

  13. Direct detection of momentum flux in atomic and molecular beams

    Science.gov (United States)

    Choi, J. G.; Hayden, J. S.; O'Connor, M. T.; Diebold, G. J.

    1981-10-01

    We describe the use of a microphone for detection of atomic and molecular beams in a high-vacuum environment. Two experiments were carried out to demonstrate this detection method. Pulsed beams of argon were detected using a conventional electret microphone where the output of the microphone was displayed directly on an oscilloscope or processed with a boxcar averager to remove the transient oscillations of the microphone diaphragm. Amplitude modulated, continuous beams of atomic argon were also detected using a lock-in amplifier. The microphone possesses a response to the pressure or momentum flux in the beam that appears to be unique among beam detectors. We use the classical equipartition theorem to calculate the magnitude of the random fluctuations in the output voltage of the microphone that is used to give an expression for the minimum detectable momentum flux in the beam. For a typical microphone we find this to be 3×10-8 Pa, (in a 1-Hz bandwidth), which corresponds to a minimum number density of 1×106 cm-3 for an effusive argon beam at 300 K.

  14. Electronically Excited C2 from Laser Photodissociated C60

    Science.gov (United States)

    Arepalli, Sivaram; Scott, Carl D.; Nikolaev, Pavel; Smalley, Richard E.

    1999-01-01

    Spectral and transient emission measurements are made of radiation from products of laser excitation of buckminsterfullerene (C60) vapor diluted in argon at 973 K. The principal radiation is from the Swan band system of C2 and, at early times, also from a black body continuum. The C2 radiation is observed only when C60 is excited by green (532 nm) and not with IR (1064 nm) laser radiation at energy densities of about 1.5 J/square cm. Transient measurements indicate that there are two characteristic periods of decay of radiation. The first period, lasting about 2 micro seconds, has a characteristic decay time of about 0.3 micro seconds. The second period, lasting at least 50 micro seconds, has a characteristic decay time of about 5 micro seconds. These characteristic times are thought to be associated with cooling of C60 molecules or nanosized carbon particles during the early period; and with electronically excited C2 that is a decomposition product of laser excited C60, C58, ... molecules during the later period.

  15. Atom Skimmers and Atom Lasers Utilizing Them

    Science.gov (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  16. Excitation equilibria in plasmas; a classification

    Energy Technology Data Exchange (ETDEWEB)

    Mullen, J.A.M. van der (Eindhoven Univ. of Tech. (Netherlands). Physics Dept.)

    1990-07-01

    This review gives a classification of the excitation kinetics ruled by electrons in plasmas. It is a study on the atomic state distribution function (ASDF) and its relation with underlying processes, which, for the case of an electron excitation kinetics (EEK) plasma, is merely a competition between free and bound electrons, the same particles in different circumstances. In a quasi steady state the population density of an atomic state results from production-destruction balances in equilibrium. If all balances are proper, i.e., consist of each other's inverse processes, then the ASDF is described by the Boltzmann-Saha relation. In other cases the balance will be denoted as improper, the ASDF will deviate from the equilibrium shape, but reflecting the underlying improper balances, it may give information about the plasma. Four improper balances and their impact on the ASDF are dealt with. An important feature is that improper balances are associated with particle transport. Special attention is paid to the distribution function of the excitation saturation balance in which the overpopulated bound electrons are subjected to frequent interactions with free electrons and the energy distribution of the free electrons is taken over. This distribution, denoted as the bound Maxwell distribution, is experimentally found in several ionizing plasmas. Its recombining counterpart, the deexcitation saturation balance, creates under certain conditions inversion in the ASDF, the basis for the recombination laser. (orig.).

  17. Towards a liquid Argon TPC without evacuation filling of a 6$m^3$ vessel with argon gas from air to ppm impurities concentration through flushing

    CERN Document Server

    Curioni, A; Gendotti, A; Knecht, L; Lussi, D; Marchionni, A; Natterer, G; Resnati, F; Rubbia, A; Coleman, J; Lewis, M; Mavrokoridis, K; McCormick, K; Touramanis, C

    2010-01-01

    In this paper we present a successful experimental test of filling a volume of 6 $m^3$ with argon gas, starting from normal ambient air and reducing the impurities content down to few parts per million (ppm) oxygen equivalent. This level of contamination was directly monitored measuring the slow component of the scintillation light of the Ar gas, which is sensitive to $all$ sources of impurities affecting directly the argon scintillation.

  18. Scattering theory of molecules, atoms and nuclei

    CERN Document Server

    Canto, L Felipe

    2012-01-01

    The aim of the book is to give a coherent and comprehensive account of quantum scattering theory with applications to atomic, molecular and nuclear systems. The motivation for this is to supply the necessary theoretical tools to calculate scattering observables of these many-body systems. Concepts which are seemingly different for atomic/molecular scattering from those of nuclear systems, are shown to be the same once physical units such as energy and length are diligently clarified. Many-body resonances excited in nuclear systems are the same as those in atomic systems and come under the name

  19. Plasmas applied atomic collision physics, v.2

    CERN Document Server

    Barnett, C F

    1984-01-01

    Applied Atomic Collision Physics, Volume 2: Plasmas covers topics on magnetically confined plasmas. The book starts by providing the history of fusion research and describing the various approaches in both magnetically and inertially confined plasmas. The text then gives a general discussion of the basic concepts and properties in confinement and heating of a plasma. The theory of atomic collisions that result in excited quantum states, particularly highly ionized impurity atoms; and diverse diagnostic topics such as emission spectra, laser scattering, electron cyclotron emission, particle bea

  20. Characterising the light output from Argon bombs by two simultaneous diagnostic techniques

    CSIR Research Space (South Africa)

    Olivier, M

    2013-01-01

    Full Text Available The light output from Argon-bombs was investigated by means of ultra high speed photography (Cordin Model 550-32 camera) and locally developed photodiode sensors. Tubes of various sizes were inflated with Argon gas, and were detonated on one side...

  1. Study of electron recombination in liquid argon with the ICARUS TPC

    Energy Technology Data Exchange (ETDEWEB)

    Amoruso, S.; Antonello, M.; Aprili, P.; Arneodo, F.; Badertscher, A.; Baiboussinov, B.; Baldo Ceolin, M.; Battistoni, G.; Bekman, B.; Benetti, P.; Bischofberger, M.; Borio di Tigliole, A.; Brunetti, R.; Bruzzese, R.; Bueno, A.; Buzzanca, M.; Calligarich, E.; Campanelli, M.; Carbonara, F.; Carpanese, C.; Cavalli, D.; Cavanna, F.; Cennini, P.; Centro, S.; Cesana, A.; Chen, C.; Chen, D.; Chen, D.B.; Chen, Y.; Cieslik, K.; Cline, D.; Cocco, A.G.; Dai, Z.; De Vecchi, C.; Dabrowska, A.; Di Cicco, A.; Dolfini, R.; Ereditato, A.; Felcini, M.; Ferrari, A.; Ferri, F.; Fiorillo, G.; Galli, S.; Ge, Y.; Gibin, D.; Gigli Berzolari, A.; Gil-Botella, I.; Graczyk, K.; Grandi, L.; Guglielmi, A.; He, K.; Holeczek, J.; Huang, X.; Juszczak, C.; Kielczewska, D.; Kisiel, J.; Kozlowski, T.; Laffranchi, M.; Lagoda, J.; Li, Z.; Lu, F.; Ma, J.; Mangano, G.; Markiewicz, M.; Martinez de la Ossa, A.; Matthey, C.; Mauri, F.; Meng, G.; Messina, M.; Montanari, C.; Muraro, S.; Navas-Concha, S.; Otwinowski, S.; Ouyang, Q.; Palamara, O.; Pascoli, D.; Periale, L.; Piano Mortari, G.B.; Piazzoli, A.; Picchi, P.; Pietropaolo, F.; Polopek, W.; Rancati, T.; Rappoldi, A.; Raselli, G.L.; Rico, J.; Rondio, E.; Rossella, M.; Rubbia, A.; Rubbia, C.; Sala, P.R. E-mail: paola.sala@cern.ch; Santorelli, R.; Scannicchio, D.; Segreto, E.; Seo, Y.; Sergiampietri, F.; Sobczyk, J.; Spinelli, N.; Stepaniak, J.; Sulej, R.; Szarska, M.; Szeptycka, M.; Terrani, M.; Velotta, R.; Ventura, S.; Vignoli, C.; Wang, H.; Wang, X.; Woo, J.; Xu, G.; Xu, Z.; Zalewska, A.; Zhang, C.; Zhang, Q.; Zhen, S.; Zipper, W

    2004-05-11

    Electron recombination in liquid argon (LAr) is studied by means of charged particle tracks collected in various ICARUS liquid argon TPC prototypes. The dependence of the recombination on the particle stopping power has been fitted with a Birks functional dependence. The simulation of the process of electron recombination in Monte Carlo calculations is discussed. A quantitative comparison with previously published data is carried out.

  2. Controlling chaos in dynamic-mode atomic force microscope

    OpenAIRE

    Yamasue, Kohei; Kobayashi, Kei; Yamada, Hirofumi; Matsushige, Kazumi; Hikihara, Takashi

    2009-01-01

    We successfully demonstrated the first experimental stabilization of irregular and non-periodic cantilever oscillation in the amplitude modulation atomic force microscopy using the time-delayed feedback control. A perturbation to cantilever excitation force stabilized an unstable periodic orbit associated with nonlinear cantilever dynamics. Instead of the typical piezoelectric excitation, the magnetic excitation was used for directly applying control force to the cantilever. The control force...

  3. Efficient transfer of francium atoms

    Science.gov (United States)

    Aubin, Seth; Behr, John; Gorelov, Alexander; Pearson, Matt; Tandecki, Michael; Collister, Robert; Gwinner, Gerald; Shiells, Kyle; Gomez, Eduardo; Orozco, Luis; Zhang, Jiehang; Zhao, Yanting; FrPNC Collaboration

    2016-05-01

    We report on the progress of the FrPNC collaboration towards Parity Non Conservation Measurements (PNC) using francium atoms at the TRIUMF accelerator. We demonstrate efficient transfer (higher than 40%) to the science vacuum chamber where the PNC measurements will be performed. The transfer uses a downward resonant push beam from the high-efficiency capture magneto optical trap (MOT) towards the science chamber where the atoms are recaptured in a second MOT. The transfer is very robust with respect to variations in the parameters (laser power, detuning, alignment, etc.). We accumulate a growing number of atoms at each transfer pulse (limited by the lifetime of the MOT) since the push beam does not eliminate the atoms already trapped in the science MOT. The number of atoms in the science MOT is on track to meet the requirements for competitive PNC measurements when high francium rates (previously demonstrated) are delivered to our apparatus. The catcher/neutralizer for the ion beam has been tested reliably to 100,000 heating/motion cycles. We present initial tests on the direct microwave excitation of the ground hyperfine transition at 45 GHz. Support from NSERC and NRC from Canada, NSF and Fulbright from USA, and CONACYT from Mexico.

  4. Coherent and non coherent atom optics experiment with an ultra-narrow beam of metastable rare gas atoms; Experiences d'optique atomique coherente ou non avec un jet superfin d'atomes metastables de gaz rares

    Energy Technology Data Exchange (ETDEWEB)

    Grucker, J

    2007-12-15

    In this thesis, we present a new type of atomic source: an ultra-narrow beam of metastable atoms produced by resonant metastability exchange inside a supersonic beam of rare gas atoms. We used the coherence properties of this beam to observe the diffraction of metastable helium, argon and neon atoms by a nano-transmission grating and by micro-reflection-gratings. Then, we evidenced transitions between Zeeman sublevels of neon metastable {sup 3}P{sub 2} state due to the quadrupolar part of Van der Waals potential. After we showed experimental proofs of the observation of this phenomenon, we calculated the transition probabilities in the Landau - Zener model. We discussed the interest of Van der Waals - Zeeman transitions for atom interferometry. Last, we described the Zeeman cooling of the supersonic metastable argon beam ({sup 3}P{sub 2}). We have succeeded in slowing down atoms to speeds below 100 m/s. We gave experimental details and showed the first time-of-flight measurements of slowed atoms.

  5. Simulation of argon response and light detection in the DarkSide-50 dual phase TPC

    Energy Technology Data Exchange (ETDEWEB)

    Agnes, P.; et al.

    2017-07-18

    A Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ~10^7, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ~3 orders of magnitude lower with respect to atmospheric argon. These results rely on the accurate simulation of the detector response to the liquid argon scintillation, its ionization, and electron-ion recombination processes. This work provides a complete overview of the DarkSide Monte Carlo and of its performance, with a particular focus on PARIS, the custom-made liquid argon response model.

  6. Index of refraction, Rayleigh scattering length, and Sellmeier coefficients in solid and liquid argon and xenon

    Science.gov (United States)

    Grace, Emily; Butcher, Alistair; Monroe, Jocelyn; Nikkel, James A.

    2017-09-01

    Large liquid argon detectors have become widely used in low rate experiments, including dark matter and neutrino research. However, the optical properties of liquid argon are not well understood at the large scales relevant for current and near-future detectors. The index of refraction of liquid argon at the scintillation wavelength has not been measured, and current Rayleigh scattering length calculations disagree with measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce a new calculation using existing data in liquid and solid argon and xenon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship.

  7. Management of Liver Cancer Argon-helium Knife Therapy with Functional Computer Tomography Perfusion Imaging.

    Science.gov (United States)

    Wang, Hongbo; Shu, Shengjie; Li, Jinping; Jiang, Huijie

    2016-02-01

    The objective of this study was to observe the change in blood perfusion of liver cancer following argon-helium knife treatment with functional computer tomography perfusion imaging. Twenty-seven patients with primary liver cancer treated with argon-helium knife and were included in this study. Plain computer tomography (CT) and computer tomography perfusion (CTP) imaging were conducted in all patients before and after treatment. Perfusion parameters including blood flows, blood volume, hepatic artery perfusion fraction, hepatic artery perfusion, and hepatic portal venous perfusion were used for evaluating therapeutic effect. All parameters in liver cancer were significantly decreased after argon-helium knife treatment (p liver tissue, but other parameters kept constant. CT perfusion imaging is able to detect decrease in blood perfusion of liver cancer post-argon-helium knife therapy. Therefore, CTP imaging would play an important role for liver cancer management followed argon-helium knife therapy. © The Author(s) 2014.

  8. Effects of Gas Flow Rate on the Discharge Characteristics of a DC Excited Plasma Jet

    Science.gov (United States)

    Li, Xuechen; Jia, Pengying; Di, Cong; Bao, Wenting; Zhang, Chunyan

    2015-09-01

    A direct current (DC) source excited plasma jet consisting of a hollow needle anode and a plate cathode has been developed to form a diffuse discharge plume in ambient air with flowing argon as the working gas. Using optical and electrical methods, the discharge characteristics are investigated for the diffuse plasma plume. Results indicate that the discharge has a pulse characteristic, under the excitation of a DC voltage. The discharge pulse corresponds to the propagation process of a plasma bullet travelling from the anode to the cathode. It is found that, with an increment of the gas flow rate, both the discharge plume length and the current peak value of the pulsed discharge decrease in the laminar flow mode, reach their minima at about 1.5 L/min, and then slightly increase in the turbulent mode. However, the frequency of the pulsed discharge increases in the laminar mode with increasing the argon flow rate until the argon flow rate equals to about 1.5 L/min, and then slightly decreases in the turbulent mode. supported by National Natural Science Foundation of China (Nos. 10805013, 11375051), Funds for Distinguished Young Scientists of Hebei Province, China (No. A2012201045), Department of Education for Outstanding Youth Project of China (No. Y2011120), and Youth Project of Hebei University of China (No. 2011Q14)

  9. Retrospective analysis for detecting seismic precursors in groundwater argon content

    Directory of Open Access Journals (Sweden)

    P. F. Biagi

    2004-01-01

    Full Text Available We examined the groundwater Argon content data sampled from 1988 to 2001 at two wells in Kamchatka (Russia and anomalous increases appeared clearly during June-July 1996. On 21 June, a shallow (1km earthquake with M=7.1 occurred at a distance less than 250km from the wells and so the previous increases could be related to this earthquake and, in particular, could be considered premonitory anomalies. In order to support this raw interpretation, we analysed the data collected in details. At first we smoothed out the high frequency fluctuations arising from the errors in a single measurement. Next we considered the known external effects on the water of a well that are the slow tectonic re-adjustment processes, the meteorology and the gravity tides and we separated these effects applying band-pass filters to the Argon content raw trends. Then we identified the largest fluctuations in these trends applying the 3 σ criterion and we found three anomalies in a case and two anomalies in other case. Comparing the time occurrence of the anomalies at the two wells we found out that a coincidence exists only in the case of the premonitory anomalies we are studying. The simultaneous appearance of well definite anomalies in the residual trends of the same parameter at two different sites supports their meaning and the possibility that they are related to some large scale effect, as the occurrence of a strong earthquake. But, other earthquakes similar to the June 1996 event took place during the Argon content measurements time and no anomaly appeared in this content. In the past, some of the authors of this paper studied the Helium content data collected in three natural springs of the Caucasus during seven years. A very similar result, that is the simultaneous appearance of clear premonitory anomalies only on the occasion of a strong (M=7.0 but shallow (2–4km earthquake, was obtained. The correspondence with the case of the Caucasus validates the

  10. Trigger readout electronics upgrade for the ATLAS Liquid Argon Calorimeters

    Science.gov (United States)

    Dinkespiler, B.

    2017-09-01

    The upgrade of the Large Hadron Collider (LHC) scheduled for the 2019-2020 shut-down period, referred to as Phase-I upgrade, will increase the instantaneous luminosity to about three times the design value. Since the current ATLAS trigger system does not allow sufficient increase of the trigger rate, an improvement of the trigger system is required. The Liquid Argon (LAr) Calorimeter read-out will therefore be modified to deliver digital trigger signals with a higher spatial granularity in order to improve the identification efficiencies of electrons, photons, tau, jets and missing energy, at high background rejection rates at the Level-1 trigger. The new trigger signals will be arranged in 34000 so-called Super Cells which achieves 5-10 times better granularity than the trigger towers currently used and allows an improved background rejection. The readout of the trigger signals will process the signal of the Super Cells at every LHC bunch-crossing at 12-bit precision and a frequency of 40 MHz. The data will be transmitted to the Back End using a custom serializer and optical converter and 5.12 Gb/s optical links. In order to verify the full functionality of the future Liquid Argon trigger system, a demonstrator set-up has been installed on the ATLAS detector and is operated in parallel to the regular ATLAS data taking during the LHC Run-2 in 2015 and 2016. Noise level and linearity on the energy measurement have been verified to be within our requirements. In addition, we have collected data from 13 TeV proton collisions during the LHC 2015 and 2016 runs, and have observed real pulses from the detector through the demonstrator system. The talk will give an overview of the Phase-I Upgrade of the ATLAS Liquid Argon Calorimeter readout and present the custom developed hardware including their role in real-time data processing and fast data transfer. This contribution will also report on the performance of the newly developed ASICs including their radiation tolerance

  11. Excitations in organic solids

    CERN Document Server

    Agranovich, Vladimir M

    2009-01-01

    During the last decade our expertise in nanotechnology has advanced considerably. The possibility of incorporating in the same nanostructure different organic and inorganic materials has opened up a promising field of research, and has greatly increased the interest in the study of properties of excitations in organic materials. In this book not only the fundamentals of Frenkel exciton and polariton theory are described, but also the electronic excitations and electronic energytransfers in quantum wells, quantum wires and quantum dots, at surfaces, at interfaces, in thin films, in multilayers,

  12. Ultraviolet 320 nm laser excitation for flow cytometry.

    Science.gov (United States)

    Telford, William; Stickland, Lynn; Koschorreck, Marco

    2017-04-01

    Although multiple lasers and high-dimensional analysis capability are now standard on advanced flow cytometers, ultraviolet (UV) lasers (usually 325-365 nm) remain an uncommon excitation source for cytometry. This is primarily due to their cost, and the small number of applications that require this wavelength. The development of the Brilliant Ultraviolet (BUV fluorochromes, however, has increased the importance of this formerly niche excitation wavelength. Historically, UV excitation was usually provided by water-cooled argon- and krypton-ion lasers. Modern flow cytometers primary rely on diode pumped solid state lasers emitting at 355 nm. While useful for all UV-excited applications, DPSS UV lasers are still large by modern solid state laser standards, and remain very expensive. Smaller and cheaper near UV laser diodes (NUVLDs) emitting at 375 nm make adequate substitutes for 355 nm sources in many situations, but do not work as well with very short wavelength probes like the fluorescent calcium chelator indo-1. In this study, we evaluate a newly available UV 320 nm laser for flow cytometry. While shorter in wavelength that conventional UV lasers, 320 is close to the 325 nm helium-cadmium wavelength used in the past on early benchtop cytometers. A UV 320 nm laser was found to excite almost all Brilliant Ultraviolet dyes to nearly the same level as 355 nm sources. Both 320 nm and 355 nm sources worked equally well for Hoechst and DyeCycle Violet side population analysis of stem cells in mouse hematopoetic tissue. The shorter wavelength UV source also showed excellent excitation of indo-1, a probe that is not compatible with NUVLD 375 nm sources. In summary, a 320 nm laser module made a suitable substitute for conventional 355 nm sources. This laser technology is available in a smaller form factor than current 355 nm units, making it useful for small cytometers with space constraints. © 2017 International Society for Advancement of Cytometry. © 2017 International

  13. Excitation Methods for Bridge Structures

    Energy Technology Data Exchange (ETDEWEB)

    Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.

    1999-02-08

    This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.

  14. Forward and backward scattering experiments in ultra-cold Rubidium atoms

    DEFF Research Database (Denmark)

    Kampel, Nir Shlomo

    project, we have studied coherent forward scattering in the form of a memory experiment. In such an experiment we convert the input light pulse to an atomic excitation, and at a later time convert back the atomic excitation into the retrieved light pulse. In the first project, we investigate the source...

  15. A new approach to entangling neutral atoms.

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jongmin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Michael J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jau, Yuan-Yu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Deutsch, Ivan H. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Biedermann, Grant W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-11-01

    Our team has developed a new approach to entangling neutral atoms with a Rydberg-dressed interaction. Entangling neutral atoms is an essential key of quantum technologies such as quantum computation, many-body quantum simulation, and high-precision atomic sensors . The demonstrated Rydberg-dressed protocol involves adiabatically imposing a light shift on the ground state by coupling an excited Rydberg state with a tuned laser field. Using this technique, we have demonstrated a strong and tunable dipole - dipole interaction between two individually trapped atoms with energy shifts of order 1 MHz, which has been challenging to achieve in other protocols . During this program, we experimentally demonstrated Bell-state entanglement and the isomorphism to the Jaynes - Cumming model of a Rydberg-dressed two-atom system. Our theoretical calculations of a CPHASE quantum logic gate and arbitrary Dicke state quantum control in this system encourage further work.

  16. Atom optics with Rydberg states in inhomogeneous electric fields

    Science.gov (United States)

    Kritsun, Oleg Anton

    Atom optics has become subject of intense investigation in recent years. Control of atomic motion is of great importance in atomic physics and applications like lithography or nanofabrication. Neutral atoms are not affected greatly by magnetic or electric field as they don't have a charge or large magnetic and electric moments. But by exciting a neutral atom to a high Rydberg state it is possible to increase its electric moment considerably. The purpose of this thesis is to demonstrate experimentally and theoretically the possibility of creating atom optical elements for the beam of neutral atoms based on the polarizability of highly excited states in an electric field. First this work will present a review of the basic concepts that are used for atom optics and also a discussion of the progress to date in realizations of the neutral atom manipulation techniques. In our earlier experiments deflection and beam-splitting was demonstrated for a beam of neutral Lithium atoms excited in a three-step scheme [3.5, 3.6]. In later experiments, metastable Helium was excited from 23S state to the 33P state using lambda = 389 nm light, and then to the 25--30 S or D states using lambda = 785--815 nm light. Because this was a two-step excitation and it had the higher laser power in the last step, this method increased the percentage of excited atoms by a factor close to 103 compared to the Lithium experiment. Furthermore coherent excitation technique, Stimulated Raman Adiabatic Population Transfer (STIRAP), is investigated in this system, which allows a complete transfer of the atoms from 23S to the Rydberg states. STIRAP is also very tolerant of experimental imperfections such as intensity and frequency fluctuations, Doppler shifts, etc. and can be done with modest laser power. Efficient excitation enables us to do the following atom manipulations in inhomogeneous electric field [3.6, 4.42]. (1) Deflection and reflection; (2) Beam-splitting; (3) Collimation and focusing. Since

  17. High Atom Number in Microsized Atom Traps

    Science.gov (United States)

    2015-12-14

    Final Performance Report on ONR Grant N00014-12-1-0608 High atom number in microsized atom traps for the period 15 May 2012 through 14 September...TYPE Final Technical Report 3. DATES COVERED (From - To) 05/15/2012-09/14/2012 4. TITLE AND SUBTITLE High atom number in microsized atom traps...forces for implementing a small-footprint, large-number atom -chip instrument. Bichromatic forces rely on absorption and stimulated emission to produce

  18. Low-energy ion implantation: Large mass fractionation of argon

    Science.gov (United States)

    Ponganis, K. V.; Graf, TH.; Marti, K.

    1993-01-01

    The isotropic signatures of noble gases in the atmospheres of the Earth and other planets are considerably evolved when compared to signatures observed in the solar wind. The mechanisms driving the evolution of planetary volatiles from original compositions in the solar accretion disk are currently poorly understood. Modeling of noble-gas compositional histories requires knowledge of fractionating processes that may have operated through the evolutionary stages. Since these gases are chemically inert, information on noble-gas fractionation processes can be used as probes. The importance of understanding these processes extends well beyond 'noble-gas planetology.' Trapped argon acquired by low-energy implantation (approximately less than 100 eV) into solids is strongly mass fractionated (approximately greater than or equal to 3 percent/amu). This has potential implications for the origin and evolution of terrestrial planet atmospheres.

  19. Grid pattern Argon Laser photocoagulation for diabetic diffuse macular edema

    Directory of Open Access Journals (Sweden)

    Karkhane R

    1998-05-01

    Full Text Available Purpose: to determine the effect of Grid pattern laser photocoagulation on diabetic diffuse macular edema with assessment of visual outcome. Patients & Methods: The author reviewed the medical records of 84 eyes of 62 patients with diabetic diffuse macular edema treated with Grid pattern green Argon laser photocoagulation in Farabi Eye Hospital between the years 1992-1995, the follow-up period was 16-48 months (average 24.55±6.42, median 28 mounths. Results: Visual acuity was improved in 11.9%; unchanged in 65.4% and worsened in 22.7% of eyes. Conclusion: In assessing long-term visual outcome, Grid laser photocoagulation is an effective modality in maintaining or improving visual acuity.

  20. The readout driver (ROD) for the ATLAS liquid argon calorimeters

    CERN Document Server

    Efthymiopoulos, I

    2001-01-01

    The Readout Driver (ROD) for the Liquid Argon calorimeter of the ATLAS detector is described. Each ROD module receives triggered data from 256 calorimeter cells via two fiber-optics 1.28 Gbit/s links with a 100 kHz event rate (25 kbit/event). Its principal function is to determine the precise energy and timing of the signal from discrete samples of the waveform, taken each period of the LHC clock (25 ns). In addition, it checks, histograms, and formats the digital data stream. A demonstrator system, consisting of a motherboard and several daughter-board processing units (PUs) was constructed and is currently used for tests in the lab. The design of this prototype board is presented here. The board offers maximum modularity and allows the development and testing of different PU designs based on today's leading integer and floating point DSPs. (3 refs).

  1. Response Uniformity of the ATLAS Liquid Argon Electromagnetic Calorimeter

    CERN Document Server

    Aharrouche, M; Di Ciaccio, L; El Kacimi, M; Gaumer, O; Gouanère, M; Goujdami, D; Lafaye, R; Laplace, S; Le Maner, C; Neukermans, L; Perrodo, P; Poggioli, L; Prieur, D; Przysiezniak, H; Sauvage, G; Wingerter-Seez, I; Zitoun, R; Lanni, F; Lü, L; Ma, H; Rajagopalan, S; Takai, H; Belymam, A; Benchekroun, D; Hakimi, M; Hoummada, A; Gao, Y; Stroynowsk, R; Aleksa, M; Carli, T; Fassnacht, P; Gianotti, F; Hervás, L; Lampl, W; Collot, J; Hostachy, J Y; Ledroit-Guillon, F; Malek, F; Martin, P; Viret, S; Leltchouk, M; Parsons, J A; Simion, S; Barreiro, F; Del Peso, J; Labarga, L; Oliver, C; Rodier, S; Barrillon, P; Benchouk, C; Djama, F; Hubaut, F; Monnier, E; Pralavorio, P; Sauvage, D; Serfon, C; Tisserant, S; Tóth, J; Banfi, D; Carminati, L; Cavalli, D; Costa, G; Delmastro, M; Fanti, M; Mandell, L; Mazzanti, M; Tartarelli, F; Kotov, K; Maslennikov, A; Pospelov, G; Tikhonov, Yu; Bourdarios, C; Fayard, L; Fournier, D; Iconomidou-Fayard, L; Kado, M; Parrour, G; Puzo, P; Rousseau, D; Sacco, R; Serin, L; Unal, G; Zerwas, D; Dekhissi, B; Derkaoui, J; EL Kharrim, A; Maaroufi, F; Cleland, W; Lacour, D; Laforge, B; Nikolic-Audit, I; Schwemling, Ph; Ghazlane, H; Cherkaoui El Moursli, R; Idrissi Fakhr-Eddine, A; Boonekamp, M; Kerschen, N; Mansoulié, B; Meyer, P; Schwindlingy, J; Lund-Jensen, B

    2007-01-01

    The construction of the ATLAS electromagnetic liquid argon calorimeter modules is completed and all the modules are assembled and inserted in the cryostats. During the production period four barrel and three endcap modules were exposed to test beams in order to assess their performance, ascertain the production quality and reproducibility, and to scrutinize the complete energy reconstruction chain from the readout and calibration electronics to the signal and energy reconstruction. It was also possible to check the full Monte Carlo simulation of the calorimeter. The analysis of the uniformity, resolution and extraction of constant term is presented. Typical non-uniformities of 0.5% and typical global constant terms of 0.6% are measured for the barrel and end-cap modules.

  2. Nanotextured Shrink Wrap Superhydrophobic Surfaces by Argon Plasma Etching

    Directory of Open Access Journals (Sweden)

    Jolie M. Nokes

    2016-03-01

    Full Text Available We present a rapid, simple, and scalable approach to achieve superhydrophobic (SH substrates directly in commodity shrink wrap film utilizing Argon (Ar plasma. Ar plasma treatment creates a stiff skin layer on the surface of the shrink film. When the film shrinks, the mismatch in stiffness between the stiff skin layer and bulk shrink film causes the formation of multiscale hierarchical wrinkles with nano-textured features. Scanning electron microscopy (SEM images confirm the presence of these biomimetic structures. Contact angle (CA and contact angle hysteresis (CAH measurements, respectively, defined as values greater than 150° and less than 10°, verified the SH nature of the substrates. Furthermore, we demonstrate the ability to reliably pattern hydrophilic regions onto the SH substrates, allowing precise capture and detection of proteins in urine. Finally, we achieved self-driven microfluidics via patterning contrasting superhydrophilic microchannels on the SH Ar substrates to induce flow for biosensing.

  3. Infrared spectrum of ruthenium tetroxide isotopomers in an argon matrix

    Science.gov (United States)

    Green, David W.; Kay, Jack G.; Zimmerman, George L.; Balko, Barbara A.

    1989-11-01

    RuO 4 isotopomer mixtures were synthesized with the natural abundances of Ru isotopes and mixtures of 16O and 18O. The bond-stretching region of the IR spectrum was examined using Fourier transform spectroscopy and in an argon matrix at 14 K. Wilson FG-matrix calculations permitted identification of all stretching frequencies except forbidden ν1 vibrations of Ru 16O 4 and Ru 18O 4 and confirmed undistorted tetrahedral geometry. Calculated and observed frequencies agreed with a mean deviation of 0.56 cm -1. Values compared well with gas values and with an average matrix shift of -3.2 ± 0.4 cm -1. Relative intensities were well matched using the simple classical concept of additive bond dipole moments. Intense UV irradiation of the mixture did not dissociate the RuO 4 into smaller fragments, contrary to the behavior of the gas.

  4. The ATLAS liquid Argon calorimeters read-out system

    CERN Document Server

    Blondel, A; Fayard, L; La Marra, D; Léger, A; Matricon, P; Perrot, G; Poggioli, L; Prast, J; Riu, I; Simion, S

    2004-01-01

    The calorimetry of the ATLAS experiment takes advantage of different detectors based on the liquid Argon (LAr) technology. Signals from the LAr calorimeters are processed by various stages before being delivered to the Data Acquisition system. The calorimeter cell signals are received by the front-end boards, which digitize a predetermined number of samples of the bipolar waveform and sends them to the Read-Out Driver (ROD) boards. The ROD board receives triggered data from 1028 calorimeter cells, and determines the precise energy and timing of the signals by processing the discrete samplings of the pulse. In addition, it formats the digital stream for the following elements of the DAQ chain, and performs monitoring. The architecture and functionality of the ATLAS LAr ROD board are discussed, along with the final design of the Processing Unit boards housing the Digital Signal Processors (DSP). (9 refs).

  5. Development of membrane cryostats for large liquid argon neutrino detectors

    CERN Document Server

    Montanari, D; Gendotti, A; Geynisman, M; Hentschel, S; Loew, T; Mladenov, D; Montanari, C; Murphy, S; Nessi, M; Norris, B; Noto, F; Rubbia, A; Sharma, R; Smargianaki, D; Stewart, J; Vignoli, C; Wilson, P; Wu, S

    2015-01-01

    A new collaboration is being formed to develop a multi-kiloton Long-Baseline neutrino experiment that will be located at the Surf Underground Research Facility (SURF) in Lead, SD. In the present design, the detector will be located inside cryostats filled with 68,400 ton of ultrapure liquid argon (less than 100 parts per trillion of oxygen equivalent contamination). To qualify the membrane technology for future very large-scale and underground implementations, a strong prototyping effort is ongoing: several smaller detectors of growing size with associated cryostats and cryogenic systems will be designed and built at Fermilab and CERN. They will take physics data and test different detector elements, filtration systems, design options and installation procedures. In addition, a 35 ton prototype is already operational at Fermilab and will take data with single-phase detector in early 2016. After the prototyping phase, the multi-kton detector will be constructed. After commissioning, it will detect and study ne...

  6. The liquid argon TPC for the ICARUS experiment

    CERN Document Server

    Arneodo, F

    1997-01-01

    The ICARUS project aims at the realisation of a large liquid argon TPC to be run at the Underground Laboratories of Gran Sasso in Italy. An intense R&D; activity has put on firm grounds this new detector technology and experimentally confirmed its feasibility on a few ton scale. Based on these solid achievements, the collaboration is now confident of being able to build and safely operate a multi-kton detector. The reseach program of the experiment involves the systematic study of a wide spectrum of physical phenomena covering many orders of magnitude in the energy deposited in the detector: from the few MeV of solar neutrino interactions, to the about one GeV of the proton decay and atmospheric neutrinos, up to the higher energies of neutrinos from accelerators.

  7. The ATLAS liquid argon calorimeters Read Out Driver (ROD) system

    CERN Document Server

    Henry-Coüannier, F

    2000-01-01

    The electronic Readout chain for the Liquid Argon calorimeters of the ATLAS detector is briefly presented. Special attention is given to the Read Out Drivers (ROD) which will receive the triggered data from approximately 200,000 calorimeter cells at a 100 kHz event rate. In the ROD boards the energy will be computed for each cell from discrete samples of the waveform using optimal filtering algorithms running in fast digital signal processors. The monitoring of the calorimeter data will also be performed at the ROD level. Performances expected in ATLAS which have been evaluated from simulation studies are presented. A demonstrator system currently under construction is described and performances of the Processing Units (DSP daughter boards) are presented. 4 Refs.

  8. Degradation of bromophenol blue molecule during argon plasma jet irradiation

    Science.gov (United States)

    Matinzadeh, Ziba; Shahgoli, Farhad; Abbasi, Hamed; Ghoranneviss, Mahmood; Salem, Mohammad Kazem

    2017-06-01

    The aim of this paper is to study degradation of a bromophenol blue molecule (C19H10Br4O5S) using direct irradiation of cold atmospheric argon plasma jet. The pH of the bromophenol blue solution has been measured as well as its absorbance spectra and conductivity before and after the irradiation of non-thermal plasma jet in various time durations. The results indicated that the lengths of conjugated systems in the molecular structure of bromophenol blue decreased, and that the bromophenol blue solution was decolorized as a result of the decomposition of bromophenol blue. This result shows that non-thermal plasma jet irradiation is capable of decomposing, and can also be used for water purification.

  9. Collisional Losses from a Light-Force Atom Trap

    Science.gov (United States)

    Sesko, D.; Walker, T.; Monroe, C.; Gallagher, A.; Wieman, C.

    We have studied the collisional loss rates for very cold cesium atoms held in a spontaneous-force optical trap. In contrast with previous work, we find that collisions involving excitation by the trapping light fields are the dominant loss mechanism. We also find that hyperfine-changing collisions between atoms in the ground state can be significant under some circumstances.

  10. Trapping of neutral atoms with resonant microwave radiation

    NARCIS (Netherlands)

    Agosta, C.C.; Silvera, I.F.; Stoof, H.T.C.; Verhaar, B.J.

    1989-01-01

    We discuss a resonant microwave trap for neutral atoms. Because of the long spontaneous radiation time this trap is remarkably different from the optical trap. It also has advantage over static magnetic traps that trap the excited spin state of the lowest electronic level, in that atoms

  11. Dynamics Resonances in Atomic States of Astrophysical Relevance

    Indian Academy of Sciences (India)

    Since spontaneous fluorescence of excited atoms is probabilistic, the description of the radiating quantized system evolution along with photon energy transfer in a cold atom medium, should include elements of stochastic dynamics. Finally, the chaotic dynamics of a weakly bound Rydberg electron over a grid of the energy ...

  12. Excited states of {sup 4}He droplets

    Energy Technology Data Exchange (ETDEWEB)

    Guardiola, R.; Navarro, J.; Portesi, M.

    2001-06-01

    We study low-lying excited states of {sup 4}He clusters up to a cluster size of 40 atoms in a variational framework. The ansatz wave function combines two- and three-body correlations, coming from a translationally invariant configuration interaction description, and Jastrow-type short-range correlation. We have previously used this scheme to determine the ground-state energies of {sup 4}He and {sup 3}He clusters. Here we present an extension of this ansatz wave function having a good quantum angular momentum L. The variational procedure is applied independently to the cases with L=0,2,4, and upper bounds for the corresponding energies are thus obtained. Moreover, centroid energies for L excitations are calculated through the use of sum rules. A comparison with previous calculations is also made.

  13. Positron excitation of neon

    Science.gov (United States)

    Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.

  14. Hardness and excitation energy

    Indian Academy of Sciences (India)

    It is shown that the first excitation energy can be given by the Kohn-Sham hardness (i.e. the energy difference of the ground-state lowest unoccupied and highest occupied levels) plus an extra term coming from the partial derivative of the ensemble exchange-correlation energy with respect to the weighting factor in the ...

  15. Excitation of Stellar Pulsations

    DEFF Research Database (Denmark)

    Houdek, G.

    2012-01-01

    In this review I present an overview of our current understanding of the physical mechanisms that are responsible for the excitation of pulsations in stars with surface convection zones. These are typically cooler stars such as the δ Scuti stars, and stars supporting solar-like oscillations....

  16. Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble

    DEFF Research Database (Denmark)

    Guerlin, Christine; Brion, Etienne; Esslinger, Tilman

    2010-01-01

    The realization of a Jaynes-Cummings model in the optical domain is proposed for an atomic ensemble. The scheme exploits the collective coupling of the atoms to a quantized cavity mode and the nonlinearity introduced by coupling to high-lying Rydberg states. A two-photon transition resonantly...... effective Jaynes-Cummings model. We use numerical simulations to show that the cavity transmission can be used to reveal detailed properties of the Jaynes-Cummings ladder of excited states and that the atomic nonlinearity gives rise to highly nontrivial photon emission from the cavity. Finally, we suggest...... couples the single-atom ground state |g> to a Rydberg state |e>via a nonresonant intermediate state |i>, but due to the interaction between Rydberg atoms only a single atom can be resonantly excited in the ensemble. This restricts the state space of the ensemble to the collective ground state |G...

  17. Elementary excitations and flow in the liquid

    Science.gov (United States)

    Egami, Takeshi

    2013-03-01

    A new mode of excitation is introduced to elucidate the dynamics in simple liquids at the atomic scale. Some properties of liquid defy easy explanations. For instance, in liquids phonons are overdamped with a very short lifetime. Nevertheless the Dulong-Petit law (CV ~ 3kB) is widely observed at high temperatures. As temperature is reduced the specific heat markedly increases in the supercooled state, only to drop down sharply at the glass transition. Viscosity shows an Arrhenian behavior at high temperatures, but increases rapidly toward the glass transition in the supercooled state. We suggest that these perplexing observations can be naturally explained in terms of the local configurational excitations (LCE's) which locally change the atomic connectivity by an atom losing or gaining one nearest neighbor. We show that the lifetime of LCE, τLC, is equal to the Maxwell relaxation time, τM, at temperatures above the crossover temperature, TA. Above TA the phonon mean-free path, ξ =cTτLC , where cT is the transverse sound velocity, becomes shorter than the interatomic distance, resulting in phonon localization. Therefore LCE's are the elementary excitations in the liquid. They are independent of each other above TA, but below TA LCE's interact through phonon exchange, resulting in the rapid increase in τM , culminatingintheglasstransition . LCE' sarealsothemechanism of flow at low temperature under strong shear stress. In this case, however, losing and gaining of the neighbors are strongly coupled, so that τM = LC / 2 [ 1 ] . Wealsodiscussdynamicheterogeneityin terms of LCE interactions. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Science and Engineering Division.

  18. Photochemistry of HI on argon and water nanoparticles: hydronium radical generation in HI·(H2O)n.

    Science.gov (United States)

    Poterya, Viktoriya; Fedor, Juraj; Pysanenko, Andriy; Tkáč, Ondřej; Lengyel, Jozef; Ončák, Milan; Slavíček, Petr; Fárník, Michal

    2011-02-14

    Photochemistry of HI molecules on large Ar(n) and (H(2)O)(n), n ∼ 100-500, clusters was investigated after excitation with 243 nm and 193 nm laser radiation. The measured H-fragment kinetic energy distributions pointed to a completely different photodissociation mechanism of HI on water than on argon clusters. Distinct features corresponding to the fragment caging (slow fragments) and direct exit (fast fragments) were observed in the spectra from HI photodissociation on Ar(n) clusters. On the other hand, the fast fragments were entirely missing in the spectrum from HI·(H(2)O)(n) and the slow-fragment part of the spectrum had a different shape from HI·Ar(n). The HI·(H(2)O)(n) spectrum was interpreted in terms of the acidic dissociation of HI on (H(2)O)(n) in the ground state, and hydronium radical H(3)O formation following the UV excitation of the ionically dissociated species into states of a charge-transfer-to-solvent character. The H(3)O generation was proved by experiments with deuterated species DI and D(2)O. The experiment was complemented by ab initio calculations of structures and absorption spectra for small HI·(H(2)O)(n) clusters, n = 0-5, supporting the proposed model.

  19. Magnetic conveyor belt for transporting and merging trapped atom clouds.

    Science.gov (United States)

    Hänsel, W; Reichel, J; Hommelhoff, P; Hänsch, T W

    2001-01-22

    We demonstrate an integrated magnetic device which transports cold atoms near a surface with very high positioning accuracy. Time-dependent currents in a lithographic conductor pattern create a moving chain of potential wells; atoms are transported in these wells while remaining confined in all three dimensions. We achieve mean fluxes up to 10(6) s(-1) with a negligible heating rate. An extension of this device allows merging of atom clouds by unification of two Ioffe-Pritchard potentials. The unification, which we demonstrate experimentally, can be performed without loss of phase space density. This novel, all-magnetic atom manipulation offers exciting perspectives, such as trapped-atom interferometry.

  20. The blue light indicator in rubidium 5S-5P-5D cascade excitation

    Science.gov (United States)

    Raja, Waseem; Ali, Md. Sabir; Chakrabarti, Alok; Ray, Ayan

    2017-07-01

    The cascade system has played an important role in contemporary research areas related to fields like Rydberg excitation, four wave mixing and non-classical light generation, etc. Depending on the specific objective, co or counter propagating pump-probe laser experimental geometry is followed. However, the stepwise excitation of atoms to states higher than the first excited state deals with increasingly much fewer number of atoms even compared to the population at first excited level. Hence, one needs a practical indicator to study the complex photon-atom interaction of the cascade system. Here, we experimentally analyze the case of rubidium 5S → 5P → 5D as a specimen of two-step excitation and highlight the efficacy of monitoring one branch, which emits 420 nm, of associated cascade decay route 5D → 6P → 5S, as an effective monitor of the coherence in the system.