Sample records for helium rydberg states

  1. Interaction of Helium Rydberg State Atoms with Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Fiedler, Steven L.; Eloranta, Jussi

    2014-03-01

    The pair potentials between ground state helium and Rydberg He atoms are calculated by the full configuration interaction electronic structure method for both the electronic singlet and the triplet manifolds. The obtained pair potentials are validated against existing experimental molecular and atomic data. Most states show remarkable energy barriers at long distances ( Å), which can effectively stabilize He against the formation of He at low nuclear kinetic energies. Bosonic density functional theory calculations, based on the calculated pair potential data, indicate that the triplet ground state He reside in spherical bubbles in superfluid helium with a barycenter radius of 6.1 Å at the liquid saturated vapor pressure. The pressure dependency of the relative He absorption line blue shift in the liquid was obtained through both the statistical line broadening theory as well as the dynamic adiabatic following method. The pronounced difference between the results from the static and dynamic models is attributed to the dynamic Jahn-Teller effect that takes places in the electronically excited state within the dephasing time of 150 fs. Transient non-thermalized liquid surroundings near He may contribute to an artificial reduction in the absorption line blue shift by up to 30 cm.

  2. Population dynamics of microwave driven helium Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Zelazny, Stephen Andrew

    2000-11-01

    The transition probability of helium Rydberg atoms out of their initially prepared 283S atomic state upon exposure to a pulse of microwave field is studied. Experimental measurements and theoretical models focus on the situation where the microwave pulse consists of two phase-coherent, linearly-polarized fields. A fast beam of n = 283S Helium Rydberg atoms is prepared via double-resonance excitation using CO2 lasers. Interaction with the pulse of microwaves consisting of two phase-locked frequencies occurs in a double-ridged waveguide operating in single mode from below 5 to above 18 GHz. The phase-coherent bichromatic microwave field is produced by filtered selection, separate amplification and post-filtering, and, finally, recombination of harmonics produced by driving a comb generator with a synthesized ? s = 1 GHz signal. The selected harmonics 5 <= p,q <= 18 (giving frequencies ?1 = p? s and ?2 = q? s), their individual amplitudes, and the relative phase ? are all easily varied. The measured transition probability shows structure most sensitive to the relative phase when p:q = 1:2, 2:1 and 3:1; the case p:q = 2:3 is insensitive to relative phase. Experimental results for the p:q = 3:1 case with ? 1 = 18 GHz and ?2 = 6 GHz show Stueckelberg oscillations with characteristics, i.e. fringe contrast and fringe period, sensitive to the phase. Models of the atom's dynamics are built upon energy levels computed with the Floquet method; the models reproduce the observed Stueckelberg oscillations. Association of the model results with the experimental measurements provides a means of obtaining an absolute calibration of the relative phase between ? 1 and ?2. A discussion of the role of broadband noise from the traveling wave tube amplifiers (TWTAs) and how it influences the level of agreement between model and experiment is included. Some experimental measurements of helium Rydberg atoms exposed to a microwave field of elliptical polarization (linear (LP) to circular (CP), and many intermediate values) are presented in an Appendix of this work. The dynamics of the atoms exposed to a pulse of a CP field show Stueckelberg oscillations. A model built upon a rotating frame calculation computed on a basis of atomic states requires inclusion of the magnetic fine structure interaction to reproduce the observed dynamics.

  3. Reactions of Rydberg states of molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.; Dehmer, J. L.; Dehmer, P. M.; Chupka, W. A.

    1994-07-01

    The Rydberg state reaction H*2+H2?H+3+H+e- was studied by exciting the (X 2?+g)np,v=0,J Rydberg states with n=30-70 by double resonance excitation via the E,F 1?+g,v=0,J=1 level and by detecting the product ions or electrons. The results are consistent with the reaction occurring between the ion core of the Rydberg molecule and the ground state molecule, with the Rydberg electron acting as a spectator. Thus, these reactions can be used to provide information on the analogous ion-molecule reactions, and the possibility of using the Rydberg state reactions to study the rotational state dependence of the corresponding ion-molecule reactions is discussed.

  4. Photoelectron angular distributions in infrared one-photon and two-photon ionization of FEL-pumped Rydberg states of helium

    NASA Astrophysics Data System (ADS)

    Mondal, S.; Fukuzawa, H.; Motomura, K.; Tachibana, T.; Nagaya, K.; Sakai, T.; Matsunami, K.; Yase, S.; Yao, M.; Wada, S.; Hayashita, H.; Saito, N.; Callegari, C.; Prince, K. C.; O'Keeffe, P.; Bolognesi, P.; Avaldi, L.; Miron, C.; Nagasono, M.; Togashi, T.; Yabashi, M.; Ishikawa, K. L.; Sazhina, I. P.; Kazansky, A. K.; Kabachnik, N. M.; Ueda, K.

    2013-10-01

    The photoelectron angular distributions (PADs) have been investigated for infrared (IR) ionization of He atoms excited to Rydberg states by extreme ultraviolet free-electron laser pulses. The experiment was carried out with two pulses which do not overlap in time. Depending on the intensity of the IR pulses, one IR photon ionization or additionally two-photon above-threshold ionization is observed. For low IR intensity, the PAD is well described by a contribution of s and d partial waves in accordance with early experiments. At high IR intensity, the PAD for two IR photon ionization clearly shows the contribution of higher partial waves. The experimental data are compared with the results of theoretical calculations based on solving the time-dependent Schrödinger equation.

  5. Transmission-line decelerators for atoms in high Rydberg states

    NASA Astrophysics Data System (ADS)

    Lancuba, P.; Hogan, S. D.

    2014-11-01

    Beams of helium atoms in Rydberg states with principal quantum number n =52 , and traveling with an initial speed of 1950 m/s, have been accelerated, decelerated, and guided while confined in moving electric traps generated above a curved, surface-based electrical transmission line with a segmented center conductor. Experiments have been performed with atoms guided at constant speed, and with accelerations exceeding 107 m /s 2. In each case, the manipulated atoms were detected by spatially resolved, pulsed electric field ionization. The effects of tangential and centripetal accelerations on the effective trapping potentials experienced by the atoms in the decelerator have been studied, with the resulting observations highlighting contributions from the density of excited Rydberg atoms to the acceleration, deceleration, and guiding efficiencies in the experiments.

  6. Many-body calculation of helium D-1-D-3 term intervals for 1snd (n=12 similar to 20) high Rydberg states

    NASA Astrophysics Data System (ADS)

    He, Liming; Cao, Wei

    2006-12-01

    With many-body perturbation theory, D-1-D-3 term intervals of helium 1snd (n = 12 similar to 20) configurations are calculated. Based on two different models, Rayleigh-Schrodinger perturbation expansion terms consisting of bound states only, and those of continua are evaluated, respectively. As for bound states, zeroth-order wave functions are strictly generated from self-iteration solutions of the Hartree equation and residues of infinite expansion series are dealt with by the integral processing method, while a simplified hydrogen potential is adopted to get the continua. Using Rayleigh-Schrodinger expansions, we evaluate exchange energy up to third-order terms. It is found that level splittings are mainly attributed to summations over bound states. The fine-structure level splittings yielded here are found to agree quite well with experimental results.

  7. Excitation of helium Rydberg states and doubly excited resonances in strong extreme ultraviolet fields: Full-dimensional quantum dynamics using exponentially tempered Gaussian basis sets

    NASA Astrophysics Data System (ADS)

    Kaprálová-Ž?ánská, Petra Ruth; Šmydke, Jan; Civiš, Svatopluk

    2013-09-01

    Recently optimized exponentially tempered Gaussian basis sets [P. R. Kapralova-Zdanska and J. Smydke, J. Chem. Phys. 138, 024105 (2013)], 10.1063/1.4772468 are employed in quantitative simulations of helium absorption cross-sections and two-photon excitation yields of doubly excited resonances. Linearly polarized half-infinite and Gaussian laser pulses at wavelengths 38-58 nm and large intensities up to 100 TW/cm2 are considered. The emphasis is laid on convergence of the results with respect to the quality of the Gaussian basis sets (typically limited by a number of partial waves, density, and spatial extent of the basis functions) as well as to the quality of the basis set of field-free states (typically limited by the maximum rotational quantum number and maximum excitation of the lower electron). Particular attention is paid to stability of the results with respect to varying complex scaling parameter. Moreover, the study of the dynamics is preceded by a thorough check of helium energies and oscillator strengths as they are obtained with the exponentially tempered Gaussian basis sets, being also compared with yet unpublished emission wavelengths measured in electric discharge experiments.

  8. Excitation of helium Rydberg states and doubly excited resonances in strong extreme ultraviolet fields: Full-dimensional quantum dynamics using exponentially tempered Gaussian basis sets

    SciTech Connect

    Kaprálová-Ž?ánská, Petra Ruth; Šmydke, Jan [J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8 (Czech Republic) [J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8 (Czech Republic); Department of Radiation and Chemical Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Civiš, Svatopluk [J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8 (Czech Republic)] [J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8 (Czech Republic)

    2013-09-14

    Recently optimized exponentially tempered Gaussian basis sets [P. R. Kapralova-Zdanska and J. Smydke, J. Chem. Phys. 138, 024105 (2013)] are employed in quantitative simulations of helium absorption cross-sections and two-photon excitation yields of doubly excited resonances. Linearly polarized half-infinite and Gaussian laser pulses at wavelengths 38–58 nm and large intensities up to 100 TW/cm{sup 2} are considered. The emphasis is laid on convergence of the results with respect to the quality of the Gaussian basis sets (typically limited by a number of partial waves, density, and spatial extent of the basis functions) as well as to the quality of the basis set of field-free states (typically limited by the maximum rotational quantum number and maximum excitation of the lower electron). Particular attention is paid to stability of the results with respect to varying complex scaling parameter. Moreover, the study of the dynamics is preceded by a thorough check of helium energies and oscillator strengths as they are obtained with the exponentially tempered Gaussian basis sets, being also compared with yet unpublished emission wavelengths measured in electric discharge experiments.

  9. Supersymmetry and radial squeezed states for Rydberg wave packets

    NASA Technical Reports Server (NTRS)

    Bluhm, Robert; Kostelecky, V. Alan

    1994-01-01

    Atomic supersymmetry provides an analytical effective-potential model useful for describing certain aspects of Rydberg atoms. Experiments have recently demonstrated the existence of Rydberg wave packets localized in the radial coordinated with p-state angular distribution. This paper shows how atomic supersymmetry can be used to treat radial Rydberg wave packets via a particular analytical type of squeezed state, called a radial squeezed state.

  10. Chirped pulse excitation of two-atom Rydberg states

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Elena

    2015-07-01

    We analyze the excitation of two ground state atoms to a double Rydberg state by a two-photon chirped optical pulse in the regime of adiabatic rapid passage (ARP). For intermediate Rydberg–Rydberg interaction strengths relevant for atoms separated by ?ten ?m, adiabatic excitation can be achieved at experimentally feasible Rabi frequencies and chirp rates of the pulses, resulting in high transfer efficiencies. We also study the adiabatic transfer between ground and Rydberg states as a means to realize a controlled phase gate between atomic qubits.

  11. State-selective all-optical detection of Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Karlewski, Florian; Mack, Markus; Grimmel, Jens; Sándor, Nóra; Fortágh, József

    2015-04-01

    We present an all-optical protocol for detecting population in a selected Rydberg state of alkali-metal atoms. The detection scheme is based on the interaction of an ensemble of ultracold atoms with two laser pulses: one weak probe pulse which is resonant with the transition between the ground state and the first excited state, and a pulse with high intensity which couples the first excited state to the selected Rydberg state. We show that by monitoring the absorption signal of the probe laser over time, one can deduce the initial population of the Rydberg state. Furthermore, it is shown that—for suitable experimental conditions—the dynamical absorption curve contains information on the initial coherence between the ground state and the selected Rydberg state. We present the results of a proof-of-principle measurement performed on a cold gas of 87Rb atoms. The method is expected to find application in quantum computing protocols based on Rydberg atoms.

  12. Rydberg States of Atoms and Molecules

    NASA Astrophysics Data System (ADS)

    Stebbings, R. F.; Dunning, F. B.

    2011-03-01

    List of contributors; Preface; 1. Rydberg atoms in astrophysics A. Dalgarno; 2. Theoretical studies of hydrogen Rydberg atoms in electric fields R. J. Damburg and V. V. Kolosov; 3. Rydberg atoms in strong fields D. Kleppner, Michael G. Littman and Myron L. Zimmerman; 4. Spectroscopy of one- and two-electron Rydberg atoms C. Fabre and S. Haroche; 5. Interaction of Rydberg atoms with blackbody radiation T. F. Gallagher; 6. Theoretical approaches to low-energy collisions of Rydberg atoms with atoms and ions A. P. Hickman, R. E. Olson and J. Pascale; 7. Experimental studies of the interaction of Rydberg atoms with atomic species at thermal energies F. Gounand and J. Berlande; 8. Theoretical studies of collisions of Rydberg atoms with molecules Michio Matsuzawa; 9. Experimental studies of thermal-energy collisions of Rydberg atoms with molecules F. B. Dunning and R. F. Stebbings; 10. High-Rydberg molecules Robert S. Freund; 11. Theory of Rydberg collisions with electrons, ions and neutrals M. R. Flannery; 12. Experimental studies of the interactions of Rydberg atoms with charged particles J. -F. Delpech; 13. Rydberg studies using fast beams Peter M. Koch; Index.

  13. The role of excited Rydberg States in electron transfer dissociation.

    PubMed

    Sobczyk, Monika; Simons, Jack

    2006-04-13

    Ab initio electronic structure methods are used to estimate the cross sections for electron transfer from donor anions having electron binding energies ranging from 0.001 to 0.6 eV to each of three sites in a model disulfide-linked molecular cation. The three sites are (1) the S-S sigma(*) orbital to which electron attachment is rendered exothermic by Coulomb stabilization from the nearby positive site, (2) the ground Rydberg orbital of the -NH(3)(+) site, and (3) excited Rydberg orbitals of the same -NH(3)(+) site. It is found that attachment to the ground Rydberg orbital has a somewhat higher cross section than attachment to either the sigma orbital or the excited Rydberg orbital. However, it is through attachment either to the sigma(*) orbital or to certain excited Rydberg orbitals that cleavage of the S-S bond is most likely to occur. Attachment to the sigma(*) orbital causes prompt cleavage because the sigma energy surface is repulsive (except at very long range). Attachment to the ground or excited Rydberg state causes the S-S bond to rupture only once a through-bond electron transfer from the Rydberg orbital to the S-S sigma(*) orbital takes place. For the ground Rydberg state, this transfer requires surmounting an approximately 0.4 eV barrier that renders the S-S bond cleavage rate slow. However, for the excited Rydberg state, the intramolecular electron transfer has a much smaller barrier and is prompt. PMID:16599533

  14. Rydberg Spectroscopy of Zeeman-Decelerated Beams of Metastable Helium Molecules

    NASA Astrophysics Data System (ADS)

    Jansen, Paul; Motsch, Michael; Sprecher, Daniel; Merkt, Frederic

    2014-06-01

    Having three and four electrons, respectively, He_2^+ and He_2 represent systems for which highly accurate ab-initio calculations might become feasible in the near future. With the goal of performing accurate measurements of the rovibrational energy-level structure of He_2^+ by Rydberg spectroscopy of He_2 and multichannel quantum-defect theory extrapolation techniques, we have produced samples of helium molecules in the a ^3?u^+ state in supersonic beams with velocities tunable down to 100 m/s by combining a cryogenic supersonic-beam source with a multistage Zeeman decelerator. The molecules are formed at an initial velocity of 500 m/s by striking a discharge in the pulsed expansion of helium gas from a reservoir kept at a cryogenic temperature of 10 K. Using rotationally-resolved PFI-ZEKE (pulsed-field-ionization zero-kinetic-energy) photoelectron spectroscopy, we have probed the rotational-state distribution of the molecules produced in the discharge and found vibrational levels up to ?" = 2 and rotational levels up to N"=21 to be populated. The molecular beam is coupled to a multistage Zeeman decelerator that employs pulsed inhomogeneous magnetic fields to further reduce the beam velocity. By measuring the quantum-state distribution of the decelerated sample using photoelectron and photoionization spectroscopy we observed no rotational or vibrational state-selectivity of the deceleration process, but found that one of the three spin-rotation components of the He_2 a ^3?u^+ rotational levels is eliminated. W.-C. Tung, M. Pavanello, L. Adamowicz, J. Chem. Phys. 136, 104309 (2012). D. Sprecher, J. Liu, T. Krähenmann, M. Schäfer, and F. Merkt, J. Chem. Phys. 140, 064304 (2014). M. Motsch, P. Jansen, J. A. Agner, H. Schmutz, and F. Merkt, arXiv:1401.7774. N. Vanhaecke, U. Meier, M. Andrist, B. H. Meier, and F. Merkt, Phys. Rev. A 75, 031402(R) (2007).

  15. Observation of New Rydberg Series and Resonances in Doubly Excited Helium at Ultrahigh Resolution

    Microsoft Academic Search

    K. Schulz; Gunter Kaindl; Michael Domke; John D. Bozek; Philip A. Heimann; Alfred S. Schlachter; J. M. Rost

    1996-01-01

    We report on a striking improvement in spectral resolution in the soft x-ray range to 1.0 meV at 64.1 eV, measured via the mueV-wide 2, -13 double-excitation resonance of helium. This ultrahigh resolution combined with the high photon flux at undulator beam line 9.0.1 of the Advanced Light Source have allowed observation of new Rydberg series and resonances below the

  16. Radiative transitions between Rydberg states of molecules

    SciTech Connect

    Balashov, E.M.; Golubkov, G.V.; Ivanov, G.K.

    1984-06-01

    The multichannel quantum defect method is used in the quasiclassical approximation for the radial motion of the electron to calculate the oscillator strengths for transitions between the highly excited Rydberg states of diatomic molecules and transitions from Rydberg states to the continuum. It is shown that, because of the nonadiabatic coupling between electron and nuclear motion, the photoabsorption spectrum (position of peaks, their intensity, and shape) depends significantly on the initial state of the molecule. The effect of the electron-rotational and electron-vibrational interactions on the shape of the spectrum is analyzed. It is shown that, in the photoionization process, the evolution of the line profiles depends in an important way on interference between direct and resonance mechanisms. The result of this is that the final profile may differ appreciably from the Fano-Feshbach profile. Numerical calculations have been performed for the hydrogen molecule and a number of features in the photoionization and photoabsorption spectra of this molecule are predicted.

  17. Spectral Aspects of the Microwave Ionization of Atomic Rydberg States

    E-print Network

    Delande, Dominique

    "coordinate" is the energy of the atomic electron in the microwave field. Even if we restrict the atomicSpectral Aspects of the Microwave Ionization of Atomic Rydberg States Andreas Buchleitner and Fractals, 5, 1125 (1995) Abstract We perform a numerical study of the microwave ionization of a Rydberg

  18. Spectroscopy of strontium Rydberg states using electromagnetically induced transparency

    E-print Network

    S. Mauger; J. Millen; M. P. A. Jones

    2007-10-07

    We report on the all-optical detection of Rydberg states in a effusive atomic beam of strontium atoms using electromagnetically induced transparency (EIT). Using narrow-linewidth CW lasers we obtain an EIT linewidth of 5 MHz. To illustrate the high spectroscopic resolution offered by this method, we have measured isotope shifts of the 5s18d ^1D_2 and 5s19s ^1S_0 Rydberg states. This technique could be applied to high-resolution, non-destructive measurements of ultra-cold Rydberg gases and plasmas.

  19. Lamb Shift in the Metastable States of the Helium Atom

    Microsoft Academic Search

    Kiu S. Suh; M. H. Zaidi

    1966-01-01

    The radiative corrections of order alpha^3 rydbergs are evaluated for the ionization energy of the metastable states 21,3S, of the helium atom. In the calculation of the average excitation energy k_0, the main contribution comes from the transition to (ms, np) and (ms, ? p) states. The oscillator strengths for transitions to (1s, ? p), (2s, ? p) and (3s,

  20. Dopant low-n Rydberg states in CF4 and CH4 near the critical point

    E-print Network

    Findley, Gary L.

    : VUV absorption, methyl iodide, xenon, critical point effect, low-n Rydberg states Corresponding. Evans). 2 #12;ular fluids. We present absorption spectra of the xenon 6s Rydberg state perturbed by CF4

  1. Relativistic and radiative energy shifts for Rydberg states

    NASA Astrophysics Data System (ADS)

    Jentschura, Ulrich D.; LeBigot, Eric-Olivier; Evers, Jörg; Mohr, Peter J.; Keitel, Christoph H.

    2005-01-01

    We investigate relativistic and quantum electrodynamic effects for highly-excited bound states in hydrogen-like systems (Rydberg states). In particular, hydrogenic one-loop Bethe logarithms are calculated for all circular states (l = n - 1) in the range 20 <= n <= 60 and successfully compared to an existing asymptotic expansion for large principal quantum number n. We provide accurate expansions of the Bethe logarithm for large values of n, for S, P and circular Rydberg states. These three expansions are expected to give any Bethe logarithm for principal quantum number n > 20 to an accuracy of five to seven decimal digits, within the specified manifolds of atomic states. Within the numerical accuracy, the results constitute unified, general formulae for quantum electrodynamic corrections whose validity is not restricted to a single atomic state. The results are relevant for accurate predictions of radiative shifts of Rydberg states and for the description of the recently investigated laser-dressed Lamb shift, which is observable in a strong coherent-wave light field.

  2. Sensitive Polarization Dependence for Helium Rydberg Atoms Driven by Strong Microwave Fields

    NASA Astrophysics Data System (ADS)

    Zelazny, S. A.; Bellermann, M. R. W.; Smith, L. L.; Koch, P. M.

    1996-05-01

    We prepare n^3S He Rydberg atoms with selected values n>=25 in a fast beam using CO2 lasers and double-resonance excitation. They then fly through a TE_121 mode cavity, exposing them to a half-sine pulse (about 350 field osc.) of 9.904 GHz electric field whose polarization can be varied: linear (LP), elliptical (EP), and circular (CP). Making EP close to LP can lead to substantial changes in microwave-power-dependent transitions to nearby bound states. In at least one case, a sharp dip in the LP signal( W. van de Water et al., Phys. Rev. A 42), 572 (1990) is transformed by EP into a pattern reminiscent of Stueckelberg oscillations, previously observed with LP at higher frequencies.( S. Yoakum et al., Phys. Rev. Lett. 69), 1919 (1992) Calculations suggest that pulse-shape-induced dynamics at Floquet avoided-crossing(s) explain the LP behavior. Changing the field to EP clearly must modify this behavior. We will discuss this kind of data as well as the polarization dependence of microwave ionization of n^3S He Rydberg atoms.

  3. Sensitive polarization dependence for helium Rydberg atoms driven by strong microwave fields

    SciTech Connect

    Zelazny, S.A.; Bellermann, M.R.W.; Smith, L.L.; Koch, P.M.

    1996-05-01

    The authors prepare n{sup 3}S He Rydberg atoms with selected values n {ge} 25 in a fast beam using CO{sub 2} lasers and double-resonance excitation. They then fly through a TE{sub 121} mode cavity, exposing them to a half-sine pulse (about 350 field osc.) of 9.904 GHz electric field whose polarization can be varied; linear (LP), elliptical (EP), and circular (CP). Making EP close to LP can lead to substantial changes in microwave-power-dependent transitions to nearby bound states. In at least one case, a sharp dip in the LP signal is transformed by EP into a pattern reminiscent of Stueckelberg oscillations, previously observed with LP at higher frequencies. Calculations suggest that pulse-shape-induced dynamics at Floquet avoided-crossing(s) explain the LP behavior. Changing the field to EP clearly must modify this behavior. The authors will discuss this kind of data as well as the polarization dependence of microwave ionization of n{sup 3}S He Rydberg atoms.

  4. Experimental investigation of long-lived "ZEKE" Rydberg states in ultracold argon

    NASA Astrophysics Data System (ADS)

    Ranjit, Gambhir

    There is considerable interest in the dynamics of ultracold plasmas and ultracold Rydberg gases. Ultracold plasmas are typically formed by photo-excitation of ultracold atoms to an energy region near (both above and below) an ionization threshold. Excitation to bound, highly-excited Rydberg states can lead to formation of a plasma via several processes, including collisions between Rydberg atoms. Three-body recombination in an ultracold plasma can also result in the production of ultracold Rydberg atoms. Understanding the dynamics of ultracold Rydberg gases is therefore important for understanding the dynamics of ultracold plasmas. In this dissertation, we have investigated the formation and survival of a particular class of Rydberg atoms. These atoms are known as ZEKE state Rydberg atoms, where the term ZEKE is derived from "Zero ?inetic E&barbelow;nergy." ZEKE Rydberg states are high angular momentum and high angular momentum projection excited states which can be formed by laser excitation in the presence of electric fields. Without the electric fields, these states would be optically dark. We have investigated ZEKE Rydberg states in ultracold argon in an energy region just below the second ionization threshold of the atoms in our magneto-optical trap. Here, low angular momentum states decay very quickly (< 1 ns) by auto-ionization through a core spin flip due to the Rydberg electron-core interaction. This interaction has been significantly reduced due to the dilution of low l and m states as a result of l and m mixing during excitation. Hence, ZEKE Rydberg states live orders of magnitude longer than low angular momentum states. We are reporting on our experimental investigation of these states in the ultracold regime and prospects for future studies in which external control of these states may be used to control ultracold plasma dynamics.

  5. Probing dissociative electron attachment through formation of heavy-Rydberg ion pair states in Rydberg atom collisions

    NASA Astrophysics Data System (ADS)

    Buathong, S.; Kelley, M.; Wang, C. H.; Dunning, F. B.

    2015-01-01

    A new approach to investigating the properties, i.e., lifetimes and decay energetics, of short-lived intermediates formed during dissociative electron attachment reactions is described that is based on measurements of the velocity and angular distributions of heavy-Rydberg ion pair states formed through electron transfer in collisions with Rydberg atoms. The experimental results are analyzed with the aid of a Monte Carlo collisions code and show that while electron capture by CF3I and CH2Br2 leads to creation of very-short-lived intermediates capture by CCl4 results in formation of much longer lived intermediates.

  6. Autoionization rates for selected double-Rydberg states of barium

    SciTech Connect

    Bhalla, C.P. (Department of Physics, Kansas State University, Manhattan, Kansas 66506 (USA)); Karim, K.R. (Department of Physics, Illinois State University, Normal, Illinois 61761 (USA)); Wilson, M. (Royal Holloway Bedford New College (University of London), Egham, Surrey, (United Kingdom))

    1990-02-01

    We have performed {ital ab} {ital initio} calculations of several autoionizing double-Rydberg states of Ba. We have also investigated the effects due to electron configuration mixing. These calculations are based on the Hartree-Fock atomic model. Numerical results are presented and are compared with the experimental data for {ital msn}{prime}{ital s} and {ital msn}{prime}{ital d} states. Although our calculated quantum-defect values are in excellent agreement with experimental values, they do not yield the same dependence of the scaled autoionization rates on the core principal quantum number as deduced from experiment.

  7. Classical energy calculations with electron correlation of condensed excited states — Rydberg Matter

    Microsoft Academic Search

    Leif Holmlid

    1998-01-01

    A classical model is used to calculate the work function and the binding energy in condensed excited states, also named Rydberg Matter. The quantum mechanical description due to Manykin et al. shows that an excited matter exists, in which Rydberg states interact to give a gaseous metallic material with very low work function. Experimental evidence on a macroscopic level exists.

  8. Atomic and Molecular Low-n Rydberg States in Near Critical Point Fluids*

    E-print Network

    Findley, Gary L.

    0 Atomic and Molecular Low-n Rydberg States in Near Critical Point Fluids* Luxi Li and Xianbo Shi at Monroe, Monroe, LA USA Abstract The structure of low-n Rydberg states doped into supercritical fluids are sensitive to the local fluid environment, dopant electronic transitions are an appropriate probe to study

  9. From the Pendulum to Rydberg Accelerator and Planetary Dynamics: Autoresonant Formation and Control of Nonlinear States

    E-print Network

    Friedland, Lazar

    From the Pendulum to Rydberg Accelerator and Planetary Dynamics: Autoresonant Formation and Control of a pendulum (Sec.II), manipulation of a classical state of a Rydberg atom in 3D [8] (Sec.IV), and a related DRIVEN PENDULUM We proceed from the problem of excitation of a pendulum to large energies

  10. Constant-ionic-state spectroscopy of high-v Rydberg states of molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.; Dehmer, P. M.; Dehmer, J. L.

    1992-09-01

    Photoelectron spectroscopy is used in combination with double-resonance excitation via the E,F 1Sigma-g(+), v = 6 state to reexamine the H2 spectrum in the region of the ion pair in order to elucidate the vibrational autoionization of the high-v Rydberg states and the details of the process of ion pair formation. The decay of the autoionizing Rydberg states is studied by both conventional and constant-ionic-state photoelectron spectrometry. The results support the Delta-v = minimum propensity rule for vibrational autoionization of Rydberg states with a high level of vibrational excitation. The relative intensities of the X 2Sigma-g(+)np, v-prime is not less than 9 Rydberg series converging to different rotational levels of the ion differ greatly from those for the analogous Rydberg series with v-prime is not greater than 2. This may be due to the dependence of the transition dipole matrix elements on the internuclear distance and to the presence of doubly excited electronic states that cross the H2(+) X 2Sigma-g(+) potential curve at a total energy close to that accessed by the two-color excitation scheme.

  11. Two-photon spectroscopy of Rydberg states of molecular oxygen

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.; Dehmer, J. L.; Dehmer, P. M.

    1990-09-01

    The (2 + 1) and two-photon ionization spectra of O2 provide a wealth of new information on the gerade Rydberg series converging to the X 2Pi(g) ground electronic state of O2(+). This paper extends these series to n = 8 for nu-prime = 0 and to n = 12 for n-prime = 1. The spectra display characteristic pairs of transitions to states with Omega(+) = 1/2 and 3/2 ion core that are separated by the O2(+) X 2Pi(1/2g) - 2Pi(3/2g) spin-orbit splitting. The quantum defects of the Omega(=) = 3/2 series members merge smoothly into that of the 3d pi 1Sigma(g)(+) state, providing a tentative assignment of this series.

  12. Two-color resonance ionization spectroscopy of Rydberg states of hafnium atoms

    SciTech Connect

    Matsuoka, Leo; Hasegawa, Shuichi [Department of Quantum Engineering and Systems Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2006-12-15

    We performed two-color resonance ionization spectroscopy to study the highly excited states of hafnium. We obtained the high-resolution spectra of the Rydberg series converging to the first ionization limit. These series of states have not been previously observed. From analyses of the main Rydberg series with Rydberg formula, we derived the ionization potential of hafnium as 55047.9{+-}0.1 cm{sup -1}. Comparing the spectra obtained through three different intermediate states, we could assign the J value of all the series in a certain energy region.

  13. Charge transport, configuration interaction and Rydberg states under density functional theory

    E-print Network

    Cheng, Chiao-Lun

    2008-01-01

    Density functional theory (DFT) is a computationally efficient formalism for studying electronic structure and dynamics. In this work, we develop DFT-based excited-state methods to study electron transport, Rydberg excited ...

  14. Self-interaction corrected density functional calculations of molecular Rydberg states

    SciTech Connect

    Gudmundsdóttir, Hildur [Science Institute of the University of Iceland, 107 Reykjavík (Iceland)] [Science Institute of the University of Iceland, 107 Reykjavík (Iceland); Zhang, Yao; Weber, Peter M. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Jónsson, Hannes [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States) [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Faculty of Physical Sciences, VR-III, University of Iceland, 107 Reykjavík (Iceland)

    2013-11-21

    A method is presented for calculating the wave function and energy of Rydberg excited states of molecules. A good estimate of the Rydberg state orbital is obtained using ground state density functional theory including Perdew-Zunger self-interaction correction and an optimized effective potential. The total energy of the excited molecule is obtained using the Delta Self-Consistent Field method where an electron is removed from the highest occupied orbital and placed in the Rydberg orbital. Results are presented for the first few Rydberg states of NH{sub 3}, H{sub 2}O, H{sub 2}CO, C{sub 2}H{sub 4}, and N(CH{sub 3}){sub 3}. The mean absolute error in the energy of the 33 molecular Rydberg states presented here is 0.18 eV. The orbitals are represented on a real space grid, avoiding the dependence on diffuse atomic basis sets. As in standard density functional theory calculations, the computational effort scales as NM{sup 2} where N is the number of orbitals and M is the number of grid points included in the calculation. Due to the slow scaling of the computational effort with system size and the high level of parallelism in the real space grid approach, the method presented here makes it possible to estimate Rydberg electron binding energy in large molecules.

  15. Generation of tunable coherent far-infrared radiation using atomic Rydberg states

    SciTech Connect

    Bookless, W.

    1980-12-01

    A source of tunable far-infrared radiation has been constructed. The system has been operated at 91.6 cm/sup -1/ with a demonstrated tunability of .63 cm/sup -1/. The system is based on a Rydberg state transition in optically pumped potassium vapor. The transition energy is tuned by the application of an electric field to the excited vapor. The transition wavelength and the shifted wavelength were detected and measured by the use of a Michelson interferometer and a liquid helium cooled Ga:Ge bolometer and the data was reduced using Fast Fourier transform techniques. Extensive spectroscopy was done on the potassium vapor to elucidate the depopulation paths and rates of the excited levels. Both theoretical and experimental results are presented to support the conclusions of the research effort. Additionally, possible alternative approaches to the population of the excited state are explored and recommendations are made for the future development of this source as well as the potential uses of it in molecular spectroscopy.

  16. State-to-state dynamics of elementary chemical reactions using Rydberg H-atom translational spectroscopy

    Microsoft Academic Search

    Xueming Yang

    2005-01-01

    In this review, a few examples of state-to-state dynamics studies of both unimolecular and bimolecular reactions using the H-atom Rydberg tagging TOF technique were presented. From the H2O photodissociation at 157 nm, a direction dissociation example is provided, while photodissociation of H2O at 121.6 has provided an excellent dynamical case of complicated, yet direct dissociation process through conical intersections. The

  17. Vibrational Autoionization and Predissociation in High Rydberg States of Nitric Oxide

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.

    1998-05-01

    New results on the competition between autoionization and predissociation in the high Rydberg states of NO are presented. These results provide insight into the earlier work of H. Park et al. [Phys. Rev. Lett. 76, 1591 (1996)] that show evidence for substantial mixing between Rydberg series and ionization continua with even and odd orbital angular momenta. New data based on fluorescence-dip spectroscopy, detection of neutral predissociation products, and photoelectron spectroscopy suggest that the A' ^2? ^+ and I ^2? ^+ dissociative valence states play an important role in this mixing. As an example, the ionization and dissociation efficiencies of the nf levels are found to depend strongly on whether the total angular momentum minus spin, N, is even or odd, indicating predissociation via a ^2? ^+ state. Zeeman splittings observed in a magnetic bottle electron spectrometer also result in an improvement in the assignment of these high Rydberg states.

  18. Coherent states of the driven Rydberg atom: Quantum-classical correspondence of periodically driven systems

    E-print Network

    Vela-Arevalo, Luz V.

    Coherent states of the driven Rydberg atom: Quantum-classical correspondence of periodically driven A methodology to calculate generalized coherent states for a periodically driven system is presented. We study wave packets constructed as a linear combination of suitable Floquet states of the three

  19. A study of Stark effects of Rydberg p states of noble gas atoms

    Microsoft Academic Search

    T. Jiang; M. D. Bowden; E. Wagenaars; E. Stoffels; G. M. W. Kroesen

    2006-01-01

    We have studied the Stark effect for Rydberg p states of noble gas atoms using laser optogalvanic spectroscopy. The measurements were performed in the sheath region of noble gas glow discharges. Laser excitation from metastable states to np states was monitored by optogalvanic spectroscopy. Clear Stark shifts were observed and the experimental results were compared with a theoretical calculation based

  20. Collisional and electric-field ionization of laser-prepared Rydberg states in an ion trap mass spectrometer

    SciTech Connect

    Ramsey, J.M.; Whitten, W.B.; Goeringer, D.E.; Buckley, B.T.

    1990-01-01

    Rydberg states of rubidium are selectively generated by one and two photon laser excitation in a quadrupole ion trap mass spectrometer. Collisional and electric-field ionization is investigated in trapping device. CCl{sub 4} is studied as a target for ionization of Rydberg states through electron attachment.

  1. Vibrational autoionization and predissociation in high Rydberg states of nitric oxide

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.

    1998-05-01

    New results on the competition between autoionization and predissociation in the high Rydberg states of nitric oxide are presented. These results provide insight into the earlier work of Park et al. [Phys. Rev. Lett. 76, 1591 (1996)] that shows evidence for substantial mixing between Rydberg series and ionization continua with even and odd orbital angular momenta (l). New data based on fluorescence-dip spectroscopy, detection of neutral predissociation products, and photoelectron spectroscopy suggest that the A' 2?+ and I 2?+ dissociative valence states play an important role in this l mixing. Zeeman splittings observed in a magnetic bottle electron spectrometer also result in an improvement in the assignment of these high Rydberg states.

  2. Photoexcitation of n 305 Rydberg States in the Presence of an rf Drive Field

    SciTech Connect

    Yoshida, S [Inst. for Theoretical Phys., Vienna Univ. of Technology; Reinhold, Carlos O [ORNL; Burgdorfer, J. [Vienna University of Technology, Austria; Ye, S [Rice Quantum Inst., Rice University; Dunning, F. B. [Rice University

    2012-01-01

    The response of highly excited potassium Rydberg states with n 305 to a sinusoidal electric drive field in the radio frequency (100 300 MHz) regime is examined by photoexcitation from the 4s ground state using a uv probe beam. The drive field couples many Rydberg levels simultaneously and results in a coherent response that leads to a variety of multiphoton processes. The excitation spectra are analyzed within the framework of Floquet theory and reveal signatures of quantum optical phenomena such as electromagnetically induced transparency and Autler-Townes splitting seen with few-level systems.

  3. CH3I low-n Rydberg states in supercritical atomic fluids near the critical point

    E-print Network

    Findley, Gary L.

    CH3I low-n Rydberg states in supercritical atomic fluids near the critical point Luxi Li a states doped into supercritical argon, krypton, and xenon perturbers were measured from low density effects, especially in supercritical fluids [2]. Both atomic [3­5] and molecular [6­11] dopant low

  4. The Stark effect in Rydberg states of a highly polar diatomic molecule: CaF.

    PubMed

    Petrovi?, Vladimir S; Kay, Jeffrey J; Coy, Stephen L; Field, Robert W

    2009-08-14

    The Stark effect in molecular Rydberg states is qualitatively different from the Stark effect in atomic Rydberg states because of the anisotropy of the ion core and the existence of rotational and vibrational degrees of freedom. These uniquely molecular features cause the electric-field-induced decoupling of the Rydberg electron from the body frame to proceed in several stages in a molecule. Because the transition dipole moment among the same-n* Rydberg states is much larger than the permanent dipole moment of the ion core, the decoupling of the Rydberg electron from the ion core proceeds gradually. In the first stage, analyzed in detail in this paper, l and N are mixed by the external electric field, while N+ is conserved. In the further stages, as the external electric field increases, N+, n*, and v+ are expected to undergo mixing. We have characterized these stages in n*=13, v+=1 states of CaF. The large permanent dipole moment of CaF+ makes CaF qualitatively different from the other molecules in which the Stark effect in Rydberg states has been described (H2, Na2, Li2, NO, and H3) and makes it an ideal testbed for documenting the competition between the external and CaF+ dipole electric fields. We use the weak-field Stark effect to gain access to the lowest-N rotational levels of f, g, and h states and to assign their actual or nominal N+ quantum number. Lowest-N rotational levels provide information needed to disentangle the short-range and long-range interactions between the Rydberg electron and the ion core. We diagonalize an effective Hamiltonian matrix to determine the l-characters of the 3 < or = l < or = 5 core-nonpenetrating 2Sigma+ states and to characterize their mixing with the core-penetrating states. We conclude that the mixing of the l=4, N-N+=-4(g(-4)) state with lower-l 2Sigma+ states is stronger than documented in our previous multichannel quantum defect theory and long-range fits to zero-field spectra. PMID:19691382

  5. Observation of g/u-symmetry mixing in the high-n Rydberg states of HD

    SciTech Connect

    Sprecher, Daniel; Merkt, Frédéric, E-mail: frederic.merkt@phys.chem.ethz.ch [Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich (Switzerland)] [Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich (Switzerland)

    2014-03-28

    The structure and dynamics of high-n Rydberg states belonging to series converging to the (v{sup +} = 0, N{sup +} = 0–2) levels of the X{sup +2}?{sub g}{sup +} electronic ground state of HD{sup +} were studied by high-resolution spectroscopy from the GK{sup 1}?{sub g}{sup +} (v= 1, N = 1) state under field-free conditions. Three effects of g/u-symmetry breaking were detected: (i) Single-photon transitions from the GK?(v = 1, N = 1) state of gerade symmetry to the 30d2{sub 1} and 31g2{sub 2} Rydberg states of gerade symmetry were observed after careful compensation of the stray electric fields. (ii) The singlet 61p1{sub 2} Rydberg state of ungerade symmetry was found to autoionize to the N{sup +} = 0,?? = 2 ionization continuum of gerade symmetry with a lifetime of 77(10)?ns. (iii) Shifts of up to 20?MHz induced by g/u-symmetry mixing were measured for members of the np1{sub 1} Rydberg series which lie close to nd2{sub 1} Rydberg states. These observations were analyzed in the framework of multichannel quantum-defect theory. From the observed level shifts, the off-diagonal eigenquantum-defect element ?{sub pd} of singlet-? symmetry was determined to be 0.0023(3) and the corresponding autoionization dynamics could be characterized. The ionization energy of the GK?(v = 1, N = 1) state of HD was determined to be 12?710.544?23(10)?cm{sup ?1}.

  6. Optical resonance detection by field ionization of Rydberg state in colinear laser spectroscopy

    E-print Network

    Paris-Sud XI, Université de

    . The collinear laser spectroscopy method, first intro- duced independently by Kaufman and Wing et al. [1, 2], has been widely used in high resolution laser spectroscopy experiments on the on line, produces short live1167 Optical resonance detection by field ionization of Rydberg state in colinear laser

  7. Redistribution of atomic Rydberg states by tunable narrow band picosecond far-infrared pulses.

    PubMed

    Raman, C; Decamp, M F; Bucksbaum, P

    1997-09-29

    We study the redistribution of Cesium atomic Rydberg states by intense, shaped, narrow-band pulses of millimeter radiation. The radiation source is a large-area photoconductive switch illuminated by a temporally shaped optical pulse. We will present our latest efforts to study atomic redistribution in the strong-field limit using these table-top THz sources. PMID:19373400

  8. Photofragmentation, state interaction, and energetics of Rydberg and ion-pair states: Resonance enhanced multiphoton ionization of HI

    SciTech Connect

    Hróðmarsson, Helgi Rafn; Wang, Huasheng; Kvaran, Ágúst, E-mail: agust@hi.is [Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavík (Iceland)

    2014-06-28

    Mass resolved resonance enhanced multiphoton ionization data for hydrogen iodide (HI), for two-photon resonance excitation to Rydberg and ion-pair states in the 69?600–72?400 cm{sup ?1} region were recorded and analyzed. Spectral perturbations due to homogeneous and heterogeneous interactions between Rydberg and ion-pair states, showing as deformations in line-positions, line-intensities, and line-widths, were focused on. Parameters relevant to photodissociation processes, state interaction strengths and spectroscopic parameters for deperturbed states were derived. Overall interaction and dynamical schemes to describe the observations are proposed.

  9. Spin--orbit configuration-interaction study of valence and Rydberg states of LiBe

    SciTech Connect

    Marino, M.M.; Ermler, W.C. (Department of Chemistry, The Ohio State University, Columbus, Ohio 43210 (United States) Molecular Science Research Center, Pacific Northwest Laboratory, Richland, Washington 99352 (United States)); Kern, C.W.; Bondybey, V.E. (Department of Chemistry, The Ohio State University, Columbus, Ohio 43210 (United States))

    1992-03-01

    {ital Ab} {ital initio} spin--orbit full configuration-interaction calculations in the context of relativistic effective core potentials are reported for the weakly bound metal dimer LiBe, a three-valence-electron system. The effects of basis set on the energies of valence and Rydberg states of the cluster are discussed, as are the effects of configuration space selection on the energy of the latter states. Results at the dissociative limit are compared to the experimental atomic spectra. Potential-energy curves and spectroscopic constants are presented for the ground state and fourteen excited states, which includes the Li and Be 2{ital p} valence states, the Li 3{ital s}, 3{ital p}, 3{ital d}, and 4{ital s} Rydberg states, as well as three low-lying states of the molecular cation.

  10. Information and entanglement measures applied to the analysis of complexity in doubly excited states of helium

    NASA Astrophysics Data System (ADS)

    Restrepo Cuartas, J. P.; Sanz-Vicario, J. L.

    2015-05-01

    Shannon entropy and Fisher information calculated from one-particle density distributions and von Neumann and linear entropies (the latter two as measures of entanglement) computed from the reduced one-particle density matrix are analyzed for the S e 1 ,3 ,P o 1 ,3 , and D e 1 ,3 Rydberg series of He doubly excited states below the second ionization threshold. In contrast with the Shannon entropy, we find that both the Fisher information and entanglement measures are able to discriminate low-energy resonances pertaining to different (K ,T ) n2A 2 series according to the Herrick-Sinano?lu-Lin classification. Contrary to bound states, which show a clear and unique asymptotic value for both Fisher information and entanglement measures in their Rydberg series 1 s n ? for n ?? (which implies a loss of spatial entanglement), the variety of behaviors and asymptotic values of entanglement above the noninteracting limit value in the Rydberg series of doubly excited states (K ,T ) n2A 2 indicates a signature of the intrinsic complexity and remnant entanglement in these high-lying resonances even with infinite excitation n2?? , for which all known attempts of resonance classifications fail in helium.

  11. Equation of state of metallic helium

    SciTech Connect

    Shvets, V. T., E-mail: tarval@breezein.net [Odessa State Academy of Refrigeration (Ukraine)

    2013-01-15

    The effective ion-ion interaction, free energy, pressure, and electric resistance of metallic liquid helium have been calculated in wide density and temperature ranges using perturbation theory in the electron-ion interaction potential. In the case of conduction electrons, the exchange interaction has been taken into account in the random-phase approximation and correlations have been taken into account in the local-field approximation. The solid-sphere model has been used for the nuclear subsystem. The diameter of these spheres is the only parameter of this theory. The diameter and density of the system at which the transition of helium from the singly ionized to doubly ionized state occurs have been estimated by analyzing the pair effective interaction between helium atoms. The case of doubly ionized helium atoms has been considered. Terms up to the third order of perturbation theory have been taken into account in the numerical calculations. The contribution of the third-order term is significant in all cases. The electric resistance and its temperature dependence for metallic helium are characteristic of simple divalent metals in the liquid state. The thermodynamic parameters-temperature and pressure densities-are within the ranges characteristic of the central regions of giant planets. This makes it possible to assume the existence of helium in the metallic state within the solar system.

  12. Rempi-Pes Studies of Some Rydberg States of Carbon Dioxide

    Microsoft Academic Search

    David Paul Taylor

    1993-01-01

    REMPI-PES studies of some Rydberg states of CO _2 were performed. The (3+1) photoelectron terminations on the ~{bf X} state of CO_sp{2} {+} were found to appear in the photoelectron spectra as long vibrational progressions thought to be associated with molecular dissociation. Additional vibrational bands from terminations at the five photon level were observed through nf intermediate states of CO_2.

  13. Photoabsorption to Stark Rydberg States of Heavy Noble Gas Atoms: Testing Limits of Closed Orbit Theory

    Microsoft Academic Search

    Heric Flores-Rueda; Matthew L. Keeler; David Wright; Thomas J. Morgan

    2003-01-01

    The selective dramatic effects of a dc electric field on the photoabsorption spectrum of Rydberg states and the associated recurrence strengths and closed orbits are studied in heavy noble gas atoms. Using collinear atom-laser beam spectroscopy, complex scaled-energy photoabsorption spectra are mapped experimentally in high resolution for pi and sigma transitions from the ns[3\\/2] and ns[1\\/2] metastable states, formed by

  14. Spin-orbit configuration-interaction study of valence and Rydberg states of LiBe

    Microsoft Academic Search

    M. M. Marino; W. C. Ermler; C. W. Kern; V. E. Bondybey

    1992-01-01

    ital initio} spin--orbit full configuration-interaction calculations in the context of relativistic effective core potentials are reported for the weakly bound metal dimer LiBe, a three-valence-electron system. The effects of basis set on the energies of valence and Rydberg states of the cluster are discussed, as are the effects of configuration space selection on the energy of the latter states. Results

  15. Spin–orbit configuration-interaction study of valence and Rydberg states of LiBe

    Microsoft Academic Search

    M. M. Marino; W. C. Ermler; C. W. Kern; V. E. Bondybey

    1992-01-01

    Abinitio spin–orbit full configuration-interaction calculations in the context of relativistic effective core potentials are reported for the weakly bound metal dimer LiBe, a three-valence-electron system. The effects of basis set on the energies of valence and Rydberg states of the cluster are discussed, as are the effects of configuration space selection on the energy of the latter states. Results at

  16. Chirped-pulse millimeter-wave spectroscopy, dynamics, and manipulation of Rydberg-Rydberg Transitions

    E-print Network

    Colombo, Anthony P. (Anthony Paul)

    2013-01-01

    The chirped-pulse millimeter-wave (CPmmW) technique is applied to transitions between Rydberg states, and calcium atoms are used as the initial test system. The unique feature of Rydberg{Rydberg transitions is that they ...

  17. Adiabatic energy levels and electric dipole moments of Rydberg states of Rb2 and Cs2 dimers

    Microsoft Academic Search

    A. A. Khuskivadze; M. I. Chibisov; I. I. Fabrikant

    2002-01-01

    We calculate potential energy curves for heavy alkali-metal dimers, Rb2 and Cs2 in which one of the atoms is in a highly excited Rydberg states. The method combines numerical integration of coupled equations, describing interaction of electron with the ground-state atom in the field of the Coulomb core of the Rydberg atom, with subsequent matching of the obtained wave function

  18. The HNCO + F reaction system: VUV-photolysis of the cyanato radical via Rydberg states

    NASA Astrophysics Data System (ADS)

    Schönnenbeck, G.; Stuhl, F.

    1997-01-01

    The VUV-photolysis of the cyanato radical, NCO, formed in the reaction of isocyanic acid with fluorine atoms, leads to the formation of electronically excited CN fragments in the B-state. Excitation spectra in the range 105-200 nm and dispersed fluorescence spectra at selected wavelengths show that CN(B 2?+) fragments are formed below ?rmex = 145 ± 1 nm. These spectra provide the first information on some properties of the excited states of the NCO radical above 6.5 eV, resulting in the tentative assignment of a ns-Rydberg series. It is proposed that the first member, 3s, gives rise to dissociation from a bent state, while the second member, 4s, and probably all higher members are governed by linear dissociative configurations. A vibrational progression in the ?1-mode is superimposed on the 4s Rydberg transition.

  19. Transport of charge and atomic particles in Rydberg state-rich plasmas

    NASA Astrophysics Data System (ADS)

    Hagström, Magnus; Davidsson, Jan; Holmlid, Leif

    1998-02-01

    New methods make it possible to form considerable flux densities of Rydberg atoms of alkali metals. It is now possible to study the transport processes in regions where the density of Rydberg atoms is large. Examples of such studies have been given by Svensson and coworkers. In the present study, 0022-3727/31/4/013/img1 ions and Rydberg states 0022-3727/31/4/013/img2 are formed by desorption at 1300-1800 K from an Ir surface covered by a thin graphite layer. Due to the very large cross sections for collision processes involving Rydberg species, the Rydberg state-rich plasma between the Ir emitter and a cold grid electrode is not collision free, even at a pressure of 0022-3727/31/4/013/img3 mbar. Electron or 0022-3727/31/4/013/img4 emission takes place from the grid at a rate controlled by the flux of 0022-3727/31/4/013/img1 and 0022-3727/31/4/013/img2. The transition to penetration of 0022-3727/31/4/013/img1 and 0022-3727/31/4/013/img2 through the cloud of excited species between the emitter and grid is observed directly by molecular beam and ion sampling to detectors in a separate chamber. There is a space-charge limited behaviour for the positive current through the plasma as well as, in some modes, a clear positive saturation current, which shows that little gas phase ionization takes place. A current larger than expected from the saturation current as well as maxima in the voltage dependences are observed at high Rydberg densities. These effects are probably caused by space charge compensation due to a dielectric phase of condensed excited species, which means, for example, that the effective distance between the emitter and grid is decreased, as observed. The temperature variation of the space charge limited behaviour gives an activation energy of 0022-3727/31/4/013/img9, while the saturation current gives an activation energy of 0022-3727/31/4/013/img10. This agrees well with the electronic excitations 0022-3727/31/4/013/img11 at 0.90 eV and 0022-3727/31/4/013/img12 at 0.84 eV, which should be important steps in a thermal excitation process from the ground state of Cs.

  20. MPI spectroscopy in the region of the 3p Rydberg state of some cycloketones

    NASA Astrophysics Data System (ADS)

    Kosmidis, C.; Boulakis, G.; Bolovinos, A.; Tsekeris, P.; Brint, P.

    1992-03-01

    The two-photon resonance three photon ionization spectra of cyclopentanone, cyclohexanone and cycloheptanone in the region of the 3p Rydberg state have been recorded, analysed and compared with the one-photon absorption spectra. A new 3p origin is identified for cyclopentanone. The absence from the MPI spectra of a sharp spectral feature that is observed in the absorption spectra is discussed. Photochemical generation of acetaldehyde is observed at high laser intensities and possible mechanisms for this are considered.

  1. Silicon as a model ion trap: time domain measurements of donor Rydberg states

    Microsoft Academic Search

    N. Q. Vinh; P. T. Greenland; K. Litvinenko; B. Redlich; S. A. Lynch; M. Warner; A. M. Stoneham; G. Aeppli; D. J. Paul; C. R. Pidgeon; B. N. Murdin

    2008-01-01

    One of the great successes of quantum physics is the description of the long-lived Rydberg states of atoms and ions. The Bohr model is equally applicable to donor impurity atoms in semiconductor physics, where the conduction band corresponds to the vacuum, and the loosely bound electron orbiting a singly charged core has a hydrogen-like spectrum according to the usual Bohr-Sommerfeld

  2. Zeeman Effect of J=2 States of Sr: g-Factor Variation for Interacting Rydberg Series

    Microsoft Academic Search

    J. J. Wynne; J. A. Armstrong; P. Esherick

    1977-01-01

    Measurements of the g factor for a series of bound, 5snd J=2 states in Sr, in the region of an avoided crossing between 1D2 and 3D2 Rydberg series, show a variation which is in agreement with the prediction of multichannel quantum-defect theory. The g factor was measured by multiphonon ionization spectroscopy. The dependence of ionization signal on laser polarization was

  3. Rydberg series of 1?u+ and 1?u states of the Li2 molecule studied by the promotion model

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Jin; Lee, Chun-Woo

    2015-01-01

    We studied the Rydberg series for the 12 1?u+, 7 1?u, and 1 1?u states. This set consists of the seventeen states derivable from the Li(2s) + Li(nl) (n = 2, 3, 4, 5) configuration, one 1?u+ state and one 1?u state derivable from Li(2s) + Li(6p) and Li(2s) + Li(6d), respectively, plus one ionic state. We used the multireference configuration interaction method, combined with the Stuttgart/Köln group’s effective core potential/core polarization potential method, to calculate their potential energy curves (PECs). Four Rydberg series, ?uns (n = 3, 4, 5, 6), ?unp (n = 2, 3, 4, 5), ?und (n = 3, 4, 5, 6), and ?unf (n = 4, 5), are identified near the potential energy minima (referred to as the ‘Rydberg region’). The promotion model is used to examine the behaviour of PECs and quantum defect curves (QDCs) by constructing diabatic PECs and QDCs. Besides QDCs, effective n and promotion curves are also used to directly examine the promotion. This reveals that the promotion model can be successfully applied to the singlet ungerade states of Li2, indicating that the Rydberg region has the same characteristics as the united atom (UA) limit. Thus, the Rydberg region in Li2 is much closer to the UA limit than the separated atoms (SA) limit. Correlation diagrams based on the promotion model show a big difference in the number of avoided crossings for the 1?u+ and 1?u states. The larger number of avoided crossings for 1?u+ states produces features in the PECs of the 1?u+ states such as shoulders, flattening, and grouping. The promotion model not only helps to identify Rydberg series, but also to explain all the major and minor aspects and subtle phenomena observed in the PECs and spectroscopic constants of the singlet ungerade Rydberg states of Li2.

  4. Photoelectron spectroscopy of the linear (Ã 2A 1)3pb 21B 2 Rydberg state of water

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.; Dehmer, J. L.; Dehmer, P. M.

    1992-08-01

    Photoelectron spectra are reported for two-photon-resonant, three-photon ionization via several vibrational levels of the linear (à 2A 1)3pb 21B 2 Rydberg state of H 2O and D 2O. In the dominant photoionization pathway, the ejection of the Rydberg electron occurs with no change in the electronic or vibrational state of the ion core, providing direct confirmation of the vibrational numbering of the 1B 2 state proposed by Abramson et al. Photoionization accompanied by excitation of the symmetric stretch in the resulting ion is also observed, reflecting the difference in bond lengths between the 1B 2 Rydberg state and the à 2A 1 ionic state.

  5. A New Wide Range Equation of State for Helium-4

    E-print Network

    Ortiz Vega, Diego O

    2013-08-01

    used for purging and pressurizing systems, it is a crucial substance in United States space exploration and defense efforts. The National Aeronautics and Space Administration (NASA) and the Department of Defense (DOD) use huge amounts of helium... helium from natural gas and sell it to the government. Some helium was also used for research, the NASA space program, and other applications, but most was injected into a storage facility known as the Federal Helium Reserve. Federal demand...

  6. Multiphoton ionization/dissociation of cyclopentanone at the lower Rydberg states

    SciTech Connect

    Philis, John G.; Kosmidis, Constantine; Tzallas, Paraskevas [Department of Physics, University of Ioannina, GR45110 Ioannina (Greece)

    1998-12-16

    The 2-photon excitation of the 3p and 3d Rydberg states in jet-cooled cyclopentanone has been investigated by resonance enhanced multiphoton ionization (REMPI) in a time of flight mass spectrometer. The three 3p{sub x,y,z} components are clearly resolved while the case for the 3d{sub i} excitations is obscure due to the S{sub 1} one-photon resonance. The ns laser induced mass spectra are characteristic of hard ionization while the fs laser induced mass spectrum is very similar to the Electron Impact one.

  7. Resonant electron capture to high Rydberg states by F ions at low energies

    NASA Astrophysics Data System (ADS)

    Bellantone, R.; Hahn, Y.; McLaughlin, D. J.

    1991-04-01

    A systematic study of resonant electron capture by Fz+ ions at low energies is carried out, where Z = 4, 5, 6, and 7, corresponding to the number of electrons N = 5, 4, 3, and 2, respectively in the initial ions. Contributions of the metastable states in the initial ion beam are also studied, especially for the N = 2 case where 1s2s 1.3S states are involved. The doubly excited states formed by the 2s ? 2p intrashell excitation and the capture of the incoming electrons to high Rydberg states are treated explicitly for n <= 12 and by extrapolation in the principal quantum number n for n >= 13. In addition, excitation transitions involving parent core states of the same configuration but with different total spins are also studied. The Z-dependence of this isonuclear sequence is used in the construction of empirical rate formulas.

  8. Multiphoton spectroscopy of Rydberg states of small molecules

    SciTech Connect

    Pratt, Stephen T.; McCormack, E. F.; Dehmer, Joseph L.; Dehmer, Patricia M.

    1990-09-01

    Multiphoton ionization techniques provide a versatile means for studying highly excited states of atoms and molecules and provide a valuable complement to traditional techniques based on single-photon absorption and ionization studies. In this paper we present the results of new multiphoton ionization studies of molecular nitrogen and molecular oxygen that serve to illustrate the power of these techniques. 30 refs., 3 figs.

  9. Efficient Production of Rydberg Positronium

    NASA Astrophysics Data System (ADS)

    Cassidy, D. B.; Hisakado, T. H.; Tom, H. W. K.; Mills, A. P., Jr.

    2012-01-01

    We demonstrate experimentally the production of Rydberg positronium (Ps) atoms in a two-step process, comprising incoherent laser excitation, first to the 2P3 state and then to states with principal quantum numbers ranging from 10 to 25. We find that excitation of 2P3 atoms to Rydberg levels occurs very efficiently (˜90%) and that the ˜25% overall efficiency of the production of Rydberg atoms is determined almost entirely by the spectral overlap of the primary excitation laser and the Doppler broadened width of the 1S3-2P3 transition. The observed efficiency of Rydberg Ps production can be explained if stimulated emission back to the 2P states is suppressed, for example, by intermixing of the Rydberg state Stark sublevels. The efficient production of long-lived Rydberg Ps in a high magnetic field may make it possible to perform direct measurements of the gravitational free fall of Ps.

  10. Dissociation dynamics of high-v Rydberg states of molecular hydrogen

    NASA Astrophysics Data System (ADS)

    McCormack, E. F.; Pratt, S. T.; Dehmer, P. M.; Dehmer, J. L.

    1993-06-01

    The dynamics of the decay of (Chi 2Sigma(+) sub g)n,p, v-prime of 9 or greater Rydberg states of H2 into the H(1s) + H(3l) and H(1s) + H(4l) dissociation continua are investigated by examining the dissociation spectrum of H2 in the energy region between the H(1s) + H(4l) dissociation threshold and the Chi 2Sigma(+) sub g, v(+) = 9 ionization threshold, using a double resonance excitation scheme via the E,F 1Sigma(+) sub g, v = 6 state. A comparison of this spectrum to the previously observed Chi 2Sigma(+) sub g, v(+) = 8 constant-ionic-state photoelectron spectrum and the ion-pair spectrum observed in the same energy region reveal strong competition between the ionization and dissociation processes through both rovibrational and electronic interactions.

  11. Electric-Field-Induced Dissociation of Heavy Rydberg Ion-Pair States

    SciTech Connect

    Reinhold, Carlos O [ORNL; Yoshida, S. [Vienna University of Technology, Austria; Dunning, F. B. [Rice University

    2011-01-01

    A classical trajectory Monte Carlo approach is used to simulate the dissociation of H+..F and K+..Cl heavy Rydberg ion pairs induced by a ramped electric-field, a technique used experimentally to detect and probe ion-pair states. The simulations include the effects of the strong short-range repulsive interaction associated with ion-pair scattering and provide results in good agreement with experimental data for Stark wavepackets probed by a ramped field, demonstrating that many of the characteristics of field-induced dissociation can be well described using a purely classical model. The data also show that states with a given value of principal quantum number (i.e., binding energy) can dissociate over a broad range of applied fields, the exact field being governed by the initial orbital angular momentum and orientation of the state.

  12. Vibrational branching ratios following two-color excitation of autoionizing np Rydberg states of H2

    NASA Astrophysics Data System (ADS)

    O'Halloran, M. A.; Dehmer, P. M.; Tomkins, F. S.; Pratt, S. T.; Dehmer, J. L.

    1988-07-01

    The vibrational branching ratios of the autoionizing ungerade np(sigma) 1Sigma(+)u and np(pi) 1Pi(u) Rydberg states of H2 are determined experimentally by means of two-color resonantly enhanced multiphoton-ionization photoelectron spectroscopy, using two-step excitation via the (E,F)1Sigma(+)g (v-prime = E2) resonant intermediate state. Sample spectra are shown, and the results are presented in a table. The branching is found to favor the v(+) = 1 channel (94-96 percent) over the v(+) = 0 channel (4-6 percent) in general, although v(+) = 0 branching ratios of up to 18 percent are observed in some cases and attributed to interchannel coupling of low-ionization-efficiency low-n/high-v interlopers.

  13. ATOMIC AND MOLECULAR PHYSICS: Investigation of odd-parity Rydberg states of Eu I with autoionization detection

    NASA Astrophysics Data System (ADS)

    Xiao, Ying; Dai, Chang-Jian; Qin, Wen-Jie

    2009-10-01

    Isolated-core-excitation (ICE) scheme and autoionization detection are employed to study the bound Rydberg states of europium atom. The high-lying states with odd parity have been measured using the autoionization detection method with three different excitation paths via 4f76s6p[8P5/2], 4f76s6p[8P7/2] and 4f76s6p[8P9/2] intermediate states, respectively. In this paper the spectra of bound Rydberg states of Eu atom are reported, which cover the energy regions from 36000 cm-1 to 38250 cm-1 and from 38900 cm-1 to 39500 cm-1. The study provides the information about level energy, the possible J values and relative line intensity as well as the effective principal quantum number n* for these states. This work not only confirms the previous results of many states, but also discovers 11 new Rydberg states of Eu atom.

  14. Observation of ultralong-range Rydberg molecules

    Microsoft Academic Search

    Vera Bendkowsky; Björn Butscher; Johannes Nipper; James P. Shaffer; Robert Löw; Tilman Pfau

    2009-01-01

    Rydberg atoms have an electron in a state with a very high principal quantum number, and as a result can exhibit unusually long-range interactions. One example is the bonding of two such atoms by multipole forces to form Rydberg-Rydberg molecules with very large internuclear distances. Notably, bonding interactions can also arise from the low-energy scattering of a Rydberg electron with

  15. Efficient Production of Rydberg Positronium

    NASA Astrophysics Data System (ADS)

    Hisakado, Tomu; Cassidy, David; Tom, Harry; Mills, Allen

    2012-06-01

    We demonstrated the efficient production of Rydberg Positronium atoms using a two-step incoherent laser excitation process. The two step process occurs first to the 23P state and then to the quantum numbers ranging from 10 to 25. We found a 90% efficiency going from the 23P state to the Rydberg levels and an overall conversion efficiency of 25% of the production of Rydberg atoms. This high efficiency is due to the overlap of the laser bandwidth with the Doppler broadened width of the 1s-2p transition and the suppression of the stimulated emission back to the 2P states, due to the intermixing of the Rydberg state Stark sublevels. By demonstrating the production of long lived Rydberg Ps atoms in a high magnetic field may make it possible to perform gravitational measurements of free falling positronium atoms.

  16. The Chemi-Ionization Processes in Slow Collisions of Rydberg Atoms with Ground State Atoms: Mechanism and Applications

    E-print Network

    Mihajlov, A A; Ignjatovic, Lj M; Klyucharev, A N; 10.1007/s10876-011-0438-7

    2012-01-01

    In this article the history and the current state of research of the chemiionization processes in atom-Rydberg atom collisions is presented. The principal assumptions of the model of such processes based on the dipole resonance mechanism, as well as the problems of stochastic ionization in atom-Rydberg atom collisions, are exposed. The properties of the collision kinetics in atom beams of various types used in contemporary experimentations are briefly described. Results of the calculation of the chemi-ionization rate coefficients are given and discussed for the range of the principal quantum number values 5 chemi-ionization processes in astrophysical and laboratory low-temperature plasmas, and the contemporary methods of their investigation are described. Also the directions of further research of chemi-ionization processes are discussed in this article.

  17. Helium-helium clustering states in 12Be

    NASA Astrophysics Data System (ADS)

    Yang, Z. H.; Ye, Y. L.; Li, Z. H.; Lou, J. L.; Wang, J. S.; Jiang, D. X.; Ge, Y. C.; Li, Q. T.; Hua, H.; Li, X. Q.; Xu, F. R.; Pei, J. C.; Qiao, R.; You, H. B.; Wang, H.; Tian, Z. Y.; Li, K. A.; Sun, Y. L.; Liu, H. N.; Chen, J.; Wu, J.; Li, J.; Jiang, W.; Wen, C.; Yang, B.; Liu, Y.; Yang, Y. Y.; Ma, P.; Ma, J. B.; Jin, S. L.; Han, J. L.; Lee, J.

    2015-02-01

    An inelastic excitation experiment was performed with a 12Be beam at 29 MeV/u on a carbon target. New resonances close to the respective cluster separation thresholds were observed in 12Be for the 4He+8He and 6He + 6He decay channels, confirming the previously proposed molecular rotational bands. Using the model-independent angular correlation analysis, a 0+ spin parity is assigned to the remarkably large peak at 10.3 MeV in the 4He + 8He channel. A distorted wave Born approximation (DWBA) calculation was compared to the experimental differential cross section of this state, resulting in a largely enhanced monopole transition matrix element of 7.0 ±1.0 fm2 , in good agreement with the generalized two-center cluster model (GTCM) prediction assuming a preformed ? -4 n -? configuration. Together with the previously reported large cluster spectroscopic factor, the strong clustering in 12Be is well demonstrated. The detection focused on the most forward angles, by using a zero-deg telescope, is essential in the present measurement.

  18. Analysis of the 8f, 9f, and 10f, v=1 Rydberg states of N2

    NASA Astrophysics Data System (ADS)

    McCormack, E. F.; Pratt, S. T.; Dehmer, J. L.; Dehmer, P. M.

    1991-09-01

    The autoionizing (X 2?+g) 8f, 9f, and 10f, v=1 states of N2 have been studied by using double-resonance ionization spectroscopy via numerous rotational levels of the a 1?g, v'=5 state. These nf states lie in a complex region of the spectrum that also contains transitions to high vibrational levels of the b' 1?+u valence state and Rydberg states that converge to the X 2?+g, A 2?u, and B 2?+u states of the ion. A long-range interaction model, which is based on the interaction of the Rydberg electron with the polarizability and quadrupole moment of the N+2 ion core, has been used to intepret the f-state structure and to identify the extent of perturbations due to interactions with nearby states. A generalized least-squares fit of the model to the energies of the unperturbed 8f state yields an effective quadrupole moment of (3.2+/-0.1)ea20 and an isotropic polarizability of (16.1+/-0.4)a30 for the 2?+g, v+=1 state of the ion. In addition, a new state that is observed to perturb the 9f, v=1 state is tentatively identified as the previously unobserved ( 2?u)3d? 1?u, v=2 state. The results presented here complete the interpretation of the single-photon absorption spectrum of N2 from the first ionization potential at ~125 667 to ~126 850 cm-1.

  19. Physics 139B Fall 2009 The Variational Computation of the Ground State Energy of Helium

    E-print Network

    California at Santa Cruz, University of

    Physics 139B Fall 2009 The Variational Computation of the Ground State Energy of Helium I. Introduction to the variational computation The Hamiltonian for the two-electron system of the helium atom is state energy of the helium atom. The ground state wave function of the helium atom is of the form: 1 2

  20. Electromagnetically induced transparency in a Y system with single Rydberg state

    NASA Astrophysics Data System (ADS)

    Tian, Xue-Dong; Liu, Yi-Mou; Yan, Xiao-Bo; Cui, Cui-Li; Zhang, Yan

    2015-06-01

    We study the transmitted intensity and correlation properties of a probe field propagating through a sample of cold interacting 87Rb atoms driven into the Y level configuration with single Rydberg state. We find two electromagnetically induced transparency (EIT) windows in the transmission spectrum. One window is linear since it is immune to the incident probe field. The other window depth is sensitive to the incident probe intensity, exhibiting cooperative nonlinearity. Meanwhile, the linear window is low but the transmissivity at the nonlinear window can reach nearly 100% in case of the weak probe intensity. When two EIT windows overlap, the cooperative optical nonlinearity plays a leading role in the degenerate window. In addition, the probe propagation is affected by its two-photon correlation which is suppressed at the center of nonlinear window and is enhanced near the boundaries of two windows. The two-photon correlation is also sensitive to the probe field, and that means we can attain the strongest photon bunching (anti-bunching) effect by controlling the probe and coupling fields.

  1. Metastable superpositions of ortho- and para-Helium states

    E-print Network

    Pedro Sancho; Luis Plaja

    2008-08-10

    We analyze superpositions of ortho- and para-Helium states, considering the possible existence of stationary and metastable states in the system. In particular, the metastable superposition of 1s2s ortho and para states seems to be accessible to experimental scrutiny.

  2. Metastable superpositions of ortho- and para-Helium states

    E-print Network

    Sancho, Pedro

    2008-01-01

    We analyze superpositions of ortho- and para-Helium states, considering the possible existence of stationary and metastable states in the system. In particular, the metastable superposition of 1s2s ortho and para states seems to be accessible to experimental scrutiny.

  3. Observation of Excitonic Rydberg States in Monolayer MoS2 and WS2 by Photoluminescence Excitation Spectroscopy.

    PubMed

    Hill, Heather M; Rigosi, Albert F; Roquelet, Cyrielle; Chernikov, Alexey; Berkelbach, Timothy C; Reichman, David R; Hybertsen, Mark S; Brus, Louis E; Heinz, Tony F

    2015-05-13

    We have identified excited exciton states in monolayers of MoS2 and WS2 supported on fused silica by means of photoluminescence excitation spectroscopy. In monolayer WS2, the positions of the excited A exciton states imply an exciton binding energy of 0.32 eV. In monolayer MoS2, excited exciton transitions are observed at energies of 2.24 and 2.34 eV. Assigning these states to the B exciton Rydberg series yields an exciton binding energy of 0.44 eV. PMID:25816155

  4. Observation of ultralong-range Rydberg molecules.

    PubMed

    Bendkowsky, Vera; Butscher, Björn; Nipper, Johannes; Shaffer, James P; Löw, Robert; Pfau, Tilman

    2009-04-23

    Rydberg atoms have an electron in a state with a very high principal quantum number, and as a result can exhibit unusually long-range interactions. One example is the bonding of two such atoms by multipole forces to form Rydberg-Rydberg molecules with very large internuclear distances. Notably, bonding interactions can also arise from the low-energy scattering of a Rydberg electron with negative scattering length from a ground-state atom. In this case, the scattering-induced attractive interaction binds the ground-state atom to the Rydberg atom at a well-localized position within the Rydberg electron wavefunction and thereby yields giant molecules that can have internuclear separations of several thousand Bohr radii. Here we report the spectroscopic characterization of such exotic molecular states formed by rubidium Rydberg atoms that are in the spherically symmetric s state and have principal quantum numbers, n, between 34 and 40. We find that the spectra of the vibrational ground state and of the first excited state of the Rydberg molecule, the rubidium dimer Rb(5s)-Rb(ns), agree well with simple model predictions. The data allow us to extract the s-wave scattering length for scattering between the Rydberg electron and the ground-state atom, Rb(5s), in the low-energy regime (kinetic energy, <100 meV), and to determine the lifetimes and the polarizabilities of the Rydberg molecules. Given our successful characterization of s-wave bound Rydberg states, we anticipate that p-wave bound states, trimer states and bound states involving a Rydberg electron with large angular momentum-so-called trilobite molecules-will also be realized and directly probed in the near future. PMID:19396141

  5. Triplet states of rubidium dimers on helium nanodroplets

    Microsoft Academic Search

    F. R. Brühl; R. A. Miron; W. E. Ernst

    2001-01-01

    Rubidium dimers in their 1 3Sigmau+ states are formed through collisions of Rb atoms that have been deposited on the surface of helium nanodroplets. Visible absorption spectra between 550 and 690 nm were probed by laser induced fluorescence and emission spectra measured for selected excitation wavelengths. A system absorbing around 595 nm with its emission to the ground state centered

  6. Triplet states of rubidium dimers on helium nanodroplets

    Microsoft Academic Search

    R. A. Miron; W. E. Ernst

    2001-01-01

    Rubidium dimers in their 1 3?u+ states are formed through collisions of Rb atoms that have been deposited on the surface of helium nanodroplets. Visible absorption spectra between 550 and 690 nm were probed by laser induced fluorescence and emission spectra measured for selected excitation wavelengths. A system absorbing around 595 nm with its emission to the ground state centered

  7. Magnetic trapping of long-lived cold Rydberg atoms.

    PubMed

    Choi, J-H; Guest, J R; Povilus, A P; Hansis, E; Raithel, G

    2005-12-01

    We report on the trapping of long-lived strongly magnetized Rydberg atoms. 85Rb atoms are laser cooled and collected in a superconducting magnetic trap with a strong bias field (2.9 T) and laser excited to Rydberg states. Collisions scatter a small fraction of the Rydberg atoms into long-lived high-angular momentum "guiding-center" Rydberg states, which are magnetically trapped. The Rydberg atomic cloud is examined using a time-delayed, position-sensitive probe. We observe magnetic trapping of these Rydberg atoms for times up to 200 ms. Oscillations of the Rydberg-atom cloud in the trap reveal an average magnetic moment of the trapped Rydberg atoms of approximately -8microB. These results provide guidance for other Rydberg-atom trapping schemes and illuminate a possible route for trapping antihydrogen. PMID:16384371

  8. Excited states of the helium-antihydrogen system.

    PubMed

    Sharipov, Vasily; Labzowsky, Leonti N; Plunien, Günter

    2007-03-01

    Potential energy curves for excited leptonic states of the helium-antihydrogen system are calculated within the Ritz variational approach. An explicitly correlated ansatz for the leptonic wave function is employed describing accurately the motion of the leptons (two electrons and positron) in the field of the helium nucleus and of the antiproton with an arbitrary orbital angular momentum projection Lambda onto the internuclear axis. Results for Lambda=0, 1, and 30 are presented. For quasibound states with large values of Lambda and rotational quantum numbers J>Lambda no annihilation and rearrangement decay channels occur; i.e., they are metastable. PMID:17358528

  9. $?^4$ Ry corrections to singlet states of helium

    E-print Network

    Krzysztof Pachucki

    2006-07-07

    Corrections of order $\\alpha^4$Ry are calculated for the singlet states $1^1S_0$ and $2^1S_0$ of the helium atom. The result for $1^1S_0$ state is in slight disagreement with that of Korobov and Yelkhovsky in [Phys. Rev. Lett. {\\bf 87}, 193003 (2001)]. The results obtained lead to a significant improvement of transition frequencies between low lying levels of the helium atom. In particular theoretical predictions for the $2^1S_0 - 1^1S_0$ transition are found to be in disagreement with experimental values.

  10. Excited states of the helium-antihydrogen system

    E-print Network

    Sharipov, V; Plunien, G

    2007-01-01

    Potential energy curves for excited leptonic states of the helium-antihydrogen system are calculated within Ritz' variational approach. An explicitly correlated ansatz for the leptonic wave function is employed describing accurately the motion of the leptons (two electrons and positron) in the field of the helium nucleus and of the antiproton with arbitrary orbital angular momentum projection $\\Lambda$ onto the internuclear axis. Results for $\\Lambda$=0, 1 and 30 are presented. For quasibound states with large values of $\\Lambda$ and rotational quantum numbers $J>\\Lambda$ no annihilation and rearrangement decay channels occur, i. e. they are metastable.

  11. Spectrum of the Autoionizing Triplet Gerade Rydberg States of H2 and its Analysis Using Multichannel Quantum-Defect Theory

    NASA Astrophysics Data System (ADS)

    Sprecher, Daniel; Jungen, Christian; Merkt, Frédéric

    2013-10-01

    A new spectrum of the autoionizing triplet states of gerade symmetry of H2 has been recorded from the -- = 1-4, N- = 1-3 rovibrational levels of the metastable c 3-u- state in a supersonic beam. The spectrum consists of overlapping ns and nd Rydberg series with n in the range between 4 and 45 converging to the -+ = 1-4, N+ = 0-5 levels of the X+ 2?g+ ground state of H2+. Numerous perturbations caused by s-d and rovibrational channel interactions are revealed in the spectrum and were fully assigned by combining double-resonance experiments and ab initio multichannel quantum-defect theory (MQDT). The energy- and internuclear-distance-dependent eigenquantum-defect parameters of MQDT were derived from available ab initio calculations of the low-lying electronic states of H2 and the ground state of H2+ and were subsequently refined in a global fit to experimental data. The positions of 552 triplet ns and nd Rydberg levels of H2 (361 of which were measured in the present study) could be reproduced with a root-mean-square deviation of 0.2 cm-1.

  12. Ab initio potential energy curves of the valence, Rydberg, and ion-pair states of iodine monochloride, ICl

    SciTech Connect

    Kalemos, Apostolos, E-mail: kalemos@chem.uoa.gr [Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Athens 15771 (Greece); Prosmiti, Rita [Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, (IFF-CSIC), Serrano 123, 28006 Madrid (Spain)

    2014-09-14

    We present for the first time a coherent ab initio study of 39 states of valence, Rydberg, and ion-pair character of the diatomic interhalogen ICl species through large scale multireference variational methods including spin-orbit effects coupled with quantitative basis sets. Various avoided crossings are responsible for a non-adiabatic behaviour creating a wonderful vista for its theoretical description. Our molecular constants are compared with all available experimental data with the aim to assist experimentalists especially in the high energy regime of up to ?95?000 cm{sup ?1}.

  13. Simulations of the effect of final state interactions on the scattering reponses of helium droplets 

    E-print Network

    Yang, Jian

    1996-01-01

    We study the effect of final state interactions (FSI) on the scattering responses of Helium droplets. By computing the s-wave component of the one-body density matrix of a Helium droplet, we find strong similarity between bulk Helium and Helium...

  14. Simulations of the effect of final state interactions on the scattering reponses of helium droplets

    E-print Network

    Yang, Jian

    1996-01-01

    We study the effect of final state interactions (FSI) on the scattering responses of Helium droplets. By computing the s-wave component of the one-body density matrix of a Helium droplet, we find strong similarity between bulk Helium and Helium...

  15. The role of dissociative attachment from Rydberg states in enhancing H - concentration in moderate- and low-pressure H 2 plasma sources

    NASA Astrophysics Data System (ADS)

    Hassouni, K.; Gicquel, A.; Capitelli, M.

    1998-07-01

    A numerical code, recently developed for describing the kinetics of H 2 microwave discharges obtained in diamond deposition plasma reactors, was used to estimate the importance of dissociative attachment from H 2 Rydberg states in enhancing the production of H - in this kind of discharge. It was also used to investigate H - production in multicusp low-pressure magnetic plasmas. Results show that the dissociative attachment from Rydberg states can be as important as the mechanism involving vibrationally excited molecules in both types of plasmas.

  16. Direct Electron Impact Excitation of Rydberg-Valence States of Molecular Nitrogen

    NASA Astrophysics Data System (ADS)

    Malone, C. P.; Johnson, P. V.; Liu, X.; Ajdari, B.; Muleady, S.; Kanik, I.; Khakoo, M. A.

    2012-12-01

    Collisions between electrons and neutral N2 molecules result in emissions that provide an important diagnostic probe for understanding the ionospheric energy balance and the effects of space weather in upper atmospheres. Also, transitions to singlet ungerade states cause N2 to be a strong absorber of solar radiation in the EUV spectral range where many ro-vibrational levels of these Rydberg-valence (RV) states are predissociative. Thus, their respective excitation and emission cross sections are important parameters for understanding the [N]/[N2] ratio in the thermosphere of nitrogen dominated atmospheres. The following work provides improved constraints on absolute and relative excitation cross sections of numerous RV states of N2, enabling more physically accurate atmospheric modeling. Here, we present recent integral cross sections (ICSs) for electron impact excitation of RV states of N2 [6], which were based on the differential cross sections (DCSs) derived from electron energy-loss (EEL) spectra of [5]. This work resulted in electronic excitation cross sections over the following measured vibrational levels: b 1?u (v?=0-14), c3 1?u (v?=0-3), o3 1?u (v?=0-3), b? 1?u+ (v?=0-10), c?4 1?u+ (v?=0-3), G 3?u (v?=0-3), and F 3?u (v?=0-3). We further adjusted the cross sections of the RV states by extending the vibronic contributions to unmeasured v?-levels via the relative excitation probabilities (REPs) as discussed in [6]. This resulted in REP-scaled ICSs over the following vibrational levels for the singlet ungerade states: b(0-19), c3(0-4), o3(0-4), b?(0-16), and c?4(0-8). Comparison of the ICSs of [6] with available EEL based measurements, theoretical calculations, and emission based work generally shows good agreement within error estimations, except with the recent reevaluation provided by [1]. Further, we have extended these results, using the recent EEL data of [3], to include the unfolding of better resolved features above ~13.82eV. This effort is to provide improved cross sections for these RV states, in particular for the b? 1?u+ and c?4 1?u+ states, with inclusion of more upper vibrational levels. Future optical emission work should include re-measurements of excitation shape functions of the singlet ungerade states utilizing better spectral resolution than past determinations (e.g., [2,4]) to avoid uncertainties associated with unresolved and/or blended spectral features as well as J-dependent predissociation. Further development of theoretical treatments of N2 excitation is also in need. We will also present analysis of our new low-energy, near-threshold excitation cross sections for the valence states of N2, including a 1?g (v?) levels. Acknowledgement: This work was performed at CSUF and JPL, Caltech, under contract with NASA. We gratefully acknowledge financial support through NASA's OPR and PATM programs and NSF-PHY-RUI-0096808 & -0965793 and NSF-AGS-0938223. References: [1] Ajello, J. M., M. H. Stevens, I. Stewart, et al. (2007), GRL, 34, L24204 [2] Ajello, J. M., G. K. James, and B. O. Franklin (1989), PRA, 40, 3524-56 [3] Heays, A. N., B. R. Lewis, S. T. Gibson, et al. (2012), PRA, 85, 012705 [4] James, G. K., J. M. Ajello, B. Franklin, and D. E. Shemansky (1990), JPB, 23, 2055-81 [5] Khakoo, M. A., C. P. Malone, P. V. Johnson, et al. (2008), PRA, 77, 012704 [6] Malone, C. P., P. V. Johnson, X. Liu, et al. (2012), PRA, 85, 062704

  17. Using uncertainty principle to find the ground-state energy of the helium and a helium-like Hookean atom

    Microsoft Academic Search

    Varun Harbola

    2011-01-01

    In this paper, we accurately estimate the ground-state energy and the atomic radius of the helium atom and a helium-like Hookean atom by employing the uncertainty principle in conjunction with the variational approach. We show that with the use of the uncertainty principle, electrons are found to be spread over a radial region, giving an electron cloud. Our calculation also

  18. Isotope Shifts and Hyperfine Structure in Calcium 4snp1P1 and 4snf F Rydberg States

    SciTech Connect

    Muller, P.; Bushaw, Bruce A.; Nortershauser, Wilfried; Wendt, K.

    2000-06-01

    Isotope shifts and hyperfine structure have been measured in 4snp 1P1 and 4snf F Rydberg states for all stable calcium isotopes and the radioisotope 41Ca using high-resolution laser spectroscopy. Triple-resonance excitation via 4s2 1S0 --- 4s4p 1P1 --- 4s4d 1D2 --- Rydberg State was followed by photoionization with a CO2 laser and mass selective ion detection. Isotope shifts for the even-mass isotopes have been analyzed to derive specific mass shift and field shift factors. The apparent isotope shifts for 41Ca and 43Ca exhibit anomalous values that are n-dependent. This is interpreted in terms of hyperfine-induced fine structure mixing, which becomes very pronounced when singlet-triplet fine structure splitting is comparable to the hyperfine interaction energy. Measurements of fine structure splittings for the predominant isotope 40Ca have been used as input parameters for theoretical calculation of the perturbed hyperfine structure. Results obtained by diagonalizing the second-order hyperfine interaction matrices agree very well with experimentally observed spectra.

  19. Rydberg States of Atoms and Molecules in a Field of Neutral Particles

    Microsoft Academic Search

    G. V. Golubkov; M. G. Golubkov; G. K. Ivanov

    2010-01-01

    \\u000a This book is devoted to the modern methods of calculating the energy eigenvalues of Rydberg atoms A** and molecules XY** perturbed by neutral particles of a medium and to the results of studying the interaction processes with them. Numerous\\u000a applications in plasma chemistry, aeronomy, and astrophysics have contributed to conducting this study. These methods are\\u000a based on the use of

  20. Engineering Very-High-n Polarized Rydberg States Using Tailored Half-Cycle-Pulse Sequences

    Microsoft Academic Search

    W. Zhao; J. J. Mestayer; J. C. Lancaster; F. B. Dunning; Carlos O Reinhold; S. Yoshida; J. Burgdörfer

    2005-01-01

    We show that strongly polarized very-high-n (ñ600) potassium Rydberg atoms can be produced by manipulating lower-n (ñ350) polarized atoms using a tailored sequence of ultrashort half-cycle pulses (HCPs). The protocol for this involves first a weak HCP that generates transient phase-space localization whereupon a second large HCP of opposite polarity excites the electron to a broad distribution of highly elongated

  1. Physics 139B Fall 2009 The Variational Computation of the Ground State Energy of Helium

    E-print Network

    California at Santa Cruz, University of

    Physics 139B Fall 2009 The Variational Computation of the Ground State Energy of Helium I. Introduction to the variational computation The Hamiltonian for the two­electron system of the helium atom is principle to compute the ground state energy of the helium atom. The ground state wave function

  2. The Jahn-Teller effect in the 3pe' Rydberg state of H3: review of experimental and ab initio determinations.

    PubMed

    Jungen, Ch; Jungen, M; Pratt, S T

    2012-11-13

    The dissociative recombination (DR) of H(3)(+) ions with electrons, producing neutral atomic and molecular fragments, is driven primarily by the vibronic Jahn-Teller (JT) interaction between the electronic components of the pe' e(-)-H(3)(+) collision (Rydberg) channel. The JT parameters characterizing this interaction are therefore of great interest as they are required for the theoretical predictions of the DR cross section. In this contribution, we review various determinations of these quantities that have been made previously, based both on spectroscopic studies of 3pe' Rydberg-excited H(3) states, and on the analysis of the corresponding ab initio H(3) Rydberg potential surfaces near the conical intersection (D(3h) symmetry) for n=3-5. The highly correlated theoretical 3pe' potential surfaces of Mistrík et al. are used for a new determination of both the linear and quadratic JT terms. PMID:23028155

  3. Electron capture into excited states of helium by helium-ion impact on helium

    Microsoft Academic Search

    Thomas G. Winter; Chun C. Lin

    1975-01-01

    Cross sections for electron capture into each excited state of He up to 4 1,3D by He+ impact on He in the energy range 100-10 000 keV have been calculated by means of the first Born approximation (Bates's version). A Gaussian technique previously developed for evaluating two-center integrals occurring in the Born amplitude has been used. One-parameter, variational wave functions

  4. Ultralong-range Rydberg Molecules: Investigation of a Novel Binding Mechanism

    Microsoft Academic Search

    Björn Butscher; Vera Bendkowsky; Johannes Nipper; Jonathan Balewski; James P. Shaffer; Robert Löw; Tilman Pfau

    2010-01-01

    For highly excited Rydberg atoms, the scattering of the Rydberg electron from a nearby polarizable ground state atom can generate an attractive mean-field potential which is able to bind the ground state atom to the Rydberg atom within the Rydberg electron wave function at binding energies ranging from a few MHz to hundreds of MHz[1]. We present spectroscopic data on

  5. State-to-state dynamics of high-n Rydberg H-atom scattering with H2: inelastic scattering and reactive scattering.

    PubMed

    Yu, Shengrui; Su, Shu; Dai, Dongxu; Yuan, Kaijun; Yang, Xueming

    2015-04-21

    The state-to-state dynamics of high-n Rydberg H-atom scattering with para-H2 at the collision energies of 0.45 and 1.07 eV have been studied using the H-atom Rydberg tagging time-of-flight technique. Both the inelastic scattering and reactive scattering are observed in the experimental time-of-flight spectra. The products H2(v', j' = odd) come only from reactive scattering and present clearly forward-backward asymmetric angular distributions, which differ from those of the corresponding ion-molecule reaction. The products H2(v', j' = even), however, come from both reactive scattering and inelastic scattering. Simulating the rotational distribution from reactive scattering, we found that most of the H2(v', j' = even) products come from inelastic scattering. The angular distributions of the product H2(v', j' = even) are consistent with what is predicted by the conventional textbook mechanism of inelastic scattering, and are a little different from those of the corresponding ion-molecule inelastic scattering. These results suggest that the effect of Rydberg electron could not be neglected in describing the differential cross sections of H* + para-H2 scattering. From the simulation, the branching ratios of the inelastic scattering channel were determined to be 66% and 79% at the collision energies of 0.45 and 1.07 eV, respectively. PMID:25162182

  6. Version 1.0 # 4 Ry corrections to singlet states of helium

    E-print Network

    Pachucki, Krzysztof

    Version 1.0 # 4 Ry corrections to singlet states of helium Krzysztof Pachucki # Institute Corrections of order # 4 Ry are calculated for the singlet states 1 1 S 0 and 2 1 S 0 of the helium atom frequencies between low lying levels of the helium atom. In particular theoretical predictions for the 2 1 S 0

  7. Radiative decay of helium doubly excited states Chien-Nan Liu,1

    E-print Network

    Lin, Chii-Dong

    yield and the other measured the yields of metastable helium atoms and VUV photon, as a functionRadiative decay of helium doubly excited states Chien-Nan Liu,1 Ming-Keh Chen,2 and C. D. Lin1 1 2001 A theoretical study of the radiative decay of low-lying doubly excited 1 Po states of Helium

  8. The Long-Range Model of High-L Rydberg Fine Structure: A Critical Comparison with Experimental Data

    Microsoft Academic Search

    Erica L. Snow; Laura E. Wright; Stephen R. Lundeen

    2006-01-01

    A simple view of the fine structure of non-penetrating Rydberg levels, suggested over 70 years ago [1], was refined to treat the fine structure of helium, lithium [2], and other atoms with S-state ion cores [3]. In this view the ion polarizabilities determine the fine structure pattern. Current experimental techniques provide access to highly excited high-L states in He [4],

  9. Rydberg atoms in ultracold plasmas

    NASA Astrophysics Data System (ADS)

    Rolston, Steven

    2009-05-01

    Ultracold plasmas are formed through the photoionization of laser-cooled atoms, or spontaneous ionization of a dense cloud of Rydberg atoms or now molecules[1]. Ultracold plasmas are inherently metastable, as the ions and electrons would be in a lower energy state bound together as atoms. The dominant process of atom formation in these plasmas is three-body recombination, a collision between two electrons and an ion that leads to the formation of a Rydberg atom. This collisional process is not only important in determining the lifetime and density of the plasma, but is also critical in determining the time evolution of the temperature. The formation of the Rydberg atoms is accompanied by an increase in electron energy for the extra electron in the collision, and is a source of heating in these plasmas. Classical three-body recombination theory scales as T-9/2, and thus as a plasma cools due to a process such as adiabatic expansion, recombination-induced heating turns on, limiting the temperature [2]. The Rydberg atoms formed live in the plasma and contribute to the temperature dynamics, as collisions with plasma electrons can change the principal quantum number of the Rydberg atom, driving it to more tightly bound states (a source of plasma heating) or to higher states (a source of plasma cooling). If the plasma is cold and dense enough to be strongly coupled, classical three-body recombination theory breaks down. Recent theoretical work [3] suggests that the rate limits as the plasma gets strongly coupled. I will review the role of Rydberg atoms in ultracold plasmas and prospects for probing Rydberg collisions in the strongly coupled environment. [4pt] [1] J. P. Morrison, et al., Phys. Rev. Lett. 101, 205005 (2008 [0pt] [2] R. S. Fletcher, X. Zhang, and S. L. Rolston, Phys. Rev. Lett. 99, 145001 (2007 [0pt] [3] T. Pohl, private communication.

  10. Helium Molecular Energy States as Detected by Collisions of the Second Kind in Helium

    Microsoft Academic Search

    Roland Meyerott

    1946-01-01

    From a survey of the literature on spectra enhanced by collisions of the second kind, which take place in helium, evidence is presented for the existence in measurable concentrations of both the helium molecule-ion and the helium metastable molecule. From the intensity distribution of the enhanced spectra, the repulsive energy between two helium atoms at separations of 1.052A and 1.090A

  11. Quantification of Entanglement Entropies for Doubly Excited States in Helium

    E-print Network

    Chien-Hao Lin; Yew Kam Ho

    2015-03-11

    In this work, we study the quantum entanglement for doubly excited resonance states in helium by using highly correlated Hylleraas type functions to represent such states of the two-electron system. The doubly-excited resonance states are determined by calculation of density of resonance states under the framework of the stabilization method. The spatial (electron-electron orbital) entanglement measures for the low-lying doubly excited 2s2, 2s3s, and 2p2 1Se states are carried out. Once a resonance state wave function is obtained, the linear entropy and von Neumann entropy for such a state are quantified using the Schmidt-Slater decomposition method. To check the consistence, linear entropy is also determined by solving analytically the needed four-electron (12-dimensional) integrals.

  12. Quantification of Entanglement Entropies for Doubly Excited States in Helium

    E-print Network

    Lin, Chien-Hao

    2015-01-01

    In this work, we study the quantum entanglement for doubly excited resonance states in helium by using highly correlated Hylleraas type functions to represent such states of the two-electron system. The doubly-excited resonance states are determined by calculation of density of resonance states under the framework of the stabilization method. The spatial (electron-electron orbital) entanglement measures for the low-lying doubly excited 2s2, 2s3s, and 2p2 1Se states are carried out. Once a resonance state wave function is obtained, the linear entropy and von Neumann entropy for such a state are quantified using the Schmidt-Slater decomposition method. To check the consistence, linear entropy is also determined by solving analytically the needed four-electron (12-dimensional) integrals.

  13. Quantification of Entanglement Entropies for Doubly Excited States in Helium

    NASA Astrophysics Data System (ADS)

    Lin, Chien-Hao; Ho, Yew Kam

    2015-05-01

    In this work, we study the quantum entanglement for doubly excited resonance states in helium by using highly correlated Hylleraas type functions to represent such states of the two-electron system. The doubly-excited resonance states are determined by calculation of density of resonance states under the framework of the stabilization method. The spatial (electron-electron orbital) entanglement measures for the low-lying doubly excited 2 s 2, 2 s3 s, and 2 p 2 1 S e states are carried out. Once a resonance state wave function is obtained, the linear entropy and von Neumann entropy for such a state are quantified using the Schmidt-Slater decomposition method. To check the consistence, linear entropy is also determined by solving analytically the needed four-electron (12-dimensional) integrals.

  14. Spectropolarimetry and IR photometry of magnetic white dwarfs: Vacuum polarization or rydberg states in their magnetic fields?

    NASA Astrophysics Data System (ADS)

    Gnedin, Yu. N.; Borisov, N. V.; Larionov, V. M.; Natsvlishvili, T. M.; Piotrovich, M. Yu.; Arkharov, A. A.

    2006-07-01

    We suggest two mechanisms to explain IR photometric and spectropolarimetric observations of magnetic white dwarfs: vacuum polarization and the existence of Rydberg atomic states with large dipole moments arising due to atomic collisions in the strong magnetic field of the white dwarf (so-called magnetic collision-induced absorption, or magnetic CIA). Both mechanisms can explain the observed rotations of the polarization ellipses and the depression of the IR spectral energy distribution. We present the results of spectropolarimetric observations of several magnetic white dwarfs with the Special Astrophysical Observatory 6-m telescope, together with photometric observations in the near-IR obtained with the Russian-Italian AZT-24 Telescope at Campo Imperatore.

  15. Mass transfer of helium, neon, argon, and xenon through a steady-state upper mantle

    Microsoft Academic Search

    D. Porcelli; G. J. Wasserburg

    1995-01-01

    We have examined the steady-state upper mantle model for helium, neon, argon, and xenon following the mass transfer approach presented by Kellogg and Wasserburg (1990) for helium and Porcelli and Wasserburg (1995a) for xenon. The model explains the available observational data of mantle helium, neon, argon, and xenon isotope compositions and provides specific predictions regarding the rare gas isotopic compositions

  16. Measurement of absolute transition frequencies of {sup 87}Rb to nS and nD Rydberg states by means of electromagnetically induced transparency

    SciTech Connect

    Mack, Markus; Karlewski, Florian; Hattermann, Helge; Hoeckh, Simone; Jessen, Florian; Cano, Daniel; Fortagh, Jozsef [CQ Center for Collective Quantum Phenomena and their Applications, Physikalisches Institut, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

    2011-05-15

    We report the measurement of absolute excitation frequencies of {sup 87}Rb to nS and nD Rydberg states. The Rydberg transition frequencies are obtained by observing electromagnetically induced transparency on a rubidium vapor cell. The accuracy of the measurement of each state is < or approx. 1 MHz, which is achieved by frequency stabilizing the two diode lasers employed for the spectroscopy to a frequency comb and a frequency comb calibrated wavelength meter, respectively. Based on the spectroscopic data we determine the quantum defects of {sup 87}Rb, and compare it with previous measurements on {sup 85}Rb. We determine the ionization frequency from the 5S{sub 1/2}(F=1) ground state of {sup 87}Rb to 1010.029 164 6(3)THz, providing the binding energy of the ground state with an accuracy improved by two orders of magnitude.

  17. A New Wide Range Equation of State for Helium-4 

    E-print Network

    Ortiz Vega, Diego O

    2013-08-01

    .1 Properties of helium ......................................................................................... 1 1.2 Supply and uses of helium ............................................................................... 5 1.2.1 Helium in cryogenics...: cryogenics, pressurizing and purging, welding, atmospheric control, leak detection, breathing mixtures, lifting, and other uses. Figure 5 presents the percentage of helium and the amount in million cubic meters in each application. Figure 5...

  18. Ionization of low-Rydberg-state He atoms by polar molecules. II. Large rotational-energy transfers and absolute values of the cross sections

    Microsoft Academic Search

    A. Pesnelle; C. Ronge; M. Perdrix; G. Watel

    1988-01-01

    The absolute values of cross sections for the collisional ionization of low-Rydberg-state He atoms in the n 1P state (n=14) by the polar molecules NH3, SO2, and acetone (C3H6O) are measured in a crossed-beam experiment at thermal kinetic energies, for a well-defined relative velocity. Simultaneous Penning ionization of NH3 by metastable He(23S) atoms is carried out in situ for calibration.

  19. Predissociative linewidths of (4p?) M 2?+ (v=1) and (3d?,?) H 2?+, H’ 2&Pgr; (v=2) Rydberg states of NO studied by the two-color laser-induced grating technique

    Microsoft Academic Search

    Juntarou Ishii; Kiyoji Uehara; Koichi Tsukiyama

    1995-01-01

    The two-color laser-induced grating (TC-LIG) technique has been employed to probe the predissociative Rydberg states (4p?) M 2?+ (v=1) and (3d?,?) H 2?+, H’ 2&Pgr;± (v=2) and the non-Rydberg B 2&Pgr; (v=26) state of nitric oxide. The ultraviolet pump laser frequency is fixed to a specific rotational line of the A 2?+ (v’=1 and 2)?X 2&Pgr;3\\/2 (v‘=0) transition of NO.

  20. Phase Modulation in Rydberg Dressed Multi-Wave Mixing processes

    PubMed Central

    Zhang, Zhaoyang; Zheng, Huaibin; Yao, Xin; Tian, Yaling; Che, Junling; Wang, Xiuxiu; Zhu, Dayu; Zhang, Yanpeng; Xiao, Min

    2015-01-01

    We study the enhancement and suppression of different multi-waving mixing (MWM) processes in a Rydberg-EIT rubidium vapor system both theoretically and experimentally. The nonlinear dispersion property of hot rubidium atoms is modulated by the Rydberg-Rydberg interaction, which can result in a nonlinear phase shift of the relative phase between dark and bright states. Such Rydberg-induced nonlinear phase shift can be quantitatively estimated by the lineshape asymmetry in the enhancedand suppressed MWM processes, which can also demonstrate the cooperative atom-light interaction caused by Rydberg blockaded regime. Current study on phase shift is applicable to phase-sensitive detection and the study of strong Rydberg-Rydberg interaction. PMID:26053438

  1. Phase Modulation in Rydberg Dressed Multi-Wave Mixing processes.

    PubMed

    Zhang, Zhaoyang; Zheng, Huaibin; Yao, Xin; Tian, Yaling; Che, Junling; Wang, Xiuxiu; Zhu, Dayu; Zhang, Yanpeng; Xiao, Min

    2015-01-01

    We study the enhancement and suppression of different multi-waving mixing (MWM) processes in a Rydberg-EIT rubidium vapor system both theoretically and experimentally. The nonlinear dispersion property of hot rubidium atoms is modulated by the Rydberg-Rydberg interaction, which can result in a nonlinear phase shift of the relative phase between dark and bright states. Such Rydberg-induced nonlinear phase shift can be quantitatively estimated by the lineshape asymmetry in the enhancedand suppressed MWM processes, which can also demonstrate the cooperative atom-light interaction caused by Rydberg blockaded regime. Current study on phase shift is applicable to phase-sensitive detection and the study of strong Rydberg-Rydberg interaction. PMID:26053438

  2. The Bethe Logarithm for resonant states. Antiprotonic helium

    E-print Network

    Korobov, Vladimir I

    2014-01-01

    We develop a numerical method to calculate the Bethe logarithm for resonant states. We use the Complex Coordinate Rotation (CCR) formalism to describe resonances as time-independent Schr\\"odinger solutions. To get a proper expression for the Bethe logarithm we apply the generalization of the second order perturbation theory to an isolated CCR eigenstate. Using the developed method we perform a systematic calculation of the Bethe logarithm for metastable states in the antiprotonic helium He$^+\\bar{p}\\,$ atoms with precision of 7--8 significant digits. We also recalculate the nonrelativistic energies with improved precision using CODATA10 recommended values of masses. Along with a complete set of corrections of $m\\alpha^7$ order and the leading contributions of $m\\alpha^8$ order that has allowed us to get new theoretical values for ro-vibrational transition frequencies for the He$^+\\bar{p}$ atoms with uncertainty of 0.1--0.3 MHz.

  3. Photodissociation of Methyl Iodide via Selected Vibrational Levels of the B? ((2)E3/2)6s Rydberg State.

    PubMed

    Xu, Hong; Pratt, S T

    2015-07-16

    We have determined the I (2)P3/2 and (2)P1/2 branching fractions following the photodissociation of methyl iodide (CH3I) via a number of vibronic bands associated with the B? ((2)E3/2)6s Rydberg state at excitation wavelengths between 201.2 and 192.7 nm. Vacuum ultraviolet light at 118.2 nm was used to ionize both the product iodine atoms and the methyl radical cofragments, and velocity map ion imaging was used to determine the product translational energy distributions and angular distributions. The known relative photoionization cross sections for I (2)P3/2 and (2)P1/2 at 118.2 nm were used to determine the corresponding branching fractions. The results extend our earlier work at 193 nm by Xu et al. (J. Chem. Phys. 2013, 139, 214310), and complement the closely related work of González et al. (J. Chem. Phys. 2011, 135, 021102). We find that for most of the excited vibronic levels of the B? state studied, the I (2)P3/2 branching ratio is small, but nonzero, and that this channel is associated with internally excited CH3 radicals. The results are discussed in relation to the recent theoretical results of Alekseyev et al. (J. Chem. Phys. 2011, 134, 044303). PMID:25946320

  4. LBNL-42730 1 Collisional Perturbation of States in Atomic Ytterbium by Helium and Neon

    E-print Network

    Budker, Dmitry

    LBNL-42730 1 Collisional Perturbation of States in Atomic Ytterbium by Helium and Neon D, CA 94720 Results of an investigation of collisional de-excitation of the metastable 6s6p 3 P0 state in atomic ytterbium by helium and neon buffer gases are reported. We find upper limits for the quenching

  5. A reexamination of the Rydberg-Klein-Rees potential of the a 3Sigma + u state of Na2

    NASA Astrophysics Data System (ADS)

    Friedman-Hill, Ernest J.; Field, Robert W.

    1992-02-01

    The ˜0.1 Å error in the inner wall of the experimental Rydberg-Klein-Rees (RKR) potential for the Na2 a 3?+u state [L. Li, S. F. Rice, and R. W. Field, J. Chem. Phys. 82, 1178 (1985)], detected by Jen? and Brandt using the reduced potential curve (RPC) method [F. Jen? and B. A. Brandt, J. Chem. Phys. 91, 3287 (1989)], was due to neglect of centrifugal distortion effects and not due to a fundamental flaw in the LeRoy-Bernstein near-dissociation expansion (NDE) G(v) and B(v) fitting expressions used to generate it. The NDE expressions, in fact, are preferable to the more traditional Dunham expansions of B(v) and G(v) for the fitting of sparse data sets. We have refined the previously published RKR curve to include centrifugal distortion effects without including additional data. The results are in excellent agreement with theoretical predictions, and are probably accurate to ±0.01 Å up to energies within 5 cm-1 of dissociation. The principal constants are Te+Y00=5848.48(22) cm-1, ?e=24.15(2) cm-1, Be=0.0562(1) cm-1, re=5.011(9) Å, and De=175.76(35) cm-1.

  6. Rotationally resolved photoelectron spectra in resonance enhanced multiphoton ionization of HCl via the F 1?2 Rydberg state

    NASA Astrophysics Data System (ADS)

    Wang, Kwanghsi; McKoy, V.

    1991-12-01

    Results of studies of rotational ion distributions in the X 2?3/2 and X 2?1/2 spin-orbit states of HCl+ resulting from (2+1') resonance enhanced multiphoton ionization (REMPI) via the S(0) branch of the F 1?2 Rydberg state are reported and compared with measured threshold-field-ionization zero-kinetic-energy spectra reported recently [K. S. Haber, Y. Jiang, G. Bryant, H. Lefebvre-Brion, and E. R. Grant, Phys. Rev. A (in press)]. These results show comparable intensities for J+=3/2 of the X 2?3/2 ion and J+=1/2 of the X 2?1/2 ion. Both transitions require an angular momentum change of ?N=-1 upon photoionization. To provide further insight into the near-threshold dynamics of this process, we also show rotationally resolved photoelectron angular distributions, alignment of the ion rotational levels, and rotational distributions for the parity components of the ion rotational levels. About 18% population is predicted to occur in the (+) parity component, which would arise from odd partial-wave contributions to the photoelectron matrix element. This behavior is similar to that in (2+1) REMPI via the S(2) branch of the F 1?2 state of HBr and was shown to arise from significant l mixing in the electronic continuum due to the nonspherical molecular ion potential. Rotational ion distributions resulting from (2+1) REMPI via the S(10) branch of the F 1?2 state are also shown.

  7. Determination of the binding energies of the np Rydberg states of H{sub 2}, HD, and D{sub 2} from high-resolution spectroscopic data by multichannel quantum-defect theory

    SciTech Connect

    Sprecher, Daniel; Merkt, Frédéric, E-mail: frederic.merkt@phys.chem.ethz.ch [Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich (Switzerland)] [Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich (Switzerland); Jungen, Christian [Laboratoire Aimé Cotton du CNRS, Université de Paris-Sud, 91405 Orsay (France)] [Laboratoire Aimé Cotton du CNRS, Université de Paris-Sud, 91405 Orsay (France)

    2014-03-14

    Multichannel quantum-defect theory (MQDT) is used to calculate the electron binding energies of np Rydberg states of H{sub 2}, HD, and D{sub 2} around n = 60 at an accuracy of better than 0.5?MHz. The theory includes the effects of rovibronic channel interactions and the hyperfine structure, and has been extended to the calculation of the asymmetric hyperfine structure of Rydberg states of a heteronuclear diatomic molecule (HD). Starting values for the eigenquantum-defect parameters of MQDT were extracted from ab initio potential-energy functions for the low-lying p Rydberg states of molecular hydrogen and subsequently refined in a global weighted fit to available experimental data on the singlet and triplet Rydberg states of H{sub 2} and D{sub 2}. The electron binding energies of high-np Rydberg states derived in this work represent important quantities for future determinations of the adiabatic ionization energies of H{sub 2}, HD, and D{sub 2} at sub-MHz accuracy.

  8. Antiferromagnetic phase transition in a nonequilibrium lattice of Rydberg atoms

    SciTech Connect

    Lee, Tony E.; Cross, M. C. [Department of Physics, California Institute of Technology, Pasadena, California 91125 (United States); Haeffner, H. [Department of Physics, University of California, Berkeley, California 94720 (United States)

    2011-09-15

    We study a driven-dissipative system of atoms in the presence of laser excitation to a Rydberg state and spontaneous emission. The atoms interact via the blockade effect, whereby an atom in the Rydberg state shifts the Rydberg level of neighboring atoms. We use mean-field theory to study how the Rydberg population varies in space. As the laser frequency changes, there is a continuous transition between the uniform and antiferromagnetic phases. The nonequilibrium nature also leads to a novel oscillatory phase and bistability between the uniform and antiferromagnetic phases.

  9. Scattering properties of strongly interacting Rydberg polaritons

    NASA Astrophysics Data System (ADS)

    Choi, Soonwon; Bienias, Przemek; Firstenberg, Ofer; Maghrebi, Mohammad; Lukin, Mikhail; Gorshkov, Alexey; Gullans, Michael; Buchler, Hanspeter

    2014-05-01

    The combination of Electromagnetically Induced Transparency(EIT) and strong Rydberg-Rydberg interaction can lead to a system of interacting polaritons. In this poster, we present a theoretical analysis of two-polariton dynamics in Rydberg EIT medium. We show that the effective polariton-polariton interaction is tunable to both attraction and repulsion and investigate its scattering properties. In the regime of attraction, we identify the formation of multiple two-polariton bound states and compute their dispersions. Finally, we discuss the implications of our results to the ongoing experiments and to the effective many body theory for strongly interacting Rydberg polaritons. We acknowledge support by the Center for Integrated Quantum Science and Technology, the Deutsche Forschungsgemeinschaft, EU Marie Curie ITN COHERENCE, and the National Science Foundation under Grant No. NSF PHY11-25915.

  10. Double-resonance spectroscopy of the high Rydberg states of HCO. II. Mode specificity in the dynamics of vibrational autoionization via CO stretch versus bend

    NASA Astrophysics Data System (ADS)

    Mayer, Eric E.; Hedderich, Hartmut G.; Grant, Edward R.

    1998-02-01

    We report ionization-detected absorption spectra of vibrationally autoionizing high Rydberg states of formyl radical. Steps of uv-visible double resonance with selected rovibrational levels of the 3p? 2? Rydberg state of HCO promote Franck-Condon vertical transitions that isolate series converging to (010) (bend) and (001) (CO stretch) excited states of HCO+. Final state energies in these spectra exceed the threshold for production of the cation ground state. Intensities and linewidths of observed resonances convey information on the dynamics of electron ejection driven by the vibronic relaxation of specific normal modes of the linear triatomic core. Many resonances in (010) and (001) autoionization spectra exhibit widths that approach the resolution of our laser. Other resonances in series converging to both limits are noticeably broadened, with linewidths that display an inverse cubic dependence on principal quantum number. Among these broader resonances, those in series that decay by relaxation of CO stretch exhibit a scaled width that is about a factor of two larger than that of the broadest resonances in series that relax via the bending fundamental. This trend mirrors to some degree one which has been seen in similar experiments on NO2. We consider these dynamics in the light of a multichannel quantum defect theory picture for the autoionization of polyatomic molecules.

  11. Helium isotopes in geothermal and volcanic gases of the Western United States, II. Long Valley Caldera

    NASA Astrophysics Data System (ADS)

    Welhan, J. A.; Poreda, R. J.; Rison, W.; Craig, H.

    1988-05-01

    Systematic trends in helium isotope ratios and gas compositions in Long Valley caldera hot-spring and fumarole gases reflect subsurface processes and conditions in the hydrothermal system. High {3He}/{4He} ratios (to 6.5 × atmospheric) indicate a magmatic helium source diluted to varying degrees by crustal radiogenic helium, as observed in western United States geothermal systems in general. Helium isotope ratios increase eastward across the caldera, which we interpret as an input of magmatic helium to the hydrothermal fluid as it flows eastward over the caldera. Decreasing He/condensible-gas (? He/CO 2) ratios accompanying this trend suggest that CO 2 addition and/or preferential helium loss due to boiling are also occurring, although near-surface, pH-related CO 2?HCO 3 equilibria obscure the nature of this effect. Substantial changes in {3He}/{4He} ratios were observed in Long Valley gases between 1978 and 1985. Helium isotope ratios increased by 15% in the Hot Creek thermal vent, with maximum ratios achieved in 1983. Helium isotope ratios subsequently decreased in this and other hot vents in the caldera. These observations indicate that substantial changes in the mixing ratio of radiogenic and magmatic helium may occur over relatively short periods of time in magmatically active systems.

  12. Density-functional calculations on singly and doubly excited Rydberg states of many-electron atoms

    E-print Network

    Chu, Shih-I; Roy, Amlan K.

    2002-05-07

    excited state energies is within about 0.01% for He (for other atoms, it is less than 0.2%), while that for the doubly excited states of He is well within 3.6%. The deviations in the calculated single- and double-excitation energies for 31 selected states...

  13. Chirped-Pulse Millimeter-Wave Spectroscopy of Rydberg-Rydberg Transitions

    SciTech Connect

    Prozument, Kirill; Colombo, Anthony P.; Zhou Yan; Park, G. Barratt; Petrovic, Vladimir S.; Coy, Stephen L.; Field, Robert W. [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2011-09-30

    Transitions between Rydberg states of Ca atoms, in a pulsed, supersonic atomic beam, are directly detected by chirped-pulse millimeter-wave spectroscopy. Broadband, high-resolution spectra with accurate relative intensities are recorded instantly. Free induction decay (FID) of atoms, polarized by the chirped pulse, at their Rydberg-Rydberg transition frequencies, is heterodyne detected, averaged in the time domain, and Fourier transformed into the frequency domain. Millimeter-wave transient nutations are observed, and the possibility of FID evolving to superradiance is discussed.

  14. Time-resolved spectroscopy of doubly-excited states in helium

    NASA Astrophysics Data System (ADS)

    Ott, Christian; Kaldun, Andreas; Raith, Philipp; Meyer, Kristina; Laux, Martin; Zhang, Yizhu; Hagstotz, Steffen; Ding, Thomas; Heck, Robert; Pfeifer, Thomas

    2013-03-01

    A two-electron wave packet among the lowest-lying doubly-excited states in helium is experimentally observed. It creates a 1-femtosecond modulation in the transient-absorption signal modified by a time-delayed coupling laser.

  15. Trapping Rydberg Atoms in an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Anderson, Sarah E.

    2012-06-01

    Optical lattice traps for Rydberg atoms are of interest in advanced science and in practical applications. After a brief discussion of these areas of interest, I will review some basics of optical Rydberg-atom trapping. The trapping potential experienced by a Rydberg atom in an optical lattice is given by the spatial average of the free-electron ponderomotive energy weighted by the Rydberg electron's probability distribution. I will then present experimental results on the trapping of ^85Rb Rydberg atoms in a one-dimensional ponderomotive optical lattice (wavelength 1064 nm). The principal methods employed to study the lattice performance are microwave spectroscopy, which is used to measure the lattice's trapping efficiency, and photo-ionization, which is used to measure the dwell time of the atoms in the lattice. I have achieved a 90% trapping efficiency for ^85Rb 50S atoms by inverting the lattice immediately after laser excitation of ground-state atoms into Rydberg states. I have characterized the dwell time of the atoms in the lattice using photo-ionization of 50D5/2 atoms. In continued work, I have explored the dependence of the Rydberg-atom trapping potential on the angular portion of the atomic wavefunction. Distinct angular states exhibit different trapping behavior in the optical lattice, depending on how their wavefunctions are oriented relative to the lattice planes. Specifically, I have measured the lattice potential depth of sublevels of ^85Rb nD atoms (50<=n<=65) in a one-dimensional optical lattice with a transverse DC electric field. The trapping behavior varies substantially for the various angular sublevels, in agreement with theory. The talk will conclude with an outlook into planned experiments.

  16. Electromagnetically induced transparency and fluorescence in blockaded Rydberg atomic system

    SciTech Connect

    Li, Cheng; Zheng, Huaibin; Zhang, Zhaoyang; Yao, Xin; Zhang, Yunzhe; Zhang, Yiqi; Zhang, Yanpeng [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic Technique, Xi'an Jiaotong University, Xi'an 710049 (China)] [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic Technique, Xi'an Jiaotong University, Xi'an 710049 (China)

    2013-10-28

    We investigate the interaction between dark states and Rydberg excitation blockade by using electromagnetically induced transparency (EIT), fluorescence, and four-wave mixing (FWM) signals both theoretically and experimentally. By scanning the frequency detunings of the probe and dressing fields, respectively, we first observe these signals (three coexisting EIT windows, two fluorescence signals, and two FWM signals) under Rydberg excitation blockade. Next, frequency detuning dependences of these signals are obtained, in which the modulated results are well explained by introducing the dressing effects (leading to the dark states) with the corrected factor of the Rydberg excitation blockade. In addition, the variations by changing the principal quantum number n of Rydberg state shown some interesting phenomena resulting from Rydberg blockade are observed. The unique nature of such blockaded signals can have potential application in the demonstration of quantum computing.

  17. New Rydberg-Rydberg transitions of the ArH and ArD molecules: Bands involving s, p and d electronic states

    SciTech Connect

    Darbrowski, I.; Tokaryk, D.; Watson, J.K.G. [Steacie Institute for Molecular Sciences, Ottawa, Ontario (Canada)] [and others

    1995-12-31

    8The previous analyses of the spectra of ArH and ArD are extended to other transitions between s, p and d complexes, using a case (d) Hamiltonian in which the rotational and centrifugal energies are expressed in powers of R{sup 2}. While l is not a perfect quantum number, it provides convenient labels for the states. The present analysis of bands involving the lowest bound state (5s) is restricted to ArD because the corresponding state of ArH is strongly predissociated. The bands 5p {r_arrow} 5s and 6p {r_arrow} 5s have been observed, but analysis of the former is hampered by interference by D{sub 3} emission. These bands show that the small {sigma} - {pi} separation found in the 4p complex is accidental. For example, 6p{sigma} - 6p{pi} is 69.9 cm{sup -1} (from the R = 0 Hamiltonian), whereas the corresponding separation in 4p is 2.0 cm{sup -1}. Observation of the 3d{delta} {r_arrow} 4p band completes the 3d complex, whose wide splitting ({sigma}, {pi} and {delta} components at 16311, 13016, and 14637 m{sup -1} relative to 5s in ArD) corresponds to an almost pure fourth-rank tensor pattern. The bands 6s {r_arrow} 4p and 8s {r_arrow} 4p have also been analysed.

  18. THE JOURNAL OF CHEMICAL PHYSICS 137, 214302 (2012) Ultrafast probing of ejection dynamics of Rydberg atoms and molecular

    E-print Network

    Neumark, Daniel M.

    2012-01-01

    on a similar time scale as the n = 3 Rydberg atoms. © 2012 American Institute of Physics. [http://dx.doi.org/10THE JOURNAL OF CHEMICAL PHYSICS 137, 214302 (2012) Ultrafast probing of ejection dynamics of Rydberg atoms and molecular fragments from electronically excited helium nanodroplets Oliver Bünermann,1

  19. Studies of Rydberg atomic xenon and molecular hydrogen

    SciTech Connect

    Wang, L.G.

    1986-01-01

    The Rydberg states of atomic xenon and molecular hydrogen were studied by laser spectroscopy of a thermal metastable atomic or molecular beam. Both xenon atoms and H/sub 2/ molecules have structured cores, resulting in similarities of their spectra. The existence of metastable states in both systems allows use of the same experimental techniques and almost the same experimental arrangement to carry out studies in both xenon and in H/sub 2/. Using the metastable-beam laser-excitation technique, even-parity bound np(1/2)/sub 1/ and nf(3/2)/sub 1/ Rydberg series in xenon to n = 51 and n = 82, respectively, were observed. Both even- and odd-parity autoionizing Rydberg states were also studied extensively. Unlike most of the previous work done on H/sub 2/, the author observed and measured the bound and autoionizing triplet nd Rydberg states of para-and ortho-H/sub 2/- (previous experimental data on H/sub 2/ were mostly that of p states of singlet H/sub 2/). In studies of Rydberg states in H/sub 2/, he carried out calculations based on a long-range ab initio Hund's case-d model to predict the transition frequencies and to identify observed transition peaks. Ten Rydberg series of more than 400 levels in atomic xenon and seven triplet Rydberg series of 150 levels in molecular hydrogen were observed and measured in this work.

  20. Spin squeezing in a Rydberg lattice clock.

    PubMed

    Gil, L I R; Mukherjee, R; Bridge, E M; Jones, M P A; Pohl, T

    2014-03-14

    We theoretically demonstrate a viable approach to spin squeezing in optical lattice clocks via optical dressing of one clock state to a highly excited Rydberg state, generating switchable atomic interactions. For realistic experimental parameters, these interactions are shown to generate over 10 dB of squeezing in large ensembles within a few microseconds and without degrading the subsequent clock interrogation. PMID:24679291

  1. Comparison of the target-thickness dependence of the convoy electron yield and the Rydberg electron yield measured in coincidence with exit charge states in fast ion-solid collisions

    SciTech Connect

    Gaither, C.C. III; Breinig, M.; Freyou, J.; Underwood, T.A.

    1988-01-01

    We have simultaneously measured the yield of convoy electrons and the yield of electrons in high Rydberg states of the projectile (n /approx gt/ 70), produced by 2MeV/u C projectiles passing through C foils, whose thicknesses range from 4--10 ug/cm/sup 2/, for incident charge states q/sub i/ = 4--6 and exit charge states q/sub e/ = 4--6. We have found that these yields exhibit similar trends as a function of foil thickness, but that, nevertheless, the ratio of the number of convoy electrons detected in coincidence with ions of exit charge state q/sub e/ to the number of electrons detected in high Rydberg states of ions with the same exit charge state is a function of foil thickness. This may be due to a broadening of the convoy electron energy spectrum with increasing foil thickness. 6 refs., 3 figs.

  2. Testing time-dependent density functional theory with depopulated molecular orbitals for predicting electronic excitation energies of valence, Rydberg, and charge-transfer states and potential energies near a conical intersection

    SciTech Connect

    Li, Shaohong L.; Truhlar, Donald G., E-mail: truhlar@umn.edu [Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-09-14

    Kohn-Sham (KS) time-dependent density functional theory (TDDFT) with most exchange-correlation functionals is well known to systematically underestimate the excitation energies of Rydberg and charge-transfer excited states of atomic and molecular systems. To improve the description of Rydberg states within the KS TDDFT framework, Gaiduk et al. [Phys. Rev. Lett. 108, 253005 (2012)] proposed a scheme that may be called HOMO depopulation. In this study, we tested this scheme on an extensive dataset of valence and Rydberg excitation energies of various atoms, ions, and molecules. It is also tested on a charge-transfer excitation of NH{sub 3}-F{sub 2} and on the potential energy curves of NH{sub 3} near a conical intersection. We found that the method can indeed significantly improve the accuracy of predicted Rydberg excitation energies while preserving reasonable accuracy for valence excitation energies. However, it does not appear to improve the description of charge-transfer excitations that are severely underestimated by standard KS TDDFT with conventional exchange-correlation functionals, nor does it perform appreciably better than standard TDDFT for the calculation of potential energy surfaces.

  3. Virial equation of state of helium, xenon, and helium-xenon mixtures from speed-of-sound and burnett P ? T measurements

    Microsoft Academic Search

    J. J. Hurly; J. W. Schmidt; S. J. Boyes; M. R. Moldover

    1997-01-01

    The virial equation of state was determined for helium, xenon, and helium-xenon mixtures for the pressure and temperature\\u000a ranges 0.5 to 5 MPa and 210 to 400 K. Two independent experimental techniques were employed: BurnettP?T measurements and speed-of-sound measurements. The temperature-dependent second and third density virial coefficients for\\u000a pure xenon and the second and third interaction density virial coefficients for

  4. Rydberg excitation of a single trapped ion

    E-print Network

    T. Feldker; P. Bachor; M. Stappel; D. Kolbe; R. Gerritsma; J. Walz; F. Schmidt-Kaler

    2015-06-19

    We demonstrate excitation of a single trapped cold $^{40}$Ca$^+$ ion to Rydberg levels by laser radiation in the vacuum-ultraviolet at 122 nm wavelength. Observed resonances are identified as 3d$^2$D$_{3/2}$ to 51 F, 52 F and 3d$^2$D$_{5/2}$ to 64F. We model the lineshape and our results imply a large state-dependent coupling to the trapping potential. Rydberg ions are of great interest for future applications in quantum computing and simulation, in which large dipolar interactions are combined with the superb experimental control offered by Paul traps.

  5. Exotic Self-trapped States of an Electron in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Elser, Veit

    2015-06-01

    We explore the possibility that the fast and exotic negative ions in superfluid helium are electrons bound to quantized vortex structures, the simplest being a ring. In the states we consider, the electron energy is only slightly below the conduction band minimum of bulk helium. To support our proposal, we present two calculations. In the first, we show that the electron pressure on the vortex core is insufficient to cavitate the helium and form an electron bubble. In the second, we estimate the equilibrium radius of the vortex ring that would bind an electron and find it is much smaller than the electron bubble, about 7 Å. The many exotic ions reported in experiments might be bound states of an electron with more complex vortex structures.

  6. Quantum optical non-linearities induced by Rydberg-Rydberg interactions: a perturbative approach

    E-print Network

    A. Grankin; E. Brion; E. Bimbard; R. Boddeda; I. Usmani; A. Ourjoumtsev; P. Grangier

    2015-02-23

    In this article, we theoretically study the quantum statistical properties of the light transmitted through or reflected from an optical cavity, filled by an atomic medium with strong optical non-linearity induced by Rydberg-Rydberg van der Waals interactions. Atoms are driven on a two-photon transition from their ground state to a Rydberg level via an intermediate state by the combination of a weak signal field and a strong control beam. By using a perturbative approach, we get analytic results which remain valid in the regime of weak feeding fields, even when the intermediate state becomes resonant. Therefore they allow us to investigate quantitatively new features associated with the resonant behaviour of the system. We also propose an effective non-linear three-boson model of the system which, in addition to leading to the same analytic results as the original problem, sheds light on the physical processes at work in the system.

  7. Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble

    SciTech Connect

    Guerlin, Christine [Institute for Quantum Electronics, ETH Zuerich, CH-8093 Zuerich (Switzerland); Thales Research and Technology, Campus Polytechnique, 1 avenue Augustin Fresnel, F-91767 Palaiseau Cedex (France); Brion, Etienne [Laboratoire Aime Cotton, CNRS, Campus d'Orsay, F-91405, Orsay (France); Esslinger, Tilman [Institute for Quantum Electronics, ETH Zuerich, CH-8093 Zuerich (Switzerland); Moelmer, Klaus [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, University of Aarhus, DK-8000 (Denmark)

    2010-11-15

    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 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> and the collectively excited state |E> with a single Rydberg excitation distributed evenly on all atoms. The collectively enhanced coupling of all atoms to the cavity field with coherent coupling strengths which are much larger than the decay rates in the system leads to the strong coupling regime of the resulting 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 that the absence of interactions between remote Rydberg atoms may, due to a combinatorial effect, induce a cavity-assisted excitation blockade whose range is larger than the typical Rydberg dipole-dipole interaction length.

  8. Electronic spectroscopy of toluene in helium nanodroplets: evidence for a long-lived excited state.

    PubMed

    Shepperson, Benjamin; Tandy, Jon; Boatwright, Adrian; Feng, Cheng; Spence, Daniel; Shirley, Andrew; Yang, Shengfu; Ellis, Andrew M

    2013-12-19

    Optical excitation of toluene to the S1 electronic state in helium nanodroplets is found to alter the rate of production of the fragment ions C7H7(+) and C5H5(+) when the droplets are subjected to subsequent electron ionization. The optical excitation process reduces the abundance of C7H7(+) ions delivered into the gas phase, whereas C5H5(+) ions become more abundant beyond a minimum droplet size. This process contrasts with normal optical depletion spectroscopy, where the optical absorption of a molecular dopant in a helium nanodroplet shrinks the helium droplet, and thus, the electron impact cross-sections because of dissipation of the absorbed energy by evaporative loss of helium atoms. The observations here are interpreted in terms of formation of an excited state in the neutral molecule, which survives for several hundred ?s. This long-lived excited state, which is assumed to be the lowest triplet electronic state, shows different cross-sections for production of C7H7(+) and C5H5(+) relative to the S0 state. PMID:24059467

  9. Interaction effects on dynamical localization in driven helium

    E-print Network

    Felix Jörder; Klaus Zimmermann; Alberto Rodriguez; Andreas Buchleitner

    2014-08-22

    Dynamical localization prevents driven atomic systems from fast fragmentation by hampering the excitation process. We present numerical simulations within a collinear model of microwave-driven helium Rydberg atoms and prove that dynamical localization survives the impact of electron-electron interaction, even for doubly excited states in the presence of fast autoionization. We conclude that the effect of electron-electron repulsion on localization can be described by an appropriate rescaling of the atomic level density and of the external field with the strength of the interaction.

  10. Dislocation-mediated melting of one-dimensional Rydberg crystals

    SciTech Connect

    Sela, Eran; Garst, Markus [Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Str. 77, DE-50937 Koeln (Germany); Punk, Matthias [Physik Department, Technische Universitaet Muenchen, James-Franck-Strasse, DE-85748 Garching (Germany); Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)

    2011-08-15

    We consider cold Rydberg atoms in a one-dimensional optical lattice in the Mott regime with a single atom per site at zero temperature. An external laser drive with Rabi frequency {Omega} and laser detuning {Delta} creates Rydberg excitations whose dynamics is governed by an effective spin-chain model with (quasi) long-range interactions. This system possesses intrinsically a large degree of frustration resulting in a ground-state phase diagram in the ({Delta},{Omega}) plane with a rich topology. As a function of {Delta}, the Rydberg blockade effect gives rise to a series of crystalline phases commensurate with the optical lattice that form a so-called devil's staircase. The Rabi frequency {Omega}, on the other hand, creates quantum fluctuations that eventually lead to a quantum melting of the crystalline states. Upon increasing {Omega}, we find that generically a commensurate-incommensurate transition to a floating Rydberg crystal that supports gapless phonon excitations occurs first. For even larger {Omega}, dislocations within the floating Rydberg crystal start to proliferate and a second, Kosterlitz-Thouless-Nelson-Halperin-Young dislocation-mediated melting transition finally destroys the crystalline arrangement of Rydberg excitations. This latter melting transition is generic for one-dimensional Rydberg crystals and persists even in the absence of an optical lattice. The floating phase and the concomitant transitions can, in principle, be detected by Bragg scattering of light.

  11. Rydberg spectroscopy in an optical lattice: blackbody thermometry for atomic clocks.

    PubMed

    Ovsiannikov, Vitali D; Derevianko, Andrei; Gibble, Kurt

    2011-08-26

    We show that optical spectroscopy of Rydberg states can provide accurate in situ thermometry at room temperature. Transitions from a metastable state to Rydberg states with principal quantum numbers of 25-30 have 200 times larger fractional frequency sensitivities to blackbody radiation than the strontium clock transition. We demonstrate that magic-wavelength lattices exist for both strontium and ytterbium transitions between the metastable and Rydberg states. Frequency measurements of Rydberg transitions with 10(-16) accuracy provide 10 mK resolution and yield a blackbody uncertainty for the clock transition of 10(-18). PMID:21929236

  12. Rydberg Spectroscopy in an Optical Lattice: Blackbody Thermometry for Atomic Clocks

    E-print Network

    Vitali D. Ovsiannikov; Andrei Derevianko; Kurt Gibble

    2011-07-15

    We show that optical spectroscopy of Rydberg states can provide accurate {\\em in situ} thermometry at room-temperature. Transitions from a metastable state to Rydberg states with principal quantum numbers of 25 to 30 have 200 times larger fractional frequency sensitivities to blackbody radiation than the Strontium clock transition. We demonstrate that magic wavelength lattices exist for both Strontium and Ytterbium transitions between the metastable and Rydberg states. Frequency measurements of Rydberg transitions with $10^{-16}$ accuracy provide $10 \\, \\mathrm{mK}$ resolution and yield a blackbody uncertainty for the clock transition of $10^{-18}$.

  13. Rydberg Spectroscopy in an Optical Lattice: Blackbody Thermometry for Atomic Clocks

    SciTech Connect

    Ovsiannikov, Vitali D. [Physics Department, Voronezh State University, Universitetskaya pl. 1, 394006, Voronezh (Russian Federation); Physics Department, University of Nevada, Reno, Nevada, 89557 (United States); Derevianko, Andrei [Physics Department, University of Nevada, Reno, Nevada, 89557 (United States); Gibble, Kurt [Pennsylvania State University, University Park, Pennsylvania, 16802 (United States)

    2011-08-26

    We show that optical spectroscopy of Rydberg states can provide accurate in situ thermometry at room temperature. Transitions from a metastable state to Rydberg states with principal quantum numbers of 25-30 have 200 times larger fractional frequency sensitivities to blackbody radiation than the strontium clock transition. We demonstrate that magic-wavelength lattices exist for both strontium and ytterbium transitions between the metastable and Rydberg states. Frequency measurements of Rydberg transitions with 10{sup -16} accuracy provide 10 mK resolution and yield a blackbody uncertainty for the clock transition of 10{sup -18}.

  14. Ground-State Entanglement Properties of Helium Atom in a Finite Spherical Cavity

    NASA Astrophysics Data System (ADS)

    Ko?cik, Przemys?aw; Saha, Jayanta K.

    2015-05-01

    The effects of the spatial confinement on the ground-state entanglement properties of the helium atom have been studied. The finite oscillator potential is used to represent the confining potential. The transition to the free atom regime and the harmonic confinement regime are discussed in detail in dependence of the control parameters of the system.

  15. Accurate Kohn-Sham potential for the S state of the helium atom: Tests

    E-print Network

    Lindgren, Ingvar

    1 Accurate Kohn-Sham potential for the 1s2s 3 S state of the helium atom: Tests of the locality and the ionization-potential theorems Sten Salomonson, Fredrik M¨oller and Ingvar Lindgren Abstract: The local Kohn from the pair-correlation program of Salomonson and ¨Oster (Phys. Rev. A 40, 5559 (1989)). The Kohn

  16. Tune-out wavelengths and landscape-modulated polarizabilities of alkali-metal Rydberg atoms in infrared optical lattices

    NASA Astrophysics Data System (ADS)

    Topcu, Turker; Derevianko, Andrei

    2013-11-01

    Intensity-modulated optical lattice potentials can change sign for an alkali-metal Rydberg atom, and the atoms are not always attracted to intensity minima in optical lattices with wavelengths near the CO2 laser band. Here we demonstrate that such IR lattices can be tuned so that the trapping potential experienced by the Rydberg atom can be made to vanish for atoms in “targeted” Rydberg states. Such state-selective trapping of Rydberg atoms can be useful in controlled cold Rydberg collisions, cooling Rydberg states, and species-selective trapping and transport of Rydberg atoms in optical lattices. We tabulate wavelengths at which the trapping potential vanishes for the ns, np, and nd Rydberg states of Na and Rb atoms and discuss advantages of using such optical lattices for state-selective trapping of Rydberg atoms. We also develop exact analytical expressions for the lattice-induced polarizability for the mz=0 Rydberg states and derive an accurate formula predicting tune-out wavelengths at which the optical trapping potential becomes invisible to Rydberg atoms in targeted l=0 states.

  17. Excitation of autoionizing states of helium-like ions by scattering of high-energy particles

    SciTech Connect

    Mikhailov, A. I.; Mikhailov, I. A.; Nefiodov, A. V., E-mail: anef@thd.pnpi.spb.ru [B. P. Konstantinov Petersburg Nuclear Physics Institute (Russian Federation); Plunien, G. [Technische Universitaet Dresden, Institut fuer Theoretische Physik (Germany)] [Technische Universitaet Dresden, Institut fuer Theoretische Physik (Germany)

    2013-03-15

    The cross sections for two-electron excitations of helium-like atomic systems into the autoionizing 2s{sup 2} ({sup 1}S)- and 2p{sup 2} ({sup 1}S)-states by collisions with high-energy electrons and photons are deduced. The evaluations are performed to the leading order of non-relativistic perturbation theory. The analytical formulas for cross sections are obtained in the form of universal scalings. A comparison of our theoretical predictions with available theoretical and experimental results for the helium atom is made.

  18. Imaging Spatial Correlations of Rydberg Excitations in Cold Atom Clouds

    NASA Astrophysics Data System (ADS)

    Schwarzkopf, A.; Sapiro, R. E.; Raithel, G.

    2011-09-01

    We use direct spatial imaging of cold Rb85 Rydberg atom clouds to measure the Rydberg-Rydberg correlation function. The results are in qualitative agreement with theoretical predictions [F. Robicheaux and J. V. Hernández, Phys. Rev. A 72, 063403 (2005)PLRAAN1050-294710.1103/PhysRevA.72.063403]. We determine the blockade radius for states 44D5/2, 60D5/2, and 70D5/2 and investigate the dependence of the correlation behavior on excitation conditions and detection delay. Experimental data hint at the existence of long-range order.

  19. Prospects for fast Rydberg gates on an atom chip

    E-print Network

    Matthias M. Müller; Harald R. Haakh; Tommaso Calarco; Christiane P. Koch; Carsten Henkel

    2011-04-14

    Atom chips are a promising candidate for a scalable architecture for quantum information processing provided a universal set of gates can be implemented with high fidelity. The difficult part in achieving universality is the entangling two-qubit gate. We consider a Rydberg phase gate for two atoms trapped on a chip and employ optimal control theory to find the shortest gate that still yields a reasonable gate error. Our parameters correspond to a situation where the Rydberg blockade regime is not yet reached. We discuss the role of spontaneous emission and the effect of noise from the chip surface on the atoms in the Rydberg state.

  20. Photon mediated transport and crystallization in optically driven Rydberg gases

    NASA Astrophysics Data System (ADS)

    Otterbach, Johannes; Lauer, Achim; Muth, Dominik; Fleischhauer, Michael

    2012-06-01

    We show that excitations in a gas of atoms driven to Rydberg states by near-resonant laser radiation in a two-photon coupling scheme experience a photon mediated transport. Thus even if the center-of-mass motion of the atoms can be neglected, this results in a kinetic Hamiltonian for the Rydberg excitations. The corresponding mass is identical to that of the dark-state polaritons of the optical coupling scheme. The kinetic energy competes with the Rydberg dipole-dipole interactions and can prevent the formation of quasi-crystal structures. Using DMRG simulations we calculate the Luttinger parameter for a one-dimensional gas of resonantly driven Rydberg atoms taking into account the photon mediated transport and derive conditions under which quasi-crystallization can be observed.

  1. Equation of State Calculations of Hydrogen-Helium Mixtures in Solar and Extrasolar Giant Planets Burkhard Militzer1

    E-print Network

    Militzer, Burkhard

    Equation of State Calculations of Hydrogen-Helium Mixtures in Solar and Extrasolar Giant Planets for hydrogen-helium mixtures at conditions of giant planet interiors of 0.2-2.3 g cm-3 and 1000-80000 K. INTRODUCTION The Kepler mission has provided us with over 2000 exo- planet candidates 1 that vary widely

  2. Femtosecond time-resolved XUV + UV photoelectron imaging of pure helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Ziemkiewicz, Michael P.; Bacellar, Camila; Siefermann, Katrin R.; Leone, Stephen R.; Neumark, Daniel M.; Gessner, Oliver

    2014-11-01

    Liquid helium nanodroplets, consisting of on average 2 × 106 atoms, are examined using femtosecond time-resolved photoelectron imaging. The droplets are excited by an extreme ultraviolet light pulse centered at 23.7 eV photon energy, leading to states within a band that is associated with the 1s3p and 1s4p Rydberg levels of free helium atoms. The initially excited states and subsequent relaxation dynamics are probed by photoionizing transient species with a 3.2 eV pulse and using velocity map imaging to measure time-dependent photoelectron kinetic energy distributions. Significant differences are seen compared to previous studies with a lower energy (1.6 eV) probe pulse. Three distinct time-dependent signals are analyzed by global fitting. A broad intense signal, centered at an electron kinetic energy (eKE) of 2.3 eV, grows in faster than the experimental time resolution and decays in ˜100 fs. This feature is attributed to the initially excited droplet state. A second broad transient feature, with eKE ranging from 0.5 to 4 eV, appears at a rate similar to the decay of the initially excited state and is attributed to rapid atomic reconfiguration resulting in Franck-Condon overlap with a broader range of cation geometries, possibly involving formation of a Rydberg-excited (Hen)* core within the droplet. An additional relaxation pathway leads to another short-lived feature with vertical binding energies ?2.4 eV, which is identified as a transient population within the lower-lying 1s2p Rydberg band. Ionization at 3.2 eV shows an enhanced contribution from electronically excited droplet states compared to ejected Rydberg atoms, which dominate at 1.6 eV. This is possibly the result of increased photoelectron generation from the bulk of the droplet by the more energetic probe photons.

  3. Rydberg atoms in hollow-core photonic crystal fibres

    PubMed Central

    Epple, G.; Kleinbach, K. S.; Euser, T. G.; Joly, N. Y.; Pfau, T.; Russell, P. St. J.; Löw, R.

    2014-01-01

    The exceptionally large polarizability of highly excited Rydberg atoms—six orders of magnitude higher than ground-state atoms—makes them of great interest in fields such as quantum optics, quantum computing, quantum simulation and metrology. However, if they are to be used routinely in applications, a major requirement is their integration into technically feasible, miniaturized devices. Here we show that a Rydberg medium based on room temperature caesium vapour can be confined in broadband-guiding kagome-style hollow-core photonic crystal fibres. Three-photon spectroscopy performed on a caesium-filled fibre detects Rydberg states up to a principal quantum number of n=40. Besides small energy-level shifts we observe narrow lines confirming the coherence of the Rydberg excitation. Using different Rydberg states and core diameters we study the influence of confinement within the fibre core after different exposure times. Understanding these effects is essential for the successful future development of novel applications based on integrated room temperature Rydberg systems. PMID:24942281

  4. Observation of ultralong range Rydberg molecules

    NASA Astrophysics Data System (ADS)

    Shaffer, James

    2009-05-01

    In 1934, Enrico Fermi described the scattering of a low energy electron from a neutral atom by using the ideas of scattering length and pseudopotential. Although the long range potential for an electron-atom interaction is always attractive, Fermi realized that the s-wave scattering length that characterizes the low energy collision can be either positive or negative. For a positive scattering length, the wavefunction of the electron is shifted away from the atom, the electron is repelled; whereas for a negative scattering length, the wavefunction of the electron is shifted to the atom, the electron is attracted. Based on Fermi's approach, Greene and co-workers predicted a novel molecular binding mechanism where a low energy Rydberg electron is scattered from a ground state atom in the case of negative scattering length. In this situation, the interaction between the electron and ground state atom is attractive and results in the formation of bound states of the ground state atom and the Rydberg atom. Molecules bound by electron scattering can have an internuclear separation of several thousand Bohr radii and are very different from molecules formed by 2 Rydberg atoms where the binding is the result of multipolar forces between the atoms alone. In this talk, we present experimental data on the observation of these exotic molecular states for Rb Rydberg atoms in S states for principal quantum numbers n between 34 and 40. The spectroscopic results for the vibrational ground and first excited state of the dimer Rb(5S)-Rb(nS) are presented and the s-wave scattering length for electron-Rb(5S) scattering in the low energy regime where the kinetic energy is less than 100 meV. Finally, we discuss and present data on the lifetimes and decay mechanisms of these molecules in a magnetic trap.

  5. Relativistic ground state of the heavy helium-like ions

    NASA Astrophysics Data System (ADS)

    Pruß-Hunzinger, S.; Mattes, M.; Sorg, M.

    2004-03-01

    The ground state of the two electrons in the Coulomb field of the highly charged ions ( Z ? 32) is analyzed within the context of Relativistic Schrödinger Theory (RST). Exploiting here the isotropic geometry of the ground state, the corresponding RST-Maxwell-Dirac eigenvalue system can be written down as a coupled system of ordinary differential equations for two radial ansatz functions R ±(r). The solutions of this coupled system are determined by numerical integration which admits to calculate the relativistic ground-state energy as the value of the RST energy functional upon these solutions. It is found that the RST predictions are of similar precision (relative to the experimental data) as the other theoretical approaches available in the literature. However it is also demonstrated that further progress can be made only by extending the RST formalism to take into account the self-energy effects.

  6. The role of correlation in the ground state energy of confined helium atom

    SciTech Connect

    Aquino, N. [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Apartado Postal 55-534, 09340 México Distrito Federal (Mexico)

    2014-01-14

    We analyze the ground state energy of helium atom confined by spherical impenetrable walls, and the role of the correlation energy in the total energy. The confinement of an atom in a cavity is one way in which we can model the effect of the external pressure on an atom. The calculations of energy of the system are carried out by the variational method. We find that the correlation energy remains almost constant for a range values of size of the boxes analyzed.

  7. Doubly excited states of the hydrogen negative ion and helium atom in astrophysical plasmas

    SciTech Connect

    Jiang Pinghui [Center for Theoretical Atomic and Molecular Physics, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080 (China); College of Electrical and Information Engineering, Heilongjiang Institute of Technology, Harbin 150050 (China); Kar, Sabyasachi; Zhou, Y. [Center for Theoretical Atomic and Molecular Physics, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080 (China)

    2013-01-15

    The nonthermal effects on the doubly excited resonance states of the hydrogen negative ion and helium atom are investigated in Lorentzian astrophysical plasma environments using highly correlated Hylleraas-type wave functions in the framework of the stabilization method. Resonance parameters (resonance position and width) are reported for the first time as functions of the spectral index and plasma parameter. The screening effects are more pronounced in the stronger screening region.

  8. Spectroscopy of triplet states of Rb by femtosecond pump-probe photoionization of doped helium nanodroplets

    Microsoft Academic Search

    M. Mudrich; Ph. Heister; T. Hippler; Ch. Giese; F. Stienkemeier; O. Dulieu

    2009-01-01

    The dynamics of vibrational wave packets in triplet states of rubidium dimers (Rb) formed on helium nanodroplets are studied using femtosecond pump-probe photoionization spectroscopy. Due to fast desorption of the excited Rb molecules off the droplets and due to their low internal temperature, wave-packet oscillations can be followed up to very long pump-probe delay times > or approx. 1.5 ns.

  9. Proposed method for laser spectroscopy of pionic helium atoms to determine the charged-pion mass

    E-print Network

    Hori, Masaki; Korobov, Vladimir I

    2014-01-01

    Metastable pionic helium ($\\pi{\\rm He}^+$) is a three-body atom composed of a helium nucleus, an electron occupying the $1s$ ground state, and a negatively charged pion $\\pi^-$ in a Rydberg state with principal- and orbital angular momentum quantum numbers of $n\\sim \\ell+1\\sim 16$. We calculate the spin-independent energies of the $\\pi{\\rm ^3He}^+$ and $\\pi{\\rm ^4He}^+$ isotopes in the region $n=15$--19. These include relativistic and quantum electrodynamics corrections of orders $R_{\\infty}\\alpha^2$ and $R_{\\infty}\\alpha^3$ in atomic units, where $R_{\\infty}$ and $\\alpha$ denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the $\\pi^-$, and the radiative and Auger decay rates of the states are also calculated. Some states $(n,\\ell)=(16,15)$ and $(17,16)$ retain nanosecond-scale lifetimes against $\\pi^-$ absorption into the helium nucleus. We propose to use laser pulses to induce $\\pi^-$ transitions from...

  10. Production of Doubly Excited Projectile States in Collisions of 0.1 Mev/u SILVER(+4) Ions with Helium, Hydrogen, and Argon Gas Target

    NASA Astrophysics Data System (ADS)

    Underwood-Lemons, Theresa Ann

    An important problem in atomic dynamics is the structure of very high doubly excited states, in which two electrons are excited away from the rest of the electrons in the ionic core, making their mutual interaction and correlation as important as their individual interaction with the remaining core. In this work, we study the formation of doubly excited projectile states near the double escape threshold in collisions of 0.1 MeV/u Ag^{+4} ions with He, H_2, and Ar gas targets. We detect projectile states in which one electron occupies a high Rydberg state and a second electron (a cusp electron) occupies a low lying continuum state. Cusp electrons are characterized by a velocity which is nearly equal in magnitude and direction to the projectile velocity. Cusp electrons are energy analyzed with a 30 ^circ parallel plate energy analyzer, and Rydberg electrons are field ionized in a spherical ionizer before being energy analyzed in a 160^ circ^herical sector analyzer. Standard coincidence measurements between a cusp and a Rydberg electron signal the production of a doubly excited projectile state. The cross sections for producing these doubly excited projectile states are on the order of 10 ^{-20} cm^2. The production probabilities are measured as a function of cusp electron laboratory frame energy with the detected Rydberg electrons arising from a fixed band of principal quantum numbers. The laboratory frame energy distributions of cusp electrons associated with these doubly excited states are then compared to the energy distribution of cusp electrons measured without imposing a Rydberg electron coincidence requirement. For the He target, the shapes of the two energy distributions are the same. However, the width of the energy distribution of cusp electrons measured in coincidence with Rydberg electrons is smaller than the width of the cusp electron energy distribution without a coincidence requirement for the H_2 and Ar gas targets, the difference being greatest for Ar. The width of the cusp electron energy spectra measured in coincidence with a Rydberg electron decreases as the fraction of doubly excited states formed by double excitation/ionization of the projectile decreases and the fraction formed by double target-electron capture increases.

  11. Solid-state ring laser gyro with similar level of performance as its Helium-Neon counterpart

    Microsoft Academic Search

    Sylvain Schwartz; Francois Gutty; Gilles Feugnet; Jean-Paul Pocholle

    2010-01-01

    Thanks to fast vibration of its gain medium, a solid-state ring laser gyro is shown to have a frequency behaviour similar to Helium-Neon commercial products, with potentially equivalent level of angular random walk.

  12. Observation of the Stark-Tuned Foerster Resonance between Two Rydberg Atoms

    SciTech Connect

    Ryabtsev, I. I.; Tretyakov, D. B.; Beterov, I. I.; Entin, V. M. [Institute of Semiconductor Physics, Prospekt Lavrentyeva 13, 630090 Novosibirsk (Russian Federation)

    2010-02-19

    Cold atoms in highly excited Rydberg states are promising candidates to implement quantum logic gates of a quantum computer via long-range dipole-dipole interaction. Two-qubit gates require a controlled interaction of only two close Rydberg atoms. We report on the first spectroscopic observation of the resonant dipole-dipole interaction between two cold rubidium Rydberg atoms confined in a small laser excitation volume. The interaction strength was controlled by fine-tuning of the Rydberg levels into a Foerster resonance using the Stark effect. The observed resonance line shapes are in good agreement with numerical Monte Carlo simulations.

  13. Excitation of lowest autoionization states in helium-like ions by photon scattering

    NASA Astrophysics Data System (ADS)

    Amusia, M. Ya; Mikhailov, A. I.; Mikhailov, I. A.

    2001-03-01

    High-frequency photon scattering by a two-electron ion with excitation of singlet autoionization states located below the first excited level of the respective one-electron ion are considered. Angular distributions of scattered photons and total cross sections are calculated for transitions to 2s2p(1P) and 2p2(1D) autoionization states (AIS) from the ground state of helium-like ions (the transitions to two lower 1S AIS were investigated earlier). In the zero approximation electrons are described by Coulomb functions and the inter-electron interaction is taken into account in the first perturbation order.

  14. Debye equation of state for fluid helium-3.

    PubMed

    Huang, Yonghua; Chen, Guobang; Arp, Vincent

    2006-08-01

    An equation of state for 3He using the Helmholtz potential function has been developed. The lower limit of the equation of 0.01 K is safely above the superfluid transition at 0.0026 K. The upper limit of 60 K is approximately the upper limit of available 3He property measurements. The new state equation form is based on Debye function which goes smoothly to zero in the limit of zero temperature and reduces to the ideal gas in the limit of zero density and/or very high temperature. The equation combines (a) necessary temperature-independent compressibility terms at the lowest temperatures, (b) terms describing the linear specific heat of a Fermi fluid below 1 K, (c) terms describing the phonon excitations which begin above about 1 K, and (d) terms which attempt to fit the conventional critical point thermodynamics at 3.3157 K and 114 604 Pa. State properties, e.g., p-V-T relations, specific heats, thermal expansion, sound velocity, etc., are determined from the Helmholtz energy by standard thermodynamics. Transport properties, e.g., thermal conductivity and viscosity, are not obtained in this work. PMID:16942224

  15. Electron-impact ionization of helium clusters close to the threshold: appearance energies.

    PubMed

    Denifl, S; Stano, M; Stamatovic, A; Scheier, P; Märk, T D

    2006-02-01

    We have investigated the ionization threshold behavior of small helium cluster ions (cluster size n=2-10) formed via electron-impact ionization of neutral helium droplets and derive appearance energies for mass-selected cluster ions using a nonlinear least-square-fitting procedure. Moreover, we report magic numbers in the mass spectrum observed at the electron energy of 70 eV. The apparatus used for the present measurements is a hemispherical electron monochromator combined with a quadrupole mass spectrometer. Our experiment demonstrates that helium clusters are not only exclusively formed via direct ionization above the atomic ionization potential but also indirectly via autoionizing Rydberg states. The present results are compared with previous electron-impact and photoionization results. PMID:16468882

  16. Ionization states of helium in He-3-rich solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Klecker, B.; Hovestadt, D.; Moebius, E.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.

    1983-01-01

    Results of a systematic study of the ionic charge state of helium in the energy range 0.6-1.0 MeV/nucleon for He-3-rich solar energetic particle events during the time period August 1978 to October 1979 are reported. The data have been obtained with the Max-Planck-Institut/University of Maryland experiment on ISEE-3. Whereas for solar energetic particle events with no enrichment of He-3 relative to He-4 surprisingly large abundances of singly ionized helium have been reported recently, He-3-rich solar energetic particle events do not show significant abundances of He-3(+). This result is consistent with current theories explaining large compositional anomalies by mass per charge dependent selective heating of the minor ion species.

  17. Chirped-pulse millimeter-wave spectroscopy: Spectrum, dynamics, and manipulation of Rydberg-Rydberg transitions

    SciTech Connect

    Colombo, Anthony P.; Zhou Yan; Prozument, Kirill; Coy, Stephen L.; Field, Robert W. [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2013-01-07

    We apply the chirped-pulse millimeter-wave (CPmmW) technique to transitions between Rydberg states in calcium atoms. The unique feature of Rydberg-Rydberg transitions is that they have enormous electric dipole transition moments ({approx}5 kiloDebye at n*{approx} 40, where n* is the effective principal quantum number), so they interact strongly with the mm-wave radiation. After polarization by a mm-wave pulse in the 70-84 GHz frequency region, the excited transitions re-radiate free induction decay (FID) at their resonant frequencies, and the FID is heterodyne-detected by the CPmmW spectrometer. Data collection and averaging are performed in the time domain. The spectral resolution is {approx}100 kHz. Because of the large transition dipole moments, the available mm-wave power is sufficient to polarize the entire bandwidth of the spectrometer (12 GHz) in each pulse, and high-resolution survey spectra may be collected. Both absorptive and emissive transitions are observed, and they are distinguished by the phase of their FID relative to that of the excitation pulse. With the combination of the large transition dipole moments and direct monitoring of transitions, we observe dynamics, such as transient nutations from the interference of the excitation pulse with the polarization that it induces in the sample. Since the waveform produced by the mm-wave source may be precisely controlled, we can populate states with high angular momentum by a sequence of pulses while recording the results of these manipulations in the time domain. We also probe the superradiant decay of the Rydberg sample using photon echoes. The application of the CPmmW technique to transitions between Rydberg states of molecules is discussed.

  18. Production of very-high-$n$ strontium Rydberg atoms

    E-print Network

    Ye, Shuzhen; Killian, Thomas C; Dunning, F Barry; Hiller, Moritz; Yoshida, Shuhei; Nagele, Stefan; Burgdörfer, Joachim

    2013-01-01

    The production of very-high-$n$, $n\\sim300$-500, strontium Rydberg atoms is explored using a crossed laser-atom beam geometry. $n$$^{1}$S$_{0}$ and $n$$^{1}$D$_{2}$ states are created by two-photon excitation via the 5s5p $^{1}$P$_{1}$ intermediate state using radiation with wavelengths of $\\sim$~461 and $\\sim$ 413 nm. Rydberg atom densities as high as $\\sim 3 \\times 10^{5}$ cm$^{-3}$ have been achieved, sufficient that Rydberg-Rydberg interactions can become important. The isotope shifts in the Rydberg series limits are determined by tuning the 461 nm light to preferentially excite the different strontium isotopes. Photoexcitation in the presence of an applied electric field is examined. The initially quadratic Stark shift of the $n$$^{1}$P$_{1}$ and $n$$^{1}$D$_{2}$ states becomes near-linear at higher fields and the possible use of $n{}^{1}$D$_{2}$ states to create strongly-polarized, quasi-one-dimensional electronic states in strontium is discussed. The data are analyzed with the aid of a two-active-elect...

  19. Frequency-doubled scattering of symmetry-breaking surface-state electrons on liquid Helium

    E-print Network

    Miao Zhang; Wenzhi Jia; Lianfu Wei

    2013-03-18

    Any systems with symmetry-breaking eigenstates can effectively radiate photons with doubled frequency of the incident light, which is known as the second harmonic generation. Here, we study the second-order nonlinear effects with the system of surface-state electrons on liquid Helium. Due to the symmetry-breaking eigenstates, we show that a Rabi oscillation between two levels of the surface-state electrons can be realized beyond the usual resonant driving. Consequently, an electromagnetic field with the doubled frequency of the applied driving could be effectively radiated. This can be regarded as a frequency-doubled fluorescence, and interestingly, it works in the unusual Terahertz range.

  20. Importance of considering helium excited states in He+ scattering by an aluminum surface

    NASA Astrophysics Data System (ADS)

    Iglesias-García, A.; García, Evelina A.; Goldberg, E. C.

    2014-11-01

    The He+/Al system is a very interesting projectile-surface combination which was thought initially as an example of a pure Auger neutralization mechanism. Then, because of the measured reionization explained by the antibonding interaction of the projectile state with the core target states, the resonant charge exchange with the band states was considered as another important contribution to the neutralization. Nevertheless, by only considering the neutralization to the ground state of helium, the measured ion survival probability is still overestimated. On the other hand, measurements of electron emission from an Al surface bombarded by He positive ions suggested the possibility of occupied excited states of helium due to the ion-surface collision. In this work, we also include the excited states of He within the time-dependent scattering process in which both neutralization mechanisms, resonant and Auger, are simultaneously contemplated. Our starting point is a multiorbital Anderson Hamiltonian projected over the selected space of ground and excited atomic configurations. An extra term related to the Auger mechanism is added to this Hamiltonian. A difference with previous works is that this approach includes the electron spin and, therefore, the spin fluctuation statistics in the charge-exchange process is correctly taken into account. We find a notable improvement in the agreement with the experiments and also that the interference between both mechanisms is not dramatic.

  1. Quantum entanglement for two electrons in the excited states of helium-like systems

    E-print Network

    Yen-Chang Lin; Yew Kam Ho

    2014-11-05

    The quantum entanglement for the two electrons in the excited states of the helium-like atom/ions is investigated using the two-electron wave functions constructed by the B-spline basis. As a measure of the spatial (electron-electron orbital) entanglement, the von Neumann entropy and linear entropy of the reduced density matrix are calculated for the 1s2s 1,3S excited states for systems with some selected Z values from Z=2 to Z=100. Results for the helium atom are compared with other available calculations. We have also investigated the entropies for these excited states when the nucleus charge is reduced from Z=2 to Z=1. At such a critical charge, all the singly-excited states of this system become unbound, and the linear entropies and the von Neumann entropies for the excited states are approaching 1/2 and 1, respectively, the limits for the entropies when one electron is bound to the nucleus, and the other being free.

  2. Rydberg spectroscopy of single-electron capture in low-energy collisions of Ar9+ and Ar8+ with cesium

    Microsoft Academic Search

    S. Martin; A. Denis; Y. Ouerdane; M. Carré; M. C. Buchet-Poulizac; J. Désesquelles

    1992-01-01

    Optical spectroscopy has been used to study electron capture into Ar9+ and Ar8+ ions from cesium at several impact energies of between 8 and 180 keV. Many Rydberg lines were observed. At high spectral resolution the quasi-l-degeneracy of final Rydberg states was removed and the fine-structure components of doubly excited Rydberg transitions were resolved. Cross sections for state-selective electron capture

  3. Xe2 gerade Rydberg states observed in the afterglow of a microplasma by laser spectroscopy of a(3)?(+)(u)(1(u), O(-)(u)) absorption in the green (545-555 nm) and near-infrared (675-800 nm).

    PubMed

    Wagner, C J; Galvin, T C; Eden, J G

    2014-06-28

    Bound?bound transitions of the Xe dimer at small internuclear separation (R < 4.0 Å) have been observed in the 545-555 nm and 675-800 nm spectral regions by laser spectroscopy in the afterglow of a pulsed Xe microplasma with a volume of ?160 nl. Transient suppression of Xe2 A(1)?(+)(u)(O(+)(u)) --> X(1)?(+)(g)(O(+)(g)) emission in the vacuum ultraviolet (?172 nm), induced by laser excitation of ?(g) ? a(3)?(+)(u)(1(u), O(-)(u)) [Rydberg?Rydberg] transitions of the molecule, has confirmed the existence of structure between 720 and 770 nm (reported by Killeen and Eden [J. Chem. Phys. 84, 6048 (1986)]) but also reveals red-degraded vibrational bands extending to wavelengths beyond 800 nm. Spectral simulations based on calculations of Franck-Condon factors for assumed ?(g) ? a(3)?(+)(u) transitions involving ? = 0(±),1 gerade Rydberg states suggest that the upper level primarily responsible for the observed spectrum is an ? = 1 state correlated, in the separated atom limit, with Xe(5p(6) (1)S0) + Xe(5p(5) 6p) and built on a predominantly A(2)?3/2g molecular ion core. Specifically, the spectroscopic constants for the upper state of the 1(g) ? 1(u), O(±)(u) absorptive transitions are determined to be Te = 13,000 ± 150?cm(-1), ?'(e) = 120 ± 10 cm(-1), ?'(e)x'(e) = 1.1 ± 0.4 cm(-1), De = 3300 ± 300?cm(-1), and ?R(e) = R'(e) = R''(e) = 0.3 ± 0.1 Å which are in general agreement with the theoretical predictions of the pseudopotential hole-particle formalism, developed by Jonin and Spiegelmann [J. Chem. Phys. 117, 3059 (2002)], for both the (5)1g and (3)O(+)(g) states of Xe2. These spectra exhibit the most extensive vibrational development, and provide evidence for the first molecular core-switching transition, observed to date for any of the rare gas dimers at small R (<4 ?). Experiments in the green (545-555 nm) also provide improved absorption spectra, relative to data reported in 1986 and 1999, associated with Xe2 Rydberg states derived from the Xe(7p) orbital. PMID:24985643

  4. An experimental approach for investigating many-body phenomena in Rydberg-interacting quantum systems

    NASA Astrophysics Data System (ADS)

    Hofmann, C. S.; Günter, G.; Schempp, H.; Müller, N. L. M.; Faber, A.; Busche, H.; Robert-de-Saint-Vincent, M.; Whitlock, S.; Weidemüller, M.

    2014-10-01

    Recent developments in the study of ultracold Rydberg gases demand an advanced level of experimental sophistication, in which high atomic and optical densities must be combined with excellent control of external fields and sensitive Rydberg atom detection. We describe a tailored experimental system used to produce and study Rydberg-interacting atoms excited from dense ultracold atomic gases. The experiment has been optimized for fast duty cycles using a high flux cold atom source and a three beam optical dipole trap. The latter enables tuning of the atomic density and temperature over several orders of magnitude, all the way to the Bose-Einstein condensation transition. An electrode structure surrounding the atoms allows for precise control over electric fields and single-particle sensitive field ionization detection of Rydberg atoms. We review two experiments which highlight the influence of strong Rydberg-Rydberg interactions on different many-body systems. First, the Rydberg blockade effect is used to pre-structure an atomic gas prior to its spontaneous evolution into an ultracold plasma. Second, hybrid states of photons and atoms called dark-state polaritons are studied. By looking at the statistical distribution of Rydberg excited atoms we reveal correlations between dark-state polaritons. These experiments will ultimately provide a deeper understanding of many-body phenomena in strongly-interacting regimes, including the study of strongly-coupled plasmas and interfaces between atoms and light at the quantum level.

  5. Spatial correlations of Rydberg excitations in optically driven atomic ensembles

    E-print Network

    Petrosyan, David; Fleischhauer, Michael

    2013-01-01

    We study the emergence of many-body correlations in the stationary state of continuously-driven, strongly-interacting dissipative system. Specifically, we examine resonant optical excitations of Rydberg states of atoms interacting via long-range dipole-dipole and van der Waals potentials employing exact numerical solutions of the density matrix equations and Monte-Carlo simulations. Collection of atoms within a blockade distance form a "superatom" that can accommodate at most one Rydberg excitation. The superatom excitation probability saturates to 1/2 for coherently driven atoms, but is significantly higher for incoherent driving, approaching unity as the number of atoms increases. In the steady state of uniformly-driven, extended one-dimensional system, the saturation of superatoms leads to quasi-crystallization of Rydberg excitations whose correlations exhibit damped spatial oscillations. The behavior of the system under the van der Waals interaction potential can be approximated by an analytically soluble...

  6. Imaging the evolution of an ultracold strontium Rydberg gas

    E-print Network

    McQuillen, P; Strickler, T; Dunning, F B; Killian, T C

    2012-01-01

    Clouds of ultracold strontium 5s48s 1S0 or 5s47d 1D2 Rydberg atoms are created by two photon excitation of laser cooled 5s2 1S0 atoms. The spontaneous evolution of the cloud of low orbital angular momentum (low-l) Rydberg states towards an ultracold neutral plasma is observed by imaging resonant light scattered from core ions, a technique that provides both spatial and temporal resolution. Evolution is observed to be faster for the S-states, which display isotropic attractive interactions, than for the D-states, which exhibit anisotropic, principally repulsive interactions. Immersion of the atoms in a dilute ultracold neutral plasma speeds up the evolution and allows the number of Rydberg atoms initially created to be determined.

  7. Rotational state-changing cold collisions of hydroxyl ions with helium

    E-print Network

    Hauser, Daniel; Carelli, Fabio; Spieler, Steffen; Lakhmanskaya, Olga; Endres, Eric S; Kumar, Sunil S; Gianturco, Franco; Wester, Roland

    2015-01-01

    Cold molecules are important for many applications, from fundamental precision measurements, quantum information processing, quantum-controlled chemistry, to understanding the cold interstellar medium. Molecular ions are known to be cooled efficiently in sympathetic collisions with cold atoms or ions. However, little knowledge is available on the elementary cooling steps, because the determination of quantum state-to-state collision rates at low temperature is prohibitively challenging for both experiment and theory. Here we present a method to manipulate molecular quantum states by non-resonant photodetachment. Based on this we provide absolute quantum scattering rate coefficients under full quantum state control for the rotationally inelastic collision of hydroxyl anions with helium. Experiment and quantum scattering theory show excellent agreement without adjustable parameters. Very similar rate coefficients are obtained for two different isotopes, which is linked to several quantum scattering resonances a...

  8. Alignment of the 2p State of 2-Mev Amu Helium-Like Sulfur 

    E-print Network

    Church, David A.; Kenefick, R. A.; Wang, D. W.; Watson, R. L.

    1982-01-01

    PHYSICAL REVIEW A VOLUME 26, NUMBER 6 DECEMBER 1982 Alignment of the 2P state of 2-MeV/amu helium1ike sulfur D. A. Church, R. A. Kenefick, D.-W. Wang, * and R. L. Watson Department ofPhysics and Cyclotron Institute, Texas AckM University... occurring at lower collision energies which 26 3093 1982 The American Physical Society 3094 CHURCH, KENEFICK, WANG, AND WATSON 26 match outer-shell electron velocities may be useful in defining the atomic character of the total ion- target interaction...

  9. Giant Rydberg excitons in the copper oxide Cu2O.

    PubMed

    Kazimierczuk, T; Fröhlich, D; Scheel, S; Stolz, H; Bayer, M

    2014-10-16

    A highly excited atom having an electron that has moved into a level with large principal quantum number is a hydrogen-like object, termed a Rydberg atom. The giant size of Rydberg atoms leads to huge interaction effects. Monitoring these interactions has provided insights into atomic and molecular physics on the single-quantum level. Excitons--the fundamental optical excitations in semiconductors, consisting of an electron and a positively charged hole--are the condensed-matter analogues of hydrogen. Highly excited excitons with extensions similar to those of Rydberg atoms are of interest because they can be placed and moved in a crystal with high precision using microscopic energy potential landscapes. The interaction of such Rydberg excitons may allow the formation of ordered exciton phases or the sensing of elementary excitations in their surroundings on a quantum level. Here we demonstrate the existence of Rydberg excitons in the copper oxide Cu2O, with principal quantum numbers as large as n = 25. These states have giant wavefunction extensions (that is, the average distance between the electron and the hole) of more than two micrometres, compared to about a nanometre for the ground state. The strong dipole-dipole interaction between such excitons is indicated by a blockade effect in which the presence of one exciton prevents the excitation of another in its vicinity. PMID:25318523

  10. Universal turning point behavior for Gaussian-Klauder states and an application for maximally eccentric Rydberg atoms

    SciTech Connect

    Mather, William H.; Fox, Ronald F. [School of Physics and Center for Nonlinear Science, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States)

    2006-10-15

    Universal behavior of Gaussian-Klauder states emerges near soft classical turning points, as expressed through a complex-valued Airy transformation that approximates the wave function. Study of these classical turning points provides analytic evidence that Gaussian-Klauder states generally display recurrent localization for many classical orbital periods. Analytic position and momentum moments of the wave function are determined from this approximation, leading in part to connections with the traditionally chosen positional Gaussian wave functions as the limit of large energy uncertainty. Application of this procedure to hydrogenic states of maximal eccentricity leads to the classical limit of recurrent collisional bouncing in the Kepler problem, via the explicit construction of states that maintain phase space localization for many orbital periods.

  11. Studies of Rydberg Atomic Xenon and Molecular Hydrogen

    Microsoft Academic Search

    Liang-Guo Wang

    1986-01-01

    This work has studied the Rydberg states of atomic xenon and molecular hydrogen by laser spectroscopy of a thermal metastable atomic or molecular beam. Both xenon atoms and H(,2) molecules have structured cores, resulting in similarities of their spectra. The existence of metastable states in both systems allows us to use the same experimental techniques and almost the same experimental

  12. Macrodimers: Ultralong Range Rydberg Molecules

    Microsoft Academic Search

    Christophe Boisseau; Ionel Simbotin; Robin Côté

    2002-01-01

    We study long range interactions between two Rydberg atoms and predict the existence of ultralong range Rydberg dimers with equilibrium distances of many thousands of Bohr radii. We calculate the dispersion coefficients C5, C6, and C8 for two rubidium atoms in the same excited level np and find that they scale like n8, n11, and n15, respectively. We show that

  13. Resonant electric dipole-dipole interactions between cold Rydberg atoms in a magnetic field K. Afrousheh, P. Bohlouli-Zanjani, J. D. Carter, A. Mugford, and J. D. D. Martin

    E-print Network

    Le Roy, Robert J.

    Resonant electric dipole-dipole interactions between cold Rydberg atoms in a magnetic field K October 2005; published 5 June 2006 Laser-cooled 85 Rb atoms were optically excited to 46d5/2 Rydberg states. A microwave pulse transferred a fraction of the atoms to the 47p3/2 Rydberg state. The resonant

  14. Photon-Photon Interactions via Rydberg Blockade

    SciTech Connect

    Gorshkov, Alexey V. [Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125 (United States); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Otterbach, Johannes [Department of Physics and Research Center OPTIMAS, Technische Universitaet Kaiserslautern, 67663, Kaiserslautern (Germany); Fleischhauer, Michael [Department of Physics and Research Center OPTIMAS, Technische Universitaet Kaiserslautern, 67663, Kaiserslautern (Germany); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Pohl, Thomas [Max Planck Institute for the Physics of Complex Systems, 01187 Dresden (Germany); Lukin, Mikhail D. [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States)

    2011-09-23

    We develop the theory of light propagation under the conditions of electromagnetically induced transparency in systems involving strongly interacting Rydberg states. Taking into account the quantum nature and the spatial propagation of light, we analyze interactions involving few-photon pulses. We show that this system can be used for the generation of nonclassical states of light including trains of single photons with an avoided volume between them, for implementing photon-photon gates, as well as for studying many-body phenomena with strongly correlated photons.

  15. Jaynes-Cummings dynamics in mesoscopic ensembles of Rydberg-blockaded atoms

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    We show that Jaynes-Cummings dynamics can be observed in mesoscopic atomic ensembles interacting with a classical electromagnetic field in the regime of a Rydberg blockade where the time dynamics of the average number of Rydberg excitations in mesoscopic ensembles displays collapses and revivals typical of this model. As the frequency of Rabi oscillations between collective states of Rydberg-blockaded ensembles depends on the number of interacting atoms, for randomly loaded optical dipole traps, we predict collapses and revivals of Rabi oscillations. We have studied the effects of finite interaction strengths and a finite laser linewidth on the visibility of the revivals. We have shown that observation of collapses and revivals of Rabi oscillations can be used as a signature of the Rydberg blockade without the need to measure the exact number of Rydberg atoms.

  16. Spatially Resolved Excitation of Rydberg Atoms and Surface Effects on an Atom Chip

    E-print Network

    Atreju Tauschinsky; Rutger M. T. Thijssen; S. Whitlock; H. B. van Linden van den Heuvell; R. J. C. Spreeuw

    2010-04-19

    We demonstrate spatially resolved, coherent excitation of Rydberg atoms on an atom chip. Electromagnetically induced transparency (EIT) is used to investigate the properties of the Rydberg atoms near the gold coated chip surface. We measure distance dependent shifts (~10 MHz) of the Rydberg energy levels caused by a spatially inhomogeneous electric field. The measured field strength and distance dependence is in agreement with a simple model for the electric field produced by a localized patch of Rb adsorbates deposited on the chip surface during experiments. The EIT resonances remain narrow (atom-surface distance down to ~20 \\mum, indicating relatively long lifetime of the Rydberg states. Our results open the way to studies of dipolar physics, collective excitations, quantum metrology and quantum information processing involving interacting Rydberg excited atoms on atom chips.

  17. Spatially resolved excitation of Rydberg atoms and surface effects on an atom chip

    SciTech Connect

    Tauschinsky, Atreju; Thijssen, Rutger M. T.; Whitlock, S.; Linden van den Heuvell, H. B. van; Spreeuw, R. J. C. [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)

    2010-06-15

    We demonstrate spatially resolved, coherent excitation of Rydberg atoms on an atom chip. Electromagnetically induced transparency (EIT) is used to investigate the properties of the Rydberg atoms near the gold-coated chip surface. We measure distance-dependent shifts ({approx}10 MHz) of the Rydberg energy levels caused by a spatially inhomogeneous electric field. The measured field strength and distance dependence is in agreement with a simple model for the electric field produced by a localized patch of Rb adsorbates deposited on the chip surface during experiments. The EIT resonances remain narrow (<4 MHz) and the observed widths are independent of atom-surface distance down to {approx} 20 {mu}m, indicating relatively long lifetime of the Rydberg states. Our results open the way to studies of dipolar physics, collective excitations, quantum metrology, and quantum information processing involving interacting Rydberg excited atoms on atom chips.

  18. XUV frequency-comb metrology on the ground state of helium

    SciTech Connect

    Kandula, Dominik Z.; Gohle, Christoph; Pinkert, Tjeerd J.; Ubachs, Wim; Eikema, Kjeld S. E. [LaserLaB Amsterdam, VU University, De Boelelaan 1081, NL-1081HV Amsterdam (Netherlands)

    2011-12-15

    The operation of a frequency comb at extreme ultraviolet (xuv) wavelengths based on pairwise amplification and nonlinear upconversion to the 15th harmonic of pulses from a frequency-comb laser in the near-infrared range is reported. It is experimentally demonstrated that the resulting spectrum at 51 nm is fully phase coherent and can be applied to precision metrology. The pulses are used in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p {sup 1} P{sub 1} states. Laser ionization by auxiliary 1064 nm pulses is used to detect the excited-state population, resulting in a cosine-like signal as a function of the repetition rate of the frequency comb with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium atom as a precision phase ruler, yields an estimated timing jitter between the two upconverted-comb laser pulses of 50 attoseconds, which is equivalent to a phase jitter of 0.38 (6) cycles in the xuv at 51 nm. This sets a quantitative figure of merit for the operation of the xuv comb and indicates that extension to even shorter wavelengths should be feasible. The helium metrology investigation results in transition frequencies of 5 740 806 993 (10) and 5 814 248 672 (6) MHz for excitation of the 1s4p and 1s5p {sup 1} P{sub 1} states, respectively. This constitutes an important frequency measurement in the xuv, attaining high accuracy in this windowless part of the electromagnetic spectrum. From the measured transition frequencies an eight-fold-improved {sup 4}He ionization energy of 5 945 204 212 (6) MHz is derived. Also, a new value for the {sup 4}He ground-state Lamb shift is found of 41 247 (6) MHz. This experimental value is in agreement with recent theoretical calculations up to order m{alpha}{sup 6} and m{sup 2}/M{alpha}{sup 5}, but with a six-times-higher precision, therewith providing a stringent test of quantum electrodynamics in bound two-electron systems.

  19. Rydberg states of C2H4 and C2D4: assignments using the technique of low-energy electron energy-loss spectroscopy

    Microsoft Academic Search

    D. G. Wilden; J. Comer

    1980-01-01

    Energy-loss spectra of C2H4 and C2D4 are presented covering the energy-loss range 6-11 eV, using incident electron energies in the range 5-100 eV above threshold, and scattering angles up to 60 degrees . Members of several optically assigned Rydberg series were identified, and their intensities measured at a number of scattering angles. Each transition was then classified as electric dipole

  20. Slow-light polaritons in Rydberg gases

    NASA Astrophysics Data System (ADS)

    Fleischhauer, Michael

    2012-02-01

    Slow-light polaritons are quasi-particles generated in the interaction of photons with laser-driven atoms with a ?- or ladder-type coupling scheme under conditions of electromagnetically induced transparency (EIT). They are a superposition of electromagnetic and collective spin excitations. If one of the states making up the atomic spin is a high lying Rydberg level, the polaritons are subject to a strong and non-local interaction mediated by a dipole-dipole or van-der Waals coupling between excited Rydberg atoms. I will present and discuss an effective many-body model for these Rydberg polaritons. Depending on the detuning of the control laser the interaction potential between the polaritons can be repulsive or attractive and can have a large imaginary component for distances less than the so-called blockade radius. The non-local effective interaction gives rize to interesting many-body phenomena such as the generation of photons with an avoided volume, visible in stronlgy suppressed two-particle correlations inside the blockade volume. Moreover the long-range, power-law scaling of the interaction can in the repulsive case give rize to the formation of quasi-crystalline structures of photons. In a one dimensional system the low-energy dynamics of the polaritons can be described in terms of a Luttinger liquid. Using DMRG simulations the Luttinger K parameter is calculated and conditions for the formation of a quasi-crystal are derived. When confined to a two-dimensional geometry, e.g. using a resonator with quasi-degenerate transversal mode spectrum, Rydberg polaritons are an interesting candidate to study the bosonic fractional quantum Hall effect. I will argue that the formation of photons with an avoided volume is essential for explaining recent experiments on stationary EIT in Rydberg gases [1,2].[4pt] [1] J.D. Pritchard et al., Phys. Rev. Lett. 105, 193603 (2010). [0pt] [2] D. Petrosyan, J. Otterbach, and M. Fleischhauer, arXiv:1106.1360

  1. Excitation of {sup 1}S and {sup 3}S Metastable Helium Atoms to Doubly Excited States

    SciTech Connect

    Alagia, M. [CNR-ISMN Sezione Roma, Piazzale A. Moro 5, I-00185 Roma (Italy); Laboratorio Nazionale TASC, CNR-INFM, I-34012 Trieste (Italy); Coreno, M. [CNR-IMIP, Montelibretti, I-00016 Roma (Italy); Farrokhpour, H.; Omidyan, R.; Tabrizchi, M. [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Franceschi, P. [Dipartimento di Fisica, Universita di Trento, I-38050 Povo (Tunisia) (Italy); Mihelic, A.; Zitnik, M. [Jozef Stefan Institute, P.O. Box 3000, SI-1001 Ljubljana (Slovenia); Moise, A.; Prince, K. C.; Richter, R. [Sincrotrone Trieste, in Area Science Park, I-34012 Basovizza, Trieste (Italy); Soederstroem, J. [Department of Physics, Uppsala University, Box 530, S-75121 Uppsala (Sweden); Synchrotron SOLEIL, l'Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex (France); Stranges, S. [Dipartimento di Chimica, Universita'La Sapienza', I-00185 Roma (Italy); Laboratorio Nazionale TASC, CNR-INFM, I-34012 Trieste (Italy)

    2009-04-17

    We present spectra of triplet and singlet metastable helium atoms resonantly photoexcited to doubly excited states. The first members of three dipole-allowed {sup 1,3}P{sup o} series have been observed and their relative photoionization cross sections determined, both in the triplet (from 1s2s {sup 3}S{sup e}) and singlet (from 1s2s {sup 1}S{sup e}) manifolds. The intensity ratios are drastically different with respect to transitions from the ground state. When radiation damping is included the results for the singlets are in agreement with theory, while for triplets spin-orbit interaction must also be taken into account.

  2. Measurement of the oscillator strength distribution in helium

    SciTech Connect

    Hussain, Shahid; Saleem, M.; Baig, M. A. [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    2007-07-15

    The oscillator strength distribution in the discrete and continuous regions of the spectrum of helium from the 2s {sup 1}S{sub 0} metastable state has been determined using a Nd: yttrium aluminum garnet (YAG) pumped dye laser system in conjunction with a low pressure rf glow discharge. The saturation technique has been employed to determine the photoionization cross section from the 2s {sup 1}S{sub 0} excited state at and above the first ionization threshold. The measured value of the photoionization cross section at the ionization threshold has been used to extract the f values for the 2s {sup 1}S{yields}np {sup 1}P Rydberg series from n=10 to n=52. The f values of the observed Rydberg series decrease smoothly with an increase of the principal quantum number. In the continuum region the oscillator strength densities have been estimated by measuring the photoionization cross sections from the 2s {sup 1}S{sub 0} excited state at five ionizing laser wavelengths above the first ionization threshold. The discrete f values smoothly merge into the continuous oscillator strength densities across the ionization threshold.

  3. Optical non-linearity in an attractive Rydberg gas

    E-print Network

    Pritchard, J D; Weatherill, K J; Adams, C S

    2011-01-01

    We use the technique of electro-magnetically induced transparency (EIT) to probe the effect of attractive dipole-dipole interactions in a highly excited Rydberg gas. The transient character of the EIT response is investigated by rapidly scanning the probe laser through resonance. We characterize the resulting cooperative optical non-linearity as a function of probe strength, density and scan direction. For the 58D$_{5/2}$ Rydberg state, an atom density of $1.6\\times10^{10} $cm$^{-3}$ and a positive frequency scan we measure a third-order non-linearity of $\\chi^{(3)}=5\\times 10^{-7}$ m$^2$V$^{-2}$. For the reverse scan we observe a second order non-linearity of $\\chi^{(2)}=5\\times 10^{-6}$ mV$^{-1}$. The contrasting behaviour can be explained in terms of motional effects and resonant excitation of Rydberg pairs.

  4. Optical non-linearity in a dynamical Rydberg gas

    E-print Network

    J D Pritchard; A Gauguet; K J Weatherill; C S Adams

    2011-05-16

    We use the technique of electro-magnetically induced transparency (EIT) to probe the effect of attractive dipole-dipole interactions in a highly excited Rydberg gas. The transient character of the EIT response is investigated by rapidly scanning the probe laser through resonance. We characterize the resulting cooperative optical non-linearity as a function of probe strength, density and scan direction. For the 58D$_{5/2}$ Rydberg state, an atom density of $1.6\\times10^{10} $cm$^{-3}$ and a positive frequency scan we measure a third-order non-linearity of $\\chi^{(3)}=5\\times 10^{-7}$ m$^2$V$^{-2}$. For the reverse scan we observe a second order non-linearity of $\\chi^{(2)}=5\\times 10^{-6}$ mV$^{-1}$. The contrasting behaviour can be explained in terms of motional effects and resonant excitation of Rydberg pairs.

  5. Rotational autoionization of np Rydberg series of D2

    NASA Astrophysics Data System (ADS)

    Pratt, S. T.; Dehmer, P. M.; Dehmer, J. L.

    1990-01-01

    The rotational autoionization of the np Rydberg states of D2 was studied near the first ionization threshold using optical-optical double resonance techniques and photoelectron spectroscopy. The spectra obtained are found to be similar in many respects to those of H2 recorded by O'Halloran et al. (1989). In particular, a number of Rydberg series were observed to decay by processes other than the conventional singlet rotational autoionization mechanism. The D2 spectra have also been extended into longer wavelength regions and show additional nominally forbidden decay processes that were not observed in H2.

  6. High 2s 2 np Rydberg series and ionization energy of B I

    Microsoft Academic Search

    W. L. Glab; Alan M. Falleur

    2002-01-01

    We have used double-resonance excitation of a laser-vaporized sample of atomic boron to measure the energies of np Rydberg states from n?35 to 70, to a precision of ±0.02cm?1. The 2s23s state was excited resonantly using light at 249nm from a frequency-doubled narrowband pulsed dye laser; subsequently, 2s2np Rydberg states were excited using a second frequency-doubled dye laser operating between

  7. Entanglement of neutral-atom chains by spin-exchange Rydberg interaction

    E-print Network

    Xiao-Feng Shi; F. Bariani; T. A. B. Kennedy

    2014-12-09

    Conditions to achieve an unusually strong Rydberg spin-exchange interaction are investigated and proposed as a means to generate pairwise entanglement and realize a SWAP-like quantum gate for neutral atoms. Ground-state entanglement is created by mapping entangled Rydberg states to ground states using optical techniques. A protocol involving SWAP gate and pairwise entanglement operations is predicted to create global entanglement of a chain of $N$ atoms in a time that is independent of $N$.

  8. Quantum Spin Ice and dimer models with Rydberg atoms

    E-print Network

    Alexander W. Glaetzle; Marcello Dalmonte; Rejish Nath; Ioannis Rousochatzakis; Roderich Moessner; Peter Zoller

    2014-04-21

    Quantum spin ice represents a paradigmatic example on how the physics of frustrated magnets is related to gauge theories. In the present work we address the problem of approximately realizing quantum spin ice in two dimensions with cold atoms in optical lattices. The relevant interactions are obtained by weakly admixing van der Waals interactions between laser admixed Rydberg states to the atomic ground state atoms, exploiting the strong angular dependence of interactions between Rydberg p-states together with the possibility of designing step-like potentials. This allows us to implement Abelian gauge theories in a series of geometries, which could be demonstrated within state of the art atomic Rydberg experiments. We numerically analyze the family of resulting microscopic Hamiltonians and find that they exhibit both classical and quantum order by disorder, the latter yielding a quantum plaquette valence bond solid. We also present strategies to implement Abelian gauge theories using both s- and p-Rydberg states in exotic geometries, e.g. on a 4-8 lattice.

  9. Noble-gas-induced collisional line broadening of atomic-lithium Rydberg superposition states 2S-nS and 2S-nD (n = 4 to 30) measured by trilevel echoes

    SciTech Connect

    Xu, E.Y.; Moshary, F.; Hartmann, S.R.

    1986-04-01

    The pioneering research of Fuchtbauer et al. on Na-3S-nP transition broadening by Ar gas demonstrated that the collisional-broadening cross section increases sharply for an increasing principal quantum number n for low n, peaks as n approaches the Rydberg regime, and then decreases to a small function of its maximum value. It appears to reach an asymptotic value (independent of n) in the high-n regime. This behavior has been corroborated by several other experimental efforts. Collisional relaxation of 2S-nS and 2S-nD superposition states in atomic Li vapor is measured with the trilevel photon-echo technique. Principal quantum numbers range from n=4 to well into the Rydberg regime with n=30. For the rare-gas perturbers (He, Ne, Ar, Kr, and Xe) the variation of collisional cross section with n is considerably weaker than that previously found with Na vapor. Keywords: Optical coherent transients; Two photon excitation; Sodium vapor.

  10. arXiv:1101.5667v1[cond-mat.mes-hall]29Jan2011 Resonant Photovoltaic Effect in Surface-State Electrons on Liquid Helium

    E-print Network

    Shepelyansky, Dima

    -State Electrons on Liquid Helium Denis Konstantinov,1, A.D. Chepelianskii,1, 2 and Kimitoshi Kono1 1 Low induced by the resonant intersubband absorption of microwaves in surface-state electrons on liquid helium. As a result, the separation of positive and negative carriers causes an electrical potential difference, known

  11. Rubidium D1 and D2 atomic lines’ pressure broadened by ground-state helium atoms

    NASA Astrophysics Data System (ADS)

    Bouhadjar, F.; Alioua, K.; Bouazza, M. T.

    2014-09-01

    Full quantum calculations are performed to determine the spectral broadening of the rubidium D1 and D2 lines induced by collisions with helium perturbers. The potential curves of the low-lying RbHe molecular states, as well as the corresponding transition dipole moments, are generated theoretically with ab initio methods based on SA-CASSCF-MRCI calculations, including the spin-orbit effects. The absorption and emission coefficients at wavelengths lying between 650 and 950\\;nm and temperatures ranging from 100 to 3000 K are determined. The absorption profile reveals it is dominated by the free-free transitions, whereas the emission spectral shape arises from the free-free and bound-free transitions. The resulting red- and blue-wing profiles are compared with previous experimental and theoretical works.

  12. Proposal for Manipulating and Detecting Spin and Orbital States of Trapped Electrons on Helium Using Cavity Quantum Electrodynamics

    E-print Network

    Dykman, Mark

    Proposal for Manipulating and Detecting Spin and Orbital States of Trapped Electrons on Helium Using Cavity Quantum Electrodynamics D. I. Schuster,1 A. Fragner,1 M. I. Dykman,2 S. A. Lyon,3 and R. J architecture in which an on-chip high finesse superconducting cavity is coupled to the lateral motion and spin

  13. Rotational state-changing cold collisions of hydroxyl ions with helium

    NASA Astrophysics Data System (ADS)

    Hauser, Daniel; Lee, Seunghyun; Carelli, Fabio; Spieler, Steffen; Lakhmanskaya, Olga; Endres, Eric S.; Kumar, Sunil S.; Gianturco, Franco; Wester, Roland

    2015-06-01

    Cold molecules are important for many applications, from fundamental precision measurements, quantum information processing, quantum-controlled chemistry, to understanding the cold interstellar medium. Molecular ions are known to be cooled efficiently in sympathetic collisions with cold atoms or ions. However, little knowledge is available on the elementary cooling steps, because the determination of quantum state-to-state collision rates at low temperature is very challenging for both experiment and theory. Here we present a method to manipulate molecular quantum states by non-resonant photodetachment. Based on this we provide absolute quantum scattering rate coefficients under full quantum state control for the rotationally inelastic collision of hydroxyl anions with helium. Experiment and quantum scattering theory show excellent agreement without adjustable parameters. Very similar rate coefficients are obtained for two different isotopes, which is linked to several quantum scattering resonances appearing at different energies. The presented method is also applicable to polyatomic systems and will help elucidate non-radiative processes in polyaromatic hydrocarbons and protein chromophores.

  14. Quantum information with Rydberg atoms

    E-print Network

    Saffman, M; Mølmer, K

    2009-01-01

    Rydberg atoms with principal quantum number n >> 1 have exaggerated atomic properties including dipole-dipole interactions that scale as n^4 and radiative lifetimes that scale as n^3. It was proposed a decade ago to take advantage of these properties to implement quantum gates between neutral atom qubits. The availability of a strong, long-range interaction that can be coherently turned on and off is an enabling resource for a wide range of quantum information tasks stretching far beyond the original gate proposal. Rydberg enabled capabilities include long-range two-qubit gates, collective encoding of multi-qubit registers, implementation of robust light-atom quantum interfaces, and the potential for simulating quantum many body physics. We review the advances of the last decade, covering both theoretical and experimental aspects of Rydberg mediated quantum information processing.

  15. Trends in autoionization of Rydberg states converging to the 4s threshold in the Kr-Rb{sup +}-Sr{sup 2+} isoelectonic sequence: Theory and experiment

    SciTech Connect

    Neogi, A.; Kennedy, E.T.; Mosnier, J.-P.; Kampen, P. van; Costello, J.T.; O'Sullivan, G.; Mansfield, M.W.D.; Demekhin, Ph.V.; Lagutin, B.M.; Sukhorukov, V.L. [National Centre for Plasma Science and Technology, School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland); Department of Experimental Physics, University College Dublin, Dublin 4 (Ireland); Department of Physics, University College Cork, Cork (Ireland); Rostov State University of TC, 344038 Rostov-on-Don (Russian Federation)

    2003-04-01

    We have measured the photoabsorption spectra of the Kr-like ions Rb{sup +} and Sr{sup 2+} at photon energies corresponding to the excitation of 4s-np resonances using, the dual laser plasma photoabsorption technique. Dramatic changes in the line profiles, with increasing ionization and also proceeding along the Rydberg series of each ion, are observed and explained by the trends in 4s-transition amplitudes computed within a framework of configuration-interaction Pauli-Fock calculations. Total photoionization cross sections show very good agreement with relative absorption data extracted from the measured spectra.

  16. Macrodimers ultralong range Rydberg molecules

    E-print Network

    Boisseau, C; Côté, R; Boisseau, Christophe; Simbotin, Ionel; Cote, Robin

    2002-01-01

    We study long range interactions between two Rydberg atoms and predict the existence of ultralong range Rydberg dimers with equilibrium distances of many thousand Bohr radii. We calculate the dispersion coefficients $C_{5}$, $C_{6}$ and $C_{8}$ for two rubidium atoms in the same excited level $np$, and find that they scale like $n^{8}$, $n^{11}$ and $n^{15}$, respectively. We show that for certain molecular symmetries, these coefficients lead to long range potential wells that can support molecular bound levels. Such macrodimers would be very sensitive to their environment, and could probe weak interactions. We suggest experiments to detect these macrodimers.

  17. Anisotropic emission in quantum-beat spectroscopy of helium excited states

    NASA Astrophysics Data System (ADS)

    Lucchini, M.; Ludwig, A.; Zimmermann, T.; Kasmi, L.; Herrmann, J.; Scrinzi, A.; Landsman, A. S.; Gallmann, L.; Keller, U.

    2015-06-01

    We present quantum-beat spectroscopy of excited states of helium atoms populated selectively with high-order-harmonic emission below the atomic ionization potential by means of low-pass filtering of the pump radiation. The created electron wave packet is ionized by few-cycle infrared (IR) pulses leading to characteristic peaks in the photoelectron yield, which beat with a frequency proportional to the energy gap between the states involved in the two-color photoionization process. Minimizing the direct ionization by the extreme ultraviolet (XUV) radiation, we can follow the evolution of the electron wave packet also in the region of temporal pump-probe overlap. A detailed time-frequency analysis of the quantum beats and direct comparison with the solution of the time-dependent Schrödinger equation reveal the existence of quantum beats characterized by a final state of mixed parity. Finally, we show that by varying the carrier-envelope offset phase of the probe pulse, one can optically control the preferred direction of photoelectron emission and the contrast of such beats.

  18. Double electron capture by fast bare ions in helium atoms: production of singly and doubly excited states

    Microsoft Academic Search

    Robert Gayet; Jocelyn Hanssen; Laurent Jacqui; Alejandra Martinez; Roberto Rivarola

    1996-01-01

    Double electron capture by fast bare ions in helium is studied in the framework of the Four-Body Continuum Distorted Wave theory. It is shown that experimental data is well reproduced when the theoretical total cross-section include both contributions from the ground state and from the first singly excited states. In addition, cross-sections for the production of the first doubly excited

  19. PHYSI CAI. 8 E VIE W A VOLUME 11, NUMBER JANUARY 1975 Variable dimensionality in atoms and its effect on the ground state of the helium

    E-print Network

    Stillinger, Frank

    effect on the ground state of the helium isoelectronic sequence David R. Herrick and Frank H. Stillinger energy of helium- like ions of arbitrary dimensionality. Dimension- ality here refers to the number) which contains some angular correlations through the interelectron separation R». %bile neither

  20. HELIUM, SOLID 1 Helium, Solid

    E-print Network

    Glyde, Henry R.

    HELIUM, SOLID 1 Helium, Solid Henry R. Glyde Introduction Helium was first solidified at the famous focused on the melting curve, the specific heat, and the thermal conductivity of solid helium as a test criterion of melting does not hold in solid helium. This pioneering work up to 1957 is elegantly

  1. Dressing effects in the attosecond transient absorption spectra of doubly excited states in helium

    NASA Astrophysics Data System (ADS)

    Argenti, L.; Jiménez-Galán, Á.; Marante, C.; Ott, C.; Pfeifer, T.; Martín, F.

    2015-06-01

    Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum (ATAS) of helium dressed by a few-cycle visible pulse [C. Ott et al., Nature (London) 516, 374 (2014), 10.1038/nature14026] provide evidence of the inversion of Fano profiles. With the support of accurate ab initio calculations that reproduce the results of the latter experiment, here we investigate the new physics that arise from ATAS when the laser intensity is increased. In particular, we show that (i) previously unnoticed signatures of the dark 2 p21S doubly excited state are observed in the experimental spectrum, (ii) inversion of Fano profiles is predicted to be periodic in the laser intensity, and (iii) the ac Stark shift of the higher terms in the s p2,n + autoionizing series exceeds the ponderomotive energy, which is the result of a genuine two-electron contribution to the polarization of the excited atom.

  2. Quantum Magnetism and Topological Ordering via Rydberg Dressing near Förster Resonances

    NASA Astrophysics Data System (ADS)

    van Bijnen, R. M. W.; Pohl, T.

    2015-06-01

    We devise a cold-atom approach to realizing a broad range of bilinear quantum magnets. Our scheme is based on off-resonant single-photon excitation of Rydberg P states (Rydberg dressing), whose strong interactions are shown to yield controllable X Y Z interactions between effective spins, represented by different atomic ground states. The distinctive features of Förster-resonant Rydberg atom interactions are exploited to enhance the effectiveness of Rydberg dressing and, thereby, yield large spin interactions that greatly exceed the corresponding decoherence rates. We illustrate the concept on a spin-1 chain implemented with cold rubidium atoms, and demonstrate that this permits the dynamical preparation of topological magnetic phases. Generally, the described approach provides a viable route to exploring quantum magnetism with dynamically tunable (an)isotropic interactions as well as variable space and spin dimensions in cold-atom experiments.

  3. Quantum Magnetism and Topological Ordering via Rydberg Dressing near Förster Resonances.

    PubMed

    van Bijnen, R M W; Pohl, T

    2015-06-19

    We devise a cold-atom approach to realizing a broad range of bilinear quantum magnets. Our scheme is based on off-resonant single-photon excitation of Rydberg P states (Rydberg dressing), whose strong interactions are shown to yield controllable XYZ interactions between effective spins, represented by different atomic ground states. The distinctive features of Förster-resonant Rydberg atom interactions are exploited to enhance the effectiveness of Rydberg dressing and, thereby, yield large spin interactions that greatly exceed the corresponding decoherence rates. We illustrate the concept on a spin-1 chain implemented with cold rubidium atoms, and demonstrate that this permits the dynamical preparation of topological magnetic phases. Generally, the described approach provides a viable route to exploring quantum magnetism with dynamically tunable (an)isotropic interactions as well as variable space and spin dimensions in cold-atom experiments. PMID:26196973

  4. Direct observation of Rydberg-Rydberg transitions via CPmmW spectroscopy

    E-print Network

    Zhou, Yan, Ph. D. Massachusetts Institute of Technology

    2014-01-01

    Rydberg-Rydberg transitions of BaF molecules have been directly observed in our lab. The key to the experimental success is our ability to combine two powerful and new technologies, Chirped-Pulse millimeter-Wave spectroscopy ...

  5. Universal nonequilibrium properties of dissipative Rydberg gases.

    PubMed

    Marcuzzi, Matteo; Levi, Emanuele; Diehl, Sebastian; Garrahan, Juan P; Lesanovsky, Igor

    2014-11-21

    We investigate the out-of-equilibrium behavior of a dissipative gas of Rydberg atoms that features a dynamical transition between two stationary states characterized by different excitation densities. We determine the structure and properties of the phase diagram and identify the universality class of the transition, both for the statics and the dynamics. We show that the proper dynamical order parameter is in fact not the excitation density and find evidence that the dynamical transition is in the "model A" universality class; i.e., it features a nontrivial Z2 symmetry and a dynamics with nonconserved order parameter. This sheds light on some relevant and observable aspects of dynamical transitions in Rydberg gases. In particular it permits a quantitative understanding of a recent experiment [C. Carr, Phys. Rev. Lett. 111, 113901 (2013)] which observed bistable behavior as well as power-law scaling of the relaxation time. The latter emerges not due to critical slowing down in the vicinity of a second order transition, but from the nonequilibrium dynamics near a so-called spinodal line. PMID:25479477

  6. Dynamical preparation of laser-excited anisotropic Rydberg crystals in 2D optical lattices

    E-print Network

    Benoît Vermersch; Matthias Punk; Alexander W. Glaetzle; Christian Gross; Peter Zoller

    2014-08-04

    We describe the dynamical preparation of anisotropic crystalline phases obtained by laser-exciting ultracold Alkali atoms to Rydberg p-states where they interact via anisotropic van der Waals interactions. We develop a time- dependent variational mean field ansatz to model large, but finite two-dimensional systems in experimentally accessible parameter regimes, and we present numerical simulations to illustrate the dynamical formation of anisotropic Rydberg crystals.

  7. Rydberg spectroscopy of single-electron capture in low-energy collisions of Ar sup 9+ and Ar sup 8+ with cesium

    Microsoft Academic Search

    S. Martin; A. Denis; Y. Ouerdane; M. Carre; M. C. Buchet-Poulizac; J. Desesquelles

    1992-01-01

    Optical spectroscopy has been used to study electron capture into Ar{sup 9+} and Ar{sup 8+} ions from cesium at several impact energies of between 8 and 180 keV. Many Rydberg lines were observed. At high spectral resolution the quasi-{ital l}-degeneracy of final Rydberg states was removed and the fine-structure components of doubly excited Rydberg transitions were resolved. Cross sections for

  8. Long-range Rydberg-Rydberg interactions in calcium, strontium and ytterbium

    E-print Network

    Vaillant, C L; Potvliege, R M

    2012-01-01

    Long-range dipole-dipole and quadrupole-quadrupole interactions between pairs of Rydberg atoms are calculated perturbatively for calcium, strontium and ytterbium within the Coulomb approximation. Quantum defects, obtained by fitting existing laser spectroscopic data, are provided for all $S$, $P$, $D$ and $F$ series of strontium and for the $^3P_2$ series of calcium. The results show qualitative differences with the alkali metal atoms, including isotropically attractive interactions of the strontium $^1S_0$ states and a greater rarity of F\\"orster resonances. Only two such resonances are identified, both in triplet series of strontium. The angular dependence of the long range interaction is briefly discussed.

  9. Long-range Rydberg-Rydberg interactions in calcium, strontium and ytterbium

    E-print Network

    C. L. Vaillant; M. P. A. Jones; R. M. Potvliege

    2012-05-11

    Long-range dipole-dipole and quadrupole-quadrupole interactions between pairs of Rydberg atoms are calculated perturbatively for calcium, strontium and ytterbium within the Coulomb approximation. Quantum defects, obtained by fitting existing laser spectroscopic data, are provided for all $S$, $P$, $D$ and $F$ series of strontium and for the $^3P_2$ series of calcium. The results show qualitative differences with the alkali metal atoms, including isotropically attractive interactions of the strontium $^1S_0$ states and a greater rarity of F\\"orster resonances. Only two such resonances are identified, both in triplet series of strontium. The angular dependence of the long range interaction is briefly discussed.

  10. Spectroscopy of triplet states of Rb2 by femtosecond pump-probe photoionization of doped helium nanodroplets

    Microsoft Academic Search

    M. Mudrich; Ph. Heister; T. Hippler; Ch. Giese; O. Dulieu; F. Stienkemeier

    2009-01-01

    The dynamics of vibrational wave packets in triplet states of rubidium dimers (Rb2) formed on helium nanodroplets are studied using femtosecond pump-probe photoionization spectroscopy. Due to fast desorption of the excited Rb2 molecules off the droplets and due to their low internal temperature, wave-packet oscillations can be followed up to very long pump-probe delay times ≳1.5ns . In the first-excited

  11. Rotational hybridization, and control of alignment and orientation in triatomic ultralong-range Rydberg molecules

    NASA Astrophysics Data System (ADS)

    González-Férez, Rosario; Sadeghpour, H. R.; Schmelcher, Peter

    2015-01-01

    We explore the electronic structure and rovibrational properties of an ultralong-range triatomic Rydberg molecule formed by a Rydberg atom and a ground state heteronuclear diatomic molecule. We focus here on the interaction of a Rb(n,l?slant 3) Rydberg atom with a KRb(N = 0) diatomic polar molecule. There is significant electronic hybridization with the Rb(n = 24, l?slant 3) degenerate manifold. The polar diatomic molecule is allowed to rotate in the electric fields generated by the Rydberg electron and core as well as an external field. We investigate the metamorphosis of the Born–Oppenheimer potential curves, essential for the binding of the molecule, with varying electric field and analyze the resulting properties such as the vibrational structure and the alignment and orientation of the polar diatomic molecule.

  12. Photo-excited states in germanium at liquid-helium temperatures

    SciTech Connect

    Culbertson, J.C.

    1982-12-01

    A wide variety of experimental work dealing with the basic properties of photoexcited states in Ge at liquid helium temperatures is presented. The primary emphasis is on the electron-hole liquid (EHL) and the free exciton (FE). The EHL is composed of two interpenetrating Fermi liquids, one of electrons and one of holes, each with its own Fermi level. The FE dealt with here is a mobile, loosely bound state of an electron and a hole. We report the first absolute measurement of the density dependence of the enhancement factor g/sub eh/(0) for the EHL in Ge. This factor g/sub eh/(0) is a measure of the electron-hole spatial correlation function, and provides a valuable and sensitive test for the predictions of various many-body-theory approximations. An EHL droplet - FE gas system confined to a strain induced potential well was used. The measurement approach relied on only a few simple and verifiable assumptions. A byproduct of this work was the measurement as a function of stress of: the electron and hole Fermi levels E/sub F//sup e/ and E/sub F//sup h/, the EHL density n/sub l/, the condensation energy phi of a FE relative to the EHL, and the binding energy of a FE (E/sub x/) relative to free carriers (FC). The decay of a FE-FC system confined to a strain induced potential well is studied. The first direct measurement of the FE diffusivity D/sub x/ is reported. The evolution in time of spatial profiles of FE luminescence were measured. From these FE density profiles, D/sub x/(4.2K) approx. = to 300 cm/sup 2/ s/sup -1/, the surface recombination velocity S approx. = 3000 cm s/sup -1/, and the FE lifetime tau/sub x/ = 27 ..mu..s with surface effects excluded were determined. (WHK)

  13. Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy

    E-print Network

    Eyler, E E; Stowe, Matthew C; Thorpe, Michael J; Schibli, T R; Ye, Jun

    2007-01-01

    We analyze several possibilities for precisely measuring electronic transitions in atomic helium by the direct use of phase-stabilized femtosecond frequency combs. Because the comb is self-calibrating and can be shifted into the ultraviolet spectral region via harmonic generation, it offers the prospect of greatly improved accuracy for UV and far-UV transitions. To take advantage of this accuracy an ultracold helium sample is needed. For measurements of the triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap metastable $2 ^3S$ state atoms. We analyze schemes for measuring the two-photon $2 ^3S \\to 4 ^3S$ interval, and for resonant two-photon excitation to high Rydberg states, $2 ^3S \\to 3 ^3P \\to n^3S,D$. We also analyze experiments on the singlet-state spectrum. To accomplish this we propose schemes for producing and trapping ultracold helium in the $1 ^1S$ or $2 ^1S$ state via intercombination transition. A particularly intriguing scenario is the possibility of direct singlet state sp...

  14. Electric field sensing near the surface microstructure of an atom chip using cold Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Martin, J. D. D.

    2013-05-01

    Rydberg atoms may enable hybrid systems that combine the benefits of gas-phase atoms with those of solid-state devices. However, these hybrid systems will require atoms to be located near a heterogeneous surface with exposed metal electrodes and dielectric insulators, which are sources of uncontrollable and unwanted electric fields. With this motivation, we have measured the electric fields near the heterogeneous metal-dielectric surface of an atom chip using cold Rydberg atoms. We have also developed a technique for reducing the influence of dc and low-frequency electric fields on Rydberg atom transitions, while retaining their sensitivity to high-frequency resonant fields. Rydberg atoms may enable hybrid systems that combine the benefits of gas-phase atoms with those of solid-state devices. However, these hybrid systems will require atoms to be located near a heterogeneous surface with exposed metal electrodes and dielectric insulators, which are sources of uncontrollable and unwanted electric fields. With this motivation, we have measured the electric fields near the heterogeneous metal-dielectric surface of an atom chip using cold Rydberg atoms. We have also developed a technique for reducing the influence of dc and low-frequency electric fields on Rydberg atom transitions, while retaining their sensitivity to high-frequency resonant fields. Work performed in collaboration with J. D. Carter, L. A. Jones, and O. Cherry and supported by NSERC.

  15. Analytical solutions for diatomic Rydberg quasimolecules in a laser field

    NASA Astrophysics Data System (ADS)

    Kryukov, Nikolay; Oks, Eugene

    2014-06-01

    In our previous works we studied analytically helical Rydberg states and circular Rydberg states of two-Coulomb-center systems consisting of two nuclei of charges Z and Z', separated by a distance R, and one electron. We obtained energy terms of these Rydberg quasimolecules for a field-free case, as well as under a static electric field or under a static magnetic field. In the present paper we study such systems under a laser field. For the situation where the laser field is linearly-polarized along the internuclear axis, we found an analytical solution for the stable helical motion of the electron valid for wide ranges of the laser field strength and frequency. We also found resonances, corresponding to a laser-induced unstable motion of the electron, that result in the destruction of the helical states. For the situation where such Rydberg quasimolecules are under a circularly-polarized field, polarization plane being perpendicular to the internuclear axis, we found an analytical solution for circular Rydberg states valid for wide ranges of the laser field strength and frequency. We showed that both under the linearly-polarized laser field and under the circularly-polarized laser field, in the electron radiation spectrum in the addition to the primary spectral component at (or near) the unperturbed revolution frequency of the electron, there appear satellites. We found that for the case of the linearly-polarized laser field, the intensities of the satellites are proportional to the squares of the Bessel functions J {/q 2}( s), ( q = 1, 2, 3, ...), where s is proportional to the laser field strength. As for the case of the circularly-polarized field, we demonstrated that there is a red shift of the primary spectral component — the shift linearly proportional to the laser field strength. Under a laser field of a known strength, in the case of the linear polarization the observation of the satellites would be the confirmation of the helical electronic motion in the Rydberg quasimolecule, while in the case of the circular polarization the observation of the red shift of the primary spectral component would be the confirmation of the specific type of the phase modulation of the electronic motion. Conversely, if the laser field strength is unknown, both the relative intensities of the satellites and the red shift of the primary spectral component could be used for measuring the laser field strength.

  16. Solid-state ring laser gyro behaving like its helium-neon counterpart at low rotation rates.

    PubMed

    Schwartz, Sylvain; Gutty, François; Feugnet, Gilles; Loil, Eric; Pocholle, Jean-Paul

    2009-12-15

    Nonlinear couplings induced by crystal diffusion and spatial inhomogeneities of the gain have been suppressed over a broad range of angular velocities in a solid-state ring laser gyro by vibrating the gain crystal at 168 kHz and 0.4 microm along the laser cavity axis. This device behaves in the same way as a typical helium-neon ring laser gyro, with a zone of frequency lock-in (or dead band) resulting from the backscattering of light on the cavity mirrors. Furthermore, it is shown that the level of angular random-walk noise in the presence of mechanical dithering depends only on the quality of the cavity mirrors, as is the case with typical helium-neon ring laser gyros. PMID:20016646

  17. Rydberg spectroscopy of single-electron capture in low-energy collisions of Ar9+ and Ar8+ with cesium

    NASA Astrophysics Data System (ADS)

    Martin, S.; Denis, A.; Ouerdane, Y.; Carré, M.; Buchet-Poulizac, M. C.; Désesquelles, J.

    1992-08-01

    Optical spectroscopy has been used to study electron capture into Ar9+ and Ar8+ ions from cesium at several impact energies of between 8 and 180 keV. Many Rydberg lines were observed. At high spectral resolution the quasi-l-degeneracy of final Rydberg states was removed and the fine-structure components of doubly excited Rydberg transitions were resolved. Cross sections for state-selective electron capture in collision of Ar8+ with cesium were determined and then compared with theoretical data calculated by means of a three-body classical-trajectory Monte Carlo method and with predictions of a classical barrier model.

  18. Robust quantum logic in neutral atoms via adiabatic Rydberg dressing

    E-print Network

    Tyler Keating; Robert L. Cook; Aaron Hankin; Yuan-Yu Jau; Grant W. Biedermann; Ivan H. Deutsch

    2015-02-23

    We study a scheme for implementing a controlled-Z (CZ) gate between two neutral-atom qubits based on the Rydberg blockade mechanism in a manner that is robust to errors caused by atomic motion. By employing adiabatic dressing of the ground electronic state, we can protect the gate from decoherence due to random phase errors that typically arise because of atomic thermal motion. In addition, the adiabatic protocol allows for a Doppler-free configuration that involves counterpropagating lasers in a $\\sigma_+/\\sigma_-$ orthogonal polarization geometry that further reduces motional errors due to Doppler shifts. The residual motional error is dominated by dipole-dipole forces acting on doubly-excited Rydberg atoms when the blockade is imperfect. For reasonable parameters, with qubits encoded into the clock states of $^{133}$Cs, we predict that our protocol could produce a CZ gate in $<10$ $\\mu$s with error probability on the order of $10^{-3}$.

  19. Controlling ultracold chemical reactions via Rydberg-dressed interactions

    E-print Network

    Jia Wang; Jason N. Byrd; Ion Simbotin; R. Côté

    2014-03-24

    We show that ultracold chemical reactions can be manipulated and controlled by using Rydberg-dressed interactions. Scattering in the ultracold regime is sensitive to long-range interactions, especially when weakly bound (or quasi-bound) states exist near the collision threshold. We investigate how, by Rydberg-dressing a reactant, one enhances its polarizability and modifies the long-range van der Waals collision complex, which can alter chemical reaction rates by shifting the position of near threshold bound states. We carry out a full quantum mechanical scattering calculation for the benchmark system H$_2$+D, and show that resonances can be moved substantially and that rate coefficients at cold and ultracold temperatures can be increased by several orders of magnitude.

  20. Tuning ultracold chemical reactions via Rydberg-dressed interactions.

    PubMed

    Wang, Jia; Byrd, Jason N; Simbotin, Ion; Côté, R

    2014-07-11

    We show that ultracold chemical reactions with an activation barrier can be tuned using Rydberg-dressed interactions. Scattering in the ultracold regime is sensitive to long-range interactions, especially when weakly bound (or quasibound) states exist near the collision threshold. We investigate how, by Rydberg dressing a reactant, one enhances its polarizability and modifies the long-range van der Waals collision complex, which can alter chemical reaction rates by shifting the position of near-threshold bound states. We carry out a full quantum mechanical scattering calculation for the benchmark system H(2)+D, and show that resonances can be moved substantially and that rate coefficients at cold and ultracold temperatures can be increased by several orders of magnitude. PMID:25062202

  1. High-resolution spectroscopy of triplet states of Rb2 by femtosecond pump-probe photoionization of doped helium nanodroplets

    E-print Network

    Mudrich, M; Hippler, T; Giese, Ch; Dulieu, O; Stienkemeier, F

    2009-01-01

    The dynamics of vibrational wave packets in triplet states of rubidium dimers (Rb2) formed on helium nanodroplets are studied using femtosecond pump-probe photoionization spectroscopy. Due to fast desorption of the excited Rb2 molecules off the droplets and due to their low internal temperature, wave packet oscillations can be followed up to very long pump-probe delay times >1.5ns. In the first excited triplet state (1)^3\\Sigma_g^+, full and fractional revivals are observed with high contrast. Fourier analysis provides high-resolution vibrational spectra which are in excellent agreement with ab initio calculations.

  2. Deterministic entanglement of two neutral atoms via Rydberg blockade

    SciTech Connect

    Zhang, X. L.; Isenhower, L.; Gill, A. T.; Walker, T. G.; Saffman, M. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States)

    2010-09-15

    We demonstrate the deterministic entanglement of two individually addressed neutral atoms using a Rydberg blockade mediated controlled-not gate. Parity oscillation measurements reveal a Bell state fidelity of F=0.58{+-}0.04, which is above the entanglement threshold of F=0.5, without any correction for atom loss, and F=0.71{+-}0.05 after correcting for background collisional losses. The fidelity results are shown to be in good agreement with a detailed error model.

  3. Fine structure of the 2 3P state in helium-like sulfur and chlorine

    NASA Astrophysics Data System (ADS)

    Livingston, A. E.; Galvez, E. J.; Zacarias, A. S.; Serpa, F. G.

    1993-06-01

    We present precision measurements of the 1s2p (3P2 - 3P0) fine structure energies in the helium-like ions S14+ and Cl15+. The fine structures are obtained from spectroscopic measurements of the 1s2s 3S1 - 1s2p 3P0,2 transition wavelengths. These results represent the most precise experimental determinations of the helium-like J=2 - 0 intervals for Z?5. They establish the magnitude of missing higher order relativistic contributions in previous high-Z calculations of this fine structure, and they are in excellent agreement with new relativistic many-body calculations.

  4. Creation of Quasi-One-Dimensional Strontium Rydberg Atoms Shuzhen Ye,1

    E-print Network

    GP-A-17 Creation of Quasi-One-Dimensional Strontium Rydberg Atoms Shuzhen Ye,1 state such as a low- state or a polarized Stark state. Here, we examine the photoexcitation of strontium. In strontium the "nd" states possess high two-photon excitation rates, display a large quantum defect

  5. Spectral backbone of excitation transport in ultracold Rydberg gases

    NASA Astrophysics Data System (ADS)

    Scholak, Torsten; Wellens, Thomas; Buchleitner, Andreas

    2014-12-01

    The spectral structure underlying excitonic energy transfer in ultracold Rydberg gases is studied numerically, in the framework of random matrix theory, and via self-consistent diagrammatic techniques. Rydberg gases are made up of randomly distributed, highly polarizable atoms that interact via strong dipolar forces. Dynamics in such a system is fundamentally different from cases in which the interactions are of short range, and is ultimately determined by the spectral and eigenvector structure. In the energy levels' spacing statistics, we find evidence for a critical energy that separates delocalized eigenstates from states that are localized at pairs or clusters of atoms separated by less than the typical nearest-neighbor distance. We argue that the dipole blockade effect in Rydberg gases can be leveraged to manipulate this transition across a wide range: As the blockade radius increases, the relative weight of localized states is reduced. At the same time, the spectral statistics, in particular, the density of states and the nearest-neighbor level-spacing statistics, exhibits a transition from approximately a 1-stable Lévy to a Gaussian orthogonal ensemble. Deviations from random matrix statistics are shown to stem from correlations between interatomic interaction strengths that lead to an asymmetry of the spectral density and profoundly affect localization properties. We discuss approximations to the self-consistent Matsubara-Toyozawa locator expansion that incorporate these effects.

  6. Attosecond XUV absorption spectroscopy of doubly excited states in helium atoms dressed by a time-delayed femtosecond infrared laser

    NASA Astrophysics Data System (ADS)

    Yang, Z. Q.; Ye, D. F.; Ding, Thomas; Pfeifer, Thomas; Fu, L. B.

    2015-01-01

    In the present paper, we investigate the time-resolved transient absorption spectroscopy of doubly excited states of helium atoms by solving the time-dependent two-electron Schrödinger equation numerically based on a one-dimensional model. The helium atoms are subjected to an extreme ultraviolet (XUV) attosecond pulse and a time-delayed infrared (IR) few-cycle laser pulse. A superposition of doubly excited states populated by the XUV pulse is identified, which interferes with the direct ionization pathway leading to Fano resonance profiles in the photoabsorption spectrum. In the presence of an IR laser, however, the Fano line profiles are strongly modified: A shifting, splitting, and broadening of the original absorption lines is observed when the XUV attosecond pulse and infrared few-cycle laser pulse overlap in time, which is in good agreement with recent experimental results. At certain time delays, we observe symmetric Lorentz, inverted Fano profiles, and even negative absorption cross sections indicating that the XUV light can be amplified during the interaction with atoms. We further prove that the above pictures are general for different doubly excited states by suitably varying the frequency of the IR field to coherently couple the corresponding states.

  7. Helium separation

    Microsoft Academic Search

    Frazier

    1965-01-01

    This is a process of separating helium from a helium-containing natural gas. The gas is contacted within a closed vessel with a mass of small, hollow, hole-free, glass particles through which the helium selectively diffuses relative to the other components of the gas mixture. A positive helium partial-pressure differential is maintained across the glass walls of the particles with the

  8. The effect of Rydberg atoms on electron temperature in ultra-cold neutral plasmas

    NASA Astrophysics Data System (ADS)

    Tate, Duncan; Crockett, Ethan

    2013-05-01

    We describe recent developments in our ongoing research in which Rydberg atoms are embedded into an ultra-cold neutral plasma (UNP). The UNP is created with initial electron temperature Te , 0 by photoionization of rubidium atoms in a MOT. At a controllable time delay (5 ns - 10 ?s), atoms in a specific Rydberg state are embedded in the UNP by a narrow bandwidth pulsed laser. In such a system, it is predicted that the plasma electrons may be cooled if the Rydberg binding energy, Eb, is greater than 4kBTe (see, for example). We have identified an experimental signature that correlates with the plasma electron temperature change, namely, whether the plasma lifetime increases or decreases when Rydbergs are added. The ``crossover'' condition, where the UNP lifetime remains the same when Rydbergs are added, can then be plotted (i.e., Eb vs. Te , 0 at crossover) and compared with theoretically derived crossover conditions for UNP expansion velocity, electron temperature, etc., using a model derived from the work of Robicheaux and Hansen. We describe recent developments in our ongoing research in which Rydberg atoms are embedded into an ultra-cold neutral plasma (UNP). The UNP is created with initial electron temperature Te , 0 by photoionization of rubidium atoms in a MOT. At a controllable time delay (5 ns - 10 ?s), atoms in a specific Rydberg state are embedded in the UNP by a narrow bandwidth pulsed laser. In such a system, it is predicted that the plasma electrons may be cooled if the Rydberg binding energy, Eb, is greater than 4kBTe (see, for example). We have identified an experimental signature that correlates with the plasma electron temperature change, namely, whether the plasma lifetime increases or decreases when Rydbergs are added. The ``crossover'' condition, where the UNP lifetime remains the same when Rydbergs are added, can then be plotted (i.e., Eb vs. Te , 0 at crossover) and compared with theoretically derived crossover conditions for UNP expansion velocity, electron temperature, etc., using a model derived from the work of Robicheaux and Hansen. Research supported by Colby College and NSF.

  9. High-resolution spectroscopy of triplet states of Rb2 by femtosecond pump-probe photoionization of doped helium nanodroplets

    Microsoft Academic Search

    M. Mudrich; Ph. Heister; T. Hippler; Ch. Giese; O. Dulieu; F. Stienkemeier

    2009-01-01

    The dynamics of vibrational wave packets in triplet states of rubidium dimers\\u000a(Rb2) formed on helium nanodroplets are studied using femtosecond pump-probe\\u000aphotoionization spectroscopy. Due to fast desorption of the excited Rb2\\u000amolecules off the droplets and due to their low internal temperature, wave\\u000apacket oscillations can be followed up to very long pump-probe delay times\\u000a>1.5ns. In the first

  10. Two-Stage Melting in Systems of Strongly Interacting Rydberg Atoms

    SciTech Connect

    Weimer, Hendrik; Buechler, Hans Peter [Institute of Theoretical Physics III, Universitaet Stuttgart, 70550 Stuttgart (Germany)

    2010-12-03

    We analyze the ground state properties of a one-dimensional cold atomic system in a lattice, where Rydberg excitations are created by an external laser drive. In the classical limit, the ground state is characterized by a complete devil's staircase for the commensurate solid structures of Rydberg excitations. Using perturbation theory and a mapping onto an effective low-energy Hamiltonian, we find a transition of these commensurate solids into a floating solid with algebraic correlations. For stronger quantum fluctuations the floating solid eventually melts within a second quantum phase transition and the ground state becomes paramagnetic.

  11. Multi channel quantum defect theory calculations of the Rydberg spectra of HCO

    NASA Astrophysics Data System (ADS)

    Douguet, Nicolas; Orel, Ann

    2014-05-01

    We present a first-principles theoretical study of the photoionization spectra of vibrationally autoionizing Rydberg states converging to excited states of HCO+. The clamped-nuclei scattering matrix, quantum defects parameters and transition dipole moments are explicitly calculated using the complex variational Kohn technique. The multi-channel quantum defect theory and vibrational frame transformation are then used to calculate the absorption spectrum. The results are compared with experimental data on double-resonance spectroscopy of the high Rydberg states of formyl radical. This work is supported by the DOE Office of Basic Energy Science and the National Science Foundation, Grant No's PHY-10-68785 and PHY-11-60611.

  12. Strongly Correlated Gases of Rydberg-Dressed Atoms: Quantum and Classical Dynamics

    SciTech Connect

    Pupillo, G.; Micheli, A.; Zoller, P. [Institute for Theoretical Physics, University of Innsbruck, and Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, Innsbruck (Austria); Boninsegni, M. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada); Institute for Theoretical Physics, University of Innsbruck, and Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, Innsbruck (Austria); Lesanovsky, I. [School of Physics and Astronomy, University of Nottingham, Nottingham (United Kingdom)

    2010-06-04

    We discuss techniques to generate long-range interactions in a gas of ground state alkali atoms, by weakly admixing excited Rydberg states with laser light. This provides a tool to engineer strongly correlated phases with reduced decoherence from inelastic collisions and spontaneous emission. As an illustration, we discuss the quantum phases of dressed atoms with dipole-dipole interactions confined in a harmonic potential, as relevant to experiments. We show that residual spontaneous emission from the Rydberg state acts as a heating mechanism, leading to a quantum-classical crossover.

  13. First analysis of the B1?+ (?=1) Rydberg state in the lesser-abundant 12C17O isotopologue on the basis of the 1-?? progression of the Ångström band system

    NASA Astrophysics Data System (ADS)

    Hakalla, Rafa?; Zachwieja, Miros?aw; Szajna, Wojciech

    2014-06-01

    So far unobserved in the 12C17O isotopologue, the 1-?? progression of the Ångström (B1?+-A1?) band system was recorded under high resolution in the 17,200-22,950 cm-1 spectral region as an emission spectrum using high-accuracy dispersive optical spectroscopy. The 12C17O molecules were formed and excited in two steps in a stainless steel hollow-cathode lamp with two anodes. The emission from the discharge was observed with a plane-grating spectrograph and recorded by a photomultiplier tube. In the studied region, the full rotational structure of the 1-1 and 1-5 bands of the B-A system was observed, in total 114 spectral emission lines up to J?=21. All those lines were precisely measured with an estimated accuracy of about 0.0030 cm-1, and rotationally analyzed. As a result, many molecular constants were determined for the B1?+ and A1? states in the 12C17O isotopologue. In this paper we have also presented the results of calculations concerning RKR turning points, Franck-Condon factors, relative intensities, and r-centroids for the Ångström band system in the 12C17O molecule. We have also determined the value of the ?G1/2 vibrational quantum, the isotope shifts, as well as the main, isotopically invariant parameters of the B1?+ Rydberg state in the CO molecule within the Born-Oppenheimer approximation. For the A1?, ?=5 state, considerable irregularities of the rotational structure have been observed and analyzed in detail. Suspected candidates responsible for these perturbations have been identified. The B1?+, ?=1 state has been thoroughly analyzed in terms of possible perturbations and it emerged to be completely regular in the 12C17O molecule up to the observed maximum J value.

  14. Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio

    E-print Network

    Hori, Masaki; Barna, Daniel; Dax, Andreas; Hayano, Ryugo; Friedreich, Susanne; Juhász, Bertalan; Pask, Thomas; Widmann, Eberhard; Horváth, Dezsö; Venturelli, Luca; Zurlo, Nicola

    2013-01-01

    Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium ($\\bar{p}{\\rm He}^+$) is a three-body atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton ($\\bar{p}$) occupying a Rydberg state with high principal and angular momentum quantum numbers, respectively $n$ and $\\ell$, such that $n\\sim\\ell\\sim 38$. These atoms are amenable to precision laser spectroscopy, the results of which can in principle be used to determine the antiproton-to-electron mass ratio and to constrain the equality between the antiproton and proton charges and masses. Here we report two-photon spectroscopy of antiprotonic helium, in which $\\bar{p}{\\rm ^3He^+}$ and $\\bar{p}{\\rm ^4He^+}$ isotopes are irradiated by two counter-propagating laser beams. This excites nonlinear, two-...

  15. Communication: atomic and molecular Rydbergs from water.

    PubMed

    Rajput, Jyoti; Safvan, C P

    2011-05-28

    We report the formation of energetic neutral Rydberg hydrogen atoms and transient Rydberg molecular ions, [(H(2)O)(q+)](?) in ion-impact dissociation of isolated water molecules. The kinetic energy spectra of the neutral Rydberg H atoms are determined from the complete study of (H(?), H(+), O(+)) dissociation channel. This channel of water dissociation is suggested as a possible additional source of the energetic neutrals detected in upper atmospheres of extra solar planets, and of slow electrons which are known to play a major role in radiation induced damage to living cells. PMID:21639412

  16. Construction of accurate Kohn-Sham potentials for the lowest states of the helium atom: Accurate test of the ionization-potential theorem

    E-print Network

    Lindgren, Ingvar

    Construction of accurate Kohn-Sham potentials for the lowest states of the helium atom: Accurate Kohn-Sham potentials have been constructed for the ground 1s2 1 S state and, in particular and the procedure of van Leeuwen and Baerends (Phys. Rev. A49, 2138 (1994)). The resulting Kohn-Sham orbitals

  17. From classical to quantum non-equilibrium dynamics of Rydberg excitations in optical lattices

    E-print Network

    Marco Mattioli; Alexander W. Glaetzle; Wolfgang Lechner

    2015-06-02

    The glass phase and its quantum analog are prominent challenges of current non-equilibrium statistical mechanics and condensed matter physics. As a model system to study the transition from classical to quantum glassy dynamics, we propose a setup of laser driven three-level atoms trapped in an optical lattice. Tuning the strength of the laser driving to the intermediate level allows one to study the transition from a classical Kinetically Constrained Model to the coherent regime. For strong driving, Rydberg excitations evolve analogously to defects in the One-Spin Facilitated Model, a minimal model known to exhibit glassy dynamics. In our setup, the constraints result from the interplay between Rydberg interactions and the laser detuning from the Rydberg state. The emerging heterogeneous relaxation timescales are tuneable over several orders of magnitudes. In the opposite limit of weak driving of the intermediate level, we find an effective cluster model which describes the dynamics in a reduced subspace of the allowed number and positions of Rydberg excitations. This subspace is uniquely determined by the initial state and is characterized by a fixed number of clusters of Rydberg excitations. In addition, we investigate the influence of random fields on the classical relaxation. We find that the glassy dynamics can relax faster in the presence of weak random fields.

  18. Helium isotopes in geothermal and volcanic gases of the western United States, I. Regional variability and magmatic origin

    NASA Astrophysics Data System (ADS)

    Welhan, J. A.; Poredai, R. J.; Rison, W.; Craig, H.

    1988-05-01

    Helium isotope ratios in gases of thirty hot springs and geothermal wells and of five natural gas wells in the western United States show no relationship to regional conductive heat flow, but do show a correlation with magma-based thermal activity and reservoir fluid temperature (or total convective heat discharge). Gases from high- T (> 200°C) reservoirs have 3He/ 4He > 2 × the atmospheric value, with high He concentrations due to the input of magmatic helium. Low- T reservoirs generally have 3He/ 4He less than the atmospheric ratio, with very low H 2 contents, which appear to be qualitative criteria for the absence of a magmatic heat source. To first order, He/(CO 2 + H 2S) ratios are inversely correlated with 3He/ 4He and are consistent with a two-component mixture of radiogenic (crustal) and magmatic (mantle) helium. The 3He-enriched high- T component has a restricted range of He/(CO 2 + H 2S) between about 5 and 50 ppmv. On the premise that CO 2 and H 2S concentrations are T-dependent due to mineral-fluid equilibria, the correlation of reservoir temperature and 3He/ 4He ratio, together with the restricted range of He/(CO 2 + H 2S) ratios observed in high- T magmatic systems, suggests that the amount of magmatic He and the amount of CO 2 (and H 2S) in these geothermal reservoirs are related to fluid temperature via the amount of magmatic heat and volatiles input to a particular geothermal reservoir.

  19. Vibronic and Rydberg series assignments in the vacuum ultraviolet absorption spectrum of nitrous oxide

    NASA Astrophysics Data System (ADS)

    Shastri, Aparna; Singh, Param Jeet; Krishnakumar, Sunanda; Mandal, Anuvab; Raja Sekhar, B. N.; D'Souza, R.; Jagatap, B. N.

    2014-11-01

    We report a comprehensive photoabsorption study of nitrous oxide (N2O) in the vacuum ultraviolet (45,000-95,000 cm-1) region using synchrotron radiation. The observed spectrum comprises of a few valence transitions and low lying Rydberg series converging to the two spin-orbit components (2?1/2,3/2) of the ground state of N2O+. Spectral analysis is aided by extensive quantum chemical calculations of vertical excited states, oscillator strengths and potential energy curves using the time dependent density functional theory. Vibronic bands observed in the first absorption system (45,000-60,000 cm-1) are assigned to hot band progressions in ?2? originating from v?=1 or 2. New insights into the assignment of the well-formed progression of bands in the X1?+?C1? system (60,000-72,000 cm-1) are afforded by consideration of the Renner-Teller interaction. A set of molecular vibrational parameters (?2=467 cm-1, x22=-2.9, ?=-0.24) for the C1? state are derived from a fitting of the experimental data. The 3p?1?+ state at ~77,600 cm-1 shows a large quantum defect (0.96) which is explained as arising due to mixed valence-Rydberg character. In the 85,000-95,000 cm-1 region, a number of absorption features are observed with greater clarity than in earlier photoabsorption studies and assigned to Rydberg series of type nl? (n=3,4; l=s,p,d; ?=?,?,?) and accompanying vibronic bands. This work has resulted in clarification of several discrepancies in earlier Rydberg series assignments. Additionally, the 3p? 3?- Rydberg state at 85,788 cm-1, the valence transition 7??3? (1?) at 87,433 cm-1 and the 3d? Rydberg series in the 91,700-92,600 cm-1 region are assigned for the first time.

  20. A Rydberg blockade CNOT gate and entanglement in a 2D array of neutral atom qubits

    E-print Network

    Maller, K M; Xia, T; Sun, Y; Piotrowicz, M J; Carr, A W; Isenhower, L; Saffman, M

    2015-01-01

    We present experimental results on two-qubit Rydberg blockade quantum gates and entanglement in a two-dimensional qubit array. Without post selection against atom loss we achieve a Bell state fidelity of $0.73\\pm 0.05$, the highest value reported to date. The experiments are performed in an array of single Cs atom qubits with a site to site spacing of $3.8 ~ \\mu\\rm m$. Using the standard protocol for a Rydberg blockade C$_Z$ gate together with single qubit operations we create Bell states and measure their fidelity using parity oscillations. We analyze the role of AC Stark shifts that occur when using two-photon Rydberg excitation and show how to tune experimental conditions for optimal gate fidelity.

  1. Attosecond two-photon interferometry for doubly excited states of helium

    E-print Network

    J. Feist; S. Nagele; C. Ticknor; B. I. Schneider; L. A. Collins; J. Burgdörfer

    2011-04-19

    We show that the correlation dynamics in coherently excited doubly excited resonances of helium can be followed in real time by two-photon interferometry. This approach promises to map the evolution of the two-electron wave packet onto experimentally easily accessible non-coincident single electron spectra. We analyze the interferometric signal in terms of a semi-analytical model which is validated by a numerical solution of the time-dependent two-electron Schr\\"odinger equation in its full dimensionality.

  2. Triple differential cross sections in the vicinity of the (2 s 2)1 S state of helium

    NASA Astrophysics Data System (ADS)

    McDonald, D. G.; Crowe, A.

    1992-12-01

    Triple differential cross sections have been measured in the vicinity of the (2 s 2)1 S autoionising state of helium, following impact by 200 eV electrons. The scattered electron detector was set at an angle of -12° (anti-clockwise) and the forward and backward ejected electron angular ranges scanned. The direct ionisation cross section at an ejected electron energy of 33.5 eV has been obtained and the results for the resonant ionisation of the1 S state are presented in the Shore/Balashov parametrisation. These measurements are compared with previous experimental data and emphasise the need for new detailed theoretical calculations on the autoionisation process.

  3. Spectroscopy of triplet states of Rb{sub 2} by femtosecond pump-probe photoionization of doped helium nanodroplets

    SciTech Connect

    Mudrich, M.; Heister, Ph.; Hippler, T.; Giese, Ch.; Stienkemeier, F. [Physikalisches Institut, Universitaet Freiburg, 79104 Freiburg (Germany); Dulieu, O. [Laboratoire Aime Cotton, CNRS, Universite Paris-Sud, Batiment 505, 91405 Orsay (France)

    2009-10-15

    The dynamics of vibrational wave packets in triplet states of rubidium dimers (Rb{sub 2}) formed on helium nanodroplets are studied using femtosecond pump-probe photoionization spectroscopy. Due to fast desorption of the excited Rb{sub 2} molecules off the droplets and due to their low internal temperature, wave-packet oscillations can be followed up to very long pump-probe delay times > or approx. 1.5 ns. In the first-excited triplet state (1){sup 3}{sigma}{sub g}{sup +}, full and fractional revivals are observed with high contrast. Fourier analysis provides high-resolution vibrational spectra which are in excellent agreement with ab initio calculations.

  4. EVOLUTION OF THE RELATIONSHIPS BETWEEN HELIUM ABUNDANCE, MINOR ION CHARGE STATE, AND SOLAR WIND SPEED OVER THE SOLAR CYCLE

    SciTech Connect

    Kasper, J. C.; Stevens, M. L.; Korreck, K. E.; Maruca, B. A.; Kiefer, K. K. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Schwadron, N. A. [Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 (United States); Lepri, S. T. [Department of Atmospheric, Oceanic and Space Studies, University of Michigan, Ann Arbor, MI 48109 (United States)

    2012-02-01

    The changing relationships between solar wind speed, helium abundance, and minor ion charge state are examined over solar cycle 23. Observations of the abundance of helium relative to hydrogen (A{sub He} {identical_to} 100 Multiplication-Sign n{sub He}/n{sub H}) by the Wind spacecraft are used to examine the dependence of A{sub He} on solar wind speed and solar activity between 1994 and 2010. This work updates an earlier study of A{sub He} from 1994 to 2004 to include the recent extreme solar minimum and broadly confirms our previous result that A{sub He} in slow wind is strongly correlated with sunspot number, reaching its lowest values in each solar minima. During the last minimum, as sunspot numbers reached their lowest levels in recent history, A{sub He} continued to decrease, falling to half the levels observed in slow wind during the previous minimum and, for the first time observed, decreasing even in the fastest solar wind. We have also extended our previous analysis by adding measurements of the mean carbon and oxygen charge states observed with the Advanced Composition Explorer spacecraft since 1998. We find that as solar activity decreased, the mean charge states of oxygen and carbon for solar wind of a given speed also fell, implying that the wind was formed in cooler regions in the corona during the recent solar minimum. The physical processes in the coronal responsible for establishing the mean charge state and speed of the solar wind have evolved with solar activity and time.

  5. Fine structure of helium and light helium-like ions Krzysztof Pachucki and Vladimir A. Yerokhin

    E-print Network

    Pachucki, Krzysztof

    1 Fine structure of helium and light helium-like ions Krzysztof Pachucki and Vladimir A. Yerokhin Abstract: Calculational results are presented for the fine-structure splitting of the 23 P state of helium and helium-like ions with the nuclear charge Z up to 10. Theoretical predictions are in agreement

  6. Rydberg Excitation of Single Atoms for Applications in Quantum Information and Metrology

    NASA Astrophysics Data System (ADS)

    Hankin, Aaron Michael

    With the advent of laser cooling and trapping, neutral atoms have become a foundational source of accuracy for applications in metrology and are showing great potential for their use as qubits in quantum information. In metrology, neutral atoms provide the most accurate references for the measurement of time and acceleration. The unsurpassed stability provided by these systems make neutral atoms an attractive avenue to explore applications in quantum information and computing. However, to fully investigate the field of quantum information, we require a method to generate entangling interactions between neutral-atom qubits. Recent progress in the use of highly-excited Rydberg states for strong dipolar interactions has shown great promise for controlled entanglement using the Rydberg blockade phenomenon. I report the use of singly-trapped cesium-133 atoms as qubits for applications in metrology and quantum information. Each atom provides a physical basis for a single qubit by encoding the required information into the ground-state hyperfine structure of cesium-133. Through the manipulation of these qubits with microwave and optical frequency sources, we demonstrate the capacity for arbitrary single-qubit control by driving qubit rotations in three orthogonal directions on the Bloch sphere. With this control, we develop an atom interferometer that far surpasses the force sensitivity of other approaches by applying the well-established technique of light-pulsed atom-matterwave interferometry to single atoms. Following this, we focus on two-qubit interactions using highly-excited Rydberg states. Through the development of a unique single-photon approach to Rydberg excitation using an ultraviolet laser at 319 nm, we observe the Rydberg blockade interaction between atoms separated by 6.6(3) ?m. Motivated by the observation of Rydberg blockade, we study the application of Rydberg-dressed states for a quantum controlled-phase gate. Using a realistic simulation of the dressed-state dynamics, we calculate a controlled-phase gate fidelity of 94% that is primarily limited by Doppler frequency shifts. Finally, we employ our single-photon excitation laser to measure the Rydberg-dressed interaction, thus demonstrating the viability of this approach.

  7. Measurement of holmium Rydberg series through magneto-optical trap depletion spectroscopy

    NASA Astrophysics Data System (ADS)

    Hostetter, J.; Pritchard, J. D.; Lawler, J. E.; Saffman, M.

    2015-01-01

    We report measurements of the absolute excitation frequencies of 165Ho 4 f116 s n s and 4 f116 s n d odd-parity Rydberg series. The states are detected through depletion of a magneto-optical trap via a two-photon excitation scheme. Measurements of 162 Rydberg levels in the range n =40 -101 yield quantum defects well described by the Rydberg-Ritz formula. We observe a strong perturbation in the n s series around n =51 due to an unidentified interloper at 48515.47(4) cm-1. From the series convergence, we determine the first ionization potential EIP=48565.910 (3 ) cm-1, which is three orders of magnitude more accurate than previous work. This work is an important step towards using Ho atoms for collective encoding of a quantum register.

  8. Parallel execution of quantum gates in a long linear ion chain via Rydberg mode shaping

    E-print Network

    Weibin Li; Alexander W. Glaetzle; Rejish Nath; Igor Lesanovsky

    2012-12-19

    We present a mechanism that permits the parallel execution of multiple quantum gate operations within a single long linear ion chain. Our approach is based on large coherent forces that occur when ions are electronically excited to long-lived Rydberg states. The presence of Rydberg ions drastically affects the vibrational mode structure of the ion crystal giving rise to modes that are spatially localized on isolated sub-crystals which can be individually and independently manipulated. We theoretically discuss this Rydberg mode shaping in an experimentally realistic setup and illustrate its power by analyzing the fidelity of two conditional phase flip gates executed in parallel. Our scheme highlights a possible route towards large-scale quantum computing via vibrational mode shaping which is controlled on the single ion level.

  9. Rydberg Atom Formation in Ultracold Plasmas: Small Energy Transfer with Large Consequences

    SciTech Connect

    Pohl, T.; Sadeghpour, H. R. [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States); Vrinceanu, D. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2008-06-06

    We present extensive Monte Carlo calculations of electron-impact-induced transitions between highly excited Rydberg states and provide accurate rate coefficients. For moderate energy changes, our calculations confirm the widely applied expressions in P. Mansbach and J. Keck [Phys. Rev. 181, 275 (1969)] but reveal strong deviations at small energy transfer. Simulations of ultracold plasmas demonstrate that these corrections significantly impact the short-time dynamics of three-body Rydberg atom formation. The improved rate coefficients yield quantitative agreement with recent ultracold plasma experiments.

  10. Electron impact double-excitation of helium 2l2l' autoionizing states using the (e, 2e) technique

    NASA Astrophysics Data System (ADS)

    Sise, Omer; Dogan, Mevlut; Okur, Ibrahim; Crowe, Albert

    2012-11-01

    Coplanar (e, 2e) triple differential cross sections (TDCS) measurements are reported for the helium autoionizing doubly excited states, (2s2)1 S, (2p2)1D, and (2s2p)1P, for an incident electron energy of 250 eV and a scattering angle of -13°, corresponding to a momentum transfer of 1.06 a.u. The presence of autoionization results in a clearly visible recoil peak in the TDCS structure with a shape that is strongly dependent on the orbital angular momentum L of the resonance. The resonance contributions together with the strong background of direct ionization processes lead to a complicated asymmetric structure of the resonance profile in the TDCS.

  11. Experimental Characterization of Singlet Scattering Channels in Long-Range Rydberg Molecules

    NASA Astrophysics Data System (ADS)

    Saßmannshausen, Heiner; Merkt, Frédéric; Deiglmayr, Johannes

    2015-04-01

    We observe the formation of long-range Cs2 Rydberg molecules consisting of a Rydberg and a ground-state atom by photoassociation spectroscopy in an ultracold Cs gas near 6 s1 /2(F =3 ,4 )?n p3 /2 resonances (n =26 - 34 ). The spectra reveal two types of molecular states recently predicted by D. A. Anderson, S. A. Miller, and G. Raithel [Phys. Rev. A 90, 062518 (2014)]: states bound purely by triplet s -wave scattering with binding energies ranging from 400 MHz at n =26 to 80 MHz at n =34 , and states bound by mixed singlet-triplet s -wave scattering with smaller and F -dependent binding energies. The experimental observations are accounted for by an effective Hamiltonian including s -wave scattering pseudopotentials, the hyperfine interaction of the ground-state atom, and the spin-orbit interaction of the Rydberg atom. The analysis enables the characterization of the role of singlet scattering in the formation of long-range Rydberg molecules and the determination of an effective singlet s -wave scattering length for low-energy-electron-Cs collisions.

  12. Two Dimensional Non-commutative Space and Rydberg Atom Model

    NASA Astrophysics Data System (ADS)

    Chung, Won Sang

    2015-06-01

    In this paper we consider the case of only space-space non-commutativity in two dimension. We also discuss the Rydberg atom model in this space and use the linear realization of the coordinate and momentum operators to solve the Schrödinger equation for the Rydberg atom through the standard perturbation method. Finally, the thermodynamics for the Rydberg atom model is discussed.

  13. Measurement of relative cross sections for simultaneous ionization and excitation of the helium 4 2s and 4 2p states

    NASA Technical Reports Server (NTRS)

    Sutton, J. F.

    1972-01-01

    The relative cross sections for simultaneous ionization and excitation of helium by 200-eV electrons into the 4 2s and 4 2p states were measured via a fast delayed coincidence technique. Results show good agreement with the relative cross sections for single electron excitation of helium and hydrogen. An application of the results of the measurement to the development of ultraviolet intensity standard is suggested. This technique involves the use of known branching ratios, a visible light flux reference, and the measured relative cross sections.

  14. High-pressure phase diagram and equation of state of solid helium from single-crystal X-ray diffraction to 23.3 GPa

    NASA Technical Reports Server (NTRS)

    Mao, H. K.; Hemley, R. J.; Jephcoat, A. P.; Finger, L. W.; Wu, Y.

    1988-01-01

    Single-crystal X-ray diffraction measurements have been performed on solid He-4 from 15.6 to 23.3 GPa at 300 K with synchrotron radiation. The diffraction patterns demonstrate that the structure of the solid is hexagonal close packed over this pressure-temperature range, contrary to both the interpretation of high-pressure optical studies and to theoretical predictions. The solid is more compressible than is indicated by equations of state calculated with recently determined helium pair potentials. The results suggest that a significant revision of current views of the phase diagram and energetics of dense solid helium is in order.

  15. High-Rydberg Xenon Submillimeter-Wave Detector

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara

    1987-01-01

    Proposed detector for infrared and submillimeter-wavelength radiation uses excited xenon atoms as Rydberg sensors instead of customary beams of sodium, potassium, or cesium. Chemically inert xenon easily stored in pressurized containers, whereas beams of dangerously reactive alkali metals must be generated in cumbersome, unreliable ovens. Xenon-based detector potential for infrared astronomy and for Earth-orbiter detection of terrestrial radiation sources. Xenon atoms excited to high energy states in two stages. Doubly excited atoms sensitive to photons in submillimeter wavelength range, further excited by these photons, then ionized and counted.

  16. The kicked Rydberg atom: Regular and stochastic motion

    SciTech Connect

    Burgdoerfer, J.

    1988-01-01

    We have investigated the dynamics of a three-dimensional classical Rydberg atom driven by a sequence of pulses. Both the deterministic system with periodic pulses and the closely related ''noisy'' system with random pulses have been studied in parallel. The Lyapunov exponent is calculated as a function of pulse height and the angular momentum of the initial state. We find differences between noisy and deterministic perturbations to be most pronounced for small pulse heights. Low angular momentum orbits show enhanced diffusion in agreement with recent experimental data for ion-solid interaction. 22 refs., 6 figs.

  17. Controlled photon-photon interactions using Rydberg polaritons

    NASA Astrophysics Data System (ADS)

    Adams, Charles

    2014-05-01

    By coupling a strong optical transition to a highly-excited Rydberg state it is possible to realise giant optical non-linearities and hence strong photon-photon interactions. A remaining challenge is to implement an interaction that does not distort the photon mode and hence to realise high-fidelity photonic quantum gates. In this talk we will discuss how to control the photon-photon interact using microwave fields and how this could be used to implement deterministic non-linear optical computation. Acknowledgements EU Marie Curie Initial Training Network coherence.

  18. Effect of dispersion forces on squeezing with Rydberg atoms

    NASA Technical Reports Server (NTRS)

    Ng, S. K.; Muhamad, M. R.; Wahiddin, M. R. B.

    1994-01-01

    We report exact results concerning the effect of dipole-dipole interaction (dispersion forces) on dynamic and steady-state characteristics of squeezing in the emitted fluorescent field from two identical coherently driven two-level atoms. The atomic system is subjected to three different damping baths in particular the normal vacuum, a broad band thermal field and a broad band squeezed vacuum. The atomic model is the Dicke model, hence possible experiments are most likely to agree with theory when performed on systems of Rydberg atoms making microwave transitions. The presence of dipole-dipole interaction can enhance squeezing for realizable values of the various parameters involved.

  19. Studies of singlet Rydberg series of LiH derived from Li(nl) + H(1s), with n ? 6 and l ? 4.

    PubMed

    Gim, Yeongrok; Lee, Chun-Woo

    2014-10-14

    The 50 singlet states of LiH composed of 49 Rydberg states and one non-Rydberg ionic state derivable from Li(nl) + H(1s), with n ? 6 and l ? 4, are studied using the multi-reference configuration interaction method combined with the Stuttgart/Köln group's effective core potential/core polarization potential method. Basis functions that can yield energy levels up to the 6g orbital of Li have been developed, and they are used with a huge number of universal Kaufmann basis functions for Rydberg states. The systematics and regularities of the physical properties such as potential energies, quantum defects, permanent dipole moments, transition dipole moments, and nonadiabatic coupling matrix elements of the Rydberg series are studied. The behaviors of potential energy curves and quantum defect curves are explained using the Fermi approximation. The permanent dipole moments of the Rydberg series reveal that they are determined by the sizes of the Rydberg orbitals, which are proportional to n(2). Interesting mirror relationships of the dipole moments are observed between l-mixed Rydberg series, with the rule ?l = ±1, except for s-d mixing, which is also accompanied by n-mixing. The members of the l-mixed Rydberg series have dipole moments with opposite directions. The first derivatives of the dipole moment curves, which show the charge-transfer component, clearly show not only mirror relationships in terms of direction but also oscillations. The transition dipole moment matrix elements of the Rydberg series are determined by the small-r region, with two consequences. One is that the transition dipole moment matrix elements show n(-3/2) dependence. The other is that the magnitudes of the transition dipole moment matrix elements decrease rapidly as l increases. PMID:25318728

  20. Studies of singlet Rydberg series of LiH derived from Li(nl) + H(1s), with n ? 6 and l ? 4

    NASA Astrophysics Data System (ADS)

    Gim, Yeongrok; Lee, Chun-Woo

    2014-10-01

    The 50 singlet states of LiH composed of 49 Rydberg states and one non-Rydberg ionic state derivable from Li(nl) + H(1s), with n ? 6 and l ? 4, are studied using the multi-reference configuration interaction method combined with the Stuttgart/Köln group's effective core potential/core polarization potential method. Basis functions that can yield energy levels up to the 6g orbital of Li have been developed, and they are used with a huge number of universal Kaufmann basis functions for Rydberg states. The systematics and regularities of the physical properties such as potential energies, quantum defects, permanent dipole moments, transition dipole moments, and nonadiabatic coupling matrix elements of the Rydberg series are studied. The behaviors of potential energy curves and quantum defect curves are explained using the Fermi approximation. The permanent dipole moments of the Rydberg series reveal that they are determined by the sizes of the Rydberg orbitals, which are proportional to n2. Interesting mirror relationships of the dipole moments are observed between l-mixed Rydberg series, with the rule ?l = ±1, except for s-d mixing, which is also accompanied by n-mixing. The members of the l-mixed Rydberg series have dipole moments with opposite directions. The first derivatives of the dipole moment curves, which show the charge-transfer component, clearly show not only mirror relationships in terms of direction but also oscillations. The transition dipole moment matrix elements of the Rydberg series are determined by the small-r region, with two consequences. One is that the transition dipole moment matrix elements show n-3/2 dependence. The other is that the magnitudes of the transition dipole moment matrix elements decrease rapidly as l increases.

  1. Ionization in a frozen Rydberg gas with attractive or repulsive potentials Matthieu Viteau1

    E-print Network

    Paris-Sud XI, Université de

    , and such a sample resembles an amorphous solid. Since Rydberg atoms have large dipole moments, scaling as the square is excited, a phenomenon termed the dipole blockade. Local, or partial, blockades have been observed in many of the atoms are ionized and one third are driven to lower states to provide the requisite energy [11, 14

  2. Spin-dependent localized Hartree-Fock density-functional calculation of singly, doubly, and triply excited and Rydberg states of He- and Li-like ions

    E-print Network

    Chu, Shih-I; Zhou, Zhongyuan

    2005-02-28

    A spin-dependent density-functional approach for the calculation of highly and multiply excited state of atomic system is proposed based on the localized Hartree-Fock density-functional method and Slater’s diagonal sum rule. In this approach...

  3. Dephasing dynamics of Rydberg atom spin waves

    NASA Astrophysics Data System (ADS)

    Bariani, F.; Goldbart, Paul M.; Kennedy, T. A. B.

    2012-10-01

    A theory of Rydberg atom interactions is used to derive analytical forms for the spin-wave pair correlation function in laser-excited cold-atom vapors. This function controls the quantum statistics of light emission from dense, inhomogeneous clouds of cold atoms of various spatial dimensionalities. The results yield distinctive scaling behaviors on the microsecond time scale, including generalized exponential decay. A detailed comparison is presented with a recent experiment on a cigar-shaped atomic ensemble [Y. Dudin and A. Kuzmich, ScienceSCIEAS0036-807510.1126/science.1217901 336, 887 (2012)], in which Rb atoms are excited to a set of Rydberg levels.

  4. Transient localization in the kicked Rydberg atom

    E-print Network

    E. Persson; S. Fürthauer; S. Wimberger; J. Burgdörfer

    2006-09-05

    We investigate the long-time limit of quantum localization of the kicked Rydberg atom. The kicked Rydberg atom is shown to possess in addition to the quantum localization time $\\tau_L$ a second cross-over time $t_D$ where quantum dynamics diverges from classical dynamics towards increased instability. The quantum localization is shown to vanish as either the strength of the kicks at fixed principal quantum number or the quantum number at fixed kick strength increases. The survival probability as a function of frequency in the transient localization regime $\\tau_L

  5. Screw Compressor Characteristics for Helium Refrigeration Systems

    Microsoft Academic Search

    Venkatarao Ganni; Peter Knudsen; Jonathan Creel; Dana Arenius; Fabio Casagrande; Matt Howell

    2008-01-01

    The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system.

  6. Circuit Quantum Electrodynamics with Electrons on Helium

    E-print Network

    Circuit Quantum Electrodynamics with Electrons on Helium A Dissertation Presented to the Faculty Fragner All rights reserved. ii #12;Abstract Circuit Quantum Electrodynamics with Electrons on Helium helium. Such a system represents a solid-state, electrical circuit analog of atomic cavity QED in which

  7. Advanced helium magnetometer for space applications

    Microsoft Academic Search

    Robert E. Slocum

    1987-01-01

    The goal of this effort was demonstration of the concepts for an advanced helium magnetometer which meets the demands of future NASA earth orbiting, interplanetary, solar, and interstellar missions. The technical effort focused on optical pumping of helium with tunable solid state lasers. We were able to demonstrate the concept of a laser pumped helium magnetometer with improved accuracy, low

  8. Noble-gas-induced collisional line broadening of atomic-lithium Rydberg superposition states 2SnS and 2S-nD (n = 4 to 30) measured by trilevel echoes

    Microsoft Academic Search

    Emily Y. Xu; F. Moshary; S. R. Hartmann

    1986-01-01

    The pioneering research of Fuchtbauer et al. on Na-3S-nP transition broadening by Ar gas demonstrated that the collisional-broadening cross section increases sharply for an increasing principal quantum number n for low n, peaks as n approaches the Rydberg regime, and then decreases to a small function of its maximum value. It appears to reach an asymptotic value (independent of n)

  9. Spin-dependent localized Hartree-Fock density-functional calculation of singly, doubly, and triply excited and Rydberg states of He and Li-like ions

    Microsoft Academic Search

    Zhongyuan Zhou; Shih-I. Chu

    2005-01-01

    A spin-dependent density-functional approach for the calculation of highly and multiply excited state of atomic system is proposed based on the localized Hartree-Fock density-functional method and Slater's diagonal sum rule. In this approach, electron spin orbitals in an electronic configuration are obtained first by solving the Kohn-Sham equation with an exact nonvariational spin-dependent localized Hartree-Fock exchange potential. Then a single-Slater-determinant

  10. Theoretical state-selective and total cross sections for electron capture from helium atoms by fully stripped ions

    NASA Astrophysics Data System (ADS)

    Man?ev, I.; Milojevi?, N.; Belki?, Dž.

    2015-03-01

    The four-body boundary-corrected first Born (CB1-4B) approximation is used to compute cross sections for single electron capture from helium targets by fully stripped ions. The projectile ions are H+, He2+, Li3+, Be4+, B5+, C6+, N7+, O8+, and F9+. An extensive list of theoretical state-to-state cross sections in these collisions at energies ranging from 20 to 10 000 keV/amu is given. This list includes the state-selective cross sections Qnlm for each individual triple of the usual quantum numbers { n , l , m } of the final hydrogen-like states alongside Qnl and Qn for the pertinent sub-shells and shells where the respective summations over m and { l , m } have been carried out. The maximal value of the principal quantum number n was chosen to vary from 4 (H+) to 10 (F9+) so as to satisfy the condition n ?ZP, where ZP is the nuclear charge of the projectile. Usually, the largest cross sections stem from those values of n that match the projectile charge (n =ZP) . The total cross sections for capture summed over all the quantum numbers { n , l , m } are also tabulated. The overall goal of this study is to fill in lacunae in the existing databases of charge exchange cross sections that are needed in several inter-disciplinary fields. For example, in particle transport physics, which is of utmost importance in such emerging branches as hadron therapy, these cross sections constitute a part of the multifaceted input data for stochastic simulations of energy losses of multiply charged ions in matter, including tissue. Other significant uses of the present data are anticipated in charge exchange diagnostics within thermonuclear research project as well as in applications covering the relevant parts of plasma physics and astrophysics.

  11. Helium-cluster decay widths of molecular states in beryllium and carbon isotopes

    E-print Network

    J. C. Pei; F. R. Xu

    2007-02-01

    The $\\alpha$ particle and $^6$He emissions from possible molecular states in beryllium and carbon isotopes have been studied using a mean-field-type cluster potential. Calculations can reproduce well the $\\alpha$-decay widths of excited states in $^{8}$Be, $^{12}$C and $^{20}$Ne. For the nucleus $^{10}$Be, we discussed the $\\alpha$-decay widths with different shapes or decay modes, in order to understand the very different decay widths of two excited states. The widths of $^{6}$He decay from $^{12}$Be and $\\alpha$ decays from $^{13,14}$C are predicted, which could be useful for future experiments.

  12. Molecular ions, Rydberg spectroscopy and dynamics

    NASA Astrophysics Data System (ADS)

    Jungen, Ch.

    2015-01-01

    Ion spectroscopy, Rydberg spectroscopy and molecular dynamics are closely related subjects. Multichannel quantum defect theory is a theoretical approach which draws on this close relationship and thereby becomes a powerful tool for the study of systems consisting of a positively charged molecular ion core interacting with an electron which may be loosely bound or freely scattering.

  13. On the Formation of (Anionic) Excited Helium Dimers in Helium Droplets

    PubMed Central

    2014-01-01

    Metastable atomic and molecular helium anions exhibiting high-spin quartet configurations can be produced in helium droplets via electron impact. Their lifetimes allow detection in mass spectrometric experiments. Formation of atomic helium anions comprises collision-induced excitation of ground state helium and concomitant electron capture. Yet the formation of molecular helium anions in helium droplets has been an unresolved issue. In this work, we explore the interaction of excited helium atoms exhibiting high-spin triplet configurations with ground state helium using the equation-of-motion coupled-cluster method. Transition barriers in the energetically lowest He*–He and He*––He interaction potentials prevent molecule formation at the extremely low temperatures present in helium droplets. In contrast, some excited states allow a barrier-free formation of molecular helium (anions). Moreover, we show that the necessary excitation energies pinpoint (higher) resonances in recently recorded mass spectra and emend the assignment of those resonances that have previously been assigned to electron-impact ionization of ground state helium necessitating subsequent double-electron capture. Embedding molecules or molecular clusters in helium droplets is a predestined experimental technique for the study of phenomena at very low temperatures. Profound knowledge about active processes in the helium environment is required for a proper assessment of experimental data. PMID:24866535

  14. Designing frustrated quantum magnets with laser-dressed Rydberg atoms.

    PubMed

    Glaetzle, Alexander W; Dalmonte, Marcello; Nath, Rejish; Gross, Christian; Bloch, Immanuel; Zoller, Peter

    2015-05-01

    We show how a broad class of lattice spin-1/2 models with angular- and distance-dependent couplings can be realized with cold alkali atoms stored in optical or magnetic trap arrays. The effective spin-1/2 is represented by a pair of atomic ground states, and spin-spin interactions are obtained by admixing van der Waals interactions between fine-structure split Rydberg states with laser light. The strengths of the diagonal spin interactions as well as the "flip-flop," and "flip-flip" and "flop-flop" interactions can be tuned by exploiting quantum interference, thus realizing different spin symmetries. The resulting energy scales of interactions compare well with typical temperatures and decoherence time scales, making the exploration of exotic forms of quantum magnetism, including emergent gauge theories and compass models, accessible within state-of-the-art experiments. PMID:25978228

  15. Designing Frustrated Quantum Magnets with Laser-Dressed Rydberg Atoms

    E-print Network

    Alexander W. Glaetzle; Marcello Dalmonte; Rejish Nath; Christian Gross; Immanuel Bloch; Peter Zoller

    2015-04-30

    We show how a broad class of lattice spin-1/2 models with angular- and distance-dependent couplings can be realized with cold alkali atoms stored in optical or magnetic trap arrays. The effective spin-1/2 is represented by a pair of atomic ground states, and spin-spin interactions are obtained by admixing van der Waals interactions between fine-structure split Rydberg states with laser light. The strengths of the diagonal spin interactions as well as the "flip-flop", and "flip-flip" and "flop-flop" interactions can be tuned by exploiting quantum interference, thus realizing different spin symmetries. The resulting energy scales of interactions compare well with typical temperatures and decoherence time-scales, making the exploration of exotic forms of quantum magnetism, including emergent gauge theories and compass models, accessible within state-of-the-art experiments.

  16. Driven-dissipative dynamics of a strongly interacting Rydberg gas

    E-print Network

    A. W. Glaetzle; R. Nath; B. Zhao; G. Pupillo; P. Zoller

    2012-07-11

    We study the non-equilibrium many-body dynamics of a cold gas of ground state alkali atoms weakly admixed by Rydberg states with laser light. On a timescale shorter than the lifetime of the dressed states, effective dipole-dipole or van der Waals interactions between atoms can lead to the formation of strongly correlated phases, such as atomic crystals. Using a semiclassical approach, we study the long-time dynamics where decoherence and dissipative processes due to spontaneous emission and blackbody radiation dominate, leading to heating and melting of atomic crystals as well as particle losses. These effects can be substantially mitigated by performing active laser cooling in the presence of atomic dressing.

  17. Entangling Atomic Spins with a Strong Rydberg-Dressed Interaction

    E-print Network

    Jau, Y -Y; Keating, Tyler; Deutsch, I H; Biedermann, G W

    2015-01-01

    Controlling quantum entanglement between parts of a many-body system is the key to unlocking the power of quantum information processing for applications such as quantum computation, highprecision sensing, and simulation of many-body physics. Spin degrees of freedom of ultracold neutral atoms in their ground electronic state provide a natural platform given their long coherence times and our ability to control them with magneto-optical fields, but creating strong coherent coupling between spins has been challenging. We demonstrate a Rydberg-dressed ground-state blockade that provides a strong tunable interaction energy (~1 MHz in units of Planck's constant) between spins of individually trapped cesium atoms. With this interaction we directly produce Bell-state entanglement between two atoms with a fidelity >= 81(2)%, excluding atom loss events, and >= 60(3)% when loss is included.

  18. Electron-detachment cross sections to low-lying excited states of hydrogen in collisions of negative hydrogen ions with helium and argon

    Microsoft Academic Search

    J S Risley; F J de Heev; C B Kerkdijk

    1978-01-01

    The intensities of the four lowest Lyman lines (Ly- alpha , Ly- beta , Ly- gamma and Ly- delta ) of atomic hydrogen produced in electron-detachment collisions of 1-6 keV negative hydrogen ions on helium and argon were measured. By applying an electric field in the direction of the ion beam, excited states of hydrogen were Stark-mixed and the effects

  19. Rydberg electrons spy conformational dynamics of hot molecules

    NASA Astrophysics Data System (ADS)

    Weber, Peter M.

    2007-03-01

    The observation of structural dynamics of flexible molecules at high temperatures is arguably one of the most challenging problems of molecular dynamics. We succeeded in observing conformational dynamics by using electrons in Rydberg orbits as spies of the molecular structure. The time-resolved photoionization from the Rydberg states, providing a purely electronic spectrum that serves to characterize the molecular structure, allows us to follow the molecular motions in real time. The internal rotation about carbon-carbon bonds affords the unsaturated hydrocarbon chain molecules N,N-dimethyl-2-butanamine (DM2BA) and N,N-dimethyl-3-hexanamine (DM3HA) an opportunity to assume multiple conformeric structures. We explore the equilibrium compositions and the dynamics of transitions between such structures. An ultrashort laser pulse rapidly increases the molecule's internal energy and changes the potential energy landscape. The molecules respond by adjusting their shape, i.e. by converting between conformeric molecular structures. For DM2BA at a total internal energy of 1.79 eV, the time constants for interconversion between conformers are 19 ps and 66 ps, respectively. In DM3HA, the respective time constants are 23 and 41 ps. Comparison with a calculated conformational energy landscape reveals the conformeric forms of DM2BA involved in the molecular shape transformation. Thus, for the first time a time-resolved and quantitative view of the conformational dynamics of a flexible hydrocarbon chain at high temperature is revealed.

  20. Quantification of the effects of Rydberg atoms on ultra-cold neutral plasma evolution

    NASA Astrophysics Data System (ADS)

    Tate, Duncan; Crockett, Ethan; Newell, Ryan

    2014-05-01

    We describe recent developments in our ongoing research in which Rydberg atoms are embedded into an ultra-cold neutral plasma (UNP). Atoms in a specific Rydberg state are embedded in the UNP within 10 ns of its creation using a second pulsed laser system. In such an environment, it is predicted that the plasma electrons may be heated or cooled by the Rydberg atoms (see, for example). We identified an experimental signature that correlates with the plasma electron temperature change, namely, the ``crossover'' between heating and cooling, where the UNP lifetime remains the same when Rydbergs are added. More recently, we have been working on quantifying the amount of heating or cooling that can be achieved using a passive technique. Specifically, we measure the time (t?) it takes for the UNP to shed a certain fraction of its electrons (?) as it expands in a small, externally applied, electric field. The work reported in shows that the quantity t?- 1 is a good proxy for the UNP asymptotic expansion velocity, which in turn depends on Te , 0. Research supported by Colby College and NSF.

  1. Green's function Monte Carlo calculation for the ground state of helium trimers

    SciTech Connect

    Cabral, F.; Kalos, M.H.

    1981-02-01

    The ground state energy of weakly bound boson trimers interacting via Lennard-Jones (12,6) pair potentials is calculated using a Monte Carlo Green's Function Method. Threshold coupling constants for self binding are obtained by extrapolation to zero binding.

  2. Electroproduction of strangeness on Lambda3,4H bound states on Helium

    Microsoft Academic Search

    F. Dohrmann; D. Abbott; A. Ahmidouch; P. Ambrozewicz; C. S. Armstrong; J. Arrington; R. Asaturyan; K. Assamagan; S. Avery; K. Bailey; S. Beedoe; H. Bitao; H. Breuer; D. S. Brown; R. Carlini; J. Cha; N. Chant; E. Christy; A. Cochran; L. Cole; G. Collins; C. Cothran; J. Crowder; W. J. Cummings; S. Danagoulian; F. Duncan; J. Dunne; D. Dutta; T. Eden; M. Elaasar; R. Ent; L. Ewell; H. Fenker; H. T. Fortune; Y. Fujii; L. Gan; H. Gao; K. Gustafsson; D. F. Geesaman; P. Gueye; K. Hafidi; J. O. Hansen; W. Hinton; H. E. Jackson; H. Juengst; C. Keppel; A. Klein; D. Koltenuk; Y. Liang; J. H. Liu; A. Lung; D. Mack; R. Madey; P. Markowitz; C. J. Martoff; D. Meekins; J. Mitchell; T. Miyoshi; H. Mkrtchyan; R. Mohring; S. K. Mtingwa; B. Mueller; T. G. O'Neill; G. Niculescu; I. Niculescu; D. Potterveld; J. W. Price; B. A. Raue; P. E. Reimer; J. Reinhold; J. Roche; P. Roos; M. Sarsour; Y. Sato; G. Savage; R. Sawafta; R. E. Segel; A. Yu. Semenov; S. Stepanyan; V. Tadevosian; S. Tajima; L. Tang; B. Terburg; A. Uzzle; S. Wood; H. Yamaguchi; C. Yan; L. Yuan; M. Zeier; B. Zeidman; B. Zihlmann

    2005-01-01

    The A(e,e'K+)X reaction has been investigated at Jefferson Laboratory. Data were taken for Q2 ~ 0.35 GeV2 at a beam energy of 3.245 GeV for 1H,3He and 4He targets. Evidence for Lambda-hypernuclear bound states is seen for 3,4He targets. This is the first time that the electroproduction of these hypernuclei has been observed.

  3. Electroproduction of strangeness on (Lambda)H-3,4 bound states on helium

    Microsoft Academic Search

    F. Dohrmann; D. Abbott; A. Ahmidouch; P. Ambrozewicz; C. S. Armstrong; J. Arrington; R. Asaturyan; K. Assamagan; S. Avery; K. Bailey; S. Beedoe; H. Bitao; H. Breuer; D. S. Brown; R. Carlini; J. Cha; N. Chant; E. Christy; A. Cochran; L. Cole; G. Collins; C. Cothran; J. Crowder; W. J. Cummings; S. Danagoulian; F. Duncan; J. Dunne; D. Dutta; T. Eden; M. Elaasar; R. Ent; L. Ewell; H. Fenker; H. T. Fortune; Y. Fujii; L. Gan; K. Garrow; D. F. Geesaman; P. Gueye; K. Gustafsson; K. Hafidi; J. O. Hansen; W. Hinton; H. E. Jackson; H. Juengst; C. Keppel; A. Klein; D. Koltenuk; Y. Liang; J. H. Liu; A. Lung; D. Mack; R. Madey; P. Markowitz; C. J. Martoff; D. Meekins; J. Mitchell; T. Miyoshi; H. Mkrtchyan; R. Mohring; S. K. Mtingwa; B. Mueller; T. G. ONeill; G. Niculescu; I. Niculescu; D. Potterveld; J. W. Price; B. A. Raue; P. E. Reimer; J. Reinhold; J. Roche; P. Roos; M. Sarsour; Y. Sato; G. Savage; R. Sawafta; R. E. Segel; A. Yu. Semenov; S. Stepanyan; V. Tadevosian; S. Tajima; L. Tang; B. Terburg; A. Uzzle; S. Wood; H. Yamaguchi; C. Yan; L. Yuan; M. Zeier; B. Zeidman; B. Zihlmann

    2005-01-01

    The A(e,eK+)X reaction has been investigated at Jefferson Laboratory. Data were taken for Q² approx. 0.35 GeV² at a beam energy of 3.245 GeV for 1H,3He and 4He targets. Evidence for Lambda-hypernuclear bound states is seen for 3,4He targets. This is the first time that the electroproduction of these hypernuclei has been observed.

  4. Excitation of lower autoionization states of the helium-like ions in x-ray scattering

    Microsoft Academic Search

    M. Ya. Amusia A. I. Mikhailov; I. A. Mikhailov

    1999-01-01

    The process of inelastic scattering of high-frequency photons leading to excitation of singlet autoionization states (AIS) with total angular momentum L = 0 located below the first excited level of the respective one-electron ion are considered. For the amplitude of the process analytical expressions are derived, which include one-dimensional integrals, the latter being evaluated numerically. The scattered photon angular distributions

  5. Excitation of lower autoionization ? states of the helium-like ions in x-ray scattering

    Microsoft Academic Search

    M. Ya Amusia; A. I. Mikhailov; I. A. Mikhailov

    1999-01-01

    The process of inelastic scattering of high-frequency photons leading to excitation of singlet autoionization states (AIS) with total angular momentum L = 0 located below the first excited level of the respective one-electron ion are considered. For the amplitude of the process analytical expressions are derived, which include one-dimensional integrals, the latter being evaluated numerically. The scattered photon angular distributions

  6. Transverse sound spectroscopy of excited Cooper pair states in superfluid helium-3

    NASA Astrophysics Data System (ADS)

    Davis, John Patrick

    We use transverse sound spectroscopy to probe excited states of the Cooper pairs in the B-phase of superfluid 3He. In particular we study those excited states with non-zero energy at zero momentum, the so called gapped, or exciton, modes. This includes precise measurements of the imaginary squashing mode energies as well as its Zeeman splitting in a magnetic field. The latter is measured through the acoustic Faraday effect, a phenomenon of acoustic birefringence induced by Zeeman splitting. Additionally, we have made measurements of the absolute velocities of transverse sound and as a result have discovered a previously unobserved collective mode near the pair-breaking threshold, 2Delta, which also exhibits acoustic birefringence. We measure its coupling strength to transverse sound and Verdet constant. Using the selection rules which govern the coupling to transverse sound, we argue that this is the so called J=4 exciton mode, which results from sub-dominant f-wave pairing interactions in this p-wave superfluid. Additionally, we have made measurements of the transverse acoustic response of 3He confined within 98% porous aerogel to explore the possibility of stabilizing new superfluid phases of 3He due to anisotropic quasiparticle scattering. We find global axial anisotropy introduced via preferential radial shrinkage produces signatures of phase transitions on warming from the B-like phase to the A-like phase, suggestive of a region of stable A-like phase, while global axial anisotropy introduced via axial compression affects only the metastable supercooling of the A-like phase, possibly by inhibiting the nucleation of the B-like phase in aerogel. In the appendices we discuss: the implications of our 2Delta-mode measurements, combined with longitudinal sound measurements, on the energy of pair-breaking; possible observation of the J=1- collective mode; measurements of the real squashing mode using longitudinal sound; a new and unusual magneto-acoustic effect; surface Andreev bound states affecting the transverse acoustic impedance; and finally, some ideas for future experiments with acoustic techniques.

  7. Excitation of lower autoionization states of the helium-like ions in x-ray scattering

    NASA Astrophysics Data System (ADS)

    Mikhailov, M. Ya. Amusia A. I.; Mikhailov, I. A.

    1999-03-01

    The process of inelastic scattering of high-frequency photons leading to excitation of singlet autoionization states (AIS) with total angular momentum L = 0 located below the first excited level of the respective one-electron ion are considered. For the amplitude of the process analytical expressions are derived, which include one-dimensional integrals, the latter being evaluated numerically. The scattered photon angular distributions and the absolute cross section of the considered process are obtained. The transitions into two lower AIS are investigated. The approximation is employed, in which the electrons are described by Coulomb functions, and their interaction is taken into account in the first order of the perturbation theory. The correct AIS functions of the zero approximation are used which are obtained as solutions of the secular equation.

  8. Exotic topological density waves in cold atomic Rydberg-dressed fermions

    PubMed Central

    Li, Xiaopeng; Sarma, S Das

    2015-01-01

    Versatile controllability of interactions in ultracold atomic and molecular gases has now reached an era where quantum correlations and unconventional many-body phases can be studied with no corresponding analogues in solid-state systems. Recent experiments in Rydberg atomic gases have achieved exquisite control over non-local interactions, allowing novel quantum phases unreachable with the usual local interactions in atomic systems. Here we study Rydberg-dressed atomic fermions in a three-dimensional optical lattice predicting the existence of hitherto unheard-of exotic mixed topological density wave phases. By varying the spatial range of the non-local interaction, we find various chiral density waves with spontaneous time-reversal symmetry breaking, whose quasiparticles form three-dimensional quantum Hall and Weyl semimetal states. Remarkably, certain density waves even exhibit mixed topologies beyond the existing topological classification. Our results suggest gapless fermionic states could exhibit far richer topology than previously expected. PMID:25972134

  9. Ultrafast quantum random access memory utilizing single Rydberg atoms in a Bose-Einstein condensate.

    PubMed

    Patton, Kelly R; Fischer, Uwe R

    2013-12-13

    We propose a long-lived and rapidly accessible quantum memory unit, for which the operational Hilbert space is spanned by states involving the two macroscopically occupied hyperfine levels of a miscible binary atomic Bose-Einstein condensate and the Rydberg state of a single atom. It is shown that an arbitrary qubit state, initially prepared using a flux qubit, can be rapidly transferred to and from the trapped atomic ensemble in approximately 10 ns and with a large fidelity of 97%, via an effective two-photon process using an external laser for the transition to the Rydberg level. The achievable ultrafast transfer of quantum information therefore enables a large number of storage and retrieval cycles from the highly controllable quantum optics setup of a dilute ultracold gas, even within the typically very short flux qubit lifetimes of the order of microseconds. PMID:24483637

  10. Ultrafast Quantum Random Access Memory Utilizing Single Rydberg Atoms in a Bose-Einstein Condensate

    NASA Astrophysics Data System (ADS)

    Patton, Kelly R.; Fischer, Uwe R.

    2013-12-01

    We propose a long-lived and rapidly accessible quantum memory unit, for which the operational Hilbert space is spanned by states involving the two macroscopically occupied hyperfine levels of a miscible binary atomic Bose-Einstein condensate and the Rydberg state of a single atom. It is shown that an arbitrary qubit state, initially prepared using a flux qubit, can be rapidly transferred to and from the trapped atomic ensemble in approximately 10 ns and with a large fidelity of 97%, via an effective two-photon process using an external laser for the transition to the Rydberg level. The achievable ultrafast transfer of quantum information therefore enables a large number of storage and retrieval cycles from the highly controllable quantum optics setup of a dilute ultracold gas, even within the typically very short flux qubit lifetimes of the order of microseconds.

  11. Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio

    E-print Network

    Masaki Hori; Anna Sótér; Daniel Barna; Andreas Dax; Ryugo Hayano; Susanne Friedreich; Bertalan Juhász; Thomas Pask; Eberhard Widmann; Dezsö Horváth; Luca Venturelli; Nicola Zurlo

    2013-06-06

    Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium ($\\bar{p}{\\rm He}^+$) is a three-body atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton ($\\bar{p}$) occupying a Rydberg state with high principal and angular momentum quantum numbers, respectively $n$ and $\\ell$, such that $n\\sim\\ell\\sim 38$. These atoms are amenable to precision laser spectroscopy, the results of which can in principle be used to determine the antiproton-to-electron mass ratio and to constrain the equality between the antiproton and proton charges and masses. Here we report two-photon spectroscopy of antiprotonic helium, in which $\\bar{p}{\\rm ^3He^+}$ and $\\bar{p}{\\rm ^4He^+}$ isotopes are irradiated by two counter-propagating laser beams. This excites nonlinear, two-photon transitions of the antiproton of the type $(n,\\ell)\\rightarrow (n-2,\\ell-2)$ at deep-ultraviolet wavelengths ($\\lambda$=139.8, 193.0 and 197.0nm), which partly cancel the Doppler broadening of the laser resonance caused by the thermal motion of the atoms. The resulting narrow spectral lines allowed us to measure three transition frequencies with fractional precisions of 2.3-5 parts in $10^9$. By comparing the results with three-body quantum electrodynamics calculations, we derived an antiproton-to-electron mass ratio of 1,836.1526736(23), where the parenthetical error represents one standard deviation. This agrees with the proton-to-electron value known to a similar precision.

  12. Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio.

    PubMed

    Hori, Masaki; Sótér, Anna; Barna, Daniel; Dax, Andreas; Hayano, Ryugo; Friedreich, Susanne; Juhász, Bertalan; Pask, Thomas; Widmann, Eberhard; Horváth, Dezso; Venturelli, Luca; Zurlo, Nicola

    2011-07-28

    Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium (pHe(+)) is a three-body atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton (p) occupying a Rydberg state with high principal and angular momentum quantum numbers, respectively n and l, such that n???l?+?1???38. These atoms are amenable to precision laser spectroscopy, the results of which can in principle be used to determine the antiproton-to-electron mass ratio and to constrain the equality between the antiproton and proton charges and masses. Here we report two-photon spectroscopy of antiprotonic helium, in which p(3)He(+) and p(4)He(+) isotopes are irradiated by two counter-propagating laser beams. This excites nonlinear, two-photon transitions of the antiproton of the type (n, l)???(n?-?2, l?-?2) at deep-ultraviolet wavelengths (? = 139.8, 193.0 and 197.0?nm), which partly cancel the Doppler broadening of the laser resonance caused by the thermal motion of the atoms. The resulting narrow spectral lines allowed us to measure three transition frequencies with fractional precisions of 2.3-5 parts in 10(9). By comparing the results with three-body quantum electrodynamics calculations, we derived an antiproton-to-electron mass ratio of 1,836.1526736(23), where the parenthetical error represents one standard deviation. This agrees with the proton-to-electron value known to a similar precision. PMID:21796208

  13. Trapping Rydberg Atoms in an Optical Lattice

    SciTech Connect

    Anderson, S. E.; Younge, K. C.; Raithel, G. [FOCUS Center, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2011-12-23

    Rubidium Rydberg atoms are laser excited and subsequently trapped in a one-dimensional optical lattice (wavelength 1064 nm). Efficient trapping is achieved by a lattice inversion immediately after laser excitation using an electro-optic technique. The trapping efficiency is probed via analysis of the trap-induced shift of the two-photon microwave transition 50S{yields}51S. The inversion technique allows us to reach a trapping efficiency of 90%. The dependence of the efficiency on the timing of the lattice inversion and on the trap laser power is studied. The dwell time of 50D{sub 5/2} Rydberg atoms in the lattice is analyzed using lattice-induced photoionization.

  14. Magnetically stimulated diffusion of Rydberg gases.

    PubMed

    Dumin, Yurii V

    2013-01-18

    The specific kind of diffusion stimulated (rather than suppressed) by the external magnetic field, which was predicted for the first time by Schmelcher and Cederbaum in 1992, is considered here for the case of high-angular-momentum (i.e., approximately "circular") Rydberg atoms. The coefficient of such diffusion was calculated by a purely analytical approach and was found to be very relevant to the experiments on antihydrogen formation. PMID:23373921

  15. Evolution from a Molecular Rydberg Gas to an Ultracold Plasma in a Seeded Supersonic Expansion of NO

    SciTech Connect

    Morrison, J. P.; Rennick, C. J.; Keller, J. S.; Grant, E. R. [Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z3 (Canada)

    2008-11-14

    We report the spontaneous formation of a plasma from a gas of cold Rydberg molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1 K in a seeded supersonic molecular beam, to single Rydberg states extending as deep as 80 cm{sup -1} below the lowest ionization threshold. The density of excited molecules in the illuminated volume approaches 1x10{sup 13} cm{sup -3}. This population evolves to produce free electrons and a durable cold plasma of electrons and intact NO{sup +} ions.

  16. Equation of state of helium and polybutene and Raman spectrum of water at high shock pressures and temperatures

    Microsoft Academic Search

    W. J. Nellis; N. C. Holmes; A. C. Mitchell; R. J. Trainor; M. B. Boslough; F. H. Ree; G. E. Walrafen

    1983-01-01

    Hugoniot EOS measurements on liquid helium are in good agreement with theory of Young et al. The Raman spectrum of shocked water showed that the O-H stretch band was red-shifted about 15 cm⁻¹ and narrowed about 20%. Hugoniot P-V and shock temperature data for polybutene are in good agreement with a Mie-Grueneisen model. (DLC)

  17. Effects Induced by Nuclear Motion on the Ground State Energies of Helium and 1s-Helium Isoelectronic Series from Lithium to Xenon

    Microsoft Academic Search

    R. L. Pavlov; J. Maruani; L. M. Mihailov; L. I. Pavlov; Ch. J. Velchev; M. Dimitrova-Ivanovich; V. O. Nesterenko

    The non-relativistic energy magnitudes for the ground state of He and He isoelec- tronic series with atomic number Z =3 ÷ 54, are calculated. Calculations are performed using an explicitly correlated trial wave-functions of the generalized Hylleraas type. We have developed a variational procedure that allows solving the two-particle Schroedinger equation for a practically unlimited number of parameters in a

  18. Field ionization of Rydberg atoms in a single-cycle pulse

    NASA Astrophysics Data System (ADS)

    Yang, B. C.; Robicheaux, F.

    2015-04-01

    We study the ionization of Rydberg atoms in a single-cycle-pulse electric field based on both classical and quantum calculations. The ionization-probability curve exhibits a "ripple" structure as a function of the pulse duration and the field amplitude. These ripple structures are found to be dependent on the angular distribution of the initial state. A large electron-emission asymmetry is observed, and the ionized electron is almost completely emitted to one side of the atom except when the pulse length is roughly one Rydberg period. In both the long-pulse and the short-pulse regimes, larger electron energy can be expected from the ionization of lower-lying Rydberg states, matching the observation in a recent experiment [S. Li and R. R. Jones, Phys. Rev. Lett. 112, 143006 (2014), 10.1103/PhysRevLett.112.143006]. This trend is closely related to the electron-emission asymmetry associated with the field-direction change in a single-cycle pulse. The possible implications of the different energy transfer in a single-cycle pulse from that in a multicycle pulse are also discussed briefly for the strong-field ionization of the ground atomic state.

  19. Spatial correlations between Rydberg atoms in an optical dipole trap

    NASA Astrophysics Data System (ADS)

    Schwarzkopf, A.; Anderson, D. A.; Thaicharoen, N.; Raithel, G.

    2013-12-01

    We use direct spatial ion imaging of cold 85Rb Rydberg atom clouds to measure the Rydberg-Rydberg correlation function, with and without light-shift potentials generated by an optical dipole trap. We find that the blockade radius depends on laser detunings and spatially varying light shifts. At certain laser detunings the probability of exciting Rydberg atoms at particular separations is enhanced, which we interpret to be a result of direct two-photon excitation of Rydberg atom pairs. The results are in accordance with predictions [F. Robicheaux and J. V. Hernández, Phys. Rev. A 72, 063403 (2005), 10.1103/PhysRevA.72.063403] and a model we develop that accounts for a one-dimensional dipole-trap potential.

  20. Rydberg Electrons in a Bose-Einstein Condensate

    NASA Astrophysics Data System (ADS)

    Wang, Jia; Gacesa, Marko; Côté, R.

    2015-06-01

    We investigate a hybrid system composed of ultracold Rydberg atoms immersed in an atomic Bose-Einstein condensate (BEC). The coupling between Rydberg electrons and BEC atoms leads to excitations of phonons, the exchange of which induces a Yukawa interaction between Rydberg atoms. Because of the small electron mass, the effective charge associated with this quasiparticle-mediated interaction can be large. Its range, equal to the BEC healing length, is tunable using Feshbach resonances to adjust the scattering length between BEC atoms. We find that for small healing lengths, the distortion of the BEC can "image" the Rydberg electron wave function, while for large healing lengths the induced attractive Yukawa potentials between Rydberg atoms are strong enough to bind them.

  1. Excitation dynamics of interacting Rydberg atoms in small lattices

    NASA Astrophysics Data System (ADS)

    Wu, G.; Kurz, M.; Liebchen, B.; Schmelcher, P.

    2015-01-01

    We study the Rydberg excitation dynamics of laser-driven atoms confined in a one-dimensional three-site lattice with open boundary conditions. Different regular excitation patterns are obtained within various parameter regimes. In the case of a weak Rydberg-Rydberg interaction, the excitation probability possesses a nodal structure which is characterized by an envelope with a period inversely proportional to the interaction. For strong Rydberg interaction we observe dipole blockade and antiblockade effects and an appropriate detuning leads to an overall oscillatory behavior of the Rydberg probability density which is modulated only by small oscillations. Besides an exact diagonalization procedure we study the system by performing first and second order perturbation theory as well as a spectral analysis.

  2. The helium fine-structure controversy Ingvar Lindgren

    E-print Network

    Lindgren, Ingvar

    The helium fine-structure controversy Ingvar Lindgren Physics Department, University of Gothenburg of the lowest P state of the neutral helium atom. We believe that we have found a minor error in the formulas is not known at present. 1 Introduction The fine structure of the lowest P state of neutral helium is of great

  3. Production of trilobite Rydberg molecule dimers with kilo-Debye permanent electric dipole moments

    NASA Astrophysics Data System (ADS)

    Booth, D.; Rittenhouse, S. T.; Yang, J.; Sadeghpour, H. R.; Shaffer, J. P.

    2015-04-01

    Permanent electric dipole moments are important for understanding symmetry breaking in molecular physics, control of chemical reactions, and realization of strongly correlated many-body quantum systems. However, large molecular permanent electric dipole moments are challenging to realize experimentally. We report the observation of ultralong-range Rydberg molecules with bond lengths of ~100 nanometers and kilo-Debye permanent electric dipole moments that form when an ultracold ground-state cesium (Cs) atom becomes bound within the electronic cloud of an extended Cs electronic orbit. The electronic character of this hybrid class of “trilobite” molecules is dominated by degenerate Rydberg manifolds, making them difficult to produce by conventional photoassociation. We used detailed coupled-channel calculations to reproduce their properties quantitatively. Our findings may lead to progress in ultracold chemistry and strongly correlated many-body physics.

  4. Formation of antiprotonic helium p ¯He+ and ionization in low-energy collisions of p ¯ with He in the ground 1 1S and metastable 2 3S and 2 1S states

    NASA Astrophysics Data System (ADS)

    Sakimoto, Kazuhiro

    2015-04-01

    Calculations of low-energy collisions of antiprotons p ¯ with helium atoms in the ground (1 1S) and metastable (2 3S and 2 1S ) states are carried out by using a semiclassical method and by further assuming that one of the two electrons is passive. Antiproton capture to form antiprotonic helium (?p ¯He++e ) and breakup ionization (?p ¯+He++e ) are investigated. The energy dependence of the capture and ionization cross sections and the distributions of the product states are presented and compared with previous theoretical calculations. For the metastable helium targets, most of the p ¯He+ atoms produced in the capture have long lifetimes against subsequent Auger decays and can be observed experimentally. For the ground-state targets, however, the formation of such long-lived states is rather a rare event at low collision energies.

  5. Equation of state of helium and polybutene and Raman spectrum of water at high shock pressures and temperatures

    SciTech Connect

    Nellis, W.J.; Holmes, N.C.; Mitchell, A.C.; Trainor, R.J.; Boslough, M.B.; Ree, F.H.; Walrafen, G.E.

    1983-08-01

    Hugoniot EOS measurements on liquid helium are in good agreement with theory of Young et al. The Raman spectrum of shocked water showed that the O-H stretch band was red-shifted about 15 cm/sup -1/ and narrowed about 20%. Hugoniot P-V and shock temperature data for polybutene are in good agreement with a Mie-Grueneisen model. (DLC)

  6. Dynamics of multiphoton excitation and quantum diffusion in Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Wang, Kwanghsi; Chu, Shih-I.

    1989-02-01

    We present a detailed two-dimensional (2D) quantal study of the dynamical evolution of microwave-driven Rydberg H atoms. We examine the range of validity of the conventional one-dimensional (1D) models and explore the frequency- and intensity-dependent excitation and ionization mechanisms. The main findings of this paper can be summarized as follows: (i) The excitation spectra of Rydberg H atoms are strongly frequency dependent and can be roughly grouped into three characteristically different regions, each with a different excitation mechanism. In this paper, we emphasize the study of the two major excitation mechanisms: quantum diffusion and multiphoton resonant excitation. The region dominated by quantum diffusion lies in the frequency range ?cstate); ?c, the classical chaotic threshold; and ?d, the quantum delocalization border. In this region, quasienergy levels are strongly perturbed and mixed and excitation is efficient, leading to the so-called underthreshold photoelectric ionization phenomenon. On the other hand, we found a series of frequency regions (in ?0>?d) where the ionization is mainly due to multiphoton resonant excitation through the more isolated quasienergy avoided crossing points. (ii) The excitation pathways (1D versus 2D) are strongly intensity dependent. For microwave (rescaled) field strength ?0 (??n40) in the range ?cRydberg atom excitation and ionization proceed through n2>0 ladders rather than the n2=0 ladder, as often assumed in the 1D model. As field strength increases above ?q, however, the 1D model improves significantly. (iii) The quantum localization phenomenon is observed in the classically chaotic region (?c?q. (iv) The stability of quantum diffusive motion is analyzed in terms of the quantal phase-space diagram and the autocorrelation function. The results lend support to the view that quantum mechanics can impose limitations on classical chaotic motion. (v) The way of turning on the field (sin?t or cos?t) does not affect significantly the dynamical evolution of the system. (vi) Finally, a computationally powerful new technique, invoking the use of artificial intelligence algorithms as well as the generalized Van Vleck perturbation theory for effectively reducing the dimensionality of the Floquet matrix, is introduced to facilitate the study of multiphoton resonant excitation of Rydberg atoms.

  7. Fixed-phase correlation-function quantum Monte Carlo calculations for ground and excited states of helium in neutron-star magnetic fields

    NASA Astrophysics Data System (ADS)

    Meyer, Dirk; Boblest, Sebastian; Wunner, Günter

    2013-03-01

    We apply the correlation-function quantum Monte Carlo (CFQMC) method to the calculation of the energies of ground and excited states for helium in neutron-star magnetic fields. The method has been successfully applied by Jones, Ortiz, and Ceperley to the calculation of helium in white dwarf magnetic fields [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.55.6202 55, 6202 (1997)]. We extend the accessible range of magnetic field strengths by introducing a fixed-phase variant of the CFQMC method. We find that with growing magnetic field strength the variances increase significantly and put a limit to the applicability of the method for atoms in strong magnetic fields. The behavior of the variances is traced back to the logarithmic divergence of the energy of the bosonic ground state with increasing magnetic field strength. We use basis sets, which account for the growing dominance of the cylindrical symmetry as the magnetic field is increased and incorporate them into the CFQMC algorithm. These basis sets are taken from Hartree-Fock calculations, performed using a B-Spline and Landau expansion beyond the adiabatic approximation.

  8. AB INITIO EQUATION OF STATE FOR HYDROGEN-HELIUM MIXTURES WITH RECALIBRATION OF THE GIANT-PLANET MASS-RADIUS RELATION

    SciTech Connect

    Militzer, B. [Departments of Earth and Planetary Science and of Astronomy, University of California, Berkeley, CA 94720 (United States); Hubbard, W. B. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

    2013-09-10

    Using density functional molecular dynamics simulations, we determine the equation of state (EOS) for hydrogen-helium mixtures spanning density-temperature conditions typical of giant-planet interiors, {approx}0.2-9 g cm{sup -3} and 1000-80,000 K for a typical helium mass fraction of 0.245. In addition to computing internal energy and pressure, we determine the entropy using an ab initio thermodynamic integration technique. A comprehensive EOS table with 391 density-temperature points is constructed and the results are presented in the form of a two-dimensional free energy fit for interpolation. Deviations between our ab initio EOS and the semi-analytical EOS model by Saumon and Chabrier are analyzed in detail, and we use the results for initial revision of the inferred thermal state of giant planets with known values for mass and radius. Changes are most pronounced for planets in the Jupiter mass range and below. We present a revision to the mass-radius relationship that makes the hottest exoplanets increase in radius by {approx}0.2 Jupiter radii at fixed entropy and for masses greater than {approx}0.5 Jupiter mass. This change is large enough to have possible implications for some discrepant ''inflated giant exoplanets''.

  9. Spatially Resolved Observation of Dipole-Dipole Interaction between Rydberg Atoms

    SciTech Connect

    Ditzhuijzen, C. S. E. van; Noordam, L. D.; Heuvell, H. B. van Linden van den [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands); Koenderink, A. F. [FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); Hernandez, J. V.; Robicheaux, F. [Department of Physics, Auburn University, Alabama 36849-5311 (United States)

    2008-06-20

    We have observed resonant energy transfer between cold Rydberg atoms in spatially separated cylinders. Resonant dipole-dipole coupling excites the 49s atoms in one cylinder to the 49p state while the 41d atoms in the second cylinder are transferred down to the 42p state. We have measured the production of the 49p state as a function of separation of the cylinders (0-80 {mu}m) and the interaction time (0-25 {mu}s). In addition, we measured the width of the electric field resonances. A full many-body quantum calculation reproduces the main features of the experiments.

  10. Computational design of solid-state interfaces using O-lattice theory: An application to mitigating helium-induced damage

    NASA Astrophysics Data System (ADS)

    Yuryev, D. V.; Demkowicz, M. J.

    2014-12-01

    Tailoring interface structure to control interface properties promises to improve performance in a wide range of structural materials. We demonstrate an approach for designing interfaces with pre-specified internal structure and functionality using O-lattice theory. To illustrate our method, we design an interface intended to mitigate helium (He)-induced damage by promoting precipitation of He into continuous linear channels. A similar top-down design process may be used to tailor interfaces for other applications such as improved mechanical properties.

  11. Femtosecond time-resolved EUV photoionization studies of ultrafast dynamics in helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Gessner, Oliver; Kornilov, Oleg; Buenermann, Oliver; Leone, Stephen; Neumark, Daniel

    2010-03-01

    By combining a femtosecond high harmonic generation (HHG) light source with state-of-the art photoelectron and ion imaging techniques, a new set of tools has been created to probe electronic and nuclear dynamics in EUV excited atoms, molecules and clusters in real-time. The new technique has been applied to the study of electronic and nuclear dynamics of electronically excited helium nanodroplets (HeN, ˜2x10^6). Femtosecond time-resolved photoelectron imaging experiments reveal two relaxation timescales, 280 fs and 2.8 ps, that we associate with an intraband transition and relaxation between two separate electronic bands, respectively. Rapid emission of Rydberg atoms is indicated by transient photoelectron spectra and preliminary results from femtosecond time-resolved ion imaging experiments. Mass- and momentum-resolved transient ion spectra reveal complex dynamics in the production of electronically excited cluster fragments. The observations are compared with first results of ab-initio calculations on the electronically excited states of the parent cluster and ionization dynamics of cluster fragments.

  12. Atmospheric helium capillary dielectric barrier discharge for soft ionization: determination of atom number densities in the lowest excited and metastable States.

    PubMed

    Horvatic, Vlasta; Müller, Saskia; Veza, Damir; Vadla, Cedomil; Franzke, Joachim

    2014-01-01

    The populations of the lowest excited helium states 2s 3S1, 2s 1S, 2p 3P0 J, and 2p 1P0 created in an atmospheric helium capillary dielectric barrier discharge were determined by means of optical emission spectroscopy. The emitted intensities of 388, 501, 587, and 667 nm lines were measured side-on and end-on with respect to the discharge axis. The comparison of optically thin side-on spectra with end-on spectra, which exhibited the absorption effects in the line kernels, enabled the determination of the average values of the number densities n1 in the considered He states along the plasma length L. The field of the theoretical profiles for a series of the n1L parameters pertinent to the experimental conditions was calculated for each line. By introducing the experimental data into the field of calculated curves, n1L corresponding to the particular state could be obtained. The measurements of the emission profiles were done as a function of the discharge voltage in the range covering homogeneous as well as filamentary DBD operation mode. Due to nonuniformity of the excited atom density distribution along the plasma, the values of n1 could be obtained only in the homogeneous operation mode where the nonuniformity was small. The following maximum values were found for the number densities in the investigated states: n1 av (2s 3S1) = (2.9 ± 1.1) × 1013 cm?3, n1 av (2s 1S) = (1.4 ± 0.5) × 1013 cm?3, n1 av (2p 3P0 J) = (1.1 ± 0.4) × 1013 cm?3, n1 av (2p 1P0) = (4.2 ± 1.6) × 1012 cm?3, and they represent the average populations along the plasma column in the capillary. PMID:24320177

  13. Rydberg series of calcium monofluoride : spectrum, structure, and dynamics

    E-print Network

    Kay, Jeffrey J

    2007-01-01

    This thesis summarizes progress toward the ultimate goal of building a complete structural and dynamical model for the CaF molecule. The quantum defects of the Rydberg series of the molecule, as well as their dependences ...

  14. A precision millimeter-wave measurement of the Rydberg frequency

    E-print Network

    De Vries, Joel Christopher, 1971-

    2002-01-01

    The Rydberg frequency, cR[infinity], sets the frequency scale for the spectrum of hydrogen atoms. From a frequency measurement of one transition in hydrogen, cR[infinity] can be extracted and the frequency of any other ...

  15. Van der Waals explosion of cold Rydberg clusters

    E-print Network

    Faoro, R; Archimi, M; Masella, G; Valado, M M; Arimondo, E; Mannella, R; Ciampini, D; Morsch, O

    2015-01-01

    We report on the direct measurement in real space of the effect of the van der Waals forces between individual Rydberg atoms on their external degrees of freedom. Clusters of Rydberg atoms with inter-particle distances of around 5 {\\mu}m are created by first generating a small number of seed excitations in a magneto-optical trap, followed by off-resonant excitation that leads to a chain of facilitated excitation events. After a variable expansion time the Rydberg atoms are field ionized, and from the arrival time distributions the size of the Rydberg cluster after expansion is calculated. Our experimental results agree well with a numerical simulation of the van der Waals explosion.

  16. Van der Waals explosion of cold Rydberg clusters

    E-print Network

    R. Faoro; C. Simonelli; M. Archimi; G. Masella; M. M. Valado; E. Arimondo; R. Mannella; D. Ciampini; O. Morsch

    2015-06-28

    We report on the direct measurement in real space of the effect of the van der Waals forces between individual Rydberg atoms on their external degrees of freedom. Clusters of Rydberg atoms with inter-particle distances of around 5 {\\mu}m are created by first generating a small number of seed excitations in a magneto-optical trap, followed by off-resonant excitation that leads to a chain of facilitated excitation events. After a variable expansion time the Rydberg atoms are field ionized, and from the arrival time distributions the size of the Rydberg cluster after expansion is calculated. Our experimental results agree well with a numerical simulation of the van der Waals explosion.

  17. version 1.0 Hyper ne structure of muonic helium

    E-print Network

    Pachucki, Krzysztof

    version 1.0 Hyper#12;ne structure of muonic helium Krzysztof Pachucki #3; Institute of Theoretical state muonic helium is calculated numer- ically using the variational approach. Comparison to former Typeset using REVT E X #3; E-mail address: krp@fuw.edu.pl 1 #12; Muonic helium is an exotic atom

  18. Quantum mechanicallycomplete measurements in electron impact excitation of helium

    E-print Network

    Quantum mechanicallycomplete measurements in electron impact excitation of helium Andrew G. Mikosza, Nedlands, Perth. 6907, Australia. Abstract. A complete quantum description of the 3! D state of helium, with the Convergent Close Coupling (CCC) calculations. Previous data for helium at 40eV incident electrons

  19. Helium fine structure theory for determination of Krzysztof Pachucki

    E-print Network

    Pachucki, Krzysztof

    Helium fine structure theory for determination of Krzysztof Pachucki Institute of Theoretical in the calculation of helium fine-structure splitting of the 23 PJ states, based on the quantum electrodynamic theory by comparison with all experimental results for light helium-like ions and with the known large nuclear charge

  20. ccsd00000660 Analysis of Photoassociation Spectra for Giant Helium Dimers.

    E-print Network

    of metastable helium atoms. The experimental spectrum obtained with the PA laser tuned closed to the 2 3 S1 $ 2 and evaporatively cooled metastable helium gas. We have thereby achieved greater state selectivity, higher density by photoas- sociation of metastable helium atoms, with the PA laser #3; Electronic address: leonard

  1. Selective population of spin-orbit levels in the autoionization of a polyatomic molecule: Branching ratios and asymmetry parameters for the Tanaka-Ogawa Rydberg series in CO2

    NASA Astrophysics Data System (ADS)

    Parr, A. C.; Dehmer, P. M.; Dehmer, J. L.; Ueda, K.; West, J. B.; Siggel, M. R. F.; Hayes, M. A.

    1994-06-01

    The spin-orbit selectivity of angle-resolved photoelectron spectra was used to provide new information on the electronic structure, symmetry, and decay dynamics of members of the autoionizing Tanaka-Ogawa Rydberg series in CO2. This represents the first time that spin-orbit selectivity has been used to obtain such information for a polyatomic molecule. The spin-orbit photoelectron branching ratios were used to show that the angular momentum quantum number ? of the excited Rydberg electron does not change upon autoionization. Furthermore, a consideration of the present results together with previous calculations of the relative intensities of the discrete and continuum ionization channels shows that the most probable electron configuration for the Tanaka-Ogawa Rydberg series is ...(?u)3(?g)4nd?g and that autoionization proceeds primarily via a d?g??f?u process for the totally symmetric vibronic components of the ion. The asymmetry parameter ? was determined for individual spin-orbit components of the various vibronic bands of the X˜ 2?g state and is discussed in terms of recent theoretical calculations. The Rydberg series appears to be well described by ?c? coupling, even for relatively low principal quantum numbers. The general utility of this technique for autoionizing Rydberg states and its extension to multiphoton ionization of Rydberg states that lie below the first ionization threshold are discussed.

  2. Supersolid vortex crystals in Rydberg-dressed Bose-Einstein condensates.

    PubMed

    Henkel, N; Cinti, F; Jain, P; Pupillo, G; Pohl, T

    2012-06-29

    We study rotating quasi-two-dimensional Bose-Einstein condensates, in which atoms are dressed to a highly excited Rydberg state. This leads to weak effective interactions that induce a transition to a mesoscopic supersolid state. Considering slow rotation, we determine its superfluidity using quantum Monte Carlo simulations as well as mean field calculations. For rapid rotation, the latter reveal an interesting competition between the supersolid crystal structure and the rotation-induced vortex lattice that gives rise to new phases, including arrays of mesoscopic vortex crystals. PMID:23004994

  3. Steady state heat transfer experimental studies of LHC superconducting cables operating in cryogenic environment of superfluid helium

    E-print Network

    Santandrea, Dario; Tuccillo, Raffaele; Granieri, Pier Paolo.

    The heat management is a basic and fundamental aspect of the superconducting magnets used in the CERN Large Hadron Collider. Indeed, the coil temperature must be kept below the critical value, despite the heat which can be generated or deposited in the magnet during the normal operations. Therefore, this thesis work aims at determining the heating power which can be extracted from the superconducting cables of the LHC, specially through their electrical insulation which represents the main thermal barrier. An experimental measurement campaign in superfluid helium bath was performed on several samples reproducting the main LHC magnets. The heating power was generated in the sample by Joule heating and the temperature increase was measured by means of Cernox bare chip and thermocouples. An innovative instrumentation technique which also includes the in-situ calibration of the thermocouples was developed. A thorough uncertainty analysis on the overall measurement chain concluded the experimental setup. The prese...

  4. One- and two-photon spectroscopy of highly excited states of alkali-metal atoms on helium nanodroplets

    SciTech Connect

    Pifrader, Alexandra; Allard, Olivier; Auboeck, Gerald; Callegari, Carlo; Ernst, Wolfgang E. [Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz (Austria); Huber, Robert [Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Ancilotto, Francesco [Dipartimento di Fisica 'G. Galilei', Universita di Padova, via Marzolo 8, I-35131 Padova, Italy and CNR-IOM-Democritos, I-34014 Trieste (Italy)

    2010-10-28

    Alkali-metal atoms captured on the surface of superfluid helium droplets are excited to high energies ({approx_equal}3 eV) by means of pulsed lasers, and their laser-induced-fluorescence spectra are recorded. We report on the one-photon excitation of the (n+1)p(leftarrow)ns transition of K, Rb, and Cs (n=4, 5, and 6, respectively) and on the two-photon one-color excitation of the 5d(leftarrow)5s transition of Rb. Gated-photon-counting measurements are consistent with the relaxation rates of the bare atoms, hence consistent with the reasonable expectation that atoms quickly desorb from the droplet and droplet-induced relaxation need not be invoked.

  5. One- and two-photon spectroscopy of highly excited states of alkali-metal atoms on helium nanodroplets.

    PubMed

    Pifrader, Alexandra; Allard, Olivier; Auböck, Gerald; Callegari, Carlo; Ernst, Wolfgang E; Huber, Robert; Ancilotto, Francesco

    2010-10-28

    Alkali-metal atoms captured on the surface of superfluid helium droplets are excited to high energies (?3?eV) by means of pulsed lasers, and their laser-induced-fluorescence spectra are recorded. We report on the one-photon excitation of the (n+1)p?ns transition of K, Rb, and Cs (n=4, 5, and 6, respectively) and on the two-photon one-color excitation of the 5d?5s transition of Rb. Gated-photon-counting measurements are consistent with the relaxation rates of the bare atoms, hence consistent with the reasonable expectation that atoms quickly desorb from the droplet and droplet-induced relaxation need not be invoked. PMID:21033800

  6. Atomic Rydberg reservoirs for polar molecules.

    PubMed

    Zhao, B; Glaetzle, A W; Pupillo, G; Zoller, P

    2012-05-11

    We discuss laser-dressed dipolar and van der Waals interactions between atoms and polar molecules, so that a cold atomic gas with laser admixed Rydberg levels acts as a designed reservoir for both elastic and inelastic collisional processes. The elastic scattering channel is characterized by large elastic scattering cross sections and repulsive shields to protect from close encounter collisions. In addition, we discuss a dissipative (inelastic) collision where a spontaneously emitted photon carries away (kinetic) energy of the collision partners, thus providing a significant energy loss in a single collision. This leads to the scenario of rapid thermalization and cooling of a molecule in the mK down to the ?K regime by cold atoms. PMID:23003036

  7. Charged clusters in liquid helium

    NASA Astrophysics Data System (ADS)

    Dyugaev, A. M.; Grigor'ev, P. D.; Lebedeva, E. V.

    2010-03-01

    The appropriateness of the experimental study of charged clusters in liquid helium has been supported. The interaction potential of negative ions (electron bubbles) with inert clusters formed by Ne, Ar, Kr, and Xe atoms or H2 and N2 molecules has been found. Small clusters levitate at a distance of 13-16 Å above the negative ion. The scalings laws for the properties of charged inert clusters have been discovered and grounded; the number of quantum levels and states of such clusters has been determined. The mobility measurement of charged clusters may provide a new technique of probing the properties of impurity nanoparticles in helium.

  8. ATOMIC AND MOLECULAR PHYSICS: Scaled-energy spectroscopy of a |M| = 1 Rydberg barium atom in an electric field

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Quan, Wei; Shen, Li; Yang, Hai-Feng; Shi, Ting-Yun; Liu, Xiao-Jun; Liu, Hong-Ping; Zhan, Ming-Sheng

    2009-11-01

    We observe strong energy-dependent quantum defects in the scaled-energy Stark spectra for |M| = 1 Rydberg states of barium atoms at three scaled energies: ? = -2.000, ? = -2.500 and ? = -3.000. In an attempt to explain the observations, theoretical calculations of closed orbit theory based on a model potential including core effect are performed for non-hydrogenic atoms. While such a potential has been uniformly successful for alkali atoms with a single valence electron, it fails to match experimental results for barium atoms in the 6snp Rydberg states with two valence electrons. Our study points out that this discrepancy is due to the strong perturbation from the 5d8p state, which voids the simple approximation for constant quantum defects of principle quantum number n.

  9. Measurement of time-varying electric fields near an atom chip using cold Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Carter, J. D.; Martin, J. D. D.

    2013-05-01

    Inhomogeneous fluctuating electric fields near metal surfaces cause undesired heating or decoherence in devices which confine atoms or ions near such a surface (microfabricated ion traps or proposed gas-phase atom/solid-state hybrid quantum systems, for example). Heating of the motion of trapped ions has been used to measure the noise spectral density of these fields but the microscopic mechanism responsible is unknown. We have implemented a complementary measurement technique using cold atoms released from an atom chip and excited to Rydberg states. The dephasing of a coherent superposition of two Rydberg states is used to measure the inhomogeneous electric field, and spin-echo techniques are used to constrain the frequency scaling of the noise spectral density. Compared to ion trap measurements, this technique has the advantage of flexibility in varying parameters such as atom-surface distance since the atoms do not need to be trapped. Field noise at levels typical for room temperature ion traps is detectable in principle, though the frequency resolution and ultimate sensitivity are inferior to ion traps. Inhomogeneous fluctuating electric fields near metal surfaces cause undesired heating or decoherence in devices which confine atoms or ions near such a surface (microfabricated ion traps or proposed gas-phase atom/solid-state hybrid quantum systems, for example). Heating of the motion of trapped ions has been used to measure the noise spectral density of these fields but the microscopic mechanism responsible is unknown. We have implemented a complementary measurement technique using cold atoms released from an atom chip and excited to Rydberg states. The dephasing of a coherent superposition of two Rydberg states is used to measure the inhomogeneous electric field, and spin-echo techniques are used to constrain the frequency scaling of the noise spectral density. Compared to ion trap measurements, this technique has the advantage of flexibility in varying parameters such as atom-surface distance since the atoms do not need to be trapped. Field noise at levels typical for room temperature ion traps is detectable in principle, though the frequency resolution and ultimate sensitivity are inferior to ion traps. Work performed in collaboration with O. Cherry and supported by NSERC.

  10. Helium-Recycling Plant

    NASA Technical Reports Server (NTRS)

    Cook, Joseph

    1996-01-01

    Proposed system recovers and stores helium gas for reuse. Maintains helium at 99.99-percent purity, preventing water vapor from atmosphere or lubricating oil from pumps from contaminating gas. System takes in gas at nearly constant low back pressure near atmospheric pressure; introduces little or no back pressure into source of helium. Concept also extended to recycling of other gases.

  11. Motion-induced signal revival in pulsed Rydberg four-wave mixing beyond the frozen-gas limit

    NASA Astrophysics Data System (ADS)

    Huber, B.; Kölle, A.; Pfau, T.

    2014-11-01

    We present measurements on pulsed four-wave mixing involving a Rydberg state in an atomic vapor cell. The excitation to the Rydberg state is conducted by a pulsed two-photon excitation on the nanosecond time scale that is combined with a third cw laser in phase-matched geometry yielding light emission on the same time scale. An additional signal peak is observed shortly after the pulse that can be attributed to a revival of constructive interference between different velocity classes of the radiating atomic dipoles. Furthermore we investigate the density dependence of the four-wave mixing signal. From the shape of the respective curve we are able to confirm energy and momentum conservation in the photonic part of the system.

  12. Frustrated tunnel ionization of noble gas dimers with Rydberg-electron shakeoff by electron charge oscillation.

    PubMed

    von Veltheim, A; Manschwetus, B; Quan, W; Borchers, B; Steinmeyer, G; Rottke, H; Sandner, W

    2013-01-11

    Strong field single ionization of homo- and heteronuclear noble gas dimers with ultrashort infrared laser pulses is experimentally investigated. A pronounced photoelectron yield maximum is found for dimers in the momentum range |p|?0.1??a.u. which is absent for the corresponding monomer. This yield enhancement can be attributed to a new two-step strong field ionization mechanism active only in the dimers. In the first step, frustrated tunnel ionization at one of the atomic centers populates Rydberg states, which then become ionized in a second step through charge oscillation within the dimer ion core. PMID:23383900

  13. Mantle helium and carbon isotopes in Separation Creek Geothermal Springs, Three Sisters area, Central Oregon: Evidence for renewed volcanic activity or a long term steady state system?

    E-print Network

    van Soest, M.C.; Kennedy, B.M.; Evans, W.C.; Mariner, R.H.

    2002-01-01

    Mantle Helium and Carbon Isotopes in Separation CreekSeparation Creek area, the locus of current uplift at South Sister volcano show strong mantle signatures in helium andhelium isotopes, ? 13 C, and CO 2 / 3 He were not analyzed for Separation

  14. Helium technology issues

    NASA Technical Reports Server (NTRS)

    Kittel, Peter

    1987-01-01

    A number of future space missions require liquid helium for cooling scientific payloads. These missions will require the long term storage and resupply of liquid helium at temperatures of 1.4 - 2.1 Kelvin. In addition, some of the proposed instruments will require refrigeration to temperatures as low as 50 mK. A variety of liquid helium based refrigerator systems could provide this subkelvin cooling. The status of helium storage and refrigeration technologies and of several alternative technologies is presented here along with areas where further research and development are needed. (Helium resupply technologies are the topic of another presentation at this symposium). The technologies covered include passive and dynamic liquid helium storage, alternatives to liquid helium storage, He -3 refrigerators, He -3/He -4 dilution refrigerators, and alternative sub-kelvin coolers.

  15. Evolution of dopant-induced helium nanoplasmas

    E-print Network

    Krishnan, S R; Fechner, L; Sharma, V; Kremer, M; Fischer, B; Camus, N; Pfeifer, T; Jha, J; Krishnamurthy, M; Schroeter, C -D; Ullrich, J; Stienkemeier, F; Moshammer, R; Fennel, Th; Mudrich, M

    2012-01-01

    Two-component nanoplasmas generated by strong-field ionization of doped helium nanodroplets are studied in a pump-probe experiment using few-cycle laser pulses in combination with molecular dynamics simulations. High yields of helium ions and a pronounced, droplet size-dependent resonance structure in the pump-probe transients reveal the evolution of the dopant-induced helium nanoplasma. The pump-probe dynamics is interpreted in terms of strong inner ionization by the pump pulse and resonant heating by the probe pulse which controls the final charge states detected via the frustration of electron-ion recombination.

  16. Ion Beam Metastable fraction deduced from Rydberg Spectroscopy Background Levels

    NASA Astrophysics Data System (ADS)

    Smith, Chris; Lundeen, Stephen; Fehrenbach, Charles

    2014-05-01

    The metastable content of U6+, Pb4+ and Pb2+ ion beams from an ECR source was measured as a bi-product of spectroscopic studies of Rydberg levels of U5+, Pb3+, and Pb+ that used the Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique. Autoionization of metastable Rydberg levels within the Stark Ionization detector proves to be the dominant background and noise source with this technique. To reduce this background, a device was introduced to induce autoionization of metastable Rydberg levels prior to the detector. Measurements with this device enabled the deduction of the initial metastable fraction of the ion beam. Results varied from 20 - 50% for these beams. Supported by the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Science, US Department of Energy.

  17. Inversion symmetry breaking of atomic bound states in strong and short laser fields

    E-print Network

    Stooß, Veit; Ott, Christian; Blättermann, Alexander; Ding, Thomas; Pfeifer, Thomas

    2015-01-01

    In any atomic species, the spherically symmetric potential originating from the charged nucleus results in fundamental symmetry properties governing the structure of atomic states and transition rules between them. If atoms are exposed to external electric fields, these properties are modified giving rise to energy shifts such as the AC Stark-effect in varying fields and, contrary to this in a constant (DC) electric field for high enough field strengths, the breaking of the atomic symmetry which causes fundamental changes in the atom's properties. This has already been observed for atomic Rydberg states with high principal quantum numbers. Here, we report on the observation of symmetry breaking effects in Helium atoms for states with principal quantum number n=2 utilizing strong visible laser fields. These findings were enabled by temporally resolving the dynamics better than the sub-optical cycle of the applied laser field, utilizing the method of attosecond transient absorption spectroscopy (ATAS). We ident...

  18. ATOMIC AND MOLECULAR PHYSICS: Model Potential Calculations of Oscillator Strength Spectra of Rydberg Li Atoms in External Fields

    NASA Astrophysics Data System (ADS)

    Meng, Hui-Yan; Shi, Ting-Yun

    2009-08-01

    By combining the B-spline basis set with model potential (B-spline + MP), we present oscillator strength spectra of Rydberg Li atoms in external fields. The photoabsorption spectra are analyzed. Over the narrow energy ranges considered in this paper, the structure of the spectra can be independent of the initial state chosen for a given atom. Our results are in good agreement with previous high-precision experimental data and theoretical calculations, where the R-matrix approach together with multichannel quantum defect theory (R-matrix+MQDT) was used. It is suggested that the present methods can be applied to deal with the oscillator strength spectra of Rydberg atoms in crossed electric and magnetic fields.

  19. Analysis of high- n dielectronic Rydberg satellites in the spectra of Na -like Zn XX and Mg -like Zn XIX.

    PubMed

    Fournier, K B; Faenov, A Ya; Pikuz, T A; Magunov, A I; Skobelev, I Yu; Flora, F; Bollanti, S; Di Lazzaro, P; Murra, D; Belyaev, V S; Vinogradov, V I; Kyrilov, A S; Matafonov, A P; Francucci, M; Martellucci, S; Petrocelli, G

    2004-01-01

    We have observed spectra from highly charged zinc ions in a variety of laser-produced plasmas. Spectral features that are Na - and Mg -like satellites to high- n Rydberg transitions in the Ne -like Zn XXI spectrum are analyzed and modeled. Identifications and analysis are made by comparison with highly accurate atomic structure calculations and steady state collisional-radiative models. Each observed Zn XX and Zn XIX feature comprises up to approximately 2 dozen individual transitions, these transitions are excited principally by dielectronic recombination through autoionizing levels in Na - and Mg -like Zn19+ and Zn18+. We find these satellites to be ubiquitous in laser-produced plasmas formed by lasers with pulse lengths that span four orders of magnitude, from 1 ps to approximately 10 ns. The diagnostic potential of these Rydberg satellite lines is demonstrated. PMID:15324177

  20. Charged Condensate and Helium Dwarf Stars

    E-print Network

    Gregory Gabadadze; Rachel A. Rosen

    2008-09-26

    White dwarf stars composed of carbon, oxygen or heavier elements are expected to crystallize as they cool down below certain temperatures. Yet, simple arguments suggest that the helium white dwarf cores may not solidify, mostly because of zero-point oscillations of the helium ions that would dissolve the crystalline structure. We argue that the interior of the helium dwarfs may instead form a macroscopic quantum state in which the charged helium-4 nuclei are in a Bose-Einstein condensate, while the relativistic electrons form a neutralizing degenerate Fermi liquid. We discuss the electric charge screening, and the spectrum of this substance, showing that the bosonic long-wavelength fluctuations exhibit a mass gap. Hence, there is a suppression at low temperatures of the boson contribution to the specific heat -- the latter being dominated by the specific heat of the electrons near the Fermi surface. This state of matter may have observational signatures.

  1. Infrared optogalvanic measurements on helium and helium-hydrogen discharges

    Microsoft Academic Search

    S. A. M. Al-Chlabi; R. S. Stewart; R. Illingworth; I. S. Ruddock

    1983-01-01

    A tunable cwF-centre laser has been used for optogalvanic detection of the helium 41,3F-61,3G transition at 2.624 mu m. From a fully quantitative analysis, including measurement of the line absorption coefficient, the authors have determined a value for the ionisation efficiency per laser photon absorbed using a steady-state model of the positive column. This value agrees well with the efficiency

  2. Strongly Correlated Growth of Rydberg Aggregates in a Vapor Cell

    NASA Astrophysics Data System (ADS)

    Urvoy, A.; Ripka, F.; Lesanovsky, I.; Booth, D.; Shaffer, J. P.; Pfau, T.; Löw, R.

    2015-05-01

    The observation of strongly interacting many-body phenomena in atomic gases typically requires ultracold samples. Here we show that the strong interaction potentials between Rydberg atoms enable the observation of many-body effects in an atomic vapor, even at room temperature. We excite Rydberg atoms in cesium vapor and observe in real time an out-of-equilibrium excitation dynamics that is consistent with an aggregation mechanism. The experimental observations show qualitative and quantitative agreement with a microscopic theoretical model. Numerical simulations reveal that the strongly correlated growth of the emerging aggregates is reminiscent of soft-matter type systems.

  3. Correlated Atomic Pair Functions by the e-?-Method. I. Ground State 11S and Lowest Excited States n1S (n > 1) and n3S of Helium

    NASA Astrophysics Data System (ADS)

    Seelig, F. F.; Becker, G. A.

    1999-12-01

    Some low n1S and n3S states of the helium atom are computed with the aid of the e-e method which formulates the electronic wave function of the 2 electrons ? = e-e F, where ?=Z(r1+r2)-½r12 and here Z = 2. Both the differential and the integral equation for F contain a pseudopotential ? instead of the true potential V that contrary to V is finite. For the ground state, F = 1 yields nearly the Hartree-Fock SCF accuracy, whereas a multinomial expansion in r1, r2 , r2 yields a relative error of about 10-7 . All integrals can be computed analytically and are derived from one single "parent" integral.

  4. Metastable Aluminum Atoms Floating on the Surface of Helium Nanodroplets

    NASA Astrophysics Data System (ADS)

    Jeffs, Jay; Besley, Nicholas A.; Stace, Anthony J.; Sarma, Gautam; Cunningham, Ethan M.; Boatwright, Adrian; Yang, Shengfu; Ellis, Andrew M.

    2015-06-01

    Metal atoms have proved to be sensitive probes of the properties of superfluid helium nanodroplets. To date, all experiments on the doping of helium droplets have concentrated on the attachment of metal atoms in their ground electronic states. Here we report the first examples of metal atoms in excited states becoming attached to helium nanodroplets. The atoms in question are aluminum, and they have been generated by laser ablation in a metastable quartet state, which attaches to and remains on the surface of helium droplets. Evidence for a surface location comes from electronic spectra, which consist of very narrow absorption profiles that show very small spectral shifts. Supporting ab initio calculations show there to be an energy incentive for a metastable Al atom to remain on the surface of a helium droplet rather than move to the interior. The results suggest that helium droplets may provide a method for the capture and transport of metastable excited atomic and molecular species.

  5. The helium trimer with soft-core potentials

    E-print Network

    A. Kievsky; E. Garrido; C. Romero-Redondo; P. Barletta

    2011-01-10

    The helium trimer is studied using two- and three-body soft-core potentials. Realistic helium-helium potentials present an extremely strong short-range repulsion and support a single, very shallow, bound state. The description of systems with more than two helium atoms is difficult due to the very large cancellation between kinetic and potential energy. We analyze the possibility of describing the three helium system in the ultracold regime using a gaussian representation of a widely used realistic potential, the LM2M2 interaction. However, in order to describe correctly the trimer ground state a three-body force has to be added to the gaussian interaction. With this potential model the two bound states of the trimer and the low energy scattering helium-dimer phase shifts obtained with the LM2M2 potential are well reproduced.

  6. Antiprotonic Helium Atoms

    E-print Network

    O. I. Kartavtsev

    1995-07-22

    Metastable antiprotonic helium atoms $^{3,4}\\! H\\! e\\bar pe$ have been discovered recently in experiments of the delayed annihilation of antiprotons in helium media. These exotic atoms survive for an enormous time (about tens of microseconds) and carry the extremely large total angular momentum $L\\sim 30-40$. The theoretical treatment of the intrinsic properties of antiprotonic helium atoms, their formation and collisions with atoms and molecules is discussed.

  7. AB INITIO EQUATIONS OF STATE FOR HYDROGEN (H-REOS.3) AND HELIUM (He-REOS.3) AND THEIR IMPLICATIONS FOR THE INTERIOR OF BROWN DWARFS

    SciTech Connect

    Becker, Andreas; Lorenzen, Winfried; Schöttler, Manuel; Redmer, Ronald [Institut für Physik, Universität Rostock, D-18051 Rostock (Germany); Fortney, Jonathan J.; Nettelmann, Nadine [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2015-01-01

    We present new equations of state (EOSs) for hydrogen and helium covering a wide range of temperatures from 60 K to 10{sup 7} K and densities from 10{sup –10} g cm{sup –3} to 10{sup 3} g cm{sup –3}. They include an extended set of ab initio EOS data for the strongly correlated quantum regime with an accurate connection to data derived from other approaches for the neighboring regions. We compare linear mixing isotherms based on our EOS tables with available real mixture data. A first important astrophysical application of this new EOS data is the calculation of interior models for Jupiter and comparison with recent results. Second, mass-radius relations are calculated for Brown Dwarfs (BDs) which we compare with predictions derived from the widely used EOS of Saumon, Chabrier, and van Horn. Furthermore, we calculate interior models for typical BDs with different masses, namely, Corot-3b, Gliese-229b, and Corot-15b, and the giant planet KOI-889b. The predictions for the central pressures and densities differ by up to 10% dependent on the EOS used. Our EOS tables are made available in the supplemental material of this paper.

  8. Two Electron Processes in Proton-Helium Collisions

    Microsoft Academic Search

    Samuel Wright Bross

    1993-01-01

    Cross sections differential in projectile scattering angle for formation of hydrogen atoms have been measured utilizing recoil ion coincidence techniques in 50 to 175 keV proton-helium collisions. The experimental method allowed separation of the post collision charge states of the target atoms. With a knowledge of the amount of each helium recoil ion charge state produced at each scattering angle,

  9. Photoionization of excited molecular states using multiphoton excitation techniques

    NASA Astrophysics Data System (ADS)

    Dehmer, P. M.; Pratt, S. T.; Dehmer, J. L.

    Resonantly enhanced multiphoton ionization (REMPI) affords the opportunity to select a specific ionization pathway in order to produce a particular ionic state for further study or to investigate detailed aspects of excited state photoionization dynamics. The production of electronic or vibrational state-selected ions using REMPI is achieved by first preparing an intermediate Rydberg state that has a potential energy curve similar to that of the final desired ionic state, and then ionizing the Rydberg state with a single additional photon. Under these circumstances, the Franck-Condon factors governing the final ionization step strongly favor the preservation of the Rydberg state core.

  10. Imaging spatial correlations of Rydberg excitations in cold atom clouds

    NASA Astrophysics Data System (ADS)

    Schwarzkopf, Andrew; Anderson, David; Raithel, Georg

    2012-06-01

    We measure correlations between excitation positions in cold Rydberg gases. We have previously observedootnotetextmark[2] Rydberg-blockade-induced structures in the Rydberg pair correlation function similar to those predicted in.ootnotetextmark[3] Here, we study the effect of Coulomb repulsion after field ionization, which could possibly influence the pair correlation measurement. We have simulated the ion trajectories in our chamber and determined that Coulomb repulsion did not play a role in any of our previous experiments. However, with higher magnification we expect to observe this effect as well. In the experiment, we already have obtained a magnification increase by about a factor of two, and progress towards even higher magnification is still being made. We will report on our progress in imaging smaller structures in the pair correlation function, induced by Coulomb repulsion and possibly by adiabatic Rydberg crystal formation.ootnotetextmark[4] ootnotetext[2]A. Schwarzkopf et al. Phys. Rev. Lett. 107, no. 10 (2011): 103001. ootnotetext[3]F. Robicheaux and J. Hernandez. Phys. Rev. A 72, 63403, 1-4 (2005). ootnotetext[4]T. Pohl et al. Phys. Rev. Lett. 104, no. 4 (January 27, 2010): 043002.

  11. Use of Microwave Dressing Fields to Enhance Rydberg Atom Interactions

    E-print Network

    Le Roy, Robert J.

    Use of Microwave Dressing Fields to Enhance Rydberg Atom Interactions by Joseph A. Petrus Presented;Abstract A microwave dressing field was used to induce resonant energy transfer in translationally cold 43d5/2 + 43d5/2 45p3/2 + 41f5/2,7/2 was enhanced due to the induced degeneracy of the initial

  12. High Rydberg atoms: newcomers to the atomic physics scene

    Microsoft Academic Search

    R. F. Stebbings

    1976-01-01

    A description is given of high Rydberg atoms which have a greatly increased size due to their having been perturbed in certain ways. The production, detection, and research on these atoms are considered. The motivation for such studies, apart from their intrinsic interest, includes laser development, laser isotope separation, energy deposition in gases, plasma diagnostics, and radio astronomy. (JFP)

  13. Electron-impact excitation of the (2p2) 1D and (2s2p) 1Po autoionizing states of helium

    NASA Astrophysics Data System (ADS)

    Sise, Omer; Dogan, Mevlut; Okur, Ibrahim; Crowe, Albert

    2011-08-01

    An experimental study of the excitation of the (2p2) 1D and (2s2p) 1Po autoionizing states of helium by 250-eV electron impact is presented. The ejected-electron angular distributions and energy spectra are measured in coincidence with the corresponding scattered electrons for a scattering angle of -13? and for a range of ejected-electron angles in both the forward and backward directions. Resonance profiles are analyzed in terms of the Shore-Balashov parametrization to obtain the resonance asymmetry A? and yield B? parameters and the direct ionization cross section f. The spectra and their parameters are compared to the previous measurements of Lower and Weigold [J. Phys. B.JPAPEH0953-407510.1088/0953-4075/23/16/023 23, 2819 (1990)] and McDonald and Crowe [J. Phys. BJPAPEH0953-407510.1088/0953-4075/26/17/021 26, 2887 (1993)]. Comparison is also made with the recent theoretical triply differential cross-section calculations based on the first and second Born approximations. In general, good qualitative agreement is found between the experimental results. Some differences are found at the forward and backward directions. These differences in the shape and magnitude of the cross sections are attributed to the different incoming electron energies used in the experiments. The second Born approximation with inclusion of the three-body Coulomb interaction in the final state agrees reasonably well with experiments in the binary region. However, the 1Po resonance yield parameter B? is significantly overestimated at the recoil region, giving a relatively large recoil peak, in contradiction to the experiment. There is also a discrepancy between the two theories available for the 1D resonance yield parameter B? in this region. Remaining discrepancies between theories and experiments are also discussed.

  14. Helium liquefier cycles with saturated vapor compression

    SciTech Connect

    Minta, M.; Smith, J.L. Jr.

    1982-01-01

    This paper is the design study of a saturated-vapor-compression helium liquefier operating at elevated pressure. The study was done to show the potential of the SVC cycle by direct comparison with a conventional cycle using the same precooling expanders and a supercritical wet expander instead of a J-T valve. A description of convential and SVC helium cycles is given with diagrams. Optimization of the SVC cycle is presented with a graph of the expander inlet temperatures. A discussion of the results includes conventional and SVC cycle dates for four states each. The SVC cycle has the potential for significant improvements of helium liquefiers producing atmospheric pressure liquid. This and other results encouraged the construction of apparatus to be used with a conventional helium liquefier to test a wet expander and a cold compressor and to demonstrate the potential of the SVC cycle.

  15. Cosmological helium production simplified

    Microsoft Academic Search

    Jeremy Bernstein; Lowell S. Brown; G. Feinberg

    1988-01-01

    Presented is a simplified model of helium synthesis in the early universe, the purpose of which is to explain the physical ideas relevant to the cosmological helium synthesis, in a manner that does not overlay these ideas with complex computer calculations. The model closely follows the standard calculation, except that it neglects the small effect of Fermi-Dirac statistics for the

  16. Cosmological helium production simplified

    Microsoft Academic Search

    Jeremy Bernstein; Lowell S. Brown; Gerald Feinberg

    1989-01-01

    The authors present a simplified model of helium synthesis in the early universe. The purpose of the model is to explain clearly the physical ideas relevant to the cosmological helium synthesis in a manner that does not overlay these ideas with complex computer calculations. The model closely follows the standard calculation, except that it neglects the small effect of Fermi-Dirac

  17. Cluster Luttinger Liquids of Rydberg-dressed Atoms in Optical Lattices

    E-print Network

    Marco Mattioli; Marcello Dalmonte; Wolfgang Lechner; Guido Pupillo

    2013-09-27

    We investigate the zero-temperature phases of bosonic and fermionic gases confined to one dimension and interacting via a class of finite-range soft-shoulder potentials (i.e. soft-core potentials with an additional hard-core onsite interaction). Using a combination of analytical and numerical methods, we demonstrate the stabilization of critical quantum liquids with qualitatively new features with respect to the Tomonaga-Luttinger liquid paradigm. These features result from frustration and cluster formation in the corresponding classical ground-state. Characteristic signatures of these liquids are accessible in state-of-the-art experimental setups with Rydberg-dressed ground-state atoms trapped in optical lattices.

  18. Deactivation of the xenon atom in the 6s metastable state in collisions with xenon and helium atoms

    Microsoft Academic Search

    D A Zayarnyi; Ludmila V Semenova; N N Ustinovskii; I V Kholin; A Yu Chugunov

    1998-01-01

    The absorption probing method was used to investigate collisional deactivation of the metastable 6s[3\\/2]°(³P) state of the xenon atom in high-pressure He - Xe mixtures with a low xenon concentration. Measurements were made of the rate constants of the plasma-chemical reactions Xe*+Xe+He Xe*+He [(1.7 {+-}0.2) x10³² cm s¹], Xe*+2He HeXe*+He (less than 3 x 10³ cm s¹), and Xe*+He products+He

  19. ACTIVE MEDIA: Deactivation of the xenon atom in the 6s metastable state in collisions with xenon and helium atoms

    Microsoft Academic Search

    D. A. Zayarnyi; Ludmila V. Semenova; N. N. Ustinovskii; I. V. Kholin; A. Yu Chugunov

    1998-01-01

    The absorption probing method was used to investigate collisional deactivation of the metastable 6s[3\\/2]20(3P2) state of the xenon atom in high-pressure He --- Xe mixtures with a low xenon concentration. Measurements were made of the rate constants of the plasma-chemical reactions Xe*+Xe+He --> Xe2*+He [(1.7 ±0.2) ×10-32 cm6 s-1], Xe*+2He--> HeXe*+He (less than 3 × 10-35 cm6 s-1), and Xe*+He-->

  20. version 2.0 Improved result for helium 2 3

    E-print Network

    Pachucki, Krzysztof

    version 2.0 Improved result for helium 2 3 S 1 ionization energy Krzysztof Pachucki #3; Institute of relativistic and quantum electrodynamic e#11;ects to order m#11; 6 on the energy of the 2 3 S 1 state in helium Typeset using REVT E X #3; E-mail address: krp@fuw.edu.pl 1 #12; The helium atom is one of the simplest

  1. Demixing of Hydrogen and Helium at Megabar Pressures

    Microsoft Academic Search

    Winfried Lorenzen; Bastian Holst; Ronald Redmer

    2009-01-01

    We present results of ab initio finite-temperature density functional theory molecular dynamics simulations for fluid hydrogen-helium mixtures at megabar pressures. The location of the miscibility gap is derived from the equation of state data. We find a close relation between hydrogen-helium phase separation and the continuous nonmetal-to-metal transition in hydrogen. Our calculations predict that demixing of hydrogen and helium occurs

  2. Deactivation of the xenon atom in the 6s metastable state in collisions with xenon and helium atoms

    SciTech Connect

    Zayarnyi, D A; Semenova, Ludmila V; Ustinovskii, N N; Kholin, I V; Chugunov, A Yu [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    1998-03-31

    The absorption probing method was used to investigate collisional deactivation of the metastable 6s[3/2]{sub 2}{sup 0}({sup 3}P{sub 2}) state of the xenon atom in high-pressure He - Xe mixtures with a low xenon concentration. Measurements were made of the rate constants of the plasma-chemical reactions Xe*+Xe+He {yields} Xe{sub 2}*+He [(1.7 {+-}0.2) x10{sup -32} cm{sup 6} s{sup -1}], Xe*+2He{yields} HeXe*+He (less than 3 x 10{sup -35} cm{sup 6} s{sup -1}), and Xe*+He{yields} products+He (less than 10{sup -15} cm{sup 3} s{sup -1}). (active media)

  3. An apparatus for pulsed ESR and DNP experiments using optically excited triplet states down to liquid helium temperatures.

    PubMed

    Eichhorn, T R; Haag, M; van den Brandt, B; Hautle, P; Wenckebach, W Th; Jannin, S; van der Klink, J J; Comment, A

    2013-09-01

    In standard Dynamic Nuclear Polarization (DNP) electron spins are polarized at low temperatures in a strong magnetic field and this polarization is transferred to the nuclear spins by means of a microwave field. To obtain high nuclear polarizations cryogenic equipment reaching temperatures of 1 K or below and superconducting magnets delivering several Tesla are required. This equipment strongly limits applications in nuclear and particle physics where beams of particles interact with the polarized nuclei, as well as in neutron scattering science. The problem can be solved using short-lived optically excited triplet states delivering the electron spin. The spin is polarized in the optical excitation process and both the cryogenic equipment and magnet can be simplified significantly. A versatile apparatus is described that allows to perform pulsed dynamic nuclear polarization experiments at X-band using short-lived optically excited triplet sates. The efficient (4)He flow cryostat that cools the sample to temperatures between 4 K and 300 K has an optical access with a coupling stage for a fiber transporting the light from a dedicated laser system. It is further designed to be operated on a neutron beam. A combined pulse ESR/DNP spectrometer has been developed to observe and characterize the triplet states and to perform pulse DNP experiments. The ESR probe is based on a dielectric ring resonator of 7 mm inner diameter that can accommodate cubic samples of 5mm length needed for neutron experiments. NMR measurements can be performed during DNP with a coil integrated in the cavity. With the presented apparatus a proton polarization of 0.5 has been achieved at 0.3 T. PMID:23838526

  4. SPECIAL TOPIC: HELIUM NANODROPLETS Experimental studies of helium droplets

    E-print Network

    Northby, Jan A.

    SPECIAL TOPIC: HELIUM NANODROPLETS Experimental studies of helium droplets J. A. Northbya) Physics September 2001 In this report I will review experimental studies of free helium droplets, with the exception of spectroscopic studies of helium droplets that contain impurities. This particular topic, as well as theoretical

  5. Exciton Binding Energy and Nonhydrogenic Rydberg Series in Monolayer WS2

    NASA Astrophysics Data System (ADS)

    Chernikov, Alexey; Berkelbach, Timothy C.; Hill, Heather M.; Rigosi, Albert; Li, Yilei; Aslan, Ozgur Burak; Reichman, David R.; Hybertsen, Mark S.; Heinz, Tony F.

    2014-08-01

    We have experimentally determined the energies of the ground and first four excited excitonic states of the fundamental optical transition in monolayer WS2, a model system for the growing class of atomically thin two-dimensional semiconductor crystals. From the spectra, we establish a large exciton binding energy of 0.32 eV and a pronounced deviation from the usual hydrogenic Rydberg series of energy levels of the excitonic states. We explain both of these results using a microscopic theory in which the nonlocal nature of the effective dielectric screening modifies the functional form of the Coulomb interaction. These strong but unconventional electron-hole interactions are expected to be ubiquitous in atomically thin materials.

  6. Two-photon spectroscopy of the (n,3s) Rydberg transition in acetaldehyde: The torsional sequence

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Fleniken, J.; Meyer, H.

    1998-09-01

    Eigenvalues and wave functions for acetaldehyde in its electronic ground state and the (n,3s) Rydberg state are calculated using the rho-axis method in combination with the high barrier approximation. The rotational structure of the first members of the torsional sequence in the two-photon spectrum is analyzed in terms of a zeroth-order rotation-torsional Hamiltonian. Combining experimental information on band positions and rotational contours, we determine the range of internal rotation constants and barrier heights, which is compatible with the experimental data. The analysis yields the following parameters: F=8.45±0.15 cm-1, V3=809±10 cm-1, ?=0.33±0.03, ?RAM=4.5°±0.8°, and APA=1.990 cm-1, BPA=0.330 cm-1, CPA=0.298 cm-1.

  7. Singlet-triplet energy splitting between 1D and 3D (1s2 2s nd), n = 3, 4, 5, and 6, Rydberg states of the beryllium atom (9Be) calculated with all-electron explicitly correlated Gaussian functions

    NASA Astrophysics Data System (ADS)

    Sharkey, Keeper L.; Bubin, Sergiy; Adamowicz, Ludwik

    2014-11-01

    Accurate variational nonrelativistic quantum-mechanical calculations are performed for the five lowest 1D and four lowest 3D states of the 9Be isotope of the beryllium atom. All-electron explicitly correlated Gaussian (ECG) functions are used in the calculations and their nonlinear parameters are optimized with the aid of the analytical energy gradient determined with respect to these parameters. The effect of the finite nuclear mass is directly included in the Hamiltonian used in the calculations. The singlet-triplet energy gaps between the corresponding 1D and 3D states, are reported.

  8. Volume 113. number 5 CHEMICAL PHYSICS LETTERS 1 February 1985 VIBKATIONAL STATE SELECTION OF AMMONIA IONS

    E-print Network

    Zare, Richard N.

    OF AMMONIA IONS USING RESONANT 2 + 1 MULTIPHOTON IONIZATION William E. CONAWAY, Richard J.S. MORRISON-enhanced multi- photon ionization of ammonia via the z and ? Rydberg states. These two Rydberg states show long that the Au = 0 transition should be strongly fa- vored in the ionization step. Thus, ammonia is an ex

  9. Precision spectroscopy of Kaonic helium-3 and helium-4 3d-->2p X-rays

    Microsoft Academic Search

    T. Ishiwatari; M. Bazzi; H. Bhang; G. Beer; L. Bombelli; A. M. Bragadireanu; M. Cargnelli; S. Choi; G. Corradi; C. Curceanu; A. D'Uffizi; S. Enomoto; C. Fiorini; T. Frizzi; H. Fujioka; Y. Fujiwara; F. Ghio; B. Girolami; C. Guaraldo; T. Hashimoto; R. S. Hayano; T. Hiraiwa; M. Iio; M. Iliescu; S. Ishimoto; K. Itahashi; M. Iwasaki; P. Kienle; H. Kou; P. Levi Sandri; A. Longoni; V. Lucherini; J. Marton; Y. Matsuda; H. Noumi; H. Ohnishi; S. Okada; H. Outa; D. Pietreanu; T. Ponta; A. Rizzo; A. Romero Vidal; F. Sakuma; M. Sato; A. Scordo; M. Sekimoto; H. Shi; D. L. Sirghi; F. Sirghi; T. Suzuki; K. Tanida; H. Tatsuno; M. Tokuda; D. Tomono; A. Toyoda; K. Tsukada; A. Tudorache; V. Tudorache; O. Vazquez Doce; E. Widmann; B. Wünschek; T. Yamazaki; J. Zmeskal

    2010-01-01

    Recently, the shift of the kaonic helium-4 2p state was precisely determined by the E570 and SIDDHARTA experiments. Prior to the experiment by E570, the average of three earlier experimental results showed -43+\\/-8 eV,while most of the theoretical calculations give ~0 eV. This five-sigma discrepancy between theory and experiment was known as the ``kaonic helium puzzle''. A recent theoretical model

  10. Detection of Negative Charge Carriers in Superfluid Helium Droplets: The Metastable Anions He*– and He2*–

    PubMed Central

    2014-01-01

    Helium droplets provide the possibility to study phenomena at the very low temperatures at which quantum mechanical effects are more pronounced and fewer quantum states have significant occupation probabilities. Understanding the migration of either positive or negative charges in liquid helium is essential to comprehend charge-induced processes in molecular systems embedded in helium droplets. Here, we report the resonant formation of excited metastable atomic and molecular helium anions in superfluid helium droplets upon electron impact. Although the molecular anion is heliophobic and migrates toward the surface of the helium droplet, the excited metastable atomic helium anion is bound within the helium droplet and exhibits high mobility. The atomic anion is shown to be responsible for the formation of molecular dopant anions upon charge transfer and thus, we clarify the nature of the previously unidentified fast exotic negative charge carrier found in bulk liquid helium. PMID:25068008

  11. Noncavitating Pump For Liquid Helium

    NASA Technical Reports Server (NTRS)

    Hasenbein, Robert; Izenson, Michael; Swift, Walter; Sixsmith, Herbert

    1996-01-01

    Immersion pump features high efficiency in cryogenic service. Simple and reliable centrifugal pump transfers liquid helium with mass-transfer efficiency of 99 percent. Liquid helium drawn into pump by helical inducer, which pressurizes helium slightly to prevent cavitation when liquid enters impeller. Impeller then pressurizes liquid. Purpose of pump to transfer liquid helium from supply to receiver vessel, or to provide liquid helium flow for testing and experimentation.

  12. Observation of metastable hcp solid helium. F. Souris, J. Grucker,

    E-print Network

    Observation of metastable hcp solid helium. F. Souris, J. Grucker, J. Dupont-Roc, and Ph. Jacquier Lhomond, 75005 Paris, France (Dated: June 9, 2011) We have produced and observed metastable solid helium-4 in an expanded metastable state and its stability limits. PACS numbers: 67.80.-s,64.60.My,67.25.dt Crystalline

  13. The descending helium balloon

    NASA Astrophysics Data System (ADS)

    Helseth, Lars Egil

    2014-07-01

    I describe a simple and fascinating experiment wherein helium leaks out of a rubber balloon, thereby causing it to descend. An estimate of the volumetric leakage rate is made by measuring its rate of descent.

  14. Mantle helium and carbon isotopes in Separation Creek Geothermal Springs, Three Sisters area, Central Oregon: Evidence for renewed volcanic activity or a long term steady state system?

    Microsoft Academic Search

    M. C. van Soest; B. M. Kennedy; W. C. Evans; R. H. Mariner

    2002-01-01

    Cold bubbling springs in the Separation Creek area, the locus of current uplift at South Sister volcano show strong mantle signatures in helium and carbon isotopes and COâ\\/³He. This suggests the presence of fresh basaltic magma in the volcanic plumbing system. Currently there is no evidence to link this system directly to the uplift, which started in 1998. To the

  15. Coherent dynamics of Rydberg atoms in cosmic microwave background radiation

    E-print Network

    Timur V. Tscherbul; Paul Brumer

    2013-12-20

    Rydberg atoms excited by cold blackbody radiation are shown to display long-lived quantum coherences on timescales of tens of picoseconds. By solving non-Markovian equations of motion with no free parameters we obtain the time evolution of the density matrix, and demonstrate that the blackbody-induced temporal coherences manifest as slowly decaying (100 ps) quantum beats in time-resolved fluorescence. An analytic model shows the dependence of the coherent dynamics on the energy splitting between atomic eigenstates, transition dipole moments, and coherence time of the radiation. Experimental detection of the fluorescence signal from a trapped ensemble of $10^8$ Rydberg atom is discussed, but shown to be technically challenging at present, requiring CMB amplification somewhat beyond current practice.

  16. Single-Photon Switch Based on Rydberg Blockade

    NASA Astrophysics Data System (ADS)

    Baur, Simon; Tiarks, Daniel; Rempe, Gerhard; Dürr, Stephan

    2014-02-01

    All-optical switching is a technique in which a gate light pulse changes the transmission of a target light pulse without the detour via electronic signal processing. We take this to the quantum regime, where the incoming gate light pulse contains only one photon on average. The gate pulse is stored as a Rydberg excitation in an ultracold atomic gas using electromagnetically induced transparency. Rydberg blockade suppresses the transmission of the subsequent target pulse. Finally, the stored gate photon can be retrieved. A retrieved photon heralds successful storage. The corresponding postselected subensemble shows an extinction of 0.05. The single-photon switch offers many interesting perspectives ranging from quantum communication to quantum information processing.

  17. Rotational state distributions from vibrational autoionization of H2

    NASA Astrophysics Data System (ADS)

    Dehmer, J. L.; Dehmer, P. M.; Pratt, S. T.; Tomkins, F. S.; O'Halloran, M. A.

    1989-06-01

    The H2(+) rotational state distributions produced by vibrational autoionization of singlet np Rydberg states of H2 were determined using optical-optical double-resonance excitation and electron spectroscopy. The expected convergence of the P(1)np sigma, Q(1)np pi, R(1)np1, and R(1)np3 Rydberg series to v(+) = 1 was found. The results suggest that vibrational autoionization of np pi Rydberg states is accompanied by rotational state changes in the H2(+) core to an unexpected degree.

  18. Giant Helium Dimers Produced by Photoassociation of Ultracold Metastable Atoms J. Leonard,* M. Walhout,

    E-print Network

    Cohen-Tannoudj, Claude

    Giant Helium Dimers Produced by Photoassociation of Ultracold Metastable Atoms J. Le´onard,* M long-range helium dimers by photoassociation of metastable helium atoms in a magnetically trapped in the metastable 23S1 (He) state absorb laser light tuned close to the 23S1 ÿ 23P0 (D0) atomic line at 1083 nm

  19. Two experiments with cold atoms: I. Application of Bessel beams for atom optics, and II. Spectroscopic measurements of Rydberg blockade effect

    NASA Astrophysics Data System (ADS)

    Arakelyan, Ilya

    In this dissertation we report the results of two experimental projects with laser-cooled rubidium atoms: I. Application of Bessel beams for atom optics, and II. Spectroscopic measurements of Rydberg blockade effect. The first part of the thesis is devoted to the development of new elements of atom optics based on blue-detuned high-order Bessel beams. Properties of a 4thorder Bessel beam as an atomic guide were investigated for various parameters of the hollow beam, such as the detuning from an atomic resonance, size and the order of the Bessel beam. We extended its application to create more complicated interferometer-type structures by demonstrating a tunnel lock, a novel device that can split an atomic cloud, transport it, delay, and switch its propagation direction between two guides. We reported a first-time demonstration of an atomic beam switch based on the combination of two crossed Bessel beams. We achieved the 30% efficiency of the switch limited by the geometrical overlap between the cloud and the intersection volume of the two tunnels, and investigate the heating processes induced by the switch. We also showed other applications of crossed Bessel beams, such as a 3-D optical trap for atoms confined in the intersection volume of two hollow beams and a splitter of the atomic density. The second part of this dissertation is devoted to the spectroscopic measurements of the Rydberg blockade effect, a conditional suppression of Rydberg excitations depending on the state of a control atom. We assembled a narrow-linewidth, tunable, frequency stabilized laser system at 480 nm to excite laser-cooled rubidium atoms to Rydberg states with a high principal quantum number n ˜ 50 through a two-photon transition. We applied the laser system to observe the Autler-Townes splitting of the intermediate 5p3/2 state and used the broadening of the resonance features to investigate the enhancement of Rydberg-Rydberg interactions in the presence of an external electric field.

  20. Dissociation of CH4 and CD4 by electron impact - Production of metastable and high-Rydberg hydrogen and carbon fragments

    NASA Technical Reports Server (NTRS)

    Finn, T. G.; Carnahan, B. L.; Wells, W. C.; Zipf, E. C.

    1975-01-01

    Production of hydrogen and carbon atoms in metastable and high-lying Rydberg states by electron-impact dissociation of methane and deuterated methane is investigated for incident electron energies ranging from threshold values to 300 eV. Threshold energies for five different processes resulting in metastable hydrogen and carbon atoms are determined in the energy range from 20 to 70 eV, and it is shown that metastable hydrogen atoms are produced in four of these collisional processes while metastable carbon atoms are produced in the other. The nature of each collisional process is described, differential cross sections are derived for the dissociative excitation of both types of atoms to metastable and high-Rydberg states at 100 eV, and the onset energy for UV photon production is measured. Much of the data is interpreted in terms of the ion core model suggested by Kupriyanov (1968) and developed by Freund (1971).

  1. Characterization of the Rydberg Bonding in (NH4)2 Robyn Barrios, Piotr Skurski, and Jack Simons*

    E-print Network

    Simons, Jack

    Characterization of the Rydberg Bonding in (NH4)2 - Robyn Barrios, Piotr Skurski, and Jack Simons City, Utah 84112 ReceiVed: April 6, 2000; In Final Form: August 28, 2000 The Rydberg bonding in (NH4 performed for comparison with the Rydberg bonding cases. The dissociation energy De for (NH4)2 - f NH4 + NH4

  2. Stark-assisted population control of coherent CS(2) 4f and 5p Rydberg wave packets studied by femtosecond time-resolved photoelectron spectroscopy.

    PubMed

    Knappenberger, Kenneth L; Lerch, Eliza-Beth W; Wen, Patrick; Leone, Stephen R

    2007-09-28

    A two-color (3+1(')) pump-probe scheme is employed to investigate Rydberg wave packet dynamics in carbon disulfide (CS(2) (*)). The state superpositions are created within the 4f and 5p Rydberg manifolds by three photons of the 400 nm pump pulse, and their temporal evolution is monitored with femtosecond time-resolved photoelectron spectroscopy using an 800 nm ionizing probe pulse. The coherent behavior of the non-stationary superpositions are observed through wavepacket revivals upon ionization to either the upper (12) or lower (32) spin-orbit components of CS(2) (+). The results show clearly that the composition of the wavepacket can be efficiently controlled by the power density of the excitation pulse over a range from 500 GWcm(2) to 10 TWcm(2). The results are consistent with the anticipated ac-Stark shift for 400 nm light and demonstrate an effective method for population control in molecular systems. Moreover, it is shown that Rydberg wavepackets can be formed in CS(2) with excitation power densities up to 10 TWcm(2) without significant fragmentation. The exponential 1e population decay (T(1)) of specific excited Rydberg states are recovered by analysis of the coherent part of the signal. The dissociation lifetimes of these states are typically 1.5 ps. However, a region exhibiting a more rapid decay ( approximately 800 fs) is observed for states residing in the energy range of 74 450-74 550 cm(-1), suggestive of an enhanced surface crossing in this region. PMID:17902914

  3. Direct evidence of three-body interactions in a cold {sup 85}Rb Rydberg gas

    SciTech Connect

    Han Jianing [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2010-11-15

    Cold Rydberg atoms trapped in a magneto-optical trap (MOT) are not isolated and they interact through dipole-dipole and multipole-multipole interactions. First-order dipole-dipole interactions and van der Waals interactions between two atoms have been intensively studied. However, the facts that the first-order dipole-dipole interactions and van der Waals interactions show the same size of broadening [A. Reinhard, K. C. Younge, T. C. Liebisch, B. Knuffman, P. R. Berman, and G. Raithel, Phys. Rev. Lett. 100, 233201 (2008)] and there are transitions between two dimer states [S. M. Farooqi, D. Tong, S. Krishnan, J. Stanojevic, Y. P. Zhang, J. R. Ensher, A. S. Estrin, C. Boisseau, R. Cote, E. E. Eyler, and P. L. Gould, Phys. Rev. Lett. 91, 183002 (2003); K. R. Overstreet, Arne Schwettmann, Jonathan Tallant, and James P. Shaffer, Phys. Rev. A 76, 011403(R) (2007)] cannot be explained by the two-atom picture. The purpose of this article is to show the few-body nature of a dense cold Rydberg gas by studying the molecular-state microwave spectra. Specifically, three-body energy levels have been calculated. Moreover, the transition from three-body energy levels to two-body coupled molecular energy levels and to isolated atomic energy levels as a function of the internuclear spacing is studied. Finally, single-body, two-body, and three-body interaction regions are estimated according to the experimental data. The results reported here provides useful information for plasma formation, further cooling, and superfluid formation.

  4. Semiclassical modeling of Rydberg wave-packet dynamics in diatomic molecules: Average decoupling theory

    E-print Network

    Cao, Jianshu

    Semiclassical modeling of Rydberg wave-packet dynamics in diatomic molecules: Average decoupling theory S. N. Altunata, J. Cao, and R. W. Field* Department of Chemistry, Massachusetts Institute 2002; published 10 May 2002 The semiclassical dynamics of Rydberg electronic wave packets in diatomic

  5. Electrical conductivity and thermopower of metallic helium

    NASA Astrophysics Data System (ADS)

    Shvets, V. T.; Kozitskii, S. V.

    2013-04-01

    The pair effective interionic interaction, electrical resistance, and thermopower of liquid metallic helium have been calculated over wide temperature and density ranges using the perturbation theory for the potential of electron-ion interaction. For conduction electrons, the random-phase approximation has been used taking into account the exchange interaction and correlations in the local-field approximation. The nuclear subsystem has been described by the hard-sphere model. The sphere diameter is the only parameter of the theory. The diameter and the system density at which helium is transformed from the singly ionized to doubly ionized state have been estimated based on an analysis of the pair effective interaction between helium nuclei. The case of doubly ionized helium atoms has been considered. The numerical calculations have been performed taking into account the perturbation theory in terms up to the third order. In all cases, the role of the third-order correction is significant. In the case of metallic helium, the values of the electrical resistance and its temperature dependence are characteristic of divalent simple liquid metals, as well as the dependences of the thermopower on the density and temperature.

  6. Improved helium line formation for EHe stars

    E-print Network

    N. Przybilla; K. Butler; U. Heber; C. S. Jeffery

    2005-12-06

    Quantitative analyses of extreme helium stars to date face the difficulty that theory fails to reproduce the observed helium lines in their entirety, wings and line cores. Here, we demonstrate how the issues can be resolved using state-of-the-art non-LTE line formation for these chemically peculiar objects. Two unique B-type objects are discussed in detail, the pulsating variable V652 Her and the metal-poor star HD144941. The improved non-LTE computations for helium show that analyses assuming LTE or based on older non-LTE model atoms can predict equivalent widths, for the HeI 10830A transition in particular, in error by up to a factor ~3. Our modelling approach also succeeds in largely resolving the general mismatch for effective temperatures of EHe stars derived from ionization equilibria and from spectral energy distributions.

  7. Dipole transition strengths in Ba{sup +} from Rydberg fine-structure measurements in Ba and Ba{sup +}

    SciTech Connect

    Woods, Shannon L.; Hanni, M. E.; Lundeen, S. R.; Snow, Erica L. [Colorado State University, Fort Collins, Colorado 80523 (United States); State University of New York at Fredonia, Fredonia, New York 14063 (United States)

    2010-07-15

    The fine structure of high-L n = 19 and 20 Rydberg states of Ba{sup +} has been measured precisely using the resonant excitation Stark ionization spectroscopy technique, allowing for a determination of the Ba{sup 2+} polarizability: {alpha}{sub D}(Ba{sup 2+}) = 10.75(10) a.u. This result, in combination with an improved model of the K splittings in Ba Rydberg levels, allows for a more precise determination of the Ba{sup +} dipole transition strengths connecting the 6 {sup 2}S{sub 1/2} ground state to the 6 {sup 2}P{sub 1/2} and 6 {sup 2}P{sub 3/2} excited states. The results, in atomic units, are <6 {sup 2}S{sub 1/2} ||D|| 6 {sup 2}P{sub 1/2}> = 3.3251(21) and <6 {sup 2}S{sub 1/2} ||D|| 6 {sup 2}P{sub 3/2}> = 4.7017(27).

  8. Cavitation in flowing superfluid helium

    NASA Technical Reports Server (NTRS)

    Daney, D. E.

    1988-01-01

    Flowing superfluid helium cavitates much more readily than normal liquid helium, and there is a marked difference in the cavitation behavior of the two fluids as the lambda point is traversed. Examples of cavitation in a turbine meter and centrifugal pump are given, together with measurements of the cavitation strength of flowing superfluid helium. The unusual cavitation behavior of superfluid helium is attributed to its immense thermal conductivity .

  9. Mining for Helium Jurriaan Hage

    E-print Network

    Utrecht, Universiteit

    Mining for Helium Jurriaan Hage Peter van Keeken Department of Information and Computing Sciences-year functional programming course using the Helium compiler. The mining of such a collection is not trivial a type error. 1 #12;1 Introduction and motivation When the Helium compiler for learning Haskell

  10. UPPER-ATMOSPHERE HELIUM IONS

    Microsoft Academic Search

    W. B. Hanson

    1962-01-01

    An experimental measurement of the ion concentration in the upper ; ionosphere is examined in light of a suggestion that helium is an important ; constituent of the high atmosphere. An isothermal region of helium ions at l600 ; deg K is found above approximately 1200 km. Consideration of the loss mechanism ; for helium ions by ion-atom interchange with

  11. Shock Compression of Liquid Helium to 56 GPa (560) Kbar

    NASA Technical Reports Server (NTRS)

    Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Trainor, R. J.; Governo, G. K.; Ross, M.; Young, D. A.

    1985-01-01

    Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

  12. Shock compression of liquid helium to 56 GPa (560 kbar)

    NASA Technical Reports Server (NTRS)

    Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Governo, G. K.; Ross, M.; Young, D. A.; Trainor, R. J.

    1984-01-01

    Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation of the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

  13. Helium in the Martian atmosphere - Thermal loss considerations

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Keating, G. M.; Prior, E. J.

    1974-01-01

    Helium concentrations in the Martian atmosphere are estimated assuming that the helium production on Mars (comparable to its production on earth) via the radioactive decay of uranium and thorium is in steady state equilibrium with its thermal escape. Although nonthermal losses would tend to reduce the estimated concentrations, these concentrations are not necessarily an upper limit since higher production rates and/or a possibly lower effective exospheric temperature over the solar activity cycle could increase them to even higher values. The computed helium concentration at the Martian exobase (200 km) is 8 million atoms/cu cm. Through the lower exosphere, the computed helium concentrations are 30-200 times greater than the Mariner-measured atomic hydrogen concentrations. It follows that helium may be the predominant constituent in the Martian lower exosphere and may well control the orbital lifetime of Mars-orbiting spacecraft.

  14. Detailed and simplified nonequilibrium helium ionization in the solar atmosphere

    SciTech Connect

    Golding, Thomas Peter; Carlsson, Mats [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Leenaarts, Jorrit, E-mail: thomas.golding@astro.uio.no, E-mail: mats.carlsson@astro.uio.no, E-mail: jorritl@astro.uio.no [Now at Institutet för Solfysik, Stockholms Universitet (Sweden)

    2014-03-20

    Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out one-dimensional radiation-hydrodynamics simulations of the solar atmosphere and find that the helium ionization is set mostly by photoionization and direct collisional ionization, counteracted by radiative recombination cascades. By introducing an additional recombination rate mimicking the recombination cascades, we construct a simplified three-level helium model atom consisting of only the ground states. This model atom is suitable for modeling nonequilibrium helium ionization in three-dimensional numerical models. We perform a brief investigation of the formation of the He I 10830 and He II 304 spectral lines. Both lines show nonequilibrium features that are not recovered with statistical equilibrium models, and caution should therefore be exercised when such models are used as a basis for interpretating observations.

  15. X-ray diffraction assisted spectroscopy of Rydberg states

    SciTech Connect

    Kirrander, Adam [ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States)

    2012-10-21

    X-ray diffraction combined with conventional spectroscopy could provide a powerful means to characterize electronically excited atoms and molecules. We demonstrate theoretically how x-ray diffraction from laser excited atoms can be used to determine electronic structure, including angular momentum composition, principal quantum numbers, and channel populations. A theoretical formalism appropriate for highly excited atoms, and easily extended to molecules, is presented together with numerical results for Xe and H atoms.

  16. COHERENT MANIPULATION OF SINGLE ATOM QUBITS USING RYDBERG STATES

    E-print Network

    Walker, Thad G.

    ) at the UNIVERSITY OF WISCONSIN­MADISON 2009 #12;c Copyright by Erich Urban 2009 All Rights Reserved #12;i To Amanda to work with Todd Johnson. Our research styles complemented each other very well [Johnson, 2008]. I would, Amanda. Meeting her was easily the most important part of my graduate career. She has been infinitely

  17. Helium in the Atmosphere

    Microsoft Academic Search

    William Crookes

    1898-01-01

    THE letter of Mr. Baly in your issue of last week, corroborating the statement of Friedländer and Kayser that helium is a constituent of the atmosphere, induces me to put on record a further confirmation of the accuracy of this observation. Having had the opportunity, on June 20 last, of examining samples of the more volatile portions from liquid air,

  18. Entanglement in helium

    E-print Network

    Giuliano Benenti; Stefano Siccardi; Giuliano Strini

    2013-05-01

    Using a configuration-interaction variational method, we accurately compute the reduced, single-electron von Neumann entropy for several low-energy, singlet and triplet eigenstates of helium atom. We estimate the amount of electron-electron orbital entanglement for such eigenstates and show that it decays with energy.

  19. Interacting Fibonacci anyons in a Rydberg gas

    E-print Network

    Lesanovsky, Igor

    2012-01-01

    A defining property of particles is their behavior under exchange. In two dimensions anyons can exist which, opposed to fermions and bosons, gain arbitrary relative phase factors or even undergo a change of their type. In the latter case one speaks of non-Abelian anyons - a particularly simple and aesthetic example of which are Fibonacci anyons. They have been studied in the context of fractional quantum Hall physics where they occur as quasiparticles in the $k=3$ Read-Rezayi state, which is conjectured to describe a fractional quantum Hall state at filling fraction $\

  20. Interacting Fibonacci anyons in a Rydberg gas

    E-print Network

    Igor Lesanovsky; Hosho Katsura

    2012-04-04

    A defining property of particles is their behavior under exchange. In two dimensions anyons can exist which, opposed to fermions and bosons, gain arbitrary relative phase factors or even undergo a change of their type. In the latter case one speaks of non-Abelian anyons - a particularly simple and aesthetic example of which are Fibonacci anyons. They have been studied in the context of fractional quantum Hall physics where they occur as quasiparticles in the $k=3$ Read-Rezayi state, which is conjectured to describe a fractional quantum Hall state at filling fraction $\

  1. Odd-parity J=11/2 autoionizing Rydberg series of europium below the 5d {sup 9}D{sub 4} threshold: Spectroscopy and multichannel quantum-defect-theory analysis

    SciTech Connect

    Bhattacharyya, S.; Razvi, M. A. N.; Nakhate, S. G. [Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Cohen, S. [Atomic and Molecular Physics Laboratory, Physics Department, University of Ioannina, GR-45110 Ioannina (Greece)

    2007-07-15

    The odd-parity J=11/2 autoionizing states of europium atom below the 5d {sup 9}D{sub 4} threshold are investigated by a two-step laser photoionization scheme via the 4f{sup 7}5d6p {sup 10}F{sub 9/2} intermediate state. The observed resonances are classified into two autoionizing Rydberg series (with n=15 to 55) converging to the 5d {sup 9}D{sub 4} limit and eight members (n=13 to 20) of two autoionizing Rydberg series converging to the higher 5d {sup 9}D{sub 5} limit. The single series converging to the 5d {sup 9}D{sub 3} limit is not efficiently excited. The observed four Rydberg series are assigned in jj coupling as 5dnd (4,j) and 5dnd (5,j) with j=3/2 and 5/2. Apart from the 5dnd (5,5/2) series, the majority of autoionizing resonances exhibits narrow linewidths and quasisymmetric line shapes, reflecting this way the weak coupling between the discrete levels and the adjacent continua. The experimental data are analyzed through the semiempirical phase-shifted multichannel quantum defect theory. The theoretically calculated energy level positions and excitation profiles are in good agreement with the experimental ones, thus confirming the identification of the observed structures. The constructed Lu-Fano plot and computed admixture coefficients reveal weak and localized interactions among the Rydberg series members.

  2. Modelling the mobility of positive ion clusters in normal liquid helium over large pressure ranges.

    PubMed

    Aitken, Frédéric; Bonifaci, Nelly; Mendoza-Luna, Luis Guillermo; von Haeften, Klaus

    2015-07-01

    Positively charged helium clusters, also called 'snowballs', have been investigated within normal liquid helium. Thermodynamic state equations for ionic helium clusters in liquid helium have been developed, allowing us to discern the 'hydrodynamic' radius for a wide range of hydrostatic pressures and temperatures. The mobilities derived from the cluster sizes using stokes law match experimental data with unsurpassed accuracy. For low pressures the compressibility of the cluster ions was found to be distinctly larger than the compressibility of solid helium suggesting that in this pressure range clusters are fully or partially liquid. PMID:26110248

  3. Microwaves Probe Dipole Blockade and van der Waals Forces in a Cold Rydberg Gas

    NASA Astrophysics Data System (ADS)

    Teixeira, R. Celistrino; Hermann-Avigliano, C.; Nguyen, T. L.; Cantat-Moltrecht, T.; Raimond, J. M.; Haroche, S.; Gleyzes, S.; Brune, M.

    2015-07-01

    We show that microwave spectroscopy of a dense Rydberg gas trapped on a superconducting atom chip in the dipole blockade regime reveals directly the dipole-dipole many-body interaction energy spectrum. We use this method to investigate the expansion of the Rydberg cloud under the effect of repulsive van der Waals forces and the breakdown of the frozen gas approximation. This study opens a promising route for quantum simulation of many-body systems and quantum information transport in chains of strongly interacting Rydberg atoms.

  4. Microwave probes Dipole Blockade and van der Waals Forces in a Cold Rydberg Gas

    E-print Network

    R. Celistrino Teixeira; C. Hermann-Avigliano; Thanh Long Nguyen; T. Cantat-Moltrecht; Jean-Michel Raimond; S. Haroche; S. Gleyzes; M. Brune

    2015-02-14

    We show that microwave spectroscopy of a dense Rydberg gas trapped on a superconducting atom chip in the dipole blockade regime reveals directly the dipole-dipole many-body interaction energy spectrum. We use this method to investigate the expansion of the Rydberg cloud under the effect of repulsive van der Waals forces and the breakdown of the frozen gas approximation. This study opens a promising route for quantum simulation of many-body systems and quantum information transport in chains of strongly interacting Rydberg atoms.

  5. Microwaves Probe Dipole Blockade and van der Waals Forces in a Cold Rydberg Gas.

    PubMed

    Teixeira, R Celistrino; Hermann-Avigliano, C; Nguyen, T L; Cantat-Moltrecht, T; Raimond, J M; Haroche, S; Gleyzes, S; Brune, M

    2015-07-01

    We show that microwave spectroscopy of a dense Rydberg gas trapped on a superconducting atom chip in the dipole blockade regime reveals directly the dipole-dipole many-body interaction energy spectrum. We use this method to investigate the expansion of the Rydberg cloud under the effect of repulsive van der Waals forces and the breakdown of the frozen gas approximation. This study opens a promising route for quantum simulation of many-body systems and quantum information transport in chains of strongly interacting Rydberg atoms. PMID:26182093

  6. Microwave probes Dipole Blockade and van der Waals Forces in a Cold Rydberg Gas

    E-print Network

    Teixeira, R Celistrino; Nguyen, Thanh Long; Cantat-Moltrecht, T; Raimond, Jean-Michel; Haroche, S; Gleyzes, S; Brune, M

    2015-01-01

    We show that microwave spectroscopy of a dense Rydberg gas trapped on a superconducting atom chip in the dipole blockade regime reveals directly the dipole-dipole many-body interaction energy spectrum. We use this method to investigate the expansion of the Rydberg cloud under the effect of repulsive van der Waals forces and the breakdown of the frozen gas approximation. This study opens a promising route for quantum simulation of many-body systems and quantum information transport in chains of strongly interacting Rydberg atoms.

  7. Positron Attachment to the He Doubly Excited States

    NASA Astrophysics Data System (ADS)

    Bromley, M. W. J.; Mitroy, J.; Varga, K.

    2012-08-01

    The projection method is used to demonstrate the existence of positron attachment to three doubly excited states of helium. The e+He(2s2Se1)deg?, e+He(3s2Se1), and the e+He(2s2pPo3) states have binding energies of 0.447, 0.256, and 0.486 eV, respectively. These energies were computed with the stochastic variational method and the configuration interaction method. These states will exist as resonances in the e+-He continuum, and the e+He(2s2Se1) state could be detectable in the e++He collision spectrum. A resonance width of 0.068 eV was computed for the e+He(2s2Se1) state by using the complex rotation method. The existence of a series of e+He(ns2Se1) resonances associated with the He(ns2) double Rydberg series is also predicted, and an explicit calculation demonstrating the existence of the e+He(3s2Se1) state is reported.

  8. Positron attachment to the He doubly excited states.

    PubMed

    Bromley, M W J; Mitroy, J; Varga, K

    2012-08-10

    The projection method is used to demonstrate the existence of positron attachment to three doubly excited states of helium. The e(+)He(2s(2) (1)S(e))deg, e(+)He(3s(2) (1)S(e)), and the e(+)He(2s2p (3)P(o)) states have binding energies of 0.447, 0.256, and 0.486 eV, respectively. These energies were computed with the stochastic variational method and the configuration interaction method. These states will exist as resonances in the e(+)-He continuum, and the e(+)He(2s(2) (1)S(e)) state could be detectable in the e(+)+He collision spectrum. A resonance width of 0.068 eV was computed for the e(+)He(2s(2) (1)S(e)) state by using the complex rotation method. The existence of a series of e(+)He(ns(2) (1)S(e)) resonances associated with the He(ns(2)) double Rydberg series is also predicted, and an explicit calculation demonstrating the existence of the e(+)He(3s(2) (1)S(e)) state is reported. PMID:23006262

  9. Demixing of hydrogen and helium at megabar pressures.

    PubMed

    Lorenzen, Winfried; Holst, Bastian; Redmer, Ronald

    2009-03-20

    We present results of ab initio finite-temperature density functional theory molecular dynamics simulations for fluid hydrogen-helium mixtures at megabar pressures. The location of the miscibility gap is derived from the equation of state data. We find a close relation between hydrogen-helium phase separation and the continuous nonmetal-to-metal transition in hydrogen. Our calculations predict that demixing of hydrogen and helium occurs in Saturn and probably also in Jupiter. These results will have a strong impact on interior models of giant solar and extrasolar planets. PMID:19392215

  10. Why does superfluid helium leak out of an open container?

    E-print Network

    V. A. Golovko

    2012-11-27

    The fact that superfluid helium always leaks out of an open container is usually explained by the phenomenon of wetting. In the present paper it is demonstrated that this explanation is unconvincing. The fact can be readily explained from the viewpoint of the interpretation of superfluidity proposed earlier by the author according to which superfluidity is an equilibrium state of liquid helium where the symmetry is spontaneously broken because of an intrinsic superflow. Experiments on the thickness of moving helium films that have given rise to much controversy are discussed as well. Some experiments concerning the phenomena considered in the paper are proposed.

  11. Many-body theory for multipole polarizabilities and dispersion forces in helium-helium interactions

    Microsoft Academic Search

    B. K. Rao

    1984-01-01

    Linked cluster many-body perturbation theory has been developed for the calculation of the dynamic quadrupole polarizabilities of the helium atom in its ground state. The polarizabilities have been used to calculate the London dispersion force constants for He-He interactions. The results for the polarizabilities and the van der Waals constants compare very well with other standard values.

  12. Photoionization Energies and Oscillator Strengths of Helium and Helium-like Ions

    Microsoft Academic Search

    N. A. B. Faye; A. S. Ndao; A. Konte; M. Biaye; A. Wague

    2005-01-01

    We first studied the resonant photoionization of helium-like ions, such as C4+, N5+, and O6+, and determined the wave functions, the excitation energies, and the partial and total widths of the autoionizing states of these ions lying under the n = 3 thresholds of the residual ion. For more detailed analysis of the theory, and a better comprehension of the

  13. Superfluid helium tanker instrumentation

    SciTech Connect

    Woodhouse, C.E. (Johns Hopkins Univ., Baltimore, MD (USA). School of Medicine); Kashani, A. (Sterling Federal Systems, Inc., NASA/Ames Research Center, Moffett Field, CA (US)); Lukemire, A.T. (National Aeronautics and Space Administration, Greenbelt, MD (USA). Goddard Space Flight Center)

    1990-02-01

    An instrumentation system for a 1992 space shuttle flight demonstration of a superfluid helium (SFHe) tanker and transfer technology is presented. This system provides measurement of helium temperatures, pressures, flow rates, mass, and the presence of liquid or vapor. The instrumentation system described consists of analog and digital portions which provide a space qualified electronics system that is fault tolerant, compact, and relatively lightweight. The data processing hardware and software are ground commandable, perform measurements asynchronously, and format telemetry for transmission to the ground. The novel heat pulse mass gaging technique is described. A new liquid/vapor sensor is presented. Flowmeters for SFHe are discussed. A SFHe fountain effect pump is described. Results of tests to date are presented.

  14. Helium in Chemically Peculiar Stars

    E-print Network

    F. Leone

    1998-05-05

    For the purpose of deriving the helium abundances in chemically peculiar stars, the importance of assuming a correct helium abundance has been investigated for determining the effective temperature and gravity of main sequence B-type stars, making full use of the present capability of reproducing their helium lines. Even if the flux distribution of main sequence B-type stars appears to depend only on the effective temperature for any helium abundance, the effective temperature, gravity and helium abundance have to be determined simultaneously by matching the Balmer line profiles. New MULTI NLTE calculations, performed adopting ATLAS9 model atmospheres and updated helium atomic parameters, reproduce most of the observed equivalent widths of neutral helium lines for main sequence B-type stars and they make us confident of the possibility to correctly derive the helium abundance in chemically peculiar stars. An application of previous methods to the helium rich star HD 37017 shows that helium could be stratified in the magnetic pole regions, as expected in the framework of the diffusion theory in the presence of mass loss.

  15. Optical Forces on Metastable Helium

    NASA Astrophysics Data System (ADS)

    Corder, Christopher Scott

    Optical forces using lasers allow precise control over the motion of atoms. The bichromatic optical force (BF) is unique in its large magnitude and velocity range, arising from the absorption and stimulated emission processes. These properties were used to transversely collimate a beam of metastable helium (He*) using the 23S - 23P transition. The collimation created a very bright beam of He*, allowing experiments of neutral atom lithography. The He* beam was used to pattern material surfaces using a resist-based lithography technique, where the pattern was determined by either mechanical or optical masks. The optical masks produced features with a separation of half the wavelength of the light used. Patterning was successfully demonstrated with both IR and UV optical masks. The etched pattern resolution was ˜ 100 nm and limited by the material surface. Further experiments were performed studying the ability of the bichromatic force to cool. The finite velocity range of the BF allows estimation of a characteristic cooling time which is independent of the excited state lifetime, only depending on the atomic mass and optical transition energy. Past experiments, including the helium collimation used for neutral atom lithography, have demonstrated that the BF can collimate and longitudinally slow atomic beams, but required long interaction times that included many spontaneous emission (SE) events. The effect of SE can be mitigated, and is predicted to not be necessary for BF cooling. Since the BF cooling time is not related to the excited state lifetime, a transition can be chosen such that the cooling time is shorter than the SE cycle time, allowing direct laser cooling on atoms and molecules that do not have cycling transitions. Experiments using the helium 2 3S-3P transition were chosen because the BF cooling time (285 ns) is on the order of the average SE cycle time (260 ns). Numerical simulations of the experimental system were run predicting compression of the atomic velocity distribution. Our experimental results demonstrate the stimulated nature of the force through many atomic recoils from the light in less than one SE cycle time. A large range of the atomic velocity distribution is accelerated and accumulates at the velocity limit of the force. This accumulation results in an increase in the velocity space density, demonstrating cooling.

  16. CP pulse-envelope-driven dynamics at Floquet anticrossings of He Rydberg atoms: the importance of fine structure

    NASA Astrophysics Data System (ADS)

    Zelazny, S. A.; Koch, P. M.

    1998-05-01

    A 14.6 keV, CO2 laser-excited beam of n^3S He Rydberg atoms flew through a TE_121 mode cavity, exposing the atoms to about 300 oscillations of a circularly polarized 9.904 GHz electric field (peak amplitude F) with a half-sine pulse envelope. Detection of a surviving Rydberg atom signal \\cal S(F) occurred downstream in a voltage-labeled 9.8 GHz cavity whose field amplitude was set empirically to ionize (n,M_l=0) atoms more efficiently than (n,|M_l|>= 1) atoms.( W. van de Water et al.), Phys. Rev. A 42, 572 (1990). The ions were detected with a particle multiplier. For both n=28,29 \\cal S(F) displayed Stueckelberg oscillations (as observed previously with LP at higher frequencies)( S. Yoakum et al.), Phys. Rev. Lett. 69, 1919 (1992). and other F-dependent structure. Calculations of Floquet quasienergy levels require inclusion of fine structure couplings to understand the origin of the oscillations. How to extract relevant diabatic states( M. Cavagnero and S. Cornett, private communication. ) and couplings from the Floquet calculations towards modelling \\cal S(F) will be discussed and experimental-theoretical comparisons presented.

  17. Education in Helium Refrigeration

    SciTech Connect

    Gistau Baguer, G. M. [38330, Biviers (France)

    2004-06-23

    On the one hand, at the end of the time I was active in helium refrigeration, I noticed that cryogenics was stepping into places where it was not yet used. For example, a conventional accelerator, operating at room temperature, was to be upgraded to reach higher particle energy. On the other hand, I was a little bit worried to let what I had so passionately learned during these years to be lost. Retirement made time available, and I came gradually to the idea to teach about what was my basic job. I thought also about other kinds of people who could be interested in such lessons: operators of refrigerators or liquefiers who, often by lack of time, did not get a proper introduction to their job when they started, young engineers who begin to work in cryogenics... and so on.Consequently, I have assembled a series of lessons about helium refrigeration. As the audiences have different levels of knowledge in the field of cryogenics, I looked for a way of teaching that is acceptable for all of them. The course is split into theory of heat exchangers, refrigeration cycles, technology and operation of main components, process control, and helium purity.

  18. NUCLEAR CONDENSATE AND HELIUM WHITE DWARFS

    SciTech Connect

    Bedaque, Paulo F.; Berkowitz, Evan [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD (United States); Cherman, Aleksey, E-mail: bedaque@umd.edu, E-mail: evanb@umd.edu, E-mail: a.cherman@damtp.cam.ac.uk [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA (United Kingdom)

    2012-04-10

    We consider a high-density region of the helium phase diagram, where the nuclei form a Bose-Einstein condensate rather than a classical plasma or a crystal. Helium in this phase may be present in helium-core white dwarfs. We show that in this regime there is a new gapless quasiparticle not previously noticed, arising when the constraints imposed by gauge symmetry are taken into account. The contribution of this quasiparticle to the specific heat of a white dwarf core turns out to be comparable in a range of temperatures to the contribution from the particle-hole excitations of the degenerate electrons. The specific heat in the condensed phase is two orders of magnitude smaller than in the uncondensed plasma phase, which is the ground state at higher temperatures, and four orders of magnitude smaller than the specific heat that an ion lattice would provide, if formed. Since the specific heat of the core is an important input for setting the rate of cooling of a white dwarf star, it may turn out that such a change in the thermal properties of the cores of helium white dwarfs has observable implications.

  19. Mantle helium and carbon isotopes in Separation Creek Geothermal Springs, Three Sisters area, Central Oregon: Evidence for renewed volcanic activity or a long term steady state system?

    SciTech Connect

    van Soest, M.C.; Kennedy, B.M.; Evans, W.C.; Mariner, R.H.

    2002-04-30

    Cold bubbling springs in the Separation Creek area, the locus of current uplift at South Sister volcano show strong mantle signatures in helium and carbon isotopes and CO{sub 2}/{sup 3}He. This suggests the presence of fresh basaltic magma in the volcanic plumbing system. Currently there is no evidence to link this system directly to the uplift, which started in 1998. To the contrary, all geochemical evidence suggests that there is a long-lived geothermal system in the Separation Creek area, which has not significantly changed since the early 1990s. There was no archived helium and carbon data, so a definite conclusion regarding the strong mantle signature observed in these tracers cannot yet be drawn. There is a distinct discrepancy between the yearly magma supply required to explain the current uplift (0.006 km{sup 3}/yr) and that required to explain the discharge of CO{sub 2} from the system (0.0005 km{sup 3}/yr). This discrepancy may imply that the chemical signal associated with the increase in magma supply has not reached the surface yet. With respect to this the small changes observed at upper Mesa Creek require further attention, due to the recent volcanic vent in that area it may be the location were the chemical signal related to the uplift can most quickly reach the surface. Occurrence of such strong mantle signals in cold/diffuse geothermal systems suggests that these systems should not be ignored during volcano monitoring or geothermal evaluation studies. Although the surface-expression of these springs in terms of heat is minimal, the chemistry carries important information concerning the size and nature of the underlying high-temperature system and any changes taking place in it.

  20. Advanced fuels modeling: Evaluating the steady-state performance of carbide fuel in helium-cooled reactors using FRAPCON 3.4

    NASA Astrophysics Data System (ADS)

    Hallman, Luther, Jr.

    Uranium carbide (UC) has long been considered a potential alternative to uranium dioxide (UO2) fuel, especially in the context of Gen IV gas-cooled reactors. It has shown promise because of its high uranium density, good irradiation stability, and especially high thermal conductivity. Despite its many benefits, UC is known to swell at a rate twice that of UO2. However, the swelling phenomenon is not well understood, and we are limited to a weak empirical understanding of the swelling mechanism. One suggested cladding for UC is silicon carbide (SiC), a ceramic that demonstrates a number of desirable properties. Among them are an increased corrosion resistance, high mechanical strength, and irradiation stability. However, with increased temperatures, SiC exhibits an extremely brittle nature. The brittle behavior of SiC is not fully understood and thus it is unknown how SiC would respond to the added stress of a swelling UC fuel. To better understand the interaction between these advanced materials, each has been implemented into FRAPCON, the preferred fuel performance code of the Nuclear Regulatory Commission (NRC); additionally, the material properties for a helium coolant have been incorporated. The implementation of UC within FRAPCON required the development of material models that described not only the thermophysical properties of UC, such as thermal conductivity and thermal expansion, but also models for the swelling, densification, and fission gas release associated with the fuel's irradiation behavior. This research is intended to supplement ongoing analysis of the performance and behavior of uranium carbide and silicon carbide in a helium-cooled reactor.

  1. hal-00120114,version2-23Feb2007 Lifetime of weakly-bound dimers of ultracold metastable helium studied by

    E-print Network

    Paris-Sud XI, Université de

    hal-00120114,version2-23Feb2007 Lifetime of weakly-bound dimers of ultracold metastable helium. INTRODUCTION Helium atoms 4 He in the metastable 23 S1 state are long lived (2 hours lifetime) and can- sociation, our group studied exotic molecules in which two spin-polarized metastable helium atoms are bound

  2. High-order harmonic generation from Rydberg atoms in inhomogeneous fields.

    PubMed

    Wang, Zhe; He, Lixin; Luo, Jianghua; Lan, Pengfei; Lu, Peixiang

    2014-10-20

    We theoretically investigate the high-order harmonic generation (HHG) from Rydberg atoms considering the spatial inhomogeneity of the driving field. It is found that in the inhomogeneous field, the effect of the cutoff extension in the harmonic spectrum from Rydberg atoms can be extended to multi-cycle regime, while in the homogeneous field case, the extension of the harmonic cutoff is limited to the few-cycle regime (less than two optical cycles). The underlying physics of the cutoff extension from Rydberg atoms in the inhomogeneous field is analyzed based on the classical and quantum-mechanical models. Furthermore, by optimizing the field inhomogeneity, the electron dynamics can be well controlled to generate a smooth supercontinuum in the extended spectral region. This can support the efficient generation of isolated attosecond pulses in Rydberg atoms from multi-cycle laser fields. PMID:25401622

  3. Resource Letter SH-1: Superfluid Helium.

    ERIC Educational Resources Information Center

    Hallock, Robert B.

    1982-01-01

    Provides an annotated list of books, textbooks, and films on superfluid helium. Also lists research reports/reviews arranged by category, including among others, early history, microscopic understanding, ions in helium, helium in rotation, vortices and quantization, helium films and constricted geometrics, persistence flow, and superfluid helium…

  4. The winter helium bulge revisited

    NASA Astrophysics Data System (ADS)

    Liu, Xianjing; Wang, Wenbin; Thayer, Jeffrey P.; Burns, Alan; Sutton, Eric; Solomon, Stanley C.; Qian, Liying; Lucas, Greg

    2014-10-01

    A newly implemented helium module in the National Center for Atmospheric Research-Thermosphere Ionosphere Electrodynamics general circulation model offers the first opportunity in three decades to describe helium behavior in the context of a first principles, self-consistent model and to test early theories of wintertime helium bulge formation. This study shows general agreement with the findings of Reber and Hays (1973) but articulates the definitive role of vertical advection in the bulge formation. Our findings indicate vertical advection and molecular diffusion are the dominate processes responsible for the solstice helium distribution. Horizontal winds indirectly contribute to the helium bulge formation by their divergent wind field that leads to vertical winds in order to maintain thermosphere mass continuity. As a minor gas, thermospheric helium does not contribute to mass continuity and its distribution is dictated by more local interactions and constraints.

  5. The helium fine-structure controversy

    E-print Network

    Ingvar Lindgren

    2008-10-05

    There is presently disagreement between theory and experiment as well as between different theoretical calculations concerning the fine-structure splitting of the lowest P state of the neutral helium atom. We believe that we have found a minor error in the formulas used by Drake et al. (Can. J. Phys. 80, 1195 (2002)) in their calculations, and we may have an explanation how the error has occurred. To what extent this might resolve (part of) the discrepancy is not known at present.

  6. Spectroscopy of barium atoms in liquid and solid helium matrices

    SciTech Connect

    Lebedev, V.; Moroshkin, P.; Weis, A. [Departement de Physique, Universite de Fribourg, Chemin du Musee 3, CH-1700 Fribourg (Switzerland)

    2011-08-15

    We present an exhaustive overview of optical absorption and laser-induced fluorescence lines of Ba atoms in liquid and solid helium matrices in visible and near-infrared spectral ranges. Due to the increased density of isolated atoms, we have found a large number of spectral lines that were not observed in condensed helium matrices before. We have also measured the lifetimes of metastable states. The lowest {sup 3}D{sub 1} metastable state has lifetime of 2.6 s and can be used as an intermediate state in two-step excitations of high-lying states. Various matrix-induced radiationless population transfer channels have been identified.

  7. Photoionization Energies and Oscillator Strengths of Helium and Helium-Like Ions with Z = 6-8 (abstract)

    Microsoft Academic Search

    N. A. B. Faye; A. S. Ndao; A. Konte; M. Biaye; A. Wague

    2009-01-01

    In the photoionization process of helium and helium-like ions with Z = 6-8 (C4+, N5+, O6+), resonance energies of doubly excited autoionizing 1,3P0 states converging on the n = 4 and n = 5 hydrogenic thresholds were calculated by use of the diagonalization method. We also evaluated the oscillator strengths for transitions from 1s2 (1Se) to continuum 1 skp (1P0)

  8. Cavitation pressure in liquid helium

    E-print Network

    Frederic Caupin; Sebastien Balibar

    2001-09-19

    Recent experiments have suggested that, at low enough temperature, the homogeneous nucleation of bubbles occurs in liquid helium near the calculated spinodal limit. This was done in pure superfluid helium 4 and in pure normal liquid helium 3. However, in such experiments, where the negative pressure is produced by focusing an acoustic wave in the bulk liquid, the local amplitude of the instantaneous pressure or density is not directly measurable. In this article, we present a series of measurements as a function of the static pressure in the experimental cell. They allowed us to obtain an upper bound for the cavitation pressure P_cav (at low temperature, P_cav -3.0 bar in helium 3, P_cav > - 10.4 bar in helium 4). In this article we thus present quantitative evidence that cavitation occurs at low temperature near the calculated spinodal limit (-3.1 bar in helium 3 and -9.5 bar in helium 4). Further information is also obtained on the comparison between the two helium isotopes. We finally discuss the magnitude of nonlinear effects in the focusing of a sound wave in liquid helium, where the pressure dependence of the compressibility is large.

  9. Helium cryopumping for fusion applications

    SciTech Connect

    Sedgley, D.W.; Batzer, T.H.; Call, W.R.

    1988-05-01

    Large quantities of helium and hydrogen isotopes will be exhausted continuously from fusion power reactors. This paper summarizes two development programs undertaken to address vacuum pumping for this application: (i) A continuous duty cryopump for pumping helium and/or hydrogen species using charcoal sorbent and (ii) a cryopump configuration with an alternative shielding arrangement using charcoal sorbent or argon spray. A test program evaluated automatic pumping of helium, helium pumping by charcoal cryosorption and with argon spray, and cryosorption of helium/hydrogen mixtures. The continuous duty cryopump pumped helium continuously and conveniently. Helium pumping speed was 7.7 l/s/cm/sup 2/ of charcoal, compared to 5.8 l/s/cm/sup 2/ for the alternative pump. Helium speed using argon spray was 18% of that obtained by charcoal cryosorption in the same (W-panel) pump. During continuous duty cryopump mixture tests with helium and hydrogen copumped on charcoal, gas was released sporadically. Testing was insufficient to explain this unacceptable event.

  10. Photoelectron studies of excited molecular states: H2 C (1)PI(sub u) and N2 o3 (1)PI(sub u)

    NASA Astrophysics Data System (ADS)

    Dehmer, J. L.; Dehmer, P. M.; Pratt, S. T.

    Resonantly enhanced multiphoton ionization (REMPI)affords the opportunity to select a specific ionization pathway in order to produce a particular ionic state for further study (such as state-selected ion-molecule reactions) or to investigate detailed aspects of excited state photoionization dynamics. The production of electronic and vibrational state-selected ions was achieved, and in some instances rotational state-selection may be possible. State-selected ions are obtained by first preparing an intermediate Rydberg state that has a potential energy curve similar to that of the desired final ionic state, and then ionizing the Rydberg state with a single additional photon. Under these circumstances, the Franck-Condon factors governing the final ionization step strongly favor the preservation of the vibrational level of the Rydberg state core. In addition, the photoionizing transition is expected to favor the further excitation of the Rydberg electron, while retaining the electronic state of the ion core.

  11. A photoionization study of OH and OD from 680A to 950A: An analysis of the Rydberg series

    NASA Technical Reports Server (NTRS)

    Cutler, J. N.; He, Z. X.; Samson, J. A. R.

    1994-01-01

    The photoionization spectra of OH(+) and OD(+) have been reported from 680 to 950 A (18.23 to 13.05 eV) at a wavelength resolution of 0.07 A. Through interpretation of both spectra, the Rydberg series and their higher vibrational members have been reported for three of the excited ionic states, a(sup 1)Delta, A(sup 3)Pi(i), and b(sup 1) Sigma(sup +). A vibrational progression has also been observed in both OH(+) and OD(+) which is apparently related to a fourth excited ionic state, c(sup 1)Pi. Finally, the dissociative ionization limits, corrected to 0 K,for H2O AND D2O have been measured to be 18.11+/-0.01 and 18.21+/-0.01 eV, respectively, and shown to be in good agreement with previously reported results.

  12. Transport coefficients of helium and argon-helium plasmas

    Microsoft Academic Search

    Anthony B. Murphy

    1997-01-01

    Calculated values of the viscosity, thermal conductivity, and electrical conductivity of helium, and mixtures of argon and helium, at high temperatures are presented. In addition, combined ordinary, pressure, and thermal diffusion coefficients are given for the mixtures. The calculations, which assume local thermodynamic equilibrium, are performed for atmospheric pressure plasmas in the temperature range from 300 to 30000 K. The

  13. Line ratio diagnostics in helium and helium seeded argon plasmas

    Microsoft Academic Search

    R F Boivin; S D Loch; C P Ballance; D Branscomb; M S Pindzola

    2007-01-01

    We investigate the potential use of line ratio diagnostics to evaluate electron temperature in either helium or helium seeded argon plasmas. Plasmas are produced in a helicon plasma source. A rf compensated Langmuir probe is used to measure both the electron temperature and plasma density while a spectrometer is used to measure He I line intensities from the plasma. For

  14. Detachment of metastable helium molecules from helium nanodroplets

    Microsoft Academic Search

    S. Yurgenson; C.-C. Hu; C. Kim; J. A. Northby

    1999-01-01

    Metastable helium a 3S + u molecules are produced in helium nanodroplets by electron bombardment, and become attached to their surface. Photo induced electronic transitions release them, and they are subsequently detected when they eject secondary electrons upon reaching a nearby surface. We report here the first high resolution spectroscopic study of this system. It reveals a highly non-thermal rotational

  15. Exciton Rydberg in T-shaped quantum wires

    NASA Astrophysics Data System (ADS)

    Brinkmann, Dirk; Fishman, Guy

    1997-12-01

    We have calculated the electronic structure of the two series of T-shaped wires experimentally studied by T. Someya et al. [Phys. Rev. Lett. 76, 2965 (1996)]. The finite depth of the wells and the cubic symmetry of the valence band are explicitly taken into account. We obtain the theoretical value of the exciton Rydberg RthX and the exciton transition energy EthX. The results derived from our theory, which has no adjustable parameters, are compared with the experimental value EexX and the estimated value ResX obtained for S1 series (GaAs-Ga0.7Al0.3 As) and S2 series (GaAs-AlAs). In the S1 sample, where the thicknesses of the two quantum wells, which define a T wire, are identical (balanced T wire), EthX=1590 meV compared to EexX=1591 and RthX=15 meV while ResX=17+/-3 meV. In the balanced S2 sample we obtain EthX=1626 meV compared to EexX=1621 meV and RthX=18 meV while ResX=27+/-3 meV. The large width of the photoluminescence line for the samples of the S2 series and the discrepancy between the experimental and calculated values suggest that the luminescence is due to excitons bound to interfaces. The values of the exciton Rydberg deduced from the experiments is therefore overestimated.

  16. Studies in superfluid helium 

    E-print Network

    Larson, Elmer Virgil

    1969-01-01

    Larson, 8 A. , Concordia College; Directed by: Dr, Charles F. Squire Fourth sound was used to study ths hydrodynamic properties of liquid helium near 1 ' 5oK ~ Standing waves were sst up in e circular sound chaeber, which was packed with a 1 ' 0... micron alumina powder. A sharp resonance frequency varied in a regular and reproducible wey as the temperature decreased from 1 ' 498 to 1 ' 463oK. After the sound chamber was rotated at 100 rpm, 8 times the critical velocity, the resonance peak had...

  17. Study by EELS of helium bubbles in a martensitic steel

    NASA Astrophysics Data System (ADS)

    Fréchard, S.; Walls, M.; Kociak, M.; Chevalier, J. P.; Henry, J.; Gorse, D.

    2009-08-01

    This work presents measurements of the helium density and pressure in small bubbles in a martensitic steel, which is a vital first step towards identifying their role in the microstructural mechanisms determining the macroscopic properties of the material. Electron Energy-Loss Spectroscopy in the Scanning Transmission Electron Microscope has been used to analyse individual bubbles. The energy shift of the 1s ? 2p transition and the helium density have been measured for each bubble analysed. The pressure inside the bubbles has been calculated from the helium density using an equation of state. In these bubbles, the values for the helium pressure seem to be smaller than the equilibrium pressure, and agree in trend with the findings of previous studies, although our results extend to smaller radii and higher pressures.

  18. Phase separation in hydrogen-helium mixtures at Mbar pressures.

    PubMed

    Morales, Miguel A; Schwegler, Eric; Ceperley, David; Pierleoni, Carlo; Hamel, Sebastien; Caspersen, Kyle

    2009-02-01

    The properties of hydrogen-helium mixtures at Mbar pressures and intermediate temperatures (4000 to 10000 K) are calculated with first-principles molecular dynamics simulations. We determine the equation of state as a function of density, temperature, and composition and, using thermodynamic integration, we estimate the Gibbs free energy of mixing, thereby determining the temperature, at a given pressure, when helium becomes insoluble in dense metallic hydrogen. These results are directly relevant to models of the interior structure and evolution of Jovian planets. We find that the temperatures for the demixing of helium and hydrogen are sufficiently high to cross the planetary adiabat of Saturn at pressures approximately 5 Mbar; helium is partially miscible throughout a significant portion of the interior of Saturn, and to a lesser extent in Jupiter. PMID:19171896

  19. Phase separation in hydrogen–helium mixtures at Mbar pressures

    PubMed Central

    Morales, Miguel A.; Schwegler, Eric; Ceperley, David; Pierleoni, Carlo; Hamel, Sebastien; Caspersen, Kyle

    2009-01-01

    The properties of hydrogen–helium mixtures at Mbar pressures and intermediate temperatures (4000 to 10000 K) are calculated with first-principles molecular dynamics simulations. We determine the equation of state as a function of density, temperature, and composition and, using thermodynamic integration, we estimate the Gibbs free energy of mixing, thereby determining the temperature, at a given pressure, when helium becomes insoluble in dense metallic hydrogen. These results are directly relevant to models of the interior structure and evolution of Jovian planets. We find that the temperatures for the demixing of helium and hydrogen are sufficiently high to cross the planetary adiabat of Saturn at pressures ?5 Mbar; helium is partially miscible throughout a significant portion of the interior of Saturn, and to a lesser extent in Jupiter. PMID:19171896

  20. Helium diffusion in carbonates

    NASA Astrophysics Data System (ADS)

    Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion directions and the maximum interstitial apertures in each 'slice' in the structure are identified. Preliminary results show that observed differences in diffusivities are consistent with the size of the smallest maximum aperture along each diffusion direction. In calcite, the smallest maximum apertures are ~0.92 and ~0.66 angstroms for cleavage-normal and c-axis parallel directions respectively. In dolomite, the smallest maximum aperture is ~0.78 angstroms for the cleavage normal direction. Work is in progress on characterizing helium diffusion for other orientations in dolomite, and in other carbonates, including aragonite and magnesite, and in implementing these diffusion findings in the interpretation and modeling of bulk volume diffusion in heterogeneous calcite crystals common in many geologic applications. Copeland et al. (2007) GCA 71, 4488-4511 Cherniak and Watson, (2011) Chem. Geo. 288, 149-161

  1. A liquid helium target system for a measurement of parity violation in neutron spin rotation

    Microsoft Academic Search

    C. D. Bass; T. D. Bass; B. R. Heckel; C. R. Huffer; D. Luo; D. M. Markoff; A. M. Micherdzinska; W. M. Snow; H. E. Swanson; S. C. Walbridge

    2009-01-01

    A liquid helium target system was designed and built to perform a precision measurement of the parity-violating neutron spin rotation in helium due to the nucleon–nucleon weak interaction. The measurement employed a beam of low energy neutrons that passed through a crossed neutron polarizer–analyzer pair with the liquid helium target system located between them. Changes between the target states generated

  2. A liquid helium target system for a measurement of parity violation in neutron spin rotation

    Microsoft Academic Search

    C. D. Bass; T. D. Bass; B. R. Heckel; C. R. Huffer; D. Luo; D. M. Markoff; A. M. Micherdzinska; W. M. Snow; H. E. Swanson; S. C. Walbridge

    2009-01-01

    A liquid helium target system was designed and built to perform a precision measurement of the parity-violating neutron spin rotation in helium due to the nucleon-nucleon weak interaction. The measurement employed a beam of low energy neutrons that passed through a crossed neutron polarizer-analyzer pair with the liquid helium target system located between them. Changes between the target states generated

  3. The role of Rydberg and continuum levels in computing high harmonic generation spectra of the hydrogen atom using time-dependent configuration interaction.

    PubMed

    Luppi, Eleonora; Head-Gordon, Martin

    2013-10-28

    We study the role of Rydberg bound-states and continuum levels in the field-induced electronic dynamics associated with the High-Harmonic Generation (HHG) spectroscopy of the hydrogen atom. Time-dependent configuration-interaction (TD-CI) is used with very large atomic orbital (AO) expansions (up to L = 4 with sextuple augmentation and off-center functions) to describe the bound Rydberg levels, and some continuum levels. To address the lack of ionization losses in TD-CI with finite AO basis sets, we employed a heuristic lifetime for energy levels above the ionization potential. The heuristic lifetime model is compared against the conventional atomic orbital treatment (infinite lifetimes), and a third approximation which is TD-CI using only the bound levels (continuum lifetimes go to zero). The results suggest that spectra calculated using conventional TD-CI do not converge with increasing AO basis set size, while the zero lifetime and heuristic lifetime models converge to qualitatively similar spectra, with implications for how best to apply bound state electronic structure methods to simulate HHG. The origin of HHG spectral features including the cutoff and extent of interference between peaks is uncovered by separating field-induced coupling between different types of levels (ground state, bound Rydberg levels, and continuum) in the simulated electronic dynamics. Thus the origin of deviations between the predictions of the semi-classical three step model and the full simulation can be associated with particular physical contributions, which helps to explain both the successes and the limitations of the three step model. PMID:24182018

  4. Radiative lifetimes along even-parity J = 1, 2 Rydberg series of neutral tin

    NASA Astrophysics Data System (ADS)

    Zhang, W.; You, S.; Sun, C.; Zhang, Y.; Xu, J.; Ma, Z.; Feng, Y.; Liu, H.; Quinet, P.; Biémont, É.; Dai, Z.

    2009-10-01

    Using the time-resolved laser-induced fluorescence (LIF) technique in a tin atomic beam, 40 natural radiative lifetimes have been measured for the even-parity J = 1~5 pnp (n = 10-13, 15-19) and J = 2~5 pnp (n = 10-13, 15-19, 27, 31, 32), 5 pnf (n = 4, 5, 9-19, 22, 23) levels along the Rydberg series and for all the 5p8p perturbing levels of neutral tin with energies in the range 52263.8 to 59099.9 cm-1. A two-step laser excitation scheme was used in the experiment. A multiconfigurational relativistic Hartree-Fock (HFR) calculation taking core-polarization effects into account has also been performed for the even-parity states for testing the ability of this approach to correctly predict the radiative properties of tin atom. Through an analysis of the energy levels structure by the multichannel quantum defect theory (MQDT), the channel admixture coefficients have been obtained and used to fit the theoretical lifetimes to the experimental ones in order to predict new values for the levels not measured. A generally good overall agreement between experimental and theoretical MQDT and HFR lifetimes has been achieved except for a few levels.

  5. Stepwise contraction of the nf Rydberg shells in the 3d photoionization of multiply-charged xenon ions

    NASA Astrophysics Data System (ADS)

    Schippers, S.; Borovik, A., Jr.; Buhr, T.; Hellhund, J.; Holste, K.; Kilcoyne, A. L. D.; Klumpp, S.; Martins, M.; Müller, A.; Ricz, S.; Fritzsche, S.

    2015-07-01

    Triple photoionization of Xe3+, Xe4+ and Xe5+ ions has been studied in the energy range 670–750 eV, including the 3d ionization threshold. The photon-ion merged-beam technique was used at a synchrotron light source to measure the absolute photoionization cross sections. These cross sections exhibit a progressively larger number of sharp resonances as the ion charge state is increased. This clearly visualizes the re-ordering of the ? f continuum into a regular series of (bound) Rydberg orbitals as the ionic core becomes more attractive. The energies and strengths of the resonances are extracted from the experimental data and are further analysed by relativistic atomic-structure calculations.

  6. Electron impact excitation-autoionisation of the (2s(sup 2)(sup 1)S, (2p(sup 2))(sup 1)D and (2s2p)(sup1)P autoionising states of helium

    NASA Astrophysics Data System (ADS)

    Samardzic, O.; Hurn, J.-A.; Weigold, E.; Brunger, M. J.

    The electron impact excitation of the (2s(sup 2)(sup 1)S, (2p(sup 2))(sup 1)D and (2s2p)(sup 1)P autoionizing states of helium and their subsequent radiationless decay was studied by observation of the ejected electrons. The present work was carried out at an incident energy of 94.6 eV and for ejected electron scattering angles in the range 25-135 deg. This study was conducted simultaneously with an (e,2e) investigation into these same autoionizing states with the results of this latter work being discussed elsewhere. The lineshapes observed in the present ejected electron spectra are analyzed using the Shore-Balashov parametrization. As part of the analysis procedure we determined numerically rigorous confidence limits for the derived parameters. We believe this is the first time that such error limits are presented in the literature for the derived parameters. No previous experimental or theoretical work has been undertaken at the incident energy of the present investigation but, where possible, the resulting parameters are qualitatively compared against the 80 eV results of other experiments and theory.

  7. PHYSICAL REVIEW A 88, 012716 (2013) Breakup of Rydberg-blockaded atom clouds via dipole-dipole interactions

    E-print Network

    Eisfeld, Alexander

    2013-01-01

    the clouds. The dynamics is akin to an ensemble average over systems where only one atom per cloudPHYSICAL REVIEW A 88, 012716 (2013) Breakup of Rydberg-blockaded atom clouds via dipole Rydberg-blockaded atom clouds where each cloud carries initially a coherently shared single excitation. We

  8. PHYSICAL REVIEW A 81, 063411 (2010) Spatially resolved excitation of Rydberg atoms and surface effects on an atom chip

    E-print Network

    Amsterdam, Universiteit van

    2010-01-01

    PHYSICAL REVIEW A 81, 063411 (2010) Spatially resolved excitation of Rydberg atoms and surface effects on an atom chip Atreju Tauschinsky,* Rutger M. T. Thijssen, S. Whitlock, H. B. van Linden van den spatially resolved, coherent excitation of Rydberg atoms on an atom chip. Electromagnetically induced

  9. PHYSICAL REVIEW A 87, 023423 (2013) Rydberg atoms with a reduced sensitivity to dc and low-frequency electric fields

    E-print Network

    Le Roy, Robert J.

    2013-01-01

    PHYSICAL REVIEW A 87, 023423 (2013) Rydberg atoms with a reduced sensitivity to dc and low-frequency electric fields L. A. Jones, J. D. Carter, and J. D. D. Martin Department of Physics and Astronomy sensitivity to high frequency fields, is applicable to sensors and/or quantum devices using Rydberg atoms. DOI

  10. Ab initio study of high-lying doubly excited states of helium in static electric fields: Complex-scaling generalized pseudospectral method in hyperspherical coordinates

    E-print Network

    Chu, Shih-I; Heslar, John

    2012-09-21

    of the energies and autoionization widths for the high-lying 1Se, 1Po, 1De, and 1Fo (n=10–20) doubly excited resonance states of He atoms. In addition, we present a theoretical prediction of the energies and widths of high-lying doubly excited resonance states...

  11. Helium runaways in white dwarfs

    NASA Technical Reports Server (NTRS)

    Taam, R. E.

    1980-01-01

    The long-term evolution of a carbon-accreting white dwarf (M = 0.5 solar mass) has been studied from the onset of accretion to the ignition of helium. The variations in the details of the helium-shell flash have been examined with respect to variations in mass accretion rate. For intermediate rates (10 to the -9th to 10 to the -8th solar mass/yr) the helium flash is potentially explosive, whereas for high rates (5 x 10 to the -8th solar mass/yr) the shell flash is relatively weak. The results are discussed in the context of the long-term evolution of novae.

  12. Quantum Cavitation: a comparison between superfluid helium-4 and normal liquid helium-3

    E-print Network

    Caupin, Frédéric

    Quantum Cavitation: a comparison between superfluid helium-4 and normal liquid helium-3 S. Balibar in superfluid helium-4 and in normal liquid helium-3, both theoretically and experimentally. We compare the two by tunneling, to classical cavitation where their nu- cleation is thermally activated. In helium-3, where

  13. Properties of Fr-like Th{sup 3+} from spectroscopy of high-L Rydberg levels of Th{sup 2+}

    SciTech Connect

    Keele, Julie A.; Hanni, M. E.; Woods, Shannon L.; Lundeen, S. R.; Fehrenbach, C. W. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States); J. R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas 66506 (United States)

    2011-06-15

    Binding energies of high-L Rydberg states (L{>=} 7) of Th{sup 2+} with n = 27-29 were studied using the resonant excitation Stark ionization spectroscopy (RESIS) method. The core of the Th{sup 2+} Rydberg ion is the Fr-like ion Th{sup 3+} whose ground state is a 5 {sup 2}F{sub 5/2} level. The large-core angular momentum results in a complex Rydberg fine-structure pattern consisting of six levels for each value of L that is only partially resolved in the RESIS excitation spectrum. The pattern is further complicated, especially for the relatively-low-L levels, by strong nonadiabatic effects due to the low-lying 6d levels. Analysis of the observed RESIS spectra leads to determination of five properties of the Th{sup 3+} ion: its electric quadrupole moment Q = 0.54(4); its adiabatic scalar and tensor dipole polarizabilities {alpha}{sub d,0} = 15.42(17) and {alpha}{sub d,2} = -3.6(1.3); and the dipole matrix elements connecting the ground 5 {sup 2}F{sub 5/2} level to the low-lying 6 {sup 2}D{sub 3/2} and 6 {sup 2}D{sub 5/2} levels, |<5 {sup 2}F{sub 5/2}||D||6{sup 2}D{sub 3/2}>|=1.435(10) and |<5{sup 2}F{sub 5/2}||D||6{sup 2}D{sub 5/2}>|=0.414(24). All are in atomic units. These are compared with theoretical calculations.

  14. The Ionization of Helium by Neutral Helium Atoms

    Microsoft Academic Search

    Frank Horton; Dorothy M. Millest

    1946-01-01

    A method is described for investigating the ionization produced in helium by collisions between quasi-stationary atoms-that is, atoms possessing only thermal velocities-and a beam of neutral helium atoms with kinetic energy less than 100 eV. Ionization is shown to begin when the kinetic energy of the bombarding atoms is twice as great as the minimum kinetic energy which electrons must

  15. Ionization coefficients in helium, neon and helium-neon mixtures

    Microsoft Academic Search

    J Dutton; M H Hughes; B C Tan

    1969-01-01

    The spatial growth of pre-breakdown ionization currents at values of E\\/N (E is the electric field and N the gas number density) within the range from 2·24 × 10-16 to 11·2 × 10-16 v cm2 was measured for helium, for neon and for eight different helium-neon mixtures with fractional concentrations of neon ranging from 0·05 to 0·95. For neon and

  16. Ab Initio simulations of dense helium plasmas.

    PubMed

    Wang, Cong; He, Xian-Tu; Zhang, Ping

    2011-04-01

    We study the thermophysical properties of dense helium plasmas by using quantum molecular dynamics and orbital-free molecular dynamics simulations, where densities are considered from 400 to 800??g/cm3 and temperatures up to 800 eV. Results are presented for the equation of state. From the Kubo-Greenwood formula, we derive the electrical conductivity and electronic thermal conductivity. In particular, with the increase in temperature, we discuss the change in the Lorenz number, which indicates a transition from strong coupling and degenerate state to moderate coupling and partial degeneracy regime for dense helium. PMID:21561197

  17. The 1s ? 1s2p(P) excitation energy for helium atoms in liquid helium, solid helium and helium bubbles in metals

    Microsoft Academic Search

    N. C. Pyper; D. W. Essex; Colm T. Whelan

    2001-01-01

    The energy of the He 1s ? 1s2p(P) transition for helium atoms in liquid helium, solid helium and helium bubbles in metals is greater than for free helium atoms by an amount known as the energy shift. The energy shift is calculated by combining the results of ab-initio self-consistent field electronic structure calculations with corrections to account for the effects

  18. Calculation of the density shift and broadening of the transition lines in pionic helium: Computational problems

    NASA Astrophysics Data System (ADS)

    Bakalov, Dimitar

    2015-03-01

    The potential energy surface and the computational codes, developed for the evaluation of the density shift and broadening of the spectral lines of laser-induced transitions from metastable states of antiprotonic helium, fail to produce convergent results in the case of pionic helium. We briefly analyze the encountered computational problems and outline possible solutions of the problems.

  19. Precision Measurement of the Three 23 PJ Helium Fine Structure Intervals

    E-print Network

    Zelevinsky, Tanya

    Precision Measurement of the Three 23 PJ Helium Fine Structure Intervals T. Zelevinsky,1,* D helium discharge presents experimental uncertainties quite different than for earlier measurements to the metastable 23 S1 state in a 60 MHz discharge. Frequency shifts due to the discharge and associated collisions

  20. Resonant charge-exchange involving excited helium atoms and reactive transport of local thermodynamic equilibrium helium plasma

    SciTech Connect

    Kosarim, A. V.; Smirnov, B. M. [Joint Institute for High Temperatures RAS, Moscow (Russian Federation); Laricchiuta, A. [CNR IMIP Bari, Bari (Italy); Capitelli, M. [CNR IMIP Bari, Bari (Italy); Department of Chemistry, University of Bari, Bari (Italy)

    2012-06-15

    The cross sections for charge-exchange and charge-transfer processes are evaluated for collisions of helium ions with parent-atoms in ground and excited states, with the principal quantum number n= 1-5, in the collision energy range from thermal up to 10 eV. Corresponding diffusion-type collision integrals are derived, and the role of 'abnormal' transport of electronically excited states on the reactive thermal conductivity of equilibrium helium plasma, at atmospheric pressure, estimated in the frame of a simplified approach.

  1. Radiation source for helium magnetometers

    NASA Technical Reports Server (NTRS)

    Slocum, Robert E. (Inventor)

    1991-01-01

    A radiation source (12) for optical magnetometers (10) which use helium isotopes as the resonance element (30) includes an electronically pumped semiconductor laser (12) which produces a single narrow line of radiation which is frequency stabilized to the center frequency of the helium resonance line to be optically pumped. The frequency stabilization is accomplished using electronic feedback (34, 40, 42, 44) to control a current sources (20) thus eliminating the need for mechanical frequency tuning.

  2. Superfluid phases of helium-3

    Microsoft Academic Search

    Dieter Vollhardt; P. Wolfle; Robert B. Hallock

    1991-01-01

    A comprehensive treatment of the theory of superfluid helium-3 is presented in this book. This treatment also illustrates many of the principal themes of theoretical condensed matter physics over the past two decades. The generalized BCS (Barden-Cooper-Schrieffer) pairing theory and the experimental properties of superfluid helium-3 are treated in detail. Extensive treatment of broken symmetries and their relation to macroscopic

  3. Electron Conductivity on Helium Films

    Microsoft Academic Search

    J. Klier; I. Doicescu; P. Leiderer; V. Shikin

    2008-01-01

    Electrons on liquid helium films form a two-dimensional (2D) array with a wide range of electron density. This system is also\\u000a very interesting for applications in restricted geometry. The conductivity ? of the electron arrays, however, strongly depends on the thickness d of the helium films adsorbed above solid substrates. This behaviour of ? is discussed in detail for a

  4. Laser ionization and spectroscopy of Cu in superfluid helium nanodroplets

    PubMed Central

    Lindebner, Friedrich; Kautsch, Andreas; Koch, Markus; Ernst, Wolfgang E.

    2014-01-01

    Mass and optical spectroscopic methods are used for the analysis of copper (Cu) atoms and clusters doped to helium nanodroplets (HeN). A two-color resonant two-photon ionization scheme is applied to study the Cu 2P1/2,3/2??2S1/2 ground state transition. The absorption is strongly broadened for Cu atoms submerged inside helium nanodroplets and a comparison with computed literature values is provided. An observed ejection of the dopant from the droplet is triggered upon excitation, populating energetically lower states. The formation of Cun clusters up to Cu7 inside helium nanodroplets was observed by means of electron impact ionization mass spectroscopy. PMID:25844053

  5. Cryogenic filter method produces super-pure helium and helium isotopes

    NASA Technical Reports Server (NTRS)

    Hildebrandt, A. F.

    1964-01-01

    Helium is purified when cooled in a low pressure environment until it becomes superfluid. The liquid helium is then filtered through iron oxide particles. Heating, cooling and filtering processes continue until the purified liquid helium is heated to a gas.

  6. 43 CFR 3195.20 - Who must purchase major helium requirements from Federal helium suppliers?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Who must purchase major helium requirements from Federal helium suppliers? 3195.20 Section 3195.20 ...THE INTERIOR MINERALS MANAGEMENT (3000) HELIUM CONTRACTS Federal Agency Requirements §...

  7. 43 CFR 3195.20 - Who must purchase major helium requirements from Federal helium suppliers?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Who must purchase major helium requirements from Federal helium suppliers? 3195.20 Section 3195.20 ...THE INTERIOR MINERALS MANAGEMENT (3000) HELIUM CONTRACTS Federal Agency Requirements §...

  8. 43 CFR 3195.20 - Who must purchase major helium requirements from Federal helium suppliers?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Who must purchase major helium requirements from Federal helium suppliers? 3195.20 Section 3195.20 ...THE INTERIOR MINERALS MANAGEMENT (3000) HELIUM CONTRACTS Federal Agency Requirements §...

  9. 43 CFR 3195.20 - Who must purchase major helium requirements from Federal helium suppliers?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Who must purchase major helium requirements from Federal helium suppliers? 3195.20 Section 3195.20 ...THE INTERIOR MINERALS MANAGEMENT (3000) HELIUM CONTRACTS Federal Agency Requirements §...

  10. Survival of Rydberg atoms in intense laser fields and the role of nondipole effects

    NASA Astrophysics Data System (ADS)

    Klaiber, Michael; Dimitrovski, Darko

    2015-02-01

    We consider the interaction of Rydberg atoms with strong infrared laser pulses using an approach based on the Magnus expansion of the time evolution operator. First-order corrections beyond the electric dipole approximation are also included in the theory. We illustrate the dynamics of the interaction at the parameters of the experiment [Eichmann et al., Phys. Rev. Lett. 110, 203002 (2013), 10.1103/PhysRevLett.110.203002]. It emerges that the depletion of Rydberg atoms in this regime comes predominantly from the nondipole effects.

  11. Implementing a neutral-atom controlled-phase gate with a single Rydberg pulse

    E-print Network

    Rui Han; Hui Khoon Ng; Berthold-Georg Englert

    2014-09-04

    One can implement fast two-qubit entangling gates by exploiting the Rydberg blockade. Although various theoretical schemes have been proposed, experimenters have not yet been able to demonstrate two-atom gates of high fidelity due to experimental constraints. We propose a novel scheme, which only uses a single Rydberg pulse, for the construction of neutral-atom controlled-phase gates. In contrast to the existing schemes, our scheme is simpler to implement and requires neither individual addressing of atoms nor adiabatic procedures. With realistically estimated experimental parameters, a gate fidelity higher than 0.99 is achievable.

  12. Rotons, Superfluidity, and Helium Crystals

    NASA Astrophysics Data System (ADS)

    Balibar, Sébastien

    2006-09-01

    Fritz London understood that quantum mechanics could show up at the macroscopic level, and, in 1938, he proposed that superfluidity was a consequence of Bose-Einstein condensation. However, Lev Landau never believed in London's ideas; instead, he introduced quasiparticles to explain the thermodynamics of superfluid 4He and a possible mechanism for its critical velocity. One of these quasiparticles, a crucial one, was his famous "roton" which he considered as an elementary vortex. At the LT0 conference (Cambridge, 1946), London criticized Landau and his "theory based on the shaky grounds of imaginary rotons". Despite their rather strong disagreement, Landau was awarded the London prize in 1960, six years after London's death. Today, we know that London and Landau had both found part of the truth: BEC takes place in 4He, and rotons exist. In my early experiments on quantum evaporation, I found direct evidence for the existence of rotons and for evaporation processes in which they play the role of photons in the photoelectric effect. But rotons are now considered as particular phonons which are nearly soft, due to some local order in superfluid 4He. Later we studied helium crystals which are model systems for the general study of crystal surfaces, but also exceptional systems with unique quantum properties. In our recent studies of nucleation, rotons show their importance again: by using acoustic techniques, we have extended the study of liquid 4He up to very high pressures where the liquid state is metastable, and we wish to demonstrate that the vanishing of the roton gap may destroy superfluidity and trigger an instability towards the crystalline state.

  13. ITER helium ash accumulation

    SciTech Connect

    Hogan, J.T.; Hillis, D.L.; Galambos, J.; Uckan, N.A. (Oak Ridge National Lab., TN (USA)); Dippel, K.H.; Finken, K.H. (Forschungszentrum Juelich GmbH (Germany, F.R.). Inst. fuer Plasmaphysik); Hulse, R.A.; Budny, R.V. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

    1990-01-01

    Many studies have shown the importance of the ratio {upsilon}{sub He}/{upsilon}{sub E} in determining the level of He ash accumulation in future reactor systems. Results of the first tokamak He removal experiments have been analysed, and a first estimate of the ratio {upsilon}{sub He}/{upsilon}{sub E} to be expected for future reactor systems has been made. The experiments were carried out for neutral beam heated plasmas in the TEXTOR tokamak, at KFA/Julich. Helium was injected both as a short puff and continuously, and subsequently extracted with the Advanced Limiter Test-II pump limiter. The rate at which the He density decays has been determined with absolutely calibrated charge exchange spectroscopy, and compared with theoretical models, using the Multiple Impurity Species Transport (MIST) code. An analysis of energy confinement has been made with PPPL TRANSP code, to distinguish beam from thermal confinement, especially for low density cases. The ALT-II pump limiter system is found to exhaust the He with maximum exhaust efficiency (8 pumps) of {approximately}8%. We find 1<{upsilon}{sub He}/{upsilon}{sub E}<3.3 for the database of cases analysed to date. Analysis with the ITER TETRA systems code shows that these values would be adequate to achieve the required He concentration with the present ITER divertor He extraction system.

  14. Polarized Helium to Image the Lung

    NASA Astrophysics Data System (ADS)

    Leduc, Michèle; Nacher, Pierre Jean

    2005-05-01

    The main findings of the european PHIL project (Polarised Helium to Image the Lung) are reported. State of the art optical pumping techniques for polarising 3He gas are described. MRI methodological improvements allow dynamical ventilation images with a good resolution, ultimately limited by gas diffusion. Diffusion imaging appears as a robust method of lung diagnosis. A discussion of the potential advantage of low field MRI is presented. Selected PHIL results for emphysema are given, with the perspectives that this joint work opens up for the future of respiratory medicine.

  15. Optical pumping of helium-3 with a frequency electromodulated M. Elbel (1), C. Larat (2), P.J. Nacher (2) and M. Leduc (2)

    E-print Network

    Paris-Sud XI, Université de

    the laser power over the Doppler absorption profile of the metastable helium atoms can enhance pumping of the 23S, metastable state of helium; metastability exchange collisions ensure the transfer39 Optical pumping of helium-3 with a frequency electromodulated laser M. Elbel (1), C. Larat (2

  16. Spectroscopic properties of the low-lying electronic states of RbHen (n = 1, 2) and their comparison with lighter alkali metal-helium systems

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Anjan

    2012-02-01

    Ab initio-based configuration interaction studies on RbHe and He-Rb-He have explored some key features of the low-lying electronic states of these van der Waals systems. The radiative lifetime of the Rb*He exciplex has been calculated to be around 24.5 ns, which is slightly higher than the HeRb*He lifetime (˜20 ns) and lower than the atomic fluorescence lifetime of Rb, by roughly 3.5 ns. Better exciplex stability of the symmetric triatomic system is evidenced by its higher binding energy value in comparison to the diatomic system by a substantial margin. BSSE-corrected spin-orbit calculations of RbHe have predicted a potential barrier of the 12?1/2 state with a height of 15 cm-1 and width of 2.57 Å. The 2?u state of the triatomic molecule shows a conical intersection of its Renner-Teller components (12A1 and 12B2) near a 99° bond angle along the bending path. Their unstable higher excited states (12?+1/2 or 12?+g,1/2) can trigger the pumping of the blue side of the ns2S1/2 ? np2P3/2 transition, and this may eventually lead to the np2P1/2 ?ns2S1/2 lasing transition. The broad fluorescence band with a peak near 11?900 cm-1 is found to arise from the 12?3/2-X2?+1/2 transition of RbHe.

  17. Electron-impact excitation of the (2p{sup 2}) {sup 1}D and (2s2p) {sup 1}P{sup o} autoionizing states of helium

    SciTech Connect

    Sise, Omer; Dogan, Mevlut; Okur, Ibrahim; Crowe, Albert [Department of Physics, Afyon Kocatepe University, 03200 Afyon (Turkey); Department of Physics, Sakarya University, Adapazari (Turkey); School of Chemistry, Newcastle University, Newcastle (United Kingdom)

    2011-08-15

    An experimental study of the excitation of the (2p{sup 2}) {sup 1}D and (2s2p) {sup 1}P{sup o} autoionizing states of helium by 250-eV electron impact is presented. The ejected-electron angular distributions and energy spectra are measured in coincidence with the corresponding scattered electrons for a scattering angle of -13 deg. and for a range of ejected-electron angles in both the forward and backward directions. Resonance profiles are analyzed in terms of the Shore-Balashov parametrization to obtain the resonance asymmetry A{sub {mu}} and yield B{sub {mu}} parameters and the direct ionization cross section f. The spectra and their parameters are compared to the previous measurements of Lower and Weigold [J. Phys. B. 23, 2819 (1990)] and McDonald and Crowe [J. Phys. B 26, 2887 (1993)]. Comparison is also made with the recent theoretical triply differential cross-section calculations based on the first and second Born approximations. In general, good qualitative agreement is found between the experimental results. Some differences are found at the forward and backward directions. These differences in the shape and magnitude of the cross sections are attributed to the different incoming electron energies used in the experiments. The second Born approximation with inclusion of the three-body Coulomb interaction in the final state agrees reasonably well with experiments in the binary region. However, the {sup 1}P{sup o} resonance yield parameter B{sub {mu}} is significantly overestimated at the recoil region, giving a relatively large recoil peak, in contradiction to the experiment. There is also a discrepancy between the two theories available for the {sup 1}D resonance yield parameter B{sub {mu}} in this region. Remaining discrepancies between theories and experiments are also discussed.

  18. Helium superfluidity. Shapes and vorticities of superfluid helium nanodroplets.

    PubMed

    Gomez, Luis F; Ferguson, Ken R; Cryan, James P; Bacellar, Camila; Tanyag, Rico Mayro P; Jones, Curtis; Schorb, Sebastian; Anielski, Denis; Belkacem, Ali; Bernando, Charles; Boll, Rebecca; Bozek, John; Carron, Sebastian; Chen, Gang; Delmas, Tjark; Englert, Lars; Epp, Sascha W; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Hexemer, Alexander; Huth, Martin; Kwok, Justin; Leone, Stephen R; Ma, Jonathan H S; Maia, Filipe R N C; Malmerberg, Erik; Marchesini, Stefano; Neumark, Daniel M; Poon, Billy; Prell, James; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Seifrid, Martin; Siefermann, Katrin R; Sturm, Felix P; Swiggers, Michele; Ullrich, Joachim; Weise, Fabian; Zwart, Petrus; Bostedt, Christoph; Gessner, Oliver; Vilesov, Andrey F

    2014-08-22

    Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging to investigate the rotation of single, isolated superfluid helium-4 droplets containing ~10(8) to 10(11) atoms. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from xenon clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than those observed in bulk liquid helium. The droplets exhibit large centrifugal deformations but retain axially symmetric shapes at angular velocities well beyond the stability range of viscous classical droplets. PMID:25146284

  19. Helium halo nuclei from low-momentum interactions

    E-print Network

    S. Bacca; A. Schwenk; G. Hagen; T. Papenbrock

    2009-05-14

    We present ground-state energies of helium halo nuclei based on chiral low-momentum interactions, using the hyperspherical-harmonics method for 6He and coupled-cluster theory for 8He, with correct asymptotics for the extended halo structure.

  20. Molecular Iodine Fluorescence Using a Green Helium-Neon Laser

    ERIC Educational Resources Information Center

    Williamson, J. Charles

    2011-01-01

    Excitation of molecular iodine vapor with a green (543.4 nm) helium-neon laser produces a fluorescence spectrum that is well suited for the upper-level undergraduate physical chemistry laboratory. Application of standard evaluation techniques to the spectrum yields ground electronic-state molecular parameters in good agreement with literature…