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1

Interaction of Helium Rydberg State Atoms with Superfluid Helium  

NASA Astrophysics Data System (ADS)

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.

Fiedler, Steven L.; Eloranta, Jussi

2014-03-01

2

Ultrafast probing of ejection dynamics of Rydberg atoms and molecular fragments from electronically excited helium nanodroplets  

SciTech Connect

The ejection dynamics of Rydberg atoms and molecular fragments from electronically excited helium nanodroplets are studied with time-resolved extreme ultraviolet ion imaging spectroscopy. At excitation energies of 23.6 {+-} 0.2 eV, Rydberg atoms in n= 3 and n= 4 states are ejected on different time scales and with significantly different kinetic energy distributions. Specifically, n= 3 Rydberg atoms are ejected with kinetic energies as high as 0.85 eV, but their appearance is delayed by approximately 200 fs. In contrast, n= 4 Rydberg atoms appear within the time resolution of the experiment with considerably lower kinetic energies. Major features in the Rydberg atom kinetic energy distributions for both principal quantum numbers can be described within a simple elastic scattering model of localized perturbed atomic Rydberg atoms that are expelled from the droplet due to their repulsive interaction with the surrounding helium bath. Time-dependent kinetic energy distributions of He{sub 2}{sup +} and He{sub 3}{sup +} ions are presented that support the formation of molecular ions in an indirect droplet ionization process and the ejection of neutral Rydberg dimers on a similar time scale as the n= 3 Rydberg atoms.

Buenermann, Oliver; Kornilov, Oleg; Neumark, Daniel M. [Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Chemistry, University of California, Berkeley, California 94720 (United States); Haxton, Daniel J.; Gessner, Oliver [Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Leone, Stephen R. [Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Chemistry, University of California, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, California 94720 (United States)

2012-12-07

3

Single-color two-photon spectroscopy of Rydberg states in electric fields  

NASA Astrophysics Data System (ADS)

Rydberg states of atomic helium with principal quantum numbers ranging from n =20 to n =100 have been prepared by non-resonance-enhanced single-color two-photon excitation from the metastable 2 3S1 state. Photoexcitation was carried out using linearly and circularly polarized pulsed laser radiation. In the case of excitation with circularly polarized radiation, Rydberg states with azimuthal quantum number | m?|=2 were prepared in zero electric field and in homogeneous electric fields oriented parallel to the propagation axis of the laser radiation. In sufficiently strong electric fields, individual Rydberg-Stark states were resolved spectroscopically, highlighting the suitability of non-resonance-enhanced multiphoton excitation schemes for the preparation of long-lived high-| m?| hydrogenic Rydberg states for deceleration and trapping experiments. Applications of similar schemes for Doppler-free excitation of positronium atoms to Rydberg states are also discussed.

Wall, T. E.; Cassidy, D. B.; Hogan, S. D.

2014-11-01

4

High-angular-momentum states in cold Rydberg gases.  

PubMed

Cold, dense Rydberg gases produced in a cold-atom trap are investigated using spectroscopic methods and time-resolved electron counting. Optical excitation on the discrete Rydberg resonances reveals long-lasting electron emission from the Rydberg gas ( >20 ms). Our observations are explained by lm-mixing collisions between Rydberg atoms and slow electrons that lead to the population of long-lived high-angular-momentum Rydberg states. These atoms thermally ionize slowly and with large probabilities. PMID:11328078

Dutta, S K; Feldbaum, D; Walz-Flannigan, A; Guest, J R; Raithel, G

2001-04-30

5

Transmission-line decelerators for atoms in high Rydberg states  

E-print Network

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 $10^7$ 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.

Lancuba, P

2014-01-01

6

Communication: Heavy Rydberg states: the H+H- system.  

PubMed

Heavy Rydberg states are analogs of electronic Rydberg states, but with the electron replaced by a much heavier ion. We calculate ab initio the extremely long-range vibrational H(+)H(-) heavy Rydberg states in H(2), and compare these to recent experiments. The calculated resonance positions and widths agree well with experiment, but we predict additional sharp interloper resonances corresponding to vibrational states trapped inside the barrier on potential energy curve 7 (1)?(g)(+). PMID:20886917

Kirrander, Adam

2010-09-28

7

Supersymmetry and radial squeezed states for Rydberg wave packets  

NASA Technical Reports Server (NTRS)

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.

Bluhm, Robert; Kostelecky, V. Alan

1994-01-01

8

Atomic Fock State Preparation Using Rydberg Blockade  

NASA Astrophysics Data System (ADS)

We use coherent excitation of 3-16 atom ensembles to demonstrate collective Rabi flopping mediated by Rydberg blockade. Using calibrated atom number measurements, we quantitatively confirm the expected ?N Rabi frequency enhancement to within 4%. The resulting atom number distributions are consistent with an essentially perfect blockade. We then use collective Rabi ? pulses to produce N =1, 2 atom number Fock states with fidelities of 62% and 48%, respectively. The N=2 Fock state shows the collective Rabi frequency enhancement without corruption from atom number fluctuations.

Ebert, Matthew; Gill, Alexander; Gibbons, Michael; Zhang, Xianli; Saffman, Mark; Walker, Thad G.

2014-01-01

9

Rydberg States of Atoms and Molecules  

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

10

Cold Rydberg atoms in circular states  

NASA Astrophysics Data System (ADS)

Circular-state Rydberg atoms are interesting in that they exhibit a unique combination of extraordinary properties; long lifetimes (˜n^5), large magnetic moments (l=|m|=n-1) and no first order Stark shift. Circular states have found applications in cavity quantum electrodynamics and precision measurements [1,2], among other studies. In this work we present the production of circular states in an atom trapping apparatus using an adiabatic state-switching method (the crossed-field method [3]). To date, we have observed lifetimes of adiabatically prepared states of several milliseconds. Their relatively large ionization electric fields have been verified by time-of-flight signatures of ion trajectories. We intend to explore the magnetic trapping of circular state Rydberg atoms, as well as their production and interaction properties in ultra-cold and degenerate samples.[4pt] [1] P. Bertet et al., Phys. Rev. Lett., 88, 14 (2002)[0pt] [2] M. Brune et al., Phys. Rev. Lett., 72, 21 (1994)[0pt] [3] D. Delande and J.C. Gay, Europhys. Lett., 5, 303-308 (1988).

Anderson, David; Schwarzkopf, Andrew; Raithel, Georg

2012-06-01

11

Spectroscopy of strontium Rydberg states using electromagnetically induced transparency  

E-print Network

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.

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

2007-10-05

12

A note on the assignments of Rydberg states of COS  

NASA Technical Reports Server (NTRS)

Assignments of the Rydberg states which converge to the respective X-tilde and B-tilde ion states of the COS(+) ion are reported. The assignments were made based on previously established orderings for the quantum defects of isoelectronic molecules. The Rydberg series I and II, which converge to the X-tilde 2 Pi state of COS(+), and the series III, IV, V, VI and VII, which converge to the B-tilde 2 Sigma + state, are assigned to molecular orbitals characterized by predominant sulfur orbitals, in contrast to those converging to the C-tilde states, which are characterized by oxygen atomic orbitals.

Wu, C. Y. R.

1982-01-01

13

Very high resolution spectroscopy of high Rydberg states  

NASA Astrophysics Data System (ADS)

Atomic and molecular Rydberg states in the range of principal quantum number n=100-500 have unusual properties: The classical orbits are extremely large (diameter larger than 1 ? m); the Rydberg electron is very weakly bound (by less than 1 meV); moreover, atoms and molecules in high Rydberg states are extremely sensitive to their environment and respond strongly to even small perturbations such as those induced by weak (stray) electric fields or particles located in their vicinity (T.F. Gallagher, Rydberg atoms) (Cambridge University Press, Cambridge, 1994),Rydberg states of atoms and molecules, Eds. R.F. Stebbings and F.B. Dunning (Cambridge University Press, Cambridge, 1983). The unusual properties of high Rydberg states are at the origin of the success of several new spectroscopic techniques, such as pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy and mass-analysed theshold ionization (MATI) spectroscopy, that have been developed recently to study molecular ions (K. Müller- Dethlefs and E. W. Schlag, Ann. Rev. Phys. Chem.) 42, 109 (1991), F. Merkt Ann. Rev. Phys. Chem. 48, 675 (1997). These techniques, which are used in an increasing number of laboratories, rely on the pulsed field ionization of high Rydberg states (n=100-500) located immediately below successive ionization thresholds in a molecule. Although possible impacts of uncontrolled external perturbations on the appearance of PFI-ZEKE spectra have been inferred recently (W.A. Chupka, J. Chem. Phys.) 98 4520 (1993), F. Merkt and R.N. Zare, J. Chem. Phys. 101 3495 (1994), these remain very difficult to assess: The experimental efforts needed to reduce, or at least quantify, the effects of stray electric fields and external perturbations on Rydberg states beyond n=100 are considerable and have not even been attempted so far by PFI-ZEKE and MATI spectroscopists. To fill in this gap, a new instrument has been developed to obtain very high resolution (250 kHz) spectra of molecular and atomic Rydberg states in the range of principal quantum number n=30-300 using a double resonance technique. Key components of the instrument are a high-resolution, broadly tunable (10-20 eV) extreme ultraviolett (XUV) laser system and a frequency stabilized source of millimeter waves. Selected results illustrating the capabilities of this instrument will be presented. First, a simple procedure (M. T. Frey, X. Ling, B. G. Lindsay, K. A. Smith and F. B. Dunning, Rev. Sci. Instrum.) 64 3649 (1993), based on the analysis of spectral line shifts of high Rydberg states as a function of electric field strength, is used to measure stray electric fields with an absolute accuracy of 50 ? V/cm and to subsequently compensate them, enabling the reduction of stray electric fields to less than 50 ?V/cm. Second, the analysis of spectral line shapes as a function of laser power is used to obtain distributions of electric field strengths as a function of the ion concentration in the experimental volume. Third, fully resolved Stark maps of high Rydberg states of krypton are obtained at n? 100 below the ^2P_3/2 ionization threshold. Finally, high precision measurement of the fine-structure splittings in p, d and f Rydberg states of the argon and the krypton atoms are reported. The hyperfine structure in high Rydberg states of the ^83Kr isotope has also been fully resolved. The implications of these results for PFI-ZEKE and MATI spectroscopy will be discussed.

Merkt, F.

1998-05-01

14

Xenon low-n Rydberg states in supercritical argon near the critical point  

E-print Network

Xenon low-n Rydberg states in supercritical argon near the critical point Luxi Li a,b , Xianbo Shi simulation of the 6s and 6s Rydberg states (including the blue satellite bands) of xenon doped into argon

Findley, Gary L.

15

Photoionization dynamics of the C2+ ion in Rydberg states  

NASA Astrophysics Data System (ADS)

The goal of this work is to examine in detail the ionization dynamics of Be-like C ion in Rydberg states. An initial calculation has been done to output the lifetime due to spontaneous decay for unperturbed 1s22sns (1Se) Rydberg states using the multi-configuration Dirac-Fock (MCDF) method with configuration interaction option implemented in the general-purpose relativistic atomic structure package (GRASP). Both the C2+ ground state and the C3+ target state energies have been carefully calculated. We report results from a detailed and systematic study of the behaviour of complex photoionization amplitudes, the lifetime due to spontaneous decay for unperturbed 1s22sns (1Se) Rydberg states, the `resonant' phase shift and the rapidly increasing of this shift from well below to well above the resonance position. The sum-over-state method is used to calculate the static dipole polarizability, while the frequency-dependent polarizability values of C2+ ion in these Rydberg states are obtained from two-state model calculation results. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Stefan Matejcik, John Tanis and Kurt H. Becker.

Stancalie, Viorica

2014-11-01

16

Efficient excitation of Rydberg states in ultracold lithium-7 atoms  

NASA Astrophysics Data System (ADS)

This work is aimed at preparing highly excited optically cooled lithium-7 atoms for producing a strongly nonideal plasma and Rydberg matter. A setup implementing a novel nondestructive technique for preparation and diagnostics of highly excited Rydberg atomic states is constructed. The operation of this setup is based on the usage of a cw high-power ultraviolet laser combined with a magneto-optical trap. The diagnostics of highly excited states is performed by the direct recording of the variations in the fluorescence of ultracold lithium-7 atoms in the magneto-optical trap.

Zelener, B. B.; Saakyan, S. A.; Sautenkov, V. A.; Manykin, E. A.; Zelener, B. V.; Fortov, V. E.

2014-11-01

17

Hâ and Dâ photon impact predissociation. [Fluorescence, Rydberg states  

Microsoft Academic Search

Atomic Lyman ..cap alpha.. and Balmer ..cap alpha.., ..beta.., and ..gamma.. emission have been observed by irradiating Hâ and Dâ in the 680--860 A region with synchrotron radiation from the ACO storage ring at Orsay. Comparison of the observed excitation spectra with the absorption spectrum shows clear evidence for the predissociation of molecular Rydberg states above the dissociation thresholds which

P. Borrell; P. M. Guyon; M. Glass-Maujean

1977-01-01

18

Rabi oscillations between ground and Rydberg states and van der Waals blockade in a mesoscopic frozen Rydberg gas  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of our recent observation of synchronous Rabi oscillations between the electronic ground state and Rydberg states in a mesoscopic ensemble containing roughly 100 ultracold atoms (Reetz-Lamour et al submitted, Preprint 0711.4321). The mesoscopic cloud is selected out of a sample of laser-cooled Rb atoms by optical pumping. The atoms are coupled to a Rydberg state with principal quantum number around 30 by a two-photon scheme employing flat-top laser beams. The influence of residual spatial intensity fluctuations as well as sources of decoherence such as redistribution to other states, radiative lifetime and laser bandwidth are analysed. The results open up new possibilities for the investigation of coherent many-body phenomena in dipolar Rydberg gases. As an example we demonstrate the van der Waals blockade, a variant of the dipole blockade, for a mesoscopic atom sample.

Reetz-Lamour, M.; Deiglmayr, J.; Amthor, T.; Weidemüller, M.

2008-04-01

19

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

20

Diamagnetic behaviour of xenon Rydberg states studied by the R.F. optogalvanic method  

E-print Network

249 Diamagnetic behaviour of xenon Rydberg states studied by the R.F. optogalvanic method J. P behaviour of xenon nf Rydberg states is studied using single-mode dye laser excita- tion and an R xenon can offer interesting opportunities for studies of this type. We want furthermore to emphasize

Paris-Sud XI, Université de

21

Pulsed-field ionization spectroscopy of high Rydberg states ,,n=50200... -benzene...chromium  

E-print Network

Pulsed-field ionization spectroscopy of high Rydberg states ,,n=50­200... of bis,, 6 -benzene...chromium The ionization behavior of the high Rydberg states of bis 6 -benzene chromium in the presence of ac and/or dc chromium, the accurate ionization potential is deduced to give IP=5.4665±0.0003 eV. Optimization

Kim, Sang Kyu

22

Electron capture from aligned Rydberg Na(25p) states.  

NASA Astrophysics Data System (ADS)

The relative charge transfer cross section of singly charged Li^+ ions incident on aligned Rydberg Na(25p) atoms was studied over approach angle ?=0^circ to 360^circ at intermediate projectile velocities. A mixture of Rydberg Na(25p_j) (j=1/2 and 3/2) states is prepared by two-step laser excitation in the presence of a Stark field followed by adiabatic switching to low field in a 16-element Stark barrel.(J.L. Horn et al./), Rev. Sci. Instrum. 69, 4086 (1998). The first laser is tuned to ? = 589.0 nm to excite the Na (3p_3/2) level overlapping all its hyperfine components. The second laser at ? = 411.6 nm is tuned to the electric dipole transition 3p_3/2arrow 25pj in the Stark field ~ 54 V/cm. After excitation the field is switched adiabatically to 1.8 V/cm and rotated through angle ? during 2 ?sec. Li^+ ions are accelerated to reduced velocity tildev = 1.0 to 2.0 where tildev = v_ion/v_n. Capture events are recorded by a CEM. Capture from the aligned Rydberg target is scanned over all angles by varying ? over 360^circ. The cross section shows maxima at 0^circ and 180^circ and minima at 90^circ and 270^circ. The results are described by the capture anisotropy parameter A = (?_0-?_90)/(?0 +?_90), which falls from ~ 0.47 at tildev = 1.0 to 1.2 as tilde v is increased from 1.4 to 2.0. This work was supported by NSF Grant PHY-9704544.

Hwang, Changsu; MacAdam, Keith B.

2001-05-01

23

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

E-print Network

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

Friedland, Lazar

24

Rabi flopping between ground and Rydberg states with dipole-dipole atomic interactions  

E-print Network

We demonstrate Rabi flopping of small numbers of $\\rm{^{87}Rb}$ atoms between ground and Rydberg states with $n\\le 43$. Coherent population oscillations are observed for single atom flopping, while the presence of two or more atoms decoheres the oscillations. We show that these observations are consistent with van der Waals interactions of Rydberg atoms.

T. A. Johnson; E. Urban; T. Henage; L. Isenhower; D. D. Yavuz; T. G. Walker; M. Saffman

2007-11-02

25

Deexcitation of high-Rydberg-state atoms with a chirped train of half-cycle pulses  

SciTech Connect

Encouraged by the experiments on production of antihydrogen atoms in high Rydberg states we have calculated the effect of deexcitation towards lower states by a chirped train of identical unidirectional half-cycle pulses. The calculations exploit both the one-dimensional and impulse approximations providing convenient analytical formulas for the Rydberg-to-Rydberg transition amplitudes. The calculated deexcitation is shown in terms of the mean value of localization of the Rydberg wave packet in the coordinate space, the Rydberg-state population distribution, the Husimi phase-space distribution function, and the probability density distribution, each of these measures vs the length of the applied train of half-cycle pulses. The results for chirped trains are compared with those for periodic trains and examples of higher deexcitation efficiency of the chirped trains are given.

Kopyciuk, T.; Parzynski, R. [Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland)

2007-05-15

26

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

SciTech Connect

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.

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

27

Dynamic polarizabilities and Rydberg states of silicon, phosphorous, and sulfur  

NASA Astrophysics Data System (ADS)

Spectral line arising out of neutral and ionized atoms of Si, P, and S are dominant in the spectra of the solar photosphere and corona. Neutral and ionized species of these atoms have been found by the IUE satellite experiments on interstellar matter. Observations of the Jupiter satellite system reveal the existence of such ions. Here, the time-dependent coupled Hartree-Fock theory is used to study the excitation properties of neutral Si, P, and S in their ground as well as their valence excited states. The Roothaan formalism is used to deal with the open-shell atoms. Excitation energies, oscillator strengths, and quantum defects are estimated for several optically allowed transitions, and analytic representations of the singly excited Rydberg orbitals are found.

Mukherjee, P. K.; Ohno, Kimio

1989-08-01

28

Four-Wave Mixing and Coherent Processes in Ultracold Atoms Using Intermediate Rydberg States.  

NASA Astrophysics Data System (ADS)

Continuous 5S-5P-nD two-photon excitation to the Rydberg state was combined with an nD-6P tuned laser to explore coherent processes using intermediate Rydberg states. In a phase-matched geometry, four-wave mixing was demonstrated in good agreement with theory. The directional emission was optimized to 50% for off-resonant Rydberg excitation. Further coherent schemes have been explored using small excitation volumes, showing promise for studying quantum effects in blockaded atom clouds.

Brekke, E.; Day, J. O.; Hardy, L.; Walker, T. G.

2009-05-01

29

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

E-print Network

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 ...

Cheng, Chiao-Lun

2008-01-01

30

Electro-optic control of atom-light interactions using Rydberg dark-state polaritons  

NASA Astrophysics Data System (ADS)

We demonstrate a multiphoton Rydberg dark resonance where a ? system is coupled to a Rydberg state. This N -type level scheme combines the ability to slow and store light pulses associated with long-lived ground-state superpositions with the strongly interacting character of Rydberg states. For the nd5/2 Rydberg state in R87b (with n=26 or 44) and a beam size of 1 mm, we observe a resonance linewidth of less than 100 kHz in a room-temperature atomic ensemble limited by transit-time broadening. The resonance is switchable with an electric field of order 1Vcm-1 . Applications in electro-optic switching and photonic phase gates are discussed.

Bason, M. G.; Mohapatra, A. K.; Weatherill, K. J.; Adams, C. S.

2008-03-01

31

Role of excited core Rydberg states in dissociative recombination.  

PubMed

Intermediate states formed during the dissociative recombination of molecular ions with electrons can play significant roles in determining the magnitude of the total rate coefficient. These resonances are Rydberg states of two types, that is, they can have the ground or excited states of the ion as a core. Those with the excited cores have a fundamentally different excitation mechanism than those with the ground state core. The importance of excited core states in dissociative recombination has received only limited attention in the literature. Theoretical calculations on the dissociative recombination of N2+ are reported which compare the two types of resonances. Potential curves, electronic widths, cross sections, and rate coefficients are calculated for dissociative recombination along the 2(1)Sigma(g)+ state, one of several routes for the dissociative recombination of N2+. The ground core resonances, in this example, are relatively unimportant compared to those with the excited core. Inclusion of the excited core resonances increases the rate coefficient by about a factor of 4 at room temperature, but the increase is not enough to establish 2(1)Sigma(g)+ as the dominant dissociative route. PMID:17547378

Guberman, Steven L

2007-11-01

32

Self-interaction corrected density functional calculations of molecular Rydberg states  

SciTech Connect

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.

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

33

Need for high resolution in VUV Rydberg state spectroscopy  

NASA Technical Reports Server (NTRS)

The paper emphasizes the necessity of high energy resolution (resolving powers greater than 100,000) in VUV spectroscopic determinations of atomic and molecular Rydberg electronic structures. Attention is given to spectral observations of Rydberg levels in Ge I near the 4p 2P(0)1/2 limit, in Sr I near the 4d 2D3/2 limit, and in diatomic hydrogen halides (especially H I) below the X2Pi3/2 limit.

Ginter, M. L.; Ginter, D. S.; Brown, C. M.

1980-01-01

34

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

SciTech Connect

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.

Bookless, W.

1980-12-01

35

Excitation of Rydberg states in rubidium with near infrared diode lasers  

NASA Astrophysics Data System (ADS)

A system of three external cavity diode lasers is used to excite Rydberg states in rubidium. The 5S?5P?5D transitions are driven using lasers with ? = 780 and 776 nm respectively. From the 5D state, atoms fluoresce down to the 6P state. The final transition to Rydberg levels is from the 6P state with laser light near ? = 1016 nm. The nS and nD Rydberg states are accessible directly and with the application of a modest electric field nP states can also be excited. As a test of this system, Stark spectra are collected for nD and nP states.

Fahey, Donald P.; Noel, Michael W.

2011-08-01

36

Magnetic stabilization of a Rydberg quasimolecule in circular states  

SciTech Connect

An exact analytical classical solution for the electronic terms of circular Rydberg states (CRS) in the presence of a magnetic field B is obtained for two-Coulomb-center systems. The classical electronic terms are shown to be significantly affected by the magnetic field. In particular, a sufficiently strong magnetic field is shown to cause the appearance of CRS above the ionization threshold. These CRS are the classical molecular counterparts of the quantal atomic quasi-Landau levels (resonances). Study of the stability of the nuclear motion in this system reveals that the system in CRS is, in the absence of the magnetic field, not really a molecule, but only a quasimolecule with antibonding molecular orbitals. We also find that the magnetic field creates a deep minimum in one of the branches of the effective potential of the relative motion of the nuclei, and thereby stabilizes the nuclear motion. We have therefore shown that a magnetic field can transform the quasimolecule into a real, classically described molecule where one of the molecular orbitals becomes bonding. This result reveals a phenomenon--the magnetically controlled stabilization of the quasimolecules in CRS--which is appropriate for future experimental studies.

Flannery, M. R. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Oks, E. [Physics Department, 206 Allison Lab., Auburn University, Auburn, Alabama 36849-5311 (United States)

2006-01-15

37

Highly polar states of Rydberg atoms in strong magnetic and weak electric fields  

NASA Astrophysics Data System (ADS)

We study the spectra of diamagnetic rubidium Rydberg atoms in strong magnetic and weak electric parallel fields, in the n-mixing regime. Our emphasis is on isolated pairs of near-degenerate, opposite-parity, diamagnetic states that become mixed by the weak electric field. Such level pairs allow for the generation of nondegenerate states with large, tunable permanent electric dipole moments and large optical excitation cross sections from the atomic ground state. We investigate how the dipole moments and the zero-electric-field energy defects of these level pairs can be tuned using small variations of the electric and magnetic fields. Using calculations, we explore the abundance of such level pairs over wide spectral regions for several magnetic quantum numbers. Applications of polar, diamagnetic Rydberg states in Rydberg-atom interaction experiments are briefly discussed.

Paradis, E.; Zigo, S.; Raithel, G.

2013-01-01

38

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

SciTech Connect

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.

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

1990-01-01

39

Circular Rydberg states of atomic hydrogen in an arbitrary magnetic field  

NASA Astrophysics Data System (ADS)

A theoretical method using a B-spline basis set has been proposed to evaluate circular Rydberg states of atomic hydrogen in a strong magnetic field. The combination of this method and a recently reported finite-basis-set technique [1] can provide a practicable scheme to implement high accuracy computations of circular Rydberg states of atomic hydrogen in an arbitrary magnetic field. Energy levels of hydrogen are presented for circular Rydberg states with azimuthal quantum numbers |m| = 10 - 70 as a function of magnetic field strengths ranging from zero to 2.35 x 10^9 T. Comparison with available theoretical data shows excellent agreement. The variation of spatial distributions of electron probability densities with magnetic field strengths is discussed and competition between Coulomb and magnetic interactions is illustrated. [4pt] [1] J. Phys. B40, 4347 (2007)

Zhao, L. B.; Saha, B. C.; Du, M. L.

2011-06-01

40

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

SciTech Connect

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.

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

41

Coherent population transfer and quantum entanglement generation involving a Rydberg state by stimulated Raman adiabatic passage  

SciTech Connect

We study a dilute sample of cold atoms to achieve efficient population transfer from a ground state to a Rydberg state. This sample is approximately divided into many independent microspheres containing only two atoms. Each pair of atoms in a microsphere may become quantum correlated via the dipole-dipole interaction characterized by a van der Waals potential. Our numerical results show that, by modulating detunings of a pump pulse and a Stokes pulse applied in the counterintuitive order, we can drive the dilute sample either into the blockade regime or into the antiblockade regime. In the blockade regime, only one atom is allowed to be coherently transferred into the Rydberg state in a microsphere, which then results in a maximal entangled state. In the antiblockade regime, however, both atoms in a microsphere can be efficiently excited into the Rydberg state, which is not accompanied by quantum entanglement. A second maximal entangled state may also be generated if we work between the blockade regime and the antiblockade regime. Note that the existence of a quasidark state is essential for exciting both atoms in a microsphere into the Rydberg state when the van der Waals potential is nonzero.

Yan Dong [College of Physics, Jilin University, Changchun 130012 (China); School of Science, Changchun University, Changchun 130022 (China); Cui Cuili; Zhang Mei; Wu Jinhui [College of Physics, Jilin University, Changchun 130012 (China)

2011-10-15

42

Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions  

SciTech Connect

Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a starlike geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S{sub 1/2}{yields}5P{sub 3/2}{yields}6S{sub 1/2}{yields}nP in Rb atoms have shown that, compared to the one- and two-photon laser excitation, this approach provides much narrower linewidth and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

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

2011-11-15

43

Non-Degenerate Four-Wave Mixing through Rydberg States in a MOT  

NASA Astrophysics Data System (ADS)

In this work, we use a three-photon near-resonant process in a laser-cooled Rb vapor to achieve phase-matched four-wave mixing using an intermediate Rydberg state. Rydberg atoms in the 36D5/2 state are efficiently produced using a 780 nm/480 nm two-photon excitation detuned 500 MHz above the 5P3/2 intermediate state. When a 1019 nm laser stimulates emission down to the 6P3/2 state, the Rydberg atom populations are significantly depleted and 422 nm 6P3/2-5S photons are observed by photon-counting photomultiplier tubes. With the 780 nm, 480 nm, and 1019 nm lasers configured in a non-collinear phase-matched geometry, we observe a coherent 422 nm phase-matched signal that is up to 10 times larger than the non-phase-matched radiation. Under these phase-matched conditions, the incoherent radiation is partially depleted. These experiments demonstrate the ability to coherently manipulate ultracold atoms at optical frequencies using Rydberg states.

Day, Jason; Brekke, Erik; Walker, Thad

2007-06-01

44

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

SciTech Connect

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}.

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

45

Photoionization from excited states of helium  

NASA Technical Reports Server (NTRS)

The cross sections for photoionization from the 2 1S, 2 3S, 2 1P and 2 3P excited states of helium are calculated for photoelectron energies below the n = 2 threshold of He(+) using Hylleraas bound state wave functions and 1s-2s-2p close coupling final state wave functions. The resonant structures associated with the lowest-lying 1S, 1P, 3P, and 1D autoionizing states of helium are found to be characterized by large values of the line profile parameter q. The cross sections and the photoelectron angular distribution asymmetry parameters for the P-states are calculated for various polarization states of the target atom and the incident photon. Experiments which would lead to the separate determinations of the S- and D- wave partial photoionization cross sections are discussed.

Jacobs, V. L.

1973-01-01

46

Electron processes in ion-Rydberg-atom collisions with emphasis on directed linear Stark states  

Microsoft Academic Search

Both classical-trajectory calculations and measurements of electron capture in A+ + B(x) collisions, where the targets are Rydberg atoms, have been performed in the intermediate velocity range. Linear Stark-state targets were created inside a novel device called the Stark barrel. With this new apparatus, off-center atomic states with axial symmetry could be prepared with their axes set at angles 0-360o

Dean Matthew Homan

1997-01-01

47

Theoretical study of the protonated hydronium radical cation H 40 + as a rydberg molecule. The ground state  

NASA Astrophysics Data System (ADS)

Ab initio calculations at HF and MP2 (the second-order Møller-Plesset perturbation ) levels with a series of extended basis sets 6-31G*, 6-31G** and 6-31G**R have been carried out for the tetrahedral H 4O + cation and its related species H 4O 2+, H 3O, H 3O +, H 2O, H 2O + and H 2 in order to study it as a Rydberg molecule. The results have shown some evidence of the Rydberg character of the ground state H 4O + including that the calculated ionization potential matches well with the estimate from the modified Rydberg formula. The ground state has been predicted to be unstable with respect to H 3O + +H or H 2O + + H 2. The potential energy curve of the dissociation into H 3O + + H has been calculated and no potential barrier has been found. Analysis of electronic details has also shown some Rydberg character of the ground state H 4O + but it has indicated a strong effect of the 3s Rydberg state interacting with the valence states. The concept of Rydberg-valence state mixing gives a good explanation of the calculated properties of the ground state of the tetrahedral H 4O + presented here.

Tao, Fu-Ming; Pan, Yuh-kang

1989-09-01

48

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

Microsoft Academic Search

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

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

1977-01-01

49

Multiphoton ionization\\/dissociation of cyclopentanone at the lower Rydberg states  

Microsoft Academic Search

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 3px,y,z components are clearly resolved while the case for the 3di excitations is obscure due to the S1 one-photon resonance. The ns laser induced mass spectra are characteristic of

John G. Philis; Constantine Kosmidis; Paraskevas Tzallas

1998-01-01

50

Tests of Theory in Rydberg States of One-Electron Ions  

NASA Astrophysics Data System (ADS)

Comparison of optical frequency measurements to predictions of quantum electrodynamics (QED) for Rydberg states of one-electron ions can test theory and allow new determinations of constants of nature to be made. Simplifications in the QED theory of high-angular-momentum states reduces the uncertainty in the prediction of transition frequencies to a level where a new value of the Rydberg constant which is independent of the proton radius can be determined. Since the energy-level spacing between neighbouring Rydberg states grows as the square of the nuclear charge number, it is possible to study transitions with optical frequencies that are accessible to femtosecond laser frequency combs. Recently at the US National Institute of Standards and Technology (NIST), highly charged ions (including bare nuclei) created in an Electron Beam Ion Trap (EBIT) were extracted and captured in a novel compact Penning trap. An ongoing experiment aims to produce one-electron ions isolated in an ion trap designed for laser spectroscopy. Tests of theory in a regime free of nuclear effects would be valuable in shedding light on the puzzle surrounding the large discrepancy in the value of the proton radius inferred from the observed Lamb shift in muonic hydrogen as compared to the value deduced from hydrogen and deuterium spectroscopy and electron scattering measurements.

Tan, Joseph N.; Mohr, Peter J.

51

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

NASA Astrophysics Data System (ADS)

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.

Kim, Hyun-Jin; Lee, Chun-Woo

2015-01-01

52

Integral Cross Sections for Electron Impact Excitation of Rydberg and Valence States of Molecular Nitrogen  

NASA Astrophysics Data System (ADS)

We present integral cross sections (ICSs) for electron impact excitation of N2 out of the ground state X (v=0), to the b, c3, o3, b', c'4, G, and F electronic states at incident energies ranging between 17.5 eV and 100 eV. The ICSs were derived from the differential cross sections (DCSs) of Khakoo et al. [Phys. Rev. A 77, 012704 (2008)], which were obtained by unfolding energy loss spectra in the ˜12-13.82 eV range. Recently, Heays et al. [Phys. Rev. A 85, 012705 (2012)] measured comparable higher resolution energy loss spectra, with a significantly different apparatus configuration, but in agreement with the Khakoo et al. (2008) spectra. This latter additional effort provided further confidence in the accuracy of the DCSs upon which the present ICS results are based. Of the higher-lying states studied, five are singlet states that radiate to the ground state via dipole allowed transitions. These include the b and b' valence states and the c'4 Rydberg state that give rise to the Birge-Hopfield I, II, and Carroll-Yoshino bands, respectively, all of which are observed in the atmospheres of Earth, Titan, and Triton. The c3 and o3 Rydberg states give rise to the Worley-Jenkins and Worley series of Rydberg bands, respectively. However, these emissions are not readily observed since predissociation for the c3 and o3 states approaches 100%. As such, direct electron excitation measurements, such as those presented here are superior to standard (spontaneous) emission based measurements in this case.

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

2012-06-01

53

Exciting Rydberg atom superposition states for control of resonant energy exchange  

NASA Astrophysics Data System (ADS)

Pairs of ultracold highly excited atoms can exchange energy over long distances through a dipole-dipole coupling. Application of a dc electric field makes it possible to tune these energy exchange processes into resonance via the Stark effect. Our experimental system allows individual |mj| sublevels of Rb Rydberg states to be excited, and then tuned into a dipole-dipole resonance. We can also excite coherent superpositions of these states, which can be used to control this energy exchange. We present experiments that investigate how this energy exchange proceeds for different initial |mj| state preparations.

Fahey, Donald P.; Noel, Michael W.; Carroll, Thomas

2012-06-01

54

Long-range interaction between metastable helium and ground state helium.  

NASA Technical Reports Server (NTRS)

Results of analysis for the long-range interaction between ground state helium and triplet metastable helium, which shows that the long-range coefficient is the same for both gerade and ungerade states. Those terms which lead to the second term on the right hand side of a developed equation vanish through spin selection rules.

Victor, G. A.; Sando, K.

1971-01-01

55

Electronic Spectroscopy and Ultrafast Energy Relaxation Pathways in the lowest Rydberg States of Trimethylamine  

PubMed Central

Resonance-enhanced multiphoton ionization photoelectron spectroscopy has been applied to study the electronic spectroscopy and relaxation pathways amongst the 3p and 3s Rydberg states of trimethylamine. The experiments used femtosecond and picosecond duration laser pulses at wavelengths of 416 nm, 266 nm, and 208 nm, and employed two-photon and three-photon ionization schemes. The binding energy of the 3s Rydberg state was found to be 3.087 ± 0.005 eV. The degenerate 3px,y states have binding energies of 2.251 ± 0.005 eV, and 3pz is at 2.204 ± 0.005 eV. Using picosecond and femtosecond time-resolved experiments we spectrally and temporally resolved an intricate sequence of energy relaxation pathways leading from the 3p states to the 3s state. With excitation at 5.96 eV, trimethylamine is found to decay from the 3pz state to 3px,y in 539 fs. The decay to 3s from all the 3p states takes place with a 2.9 ps time constant. On these time scales, trimethylamine does not fragment at the given internal energies, which range from 0.42 to 1.54 eV depending on the excitation wavelength and the electronic state. PMID:18834091

Cardoza, Job D.; Rudakov, Fedor M.; Weber, Peter M.

2009-01-01

56

Autoionizing high-Rydberg states of very heavy Belike ions: A tool for precision spectroscopy  

Microsoft Academic Search

Autoionizing high-Rydberg states formed during the initial electron capture phase of dielectronic recombination (DR) provide a unique access to spectroscopic information of highly charged heavy ions. This paper summarizes recent experimental and theoretical studies on the low energy 1s22pjnlj? (j=1\\/2, 3\\/2) Be-like DR resonances associated with the 2s1\\/2?2pj core excitations of the Li-like ions 19779Au76+, 20892Pb79+ and 23892U89+. An extrapolation

C. Brandau; T. Bartsch; S. Böhm; C. Böhme; A. Hoffknecht; H. Knopp; S. Schippers; W. Shi; A. Müller; N. Grün; W. Scheid; T. Steih; F. Bosch; B. Franzke; C. Kozhuharov; P. H Mokler; F. Nolden; M. Steck; T. Stöhlker; Z. Stachura

2003-01-01

57

Multiphoton ionization/dissociation of cyclopentanone at the lower Rydberg states  

SciTech Connect

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.

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

1998-12-16

58

Multiphoton ionization/dissociation of cyclopentanone at the lower Rydberg states  

NASA Astrophysics Data System (ADS)

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 3px,y,z components are clearly resolved while the case for the 3di excitations is obscure due to the S1 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.

Philis, John G.; Kosmidis, Constantine; Tzallas, Paraskevas

1998-12-01

59

Formation And Decay Of The Rydberg States Of Multiply Charged Ions Interacting With Solid Surfaces  

NASA Astrophysics Data System (ADS)

Processes of formation and decay of the Rydberg states of multiply charged ions escaping solid surfaces with intermediate velocities ( v Ë?1 a.u.) are complex quantum events that require a detailed quantum description. We developed a two-state vector model of electron captures into lower-n, but high-l Rydberg states. The electron exchange process is described by a mixed flux through a moving plane, positioned between the solid surface and the ionic projectile. Generally, the lower-n model reproduced the experimentally observed non-linear trend of the l distributions from l = 0 to lmax = n - 1. In the case of large values of the angular momentum quantum numbers l , the model takes into account an importance of a wide space region around the projectile trajectory. The reionization of the previously populated states is also taken account and can be described as a decay process of the electron wave function. The coresponding ionization rates are obtained by an appropriate etalon equation method: in the large- l case the radial electronic coordinate ? is treated as variational parameter. The theoretical predictions based on that population-reionization mechanism fit the available beam-foil experimental data concerning the SVI, ClVII and ArVIII ions, as well as the experimental data obtained in the interaction of multiply charged ions with micro-capillary foil.

Mirkovic, M. A.; Nedeljkovic, N. N.; Bozanic, D. K.

2010-07-01

60

Final Rydberg state population probabilities of multiply charged ions escaping solid surfaces  

NASA Astrophysics Data System (ADS)

The two-state vector model is used to investigate the final population of the Rydberg states (nA?1,lA=0-2,mA=0) of multiply charged ions escaping solid surfaces at intermediate velocities ( v?1 a.u.). Within the framework of the proposed time-symmetrized quantum model, the electron capture is a non-resonant, velocity dependent process, characterized by the selective population of the ionic Rydberg states. The final population probabilities are obtained in a relatively simple analytical form, which enables us to elucidate the role of the ionic core polarization and to analyze the nA, lA and v probability distributions. We consider the ions SVI, ClVII and ArVIII with core charges Z=6, 7 and 8, respectively, and the ions KrVIII and XeVIII with Z=8. The results are obtained for two type of surfaces and compared with available beam-foil experimental data.

Nedeljkovi?, N. N.; Galijaš, S. M. D.; Majki?, M. D.

2009-08-01

61

Calculation of Hydrogenic Bethe Logarithms for Rydberg States  

E-print Network

We describe the calculation of hydrogenic (one-loop) Bethe logarithms for all states with principal quantum numbers n calculation of the Bethe logarithm is a rather easy computational problem involving only the nonrelativistic (Schroedinger) theory of the hydrogen atom, certain calculational difficulties affect highly excited states, and in particular states for which the principal quantum number is much larger than the orbital angular momentum quantum number. Two evaluation methods are contrasted. One of these is based on the calculation of the principal value of a specific integral over a virtual photon energy. The other method relies directly on the spectral representation of the Schroedinger-Coulomb propagator. Selected numerical results are presented. The full set of values is available at quant-ph/0504002.

Ulrich D. Jentschura; Peter J. Mohr

2005-04-01

62

Multiphoton spectroscopy of Rydberg states of small molecules  

SciTech Connect

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.

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

1990-01-01

63

Far-infrared amplified emission from the v = 1 autoionizing Rydberg states of NO  

NASA Astrophysics Data System (ADS)

Far-infrared amplified emission from the v = 1 autoionizing levels of the ns (n = 9-14), np (n = 12-15) and nf (n = 8-14) Rydberg states of NO is reported in the gas phase. The dominant emission process for nf is assigned as the nf ? (n - 1)g transition. Following the excitation of ns (n = 11-14), the emission from (n - 1)f energetically located above ns is detected. Following the excitation of np (n = 12 and 13), the emission from (n - 1)f is also detected. The absence of the emission from 11p leads to ?3 ps as a threshold lifetime of the upper state needed for amplification.

Araki, Mitsunori; Abe, Kyoko; Furukawa, Hiroki; Tsukiyama, Koichi

2014-05-01

64

Self-interaction corrected density functional calculations of Rydberg states of molecular clusters: N,N-dimethylisopropylamine.  

PubMed

Theoretical calculations of Rydberg excited states of molecular clusters consisting of N,N-dimethylisopropylamine molecules using a Perdew-Zunger self-interaction corrected energy functional are presented and compared with results of resonant multiphoton ionization measurements. The binding energy of the Rydberg electron in the monomer is calculated to be 2.79 eV and 2.27 eV in the 3s and 3p state, respectively, which compares well with measured values of 2.88 eV and 2.21 eV. Three different stable configurations of the dimer in the ground state were found using an energy functional that includes van der Waals interaction. The lowest ground state energy conformation has the two N-atoms widely separated, by 6.2 Å, while the Rydberg state energy is lowest for a configuration where the N-atoms of the two molecules come close together, separated by 3.7 Å. This conformational change is found to lower the Rydberg electron binding energy by 0.2 eV. The self-interaction corrected functional gives a highly localized hole on one of the two molecules, unlike results obtained using the PBE functional or the hybrid B3LYP functional which give a delocalized hole. For the trimer, the self-interaction corrected calculation gives a Rydberg electron binding energy lowered further by 0.13 eV as compared with the dimer. The calculated results compare well with trends observed in experimental measurements. The reduction of the Rydberg electron binding energy with cluster size can be ascribed to an effective delocalization of the positive charge of the hole by the induced and permanent dipole moments of the neighboring molecules. A further decrease observed to occur on a time scale of tens of ps can be ascribed to a structural rearrangement of the clusters in the Rydberg state where molecules rotate to orient their dipoles in response to the formation of the localized hole. PMID:25527936

Gudmundsdóttir, Hildur; Zhang, Yao; Weber, Peter M; Jónsson, Hannes

2014-12-21

65

Extensive double-excitation states in atomic helium  

NASA Astrophysics Data System (ADS)

High-resolution photoionization studies of He have revealed more than 50 states below the N=2-7 thresholds of He+, including sixteen (sp,2n+) and five (sp,2n-) states in the N=2 series. With a resolving power of E/?E~=10 000, states as narrow as 0.1 meV could be observed and linewidths were determined with an accuracy up to +/-0.5 meV. Interchannel interferences, evident through effects on positions, shapes, and intensities of Rydberg lines, were interpreted within the framework of the multichannel quantum-defect theory.

Domke, M.; Xue, C.; Puschmann, A.; Mandel, T.; Hudson, E.; Shirley, D. A.; Kaindl, G.; Greene, C. H.; Sadeghpour, H. R.; Petersen, H.

1991-03-01

66

Antiferromagnetic phase transition in a nonequilibrium lattice of Rydberg atoms  

Microsoft Academic Search

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

Tony E. Lee; H. Häffner; M. C. Cross

2011-01-01

67

Rydberg atoms for quantum information  

NASA Astrophysics Data System (ADS)

I examine interactions between ensembles of cold Rydberg atoms, and between Rydberg atoms and an intense, optical standing wave. Because of their strong electrostatic interactions, Rydberg atoms are prime candidates for quantum information and quantum computation. To this end, I study excitation dynamics in many-body Rydberg systems using a rotary echo technique similar to the echo sequences used in nuclear magnetic resonance schemes. In this method, a phase reversal of a narrow-band excitation field is applied at a variable time during the excitation pulse. The visibility of the resulting echo signal reveals the degree of coherence of the excitation process. Rotary echoes are measured for several nD5/2 Rydberg levels of rubidium with principal quantum numbers near n = 43, where the strength of electrostatic Rydberg-atom interactions is sharply modulated by a Forster resonance The Rydberg-atom interactions diminish the echo visibility, in agreement with theoretical work. The equivalence of echo signals with spectroscopic data is also examined. Applications of Rydberg atoms based on controlled interactions require a trapping device that holds the atoms at well-defined positions several microns apart. Rydberg atoms in ponderomotive optical lattices present a unique platform to meet this requirement, as well as to study properties and interactions of these highly excited atoms. Because the Rydberg electron is so loosely bound, the ponderomotive interaction for a Rydberg electron is very similar to a free electron. Ponderomotive lattices tailored to trap Rydberg atoms will allow new experiments in quantum information physics and high-precision spectroscopy. Microwave spectroscopy is used as a powerful technique to probe the motion and to verify trapping of Rydberg atoms in ponderomotive lattices. The potentials for non-degenerate, low angular momentum states, are used to obtain ensembles of Rydberg-atom trajectories in the lattice, and to simulate the spectra of microwave transitions of Rydberg atoms moving through the lattice. Additionally, adiabatic potentials are calculated for Rydberg atoms in one-dimensional ponderomotive lattices for a variety of atomic states and lattice parameters. The lattice induced mixing of nearly-degenerate, high-angular-momentum states is explained in terms of effective electric and magnetic fields.

Younge, Kelly Cooper

68

Manipulating Rydberg atoms close to surfaces at cryogenic temperatures  

NASA Astrophysics Data System (ADS)

Helium atoms in Rydberg states have been manipulated coherently with microwave radiation pulses near a gold surface and near a superconducting NbTiN surface at a temperature of 3K. The experiments were carried out with a skimmed supersonic beam of metastable (1s)1(2s)11S0 helium atoms excited with laser radiation to np Rydberg levels with principal quantum number n between 30 and 40. The separation between the cold surface and the center of the collimated beam is adjustable down to 250?m. Short-lived np Rydberg states were coherently transferred to the long-lived ns state to avoid radiative decay of the Rydberg atoms between the photoexcitation region and the region above the cold surfaces. Further coherent manipulation of the ns Rydberg states with pulsed microwave radiation above the surfaces enabled measurements of stray electric fields and allowed us to study the decoherence of the atomic ensemble. Adsorption of residual gas onto the surfaces and the resulting slow buildup of stray fields was minimized by controlling the temperature of the surface and monitoring the partial pressures of H2O, N2, O2, and CO2 in the experimental chamber during the cool-down procedure. Compensation of the stray electric fields to levels below 100mV /cm was achieved over a region of 6mm along the beam-propagation direction which, for the 1770-m/s beam velocity, implies the possibility to preserve the coherence of the atomic sample for several microseconds above the cold surfaces.

Thiele, T.; Filipp, S.; Agner, J. A.; Schmutz, H.; Deiglmayr, J.; Stammeier, M.; Allmendinger, P.; Merkt, F.; Wallraff, A.

2014-07-01

69

An Ordered State of Dislocations in Solid Helium  

NASA Astrophysics Data System (ADS)

An ordered state of dislocations, see e.g. [1], is disclosed from neutron inelastic scattering data taken from solid helium at 40mK and a pressure of about 30bar. A characteristic feature is the phonon gap at the origin of about 0.15 meV, which reveals the non-equilibrium state of stressed helium created by rapid cooling with the blocked-capillary method. Energy gain scattering starts to appear at a temperature of 0.5 K that underlines the non-equilibrium state of stressed helium and the non-applicability of the detailed balance. The increasing thermal occupation of phonon-states observed as increasing intensity in energy gain scattering builds to a phase transition close to 1.4K. The creation of a helium single crystal with hcp-structure in thermal equilibrium [2] is observed at this temperature. This phase transition is in agreement with the vanishing quasi two-dimensional superfluid helium in solid helium confined in aerogel around 1.3K [3]. The event of the ``supersolid'' transition around 100mK is not observed in the two neutron scattering experiments.[4pt] [1] G. S"oyler, et. al., Phys. Rev. Lett. 103, 175301 (2009)[0pt] [2] E. Blackburn, et. al., PRAMANA 71, 673 (2008)[0pt] [3] H.Lauter, et. al., Phys. Rev. Lett. 107, 265301 (2011)

Lauter, Hans Jochen; Krotscheck, Eckhard; Kats, Efim; Herwig, Kenneth; Podlesnyak, Andrey; Souleymane, Diallo; Henry, Glyde; Savici, Andreii

2013-03-01

70

Electron processes in ion-Rydberg-atom collisions with emphasis on directed linear Stark states  

NASA Astrophysics Data System (ADS)

Both classical-trajectory calculations and measurements of electron capture in A+ + B(x) collisions, where the targets are Rydberg atoms, have been performed in the intermediate velocity range. Linear Stark-state targets were created inside a novel device called the Stark barrel. With this new apparatus, off-center atomic states with axial symmetry could be prepared with their axes set at angles 0-360o with respect to the ion beam. Comparison of calculated and measured total-capture cross sections has revealed a new spatial capture mechanism called variously 'three-swap', 'type-two', or 'low- velocity Thomas capture.' In Part I of this Dissertation a classical model of electron capture and ionization by singly charged ions from oriented and aligned elliptic and linear-state Rydberg targets will be introduced to describe the Coulomb three-body dynamics of these processes. Parameter space maps, which correlate initial conditions in the collision system with the final collision channels, are employed to demonstrate that capture events are confined to well-defined regions of phase space. These islands of capture can be characterized by the number of swaps. The number of swaps is defined as the number of times the electron crosses the mid-plane between the passing charge centers during a collision that leads to capture. In Part II measurements of the total electron capture by Li+,/ K+ or Cs+ from a linear-Rydberg target atom are presented as a function of the angle ? between the atom's electric-dipole moment and the ion-beam axis in the reduced-velocity range 0.15/le/tilde v/le 2.4, where /tilde v=Vp/vBohr. The capture cross section versus angle reveals a peak at /theta =180o for /tilde v=0.3 which bifurcates into two distinct peaks at /tilde v=0.7 and then becomes again a single peak near /tilde v=1.0. At /tilde v=1.6 two symmetric shoulders appear near /theta=120o and 240o on a peak at 180o and remain a feature of the capture cross section at higher velocities. Peaks and shoulders are also observed at /tilde v=0.25, 0.5 and 1.0 in the ratio of the capture cross section for electronic charge polarization parallel (/theta=180o) and anti-parallel (0o) to the ion beam direction. The resonance structures seen in these experiments are described classically as overlapping contributions from one-swap, three-swap, and five and greater odd-swap trajectories. Previously unexpected structure seen in the experimental cross sections has been reproduced qualitatively by classical- trajectory and close-coupling models, and in turn the theories have given new insight and direction for experimental work.

Homan, Dean Matthew

71

Manipulating Rydberg atoms close to surfaces at cryogenic temperatures  

E-print Network

Helium atoms in Rydberg states have been manipulated coherently with microwave radiation pulses near a gold surface and near a superconducting NbTiN surface at a temperature of $3 \\text{K}$. The experiments were carried out with a skimmed supersonic beam of metastable $(1\\text{s})^1(2\\text{s})^1\\, {}^1\\text{S}_0$ helium atoms excited with laser radiation to $n\\text{p}$ Rydberg levels with principal quantum number $n$ between $30$ and $40$. The separation between the cold surface and the center of the collimated beam is adjustable down to $250 \\mu\\text{m}$. Short-lived $n\\text{p}$ Rydberg levels were coherently transferred to the long-lived $n\\text{s}$ state to avoid radiative decay of the Rydberg atoms between the photoexcitation region and the region above the cold surfaces. Further coherent manipulation of the $n\\text{s}$ Rydberg levels with pulsed microwave radiation above the surfaces enabled measurements of stray electric fields and allowed us to study the decoherence of the atomic ensemble. Adsorption of residual gas onto the surfaces and the resulting slow build-up of stray fields was minimized by controlling the temperature of the surface and monitoring the partial pressures of H$_2$O, N$_2$, O$_2$ and CO$_2$ in the experimental chamber during the cool-down. Compensation of the stray electric fields to levels below $100 \\text{mV}/\\text{cm}$ was achieved over a region of $6 \\text{mm}$ along the beam-propagation direction which, for the $1770 \\text{m}/\\text{s}$ beam velocity, implies the possibility to preserve the coherence of the atomic sample for several microseconds above the cold surfaces.

Tobias Thiele; Stefan Filipp; Josef Anton Agner; Hansjürg Schmutz; Johannes Deiglmayr; Mathias Stammeier; Pitt Allmendinger; Frédéric Merkt; Andreas Wallraff

2014-02-28

72

Spectroscopy of a cold strontium Rydberg gas  

E-print Network

We present a study of a cold strontium Rydberg gas. The narrowband laser excitation of Rydberg states in the range n=20-80 from a 6~mK cloud of strontium atoms is detected using the spontaneous ionization of the Rydberg atoms. Using a high-resolution step-scanning technique, we perform detailed measurements of the Stark maps of selected Rydberg states. We find excellent agreement between the measured Stark maps and a numerical calculation based on an independent-electron model. Finally we show that excitation of the second valence electron can be used to probe the dynamics of the Rydberg gas with nanosecond temporal resolution via autoionization.

Millen, J; Corbett, G R; Potvliege, R M; Jones, M P A

2011-01-01

73

Formation of Triplet Positron-helium Bound State by Stripping of Positronium Atoms in Collision with Ground State Helium  

NASA Technical Reports Server (NTRS)

Formation of triplet positron-helium bound state by stripping of positronium atoms in collision with ground state helium JOSEPH DI RlENZI, College of Notre Dame of Maryland, RICHARD J. DRACHMAN, NASA/Goddard Space Flight Center - The system consisting of a positron and a helium atom in the triplet state e(+)He(S-3)(sup e) was conjectured long ago to be stable [1]. Its stability has recently been established rigorously [2], and the values of the energies of dissociation into the ground states of Ps and He(+) have also been reported [3] and [4]. We have evaluated the cross-section for this system formed by radiative attachment of a positron in triplet He state and found it to be small [5]. The mechanism of production suggested here should result in a larger cross-section (of atomic size) which we are determining using the Born approximation with simplified initial and final wave functions.

Drachman, Richard J.

2006-01-01

74

(?*,?*), (?*,?*) and Rydberg triplet excited states of hydrogen peroxide and other molecules bearing two adjacent heteroatoms.  

PubMed

The properties of the lowest triplet excited states of a series of small molecules containing two or more adjacent heteroatoms have been investigated. High-level coupled cluster and MRCI+Q calculations were employed to probe the properties of the triplet excited states of hydrogen peroxide, hydrazine, hydroxylamine, fluoroamines, oxygen difluoride, hypofluorous acid, chlorine, fluorine, and disulfane. All of the molecules investigated except hydroxylamine are predicted to have bound lowest triplet excited states that are either (?*,?*) or (?*,?*) as in H2O2, HOF, OF2, H2S2, Cl2, NH2F, NHF2, or NF3, or are Rydberg states (hydrazine, also H2O2 and H2S2). The heteroatom-heteroatom bond dissociation enthalpies of the triplet states range from very small values as predicted for hydrogen peroxide or fluorine, to BDEs around 8-9 kcal mol(-1) that should allow for an experimental observation of the triplet state, such as in disulfane or monofluoroamine. For all triplet minima investigated except NF3 and F2, CCSD(T) gave results in agreement with the multireference method MRCI+Q, and in excellent agreement with available experimental data (BDEs, ground-state geometries). Due to multireference problems, CCSD(T) does not provide a good description for longer heteroatom-heteroatom distances, and in some cases (e.g., Cl2) it wrongly predicts the presence of a transition state for bond formation on the triplet spin manifold, where the reaction is known experimentally and, as predicted by MRCI+Q, is known to be barrierless. Finally, the (3)?(u) state of F2 is poorly described by CCSD(T) theory, the equilibrium bond distance is significantly underestimated relative to MRCI+Q, and CCSD(T) places the triplet state above the energy of two fluorine atoms. The T1 diagnostic, frequently used to assess the quality of CCSD(T) calculations, does not appear to provide a valid criterion for the systems studied. The formation of H2O2 on the triplet potential energy hypersurface might possibly open up an additional channel for formation of hydrogen peroxide from two hydroxyl radicals. Due to a low density of states in triplet H2O2, and due to competing formation of water + O((3)P) from a hydrogen-bridged HO···HO triplet radical pair, such a reaction channel probably only can play a role at low temperatures. PMID:24592897

Hill, J Grant; Bucher, Götz

2014-03-27

75

Using Uncertainty Principle to Find the Ground-State Energy of the Helium and a Helium-like Hookean Atom  

ERIC Educational Resources Information Center

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…

Harbola, Varun

2011-01-01

76

Electron energy-loss spectra of coupled electronic states: Effects of Rydberg-valence interactions in O2  

NASA Astrophysics Data System (ADS)

The concept of the ``generalized transition moment'' is extended beyond the region of applicability of the first Born approximation and is used in the analysis of electron energy-loss spectra for O2, presented here, which have been measured at intermediate impact energies. A coupled-channel theoretical treatment of the strongly mixed Rydberg and valence states that dominate the optically allowed spectrum is used to explain the relative intensities of many unusual features occurring in the 7-11.2-eV energy-loss region. For these electronically excited states of 3?-u and 3?u symmetry, the evolution of the shape of the corresponding electron energy-loss spectrum as the scattering conditions are changed is controlled essentially by one parameter: the ratio of the diabatic generalized transition moments into the Rydberg and valence components of the mixed electronic states. The generalized Rydberg transition moment is found to decrease much faster than the valence moment as the momentum transferred in the collision increases. The results of the coupled-channel analysis also indicate that the more diffuse spectral features are generally asymmetric, those in the 7-9.8-eV region changing slightly in position as the scattering conditions are altered. Thus, the Gaussian-line-shape-based models that have been employed previously in attempts to decompose the diffuse part of the electron energy-loss spectrum for O2, into contributions from different electronic states, are unlikely to have given meaningful results. As a consequence of the Rydberg-valence interactions, it is found that some vibrational levels of the mixed states give rise to features in the electron energy-loss spectrum which are anomalously strong at the low impact energies and large scattering angles for which normal optically allowed transitions are expected to decline in relative strength. These ``persistent lines'' are easily confused with those from the optically forbidden transitions which increase in relative intensity under such conditions. Thus, the coupled-channel technique is found to be a valuable aid to the assignment of features in the electron energy-loss spectrum.

Lewis, B. R.; England, J. P.; Gibson, S. T.; Brunger, M. J.; Allan, M.

2001-02-01

77

Initial population of large-l Rydberg states for the radiative deexcitation in the beam-foil geometry  

NASA Astrophysics Data System (ADS)

In the recent beam-foil experiment, resonances have been observed in decay of the beam-foil excited 2p and 2s states of H-like Fe ions at very large times. Qualitatively, the resonances were explained as a consequence of cascading down from the Rydberg states (n?1,l=n-1) to 2p state. Full explanation requires the theoretical values of the population probabilities P of the large-l Rydberg states of multiply charged ions of core charges Z?1 a.u. escaping the solid surfaces at velocities v?1 a.u. The resonances observed in the time dependent photon intensity indicate the existence of resonances (pronounced maxima at several n=nres) in the P distributions. Considering the population process within the framework of the time-symmetrized two-state vector model, with dynamically generalized interaction Hamiltonian, we found that the nonresonant electron pick up from the foil conduction band into the field of ionic core when the ion leaves the surface represents an important population mechanism. The obtained population distributions have the resonance-like structure like the ones simulated from the experimental signal, and the overlap shape and magnitude in accordance with the wake field model estimations.

Nedeljkovi?, N. N.; Galijaš, S. M. D.; Mirkovi?, M. A.

2014-02-01

78

Ground State Hyperfine Structure of Muonic Helium Atom  

E-print Network

On the basis of the perturbation theory in the fine structure constant $\\alpha$ and the ratio of the electron to muon masses we calculate one-loop vacuum polarization and electron vertex corrections and the nuclear structure corrections to the hyperfine splitting of the ground state of muonic helium atom $(\\mu e ^4_2He)$. We obtain total result for the ground state hyperfine splitting $\\Delta \

A. A. Krutov; A. P. Martynenko

2008-07-21

79

Ultrafast dissociation dynamics of acetone: A revisit to the S1 state and 3s Rydberg state  

NASA Astrophysics Data System (ADS)

Because of the dispute in the literature over the dissociation rate and energy partitioning of the acetone molecule upon photoexcitation to the S1 state (?*?n) and 3s Rydberg state (3s?n), we have remeasured the lifetime of acetone (also d6-acetone) on the S1 and 3s surfaces by a femtosecond time-resolved multiphoton ionization technique, coupled with a reflectron time-of-flight mass spectrometer. The measured dissociation rate of acetone on the S1 surface is prompt, and the acetyl radical is long lived. The lifetime of acetone on the 3s surface is measured to be 3.2±0.4 ps (6.0±0.5 ps for d6-acetone). The dissociation rate of acetyl is approximately 1.7 ps (2.5 ps for d3-acetyl) from the curve fitting. This agrees well with the Rice-Ramsperger-Kassel-Marcus theory predicted lifetime of 1.0 ps (1.9 ps for d3-acetyl) when the internal excitation energy of the acetyl radical is treated by a statistical-adiabatic-impulsive model.

Zhong, Q.; Poth, L.; Castleman, A. W.

1999-01-01

80

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

Microsoft Academic Search

\\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

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

2010-01-01

81

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

SciTech Connect

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.

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

2000-06-01

82

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

PubMed

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

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

2012-11-13

83

Ultrafast studies of the photodissociation of the acetone 3s Rydberg state at 195 nm: Formation and unimolecular dissociation of the acetyl radical  

NASA Astrophysics Data System (ADS)

Ultrafast deep UV mass-resolved photoionization spectroscopy has been used to investigate the photodissociation dynamics of the 3s Rydberg state of acetone. Single photon excitation at 193-195 nm is followed by single photon (at 260 nm) and two photon (at 390 nm) ionization and the signal is measured for both the acetone and acetyl photoions. The acetone Rydberg state lifetime determined from both single and two photon detection is surprisingly long, 4.7±0.2 ps. The higher probe energy for two photon ionization results in a lower minimum acetyl internal energy for ionization, so that part of the measured signal is due to neutral acetyl dissociation dynamics rather than only dissociative ionization of excited state acetone (which is the case for single photon ionization at 260 nm). The secondary dissociation rate of the neutral acetyl intermediate is measured, clearly establishing that photodissociation via the first Rydberg state of acetone occurs by a sequential dissociation mechanism. The acetyl dissociation occurs with a characteristic time of 3.1±0.5 ps. Based on RRKM (Rice-Ramsperger-Kassel-Marcus) calculations, this suggests an average acetyl internal energy of ˜25 kcal/mole. The long lifetime of the 3s Rydberg state suggests that the dissociation dynamics may be described in terms of a fully statistical dissociation mechanism.

Owrutsky, J. C.; Baronavski, A. P.

1998-04-01

84

How does LCDFT compare to SAC-CI for the treatment of valence and Rydberg excited states of organic compounds?  

PubMed

The computation of excitation energies for electronically excited states poses a challenge in quantum chemistry. In the present work, the performance of two related methodologies in this context, symmetry-adapted cluster-configuration interaction (SAC-CI) and time-dependent long-range corrected density functional theory (TDLCDFT), is compared in detail for the calculation of valence and Rydberg excitation energies against an experimental benchmark set comprising some organic compounds from different categories. Practically, the single- and double-linked excitation operators are considered in the SAC-CI wave functions. The considered LC density functionals include the combination forms of exchange and correlation functionals (BLYP, PBE, TPSS), pure functionals (tHCTH and B97-D), exchange-only functionals (HFS, HFB, and XAlpha), hybrid functionals (CAM-B3LYP, LC-?PBE, ?B97, ?B97X), and dispersion-corrected hybrid functional ?B97X-D. Our results reveal that the SAC-CI gives the best performance for Rydberg excited states. However, the values of mean absolute deviation show that the applicability of some LC functionals is comparable to SAC-CI. For valence excited states, the functionals ?B97X-D, ?B97X, and LC-?PBE outperform the other tested methods. Overall, the ?B97X-D functional is found to offer the best performance, and its validity compared with SAC-CI has also been verified by computing low-lying excited states of a few molecules as representative examples. Lastly, it is shown that not only is there a reasonable agreement between TDLCDFT and SAC-CI methods for the calculation of excitation energies but also the LC density functionals have quantitatively better overall performance for some excited states than the SAC-CI approach. PMID:24559047

Alipour, Mojtaba

2014-03-01

85

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

Microsoft Academic Search

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

D. Porcelli; G. J. Wasserburg

1995-01-01

86

Spectrum and polarization of helium doubly excited triplet states  

NASA Astrophysics Data System (ADS)

The beam-foil spectrum of helium from 2050 to 3600 Å has been acquired at 160-keV incident ion energy using a multiple-scan, computerized system. Eleven doubly-excited-state transitions, including two not previously observed, have been assigned, and the agreement between experimental and theoretical energy levels is excellent. The Stokes parameters as a function of foil-tilt angle have been measured for the two strongest transitions (2578 and 3013 Å) from 0° to 80° in 10° increments and for two weaker transitions (2562 and 2818 Å) at 0°, 20°, 40°, and 60°. The polarization patterns are quite different from those of the helium singlets and include the first measurement of negative MI (a Stokes parameter) at 0° foil tilt for helium at this energy. The lifetime of the 2578-Å transition has been investigated in detail. The present result, 0.109+/-0.004 ns, agrees with previous measurements and yields an upper limit to the autoionization width of the 2p3p 3D levels of 6×10-6 eV.

Brooks, Robert L.; Pinnington, Eric H.

1980-08-01

87

Singlet-Triplet Mixing in the n=3 States of Helium  

Microsoft Academic Search

We have measured the energy-independent ratio of the proton apparent-excitation cross sections between corresponding triplet and singlet states of helium for the n=3 level. In the Russell-Saunders description of the states of helium, proton excitation of triplet states is forbidden; i. e., DeltaS=1 transitions are not allowed (Wigner spin rule). However, the spin-orbit interaction for the two electrons in helium

Daniel Krause; Edward A. Soltysik

1972-01-01

88

A Rydberg Quantum Simulator  

E-print Network

Following Feynman and as elaborated on by Lloyd, a universal quantum simulator (QS) is a controlled quantum device which reproduces the dynamics of any other many particle quantum system with short range interactions. This dynamics can refer to both coherent Hamiltonian and dissipative open system evolution. We investigate how laser excited Rydberg atoms in large spacing optical or magnetic lattices can provide an efficient implementation of a universal QS for spin models involving (high order) n-body interactions. This includes the simulation of Hamiltonians of exotic spin models involving n-particle constraints such as the Kitaev toric code, color code, and lattice gauge theories with spin liquid phases. In addition, it provides the ingredients for dissipative preparation of entangled states based on engineering n-particle reservoir couplings. The key basic building blocks of our architecture are efficient and high-fidelity n-qubit entangling gates via auxiliary Rydberg atoms, including a possible dissipative time step via optical pumping. This allows to mimic the time evolution of the system by a sequence of fast, parallel and high-fidelity n-particle coherent and dissipative Rydberg gates.

Hendrik Weimer; Markus Müller; Igor Lesanovsky; Peter Zoller; Hans Peter Büchler

2009-07-10

89

Rapid and precise scanning helium ion microscope milling of solid-state nanopores for biomolecule detection  

E-print Network

Rapid and precise scanning helium ion microscope milling of solid-state nanopores for biomolecule microscope milling of solid-state nanopores for biomolecule detection Jijin Yang1,4 , David C Ferranti1 the formation of solid-state nanopores using a scanning helium ion microscope. The fabrication process offers

Qin, Lu-Chang

90

Ground state and excitation dynamics in Ag doped helium clusters  

NASA Astrophysics Data System (ADS)

We present a quantum Monte Carlo study of the structure and energetics of silver doped helium clusters AgHen for n up to 100. Our simulations show the first solvation shell of the Ag atom to include roughly 20 He atoms, and to possess a structured angular distribution. Moreover, the 2P1/2?2S1/2 and 2P3/2?2S1/2 electronic transitions of the embedded silver impurity have been studied as a function of the number of helium atoms. The computed spectra show a redshift for n?15 and an increasing blueshift for larger clusters, a feature attributed to the effect of the second solvation shell of He atoms. For the largest cluster, the computed excitation spectrum is found in excellent agreement with the ones recorded in superfluid He clusters and bulk. No signature of the direct formation of the proposed AgHe2 exciplex is present in the computed spectrum of AgHe100. To explain the absence of the fluorescent D2 line in the experiments, a relaxation mechanism between the 2P3/2 and the 2P1/2 states is proposed on the basis of the partial overlap of the excitation bands in the simulated spectra.

Mella, Massimo; Colombo, Maria Carola; Morosi, Gabriele

2002-12-01

91

Atomic orientation following predissociation of the C {sup 3}{Pi}{sub g} Rydberg state of molecular oxygen  

SciTech Connect

(2 + 1) resonance enhanced multiphoton ionization in combination with time-of-flight mass spectroscopy (TOF-MS) has been used to detect both the O({sup 3}P) and O({sup 1}D) fragments produced as a result of predissociation of the C {sup 3}{Pi}{sub g} (v= 0) and (v= 1) Rydberg states of O{sub 2}, accessed via two-photon absorption from the ground X {sup 3}{Sigma}{sub g}{sup -} state. In particular, TOF profiles have been recorded at various fixed two-photon absorption wavelengths within the two bands, with circular polarized probe laser light used to probe the angular momentum orientation of these photofragments. All photofragments are found to display coherent orientation resulting from interference between two possible two-photon absorption pathways. The measured orientation is affected by rotational depolarization due to the long lifetime of the excited C state; once this effect is accounted for the orientation is found to be nearly constant over all dissociation wavelengths. The origin of the coherent orientation is attributed to two-photon absorption to different spin-orbit components of the C state.

Gilchrist, A. J.; Ritchie, G. A. D. [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ (United Kingdom)

2013-06-07

92

Two-Electron Excitation of an Interacting Cold Rydberg Gas  

SciTech Connect

We report the creation of an interacting cold Rydberg gas of strontium atoms. We show that the excitation spectrum of the inner valence electron is sensitive to the interactions in the Rydberg gas, even though they are mediated by the outer Rydberg electron. By studying the evolution of this spectrum we observe density-dependent population transfer to a state of higher angular momentum l. We determine the fraction of Rydberg atoms transferred, and identify the dominant transfer mechanism to be l-changing electron-Rydberg collisions associated with the formation of a cold plasma.

Millen, J.; Lochead, G.; Jones, M. P. A. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)

2010-11-19

93

A New Wide Range Equation of State for Helium-4  

E-print Network

................................................ 114 5.4 Caloric data .................................................................................................. 123 5.5 Ideal curves .................................................................................................. 127 5... and academia. Indeed, helium leak detection is the standard in any activity requiring leak-tight systems. The usual procedure in leak testing is to spray the area outside the system being tested with helium and then try to detect its presence on the inside...

Ortiz Vega, Diego O

2013-08-01

94

Quantum-classical model for the formation of Rydberg molecules  

NASA Astrophysics Data System (ADS)

A fascinating aspect of Rydberg atoms is their ability to form huge but very weakly bound molecules with a ground-state atom, only held together by a scattering process between the latter and the Rydberg electron. Beyond the usual way of creating such molecules by laser excitation from two ground-state atoms with a distance of less than the Rydberg radius, we demonstrate that Rydberg molecules can also be formed by capturing a ground-state atom which is initially located outside the range of the Rydberg atom when it comes in contact with it. To demonstrate this effect, we investigate the scattering process between the Rydberg electron and the ground-state atom within a quantum-classical framework. In this picture, the capture results from a dissipative finite-mass correction term in the classical equations of motion. We show that, and under which conditions the capturing takes place.

Junginger, Andrej; Main, Jörg; Wunner, Günter

2012-07-01

95

Assignment of the {tilde B}{sup +} state of the chlorobenzene cation using photoinduced Rydberg ionization (PIRI) spectroscopy  

SciTech Connect

The photoinduced Rydberg ionization (PIRI) spectra of the {tilde B}{sup +} state of the chlorobenzene cation were recorded via the origin, 6b, and 16a16b vibrations of the cation ground state ({tilde X}{sup +}). The resonance-enhanced multi photon dissociation spectroscopy (REMPD) spectrum of the {tilde B}{sup +} {l{underscore}arrow} {tilde X}{sup +} transition of the chlorobenzene cation was also obtained. To date it has been thought that {tilde B}{sup +} {l{underscore}arrow} X{sup +} is an electronically forbidden transition (C{sub 2{nu}} symmetry), taking place from the {sup 2}B{sub 1} ground state to a {sup 2}B{sub 2} excited state. The ability of PIRI to provide spectra from specific lower-state vibrational levels allowed this hypothesis to be tested, because the 16a vibration would be the primary inducing mode in the transition. Assuming a forbidden transition, a comparison between the spectrum from the ground-state origin and that from the 16a16b vibration would necessitate an assignment that gives unlikely vibrational frequencies. It is therefore concluded that the {tilde B}{sup +} {l{underscore}arrow} {tilde X}{sup +} transition of chlorobenzene is electronically allowed. Configuration interaction of singles (CIS) and complete active space multiconfigurational self-consistent field (CASSCF) calculations with 6-31G** basis sets were performed to ascertain the symmetry assignments of the excited ionic states. These calculations resulted in the possibility that at least one excited state of the cation of {sup 2}B{sub 1} symmetry lies below any state of {sup 2}B{sub 2} symmetry. Hence, the authors propose that the ionic transition observed in the acquired PIRI/REMPD spectra of the cation is an allowed transition to a {sup 2}B{sub 1} state, thus giving rise to the observation of the origin of the {tilde B}{sup +} state at 18,219 cm{sup {minus}1}.

Anand, R.; Hofstein, J.D.; LeClaire, J.E.; Johnson, P.M.; Cossart-Magos, C.

1999-11-11

96

Stimulated emission studies of ultracold Rydberg atoms  

NASA Astrophysics Data System (ADS)

Rydberg atoms have many novel properties that make them appealing, most noticeably their long lifetimes and very strong dipole interactions. This dissertation describes experiments involving the optical detection and manipulation of ultracold Rydberg atoms using a novel stimulated emission probe. This stimulated emission probe was first used to explore the dynamics of ultracold Rydberg atoms. Two-photon excitation creates Rydberg atoms which can be observed via loss of atoms from the MOT, or by fluorescent emission. The addition of a stimulated-emission probe enabled further measurement of the rate of transfer from the Rydberg state. A model was developed to better understand the data, revealing that superradiant transfer is an important mechanism in the atom dynamics at these densities. We have further performed non-degenerate four-wave mixing through the Rydberg states using the stimulated emission probe, causing preferential emission into a diffraction limited direction. This result can be optimized by detuning the excitation lasers from the Rydberg resonance, resulting in up to 50 percent of the light emitted in a diffraction limited direction. The final experiment described in this dissertation is the investigation of atom-atom interactions within a small excitation volume. We have shown that these interactions can be enhanced through the application of resonant microwaves. Suppression of Rydberg atom excitation was qualitatively observed and quantitatively analyzed using a universal scaling law. This gave a measure of the atom-atom interaction strength in agreement with the theoretical prediction. This represents a large advance in the understanding of Rydberg atom interactions, and their possible use in quantum computing or single photon applications.

Brekke, Erik Gallup

97

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

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.

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

98

Helium Abundance and Minor Ion Charge State Variations in the Solar Wind over the Solar Cycle  

NASA Astrophysics Data System (ADS)

Prior studies have shown that the abundance of helium relative to hydrogen in the solar wind is a highly variable quantity. Kasper, et al. (2007) used observations from the Wind spacecraft to show that that the helium abundance in slow solar wind is strongly correlated with sunspot number. During the penultimate solar minimum, helium abundance was a linear function of solar wind speed. However, this dependence vanished as solar activity increased. We extended this study through the recent deep solar minimum and found that the strong correlation between helium abundance and sunspot number for slow solar wind continued. Moreover, as the deep minimum persisted, the helium abundance reached even lower values than observed previously. The strong linear dependence of helium abundance on winds speed also returned during this solar minimum. Motivated by these results, we used data from the ACE spacecraft to determine if the charge states of minor ions, which are strong indicators of coronal temperature, show similar trends. Indeed, the charge states of carbon and oxygen appear to be related to both solar activity and wind speed. Higher charge state ratios were observed for periods of greater activity, but lower ratios were seen as activity decreased. However, while helium abundance increased with solar wind speed, charge state (and thus coronal temperature) decreased with speed. This suggests that during solar minimum slow solar wind originates in cooler plasma. More broadly, these results challenge solar wind acceleration models that link the final speed of the solar wind to a single coronal temperature.

Kiefer, K. K.; Kasper, J. C.; Maruca, B. A.; Stevens, M. L.

2010-12-01

99

Millimeter-wave spectroscopy and multichannel quantum-defect-theory analysis of high Rydberg states of xenon: The hyperfine structure of {sup 129}Xe{sup +} and {sup 131}Xe{sup +}  

SciTech Connect

Millimeter-wave transitions between high-n Rydberg states of several isotopes of xenon have been recorded at sub-megahertz resolution. The fine and, for {sup 129}Xe and {sup 131}Xe, hyperfine structures of s, p, d, and f Rydberg states with principal quantum number in the range 52{<=}n{<=}64 have been determined from combination differences and analyzed using multichannel quantum defect theory. Improved eigenquantum defects and channel interaction parameters for the odd- and even-parity Rydberg states of xenon and the hyperfine structure of the {sup 2}P{sub 3/2} ground state of {sup 129}Xe{sup +} and {sup 131}Xe{sup +} have been obtained. Nearly degenerate p and d fine or hyperfine levels are very easily mixed by even weak stray electric fields.

Schaefer, Martin; Raunhardt, Matthias; Merkt, Frederic [Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich (Switzerland)

2010-03-15

100

Antiferromagnetic phase transition in a nonequilibrium lattice of Rydberg atoms  

SciTech Connect

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.

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

101

Universal scaling in a strongly interacting Rydberg gas  

E-print Network

We study a gas of ultracold atoms resonantly driven into a strongly interacting Rydberg state. The long distance behavior of the spatially frozen effective pseudospin system is determined by a set of dimensionless parameters, and we find that the experimental data exhibits algebraic scaling laws for the excitation dynamics and the saturation of Rydberg excitation. Mean field calculations as well as numerical simulations provide an excellent agreement with the experimental finding, and are evidence for universality in a strongly interacting frozen Rydberg gas.

Robert Löw; Hendrik Weimer; Ulrich Krohn; Rolf Heidemann; Vera Bendkowsky; Björn Butscher; Hans Peter Büchler; Tilman Pfau

2009-02-26

102

An analysis of Helium resonant states in terms of entropy, information, complexity and entanglement measures  

NASA Astrophysics Data System (ADS)

Shannon entropies and Fisher information calculated from one-particle density distributions and von Neumann and linear entropies (the latter two as a measure of entanglement) computed from the reduced one-particle density matrix are analyzed for the 1,3se,1,3 P0 and 1,3De Rydberg series of He doubly excited states below the second ionization threshold. We find that both Fisher information and entanglement measures are able to discriminate resonances pertaining to different (K,T)A series.

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

2014-04-01

103

S-states of helium-like ions  

NASA Astrophysics Data System (ADS)

A simple Mathematica (version 7) code for computing S-state energies and wave functions of two-electron (helium-like) ions is presented. The elegant technique derived from the classical papers of Pekeris is applied. The basis functions are composed of the Laguerre functions. The method is based on the perimetric coordinates and specific properties of the Laguerre polynomials. Direct solution of the generalized eigenvalues and eigenvectors problem is used, distinct from the Pekeris works. No special subroutines were used, only built-in objects supported by Mathematica. The accuracy of the results and computation times depend on the basis size. The ground state and the lowest triplet state energies can be computed with a precision of 12 and 14 significant figures, respectively. The accuracy of the higher excited states calculations is slightly worse. The resultant wave functions have a simple analytical form, that enables calculation of expectation values for arbitrary physical operators without any difficulties. Only three natural parameters are required in the input. The new version of Mathematica code takes into account the fact that the negative hydrogen ion has only one bound state. New version program summaryProgram title: TwoElAtomSL(SH) Catalogue identifier: AEHY_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHY_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 27 998 No. of bytes in distributed program, including test data, etc.: 286 543 Distribution format: tar.gz Programming language: Mathematica 7.0 and 8.0 Computer: Any PC with a Mathematica installation Operating system: Any which supports Mathematica; tested under Microsoft Windows XP and Linux SUSE 11.0 RAM:?10 bytes Classification: 2.1, 2.2, 2.7, 2.9 Catalogue identifier of previous version: AEHY_v1_0 Journal reference of previous version: Comput. Phys. Comm. 182 (2011) 1790 Does the new version supersede the previous version?: Yes Nature of problem: The Schrödinger equation for atoms (ions) with more than one electron has not been solved analytically. Approximate methods must be applied in order to obtain the wave functions or other physical attributes from quantum mechanical calculations. Solution method: The S-wave function is expanded into a triple set of basis functions which are composed of the exponentials combined with the Laguerre polynomials in the perimetric coordinates. Using specific properties of the Laguerre polynomials, solution of the two-electron Schrödinger equation reduces to solving the generalized eigenvalues and eigenvector problem for the proper Hamiltonian. The unknown exponential parameter is determined by means of minimization of the corresponding eigenvalue (energy). Reasons for new version: The need to take into account the fact that the negative hydrogen ion ( Z=1) has only one bound (ground) state. Summary of revisions: Minor amendments were made in Cell 2 and Cell 5 of both TwoElAtomSH and TwoElAtomSL programs. Restrictions: Firstly, the too large length of expansion (basis size) takes too much computation time and operative memory giving no perceptible improvement in accuracy. Secondly, the number of shells ? in the wave function expansion enables one to calculate the excited nS-states up to n=?+1 inclusive. Running time: 2-60 minutes (depends on basis size and computer speed).

Liverts, Evgeny Z.; Barnea, Nir

2012-03-01

104

Lifetimes of Rydberg states for ions of the group 2 elements  

NASA Astrophysics Data System (ADS)

An analysis is given of data in the literature on radiative lifetimes of excited ionic states for elements of group 2 of the Periodic Table. Tabular values of constants are recommended on the basis of the analysis.

Rykova, O. V.; Verolainen, Ya. F.

1994-01-01

105

S-states of helium-like ions  

NASA Astrophysics Data System (ADS)

A simple Mathematica (version 7) code for computing S-state energies and wave functions of two-electron (helium-like) ions is presented. The elegant technique derived from the classical papers of Pekeris (1958, 1959, 1962, 1965, 1971) [1-3] is applied. The basis functions are composed of the Laguerre functions. The method is based on the perimetric coordinates and specific properties of the Laguerre polynomials. Direct solution of the generalized eigenvalues and eigenvectors problem is used, distinct from the Pekeris works. No special subroutines were used, only built-in objects supported by Mathematica. The accuracy of the results and computation times depend on the basis size. The ground state and the lowest triplet state energies can be computed with a precision of 12 and 14 significant figures, respectively. The accuracy of the higher excited states calculations is slightly worse. The resultant wave functions have a simple analytical form, that enables calculation of expectation values for arbitrary physical operators without any difficulties. Only three natural parameters are required in the input. The above Mathematica code is simpler than the earlier version (Liverts and Barnea, 2010 [4]). At the same time, it is faster and more accurate. Program summaryProgram title: TwoElAtomSL(SH) Catalogue identifier: AEHY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHY_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 11 434 No. of bytes in distributed program, including test data, etc.: 540 063 Distribution format: tar.gz Programming language: Mathematica 7.0 Computer: Any PC Operating system: Any which supports Mathematica; tested under Microsoft Windows XP and Linux SUSE 11.0 RAM:?10 bytes Classification: 2.1, 2.2, 2.7, 2.9 Nature of problem: The Schrödinger equation for atoms (ions) with more than one electron has not been solved analytically. Approximate methods must be applied in order to obtain the wave functions or another physical attributes from quantum mechanical calculations. Solution method: The S-wave function is expanded into a triple set of basis functions which are composed of the exponentials combined with the Laguerre polynomials in the perimetric coordinates. Using specific properties of the Laguerre polynomials, solution of the two-electron Schrödinger equation reduces to solving the generalized eigenvalues and eigenvector problem for the proper Hamiltonian. The unknown exponential parameter is determined by means of minimization of the corresponding eigenvalue (energy). Restrictions: First, the too large length of expansion (basis size) takes the too large computation time and operative memory giving no perceptible improvement in accuracy. Second, the number of shells ? in the wave function expansion enables one to calculate the excited nS-states up to n=?+1 inclusive. Running time: 2-60 minutes (depends on basis size and computer speed).

Liverts, Evgeny Z.; Barnea, Nir

2011-09-01

106

Metastable Helium: A New Determination of the Longest Atomic Excited-State Lifetime  

NASA Astrophysics Data System (ADS)

Exited atoms may relax to the ground state by radiative decay, a process which is usually very fast (of order nanoseconds). However, quantum-mechanical selection rules can prevent such rapid decay, in which case these “metastable” states can have lifetimes of order seconds or longer. In this Letter, we determine experimentally the lifetime of the longest-lived neutral atomic state—the first excited state of helium (the 2S13 metastable state)—to the highest accuracy yet measured. We use laser cooling and magnetic trapping to isolate a cloud of metastable helium (He*) atoms from their surrounding environment, and measure the decay rate to the ground 1S01 state via extreme ultraviolet (XUV) photon emission. This is the first measurement using a virtually unperturbed ensemble of isolated helium atoms, and yields a value of 7870(510) seconds, in excellent agreement with the predictions of quantum electrodynamic theory.

Hodgman, S. S.; Dall, R. G.; Byron, L. J.; Baldwin, K. G. H.; Buckman, S. J.; Truscott, A. G.

2009-07-01

107

Redistribution of atomic population among nearly degenerate Rydberg states through dipole-dipole interactions  

NASA Astrophysics Data System (ADS)

Ultra-cold highly-excited atoms in a magneto-optical trap are strongly coupled by the dipole-dipole interaction. Rubidium atoms that have been excited to the 32d5/2, |mj| = 1/2 sublevel can exchange energy when an applied static electric field tunes the Stark states into resonance. They do so via the densely packed set of resonant interactions 32d+32d->34p+30g near 0.3 V/cm. Atoms that have exchanged energy and are now in the final p and manifold states can be coupled to a resonance involving 32d5/2, |mj| = 3/2 and 1/2 states, which redistributes population among the |mj| sublevels. We present experimental and computational studies that investigate this redistribution.

Carroll, Thomas J.; Fahey, Donald P.; Noel, Michael W.; Mellus, Alex; Ward, Jon

2012-06-01

108

Oscillations in dipole-dipole transitions from nearly degenerate Rydberg states  

NASA Astrophysics Data System (ADS)

Pairs of ultracold highly excited atoms can exchange energy over long distances through a dipole-dipole coupling. We present an experimental study of the time dependence of this interaction. Rubidium atoms in a magneto-optical trap are impulsively excited to a coherent superposition of three closely spaced (<10 MHz) 32d5/2 |mj| sublevels. An electric field is used to control the |mj| Stark splitting. Atoms are allowed to exchange energy according to 32d+32d->34p+30f, and the distribution of final states is measured using state selective field ionization. As the time between excitation and ionization is varied, oscillations in the energy exchange are observed. The period of these oscillations is seen to decrease as the initial |mj| state separation is increased.

Fahey, Donald P.; Noel, Michael W.; Carroll, Thomas J.

2011-06-01

109

Linewidths in bound state resonances for helium scattering from Si(111)-(1 × 1)H  

Microsoft Academic Search

Helium-3 spin-echo measurements of resonant scattering from the Si(111)-(1 × 1)H surface, in the energy range 4-14 meV, are presented. The measurements have high energy resolution yet they reveal bound state resonance features with uniformly broad linewidths. We show that exact quantum mechanical calculations of the elastic scattering, using the existing potential for the helium\\/Si(111)-(1 × 1)H interaction, cannot reproduce

F. E. Tuddenham; H. Hedgeland; J. Knowling; A. P. Jardine; D. A. MacLaren; G. Alexandrowicz; J. Ellis; W. Allison

2009-01-01

110

The polaron state of surface electrons on helium covering a structured substrate  

NASA Astrophysics Data System (ADS)

In the temperature range 1.5-2.7 K the conductivity of surface electrons over a liquid helium film that covers a structured silicon substrate containing a regular system of micropores is investigated experimentally. It is found that in the range T ? 2.5 K the conductivity drops sharply, which can be explained by the formation of the autolocalized polaron state of an electron over the helium film. The hypothesis that the polaron state of a surface electron appears in a dense helium vapor was examined by calculating the free energy of the polaron with a minimum showing up when the temperature rises up to a certain critical value, and the dependence of the pressing field is in a qualitative agreement with experimental data on the temperature of the sharp drop in the conductivity. The calculation predicts a dependence of the critical temperature on parameters of the potential acting in a plane of the helium surface and associated with distortion of the helium surface due to the structure of the substrate, which favors the appearance of the localized charge over the helium film.

Smorodin, A. V.; Nikolaenko, V. A.; Sokolov, S. S.

2013-10-01

111

Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. II. Ion-pair formation and resonant quenching of the Rb(nl) and Ne(nl) States by Ca, Sr, and Ba atoms  

SciTech Connect

Electron-transfer processes are studied in thermal collisions of Rydberg atoms with alkaline-earth Ca(4s{sup 2}), Sr(5s{sup 2}), and Ba(6s{sup 2}) atoms capable of forming negative ions with a weakly bound outermost p-electron. We consider the ion-pair formation and resonant quenching of highly excited atomic states caused by transitions between Rydberg covalent and ionic terms of a quasi-molecule produced in collisions of particles. The contributions of these reaction channels to the total depopulation cross section of Rydberg states of Rb(nl) and Ne(nl) atoms as functions of the principal quantum number n are compared for selectively excited nl-levels with l Much-Less-Than n and for states with large orbital quantum numbers l = n - 1, n - 2. It is shown that the contribution from resonant quenching dominates at small values of n, and the ion-pair formation process begins to dominate with increasing n. The values and positions of the maxima of cross sections for both processes strongly depend on the electron affinity of an alkaline-earth atom and on the orbital angular momentum l of a highly excited atom. It is shown that in the case of Rydberg atoms in states with large l {approx} n - 1, the rate constants of ion-pair formation and collisional quenching are considerably lower than those for nl-levels with l Much-Less-Than n.

Narits, A. A. [Russian Academy of Sciences, Lebedev Physics Institute (Russian Federation)] [Russian Academy of Sciences, Lebedev Physics Institute (Russian Federation); Mironchuk, E. S. [Moscow Institute of Physics and Technology (State University) (Russian Federation)] [Moscow Institute of Physics and Technology (State University) (Russian Federation); Lebedev, V. S., E-mail: vlebedev@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physics Institute (Russian Federation)

2013-10-15

112

Rabi Oscillations between Ground and Rydberg States with Dipole-Dipole Atomic Interactions T. A. Johnson, E. Urban, T. Henage, L. Isenhower, D. D. Yavuz, T. G. Walker, and M. Saffman  

E-print Network

Rabi Oscillations between Ground and Rydberg States with Dipole-Dipole Atomic Interactions T. A November 2007; published 19 March 2008) We demonstrate Rabi oscillations of small numbers of 87 Rb atoms interaction effects between as few as two atoms and by observation of coherent Rabi oscillations between

Yavuz, Deniz

113

One photon two electron excitations between doubly excited states of helium  

SciTech Connect

Variational calculations using Hylleraas coordinates have been performed for the first time for estimating the energies of 3dnf({sup 1,3}D{sup o}) state of helium for n=4,5,6. We predict absorption peaks at 12.219, 12.647, and 12.857 eV for the {sup 3}D{sup o} series converging to N=3 ionization threshold of He{sup +} which can be expected to be observed in the experiment of single photon double excitation of lowest {sup 3}P{sup e} state of helium placed in synchrotron radiation.

Bhattacharyya, S.; Sil, A. N.; Mukherjee, T. K.; Mukherjee, P. K. [Kandi Raj College, Kandi, Murshidabad, West Bengal 742 137 (India); Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Narula Institute of Technology, Agarpara, Kolkata 700 109 (India); Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

2007-01-07

114

Comment on 'Measurement of the lifetimes of S and D states below n=31 using cold Rydberg gas'  

SciTech Connect

A recent paper by [Nascimento et al., Phys. Rev. A 74, 054501 (2006)], and a previous paper from the same group [de Oliveira et al., Phys. Rev. A 65 031401(R) (2002)], report measurements of Rydberg lifetimes in rubidium in the range 27{<=}n{<=}44. In this Comment, we point out one apparent flaw of experimental technique in these papers that may lead to systematic errors in the results. We also clarify a point of theoretical interpretation used in these papers which suggests that the agreement between experiment and theory may not be as good as it seems.

Tate, D. A. [Department of Physics and Astronomy, Colby College, Waterville, Maine 04901 (United States)

2007-06-15

115

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

E-print Network

Proposal for Manipulating and Detecting Spin and Orbital States of Trapped Electrons on Helium architecture in which an on-chip high finesse superconducting cavity is coupled to the lateral motion and spin state of a single electron trapped on the surface of superfluid helium. We estimate the motional

Dykman, Mark

116

Filtering single atoms from Rydberg blockaded mesoscopic ensembles  

E-print Network

We propose an efficient method to filter out single atoms from trapped ensembles with unknown number of atoms. The method employs stimulated adiabatic passage to reversibly transfer a single atom to the Rydberg state which blocks subsequent Rydberg excitation of all the other atoms within the ensemble. This triggers the excitation of Rydberg blockaded atoms to short lived intermediate states and their subsequent decay to untrapped states. Using an auxiliary microwave field to carefully engineer the dissipation, we obtain a nearly deterministic single-atom source. Our method is applicable to small atomic ensembles in individual microtraps and in lattice arrays.

Petrosyan, David; Mølmer, Klaus

2015-01-01

117

Deterministic entanglement of Rydberg ensembles by engineered dissipation  

NASA Astrophysics Data System (ADS)

We propose a scheme that employs dissipation to deterministically generate entanglement in an ensemble of strongly interacting Rydberg atoms. With a combination of microwave driving between different Rydberg levels and a resonant laser coupling to a short-lived atomic state, the ensemble can be driven towards a dark steady state that entangles all atoms. The long-range resonant dipole-dipole interaction between different Rydberg states extends the entanglement beyond the van der Waals interaction range with perspectives for entangling atoms in separate ensembles.

Rao, D. D. Bhaktavatsala; Mølmer, Klaus

2014-12-01

118

Attosecond Transient Absorption Spectroscopy of doubly-excited states in helium  

NASA Astrophysics Data System (ADS)

Theoretical calculations of the XUV attosecond transient absorption spectrum (ATAS) of helium in the doubly-excited state region reproduce recent high-precision measurements, reveal novel means of controlling the dynamics of transiently-bound electronic wavepackets in intense laser fields, and indicates a possible extension of 2D-spectroscopies to the XUV range.

Argenti, Luca; Ott, Christian; Pfeifer, Thomas; Martín, Fernando

2014-04-01

119

The equation of state, electronic thermal conductivity, and opacity of hot dense deuterium-helium plasmas  

NASA Astrophysics Data System (ADS)

Thermophysical properties of dense deuterium-helium plasmas along the 160 g/cm3 isochore with temperatures up to 800 electron-volt are reported. From Kubo-Greenwood formula, the electronic thermal conductivity and Rosseland mean opacity are determined by means of quantum molecular dynamics (QMD) simulations. Equation of states is obtained by QMD and orbital free molecular dynamics. The electronic heat conductance is compared with several models currently used in inertial confinement fusion designs. Our results indicate that only in the weak coupling regime, the opacity is sensitive to the concentration of helium.

Wang, Cong; He, Xian-Tu; Zhang, Ping

2012-04-01

120

Giant Rydberg Excitons in Cuprous Oxide  

E-print Network

Highly excited atoms with an electron moved into a level with large principal quantum number are fascinating hydrogen-like objects. The giant extension of these Rydberg atoms leads to huge interaction effects. Monitoring these interactions has provided novel insights into molecular and condensed matter physics problems on a single quantum level. Excitons, the fundamental optical excitations in semiconductors consisting of a negatively charged electron and a positively charged hole, are the condensed matter analogues of hydrogen. Highly excited excitons with extensions similar to Rydberg atoms are attractive because they may be placed and moved in a crystal with high precision using microscopic potential landscapes. Their interaction may allow formation of ordered exciton phases or sensing of elementary excitations in the surrounding, also on a quantum level. Here we demonstrate the existence of Rydberg excitons in cuprous oxide, Cu2O, with principal quantum numbers as large as n=25 . These states have giant w...

Kazimierczuk, Tomasz; Scheel, Stefan; Stolz, Heinrich; Bayer, Manfred

2014-01-01

121

From molecular spectra to a density shift in dense Rydberg gases  

PubMed Central

In Rydberg atoms, at least one electron is excited to a state with a high principal quantum number. In an ultracold environment, this low-energy electron can scatter off a ground state atom allowing for the formation of a Rydberg molecule consisting of one Rydberg atom and several ground state atoms. Here we investigate those Rydberg molecules created by photoassociation for the spherically symmetric S-states. A step by step increase of the principal quantum number up to n=111 enables us to go beyond the previously observed dimer and trimer states up to a molecule, where four ground state atoms are bound by one Rydberg atom. The increase of bound atoms and the decreasing binding potential per atom with principal quantum number results finally in an overlap of spectral lines. The associated density-dependent line broadening sets a fundamental limit, for example, for the optical thickness per blockade volume in Rydberg quantum optics experiments. PMID:25082599

Gaj, A.; Krupp, A. T.; Balewski, J. B.; Löw, R.; Hofferberth, S.; Pfau, T.

2014-01-01

122

Quantum critical behavior in strongly interacting Rydberg gases  

E-print Network

We study the appearance of correlated many-body phenomena in an ensemble of atoms driven resonantly into a strongly interacting Rydberg state. The ground state of the Hamiltonian describing the driven system exhibits a second order quantum phase transition. We derive the critical theory for the quantum phase transition and show that it describes the properties of the driven Rydberg system in the saturated regime. We find that the suppression of Rydberg excitations known as blockade phenomena exhibits an algebraic scaling law with a universal exponent.

Hendrik Weimer; Robert Löw; Tilman Pfau; Hans Peter Büchler

2008-06-24

123

Final-state ?2 wave function in ion-helium collisions  

NASA Astrophysics Data System (ADS)

In this work we study the double-differential cross sections (DDCSs) of ejected electrons in single-ionization collisions of protons with helium atoms. The final state of the emitted electron is modeled by the correlated wave function ?2, a confluent hypergeometric function of two variables. We introduce a series representation of the ?2 wave function in terms of two-body Coulomb-like states, corresponding to the electron-projectile and electron-target relative motions. We consider undistorted and eikonal initial states that give rise to the Born ?2 and eikonal initial-state ?2 approximations, respectively. In both cases we obtain analytic series representations of the transition matrices, which exhibit a strong numerical convergence. We obtain DDCSs in ion-helium collisions in the intermediate- to high-energy regime with the Born ?2 approximation and show that it qualitatively agrees with the available experimental data.

Colavecchia, F. D.; Gasaneo, G.; Garibotti, C. R.

1998-10-01

124

Final-state Phi2 wave function in ion-helium collisions  

Microsoft Academic Search

In this work we study the double-differential cross sections (DDCSs) of ejected electrons in single-ionization collisions of protons with helium atoms. The final state of the emitted electron is modeled by the correlated wave function Phi2, a confluent hypergeometric function of two variables. We introduce a series representation of the Phi2 wave function in terms of two-body Coulomb-like states, corresponding

F. D. Colavecchia; G. Gasaneo; C. R. Garibotti

1998-01-01

125

A Study of Final State Effects in the electrodisintegration of a polarized Helium-3 target  

E-print Network

An approach for the description of the final state interaction in the evaluation of inclusive electromagnetic responses of a polarized Helium-3 target, is briefly illustrated. Preliminary results of calculations, where the final state interaction is fully taken into account for the two-body break-up channel, are compared with experimental data, showing a very encouraging improvement with respect to the plane wave impulse approximation results.

A. Kievsky; E. Pace; G. Salme`

2005-01-25

126

Photoionization of Alkali-Doped Helium Nanodroplets  

NASA Astrophysics Data System (ADS)

Superfluid helium droplets (He_N) provide a cold, weakly-interacting environment for the investigation of weakly bound molecules. Whereas the host-dopant interaction is weak for neutral molecules, ion impurities may be surrounded by frozen shells of polarized helium atoms. An extreme example of the different behavior is given by alkali metal impurities that stay at the surface of the droplet as neutrals but immerse into the droplet as cations releasing a considerable amount of binding energy. We report measurements of the photoionization efficiency for the rubidium-He_N and cesium-He_N systems and find that the ionization threshold is lowered compared with the free atoms and is in good agreement with Rydberg state spectroscopy of these systems. The corresponding energy shift increases when going from heavy to light alkali metals and from small to large helium droplets. Both effects can be explained by the difference in polarization energies associated with submerged alkali metal cations. The findings agree qualitatively well with recent calculations of helium snowball formation around alkali metal cations. M. Theisen, F. Lackner, G. Krois, and W. E. Ernst, J. Phys. Chem. Lett. 2, 2778 (2011). F. Lackner, G. Krois, M. Theisen, M. Koch, and W. E. Ernst, Phys. Chem. Chem. Phys. 13, 18781 (2011). D. E. Galli, D. M. Ceperley, and L. Reatto, J. Phys. Chem. A 115, 7300 (2011).

Theisen, Moritz; Lackner, Florian; Krois, Günter; Koch, Markus; Ernst, Wolfgang E.

2012-06-01

127

Equation of State and Electrical Conductivity of Helium at High Pressures and Temperatures  

NASA Astrophysics Data System (ADS)

Helium, the second-most abundant element in the universe and giant planets, is expected to metallize at much higher pressures and temperatures than the most abundant element, hydrogen. The difference in chemical-bonding character, between insulator and metal, is expected to make hydrogen-helium mixtures immiscible throughout large fractions of planetary interiors, and therefore subject to gravitational separation contributing significantly to the internal dynamics of giant planets. Using laser-driven shock waves on samples pre-compressed in high-pressure cells, we have obtained the first measurements of optical reflectivity from the shock front in helium to pressures of 146 GPa. The reflectivity exceeds 5% above \\ensuremath{\\sim} 100 GPa, indicating high electrical conductivity. By varying the initial pressure (hence density) of the sample, we can access a much wider range of final pressure-temperature conditions than is possible in conventional Hugoniot experiments. Our work increases by nine-fold the pressure range of single-shock measurements, in comparison with gas-gun experiments, and yields results in agreement with the Saumon, Chabrier and Van Horn (1994) equation of state for helium. This changes the internal structures inferred for Jupiter-size planets, relative to models based on earlier equations of state (e. g., SESAME).

McWilliams, R. S.; Eggert, J. H.; Loubeyre, P.; Brygoo, S.; Collins, G.; Jeanloz, R.

2004-12-01

128

Logarithmic mean excitation energies: II. Helium, lithium, beryllium, and the 2s state of hydrogen  

NASA Astrophysics Data System (ADS)

The four logarithmic excitation eneriges I(?) for ?=-1, 0, 1, and 2 have been calculated for helium, lithium, beryllium, and the 2s state of hydrogen. They appear in the expressions of the total cross section, the stopping power, and the straggling effect for fast charged particles, and in the expressions of the Lamb shift of atomic energy levels. The method was introduced some years ago [Rosendorff and Birman, Phys. Rev. A 31, 612 (1985)]. For hydrogen the method is rigorous. Exact one-particle wave functions given by Clementi were used. Thus, correlation and symmetrization effects were neglected. For the nonhydrogen states, the relevant differential equations were solved by using a computer. An effective charge was defined which has interesting features. It is helpful in gaining some physical insight into the results obtained for helium and the 1s and 2s states of lithium and beryllium.

Rosendorff, S.; Schlaile, H. G.

1993-10-01

129

Dislocation-mediated melting of one-dimensional Rydberg crystals  

SciTech Connect

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.

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

130

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

SciTech Connect

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}.

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

131

An experimental and theoretical guide to strongly interacting Rydberg gases  

E-print Network

We review experimental and theoretical tools to excite, study and understand strongly interacting Rydberg gases. The focus lies on the excitation of dense ultracold atomic samples close to, or within quantum degeneracy, to high lying Rydberg states. The major part is dedicated to highly excited S-states of Rubidium, which feature an isotropic van-der-Waals potential. Nevertheless, the setup and the methods presented are also applicable to other atomic species used in the field of laser cooling and atom trapping.

Robert Löw; Hendrik Weimer; Johannes Nipper; Jonathan B. Balewski; Björn Butscher; Hans Peter Büchler; Tilman Pfau

2012-02-10

132

Ultrafast structural dynamics and isomerization in Rydberg-exited Quadricyclane  

SciTech Connect

The quadricyclane - norbornadiene system is an important model for the isomerization dynamics between highly strained molecules. In a breakthrough observation for a polyatomic molecular system of that complexity, we follow the photoionization from Rydberg states in the time-domain to derive a measure for the time-dependent structural dynamics and the time-evolving structural dispersion even while the molecule is crossing electronic surfaces. The photoexcitation to the 3s and 3p Rydberg states deposits significant amounts of energy into vibrational motions. We observe the formation and evolution of the vibrational wavepacket on the Rydberg surface and the internal conversion from the 3p Rydberg states to the 3s state. In that state, quadricyclane isomerizes to norbornadiene with a time constant of {tau}{sub 2} = 136(45) fs. The lifetime of the 3p Rydberg state in quadricyclane is {tau}{sub 1} = 320(31) and the lifetime of the 3s Rydberg state in norbornadiene is {tau}{sub 3} = 394(32).

Rudakov, Fedor M [ORNL

2012-01-01

133

Ultracold Rydberg Atoms in a Ioffe-Pritchard Trap  

E-print Network

We discuss the properties of ultracold Rydberg atoms in a Ioffe-Pritchard magnetic field configuration. The derived two-body Hamiltonian unveils how the large size of Rydberg atoms affects their coupling to the inhomogeneous magnetic field. The properties of the compound electronic and center of mass quantum states are thoroughly analyzed. We find very tight confinement of the center of mass motion in two dimensions to be achievable while barely changing the electronic structure compared to the field free case. This paves the way for generating a one-dimensional ultracold quantum Rydberg gas.

Hezel, Bernd; Schmelcher, Peter

2007-01-01

134

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

NASA Astrophysics Data System (ADS)

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.

Topcu, Turker; Derevianko, Andrei

2013-11-01

135

Collisions of Rydberg Atoms with Charged Particles  

NASA Astrophysics Data System (ADS)

The long range of Coulomb interactions, together with the large size, long radiative lifetimes and high state densities of highly excited Rydberg atoms, results in inelastic collision cross sections of prodigious size -- often large enough to outweigh small number densities in astrophysica and cool laboratory plasmas -- and in other unusual features. This talk will provide: (a) a brief survey of the significant features of collisions between electron or positive ions and state-selected Rydberg atoms and of recent experiments( O. Makarov and K.B. MacAdam, Phys. Rev. A 60), 2131-8 (1999); and K.B. MacAdam, J.C. Day and D.M. Homan, Comm. At. Mol. Phys./Comm. Mod. Phys. 1(2), Part D, 57-73 (1999). to investigate them; (b) an introduction to some of the special techniques that have been developed(J.L. Horn, D.M. Homan, C.S. Hwang, W.L. Fuqua III and K.B. MacAdam, Rev. Sci. Instrum. 69), 4086-93 (1998). for preparation, manipulation and detection of Rydberg atoms; and (c) a glimpse at new directions in Rydberg atom collision research.

MacAdam, Keith B.

2000-10-01

136

Standoff detection of large organic molecules using Rydberg fingerprint spectroscopy and microwave Rayleigh scattering.  

PubMed

We present a technique for nonintrusive and standoff detection of large organic molecules using coherent microwave Rayleigh scattering from plasma produced by structure sensitive photoionization through Rydberg states. We test the method on 1,4-diazobicyclooctane. Transitions between the 3s Rydberg state and higher lying Rydberg states are probed using two-color photoionization with 266 nm photons and photons in the range of 460-2400 nm. Photoionization is detected using microwave radiation, which is scattered by the unbounded electrons. Highly resolved Rydberg spectra are acquired in vacuum and in air. PMID:22854448

Rudakov, Fedor; Zhang, Zhili

2012-01-15

137

Standoff detection of large organic molecules using Rydberg fingerprint spectroscopy and microwave Rayleigh scattering  

SciTech Connect

We present a technique for nonintrusive and standoff detection of large organic molecules using coherent microwave Rayleigh scattering from plasma produced by structure sensitive photoionization through Rydberg states. We test the method on 1,4-diazobicyclooctane. Transitions between the 3s Rydberg state and higher lying Rydberg states are probed using two-color photoionization with 266?nm photons and photons in the range of 460-2400 nm. Photoionization is detected using microwave radiation, which is scattered by the unbounded electrons. Highly resolved Rydberg spectra are acquired in vacuum and in air.

Rudakov, Fedor M [ORNL; Zhang, Zhili [ORNL

2012-01-01

138

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

SciTech Connect

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.

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

2014-01-14

139

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)

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.

Underwood-Lemons, Theresa Ann

140

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

141

Rydberg atoms in hollow-core photonic crystal fibres  

PubMed Central

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

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

2014-01-01

142

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

143

Observation of ultralong range Rydberg molecules  

NASA Astrophysics Data System (ADS)

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.

Shaffer, James

2009-05-01

144

The role of Rydberg states in photoionization of NO2 and (NO+, O-) ion pair formation induced by one VUV photon  

NASA Astrophysics Data System (ADS)

We report a combined experimental and theoretical study of photoionization (PI) of the NO2 molecule into the NO2+ (X 1?g+) ground state and the photodissociation of NO2 into the NO+(1?+) + O-(2P) ion pair. These processes were induced by 10.9 eV-13 eV synchrotron radiation and the products were detected using electron-ion or O--NO+ coincident momentum spectroscopy. The results demonstrate the strong influence of [R*(4b2)-1, nl?i, v_2^' ] Rydberg states vibrationally resolved in the v_2^' bending modes for both processes. In particular, we emphasize two regions around 11.5 eV and 12.5 eV that were studied in more detail for their relevance to 400 nm multiphoton ionization induced by femtosecond pulses. The photoelectron energy spectra and asymmetry parameters support the existence of two PI mechanisms, as probed with the help of fixed-nuclei frozen-core Hartree-Fock calculations. We found significant deviations from Franck-Condon ionization predictions which may be assigned to vibronic coupling of NO2* states such as that induced by a conical intersection. The limited agreement between theory and experiment, even for the non-resonant processes, indicates the need for calculations that go beyond the approximations used in the current study. Ion pair formation leads to strong vibrational and rotational excitation of the NO+(1?+,v) product, with an ion fragment angular anisotropy depending on both the v_2^' bending quantum number of the excited parent molecule and the v vibrational level of the fragment.

Marggi Poullain, S.; Veyrinas, K.; Billaud, P.; Lebech, M.; Picard, Y. J.; Lucchese, R. R.; Dowek, D.

2013-07-01

145

Learning Approach on the Ground State Energy Calculation of Helium Atom  

SciTech Connect

This research investigated the role of learning approach on the ground state energy calculation of Helium atom in improving the concepts of science teachers at university level. As the exact solution of several particles is not possible here we used approximation methods. Using this method one can understand easily the calculation of ground state energy of any given function. Variation Method is one of the most useful approximation methods in estimating the energy eigen values of the ground state and the first few excited states of a system, which we only have a qualitative idea about the wave function.The objective of this approach is to introduce and involve university teacher in new research, to improve their class room practices and to enable teachers to foster critical thinking in students.

Shah, Syed Naseem Hussain [Department of Physics, Federal Urdu University of Art, Sciences and Technology, Gulshan Campus Gulshan-e-Iqbal, University Road Karachi-75300 (Pakistan)

2010-07-28

146

Topological matter with collective encoding and Rydberg blockade  

SciTech Connect

We propose to use a permutation symmetric sample of multilevel atoms to simulate the properties of topologically ordered states. The Rydberg blockade interaction is used to prepare states of the sample which are equivalent to resonating valence bond states, Laughlin states, and string-net condensates and to create and study the properties of their quasi-particle-like fundamental excitations.

Nielsen, Anne E. B.; Moelmer, Klaus [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

2010-11-15

147

Simulations of the dissociation of small helium clusters with ab initio molecular dynamics in electronically excited states  

SciTech Connect

The dynamics resulting from electronic excitations of helium clusters were explored using ab initio molecular dynamics. The simulations were performed with configuration interaction singles and adiabatic classical dynamics coupled to a state-following algorithm. 100 different configurations of He{sub 7} were excited into the 2s and 2p manifold for a total of 2800 trajectories. While the most common outcome (90%) was complete fragmentation to 6 ground state atoms and 1 excited state atom, 3% of trajectories yielded bound, He {sub 2}{sup *}, and <0.5% yielded an excited helium trimer. The nature of the dynamics, kinetic energy release, and connections to experiments are discussed.

Closser, Kristina D.; Head-Gordon, Martin, E-mail: mhg@cchem.berkeley.edu [Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (United States) [Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (United States); Ultrafast X-Ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Gessner, Oliver [Ultrafast X-Ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Ultrafast X-Ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2014-04-07

148

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

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

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

2014-06-28

149

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)  

NASA Astrophysics Data System (ADS)

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^ + }) to X^1 {? }_g^ + ( {O_g^ + }) emission in the vacuum ultraviolet (˜172 nm), induced by laser excitation of {? }_g leftarrow 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 leftarrow 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(5p6 1S0) + Xe(5p5 6p) and built on a predominantly A2?3/2g molecular ion core. Specifically, the spectroscopic constants for the upper state of the 1_g leftarrow 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.

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

2014-06-01

150

Magic-wavelength optical traps for Rydberg atoms  

SciTech Connect

We propose blue-detuned optical traps that are suitable for trapping of both ground-state and Rydberg excited atoms. The addition of a background compensation field or a suitable choice of the trap geometry provides a magic trapping condition for ground-state and Rydberg atoms at the trap center. Deviations from the magic condition at finite temperature are calculated. Designs that achieve less than 200-kHz differential trap shift between Cs ground states and 125s Rydberg states for 10 {mu}K Cs atoms are presented. Consideration of the trapping potential and photoionization rates suggests that these traps will be useful for quantum-information experiments with atomic qubits.

Zhang, S.; Saffman, M. [Department of Physics, 1150 University Avenue, University of Wisconsin, Madison, Wisconsin 53706 (United States); Robicheaux, F. [Department of Physics, Auburn University, Auburn, Alabama 36849-5311 (United States)

2011-10-15

151

Spectroscopic Observation of Resonant Electric Dipole-Dipole Interactions between Cold Rydberg Atoms  

E-print Network

Atoms K. Afrousheh, P. Bohlouli-Zanjani, D. Vagale, A. Mugford, M. Fedorov, and J. D. D. Martin between cold Rydberg atoms were observed using microwave spectroscopy. Laser-cooled 85Rb atoms pulse transferred a fraction of these Rydberg atoms to the 46p3=2 state. A second microwave pulse

Le Roy, Robert J.

152

Two-Atom Rydberg Blockade using Direct 6S to nP Excitation  

E-print Network

We explore a single-photon approach to Rydberg state excitation and Rydberg blockade. Using detailed theoretical models, we show the feasibility of direct excitation, predict the effect of background electric fields, and calculate the required interatomic distance to observe Rydberg blockade. We then measure and control the electric field environment to enable coherent control of Rydberg states. With this coherent control, we demonstrate Rydberg blockade of two atoms separated by 6.6(3) {\\mu}m. When compared with the more common two-photon excitation method, this single-photon approach is advantageous because it eliminates channels for decoherence through photon scattering and AC Stark shifts from the intermediate state while moderately increasing Doppler sensitivity.

A. M. Hankin; Y. -Y. Jau; L. P. Parazzoli; C. W. Chou; D. J. Armstrong; A. J. Landahl; G. W. Biedermann

2014-04-21

153

XUV frequency-comb metrology on the ground state of helium  

SciTech Connect

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.

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

154

Ab initio Equation of State data for hydrogen, helium, and water and the internal structure of Jupiter  

E-print Network

The equation of state of hydrogen, helium, and water effects interior structure models of giant planets significantly. We present a new equation of state data table, LM-REOS, generated by large scale quantum molecular dynamics simulations for hydrogen, helium, and water in the warm dense matter regime, i.e.for megabar pressures and temperatures of several thousand Kelvin, and by advanced chemical methods in the complementary regions. The influence of LM-REOS on the structure of Jupiter is investigated and compared with state-of-the-art results within a standard three-layer model consistent with astrophysical observations of Jupiter. Our new Jupiter models predict an important impact of mixing effects of helium in hydrogen with respect to an altered compressibility and immiscibility.

N. Nettelmann; B. Holst; A. Kietzmann; M. French; R. Redmer; D. Blaschke

2008-06-06

155

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

E-print Network

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 these metastable states, to states with large ($\\sim 10^{11}$ s$^{-1}$) Auger rates. The $\\pi{\\rm He}^{2+}$ ion that remains after Auger emission of the $1s$ electron undergoes Stark mixing with the $s$, $p$, and $d$ states during collisions with the helium atoms in the experimental target. This leads to immediate nuclear absorption of the $\\pi^-$. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge....(continued)

Masaki Hori; Anna Sótér; Vladimir I. Korobov

2014-04-30

156

Benchmark Integral Cross Sections for Electron Impact Excitation of the n = 2 States in Helium  

NASA Astrophysics Data System (ADS)

In this paper, we present integral cross sections (ICS) for electron impact excitation of the n = 2 levels in helium in the impact energy range of 23.5 eV to 35 eV. The ICS of each final state, 23S, 21S, 23P and 21P, has been determined by integration of the angular differential cross sections (DCS) over all of 0° to 180°, where those DCS were obtained from both our previous experiments and the extrapolation using the convergent close coupling calculation. The present experimental ICS for the optically allowed 21P transition state are also compared with those obtained from the BEf-scaling method. Very good agreement between the experimental and BEf-scaled 21P ICSs is generally found in the measured impact energy region.

Hoshino, M.; Kato, H.; Suzuki, D.; Tanaka, H.; Bray, I.; V. Fursa, D.; Buckman, S. J.; Ingólfsson, O.; Brunger, M. J.

2010-06-01

157

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

NASA Astrophysics Data System (ADS)

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.

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

158

Imaging the evolution of an ultracold strontium Rydberg gas  

E-print Network

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.

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

2012-01-01

159

Deflection and deceleration of hydrogen Rydberg molecules in inhomogeneous electric fields.  

PubMed

Hydrogen molecules are excited in a molecular beam to Rydberg states around n=17-18 and are exposed to the inhomogeneous electric field of an electric dipole. The large dipole moment produced in the selected Stark eigenstates leads to strong forces on the H2 molecules in the inhomogeneous electric field. The trajectories of the molecules are monitored using ion-imaging and time of flight measurements. With the dipole rods mounted parallel to the beam direction, the high-field-seeking and low-field-seeking Stark states are deflected towards and away from the dipole, respectively. The magnitude of the deflection is measured as a function of the parabolic quantum number k and of the duration of the applied field. It is also shown that a large deflection is observed when populating the (17d2)1 state at zero field and switching the dipole field on after a delay. With the dipole mounted perpendicular to the beam direction, the molecules are either accelerated or decelerated as they move towards the dipole. The Rydberg states are found to survive for over 100 micros after the dipole field is switched off before being ionized at the detector and the time of flight is measured. A greater percentage change in kinetic energy is achieved by initial seeding of the beam in helium or neon followed by inhomogeneous field deceleration/acceleration. Molecular dynamics trajectory simulations are presented highlighting the extent to which the trajectories can be predicted based on the known Stark map. The spectroscopy of the populated states is discussed in detail and it is established that the N+=2, J=1, MJ=0 states populated here have a special stability with respect to decay by predissociation. PMID:15260687

Yamakita, Y; Procter, S R; Goodgame, A L; Softley, T P; Merkt, F

2004-07-15

160

Optical imaging of Rydberg atoms  

E-print Network

We present an experiment exploring electromagnetically induced transparency (EIT) in Rydberg atoms in order to observe optical nonlinearities at the single photon level. ??Rb atoms are trapped and cooled using a magneto-optical ...

Mazurenko, Anton

2012-01-01

161

Echo Experiments in a Strongly Interacting Rydberg Gas  

NASA Astrophysics Data System (ADS)

When ground state atoms are excited to a Rydberg state, van der Waals interactions among them can lead to a strong suppression of the excitation. Despite the strong interactions the evolution can still be reversed by a simple phase shift in the excitation laser field. We experimentally prove the coherence of the excitation in the strong blockade regime by applying an “optical rotary echo” technique to a sample of magnetically trapped ultracold atoms, analogous to a method known from nuclear magnetic resonance. We additionally measured the dephasing time due to the interaction between the Rydberg atoms.

Raitzsch, Ulrich; Bendkowsky, Vera; Heidemann, Rolf; Butscher, Björn; Löw, Robert; Pfau, Tilman

2008-01-01

162

Helium irradiated high-power P i N diode with low ON-state voltage drop  

NASA Astrophysics Data System (ADS)

The application of a 300 nm thick platinum silicide (PtSi) layer at the place of the anode contact layer of a soft recovery 2.5 kV/100 A high-power P-i-N diode brought a reduction of the forward voltage drop at several tens percent (for the rating current of 100 A) compared to that of the conventional aluminum and Ti-Ni-Ag layers. This enabled us to greatly improve the trade-off curve between the ON-state and turn-OFF losses of the diode subjected to helium irradiation into the anode and anode junction region. The application of PtSi layers thus opens a new way for the improvement of power devices.

Vobecký, J.; Hazdra, P.; Záhlava, V.

2003-01-01

163

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

164

Model atmospheres for low temperature, helium-rich white dwarfs: Problems with the equation of state  

NASA Astrophysics Data System (ADS)

The Hummer-Mihalas equations are used to calculate an equation of state appropriate for low temperature, helium-rich white dwarfs. These equations take into account non-ideal gas effects, most importantly pressure ionization. New thermodynamic properties and opacities of two mixtures are calculated and used to construct model atmospheres for DZ stars with effective temperatures ranging from 4000 K to 7000 K. A temperature reversal is found to occur in the optically thin outer layers. The pressure ionization of Ca, Mg, and Fe is also found to occur already at small optical depths. This indicates that the abundances of these elements in stars like van Maanen 2 may be larger than previously believed. This could be important for the accretion hypothesis generally believed to explain the origin of heavy elements in DZ stars. Exploratory synthetic spectra are calculated for van Maanen 2.

Peterson, Eric Roger

165

HIGH RESOLUTION MICROWAVE SPECTROSCOPY OF ULTRA COLD RYDBERG ATOMS AS A PROBE OF  

E-print Network

. The low ionization threshold of Rydberg states results in effective state-specific detection to be patient and strong in the face of adversity. A warm thank you to my father who inspired me with the love

Le Roy, Robert J.

166

Photon-Photon Interactions via Rydberg Blockade  

SciTech Connect

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.

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

167

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

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

Le Roy, Robert J.

168

Variational calculation for the doubly excited state (2p{sup 2}){sup 3}P{sup e} of helium  

SciTech Connect

Highly precise variational calculations of nonrelativistic energies of the (2p{sup 2}){sup 3}P{sup e} state of the helium atom are presented. We get an upper bound energy E=-0.7105 001 556 5678 a.u., the lowest yet obtained.

Mukherjee, Tapan K.; Mukherjee, Prasanta K. [Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

2004-06-01

169

Mechanism of the parametric four-wave mixing processes involving the C 2? and D 2?+ Rydberg states of NO  

NASA Astrophysics Data System (ADS)

When the 3p? C 2? and 3p? D 2?+ states of the NO molecule were populated through the two-photon resonant excitation, highly directional emission was generated in IR and UV regions along the laser propagation. It was concluded that amplified spontaneous emission (ASE) was mainly responsible for the IR wave corresponding to the C 2?, D 2?+?3s? A 2?+(0, 0) bands because the IR emission was detected in the backward direction as well as forward. The UV radiation composed only of the A 2?+?X 2?(0, 0) band evidenced the existence of the parametric four-wave mixing (PFWM) process. The analyses of emission properties revealed that the interaction of the forward propagating ASE with a two-photon field of the input laser produced the UV wave as the fourth wave in the PFWM process.

Ogi, Yoshihiro; Tsukiyama, Koichi

1998-10-01

170

Observation of the nd 1Delta(g) (n = 6, 7, and 8) Rydberg states of Na2 by optical-optical double resonance spectroscopy: L uncoupling and perturbations.  

PubMed

The nd (1)Delta(g) (n = 6, 7, and 8) Rydberg states of Na(2) correlating with the asymptotic limits of Na(3s) + Na(nd) have been observed using high-resolution cw optical-optical double resonance spectroscopy corresponding to the rovibrational transitions X (1)Sigma(g)(+)(v("),J(")) + h nu(pump) --> B (1)Pi(u)(v('),J(')) + h nu(probe) --> nd (1)Delta(g)(v,J). Totals of 104, 83, and 45 identified rovibrational e/f-parity levels in the ranges of v = 0-11, 11 < or = J < or = 83; v = 0-10, 11 < or = J < or = 83; and v = 0-10, 11 < or = J < or = 65, have been assigned to the 6d (1)Delta(g), 7d (1)Delta(g), and 8d (1)Delta(g) states, respectively. Using the observed quantum levels, molecular constants were determined from the Dunham fits of the e-parity levels and the Rydberg-Klein-Rees potential curves were constructed for the nd (1)Delta(g)(n = 6-8) states. The characteristics of the estimated Lambda-doubling splitting constants (q(0), q(v), and mu) with n(= 5-8) of the nd (1)Delta(g) series have been explored. Detailed investigations reveal that the nd (1)Delta(g)(n = 6-8) states involve L uncoupling from the internuclear axis and each of these states is affected by an asymmetric perturbation caused by the up and down adjacent states. The rotational-branch intensity and position anomalies in the observed spectra of the nd (1)Delta(g) series (n = 5-8) of Na(2) lead to the conclusion that due to the effects of the L-uncoupling perturbations, the same l complexes approaching the same ion-core limits result in the same l-mixing processes which lead to the formation of the supercomplexes due to the anisotropy of the molecular-ion [Na(2)(+)(3s)] field. This would open up opportunities to study the effects of L uncoupling and perturbations in the nd series and high Rydberg states of other alkali dimers. PMID:18624529

Chaudhuri, Chanchal; Chang, Ray-Yuan; Tsai, Chin-Chun; Cheng, Chuen-Ping; Whang, Thou-Jen

2008-07-14

171

Observation of Rydberg Series in Sodium Vapour by Two-Photon Resonant Nondegenerate Four-Wave Mixing  

NASA Astrophysics Data System (ADS)

We apply two-photon resonant nondegenerate four-wave mixing with a resonant intermediate state for the observation of Rydberg states in sodium vapour. The broadening and shift of the sodium 3S-11D transition perturbed by argon are investigated. This technique can achieve Doppler-free resolution of narrow spectral structures of Rydberg levels if lasers with narrow bandwidths are employed.

Wang, Yan-Bang; Jiang, Qian; Li, Long; Mi, Xin; Yu, Zu-He; Fu, Pan-Ming

2001-09-01

172

Measurement of Holmium Rydberg series through MOT depletion spectroscopy  

E-print Network

We report measurements of the absolute excitation frequencies of $^{165}$Ho $4f^{11}6sns$ and $4f^{11}6snd$ 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 $ns$ 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 $E_\\mathrm{IP}=48565.939(4)$ cm$^{-1}$, which is three orders of magnitude more accurate than previous work. This work represents the first time such spectroscopy has been done in Holmium and is an important step towards using Ho atoms for collective encoding of a quantum register.

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

2014-12-03

173

Observation of coherent wave packets in a heavy Rydberg system.  

PubMed

Coherent dynamical behavior is observed in the heavy Rydberg system H+H-. Because of the large mass, time scales of the wave-packet evolution are orders of magnitude slower than for a Rydberg electron. In the presence of a weak electric field, wave packets made up of about 1000 Stark states are excited by near-Fourier transform limited nanosecond laser pulses. Pulsed-field dissociation reveals coherent time evolution on a microsecond time scale, observed as oscillations with frequencies explained by a linear Stark model applied to the H+H- system. PMID:11800941

Reinhold, E; Ubachs, W

2002-01-01

174

Collective many-body interaction in Rydberg dressed atoms  

E-print Network

We present a method to control the shape and character of the interaction potential between cold atomic gases by weakly dressing the atomic ground state with a Rydberg level. For increasing particle densities, a crossover takes place from a two-particle interaction into a collective many-body interaction, where the dipole-dipole/van der Waals Blockade phenomenon between the Rydberg levels plays a dominant role. We study the influence of these collective interaction potential on a Bose-Einstein condensate, and present the optimal parameters for its experimental detection.

Jens Honer; Hendrik Weimer; Tilman Pfau; Hans Peter Büchler

2010-04-14

175

All-optical quantum information processing using Rydberg gates.  

PubMed

In this Letter, we propose a hybrid scheme to implement a photonic controlled-z (CZ) gate using photon storage in highly excited Rydberg states, which controls the effective photon-photon interaction using resonant microwave fields. Our scheme decouples the light propagation from the interaction and exploits the spatial properties of the dipole blockade phenomenon to realize a CZ gate with minimal loss and mode distortion. By excluding the coupling efficiency, fidelities exceeding 95% are achievable and are found to be mainly limited by motional dephasing and the finite lifetime of the Rydberg levels. PMID:24580425

Paredes-Barato, D; Adams, C S

2014-01-31

176

Quantum Spin Ice and dimer models with Rydberg atoms  

E-print Network

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.

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

2014-04-21

177

Quantum Spin-Ice and Dimer Models with Rydberg Atoms  

NASA Astrophysics Data System (ADS)

Quantum spin-ice represents a paradigmatic example of 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 laser-admixing Rydberg states to the atomic ground-states, exploiting the strong angular dependence of van der Waals interactions between Rydberg p states together with the possibility of designing steplike 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.

Glaetzle, A. W.; Dalmonte, M.; Nath, R.; Rousochatzakis, I.; Moessner, R.; Zoller, P.

2014-10-01

178

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

NASA Astrophysics Data System (ADS)

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 .

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

2014-12-01

179

Binding Potentials and Interaction Gates between Microwave-Dressed Rydberg Atoms  

NASA Astrophysics Data System (ADS)

We demonstrate finite range binding potentials between pairs of Rydberg atoms interacting with each other via attractive and repulsive van der Waals potentials and driven by a microwave field. We show that, using destructive quantum interference to cancel single-atom Rydberg excitation, the Rydberg-dimer states can be selectively and coherently populated from the two-atom ground state. This can be used to realize a two-qubit interaction gate which is not susceptible to mechanical forces between the atoms and is therefore immune to motional decoherence.

Petrosyan, David; Mølmer, Klaus

2014-09-01

180

Microwave control of Rydberg atom interactions  

NASA Astrophysics Data System (ADS)

We investigate the interaction between Rydberg atoms, whose electronic states are dressed by multiple microwave fields. Numerical calculations are used for an exact description of the microwave induced interactions, and employed to benchmark a perturbative treatment that yields simple insights into the involved mechanisms. Based on this theory, we demonstrate that microwave dressing provides a powerful approach to control dipolar as well as van der Waals interactions and even permits us to turn them off entirely. In addition, the proposed scheme also opens up possibilities for engineering dominant three-body interactions.

Sevinçli, S.; Pohl, T.

2014-12-01

181

Divalent Rydberg atoms in optical lattices: Intensity landscape and magic trapping  

NASA Astrophysics Data System (ADS)

We develop a theoretical understanding of the trapping of divalent Rydberg atoms in optical lattices. Because the size of the Rydberg electron cloud can be comparable to the scale of spatial variations of laser intensity, we pay special attention to averaging optical fields over the atomic wave functions. The optical potential is proportional to the ac Stark polarizability. We find that in the independent-particle approximation for the valence electrons, this polarizability breaks into two contributions: the singly ionized core polarizability and the contribution from the Rydberg electron. Unlike the usually employed free-electron polarizability, the Rydberg contribution depends both on the laser intensity profile and on the rotational symmetry of the total electronic wave function. We focus on the J =0 Rydberg states of Sr and evaluate the dynamic polarizabilities of the 5sns(1S0) and 5snp(3P0) Rydberg states. We specifically chose the Sr atom for its optical-lattice clock applications. We find that there are several magic wavelengths in the infrared region of the spectrum at which the differential Stark shift between the clock states [5s2(1S0) and 5s5p(3P0)] and the J =0 Rydberg states [5sns(1S0) and 5snp(3P0)] vanishes. We tabulate these wavelengths as a function of the principal quantum number n of the Rydberg electron. We find that because the contribution to the total polarizability from the Rydberg electron vanishes at short wavelengths, magic wavelengths below ˜1000 nm are "universal" as they do not depend on the principal quantum number n.

Topcu, Turker; Derevianko, Andrei

2014-02-01

182

176 / QELS'99 / THURSDAY MORNING clude using shaped Rydberg atoms astransient  

E-print Network

vibrational wave- packet, and (ii) a vibrational Schrodinger Cat state optically excited by femtosecond laser on reconstruction of elec- tronic wavepackets in Rydberg atoms are dis- cussed. *Abteilung fur Quantenphysik

Oldenburg, Amy

183

Collisional dissociative recombination in helium-hydrogen afterglow plasmas  

NASA Astrophysics Data System (ADS)

The puzzling dependence of electron-ion recombination in helium-hydrogen afterglows on neutralfootnotetextGlos'ik et al., Phys. Rev.A 79, 052707 (2009) and electronfootnotetextGougousi et al., Int. J. Mass Spec. Ion Proc. 149-150, 131 (1995) densities is shown to be compatible with the ``Collisional Dissociative Recombination'' mechanism, originally proposed by Collins,footnotetextCollins, Phys. Rev.A 140, 1850 (1965) in which three-body capture of electrons into molecular high Rydberg states of H3^+ leads to predissociation of the molecular core. While both electrons and neutrals play a role in the three-body capture, their effects on recombination do not add in a simple manner, which makes it difficult to distinguish three-body and binary dissociative recombination. Collision-induced angular momentum mixing (l-mixing), invoked in earlier models, also occurs but does not provide the rate-limiting step that controls the overall recombination rate.

Johnsen, Rainer

2012-10-01

184

Coherent Control of Population Transfer in Rydberg Atoms via Chirped Microwave Pulses Juan J. Carrera, and Shih-I Chu*,,  

E-print Network

Coherent Control of Population Transfer in Rydberg Atoms via Chirped Microwave Pulses Juan J. It is shown that the coherent control of the population transfer from the high n to the low n states can nonperturbative investigation of the coherent population transfer among the 3D high-lying Rydberg hydrogen

Chu, Shih-I

185

Polarized dressing suppression and enhancement involving Rydberg in a thermal vapor cell  

NASA Astrophysics Data System (ADS)

In this letter, we show polarized dressing suppression and enhancement of six-wave mixing involving Rydberg in a multi-Zeeman-level atomic system. By scanning the frequency detuning of the dressing field, we observe the suppression and enhancement of Rydberg six-wave mixing with different polarization of the probe field in thermal vapors. Since different polarization states of the dressing field can select different transitions among multi-Zeeman levels, the polarization dependence of Rydberg dressing is investigated for the first time. Theoretical calculations are given and are in good agreement with the experimental results.

Che, Junling; Zhang, Zhaoyang; Li, Changbiao; Tian, Yaling; Zhang, Yunzhe; Wang, Xiuxiu; Zhang, Yanpeng

2015-02-01

186

Spin exchange cross sections for collisions of metastable helium atoms with lithium atoms in the ground state  

NASA Astrophysics Data System (ADS)

The spin exchange and chemi-ionization cross sections for the metastable helium atom-lithium atom in the ground state system have been calculated. Using data on the interaction potentials obtained in this study, the spin exchange cross sections are determined for the first time for the He(23 S 1)-Li(22 S 1/2) system in the interval of collision energies from 5 × 10-3 to 16 eV.

Kartoshkin, V. A.

2007-12-01

187

Digital Quantum Simulation with Rydberg Atoms  

E-print Network

We discuss in detail the implementation of an open-system quantum simulator with Rydberg states of neutral atoms held in an optical lattice. Our scheme allows one to realize both coherent as well as dissipative dynamics of complex spin models involving many-body interactions and constraints. The central building block of the simulation scheme is constituted by a mesoscopic Rydberg gate that permits the entanglement of several atoms in an efficient, robust and quick protocol. In addition, optical pumping on ancillary atoms provides the dissipative ingredient for engineering the coupling between the system and a tailored environment. As an illustration, we discuss how the simulator enables the simulation of coherent evolution of quantum spin models such as the two-dimensional Heisenberg model and Kitaev's toric code, which involves four-body spin interactions. We moreover show that in principle also the simulation of lattice fermions can be achieved. As an example for controlled dissipative dynamics, we discuss ground state cooling of frustration-free spin Hamiltonians.

H. Weimer; M. Müller; H. P. Büchler; I. Lesanovsky

2011-04-15

188

Proposal for manipulating and detecting spin and orbital States of trapped electrons on helium using cavity quantum electrodynamics.  

PubMed

We propose a hybrid architecture in which an on-chip high finesse superconducting cavity is coupled to the lateral motion and spin state of a single electron trapped on the surface of superfluid helium. We estimate the motional coherence times to exceed 15???s, while energy will be coherently exchanged with the cavity photons in less than 10 ns for charge states and faster than 1???s for spin states, making the system attractive for quantum information processing and strong coupling cavity quantum electrodynamics experiments. The cavity is used for nondestructive readout and as a quantum bus mediating interactions between distant electrons or an electron and a superconducting qubit. PMID:20867827

Schuster, D I; Fragner, A; Dykman, M I; Lyon, S A; Schoelkopf, R J

2010-07-23

189

Proposal for manipulating and detecting spin and orbital states of trapped electrons on helium using cavity quantum electrodynamics  

E-print Network

We propose to couple an on-chip high finesse superconducting cavity to the lateral-motion and spin state of a single electron trapped on the surface of superfluid helium. We estimate the motional coherence times to exceed 15 microseconds, while energy will be coherently exchanged with the cavity photons in less than 10 nanoseconds for charge states and faster than 1 microsecond for spin states, making the system attractive for quantum information processing and cavity quantum electrodynamics experiments. Strong interaction with cavity photons will provide the means for both nondestructive readout and coupling of distant electrons.

D. I. Schuster; A. Fragner; M. I. Dykman; S. A. Lyon; R. J. Schoelkopf

2010-08-16

190

Fermionic Collective Excitations in a Lattice Gas of Rydberg Atoms  

SciTech Connect

We investigate the many-body quantum states of a laser-driven gas of Rydberg atoms confined to a large spacing ring lattice. If the laser driving is much stronger than the van der Waals interaction among the Rydberg atoms, these many-body states are collective fermionic excitations. The first excited state is a spin wave that extends over the entire lattice. We demonstrate that our system permits us to study fermions in the presence of disorder although no external atomic motion takes place. We analyze how this disorder influences the excitation properties of the fermionic states. Our work shows a route towards the creation of complex many-particle states with atoms in lattices.

Olmos, B. [Instituto 'Carlos I' de Fisica Teorica y Computacional and Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain); Midlands Ultracold Atom Research Centre-MUARC, The University of Nottingham, School of Physics and Astronomy, Nottingham (United Kingdom); Gonzalez-Ferez, R. [Instituto 'Carlos I' de Fisica Teorica y Computacional and Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain); Lesanovsky, I. [Midlands Ultracold Atom Research Centre-MUARC, The University of Nottingham, School of Physics and Astronomy, Nottingham (United Kingdom)

2009-10-30

191

Direct observation of Rydberg-Rydberg transitions via CPmmW spectroscopy  

E-print Network

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 ...

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

2014-01-01

192

High Angular Momentum Rydberg Wave Packets  

NASA Astrophysics Data System (ADS)

High angular momentum Rydberg wave packets are studied. Application of carefully tailored electric fields to low angular momentum, high- n (n ˜ 300) Rydberg atoms creates coherent superpositions of Stark states with near extreme values of angular momentum, ?. Wave packet components orbit the parent nucleus at rates that depend on their energy, leading to periods of localization and delocalization as the components come into and go out of phase with each other. Monitoring survival probability signals in the presence of position dependent probing leads to observation of characteristic oscillations based on the composition of the wave packet. The discrete nature of electron energy levels is observed through the measurement of quantum revivals in the wave packet localization signal. Time-domain spectroscopy of these signals allows determination of both the population and phase of individual superposition components. Precise manipulation of wave packets is achieved through further application of pulsed electric fields. Decoherence effects due to background gas collisions and electrical noise are also detailed. Quantized classical trajectory Monte-Carlo simulations are introduced and agree remarkably well with experimental results.

Wyker, Brendan

2011-12-01

193

Universal nonequilibrium properties of dissipative Rydberg gases.  

PubMed

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 Z_{2} 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

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

2014-11-21

194

Universal Nonequilibrium Properties of Dissipative Rydberg Gases  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

195

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

E-print Network

calculations by Drake [17] for helium and by Zhang et al. [12] for helium-like ions. 2. The spin-dependent m71 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

Pachucki, Krzysztof

196

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

NASA Astrophysics Data System (ADS)

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.

Vermersch, B.; Punk, M.; Glaetzle, A. W.; Gross, C.; Zoller, P.

2015-01-01

197

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

E-print Network

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.

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

2012-03-16

198

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

E-print Network

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.

Vaillant, C L; Potvliege, R M

2012-01-01

199

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

NASA Astrophysics Data System (ADS)

Metastable pionic helium (?He+) is a three-body atom composed of a helium nucleus, an electron occupying the 1s ground state, and a negatively charged pion ?- in a Rydberg state with principal and orbital angular momentum quantum numbers of n ˜?+1˜16. We calculate the spin-independent energies of the ?3He+ and ?4He+ isotopes in the region n =15-19. These include relativistic and quantum electrodynamics corrections of orders R??2 and R??3 in atomic units, where R? and ? 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 ?- and the radiative and Auger decay rates of the states are also calculated. Some states (n,?)=(16,15) and (17,16) retain nanosecond-scale lifetimes against ?- absorption into the helium nucleus. We propose the use of laser pulses to induce ?- transitions from these metastable states to states with large (˜1011 s-1) Auger rates. The ?He2+ ion that remains after Auger emission of the 1s electron undergoes Stark mixing with the s, p, and d states during collisions with the helium atoms in the experimental target. This leads to immediate nuclear absorption of the ? -. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge. A resonance curve is obtained from which the ?He+ transition frequency can in principle be determined with a fractional precision of 10-8-10-6 provided the systematic uncertainties can be controlled. By comparing the measured ?He+ frequencies with the calculated values, the ?- mass may be determined with a similar precision. The ?He+ will be synthesized by allowing a high-intensity (>108 s-1) beam of ?-produced by a cyclotron to come to rest in a helium target. The precise time structure of the ?- beam is used to ensure a sufficient rate of coincidence between the resonant laser pulses and the ?He+ atoms.

Hori, Masaki; Sótér, Anna; Korobov, Vladimir I.

2014-04-01

200

Classical limit states of the helium atom J. A. West,1,2  

E-print Network

and intuitive appeal of Bohr's atomic model have given the classical hydrogen atom an important and pervasive role in atomic physics. Even today, the Bohr model remains as a cornerstone underlying quan- tum for the simplest such atom, helium, this extension is nontrivial because the old quantum theory of Bohr was never

Stroud, Carlos R.

201

Study on Off-Design Steady State Performances of Helium Gas Turbo-compressor for HTGR-GT  

SciTech Connect

The high temperature gas-cooled reactor (HTGR) coupled with direct gas turbine cycle is a promising concept in the future of nuclear power development. Both helium gas turbine and compressor are key components in the cycle. Under normal conditions, the mode of power adjustment is to control total helium mass in the primary loop using gas storage vessels. Meanwhile, thermal power of reactor core is regulated. This article analyzes off-design performances of helium gas turbine and compressors for high temperature gas-cooled reactor with gas turbine cycle (HTGR-GT) at steady state level of electric power adjustment. Moreover, performances of the cycle were simply discussed. Results show that the expansion ratio of turbine decreases as electric power reduces but the compression ratios of compressors increase, efficiencies of both turbine and compressors decrease to some extent. Thermal power does not vary consistently with electric power, the difference between these two powers increases as electric power reduces. As a result of much thermal energy dissipated in the temperature modulator set at core inlet, thermal efficiency of the cycle has a widely reduction under partial load conditions. (authors)

Qisen Ren; Xiaoyong Yang; Zhiyong Huang; Jie Wang [Tsinghua University, Beijing, 100084 (China)

2006-07-01

202

Controlling the interactions of a few cold Rb Rydberg atoms by radiofrequency-assisted Förster resonances  

E-print Network

Long-range interactions between cold Rydberg atoms, which are used in many important applications, can be enhanced using F\\"orster resonances between collective many-body states controlled by an external electric field. Here we report on the first experimental observation of highly-resolved radio-frequency-assisted F\\"orster resonances in a few cold Rb Rydberg atoms. We also observed radio-frequency-induced F\\"orster resonances which cannot be tuned by a dc electric field. They imply an efficient transition from van der Waals to resonant dipole-dipole interaction due to Floquet sidebands of Rydberg levels appearing in the rf-field. This method can be applied to enhance the interactions of almost arbitrary Rydberg atoms with large principal quantum numbers.

D. B. Tretyakov; V. M. Entin; E. A. Yakshina; I. I. Beterov; C. Andreeva; I. I. Ryabtsev

2014-12-04

203

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

204

Experimental Determination of the Lifetime for the 2p3d(1P0) Helium Doubly Excited State  

NASA Astrophysics Data System (ADS)

Two recent theoretical studies [

C. Liu et al., Phys. Rev. APLRAAN1050-2947 64, 010501 (2001)
;
M. Žitnik et al., ibid. 65, 032520 (2002)
] predict that the fluorescence lifetimes of helium doubly excited states converging to He+ N=2 should be longer than that of the He+ 2p ion state. This effect is caused by the electric field of the outer electron which, through Stark mixing, gives the inner fluorescing electron some series specific, stabilizing 2s character. We have obtained the first experimental evidence that confirms this effect by measuring the lifetime of the 2p3d(1P0) doubly excited state. This was determined to be 190±30 ps compared to 100 ps for the He+ 2p ion state. The measurements were performed using short pulses of synchrotron radiation to form doubly excited states and recording the arrival time of photons from fluorescence.

Lambourne, J. G.; Penent, F.; Lablanquie, P.; Hall, R. I.; Ahmad, M.; Žitnik, M.; Bu?ar, K.; Odling-Smee, M. K.; Harries, J. R.; Hammond, P.; Waterhouse, D. K.; Stranges, S.; Richter, R.; Alagia, M.; Coreno, M.; Ferianis, M.

2003-04-01

205

Pipkin Award Talk: Rydberg Charge Exchange: A Method for Producing Rydberg Positronium and Antihydrogen Atoms  

NASA Astrophysics Data System (ADS)

Antihydrogen production via two-stage charge exchange(E.A.Hessels, D.M. Homan and M.J. Cavagnero, Phys. Rev. A. 57), (1998) 1668. may provide extremely cold antimatter atoms that can be trapped for spectroscopic studies. Positrons(J. Estrada, T. Roach, J.N. Tan, P. Yesley, and G. Gabrielse, Phys. Rev. Lett. 84), (2000) 859. and antiprotons(G. Gabrielse, N. S. Bowden, P. Oxley, A. Speck, C. H. Storry, J. N. Tan, M. Wessels, D. Grozonka, W. Oelert, G. Schepers, T. Sefzick, J. Walz, H. Pittner, T. W. Hansch, E. A. Hessels, Phys. Lett. B 548), (2002) 140-145., both cooled to 4 K and loaded into adjacent wells of a Penning trap, provide the basic components. Laser-excited Rydberg cesium atoms are passed through the cloud of trapped positrons and charge exchange with the positrons to form Rydberg states of positronium. These positronium atoms have been observed and are studied by ionizing them and counting the resulting positrons. State analysis of the positronium is obtained by varying the electric field used to ionize the atoms. Large numbers of positronium atoms are produced and their binding energies are found to be similar to that of the incoming Rydberg cesium atoms. A second charge exchange is proposed, in which the neutral positronium travels a short distance to an adjacent antiproton cloud. The result of this second charge exchange would be antihydrogen atoms. The apparatus to test this second charge exchange has already been constructed and preliminary studies have already been made.

Hessels, E. A.

2003-05-01

206

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

207

Analytical solutions for diatomic Rydberg quasimolecules in a laser field  

NASA Astrophysics Data System (ADS)

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.

Kryukov, Nikolay; Oks, Eugene

2014-06-01

208

Radioprotection in depressed metabolic states: The physiology of helium-cold hypothermia  

NASA Technical Reports Server (NTRS)

The use of hypothermia as a means of radiation protection was studied on a variety of mammals exposed to 80% helium-20% oxygen atmospheres at low ambient temperatures. Results show that the LD for normothermic animals significantly increased compared with hypothermic animals; similar results were obtained for hibernating mammalians. Pre-exposure of animals to cold temperatures increased their ability to withstand radiation levels close to LD sub 50.

Musacchia, X. J.

1973-01-01

209

Robust quantum logic in neutral atoms via adiabatic Rydberg dressing  

NASA Astrophysics Data System (ADS)

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 ?+/?- 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 133Cs, we predict that our protocol could produce a cz gate in <10 ? s with error probability on the order of 10-3.

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

2015-01-01

210

Investigation of dephasing rates in an interacting Rydberg gas  

NASA Astrophysics Data System (ADS)

We experimentally and theoretically investigate the dephasing rates of the coherent evolution of a resonantly driven pseudo spin emersed in a reservoir of pseudo spins. The pseudo spin is realized by optically exciting 87Rb atoms into a Rydberg state. Hence, the upper spin states are coupled via the strong van der Waals interaction. Two different experimental techniques to measure the dephasing rates are shown: the 'rotary echo' technique, known from nuclear magnetic resonance physics, and electromagnetically induced transparency. The experiments are performed in a dense frozen Rydberg gas, either confined in a magnetic trap or in an optical dipole trap. Additionally, a numerical simulation is used to analyse the dephasing in the rotary echo experiments.

Raitzsch, U.; Heidemann, R.; Weimer, H.; Butscher, B.; Kollmann, P.; Löw, R.; Büchler, H. P.; Pfau, T.

2009-05-01

211

Entropy and complexity analysis of hydrogenic Rydberg atoms  

SciTech Connect

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

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

2013-05-15

212

Investigation of dephasing rates in an interacting Rydberg gas  

E-print Network

We experimentally and theoretically investigate the dephasing rates of the coherent evolution of a resonantly driven pseudo spin emersed in a reservoir of pseudo spins. The pseudo spin is realized by optically exciting 87 Rb atoms to a Rydberg state. Hence, the upper spin states are coupled via the strong van der Waals interaction. Two different experimental techniques to measure the dephasing rates are shown: the 'rotary echo' technique known from nuclear magnetic resonance physics and electromagnetically induced transparency. The experiments are performed in a dense frozen Rydberg gas, either confined in a magnetic trap or in an optical dipole trap. Additionally, a numerical simulation is used to analyse the dephasing in the rotary echo experiments.

U. Raitzsch; R. Heidemann; H. Weimer; V. Bendkowsky; B. Butscher; P. Kollmann; R. Löw; H. P. Büchler; T. Pfau

2008-11-25

213

Deterministic entanglement of two neutral atoms via Rydberg blockade  

SciTech Connect

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.

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

214

Spectral backbone of excitation transport in ultracold Rydberg gases  

NASA Astrophysics Data System (ADS)

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.

Scholak, Torsten; Wellens, Thomas; Buchleitner, Andreas

2014-12-01

215

Experimental characterization of singlet scattering channels in long-range Rydberg molecules  

E-print Network

We observe the formation of long-range Cs$_2$ Rydberg molecules consisting of a Rydberg and a ground-state atom by photoassociation spectroscopy in an ultracold Cs Rydberg gas near 6s$_{1/2}$($F$=3,4)$\\rightarrow$$n$p$_{3/2}$ resonances ($n$=26-34). The spectra reveal two types of molecular states recently predicted by D. A. Anderson, S. A. Miller, and G. Raithel [arXiv:1409.2543 (2014)]: Pure triplet ($^3\\Sigma$) states with binding energies ranging from 400 MHz at $n$=26 to 80 MHz at $n$=34, and states of mixed singlet and triplet ($^{1,3}\\Sigma$) character with smaller and $F$-dependent binding energies. The experimental observations are accounted for by an effective Hamiltonian including Fermi-contact $s$-wave scattering pseudopotentials, the hyperfine interaction of the ground-state atom, and the spin-orbit interaction of the Rydberg atom. The analysis enabled 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.

Heiner Saßmannshausen; Frédéric Merkt; Johannes Deiglmayr

2014-12-02

216

Collective Excitation of Rydberg-Atom Ensembles beyond the Superatom Model  

NASA Astrophysics Data System (ADS)

In an ensemble of laser-driven atoms involving strongly interacting Rydberg states, the steady-state excitation probability is usually substantially suppressed. In contrast, here we identify a regime in which the Rydberg excited fraction is enhanced by the interaction. This effect is associated with the buildup of many-body coherences induced by coherent multiphoton excitations between collective states. The excitation enhancement should be observable under currently existing experimental conditions and may serve as a direct probe for the presence of coherent multiphoton dynamics involving collective quantum states.

Gärttner, Martin; Whitlock, Shannon; Schönleber, David W.; Evers, Jörg

2014-12-01

217

Collective Excitation of Rydberg-Atom Ensembles beyond the Superatom Model.  

PubMed

In an ensemble of laser-driven atoms involving strongly interacting Rydberg states, the steady-state excitation probability is usually substantially suppressed. In contrast, here we identify a regime in which the Rydberg excited fraction is enhanced by the interaction. This effect is associated with the buildup of many-body coherences induced by coherent multiphoton excitations between collective states. The excitation enhancement should be observable under currently existing experimental conditions and may serve as a direct probe for the presence of coherent multiphoton dynamics involving collective quantum states. PMID:25526126

Gärttner, Martin; Whitlock, Shannon; Schönleber, David W; Evers, Jörg

2014-12-01

218

Origin of Hund's multiplicity rule in singly excited helium: Existence of a conjugate Fermi hole in the lower spin state  

SciTech Connect

The origin of Hund's multiplicity rule in the low-lying excited states of the helium atom has been studied by considering the two-dimensional helium atom. The internal part of the full configuration interaction wave functions for the (2s) and (2p) singlet-triplet pairs of states has been extracted and visualized in the three-dimensional internal space (r{sub 1},r{sub 2}, {phi}{sub -}). The internal wave function of the singlet states without electron repulsion has a significant probability around the origin of the internal space while the corresponding probability of the triplet wave function is negligible in this region due to the presence of a Fermi hole. The electron-electron repulsion potential has been visualized also in the internal space. It manifests itself by three striking poles penetrating exactly into the spatial region defined by the Fermi hole. Because of the existence of these strong potential poles in the vicinity of the Fermi hole a major part of the singlet probability migrates out of this region. In contrast, the corresponding triplet wave function is less affected by these poles due to the presence of the Fermi hole. The singlet probability is shown to migrate from its original region close to the origin to a region far away where either r{sub 1} or r{sub 2} are large. This results in a more diffuse electron density distribution and a smaller electron repulsion energy of the singlet state than of the corresponding triplet state. The mechanism of the evolution of the singlet probability toward the region of large r{sub i} (i =1, 2) in the presence of the electron repulsion potential has been rationalized on the basis of a new concept called conjugate Fermi hole.

Sako, Tokuei; Paldus, Josef; Ichimura, Atsushi; Diercksen, Geerd H. F. [Laboratory of Physics, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, 274-8501 Chiba (Japan); Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Institute of Space and Astronautical Science, JAXA, Sagamihara 229-8510 (Japan); Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Strasse 1, D-85741 Garching (Germany)

2011-03-15

219

PHYSICAL REVIEW A 86, 053401 (2012) Electric-field sensing near the surface microstructure of an atom chip using cold Rydberg atoms  

E-print Network

of an atom chip using cold Rydberg atoms J. D. Carter, O. Cherry, and J. D. D. Martin Department of Physics fields near the heterogeneous metal-dielectric surface of an atom chip were measured using cold atoms. The atomic sensitivity to electric fields was enhanced by exciting the atoms to Rydberg states that are 108

Le Roy, Robert J.

220

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

SciTech Connect

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.

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

221

Two-Stage Melting in Systems of Strongly Interacting Rydberg Atoms  

SciTech Connect

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.

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

2010-12-03

222

Two-Stage Melting in Systems of Strongly Interacting Rydberg Atoms  

E-print Network

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.

Hendrik Weimer; Hans Peter Büchler

2010-07-13

223

Angular-momentum couplings in long-range Rb$_2$ Rydberg molecules  

E-print Network

We study angular-momentum couplings in $^{87}$Rb$_2$ Rydberg molecules formed between Rydberg and 5S$_{1/2}$ ground-state atoms. We use a Fermi model that includes S-wave and P-wave singlet and triplet scattering of the Rydberg electron with the 5S$_{1/2}$ atom, along with the fine structure coupling of the Rydberg atom and hyperfine structure coupling of the 5S$_{1/2}$ atom. We discuss the effects of these couplings on the adiabatic molecular potentials. We obtain bound-state energies, lifetimes, and electric and magnetic dipole moments for the vibrational ground states of the $^{87}$Rb$(n$D$+5$S$_{1/2})$ molecules in all adiabatic potentials, with fine and hyperfine structure included. We also study the effect of the hyperfine structure on the deep $^3$S-wave- and $^3$P-wave-dominated adiabatic molecular potentials, which support high-$\\ell$ $^{87}$Rb$_2$ Rydberg molecules.

Anderson, David A; Raithel, Georg

2014-01-01

224

Angular-momentum couplings in long-range Rb2 Rydberg molecules  

NASA Astrophysics Data System (ADS)

We study angular-momentum couplings in 87Rb2 Rydberg molecules formed between a Rydberg and 5 S1 /2 ground-state atom. We use a Fermi model that includes S -wave and P -wave singlet and triplet scattering of the Rydberg electron with the 5 S1 /2 atom, along with the fine-structure coupling of the Rydberg atom and hyperfine-structure coupling of the 5 S1 /2 atom. We discuss the effects of these couplings on the adiabatic molecular potentials. We obtain bound-state energies, lifetimes, and electric and magnetic dipole moments for the vibrational ground states of the 87Rb(n D +5 S1 /2) molecules in all adiabatic potentials, with fine and hyperfine structure included. The hyperfine structure gives rise to mixed singlet-triplet potentials. We also study the effect of the hyperfine structure on the deep 3S -wave- and 3P -wave-dominated adiabatic molecular potentials, which support high-? 87Rb2 Rydberg molecules.

Anderson, D. A.; Miller, S. A.; Raithel, G.

2014-12-01

225

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

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

226

Photoabsorption profile and satellite features of the potassium 4s?4p transition perturbed by ground-state helium atoms  

NASA Astrophysics Data System (ADS)

Quantal calculations are performed to determine the absorption profile of the broadened potassium resonance line 4p?4s in its far wings provoked by helium perturbers. First, the X2?+, A2?, and B2?+ potentials, as well as the transition dipole moments, are carefully computed through ab initio methods, based on state-averaged complete active space self-consistent field multireference configuration interaction (SA-CASSCF-MRCI) calculations involving the Davidson and basis-set superposition error (BSSE) corrections. The data are then used to generate the KHe photoabsorption spectra and to examine their behavior with temperature. The theoretical profile is dominated by the free-free transitions and exhibits, in the vicinity of the wavelength position of 693 nm, a satellite peak in the blue wing attributed to the B?X transitions. The results are compared with previous theoretical and experimental investigations and, in general, good agreement is found.

Boutarfa, H.; Alioua, K.; Bouledroua, M.; Allouche, A.-R.; Aubert-Frécon, M.

2012-11-01

227

Anisotropic emission of neutral atoms: evidence of an anisotropic Rydberg sheath in nanoplasma  

NASA Astrophysics Data System (ADS)

Intense laser-produced plasma is a complex amalgam of ions, electrons and atoms both in ground and excited states. Little is known about the spatial composition of the excited states that are an integral part of most gaseous or cluster plasma. In cluster-plasma, Rydberg excitations change the charge composition of the ions through charge transfer reactions and shape the angular distributions. Here, we demonstrate a non-invasive technique that reveals the anisotropic Rydberg excited cluster sheath by measuring anisotropy in fast neutral atoms. The sheath is stronger in the direction of light polarization and the enhanced charge transfer by the excited clusters results in larger neutralization.

Rajeev, R.; Madhu Trivikram, T.; Rishad, K. P. M.; Krishnamurthy, M.

2015-02-01

228

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

229

The Spectral Backbone of Excitation Transport in Ultra-Cold Rydberg Gases  

E-print Network

The spectral structure underlying excitonic energy transfer in ultra-cold 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 den...

Scholak, Torsten; Buchleitner, Andreas

2014-01-01

230

Fractional quantum Hall physics with ultracold Rydberg gases in artificial gauge fields  

NASA Astrophysics Data System (ADS)

We study ultracold Rydberg-dressed Bose gases subject to artificial gauge fields in the fractional quantum Hall (FQH) regime. The characteristics of the Rydberg interaction give rise to interesting many-body ground states different from standard FQH physics in the lowest Landau level. The nonlocal but rapidly decreasing interaction potential favors crystalline ground states for very dilute systems. While a simple Wigner crystal becomes energetically favorable compared to the Laughlin liquid for filling fractions ?<1/12, a correlated crystal of composite particles emerges already for ??1/6 with a large energy gap to the simple Wigner crystal. The presence of a new length scale, the Rydberg blockade radius aB, gives rise to a bubble crystal phase for ??1/4 when the average particle distance becomes less than aB, which describes the region of saturated, almost constant interaction potential. For larger fillings indications for strongly correlated cluster liquids are found.

Grusdt, F.; Fleischhauer, M.

2013-04-01

231

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

NASA Technical Reports Server (NTRS)

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.

Sutton, J. F.

1972-01-01

232

Power law decay and phase rigidity for large-amplitude coherent phonons in bismuth at helium temperature: Possible evidence for transient supersolid state  

E-print Network

Intense ultrafast laser excitation can produce transient states of condensed matter that would otherwise be inaccessible. At high excitation level, the interatomic forces can be altered resulting in an unusual lattice dynamics. Here we report the study of coherent lattice dynamics in Bi made for various excitation levels at helium temperature. We demonstrate that under certain conditions the fully symmetric phonons of large amplitude exhibit anomalous decay and phase rigidity, both of which possibly signaling the attainment of transient supersolid state.

O. V. Misochko; M. V. Lebedev

2011-03-17

233

Power law decay and phase rigidity for large-amplitude coherent phonons in bismuth at helium temperature: Possible evidence for transient supersolid state  

E-print Network

Intense ultrafast laser excitation can produce transient states of condensed matter that would otherwise be inaccessible. At high excitation level, the interatomic forces can be altered resulting in an unusual lattice dynamics. Here we report the study of coherent lattice dynamics in Bi made for various excitation levels at helium temperature. We demonstrate that under certain conditions the fully symmetric phonons of large amplitude exhibit anomalous decay and phase rigidity, both of which possibly signaling the attainment of transient supersolid state.

Misochko, O V

2011-01-01

234

Semi-analytical model for nonlinear light propagation in strongly interacting Rydberg gases  

E-print Network

Rate equation models are extensively used to describe the many-body states of laser driven atomic gases. We show that the properties of the rate equation model used to describe nonlinear optical effects arising in interacting Rydberg gases can be understood by considering the excitation of individual super-atoms. From this we deduce a simple semi-analytic model that accurately describes the Rydberg density and optical susceptibility for different dimensionalities. We identify the previously reported universal dependence of the susceptibility on the Rydberg excited fraction as an intrinsic property of the rate equation model that is rooted in one-body properties. Benchmarking against exact master equation calculations, we identify regimes in which the semi-analytic model is particularly reliable. The performance of the model improves in the presence of dephasing which destroys higher order atomic coherences.

M. Gärttner; S. Whitlock; D. W. Schönleber; J. Evers

2014-02-19

235

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

236

Rydberg-induced solitons: three-dimensional self-trapping of matter waves.  

PubMed

We propose a scheme for the creation of stable three-dimensional bright solitons in Bose-Einstein condensates, i.e., the matter-wave analog of so-called spatiotemporal "light bullets." Off-resonant dressing to Rydberg nD states is shown to provide nonlocal attractive interactions, leading to self-trapping of mesoscopic atomic clouds by a collective excitation of a Rydberg atom pair. We present detailed potential calculations and demonstrate the existence of stable solitons under realistic experimental conditions by means of numerical simulations. PMID:21635018

Maucher, F; Henkel, N; Saffman, M; Królikowski, W; Skupin, S; Pohl, T

2011-04-29

237

Rydberg-Induced Solitons: Three-Dimensional Self-Trapping of Matter Waves  

SciTech Connect

We propose a scheme for the creation of stable three-dimensional bright solitons in Bose-Einstein condensates, i.e., the matter-wave analog of so-called spatiotemporal ''light bullets.'' Off-resonant dressing to Rydberg nD states is shown to provide nonlocal attractive interactions, leading to self-trapping of mesoscopic atomic clouds by a collective excitation of a Rydberg atom pair. We present detailed potential calculations and demonstrate the existence of stable solitons under realistic experimental conditions by means of numerical simulations.

Maucher, F.; Henkel, N.; Pohl, T. [Max Planck Institute for the Physics of Complex Systems, 01187 Dresden (Germany); Saffman, M. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Krolikowski, W. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Skupin, S. [Max Planck Institute for the Physics of Complex Systems, 01187 Dresden (Germany); Friedrich Schiller University, Institute of Condensed Matter Theory and Optics, 07743 Jena (Germany)

2011-04-29

238

Polarization dependence and interference in four-wave mixing with Rydberg levels in rubidium vapor  

NASA Astrophysics Data System (ADS)

We have observed an interference in four-wave mixing involving two Rydberg states that play the key role of near two-photon resonant intermediate levels. This interference, due to the coherence of the nonlinear process, can be explained either classically or quantum mechanically and it depends on the lasers' polarizations and detunings. We have performed calculations that are in very good agreement with the experimental data. Our results provide new information about the system, such as ionization rates of the Rydberg levels and the ratio of reduced matrix elements involved.

Vianna, S. S.; Nussenzveig, P.; Magno, W. C.; Tabosa, J. W.

1998-10-01

239

Atom-based vector microwave electrometry using rubidium Rydberg atoms in a vapor cell.  

PubMed

It is clearly important to pursue atomic standards for quantities like electromagnetic fields, time, length, and gravity. We have recently shown using Rydberg states that Rb atoms in a vapor cell can serve as a practical, compact standard for microwave electric field strength. Here we demonstrate for the first time that Rb atoms excited in a vapor cell can also be used for vector microwave electrometry by using Rydberg-atom electromagnetically induced transparency. We describe the measurements necessary to obtain an arbitrary microwave electric field polarization at a resolution of 0.5°. We compare the experiments to theory and find them to be in excellent agreement. PMID:23971570

Sedlacek, J A; Schwettmann, A; Kübler, H; Shaffer, J P

2013-08-01

240

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

E-print Network

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.

J. C. Pei; F. R. Xu

2007-02-01

241

Effect of dispersion forces on squeezing with Rydberg atoms  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

242

The kicked Rydberg atom: Regular and stochastic motion  

SciTech Connect

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.

Burgdoerfer, J.

1988-01-01

243

Ground-state properties of hcp helium-4 on the basis of a cell model  

NASA Technical Reports Server (NTRS)

A simple cell model is used to compute the ground-state energy and the volume-pressure relation for hcp He-4, in good agreement with experiments and with more sophisticated quantum mechanical calculations.

Jacobi, N.; Zmuidzinas, J. S.

1977-01-01

244

Enhanced production of excited neutrals following core-to-Rydberg excitation in molecules: SiCl4  

NASA Astrophysics Data System (ADS)

Using monochromatized synchrotron radiation in the range 103 to 112 eV we have monitored the dispersed UV/optical fluorescence resulting from excitation of a Si 2p electron in SiCl4. The main features in the fluorescence spectrum have been identified as emission from the SiCl4+ C state and from excited Si atoms. Features in the fluorescence excitation spectra are assigned to excitation of a Si 2p electron to unoccupied valence and Rydberg orbitals. For the SiCl4+ C state emission there is significant enhancement in the yield following excitation to valence orbitals and very little enhancement as a result of Rydberg excitation. The opposite is true for emission from excited Si atoms. Enhancement in the SiCl4+ C state production upon valence excitation results from autoionization of the core-excited state. The relatively large yield of excited Si atoms following Rydberg excitation is due to the greater probability of the core-excited Rydberg state decaying, via a resonant Auger process, to highly excited, unbound states of SiCl4+. The molecular ion then fragments before the excited Rydberg electron can relax.

Rosenberg, R. A.; Wen, C.-R.; Tan, K.; Chen, J.-M.

1990-04-01

245

Multichannel Quantum Defect Theory of Strontium Rydberg Series  

E-print Network

Using the reactance matrix approach, we systematically develop new multichannel quantum defect theory models for the singlet and triplet S, P, D and F states of strontium based on improved energy level measurements. The new models reveal additional insights into the character of doubly excited perturber states, and the improved energy level measurements for certain series allow fine structure to be resolved for those series' perturbers. Comparison between the predictions of the new models and those of previous empirical and \\emph{ab initio} studies reveals good agreement with most series, however some discrepancies are highlighted. Using the multichannel quantum defect theory wave functions derived from our models we calculate other observables such as Land\\'e $g_J$-factors and radiative lifetimes. The analysis reveals the impact of perturbers on the Rydberg state properties of divalent atoms, highlighting the importance of including two-electron effects in the calculations of these properties. The work enables future investigations of properties such as Stark maps and long-range interactions of Rydberg states of strontium.

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

2014-02-24

246

Atom-molecule coherence and Ramsey interferometry in ultracold Rydberg gases  

NASA Astrophysics Data System (ADS)

Ultralong-range Rydberg molecules are bound states of a Rydberg atom with ground state atoms [1]. We report on experiments studying the coherence properties of this new class of molecular bond. We demonstrate the coherent transfer of initially free pairs of rubidium ground-state atoms to ultralong-range Rydberg molecules using rotary echo and Ramsey-pulse sequences. The coherent evolution of the molecular system is characterized by measuring the timescales for the energy-conserving dephasing rate, T2, and for non-energy-conserving decay processes, T1 [2]. Furthermore, these Ramsey experiments can be viewed as an atom-molecule interferometer where the unbound ground state atoms and the ultalong-range Ryberg molecules form two branches. The relative phase in the arms of such an interferometer can be precisely controlled and varied over a wide range using additional electric field pulses. Besides this proof of principle, this technique provides a phase sensitive tool to measure interactions between Rydberg atoms or molecules. [4pt] [1] V. Bendkowsky et al., Nature 458, 1005 (2009) [0pt] [2] B. Butscher et al., Nature Physics, nphys1828 (2010)

Loew, Robert; Balewski, Jonathan; Nipper, Johannes; Butscher, Bjoern; Pfau, Tilman

2011-06-01

247

E1 transitions between states with n = 1 to 6 in helium-like carbon, nitrogen, oxygen, neon, silicon, and argon  

E-print Network

Wavelengths and transition rates are given for E1 transitions between singlet S, P, D, and F states, between triplet S, P, and D states, and between triplet P and singlet S states in ions of astrophysical interest: helium-like carbon, nitrogen, oxygen, neon, silicon, and argon. All possible E1 transitions between states with J < 4 and n < 7 are considered. Energy levels and wave functions used in calculations of the transition rates are obtained from relativistic configuration-interaction calculations that include both Coulomb and Breit interactions.

W. R. Johnson; I. M. Savukov; U. I. Safronova; A. Dalgarno

2002-02-13

248

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

PubMed

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

Gim, Yeongrok; Lee, Chun-Woo

2014-10-14

249

Heteronuclear rare-gas dimer bonding: Understanding the nature of the Rydberg states that dissociate to the highest energy level of the Xe*(5d) manifold  

NASA Astrophysics Data System (ADS)

(1+1') resonance enhanced multiphoton ionization (REMPI) spectra of jet-cooled KrXe and ArXe in the vicinity of the high energy Xe*5d[3/2]10?Xe(1S0) atomic line at 83889.99 cm-1 were obtained by exciting the neutral dimers with tunable coherent vacuum ultraviolet (VUV) radiation generated by four-wave sum mixing in mercury vapor, and then detecting the resultant ions in a time-of-flight (TOF) mass spectrometer. Precise excited state constants were derived from analyses of the resultant vibrational fine structure, while equilibrium bond lengths were estimated from Franck-Condon factor intensity simulations. Excited state symmetries were deduced from separate ultraviolet (UV) (2+1) REMPI spectra recorded with linearly and circularly polarized light. The results of this work confirm a recent model proposed by Lipson and Field, where the RgXe*(5d) states are predicted to be strongly destabilized relative to RgXe*(6p) due to strong 5d-6p Xe* l-mixing induced by the ground state Rg atom partner making up the dimer. Orbital mixing is also responsible for the observation of appreciably strong RgXe*(5d) spectra in both one- and two-photon excitation.

Mao, D. M.; Hu, X. K.; Shi, Y. J.; Lipson, R. H.

1999-08-01

250

Theoretical energies for the n = 1 and 2 states of the helium isoelectronic sequence up to Z = 100  

NASA Astrophysics Data System (ADS)

The unified method described previously for combining high-precision nonrelativistic variational calculations with relativistic and quantum electrodynamic corrections is applied to the 1s2 1S0, 1s2s 1S0, 1s2s 1S0, 1s2s 3S1, 1s2p 1P1, and 1s2p 3P(0.1,2) states of helium-like ions. Detailed tabulations are presented for all ions in the range Z = 2-100 and are compared with a wide range of experimental data up to (Kr-34)+. The results for (U-90)+ significantly alter the recent Lamb shift measurement of Munger and Gould (1986) from 70.4 + or - 8.3 to 71.0 + or - 8.3 eV, in comparison with a revised theoretical value of 74.3 + or - 0.4 eV. The improved agreement is due to the inclusion of higher order two-electron corrections in the present work.

Drake, G. W.

1988-07-01

251

Theoretical energies for the n = 1 and 2 states of the helium isoelectronic sequence up to Z = 100  

NASA Technical Reports Server (NTRS)

The unified method described previously for combining high-precision nonrelativistic variational calculations with relativistic and quantum electrodynamic corrections is applied to the 1s2 1S0, 1s2s 1S0, 1s2s 1S0, 1s2s 3S1, 1s2p 1P1, and 1s2p 3P(0.1,2) states of helium-like ions. Detailed tabulations are presented for all ions in the range Z = 2-100 and are compared with a wide range of experimental data up to (Kr-34)+. The results for (U-90)+ significantly alter the recent Lamb shift measurement of Munger and Gould (1986) from 70.4 + or - 8.3 to 71.0 + or - 8.3 eV, in comparison with a revised theoretical value of 74.3 + or - 0.4 eV. The improved agreement is due to the inclusion of higher order two-electron corrections in the present work.

Drake, G. W.

1988-01-01

252

Dipole-dipole interaction between rubidium Rydberg atoms  

SciTech Connect

Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (Foerster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that interact. Dipole-dipole interaction spectra are presented for initially excited rubidium nd states for n=31 to 46 and for four different pairs of initially excited rubidium ns states. We also present the dipole-dipole interaction spectra for individual rubidium 32d (j, m{sub j}) fine structure levels that have been selectively excited. The data are compared to calculated spectra.

Altiere, Emily; Fahey, Donald P.; Noel, Michael W. [Physics Department, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010 (United States); Smith, Rachel J.; Carroll, Thomas J. [Department of Physics and Astronomy, Ursinus College, Collegeville, Pennsylvania 19426 (United States)

2011-11-15

253

Dipole-dipole interaction between rubidium Rydberg atoms  

NASA Astrophysics Data System (ADS)

Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (Förster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that interact. Dipole-dipole interaction spectra are presented for initially excited rubidium nd states for n=31 to 46 and for four different pairs of initially excited rubidium ns states. We also present the dipole-dipole interaction spectra for individual rubidium 32d (j,mj) fine structure levels that have been selectively excited. The data are compared to calculated spectra.

Altiere, Emily; Fahey, Donald P.; Noel, Michael W.; Smith, Rachel J.; Carroll, Thomas J.

2011-11-01

254

Ground states of helium to neon and their ions in strong magnetic fields  

NASA Astrophysics Data System (ADS)

We use the combination of a two-dimensional Hartree-Fock and a diffusion quantum Monte Carlo method, both of which we recently presented in this journal [C. Schimeczek et al., Phys. Rev. A 88, 012509 (2013), 10.1103/PhysRevA.88.012509], for a thorough investigation of the ground state configurations of all atoms and ions with Z =2-10 with the exception of hydrogen-like systems in strong magnetic fields. We obtain the most comprehensive data set of ground state configurations as a function of the magnetic field strength currently available and hence are able to analyze and compare the properties of systems with different core charges and electron numbers in detail.

Boblest, Sebastian; Schimeczek, Christoph; Wunner, Günter

2014-01-01

255

Smooth exterior complex-scaling, full-angular-momentum, and three-dimensional finite-element method applied to doubly excited states of helium  

SciTech Connect

A technique based on the total-angular-momentum representation the smooth exterior complex-scaling procedure, and the three-dimensional finite-element method, is applied to calculations of S, P, and D resonant, so-called doubly excited, states of the helium atom. The resonances are calculated with an accuracy better than 10{sup -5} a.u. The applicability of an extrapolation procedure to complex energies is analyzed.

Elander, Nils [Department of Physics, Stockholm University, Alba Nova University Center, SE-106 91 Stockholm (Sweden); Levin, Sergey [Department of Physics, Stockholm University, Alba Nova University Center, SE-106 91 Stockholm (Sweden); Institute for Physics, St. Petersburg University, Uljanovskaya 1, St. Petersburg 198904 (Russian Federation); Institute for Theoretical Atomic and Molecular Physics at Harvard University and Smithsonian Astrophysical Observatory, 60 Garden Street, MS 14 Cambridge, Massachusetts 02138 (United States); Yarevsky, Evgeny [Institute for Physics, St. Petersburg University, Uljanovskaya 1, St. Petersburg 198904 (Russian Federation); International Solvay Institutes for Physics and Chemistry, Case Postale 231, Campus Plaine ULB Boulevard du Triomphe, Brussels 1050 (Belgium)

2003-06-01

256

On the formation of (anionic) excited helium dimers in helium droplets.  

PubMed

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

Huber, Stefan E; Mauracher, Andreas

2014-08-21

257

Transient localization in the kicked Rydberg atom  

E-print Network

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

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

2006-09-05

258

Transient localization in the kicked Rydberg atom  

SciTech Connect

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}{sub L} a second crossover time t{sub 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}{sub L}

Persson, Emil; Fuerthauer, S.; Burgdoerfer, J. [Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna (Austria); Wimberger, S. [CNR-INFM, Dipartimento di Fisica 'Enrico Fermi', Largo Pontecorvo 3, I-56127 Pisa (Italy)

2006-11-15

259

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

E-print Network

into equation 1. 6, we get: f dt qr kr q SIA(q, a') = N f ? & (to I exp(2(14) ? ? )t) I ito & J2 2M M (I. 8) Calculating Srx by expanding ~ 2/dp & in the complete momentum states: ~ I/Ip &= f d'h, d hrv ~ k, k)v & dk(k?. , kdv), we have: Srx(q, o)) = Srx... 'qr, pie'urq(o) ~ I/Ip & (111) Equation I. 10 can be explicitly written in the 3-dimensional h variable as: S (q, ) = N f dk, dk?dk, (/I +4k2 ?4 4 kI, )k'( ? ? *). (1. 12) 2M M We can simplify Srx by introducing Y = M(N/q ? q/2, which...

Yang, Jian

1996-01-01

260

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

E-print Network

) =0.35+0.05 P(Kai ) = ?15(o'p ?o'i)/(67o'p ?149o'i) P (Ko4) =(op ai)/(7o p+13o i?) . and P( P)= ?0.11+0.05 . Full spin-orbit coupling is assumed for the P state. In general ~ap ~ & ~ o.i ~, and so it is to be expected that P(Ka3... (private communications). I. C. Percival and M. J. Seaton, Philos. Trans. R. Soc. London A251, 113 (1958). U. Fano and J. Macek, Rev. Mod. Phys. 45, 553 (1973). SK. A. Jamison and P. Richard, Phys. Rev. Lett. 38, 484 (1977). K. A. Jamison, P. Richard...

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

1982-01-01

261

Exotic topological density waves in cold atomic Rydberg fermions  

E-print Network

Versatile controllability of interactions in ultracold atomic and molecular gases has now reached an unprecedented era where quantum correlations and unconventional many-body phases can be studied with no corresponding analogs 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. We show that varying spatial range of the non-local interaction leads to a rich phase diagram containing various bond density waves, with unexpected spontaneous time-reversal symmetry breaking. Quasiparticles in these chiral phases experience emergent gauge fields and form three dimensional quantum Hall and Weyl semimetal states. Remarkably, certain density waves even exhibit mixed topologies beyond the existing topological classification. Experimental signatures of density waves and their topological properties are predicted in time-of-flight measurements.

Xiaopeng Li; S. Das Sarma

2015-01-21

262

Measurement of the argon-gas-induced broadening and line shifting of the barium Rydberg level 6s24d 1D2 by two-photon resonant nondegenerate four-wave mixing  

NASA Astrophysics Data System (ADS)

We apply two-photon resonant nondegenerate four-wave mixing with a resonant intermediate state to the observation of the broadening and shifting of the barium Rydberg level 6s24d 1D2 by collision with argon. The collision broadening and shifting cross sections are measured. This technique is purely optical, and can investigate the pressure dependence of the transverse relaxation rate ?21 between the Rydberg state and an intermediate state, as well as the transverse relaxation rate ?20 between the Rydberg state and the ground state.

Sun, Jiang; Xiong, Zhi-Qiang; Sun, Juan; Wang, Ying; Su, Hong-Xin

2012-06-01

263

Molecular ions, Rydberg spectroscopy and dynamics  

NASA Astrophysics Data System (ADS)

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.

Jungen, Ch.

2015-01-01

264

Multichannel Quantum Defect Theory of Strontium Rydberg Series  

E-print Network

Using the reactance matrix approach, we systematically develop new multichannel quantum defect theory models for the singlet and triplet S, P, D and F states of strontium based on improved energy level measurements. The new models reveal additional insights into the character of doubly excited perturber states, and the improved energy level measurements for certain series allow fine structure to be resolved for those series' perturbers. Comparison between the predictions of the new models and those of previous empirical and \\emph{ab initio} studies reveals good agreement with most series, however some discrepancies are highlighted. Using the multichannel quantum defect theory wave functions derived from our models we calculate other observables such as Land\\'e $g_J$-factors and radiative lifetimes. The analysis reveals the impact of perturbers on the Rydberg state properties of divalent atoms, highlighting the importance of including two-electron effects in the calculations of these properties. The work enabl...

Vaillant, C L; Potvliege, R M

2014-01-01

265

Frustrated Quantum Magnetism with Laser-Dressed Rydberg Atoms  

E-print Network

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.

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

2014-10-13

266

Natural widths and blackbody radiation induced shift and broadening of Rydberg levels in magnesium ions  

NASA Astrophysics Data System (ADS)

Theoretical analysis is presented of the natural lifetimes and blackbody-radiation (BBR)-induced shifts and widths of Rydberg states with small and large angular momenta l. Asymptotic presentations in elementary functions are derived for matrix elements of bound-bound, bound-free and threshold radiative transitions from hydrogenic-type states with large angular momenta, applicable to both hydrogen-like and many-electron atoms and ions. For states with small angular momenta two numerical methods based on the quantum defects were used and corresponding data are compared with one another and with the most reliable data of the literature. Asymptotic approximations are derived for natural lifetimes, thermal shifts and broadening of Rydberg states of small and high l and principal quantum numbers n ? 1.

Glukhov, Igor L.; Mokhnenko, Sergey N.; Nikitina, Elizaveta A.; Ovsiannikov, Vitaly D.

2015-01-01

267

Towards the determination of the equation of state of hydrogen and helium at extreme densities: Laser induced shocks on pre-compressed samples.  

NASA Astrophysics Data System (ADS)

The determination of the equation of state of helium and hydrogen at very high density is an important problem at the frontier between condensed matter physics and plasma physics. It is also an important issue in planetary physics for understanding the formation of giant and extrasolar planets. However, the extreme densities relevant to most of the interior of Jupiter are unreachable by either static or single-shock compression techniques alone. Recently, a laser-driven shock-wave in a hydrogen sample, pre-compressed in a diamond anvil cell, has been demonstrated [1]. Consequently, the compression factors of the dynamic and static techniques can now be multiplied. We will present our current effort with the Omega laser at LLE to measure accurately the Hugoniot curves of hydrogen and helium pre-compressed up to 1.5 GPa. The metrology and error bars of the measurements will be discussed. The Hugoniot data points will be compared to published calculations, and an interesting difference in the insulator-metal transition of hydrogen and helium will be discussed. Co-authors are Stephanie Brygoo, CEA, France; Jon Eggert, Peter Celliers, Guilbert Collins, LLNL, Livermore CA 94551 USA; Ryan McWilliam, Raymond Jeanloz, University of California, CA 94720 USA; and Tom Boehly, LLE, New-York 14623 USA. [1] P. Loubeyre et al., High Pressure Research 24, 25- 31 (2004).

Loubeyre, Paul

2005-03-01

268

Charge state distribution of 86Kr in hydrogen and helium gas charge strippers at 2.7 MeV /nucleon  

NASA Astrophysics Data System (ADS)

The charge state distributions of krypton (86Kr) with an energy of 2.7 MeV /nucleon were measured using hydrogen (H2 ) and helium (He) gas charge strippers. A differential pumping system was constructed to confine H2 and He gases to a thickness sufficient for the charge state distributions to attain equilibrium. The mean charge states of 86Kr in H2 and He gases attained equilibrium at 25.1 and 23.2, respectively, whereas the mean charge state in N2 gas at equilibrium was estimated to be less than 20. The charge distributions are successfully reproduced by the cross sections of ionization and electron capture processes optimized by a fitting procedure.

Kuboki, H.; Okuno, H.; Hasebe, H.; Fukunishi, N.; Ikezawa, E.; Imao, H.; Kamigaito, O.; Kase, M.

2014-12-01

269

Measurement of Atomic Oscillator Strength Distribution from the Excited States  

SciTech Connect

Saturation technique has been employed to measure the oscillator strength distribution in spectra of helium lithium using an electrical discharge cell a thermionic diode ion detector respectively. The photoabsorption cross sections in the discrete or bound region (commonly known as f-values) have been determined form the Rydberg series accessed from a particular excited state calibrating it with the absolute value of the photoionization cross section measured at the ionization threshold. The extracted discrete f-values merge into the oscillator strength densities, estimated from the measured photoionization cross sections at different photon energies above the first ionization threshold. The experimental data on helium and lithium show continuity between the discrete and the continuous oscillator strengths across the ionization threshold.

Hussain, Shahid [National Tokamak Fusion Program P.O. Box 3329 Islamabad Pakistan (Pakistan); Saleem, M. [Optics Laboratory PINSTECH Nilore Islamabad (Pakistan); Baig, M. A. [Atomic Molecular Physics Laboratory, Department of Physics Quaid-i-Azam University, Islamabad 45320 (Pakistan)

2008-10-22

270

Modeling many-particle mechanical effects of an interacting Rydberg gas  

SciTech Connect

In a recent work [Phys. Rev. Lett. 98, 023004 (2007)], we investigated the influence of the attractive van der Waals interaction on the pair distribution and Penning ionization dynamics of ultracold Rydberg gases. Here we extend this description to atoms initially prepared in Rydberg states exhibiting repulsive interaction. We present calculations based on a Monte Carlo algorithm to simulate the dynamics of many atoms under the influence of both repulsive and attractive long-range interatomic forces. Redistribution to nearby states induced by blackbody radiation is taken into account, changing the effective interaction potentials. The model agrees with experimental observations, where the ionization rate is found to increase when the excitation laser is blue detuned from the atomic resonance.

Amthor, Thomas; Reetz-Lamour, Markus; Giese, Christian; Weidemueller, Matthias [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg (Germany)

2007-11-15

271

Phases and collective modes of Rydberg atoms in an optical lattice  

NASA Astrophysics Data System (ADS)

We chart out the possible phases of laser-driven Rydberg atoms in the presence of a hypercubic optical lattice. We define a pseudospin degree of freedom whose up (down) components correspond to the excited (ground) states of the Rydberg atoms and use them to demonstrate the realization of a canted Ising antiferromagnetic (CIAF) Mott phase of the atoms in these systems. We also show that, on lowering the lattice depth, the quantum melting of the CIAF and density-wave Mott states (which are also realized in these systems) leads to supersolid phases of the atoms. We provide analytical expressions for the phase boundaries and collective excitations of these phases in the hard-core limit within mean-field theory and discuss possible experiments to test our theory.

Saha, K.; Sinha, S.; Sengupta, K.

2014-02-01

272

Symmetry and symmetry breaking in Rydberg-atom intrashell dynamics  

SciTech Connect

We have investigated experimentally and theoretically the dynamics of Stark-Zeeman split states in Li(n=25) Rydberg atoms when they are exposed to a superposition of a slowly varying field and a harmonic RF field. Regular oscillatory structures are observed in the intrashell transitions. By solving the time-dependent Schroedinger equation for the problem it is shown that the dynamics is strongly influenced by the nonhydrogenic core which breaks the dynamical symmetry of the Coulomb problem. It is also shown that the dynamics effectively reduces to that of a two-level atom. The oscillations are remnants of interferences that arise partly due to a phase difference which develops between the two levels when they go through two consecutive one-photon resonances, and partly due to an effective change of the carrier-envelope phase of the coupling field.

Pilskog, I. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Laboratoire de Chimie Physique Matiere et Rayonnement, Universite Pierre et Marie Curie - CNRS (UMR 7614), F-75231 Paris Cedex 05 (France); Fregenal, D. [Centro Atomico Bariloche and Consejo Nacional de Investigaciones Cienticas y Tecnicas. R8402AGP S.C. de Bariloche (Argentina); Frette, O.; Foerre, M. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Horsdal, E. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Waheed, A. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Higher Education Commission of Pakistan, Islamabad (Pakistan)

2011-04-15

273

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

SciTech Connect

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''.

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

274

O the Rydberg-Ritz Formula in Quantum Mechanics  

Microsoft Academic Search

A derivation is given of the Rydberg-Ritz formula for series spectra. Simple expressions are obtained for the Rydberg and Ritz coefficients. It is shown that the Ritz coefficient is proportional to the difference between the radial period of the electron and the period of the hypothetical orbit, with the same energy which would exist if the atomic core were to

Robert Jastrow

1948-01-01

275

Ejection of quasi-free electron pairs from the helium atom ground state by single photon absorption  

E-print Network

We investigate single photon double ionization (PDI) of helium at photon energies of 440 and 800 eV. We observe doubly charged ions with close to zero momentum corresponding to electrons emitted back-to-back with equal energy. These slow ions are the unique fingerprint of an elusive quasi-free PDI mechanism predicted by Amusia et al. nearly four decades years ago [J. Phys. B 8, 1248, (1975)] . It results from the non-dipole part of the electromagnetic interaction. Our experimental data are in excellent agreement with calculations performed using the convergent close coupling and time dependent close coupling methods.

Schöffler, M S; Waitz, M; Trinter, F; Jahnke, T; Lenz, U; Jones, M; Belkacem, A; Landers, A; Pindzola, M S; Cocke, C L; Colgan, J; Kheifets, A; Bray, I; Schmidt-Böcking, H; Dörner, R; Weber, Th

2012-01-01

276

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

277

Pseudospin orders in the supersolid phases in binary Rydberg-dressed Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

We show that the five possible ordered states in a two-dimensional quantum spin-1/2 system with long-range exchange interactions (Néel, ladder, Peierls, longitudinal-domain, and transversal-domain states) can be realized in a binary Rydberg-dressed BEC system in the supersolid phase. In such a system, blockade phenomenon is shown to also occur for pairs of different excited-state atoms, which results in similar intraspecies and interspecies long-range interactions between ground-state atoms. It suggests that a pseudospin system can be possibly formed in the ground state of ultracold rubidium.

Hsueh, C.-H.; Tsai, Y.-C.; Wu, K.-S.; Chang, M.-S.; Wu, W. C.

2013-10-01

278

Excitation dynamics of interacting Rydberg atoms in small lattices  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

279

Thermal Conductivity of Helium  

SciTech Connect

This engineering note examines the thermal conductivity of helium as a function of temperature and pressure. The note attempts to determine the effect of varying pressure on the thermal conductivity of the vapor state over various temperature ranges. The plots clearly show that at temperatures above 20 degrees Kelvin. pressure does not have a significant effect on the thermal conductivity of Helium. In figures 1 and 2 the four isobaric curves are indistinguishable. This is also evident from the numeric data in table 1. Comparing the thermal conductivity of any particular row in table I, the thermal conductivity does not change by more than one percent from one column to another. Below 20K, the curves begin to diverge as they approach the saturation dome. This affect is more pronounced at pressures above the critical pressure of 0.23MPa, At which point the fluid is neither a liqUid or vapor. At pressures between atmospheriC pressure and 0.01 MPa, the thermal conductivity of Helium is independent of pressure below 20K as well as above 20K.

Clark, D.; /Fermilab

1992-08-26

280

The Spectral Backbone of Excitation Transport in Ultra-Cold Rydberg Gases  

E-print Network

The spectral structure underlying excitonic energy transfer in ultra-cold 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 L\\'evy 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.

Torsten Scholak; Thomas Wellens; Andreas Buchleitner

2014-11-26

281

Effect of electric fields on the decay branching ratio of {sup 1}P{sup e} doubly excited states in helium measured by time-resolved fluorescence  

SciTech Connect

We have measured the lifetimes of {sup 1}P{sup e} (n=9-12) doubly excited states in static electric fields (1-6 kV/cm) by observing the decay of the fluorescence signal as a function of time. The effects of the field on these helium states below the second ionization threshold are twofold: their excitation becomes possible due to the Stark mixing with the optically allowed {sup 1}P{sup o} series, and their lifetime is strongly modified by the opening of the autoionization channel, not accessible in zero field. Although the electric field represents only a tiny perturbation of the atomic potential, a substantial shortening of the lifetimes below 100 ps is observed. This is the simplest quantum system where the ratio of autoionization to fluorescence decay probability can be effectively controlled by an electric field of moderate strength.

Zitnik, Matjaz; Mihelic, A.; Bucar, K. [Jozef Stefan Institute, P. O. Box 3000, SI-1001 Ljubljana (Slovenia); Penent, F.; Lablanquie, P. [LCP-MR, Universite Pierre et Marie Curie 6 and CNRS (UMR 7614), 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Richter, R. [Sincrotrone Trieste, I-340 12 Trieste (Italy); Alagia, M. [INFM-TASC, Padriciano 99, I-340 12 Trieste (Italy); Stranges, S. [Dipartimento di Chimica, Universita di Roma 'La Sapienza' and INFM Unit, 00185 Rome (Italy)

2006-11-15

282

The problem of the structure (state of helium) in small He{sub N}-CO clusters  

SciTech Connect

A second-order perturbation theory, developed for calculating the energy levels of the He-CO binary complex, is applied to small He{sub N}-CO clusters with N = 2-4, the helium atoms being considered as a single bound object. The interaction potential between the CO molecule and HeN is represented as a linear expansion in Legendre polynomials, in which the free rotation limit is chosen as the zero approximation and the angular dependence of the interaction is considered as a small perturbation. By fitting calculated rotational transitions to experimental values it was possible to determine the optimal parameters of the potential and to achieve good agreement (to within less than 1%) between calculated and experimental energy levels. As a result, the shape of the angular anisotropy of the interaction potential is obtained for various clusters. It turns out that the minimum of the potential energy is smoothly shifted from an angle between the axes of the CO molecule and the cluster of {theta} = 100{sup o} in He-CO to {theta} = 180{sup o} (the oxygen end) in He{sub 3}-CO and He{sub 4}-CO clusters. Under the assumption that the distribution of helium atoms with respect to the cluster axis is cylindrically symmetric, the structure of the cluster can be represented as a pyramid with the CO molecule at the vertex.

Potapov, A. V., E-mail: potapov@isan.troitsk.ru; Panfilov, V. A.; Surin, L. A.; Dumesh, B. S. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)

2010-11-15

283

Helium-cooled high temperature reactors  

SciTech Connect

Experience with several helium cooled reactors has been favorable, and two commercial plants are now operating. Both of these units are of the High Temperature Graphite Gas Cooled concept, one in the United States and the other in the Federal Republic of Germany. The initial helium charge for a reactor of the 1000 MW(e) size is modest, approx.15,000 kg.

Trauger, D.B.

1985-01-01

284

Structural dynamics and energy flow in Rydberg-excited clusters of N,N-dimethylisopropylamine  

NASA Astrophysics Data System (ADS)

In molecular beams, the tertiary amine N,N-dimethylisopropyl amine can form molecular clusters that are evident in photoelectron and mass spectra obtained upon resonant multiphoton ionization via the 3p and 3s Rydberg states. By delaying the ionization pulse from the excitation pulse we follow, in time, the ultrafast energy relaxation dynamics of the 3p to 3s internal conversion and the ensuing cluster evaporation, proton transfer, and structural dynamics. While evaporation of the cluster occurs in the 3s Rydberg state, proton transfer dominates on the ion surface. The mass-spectrum shows protonated species that arise from a proton transfer from the alpha-carbon of the neutral parent molecule to the N-atom of its ionized partner in the dimer. DFT calculations support the proton transfer mechanism between tightly bonded cluster components. The photoelectron spectrum shows broad peaks, ascribed to molecular clusters, which have an instantaneous shift of about 0.5 eV toward lower binding energies. That shift is attributed to the charge redistribution associated with the induced dipoles in surrounding cluster molecules. A time-dependent shift that decreases the Rydberg electron binding energy by a further 0.4 eV arises from the structural reorganization of the cluster solvent molecules as they react to the sudden creation of a charge.

Deb, Sanghamitra; Minitti, Michael P.; Weber, Peter M.

2011-07-01

285

On the Tricomi expansion in Rydberg collisions  

NASA Astrophysics Data System (ADS)

Expressions of the first Born cross sections for Rydberg transitions contain hypergeometric functions of large arguments. Their numerical computation becomes difficult due to severe cancellation errors. The use of their asymptotic expression overcomes this problem and helps analytical studies. We examine two such asymptotic approaches, the Tricomi expansion and Jacobi polynomial representation methods. We show that the asymptotic expression of the Jacobi polynomial representation gives remarkably accurate results over the entire range of the physical momentum transfer whereas that of the Tricomi expansion method gives a good estimate only in the region near the minimum momentum transfer.

Dewangan, D. P.

2002-01-01

286

Steady state heat transfer experimental studies of LHC superconducting cables operating in cryogenic environment of superfluid helium  

E-print Network

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...

Santandrea, Dario; Tuccillo, Raffaele;; Granieri, Pier Paolo.

287

Spin-forbidden radiative decay rates from the 3 {sup 3}P{sub 1,2} and 3 {sup 1}P{sub 1} states of helium  

SciTech Connect

We have calculated atomic helium spontaneous decay rates and absorption oscillator strengths for the spin-forbidden transitions from 3 {sup 3}P{sub 1,2} and 3 {sup 1}P{sub 1} to all lower {sup 1}S{sub 0} and {sup 3}S{sub 1} states. In particular we found A{sub 10}=44.33(4) s{sup -1} for the E1 transition 3 {sup 3}P{sub 1}-1 {sup 1}S{sub 0} and 0.1147(1) s{sup -1} for the M2 transition 3 {sup 3}P{sub 2}-1 {sup 1}S{sub 0}.

Morton, Donald C. [Herzberg Institute of Astrophysics, National Research Council, Victoria, British Columbia, V9E 2E7 (Canada); Drake, G. W. F. [Department of Physics, University of Windsor, Windsor, Ontario, N9B 3P4 (Canada)

2011-04-15

288

Rydberg series of calcium monofluoride : spectrum, structure, and dynamics  

E-print Network

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 ...

Kay, Jeffrey J

2007-01-01

289

Rotary echo tests of coherence in Rydberg-atom excitation  

NASA Astrophysics Data System (ADS)

Rotary echoes are employed to study excitation dynamics in many-body Rydberg systems. In this method, a phase reversal of a narrow-band excitation field is applied at a variable time during the excitation pulse. The visibility of the resulting echo signal reveals the degree of coherence of the excitation process. Rotary echoes are measured for several nD5/2 Rydberg levels of rubidium with principal quantum numbers near n=43, where the strength of electrostatic Rydberg-atom interactions is modulated by a Förster resonance. The Rydberg-atom interactions are shown to diminish the echo visibility, in agreement with recent theoretical work. The equivalence of echo signals with spectroscopic data is demonstrated.

Younge, Kelly Cooper; Raithel, Georg

2009-04-01

290

Rotary echo tests of coherence in Rydberg-atom excitation  

NASA Astrophysics Data System (ADS)

Rotary echoes are employed to study excitation dynamics in many-body Rydberg systems. In this method, a phase reversal of a narrow-band excitation field, applied at a variable time during the excitation pulse, results in echo signals the visibility of which reveal the degree of coherence of the excitation process. Rotary echoes are measured for several nD5/2 Rydberg levels of rubidium with principal quantum numbers near n=43, where the strength of electrostatic Rydberg-atom interactions is modulated by a Förster resonance. The Rydberg-atom interactions are shown to diminish the echo visibility, in agreement with recent theoretical work. The equivalence of echo signals with spectroscopic data is demonstrated.

Cooper Younge, Kelly; Raithel, Georg

2009-05-01

291

A precision millimeter-wave measurement of the Rydberg frequency  

E-print Network

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 ...

De Vries, Joel Christopher, 1971-

2001-01-01

292

Avoided curve crossings for the dissociation reaction of the Rydberg H 3O radical into (OH+H 2)  

NASA Astrophysics Data System (ADS)

Potential energy curves of the ground and excited states for the dissociation of the Rydberg H 3O radical into (OH+H 2) have been calculated using ab initio Hartree-Fock (HF) and singly and doubly excited configuration interaction (SDCI) methods with a large basis set including Rydberg basis functions. Under C 2v symmetry constraint, the ground 2A1 potential curve of (H 3O +)(e -) 3s adiabatically correlates to [ OH( A2? +)+ H2( X1? g+) ], while the first excited 2E state of (H 3O +)(e -) 3s correlates to [ OH( X2?)+ H2( X1? g+) ]. The avoided curve crossings between the attractive diabatic states emerging from the cation-anion pair of [OH ++H 2-] and the repulsive diabatic states from antibonding orbitals of [ OH?+ H2] occurs around ROH?1.8 Å.

Park, Jong Keun; Kim, Bong Gon; Koo, In Sun

2002-04-01

293

Dynamics of heavy-Rydberg ion-pair formation in K(14p,20p)-SF6, CCl4 collisions  

NASA Astrophysics Data System (ADS)

The dynamics of formation of heavy-Rydberg ion-pair states through electron transfer in K(np)-SF6, CCl4 collisions is examined by measuring the velocity, angular, and binding energy distributions of the product ion pairs. The results are analyzed with the aid of a Monte Carlo collision code that models both the initial electron capture and the subsequent evolution of the ion pairs. The model simulations are in good agreement with the experimental data and highlight the factors such as Rydberg atom size, the kinetic energy of relative motion of the Rydberg atom and target particle, and (in the case of attaching targets that dissociate) the energetics of dissociation that can be used to control the properties of the product ion-pair states.

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

2014-06-01

294

Oscillator Strengths and Predissociation Rates for Rydberg Transitions in 12C16O, 13C16O, and 13C18O Involving the E 1?, B 1?+, and W 1? States  

NASA Astrophysics Data System (ADS)

One of the processes controlling the interstellar CO abundance and the ratio of its isotopologues is photodissociation. Accurate oscillator strengths and predissociation rates for Rydberg transitions are needed for modeling this process. We present results on absorption from the E 1?-X 1?+ (1-0) and B 1?+-X 1?+ (6-0) bands at 1051 and 1002 Å, respectively, and the vibrational progression W 1?-X 1?+ (v'-0) bands with v'=0-3 at 972, 956, 941, and 925 Å, respectively. The corresponding spectra were acquired at the high resolution (R~30,000) SU5 beam line at the Super ACO Synchrotron in Orsay, France. Spectra were obtained for the 12C16O, 13C 16O, and 13C18O isotopologues. These represent the most complete set of measurements available. Comparison is made with earlier results, both empirical and theoretical. While earlier determinations of oscillator strengths based on absorption from synchrotron radiation tend to be somewhat smaller than ours, the suite of measurements from a variety of techniques agree for the most part, considering the mutual uncertainties. For the bands studied here, their relative weakness, or their significant line widths arising from predissociation, minimizes potential problems from large optical depths at line center in absorption measurements. Predissociating line widths could generally be extracted from the spectra thanks to the profile simulations used in the analysis. In many cases, these simulations allowed us to consider e and f parity levels separately and to determine the dependence of the width on rotational quantum number, J. Our results are consistent with earlier determinations, especially the widths inferred from laser experiments.

Eidelsberg, M.; Sheffer, Y.; Federman, S. R.; Lemaire, J. L.; Fillion, J. H.; Rostas, F.; Ruiz, J.

2006-08-01

295

Double photon excitation of high-Rydberg atoms as a long-lived submillimeter detector  

NASA Technical Reports Server (NTRS)

A method and apparatus for detecting submillimeter or IR radiation is disclosed. A rare gas, such as xenon, is supplied at its ground state via a pressurized cylinder and an adjustable leak valve into a cryogenically cooled detection area. The ground state of xenon is double photon excited to a particularized level of the Rydberg series by a resonance lamp and a laser. The doubly excited gas is then further excited by the radiation to be measured. A field ionization and an ion measurement indicative of the radiation intensity is achieved.

Chutjian, A. N. (inventor)

1986-01-01

296

Rydberg and pulsed field ionization-zero electron kinetic energy spectra of YO  

Microsoft Academic Search

A spectroscopic study of the Rydberg states of YO accessed from\\u000a particular rotational levels of the A (2)Pi(1\\/2), v=0 state has been\\u000a combined with a pulsed field ionization, zero electron kinetic energy\\u000a (PFI-ZEKE) investigation. The results provide accurate values of the\\u000a ionization energy of YO, ionization energy I.E.(YO)=49 304.316(31)\\u000a cm(-1) {[}6.112 958(4) eV], and of the rotational constant (and bond

Colan Linton; Benoit Simard; HP Loock; Sara Wallin; Gretchen K. Rothschopf; Robert F. Gunion; Michael D. Morse; Peter B. Armentrout

1999-01-01

297

Precise manipulation of Rydberg wave packets  

NASA Astrophysics Data System (ADS)

The creation and control of mesoscopic, very-high-n (n ˜300) near-circular Rydberg wave packets, whose quantum coherence can be maintained over hundreds of classical orbital periods, is described. We show that the n distributions in such wave packets can be controlled during production by the size and shape of the generating field and further tailored through the application, after production, of precisely timed half-cycle pulses. The remarkable level of precision that can be achieved is demonstrated using time domain spectroscopy. The protocols employed are described with the aid of ``quantized'' classical trajectory Monte Carlo simulations. Research supported by the NSF, the Robert A. Welch Foundation, the OBES, U.S. DoE to ORNL, and by the FWF (Austria).

Wyker, B.; Dunning, F. B.; Reinhold, C. O.; Yoshida, S.; Burgdörfer, J.

2010-03-01

298

Experimental investigation of non-hydrogenic orbits in helium recurrence spectra  

SciTech Connect

Refinements in data aquisition have allowed the authors to capture the first recurrence spectra of helium. Using experimental techniques previously described, they have obtained recurrence spectra for scaled energies {epsilon} ={minus}3,{minus}4, and {minus}5 in the principal quantum number region n=20-30 ({epsilon}=EF{sup {minus}1/2}, where E is the binding energy of the Rydberg electron, and F is the strength of the Stark field in a.u.). Calculated recurrence spectra developed using theoretical Stark map data agree reasonably well with the present experimental results. With continued refinements in both theoretical and experimental methods the authors expect to produce clearer correlation between calculated and experimental spectra. For {epsilon} ={minus}5, the primary non-hydrogenic characteristics in the helium scaled action spectra prior to taking the Fourier transform is in the {open_quotes}p-branch{close_quotes} of the Stark manifold. By eliminating selected hydrogenic features from the experimental spectra the authors have identified the scaled action of several helium-specific orbits. Future experimentation will yield precision scaled action maps of helium-specific orbits as a function of scaled energy, providing detailed information on the effects of the core electron on classical Rydberg orbits.

Keeler, M.L.; Cullinan, D.W.; Morgan, T.J.

1996-05-01

299

Solving the electron and electron-nuclear Schroedinger equations for the excited states of helium atom with the free iterative-complement-interaction method  

SciTech Connect

Very accurate variational calculations with the free iterative-complement-interaction (ICI) method for solving the Schroedinger equation were performed for the 1sNs singlet and triplet excited states of helium atom up to N=24. This is the first extensive applications of the free ICI method to the calculations of excited states to very high levels. We performed the calculations with the fixed-nucleus Hamiltonian and moving-nucleus Hamiltonian. The latter case is the Schroedinger equation for the electron-nuclear Hamiltonian and includes the quantum effect of nuclear motion. This solution corresponds to the nonrelativistic limit and reproduced the experimental values up to five decimal figures. The small differences from the experimental values are not at all the theoretical errors but represent the physical effects that are not included in the present calculations, such as relativistic effect, quantum electrodynamic effect, and even the experimental errors. The present calculations constitute a small step toward the accurately predictive quantum chemistry.

Nakashima, Hiroyuki; Hijikata, Yuh; Nakatsuji, Hiroshi [Quantum Chemistry Research Institute, JST CREST, Kyodai Katsura Venture Plaza 106, Goryo Oohara 1-36, Nishikyo-ku, Kyoto 615-8245 (Japan) and Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)

2008-04-21

300

Sub-wavelength imaging and field mapping via electromagnetically induced transparency and Autler-Townes splitting in Rydberg atoms  

SciTech Connect

We present a technique for measuring radio-frequency (RF) electric field strengths with sub-wavelength resolution. We use Rydberg states of rubidium atoms to probe the RF field. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect, and we detect the splitting via electromagnetically induced transparency (EIT). We use this technique to measure the electric field distribution inside a glass cylinder with applied RF fields at 17.04?GHz and 104.77?GHz. We achieve a spatial resolution of ?100??m, limited by the widths of the laser beams utilized for the EIT spectroscopy. We numerically simulate the fields in the glass cylinder and find good agreement with the measured fields. Our results suggest that this technique could be applied to image fields on a small spatial scale over a large range of frequencies, up into the sub-terahertz regime.

Holloway, Christopher L., E-mail: holloway@boulder.nist.gov; Gordon, Joshua A. [National Institute of Standards and Technology (NIST), Electromagnetics Division, U.S. Department of Commerce, Boulder Laboratories, Boulder, Colorado 80305 (United States); Schwarzkopf, Andrew; Anderson, David A.; Miller, Stephanie A.; Thaicharoen, Nithiwadee; Raithel, Georg [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2014-06-16

301

Motion-induced signal revival in pulsed Rydberg four-wave mixing beyond the frozen gas limit  

E-print Network

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 timescale that is combined with a third CW laser in phase-matched geometry yielding light emission on the same timescale. 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.

Huber, B; Pfau, T

2014-01-01

302

Sub-wavelength imaging and field mapping via electromagnetically induced transparency and Autler-Townes splitting in Rydberg atoms  

NASA Astrophysics Data System (ADS)

We present a technique for measuring radio-frequency (RF) electric field strengths with sub-wavelength resolution. We use Rydberg states of rubidium atoms to probe the RF field. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect, and we detect the splitting via electromagnetically induced transparency (EIT). We use this technique to measure the electric field distribution inside a glass cylinder with applied RF fields at 17.04 GHz and 104.77 GHz. We achieve a spatial resolution of ?100 ?m, limited by the widths of the laser beams utilized for the EIT spectroscopy. We numerically simulate the fields in the glass cylinder and find good agreement with the measured fields. Our results suggest that this technique could be applied to image fields on a small spatial scale over a large range of frequencies, up into the sub-terahertz regime.

Holloway, Christopher L.; Gordon, Joshua A.; Schwarzkopf, Andrew; Anderson, David A.; Miller, Stephanie A.; Thaicharoen, Nithiwadee; Raithel, Georg

2014-06-01

303

Ab Initio Equations of State for Hydrogen (H-REOS.3) and Helium (He-REOS.3) and their Implications for the Interior of Brown Dwarfs  

NASA Astrophysics Data System (ADS)

We present new equations of state (EOSs) for hydrogen and helium covering a wide range of temperatures from 60 K to 107 K and densities from 10-10 g cm-3 to 103 g cm-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.

Becker, Andreas; Lorenzen, Winfried; Fortney, Jonathan J.; Nettelmann, Nadine; Schöttler, Manuel; Redmer, Ronald

2014-12-01

304

Ab initio equations of state for hydrogen (H-REOS.3) and helium (He-REOS.3) and their implications for the interior of Brown Dwarfs  

E-print Network

We present new equations of state (EOS) for hydrogen and helium covering a wide range of temperatures from 60 K to 10$^7$ K and densities from $10^{-10}$ g/cm$^3$ to $10^3$ g/cm$^3$. 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 the comparison with recent results. Secondly, mass-radius relations are calculated for Brown Dwarfs which we compare with predictions derived from the widely used EOS of Saumon, Chabrier and van Horn. Furthermore, we calculate interior models for typical Brown Dwarfs 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...

Becker, Andreas; Fortney, Jonathan J; Nettelmann, Nadine; Schöttler, Manuel; Redmer, Ronald

2014-01-01

305

Steady-state temperature distribution within a Brayton rotating unit operating in a power conversion system using helium-xenon gas  

NASA Technical Reports Server (NTRS)

The Brayton rotating unit (BRU), consisting of a turbine, an alternator, and a compressor, was tested as part of a Brayton cycle power conversion system over a side range of steady state operating conditions. The working fluid in the system was a mixture of helium-xenon gases. Turbine inlet temperature was varied from 1200 to 1600 F, compressor inlet temperature from 60 to 120 F, compressor discharge pressure from 20 to 45 psia, rotative speed from 32 400 to 39 600 rpm, and alternator liquid-coolant flow rate from 0.01 to 0.27 pound per second. Test results indicated that the BRU internal temperatures were highly sensitive to alternator coolant flow below the design value of 0.12 pound per second but much less so at higher values. The armature winding temperature was not influenced significantly by turbine inlet temperature, but was sensitive, up to 20 F per kVA alternator output, to varying alternator output. When only the rotational speed was changed (+ or - 10% of rated value), the BRU internal temperatures varied directly with the speed.

Johnsen, R. L.; Namkoong, D.; Edkin, R. A.

1971-01-01

306

Alternate circulator design concept No. 1 for a 300 MW(e) GCFR demonstration plant: two state axial flow helium circulator and two stage steam turbine drive  

Microsoft Academic Search

The report describes the preliminary design of a main helium circulator for the 300 MW(e) GCFR demonstration plant. Three main circulators and three auxiliary circulators are to be used in the demonstration plant. The main circulator consists of an axial flow, two-stage helium circulator (compressor) driven by an axial flow, and a two-stage turbine which employs superheated steam in series

Mouritzen

1977-01-01

307

Field-ionization threshold and its induced ionization-window phenomenon for Rydberg atoms in a short single-cycle pulse  

NASA Astrophysics Data System (ADS)

We study the field-ionization threshold behavior when a Rydberg atom is ionized by a short single-cycle pulse field. Both hydrogen and sodium atoms are considered. The required threshold field amplitude is found to scale inversely with the binding energy when the pulse duration becomes shorter than the classical Rydberg period, and, thus, more weakly bound electrons require larger fields for ionization. This threshold scaling behavior is confirmed by both three-dimensional classical trajectory Monte Carlo simulations and numerically solving the time-dependent Schrödinger equation. More surprisingly, the same scaling behavior in the short pulse limit is also followed by the ionization thresholds for much lower bound states, including the hydrogen ground state. An empirical formula is obtained from a simple model, and the dominant ionization mechanism is identified as a nonzero spatial displacement of the electron. This displacement ionization should be another important mechanism beyond the tunneling ionization and the multiphoton ionization. In addition, an "ionization window" is shown to exist for the ionization of Rydberg states, which may have potential applications to selectively modify and control the Rydberg-state population of atoms and molecules.

Yang, B. C.; Robicheaux, F.

2014-12-01

308

Ground state of small mixed helium and spin-polarized tritium clusters: A quantum Monte Carlo study  

Microsoft Academic Search

We report results for the ground-state energy and structural properties of small 4He-T? clusters consisting of up to four T? and eight 4He atoms. These results have been obtained using very well-known 4He-4He and T?- T? interaction potentials and several models for the 4He- T? interatomic potential. All the calculations have been performed with variational and diffusion Monte Carlo methods.

P. Stipanovic; L. Vranjes Markic; J. Boronat; B. Kezic

2011-01-01

309

Ground state of small mixed helium and spin-polarized tritium clusters: A quantum Monte Carlo study  

Microsoft Academic Search

We report results for the ground-state energy and structural properties of small 4He–T? clusters consisting of up to four T? and eight 4He atoms. These results have been obtained using very well-known 4He–4He and T?– T? interaction potentials and several models for the 4He– T? interatomic potential. All the calculations have been performed with variational and diffusion Monte Carlo methods.

P. Stipanovic´; J. Boronat

2011-01-01

310

Ground state of small mixed helium and spin-polarized tritium clusters: a quantum Monte Carlo study.  

PubMed

We report results for the ground-state energy and structural properties of small (4)He-T? clusters consisting of up to four T? and eight (4)He atoms. These results have been obtained using very well-known (4)He-(4)He and T?- T? interaction potentials and several models for the (4)He- T? interatomic potential. All the calculations have been performed with variational and diffusion Monte Carlo methods. It takes at least three atoms to form a mixed bound state. In particular, for small clusters the binding energies are significantly affected by the precise form of the (4)He- T? interatomic potential but the stability limits remain unchanged. The only exception is the (4)He(2)T? trimer whose stability in the case of the weakest (4)He- T? interaction potential is uncertain while it seems stable for other potentials. The mixed trimer (4)He(T?)(2), a candidate for the Borromean state, is not bound. All other studied clusters are stable. Some of the weakest bound clusters can be classified as quantum halo as a consequence of having high probability of being in a classically forbidden region. PMID:21303140

Stipanovi?, P; Marki?, L Vranješ; Boronat, J; Keži?, B

2011-02-01

311

Ground state of small mixed helium and spin-polarized tritium clusters: a quantum Monte Carlo stud  

Microsoft Academic Search

We report results for the ground-state energy and structural properties of\\u000asmall $^4$He-T$\\\\downarrow$ clusters consisting of up to 4 T$\\\\downarrow$ and 8\\u000a$^4$He atoms. These results have been obtained using very well-known\\u000a$^4$He-$^4$He and T$\\\\downarrow$-T$\\\\downarrow$ interaction potentials and\\u000aseveral models for the $^4$He-T$\\\\downarrow$ interatomic potential. All the\\u000acalculations have been performed with variational and diffusion Monte Carlo\\u000amethods. It takes

P. Stipanovi?; L. Vranjevs Marki?; J. Boronat; B. Kevzi?

2010-01-01

312

The non-resonant neutralization dynamics of the multiply charged Rydberg ions escaping solid surfaces  

NASA Astrophysics Data System (ADS)

We investigate the intermediate and final population of the Rydberg states (nA >> 1, lA = 0 - 3, mA) of multiply charged ions escaping solid surfaces by using the two-state vector model. All our calculations have been carried out for intermediate projectile velocities (v ? 1 a.u.). The electron capture is non-resonant and characterized by the selective population of the ionic Rydberg states. The final population probabilities enable us to elucidate the role of the ionic core polarization and to analyze the nA, l A and v probability distributions. We consider the ions SVI, C1VII and ArVIII with core charges Z = 6,7 and 8, respectively, and the ions KrVIII and XeVIII with Z = 8. The model is applied on two different ion-surface systems in order to emphasize the influence of the solid work function. We discuss the appearance of resonances (pronounced maxima) in the probability distributions. The resonances are explained by means of the electron tunneling in the very vicinity of the ion-surface potential barrier top. It is demonstrated that the resonances are characteristic only for some combination of the surface and ionic characteristics (argon anomaly), in agreement with available beam-foil experimental data.

Galijaš, S. M. D.; Nedeljkovi?, N. N.; Majki?, M. D.

2012-11-01

313

The Primordial Helium Abundance  

Microsoft Academic Search

I present a brief review on the determination of the primordial helium abundance by unit mass, Yp. I discuss the importance of the primordial helium abundance in: (a) cosmology, (b) testing the standard big bang nucleosynthesis, (c) studying the physical conditions in H II regions, (d) providing the initial conditions for stellar evolution models, and (e) testing the galactic chemical

Manuel Peimbert

2008-01-01

314

Characterizing high-n quasi-one-dimensional strontium Rydberg atoms  

NASA Astrophysics Data System (ADS)

The production of high-n, n ˜300, quasi-one-dimensional (quasi-1D) strontium Rydberg atoms through two-photon excitation of selected extreme Stark states in the presence of a weak dc field is examined using a crossed laser-atom beam geometry. The dipolar polarization of the electron wave function in the product states is probed using two independent techniques. The experimental data are analyzed with a classical trajectory Monte Carlo simulation employing initial ensembles that are obtained with the aid of quantum calculations based on a two-active-electron model. Comparisons between theory and experiment highlight different characteristics of the product quasi-1D states, in particular, their large permanent dipole moments, ˜1.0 to 1.2n2ea0, where e is the electronic charge and a0 is the Bohr radius. Such states can be engineered using pulsed electric fields to create a wide variety of target states.

Hiller, M.; Yoshida, S.; Burgdörfer, J.; Ye, S.; Zhang, X.; Dunning, F. B.

2014-02-01

315

An apparatus for pulsed ESR and DNP experiments using optically excited triplet states down to liquid helium temperatures.  

PubMed

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

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

316

Oscillator strength measurements of the 5s6s S10?5snp P11 Rydberg transitions of strontium  

NASA Astrophysics Data System (ADS)

We report the experimentally determined oscillator strengths for the 5s6s S10?5snp P11 Rydberg transitions of strontium using two-step excitation in conjunction with a thermionic diode ion detector. The absolute photoionization cross section from the 5s6s S10 excited state has been determined by adjusting the polarization vector of the ionizing laser beam parallel, perpendicular, and at the magic angle with respect to that of the exciting dye laser. The measured absolute value of the photoionization cross section 0.9±0.2Mb at the 5s threshold is used to extract the f values of the 5s6s S10?5snp P11 (26?n?73) Rydberg transitions. The oscillator strength in the discrete region merges smoothly to the oscillator strength density at the ionization threshold.

Haq, S. U.; Kalyar, M. A.; Rafiq, M.; Ali, R.; Piracha, N. K.; Baig, M. A.

2009-04-01

317

Periodic Orbit Theory for Rydberg Atoms in External Fields  

E-print Network

Although hydrogen in external fields is a paradigm for the application of periodic orbits and the Gutzwiller trace formula to a real system, the trace formula has never been applied successfully to other Rydberg atoms. We show that spectral fluctuations of general Rydberg atoms are given with remarkable precision by the addition of diffractive terms. Previously unknown features in atomic spectra are exposed: there are new modulations that are neither periodic orbits nor combinations of periodic orbits; `core-shadowing' generally decreases primitive periodic orbit amplitudes but can also lead to increases.

P. A. Dando; T. S. Monteiro; S. M. Owen

1998-03-13

318

Single-Photon Transistor Mediated by Interstate Rydberg Interactions  

NASA Astrophysics Data System (ADS)

We report on the realization of an all-optical transistor by mapping gate and source photons into strongly interacting Rydberg excitations with different principal quantum numbers in an ultracold atomic ensemble. We obtain a record switch contrast of 40% for a coherent gate input with mean photon number one and demonstrate attenuation of source transmission by over ten photons with a single gate photon. We use our optical transistor to demonstrate the nondestructive detection of a single Rydberg atom with a fidelity of 0.72(4).

Gorniaczyk, H.; Tresp, C.; Schmidt, J.; Fedder, H.; Hofferberth, S.

2014-08-01

319

Single-Particle and Collective States in Heavy Nuclei and the Specific Heat of the Normal Liquid Helium -3.  

NASA Astrophysics Data System (ADS)

The present dissertation consists of three parts each of which is divided into two sections. The first sections of each part contains the necessary formal and conceptual background for the preprints and published materials contained in the second section. The unifying theme of the dissertaion is the Green's function approach to the interaction between the single-particle and the collective modes of a many-body Fermi system--the heavy nucleus ('208)Pb in part 1 and the normal liquid ('3)He in parts 2 and 3. In part 1, corrections to the single-particle Green's function and the density correlation function beyond the mean field approach induced by the coupling of the quasiparticles to the two-particle one-hole states have been calculated in the framework of the Landau-Migdal theory applied to the heavy nucleus. It is found that the nucleon effective mass first rises and then falls sharply as a function of energy. A model containing the surface and the absorption effects is formulated which exhibits these properties. The centroid energies, widths and the strength functions of the isoscalar monopole, isovector dipole and the isoscalar quadrupole giant resonances were calculated which showed that the coupling of the single-particles to the coherent surface modes is a very important effect and varies with spin and isospin of the mode. In part 2, the specific heat of the normal liquid ('3)He is calculated under the assumption that the energy dependence of the effective mass is related to the sharp variation of the specific heat with temperature seen in the recent experiments. A model is proposed which attributes all of this energy dependence to the spin related collective mode called the paramagnons. The dynamical properties thus found are converted to the statistical ones which are used to calculate the specific heat. Good agreement wth experimental data at low temperatures is found. In part 3, a direct calculation of the specific heat from thermodynamic potential is described using the finite temperature Green's function formalism. The model is connected to the Landau theory at the low temperatures and to the Paramagnon model parameters at the high temperatues. The interaction parameter becomes temperature dependent and a simple quadratic dependence is assumed. The model gives a good fit to the experimental data upto higher temperatures.

Mishra, Vinod Kumar

320

Ultralong-range Rydberg molecules in combined electric and magnetic fields  

NASA Astrophysics Data System (ADS)

We investigate the impact of combined electric and magnetic fields on the structure of ultralong-range polar Rydberg molecules. Our focus is hereby on the parallel as well as the crossed field configuration, taking into account both the s-wave and p-wave interactions of the Rydberg electron and the neutral ground state atom. We show the strong impact of the p-wave interaction on the ultralong-range molecular states for a pure B-field configuration. In the presence of external fields, the angular degrees of freedom acquire vibrational character, and we encounter two- and three-dimensional oscillatory adiabatic potential energy surfaces for the parallel and crossed field configuration, respectively. The equilibrium configurations of local potential wells can be controlled via the external field parameters for both field configurations depending on the specific degree of electronic excitation. This allows us to tune the molecular alignment and orientation. The resulting electric dipole moment is in the order of several kDebye, and the rovibrational level spacings are in the range of 2-250\\;MHz. Both properties are analyzed with varying field strengths.

Kurz, Markus; Schmelcher, Peter

2014-08-01

321

Separation of compressor oil from helium  

SciTech Connect

Compression of helium by an oil-sealed rorary screw compressor entrains as much as 4000 parts per million by weight of liquid and vapor oil impurities in the gas. The reduction below about 0.1 ppm for cryogenic applications is discussed. Oil seperation equipment designed for compressed air must be modified significantly to produce the desired results with helium. The main differences between air and helium filtration are described. A description of the coalescers is given with the continuous coalescing of liquid mist from air or other gas illustrated. Oil vapor in helium is discussed in terms of typical compressor oils, experimental procedure for measuring oil vapor concentration, measured volatile hydrocarbons in the lubricants, and calculated concentration of oil vapor in Helium. Liquid oil contamination in helium gas can be reduced well below 0.1 ppm by a properly designed multiple state coalescing filter system containing graded efficiency filter elements. The oil vapor problem is best attached by efficiently treating the oil to remove most of the colatiles before charging the compressor.

Strauss, R.; Perrotta, K.A.

1982-01-01

322

The local interstellar helium density  

NASA Technical Reports Server (NTRS)

During the Apollo-Soyuz Test Project, an extreme-ultraviolet telescope observed the region of the sky from which the interstellar medium approaches the sun. The instrument had a tin filter whose bandpass included the 584-A line of neutral helium. The observations set an upper bound for the number density of neutral helium in the local interstellar medium of 0.004 + or - 0.0022 per cu cm, which is significantly lower than previously reported. The stated error is dominated by the present uncertainty in the solar 584-A flux, which is taken to be approximately 200 million photons/sq cm per sec at earth's orbit. The result is not consistent with previous resonant-scattering Ly-alpha observations of interstellar hydrogen passing through the solar system, which generally yield a hydrogen number density of about 0.1 per cu cm, unless interstellar helium is locally depleted below its cosmic abundance. The result is consistent with cosmic abundances if the much lower average hydrogen densities inferred from recent column-density measurements to nearby hot stars are in fact representative of the immediate solar neighborhood.

Freeman, J.; Paresce, F.; Bowyer, S.; Lampton, M.; Stern, R.; Margon, B.

1977-01-01

323

The Descending Helium Balloon  

ERIC Educational Resources Information Center

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.

Helseth, Lars Egil

2014-01-01

324

Efficient three-photon excitation of quasi-one-dimensional strontium Rydberg atoms with n ˜300  

NASA Astrophysics Data System (ADS)

The efficient production of very-high-n, n ˜300, quasi-one-dimensional (quasi-1D) strontium Rydberg atoms through three-photon excitation of extreme Stark states in the presence of a weak dc field is demonstrated using a crossed laser-atom beam geometry. Strongly polarized quasi-1D states with large permanent dipole moments ˜1.2n2 a.u. can be created in the beam at densities (˜106 cm-3) where dipole blockade effects should become important. A further advantage of three-photon excitation is that the product F states are sensitive to the presence of external fields, allowing stray fields to be reduced to very small values. The experimental data are analyzed using quantum calculations based on a two-active-electron model together with classical trajectory Monte Carlo simulations. These allow determination of the atomic dipole moments and confirm that stray fields can be reduced to ?25?V cm-1.

Ye, S.; Zhang, X.; Dunning, F. B.; Yoshida, S.; Hiller, M.; Burgdörfer, J.

2014-07-01

325

Ionization of Rb Rydberg atoms in the attractive nsnp dipole-dipole potential  

SciTech Connect

We have observed the ionization of a cold gas of Rb Rydberg atoms which occurs when nsns van der Waals pairs of ns atoms of n{approx_equal} 40 on a weakly repulsive potential are transferred to an attractive dipole-dipole nsnp potential by a microwave transition. Comparing the measurements to a simple model shows that the initial 300-{mu}K thermal velocity of the atoms plays an important role. Excitation to a repulsive dipole-dipole potential does not lead to more ionization on a 15-{mu}s time scale than leaving the atoms in the weakly repulsive nsns state. This observation is slightly surprising since a radiative transition must occur to allow ionization in the latter case. Finally, by power broadening of the microwave transition, to allow transitions from the initial nsns state to the nsnp state over a broad range of internuclear spacings, it is possible to accelerate markedly the evolution to a plasma.

Park, Hyunwook; Shuman, E. S.; Gallagher, T. F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904-0714 (United States)

2011-11-15

326

The effect of random positions for dipole hopping through a Rydberg gas  

E-print Network

We calculate the effect of two kinds of randomness on the hopping of an excitation through a nearly regular Rydberg gas. We present calculations for how fast the excitation can hop away from its starting position for different dimensional lattices and for different levels of randomness. We also examine the asymptotic in time final position of the excitation to determine whether or not the excitation can be localized. The one dimensional system is an example of Anderson localization where the randomness is in the off-diagonal elements although the long-range nature of the interaction leads to non-exponential decay with distance. The two dimensional square lattice shows a mixture of extended and localized states for large randomness while there is no visible sign of localized states for weak randomness. The three dimensional cubic lattice has few localized states even for strong randomness.

F. Robicheaux; N. M. Gill

2014-01-20

327

Superfluidity of helium-3  

Microsoft Academic Search

This article presents a phenomenological dynamic phase transition theory–modeling and analysis–for liquid helium-3. We derived two new models, for liquid helium-3 with or without applied field, by introducing three wave functions and using a unified dynamical Ginzburg–Landau model. The analysis of these new models leads to predictions of existence of (1) a metastable region, (2) a new phase C in

Tian Ma; Shouhong Wang

2008-01-01

328

Superfluid helium tanker instrumentation  

Microsoft Academic Search

An instrumentation system for a 1992 Space Shuttle flight demonstration of superfluid-helium tanker and transfer technology is presented. The system measures helium temperatures, pressures, flow rates and mass and the amount of liquid or vapor present. It consists of analog and digital portions which provide a fault-tolerant, compact, relatively lightweight, space-qualified electronics system. The data-processing hardware and software are ground-commandable,

C. E. Woodhouse; A. Kashani; A. T. Lukemire

1989-01-01

329

Helium liquefaction using cryorefrigerators  

NASA Astrophysics Data System (ADS)

A two-stage Gifford-McMahon refrigerator with a Joule-Thomson (J-T) stage connected in series, was extended to a small helium liquefier. The plant can operate automatically. Helium is liquefied within the J-T cycle, directly after the J-T valve, into a 3l tank. This liquid He is used for the indirect cooling of an externally accessible sample chamber, either by using helium contact gas, or by means of liquid He condensed from an external helium gas source. The second design is meant for laboratory applications. The liquid helium tank is not incorporated in the J-T cycle, but thermally connected to the J-T stage of the refrigerator. The He gas from an external source is then condensed into the 2l tank. The liquid helium is accessible via a top-loading sample tube. The refrigerating capacity of both devices is 2W at 4.5K. The cleaning procedures for the He gas to be condensed into the tanks, and the production of temperatures below 4.2K in the He bath are described.

Forth, Hans-Joachim

1986-12-01

330

Detection of Negative Charge Carriers in Superfluid Helium Droplets: The Metastable Anions He*– and He2*–  

PubMed Central

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

2014-01-01

331

The vacuum UV photoabsorption spectrum of methyl bromide (CH 3Br) and its perdeuterated isotopomer CD 3Br: a Rydberg series analysis  

NASA Astrophysics Data System (ADS)

The vacuum UV photoabsorption spectrum of CH 3Br has been recorded between 6 and 25 eV. A large number of vibronic bands are observed. They were partly ascribed to vibrationless Rydberg transitions. In the high photon energy range of 12-25 eV, very weak diffuse bands are mostly assigned to transitions from the 3a 1, 1e and (2a 1 + 1a 1) to 3s orbitals. In the 6-12 eV photon energy range, numerous weak to strong bands are observed. The sharpness is very variable over the entire spectral region. In a first step, the interpretation of the spectrum and the assignment of the Rydberg transitions is based on the simple Rydberg formula. The observed features are classified in two groups of four series, each converging to one of the two spin-orbit components of the X˜2E state of CH 3Br +. Rydberg series of nsa 1, npa 1, npe, nd and possibly nf characters are observed. The same measurements have been made for the first time on CD 3Br in the 6-12 eV photon energy range. The observed features are classified into the same Rydberg series characterized by nearly the same ? values. Ionization energies for CD 3Br X˜2E at 10.565 eV and X˜2E at 10.902 eV are deduced. In a second step, we fitted the experimental data to an energy expression taking into account both the exchange interaction and the spin-orbit coupling. Already states with n = 6 are found to correspond to Hund's case (c). Constant values of the quantum defects are deduced.

Locht, R.; Leyh, B.; Jochims, H. W.; Baumgärtel, H.

2005-10-01

332

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)

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.

Sharkey, Keeper L.; Bubin, Sergiy; Adamowicz, Ludwik

2014-11-01

333

Many-body Rabi oscillations of Rydberg excitation in small mesoscopic samples  

E-print Network

We investigate the collective aspects of Rydberg excitation in ultracold mesoscopic systems. Strong interactions between Rydberg atoms influence the excitation process and impose correlations between excited atoms. The manifestations of the collective behavior of Rydberg excitation are the many-body Rabi oscillations, spatial correlations between atoms as well as the fluctuations of the number of excited atoms. We study these phenomena in detail by numerically solving the many-body Schr\\"edinger equation.

J. Stanojevic; R. Côté

2008-01-15

334

Spin-orbit corrections of order m{alpha}{sup 6} to the fine structure of the (37,35) state in the {sup 4}He p antiprotonic helium atom  

SciTech Connect

Precise numerical calculation of radiofrequency intervals between hyperfine sublevels of the (37,35) state of the antiprotonic helium-4 atom is presented. Theoretical consideration includes the QED corrections of order m{alpha}{sup 6} to the electron spin-orbit interaction. Only the leading order contribution in the electron-to-antiproton and electron-to-{alpha} particle mass ratios is considered, so the {alpha} particle and antiproton are treated nonrelativistically. The effective Hamiltonian is derived using the formalism of the nonrelativistic quantum electrodynamics.

Korobov, Vladimir I.; Zhong Zhenxiang [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, 430071 Wuhan (China)

2009-10-15

335

Volume 113. number 5 CHEMICAL PHYSICS LETTERS 1 February 1985 VIBKATIONAL STATE SELECTION OF AMMONIA IONS  

E-print Network

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

Zare, Richard N.

336

Helium cooled Flibe blanket  

SciTech Connect

The blanket design uses a pressure vessel to contain the 50 atmosphere helium gas. Helium cools the first wall and blanket internals. The internals consist of a bed of beryllium balls nominally 1 cm diameter in which neutrons are multiplied and later captured, breeding adequate (even excess) amounts of tritium and releasing energy in exothermic nuclear reactions. Tritium is bred in the molten flibe salt which flows slowly (0.1m/sec) in steel tubes. The salt is kept reducing by periodic reacting with beryllium so the tritium will be in the T/sub 2/ form, however with somewhat enhanced corrosion rate the salt could be kept oxidizing in which case the tritium would be in the TF form. To prevent the tritium from permitting too much into the helium stream, a tungsten coating on the inside of the tubes is proposed. Tritium is removed from the salt and helium by processing both. Because the solubility of tritium in Flibe is so low, there will be a strong driving force for tritium permeation and this places a great burden on a high integrity tungsten permeation barrier. The tritium in the helium is prevented from permeating excessively into the steam system by jacketing the steel steam generator tubes with a 1 mm aluminum jacket. Clearly, tritium containment and barrier development are the most important feasibility issues for this design.

Moir, R.

1984-10-01

337

Double electron capture by protons from helium  

Microsoft Academic Search

The double electron capture process for protons passing through helium is studied using the impact parameter method in the atomic state expansion. The effect of the translatory motion of the electrons and the Pauli principle have been incorporated. Permanent address: Department of Physics, Jadavpur University, Calcutta - 32, India.

K. Roy; S. C. Mukherjee; D. P. Sural

1975-01-01

338

Hyperfine structure in hydrogen and helium ion  

Microsoft Academic Search

The hyperfine structure (HFS) intervals of the ground state in a number of neutral atoms and singly charged ions can be measured with a high accuracy. However, theory even in the case of the simplest of them (such as hydrogen isotopes and the helium-3 ion) is essentially af- fected by nuclear structure effects which contribute from 30 to 200 ppm

Savely G. Karshenboima; D. I. Mendeleev

339

Single-Photon Switch Based on Rydberg Blockade  

NASA Astrophysics Data System (ADS)

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.

Baur, Simon; Tiarks, Daniel; Rempe, Gerhard; Dürr, Stephan

2014-02-01

340

Cosmic Helium Production  

NASA Astrophysics Data System (ADS)

K-dwarfs are very long lived, slowly evolving stars, so that their present day helium Y and metal content (metallicity Z) is essentially the same as when they were born. K-dwarfs thus contain a fossil record of the amount of helium and metals which has been produced in successive stellar generations over the lifetime of the Galaxy. We here estimate the amount of helium compared to the amount of metals produced via stellar fusion (? Y/?Z). We use K-dwarfs in the Hipparcos catalogue for which accurate metallicities and luminosities are available. By including recently measured K-dwarfs with super-solar metallicities we are able to obtain a very significant improvement on previous studies. The best fitting value is ?Y/?Z=2.4+/-0.4 at the 68% confidence level. Values as low as 1 or as high as 4 are excluded with more than 99% confidence.

Flynn, Chris

341

Evolution of helium stars  

NASA Technical Reports Server (NTRS)

The evolution of helium stars in the mass range from 4 to 15 solar masses has been followed from the initial helium main sequence to the end of carbon burning in the core, with the use of Carson's (1976) radiative opacities. As compared with earlier work based on smaller opacities, the main-sequence band in the H-R diagram is now both wider and cooler than before. If neutrino losses are neglected in the stellar models, the phase of carbon burning in the core occurs in the red-supergiant region; otherwise, it occurs, as it does in the earlier models with or without neutrino emission, close to the helium main sequence. Observational data for Wolf-Rayet stars and R Coronae Borealis variables are found to lend some support to the present models.

Stothers, R.; Chin, C.-W.

1977-01-01

342

SCREW COMPRESSOR CHARACTERISTICS FOR HELIUM REFRIGERATION SYSTEMS  

SciTech Connect

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. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss

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

2008-03-01

343

Screw Compressor Characteristics for Helium Refrigeration Systems  

NASA Astrophysics Data System (ADS)

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. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss mechanisms, as well as to implement practical solutions.

Ganni, V.; Knudsen, P.; Creel, J.; Arenius, D.; Casagrande, F.; Howell, M.

2008-03-01

344

Superfluidity of helium-3  

NASA Astrophysics Data System (ADS)

This article presents a phenomenological dynamic phase transition theory-modeling and analysis-for liquid helium-3. We derived two new models, for liquid helium-3 with or without applied field, by introducing three wave functions and using a unified dynamical Ginzburg-Landau model. The analysis of these new models leads to predictions of existence of (1) a metastable region, (2) a new phase C in a narrow region, and (3) switch points of transition types on the coexistence curves near two triple points. It is hoped that these predictions will be useful for designing better physical experiments and lead to better understanding of the physical mechanism of superfluidity.

Ma, Tian; Wang, Shouhong

2008-10-01

345

Cavitation in flowing superfluid helium  

NASA Technical Reports Server (NTRS)

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 .

Daney, D. E.

1988-01-01

346

Dissipative Preparation of Spatial Order in Rydberg-Dressed Bose-Einstein Condensates  

E-print Network

We propose a technique for engineering momentum-dependent dissipation in Bose-Einstein condensates with non-local interactions. The scheme relies on the use of momentum-dependent dark-states in close analogy to velocity-selective coherent population trapping. During the short-time dissipative dynamics, the system is driven into a particular finite-momentum phonon mode, which in real space corresponds to an ordered structure with non-local density-density correlations. Dissipation-induced ordering can be observed and studied in present-day experiments using cold atoms with dipole-dipole or off-resonant Rydberg interactions. Due to its dissipative nature, the ordering does not require artificial breaking of translational symmetry by an opticallattice or harmonic trap. This opens up a perspective of direct cooling of quantum gases into strongly-interacting phases.

Johannes Otterbach; Mikhail Lemeshko

2014-06-07

347

Simulations using echo sequences to observe coherence in a cold Rydberg gas  

NASA Astrophysics Data System (ADS)

We simulate the effect of special excitation pulses on a cold gas of atoms. First a rotary echo sequence is used to examine the coherent nature of a frozen Rydberg gas. If collective excitation and de-excitation is present with little or no source of dephasing, after these pulses the system should be returned to a state with few excitations, and a strong echo signal should occur. We investigate systems that should display a perfect echo and systems where the interaction between atoms reduces the echo signal. A spin echo sequence is also used on a system of coherent hopping excitations, and we simulate how the strength of a spin echo signal is affected by thermal motion.

Hernández, Jesús V.; Robicheaux, Francis

2009-05-01

348

Simulations using echo sequences to observe coherence in a cold Rydberg gas  

NASA Astrophysics Data System (ADS)

We simulate the effect of special excitation pulses on a cold gas of atoms. First, a rotary echo sequence is used to examine the coherent nature of a frozen Rydberg gas. If collective excitation and de-excitation is present with little or no source of dephasing, after these pulses the system should be returned to a state with few excitations, and a strong echo signal should occur. We investigate systems that should display a perfect echo and systems where the interaction between atoms reduces the echo signal. A spin echo sequence is also used on a system of coherent hopping excitations, and we simulate how the strength of a spin echo signal is affected by thermal motion.

Hernández, J. V.; Robicheaux, F.

2008-10-01

349

Helium Neon Laser  

NSDL National Science Digital Library

This resource, part of the Spectroscopy Lab Suite, illustrates the physics of a Helium-Neon Laser. Students can create energy levels for both the He and Ne atoms. The basic processes for light emission, including collisions and level transitions, are shown. The atomic energy levels and the pumping energy can be adjusted to achieve an output spectrum similar to the measured physical spectrum.

Zollman, Dean

350

Helium in the Martian atmosphere - Thermal loss considerations  

NASA Technical Reports Server (NTRS)

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.

Levine, J. S.; Keating, G. M.; Prior, E. J.

1974-01-01

351

Stark-assisted population control of coherent CS(2) 4f and 5p Rydberg wave packets studied by femtosecond time-resolved photoelectron spectroscopy.  

PubMed

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

Knappenberger, Kenneth L; Lerch, Eliza-Beth W; Wen, Patrick; Leone, Stephen R

2007-09-28

352

ccsd00002314, Coherence-preserving trap architecture for long-term control of giant Rydberg atoms  

E-print Network

of giant Rydberg atoms P. Hya#12;l, 1 J. Mozley, 1 A. Perrin, 1 J. Tailleur, 1 G. Nogues, 1 M. Brune, 1 J a single Rydberg atom, make it long-lived and preserve an internal coherence over time scales reaching of the atomic energies using an external microwave #12;eld. We thoroughly identify and account for many causes

353

Rydberg dressing evolution via Rabi frequency control in thermal atomic vapors.  

PubMed

We report for the first time the theoretical and experimental research on Rydberg electromagnetically induced transparency and second-order fluorescence dressing evolution by Rabi frequency control in thermal atomic vapors, in which the controlled results are well explained by the dressing effect and the Rydberg excitation blockade. Based on the certification of the Rydberg excitation blockade fraction through the dependence on principle quantum number n, we obtain dressing evolution curves, consisting of single-dressing and double-dressing in local and nonlocal blockade samples by scanning the probe and dressing fields. In addition, the competition between the Rydberg dressing second-order fluorescence and fourth-order fluorescence is first investigated. A corresponding theory is presented, which is consistent with the experimental results. Such blockade evolution regularity has potential applications in quantum control, and the Rydberg dressing may be useful for investigating multiple-body interactions, as well as for inducing short range interactions in Bose-Einstein condensates. PMID:25078686

Che, Junling; Zheng, Huaibin; Zhang, Zhaoyang; Yao, Xin; Li, Cheng; Wu, Zhenkun; Zhang, Yanpeng

2014-09-21

354

X-ray diffraction assisted spectroscopy of Rydberg states  

SciTech Connect

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.

Kirrander, Adam [ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States)

2012-10-21

355

Stark broadening of lines from transition between states n = 3 to n = 2 in neutral helium. An experimental and computer-simulation study  

NASA Astrophysics Data System (ADS)

Context. The Stark broadening of the spectral lines of the wavelengths 501.6, 667.8, 728.1, 388.9, 587.6, and 706.5 nm from neutral helium in plasmas are studied theoretically and experimentally. Aims: The aim of this work is to provide information about the connection between the shape and width of spectral lines and the electron density and temperature to be used as a diagnostic tool. Methods: The theoretical calculations were carried out through molecular dynamics computer simulations with noninteracting particles. The experimental measurements were done in a plasma of pure helium generated in an electromagnetically driven T-tube. The plasma diagnostics used previous results about the Stark broadening of the He I 447.1 nm and He I 492.2 nm lines and the coherence between the shape of these spectra and those obtained here. The electron temperature was obtained through a Boltzmann-plot of eight lines of Si II. Results: Several tables of width and shift are provided in a wide range of electron density and temperature. Furthermore, we supply several fitting formulas, which allow calculating the plasma electron density from the measured values of the spectral line widths. The results obtained in the laboratory and in the simulations are compared with the data from the literature. Tables of FWHM and shifts are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A135

Gigosos, M. A.; Djurovi?, S.; Savi?, I.; González-Herrero, D.; Mijatovi?, Z.; Kobilarov, R.

2014-01-01

356

Education in Helium Refrigeration  

SciTech Connect

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.

Gistau Baguer, G. M. [38330, Biviers (France)

2004-06-23

357

Millimeter Wave Spectroscopy of cold Rb Rydberg atoms  

NASA Astrophysics Data System (ADS)

By using the cold ^85Rb Rydberg atoms in a magneto optical trap, we have measured the single photon ^85Rb nd-(n-2)f millimeter wave transitions for 32<=n<=39. The measurements were carried out at densities of 10^9 atoms/cm-3, roughly five orders of magnitude lower than those used in optical measurements. Since the 10 G/cm gradient of the trap magnetic field would result in 5 MHz wide resonances, we switched off the field during the measurements. The observed narrow resonances will be used to improve the accuracy of the f quantum defect of ^85Rb.

Han, Jianing; Jamil, Yasir; Tanner, Paul; Norum, Don; Gallagher, T. F.

2006-05-01

358

Interacting Fibonacci anyons in a Rydberg gas  

E-print Network

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 $\

Igor Lesanovsky; Hosho Katsura

2012-04-04

359

Interacting Fibonacci anyons in a Rydberg gas  

E-print Network

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 $\

Lesanovsky, Igor

2012-01-01

360

NUCLEAR CONDENSATE AND HELIUM WHITE DWARFS  

SciTech Connect

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.

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

361

Oxidation characteristics of the electron beam surface-treated Alloy 617 in high temperature helium environments  

NASA Astrophysics Data System (ADS)

The oxidation characteristics of the electron beam surface-treated Alloy 617, which has an Al-rich surface layer, were evaluated in high temperature helium environments. Isothermal oxidation tests were performed in helium (99.999% purity) and VHTR-helium (helium of prototypical VHTR chemistry containing impurities like CO, CO2, CH4, and H2) environments at 900 °C for up to 1000 h. The surface-treated Alloy 617 showed an initial transient oxidation stage followed by the steady-state oxidation in all test environments. In addition, the steady-state oxidation kinetics of the surface-treated Alloy 617 was 2-order of magnitude lower than that of the as-received Alloy 617 in both helium environments as well as in air. The improvement in oxidation resistance was primarily due to the formation of the protective Al2O3 layer on the surface. The weight gain was larger in the order of air, helium, and VHTR-helium, while the parabolic rate constants (kp) at steady-state were similar for all test environments. In both helium environments, the oxide structure consisted of the outer transition Al2O3 with a small amount of Cr2O3 and inner columnar structured Al2O3 without an internal oxide. In the VHTR-helium environment, where the impurities were added to helium, the initial transient oxidation increased but the steady state kinetics was not affected.

Lee, Ho Jung; Sah, Injin; Kim, Donghoon; Kim, Hyunmyung; Jang, Changheui

2015-01-01

362

Helium in near Earth orbit  

Microsoft Academic Search

The helium spectrum from 0.1 to 100 GeV\\/nucleon was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380 km. Above the geomagnetic cutoff the spectrum is parameterized by a power law. Below the geomagnetic cutoff a second helium spectrum was observed. In the second helium spectra over the energy range 0.1 to 1.2 GeV\\/nucleon the flux

J. Alcaraz; B. Alpat; G. Ambrosi; H. Anderhub; L. Ao; A. Arefiev; P. Azzarello; E. Babucci; L. Baldini; M. Basile; D. Barancourt; F. Barao; G. Barbier; G. Barreira; R. Battiston; U. Becker; L. Bellagamba; P. Béné; J. Berdugo; P. Berges; B. Bertucci; A. Biland; S. Bizzaglia; G. Boella; M. Boschini; L. Brocco; G. Bruni; M. Buenerd; J. D. Burger; W. J. Burger; X. D. Cai; C. Camps; P. Cannarsa; M. Capell; D. Casadei; J. Casaus; G. Castellini; C. Cecchi; Y. H. Chang; Y. H. Chang; H. S. Chen; Z. G. Chen; N. A. Chernoplekov; T. H. Chiueh; Y. L. Chuang; F. Cindolo; V. Commichau; A. Contin; M. Cristinziani; J. P. da Cunha; T. S. Dai; J. D. Deus; N. Dinu; L. Djambazov; I. D'Antone; Z. R. Dong; P. Emonet; J. Engelberg; F. J. Eppling; T. Eronen; G. Esposito; P. Extermann; J. Favier; E. Fiandrini; P. H. Fisher; G. Fluegge; N. Fouque; Yu. Galaktionov; M. Gervasi; P. Giusti; D. Grandi; O. Grimm; W. Q. Gu; K. Hangarter; A. Hasan; V. Hermel; H. Hofer; M. A. Huang; W. Hungerford; M. Ionica; R. Ionica; M. Jongmanns; K. Karlamaa; W. Karpinski; G. Kenney; J. Kenny; W. Kim; A. Klimentov; R. Kossakowski; V. Koutsenko; M. Kraeber; G. Laborie; T. Laitinen; G. Lamanna; G. Laurenti; A. Lebedev; S. C. Lee; G. Levi; P. Levtchenko; C. L. Liu; H. T. Liu; I. Lopes; G. Lu; Y. S. Lu; K. Lübelsmeyer; D. Luckey; W. Lustermann; C. Maña; A. Margotti; F. Mayet; R. R. McNeil; B. Meillon; M. Menichelli; A. Mihul; A. Mourao; A. Mujunen; F. Palmonari; A. Papi; I. H. Park; M. Pauluzzi; F. Pauss; E. Perrin; A. Pesci; A. Pevsner; M. Pimenta; V. Plyaskin; V. Pojidaev; M. Pohl; V. Postolache; N. Produit; P. G. Rancoita; D. Rapin; F. Raupach; D. Ren; Z. Ren; M. Ribordy; J. P. Richeux; E. Riihonen; J. Ritakari; U. Roeser; C. Roissin; R. Sagdeev; G. Sartorelli; G. Schwering; G. Schwering; E. S. Seo; V. Shoutko; E. Shoumilov; R. Siedling; D. Son; T. Song; M. Steuer; G. S. Sun; H. Suter; X. W. Tang; Samuel C. C. Ting; S. M. Ting; M. Tornikoski; J. Torsti; J. Trümper; J. Ulbricht; S. Urpo; I. Usoskin; E. Valtonen; J. Vandenhirtz; F. Velcea; E. Velikhov; B. Verlaat; I. Vetlitsky; F. Vezzu; J. P. Vialle; G. Viertel; D. Vité; H. Von Gunten; S. Waldmeier Wicki; W. Wallraff; B. C. Wang; J. Z. Wang; Y. H. Wang; K. Wiik; C. Williams; S. X. Wu; P. C. Xia; J. L. Yan; J. L. Yan; C. G. Yang; M. Yang; S. W. Ye; P. Yeh; Z. Z. Xu; H. Y. Zhang; Z. P. Zhang; D. X. Zhao; G. Y. Zhu; W. Z. Zhu; H. L. Zhuang; A. Zichichi; B. Zimmermann; P. Zuccon

2000-01-01

363

Three-body exchange interaction in dense helium  

Microsoft Academic Search

Self-consistent phonon and Monte Carlo calculations show that the three-body exchange interaction is important to dense helium. Together with a realistic pair potential and the Axilrod-Teller three-body dispersion interaction, it brings calculations into agreement with the experimental equation of state. This interaction stabilizes the hcp structure for pressures greater than about 60 GPa. A speculative phase diagram of high-pressure helium

P. Loubeyre

1987-01-01

364

Helium jet dispersion to atmosphere  

NASA Technical Reports Server (NTRS)

On the event of loss of vacuum guard of superinsulated helium dewar, high rate of heat transfer into the tank occurs. The rapid boiling of liquid helium causes the burst disk to rupture at four atmospheres and consequently the helium passes to the atmosphere through vent lines. The gaseous helium forms a vertical buoyant jet as it exits the vent line into a stagnant environment. Characterization of the gaseous jet is achieved by detailed analysis of the axial and radial dependence of the flow parameters.

Khan, Hasna J.

1986-01-01

365

Helium cryopumping for fusion applications  

SciTech Connect

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.

Sedgley, D.W.; Batzer, T.H.; Call, W.R.

1988-05-01

366

Accurate Determination of the Scattering Length of Metastable Helium Atoms Using Dark Resonances between Atoms and Exotic Molecules  

E-print Network

a new measurement of the s-wave scattering length a of spin-polarized helium atoms in the 2 3S1Accurate Determination of the Scattering Length of Metastable Helium Atoms Using Dark Resonances helium atoms in the 2 3 S1 state [1,2], several esti- mates for their s-wave scattering length a were

Cohen-Tannoudj, Claude

367

hal-00120114,version2-23Feb2007 Lifetime of weakly-bound dimers of ultracold metastable helium studied by  

E-print Network

between two 23 S1 spin polarized helium atoms. This inhibition has a limit set by spin relaxation pro- sociation, our group studied exotic molecules in which two spin-polarized metastable helium atoms are bound between two spin-polarized 23 S1 helium atoms, v = 14 being the least- bound vibrational state

Paris-Sud XI, Université de

368

LETTERS TO THE EDITOR Structure and photoluminescence of helium-intercalated fullerite C60  

E-print Network

. The presence of helium in lattice voids is shown to reduce that part of the luminescent intensity which is due excited states and symmetry forbidden transitions between these states and the ground state

369

Medium and high resolution vacuum UV photoabsorption spectroscopy of methyl iodide (CH 3I) and its deuterated isotopomers CD 3I and CH 2DI. A Rydberg series analysis  

NASA Astrophysics Data System (ADS)

The vacuum UV photoabsorption spectrum of CH 3I has been investigated between 5 eV and 20 eV. Numerous vibronic transitions are observed. In the high 10-20 eV photon energy range weak to very weak diffuse bands are observed and ascribed to electronic transitions from 3a 1, 1e and 2a 1 to Rydberg orbitals. In the 6-10.5 eV photon energy range more than 200 sharp and strong to weak lines have been observed. Several photon energy ranges were explored under high resolution conditions allowing us to observe many series up to high values of the principal quantum number n. They are assigned to vibrationless Rydberg transitions and classified into two groups converging to the two components of the spin-orbit split XE state of CH 3I +. These two groups consist of six different Rydberg series, i.e., nsa 1, npa 1, npe, nda 1, nde and nf. A very close correlation has been established between the term values of the Rydberg states in CH 3I and in Xe for ns, np, nd and nf Rydberg transitions. For the first time, the same measurements have been performed and the interpretation has been proposed for the photoabsorption spectrum of CH 2DI and CD 3I in the 6-10.5 eV photon energy range. For these two species, ionization energies are deduced: for the XE 3/2 and XE 1/2 states of CH 2DI, these are IE ad = 9.544 eV and IE ad = 10.168 eV, respectively, and the corresponding energies are 9.552 eV and 10.173 eV in CD 3I.

Locht, R.; Leyh, B.; Jochims, H. W.; Baumgärtel, H.

2009-11-01

370

Spectroscopy of barium atoms in liquid and solid helium matrices  

SciTech Connect

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.

Lebedev, V.; Moroshkin, P.; Weis, A. [Departement de Physique, Universite de Fribourg, Chemin du Musee 3, CH-1700 Fribourg (Switzerland)

2011-08-15

371

Ionization and dissociation equilibrium in strongly-magnetized helium atmosphere  

E-print Network

Recent observations and theoretical investigations of neutron stars indicate that their atmospheres consist not of hydrogen or iron but possibly other elements such as helium. We calculate the ionization and dissociation equilibrium of helium in the conditions found in the atmospheres of magnetized neutron stars. For the first time this investigation includes the internal degrees of freedom of the helium molecule. We found that at the temperatures and densities of neutron star atmospheres the rotovibrational excitations of helium molecules are populated. Including these excitations increases the expected abundance of molecules by up to two orders of magnitude relative to calculations that ignore the internal states of the molecule; therefore, if the atmospheres of neutron stars indeed consist of helium, helium molecules and possibly polymers will make the bulk of the atmosphere and leave signatures on the observed spectra from neutron stars. We applied our calculation to nearby radio-quiet neutron stars with B_{dipole}~10^{13}-10^{14} G. If helium comprises their atmospheres, our study indicates that isolated neutron stars with T_{BB}~10^6 K such as RXJ0720.4-3125 and RXJ1605.3+3249 will have He^+ ions predominantly, while isolated neutron stars with lower temperature (T_{BB}~5x10^5 K) such as RXJ1856.5-3754 and RXJ0420.0-5022 will have some fraction of helium molecules. If helium molecules are abundant, their spectroscopic signatures may be detected in the optical, UV and X-ray band. (Abridged)

Kaya Mori; Jeremy S. Heyl

2006-10-09

372

Helium dilution refrigeration system  

DOEpatents

A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains .sup.3 He and .sup.4 He liquids which are precooled by a coupled container containing .sup.3 He liquid, enabling the phase separation of a .sup.3 He rich liquid phase from a dilute .sup.3 He-.sup.4 He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the .sup.3 He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute .sup.3 He-.sup.4 He liquid phase.

Roach, Patrick R. (Darien, IL); Gray, Kenneth E. (Naperville, IL)

1988-01-01

373

A helium regenerative compressor  

SciTech Connect

This paper discusses the design and performance of a regenerative compressor that was developed primarily for use in cryogenic helium systems. The objectives for the development were to achieve acceptable efficiency in the machine using conventional motor and bearing technology while reducing the complexity of the system required to control contamination from the lubricants. A single stage compressor was built and tested. The compressor incorporates aerodynamically shaped blades on a 218 mm (8.6 inches) diameter impeller to achieve high efficiency. A gas-buffered non-contact shaft seal is used to oppose the diffusion of lubricant from the motor bearings into the cryogenic circuit. Since it is a rotating machine, the flow is continuous and steady, and the machine is very quiet. During performance testing with helium, the single stage machine has demonstrated a pressure ratio of 1.5 at a flow rate of 12 g/s with measured isothermal efficiencies in excess of 30%. This performance compares favorably with efficiencies generally achieved in oil flooded screw compressors.

Swift, W.L.; Nutt, W.E.; Sixsmith, H. [Creare Incorporated, Hanover, NH (United States)

1994-12-31

374

Level Indicator for Liquid Helium  

Microsoft Academic Search

A capacitor probe was developed for locating the level of liquid helium ; in a Dewar vessel. The problem of the very small difference in dielectric ; constant between liquid and gaseous helium is solved by complete guarding of the ; connecting cables and measuring probe except the capacitor. The capacitance ; meter is set at zero when the capacitor

S. Meiboom; J. P. O'Brien

1963-01-01

375

Absolute high-resolution Se+ photoionization cross-section measurements with Rydberg-series analysis  

NASA Astrophysics Data System (ADS)

Absolute single photoionization cross-section measurements for Se+ ions were performed at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory using the photo-ion merged-beams technique. Measurements were made at a photon energy resolution of 5.5 meV from 17.75 to 21.85 eV spanning the 4s24p3 4S3/2o ground-state ionization threshold and the 2P3/2o,2P1/2o,2D5/2o, and2D3/2o metastable state thresholds. Extensive analysis of the complex resonant structure in this region identified numerous Rydberg series of resonances and obtained the Se2+ 4s24p23P2 and 4s24p21S0 state energies. In addition, particular attention was given to removing significant effects in the measurements due to a small percentage of higher-order undulator radiation.

Esteves, D. A.; Bilodeau, R. C.; Sterling, N. C.; Phaneuf, R. A.; Kilcoyne, A. L. D.; Red, E. C.; Aguilar, A.

2011-07-01

376

Rydberg-Atom Quantum Simulation and Chern Number Characterization of a Topological Mott Insulator  

NASA Astrophysics Data System (ADS)

In this talk we consider a system of spinless fermions with nearest and next-to-nearest neighbor repulsive Hubbard interactions on a honeycomb lattice within the mean-field treatment, and propose and analyze a realistic scheme for analog quantum simulation of this model with cold atoms in a two-dimensional hexagonal optical lattice. Besides a semi-metallic and a charge-density-wave ordered phase, the system exhibits a quantum anomalous Hall phase, which is generated dynamically, i.e. purely as a result of the repulsive fermionic interactions and in the absence of any external gauge fields. We establish the topological nature of this dynamically created Mott insulating phase by the numerical calculation of a Chern number, and study the possibility of coexistence of this phase with the other phases characterized by local order parameters. Based on the knowledge of the mean-field phase diagram, we then discuss in detail how the interacting Hamiltonian can be engineered effective ly by state-of-the-art experimental techniques for laser-dressing of cold fermionic ground-state atoms with electronically excited Rydberg states that exhibit strong dipolar interactions.[4pt] [1] A. Dauphin, M. Mueller, and M. A. Martin-Delgado, arXiv:1207.6373. Submitted to PRA and accepted on Sep 26, 2012.

Dauphin, Alexandre; Mueller, Markus; Martin-Delgado, Miguel-Angel

2013-03-01

377

High-order harmonic generation from Rydberg atoms in inhomogeneous fields.  

PubMed

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

Wang, Zhe; He, Lixin; Luo, Jianghua; Lan, Pengfei; Lu, Peixiang

2014-10-20

378

Interstellar helium in the heliosphere  

NASA Astrophysics Data System (ADS)

Several years of neutral measurements by NASA/IBEX-Lo have yielded detailed observations of direct interstellar neutral helium (primary particles). Prior to IBEX, interstellar helium had been observed through UV backscattering, pickup ions, and directly by Ulysses-GAS. The IBEX measurements now also provide strong indications for the presence of secondary neutral helium that is thought to originate in the outer heliosheath from charge exchange. In order to model both primary and secondary particle populations and characterize them throughout the heliosphere, a detailed calculation method based on Keplerian orbits is used, and some sample results are presented. The helium velocity distribution functions throughout the heliosphere are characterized. In the inner heliosphere they exhibit an intricate structure, in particular downwind of the Sun where the helium focusing cone resides as well.

Müller, Hans-Reinhard; Bzowski, Maciej; Möbius, Eberhard; Zank, Gary P.

2013-06-01

379

Phase separation in hydrogen–helium mixtures at Mbar pressures  

PubMed Central

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

Morales, Miguel A.; Schwegler, Eric; Ceperley, David; Pierleoni, Carlo; Hamel, Sebastien; Caspersen, Kyle

2009-01-01

380

Coincidence measurements between photons, projectiles and recoil ions in low energy Kr18+ + Kr collisions. Auto-ionizing and radiative effect of multi-excited states  

Microsoft Academic Search

We present results of experiments using coincidence methods between visible photons of Rydberg transitions, projectiles and recoil ions arising from the low energy collision of Kr18+ on Kr. For each observed Rydberg transition, we have determined the charge state distributions for both the recoil ions and the projectiles. From these results we have deduced some information on the creation of

S. Martin; A. Denis; Y. Ouerdane; M. Carré

1992-01-01

381

Density functional study of multiplicity-changing valence and Rydberg excitations of p-block elements: Delta self-consistent field, collinear spin-flip time-dependent density functional theory (DFT), and conventional time-dependent DFT  

Microsoft Academic Search

A database containing 17 multiplicity-changing valence and Rydberg excitation energies of p-block elements is used to test the performance of density functional theory (DFT) with approximate density functionals for calculating relative energies of spin states. We consider only systems where both the low-spin and high-spin state are well described by a single Slater determinant, thereby avoiding complications due to broken-symmetry

Ke Yang; Roberto Peverati; Donald G. Truhlar; Rosendo Valero

2011-01-01

382

The interaction of 193 nm excimer laser radiation with single-crystal zinc oxide: generation of long lived highly excited particles with evidence of Zn Rydberg formation  

SciTech Connect

We observe intense Zn ion and atom emissions when single-crystal ZnO is exposed to 193-nm excimer laser radiation at fluences below the threshold for optical breakdown. Zn+ and ground state Zn are readily identified by mass-selected, time-of-flight techniques using a quadrupole mass spectrometer. Particles are also detected with Channeltron electron multipliers that cannot be mass selected. We provide evidence that these particles correspond to high lying Rydberg states of atomic Zn produced by a resonance excitation involving two laser photons.

Kahn, E. H. [Washington State University, Pullman; Langford, S. C. [Washington State University, Pullman; Dickinson, J. T. [Washington State University, Pullman; Boatner, Lynn A [ORNL

2014-01-01

383

LETTER TO THE EDITOR: Asymptotic methods in Rydberg collisions  

NASA Astrophysics Data System (ADS)

Analytic expressions of some physical quantities for Rydberg transitions, like the first Born cross section for the n ? n' transition, are found to contain terminating hypergeometric functions of large arguments which pose certain analytical and numerical problems that are well documented. We describe a simple method based on the use of the Jacobi polynomial to understand analytic properties and deduce an asymptotic expression of a general terminating hypergeometric function. To illustrate the utility, we apply the method to the n ? n' Born cross section, for which situation the Tricomi asymptotic method had been used earlier in the literature. It is found that the Jacobi polynomial method gives strikingly good results for n ? n' transitions over the entire range of the physical momentum transfer, in contrast to the Tricomi asymptotic method which gives unrealistically large results for large momentum transfers.

Dewangan, D. P.

2002-10-01

384

Rydberg-electron decoherence in experimentally obtained recurrence spectra  

SciTech Connect

Using scaled-energy spectroscopy techniques (recurrence spectroscopy) we investigate the influence of collisionally induced decoherence on semiclassical orbits in the Stark-Rydberg system. This experimental investigation represents the first application of recurrence spectroscopy to an atomic system perturbed by collisions with external gas partners. We present high-resolution recurrence spectra of potassium, revealing core-scattered combination orbits, and with minor modifications to the data acquisition process, recurrence spectra were also obtained with the system perturbed by 10 torr of krypton gas. A simple decoherence model is applied to semiclassical theory to explain the loss of recurrence strength at high actions. In several cases we also observe the loss of coherent interference between orbits. The loss of coherent destructive interference causes an increase in the recurrence strength of several core-scattered combination orbits.

Keeler, M. L.; Setzer, W.; Martin, W. W. [Physics Department, University of Minnesota-Morris, Morris, Minnesota 56267 (United States)

2010-11-15

385

Rydberg electron transfer to SF6: Product ion lifetimes  

NASA Astrophysics Data System (ADS)

The lifetimes of SF6- ions produced by Rydberg electron transfer in K(np )/SF6 collisions at high n, n ?30, are examined using a Penning ion trap. The data point to the formation of ions with a range of lifetimes that extends from ˜1to?10ms. Sizable numbers of ions remain in the trap even 40ms after initial injection and at least part of this signal can be attributed to radiative stabilization. Measurements of free low-energy electron attachment to SF6 in the trap show that the product ions have lifetimes similar to those of SF6- ions formed by electron transfer in high-n collisions.

Liu, Y.; Suess, L.; Dunning, F. B.

2005-06-01

386

Time-dependent electron interactions in double Rydberg wave packets.  

PubMed

We investigate the time-dependent evolution of a nonstationary three-body Coulomb system at energies just below the threshold for three-body breakup. Experimentally, short-pulse lasers excite two electrons in Ba to radially localized Rydberg wave packets with well-defined energy and angular momentum. Time-dependent interactions between the two electrons are probed using half-cycle electric field pulses. The measurements indicate that substantial energy exchange between the two electrons is nearly immediate upon the launch of the second wave packet. Fully quantum and classical calculations support this observation, predicting extremely rapid autoionization under the experimental conditions. The calculations also show very fast angular momentum exchange and sensitivity to the relative binding energies of the two electrons. PMID:23383901

Zhang, X; Jones, R R; Robicheaux, F

2013-01-11

387

A photoionization study of OH and OD from 680A to 950A: An analysis of the Rydberg series  

NASA Technical Reports Server (NTRS)

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.

Cutler, J. N.; He, Z. X.; Samson, J. A. R.

1994-01-01

388

ANGULAR MOMENTUM CHANGING TRANSITIONS IN PROTON-RYDBERG HYDROGEN ATOM COLLISIONS  

SciTech Connect

Collisions between electrically charged particles and neutral atoms are central for understanding the dynamics of neutral gases and plasmas in a variety of physical situations of terrestrial and astronomical interest. Specifically, redistribution of angular momentum states within the degenerate shell of highly excited Rydberg atoms occurs efficiently in distant collisions with ions. This process is crucial in establishing the validity of the local thermal equilibrium assumption and may also play a role in determining a precise ionization fraction in primordial recombination. We provide an accurate expression for the non-perturbative rate coefficient of collisions between protons and H(nl) ending in a final state H(nl'), with n being the principal quantum number and l, l' the initial and final angular momentum quantum numbers, respectively. The validity of this result is confirmed by results of classical trajectory Monte Carlo simulations. Previous results, obtained by Pengelly and Seaton only for dipole-allowed transitions l {yields} l {+-} 1, overestimate the l-changing collisional rate coefficients approximately by a factor of six, and the physical origin of this overestimation is discussed.

Vrinceanu, D. [Department of Physics, Texas Southern University, Houston, TX 77004 (United States); Onofrio, R. [Dipartimento di Fisica e Astronomia 'Galileo Galilei', Universita di Padova, 35131 Padova (Italy); Sadeghpour, H. R., E-mail: daniel.vrinceanu@gmail.com, E-mail: onofrior@gmail.com, E-mail: hrsadeghpour@gmail.com [ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

2012-03-01

389

The Zel'dovich effect and evolution of atomic Rydberg spectra along the Periodic Table  

E-print Network

In 1959 Ya. B. Zel'dovich predicted that the bound-state spectrum of the non-relativistic Coulomb problem distorted at small distances by a short-range potential undergoes a peculiar reconstruction whenever this potential alone supports a low-energy scattering resonance. However documented experimental evidence of this effect has been lacking. Previous theoretical studies of this phenomenon were confined to the regime where the range of the short-ranged potential is much smaller than Bohr's radius of the Coulomb field. We go beyond this limitation by restricting ourselves to highly-excited s states. This allows us to demonstrate that along the Periodic Table of elements the Zel'dovich effect manifests itself as systematic periodic variation of the Rydberg spectra with a period proportional to the cubic root of the atomic number. This dependence, which is supported by analysis of experimental and numerical data, has its origin in the binding properties of the ionic core of the atom.

Eugene B. Kolomeisky; Michael Timmins

2005-04-21

390

Mapping of Surface Potentials by Electrons on a Helium Film  

Microsoft Academic Search

A novel way to investigate perturbations of the electrostatic potential across a sample surface is presented, aiming at application in 2D contact phenomena. The idea is to deposit surface state electrons (SSE) on a thin layer of liquid helium covering the surface of a solid state sample. The density of the SSE adjusts to screen perturbations of the electrostatic potential

E. Teske; P. Leiderer; P. Wyder; V. Shikin

1998-01-01

391

Divertor Configurations which Optimize Helium Pumping  

Microsoft Academic Search

Helium accumulation in DT plasmas is often presumed to be one limitation to the fusion power production. The core helium density has an unavoidable central source and a confinement time which tends to be long as is consistent with the required energy confinement times. Any pumping of the helium can only act to reduce the helium recycling. Within that constraint,

James Strachan

2008-01-01

392

Hydrogen Production Using the Modular Helium Reactor  

SciTech Connect

The high-temperature characteristics of the Modular Helium Reactor (MHR) make it a strong candidate for the production of hydrogen using either thermochemical or high-temperature electrolysis (HTE) processes. Using heat from the MHR to drive a Sulfur-Iodine (S-I) thermochemical hydrogen process has been the subject of a DOE sponsored Nuclear Engineering Research Initiative (NERI) project lead by General Atomics, with participation from the Idaho National Engineering and Environmental Laboratory (INEEL) and Texas A&M University. While the focus of much of the initial work was on the S-I thermochemical production of hydrogen, recent activities have also included development of a preconceptual design for an integral HTE hydrogen production plant driven by the process heat and electricity produced by a 600 MWt MHR. This paper describes RELAP5-3D analyses performed to evaluate alternative primary system cooling configurations for the MHR to minimize peak reactor vessel and core temperatures while achieving core helium outlet temperatures in the range of 900 oC to 1000 oC, needed for the efficient production of hydrogen using either the S-I thermochemical or HTE process. The cooling schemes investigated are intended to ensure peak fuel temperatures do not exceed specified limits under normal or transient upset conditions, and that reactor vessel temperatures do not exceed ASME code limits for steady-state or transient conditions using standard LWR vessel materials. Preconceptual designs for both an S-I thermochemical and HTE hydrogen production plant driven by a 600 MWt MHR at helium outlet temperatures in the range of 900 oC to 1000 oC are described and compared. An initial SAPHIRE model to evaluate the reliability, maintainablility, and availability of the S-I hydrogen production plant is also discussed, and plans for future assessments of conceptual designs for both a S-I thermochemical and HTE hydrogen production plant coupled to a 600 MWt modular helium reactor are described.

E. A. Harvego; S. M. Reza; M. Richards; A. Shenoy

2005-05-01

393

An atomistic assessment of helium behavior in iron  

NASA Astrophysics Data System (ADS)

High helium generation rates in irradiated materials leads to the formation of small He-vacancy clusters that can evolve into larger bubbles and voids. An equation of state that accurately reproduces their pressure-volume relationship is necessary to understand and predict the behaviour of these He-vacancy defects. Previous research has employed equations of state of varying complexity, including the ideal gas, van der Waals, and hard sphere models. We recently used ab initio calculations to determine the energetics of helium-vacancy clusters and applied the results to develop a new three-body interatomic potential that describes the behaviour of helium in iron. This potential was employed in molecular dynamics simulations to determine the conditions for mechanical equilibrium between small helium-stabilized bubbles and an iron matrix, and to systematically map the pressure-volume relationship for the bubbles at a range of temperatures. These atomistic results are compared to an existing equation of state and a modification is proposed for bubbles with high helium densities.

Stoller, R. E.; Osetsky, Yu. N.

2014-12-01

394

Improved Helium-Barrier Bag  

NASA Technical Reports Server (NTRS)

Specially designed bag maintains helium atmosphere around large, low-temperature duct. Easy to install, durable, and reusable. Intended to prevent cryopumping occurring if air or nitrogen allowed to make contact with cold surface of duct.

Viger, Brent J.; Logan, Robert F.; Fink, Jeffrey E.

1992-01-01

395

The effects of helium on hydrogen isotope retention in Hastelloy-N  

NASA Astrophysics Data System (ADS)

Thermal desorption spectrometry was used to investigate the temperature range of hydrogen isotope retention in a Hastelloy-N type alloy that had previously been implanted with helium. Helium implanted in the dose range from 1 × 10 16 to 1.2 × 10 17 He/cm 2 provided additional traps for retention of hydrogen, with the hydrogen release temperature increasing as the implanted helium dose increased. The step character of the release and retention processes bears witness to the presence of two-phase states in the Hastelloy-helium system.

Neklyudov, I. M.; Morozov, O. M.; Kulish, V. G.; Azhazha, V. M.; Lavrinenko, S. D.; Zhurba, V. I.

2011-10-01

396

Energetic ionized helium in the quiet time radiation belts - Theory and comparison with observation  

NASA Technical Reports Server (NTRS)

Theoretical calculations of helium ion distributions in the inner magnetosphere are compared to observations made by ATS-6 and Explorer-45. Coupled transport equations for equatorially mirroring singly and doubly ionized helium ions in the steady state limit with an outer boundary of L = 7 are solved. Radial profiles and energy spectra are computed at all lower L values. Theoretical quiet time predictions are compared to satellite observations of energetic helium ions in the lower MeV range. It is found that the theory adequately represents the principal characteristics of the radiation belt helium ion population.

Spjeldvik, W. N.; Fritz, T. A.

1978-01-01

397

Laser Induced Fluorescence Spectroscopy of the Ca Dimer Deposited on Helium and Mixed Helium/Argon Clusters  

SciTech Connect

We study the laser induced fluorescence spectroscopy of the calcium dimer deposited on helium and mixed helium/argon clusters. In the wavelength range between 365 and 385 nm, the Ca dimer is excited from its ground state up to two excited electronic states leading to its photodissociation in Ca({sup 1}P)+Ca({sup 1}S): this process is monitored by recording the Ca({sup 1}P) fluorescence about 422.7 nm. These electronic excited states of Ca{sub 2} are respectively a diexcited one correlating to the Ca(4s 4p {sup 3}P)+Ca(4s 3d {sup 3}D) and a repulsive one correlating diabatically to the Ca(4s 4p {sup 1}P)+Ca(4s{sup 2} {sup 1}S) asymptote, accounting for the dissociation of Ca{sub 2} and the observation of the subsequent Ca({sup 1}P) emission. On pure helium clusters, the fluorescence consists of the calcium atomic resonance line Ca({sup 1}S(leftarrow){sup 1}P) at 422.7 nm (23652 cm{sup -1}) assigned to ejected calcium, and a narrow red sided band corresponding to calcium that remains solvated on the helium cluster. Interestingly, the branching ratio to the ejection of Ca({sup 1}P) increases along with the wavelength of the excitation photon, i.e. when its energy decreases. This is contrary to what is intuitively expected and to what is really found on pure argon clusters. On mixed helium/argon clusters, a new spectral band appears on the red side of the calcium resonance line; the intensity and the red shift of this component increase along with the argon quantity deposited on the helium cluster: it is assigned to the emission of Ca({sup 1}P) associated with the small argon aggregate embedded inside the helium cluster.

Masson, A.; Briant, M.; Mestdagh, J. M.; Gaveau, M. A. [Laboratoire Francis Perrin, CNRS URA 2453, DSM/IRAMIS/SPAM, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France)

2011-05-20

398

Lifetime of metastable helium molecule in intense laser fields  

NASA Astrophysics Data System (ADS)

On the basis of the Floquet formalism linked with the McCurdy-McNutt stabilization technique, metastable states of helium dimer in intense laser fields were investigated. The potential energy curve of helium dimer is found to become attractive when the laser intensity is sufficiently high, and the previous prediction [T. Yasuike and K. Someda, J. Phys. B 37, 3149 (2004)] based on the Kramers-Henneberger high-frequency approximation is confirmed. Under appropriate laser conditions, the lifetime is found to be sufficiently long to discretize vibrational states, owing to the nonperturbative stabilization effect in photoionization.

Yasuike, Tomokazu; Someda, Kiyohiko

2008-07-01

399

Ab Initio simulations of dense helium plasmas.  

PubMed

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

Wang, Cong; He, Xian-Tu; Zhang, Ping

2011-04-01

400

High resolution multiphoton ionization and dissociation of acetone via 3sleftarrow n Rydberg transitions  

NASA Astrophysics Data System (ADS)

Measurements of multiphoton ionization and dissociation of acetone are reported in the wavelength range 582.60-585.80 nm at photon energy resolution of 0.3 cm-1. To our knowledge there are not available results of (3 + 2) REMPI on acetone at 0.01 nm in this region. The experiments were performed using an Nd: YAG-OPO (optical parametric oscillator) laser system coupled to time-of-flight mass spectrometer. The ion yield and the single ion channel are presented. The high-resolution three-photon resonance multiphoton spectrum of the acetone 3sleftarrow n Rydberg transition is also reported. The experimental results show three dissociation channels of the acetone ion, leading to the products: (CH3CO + ), (CH3 + ) and (COH + ); the channel CH3COCH 3^{ + } to CH 3CO + + CH3 being the most favored. The acetone and acetyl ions are observed in all wavelength range investigated. In addition, we have measured the origin of the 3sleftarrow n and 4sleftarrow n transitions, and vibrational bands of the 3 s state.

Mejía-Ospino, E.; García, G.; Guerrero, A.; Álvarez, I.; Cisneros, C.

2004-07-01

401

Performance of recent and high-performance approximate density functionals for time-dependent density functional theory calculations of valence and Rydberg electronic transition energies  

NASA Astrophysics Data System (ADS)

We report a test of 30 density functionals, including several recent ones, for their predictions of 69 singlet-to-singlet excitation energies of 11 molecules. The reference values are experimental results collected by Caricato et al. for 30 valence excitations and 39 Rydberg excitations. All calculations employ time-dependent density functional theory in the adiabatic, linear-response approximation. As far as reasonable, all of the assignments are performed by essentially the same protocol as used by Caricato et al., and this allows us to merge our mean unsigned errors (MUEs) with the ones they calculated for both density functional and wave function methods. We find 21 of the 30 density functionals calculated here have smaller MUEs for the 30 valence states than what they obtained (0.47 eV) for the state-of-the-art EOM-CCSD wave function. In contrast, for all of density functionals the MUE for 39 Rydberg states is larger than that (0.11 eV) of EOM-CCSD. Merging the 30 density functionals calculated here with the 26 calculated by Caricato et al. makes a set of 56 density functionals. Averaging the unsigned errors over both the valence excitations and the Rydberg excitations, none of the 56 density functionals shows a lower mean unsigned error than that (0.27 eV) of EOM-CCSD. Nevertheless, two functionals are successful in having an overall mean unsigned error of 0.30 eV, and another nine are moderately successful in having overall mean unsigned errors in the range 0.32-0.36 eV. Successful or moderately successful density functionals include seven hybrid density functionals with 41% to 54% Hartree-Fock exchange, and four range-separated hybrid density functionals in which the percentage of Hartree-Fock exchange increases from 0% to 19% at small interelectronic separation to 65%-100% at long range.

Isegawa, Miho; Peverati, Roberto; Truhlar, Donald G.

2012-12-01

402

Cryogenic filter method produces super-pure helium and helium isotopes  

NASA Technical Reports Server (NTRS)

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.

Hildebrandt, A. F.

1964-01-01

403

Signal and charge transfer efficiency of few electrons clocked on microscopic superfluid helium channels  

Microsoft Academic Search

Electrons floating on the surface of liquid helium are possible spin qubits for quantum information processing. Varying electric potentials are not expected to modify spin states, which allows their transport on helium using a charge-coupled device (CCD)-like array of underlying gates. This approach depends upon efficient intergate transfer of individual electrons. Measurements are presented here of the charge transfer efficiency

G. Sabouret; F. R. Bradbury; S. Shankar; J. A. Bert; S. A. Lyon

2008-01-01

404

Circuit Quantum Electrodynamics with Electrons on Helium D. I. Schuster,1  

E-print Network

Circuit Quantum Electrodynamics with Electrons on Helium D. I. Schuster,1 A. Fragner,1 M. I. Dykman cavity to the lateral-motion and spin state of a single electron trapped on the surface of superfluid helium. We estimate the motional coherence times to exceed 15 µs, while energy will be coherently

405

Two-photon microwave transitions and strong-field effects in a room-temperature Rydberg-atom gas  

NASA Astrophysics Data System (ADS)

We investigate two-photon Autler-Townes splitting and strong-field effects of 85Rb Rydberg atoms in a room-temperature vapor cell. To observe the level structure we employ electromagnetically induced transparency. We first study the two-photon 62 S1 /2-63 S1 /2 microwave transition using an electric-field reference measurement obtained with the one-photon 62 S1 /2-62 P3 /2 transition. We then study the 61 D5 /2-62 D5 /2 transition where the microwave electric-field range is extended up to ˜40 V /m . A Floquet analysis is used to model field-induced level shifts and state-mixing effects present in the strongly driven quantum systems under consideration. Calculations are found to be in good agreement with experimental observations.

Anderson, D. A.; Schwarzkopf, A.; Miller, S. A.; Thaicharoen, N.; Raithel, G.; Gordon, J. A.; Holloway, C. L.

2014-10-01

406

Stepwise contraction of the nf Rydberg shells in the 3d photoionization of multiply-charged xenon ions  

E-print Network

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 $\\epsilon$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 analyzed by relativistic atomic-structure calculations.

Schippers, S; Buhr, T; Hellhund, J; Holste, K; Kilcoyne, A L D; Klumpp, S; Martins, M; Müller, A; Ricz, S; Fritzsche, S

2014-01-01

407

C{sup 6+}-impact ionization of helium in the perpendicular plane: Ionization to the ground state, excitation-ionization, and relativistic effects  

SciTech Connect

In search of the discrepancy between theory and experiment in perpendicular plane geometry for C{sup 6+} ionization of He at 100 MeV/amu, we have used the first and second Born approximations to examine whether ionization to an excited He{sup +} state could be significant, whether relativistic effects could be important, and whether there is substantive sensitivity to the He wave functions used in the calculations. We fail to find any explanation of the discrepancy. Of the three possibilities, only relativistic effects turn out to be significant but then only in changing the overall normalization of the cross section, not in changing its shape, which is a prerequisite to getting agreement with experiment. The second Born calculations are in excellent accord with previous impact parameter coupled pseudostate results [Phys. Rev. A 81, 042704 (2010)] and confirm, yet again, that elastic scattering of the projectile by the target nucleus cannot explain the discrepancy. The calculations are extended to the lower impact energy of 2 MeV/amu. Here, in perpendicular plane geometry, ionization to excited He{sup +} states becomes significant and we find an interesting ''oscillatory'' structure in both the ground- and excited-state cross sections. Comparison is made with some relative experimental data and, although the agreement is poor, possibly because of the need to include experimental resolutions, there are nuances in the data that mirror the structures in the calculations.

McGovern, M.; Walters, H. R. J. [Department of Applied Mathematics and Theoretical Physics, Queen's University, Belfast BT7 1NN (United Kingdom); Whelan, Colm T. [Department of Physics, Old Dominion University, Norfolk, Virginia 23529-0116 (United States)

2010-09-15

408

Dipole and quadrupole transition strengths in Ba{sup +} from measurements of K splittings in high-L barium Rydberg levels  

SciTech Connect

Measurements of K splittings in high-L Rydberg states of barium are used to deduce electric-dipole and electric-quadrupole matrix elements in Ba{sup +}. The model used to interpret these splittings is extended here to include the contributions of third- and fourth-order perturbation terms, altering the conclusions of a previous report that omitted those contributions. The analysis leads to improved experimental determinations of dipole (6s-6p) and quadrupole (6s-5d) transition strengths in Ba{sup +} that are in good agreement with recent a priori calculations.

Woods, Shannon L.; Lundeen, S. R.; Snow, Erica L. [Colorado State University, Fort Collins, Colorado 80523 (United States); SUNY Fredonia, Fredonia, New York 14063 (United States)

2009-10-15

409

Helium atom in an external electric field: Exact diagonalization  

NASA Astrophysics Data System (ADS)

An exact diagonalization method is applied to solve the quantum-mechanical problem of spinless helium atom in an external electric field of arbitrary magnitude. The basis set for two-electron problem is built from different pair combinations ?nalama(?ra)?nblbmb(?rb) of orthonormalized single-particle hydrogen-like wave functions ?nml(r) belonging to any possibly bound states of the individual a- and b-electrons in the Coulomb central field renormalized by the scale parameter ? > 0. Within the selected basis the matrix elements of the total Hamiltonian allows an exact analytical representation in the form of finite numerical sums. The diagonalization procedure is performed by Jacobi algorithm for N × N square Hermitian matrix built on the basis of dimension N = 25. The systematics and the numerical values of the low-lying energy levels at zero field are in good agreement with known experimental data. The field dependences of low-lying levels (Stark effect) and polarizability in the ground state of helium atom are presented. It is shown that even extremely high external fields lead only to shifting or splitting of existing low levels, without disturbance of their systematics. Typically, no new low-energy excitation can be created under external electric field of moderate intensity. Radical reconstruction in spectrum of individual helium atoms can be expected in condensed helium phases where each atom is deeply affected by interaction fields from neighbors. This result should be taken into account at interpretation of electrodynamic experiments on superfluid helium.

Antsygina, T. N.; Chishko, K. A.

2014-09-01

410

PHYSICAL REVIEW A 81, 063411 (2010) Spatially resolved excitation of Rydberg atoms and surface effects on an atom chip  

E-print Network

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

Amsterdam, Universiteit van

411

1426 J. Opt. Soc. Am. B/Vol. 4, No. 9/September 1987 Bell's inequalities for Rydberg atoms  

E-print Network

1426 J. Opt. Soc. Am. B/Vol. 4, No. 9/September 1987 Bell's inequalities for Rydberg atoms Brian J February 13, 1987; accepted May 7, 1987 The analogy between two-level atoms and spins is used to show that Rydberg atoms provide a new medium through whichBell's inequalities may be studied. The low

Stroud Jr., Carlos R.

412

Helium Diffusion in Olivine  

NASA Astrophysics Data System (ADS)

Diffusion of helium has been characterized in natural Fe-bearing olivine (~Fo90) and synthetic forsterite. Polished, oriented slabs of olivine were implanted with 3He, at 100 keV at a dose of 5x1015/cm2 or at 3.0 MeV at a dose of 1x1016/cm2. A set of experiments on the implanted olivine were run in 1-atm furnaces. In addition to the one-atm experiments, experiments on implanted samples were also run at higher pressures (2.6 and 2.7 GPa) to assess the potential effects of pressure on He diffusion and the applicability of the measured diffusivities in describing He transport in the mantle. The high-pressure experiments were conducted in a piston-cylinder apparatus using an "ultra-soft" pressure cell, with the diffusion sample directly surrounded by AgCl. 3He distributions following experiments were measured with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. This direct profiling method permits us to evaluate anisotropy of diffusion, which cannot be easily assessed using bulk-release methods. For diffusion in forsterite parallel to c we obtain the following Arrhenius relation over the temperatures 250-950°C: D = 3.91x10-6exp(-159 ± 4 kJ mol-1/RT) m2/sec. The data define a single Arrhenius line spanning more than 7 orders of magnitude in D and 700°C in temperature. Diffusion parallel to a appears slightly slower, yielding an activation energy for diffusion of 135 kJ/mol and a pre-exponential factor of 3.73x10-8 m2/sec. Diffusion parallel to b is slower than diffusion parallel to a (by about two-thirds of a log unit); for this orientation an activation energy of 138 kJ/mol and a pre-exponential factor of 1.34x10-8 m2/sec are obtained. This anisotropy is broadly consistent with observations for diffusion of Ni and Fe-Mg in olivine. Diffusion in Fe-bearing olivine (transport parallel to b) agrees within uncertainty with findings for He diffusion in forsterite. The higher-pressure experiments yield diffusivities in agreement with those from the 1-atm experiments, indicating that the results reported here can be reasonably applied to modeling He transport in the upper mantle. The insensitivity of He diffusion to pressure over the investigated range of conditions suggests that compression of the mineral lattice is not sufficient to significantly influence migration of the relatively small helium atoms, which likely diffuse via crystal interstices. The He diffusivities in this work are generally consistent with results from the study of Futagami et al. (1993), who measured He diffusion in natural olivine by outgassing 4He implanted samples, and with the diffusivities measured by bulk-release of 4He and 3He by Shuster et al. (2003), but are about 2 orders of magnitude slower than the recent findings of Tolstikhin et al. (2010) and Blard et al. (2008) . An up-temperature extrapolation of our data also show reasonable agreement with the higher-temperature measurements of Hart (1984). Blard et al. (2008) GCA 72, 3788-3803; Futagami et al. (1993) GCA 57, 3177-3194; Hart (1984) EPSL 70, 297-302; Shuster et al.( 2003) EPSL 217, 19-32; Tolstikhin et al. (2010) GCA 74, 1436-1447

Cherniak, D. J.; Watson, E. B.

2011-12-01

413

The electronic states of isothiazole studied by VUV absorption spectroscopy and ab initio configuration interaction methods  

NASA Astrophysics Data System (ADS)

The isothiazole VUV absorption spectrum over the range 5-12 eV shows (broad) intense bands centred near 5.17, 6.11, 7.37, 7.75, 9.18 and 10.43 eV. The lowest Rydberg states relating to the first ionisation energy are difficult to identify, but higher members are particularly numerous on the region from 8.4 to 9.6 eV. Electronic excitation energies for valence (singlet and triplet) and Rydberg-type states have been computed using ab initio multi-reference multi-root CI methods. These studies used a triple zeta + double polarisation basis set, augmented by diffuse (Rydberg) orbitals. The theoretical study shows the nature of the more intense Rydberg state types, and positions of the main valence and Rydberg bands. By study of the excitation energies to specific upper states, the vertical ionisation energies (IE) are confirmed as ?4-1states have been obtained. Calculated energies for low-lying Rydberg states are close to those observed, and there is generally a good correlation between the theoretical intensities and the experimental envelope. The ground state atomic and molecular properties are in good agreement with experiment.

Palmer, Michael H.; Gordon, Agnieszka J.

2007-12-01

414

Helium superfluidity. Shapes and vorticities of superfluid helium nanodroplets.  

PubMed

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

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

415

Laser induced fluorescence spectroscopy of the Ca dimer deposited on helium and mixed helium/xenon clusters  

NASA Astrophysics Data System (ADS)

We study how the laser induced fluorescence spectroscopy of the calcium dimer deposited on pure helium clusters is modified by the addition of xenon atoms. In the wavelength range between 365 and 385 nm, the Ca dimer is excited from its ground state up to two excited electronic states leading to its photodissociation in Ca (1P )+ Ca (1S ) : this process is monitored by recording the Ca (1P ) fluorescence at 422.7nm. One of these electronic states of Ca2 is a diexcited one correlating to the Ca (4s 4 p3P (+ Ca (4s 3 d3D ) , the other one is a repulsive state correlating to the Ca (4s 4 p 1 P )+ Ca (4s 21 S ) asymptote, accounting for the dissociation of Ca2 and the observation of the subsequent Ca (1P ) emission. On pure helium clusters, the fluorescence exhibits the calcium atomic resonance line Ca (1S ?1P ) at 422.7 nm (23652 cm-1) assigned to ejected calcium, and a narrow red sided band corresponding to calcium that remains solvated on the helium cluster. When adding xenon atoms to the helium clusters, the intensity of these two features decreases and a new spectral band appears on the red side of calcium resonance line; the intensity and the red shift of this component increase along with the xenon quantity deposited on the helium cluster: it is assigned to the emission of Ca (1P ) associated with the small xenon aggregate embedded inside the helium cluster.

Gaveau, Marc-André; Pothier, Christophe; Briant, Marc; Mestdagh, Jean-Michel

2014-12-01

416

Scattering of H(1s) off metastable helium atom at thermal energies  

SciTech Connect

Quantal calculations for scattering of ground-state antihydrogen by metastable (n=2S) helium atoms have been performed using the nonadiabatic, atomic orbital expansion technique at thermal energies. The zero-energy elastic cross sections of the present systems are much greater than the corresponding value for the ground-state helium target. The low-energy elastic cross section for the singlet metastable helium [He(2 {sup 1}S)] target is higher than the corresponding value when the target is in the metastable triplet state [He(2 {sup 3}S)].

Sinha, Prabal K.; Ghosh, A. S. [Department of Physics, Bangabasi College, 19, Raj Kumar Chakravorty Sarani, Kolkata 700 009 (India); Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

2006-06-15

417

Experiments with electron bubbles in liquid helium  

NASA Astrophysics Data System (ADS)

When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms. The electron bubble is an excellent textbook example of a quantum mechanical particle confined in a potential well. The bubble is also a powerful tool to study superfluidity. In this dissertation, we describe various experiments on electron bubbles using standard ultrasonic techniques. By using a focused sound wave, we create a region in liquid helium where the pressure was negative. The bubble becomes unstable, and can grow without limit when the ambient pressure is lower than some critical value. This macroscopic bubble can then be detected by light scattering. The critical pressure of the bubble depends on many factors. For example, a bubble containing an electron in an excited state has a lower magnitude of critical pressure, and is therefore easier to explode than a bubble with the electron in the ground state. Similarly, bubbles trapped on vortices are easier to explode than normal, untrapped bubbles. In our experiments, we injected electrons in liquid helium by either a field emission tip or a radioactive beta source. We investigated the different experimental conditions under which the bubbles were trapped on vortices. We measured the difference of critical pressures between bubbles on and off vortices as a function of temperature. In the course of our experiments, we were able to detect electrons that were formed by the Penning ionization of dimers. At temperatures lower than 1 K, we have discovered new objects that can be exploded very easily. These objects depend on different experimental parameters in a complicated way, and are not completely understood. In a second series of experiments, we used infrared radiation to excite the electron bubbles. By analyzing the data carefully, we estimated the lifetime of these excited state bubbles; and concluded that the decay mechanism is non-radiative in nature. We also studied the effect of infrared radiation on bubbles trapped on vortices. Finally, we measured the current arising from the secondary ionization of the beta particles emitted from a radioactive source. The current had an interesting dependence on different experimental parameters, especially temperature and electric field.

Ghosh, Ambarish

418

COSMIC-RAY HELIUM HARDENING  

SciTech Connect

Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10{sup 15}eV, and (2) all CR spectra become hard at {approx}>10{sup 11}eV nucleon{sup -1}. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at {approx}100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with {approx}10{sup 6} K. Our model predicts hard and concave spectra for heavier CR elements.

Ohira, Yutaka; Ioka, Kunihito, E-mail: ohira@post.kek.jp [Theory Center, Institute of Particle and Nuclear Studies, KEK (High Energy Accelerator Research Organization), 1-1 Oho, Tsukuba 305-0801 (Japan)

2011-03-01

419

Hydrogen Balmer series measurements and determination of Rydberg's constant using two different spectrometers  

NASA Astrophysics Data System (ADS)

This paper investigates the use of two different methods, the optical and the computer-aided diffraction-grating spectrometer, to measure the wavelength of visible lines of Balmer series from the hydrogen atomic spectrum and estimate the value of Rydberg's constant. Analysis and interpretation of data showed that both methods, despite their difference in terms of the type of equipment used, displayed good performance in terms of precision of measurements of wavelengths of spectral lines. A comparison was carried out between the experimental value of Rydberg's constant obtained with both methods and the accepted value. The results of Rydberg's constant obtained with both the optical and computer-aided spectrometers were 1.099 28 × 10-7 m-1 and 1.095 13 × 10-7 m-1 with an error difference of 0.17% and 0.20% compared to the accepted value 1.097 373 × 10-7 m-1, respectively.

Amrani, D.

2014-07-01

420

Measurement of the Cascade Transition via the First Excited State of O16 in the C12(?,?)O16 Reaction, and Its S Factor in Stellar Helium Burning  

NASA Astrophysics Data System (ADS)

Radiative ?-particle capture into the first excited, J?=0+ state of O16 at 6.049 MeV excitation energy has rarely been discussed as contributing to the C12(?,?)O16 reaction cross section due to experimental difficulties in observing this transition. We report here measurements of this radiative capture in C12(?,?)O16 for center-of-mass energies of E=2.22MeV to 5.42 MeV at the DRAGON recoil separator. To determine cross sections, the acceptance of the recoil separator has been simulated in GEANT as well as measured directly. The transition strength between resonances has been identified in R-matrix fits as resulting both from E2 contributions as well as E1 radiative capture. Details of the extrapolation of the total cross section to low energies are then discussed [S6.0(300)=25-15+16keVb] showing that this transition is likely the most important cascade contribution for C12(?,?)O16.

Matei, C.; Buchmann, L.; Hannes, W. R.; Hutcheon, D. A.; Ruiz, C.; Brune, C. R.; Caggiano, J.; Chen, A. A.; D'Auria, J.; Laird, A.; Lamey, M.; Li, Zh.; Liu, Wp.; Olin, A.; Ottewell, D.; Pearson, J.; Ruprecht, G.; Trinczek, M.; Vockenhuber, C.; Wrede, C.

2006-12-01

421

The Pauli Principle and Electronic Repulsion in Helium  

ERIC Educational Resources Information Center

The authors indicate that several recent textbooks in quantum chemistry use a discussion of the excited states of the helium atom to demonstrate the importance of the Pauli principle in determining electronic repulsions. They present data suggesting "Pauli forces" do not keep electrons of parallel spins separated in space. (RH)

Snow, Richard L.; Bills, James L.

1974-01-01

422

The Helium Atom and Isoelectronic Ions in Two Dimensions  

ERIC Educational Resources Information Center

The energy levels of the helium atom and isoelectronic ions in two dimensions are considered. The difficulties encountered in the analytical evaluation of the perturbative and variational expressions for the ground state, promote an interesting factorization of the inter-electronic interaction, leading to simple expressions for the energy. This…

Patil, S. H.

2008-01-01

423

Molecular Iodine Fluorescence Using a Green Helium-Neon Laser  

ERIC Educational Resources Information Center

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…

Williamson, J. Charles

2011-01-01

424

Stabilization of Multi-electron Bubbles in Superfluid Helium  

NASA Astrophysics Data System (ADS)

Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes and the difficulty to localize them. We report the observation of long- lived MEBs in a novel cell filled with superfluid helium at static negative pressures. MEBs were extracted from the electron filled vapor sheath of a heated filament loop embedded in the superfluid helium and observed by high-speed photography. MEBs are 2D electron gases on the 3D surface of hollow helium bubbles. Diameters can range from nanometers to millimeters, depending on the number of enclosed electrons. Electrons move in angular momentum states; deformations of the surface are called spherical ripplons. The attractive electron-ripplon interaction leads to an unusual form of superconductivity. If they can be compressed, Wigner crystallization and quantum melting can be observed, as well as a new phase for localization called the ripplo- polaron lattice. MEBs are unstable to tunneling discharge when pressed against a surface. Just as Bose gases are captured in a trap for study, MEBs must also be localized away from walls. We shall discuss methods of capturing them in an electromagnetic trap embedded in the liquid helium.

Silvera, Isaac F.; Fang, Jieping; Tempere, Jacques

2014-12-01

425

Sub-wavelength microwave electric field imaging using Rydberg atoms inside atomic vapor cells  

E-print Network

We have recently shown that Alkali atoms contained in a vapor cell can serve as a highly accurate standard for microwave electric field strength as well as polarization using the principles of Rydberg atom electromagnetically induced transparency. Here, we show, for the first time, that Rydberg atom electromagnetically induced transparency can be used to image microwave electric fields with unprecedented precision. The spatial resolution of the method is far into the sub-wavelength regime. The electric field resolutions are similar to those we have demonstrated in our prior experiments. Our experimental results agree with finite element calculations of test electric field patterns.

H. Q. Fan; S. Kumar; R. Daschner; H. Kübler; J. P. Shaffer

2014-03-14

426

Pulsed helium ionization detection system  

DOEpatents

A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

Ramsey, R.S.; Todd, R.A.

1985-04-09

427

Helium retention properties of plasma facing materials  

NASA Astrophysics Data System (ADS)

In a fusion reactor, the continuous removal of helium from the core plasma is needed in order to sustain the ignition condition. For this purpose, it has been proposed to place helium selective pumping metals, which can trap more helium than hydrogen, in the vicinity of the divertor. In this study, the helium and hydrogen trapping properties of nickel, tungsten, molybdenum, SS 304 and Inconel 625 were examined. Namely, the dependencies of irradiation temperature on the amount of trapped helium and hydrogen were obtained by thermal desorption spectroscopy (TDS), after helium or hydrogen plasma irradiation. In those metals, nickel showed the most suitable selective pumping capability. Nickel had the helium selective pumping property above 100°C. The maximum amount of trapped helium was (2-3) × 10 16He/ cm2 at an irradiation temperature of 200°C and 600°C. The optimum temperature becomes about 600°C when nickel is used for a selective pumping material.

Yanagihara, H.; Yamauchi, Y.; Hino, T.; Hirohata, Y.; Yamashina, T.

1997-02-01

428

Investigation of particle diffusion and suprathermal electrons in a magnetized helium plasma column  

SciTech Connect

Studying radiative properties of magnetized helium plasma via high-resolution spectroscopy identified close correlations between the particle diffusion and suprathermal electrons for different modes of operation of the MISTRAL installation. The standard diagnostic emission lines in neutral helium (1s3d {sup 3}D-1s2p {sup 3}P, 1s3s {sup 3}S-1s2p {sup 3}P, 1s3d {sup 1}D-1s2p {sup 1}P, and 1s3s {sup 1}S-1s2p {sup 1}P) show anomalous ratios that are related to enhanced particle diffusion and suprathermal electron generation. The supplementary investigation of singlet/triplet Rydberg series (transitions 1snd {sup 3}D-1s2p {sup 3}P and 1s5p {sup 1}P-1s2s {sup 1}S) as well as ionic lines (HeII, transitions n?=?3–4 at 469?nm and n?=?4–6 at 656?nm) allowed quantitative characterization. Simulations carried out with the atomic physics code SOPHIA demonstrate that simultaneous implementation of diffusion processes and suprathermal electrons matches all experimental findings. Single consideration, however, of either diffusion or hot electrons is in contradiction to the proposed extended set of HeI and HeII emission lines. The high precision achieved with the LSJ-split level structure of SOPHIA coupled to Langmuir probe measurements allowed to conclude to a Bohm type diffusion in MISTRAL.

Lefevre, T.; Escarguel, A.; Stamm, R.; Godbert-Mouret, L. [Aix-Marseille Université, CNRS, PIIM UMR 7345, F13397 CEDEX 20, Marseille (France)] [Aix-Marseille Université, CNRS, PIIM UMR 7345, F13397 CEDEX 20, Marseille (France); Rosmej, F. B. [Sorbonne Universités, Pierre et Marie Curie, UMR 7605, LULI, case 128, 4 place Jussieu, F-75252 Paris Cedex 05 (France) [Sorbonne Universités, Pierre et Marie Curie, UMR 7605, LULI, case 128, 4 place Jussieu, F-75252 Paris Cedex 05 (France); LULI, Ecole Polytechnique, CNRS, CEA, Physique Atomique dans les Plasmas Denses PAPD, Route de Saclay, F-91128 Palaiseau (France)

2014-02-15

429

Calculations of resonances parameters for the ((2s2) 1Se, (2s2p) 1,3P0) and ((3s2) 1Se, (3s3p) 1,3P0) doubly excited states of helium-like ions with Z?10 using a complex rotation method implemented in Scilab  

NASA Astrophysics Data System (ADS)

In the present work a special computational program Scilab (Scientific Laboratory) in the complex rotation method has been used to calculate resonance parameters of ((2s2) 1Se, (2s2p) 1,3P0) and ((3s2) 1Se, (3s3p) 1,3P0) states of helium-like ions with Z?10. The purpose of this study required a mathematical development of the Hamiltonian applied to Hylleraas wave function for intrashell states, leading to analytical expressions which are carried out under Scilab computational program. Results are in compliance with recent theoretical calculations.

Gning, Youssou; Sow, Malick; Traoré, Alassane; Dieng, Matabara; Diakhate, Babacar; Biaye, Mamadi; Wagué, Ahmadou

2015-01-01

430

Applying the helium ionization detector in chromatography  

NASA Technical Reports Server (NTRS)

High noise levels and oversensitivity of helium detector make flame-ionization and thermal-conductivity detectors more suitable for chromotography. Deficiencies are eliminated by modifying helium device to operate in saturation rather than multiplication mode. Result is low background current, low noise, high stability, and high sensitivity. Detector analyzes halocarbons, hydrocarbons, hydrogen cyanide, ammonia, and inorganics without requiring expensive research-grade helium.

Gibson, E. K.; Andrawes, F. F.; Brazell, R. S.

1981-01-01

431

Prediction of 2D Rydberg energy levels of 6Li and 7Li based on very accurate quantum mechanical calculations performed with explicitly correlated Gaussian functions  

NASA Astrophysics Data System (ADS)

Very accurate variational nonrelativistic finite-nuclear-mass calculations employing all-electron explicitly correlated Gaussian basis functions are carried out for six Rydberg 2D states (1s2nd, n = 6, …, 11) of the 7Li and 6Li isotopes. The exponential parameters of the Gaussian functions are optimized using the variational method with the aid of the analytical energy gradient determined with respect to these parameters. The experimental results for the lower states (n = 3, …, 6) and the calculated results for the higher states (n = 7, …, 11) fitted with quantum-defect-like formulas are used to predict the energies of 2D 1s2nd states for 7Li and 6Li with n up to 30.

Bubin, Sergiy; Sharkey, Keeper L.; Adamowicz, Ludwik

2013-04-01

432

Helium resources of Mare Tranquillitatis  

NASA Technical Reports Server (NTRS)

Wisconsin Center for Space Automation and Robotics, Univ. of Wisc., Madison, Wisc. Mare Tranquillitatis, about 300000 sq km in area, is currently the most promising lunar source of He-3 for fueling fusion power plants on Earth. About 60 pct. of the mare regolith consists of particles 100 microns or less in diameter. Helium and other gases derived from the solar wind are concentrated in the fine size fractions. Studies of very small craters indicate that the average regolith exceeds 3 m in areas away from larger craters and other mare features not amenable to mining. There is no evidence of decrease of helium content of regolith and depth. Helium is known to be enriched in regoliths that are high in TiO2 content. Remote sensing indicates that about 90 pct. of Mare Tranquillitatis is covered by regolith ranging from about 6 to +7.5 pct. TiO2; inferred He contents range from 20 to at least 45 wppm total helium (7 to 18 wppb He-3). Detailed studies of craters and inferred ejecta halos displayed on high resolution photographs of the Apollo 11 and Ranger 8 areas suggest that as much as 50 pct. of the mare regolith may be physically minable, on average, with appropriate mining equipment. Assuming that the average thickness of regolith is 3 m, and that 50 pct. of the mare area is minable, the He-3 content of minable regolith containing 20 to 45 wppm total He is estimated at about 94,000 tonnes.

Cameron, Eugene N.

1991-01-01

433

Energy storage in solid helium  

NASA Technical Reports Server (NTRS)

The problem of storing large amounts of energy in electronically excited solid helium, briefly He-4, is discussed. Important physical processes in He-4 are identified, and a study program is proposed with the aim of making energy storage in He-4 a practical reality.

Zmuidzinas, J. S.

1973-01-01

434

Modified GR and Helium Nucleosynthesis  

E-print Network

We show that a previously proposed cosmological model based on general relativity with non vanishing divergence for the energy-momentum tensor is consistent with the observed values for the nucleosynthesis of helium for some values of the arbitrary parameter $\\alpha$ presented in this model. Further more values of $\\alpha$ can be accommodated if we adopt the Randall-Sundrum single brane model.

A. S. Al-Rawaf

2006-06-12

435

Helium II level measurement techniques  

Microsoft Academic Search

In this paper, a survey of cryogenic liquid level measurement techniques applicable to superfluid helium (He II) is given. The survey includes both continuous and discrete measurement techniques. A number of different probes and controlling circuits for this purpose have been described in the literature. They fall into one of the following categories: capacitive liquid level gauges, superconducting wire liquid

D Celik; D. K Hilton; T Zhang; S. W Van Sciver

2001-01-01

436

Helium diffusion in the sun  

NASA Technical Reports Server (NTRS)

We calculate improved standard solar models using the new Livermore (OPAL) opacity tables, an accurate (exportable) nuclear energy generation routine which takes account of recent measurements and analyses, and the recent Anders-Grevesse determination of heavy element abundances. We also evaluate directly the effect of the diffusion of helium with respect to hydrogen on the calculated neutrino fluxes, on the primordial solar helium abundance, and on the depth of the convective zone. Helium diffusion increases the predicted event rates by about 0.8 SNU, or 11 percent of the total rate, in the chlorine solar neutrino experiment, by about 3.5 SNU, or 3 percent, in the gallium solar neutrino experiments, and by about 12 percent in the Kamiokande and SNO solar neutrino experiments. The best standard solar model including helium diffusion and the most accurate nuclear parameters, element abundances, and radiative opacity predicts a value of 8.0 SNU +/- 3.0 SNU for the C1-37 experiment and 132 +21/-17 SNU for the Ga - 71 experiment, where the uncertainties include 3 sigma errors for all measured input parameters.

Bahcall, J. N.; Pinsonneault, M. H.

1992-01-01

437

Classical limit states of the helium atom  

Microsoft Academic Search

The classical simplicity and intuitive appeal of Bohr's atomic model have given the classical hydrogen atom an important and pervasive role in atomic physics. Even today, the Bohr model remains as a cornerstone underlying quan- tum mechanics. However, the precise role of this classical foundation has been debated since the early days of quantum theory. Recently, a series of experimental

J. A. West; Z. D. Gaeta; C. R. Stroud

1998-01-01

438

Photoionization of atoms and molecules. [of hydrogen, helium, and xenon  

NASA Technical Reports Server (NTRS)

A literature review on the present state of knowledge in photoionization is presented. Various experimental techniques that have been developed to study photoionization, such as fluorescence and photoelectron spectroscopy, mass spectroscopy, are examined. Various atoms and molecules were chosen to illustrate these techniques, specifically helium and xenon atoms and hydrogen molecules. Specialized photoionization such as in positive and negative ions, excited states, and free radicals is also treated. Absorption cross sections and ionization potentials are also discussed.

Samson, J. A. R.

1976-01-01

439

Numerical Studies of Properties of Confined Helium  

NASA Technical Reports Server (NTRS)

We carry out state of the art simulations of properties of confined liquid helium near the superfluid transition to a degree of accuracy which allows to make predictions for the outcome of fundamental physics experiments in microgravity. First we report our results for the finite-size scaling behavior of heat capacity of superfluids for cubic and parallel-plate geometry. This allows us to study the crossover from zero and two dimensions to three dimensions. Our calculated scaling functions are in good agreement with recently measured specific heat scaling functions for the above mentioned geometries. We also present our results of a quantum simulation of submonolayer of molecular hydrogen deposited on an ideal graphite substrate using path-integral quantum Monte Carlo simulation. We find that the monolayer phase diagram is rich and very similar to that of helium monolayer. We are able to uncover the main features of the complex monolayer phase diagram, such as the commensurate solid phases and the commensurate to incommensurate transition, in agreement with the experiments and to find some features which are missing from the experimental analysis.

Manousakis, Efstratios

2003-01-01

440

RYDBERG ATOMS, VARIABLE STARS, KEPLER'S THIRD LAW AND E=hv  

Microsoft Academic Search

Observed radii and oscillation periods of pulsating stars representing several distinct classes or variable stars are shown to obey approximate physical laws that are self-similar analogues to those that are known to correlate the radii and oscillation periods of Rydberg atoms. Magnitudes of the relevant atomic scale parameters and their stellar scale counterparts are quantitatively related by a previously identified

ROBERT L. OLDERSHAW

1988-01-01

441

Helium-Based Soundwave Chiller: Trillium: A Helium-Based Sonic Chiller- Tons of Freezing with 0 GWP Refrigerants  

SciTech Connect

BEETIT Project: Penn State is designing a freezer that substitutes the use of sound waves and environmentally benign refrigerant for synthetic refrigerants found in conventional freezers. Called a thermoacoustic chiller, the technology is based on the fact that the pressure oscillations in a sound wave result in temperature changes. Areas of higher pressure raise temperatures and areas of low pressure decrease temperatures. By carefully arranging a series of heat exchangers in a sound field, the chiller is able to isolate the hot and cold regions of the sound waves. Penn State’s chiller uses helium gas to replace synthetic refrigerants. Because helium does not burn, explode or combine with other chemicals, it is an environmentally-friendly alternative to other polluting refrigerants. Penn State is working to apply this technology on a large scale.

None

2010-09-01

442

Pressure-Volume-Temperature (PVT) Gauging of an Isothermal Cryogenic Propellant Tank Pressurized with Gaseous Helium  

NASA Technical Reports Server (NTRS)

Results are presented for pressure-volume-temperature (PVT) gauging of a liquid oxygen/liquid nitrogen tank pressurized with gaseous helium that was supplied by a high-pressure cryogenic tank simulating a cold helium supply bottle on a spacecraft. The fluid inside the test tank was kept isothermal by frequent operation of a liquid circulation pump and spray system, and the propellant tank was suspended from load cells to obtain a high-accuracy reference standard for the gauging measurements. Liquid quantity gauging errors of less than 2 percent of the tank volume were obtained when quasi-steady-state conditions existed in the propellant and helium supply tanks. Accurate gauging required careful attention to, and corrections for, second-order effects of helium solubility in the liquid propellant plus differences in the propellant/helium composition and temperature in the various plumbing lines attached to the tanks. On the basis of results from a helium solubility test, a model was developed to predict the amount of helium dissolved in the liquid as a function of cumulative pump operation time. Use of this model allowed correction of the basic PVT gauging calculations and attainment of the reported gauging accuracy. This helium solubility model is system specific, but it may be adaptable to other hardware systems.

VanDresar, Neil T.; Zimmerli, Gregory A.

2014-01-01

443

Helium-cooled divertor module for fusion devices  

NASA Astrophysics Data System (ADS)

The advanced fusion machines such as TPX, NET, and ITER have to be designed to handle a heat flux of about 5 to 15 MW/m2 in the diverter region. The present conceptual designs use water cooling. However water leaks will have very serious consequences in these machines. Cooling with a gas like helium is a very attractive alternative, if the pumping power can be limited to a reasonable value. Different concepts to cool diverter by helium gas were compared. It was found that it is feasible to remove significant steady state heat flux (10 to 20 MW/m2) by using helium at a pressure of 4 MPa (580 psia) and with pumping power less than 0.5% of the power removed, by using optimized designs. From pumping power consideration, various concepts rank in the following order: offset fins (best), fins, jets, 3-D roughness, 2-D roughness, smooth tubes (worst). A module based on this study has been designed and fabricated for a steady state operation at 10 MW/m2 and was tested at the High Heat Flux facility at Sandia National Laboratory. This paper also presents some preliminary studies of helium cooled ITER diverter.

Baxi, Chandrakant B.

1993-11-01

444

Two-photon photodissociation of NO through Rydberg levels in the 265-278 nm region: Spectra and photofragment angular distributions  

NASA Astrophysics Data System (ADS)

The spectroscopy and dynamics of the NO photodissociation through Rydberg levels near 74 000 cm-1 have been investigated following two-photon excitation. The 6dpi-)(v=1 and 5ssigma(v=3) levels overlap near 74 070 cm-1. Assignment of the rotational transitions for these levels has been aided by the use of the photoproduct angular distributions measured using product imaging techniques. Product imaging was also used to investigate the 8dpi-)(v=1 and 5ssigma(v=2) regions assigned by previous investigators. In all cases, the major products were N(2)D+O(3)P. The angular distributions vary strongly with rotational transition and with the assumed intermediate in the two-photon excitation scheme and can, for the most part, be predicted by calculation. They demonstrate that, for the Rydberg levels examined, the major contribution to the two-photon line strength is a Pi intermediate, likely the C 2Pi state, with less than a 30% amplitude contribution from either a Sigma or Delta intermediate.

Cosofret, B. R.; Lambert, H. M.; Houston, P. L.

2002-11-01

445

Giant helium dimers produced by photoassociation of ultracold metastable atoms.  

PubMed

We produce giant, purely long-range helium dimers by photoassociation of metastable helium atoms in a magnetically trapped, ultracold cloud. The photoassociation laser is detuned close to the atomic 2(3)S1-2(3)P0 line and produces strong heating of the sample when resonant with molecular bound states. The temperature of the cloud serves as an indicator of the molecular spectrum. We report good agreement between our spectroscopic measurements and our calculations of the five bound states belonging to a 0(+)(u) purely long-range potential well. These previously unobserved states have classical inner turning points of about 150a(0) and outer turning points as large as 1150a(0). PMID:12935015

Léonard, J; Walhout, M; Mosk, A P; Müller, T; Leduc, M; Cohen-Tannoudji, C

2003-08-15

446

Exploring high-energy doubly excited states of NH by dissociative recombination of NH+  

NASA Astrophysics Data System (ADS)

We have investigated electron capture by NH+ resulting in dissociative recombination (DR). The impact energies studied of ˜4-12 eV extend over the range below the two lowest predicted NH+ dissociative states in the Franck-Condon (FC) region of the ion. Our focus has been on the final state populations of the resulting N and H atoms. The neutral DR fragments are detected downstream of a merged electron and ion beam interaction zone in the TSR storage ring, which is located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Transverse fragment distances were measured on a recently developed high count-rate imaging detector. The distance distributions enabled a detailed tracking of the final state populations as a function of the electron collision energy. These can be correlated with doubly excited neutral states in the FC region of the ion. At low electron energy of ˜5 eV, the atomic product final levels are nitrogen Rydberg states together with ground-state hydrogen. In a small electron energy interval near 7 eV, a significant part of the final state population forms hydrogen Rydberg atoms with nitrogen atoms in the first excited (^2D) term, showing the effect of Rydberg doubly excited states below the predicted 2?2? ionic potential. The distance distributions above ˜10 eV are compatible with nitrogen Rydberg states correlating to the doubly excited Rydberg state manifold below the ionic 2?4?- level.

Yang, B.; Novotný, O.; Krantz, C.; Buhr, H.; Mendes, M.; Nordhorn, C.; Geppert, W. D.; Grieser, M.; Repnow, R.; Berg, M.; Bing, D.; Domesle, C.; Grussie, F.; Savin, D. Wolf; Schwalm, D.; Cai, X.; Wolf, A.

2014-02-01

447

Effect of radiogenic helium on stainless steel 12Cr18Ni10Ti mechanical properties and hydrogen permeability  

SciTech Connect

Samples of stainless steel 12Cr18Ni10Ti with radiogenic helium were subjected to mechanical tests with a constant extension rate. The presence of {sup 3}He does not markedly affect the strength characteristic, but significantly decreases plasticity of steel. The presence of hydrogen enhances the embrittlement of steel, containing {sup 3}He. The diffusion coefficient of hydrogen does not change significantly in the presence of helium, but the traps for hydrogen, which occur due to the presence of helium, delay the kinetics of a steady state flux onset at helium concentration of 50 appm. (authors)

Boitsov, I. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation); Kanashenko, S. [Inst. of Physical Chemistry, Russian Academy of Sciences, Leninsky pr., 31, Moscow, 119991 (Russian Federation); Causey, R. [Sandia National Laboratories, MS 9161, P.O. Box 969, Livermore, CA 94551-0969 (United States); Denisov, E. [V.A. Fock Research Inst. of Physics, St. Petersburg State Univ., Ulyanovskaya st., 1, Peterhof, St. Petersburg 198904 (Russian Federation); Glugla, M. [Forschungszentrum Karlsruhe, Tritium Laboratory TLK, PO Box 3640, D 76021 Karlsruhe (Germany); Grishechkin, S. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation); Hassanein, A. [Argonne National Laboratory, Bldg. 362, South Cass Avenue, Argonne, 9700 (United States); Lebedev, B. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation); Kompaniets, T.; Kurdyumov, A. [V.A. Fock Research Inst. of Physics, St. Petersburg State Univ., Ulyanovskaya st., 1, Peterhof, St. Petersburg 198904 (Russian Federation); Malkov, I.; Yukhimchuk, A. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation)

2008-07-15