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1

Rydberg States of rb and cs Atoms on Helium Nanodroplets: a Rydberg-Ritz Analysis  

NASA Astrophysics Data System (ADS)

Rydberg series of Rb and Cs atoms on the surface of helium nanodroplets (He_{N}) have been studied by resonance enhanced multi-photon ionization spectroscopy and laser induced fluorescence spectroscopy. The recorded excitation spectra are analyzed by using a Rydberg-Ritz approach. The dependence of the quantum defects on the principal quantum number within a Rydberg series gives insight into the interaction between the alkali atom's valence electron and the superfluid helium droplet. For higher excited states a screening of the valence electron from the alkali atom core by the helium droplet is observed. For lower states the strength of the screening effect decreases and the quantum defects are found to lie closer to free atom values. In addition, the large spin-orbit (SO) constant of the Cs-He_{N} nP(^{2}?) states allows a detailed study of the influence of the helium droplet on the SO splitting as function of the principal quantum number. Within the pseudo-diatomic picture the alkali-He_{N} system represents a diatomic molecule. The coupling of the Cs valence electrons spin and the orbital angular momentum with the intermolecular axis, which is defined by the connection between the droplet center and the alkali nucleus, depends on the strength of the atomic SO interaction. While the splitting of the 6^{2}P_{1/2}(^{2}?_{1/2}) and 6^{2}P_{3/2}(^{2}?_{3/2}) components has an atom-like character (Hund's case (c) coupling), the SO splitting of higher n states is lower than the atomic value (Hund's case (a) coupling). C. Callegari and W. E. Ernst, Helium Droplets as Nanocryostats for Molecular Spectroscopy - from the Vacuum Ultraviolet to the Microwave Regime, in: Handbook of High-Resolution Spectroscopy, eds. M. Quack and F. Merkt, John Wiley & Sons, Chichester, (2011) F. Lackner, G. Krois, M. Theisen, M. Koch, and W.E. Ernst, Phys. Chem. Chem. Phys., 13, 18781-18788 (2011) F. Lackner, G. Krois, and W.E. Ernst, J. Phys. Chem. Lett., 3, 1404-1408 (2012)

Lackner, Florian; Krois, Gunter; Ernst, Wolfgang E.

2013-06-01

2

Effects of transverse photon exchange in helium Rydberg states - Corrections beyond the Coulomb-Breit interaction  

NASA Technical Reports Server (NTRS)

The Breit correction only accounts for part of the transverse photon exchange correction in the calculation of the energy levels in helium Rydberg states. The remaining leading corrections are identified and each is expressed in an effective potential form. The relevance to the Casimir correction potential in various limits is also discussed.

Au, C. K.

1989-01-01

3

Stark manifolds and electric-field-induced avoided level crossings in helium Rydberg states  

SciTech Connect

The linear Stark effect in 1/ital snp/ /sup 1,3/P Rydberg states (/ital n/approx.40) of the fundamental two-electron atom helium was studied with the resolution of cw laser spectroscopy. The evolution of the angular-momentum manifolds was followed up to the regime where Stark states originating from different /ital n/ values interact. Narrow avoided level crossings were detected with high precision. Stark manifolds were also calculated by diagonalization of the complete energy matrix in the presence of an electric field. In these calculations, even at moderate values of the field up to five /ital n/ values have to be included to accurately reproduce the experimental data.

Lahaye, C. T. W.; Hogervorst, W.

1989-06-01

4

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

5

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

NASA Astrophysics Data System (ADS)

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 He2+ and He3+ 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.

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

2012-12-01

6

Atomic Fock State Preparation Using Rydberg Blockade Matthew Ebert,*  

E-print Network

Atomic Fock State Preparation Using Rydberg Blockade Matthew Ebert,* Alexander Gill, Michael 2014) We use coherent excitation of 3­16 atom ensembles to demonstrate collective Rabi flopping mediated by Rydberg blockade. Using calibrated atom number measurements, we quantitatively confirm

Yavuz, Deniz

7

Logic gates using high Rydberg states  

PubMed Central

Connected logic gates can be operated on the levels of one molecule by making use of the special properties of high Rydberg states. Explicit experimental results for the NO molecule are provided as an example. A number of other options, including that of several gates concatenated so as to operate as a full adder, are discussed. Specific properties of high Rydberg states that are used are: their autoionization is delayed so that they can be distinguished from direct multiphoton ionization, during their long life such states also can decay by energy transfer to the molecular core in a way that can be controlled by the judicious application of very weak external electrical fields, and the Rydberg states can be detected by the application of an ionizing electrical field. The combination of two (or three) color photons with and without external weak fields allows the construction of quite elaborate logic circuit diagrams and shows that taking advantage of the different intramolecular dynamics of levels that differ by their excitation enables the compounding of logic operations on one molecular frame. PMID:11248016

Remacle, F.; Schlag, E. W.; Selzle, H.; Kompa, K. L.; Even, U.; Levine, R. D.

2001-01-01

8

Alignment of D-state Rydberg molecules.  

PubMed

We report on the formation of ultralong-range Rydberg D-state molecules via photoassociation in an ultracold cloud of rubidium atoms. By applying a magnetic offset field on the order of 10 G and high resolution spectroscopy, we are able to resolve individual rovibrational molecular states. A full theory, using a Fermi pseudopotential approach including s- and p-wave scattering terms, reproduces the measured binding energies. The calculated molecular wave functions show that in the experiment we can selectively excite stationary molecular states with an extraordinary degree of alignment or antialignment with respect to the magnetic field axis. PMID:24765956

Krupp, A T; Gaj, A; Balewski, J B; Ilzhöfer, P; Hofferberth, S; Löw, R; Pfau, T; Kurz, M; Schmelcher, P

2014-04-11

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

Four-wave mixing involving Rydberg states in thermal vapor  

NASA Astrophysics Data System (ADS)

We present experimental results on nondegenerate four-wave mixing in a thermal vapor cell of rubidium atoms via highly excited Rydberg states. We observe sub-Doppler spectral features and a large sensitivity of the mixed light mode to small electric fields due to the large polarizabilities of the involved Rydberg state. We observe a saturation of the optical response due to the nonlinear four-level physics. The strong interaction between Rydberg atoms and the associated Rydberg blockade could potentially increase the nonlinearity dramatically.

Kölle, A.; Epple, G.; Kübler, H.; Löw, R.; Pfau, T.

2012-06-01

11

The role of excited Rydberg States in electron transfer dissociation.  

PubMed

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

Sobczyk, Monika; Simons, Jack

2006-04-13

12

Threshold Photoionization Spectroscopy with Heavy Rydberg States  

NASA Astrophysics Data System (ADS)

We have shown that it is possible to excite and detect Rydberg-like states just below the threshold for dissociation into ion pairs in a molecule. (J.D.D. Martin and J.W. Hepburn, Phys. Rev. Lett. 79 , 3154 (1997)) This type of threshold spectroscopy, called TIPPS for threshold ion-pair production spectroscopy, can be used to determine dissociation energies to very high accuracy (<1cm-1) and to record the spectra of fragment ions. In this talk some of the applications of TIPPS will be discussed, including a recent determination of the Born-Oppenheimer breakdown in HCl and HF.

Hepburn, John W.

2002-05-01

13

Rotational-state-selective field ionization of molecular Rydberg states  

Microsoft Academic Search

This paper presents state-selective field ionization spectra of highly excited Rydberg states of NO. The competition between electron-nuclear coupling and electron-field coupling is investigated and it is shown that the slew rate of the electric field can be exploited to control the rotational quantum state composition of field-ionized molecules.

R. Patel; N. J. A. Jones; H. H. Fielding

2007-01-01

14

On the Use of a Mixed Gaussian/Finite-Element Basis Set for the Calculation of Rydberg States  

NASA Technical Reports Server (NTRS)

Configuration-interaction studies are reported for the Rydberg states of the helium atom using mixed Gaussian/finite-element (GTO/FE) one particle basis sets. Standard Gaussian valence basis sets are employed, like those, used extensively in quantum chemistry calculations. It is shown that the term values for high-lying Rydberg states of the helium atom can be obtained accurately (within 1 cm -1), even for a small GTO set, by augmenting the n-particle space with configurations, where orthonormalized interpolation polynomials are singly occupied.

Thuemmel, Helmar T.; Langhoff, Stephen (Technical Monitor)

1996-01-01

15

Coherent control of Rydberg states in silicon.  

PubMed

Laser cooling and electromagnetic traps have led to a revolution in atomic physics, yielding dramatic discoveries ranging from Bose-Einstein condensation to the quantum control of single atoms. Of particular interest, because they can be used in the quantum control of one atom by another, are excited Rydberg states, where wavefunctions are expanded from their ground-state extents of less than 0.1 nm to several nanometres and even beyond; this allows atoms far enough apart to be non-interacting in their ground states to strongly interact in their excited states. For eventual application of such states, a solid-state implementation is very desirable. Here we demonstrate the coherent control of impurity wavefunctions in the most ubiquitous donor in a semiconductor, namely phosphorus-doped silicon. In our experiments, we use a free-electron laser to stimulate and observe photon echoes, the orbital analogue of the Hahn spin echo, and Rabi oscillations familiar from magnetic resonance spectroscopy. As well as extending atomic physicists' explorations of quantum phenomena to the solid state, our work adds coherent terahertz radiation, as a particularly precise regulator of orbitals in solids, to the list of controls, such as pressure and chemical composition, already familiar to materials scientists. PMID:20577211

Greenland, P T; Lynch, S A; van der Meer, A F G; Murdin, B N; Pidgeon, C R; Redlich, B; Vinh, N Q; Aeppli, G

2010-06-24

16

Coherent excitation of a single atom to a Rydberg state  

SciTech Connect

We present the coherent excitation of a single Rubidium atom to the Rydberg state 58d{sub 3/2} using a two-photon transition. The experimental setup is described in detail, as are experimental techniques and procedures. The coherence of the excitation is revealed by observing Rabi oscillations between ground and Rydberg states of the atom. We analyze the observed oscillations in detail and compare them to numerical simulations which include imperfections of our experimental system. Strategies for future improvements on the coherent manipulation of a single atom in our settings are given.

Miroshnychenko, Y.; Gaeetan, A.; Evellin, C.; Grangier, P.; Wilk, T.; Browaeys, A. [Laboratoire Charles Fabry, Institut d'Optique, Centre National de la Recherche Scientifique, Universite Paris-Sud, Campus Polytechnique, RD 128, F-91127 Palaiseau CEDEX (France); Comparat, D.; Pillet, P. [Laboratoire Aime Cotton, Centre National de la Recherche Scientifique, Universite Paris-Sud, Batiment 505, Campus d'Orsay, F-91405 Orsay CEDEX (France)

2010-07-15

17

Three-photon electromagnetically induced transparency using Rydberg states.  

PubMed

We demonstrate electromagnetically induced transparency in a four-level cascade system where the upper level is a Rydberg state. The observed spectral features are sub-Doppler and can be enhanced due to the compensation of Doppler shifts with AC Stark shifts. A theoretical description of the system is developed that agrees well with the experimental results, and an expression for the optimum parameters is derived. PMID:23041883

Carr, Christopher; Tanasittikosol, Monsit; Sargsyan, Armen; Sarkisyan, David; Adams, Charles S; Weatherill, Kevin J

2012-09-15

18

Study of energy levels and decay mechanisms for Singlet Rydberg states of molecular nitrogen  

Microsoft Academic Search

This report summarizes a series of investigations of the singlet Rydberg states of molecular nitrogen. The object of the research was to use laser excitation out of the metastable state of N2 to study the energy levels and decay mechanisms for the high lying singlet Rydberg and valence states. Two techniques were used to produce molecules in the metastable state

F. M. Pipkin

1991-01-01

19

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

NASA Astrophysics Data System (ADS)

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

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

1996-05-01

20

Scattering resonances and bound states for strongly interacting Rydberg polaritons  

NASA Astrophysics Data System (ADS)

We provide a theoretical framework describing slow-light polaritons interacting via atomic Rydberg states. The method allows us to analytically derive the scattering properties of two polaritons. We identify parameter regimes where polariton-polariton interactions are repulsive. Furthermore, in the regime of attractive interactions, we identify multiple two-polariton bound states, calculate their dispersion, and study the resulting scattering resonances. Finally, the two-particle scattering properties allow us to derive the effective low-energy many-body Hamiltonian. This theoretical platform is applicable to ongoing experiments.

Bienias, P.; Choi, S.; Firstenberg, O.; Maghrebi, M. F.; Gullans, M.; Lukin, M. D.; Gorshkov, A. V.; Büchler, H. P.

2014-11-01

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

Revisiting Mulliken's concepts about Rydberg states and Rydberg-valence interactions from large-scale Ab initio calculations on the acetylene molecule.  

PubMed

A quantitative characterization of the Rydberg and valence singlet electronic states of acetylene lying in the 5-10.7 eV region is performed by using large-scale ab initio calculations. A special attention is paid on the comparison between the present calculations and Mulliken's concepts for Rydberg states, based on single-electron and single-configuration description. Most of the properties of the Rydberg states have been qualitatively understood via this comparison, mainly shown by the shape and size of the outer Rydberg molecular orbital. More quantitatively, Rydberg-valence mixing has been evaluated in several excited energy regions, as for instance, the interaction between the ' (1pig)2 1Ag doubly excited valence state and the manifold of electronic components of the np series, or the interaction between the 1pig 1Bu valence state and the 3dpig 1Sigma(u)+ Rydberg state. The rapid predissociation of the lowest 3s(sigma) 1Piu Rydberg state has been interpreted as a case of Rydbergization, earlier predicted by Mulliken. PMID:19639976

Laruelle, Fabrice; Boyé-Péronne, Séverine; Gauyacq, Dolores; Liévin, Jacques

2009-11-26

23

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

24

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

25

Sub-Poissonian statistics of Rydberg-interacting dark-state polaritons.  

PubMed

We observe individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states coupled via an electromagnetically induced transparency resonance. Strong long-range interactions between Rydberg excitations give rise to a blockade between polaritons, resulting in large optical nonlinearities and modified polariton number statistics. By combining optical imaging and high-fidelity detection of the Rydberg polaritons we investigate both aspects of this coupled atom-light system. We map out the full nonlinear optical response as a function of atomic density and follow the temporal evolution of polaritons through the atomic cloud. In the blockade regime, the statistical fluctuations of the polariton number drop well below the quantum noise limit. The low level of fluctuations indicates that photon correlations modified by the strong interactions have a significant backaction on the Rydberg atom statistics. PMID:25167407

Hofmann, C S; Günter, G; Schempp, H; Robert-de-Saint-Vincent, M; Gärttner, M; Evers, J; Whitlock, S; Weidemüller, M

2013-05-17

26

Excited states of the water molecule: Analysis of the valence and Rydberg character  

NASA Astrophysics Data System (ADS)

The excited states of the water molecule have been analyzed by using the extended quantum-chemical multistate CASPT2 method, namely, MS-CASPT2, in conjunction with large one-electron basis sets of atomic natural orbital type. The study includes 13 singlet and triplet excited states, both valence and 3s-, 3p-, and 3d-members of the Rydberg series converging to the lowest ionization potential and the 3s- and 3p-Rydberg members converging to the second low-lying state of the cation, 1A12. The research has been focused on the analysis of the valence or Rydberg character of the low-lying states. The computation of the 1B11 state of water at different geometries indicates that it has a predominant 3s-Rydberg character at the equilibrium geometry of the molecule but it becomes progressively a valence state described mainly by the one-electron 1b1?4a1 promotion, as expected from a textbook of general chemistry, upon elongation of the O-H bonds. The described valence-Rydberg mixing is established to be originated by a molecular orbital (MO) Rydbergization process, as suggested earlier by R. S. Mulliken [Acc. Chem. Res. 9, 7 (1976)]. The same phenomenon occurs also for the 1A21 state whereas a more complex behavior has been determined for the 2A11 state, where both MO Rydbergization and configurational mixing take place. Similar conclusions have been obtained for the triplet states of the molecule.

Rubio, Mercedes; Serrano-Andrés, Luis; Merchán, Manuela

2008-03-01

27

Predissociation of high-lying Rydberg states of molecular iodine via ion-pair states.  

PubMed

Velocity map imaging of the photofragments arising from two-photon photoexcitation of molecular iodine in the energy range 73?500-74?500 cm(-1) covering the bands of high-lying gerade Rydberg states [(2)?1/2]c6d;0g (+) and [(2)?1/2]c6d;2g has been applied. The ion signal was dominated by the atomic fragment ion I(+). Up to 5 dissociation channels yielding I(+) ions with different kinetic energies were observed when the I2 molecule was excited within discrete peaks of Rydberg states and their satellites in this region. One of these channels gives rise to images of I(+) and I(-) ions with equal kinetic energy indicating predissociation of I2 via ion-pair states. The contribution of this channel was up to about 50% of the total I(+) signal. The four other channels correspond to predissociation via lower lying Rydberg states giving rise to excited iodine atoms providing I(+) ions by subsequent one-photon ionization by the same laser pulse. The ratio of these channels varied from peak to peak in the spectrum but their total ionic signal was always much higher than the signal of (2 + 1) resonance enhanced multi-photon ionization of I2, which was previously considered to be the origin of ionic signal in this spectral range. The first-tier E0g (+) and D(')2g ion-pair states are concluded to be responsible for predissociation of Rydberg states [(2)?1/2]c6d;0g (+) and [(2)?1/2]c6d;2g, respectively. Further predissociation of these ion-pair states via lower lying Rydberg states gives rise to excited I(5s(2)5p(4)6s(1)) atoms responsible for major part of ion signal. The isotropic angular distribution of the photofragment recoil directions observed for all channels indicates that the studied Rydberg states are long-lived compared with the rotational period of the I2 molecule. PMID:24697445

Bogomolov, Alexandr S; Grüner, Barbara; Kochubei, Sergei A; Mudrich, Marcel; Baklanov, Alexey V

2014-03-28

28

Predissociation of high-lying Rydberg states of molecular iodine via ion-pair states  

NASA Astrophysics Data System (ADS)

Velocity map imaging of the photofragments arising from two-photon photoexcitation of molecular iodine in the energy range 73 500-74 500 cm-1 covering the bands of high-lying gerade Rydberg states [2?1/2]c6d;0g+ and [2?1/2]c6d;2g has been applied. The ion signal was dominated by the atomic fragment ion I+. Up to 5 dissociation channels yielding I+ ions with different kinetic energies were observed when the I2 molecule was excited within discrete peaks of Rydberg states and their satellites in this region. One of these channels gives rise to images of I+ and I- ions with equal kinetic energy indicating predissociation of I2 via ion-pair states. The contribution of this channel was up to about 50% of the total I+ signal. The four other channels correspond to predissociation via lower lying Rydberg states giving rise to excited iodine atoms providing I+ ions by subsequent one-photon ionization by the same laser pulse. The ratio of these channels varied from peak to peak in the spectrum but their total ionic signal was always much higher than the signal of (2 + 1) resonance enhanced multi-photon ionization of I2, which was previously considered to be the origin of ionic signal in this spectral range. The first-tier E0g+ and D'2g ion-pair states are concluded to be responsible for predissociation of Rydberg states [2?1/2]c6d;0g+ and [2?1/2]c6d;2g, respectively. Further predissociation of these ion-pair states via lower lying Rydberg states gives rise to excited I(5s25p46s1) atoms responsible for major part of ion signal. The isotropic angular distribution of the photofragment recoil directions observed for all channels indicates that the studied Rydberg states are long-lived compared with the rotational period of the I2 molecule.

Bogomolov, Alexandr S.; Grüner, Barbara; Kochubei, Sergei A.; Mudrich, Marcel; Baklanov, Alexey V.

2014-03-01

29

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

NASA Astrophysics Data System (ADS)

The structure and dynamics of high-n Rydberg states belonging to series converging to the (v+ = 0, N+ = 0-2) levels of the X^+ ^2? _g^+ electronic ground state of HD+ were studied by high-resolution spectroscopy from the GK ^1? _g^+ (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 30d21 and 31g22 Rydberg states of gerade symmetry were observed after careful compensation of the stray electric fields. (ii) The singlet 61p12 Rydberg state of ungerade symmetry was found to autoionize to the N+ = 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 np11 Rydberg series which lie close to nd21 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 ? _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-1.

Sprecher, Daniel; Merkt, Frédéric

2014-03-01

30

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

31

Single Photon Transistor Mediated by Inter-State Rydberg Interaction  

E-print Network

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 10 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).

Hannes Gorniaczyk; Christoph Tresp; Johannes Schmidt; Helmut Fedder; Sebastian Hofferberth

2014-04-10

32

Sub-Poissonian statistics of Rydberg-interacting dark-state polaritons  

E-print Network

Interfacing light and matter at the quantum level is at the heart of modern atomic and optical physics and enables new quantum technologies involving the manipulation of single photons and atoms. A prototypical atom-light interface is electromagnetically induced transparency, in which quantum interference gives rise to hybrid states of photons and atoms called dark-state polaritons. We have observed individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states. Strong long-range interactions between Rydberg atoms give rise to an effective interaction blockade for dark-state polaritons, which results in large optical nonlinearities and modified polariton number statistics. The observed statistical fluctuations drop well below the quantum noise limit indicating that photon correlations modified by the strong interactions have a significant back-action on the Rydberg atom statistics.

Christoph S. Hofmann; Georg Günter; Hanna Schempp; Martin Robert-de-Saint-Vincent; Martin Gärttner; Jörg Evers; Shannon Whitlock; Matthias Weidemüller

2012-11-30

33

PHYSICAL REVIEW A 87, 063405 (2013) Photoelectron spectra and high Rydberg states of lithium generated by intense lasers  

E-print Network

PHYSICAL REVIEW A 87, 063405 (2013) Photoelectron spectra and high Rydberg states of lithium photoelectron energy and momentum spectra and the population of high Rydberg states of lithium atoms by intense)]. It is shown that in the OBI regime, due to strong depletion of the ground state, the photoelectron spectra

Lin, Chii-Dong

34

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

35

Rydberg states in the strong field ionization of hydrogen by 800, 1200 and 1600 nm lasers  

NASA Astrophysics Data System (ADS)

We study the population of Rydberg excited states in the strong field interaction of atomic hydrogen with 800, 1200 and 1600 nm laser pulses. The total excitation probability displays strong out-of-phase modulation with respect to the weak modulation in the total ionization probability as the laser intensity is increased. The results are explained in terms of channel closing, to demonstrate multiphoton ionization features in the strong tunnel ionization regime. We also explain the stability of high Rydberg states in strong laser fields in contrast to other previous ionization stabilization models.

Li, Qianguang; Tong, Xiao-Min; Morishita, Toru; Jin, Cheng; Wei, Hui; Lin, C. D.

2014-10-01

36

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

37

Collective photon emission from symmetric states created with Rydberg atoms on a ring lattice  

Microsoft Academic Search

We discuss the creation of nonclassical light from collective atomic states that are prepared in a ring-shaped lattice. These states are realized by exploiting the strong interaction between atoms in high-lying energy levels---the so-called Rydberg states---and yield a resource for creating excitations of the electromagnetic field that carry few photons. We characterize the properties of these photonic states showing that

B. Olmos; I. Lesanovsky

2010-01-01

38

Collective photon emission from symmetric states created with Rydberg atoms on a ring lattice  

Microsoft Academic Search

We discuss the creation of nonclassical light from collective atomic states that are prepared in a ring-shaped lattice. These states are realized by exploiting the strong interaction between atoms in high-lying energy levels--the so-called Rydberg states--and yield a resource for creating excitations of the electromagnetic field that carry few photons. We characterize the properties of these photonic states showing that

B. Olmos; I. Lesanovsky

2010-01-01

39

Observation of the Stark effect in ?+ = 0 Rydberg states of NO: a comparison between predissociating and bound states  

Microsoft Academic Search

The Stark spectra of Rydberg states of NO below the ?+ = 0 ionization limit, with principal quantum numbers n = 25–30, have been investigated in the presence of dc electric fields in the range 0–150 V cm?1. The Stark states were accessed by two-colour, double-resonance excitation via the ?? = 0, N? = 0 rovibrational state of the A2?+

N J A Jones; R S Minns; R Patel; H H Fielding

2008-01-01

40

Multichannel-quantum-defect-theory analysis of the Stark effect in autoionizing Rydberg states of H[sub 2  

Microsoft Academic Search

The multichannel-quantum-defect theory (MQDT) of the Stark effect is applied to the simulation of transitions in molecular hydrogen to the autoionizing Rydberg states in the region between the [ital v][sup +]=1 and [ital v][sup +]=2 thresholds, with principal quantum numbers 13--19, for applied electric fields in the range 100--1300 V\\/cm. The vibrational coupling between Rydberg states belonging to different series

H. H. Fielding; T. P. Softley

1994-01-01

41

Multichannel-quantum-defect-theory analysis of the Stark effect in autoionizing Rydberg states of H2  

Microsoft Academic Search

The multichannel-quantum-defect theory (MQDT) of the Stark effect is applied to the simulation of transitions in molecular hydrogen to the autoionizing Rydberg states in the region between the v+=1 and v+=2 thresholds, with principal quantum numbers 13-19, for applied electric fields in the range 100-1300 V\\/cm. The vibrational coupling between Rydberg states belonging to different series is included for the

H. H. Fielding; T. P. Softley

1994-01-01

42

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

E-print Network

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

Colombo, Anthony P. (Anthony Paul)

2013-01-01

43

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

E-print Network

We apply the chirped-pulse millimeter-wave (CPmmW) technique to transitions between Rydberg states in calcium atoms. The unique feature of Rydberg–Rydberg transitions is that they have enormous electric dipole transition ...

Colombo, Anthony P.

2013-01-01

44

Observation of classical subharmonic resonances in pulsed microwave ionization of Sr Rydberg states  

NASA Astrophysics Data System (ADS)

We have studied ionization of strontium 5snd Rydberg atoms by short-pulsed MW fields. A series of resonances has been observed where the atoms are relatively stable against MW ionization. This ionization behavior of Sr Rydberg states are quite similar to those seen previously in hydrogen [1] and lithium [2], but with some qualitative differences, due possibly to effects of a larger ionic core of Sr. We have also measured the final-state distribution of Rydberg states which remain bound after the pulsed MW ionization near one of the classical subharmonic resonances. The data clearly shows that population of the final states tends to be pulled into the near-by subharmonic resonance, as was already observed in the previous study of Li [2], suggesting a formation of a wave packet that is synchronized with the MW field. Currently we are on the way to detect its time-dependent motion to have a clear evidence of formation of MW-driven wave packets in Sr starting from the eigenstates. [1] K.A.H. van Leeuwen et al., Phys. Rev. Lett. 55, 2231 (1985). [2] M. W. Noel et al., Phys. Rev. A 62, 063401 (2000).

Maeda, H.; Gallagher, T. F.

2002-05-01

45

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 hydrogénoïde et avec les prédictions d'une approximation semi-clas- sique. Abstract 2014 The diamagnetic-l and inter-n diamagnetic mixing regimes, until they reach the zero-field 2P3/2 ionization threshold, where

Paris-Sud XI, Université de

46

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

Microsoft Academic Search

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

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

2008-01-01

47

Experimentally probing the three-body predissociation dynamics of the low-lying Rydberg states of H3 and D3  

E-print Network

Experimentally probing the three-body predissociation dynamics of the low-lying Rydberg states of H preparation of the low-lying Rydberg states of H3. These states are predissociated by the repulsive ground for the three lowest-lying 2s 2 A1, 2p 2 A2 and 3p 2 E bound Rydberg states of H3 and the two 2s 2 A1 and 2p 2 A

Continetti, Robert E.

48

Scaled-Energy Spectroscopy of Helium and Barium Rydberg Atoms in External Fields  

Microsoft Academic Search

and which at low field strength is responsible for the mixing of angular momentum states (r is the radius of the electron orbit). When diamagnetism dominates only two conserved quantities (energy W and z-component of angular momentum l) exist for this system with three spatial degrees of freedom, a prerequisite for chaos in classical physics. The diamagnetic effect not only

W. Hogervorst; A. Kips; K. Karremans; T. van der Veldt; G. J. Kuik; W. Vassen

1998-01-01

49

The role of optical transitions between ionic and Rydberg states in a KrF laser  

SciTech Connect

The upper laser level of a KrF laser is treated as a cluster containing several hundreds vibration-rotation energy levels of the electronic state B, which is mixed due to collisions with the close ionic state C. The KrF (C) state is depleted as a result of optical transitions to a higher Rydberg state. This model explains the experimental data on the picosecond dynamics of the light amplification. The possibility of using a KrF laser as an amplifier of radiation with a wavelength of 120 nm is discussed. (lasers and amplifiers)

Datsyuk, V V [Department of Physics and Mathematics, T.G. Shevchenko Pridnestrie State University (Moldova, Republic of)

2001-05-31

50

Theoretical description of electronically excited vinylidene up to 10 eV: First high level ab initio study of singlet valence and Rydberg states.  

PubMed

The first quantitative description of the Rydberg and valence singlet electronic states of vinylidene lying in the 0-10 eV region is performed by using large scale ab initio calculations. A deep analysis of Rydberg-valence interactions has been achieved thanks to the comprehensive information contained in the accurate Multi-Reference Configuration Interaction wavefunctions and an original population analysis highlighting the respective role played by orbital and state mixing in such interactions. The present theoretical approach is thus adequate for dealing with larger than diatomic Rydberg systems. The nine lowest singlet valence states have been optimized. Among them, some are involved in strong Rydberg-valence interactions in the region of the Rydberg state equilibrium geometry. The Rydberg states of vinylidene present a great similarity with the acetylene isomer, concerning their quantum defects and Rydberg molecular orbital character. As in acetylene, strong s-d mixing is revealed in the n = 3 s-d supercomplex. Nevertheless, unlike in acetylene, the close-energy of the two vinylidene ionic cores (2)A1 and (2)B1 results into two overlapped Rydberg series. These Rydberg series exhibit local perturbations when an accidental degeneracy occurs between them and results in avoided crossings. In addition, some ?l = 1 (s-p and p-d) mixings arise for some Rydberg states and are rationalized in term of electrostatic interaction from the electric dipole moment of the ionic core. The strongest dipole moment of the (2)B1 cationic state also stabilizes the lowest members of the n = 3 Rydberg series converging to this excited state, as compared to the adjacent series converging toward the (2)A1 ionic ground state. The overall energies of vinylidene Rydberg states lie above their acetylene counterpart. Finally, predictions for optical transitions in singlet vinylidene are suggested for further experimental spectroscopic characterization of vinylidene. PMID:25381524

Boyé-Péronne, Séverine; Gauyacq, Dolores; Liévin, Jacques

2014-11-01

51

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

52

Laser optogalvanic spectroscopy of the even-parity Rydberg states of atomic mercury  

SciTech Connect

We present new experimental data on the highly excited levels in mercury using the optogalvanic detection technique in conjunction with a dc discharge cell. The collisionally populated 6s6p {sup 3}P{sub 2} metastable level has been used as an intermediate level to access the Rydberg states using a frequency-doubled dye laser covering the wavelength region between 370 and 249 nm. The optogalvanic data reveal 6sns {sup 3}S{sub 1}(13{<=}n{<=}50), 6snd {sup 1}D{sub 2}(6{<=}n{<=}18), 6snp {sup 3}D{sub 1}(6{<=}n{<=}14), 6snd {sup 3}D{sub 2}(6{<=}n{<=}15), and 6snd {sup 3}D{sub 3}(6{<=}n{<=}59) Rydberg series. The 6sns {sup 3}S{sub 1} and 6snd {sup 3}D{sub 3} Rydberg series to such a high n value have been reported for the first time. In addition, collisionally induced parity-forbidden transitions 6snp {sup 3}P{sub 1}(44{<=}n{<=}50) have been detected.

Zia, M.A.; Baig, M.A. [Atomic and Molecular Physics Laboratory, Quaid-i-Azam University 54320 Islamabad (Pakistan)

2005-12-01

53

Observation of the Stark effect in upsilo+ = 0 Rydberg states of NO: a comparison between predissociating and bound states  

Microsoft Academic Search

The Stark spectra of Rydberg states of NO below the upsilo+ = 0 ionization limit, with principal quantum numbers n = 25-30, have been investigated in the presence of dc electric fields in the range 0-150 V cm-1. The Stark states were accessed by two-colour, double-resonance excitation via the upsilo' = 0, N' = 0 rovibrational state of the A2Sigma+

N. J. A. Jones; R. S. Minns; R. Patel; H. H. Fielding

2008-01-01

54

Singlet-triplet mixing in ns(n=12-14) Rydberg states of 3He  

Microsoft Academic Search

The hyperfine structure of the n3S (n=12-14) Rydberg levels in 3He have been studied by ultraviolet-infrared double-resonance laser spectroscopy. Using the frequency-doubled output of a CW ring dye laser the authors have populated the 1s5p 3P state of 3He by excitation from the metastable 1s2s 3S state at 294.5 nm. In a second step, an infrared single-mode colour-centre laser is

L. A. Bloomfield; H. Gerhardt; T. W. Hansch

1983-01-01

55

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

NASA Astrophysics Data System (ADS)

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

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

1992-08-01

56

Photoionization, photodissociation, and long-range bond formation in molecular Rydberg states  

Microsoft Academic Search

The Rydberg spectra of atoms and small molecules offers an experimentally convenient probe for exploring the exchange of energy between Rydberg electrons and other forms of electronic, vibrational, and rotational excitation. This thesis investigates a series of special topics in the field of molecular Rydberg spectra, using a diverse set of theoretical techniques all designed to take advantage of the

Edward Lees Hamilton

2003-01-01

57

Observation of the Stark effect in upsilo+ = 0 Rydberg states of NO with a matrix-diagonalization analysis  

Microsoft Academic Search

Rydberg states with the principal quantum number n = 25-32, below the upsilo+ = 0 ionization limit, are excited by double resonance via the upsilo' = 0, N' = 0 and upsilo' = 0, N' = 2 rovibrational states of the A2Sigma+ state. In the presence of dc electric fields in the range 0-120 V cm-1, new resonances and hydrogenic

R. Patel; N. J. A. Jones; H. H. Fielding

2007-01-01

58

Dipole Blockade at Foerster Resonances in High Resolution Laser Excitation of Rydberg States of Cesium Atoms  

SciTech Connect

High resolution laser excitation of np Rydberg states of cesium atoms shows a dipole blockade at Foerster resonances corresponding to the resonant dipole-dipole energy transfer of the np+np{yields}ns+(n+1)s reaction. The dipole-dipole interaction can be tuned on and off by the Stark effect, and such a process, observed for relatively low n(25-41), is promising for quantum gate devices. Both Penning ionization and saturation in the laser excitation can limit the range of observation of the dipole blockade.

Vogt, Thibault; Viteau, Matthieu; Zhao Jianming; Chotia, Amodsen; Comparat, Daniel; Pillet, Pierre [Laboratoire Aime Cotton, CNRS, Batiment 505, Campus d'Orsay, 91405 Orsay (France)

2006-08-25

59

Photoelectron recapture as a tool for the spectroscopy of ionic Rydberg states  

SciTech Connect

We use recapture of near-threshold photoelectrons by postcollision interaction with Auger electrons as an effective method for population of the high-Rydberg states of subvalence ionized Ne ions. The subsequent intermultiplet Auger transitions are detected by high-resolution electron spectrometry. The series of transitions 2p{sup 4}({sup 1}D)np {sup 2}D,{sup 2}F{yields}2p{sup 4} {sup 3}P up to n=20 are observed and identified with the help of multiconfiguration Dirac-Fock ab initio calculations.

De Fanis, A. [Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo 679-5198 (Japan); Pruemper, G.; Ueda, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Hergenhahn, U. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Max-Planck-Institut fuer Plasmaphysik EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany); Oura, M. [RIKEN, Spring-8 Sayo-gun, Hyogo 679-5198 (Japan); Kitajima, M.; Tanaka, T.; Tanaka, H. [Department of Physics, Sophia University, Tokyo 102-8554 (Japan); Fritzsche, S. [Fachbereich Physik, Universitaet Kassel, D-34132 Kassel (Germany); Kabachnik, N.M. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany)

2004-10-01

60

Evolution of Rydberg states in half-cycle pulses: Classical, semiclassical, and quantum dynamics  

SciTech Connect

We summarize recent theoretical advances in the description of the evolution of Rydberg atoms subject to ultrashort pulses extending only a fraction of an optical cycle. We have performed classical. semiclassical and full quantum calculations in order to delineate the classical-quantum correspondence for impulsively perturbed atomic systems. We observe classical and quantum (or semiclassical) oscillations in excitation and ionization which depend on the initial state of atoms and on the strength of the perturbation. These predictions can be experimentally tested. 4 figs.

Burgdoerfer, J.; Reinhold, C. [Tennessee Univ., Knoxville, TN (United States). Dept. of Physics]|[Oak Ridge National Lab., TN (United States)

1994-12-31

61

Microwave multiphoton transitions between Rydberg states of potassium  

Microsoft Academic Search

We report the observation of sequences of from 1- to as many as 28-photon transitions between potassium (n+2)s states and the lowest-energy Stark states of the n manifolds for n=15-18. The sequences are observed by the scanning of a static electric field from the field at which these pairs of levels nearly cross, to zero field where they are well

L. A. Bloomfield; R. C. Stoneman; T. F. Gallagher

1986-01-01

62

Rydberg states of the hydrogen-antihydrogen quasimolecule  

NASA Astrophysics Data System (ADS)

A description of the excited lepton states of the hydrogen-antihydrogen quasimolecule is presented. Potential energy curves and the leptonic part of the wave functions corresponding to a variety of such states are calculated within the Born-Oppenheimer approximation employing the Ritz variational principle. Nonadiabatic corrections to the leptonic potentials are also obtained. Basis functions are constructed as products of explicitly correlated Gaussians and spherical harmonics which describe correctly the motion of leptons with arbitrary orbital angular momentum projection onto the molecular (internuclear) axis. The hadronic part of the wave function for each leptonic level of the hydrogen-antihydrogen system is calculated by solving the Schrödinger equation with the obtained leptonic potentials. Corresponding solutions are generated utilizing precise B-spline representations. Employing leptonic and hadronic parts of the wave function the electron-positron and proton-antiproton annihilation rates are computed for a number of quasimolecular states. The decay rates of the hydrogen-antihydrogen system into separate positronium and protonium atoms are also estimated for the quasimolecular levels under consideration.

Sharipov, V.; Labzowsky, L.; Plunien, G.

2006-05-01

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

Ultraviolet-infrared double-resonance laser spectroscopy of nd (n=12-17) Rydberg states in 3He  

Microsoft Academic Search

The hyperfine structure of the singlet and triplet nd Rydberg states (n=12-17) in 3He have been studied by Doppler-free ultraviolet-infrared double-resonance laser spectroscopy. Using the frequency-doubled output of a cw dye ring laser we have populated the 1s 5p 3P state of 3He by excitation from the metastable 1s 2s 3S state at 294.5 nm. In a second step, an

L. A. Bloomfield; H. Gerhardt; T. W. Hänsch

1983-01-01

65

Coupled Electronic and Structural Relaxation Pathways in the Postexcitation Dynamics of Rydberg States of BaArN Clusters  

NASA Astrophysics Data System (ADS)

We investigate, theoretically, the joint relaxation of orbital and structure in postexcitation dynamics of Rydberg states of cluster BaArN (N =250). Mixed quantum-classical dynamics is used to account for the nonadiabatic transitions among more than 160 electronic states, represented via a diatomics-in-molecules Hamiltonian. The simulation illustrates the complex multistep relaxation processes and provides detailed insight in the mechanisms contributing to the final-time experimental photoelectron spectrum.

Masson, A.; Heitz, M.-C.; Mestdagh, J.-M.; Gaveau, M.-A.; Poisson, L.; Spiegelman, F.

2014-09-01

66

Singlet-Triplet Mixing in the 13d Rydberg state of ³He observed with stepwise laser excitation  

Microsoft Academic Search

The hyperfine structure of the singlet and triplet 13d Rydberg states in ³He have been studied by stepwise excitation with a single-mode uv laser (294.5 nm) and single-mode color-center laser (2.590 ..mu..m). The experimental results for the 13d state are in good agreement with semiempirical calculations. No difference in the electrostatic energy interval was found between the ³He and ⁴He

L. A. Bloomfield; H. Gerhardt; T. W. Haensch

1982-01-01

67

Singlet-triplet mixing in the 13d Rydberg state of 3He observed with stepwise laser excitation  

Microsoft Academic Search

The hyperfine structure of the singlet and triplet 13d Rydberg states in 3He have been studied by stepwise excitation with a single-mode uv laser (294.5 nm) and single-mode color-center laser (2.590 mum). The experimental results for the 13d state are in good agreement with semi-empirical calculations. No difference in the electrostatic energy interval was found between the 3He and 4He

L. A. Bloomfield; H. Gerhardt; T. W. Hänsch

1982-01-01

68

Observation of the Stark effect in autoionizing Rydberg states of Ar with a multichannel quantum-defect analysis  

Microsoft Academic Search

The Stark spectra of autoionizing Rydberg states of Ar converging to the second ionization limit 3p52P1\\/2 have been investigated, experimentally and theoretically, as a function of electric field strength, in the range 15-2000 V cm-1. The levels with effective principal quantum number v=12-19, are excited by single-photon absorption from the ground state using a coherent extreme ultraviolet laser source (bandwidth

H. Fielding; T. P. Softley

1992-01-01

69

Excitation of Rydberg states of HgCl2 and HgBr2 by electron impact  

NASA Astrophysics Data System (ADS)

We have examined the electronic structure of HgCl2 and HgBr2 from 5 to 14 eV by high resolution electron energy loss spectroscopy. Our measurements include the near-UV region which has not been examined by any previous technique and which is found to be rich in Rydberg states. In particular, in each molecule we identify members of two optically allowed Rydberg series and one forbidden series with electronic structues ?2g?2u?4u?3g [np?u, np?u, and nd?g, or (n+1)s?g] which converge to the 2?g ground ionic state. In addition, other structures which form the dominant energy loss mechanisms in our spectra are identified as arising from optically allowed Rydberg states associated with the excited ionic states 2?u, 2?u, and 2?g. Measurements at energy loss below 9 eV confirm previous valence states observed in photoabsorbtion and suggest the existence of two new valence states in each molecule. Angular measurements facilitate identification of many of the newly observed structures in our electron-energy loss spectra.

Spence, David; Wang, R.-G.; Dillon, Michael A.

1985-02-01

70

Multireference configuration interaction studies on higher valence and Rydberg states of OClO, ionization potentials, and electron detachment energies.  

PubMed

MRCI results are reported for the vertical excitation energies (VEE) and oscillator strengths f of doublet states of OClO up to 11 eV, including 3b(1) ? 4s, 4p, 3d, 5s, 5p, 4d, and most 1a(2), 8a(1), 5b(2) ? 4s and 4p Rydberg states. The lowest Rydberg states 3b(1) ? 4s and 3b(1) ? 4p(x) have mixed valence-Rydberg character. The observed spectral bands were reassigned to include valence states which have generally higher oscillator strengths. The well-known valence state 1(2)A(2) has a VEE of 3.63 eV, and a relatively high f of 0.042. Overall, the calculated oscillator strengths are in good agreement with measured values. The lowest quartet state, 1(4)B(2), lies at 6.95 eV. Quartet Rydberg states start with 1a(2) ? 4s at 9.28 eV. According to calculated vertical ionization potentials (VIP) of OClO, the second VIP at 12.59 eV is reassigned from 1(3)B(1) to 1(3)B(2) (ionization from 1a(2), rather than 8a(1)), and the third VIP at 12.63 eV from 1(1)B(1) to 1(3)B(1) (ionization from 8a(1)). Vertical electron detachment energies of OClO(-) have been calculated up to 8.9 eV. There is good agreement with experimental values. PMID:21806116

Grein, Friedrich

2011-07-28

71

Modeling Two-Charge State Helium Plasmas  

NASA Astrophysics Data System (ADS)

A computational model for the flow of energetic helium ions and atoms through a background neutral helium gas is being developed. The essence of the method is to consider atomic reactions as creating a new source of ions or neutrals if the energy or charge state of the resulting particle is changed. A set of conservation equations in a two-dimensional (position -- energy) phase space is formulated. Atomic reactions that lead to ions being born with zero kinetic energy are modeled with a 1-D Volterra integral equation [1] that can quickly be solved numerically by finite differences. Atomic reactions leading to ions being born with finite kinetic energy are formulated as source terms in the position-energy phase space. The conservation equations are solved iteratively using the solution to the Volterra equation as a starting point. The current work focuses on multiple-pass, 1-D ion flow through neutral gas in a nearly transparent anode and cathode pair in planar, cylindrical, and spherical geometry for application to ^3He-^3He and D-^3He inertial electrostatic experiments.[4pt] [1] G.A. Emmert and J.F. Santarius, ``Atomic and Molecular Effects on Spherically Convergent Ion Flow I: Single Atomic Species,'' Phys. Plasmas 17, 013502 (2010)

Emmert, Gilbert; Santarius, John

2012-10-01

72

Collisional and thermal ionization of sodium Rydberg atoms: II. Theory for nS, nP and nD states with n = 5 25  

Microsoft Academic Search

A stochastic model of associative ionization in collisions of Rydberg atoms with ground-state atoms is presented. The conventional Duman-Shmatov-Mihajlov-Janev (DSMJ) model treats the ionization as excitation of Rydberg electron to the continuum by the electric-dipole field generated by exchange interaction within the quasi-molecular ion. The stochastic model essentially extends this treatment by taking into account redistribution of population over a

K. Miculis; I. I. Beterov; N. N. Bezuglov; I. I. Ryabtsev; D. B. Tretyakov; A. Ekers; A. N. Klucharev

2005-01-01

73

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

74

Ultraviolet-infrared double-resonance laser spectroscopy of nd (n = 12--17) Rydberg states in ³He  

Microsoft Academic Search

The hyperfine structure of the singlet and triplet nd Rydberg states (n = 12--17) in ³He have been studied by Doppler-free ultraviolet-infrared double-resonance laser spectroscopy. Using the frequency-doubled output of a cw dye ring laser we have populated the 1s5p ³P state of ³He by excitation from the metastable 1s2s ³S state at 294.5 nm. In a second step, an

L. A. Bloomfield; H. Gerhardt; T. W. Haensch

1983-01-01

75

Electric-field induced dissociation of molecules in Rydberg-like highly vibrationally excited ion-pair states  

NASA Astrophysics Data System (ADS)

Highly vibrationally excited (high-v) ion-pair states of molecules share many of the same properties as high-n Rydberg states. In high-v ion-pair states, a weakly bound pair-an anion and cation-play the roles of electron and ion-core. high-v ion-pair states have an infinite number of vibrational levels below their dissociation threshold, and these follow a Rydberg-like formula. It is demonstrated that high- v ion-pair states can be dissociated by the application of weak pulsed electric fields, in a similar manner to the electric-field induced ionization of high-n Rydberg states. It has been possible to exploit this effect-using a technique similar to pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy (PFI-ZEKE) and mass-analyzed threshold ionization spectroscopy (MATI)-to determine field-free energetic thresholds for ion-pair formation. The thresholds for three processes were studied using this technique: HCl + h? --> H+ + Cl-, O2 + h? --> O+ + O -, and HF + h? --> H+ + F-. The accurately determined field-free ion-pair formation threshold of HCl, together with the known values of the ionization potential of H and the electron affinity of Cl, allowed the dissociation energy of HCl to be determined to within +/-1 cm-1-a significant improvement over the literature value. This new technique-threshold ion-pair production spectroscopy (TIPPS)-should be applicable to polyatomics, for which many bond energies are only known thermochemically.

Martin, James D. D.

1999-11-01

76

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

77

Collisions of Na+ ions with Na Rydberg atoms in electric fields: depopulation cross sections and final-state distributions from 36s and 30p initial states  

Microsoft Academic Search

An experimental study of the depopulation and final-state distribution of Na 36s and 30p Rydberg states under Na+ bombardment in the presence of electric fields up to 50 V cm-1 has been carried out. Incident energies E from 171 to 967 eV span the range from 0.6 to. 1.4 times the mean orbital speed of the excited electron in the

R. G. Rolfes; L. G. Gray; K. B. MacAdam

1992-01-01

78

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

NASA Astrophysics Data System (ADS)

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

Kalemos, Apostolos; Prosmiti, Rita

2014-09-01

79

The influence of autoionizing Rydberg states on the H2+ X 2?g+ v+ = 0, 1, 2 state rotationally resolved photoelectron angular distributions and branching ratios  

NASA Astrophysics Data System (ADS)

The effect of vibrational autoionization on the H2+ X 2?g+ v+ = 0, 1, 2, N+ state rotationally resolved photoelectron angular distributions and branching ratios has been investigated with a velocity map imaging spectrometer and synchrotron radiation. Measurements have been made in the energy regions close to the v+ = 0, 1 or 2 ionization thresholds where the photoabsorption spectrum is dominated by structure due to autoionizing Rydberg states. The photoelectron anisotropy parameter associated with the X 1?g+ v? = 0, N? = 1 ? X 2?g+ v+ = 0, 1 or 2, N+ = 1 transition has a high value, characteristic of emission predominantly along the polarization axis of the incident radiation, when ionization occurs directly but in the vicinity of an autoionizing Rydberg state a more isotropic angular distribution is observed. For the v+ = 1 level, the present experimental data are compared with existing theoretical predictions in the energy range encompassing the R(1) 8p? v? = 2 and the Q(1) 8p? v? = 2 states. Qualitative agreement has been obtained between the measured and the predicted rotationally resolved photoelectron anisotropy parameters. The experimental values of the rotationally unresolved S-branch photoelectron anisotropy parameter are found to lie considerably higher than that (0.2, independent of excitation energy) predicted under the assumption of p-wave emission, and, moreover, exhibit deviations which appear to correlate with autoionizing Rydberg states. These observations suggest that a proper description of the photoionization dynamics requires the inclusion of partial waves higher than l = 1. In the neighbourhood of an autoionizing resonance, the variations occurring in the rotationally resolved branching ratios depend upon the rotational level of the Rydberg state.

Holland, D. M. P.; Shaw, D. A.

2014-09-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

81

Absolute Photoionization Cross Section with an Ultra-high Energy Resolution for Ne in the Region of 1s Rydberg States  

SciTech Connect

The high-resolution absolute photoabsorption cross section with an absolute photon energy scale for Ne in the energy region of 864-872 eV (1s-1np Rydberg states) has been measured using a multi-electrode ionization chamber and monochromatized synchrotron radiation. The natural lifetime width of Ne 1s-13p resonance state has been obtained to be 252 {+-} 5 meV. The Ne+ (1s-1) ionization potential is determined to be 870.16 {+-} 0.04 eV by using the Rydberg formula. These absolute values are supposed to be more reliable than those previously reported.

Kato, M.; Morishita, Y.; Suzuki, I. H.; Saito, N. [AIST, NMIJ, Tsukuba, 305-8568 (Japan); Oura, M.; Yamaoka, H. [SPring-8/JASRI, Sayo, Hyogo 679-5198 (Japan); Tamenori, Y. [RIKEN, Harima Institute, Sayo, Hyogo 679-5148 (Japan); Okada, K.; Matsudo, T. [Department of Chemistry, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Gejo, T. [University of Hyogo, Kamigori, Hyogo 678-1297 (Japan)

2007-01-19

82

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

E-print Network

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

California at Santa Cruz, University of

83

Physics 216 Spring 2012 The Variational Computation of the Ground State Energy of Helium  

E-print Network

Physics 216 Spring 2012 The Variational Computation of the Ground State Energy of Helium I. Introduction to the variational computation The Hamiltonian for the two-electron system of the helium atom is state energy of the helium atom. The ground state wave function of the helium atom is of the form: 1 2

California at Santa Cruz, University of

84

Excitation transport through Rydberg dressing  

NASA Astrophysics Data System (ADS)

We show how to create long-range interactions between alkali atoms in different hyperfine ground states, with the goal of coherent quantum transport. The scheme uses off-resonant dressing with atomic Rydberg states. We demonstrate coherent migration of electronic excitation through dressed dipole-dipole interaction by full solutions of models with four essential states per atom and give the structure of the spectrum of dressed states for a dimer. In addition, we present an effective (perturbative) Hamiltonian for the ground-state manifold and show that it correctly describes the full multi-state dynamics. We discuss excitation transport in detail for a chain of five atoms. In the presented scheme, the actual population in the Rydberg state is kept small. Dressing offers many advantages over the direct use of Rydberg levels: it reduces ionization probabilities and provides an additional tuning parameter for lifetimes and interaction strengths.

Wüster, S.; Ates, C.; Eisfeld, A.; Rost, J. M.

2011-07-01

85

An optogalvanic study of rydberg oxygen atoms  

NASA Astrophysics Data System (ADS)

Rydberg oxygen atoms were produced in a dc glow discharge by laser excitation of metastable states. Transitions were detected via the optogalvanic effect. The observed states of these Rydberg atoms were found to be significantly perturbed and mixed by the electric field present in the discharge.

Keaton, G. L.; Nogar, N. S.; Downey, S. W.

1987-05-01

86

Wireless network control of interacting Rydberg atoms.  

PubMed

We identify a relation between the dynamics of ultracold Rydberg gases in which atoms experience a strong dipole blockade and spontaneous emission, and a stochastic process that models certain wireless random-access networks. We then transfer insights and techniques initially developed for these wireless networks to the realm of Rydberg gases, and explain how the Rydberg gas can be driven into crystal formations using our understanding of wireless networks. Finally, we propose a method to determine Rabi frequencies (laser intensities) such that particles in the Rydberg gas are excited with specified target excitation probabilities, providing control over mixed-state populations. PMID:24815645

Sanders, Jaron; van Bijnen, Rick; Vredenbregt, Edgar; Kokkelmans, Servaas

2014-04-25

87

Wireless Network Control of Interacting Rydberg Atoms  

NASA Astrophysics Data System (ADS)

We identify a relation between the dynamics of ultracold Rydberg gases in which atoms experience a strong dipole blockade and spontaneous emission, and a stochastic process that models certain wireless random-access networks. We then transfer insights and techniques initially developed for these wireless networks to the realm of Rydberg gases, and explain how the Rydberg gas can be driven into crystal formations using our understanding of wireless networks. Finally, we propose a method to determine Rabi frequencies (laser intensities) such that particles in the Rydberg gas are excited with specified target excitation probabilities, providing control over mixed-state populations.

Sanders, Jaron; van Bijnen, Rick; Vredenbregt, Edgar; Kokkelmans, Servaas

2014-04-01

88

Ultracold Rydberg Gases and Plasmas  

NASA Astrophysics Data System (ADS)

Ultracold Rb atoms, prepared by laser cooling techniques, are excited with pulsed UV light to near their ionization threshold. Depending on the photon energy, this results in either an ultracold gas of highly-excited Rydberg atoms or an ultracold plasma. We have observed these two phenomena together. Starting with a cold dense Rydberg gas, collisional ionization proceeds slowly until a threshold is reached, at which point superelastic electron collisions cause the ionization to "avalanche"[1], rapidly converting most of the atoms into a plasma. Surprisingly, if we wait long enough, the plasma partially reverts back to bound Rydberg atoms, presumably by the process of three-body recombination[2]. Measurements of the Rydberg state distribution at various times during this evolution should help us better understand this fascinating behavior. Due to their large polarizability, ultracold Rydberg atoms at high density can interact quite strongly. Besides possibly leading to ionization, these interactions cause line broadening and are responsible for molecular resonances which we have observed in the spectrum. These resonances result from avoided crossings of potential curves involving pairs of highly-excited atoms. These strong interactions can also cause conditional suppression of resonant Rydberg excitation, with potential applications in quantum computing. [1] M.P. Robinson, B. Laburthe Tolra, M.W. Noel, T.F. Gallagher, and P. Pillet, Phys. Rev. Lett. 85, 4466 (2000). [2] T.C. Killian, M.J. Lim, S. Kulin, R. Dumke, S.D. Bergeson, and S.L. Rolston, Phys. Rev. Lett. 86, 3579 (2001).

Gould, Phillip

2003-10-01

89

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

90

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

E-print Network

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

Krzysztof Pachucki

2006-07-07

91

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

NASA Astrophysics Data System (ADS)

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

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

2006-07-01

92

Interactions between Rydberg-dressed atoms  

SciTech Connect

We examine interactions between atoms continuously and coherently driven between the ground state and a Rydberg state, producing 'Rydberg-dressed atoms'. Because of the large dipolar coupling between two Rydberg atoms, a small admixture of Rydberg character into a ground state can produce an atom with a dipole moment of a few debye, the appropriate size to observe interesting dipolar physics effects in cold atom systems. We have calculated the interaction energies for atoms that interact via the dipole-dipole interaction and find that because of blockade effects, the R dependent two-atom interaction terms are limited in size and can be R independent up until the dipolar energy is equal to the detuning. This produces R dependent interactions different from the expected 1/R{sup 3} dipolar form that have no direct analogy in condensed-matter physics and could lead to interesting quantum phases in trapped Rydberg systems.

Johnson, J. E.; Rolston, S. L. [Joint Quantum Institute, Department of Physics, University of Maryland (United States) and National Institute of Standards and Technology, College Park, Maryland 20742-4111 (United States)

2010-09-15

93

Ground-state energies for the helium isoelectronic series  

SciTech Connect

Variational calculations are reported for the ground state of the helium isoelectronic series. An ansatz is introduced and it achieves an accuracy comparable to that hitherto achieved only with basis functions containing logarithmic terms. Energies accurate to better than one part in 10[sup 14] are obtained for the ground states of He through Ne[sup 8+] using 308-term expansions, and the ground state of H[sup [minus

Thakkar, A.J. (Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick E3B 6E2 (Canada)); Koga, T. (Department of Applied Chemistry, Muroran Institute of Technology, Muroran, Hokkaido 050 (Japan))

1994-07-01

94

Influence of inelastic Rydberg atom-atom collisional process on kinetic and optical properties of low-temperature laboratory and astrophysical plasmas  

NASA Astrophysics Data System (ADS)

Elementary processes in plasma phenomena traditionally attract physicist's attention. The channel of charged-particle formation in Rydberg atom-atom thermal and sub-thermal collisions (the low temperature plasmas conditions) leads to creation of the molecular ions - associative ionization (AI). atomic ions - Penning-like ionization (PI) and the pair of the negative and positive ions. In our universe the chemical composition of the primordial gas consists mainly of Hydrogen and Helium (H, H-, H+, H2, He,He+). Hydrogen-like alkali-metal Lithium (Li, Li+,Li-) and combinations (HeH+, LiH-, LiH+). There is a wide range of plasma parameters in which the Rydberg atoms of the elements mentioned above make the dominant contribution to ionization and that process may be regarded as a prototype of the elementary process of light excitation energy transformation into electric one. The latest stochastic version of chemi-ionisation (AI+PI) on Rydberg atom-atom collisions extends the treatment of the "dipole resonant" model by taking into account redistribution of population over a range of Rydberg states prior to ionization. This redistribution is modelled as diffusion within the frame of stochastic dynamic of the Rydberg electron in the Rydberg energy spectrum. This may lead to anomalies of Rydberg atom spectra. Another result obtained in recent time is understanding that experimental results on chemi-ionization relate to the group of mixed Rydberg atom closed to the primary selected one. The Rydberg atoms ionisation theory today makes a valuable contribution in the deterministic and stochastic approaches correlation in atomic physic.

Klyucharev, A. N.; Bezuglov, N. N.; Mihajlov, A. A.; Ignjatovi?, Lj M.

2010-11-01

95

Evidence for strong van der Waals-type Rydberg-Rydberg interaction in thermal vapor  

E-print Network

We present evidence for Rydberg-Rydberg interaction in a gas of rubidium atoms above room temperature. Rabi oscillations on the nanosecond timescale to different Rydberg states are investigated in a vapor cell experiment. Analyzing the atomic time evolution and comparing to a dephasing model we find a scaling with the Rydberg quantum number n that is consistent with van der Waals interaction. Our results show that the interaction strength can be larger than the kinetic energy scale (Doppler width) which is the requirement for realization of thermal quantum devices in the GHz regime.

T. Baluktsian; B. Huber; R. Löw; T. Pfau

2012-12-04

96

BF3 Valence and Rydberg States As Probed by Electron Energy Loss Spectroscopy and ab Initio Calculations.  

PubMed

In this contribution we probe BF3 low-lying excited singlet states measured at 100 eV, 2.8° scattering angle and triplet states at 40 eV, 40° scattering angle, while sweeping the energy loss over the range 10.0-20.0 eV. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. This provides the first comprehensive investigation of all singlet and triplet excited electronic states of boron trifluoride up to the first ionization potential. A generalized oscillator strength analysis is employed to derive oscillator strength f0 value and integral cross sections (ICSs) from the corresponding differential cross sections (DCSs). The f0 value is compared with the optical oscillator strength (OOS) from photoabsorption, and the unscaled Born ICSs are then compared with relevant energy and binary-encounter and f-scaled Born cross section (BEf-scaling) results determined as a part of this investigation. The lowest n members of the Rydberg series have been assigned as converging to the lowest ionization energy limits of boron trifluoride and classified according to the magnitude of the quantum defects (?). PMID:25338148

Duflot, D; Hoshino, M; Limão-Vieira, P; Suga, A; Kato, H; Tanaka, H

2014-11-20

97

Physics 216 Spring 2012 The Variational Computation of the Ground State Energy of Helium  

E-print Network

Physics 216 Spring 2012 The Variational Computation of the Ground State Energy of Helium I. Introduction to the variational computation The Hamiltonian for the two­electron system of the helium atom is principle to compute the ground state energy of the helium atom. The ground state wave function

California at Santa Cruz, University of

98

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

E-print Network

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

California at Santa Cruz, University of

99

Three-Body Dissociation Dynamics of the Low-Lying Rydberg States of H3 and D3 Christopher M. Laperle, Jennifer E. Mann, Todd G. Clements, and Robert E. Continetti*  

E-print Network

Three-Body Dissociation Dynamics of the Low-Lying Rydberg States of H3 and D3 Christopher M into the nuclear motion during dissociation for the three lowest-lying 2s 2A0 1, 2p 2A00 2 , and 3p 2E0 metastable information on the nonadiabatic couplings that govern the three-body dissociation of the lowest-lying Rydberg

Continetti, Robert E.

100

Deceleration and trapping of a fast supersonic beam of metastable helium atoms with a 44-electrode chip decelerator  

NASA Astrophysics Data System (ADS)

A surface-electrode decelerator consisting of 44 electrodes has been used to decelerate supersonic beams of helium Rydberg atoms moving with an initial velocity of 1200 m/s. Prior to the deceleration, the helium atoms were excited from the 1s2s1S0 metastable state to selected Rydberg-Stark states with a narrow-band tunable UV laser. Complete deceleration could be achieved over a distance of 36 mm and in 60 ?s, corresponding to an acceleration of -2.0×107 m/s2. After deceleration, the atoms were held in stationary electric traps above the chip surface, reaccelerated off the chip, and detected by pulsed electric-field ionization. The decelerator was also used to generate helium Rydberg-atom beams with a final velocity tunable between 0 and 1200 m/s. Transitions between low- and high-field-seeking Rydberg-Stark states were observed during trap loading and are attributed to adiabatic Landau-Zener dynamics at electric fields exceeding the Inglis-Teller field. By comparing the experimental results with the results of particle-trajectory simulations, the velocity distribution of the decelerated atoms was found to be characterized by temperatures ranging between 50 and 200 mK, depending on the magnitude of the electric dipole moment of the Rydberg-Stark states selected prior to the deceleration.

Allmendinger, P.; Agner, J. A.; Schmutz, H.; Merkt, F.

2013-10-01

101

Angular Momentum Dependence of Autoionization Rates in Doubly Excited Rydberg States of Ba  

Microsoft Academic Search

The results of an experimental laser study of state-selected, doubly excited states msnl (m=7-11, n=13-20) in barium are reported. Measurements are made of the autoionization rates of the doubly excited states as a function of \\

L. A. Bloomfield; R. R. Freeman; W. E. Cooke; J. Bokor

1984-01-01

102

Hyperfine Structure of S-States in Muonic Helium Ion  

E-print Network

Corrections of orders alpha^5 and alpha^6 are calculated in the hyperfine splittings of 1S and 2S - energy levels in the ion of muonic helium. The electron vacuum polarization effects, the nuclear structure corrections and recoil corrections are taken into account. The obtained numerical values of the hyperfine splittings -1334.56 meV (1S state), -166.62 meV (2S state) can be considered as a reliable estimate for the comparison with the future experimental data. The hyperfine splitting interval Delta_{12}=(8 Delta E^{hfs}(2S)- Delta E^{hfs}(1S)) = 1.64 meV can be used for the check of quantum electrodynamics.

A. P. Martynenko

2007-10-17

103

Counterfactual Rydberg gate for photons  

NASA Astrophysics Data System (ADS)

Quantum computation with photons requires efficient two-photon gates. We put forward a two-photon entangling gate which uses an intermediate atomic system. The system includes a single Rydberg atom which can switch on and off photon absorption in an ensemble using the dipole blockade. The gate is based in a counterfactual protocol. The mere possibility of an absorption that can only occur with a vanishing probability steers the photons to the desired final state.

Garcia-Escartin, Juan Carlos; Chamorro-Posada, Pedro

2012-03-01

104

Evidence for a non-Rydberg molecular doubly excited state of Ca2  

E-print Network

as two-electron systems and which can receive almost exact valence treatment, accurate theoretical and coll. [3]. If we now consider actual electron configuration double excitations (not involving fine crossing between adia- batic states 31u and 41u, reflecting the mixing of doubly excited configurations

Paris-Sud XI, Université de

105

Guiding Rydberg atoms above surface-based transmission lines  

NASA Astrophysics Data System (ADS)

Beams of helium atoms in selected Rydberg-Stark states with principal quantum number n=52 and electric dipole moments as large as 9910 D have been guided and deflected in the electrostatic fields surrounding surface-based electrical transmission lines. The guided atoms were detected by pulsed-electric-field ionization. Information on their position at the time of ionization was obtained from the flight time of the resulting ions to a microchannel plate detector. Comparison of the experimentally recorded data with the results of numerical calculations of particle trajectories through the guide highlight the sensitivity of the guided signal to the interaction of the atoms with each other and the surrounding 300 K blackbody radiation field.

Lancuba, P.; Hogan, S. D.

2013-10-01

106

Resonant Photovoltaic Effect in Surface State Electrons on Liquid Helium Denis KONSTANTINOV  

E-print Network

Resonant Photovoltaic Effect in Surface State Electrons on Liquid Helium Denis KONSTANTINOV 1;2Ã?. KEYWORDS: surface-state electrons on liquid helium, inter-subband absorption resonance, magneto a schematic diagram of the experimental apparatus. Liquid 3 He is condensed into a cell having flat

Shepelyansky, Dima

107

Quantum Field Theory and the Helium Atom: 101 Years Later  

E-print Network

Helium was first isolated on Earth in 1895, by Sir William Ramsey. One hundred and one years later, it seems like a good time to review our current theoretical understanding of the helium atom. Helium has played an important role in the development of both quantum mechanics and of quantum field theory. The early history of helium is sketched. Various aspects of the modern theory are described in some detail, including (1) the computation of fine structure to order \\alpha^2 Ry and \\alpha^3 Ry, (2) the decay of metastable states, and (3) Rydberg states and long-range forces. A brief survey is made of some of the recent work on the quantum field theory of He and He-like ions.

J. Sucher

1996-12-11

108

Electromagnetically induced transparency and fluorescence in blockaded Rydberg atomic system.  

PubMed

We investigate the interaction between dark states and Rydberg excitation blockade by using electromagnetically induced transparency (EIT), fluorescence, and four-wave mixing (FWM) signals both theoretically and experimentally. By scanning the frequency detunings of the probe and dressing fields, respectively, we first observe these signals (three coexisting EIT windows, two fluorescence signals, and two FWM signals) under Rydberg excitation blockade. Next, frequency detuning dependences of these signals are obtained, in which the modulated results are well explained by introducing the dressing effects (leading to the dark states) with the corrected factor of the Rydberg excitation blockade. In addition, the variations by changing the principal quantum number n of Rydberg state shown some interesting phenomena resulting from Rydberg blockade are observed. The unique nature of such blockaded signals can have potential application in the demonstration of quantum computing. PMID:24182038

Li, Cheng; Zheng, Huaibin; Zhang, Zhaoyang; Yao, Xin; Zhang, Yunzhe; Zhang, Yiqi; Zhang, Yanpeng

2013-10-28

109

Rydberg atoms in hollow-core photonic crystal fibres  

E-print Network

The exceptionally large polarisability 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. If however they are to be used routinely in applications, a major requirement is their integration into technically feasible, miniaturised 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 ...

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

2014-01-01

110

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

111

Entanglement entropies in the ground states of helium-like atoms  

E-print Network

We examine the entanglement in the ground states of helium and helium-like ions using an original Hylleraas expansion. The von Neumann and linear entropies of the reduced density matrix are accurately computed by performing the Schmidt decomposition of the S singlet spatial wavefunctions. The results presented are more accurate than currently available in published literature.

Przemyslaw Koscik; Anna Okopinska

2014-04-18

112

Resonant collisions of K Rydberg atoms  

Microsoft Academic Search

We have studied the collisional energy transfer process K (ns) +K (n-2) d â K (np) +K (n-1) p which is tuned into resonance with an applied static electric field. The initial Rydberg states are excited stepwise with two dye laser pulses. The resonant energy transfer is detected by selectively field ionizing the final K(np) state as the static field

M. J. Renn; W. A. Anderson; J. R. Veale; T. F. Gallagher

1993-01-01

113

Finite-element calculations for the S states of helium  

NASA Astrophysics Data System (ADS)

The finite-element method provides a convenient and accurate procedure for the calculation of the expectation values of quantum observables. We calculated energies, wave functions, and expectation values of rn1 for n=-1, 1, and 2, and of ??(r1) for the singlet n 1S and triplet n 3S states (n=1,2,3,4) of helium. In contrast to the standard methods with globally defined basis functions, the accuracy of the expectation values of physical observables is comparable to the accuracy of the eigenvalues. The results are reported here and compared with those of Baker et al. 2 [Relativistic, Quantum Electrodynamic, and Weak Interaction Effects in Atoms, edited by Walter Johnson, Peter Mohr, and Joseph Sucher, AIP Conf. Proc. No. 189 (AIP, New York, 1989); Phys. Rev. A 41, 1247 (1990)], Drake [Nucl. Instrum. Methods Phys. Res. B 31, 7 (1988)], Pekeris [Phys. Rev. 115, 1216 (1959)], Accad et al. [Phys. Rev. A 4, 516 (1971)], and Haftel and Mandelzweig [Phys. Rev. A 38, 5995 (1988)].

Braun, M.; Schweizer, W.; Herold, H.

1993-09-01

114

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

NASA Astrophysics Data System (ADS)

Kohn-Sham (KS) time-dependent density functional theory (TDDFT) with most exchange-correlation functionals is well known to systematically underestimate the excitation energies of Rydberg and charge-transfer excited states of atomic and molecular systems. To improve the description of Rydberg states within the KS TDDFT framework, Gaiduk et al. [Phys. Rev. Lett. 108, 253005 (2012)] proposed a scheme that may be called HOMO depopulation. In this study, we tested this scheme on an extensive dataset of valence and Rydberg excitation energies of various atoms, ions, and molecules. It is also tested on a charge-transfer excitation of NH3-F2 and on the potential energy curves of NH3 near a conical intersection. We found that the method can indeed significantly improve the accuracy of predicted Rydberg excitation energies while preserving reasonable accuracy for valence excitation energies. However, it does not appear to improve the description of charge-transfer excitations that are severely underestimated by standard KS TDDFT with conventional exchange-correlation functionals, nor does it perform appreciably better than standard TDDFT for the calculation of potential energy surfaces.

Li, Shaohong L.; Truhlar, Donald G.

2014-09-01

115

Coherence in Rydberg Atoms: Measurement and Control  

NASA Astrophysics Data System (ADS)

We demonstrate a variety of techniques for measuring and controlling dephasing and decoherence in alkali metal Rydberg atom systems. Specifically, we investigate the coherence of the spin-orbit interaction in individual atoms and of dipole-dipole resonant energy exchange between pairs of atoms. Rydberg atoms are a good model system for exploring decoherence because they are sensitive to noise in their environments. The phase coherence of wave packets encoded on the fine-structure Rydberg states of lithium atoms is measured using a population echo and preserved using pulsed and continuous dynamic decoupling techniques. Pulsed electric fields toggle the spin-orbit coupling, repeatedly flipping the state vector, and preventing the slow acquisition of phase noise in a bang-bang scheme. Continuous dynamic decoupling is implemented by driving population between the relevant electronic states with a resonant rf field. The energy spacing between the levels is locked to the rf frequency as long as the Rabi rate is much greater than the dephasing rate. We demonstrate a technique which reduces the average relative velocity between interacting potassium Rydberg atoms, extending the atom transit time and allowing us to control when all resonant energy exchange interactions in the ensemble begin and end. Velocity reduction is achieved without the use of a chopper wheel by exciting a small cylinder of atoms and allowing them to thermally expand prior to tuning them into resonance. Resonant energy transfer is explored further in a nearly frozen rubidium Rydberg gas. We observe enhancement in the transition signal when the probability amplitudes acquired on opposite sides of the resonance interfere constructively compared to the population transferred when remaining on either side of the resonance. This enhancement reflects the coherence of the energy exchange interaction and decays over 10 us microseconds. The observed coherence time is much longer than previously measured dephasing times in nearly frozen Rydberg gases.

Kutteruf, Mary

116

Deterministic entanglement of Rydberg ensembles by engineered dissipation  

E-print Network

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 Walls interaction range with perspectives for entangling large and distant ensembles.

D. D. Bhaktavatsala Rao; Klaus Mølmer

2014-07-04

117

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

118

Spontaneous avalanche ionization of a strongly blockaded Rydberg gas.  

PubMed

We report the sudden and spontaneous evolution of an initially correlated gas of repulsively interacting Rydberg atoms to an ultracold plasma. Under continuous laser coupling we create a Rydberg ensemble in the strong blockade regime, which at longer times undergoes an ionization avalanche. By combining optical imaging and ion detection, we access the full information on the dynamical evolution of the system, including the rapid increase in the number of ions and a sudden depletion of the Rydberg and ground state densities. Rydberg-Rydberg interactions are observed to strongly affect the dynamics of plasma formation. Using a coupled rate-equation model to describe our data, we extract the average energy of electrons trapped in the plasma, and an effective cross section for ionizing collisions between Rydberg atoms and atoms in low-lying states. Our results suggest that the initial correlations of the Rydberg ensemble should persist through the avalanche. This would provide the means to overcome disorder-induced heating, and offer a route to enter new strongly coupled regimes. PMID:25166173

Robert-de-Saint-Vincent, M; Hofmann, C S; Schempp, H; Günter, G; Whitlock, S; Weidemüller, M

2013-01-25

119

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

120

Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble  

SciTech Connect

The realization of a Jaynes-Cummings model in the optical domain is proposed for an atomic ensemble. The scheme exploits the collective coupling of the atoms to a quantized cavity mode and the nonlinearity introduced by coupling to high-lying Rydberg states. A two-photon transition resonantly couples the single-atom ground state |g> to a Rydberg state |e> via a nonresonant intermediate state |i>, but due to the interaction between Rydberg atoms only a single atom can be resonantly excited in the ensemble. This restricts the state space of the ensemble to the collective ground state |G> and the collectively excited state |E> with a single Rydberg excitation distributed evenly on all atoms. The collectively enhanced coupling of all atoms to the cavity field with coherent coupling strengths which are much larger than the decay rates in the system leads to the strong coupling regime of the resulting effective Jaynes-Cummings model. We use numerical simulations to show that the cavity transmission can be used to reveal detailed properties of the Jaynes-Cummings ladder of excited states and that the atomic nonlinearity gives rise to highly nontrivial photon emission from the cavity. Finally, we suggest that the absence of interactions between remote Rydberg atoms may, due to a combinatorial effect, induce a cavity-assisted excitation blockade whose range is larger than the typical Rydberg dipole-dipole interaction length.

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

2010-11-15

121

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

122

Dissipation-sensitive multiphoton excitations of strongly interacting Rydberg atoms  

NASA Astrophysics Data System (ADS)

We theoretically investigate the effect of dissipation on multiphoton excitation of Rydberg atoms. The steady states and the dynamics are compared via two types of four-level excitation schemes with different dissipative paths of spontaneous emission. We find that in the case of strong Rydberg-Rydberg interaction, the schemes will settle in several different nonequilibrium steady states. The interesting aspect is that there exist the multistable steady states, which reveals the competition between interaction-induced nonlinearity and dissipation caused by spontaneous emission. A numerical simulation on the Rydberg population dynamics in the bistable region exhibits different features existing in the two schemes even with the same initial conditions, which accounts for the influence of the dissipation on the dynamics.

Qian, Jing; Zhang, Weiping

2014-09-01

123

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

124

C-NOT gate based on ultracold Rydberg atom interactions  

NASA Astrophysics Data System (ADS)

The Rydberg states of neutral atoms are strongly polarisable and possess long lifetimes because of high energies which can lead to strong and long range dipole-dipole interactions. The energy levels corresponding to these states are shifted because of dipole-dipole interactions and can be used to block transitions of more than one excitation in the Rydberg regime. This reputed Rydberg blockade is obtained when the excitation is shifted out of resonance by these interactions. Electromagnetically induced transparency (EIT) is sensitive to a small detuning. At large distances, up to several micrometers, the interactions can interrupt the EIT consequence. Herein we investigate a novel scheme based on EIT and Rydberg blockade and performed a simulation of a controlled-NOT (C-NOT) quantum gate which is critical for quantum computation by using neutral atoms.

Rashid, Muhammad; Maarten, Hoogerland; Yasir, Jamil

2013-11-01

125

Newly Identified Rydberg Emission Lines in Novae  

NASA Astrophysics Data System (ADS)

Newly Identified Rydberg Emission Lines in Novae David K. Lynch, Richard. J. Rudy (The Aerospace Corporation) & Lawrence S. Bernstein (Spectral Sciences, Inc.) Novae spectra in the near infrared frequently show a set of six emission lines that have not been positively identified (Williams, Longmore, & Geballe 1996, MNRAS, 279, 804; Lynch et al. 2001, AJ, 122, 2013; Rudy et al. 2002 ApJ, 573, 794; Lynch et al. 2004 Astron. J. 127, 1089-1097). These lines are at 0.8926, 1.1114, 1.1901, 1.5545, 2.0996 and 2.425 µm ± 0.005 µm. Krautter et al. (1984 A&A 137, 304) suggested that three of the lines were due to rydberg (hydrogenic) transitions in an unspecified atomic species that was in the 4th or 5th ionization stage (core charge = 4 & 5). We believe that Krautter et al.'s explanation is correct based on 4 additional lines that we have identified in the visible and near infrared spectrum of V723 Cassiopeiae. The observed Rydberg lines appear to originate from high angular momentum states with negligible quantum defects. The species cannot be determined with any certainty because in rydberg states, the outer electron sees a nucleus shielded by the inner electrons and together the inner atom appears to have a charge of +1, like hydrogen. As a result, the atom looks hydrogenic and species such as CV, NV, OV, MgV, SiV, etc. have their rydberg transitions at very similar wavelengths. All the lines represent permitted transitions, most likely formed by recombination. Atoms with core charges 4, 5 & 6 are rarely seen in the astrophysical environment because an extremely hot radiation field is necessary to ionize them. Thermonuclear runaways on the surface of a white dwarf can reach millions of degrees K, and thus there are enough X-ray photons available to achieve the necessary high ionization levels.

Lynch, David K.; Rudy, R. J.; Bernstein, L. S.

2008-09-01

126

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

127

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.; Low, R.

2014-01-01

128

Rydberg atoms in hollow-core photonic crystal fibres  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

129

Entrance channel localized states in ozone: Possible application to helium nanodroplet isolation spectroscopy  

E-print Network

Entrance channel localized states in ozone: Possible application to helium nanodroplet isolation-vibrational states of ozone are performed in the region of high vibrational excitation. Two unusual vibrational nanodroplet isolation ro-vibrational spectroscopy of ozone. © 2003 American Institute of Physics. DOI: 10

Ryan, Michael D.

130

PHYSICAL REVIEW A 84, 062512 (2011) XUV frequency-comb metrology on the ground state of helium  

E-print Network

PHYSICAL REVIEW A 84, 062512 (2011) XUV frequency-comb metrology on the ground state of helium in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p 1 P with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium

131

Interaction effects on dynamical localization in driven helium  

E-print Network

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

Felix Jörder; Klaus Zimmermann; Alberto Rodriguez; Andreas Buchleitner

2013-11-22

132

Inelastic electron collisions with Rydberg atoms  

SciTech Connect

The standard classical method of computer simulation is used for evaluation of the inelastic cross section in electron collisions with a highly excited (Rydberg) atom. In the course of collision, the incident and bound electrons move along classical trajectories in the Coulomb field of the nucleus, and the scattering parameters are averaged over many initial conditions. The reduced ionization cross section of a Rydberg atom by electron impact approximately corresponds to that of atoms in the ground states with valence s-electrons and coincides with the results of the previous Monte Carlo calculations. The cross section of an atom transition between Rydberg atom states as a result of electron impact is used for finding the stepwise ionization rate constant of atoms in collisions with electrons or the rate constant of three-body electron-ion recombination in a dense ionized gas because these processes are determined by kinetics of highly excited atom states. Surprisingly, the low-temperature limit of electron temperatures is realized when the electron thermal energy is lower than the atom ionization potential by about three orders of magnitude, as follows from the kinetics of excited atom states.

Kashtanov, P. V., E-mail: kashtanovpv@gmail.com; Myasnikov, M. I.; Smirnov, B. M. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2009-01-15

133

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

PubMed

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

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

2013-12-19

134

High Resolution Rydberg Spectroscopy of ultracold Rubidium Atoms  

E-print Network

We present experiments on two-photon excitation of ${\\rm ^{87}}$Rb atoms to Rydberg states. For this purpose, two continuous-wave (cw)-laser systems for both 780 nm and 480 nm have been set up. These systems are optimized to a small linewidth (well below 1 MHz) to get both an efficient excitation process and good spectroscopic resolution. To test the performance of our laser system, we investigated the Stark splitting of Rydberg states. For n=40 we were able to see the hyperfine levels splitting in the electrical field for different finestructure states. To show the ability of spatially selective excitation to Rydberg states, we excited rubidium atoms in an electrical field gradient and investigated both linewidths and lineshifts. Furthermore we were able to excite the atoms selectively from the two hyperfine ground states to Rydberg states. Finally, we investigated the Autler-Townes splitting of the 5S$_{1/2}$$\\to$5P$_{3/2}$ transition via a Rydberg state to determine the Rabi frequency of this excitation step.

Axel Grabowski; Rolf Heidemann; Robert Löw; Jürgen Stuhler; Tilman Pfau

2005-08-10

135

Preserving coherence in Rydberg quantum bits.  

PubMed

The effectiveness of decoherence suppression schemes is explored using quantum bits (qubits) stored in Li np Rydberg states. Following laser excitation, pulsed electric fields coherently control the electronic spin-orbit coupling, facilitating qubit creation, manipulation, and measurement. Spin-orbit coupling creates an approximate decoherence-free subspace for extending qubit storage times. However, sequences of fast NOT operations are found to be substantially more effective for preserving coherence. PMID:16907558

Minns, R S; Kutteruf, M R; Zaidi, H; Ko, L; Jones, R R

2006-07-28

136

Helium AtomSCF-LCAO Calculation of the (1s)2 Ground State of the  

NSDL National Science Digital Library

Using a double-zeta basis of Slater-type orbitals [STOs], this Java applet calculates the single determinant singlet ground state 1s2 wavefunction of the helium atom. The doubly occupied orbital is expanded in terms of two basis functions, 1s and 1s`.

137

Does the Helium Trimer Have Bound Rotational States?  

NASA Astrophysics Data System (ADS)

For the 4He3 trimer, calculations predict two bound states with total angular momentum J = 0. This result gave rise to speculations that also bound states with J ? 0 might exist. Using the symmetry-adapted version of the adiabatic hyperradial approach (SAHA) we search for such bound states. Our conclusion is that 4He3 has no bound rotationally excited states.

Matveenko, A. V.; Alt, E. O.

2001-12-01

138

An experimental test for the charge state of the 'anomalous' helium component. [galactic cosmic radiation  

NASA Technical Reports Server (NTRS)

Observations of phase lags between intensity variations for various particle species and energy ranges in the low-energy galactic cosmic radiation during the general intensity decrease observed in 1974-1975 show that, for particles whose charge state is known (i.e., 'normal' cosmic-ray components), particles with higher rigidities respond more quickly to changes in modulation conditions than do those with lower rigidities. When compared with particles of known energy and charge, the behavior of the 'anomalous' low-energy helium component is consistent with these observations only if the helium is singly rather than doubly charged.

Mckibben, R. B.

1977-01-01

139

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

140

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

SciTech Connect

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

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

2013-01-07

141

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

142

Diffusion Monte Carlo for excited states: Application to liquid helium  

Microsoft Academic Search

The extension of ab initio Monte Carlo methods to the study of excited states is a challenging problem at the forefront of\\u000a present research in the field of computational techniques applied to the quantum many-body problem. The aim is to calculate\\u000a excited states with similar accuracy to the one achieved in the study of the ground-state properties. We present a

Jordi Boronat; Departament de Fisica

1998-01-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

144

Diffusion ionization of the Rydberg diatomic quasi-molecular complex formed upon collisions of rubidium atoms  

Microsoft Academic Search

The problem of impact ionization of two Rb atoms, one of which belongs to the Rydberg P series and the other of which is in the ground state, is studied and solved with the use of the methods of stochastic dynamics\\u000a for description of the path instability of a Rydberg electron in a collision diatomic complex. The actual potential of

N. N. Bezuglov; V. M. Borodin; V. Grushevskii; A. N. Klyucharev; K. Michulis; F. Fuzo; M. Allegrini

2003-01-01

145

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.

146

Electronic structures of the bound excited quartet states of the helium anion  

NASA Astrophysics Data System (ADS)

The radial and electron-pair density functions of two bound excited states of the helium anion have been calculated at the full configuration-interaction level with an extended basis set. It is shown that the form of the radial density in the (1s2s2p)4P and (2p3)4S states of He- is readily interpreted in terms of orbital contributions, even at the full configuration level at which level of theory the notion of an electronic configuration loses its precise meaning. The smaller radial distance of the L-shell maximum in the 4S state relative to the lower-lying 4P state is interpreted in terms of a higher effective nuclear charge in the 4S state. The more compact electron cloud of the 4S state leads to a narrower intracule density than that observed for the 4P state. The 4S state is shown to have a Coulomb hole with the same classic form as the ground state of helium but with a radius that is about six times larger. The depth of the Coulomb hole is substantially greater in the 4S state than in the 4P state, as expected from the fact that the correlation energy is greater in the former state. The Coulomb holes of both states exhibit a vanishingly small depth at small interelectronic distances due to the presence of the Fermi hole.

Mercero, Jose M.; Elorza, Jose M.; Ugalde, Jesus M.; Boyd, Russell J.

1999-12-01

147

A New Wide Range Equation of State for Helium-4  

E-print Network

calculate all thermodynamic properties, including density, heat capacity, speed of sound, energies, entropy and saturation properties. A new equation of state is necessary to overcome difficulties associated with the current standard in the asymptotic region...

Ortiz Vega, Diego O

2013-08-01

148

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

149

Rydberg excitation of Bose-Einstein condensates  

E-print Network

Rydberg atoms provide a wide range of possibilities to tailor interactions in a quantum gas. Here we report on Rydberg excitation of Bose-Einstein condensed 87Rb atoms. The Rydberg fraction was investigated for various excitation times and temperatures above and below the condensation temperature. The excitation is locally blocked by the van der Waals interaction between Rydberg atoms to a density-dependent limit. Therefore the abrupt change of the thermal atomic density distribution to the characteristic bimodal distribution upon condensation could be observed in the Rydberg fraction. The observed features are reproduced by a simulation based on local collective Rydberg excitations.

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

2007-10-30

150

Giant Rydberg excitons in the copper oxide Cu2O.  

PubMed

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

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

2014-10-16

151

Debye equation of state for fluid helium-3.  

PubMed

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

Huang, Yonghua; Chen, Guobang; Arp, Vincent

2006-08-01

152

Quantum statistics of light transmitted through an intracavity Rydberg medium  

NASA Astrophysics Data System (ADS)

We theoretically investigate the quantum statistical properties of light transmitted through an atomic medium with strong optical nonlinearity induced by Rydberg-Rydberg van der Waals interactions. In our setup, atoms are located in a cavity and nonresonantly driven on a two-photon transition from their ground state to a Rydberg level via an intermediate state by the combination of the weak signal field and a strong control beam. To characterize the transmitted light, we compute the second-order correlation function {{g}^{\\left( 2 \\right)}}\\left( \\tau \\right). The simulations we obtained on the specific case of rubidium atoms suggest that the bunched or antibunched nature of the outgoing beam can be chosen at will by tuning the physical parameters appropriately.

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

2014-04-01

153

Quantum statistics of light transmitted through an intracavity Rydberg medium  

E-print Network

We theoretically investigate the quantum statistical properties of light transmitted through an atomic medium with strong optical non-linearity induced by Rydberg-Rydberg van der Waals interactions. In our setup, atoms are located in a cavity and non-resonantly driven on a two-photon transition from their ground state to a Rydberg level via an intermediate state by the combination of the weak signal field and a strong control beam. To characterize the transmitted light we compute the second-order correlation function $g^{\\left(2\\right)}\\left(\\tau\\right)$. The simulations we obtained on the specific case of rubidium atoms suggest that the bunched or antibunched nature of the outgoing beam can be chosen at will by appropriately tuning the physical parameters.

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

2013-12-09

154

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...

Hori, Masaki; Korobov, Vladimir I

2014-01-01

155

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

SciTech Connect

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

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

2013-01-15

156

Photon-Photon Interactions via Rydberg Blockade  

E-print Network

We develop the theory of light propagation under the conditions of electromagnetically induced transparency (EIT) 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 demonstrate 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 quantum gates, as well as for studying many-body phenomena with strongly correlated photons.

Alexey V. Gorshkov; Johannes Otterbach; Michael Fleischhauer; Thomas Pohl; Mikhail D. Lukin

2011-03-18

157

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

158

Slow-light polaritons in Rydberg gases  

NASA Astrophysics Data System (ADS)

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

Fleischhauer, Michael

2012-02-01

159

Rydberg molecules: The making and breaking of bonds  

Microsoft Academic Search

Rydberg molecules, which consist of one atom in its electronic ground state and one in a highly excited state, can extend to the size of a virus. But size is only one oddity of these molecules. As has now been demonstrated, the chemical bond that holds the atoms together in this fragile molecule can be coherently controlled using laser light.

Antoine Browaeys; Pierre Pillet

2011-01-01

160

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

SciTech Connect

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

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

2010-06-15

161

Stability limit of a metastable state of hcp solid helium-4  

NASA Astrophysics Data System (ADS)

Solid helium has the unique feature of having an horizontal melting curve in the P,T plane. This offers novel opportunities to study the stability limits of a metastable solid, by using the pressure as a control parameter of the metastability. The metastable state is obtained by focusing a 1 MHz ultrasonic sound wave inside an helium-4 crystal. Around 4 bar below the melting pressure, the metastable crystal becomes unstable. Different configurations with one or two ultrasonic emitters have been used and lead to the same stability limit. This happens at much lower depression than predicted by nucleation theory or by quantum Monte Carlo simulations. Repeated experiments show that the instability initially appears as a small defect (˜0.2 mm) located at the maximum isotropic strain. Further studies are performed to understand the underlying mechanism of the instability. Possible scenarios accounting for this unexpected observation are discussed.

Souris, Fabien; Grucker, Jules; Dupont-Roc, Jacques; Jacquier, Philippe

2013-03-01

162

Interfering Rydberg wave packets in Na  

Microsoft Academic Search

This paper presents an experimental and theoretical analysis of quantum interference between Rydberg wave packets in Na. Pairs of phase-locked wave packets manipulate the total orbital angular momentum of Na Rydberg atoms. Initially, the wave packet is composed of a superposition of s and d Rydberg series. Exploitation of the difference between the quantum defects of the two series allows

R. E. Carley; E. D. Boléat; R. S. Minns; R. Patel; H. H. Fielding

2005-01-01

163

Semianalytical model for nonlinear absorption in strongly interacting Rydberg gases  

NASA Astrophysics Data System (ADS)

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 superatoms. From this we deduce a simple semianalytical 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 semianalytical model is particularly reliable. The performance of the model improves in the presence of dephasing which destroys higher-order atomic coherences.

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

2014-06-01

164

Collective Many-Body Interaction in Rydberg Dressed Atoms  

SciTech Connect

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 or van der Waals blockade phenomenon between the Rydberg levels plays a dominant role. We study the influence of these collective interaction potentials on a Bose-Einstein condensate and present the optimal parameters for its experimental detection.

Honer, Jens; Weimer, Hendrik; Buechler, Hans Peter [Institute for Theoretical Physics III, University of Stuttgart, Stuttgart (Germany); Pfau, Tilman [5. Physikalische Institut, University of Stuttgart, Stuttgart (Germany)

2010-10-15

165

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

E-print Network

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

Miao Zhang; Wenzhi Jia; Lianfu Wei

2010-12-28

166

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

167

Binding potentials and interaction gates between microwave-dressed Rydberg atoms  

E-print Network

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

2014-01-01

168

Binding potentials and interaction gates between microwave-dressed Rydberg atoms  

E-print Network

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.

David Petrosyan; Klaus Mølmer

2014-04-13

169

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

170

Electron impact ionization of helium: test of screening potential in the final state  

NASA Astrophysics Data System (ADS)

The triple differential cross sections for electron impact ionization of a helium atom is studied using the 70.6 eV incident electron. The initial state which includes both bound and continuum wave functions is calculated using the Hartree-Fock approximation. The final state continuum electron wave functions are computed in the potential of the H{{e}^{+}}(1s) core. The interaction potential between the two continuum electrons in the final state is approximated with the screening potential determined variationally. It is found that there is qualitative agreement between the present triple differential cross section results and the available experimental and the other theoretical data for equal and unequal sharing of 46 eV excess energy by the two final state continuum electrons. It is concluded that the screening potential which is an approximation to the actual Coulomb interaction potential between the two final state continuum electrons can produce qualitative agreement with the experiment.

Saha, Hari P.

2014-09-01

171

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

SciTech Connect

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

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

2003-04-01

172

Rydberg dressing: understanding of collective many-body effects and implications for experiments  

NASA Astrophysics Data System (ADS)

The strong interaction between Rydberg atoms can be used to control the strength and character of the interatomic interaction in ultracold gases by weakly dressing the atoms with a Rydberg state. Elaborate theoretical proposals for the realization of various complex phases and applications in quantum simulation exist. Also a simple model has been already developed that describes the basic idea of Rydberg dressing in a two-atom basis. However, an experimental realization has been elusive so far. We present a model describing the ground state of a Bose-Einstein condensate dressed with a Rydberg level based on the Rydberg blockade. This approach provides an intuitive understanding of the transition from pure two-body interaction to a regime of collective interactions. Furthermore it enables us to calculate the deformation of a three-dimensional sample under realistic experimental conditions in mean-field approximation. We compare full three-dimensional numerical calculations of the ground state to an analytic expression obtained within Thomas-Fermi approximation. Finally we discuss limitations and problems arising in an experimental realization of Rydberg dressing based on our experimental results and point out possible solutions for future approaches. Our work enables the reader to straight forwardly estimate the experimental feasibility of Rydberg dressing in realistic three-dimensional atomic samples.

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

2014-06-01

173

Enhancement of Rydberg-atom trapping efficiency in a ponderomotive optical lattice using lattice translations  

NASA Astrophysics Data System (ADS)

We present experimental results on the one-dimensional trapping of cold ^85Rb Rydberg atoms in a ponderomotive optical lattice of laser wavelength 1064 nm. The challenge associated with this red-detuned lattice is that locations of potential minima in the ground state correspond to potential maxima in the Rydberg state. When ground state atoms in the lattice are excited to Rydberg states, they are located near potential maxima, and consequently trapping is limited. We present a method to overcome this difficulty by translating the lattice by ?/4 immediately after excitation, thus bringing the locations of the potential minima in the Rydberg state to the locations of the atoms. We report experimental microwave spectroscopy results that confirm this lattice phase-shift technique as an effective method to enhance the lattice's trapping efficiency.

Anderson, Sarah E.; Raithel, Georg

2011-06-01

174

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

175

Population of individual Ne 1s{sup -1}np Rydberg states measured across the 1s ionization threshold and the evolution of shake-up into shake-down  

SciTech Connect

New high-resolution experimental results on Ne 1s near-threshold photoionization with subsequent decay into a 2p{sup 4}({sup 1}D{sub 2})n{sup '}p or 2p{sup 4}({sup 1}D{sub 2}){epsilon}{sup '}p state are presented. The population of Rydberg states up to n{sup '}=12 is determined as a function of excess energy. These data allow one to track in detail the transition from resonant Auger decay going along with shake-up of the spectator electron to shake-down and photoionization with recapture of the photoelectron. Results are in good agreement with a time-dependent quantum mechanical theory of Auger decay in the presence of a slow photoelectron.

Hergenhahn, U. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching (Germany); De Fanis, A. [Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo 679-5198 (Japan); Pruemper, G.; Ueda, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Kazansky, A. K. [Fock Institute of Physics, State University of Sankt-Petersburg, 198504 Saint-Petersburg (Russian Federation); Kabachnik, N. M. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Fakultaet fuer Physik, Universitaet Bielefeld, 33615 Bielefeld (Germany); Institute of Nuclear Physics, Moscow State University, Moscow 119992 (Russian Federation)

2006-02-15

176

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

177

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

178

Long-lived entanglement of neutral-atom chains by spin-exchange Rydberg interaction  

E-print Network

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. Long-lived 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; Kennedy, T A B

2014-01-01

179

Long-lived entanglement of neutral-atom chains by spin-exchange Rydberg interaction  

E-print Network

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. Long-lived 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.

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

2014-10-13

180

Mass-polarization effects in the 1 s 2 s sup 1 S and sup 3 S states of helium  

SciTech Connect

From a laser spectroscopic study of isotope shifts in the 1{ital s}2{ital s} {sup 1}{ital S},{sup 3}{ital S}{r arrow}1{ital snp} transitions in {sup 3}He and {sup 4}He and of the hyperfine structure in the 1{ital snp} Rydberg states of {sup 3}He we have derived highly accurate information on mass-polarization effects in the 1{ital s}2{ital s} {sup 1}{ital S} and {sup 3}{ital S} states. The experimental results, which are in good agreement with recent, high-precision variational calculations, confirm an isotope dependence of {l angle}{bold p}{sub 1}{center dot}{bold p}{sub 2}{r angle}.

Veldt, T. van der; Vassen, W.; Hogervorst, W. (Faculteit Natuurkunde en Sterrenkunde, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands (NL))

1990-04-01

181

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

PubMed

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 He7 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, He2(*), and <0.5% yielded an excited helium trimer. The nature of the dynamics, kinetic energy release, and connections to experiments are discussed. PMID:24712792

Closser, Kristina D; Gessner, Oliver; Head-Gordon, Martin

2014-04-01

182

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

NASA Astrophysics Data System (ADS)

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 He7 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, He2^*, 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.; Gessner, Oliver; Head-Gordon, Martin

2014-04-01

183

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

2007-12-06

184

Measurement of the oscillator strength distribution in helium  

SciTech Connect

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

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

2007-07-15

185

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

SciTech Connect

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

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

2009-04-17

186

Quantum Simulation of Helium Hydride in a Solid-State Spin Register  

E-print Network

\\emph{Ab initio} computation of molecular properties is one of the most promising applications of quantum computing. While this problem is widely believed to be intractable for classical computers, efficient quantum algorithms exist which have the potential to vastly accelerate research throughput in fields ranging from material science to drug discovery. Using a solid-state quantum register realized in a nitrogen-vacancy (NV) defect in diamond, we compute the bond dissociation curve of the minimal basis helium hydride cation, HeH$^+$. Moreover, we report an energy uncertainty (given our model basis) of the order of $10^{-14}$ Hartree, which is ten orders of magnitude below desired chemical precision. As NV centers in diamond provide a robust and straightforward platform for quantum information processing, our work provides several important steps towards a fully scalable solid state implementation of a quantum chemistry simulator.

Ya Wang; Florian Dolde; Jacob Biamonte; Ryan Babbush; Ville Bergholm; Sen Yang; Ingmar Jakobi; Philipp Neumann; Alán Aspuru-Guzik; James D. Whitfield; Jörg Wrachtrup

2014-05-12

187

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

188

Giant resonance and Rydberg series of laser excited chromium atoms  

SciTech Connect

Theoretical and experimental photoelectron spectra of ground state and laser excited Cr atoms in the region of the 3p-excitation are presented. The 3p{yields}4d,5d Rydberg excitations, which are very prominent in the 3d partial cross section of ground state Cr, and dramatically reduced by exciting the 4s electron into the 4p-shell. SPHF (spin polarized Hartree-Fock) calculations suggest that the well developed Rydberg series of ground state atoms are due to the delocalization of the 3d{down_arrow}, 4d{down_arrow} and 5d{down_arrow} wavefunctions, whereas, the corresponding wavefunctions of laser excited Cr do not undergo such an anticollapse.

Dohrmann, Th.; Arp, U.; Sonntag, B.; Wedowski, M.; Weisbarth, F.; Zimmermann, P.; Dolmatov, V. K. [II. Institut fuer Experimentalphysik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Institut fuer Strahlungs- und Kernphysik, TU Berlin, Hardenbergstrasse 36, D-10623 Berlin (Germany); S.V. Starodubtsev Physical-Technical Institute, G. Mavlyanova Str. 2, 700084 Tashkent (Uzbekistan)

1995-04-01

189

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

190

M1 decay of the 2 sup 3 S sub 1 state of helium-like bromine  

SciTech Connect

We have measured the lifetime of the 2 {sup 3}S{sub 1} level in helium-like bromine with the result {tau}{sup exp} 2 {sup 3}S{sub 1}=224.1 (7.1) ps, in agreement with theory. Our error is dominated by uncertainties in the correction for the effects of cascades from highly excited states.

Dunford, R.W.; Liu, C.J.; Berry, H.G.; Raphaelian, M.L.A. (Argonne National Laboratory, Argonne Illinois 60439 (United States)); Church, D.A. (Texas A M University, College Station, Texas 77843 (United States)); Hass, M. (University of Rochester, Rochester, NY 14627 (United States)); Curtis, L.J. (University of Toledo, Toledo, Ohio 43606 (United States))

1991-08-05

191

Controlling ultracold chemical reactions via Rydberg-dressed interactions  

E-print Network

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

Wang, Jia; Simbotin, Ion; Côté, R

2014-01-01

192

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

193

Entropy and complexity analysis of hydrogenic Rydberg atoms  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

194

Two-photon dynamics in coherent Rydberg atomic ensemble.  

PubMed

We study the interaction of two photons in a Rydberg atomic ensemble under the condition of electromagnetically induced transparency, combining a semiclassical approach for pulse propagation and a complete quantum treatment for quantum state evolution. We find that the blockade regime is not suitable for implementing photon-photon cross-phase modulation due to pulse absorption and dispersion. However, approximately ideal cross-phase modulation can be realized based on relatively weak interactions, with counterpropagating and transversely separated pulses. PMID:24745419

He, Bing; Sharypov, A V; Sheng, Jiteng; Simon, Christoph; Xiao, Min

2014-04-01

195

Patterned Rydberg excitation and ionisation with a spatial light modulator  

E-print Network

We demonstrate the ability to excite atoms at well-defined, programmable locations in a magneto-optical trap, either to the continuum (ionisation), or to a Rydberg state. To this end, excitation laser light is shaped into arbitrary intensity patterns with a spatial light modulator. These optical patterns are sensitive to aberrations of the phase of the light field, occuring while traversing the optical beamline. These aberrations are characterised and corrected without observing the actual light field in the vacuum chamber.

van Bijnen, R M W; Bakker, D J; Dijk, G J; Kokkelmans, S J J M F; Vredenbregt, E J D

2014-01-01

196

Patterned Rydberg excitation and ionisation with a spatial light modulator  

E-print Network

We demonstrate the ability to excite atoms at well-defined, programmable locations in a magneto-optical trap, either to the continuum (ionisation), or to a Rydberg state. To this end, excitation laser light is shaped into arbitrary intensity patterns with a spatial light modulator. These optical patterns are sensitive to aberrations of the phase of the light field, occuring while traversing the optical beamline. These aberrations are characterised and corrected without observing the actual light field in the vacuum chamber.

R. M. W. van Bijnen; C. Ravensbergen; D. J. Bakker; G. J. Dijk; S. J. J. M. F. Kokkelmans; E. J. D. Vredenbregt

2014-07-25

197

Properties of He-rich stars. I. Their evolutionary state and helium abundance  

Microsoft Academic Search

A determination of the surface gravity and an abundance analysis of helium in a sample of 17 He-rich and 5 normal, reference stars is presented. These results are derived from low resolution CCD spectra, but each star was measured at least 6 times in order to obtain a significant average spectrum for the spectroscopic variables. The helium abundances derived from

M. Zboril; P. North; Yu. V. Glagolevskij; F. Betrix

1997-01-01

198

Wigner crystallization of single photons in cold Rydberg ensembles.  

PubMed

The coupling of weak light fields to Rydberg states of atoms under conditions of electromagnetically induced transparency leads to the formation of Rydberg polaritons which are quasiparticles with tunable effective mass and nonlocal interactions. Confined to one spatial dimension their low energy physics is that of a moving-frame Luttinger liquid which, due to the nonlocal character of the repulsive interaction, can form a Wigner crystal of individual photons. We calculate the Luttinger K parameter using density-matrix renormalization group simulations and find that under typical slow-light conditions kinetic energy contributions are too strong for crystal formation. However, adiabatically increasing the polariton mass by turning a light pulse into stationary spin excitations allows us to generate true crystalline order over a finite length. The dynamics of this process and asymptotic correlations are analyzed in terms of a time-dependent Luttinger theory. PMID:24074081

Otterbach, Johannes; Moos, Matthias; Muth, Dominik; Fleischhauer, Michael

2013-09-13

199

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

PubMed

Liquid helium nanodroplets, consisting of on average 2 × 10(6) atoms, are examined using femtosecond time-resolved photoelectron imaging. The droplets are excited by an extreme ultraviolet light pulse centered at 23.7 eV photon energy, leading to states within a band that is associated with the 1s3p and 1s4p Rydberg levels of free helium atoms. The initially excited states and subsequent relaxation dynamics are probed by photoionizing transient species with a 3.2 eV pulse and using velocity map imaging to measure time-dependent photoelectron kinetic energy distributions. Significant differences are seen compared to previous studies with a lower energy (1.6 eV) probe pulse. Three distinct time-dependent signals are analyzed by global fitting. A broad intense signal, centered at an electron kinetic energy (eKE) of 2.3 eV, grows in faster than the experimental time resolution and decays in ?100 fs. This feature is attributed to the initially excited droplet state. A second broad transient feature, with eKE ranging from 0.5 to 4 eV, appears at a rate similar to the decay of the initially excited state and is attributed to rapid atomic reconfiguration resulting in Franck-Condon overlap with a broader range of cation geometries, possibly involving formation of a Rydberg-excited (Hen)* core within the droplet. An additional relaxation pathway leads to another short-lived feature with vertical binding energies ?2.4 eV, which is identified as a transient population within the lower-lying 1s2p Rydberg band. Ionization at 3.2 eV shows an enhanced contribution from electronically excited droplet states compared to ejected Rydberg atoms, which dominate at 1.6 eV. This is possibly the result of increased photoelectron generation from the bulk of the droplet by the more energetic probe photons. PMID:25381513

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

2014-11-01

200

Autoionization of an ultracold Rydberg gas through resonant dipole coupling  

NASA Astrophysics Data System (ADS)

We investigate a possible mechanism for the autoionization of ultracold Rydberg gases, based on the resonant coupling of Rydberg pair states to the ionization continuum. Unlike an atomic collision where the wave functions begin to overlap, the mechanism considered here involves only the long-range dipole interaction and is in principle possible in a static system. It is related to the process of intermolecular Coulombic decay (ICD). In addition, we include the interaction-induced motion of the atoms and the effect of multi-particle systems in this work. We find that the probability for this ionization mechanism can be increased in many-particle systems featuring attractive or repulsive van der Waals interactions. However, the rates for ionization through resonant dipole coupling are very low. It is thus unlikely that this process contributes to the autoionization of Rydberg gases in the form presented here, but it may still act as a trigger for secondary ionization processes. As our picture involves only binary interactions, it remains to be investigated if collective effects of an ensemble of atoms can significantly influence the ionization probability. Nevertheless our calculations may serve as a starting point for the investigation of more complex systems, such as the coupling of many pair states proposed in [P.J. Tanner et al., Phys. Rev. Lett. 100, 043002 (2008)].

Amthor, T.; Denskat, J.; Giese, C.; Bezuglov, N. N.; Ekers, A.; Cederbaum, L. S.; Weidemüller, M.

2009-06-01

201

HELIUM, SOLID 1 Helium, Solid  

E-print Network

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

Glyde, Henry R.

202

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.

203

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.

David A. Anderson; Stephanie A. Miller; Georg Raithel

2014-09-08

204

Information Storage and Processing in Rydberg Atoms.  

National Technical Information Service (NTIS)

Experiments performed under this grant were designed to exploit the extreme electric field sensitivity of highly-excited Rydberg atoms to test methods for asserting coherent control over inter- and intra-atomic dynamics. The work focused on the applicatio...

R. R. Jones

2008-01-01

205

Non-linear absorption and density dependent dephasing in Rydberg EIT-media  

E-print Network

Light propagation through an ensemble of ultra-cold Rydberg atoms in electromagnetically induced transparency (EIT) configuration is studied. In strongly interacting Rydberg EIT media, non-linear optical effects lead to a non-trivial dependence of the degree of probe beam attenuation on the medium density and on its initial intensity. We develop a Monte Carlo rate equation model that self-consistently includes the effect of the probe beam attenuation to investigate the steady state of the Rydberg medium driven by two laser fields. We compare our results to recent experimental data and to results of other state-of-the-art models for light propagation in Rydberg EIT-media. We find that for low probe field intensities, our results match the experimental data best if a density-dependent dephasing rate is included in the model. At higher probe intensities, our model deviates from other theoretical approaches, as it predicts a spectral asymmetry together with line broadening. These are likely due to off-resonant excitation channels, which however have not been observed in recent experiments. Atomic motion and coupling to additional Rydberg levels are discussed as possible origins for these deviations.

Martin Gärttner; Jörg Evers

2013-05-07

206

Vapour-liquid and liquid-liquid phase equilibria of binary mixtures containing helium: comparison of experiment with predictions using equations of state  

Microsoft Academic Search

The unlike interaction parameters for binary mixtures of helium + non-polar gases are obtained by comparing experimental critical data with calculations using the Guggenheim and Heilig-Franck equations of state. These interaction parameters and equations of state are used to predict a priori both the vapour-liquid and liquid-liquid equilibria for helium + non-polar gas mixtures. The predicted phase diagrams are compared

Ya Song Wei; Richard J Sadus

1996-01-01

207

Emission-line intensity of helium-like ions from the solar corona - Excitation cross section and plasma state  

NASA Astrophysics Data System (ADS)

It has been pointed out by Fujimoto (1979) that the ionization ratio (ratio of hydrogen-like to helium-like ion densities in the considered problem) is one of the most fundamental parameters in determining the line intensities, as well as the electron density and electron temperature of the plasma. A quasi-steady-state analysis of the observed helium-like line intensities in the one-temperature model is conducted. It is found that the line-intensity ratio is useful to estimate the electron density or to test the reliability of an observation. For the excitation cross section, the most reasonable value is given by distorted-wave calculations. Many of the coronal plasmas are interpreted as equilibrium plasmas, while some are recombining.

Fujimoto, T.; Kato, T.

1981-06-01

208

Stabilization of circular Rydberg atoms by circularly polarized infrared laser fields  

SciTech Connect

The ionization dynamics of circular Rydberg states in strong circularly polarized infrared (800 nm) laser fields is studied by means of numerical simulations with the time-dependent Schroedinger equation. We find that at certain intensities, related to the radius of the Rydberg states, atomic stabilization sets in, and the ionization probability decreases as the intensity is further increased. Moreover, there is a strong dependence of the ionization probability on the rotational direction of the applied laser field, which can be understood from a simple classical analogy.

Askeland, S.; Soerngaard, S. A.; Nepstad, R.; Foerre, M. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); 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)

2011-09-15

209

Auto-ionization and stochastic diffusion of Rydberg electrons in fluctuating laser fields  

NASA Astrophysics Data System (ADS)

The influence of laser fluctuations on the excitation of auto-ionizing Rydberg states close to an ionization threshold is investigated. Based on quantum defect theory a theoretical framework is developed within which all threshold phenomena originating from the infinitely many Rydberg states converging towards the ionization threshold as well as the stochastic influence of the exciting laser field can be described conveniently. It is demonstrated that the competition between the coherent process of auto-ionization and the incoherent processes induced by the fluctuating laser field leads to a variety of novel phenomena.

Eggers, B.; Alber, G.

1999-02-01

210

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

211

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

212

Full counting statistics and phase diagram of a dissipative Rydberg gas.  

PubMed

Ultracold gases excited to strongly interacting Rydberg states are a promising system for quantum simulations of many-body systems. For off-resonant excitation of such systems in the dissipative regime, highly correlated many-body states exhibiting, among other characteristics, intermittency and multimodal counting distributions are expected to be created. Here we report on the realization of a dissipative gas of rubidium Rydberg atoms and on the measurement of its full counting statistics and phase diagram for both resonant and off-resonant excitation. We find strongly bimodal counting distributions in the off-resonant regime that are compatible with intermittency due to the coexistence of dynamical phases. Our results pave the way towards detailed studies of many-body effects in Rydberg gases. PMID:25062177

Malossi, N; Valado, M M; Scotto, S; Huillery, P; Pillet, P; Ciampini, D; Arimondo, E; Morsch, O

2014-07-11

213

Molecular constants and RydbergKleinRees ,,RKR... potential curve for the Na2 1 3  

E-print Network

Molecular constants and Rydberg­Klein­Rees ,,RKR... potential curve for the Na2 1 3 g state Yaoming March 1999 Transitions into the doubly excited Na2 1 3 g state have been analyzed using near-dissociation expansions NDE to represent the vibrational energies and inertial rotational constants, while the centrifugal

Le Roy, Robert J.

214

Surface-electrode decelerator and deflector for Rydberg atoms and molecules  

NASA Astrophysics Data System (ADS)

A surface-electrode decelerator and deflector for Rydberg atoms and molecules has been developed with the goal of performing collisional experiments. Translationally cold H2 molecules in a supersonic beam were excited to Rydberg-Stark states of principal quantum number n =31, loaded into electric traps moving at a predetermined speed above the surface of a bent printed circuit board, decelerated, and deflected from the original direction of the supersonic beam by an angle of 10?. The phase-space characteristics of the deflected beam were characterized by measuring the time-of-flight distribution and images of the Rydberg molecules and comparing them to the results of numerical particle-trajectory simulations. More than 1000 H2 molecules were deflected per experimental cycle at a repetition rate of 25 Hz. The phase-space characteristics of the deflector make it attractive to study ion-molecule reactions at low collision energies.

Allmendinger, P.; Deiglmayr, J.; Agner, J. A.; Schmutz, H.; Merkt, F.

2014-10-01

215

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

216

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

217

Coherent manipulation of cold Rydberg atoms near the surface of an atom chip  

NASA Astrophysics Data System (ADS)

Coherent superpositions of the 49s1/2 and 48s1/2 Rydberg states of cold 87Rb atoms were studied near the surface of an atom chip. The superpositions were created and manipulated using microwaves resonant with the two-photon 49s1/2-48s1/2 transition. Coherent behavior was observed using Rabi flopping, Ramsey sequences, spin echo, and spin locking. These results are discussed in the context of Rydberg atoms as electric field noise sensors. We consider the coherence of systems quadratically coupled to noise fields with 1/f? power spectral densities (??1).

Carter, J. D.; Martin, J. D. D.

2013-10-01

218

Dissipative many-body quantum optics in Rydberg media.  

PubMed

We develop a theoretical framework for the dissipative propagation of quantized light under conditions of electromagnetically induced transparency in atomic media involving strongly interacting Rydberg states. The theory allows us to determine the peculiar spatiotemporal structure of the output of the recently demonstrated single-photon filter and the recently proposed single-photon subtractor, which, respectively, let through and absorb a single photon. In addition to being crucial for applications of these and other optical quantum devices, the theory opens the door to the study of exotic dissipative many-body dynamics of strongly interacting photons in nonlinear nonlocal media. PMID:25167264

Gorshkov, Alexey V; Nath, Rejish; Pohl, Thomas

2013-04-12

219

Landau-Zener Transitions in Frozen Pairs of Rydberg Atoms  

SciTech Connect

We have induced adiabatic transitions in pairs of frozen Rydberg sodium atoms of a supersonic beam. The diatomic ns+ns{yields}np+(n-1)p transition takes place in a time-dependent electric field and originates from the adiabatic change of the internal state of the pair induced by the dipole-dipole interaction. This is experimentally achieved by sweeping an electric field across the energy degeneracy ns ns-np(n-1)p. Our results fully agree with a two-level Landau-Zener model in the diatom system.

Saquet, Nicolas; Cournol, Anne; Beugnon, Jerome; Robert, Jacques; Pillet, Pierre; Vanhaecke, Nicolas [Laboratoire Aime Cotton, CNRS, Batiment 505, Universite Paris-Sud, 91405 Orsay (France)

2010-04-02

220

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

221

Two-photon dynamics in coherent Rydberg atomic ensemble  

E-print Network

We study the interaction of two photons in a Rydberg atomic ensemble under the condition of electromagnetically induced transparency, combining a semi-classical approach for pulse propagation and a complete quantum treatment for quantum state evolution. We find that the blockade regime is not suitable for implementing photon-photon cross-phase modulation due to pulse absorption and dispersion. However, approximately ideal cross-phase modulation can be realized based on relatively weak interactions, with counter-propagating and transversely separated pulses.

Bing He; A. V. Sharypov; Jiteng Sheng; Christoph Simon; Min Xiao

2014-01-07

222

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

223

Opto-nanomechanics strongly coupled to a Rydberg superatom: coherent versus incoherent dynamics  

NASA Astrophysics Data System (ADS)

We propose a hybrid optomechanical quantum system consisting of a moving membrane strongly coupled to an ensemble of N atoms with a Rydberg state. Due to the strong van-der-Waals interaction between the atoms, the ensemble forms an effective two-level system, a Rydberg superatom, with a collectively enhanced atom-light coupling. Using this superatom imposed collective enhancement strong coupling between membrane and superatom is feasible for parameters within the range of current experiments. The quantum interface to couple the membrane and the superatom can be a pumped single mode cavity, or a laser field in free space, where the Rydberg superatom and the membrane are spatially separated. In addition to the coherent dynamics, we study in detail the impact of the typical dissipation processes, in particular the radiative decay as a source for incoherent superpositions of atomic excitations. We identify the conditions to suppress these incoherent dynamics and thereby a parameter regime for strong coupling. The Rydberg superatom in this hybrid system serves as a toolbox for the nanomechanical resonator allowing for a wide range of applications such as state transfer, sympathetic cooling and non-classical state preparation. As an illustration, we show that a thermally occupied membrane can be prepared in a non-classical state without the necessity of ground state cooling.

Carmele, Alexander; Vogell, Berit; Stannigel, Kai; Zoller, Peter

2014-06-01

224

Opto-Nanomechanics Strongly Coupled to a Rydberg Superatom: Coherent vs. Incoherent Dynamics  

E-print Network

We propose a hybrid optomechanical quantum system consisting of a moving membrane strongly coupled to an ensemble of N atoms with a Rydberg state. Due to the strong van-der-Waals interaction between the atoms, the ensemble forms an effective two-level system, a Rydberg superatom, with a collectively enhanced atom-light coupling. Using this superatom imposed collective enhancement strong coupling between membrane and superatom is feasible for parameters within the range of current experiments. The quantum interface to couple the membrane and the superatom can be a pumped single mode cavity, or a laser field in free space, where the Rydberg superatom and the membrane are spatially separated. In addition to the coherent dynamics, we study in detail the impact of the typical dissipation processes, in particular the radiative decay as a source for incoherent superpositions of atomic excitations. We identify the conditions to suppress these incoherent dynamics and thereby a parameter regime for strong coupling. The Rydberg superatom in this hybrid system serves as a toolbox for the nanomechanical resonator allowing for a wide range of applications such as state transfer, sympathetic cooling and non-classical state preparation. As an illustration, we show that a thermally occupied membrane can be prepared in a non-classical state without the necessity of ground state cooling.

A. Carmele; B. Vogell; K. Stannigel; P. Zoller

2013-12-23

225

Van-der-Waals stabilized Rydberg aggregates  

E-print Network

Assemblies of Rydberg atoms subject to resonant dipole-dipole interactions form Frenkel excitons. We show that van-der-Waals shifts can significantly modify the exciton wave function, whenever atoms approach each other closely. As a result, attractive excitons and repulsive van-der-Waals interactions can be combined to form stable one-dimensional atom chains, akin to bound aggregates. Here the van-der-Waals shifts ensure a stronger homogeneous delocalisation of a single excitation over the whole chain, enabling it to bind up to six atoms. When brought into unstable configurations, such Rydberg aggregates allow the direct monitoring of their dissociation dynamics.

Zoubi, Hashem; Wüster, Sebastian

2013-01-01

226

Van-der-Waals stabilized Rydberg aggregates  

E-print Network

Assemblies of Rydberg atoms subject to resonant dipole-dipole interactions form Frenkel excitons. We show that van-der-Waals shifts can significantly modify the exciton wave function, whenever atoms approach each other closely. As a result, attractive excitons and repulsive van-der-Waals interactions can be combined to form stable one-dimensional atom chains, akin to bound aggregates. Here the van-der-Waals shifts ensure a stronger homogeneous delocalisation of a single excitation over the whole chain, enabling it to bind up to six atoms. When brought into unstable configurations, such Rydberg aggregates allow the direct monitoring of their dissociation dynamics.

Hashem Zoubi; Alex Eisfeld; Sebastian Wüster

2013-12-23

227

PUBLISHED ONLINE: 14 MARCH 2010 | DOI: 10.1038/NPHYS1614 A Rydberg quantum simulator  

E-print Network

individual manipulation and readout of atomic spins. Exciting atoms with lasers to high-lying Rydberg states provides fast and addressable two-qubit entangling operations or effective spin­spin interactions; recent demonstrated recently in the laboratory by several groups12,13 . Motivated by and building on these new

Loss, Daniel

228

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

NASA Astrophysics Data System (ADS)

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

Gim, Yeongrok; Lee, Chun-Woo

2014-10-01

229

Multi-grid experimental apparatus for the study of ultracold Rydberg-Rydberg interaction  

NASA Astrophysics Data System (ADS)

We have designed and constructed a new experimental setup for the study of ultracold Rydberg processes. A cold Cs MOT is centered between four parallel wire mesh grids, with two microchannel plate (MCP) detectors mounted perpendicular to the grids. Use of a phosphor screen behind one of the MCP detectors allows for spatial imaging of the ionized Rydberg atoms. This experimental apparatus allows for the study of both Rydberg many-body physics, as well as ion and electron imaging experiments. By controlling the voltages applied to the grids, ionized Rydberg atoms can be imaged on the MCP. Magnifications greater than ten have been observed, as well as strong focusing. We present initial results from this new experimental setup.

Gurian, Joshua; Huillery, Paul; Bruneau, Yoann; Cheinet, Patrick; Fioretti, Andrea; Comparat, Daniel; Pillet, Pierre

2011-06-01

230

Atomic-Orbital Close-Coupling Calculations Of Electron Capture From Hydrogen Atoms Into Highly Excited Rydberg States Of Multiply Charged Ions  

SciTech Connect

Collisions of neutral hydrogen atoms with multiply charged ions have been studied in the past using the semi-classical atomic-orbital close-coupling method. We present total and state-resolved cross sections for charge exchange as well as ionization. The advent of supercomputers and parallel programming facilities now allow treatment of collision systems that have been out of reach before, because much larger basis sets involving high quantum numbers are now feasible.

Igenbergs, Katharina; Wallerberger, Markus; Aumayr, Friedrich [Institute of Applied Physics, Vienna University of Technology, Association OeAW-EURATOM, Wiedner Hauptstr.8-10/E134, 1040 Vienna (Austria); Schweinzer, Josef [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr.2, 85748 Garching (Germany)

2011-06-01

231

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

E-print Network

correlation. No orientation of atom- ic levels by bulk excitation has yet been observed or predicted theoretically. At significantly lower en- ergies than discussed here, differences between 3 P and 3'P anisotropic excitation of neutral helium by foil..., but t ebroadening inside An exan1ple of3 was set to zero.0f the P transition w rum of sulfur pro]ec i et'1 x-rays is d the peaks are pro. Theareasun er eS. m flux by the monitor count. i 3spect a eatu e y g 'P x rays emitted in-S .i uration. It was possi e...

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

1982-01-01

232

Attosecond two-photon interferometry for doubly excited states of helium  

E-print Network

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

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

2011-04-19

233

Evolution from Rydberg gas to ultracold plasma in a supersonic atomic beam of Xe  

NASA Astrophysics Data System (ADS)

A Rydberg gas of xenon, entrained in a supersonic atomic beam, evolves slowly to form an ultracold plasma. In the early stages of this evolution, when the free-electron density is low, Rydberg atoms undergo long-range \\ell -mixing collisions, yielding states of high orbital angular momentum. The development of high-\\ell states promotes dipole–dipole interactions that help to drive Penning ionization. The electron density increases until it reaches the threshold for avalanche. Ninety ?s after the production of a Rydberg gas with the initial state, {{n}_{0}}{{\\ell }_{0}}=42d, a 432 V cm?1 electrostatic pulse fails to separate charge in the excited volume, an effect which is ascribed to screening by free electrons. Photoexcitation cross sections, observed rates of \\ell -mixing, and a coupled-rate-equation model simulating the onset of the electron-impact avalanche point consistently to an initial Rydberg gas density of 5\\times {{10}^{8}}\\;c{{m}^{-3}}.

Hung, J.; Sadeghi, H.; Schulz-Weiling, M.; Grant, E. R.

2014-08-01

234

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

235

PHYSICAL REVIEW A 86, 032506 (2012) Ab initio study of high-lying doubly excited states of helium in static electric fields: Complex-scaling  

E-print Network

PHYSICAL REVIEW A 86, 032506 (2012) Ab initio study of high-lying doubly excited states of helium is applied for the first precision calculation of the energies and autoionization widths for the high-lying 1 present a theoretical prediction of the energies and widths of high-lying doubly excited resonance states

Chu, Shih-I

236

Hyperfine structure of S- and P-wave states in muonic-helium ion  

SciTech Connect

Corrections of order {alpha}{sup 5} and {alpha}{sup 6} to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, -1334.73 meV (1S), -166.64 meV (2S), -58 712.90 {mu}eV (2P{sub 1/2}), and -24 290.69 {mu}eV (2P{sub 3/2}), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of {Delta}{sub 12} = 8{Delta}E{sup hfs}(2S) - {Delta}E{sup hfs}(1S) = 1.59 meV can be used to test QED predictions.

Martynenko, A. P., E-mail: mart@ssu.samara.ru; Elekina, E. N. [Samara State University (Russian Federation)

2010-12-15

237

Universal non-equilibrium properties of dissipative Rydberg gases  

E-print Network

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 non-trivial $\\mathbb{Z}_2$ symmetry and a dynamics with non-conserved 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.G. Wade et al., Phys. Rev. Lett. 111, 113901 (2013)] which observed bistable behaviour as well as power-law scaling of the relaxation time. The latter emerges not due to critical slowing down in the vici...

Marcuzzi, M; Diehl, S; Garrahan, J P; Lesanovsky, I

2014-01-01

238

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

239

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

E-print Network

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

Pachucki, Krzysztof

240

Electromagnetically induced transparency in strongly interacting Rydberg gases  

SciTech Connect

We develop an efficient Monte Carlo approach to describe the optical response of cold three-level atoms in the presence of electromagnetically induced transparency (EIT) and strong atomic interactions. In particular, we consider a Rydberg-EIT medium where one involved level is subject to large shifts due to strong van der Waals interactions with surrounding Rydberg atoms. Agreement with much more involved quantum calculations is excellent, demonstrating its applicability over a wide range of densities and interaction strengths. The calculations show that nonlinear absorption due to Rydberg-Rydberg atom interactions exhibits universal behavior.

Ates, C. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Max Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, D-01187 Dresden (Germany); Sevincli, S.; Pohl, T. [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, D-01187 Dresden (Germany)

2011-04-15

241

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

242

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

243

On the Binary Helium Star DY Centauri: Chemical Composition and Evolutionary State  

NASA Astrophysics Data System (ADS)

DY Cen has shown a steady fading of its visual light by about one magnitude in the last 40 yr, suggesting a secular increase in its effective temperature. We have conducted non-local thermodynamic equilibrium (LTE) and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 yr. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of a He white dwarf with a C-O white dwarf. Thus DY Cen by chemical composition appears to also be a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.

Pandey, Gajendra; Kameswara Rao, N.; Jeffery, C. Simon; Lambert, David L.

2014-10-01

244

On the binary helium star DY Centauri: Chemical composition and evolutionary state  

E-print Network

DY Cen has shown a steady fading of its visual light by about 1 magnitude in the last 40 years suggesting a secular increase in its effective temperature. We have conducted non-LTE and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 years. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of an He white dwarf with a C-O white dwarf. Thus, DY Cen by chemical composition appears to be also a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.

Pandey, Gajendra; Jeffery, C Simon; Lambert, David L

2014-01-01

245

Trapping Rydberg Atoms in an Optical Lattice  

SciTech Connect

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

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

2011-12-23

246

Neutralization Of Multiply Charged Rydberg Ions Interacting With Solid Surfaces Under The Grazing Incidence Geometry  

Microsoft Academic Search

We elaborated the time-symmetric, two-state vector model to investigate the intermediate stages of the electron capture into the Rydberg states of multiply charged ions interacting with solid surface under the grazing incidence geometry. The neutralization distances for the ions XeZ+ interacting with Al-surface are calculated, for core charges Z ?[5,30]. The corresponding mean neutralization distances are in agreement with the

M. D. Majkic; N. N. Nedeljkovic; S. M. D. Galijas

2010-01-01

247

Effective dynamics of strongly dissipative Rydberg gases  

E-print Network

We investigate the evolution of interacting Rydberg gases in the limit of strong noise and dissipation. Starting from a description in terms of a Markovian quantum master equation we derive effective equations of motion that govern the dynamics on a "coarse-grained" timescale where fast dissipative degrees of freedom have been adiabatically eliminated. Specifically, we consider two scenarios which are of relevance for current theoretical and experimental studies --- Rydberg atoms in a two-level (spin) approximation subject to strong dephasing noise as well as Rydberg atoms under so-called electromagnetically induced transparency (EIT) conditions and fast radiative decay. In the former case we find that the effective dynamics is described by classical rate equations up to second order in an appropriate perturbative expansion. This drastically reduces the computational complexity of numerical simulations in comparison to the full quantum master equation. When accounting for the fourth order correction in this expansion, however, we find that the resulting equation breaks the preservation of positivity and thus cannot be interpreted as a proper classical master rate equation. In the EIT system we find that the expansion up to second order retains information not only on the "classical" observables, but also on some quantum coherences. Nevertheless, this perturbative treatment still achieves a non-trivial reduction of complexity with respect to the original problem.

M Marcuzzi; J Schick; B Olmos; I Lesanovsky

2014-09-29

248

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

2006-12-06

249

Demonstration of a strong Rydberg blockade in three-atom systems with anisotropic interactions  

E-print Network

We study the Rydberg blockade in a system of three atoms arranged in different 2D geometries (linear and triangular configurations). In the strong blockade regime, we observe high-contrast, coherent collective oscillations of the single excitation probability, and an almost perfect van der Waals blockade. Our data is consistent with a total population in doubly and triply excited states below 2%. In the partial blockade regime, we directly observe the anisotropy of the van der Waals interactions between $|nD\\rangle$ Rydberg states in the triangular configuration. A simple model, that only uses independently measured two-body van der Waals interactions, fully reproduces the dynamics of the system without any adjustable parameter. These results are extremely promising for scalable quantum information processing and quantum simulation with neutral atoms.

Daniel Barredo; Sylvain Ravets; Henning Labuhn; Lucas Béguin; Aline Vernier; Florence Nogrette; Thierry Lahaye; Antoine Browaeys

2014-02-17

250

Demonstration of strong Rydberg blockade in three-atom systems with anisotropic interactions  

E-print Network

We study the Rydberg blockade in a system of three atoms arranged in different 2D geometries (linear and triangular configurations). In the strong blockade regime, we observe high-contrast, coherent collective oscillations of the single excitation probability, and an almost perfect van der Waals blockade. Our data is consistent with a total population in doubly and triply excited states below 2%. In the partial blockade regime, we directly observe the anisotropy of the van der Waals interactions between $|nD\\rangle$ Rydberg states in the triangular configuration. A simple model, that only uses independently measured two-body van der Waals interactions, fully reproduces the dynamics of the system without any adjustable parameter. These results are extremely promising for scalable quantum information processing and quantum simulation with neutral atoms.

Barredo, Daniel; Labuhn, Henning; Béguin, Lucas; Vernier, Aline; Nogrette, Florence; Lahaye, Thierry; Browaeys, Antoine

2014-01-01

251

Demonstration of a Strong Rydberg Blockade in Three-Atom Systems with Anisotropic Interactions  

NASA Astrophysics Data System (ADS)

We study the Rydberg blockade in a system of three atoms arranged in different two-dimensional geometries (linear and triangular configurations). In the strong blockade regime, we observe high-contrast, coherent collective oscillations of the single excitation probability and an almost perfect van der Waals blockade. Our data are consistent with a total population in doubly and triply excited states below 2%. In the partial blockade regime, we directly observe the anisotropy of the van der Waals interactions between |nD? Rydberg states in the triangular configuration. A simple model that only uses independently measured two-body van der Waals interactions fully reproduces the dynamics of the system without any adjustable parameter. These results are extremely promising for scalable quantum information processing and quantum simulation with neutral atoms.

Barredo, D.; Ravets, S.; Labuhn, H.; Béguin, L.; Vernier, A.; Nogrette, F.; Lahaye, T.; Browaeys, A.

2014-05-01

252

Femtosecond Dynamics and Control: From Rydberg Molecules to Photochemistry and Photobiology  

Microsoft Academic Search

Significant advances in laser technology have led to an increasing interest in the observation and control of excited state\\u000a dynamics in atoms, molecules and biomolecules. We begin by describing a simple intuitive control scheme based on an analogue\\u000a of Young's double-slit experiment in a Rydberg atom. We then describe how sequences of optical pulses can be employed to control\\u000a the

Helen H. Fielding

253

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

254

Electroproduction of strangeness on ?3,4H bound states on Helium  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

255

Flow and Supersolidity in Helium  

NASA Astrophysics Data System (ADS)

Recent torsional oscillator measurements showed evidence of non-classical rotational inertia in solid helium at temperatures below 200 mK and generated a great deal of interest in a possible supersolid state. The nature and properties of such a state are still unclear, although experiments involving 3He impurities and crystal annealing may provide clues. It would be very interesting to know whether supersolids share any of the other unusual properties of superfluids: superleaks, persistent currents, second sound and quantized vortices. We have studied the response of solid helium to pressure differences, in order to look for unusual flow properties that might be associated with supersolidity. Our measurements involved both helium confined in the nanometer pores of Vycor glass and bulk solid helium, at temperatures as low as 30 mK. Near melting, solid helium flows very easily but we did not see any evidence of superflow at low temperatures. If helium does become a supersolid at low temperatures, then its response to pressure gradients must be very different from that of liquid helium. We describe these and other experiments and discuss the role that defects may play in the low temperature behavior of solid helium.

Day, James; Beamish, John

2007-09-01

256

Emergence of stationary many-body entanglement in driven-dissipative Rydberg lattice gases  

E-print Network

Non-equilibrium quantum dynamics represents an emerging paradigm for condensed matter physics, quantum information science, and statistical mechanics. Strongly interacting Rydberg atoms offer an attractive platform to study driven-dissipative dynamics of quantum spin models with long-range order. Here, we explore the conditions under which stationary many-body entanglement persists with near-unit fidelity and high scalability. In our approach, coherent many-body dynamics is driven by Rydberg-mediated laser transitions, while atoms at the lattice boundary reduce the entropy of the many-body state. Surprisingly, the many-body entanglement is established by continuously evolving a locally dissipative Rydberg system towards the steady-state, as with optical pumping. We characterize the dynamics of multipartite entanglement in a 1D lattice by way of quantum uncertainty relations, and demonstrate the long-range behavior of the stationary entanglement with finite-size scaling, reaching "hectapartite" entanglement under experimental conditions. Our work opens a route towards dissipative preparation of many-body entanglement with unprecedented scaling behavior.

S. K. Lee; J. Cho; K. S. Choi

2013-12-30

257

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

PubMed Central

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

2014-01-01

258

Strongly correlated growth of Rydberg aggregates in a vapour cell  

E-print Network

The observation of strongly interacting many-body phenomena in gaseous samples typically requires ultracold atomic gases. Here we show that the very strong interaction potentials between Rydberg atoms enable the observation of many body effects in an atomic vapour, even at room temperature. We excite Rydberg atoms in caesium vapour and observe in real-time excitation dynamics far from resonance consistent with the formation of aggregates composed of several 10,000 Rydberg atoms. The experimental observations show qualitative and quantitative agreement with a microscopic theoretical model. Numerical simulations reveal that the strongly correlated growth of the emerging aggregates is reminiscent of soft-matter type systems.

Urvoy, A; Lesanovsky, I; Booth, D; Shaffer, J P; Pfau, T; Löw, R

2014-01-01

259

Strongly correlated growth of Rydberg aggregates in a vapour cell  

E-print Network

The observation of strongly interacting many-body phenomena in gaseous samples typically requires ultracold atomic gases. Here we show that the very strong interaction potentials between Rydberg atoms enable the observation of many body effects in an atomic vapour, even at room temperature. We excite Rydberg atoms in caesium vapour and observe in real-time excitation dynamics far from resonance consistent with the formation of aggregates composed of several 10,000 Rydberg atoms. The experimental observations show qualitative and quantitative agreement with a microscopic theoretical model. Numerical simulations reveal that the strongly correlated growth of the emerging aggregates is reminiscent of soft-matter type systems.

A. Urvoy; F. Ripka; I. Lesanovsky; D. Booth; J. P. Shaffer; T. Pfau; R. Löw

2014-07-31

260

Helium tables.  

NASA Technical Reports Server (NTRS)

These tables are intended to provide a standard method and to facilitate the calculation of the quantity of "Standard Helium" in high pressure containers. The research data and the formulas used in the preparation of the tables were furnished by the Research Laboratory of Physical Chemistry, of the Massachusetts Institute of Technology.

Havill, Clinton H

1928-01-01

261

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

262

Effect of charge polarization on inelastic scattering - Differential and integral cross sections for excitation of the 2/super 1/S state of helium by electron impact.  

NASA Technical Reports Server (NTRS)

Experimental differential scattering cross sections for excitation of helium by electron impact from its ground state to its 2(super 1)S state are presented at four incident electron energies in the range from 26 to 55.5 eV for scattering angles between 10 and 70 deg and at 81.6 eV for scattering angles between 10 and 80 deg. These cross sections are normalized and compared with results predicted by the Born approximation, the polarized Born approximation, and several other first-order approximations in which direct excitation is calculated in the Born approximation and exchange scattering in various Ochkur-like approximations.

Rice, J. K.; Truhlar, D. G.; Cartwright, D. C.; Trajmar, S.

1972-01-01

263

Photoionization cross section measurements of the 3p {sup 1,3}P excited states of helium in the near-threshold region  

SciTech Connect

We present measurements of photoionization cross sections of the 3p {sup 1}P and 3p {sup 3}P excited states of helium, at threshold and near-threshold region (0-0.2 Ry). The experiments have been performed using a dc glow discharge and employed the saturation technique to determine the photoionization cross sections. A smooth frequency dependence of the cross section has been observed for both the excited states in accordance to the theoretical calculations. The measured values of the photoionization cross section, using a simple experimental setup, are in good agreement with the earlier reported theoretical and experimental values.

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

2006-08-15

264

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

265

Three-Dimensional Roton Excitations and Supersolid Formation in Rydberg-Excited Bose-Einstein Condensates  

SciTech Connect

We study the behavior of a Bose-Einstein condensate in which atoms are weakly coupled to a highly excited Rydberg state. Since the latter have very strong van der Waals interactions, this coupling induces effective, nonlocal interactions between the dressed ground state atoms, which, opposed to dipolar interactions, are isotropically repulsive. Yet, one finds partial attraction in momentum space, giving rise to a roton-maxon excitation spectrum and a transition to a supersolid state in three-dimensional condensates. A detailed analysis of decoherence and loss mechanisms suggests that these phenomena are observable with current experimental capabilities.

Henkel, N.; Nath, R.; Pohl, T. [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany)

2010-05-14

266

Spatially Resolved Observation of Dipole-Dipole Interaction between Rydberg Atoms  

SciTech Connect

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

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

2008-06-20

267

Atomic Rydberg reservoirs for polar molecules.  

PubMed

We discuss laser-dressed dipolar and van der Waals interactions between atoms and polar molecules, so that a cold atomic gas with laser admixed Rydberg levels acts as a designed reservoir for both elastic and inelastic collisional processes. The elastic scattering channel is characterized by large elastic scattering cross sections and repulsive shields to protect from close encounter collisions. In addition, we discuss a dissipative (inelastic) collision where a spontaneously emitted photon carries away (kinetic) energy of the collision partners, thus providing a significant energy loss in a single collision. This leads to the scenario of rapid thermalization and cooling of a molecule in the mK down to the ?K regime by cold atoms. PMID:23003036

Zhao, B; Glaetzle, A W; Pupillo, G; Zoller, P

2012-05-11

268

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

269

Rydberg and multiple-electron excitations in x-ray photoabsorption spectra of N2 adsorbed on Fe(111)  

Microsoft Academic Search

Near-edge x-ray-absorption fine-structure spectra from K-shell excitation of N2 molecules adsorbed on an Fe(111) surface (gamma state) exhibit structures which, by comparison with corresponding gas-phase data, are identified as Rydberg and pi* multiple-electron excitations. These may obviously survive in the adsorbed state because of very weak valence-orbital interactions and large internuclear separations (approximately 2.5 Å) between the adsorbate and the

L. Wenzel; D. Arvanitis; R. Schlögl; M. Muhler; D. Norman; K. Baberschke; G. Ertl

1989-01-01

270

Ab Initio Equation of State for Hydrogen-Helium Mixtures with Recalibration of the Giant-planet Mass-Radius Relation  

NASA Astrophysics Data System (ADS)

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, ~0.2-9 g cm-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 ~0.2 Jupiter radii at fixed entropy and for masses greater than ~0.5 Jupiter mass. This change is large enough to have possible implications for some discrepant "inflated giant exoplanets."

Militzer, B.; Hubbard, W. B.

2013-09-01

271

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

272

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

273

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

NASA Astrophysics Data System (ADS)

We present measurements on pulsed four-wave mixing involving a Rydberg state in an atomic vapor cell. The excitation to the Rydberg state is conducted by a pulsed two-photon excitation on the nanosecond time scale that is combined with a third cw laser in phase-matched geometry yielding light emission on the same time scale. An additional signal peak is observed shortly after the pulse that can be attributed to a revival of constructive interference between different velocity classes of the radiating atomic dipoles. Furthermore we investigate the density dependence of the four-wave mixing signal. From the shape of the respective curve we are able to confirm energy and momentum conservation in the photonic part of the system.

Huber, B.; Kölle, A.; Pfau, T.

2014-11-01

274

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

275

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

E-print Network

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 \\emph{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 3D classical trajectory Monte Carlo simulations and numerically solving the time-dependent Schr\\"{o}dinger 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 analytic formula is obtained based on a simple model, and the dominant ionization mechanism is identified as a nonzero spatial displacement of the electron. Based on these observations, an "ionization window" is shown to exist for the ionization of Rydber...

Yang, B C

2014-01-01

276

Dynamical effects at avoided level crossings: A study of the Landau-Zener effect using Rydberg atoms  

NASA Astrophysics Data System (ADS)

We present a study of the dynamics of traversing an avoided energy level crossing. A pair of Stark levels of Rydberg states of lithium are used as a test system for measuring the diabatic transition probability. The experimental conditions are close to those assumed by the Landau-Zener theory. Possible corrections to the Landau-Zener theory are analyzed, and applications of the results to pulsed-field ionization are discussed.

Rubbmark, Jan R.; Kash, Michael M.; Littman, Michael G.; Kleppner, Daniel

1981-06-01

277

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

278

Thermodynamic Properties and Melting of Solid Helium  

Microsoft Academic Search

The melting properties and thermodynamic functions of solid helium have been determined at temperatures from 4 to 26 degrees K and at pressures up to 3000 atm. The upper temperature corresponds to about five times the critical temperature of helium; it was therefore possible to measure properties of the solid state in a range which has not yet been attained

J. S. Dugdale; F. E. Simon

1953-01-01

279

Ionization of nS, nP, and nD lithium, potassium, and cesium Rydberg atoms by blackbody radiation  

NASA Astrophysics Data System (ADS)

The results of theoretical calculations of the blackbody ionization rates of lithium, potassium, and cesium atoms residing in Rydberg states are presented. The calculations are performed for nS, nP, and nD states in a wide range of principal quantum numbers, n = 8-65, for blackbody radiation temperatures T = 77, 300, and 600 K. The calculations are performed using the known quasi-classical formulas for the photoionization cross sections and for the radial matrix elements of transitions in the discrete spectrum. The effect of the blackbody-radiation-induced population redistribution between Rydberg states on the blackbody ionization rates measured under laboratory conditions is quantitatively analyzed. Simple analytical formulas that approximate the numerical results and that can be used to estimate the blackbody ionization rates of Rydberg atoms are presented. For the S series of lithium, the rate of population of high-lying Rydberg levels by blackbody radiation is found to anomalously behave as a function of n. This anomaly is similar to the occurrence of the Cooper minimum in the discrete spectrum.

Beterov, I. I.; Ryabtsev, I. I.; Tretyakov, D. B.; Bezuglov, N. N.; Ékers, A.

2008-07-01

280

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

281

Deep permeable fault-controlled helium transport and limited mantle flux in two extensional geothermal systems in the Great Basin, United States  

USGS Publications Warehouse

This study assesses the relative importance of deeply circulating meteoric water and direct mantle fluid inputs on near-surface 3He/4He anomalies reported at the Coso and Beowawe geothermal fields of the western United States. The depth of meteoric fluid circulation is a critical factor that controls the temperature, extent of fluid-rock isotope exchange, and mixing with deeply sourced fluids containing mantle volatiles. The influence of mantle fluid flux on the reported helium anomalies appears to be negligible in both systems. This study illustrates the importance of deeply penetrating permeable fault zones (10-12 to 10-15 m2) in focusing groundwater and mantle volatiles with high 3He/4He ratios to shallow crustal levels. These continental geothermal systems are driven by free convection.

Banerjee, Amlan; Person, Mark; Hofstra, Albert; Sweetkind, Donald; Cohen, Denis; Sabin, Andrew; Unruh, Jeff; Zyvoloski, George; Gable, Carl W.; Crossey, Laura; Karlstrom, Karl

2011-01-01

282

Nr 123 2012 sa Myrbeck och Tomas Rydberg  

E-print Network

hydroteknik, SLU, mars 2011 Ã?sa Myrbeck, Tomas Rydberg #12;2 #12;3 Summary This field experiment autumn after early mouldboard ploughing than after delayed tillage. Use of a catch crop, incorporated and no catch crop, incorporation in spring reduced the amount of SMN (measured in December) by 25 kg ha-1

283

Quantum mechanicallycomplete measurements in electron impact excitation of helium  

E-print Network

Quantum mechanicallycomplete measurements in electron impact excitation of helium Andrew G. Mikosza, Nedlands, Perth. 6907, Australia. Abstract. A complete quantum description of the 3! D state of helium, with the Convergent Close Coupling (CCC) calculations. Previous data for helium at 40eV incident electrons

284

Helium fine structure theory for determination of Krzysztof Pachucki  

E-print Network

Helium fine structure theory for determination of Krzysztof Pachucki Institute of Theoretical in the calculation of helium fine-structure splitting of the 23 PJ states, based on the quantum electrodynamic theory by comparison with all experimental results for light helium-like ions and with the known large nuclear charge

Pachucki, Krzysztof

285

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

286

Electron Bubbles in Liquid Helium  

E-print Network

When an electron (or positronium atom) is injected into liquid helium with nearly zero energy, a bubble quickly forms around it. This phenomenon (which also occurs in liquid hydrogen, liquid neon and possibly in solid helium) lowers the mobility of the electron to a value similar to that for a positive ion. We estimate the radius of the bubble at zero pressure and temperature based on the zero point energy of the electron. If the liquid is held in a state of negative pressure, the bubble will expand beyond the radius at zero pressure. We also estimate the negative pressure such that a bubble once formed will grow without limit.

Kirk T. McDonald

2003-12-03

287

Pressure-driven Flow of Solid Helium  

NASA Astrophysics Data System (ADS)

Recent torsional oscillator measurements by Moses Chan's Penn State group showed evidence of ``non-classical rotational inertia'' for solid helium at temperatures below 200 mK. This discovery followed decades of theoretical speculation and experimental searches for ``supersolidity'' in helium. The experiments generated a great deal of interest but the origin and properties of such a state are still unclear. It would be very interesting to know whether supersolids share any of the other unusual properties of superfluids: persistent currents, second sound and quantized vortices. We have studied the response of solid helium to pressure changes in order to look for unusual flow properties that might be associated with supersolidity. The measurements involved both helium confined in the nanometer pores of Vycor glass and bulk solid helium, at temperatures as low as 30 mK. Pressure changes were generated with piezoelectrically driven diaphragm and flow was monitored with sensitive capacitive techniques. Near melting, solid helium flows very easily but we did not see any evidence of superflow at low temperatures. If helium does become a supersolid at low temperatures then its response to pressure gradients must be very different from that of liquid helium.

Beamish, John

2006-03-01

288

Helium-Recycling Plant  

NASA Technical Reports Server (NTRS)

Proposed system recovers and stores helium gas for reuse. Maintains helium at 99.99-percent purity, preventing water vapor from atmosphere or lubricating oil from pumps from contaminating gas. System takes in gas at nearly constant low back pressure near atmospheric pressure; introduces little or no back pressure into source of helium. Concept also extended to recycling of other gases.

Cook, Joseph

1996-01-01

289

A portable helium sniffer  

USGS Publications Warehouse

A portable helium sniffer has been developed for field use. The instrument is mounted in a four-wheel-drive pickup truck and can detect 50 parts per billion of helium in soil gas. The usefulness of helium sniffing in soil is being investigated as a prospecting tool in gas, oil, uranium, and geothermal prospecting as well as in earthquake prediction.

Friedman, Irving; Denton, E.H.

1976-01-01

290

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

291

Coherent dynamics of Rydberg atoms in cosmic microwave background radiation  

E-print Network

Rydberg atoms excited by cold blackbody radiation are shown to display long-lived quantum coherences on timescales of tens of picoseconds. By solving non-Markovian equations of motion with no free parameters we obtain the time evolution of the density matrix, and demonstrate that the blackbody-induced temporal coherences manifest as slowly decaying (100 ps) quantum beats in time-resolved fluorescence. An analytic model shows the dependence of the coherent dynamics on the energy splitting between atomic eigenstates, transition dipole moments, and coherence time of the radiation. Experimental detection of the fluorescence signal from a trapped ensemble of $10^8$ Rydberg atom is discussed, but shown to be technically challenging at present, requiring CMB amplification somewhat beyond current practice.

Timur V. Tscherbul; Paul Brumer

2013-05-23

292

Single-photon switch based on Rydberg blockade.  

PubMed

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. PMID:24579599

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

2014-02-21

293

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

294

Photon blockade induced by atoms with Rydberg coupling  

E-print Network

We study the photon blockade of two-photon scattering in a one-dimensional waveguide, which contains two atoms coupled via the Rydberg interaction. We obtain the analytic scattering solution of photonic wave packets with the Laplace transform method. We examine the photon correlation by addressing the two-photon relative wave function and the second-order correlation function in the single- and two-photon resonance cases. It is found that, under the single-photon resonance condition, photon bunching and antibunching can be observed in the two-photon transmission and reflection, respectively. In particular, the bunching and antibunching effects become stronger with the increasing of the Rydberg coupling strength. In addition, we find a phenomenon of bunching-antibunching transition caused by the two-photon resonance.

Jin-Feng Huang; Jie-Qiao Liao; C. P. Sun

2012-09-18

295

Ultracold Giant Polyatomic Rydberg Molecules: Coherent Control of Molecular Orientation  

NASA Astrophysics Data System (ADS)

We predict the existence of a class of ultracold giant molecules formed from trapped ultracold Rydberg atoms and polar molecules. The interaction which leads to the formation of such molecules is the anisotropic, long-range charge-dipole interaction. We show that prominent candidate molecules such as deuterated hydroxyl (OD) and KRb should bind to Rydberg rubidium atoms, with energies Eb?5-25GHz at distances R?0.1-1?m. These molecules form in double wells, mimicking chiral molecules, with each well containing a particular dipole orientation. We prepare a set of correlated dressed electron-dipole eigenstates which are used in an on-resonance Raman scheme to coherently control the molecular dipole orientation.

Rittenhouse, Seth T.; Sadeghpour, H. R.

2010-06-01

296

Zel'dovich effect and evolution of atomic Rydberg spectra along the periodic table  

SciTech Connect

In 1959, Zel'dovich predicted that the bound-state spectrum of the nonrelativistic 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 an analysis of experimental and numerical data, has its origin in the binding properties of the ionic core of the atom.

Kolomeisky, Eugene B.; Timmins, Michael [Department of Physics, University of Virginia, 382 McCormick Road, P. O. Box 400714, Charlottesville, Virginia 22904-4714 (United States)

2005-08-15

297

Helium Spectra in Atonic Mechanics  

NASA Astrophysics Data System (ADS)

In our model of the helium atom, we postulate that the angular momentum of each electron divided by equals an integer, n, plus a fraction,?n. By minimizing the energy the energy of the helium atom, we find that the ?n values are a function of the total angular momenta, J, irrespective of the integer, n. We thus obtain a set of ?n values for the singlet and triplet states of helium. The ?n values are related to fractals. In our model, we made adjustments to the electron mass so that the calculated energy values agree with the seventeen values for the singlet 1s-ns configurations listed in NIST Atomic Spectra Database Levels Data. The adjustments to the electron mass were usually very close to unity except for the ground state for which the adjustment was ˜5%. (Adjustments like these suggest that we may be able to study three-body effects with spectral accuracy.) By doing this, we had good agreement with all of the NIST spectral values for helium (191 lines of He I, and 243 lines of He II). This conceptually and mathematically simple procedure can be used for other atoms.

Phillips, Alfred, Jr.

2008-03-01

298

Rydberg-Klein-Rees (RKR) Franck-Condon factors for the O2 Schumann-Runge system including high vibrational quantum numbers  

Microsoft Academic Search

Franck-Condon factors and r-centroids for the O2 Schumann-Runge system have been calculated using the Rydberg-Klein-Rees approach. The range covers 21 vibrational levels for the upper (B3Sigmau-) state and 24 for the lower (X3Sigmag-) state. Results are in poor agreement with Franck-Condon factors derived from Morse potentials, but agree fairly well with those calculated by the Jarmain-Klein-Dunham method.

R. Harris; M. Blackledge; J. Generosa

1969-01-01

299

State-resolved measurements of single-electron capture in slow Ne7+- and Ne8+-helium collisions  

NASA Astrophysics Data System (ADS)

Single-electron capture in collisions of 9 keV × q Ne8+ and Ne7+ ions with He has been studied using cold-target recoil-ion momentum spectroscopy. With an improved apparatus a longitudinal momentum resolution of 0.07 au has been achieved. This momentum component is directly proportional to the difference in the binding energy of the active electron between the final and the initial state. For the first time state-resolved differential cross sections have been determined with respect to the main quantum number, subshell level and spin state of the captured electron. A comparison with recent theoretical results for energy levels in Be-like Ne is given.

Fischer, D.; Feuerstein, B.; Du Bois, R. D.; Moshammer, R.; Crespo López-Urrutia, J. R.; Draganic, I.; Lörch, H.; Perumal, A. N.; Ullrich, J.

2002-03-01

300

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

301

Nonvariational calculation of the relativistic, finite-size, and QED corrections for the 2 1S excited state of the helium atom  

NASA Astrophysics Data System (ADS)

Relativistic and QED corrections are calculated by using a direct solution of the Schrödinger equation for the 2 1S excited state of the helium atom obtained with the correlation-function hyperspherical-harmonic method. Our extremely accurate nonvariational results for relativistic, QED, and finite-size corrections coincide exactly (up to 0.000 03 cm-1) with the values obtained in precision variational calculations of Drake [Nucl. Instrum. Methods Phys. Res. B 5, 2207 (1988)] and Baker, Hill, and Morgan [in Relativistic, Quantum Electrodynamic and Weak Interaction Effects in Atoms, edited by Walter Johnson, Peter Mohr, and Joseph Sucher, AIP Conf. Proc. No. 189 (AIP, New York, 1989), p. 123] for both infinite and finite nuclear masses. This confirms that a discrepancy of 0.0033 cm-1 between theory and experiment is not a result of an inaccuracy of variational wave functions, but is rooted in our inadequate knowledge of the QED operators. A better understanding of the different QED contributions to the operators (such as, for example, a more precise estimate of the Bethe logarithm) is therefore needed to explain the discrepancy.

Haftel, M. I.; Mandelzweig, V. B.

1994-05-01

302

Reply to 'Comment on 'Doubly excited bound and resonance ({sup 3}P{sup e}) states of helium''  

SciTech Connect

In response to the comment by Kar and Ho [Phys. Rev. A 82, 036501 (2010)], we have clarified the reason for anomaly between our and their results for the resonance states below the N=5 ionization threshold of He{sup +}.

Saha, Jayanta K.; Mukherjee, Tapan K. [Narula Institute of Technology, Agarpara, Kolkata 700 109 (India)

2010-09-15

303

Quenching of the 2pnd Po1 doubly excited states of helium by a dc electric field  

NASA Astrophysics Data System (ADS)

The fluorescence yield quenching of low-lying doubly excited 2pnd Po1 states is observed to depend strongly on a dc electric field strength and its orientation with respect to the polarization of the incoming photon beam. The reduction of the yield accompanied by the lifetime shortening is attributed to the Stark mixing with the neighboring 2sns Se1 states, which redirects the 2pnd Po1 decay to the prompt autoionization channel. For n ?4, the lifetimes decrease from several hundred picoseconds down to several tens of picoseconds when an electric field in the kV/cm range is applied parallel to the photon probe polarization. Practically no lifetime change is observed for polarization perpendicular to the electric field direction. The results of the complex-scaling calculations are in a good agreement with the experimental data.

Bu?ar, K.; Žitnik, M.; Miheli?, A.; Penent, F.; Lablanquie, P.; Palaudoux, J.; Andri?, L.; Braune, M.; Püttner, R.

2014-07-01

304

Dissipative preparation of spatial order in Rydberg-dressed Bose-Einstein condensates.  

PubMed

We propose a technique for engineering momentum-dependent dissipation in Bose-Einstein condensates with nonlocal 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 nonlocal 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. Because of its dissipative nature, the ordering does not require artificial breaking of translational symmetry by an optical lattice or harmonic trap. This opens up a perspective of direct cooling of quantum gases into strongly interacting phases. PMID:25170691

Otterbach, Johannes; Lemeshko, Mikhail

2014-08-15

305

Production of trilobite Rydberg molecule dimers with thousand-Debye permanent electric dipole moments  

E-print Network

We observe that when an ultracold ground state cesium (Cs) atom becomes bound within the electronic cloud of an extended Cs electronic orbit, ultralong-range molecules with giant (kilo-Debye) permanent electric dipole moments form. Large molecular permanent electric dipole moments are challenging to experimentally realize. Meeting this challenge has garnered significant interest because permanent electric dipole moments are important for understanding symmetry breaking in molecular physics, control of chemical reactions and realization of strongly correlated many-body quantum systems. These new hybrid class of `trilobite' molecules are predominated with degenerate Rydberg manifolds, making them difficult to produce with conventional optical association. Their behavior is quantitatively reproduced with detailed coupled-channel calculations.

Booth, Donald; Yang, Jin; Sadeghpour, Hossein; Shaffer, James

2014-01-01

306

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

307

Classical Helium Model  

NSDL National Science Digital Library

The EJS Classical Helium Model is an example of a three-body problem that is similar to the gravitational three-body problem of a heavy sun and two light planets. The important difference is that the helium atom's two electrons repel one another, unlike the planetary case where the intraplanetary interaction is attractive. The EJS Classical Helium Model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_mech_orbits_ClassicalHelium.jar file will run the program if Java is installed.

Christian, Wolfgang

2009-03-14

308

Direct evidence of three-body interactions in a cold {sup 85}Rb Rydberg gas  

SciTech Connect

Cold Rydberg atoms trapped in a magneto-optical trap (MOT) are not isolated and they interact through dipole-dipole and multipole-multipole interactions. First-order dipole-dipole interactions and van der Waals interactions between two atoms have been intensively studied. However, the facts that the first-order dipole-dipole interactions and van der Waals interactions show the same size of broadening [A. Reinhard, K. C. Younge, T. C. Liebisch, B. Knuffman, P. R. Berman, and G. Raithel, Phys. Rev. Lett. 100, 233201 (2008)] and there are transitions between two dimer states [S. M. Farooqi, D. Tong, S. Krishnan, J. Stanojevic, Y. P. Zhang, J. R. Ensher, A. S. Estrin, C. Boisseau, R. Cote, E. E. Eyler, and P. L. Gould, Phys. Rev. Lett. 91, 183002 (2003); K. R. Overstreet, Arne Schwettmann, Jonathan Tallant, and James P. Shaffer, Phys. Rev. A 76, 011403(R) (2007)] cannot be explained by the two-atom picture. The purpose of this article is to show the few-body nature of a dense cold Rydberg gas by studying the molecular-state microwave spectra. Specifically, three-body energy levels have been calculated. Moreover, the transition from three-body energy levels to two-body coupled molecular energy levels and to isolated atomic energy levels as a function of the internuclear spacing is studied. Finally, single-body, two-body, and three-body interaction regions are estimated according to the experimental data. The results reported here provides useful information for plasma formation, further cooling, and superfluid formation.

Han Jianing [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

2010-11-15

309

Analysis of a quantum logic device based on dipole-dipole interactions of optically trapped Rydberg atoms  

SciTech Connect

We present a detailed analysis and design of a neutral atom quantum logic device based on atoms in optical traps interacting via dipole-dipole coupling of Rydberg states. The dominant physical mechanisms leading to decoherence and loss of fidelity are enumerated. Our results support the feasibility of performing single- and two-qubit gates at MHz rates with decoherence probability and fidelity errors at the level of 10{sup -3} for each operation. Current limitations and possible approaches to further improvement of the device are discussed.

Saffman, M.; Walker, T.G. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States)

2005-08-15

310

Analysis of a quantum logic device based on dipole-dipole interactions of optically trapped Rydberg atoms  

E-print Network

We present a detailed analysis and design of a neutral atom quantum logic device based on atoms in optical traps interacting via dipole-dipole coupling of Rydberg states. The dominant physical mechanisms leading to decoherence and loss of fidelity are enumerated. Our results support the feasibility of performing single and two-qubit gates at MHz rates with decoherence probability and fidelity errors at the level of $10^{-3}$ for each operation. Current limitations and possible approaches to further improvement of the device are discussed.

M. Saffman; T. G. Walker

2005-02-09

311

The helium trimer with soft-core potentials  

E-print Network

The helium trimer is studied using two- and three-body soft-core potentials. Realistic helium-helium potentials present an extremely strong short-range repulsion and support a single, very shallow, bound state. The description of systems with more than two helium atoms is difficult due to the very large cancellation between kinetic and potential energy. We analyze the possibility of describing the three helium system in the ultracold regime using a gaussian representation of a widely used realistic potential, the LM2M2 interaction. However, in order to describe correctly the trimer ground state a three-body force has to be added to the gaussian interaction. With this potential model the two bound states of the trimer and the low energy scattering helium-dimer phase shifts obtained with the LM2M2 potential are well reproduced.

A. Kievsky; E. Garrido; C. Romero-Redondo; P. Barletta

2011-01-10

312

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

313

Spectroscopy of the E State of Iodine Monofluoride and Rotational Energy Transfer of the B State in Collisions with Helium, Using Two-Photon Sequential Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

The Two Photon Sequential Absorption (TPSA) technique has been used to investigate a state of 0('+) symmetry of IF (iodine monofluoride) which has T(,e) = 41292 cm(' -1), (omega)(,e) = 248.8 cm('-1), and B(,e) = .1292 cm(' -1). This state has been designated the E state and dissociates to I('+)(('3)P(,2)) and F('-)(('1)S(,0)) ionic partners. The TPSA technique was also used to study collisions between IF molecules in specific rotational levels of the B state and He atoms. The total depopulation rate of an individual rotational level for V(,B) = 6 of IF(B state) in He was found to be 4 x 10('-10) cm('3) molecule('-1) s('-1). In both experiments, individual rotational-vibrational levels in the B state were initially populated with pulsed dye laser radiation. A second pulsed dye laser was scanned through its dye profile, inducing transitions from the B state to the E state. In the initial investigation of the E state, the total cell pressure was maintained at 1 Torr and no collisionally populated B state levels were encountered. After the E state characteristics were determined, the cell pressure was increased to between 3 Torr and 9 Torr, and collisionally populated B state levels were observed.

Clark, Brian Keith

314

Relaxation of antihydrogen from Rydberg to ground state  

SciTech Connect

Atoms formed in highly-magnetized, cryogenic Penning trap plasmas, such as those used in the Athena and ATRAP antihydrogen experiments, form in the guiding-center atom regime. In this regime, the positron orbit is well described by classical guiding-center drift dynamics. Electromagnetic radiation from such atoms is minimal, and energy loss is accomplished primarily through collisions between the atom and free positrons. With Fokker-Planck theory and Monte-Carlo simulation, we calculate the mean energy change an ensemble of such atoms experiences after the atom has been formed. Using this result, we show that the bulk of atoms formed in antihydrogen experiments do not relax out of the guiding-center regime to binding energies where radiation can become important.

Bass, Eric M.; Dubin, Daniel H. E. [Department of Physics, University of California at San Diego, La Jolla, CA 92093-0319 (United States)

2006-10-18

315

The Primordial Helium Abundance  

E-print Network

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 evolution models.

Manuel Peimbert

2008-11-18

316

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

317

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

318

Advanced helium magnetometer for space applications  

NASA Technical Reports Server (NTRS)

The goal of this effort was demonstration of the concepts for an advanced helium magnetometer which meets the demands of future NASA earth orbiting, interplanetary, solar, and interstellar missions. The technical effort focused on optical pumping of helium with tunable solid state lasers. We were able to demonstrate the concept of a laser pumped helium magnetometer with improved accuracy, low power, and sensitivity of the order of 1 pT. A number of technical approaches were investigated for building a solid state laser tunable to the helium absorption line at 1083 nm. The laser selected was an Nd-doped LNA crystal pumped by a diode laser. Two laboratory versions of the lanthanum neodymium hexa-aluminate (LNA) laser were fabricated and used to conduct optical pumping experiments in helium and demonstrate laser pumped magnetometer concepts for both the low field vector mode and the scalar mode of operation. A digital resonance spectrometer was designed and built in order to evaluate the helium resonance signals and observe scalar magnetometer operation. The results indicate that the laser pumped sensor in the VHM mode is 45 times more sensitive than a lamp pumped sensor for identical system noise levels. A study was made of typical laser pumped resonance signals in the conventional magnetic resonance mode. The laser pumped sensor was operated as a scalar magnetometer, and it is concluded that magnetometers with 1 pT sensitivity can be achieved with the use of laser pumping and stable laser pump sources.

Slocum, Robert E.

1987-01-01

319

SPECIAL TOPIC: HELIUM NANODROPLETS Experimental studies of helium droplets  

E-print Network

SPECIAL TOPIC: HELIUM NANODROPLETS Experimental studies of helium droplets J. A. Northbya) Physics September 2001 In this report I will review experimental studies of free helium droplets, with the exception of spectroscopic studies of helium droplets that contain impurities. This particular topic, as well as theoretical

Northby, Jan A.

320

Precision spectroscopy of Kaonic helium-3 and helium-4 3d-->2p X-rays  

NASA Astrophysics Data System (ADS)

Recently, the shift of the kaonic helium-4 2p state was precisely determined by the E570 and SIDDHARTA experiments. Prior to the experiment by E570, the average of three earlier experimental results showed -43±8 eV, while most of the theoretical calculations give ˜0 eV. This five-sigma discrepancy between theory and experiment was known as the "kaonic helium puzzle". A recent theoretical model showed a possible resonance-like shift of maximum 10 eV for a certain value of a deep antikaon-nucleon interaction potential, which is different in helium 3 and helium 4. The E570 experiment determined the shift of the kaonic helium-4 2p state as +2±2 (stat)±2 (sys) eV in 2007. The SIDDHARTA experiment determined the shift as 0±6(stat)±2(sys) eV in 2009. The results of these experiments resolved the long-standing puzzle. A new experiment of the kaonic helium-3 X-ray measurement is being prepared by the J-PARC E17 collaborators, and the kaonic helium-3 X-ray data taken very recently by the SIDDHARTA experiment are on the way to be analyzed. The results of the E570, E17 and SIDDHARTA experiments examine the strong interaction for light nuclei with different isospin, and test furthermore recent theoretical predictions.

Ishiwatari, T.; Bazzi, M.; Bhang, H.; Beer, G.; Bombelli, L.; Bragadireanu, A. M.; Cargnelli, M.; Choi, S.; Corradi, G.; Curceanu, C.; d'Uffizi, A.; Enomoto, S.; Fiorini, C.; Frizzi, T.; Fujioka, H.; Fujiwara, Y.; Ghio, F.; Girolami, B.; Guaraldo, C.; Hashimoto, T.; Hayano, R. S.; Hiraiwa, T.; Iio, M.; Iliescu, M.; Ishimoto, S.; Itahashi, K.; Iwasaki, M.; Kienle, P.; Kou, H.; Levi Sandri, P.; Longoni, A.; Lucherini, V.; Marton, J.; Matsuda, Y.; Noumi, H.; Ohnishi, H.; Okada, S.; Outa, H.; Pietreanu, D.; Ponta, T.; Rizzo, A.; Romero Vidal, A.; Sakuma, F.; Sato, M.; Scordo, A.; Sekimoto, M.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Suzuki, T.; Tanida, K.; Tatsuno, H.; Tokuda, M.; Tomono, D.; Toyoda, A.; Tsukada, K.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Widmann, E.; Wünschek, B.; Yamazaki, T.; Zmeskal, J.

2010-08-01

321

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

322

The descending helium balloon  

NASA Astrophysics Data System (ADS)

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

2014-07-01

323

Ab Initio Simulations of Dense Helium Plasmas  

SciTech Connect

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/cm{sup 3} 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.

Wang Cong [LCP, Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088 (China); He Xiantu; Zhang Ping [LCP, Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China)

2011-04-08

324

a Luttinger Liquid Core Inside HELIUM-4 Filled Nanopores  

NASA Astrophysics Data System (ADS)

As helium-4 is cooled below 2.17 K it undergoes a phase transition to a fundamentally quantum mechanical state of matter known as a superfluid which supports flow without viscosity. This type of dissipationless transport can be observed by forcing helium to travel through a narrow constriction that the normal liquid could not penetrate. Recent experiments have highlighted the feasibility of fabricating smooth pores with nanometer radii, that approach the truly one-dimensional limit where it is believed that a system of bosons (like helium-4) may have startlingly different behavior than in three dimensions. The one-dimensional system is predicted to have a linear hydrodynamic description known as Luttinger liquid (LL) theory, where no type of long range order can be sustained. In the limit where the pore radius is small, LL theory would predict that helium inside the channel behaves as a sort of quasi-supersolid with all correlations decaying as power-law functions of distance at zero temperature. We have performed large scale quantum Monte Carlo simulations of helium-4 inside nanopores of varying radii at low temperature with realistic helium.helium and helium-pore interactions. The results indicate that helium inside the nanopore forms concentric cylindrical shells surrounding a core that can be described via LL theory and provides insights into the exciting possibility of the experimental detection of this intriguing low-dimensional state of matter.

Del Maestro, Adrian

2014-10-01

325

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

326

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

327

CP pulse-envelope-driven dynamics at Floquet anticrossings of He Rydberg atoms: the importance of fine structure  

NASA Astrophysics Data System (ADS)

A 14.6 keV, CO2 laser-excited beam of n^3S He Rydberg atoms flew through a TE_121 mode cavity, exposing the atoms to about 300 oscillations of a circularly polarized 9.904 GHz electric field (peak amplitude F) with a half-sine pulse envelope. Detection of a surviving Rydberg atom signal \\cal S(F) occurred downstream in a voltage-labeled 9.8 GHz cavity whose field amplitude was set empirically to ionize (n,M_l=0) atoms more efficiently than (n,|M_l|>= 1) atoms.( W. van de Water et al.), Phys. Rev. A 42, 572 (1990). The ions were detected with a particle multiplier. For both n=28,29 \\cal S(F) displayed Stueckelberg oscillations (as observed previously with LP at higher frequencies)( S. Yoakum et al.), Phys. Rev. Lett. 69, 1919 (1992). and other F-dependent structure. Calculations of Floquet quasienergy levels require inclusion of fine structure couplings to understand the origin of the oscillations. How to extract relevant diabatic states( M. Cavagnero and S. Cornett, private communication. ) and couplings from the Floquet calculations towards modelling \\cal S(F) will be discussed and experimental-theoretical comparisons presented.

Zelazny, S. A.; Koch, P. M.

1998-05-01

328

Electron states in a quasi-one-dimensional charge channel over liquid helium in the presence of a transverse magnetic field  

SciTech Connect

Calculations are carried out for single-particle energy levels and wave functions for electrons in a quasi-one-dimensional charge channel formed on the surface of liquid helium. The expressions for the spectrum are obtained for two different orientations of the magnetic field perpendicular to the channel. The conditions for the applicability of the formulas derived are established and they can be used in experimental studies of spectroscopic transitions between

Sokolov, S.S. (Departamento de Fisica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, Sao Paulo (Brazil) B. I. Verkin Institute for Low Temperature Physics and Engineering, Academy of Sciences of Ukraine, 310164 Kharkov (Ukraine)); Studart, N. (Departamento de Fisica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, Sao Paulo (Brazil))

1995-01-15

329

The regularities of the Rydberg energy levels of many-valence electron atom Al  

Microsoft Academic Search

Within the scheme of the weakest bound electron potential model theory, the concept of spectral-level-like series is presented\\u000a by reasonably classifying the Rydberg energy level of atom Al. Based on this concept, the regularities of the Rydberg energy\\u000a levels are systematically studied. The deviations of the calculated values from the experimental values are generally about\\u000a several percent of 1 cm,

Nengwu Zheng; Yujie Sun

2000-01-01

330

Rydberg-atom quantum simulation and Chern-number characterization of a topological Mott insulator  

NASA Astrophysics Data System (ADS)

In this work we consider a system of spinless fermions with nearest and next-to-nearest neighbor repulsive Hubbard interactions on a honeycomb lattice, and propose and analyze a realistic scheme for analog quantum simulation of this model with cold atoms in a two-dimensional hexagonal optical lattice. To this end, we first derive the zero-temperature phase diagram of the interacting model within a mean-field theory treatment. We show that besides a semimetallic 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 we study the possibility of coexistence of this phase with any of 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 effectively 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.

Dauphin, A.; Müller, M.; Martin-Delgado, M. A.

2012-11-01

331

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

E-print Network

In this work we consider a system of spinless fermions with nearest and next-to-nearest neighbor repulsive Hubbard interactions on a honeycomb lattice, and propose and analyze a realistic scheme for analog quantum simulation of this model with cold atoms in a two-dimensional hexagonal optical lattice. To this end, we first derive the zero-temperature phase diagram of the interacting model within a mean-field theory treatment. We show that 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. Based on the knowledge of the mean-field phase diagram, we then discuss in detail how the interacting Hamiltonian can be engineered effectively 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.

A. Dauphin; M. Müller; M. A. Martin-Delgado

2012-07-26

332

Rydberg assisted light shift imbalance induced blockade in an atomic ensemble  

E-print Network

Previously, we had proposed the technique of light shift imbalance induced blockade which leads to a condition where a collection of non-interacting atoms under laser excitation remains combined to a superposition of the ground and the first excited states, thus realizing a collective state quantum bit which in turn can be used to realize a quantum computer. In this paper, we show first that the light shift imbalance by itself is actually not enough to produce such a blockade, and explain the reason why the limitation of our previous analysis had reached this constraint. We then show that by introducing Rydberg interaction, it is possible to achieve such a blockade for a wide range of parameters. Analytic arguments used to establish these results are confirmed by numerical simulations. The fidelity of coupled quantum gates based on such collective state qubits is highly insensitive to the exact number of atoms in the ensemble. As such, this approach may prove to be viable for scalable quantum computing based ...

Tu, Yanfei; Shahriar, Selim M

2014-01-01

333

Spectra of the rare gas hydrides V: The np Rydberg series of KrD  

NASA Astrophysics Data System (ADS)

The 23 920 cm-1, 21 950 cm-1, and 17 840 cm-1 emission bands of KrD have been analysed successfully as transitions from the 8p, 7p, and 6p Rydberg complexes to the lowest bound state, 2?. It was found that the structure of these states corresponds to a special case of l uncoupling with a Coriolis-like linear dependence of the case (d) electron-rotation energies on the quantum number R. The structure of the lowest member of the series, the 5p(2?, 2?) complex, has been obtained from the simultaneous analysis of the 5 050 cm-1 and 5 800 cm-1 emission bands as transitions from the 4d2? case (b) upper state to the 5p2? and 5p2? components of the complex. The latter are widely split, E? - E? = 735 cm-1, due to electronic interactions and are further distorted by strong spin-orbit interactions. The 5p(2?, 2?) complex corresponds to the p complex of ArD studied recently by Dabrowski, I., Dilonardo, G., Herzberg, G., Johns, J. W. C., Sadowskii, D. A., and Vervloet, M., 1992, J. chem. Phys., 97, 7093.

Dabrowski, I.; Sadovskií, D. A.

334

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

335

Controlling the interactions of a few cold Rb Rydberg atoms by radiofrequency-assisted F\\"orster resonances  

E-print Network

Long-range interactions between cold Rydberg atoms are being investigated for neutral-atom quantum computing, quantum simulations, phase transitions in cold Rydberg gases and other important applications. These applications often require fine tuning of the interaction strength. It can be implemented using F\\"orster resonances between Rydberg atoms controlled by a dc, microwave or radiofrequency (rf) electric field. Here we report on the experimental observation of highly-resolved rf-assisted F\\"orster resonances in a few cold Rb Rydberg atoms. We also observed rf-induced F\\"orster resonances which cannot be tuned by dc electric field. They correspond to an efficient conversion between the van der Waals and dipole-dipole interactions due to Floquet sidebands of Rydberg levels appearing in the rf-field. These observations pave the way to many applications of rf-assisted F\\"orster resonances in studying the many-body phenomena with cold Rydberg atoms.

Tretyakov, D B; Yakshina, E A; Beterov, I I; Andreeva, Ch; Ryabtsev, I I

2014-01-01

336

Core-to-Rydberg band shift and broadening of hydrogen bonded ammonia clusters studied with nitrogen K-edge excitation spectroscopy  

SciTech Connect

Nitrogen 1s (N ls) core-to-Rydberg excitation spectra of hydrogen-bonded clusters of ammonia (AM) have been studied in the small cluster regime of beam conditions with time-of-flight (TOF) fragment-mass spectroscopy. By monitoring partial-ion-yield spectra of cluster-origin products, ''cluster'' specific excitation spectra could be recorded. Comparison of the ''cluster'' band with ''monomer'' band revealed that the first resonance bands of clusters corresponding to N 1s{yields} 3sa{sub 1}/3pe of AM monomer are considerably broadened. The changes of the experimental core-to-Rydberg transitions {Delta}FWHM (N 1s{yields} 3sa{sub 1}/3pe) ={approx}0.20/{approx}0.50 eV compare well with the x ray absorption spectra of the clusters generated by using density functional theory (DFT) calculation. The broadening of the core-to-Rydberg bands in small clusters is interpreted as being primarily due to the splitting of non-equivalent core-hole N 1s states caused by both electrostatic core-hole and hydrogen-bonding (H{sub 3}N{center_dot}{center_dot}{center_dot}H-NH{sub 2}) interactions upon dimerization. Under Cs dimer configuration, core-electron binding energy of H-N (H-donor) is significantly decreased by the intermolecular core-hole interaction and causes notable redshifts of core-excitation energies, whereas that of lone-pair nitrogen (H-acceptor) is slightly increased and results in appreciable blueshifts in the core-excitation bands. The result of the hydrogen-bonding interaction strongly appears in the n-{sigma}* orbital correlation, destabilizing H-N donor Rydberg states in the direction opposite to the core-hole interaction, when excited N atom with H-N donor configuration strongly possesses the Rydberg component of anti-bonding {sigma}* (N-H) character. Contributions of other cyclic H-bonded clusters (AM){sub n} with n{>=} 3 to the spectral changes of the N 1s{yields} 3sa{sub 1}/3pe bands are also examined.

Yamanaka, Takeshi; Takahashi, Osamu [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan); Tabayashi, Kiyohiko; Namatame, Hirofumi; Taniguchi, Masaki [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan); Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046 (Japan); Tanaka, Kenichiro [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan); XFEL Division, Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Hyogo 679-5198 (Japan)

2012-01-07

337

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

338

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

339

Excitation of helium ion by positron impact  

SciTech Connect

Three (1s,2s,2p) and five (1s,2s,2p,3s-bar,3p-bar) -state close-coupling methods have been employed to calculate the n = 2 excitation cross sections of helium ion by positron impact. The effect of pseudostate is found to be very pronounced in the case of 1s-2s excitation.

Khan, P.; Ghosh, A.S.

1986-01-01

340

Helium and the Genesis of Petroleum  

Microsoft Academic Search

VARIOUS hydrocarbons, but more especially methane, are common constituents of the natural gas effusions in many parts of the world, and another very common constituent is helium, though in relatively small quantities, which vary from simple traces to about 1 per cent or more. In the mid-United States of America, where large oilfields exist, and for which more complete information

C. Coleridge Farr; M. N. Rogers

1928-01-01

341

Intensity landscape and the possibility of magic trapping of alkali-metal Rydberg atoms in infrared optical lattices  

NASA Astrophysics Data System (ADS)

Motivated by compelling advances in manipulating cold Rydberg (Ry) atoms in optical traps, we consider the effect of the large extent of a Ry electron wave function on trapping potentials. We find that, when the Ry orbit lies outside inflection points in the laser intensity landscape, the atom can stably reside in laser intensity maxima. Effectively, the free-electron ac polarizability of the Ry electron is modulated by the intensity landscape and can accept both positive and negative values. We apply these insights to determining the magic wavelengths for Ry-ground-state transitions for alkali-metal atoms trapped in infrared optical lattices. We find magic wavelengths to be around 10?m with exact values that depend on Ry-state quantum numbers.

Topcu, Turker; Derevianko, Andrei

2013-10-01

342

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

343

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

344

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

345

Helium dilution refrigeration  

E-print Network

. The refrigerator was then leak tested on a Veeco NS-9 Helium Leak Detector. A small leak was found at the capillary joint between the still and mixing cham'oer and repaired. No other leaks were detectable on the most sensitive scale of the detector. 6.... The refrigerator was then leak tested on a Veeco NS-9 Helium Leak Detector. A small leak was found at the capillary joint between the still and mixing cham'oer and repaired. No other leaks were detectable on the most sensitive scale of the detector. 6...

McKee, Thomas Raymond

2012-06-07

346

Mantle Helium and Carbon Isotopes in Separation Creek Geothermal Springs, Three Sisters Area, Central Oregon: Evidence for Renewed Volcanic Activity or a Long Term Steady State System?  

USGS Publications Warehouse

Here we present the helium and carbon isotope results from the initial study of a fluid chemistry-monitoring program started in the summer of 2001 near the South Sister volcano in central Oregon. The Separation Creek area which is several miles due west of the volcano is the locus of strong crustal uplift currently occurring at a rate of 4-5 cm/yr (Wicks, et. al., 2001).Helium [RC/RA = 7.44 and 8.61 RA (RC/R A = (3He/4He)sample-. air corrected/(3He/4He)air))] and carbon (??13C = -11.59 to -9.03??? vs PDB) isotope data and CO2/3He (5 and 9 ?? 109) show that bubbling cold springs in the Separation Creek area near South Sister volcano carry a strong mantle signal, indicating the presence of fresh basaltic magma in the volcanic plumbing system. There is no evidence though, to directly relate this signal to the crustal uplift that is currently taking place in the area, which started in 1998. The geothermal system in the area is apparently much longer lived and shows no significant changes in chemistry compared to data from the early 1990s. Hot springs in the area, which are relatively far removed from the volcanic edifice, do not carry a strong mantle signal in helium isotope ratios (2.79 to 5.08 RA), unlike the cold springs, and also do not show any significant changes in helium isotope ratios compared to literature data for the same springs of over two decades ago. The cold springs of the Separation Creek area form a very diffuse but significant low temperature geothermal system, that should, due to its close vicinity to the center of up uplift, be more sensitive to changes in the deeper volcanic plumbing system than the far removed hot springs and therefore require much more study and consideration when dealing with volcano monitoring in the Cascade range or possibly with geothermal exploration in general.

Van Soest, M. C.; Kennedy, B.M.; Evans, W.C.; Mariner, R.H.

2002-01-01

347

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  

NASA Astrophysics Data System (ADS)

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 solutions. Because the excitations studied involve a spin change, they require a balanced treatment of exchange and correlation, thus providing a hard test for approximate density functionals. We test three formalisms for predicting the multiplicity-changing transition energies. First is the ?SCF method; we also test time-dependent density functional theory (TDDFT), both in its conventional form starting from the low-spin state and in its collinear spin-flip form starting from the high-spin state. Very diffuse basis functions are needed to give a qualitatively correct description of the Rydberg excitations. The scalar relativistic effect needs to be considered when quantitative results are desired, and we include it in the comparisons. With the ?SCF method, most of the tested functionals give mean unsigned errors (MUEs) larger than 6 kcal/mol for valence excitations and MUEs larger than 3 kcal/mol for Rydberg excitations, but the performance for the Rydberg states is much better than can be obtained with time-dependent DFT. It is surprising to see that the long-range corrected functionals, which have 100% Hartree-Fock exchange at large inter-electronic distance, do not improve the performance for Rydberg excitations. Among all tested density functionals, ?SCF calculations with the O3LYP, M08-HX, and OLYP functionals give the best overall performance for both valence and Rydberg excitations, with MUEs of 2.1, 2.6, and 2.7 kcal/mol, respectively. This is very encouraging since the MUE of the CCSD(T) coupled cluster method with quintuple zeta basis sets is 2.0 kcal/mol however, caution is advised since many popular density functionals give poor results, and there can be very significant differences between the ?SCF predictions and those from TDDFT.

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

2011-07-01

348

Cavitation pressure in liquid helium  

Microsoft Academic Search

Recent experiments have suggested that, at low enough temperature, the homogeneous nucleation of bubbles occurs in liquid helium near the calculated spinodal limit. This was done in pure superfluid helium 4 and in pure normal liquid helium 3. However, in such experiments, where the negative pressure is produced by focusing an acoustic wave in the bulk liquid, the local amplitude

Frederic Caupin; Sebastien Balibar

2001-01-01

349

Mining for Helium Jurriaan Hage  

E-print Network

Mining for Helium Jurriaan Hage Peter van Keeken Department of Information and Computing Sciences-year functional programming course using the Helium compiler. The mining of such a collection is not trivial a type error. 1 #12;1 Introduction and motivation When the Helium compiler for learning Haskell

Utrecht, Universiteit

350

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

2010-08-13

351

Entanglement in helium  

E-print Network

Using a configuration-interaction variational method, we accurately compute the reduced, single-electron von Neumann entropy for several low-energy, singlet and triplet eigenstates of helium atom. We estimate the amount of electron-electron orbital entanglement for such eigenstates and show that it decays with energy.

Giuliano Benenti; Stefano Siccardi; Giuliano Strini

2012-04-30

352

Helium liquefaction plant  

Microsoft Academic Search

In a helium liquefaction plant, a compressor includes first, second and third stages and a precooling section includes first, second and third turboexpanders in series between high and low pressure lines of a heat exchanger. A portion of the medium pressure gas at the output of the second turboexpander is directed back through the heat exchanger and mixed with the

Toscano

1981-01-01

353

Shock compression of liquid helium to 56 GPa (560) kbar  

NASA Technical Reports Server (NTRS)

Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Trainor, R. J.; Governo, G. K.; Ross, M.; Young, D. A.

1985-01-01

354

Shock compression of liquid helium to 56 GPa (560 kbar)  

NASA Technical Reports Server (NTRS)

Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation of the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Governo, G. K.; Ross, M.; Young, D. A.; Trainor, R. J.

1984-01-01

355

Shock Compression of Liquid Helium to 56 GPa (560) Kbar  

NASA Technical Reports Server (NTRS)

Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Trainor, R. J.; Governo, G. K.; Ross, M.; Young, D. A.

1985-01-01

356

Detailed and Simplified Nonequilibrium Helium Ionization in the Solar Atmosphere  

NASA Astrophysics Data System (ADS)

Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out one-dimensional radiation-hydrodynamics simulations of the solar atmosphere and find that the helium ionization is set mostly by photoionization and direct collisional ionization, counteracted by radiative recombination cascades. By introducing an additional recombination rate mimicking the recombination cascades, we construct a simplified three-level helium model atom consisting of only the ground states. This model atom is suitable for modeling nonequilibrium helium ionization in three-dimensional numerical models. We perform a brief investigation of the formation of the He I 10830 and He II 304 spectral lines. Both lines show nonequilibrium features that are not recovered with statistical equilibrium models, and caution should therefore be exercised when such models are used as a basis for interpretating observations.

Golding, Thomas Peter; Carlsson, Mats; Leenaarts, Jorrit

2014-03-01

357

Non-ending helium story  

SciTech Connect

Why an adequate supply of helium is of importance to cryoengineering is obvious to everyone present at this conference. Why there is a non-ending helium problem - or more specifically why helium supply problems have arisen in the past, why they may arise again in the future, what are those problems and what solutions appear to exist - is more complicated. To answer these questions this paper is divided into three sections: resource availability, the demand for helium and the supply of helium. 17 refs.

Hammel, E.F.; Krupka, M.C.; Williamson, K.D. Jr.

1986-01-01

358

Robustness of high-fidelity Rydberg gates with single-site addressability  

NASA Astrophysics Data System (ADS)

Controlled-phase (cphase) gates can be realized with trapped neutral atoms by making use of the Rydberg blockade. Achieving the ultrahigh fidelities required for quantum computation with such Rydberg gates, however, is compromised by experimental inaccuracies in pulse amplitudes and timings, as well as by stray fields that cause fluctuations of the Rydberg levels. We report here a comparative study of analytic and numerical pulse sequences for the Rydberg cphase gate that specifically examines the robustness of the gate fidelity with respect to such experimental perturbations. Analytical pulse sequences of both simultaneous and stimulated Raman adiabatic passage (STIRAP) are found to be at best moderately robust under these perturbations. In contrast, optimal control theory is seen to allow generation of numerical pulses that are inherently robust within a predefined tolerance window. The resulting numerical pulse shapes display simple modulation patterns and can be rationalized in terms of an interference between distinct two-photon Rydberg excitation pathways. Pulses of such low complexity should be experimentally feasible, allowing gate fidelities of order 99.90-99.99% to be achievable under realistic experimental conditions.

Goerz, Michael H.; Halperin, Eli J.; Aytac, Jon M.; Koch, Christiane P.; Whaley, K. Birgitta

2014-09-01

359

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

360

Solvation of intrinsic positive charge in superfluid helium.  

PubMed

On the basis of electronic structure calculations, the structure of intrinsic positive charge solvated in superfluid helium is identified as triatomic He3(+) ion, which is bound to the surrounding ground state helium atoms through the charge–charge induced dipole interaction in a pairwise additive manner. Bosonic density functional theory calculations show that this ion forms the well-known Atkins’ snowball solvation structure where the first rigid helium shell is effectively disconnected from the rest of the liquid. Evaluation of the total energy vs helium droplet size N shows distinct regions related to the completion of solvent shells near N = 16 and N = 47. These regions can be assigned to magic numbers observed in positively charged helium droplets appearing at N = 15 and in the range between 20 and 50 helium atoms. The calculated added mass for the positive ion in bulk superfluid helium (18 mHe) is much smaller than the previous experiments suggest (30–40 mHe), indicating that there may be yet some unidentified additional factor contributing to the measured effective mass. Both previous experiments and the present calculations agree on the effective mass of the negative charge (240–250 mHe). The main difference between the solvated negative and positive charges in liquid helium is that the latter forms a chemically bound triatomic molecule surrounded by highly inhomogeneous liquid structure whereas the former remains as a separated charge with a smoothly varying liquid density around it. PMID:24654777

Mateo, David; Eloranta, Jussi

2014-08-21

361

The cryogenic helium cooling system for the Tokamak physics experiment  

SciTech Connect

The Tokamak Physics Experiment (TPX) will use supercritical helium to cool all the magnets and supply helium to the Vacuum cryopumping subsystem. The heat loads will come from the standard steady state conduction and thermal radiation sources and from the pulsed loads of the nuclear and eddy currents caused by the Central Solenoid Coils and the plasma positioning coils. The operations of the TPX will begin with pulses of up to 1000 seconds in duration every 75 minutes. The helium system utilizes a pulse load leveling scheme to buffer out the effects of the pulse load and maintain a constant cryogenic plant operation. The pulse load leveling scheme utilizes the thermal mass of liquid and gaseous helium stored in a remote dewar to absorb the pulses of the tokamak loads. The mass of the stored helium will buffer out the temperature pulses allowing 5 K helium to be delivered to the magnets throughout the length of the pulse. The temperature of the dewar will remain below 5 K with all the energy of the pulse absorbed. This paper will present the details of the heat load sources, of the pulse load leveling scheme operations, a partial helium schematic, dewar temperature as a function of time, the heat load sources as a function of time and the helium temperature as a function of length along the various components that will be cooled.

Felker, B.; Slack, D.S.; Wendland, C.R.

1995-09-29

362

The role of Rydberg and continuum levels in computing high harmonic generation spectra of the hydrogen atom using time-dependent configuration interaction  

SciTech Connect

We study the role of Rydberg bound-states and continuum levels in the field-induced electronic dynamics associated with the High-Harmonic Generation (HHG) spectroscopy of the hydrogen atom. Time-dependent configuration-interaction (TD-CI) is used with very large atomic orbital (AO) expansions (up to L= 4 with sextuple augmentation and off-center functions) to describe the bound Rydberg levels, and some continuum levels. To address the lack of ionization losses in TD-CI with finite AO basis sets, we employed a heuristic lifetime for energy levels above the ionization potential. The heuristic lifetime model is compared against the conventional atomic orbital treatment (infinite lifetimes), and a third approximation which is TD-CI using only the bound levels (continuum lifetimes go to zero). The results suggest that spectra calculated using conventional TD-CI do not converge with increasing AO basis set size, while the zero lifetime and heuristic lifetime models converge to qualitatively similar spectra, with implications for how best to apply bound state electronic structure methods to simulate HHG. The origin of HHG spectral features including the cutoff and extent of interference between peaks is uncovered by separating field-induced coupling between different types of levels (ground state, bound Rydberg levels, and continuum) in the simulated electronic dynamics. Thus the origin of deviations between the predictions of the semi-classical three step model and the full simulation can be associated with particular physical contributions, which helps to explain both the successes and the limitations of the three step model.

Luppi, Eleonora [Laboratoire de Chimie Théorique, Université Pierre et Marie Curie, 75005 Paris (France)] [Laboratoire de Chimie Théorique, Université Pierre et Marie Curie, 75005 Paris (France); Head-Gordon, Martin [Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2013-10-28

363

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

364

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.

365

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

366

Properties of Fr-like Th{sup 3+} from spectroscopy of high-L Rydberg levels of Th{sup 2+}  

SciTech Connect

Binding energies of high-L Rydberg states (L{>=} 7) of Th{sup 2+} with n = 27-29 were studied using the resonant excitation Stark ionization spectroscopy (RESIS) method. The core of the Th{sup 2+} Rydberg ion is the Fr-like ion Th{sup 3+} whose ground state is a 5 {sup 2}F{sub 5/2} level. The large-core angular momentum results in a complex Rydberg fine-structure pattern consisting of six levels for each value of L that is only partially resolved in the RESIS excitation spectrum. The pattern is further complicated, especially for the relatively-low-L levels, by strong nonadiabatic effects due to the low-lying 6d levels. Analysis of the observed RESIS spectra leads to determination of five properties of the Th{sup 3+} ion: its electric quadrupole moment Q = 0.54(4); its adiabatic scalar and tensor dipole polarizabilities {alpha}{sub d,0} = 15.42(17) and {alpha}{sub d,2} = -3.6(1.3); and the dipole matrix elements connecting the ground 5 {sup 2}F{sub 5/2} level to the low-lying 6 {sup 2}D{sub 3/2} and 6 {sup 2}D{sub 5/2} levels, |<5 {sup 2}F{sub 5/2}||D||6{sup 2}D{sub 3/2}>|=1.435(10) and |<5{sup 2}F{sub 5/2}||D||6{sup 2}D{sub 5/2}>|=0.414(24). All are in atomic units. These are compared with theoretical calculations.

Keele, Julie A.; Hanni, M. E.; Woods, Shannon L.; Lundeen, S. R.; Fehrenbach, C. W. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States); J. R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas 66506 (United States)

2011-06-15

367

Classical Helium Program  

NSDL National Science Digital Library

The classical-physics model of helium is a simple example of a three body problem and is similar to gravitational problem of a heavy sun and two light planets. It consists of two electrons moving in a 2/r potential well and interacting through a 1/r potential. Initial conditions can be set to show phenomena such as autoionization or braided orbits. These conditions are stored in an xml document.

Christian, Wolfgang; Gould, Harvey; Tobochnik, Jan

2008-05-21

368

Helium liquefaction plant  

SciTech Connect

In a helium liquefaction plant, a compressor includes first, second and third stages and a precooling section includes first, second and third turboexpanders in series between high and low pressure lines of a heat exchanger. A portion of the medium pressure gas at the output of the second turboexpander is directed back through the heat exchanger and mixed with the output of the first compressor stage. The third turboexpander is positioned between the medium and low pressure lines.

Toscano, W.M.

1981-05-19

369

Applications of Groundwater Helium  

USGS Publications Warehouse

Helium abundance and isotope variations have widespread application in groundwater-related studies. This stems from the inert nature of this noble gas and the fact that its two isotopes ? helium-3 and helium-4 ? have distinct origins and vary widely in different terrestrial reservoirs. These attributes allow He concentrations and 3He/4He isotope ratios to be used to recognize and quantify the influence of a number of potential contributors to the total He budget of a groundwater sample. These are atmospheric components, such as air-equilibrated and air-entrained He, as well as terrigenic components, including in situ (aquifer) He, deep crustal and/or mantle He and tritiogenic 3He. Each of these components can be exploited to reveal information on a number of topics, from groundwater chronology, through degassing of the Earth?s crust to the role of faults in the transfer of mantle-derived volatiles to the surface. In this review, we present a guide to how groundwater He is collected from aquifer systems and quantitatively measured in the laboratory. We then illustrate the approach of resolving the measured He characteristics into its component structures using assumptions of endmember compositions. This is followed by a discussion of the application of groundwater He to the types of topics mentioned above using case studies from aquifers in California and Australia. Finally, we present possible future research directions involving dissolved He in groundwater.

Kulongoski, Justin T.; Hilton, David R.

2011-01-01

370

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

371

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.

Fan, H Q; Daschner, R; Kübler, H; Shaffer, J P

2014-01-01

372

Subwavelength microwave electric-field imaging using Rydberg atoms inside atomic vapor cells  

NASA Astrophysics Data System (ADS)

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.

Fan, H. Q.; Kumar, S.; Daschner, R.; Kübler, H.; Shaffer, J. P.

2014-05-01

373

Precision spectroscopy of Kaonic helium-3 and helium-4 3d{yields}2p X-rays  

SciTech Connect

Recently, the shift of the kaonic helium-4 2p state was precisely determined by the E570 and SIDDHARTA experiments. Prior to the experiment by E570, the average of three earlier experimental results showed -43{+-}8 eV,while most of the theoretical calculations give {approx}0 eV. This five-sigma discrepancy between theory and experiment was known as the 'kaonic helium puzzle'. A recent theoretical model showed a possible resonance-like shift of maximum 10 eV for a certain value of a deep antikaon-nucleon interaction potential, which is different in helium 3 and helium 4.The E570 experiment determined the shift of the kaonic helium-4 2p state as +2{+-}2 (stat){+-}2 (sys) eV in 2007. The SIDDHARTA experiment determined the shift as 0{+-}6(stat){+-}2(sys) eV in 2009. The results of these experiments resolved the long-standing puzzle. A new experiment of the kaonic helium-3 X-ray measurement is being prepared by the J-PARC E17 collaborators, and the kaonic helium-3 X-ray data taken very recently by the SIDDHARTA experiment are on the way to be analyzed. The results of the E570, E17 and SIDDHARTA experiments examine the strong interaction for light nuclei with different isospin, and test furthermore recent theoretical predictions.

Ishiwatari, T.; Cargnelli, M.; Marton, J.; Widmann, E.; Wuenschek, B.; Zmeskal, J. [Stefan-Meyer-Institut fuer subatomare Physik, Vienna (Austria); Bazzi, M.; Corradi, G.; Curceanu, C.; D'Uffizi, A.; Guaraldo, C.; Levi Sandri, P.; Lucherini, V.; Okada, S.; Pietreanu, D.; Rizzo, A.; Romero Vidal, A.; Scordo, A.; Vazquez Doce, O. [INFN, Laboratori Nazionali di Frascati, Frascati (Roma) (Italy); Bhang, H. [Department of Physics, Seoul National University, Seoul (Korea, Republic of)

2010-08-05

374

The winter helium bulge revisited  

NASA Astrophysics Data System (ADS)

newly implemented helium module in the National Center for Atmospheric Research-Thermosphere Ionosphere Electrodynamics general circulation model offers the first opportunity in three decades to describe helium behavior in the context of a first principles, self-consistent model and to test early theories of wintertime helium bulge formation. This study shows general agreement with the findings of Reber and Hays (1973) but articulates the definitive role of vertical advection in the bulge formation. Our findings indicate vertical advection and molecular diffusion are the dominate processes responsible for the solstice helium distribution. Horizontal winds indirectly contribute to the helium bulge formation by their divergent wind field that leads to vertical winds in order to maintain thermosphere mass continuity. As a minor gas, thermospheric helium does not contribute to mass continuity and its distribution is dictated by more local interactions and constraints.

Liu, Xianjing; Wang, Wenbin; Thayer, Jeffrey P.; Burns, Alan; Sutton, Eric; Solomon, Stanley C.; Qian, Liying; Lucas, Greg

2014-10-01

375

Resource Letter SH-1: Superfluid Helium.  

ERIC Educational Resources Information Center

Provides an annotated list of books, textbooks, and films on superfluid helium. Also lists research reports/reviews arranged by category, including among others, early history, microscopic understanding, ions in helium, helium in rotation, vortices and quantization, helium films and constricted geometrics, persistence flow, and superfluid helium…

Hallock, Robert B.

1982-01-01

376

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

377

Helium runaways in white dwarfs  

NASA Technical Reports Server (NTRS)

The long term evolution of an accreting carbon white dwarf was studied from the onset of accretion to the ignition of helium. The variations in the details of the helium shell flash examined with respect to variations in mass accretion rate. For intermediate rates the helium flash is potentially explosive whereas for high rates the shell flash is relatively weak. The results are discussed in the context of the long term evolution of novae.

Taam, R. E.

1979-01-01

378

Neutral photodissociation of superexcited states of molecular iodine P. O'Keeffe  

E-print Network

-photon excitation of molecular iodine using an ArF laser has been investigated. The high-n Rydberg atoms INeutral photodissociation of superexcited states of molecular iodine P. O'Keeffe Dipartimento di

Houston, Paul L.

379

The helium fine-structure controversy  

E-print Network

There is presently disagreement between theory and experiment as well as between different theoretical calculations concerning the fine-structure splitting of the lowest P state of the neutral helium atom. We believe that we have found a minor error in the formulas used by Drake et al. (Can. J. Phys. 80, 1195 (2002)) in their calculations, and we may have an explanation how the error has occurred. To what extent this might resolve (part of) the discrepancy is not known at present.

Ingvar Lindgren

2008-10-05

380

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

381

Portable detector set discloses helium leak rates  

NASA Technical Reports Server (NTRS)

Portable helium detector measuring helium leak rates makes possible the use of the inert gas helium as a tracer. This helps solve safety and contamination problems in detecting leaks in closed fluid systems.

Anderson, G. E.

1967-01-01

382

Rotationally resolved photoelectron spectra from vibrational autoionization of NO Rydberg levels  

E-print Network

Rotationally resolved photoelectron spectra from vibrational autoionization of NO Rydberg levels Received 3 September 1996; accepted 25 October 1996 Rotationally resolved photoelectron spectra from-of-flight photoelectron spectroscopy. The photoelectron spectra show that both even-l and odd-l continuum partial waves

Zare, Richard N.

383

The role of the quantum defect and of high-order dispersion in rydberg wave packets  

Microsoft Academic Search

Experimental and theoretical recurrence spectra of Rydberg electron wave packets are presented. Fractional revivals up to the seventh order are observed. In addition we observe a new interference effect: a forerunner wave packet in the first full revival, due to second-order dispersion. Also it is shown that the quantum defect of rubidium shifts the peaks in the interference pattern by

J. Wals; H. H. Fielding; H. B. van Linden van den Heuvell

1995-01-01

384

Influence of weak electric fields on Rydberg electron wavepacket dynamics in the radial coordinate  

Microsoft Academic Search

The spin–orbit autoionisation dynamics of Rydberg electron wavepackets in Ar are investigated in weak electric fields, where ???13.8 and ? is the scaled energy in atomic units. The electric field modifies both the interference pattern and revival time of the recurrence spectrum. By writing the energies of the eigenstates included in the superposition as a Taylor's expansion, a quantitative description

V. G. Stavros; H. H. Fielding

1998-01-01

385

Observation of Rydberg wave packet dynamics in a Coulombic and magnetic field  

Microsoft Academic Search

Rydberg electron wave packets are investigated, using phase-modulated detection. In the absence of any external field we observe pure radial motion of a bound electron wave packet showing both the first integer revival and all fractional revivals up to the seventh order; in the presence of a magnetic field (0.81 T) both paramagnetic and diamagnetic effects are observed. Paramagnetism is

J. Wals; H. H. Fielding; J. F. Christian; L. C. Snoek; W. J. van der Zande; H. B. van Linden van den Heuvell

1994-01-01

386

ChemicalPhysicsLetters240(1995)278-282 Time evolution and multiphoton ionization of Rydberg  

E-print Network

ELSEVIER 30June1995 ChemicalPhysicsLetters240(1995)278-282 CHEMICAL PHYSICS LETTERS Time evolution of Physics, National Chiao-Tung University, Hsinehu, Taiwan, ROC bDepartment of Chemistry, University a theoretical study of the time evolution of Rydberg wavepacket, initially localized in radial space

Chu, Shih-I

387

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

388

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

389

Helium dilution refrigeration system  

DOEpatents

A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. 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. 2 figs.

Roach, P.R.; Gray, K.E.

1988-09-13

390

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

391

Helium diffusion in carbonates  

NASA Astrophysics Data System (ADS)

The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion directions and the maximum interstitial apertures in each 'slice' in the structure are identified. Preliminary results show that observed differences in diffusivities are consistent with the size of the smallest maximum aperture along each diffusion direction. In calcite, the smallest maximum apertures are ~0.92 and ~0.66 angstroms for cleavage-normal and c-axis parallel directions respectively. In dolomite, the smallest maximum aperture is ~0.78 angstroms for the cleavage normal direction. Work is in progress on characterizing helium diffusion for other orientations in dolomite, and in other carbonates, including aragonite and magnesite, and in implementing these diffusion findings in the interpretation and modeling of bulk volume diffusion in heterogeneous calcite crystals common in many geologic applications. Copeland et al. (2007) GCA 71, 4488-4511 Cherniak and Watson, (2011) Chem. Geo. 288, 149-161

Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.

2013-12-01

392

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

393

Narrow chaotic compound autoionizing states in atomic spectra V. V. Flambaum, A. A. Gribakina, and G. F. Gribakin  

E-print Network

. This behavior follows from simple combinatorial consideration, and is realized in excited states of rare- mentalists see, e.g., 2 and 3 , where the first observation of Rydberg series in any actinide was made for U

Gribakin, Gleb

394

A quantum defect model for the s, p, d, and f Rydberg series of CaF  

E-print Network

We present an improved quantum defect theory model for the “s,” “p,” “d,” and “f” Rydberg series of CaF. The model, which is the result of an exhaustive fit of high-resolution spectroscopic data, parameterizes the electronic ...

Kay, Jeffrey J.

395

Space helium refrigerator  

NASA Astrophysics Data System (ADS)

Design studies and flight tests of an automatic closed-cycle three-cascade helium refrigerator are presented. Intended for cooling submillimeter telescope detectors to 4.4 K on the orbital station Salyut-6, the cryogenic system is based on the Joule-Thomson cooling effect, with two gas cooling machines operating under the Stirling cycle for preliminary cooling levels of 80 K and 20 K. Power requirements are less than 1.5 kW, while providing useful refrigeration of 0.5 W. Results of two years of flight tests indicate successful operation, including the merits of high accuracy and stability in maintaining operation temperature, short cool-down period, high efficiency, reliability and simplicity of operation.

Salomonovich, A. E.; Sidiakina, T. M.; Khaikin, A. S.; Bakun, V. N.; Nikonov, A. A.; Maslakov, V. A.; Klimenko, E. I.; Kurkin, V. N.

1981-08-01

396

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  

NASA Astrophysics Data System (ADS)

In past studies, we have observed copious emissions of ionic and atomic Zn from single-crystal ZnO accompanying irradiation of single-crystal ZnO with 193-nm excimer laser irradiation at fluences below the onset of optical breakdown. The Zn+ and ground state Zn° are studied using time-of-flight techniques and are mass selected using a quadrupole mass spectrometer. Simultaneously, we have observed emitted particles that are detectable with a Channeltron electron multiplier but cannot be mass selected. It is a reasonable hypothesis that these particles correspond to a neutral atom or molecule in highly excited long lived states. We provide strong evidence that they correspond to high lying Rydberg states of atomic Zn. We propose a production mechanism involving laser excitation via a two photon resonance excitation of Zn°.

Khan, Enamul H.; Langford, S. C.; Dickinson, J. T.; Boatner, L. A.

2014-08-01

397

Rydberg-electron wave-packet dynamics in parallel electric and magnetic fields and evidence for stabilization  

Microsoft Academic Search

The dynamics of short-lived quasibound Rydberg-electron wave packets above the classical field-ionization limit are investigated in the presence of parallel electric and magnetic fields. The observed variations in relative peak intensities in the recurrence spectra are understood both in terms of a quantum-mechanical picture and in terms of the classical electron trajectories. The linear Zeeman term causes the Rydberg wave

H. H. Fielding; J. Wals; W. J. van der Zande; H. B. van Linden van den Heuvell

1995-01-01

398

First-principles investigation on Rydberg and resonance excitations: A case study of the firefly luciferin anion.  

PubMed

The optical properties of an isolated firefly luciferin anion are investigated by using first-principles calculations, employing the many-body perturbation theory to take into account the excitonic effect. The calculated photoabsorption spectra are compared with the results obtained using the time-dependent density functional theory (TDDFT) employing the localized atomic orbital (AO) basis sets and a recent experiment in vacuum. The present method well reproduces the line shape at the photon energy corresponding to the Rydberg and resonance excitations but overestimates the peak positions by about 0.5 eV. However, the TDDFT-calculated positions of some peaks are closer to those of the experiment. We also investigate the basis set dependency in describing the free electron states above vacuum level and the excitons involving the transitions to the free electron states and conclude that AO-only basis sets are inaccurate for free electron states and the use of a plane wave basis set is required. PMID:25084912

Noguchi, Yoshifumi; Hiyama, Miyabi; Akiyama, Hidefumi; Koga, Nobuaki

2014-07-28

399

First-principles investigation on Rydberg and resonance excitations: A case study of the firefly luciferin anion  

NASA Astrophysics Data System (ADS)

The optical properties of an isolated firefly luciferin anion are investigated by using first-principles calculations, employing the many-body perturbation theory to take into account the excitonic effect. The calculated photoabsorption spectra are compared with the results obtained using the time-dependent density functional theory (TDDFT) employing the localized atomic orbital (AO) basis sets and a recent experiment in vacuum. The present method well reproduces the line shape at the photon energy corresponding to the Rydberg and resonance excitations but overestimates the peak positions by about 0.5 eV. However, the TDDFT-calculated positions of some peaks are closer to those of the experiment. We also investigate the basis set dependency in describing the free electron states above vacuum level and the excitons involving the transitions to the free electron states and conclude that AO-only basis sets are inaccurate for free electron states and the use of a plane wave basis set is required.

Noguchi, Yoshifumi; Hiyama, Miyabi; Akiyama, Hidefumi; Koga, Nobuaki

2014-07-01

400

Neutrino Emission from Helium White Dwarfs with Condensed Cores  

E-print Network

The possibility that ions in a helium white dwarf star are in a Bose-Einstein condensed state has been explored recently. In particular, it has been argued that the resulting novel quantum liquid has a new kind of quasiparticle excitation with a phonon-like dispersion relation. We investigate the neutrino emission rate due to this gapless state and the resulting impact on the total luminosity of helium white dwarf stars, as a possible observable way of detecting this exotic phase. If the condensation temperature for the quantum liquid state, which is currently not known very precisely, turns out to be high enough, our calculations indicate that neutrino emission due to the gapless mode would make a large contribution to the total luminosity of the helium white dwarf stars.

Paulo F. Bedaque; Evan Berkowitz; Aleksey Cherman

2012-03-05

401

Quantum Cavitation: a comparison between superfluid helium-4 and normal liquid helium-3  

E-print Network

Quantum Cavitation: a comparison between superfluid helium-4 and normal liquid helium-3 S. Balibar in superfluid helium-4 and in normal liquid helium-3, both theoretically and experimentally. We compare the two by tunneling, to classical cavitation where their nu- cleation is thermally activated. In helium-3, where

Caupin, Frédéric

402

Cross sections for the production of excited He{sup +} ({ital np}){sup 2}{ital P}{sup {ital o}} states by 50{endash}150-keV proton impact on helium  

SciTech Connect

Cross sections have been measured for the production of He{sup +} ({ital np}){sup 2}{ital P}{sup {ital o}} states, {ital n}=2,3,4, by proton impact on helium over a projectile velocity range of 1.42{endash}2.45 a.u. (50 {le}{ital E}{le}150 keV). Cross sections were determined by measuring the extreme ultraviolet photons emitted from excited He{sup +} ions. The data indicate a lower energy than expected for the maximum cross section. A comparison of the present results in terms of projectile energy dependance with the cross sections for excitation to He (1{ital snp}){sup 1}{ital P}{sup {ital o}}, ionization, and total electron capture suggests the primary mechanism for the production of excited He{sup +} at low energies is transfer excitation, with ionization excitation being the dominant mechanism at higher energies. {copyright} {ital 1996 The American Physical Society.}

Stolte, W.C.; Bruch, R. [Department of Physics, University of Nevada, Reno, Nevada 89557-0058 (United States)] [Department of Physics, University of Nevada, Reno, Nevada 89557-0058 (United States)

1996-09-01

403

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

404

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

405

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

406

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

407

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

408

Radiation source for helium magnetometers  

NASA Technical Reports Server (NTRS)

A radiation source (12) for optical magnetometers (10) which use helium isotopes as the resonance element (30) includes an electronically pumped semiconductor laser (12) which produces a single narrow line of radiation which is frequency stabilized to the center frequency of the helium resonance line to be optically pumped. The frequency stabilization is accomplished using electronic feedback (34, 40, 42, 44) to control a current sources (20) thus eliminating the need for mechanical frequency tuning.

Slocum, Robert E. (Inventor)

1991-01-01

409

Phonon transmission at a liquid helium-solid interface: the influence of surface roughness and finite lifetimes of the He states  

SciTech Connect

In a one-dimensional quantum mechanical model the phonon transmission between a solid and liquid He is calculated. It is shown how surface roughness changes the binding forces between the He atoms and the solid and therefore can lead to an increased transmission of low-energy phonons. In addition it turns out that the finite lifetimes of the He states also enhance the transmission probability.

Haug, R.; Sigmund, E.; Weiss, K.

1987-04-01

410

Superfluid Helium Orbital Resupply Coupling  

NASA Technical Reports Server (NTRS)

The resupply of superfluid helium to satellites and other space-based experiment packages can increase the useful longevity of these devices far beyond their present life expectancies which are many times determined by the supply of helium coolant. The transfer of superfluid helium to spacecraft in space will require a reusable coupling that functions at 1.8 Kelvin with little heat leak and low pressure drop. Moog has designed the Helium Resupply Coupling to meet these operational requirements. Initially, the coupling manual mode operation will be demonstrated on orbit by an EVA crew member during the Space Shuttle borne Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The ultimate application will use robotic (automatic) coupling operation to which the present design readily adapts. The utilization of Moog's exclusive Rotary Shut-Off (RSO) technology in the development of the Superfluid Helium Resupply Coupling is described. The coupling not only performs the function of a flow control valve and disconnect but also provides adequate safety features for a shuttle launched man-rated payload. In addition, the coupling incorporates the necessary features to provide the high thermal isolation of the internal flow path from the external environment.

Ryder, M. O.; Morash, D. H.; Schoenberg, R. J.

1989-01-01

411

Simulations of prompt many-body ionization in a frozen Rydberg gas  

NASA Astrophysics Data System (ADS)

The results of a theoretical investigation of prompt many-body ionization are reported. Our calculations address an experiment that reported ionization in Rydberg gases for densities two orders of magnitude less than expected from ionization between pairs of atoms. The authors argued that the results were due to the simultaneous interaction between many atoms. We performed classical calculations for many interacting Rydberg atoms with the ions fixed in space and have found that the many-atom interaction does allow ionization at lower densities than estimates from two-atom interactions. However, we found that the density fluctuations in a gas play a larger role. These two effects are an order of magnitude too small to account for the experimental results suggesting at least one other mechanism strongly affects ionization.

Robicheaux, F.; Goforth, M. M.; Phillips, M. A.

2014-08-01

412

Electron impact excitation of helium: A polarization correlation study of the 3(1)P state at 40 eV incident energy  

NASA Astrophysics Data System (ADS)

The present work reports the development and implementation of an electron scattering apparatus able to investigate a wide range of electron impact processes by coincidence methods. The electron gun is capable of producing a collimated electron beam of approximately 1 ? A throughout an energy range of 30eV to 200eV. A hemispherical electrostatic analyzer is used to collect scattered electrons. It was designed to allow constant energy resolution independent of the scattered energy. The gas target used was an effusive gas jet. The linear and circular polarization state of deexcitation photons emitted perpendicular to the scattering plane can be determined by a vertically mounted polarization analyzer. Polarization analysis of photons emitted in the scattering plane and perpendicular to the incident electron beam direction is also possible. In addition, detection of photons over a wide angular range in the scattering plane is possible. Two automated coincidence data accumulation systems were developed. One is based on a Nucleus PCA card, and the other on a Scientific Solution LabMaster DMA card. Basic modules were written to control Polaroid rotation, and to provide synchronization between data acquisition computers. Custom software packages were developed to provide Pulse-Height Analysis and Multi-Channel Scaling capabilities for the collection of coincidence and energy-loss spectra. The performance of the system has been tested and verified using the polarization correlation technique to study electron impact excitation of He (3 1P) from the ground state. Values of the relative Stokes parameters and the Electron Impact Coherence Parameters over a range of electron scattering angles from 45° to 120°, and at an energy of 40eV, are reported here for the first time. The data are in good agreement with recent predictions of a 111-state convergent close coupling calculation.

Harris, Clifford Lee

413

Electron-impact excitation of the (2p{sup 2}) {sup 1}D and (2s2p) {sup 1}P{sup o} autoionizing states of helium  

SciTech Connect

An experimental study of the excitation of the (2p{sup 2}) {sup 1}D and (2s2p) {sup 1}P{sup o} autoionizing states of helium by 250-eV electron impact is presented. The ejected-electron angular distributions and energy spectra are measured in coincidence with the corresponding scattered electrons for a scattering angle of -13 deg. and for a range of ejected-electron angles in both the forward and backward directions. Resonance profiles are analyzed in terms of the Shore-Balashov parametrization to obtain the resonance asymmetry A{sub {mu}} and yield B{sub {mu}} parameters and the direct ionization cross section f. The spectra and their parameters are compared to the previous measurements of Lower and Weigold [J. Phys. B. 23, 2819 (1990)] and McDonald and Crowe [J. Phys. B 26, 2887 (1993)]. Comparison is also made with the recent theoretical triply differential cross-section calculations based on the first and second Born approximations. In general, good qualitative agreement is found between the experimental results. Some differences are found at the forward and backward directions. These differences in the shape and magnitude of the cross sections are attributed to the different incoming electron energies used in the experiments. The second Born approximation with inclusion of the three-body Coulomb interaction in the final state agrees reasonably well with experiments in the binary region. However, the {sup 1}P{sup o} resonance yield parameter B{sub {mu}} is significantly overestimated at the recoil region, giving a relatively large recoil peak, in contradiction to the experiment. There is also a discrepancy between the two theories available for the {sup 1}D resonance yield parameter B{sub {mu}} in this region. Remaining discrepancies between theories and experiments are also discussed.

Sise, Omer; Dogan, Mevlut; Okur, Ibrahim; Crowe, Albert [Department of Physics, Afyon Kocatepe University, 03200 Afyon (Turkey); Department of Physics, Sakarya University, Adapazari (Turkey); School of Chemistry, Newcastle University, Newcastle (United Kingdom)

2011-08-15

414

SPIN POLARIZED HELIUM3, A PLAYGROUND IN MANY DOMAINS OF PHYSICS  

Microsoft Academic Search

This article gives a survey of the different methods which can be used to polarize the nuclear spin of helium-3. These techniques are particularly discussed in relation to the production of polarized helium-3 targets for nuclear physics experiments, such as electron or proton scattering and neutron spin filters. Some emphasis is given to the development of new powerful solid state

M. LEDUC

1990-01-01

415

Control of autoionization widths: Doubly excited coherent elliptic states  

NASA Astrophysics Data System (ADS)

Doubly excited coherent elliptic states (DECESs) of an atom could be produced by exciting an atomic electron to a Rydberg state, applying the adiabatic field-switching technique to obtain a coherent elliptic state (CES) and by subsequent excitation of an atomic core electron into a low-lying excited state. The DECESs decay by autoionization and radiative transitions. As an example, the autoionization widths are calculated for DECESs in He. The dependence of the widths on the eccentricity of the CES, principal quantum number of the Rydberg electron, orientation of the inner electron orbital and electron exchange is studied and interpreted.

Janby, Daniel; Bojer Madsen, Lars; Ostrovsky, Valentin N.

2006-06-01

416

Control of autoionization widths: Doubly excited coherent elliptic states  

SciTech Connect

Doubly excited coherent elliptic states (DECESs) of an atom could be produced by exciting an atomic electron to a Rydberg state, applying the adiabatic field-switching technique to obtain a coherent elliptic state (CES) and by subsequent excitation of an atomic core electron into a low-lying excited state. The DECESs decay by autoionization and radiative transitions. As an example, the autoionization widths are calculated for DECESs in He. The dependence of the widths on the eccentricity of the CES, principal quantum number of the Rydberg electron, orientation of the inner electron orbital and electron exchange is studied and interpreted.

Janby, Daniel; Bojer Madsen, Lars; Ostrovsky, Valentin N. [Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark); V. Fock Institute of Physics, St. Petersburg State University, St. Petersburg 198504 (Russian Federation)

2006-06-15

417

Optomechanical Rydberg-Atom Excitation via Dynamic Casimir-Polder Coupling  

NASA Astrophysics Data System (ADS)

We study the optomechanical coupling of a oscillating effective mirror with a Rydberg atomic gas, mediated by the dynamical atom-mirror Casimir-Polder force. This coupling may produce a near-field resonant atomic excitation whose probability scales as ?(d2an4t)2/z08, where z0 is the average atom-surface distance, d the atomic dipole moment, a the mirror's effective oscillation amplitude, n the initial principal quantum number, and t the time. We propose an experimental configuration to realize this system with a cold atom gas trapped at a distance ˜2×10 ?m from a semiconductor substrate whose dielectric constant is periodically driven by an external laser pulse, hence realizing an effective mechanical mirror motion due to the periodic change of the substrate from transparent to reflecting. For a parabolic gas shape, this effect is predicted to excite about ˜102 atoms of a dilute gas of 103 trapped Rydberg atoms with n =75 after about 0.5 ?s, which is high enough to be detected in typical Rydberg gas experimental conditions.

Antezza, Mauro; Braggio, Caterina; Carugno, Giovanni; Noto, Antonio; Passante, Roberto; Rizzuto, Lucia; Ruoso, Giuseppe; Spagnolo, Salvatore

2014-07-01

418

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

419

Simulation program for central helium liquefier  

SciTech Connect

The computer program described here analyzes the performance of Fermilab Central Helium Liquefier (CHL) and predicts the values of the plant thermodynamic variables at all process points in the plant. To simulate CHL, this program is modified from the prototype program which was developed by Hitachi Ltd. a couple of years ago. This program takes care of only the steady state simulation and takes account of the change of the turbine efficiency, the pressure drops and the UA values of the heat exchangers. How to use the program is shown.

Kawamura, S.

1984-02-20

420

Stability of the Helium-Antiproton System  

NASA Technical Reports Server (NTRS)

In the course of their Born-Oppenheimer calculations of this system Todd and Armour noted that the lowest-lying state closely resembles the hydrogen negative ion, since the antiproton lies very close to the helium nucleus and shields one unit of nuclear charge. In the present paper this observation will be taken seriously to produce a variationally correct estimate of the total energy of this system, along with a similar estimate of the energy of the once-ionized system. The nonadiabatic effect of exactly treating the reduced masses improves the results.

Drachman, Richard J.

2006-01-01

421

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

422

Towards helium-3 neutron polarizers  

NASA Astrophysics Data System (ADS)

With a large absorption cross-section entirely due to antiparallel spin capture, polarized helium-3 is presently the most promising broad-band polarizer for thermal and epithermal neutrons. Immediate interest was raised amongst the neutron community when a dense gaseous 3He polarizer was used for the first time in 1988, on a pulsed neutron beam at Los Alamos. With 20 W of laser power on a 30 cm long, 8.6 atm target, 40% 3He polarization was achieved in a recent polarized electron scattering experiment at SLAC. In this technique the 4He nuclei are polarized directly at an appropriate high pressure through spin-exchange collisions with a thick, optically pumped rubidium vapor. A different and competitive approach is being presently developed at Mainz University in collaboration with ENS Paris and now the ILL. A discharge is established in pure 3He at low pressure producing excited metastable atoms which can be optically pumped with infra-red light. Highly effective exchange collision with the atoms remaining in the ground state quickly produces 75% polarization at 1.5 mbar. A truly non-magnetic system then compresses the polarized gas up to several bars as required. The most recent machine comprises a two-stage glass-titanium compressor. In less than 1 h it can inflate a 100 cm 3 target cell with three bars of polarized gas. The very long relaxation times (several days) now being obtained at high pressure with a special metallic coating on the glass walls, the polarized cell can be detached and inserted in the neutron beam as polarizer. We expect 50% 3He-polarization to be reached soon, allowing such filters to compete favorably with existing Heusler-crystal polarizers at thermal and short neutron wavelengths. It must be stressed that such a system based on a 3He polarization factory able to feed several passive, transportable, polarizers is well matched to neutron scattering needs.

Tasset, F.

1995-02-01

423

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

424

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

425

version 1.0 Hyper ne structure of muonic helium  

E-print Network

state muonic helium is calculated numer- ically using the variational approach. Comparison to former consisting of an electron, muon, and an alpha particle nucleus [1]. It is almost a hydrogenic atom, as the muon and alpha particle can be treated as a soft nucleus as a #12;rst approximation. However, when

Pachucki, Krzysztof

426

Helium halo nuclei from low-momentum interactions  

E-print Network

We present ground-state energies of helium halo nuclei based on chiral low-momentum interactions, using the hyperspherical-harmonics method for 6He and coupled-cluster theory for 8He, with correct asymptotics for the extended halo structure.

S. Bacca; A. Schwenk; G. Hagen; T. Papenbrock

2009-02-10

427

Rogue mantle helium and neon.  

PubMed

The canonical model of helium isotope geochemistry describes the lower mantle as undegassed, but this view conflicts with evidence of recycled material in the source of ocean island basalts. Because mantle helium is efficiently extracted by magmatic activity, it cannot remain in fertile mantle rocks for long periods of time. Here, I suggest that helium with high 3He/4He ratios, as well as neon rich in the solar component, diffused early in Earth's history from low-melting-point primordial material into residual refractory "reservoir" rocks, such as dunites. The difference in 3He/4He ratios of ocean-island and mid-ocean ridge basalts and the preservation of solar neon are ascribed to the reservoir rocks being stretched and tapped to different extents during melting. PMID:18202257

Albarède, Francis

2008-02-15

428

Anomalies in radiation-collisional kinetics of Rydberg atoms induced by the effects of dynamical chaos and the double Stark resonance  

NASA Astrophysics Data System (ADS)

Radiative and collisional constants of excited atoms contain the matrix elements of the dipole transitions and when they are blocked one can expect occurring a number of interesting phenomena in radiation-collisional kinetics. In recent astrophysical studies of IR emission spectra it was revealed a gap in the radiation emitted by Rydberg atoms (RA) with values of the principal quantum number of n?10. Under the presence of external electric fields a rearrangement of RA emission spectra is possible to associate with manifestations of the Stark effect. The threshold for electric field ionization of RA is E?3·104 V/cm for states with n>10. This means that the emission of RA with n?10 is effectively blocked for such fields. In the region of lower electric field intensities the double Stark resonance (or Förster resonance) becomes a key player. On this basis it is established the fact that the static magnetic or electric fields may strongly affect the radiative constants of optical transitions in the vicinity of the Föster resonance resulting, for instance, in an order of magnitude reduction of the intensity in some lines. Then, it is shown in this work that in the atmospheres of celestial objects lifetimes of comparatively long-lived RA states and intensities of corresponding radiative transitions can be associated with the effects of dynamic chaos via collisional ionization. The Föster resonance allows us to manipulate the random walk of the Rydberg electron (RE) in the manifold of quantum levels and hence change the excitation energies of RA, which lead to anomalies in the IR spectra.

Bezuglov, N. N.; Klyucharev, A. N.; Mihajlov, A. A.; Sre?kovi?, V. A.

2014-10-01

429

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, Roswitha S. (Knoxville, TN); Todd, Richard A. (Knoxville, TN)

1987-01-01

430

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

431

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

432

Circuit Quantum Electrodynamics with Electrons on Helium  

E-print Network

Circuit Quantum Electrodynamics with Electrons on Helium A Dissertation Presented to the Faculty Fragner All rights reserved. ii #12;Abstract Circuit Quantum Electrodynamics with Electrons on Helium quantum electro- dynamics (QED) architecture with electrons floating above the surface of superfluid

433

48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Required Sources for Helium and Helium Usage Data. 52.208-8 Section 52.208-8...Provisions and Clauses 52.208-8 Required Sources for Helium and Helium Usage Data. As prescribed in...

2010-10-01

434

Determination of absolute cross sections and rate coefficients for state-to-state reactions He +(X 2S)+H 2(X 1? g+)?He(1 snl+H 2+( j2A) in ion beam experiments  

NASA Astrophysics Data System (ADS)

The beam collision cell technique has been employed to determine the absolute cross sections for the formation of molecular hydrogen ions from reactions of He +(1s) with H 2(X 1? g+, ? = 0). The subthermal rate coefficient for the formation of H 2+(X 2? g+, ?')+He(X 1S) is presently obtained as 1.48×10 -13 cm 3 s -1. This result is estimated to be correct to within a factor of 2. The near thermal cross section data are well represented by the expression ?( EFC) = AER- 1/2, where A = 4.91 × 10 -33 m 3kg 1/2 s -1 and ER is the relative energy. The present evidence for H 2+ from thermal He ++H 2 collisions supports our previous theoretical and experimental results. The mechanism is associative radiation: He ++H 2?He +?H 2; He +?H 2?[He?H 2+]+ hv(153nm); [He?H 2+]?He+H 2+. The measured cross section for H 2+ drops precipitously as the relative collision energy is raised from new zero to about 2 eV. Then the total H 2+ cross section rises again as the channels yielding helium He(1s 2) and Rydberg molecular hydrogen ion states, H 2+*( j2A), open up. The cross section remains large above 4 eV all the way up to 57 eV, supported by access to a second series of Rydberg channels, namely He*(1 snl)+H 2+(X 2? g+, ?' above 13 eV. The reaction of H 2+ with H 2 to yield H 3+(X 1A 1)+H(1s) was also examined—the rate at quasithermal collision energies is presently obtained as 1.7×10 -9 cm 3 s -1, in excellent agreement with previous work. Further theoretical analysis shows that the H 2+*( j2A) from extrathermal He ++H 2 collisions are the Rydberg states H 2+(2s? g, 2p? g, 2p? u, etc.). The mechanism for their formation is similar to that previously discussed for H + and HeH +. That is, a two electron transition 1?2? 2? 1? 24?, where 1? = 1sHe, 2? = 1s? gH 2 and 4? = nl2AH 2+ n ? 2, occurs for collisions with collision energy sufficient to take the HeH 2+ system up the potential surface for the 2 2A v' valence state of the reactants to the relevant avoided intersection with the triatomic Rydberg states arising from the asymptotes He(1s 2)+H 2+*( j2A), n ? 2. However, in this case the avoided intersection is encountered at extended value of the coor¯dinate RHH. Consequently, only that fraction of the collitions involving He?H 2 orientations near the colinear C oov coordinate will be effective. For this reason, the extrathermal cross sections for H 2+* are apparently low compared to those previously reported for H + and HeH +. Similar considerations apply to the somewhat higher lying HeH 2+ channels leading to the He*(1 snl) + H 2+(X 2? g+) channels, which are accessed via one-electron transitions at the relevant avoided intersections of HeH 2+ 2A' states.

Wu, Richard L. C.; Hopper, Darrel G.

1981-05-01

435

Spectral shifts and helium configurations in 4HeN-tetracene clusters  

SciTech Connect

Spectral shifts of electronic transitions of tetracene in helium droplets are investigated in a theoretical study of {sup 4}He{sub N}-tetracene clusters with 1 {le} N {le} 150. Utilizing a pair-wise interaction for the S{sub 0} state of tetracene with helium that is extended by semi-empirical terms to construct a potential for the S1 state of tetracene with helium, the spectral shift is calculated from path integral Monte Carlo calculations of the helium equilibrium properties with tetracene in the S{sub 0} and S{sub 1} states at T = 0 and at T = 0.625 K. The calculated spectral shifts are in quantitative agreement with available experimental measurements for small values of N ({le} 8) at T {approx} 0.4 K and show qualitative agreement for larger N (10-20). The extrapolated value of the spectral shift in large droplets (N {approx} 10{sup 4}) is {approx} 90% of the experimentally measured value. We find no evidence of multiple configurations of helium for any cluster size, for both the S{sub 0} or S{sub 1} states of tetracene. These results suggest that the observed spectral splitting of electronic transitions of tetracene in large helium droplets is not due to co-existence of static meta-stable helium densities, unlike the situation previously analyzed for the phthalocyanine molecule.

Whitley, H D; DuBois, J L; Whaley, K B

2009-05-20

436

30 CFR 256.11 - Helium.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Helium. 256.11 Section 256.11 Mineral...Sulphur Management, General § 256.11 Helium. (a) Each lease issued or continued...the ownership of and the right to extract helium from all gas produced from the...

2010-07-01

437

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

438

QUANTUM STATISTICS OF METASTABLE LIQUID HELIUM  

E-print Network

QUANTUM STATISTICS OF METASTABLE LIQUID HELIUM FR´ED´ERIC CAUPIN AND S´EBASTIEN BALIBAR Laboratoire in the spinodal line of liquid helium 3, for which experimental evidence has been reported. The calculations in the case of superfluid helium 4; we also consider the overpressurized region, and the location

Caupin, Frédéric

439

Characterization of reconnecting vortices in superfluid helium  

E-print Network

Characterization of reconnecting vortices in superfluid helium Gregory P. Bewley*, Matthew S experimental observations of reconnection between quantized vortices in superfluid helium. We do so by imaging. reconnection Vorticity in superfluid helium is confined to filaments that are only angstroms in diameter

Texas at Austin. University of

440

Helium Migration in Iron Christ's College  

E-print Network

Helium Migration in Iron Y. Zhang Christ's College Department of Materials Science and Metallurgy the achievement at all. ii #12;Abstract A theoretical model of helium migration in body centred cubic (BCC)structure irons has been developed using the concept of the effective helium diffusion coeffi- cient

Cambridge, University of

441

Mining Helium programs with Neon Jurriaan Hage  

E-print Network

Mining Helium programs with Neon Jurriaan Hage Peter van Keeken Department of Information in a first-year functional programming course using the Helium compiler. The mining of such a collection to resolve a type error. 1 #12;1 Introduction and motivation When the Helium compiler for learning Haskell

Utrecht, Universiteit

442

30 CFR 556.11 - Helium.  

...2014-07-01 2014-07-01 false Helium. 556.11 Section 556.11 Mineral...Sulphur Management, General § 556.11 Helium. (a) Each lease issued or continued...the ownership of and the right to extract helium from all gas produced from the...

2014-07-01

443

DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART II.  

SciTech Connect

Six new samples of tritium-aged bulk titanium have been examined by thermal desorption and isotope exchange chemistry. The discovery of a lower temperature hydrogen desorption state in these materials, previously reported, has been confirmed in one of the new samples. The helium release of the samples shows the more severe effects obtained from longer aging periods, i.e. higher initial He/M ratios. Several of the more aged samples were spontaneously releasing helium. Part I discussed the new results on the new lower temperature hydrogen desorption state found in one more extensively studied sample. Part II will discuss the hydrogen/helium release behavior of the remaining samples.

Shanahan, K; Jeffrey Holder, J

2006-08-17

444

DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART I.  

SciTech Connect

Six new samples of tritium-aged bulk titanium have been examined by thermal desorption and isotope exchange chemistry. The discovery of a lower temperature hydrogen desorption state in these materials, previously reported, has been confirmed in one of the new samples. The helium release of the samples shows the more severe effects obtained from longer aging periods, i.e. higher initial He/M ratios. Several of the more aged samples were spontaneously releasing helium. Part I will discuss the new results on the new lower temperature hydrogen desorption state found in one more extensively studied sample. Part II will discuss the hydrogen/helium release behavior of the remaining samples.

Shanahan, K; Jeffrey Holder, J

2006-07-10

445

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

446

Why Helium Ends in "-Ium"  

ERIC Educational Resources Information Center

Edward Frankland and Norman Lockyer researched upon a gaseous spectra in relation to the physical constitution of the sun and named it as "helium" (from Greek "helios" meaning "sun"). Since Lockyer apparently never formally proposed the name in print, it is not known why he chose to use a metallic end "ium".

Jensen, William B.; Holme, Thomas; Cooper, Melanie; White, Carol

2004-01-01

447

Pulsed discharge helium ionization detector  

Microsoft Academic Search

A pulsed discharge helium ionization detector (PDHID) (patent pending) for gas chromatography has been developed. This detector uses a non-radioactive pulsed high voltage discharge source for generation of electrons and pulsed collection of these electrons. We have evaluated this detector for the analysis of a wide range of chemical compounds. In this paper the analytes are passed through the discharge

W. E. Wentworth; S. V. Vasnin; S. D. Stearns; C. J. Meyer

1992-01-01

448

NUCLOTRON HELIUM PLANT CONTROL SYSTEM  

Microsoft Academic Search

The heavy ion superconducting synchrotron Nuclotron intended to accelerate nuclei and multicharged ions with q\\/A = ½ up to an energy of 6 Gev\\/u was put into operation in the Laboratory of High Energies of the Joint Institute for Nuclear Research (Dubna, Russia) in 1993. The Nuclotron cryogenic supply is based on three helium refrigerators of 1600 W capacity at

N. Agapov; V. Batin; V. Gorchenko; A. Kirichenko; A. Kovalenko; I. Kulikov; S. Romanov; B. Vasilishin; V. Volkov; L. Vergov; T. Yordanov

2003-01-01

449

Helium-antihydrogen scattering at low energies  

NASA Astrophysics Data System (ADS)

We calculate cross sections for helium-antihydrogen scattering for energies up to 0.01 atomic unit. Our calculation includes elastic scattering, direct antiproton-alpha particle annihilation and rearrangement into He^+\\bar p and ground-state positronium. Elastic scattering is calculated within the Born-Oppenheimer approximation using the potential calculated by Strasburger et al (2005 J. Phys. B: At. Mol. Opt. Phys. 38 3091). Matrix elements for rearrangement are calculated using the T-matrix in the distorted wave approximation, with the initial state represented by Hylleraas-type functions. The strong force, leading to direct annihilation, was included as a short-range boundary condition in terms of the strong-force scattering length.

Jonsell, S.; Armour, E. A. G.; Plummer, M.; Liu, Y.; Todd, A. C.

2012-03-01

450

Torsional oscillator measurements on solid helium in a partially blocked annular channel  

NASA Astrophysics Data System (ADS)

We employed a torsional oscillator technique to investigate the non-classical response of solid helium. We grow solid helium samples within an annular channel that is divided by two Vycor blocks. The melting pressure of helium in narrow pores of Vycor glass is elevated up to about 37 bar due to the strong confinement. This effect is used to engineer various combinations of adjacent helium states. When a helium sample is prepared in the pressure range of 25 and 37 bar a solid-liquid-solid sandwich is formed in and outside the Vycor. Non-classical rotational inertia fraction (NCRIF) of 0.02% is observed under this circumstance below about 200mK. For the pressure higher than 37 bar Vycor glasses in the channel can be utilized as partial blocks and the strength of blockage can be modified by gas adsorption on to the pore wall. Supersolid behavior with a number of different partial blockages will be presented.

Kim, Duk Young; Kwon, Sang-Il; Choi, Hyoungsoon; Kim, Eunseong

2009-03-01

451

Experiments on solid Helium-4  

NASA Astrophysics Data System (ADS)

This thesis presents data on experiments done with hcp 4He. The main focus is on the possibility of superfluidity inside solid 4He. The presence of superfluidity inside the solid should be manifested by a flow through the solid. The aim of these experiments was to search for a D.C. flow, characterize it and determine if the flow is due to superfluidity. A cell was designed that exploits the properties of helium in confined geometries to provide an interface between superfluid liquid helium, and hcp solid helium at pressures greater than the bulk melting curve. This interface allowed for a direct injection of atoms into the solid from the superfluid. With this cell, two different methods can be used to induce flow. In the first method, mass is injected directly into one side of the solid, while the pressure of the other side is monitored for a response. In the second method, flow is induced by changing the temperature of liquid reservoirs connected to the solid through porous Vycor glass. In addition to observing flow, it is also seen that a fountain pressure exists between the two liquid reservoirs connected to each other through the Vycor, and solid helium. Using this same design, the growth of solid helium was also studied at pressure higher than the bulk melting curve. Here, the solid cannot grow along a free surface, since off the melting curve the cell is supposed to be completely filled with solid. Near the melting curve, transients of 1--5 mK are seen in the temperature along with pressure drops ? 160 mbar. These transients are shown to probably be due to the solidification of metastable liquid regions imbedded in the solid. Off the melting curve, growth of the solid continues, and this growth is studied in the context of, "isochoric compressibility."

Ray, Michael William

452

Subwavelength microwave electric-field imaging using Rydberg atoms inside atomic vapor cells.  

PubMed

We have recently shown [Nat. Phys.8, 819 (2012)] that Alkali atoms contained in a vapor cell can serve as a highly accurate standard for microwave (MW) electric field strength as well as polarization. Here we show for the first time that Rydberg atom electromagnetically induced transparency can be used to image MW electric fields with unprecedented precision. The spatial resolution of the method is far into the subwavelength regime ??/650 or 66 ?m at 6.9 GHz. The electric field resolutions are similar to those we have already demonstrated ?50???V?cm(-1). Our experimental results agree with finite element calculations of test electric-field patterns. PMID:24978265

Fan, H Q; Kumar, S; Daschner, R; Kübler, H; Shaffer, J P

2014-05-15

453