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1

Microwave saturation of the Rydberg States of electrons on helium.

We present measurements of the resonant microwave excitation of Rydberg energy levels for surface-state electrons on superfluid helium. The temperature-dependent contribution to the linewidth gamma(T) agrees with theoretical predictions and is very small below 700 mK, in the ripplon scattering regime. Absorption saturation and power broadening were observed as the fraction of electrons in the first excited state was increased to 0.49, close to the thermal excitation limit of 0.5. The Rabi frequency Omega was determined as a function of microwave power. High values of the ratio Omega/gamma confirm this system as an excellent candidate for creating qubits. PMID:12484952

Collin, E; Bailey, W; Fozooni, P; Frayne, P G; Glasson, P; Harrabi, K; Lea, M J; Papageorgiou, G

2002-11-20

2

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

3

National Technical Information Service (NTIS)

The influence of an external electric field on thermal collisions between a sodium atom excited in a ''circular'' Rydberg state and a ground-state helium atom is studied numerically within the framework of the impulse approximation. The effect of the fiel...

E. Prunele

1986-01-01

4

Lineshapes of Ionizing Stark Resonances in Rydberg States of Helium and Nitric Oxide.

NASA Astrophysics Data System (ADS)

High resolution laser spectroscopy is used to study the Stark effect in helium and nitric oxide. The energies, widths, intensities and shapes of resonances in helium above the classical ionization threshold are measured for a wide range of field values. The high resolution of the lasers combined with careful design of the electric field plates allow accurate determination of the lineshape parameters, including linewidths and asymmetries accurate in the best cases to 6%. A modified Wentzel-Kramers-Brillouin (WKB) method is used to obtain detailed theoretical predictions for these Stark resonances with no adjustable parameters. The experiment concentrates on the diabatic states of greatest slope arising from the zero-field n = 32 and n = 40 manifolds in regions where these levels are fairly isolated and fit well to Fano profiles. In all cases, excellent agreement between experimental and theoretical lineshape parameters is obtained. A simpler autoionization model also reproduces the results, although less accurately. In nitric oxide, the lineshapes of the Rydberg 8s and 9s states with N = 0-3 and v = 1 are studied. The 8s levels lie just below the N^+ = 0, v ^+ = 0 continuum. Application of a small electric field will force the molecule to ionize, in the process giving up both rotational and vibrational energy. The lineshape of the 8s state will then appear as an autoionization resonance. This "forced autoionization" is compared with the zero field autoionization of the 9s state. Finally, data on the Rydberg states of carbon monoxide for regions near n = 9 and n = 10 with v = 1 are presented. These measurements are the first to show clearly resolved structure in autoionizing Rydberg states of carbon monoxide.

Nussenzweig, Andre

5

NASA Astrophysics Data System (ADS)

New features of the blackbody-induced radiation processes on Rydberg atoms were discovered on the basis of numerical data for the blackbody-induced decay Pdnl(T), excitation Penl(T) and ionization Pionnl(T) rates of nS, nP and nD Rydberg states calculated together with the spontaneous decay rates Pspnl in neutral hydrogen, and singlet and triplet helium atoms for some values of the principal quantum number n from 10 to 500 at temperatures from T = 100 K to 2000 K. The fractional rates Rd(e, ion)nl(T) = Pnld(e, ion)(T)/Pspnl equal to the ratio of the induced decay (excitation, ionization) rates to the rate of spontaneous decay were determined as functions of T and n in every series of states with a given angular momentum l = 0, 1, 2. The calculated data reveal an essential difference between the asymptotic dependence of the ionization rate Pionnl(T) and the rates of decay and excitation Pd(e)nl(T)~T/n2. The departures appear in each Rydberg series for n > 100 and introduce appreciable corrections to the formula of Cooke and Gallagher. Two different approximation formulae are proposed on the basis of the numerical data, one for Rd(e)nl(T) and another one for Rionnl(T), which reproduce the calculated values in wide ranges of principal quantum number from n = 10 to 1000 and temperatures between T = 100 K and T = 2000 K with an accuracy of 2% or better. Modified Fues' model potential approach was used for calculating matrix elements of bound-bound and bound-free radiation transitions in helium.

Glukhov, I. L.; Nekipelov, E. A.; Ovsiannikov, V. D.

2010-06-01

6

We present numerical results for the correction potential beyond the Coulomb-Breit and the Araki-Sucher interaction potentials due to transverse photon exchange between the Rydberg electron and the core in helium Rydberg atoms.

Au, C.K.; Mesa, M.A. (Department of Physics, University of South Carolina, Columbia, South Carolina 29208 (USA) Department of Astronomy, University of South Carolina, Columbia, South Carolina 29208 (USA))

1990-03-01

7

The results of an extended series of high-precision variational calculations for all states of helium up to {ital n}=10 and {ital L}=7 (excluding {ital S} states above {ital n}=2) are presented. Convergence of the nonrelativistic eigenvalues ranges from five parts in 10{sup 15} for the 2{ital P} states to four parts in 10{sup 19} for the 10{ital K} states. Relativistic and quantum electrodynamic corrections of order {alpha}{sup 2}, {alpha}{sup 3}, {alpha}{sup 2}{mu}/{ital M}, {alpha}{sup 2}({mu}/{ital M}){sup 2}, and {alpha}{sup 3}{mu}/{ital M} are included and the required matrix elements listed for each state. For the 1{ital s}2{ital p} {sup 3}{ital P}{sub {ital J}} states, the lowest-order spin-dependent matrix elements of the Breit interaction are determined to an accuracy of three parts in 10{sup 9}, which, together with higher-order corrections, would be sufficient to allow an improved measurement of the fine-structure constant. Methods of asymptotic analysis are extended to provide improved precision for the relativistic and relativistic-recoil corrections. A comparison with the variational results for the high-angular-momentum states shows that the standard-atomic-theory'' and long-range-interaction'' pictures discussed by Hessels {ital et} {ital al}. (Phys. Rev. Lett. 65, 2765 (1990)) come into agreement, thereby resolving what appeared to be a discrepancy. The comparison shows that the asymptotic expansions for the total energies are accurate to better than {plus minus}100 Hz for {ital L}{gt}7, and results are presented for the 9{ital L}, 10{ital L}, and 10{ital M} states (i.e., angular momentum {ital L}=8 and 9). Significant discrepancies with experiment persist for transitions among the {ital n}=10 states, which cannot be easily accommodated by supposed higher-order corrections or additional terms.

Drake, G.W.F.; Yan, Z. (Department of Physics, University of Windsor, Windsor, Ontario, N9B3P4 (Canada))

1992-09-01

8

Lineshapes of Ionizing Stark Resonances in Rydberg States of Helium and Nitric Oxide

High resolution laser spectroscopy is used to study the Stark effect in helium and nitric oxide. The energies, widths, intensities and shapes of resonances in helium above the classical ionization threshold are measured for a wide range of field values. The high resolution of the lasers combined with careful design of the electric field plates allow accurate determination of the

Andre Nussenzweig

1989-01-01

9

NASA Astrophysics Data System (ADS)

The fine structure intervals separating high-L n=9 and 10 Rydberg states of H2 and D2 that are built on v=0, R=0 states of H_2^+ and D_2^+ were measured using fast beam microwave optical techniques(W.G. Sturrus et. al. Phys. Rev. Lett. 44, 3032 (1991)). These states have a helium-like fine structure since the R=0 core is isotropic. The measured intervals determine the dipole polarizabilities of the ground states of H_2^+ and D_2^+.

Jacobson, P. L.; Stevens, G. D.; Lundeen, S. R.; Sturrus, W. G.

1997-04-01

10

Theory of Molecular Rydberg States

NASA Astrophysics Data System (ADS)

Preface; 1. Molecular Rydberg states; 2. Ab initio quantum defects; 3. Frame transformations and channel interactions; 4. Competitive fragmentation; 5. Photo-excitation; 6. Photo-ionization; 7. Manipulating Rydberg states; Appendices; Index.

Child, M. S.

2011-08-01

11

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

12

Rubidium Atoms on Helium Droplets: Analysis of AN Exotic Rydberg Complex

NASA Astrophysics Data System (ADS)

Rubidium atoms on the surface of superfluid helium droplets have been excited into Rydberg states. The excitation spectrum of the Rb-He_N system has been recorded from the 5^2D state manifold up to the ionization threshold by resonant three-photon-ionization time-of-flight spectroscopy. The observation of droplet size dependent shifts of excited states with respect to bare atom states is explained by a decreased quantum defect and a lowered ionization threshold. Within the scope of a Rydberg model we demonstrate that quantum defects and ionization thresholds are constant for each specific Rydberg series, which confirms the Rydberg character of excited Rubidium states on helium droplets. A set of six Rydberg series could be identified. Individual Rydberg states are observed with effective principle quantum numbers up to n* ? 19 and l ? 3, for which the expectation value of the electron orbital radius is about ten times larger than the droplet radius. M. Theisen, F. Lackner, G. Krois, and W.E. Ernst, J. Phys. Chem. Lett., 2, 2778-2782 (2011) F. Lackner, G. Krois, M. Theisen, M. Koch, and W.E. Ernst, Phys. Chem. Chem. Phys., 13, 18781-18788 (2011) J.E. Murphy, J.M. Berg, A.J. Merer, N.A. Harris, and R.W. Field, Phys. Rev. Lett. 65, 1861 (1990)

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

2012-06-01

13

NASA Astrophysics Data System (ADS)

Metastable ^4He_2 molecules [a ^3? u^+ (v=0,N=1,3,5,7)] were produced in a supersonic expansion of neat helium atoms by striking a discharge at the orifice of a pulsed valve. Transitions to np Rydberg states (n up to 150) converging to the first rotational levels of the ground state of He_2^+ [ X^+ ^2? u^+ (v^+=0,N^+=1,3,5)] were recorded at a precision better than 10-3 cm-1 using the technique of Rydberg-state-resolved threshold ionization spectroscopy. The observed Rydberg series reveal strong perturbations caused by rotational channel interactions and the appearance of the spectra is strongly influenced by weak electric fields present in the excitation region. The extrapolation of the Rydberg series to their limits using multichannel quantum defect theory enabled the determination of the rotational structure of the helium dimer cation and of quantum defect parameters for the corresponding ionization channels. These results represent a benchmark for ab initio calculations on three-electron systems. M. Raunhardt, M. Schäfer, N. Vanhaecke, and F. Merkt, J. Chem. Phys. 128, 164310 (2008) R. Seiler, U. Hollenstein, G. M. Greetham, and F. Merkt, Chem. Phys. Lett. 346, 201 (2001) A. Carrington, Ch. H. Pyne, and P. J. Knowles, J. Chem. Phys. 102, 5979 (1995) J. Xie, B. Poirier, and G. I. Gellene, J. Chem. Phys. 122, 184310 (2005)

Sprecher, Daniel; Liu, Jinjun; Krähenmann, Tobias; Schäfer, Martin; Merkt, Frédéric

2010-06-01

14

Trojan wavepackets in helium - by core-Rydberg interaction

NASA Astrophysics Data System (ADS)

We exhibit the existence of core-induced shape invariant wave packets in helium analogous to the Trojan wave packets predicted for hydrogen [1]. We show that the core dipole moment oscillating with the Rabi frequency in the presence of a laser field will cause both radial and angular confinement of an outer Rydberg electron moving around a nearly circular orbit if the parameters of the orbit are properly chosen. We find the relation between the Rabi frequency of the core electron oscillations, laser field strength and the parameters of the Rydberg orbit of the outer electron. Work supported by the NSF grants INT93-11766 and PHY94-08733 [1] I. Bialynicki-Birula, M. Kalinski and J. H. Eberly, Phys. Rev. Lett. 73, 1777 (1994); see also H. Klar, Z. Phys. D 11, 45 (1989)

Kalinski, Maciej; Eberly, J. H.

1996-05-01

15

Rydberg States of Triatomic Hydrogen and Deuterium

NASA Astrophysics Data System (ADS)

The triatomic hydrogen ion (H3+) has spurred tremendous interest in astrophysics in recent decades, and Rydberg states of H3 have also maintained an important role for understanding H3+ experiments. In a previous study (J. Chem. Phys. 2010, 133, 234302), radiative transitions between neutral H3 Rydberg states were calculated at wavelengths near 7 -m and could be compared with mid-infrared laser lines observed in hydrogen/rare gas discharges. The present study extends the investigation to wavelengths near 10-13 -m. Rydberg states of D3 are also treated.

Wang, Jia; Greene, Chris H.

2013-10-01

16

NASA Astrophysics Data System (ADS)

In the present experimental and theoretical dissertation, we study the quantum photoabsorption spectrum of Rydberg states of helium and argon in a strong electric field, and the classical closed orbit spectral counterpart, the recurrence spectrum. Connections between classical and quantum descriptions are investigated. We present a complete experimental scaled energy absorption spectra for m = 0 and 1 singlet and triplet helium atoms, over a scaled energy range epsilon = -2.0 to -3.5 and principle quantum number range n = 15 to 25. Agreement with semiclassical theory is excellent. Also, we present experimental results for the many electron Rydberg atom argon, with core angular momentum state J = 3/2, for epsilon = -2.0 to -3.5 and for n = 15 to 25. Measurements of anomalous long-lived states above the classical ionization threshold in m = 1 singlet helium are presented and we show that hydrogenic theory is not valid in this case. We describe a calculation for all the primitive orbits for m = 1 hydrogen, in the range epsilon = -2.0 to -1.8, and find a simple way to calculate the initial launching radius. Measured trajectories show very good agreement with computed classical trajectories. Also, we present a simple formula to calculate the scaled action with respect to the scaled energy that agrees well with observation. Finally, the importance of the primitive orbit and its repetitions in the recurrence map is examined.

Flores-Rueda, Heric

17

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

18

Autoionizing process of double rydberg states in atom

We have studied the autoionization distribution of penetrating double Rydberg (DR) states NLnl(N

Xu, X. Y.; Huang, W.; Xu, C. B.; Xue, P.; Chen, D. Y. [Department of Modern Applied Physics, Tsinghua University, Beijing 100084 (China)

1997-01-15

19

Rydberg state creation by tunnel ionization

NASA Astrophysics Data System (ADS)

It is well known from numerical and experimental results that the fraction of Rydberg states (excited neutral atoms) created by tunnel ionization declines dramatically with increasing ellipticity of laser light, in a way that is similar to high harmonic generation (HHG). We present a method to analyze this dependence on ellipticity, deriving a probability distribution of Rydberg states that agrees closely with experimental (Nubbemeyer et al 2008 Phys. Rev. Lett. 101 233001) and numerical results. We show using analysis and numerics that most Rydberg electrons are ionized before the peak of the electric field and therefore do not come back to the parent ion. Our work shows, for the first time, the similarities and differences in the process that distinguishes formation of Rydberg electrons from electrons involved in HHG: ionization occurs in a different part of the laser cycle, but the post-ionization dynamics are very similar in both cases, explaining why the same dependence on ellipticity is observed.

Landsman, A. S.; Pfeiffer, A. N.; Hofmann, C.; Smolarski, M.; Cirelli, C.; Keller, U.

2013-01-01

20

Excitation and ionization of hydrogen Rydberg states in a plasma

Hydrogen Rydberg states in a hydrogen plasma are optically excited from the plasma-excited n = 2 state. Photoionization and optogalvanic, which are due to electron-impact ionization and other collisional processes, are used to monitor the Rydberg states. This process may be used to study collisional ionization of the Rydberg states.

Glab, W.; Nayfeh, M.H.

1982-08-01

21

NASA Astrophysics Data System (ADS)

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

He, Liming; Cao, Wei

2006-12-01

22

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

23

Calculated photoexcitation spectra of positronium Rydberg states

NASA Astrophysics Data System (ADS)

Calculations of the photoexcitation spectra of ortho-positronium Rydberg states with principal quantum numbers between 10 and 30 are presented. The effects of Doppler broadening and saturation of the corresponding electric-dipole transitions are studied, together with the role of static and motionally induced electric fields. This is done in the context of recent measurements reported by Cassidy [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.108.043401 108, 043401 (2012)], and with regard to experiments involving the production of antihydrogen by charge-exchange between Rydberg positronium and cold antiprotons.

Hogan, S. D.

2013-06-01

24

Logic gates using high Rydberg states

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.

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

2001-01-01

25

Measurements of G-H and H-I fine-structure intervals in n=7, 9, and 10 helium Rydberg states

NASA Astrophysics Data System (ADS)

We have made measurements of the 7G-H, 7H-I, 9G-H, 9H-I, and the 10G-H intervals in helium. These measurements are in good agreement with theoretical calculations up to the level of about 1 kHz precision. This confirms the importance of retardation to the intervals with about 1% precision. At the 1 kHz level, however, systematic discrepancies are seen which cannot be accounted for by suggested additional retardation corrections.

Stevens, G. D.; Lundeen, S. R.

1999-12-01

26

Millimetre Wave Spectroscopy and MQDT Calculations of High Rydberg States

Millimetre wave sources have been combined with high resolution VUV laser systems to study the hyperfine structure of high n Rydberg states at sub-MHz resolution. Multichannel quantum defect theory has been used to analyse the hyperfine structure of the Rydberg states and to derive the hyperfine structure of the corresponding ionic states.

Schaefer, Martin; Merkt, Frederic [Laboratorium fuer Physikalische Chemie, ETH Zuerich, 8093 Zurich (Switzerland)

2007-09-19

27

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

28

Indirect spin orbit interaction in high-L Rydberg states with ^2S_1/2 cores

NASA Astrophysics Data System (ADS)

In high-L Rydberg states, where exchange interactions are of negligible size, spin orbit interactions determine the energy differences between states of different spin orientation. This is well-studied in the case of helium[1], where it results in a four-fold splitting of each term, coming from the two electron's spin orbit interactions. A similar structure might be expected in heavier Rydberg states whose core ion is a ^2S_1/2 state. However, observations in Barium Rydberg states[2] and recent observations in Rydberg states of Si^2+ [3]reveal significant deviations from this expectation. Both can be explained as an indirect effect of spin orbit interactions in excited states of the core ion which become admixed into the core electronic wavefunction as a result of the electric field of the Rydberg electron. A perturbative treatment predicts an additional spin-orbit interaction proportional to the inverse sixth power of the Rydberg radial coordinate whose size depends on characteristics of the core ion. Numerical estimates explain both the observations in Ba and Si^2+, and are of negligible importance in helium. [1] E.A. Hessels, W.G. Sturrus, and S.R. Lundeen, Phys. Rev. A 35, 4489 (1987) [2] T.F. Gallagher, R. Kachru, and N.H. Tran, Phys. Rev. A 26, 2611 (1982) [3] R.A. Komara (private communication)

Snow, E. L.; Komara, R. A.; Gearba, M. A.; Lundeen, S. R.

2003-05-01

29

Rydberg state decay in inhomogeneous electric fields

NASA Astrophysics Data System (ADS)

An extension of the model of Merkt and Zare [J. Chem. Phys. 101, 3495 (1994)] is presented to describe the effects of static inhomogeneous electric fields, which arise experimentally from combinations of applied (or stray) homogeneous fields and the presence of charged particles, on Rydberg states of atoms and molecules. The effect of an arbitrary number of charged particles is included and the effects of nonzero quantum defects are investigated. A quantization axis rotation procedure is defined, allowing clear distinction between homogeneous and inhomogeneous field effects. Calculations are reported of the time-dependent decay of a coherent population of eigenstates for n=20, 33, and 50, involving diagonalization of the full n2×n2 matrix. Calculations are also carried out for n=100 by pre-diagonalization of the full homogeneous field perturbation followed by a restricted basis set diagonalization for the inhomogeneous part of the perturbation. The inclusion of nonzero quantum defects has a substantial impact on the ml mixing, confining significant mixing to a narrow range of radial and angular positions of the ion. An applied homogeneous field of order the Inglis-Teller field is required in combination with the field due to the ions. The dynamics are very different according to whether np or nf series carry the transition probability. For np-state population, the maximum stabilization is achieved at ion-Rydberg distances of around 5n2a0, with the ion almost perpendicular to the applied homogeneous field. For an initial nf population the ion perturbation may have a destabilizing effect at sufficiently small homogeneous field (<=0.1FIT). Significant effects of laser polarization on the stability are reported. Calculations for a realistic pseudo-random distribution of ions and Rydbergs suggest that ml mixing by ions will never reach the complete mixing limit, but that at least an order of magnitude stabilization is achievable under a restricted range of conditions.

Softley, T. P.; Rednall, R. J.

2000-05-01

30

Applications of molecular Rydberg states in chemical dynamics and spectroscopy

NASA Astrophysics Data System (ADS)

Molecules in high Rydberg states, in which one electron has been excited into a hydrogenic orbital of large mean radius, have many unusual properties compared to ground state molecules. These properties, which are reviewed in this article, make them suitable for a diverse and growing number of applications in chemical dynamics. The most recent methods for studying molecular Rydberg states using high-resolution spectroscopy and theory, including effects of electric fields, are described here. An important feature is the high susceptibility of Rydberg states to external field perturbation which not only has a profound effect on the observable energy levels, spectroscopic intensities and lifetimes, but is also useful for state-selective detection through field ionization. The large dipole moment that can be created in a field is also useful for controlling the motion of molecules in Rydberg states. The applications reviewed here include: ZEKE (zero kinetic energy), MATI (mass-analyzed threshold ionization) and PIRI (photo-induced Rydberg ionization) spectroscopy; pulsed-field recombination of ions and electrons; the state selection and reaction of molecular ions; collisions of Rydberg states with neutrals, ions and metallic surfaces; Rydberg tagging and imaging of products of photodissociation; and the control of translational motion and orientation via the use of inhomogeneous fields.

Softley, T. P.

31

Equivalent multipole operators for degenerate Rydberg states

NASA Astrophysics Data System (ADS)

As shown by Pauli, [Z. Phys. 36, 336 (1926)], the electric dipole operator r can be replaced by the Runge-Lenz vector A when operating within the n2 degenerate manifold of hydrogenic states of principal quantum number n . We seek to develop similar rules for higher multipole operators by expressing equivalent operators in terms only of the two vector constants of motion—the orbital angular momentum L and the Runge-Lenz vector A —appropriate to the degenerate hydrogenic shell. Equivalence of two operators means here that they yield identical matrix elements within a subspace of Hilbert space that corresponds to fixed n . Such equivalent-operator techniques permit direct algebraic calculation of perturbations of Rydberg atoms by external fields and often exact analytical results for transition probabilities. Explicit expressions for equivalent quadrupole and octupole operators are derived, examples are provided, and general aspects of the problem are discussed.

Ostrovsky, V. N.; Vrinceanu, D.; Flannery, M. R.

2006-08-01

32

Equivalent multipole operators for degenerate Rydberg states

As shown by Pauli, [Z. Phys. 36, 336 (1926)], the electric dipole operator r can be replaced by the Runge-Lenz vector A when operating within the n{sup 2} degenerate manifold of hydrogenic states of principal quantum number n. We seek to develop similar rules for higher multipole operators by expressing equivalent operators in terms only of the two vector constants of motion - the orbital angular momentum L and the Runge-Lenz vector A - appropriate to the degenerate hydrogenic shell. Equivalence of two operators means here that they yield identical matrix elements within a subspace of Hilbert space that corresponds to fixed n. Such equivalent-operator techniques permit direct algebraic calculation of perturbations of Rydberg atoms by external fields and often exact analytical results for transition probabilities. Explicit expressions for equivalent quadrupole and octupole operators are derived, examples are provided, and general aspects of the problem are discussed.

Ostrovsky, V. N.; Vrinceanu, D.; Flannery, M. R. [V. Fock Institute of Physics, St. Petersburg State University, 198904 St. Petersburg (Russian Federation); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2006-08-15

33

Broad shape resonance effects in CaF Rydberg states.

Results of ab initio R-matrix calculations [S. N. Altunata et al., J. Chem. Phys. 123, 084319 (2005)] indicate the presence of a broad shape resonance in electron-CaF(+) scattering for the (2)Sigma(+) electronic symmetry near the ionization threshold. The properties of this shape resonance are analyzed using the adiabatic partial-wave expansion of the scattered electron wave function introduced by Le Dourneuf et al. [J. Phys. B 15, L685 (1982)]. The qualitative aspects of the shape resonance are explained by an adiabatic approximation on the electronic motion. Mulliken's rule for the structure of the Rydberg state wave functions [R. S. Mulliken, J. Am. Chem. Soc. 86, 3183 (1964)] specifies that, except for an (n*)(-32) amplitude scale factor, every excited state wave function within one Rydberg series is built on an innermost lobe that remains invariant in shape and nodal position as a function of the excitation energy. Mulliken's rule implies a weak energy dependence of the quantum defects for an unperturbed molecular Rydberg series, which is given by the Rydberg-Ritz formula. This zero-order picture is violated by a single (2)Sigma(+) CaF Rydberg series at all Rydberg state energies (n*=5-->infinity, more so with increasing n*) below the ionization threshold, under the broad width of the shape resonance. Such a violation is diagnostic of a global "scarring" of the Rydberg spectrum, which is distinct from the more familiar local level perturbations. PMID:16729809

Altunata, Serhan N; Coy, Stephen L; Field, Robert W

2006-05-21

34

Coherent manipulation of single atom qubits using Rydberg states

NASA Astrophysics Data System (ADS)

This thesis presents experimental observations of the coherent manipulations of Rubidium-87 atoms via two photon excitations. Atoms are cooled using a magneto-optical trap (MOT) into two far off resonance traps (FORT) that are separated by 10 micrometers. State sensitive single atom detection is performed by gathering the fluorescence signal of two atoms trapped in the FORT potentials with an electron-multiplying CCD camera. A custom built multiplexing optical system is used to individually address the FORT potentials. A microwave modulated 780nm laser is used to coherently Rabi flop atoms between the F=1 and F=2 hyperfine ground states via two photon excitations. Cavity stabilized lasers at 780nm and 480nm are used to conduct two photon excitations of F=2 hyperfine ground state atoms to Rydberg states with principal quantum numbers ranging from n=43 to n=97. This experiment is the first to observe coherent Rabi oscillations at megahertz rates between ground and Rydberg levels. These coherent Rydberg Rabi oscillations are used to demonstrate Rydberg blockade at a single atom level for the first time. The Rydberg Rabi oscillations of a target atom are observed to be 75% blockaded by the presence of a Rydberg atom more than 10 micrometers away. This paper reports on the preliminary work towards the first neutral atom controlled-NOT (CNOT) gate, and on preliminary experiments working towards deterministic loading of single atoms in a FORT potential.

Urban, Erich

35

Coherent Excitation of Lithium to Rydberg States and Application to Rydberg Atom Optics

NASA Astrophysics Data System (ADS)

We present a theoretical analysis of several schemes for coherently exciting lithium atoms in a thermal beam to Rydberg states in a four level/three laser system, previously discussed by Oreg et al.(J. Oreg et al.), Phys. Rev. A 45, 4888 (1992). The time evolution of the dressed states and their populations are calculated numerically, solving the optical Bloch equations by a fourth order Runge-Kutta integration. Our code closely models actual experimental conditions, including spontaneous decay, beam profiles, intensities and detunings. Large Rydberg populations (50%) around n=15 may be obtained by non-adiabatic excitation, with each laser power on the order of 1 mW. We discuss the effects of an externally controlled time dependent detuning in the Rydberg state, for example as produced by atoms traversing an inhomogeneous electric field. An understanding of this excitation mechanism is important for large angle reflection of coherently excited atoms using field gradients. Some primitive ideas of Stark-Rydberg atom optics are presented.

Stevens, G.; Widmer, M.; Tudorica, F.; Iu, C.-H.; Metcalf, H.

1996-05-01

36

Very high resolution spectroscopy of high Rydberg states

NASA Astrophysics Data System (ADS)

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

Merkt, F.

1998-05-01

37

Plasma screening within Rydberg atoms in circular states

NASA Astrophysics Data System (ADS)

A Rydberg atom embedded in a plasma can experience penetration by slowly moving electrons within its volume. The original pure Coulomb potential must now be replaced by a screened Coulomb potential which contains either a screening length Rs or a screening factor A = Rs -1 . For any given discrete energy level, there is a Critical Screening Factor (CSF) Ac beyond which the energy level disappears (by merging into the continuum). Analytical results are obtained for the classical dependence of the energy on the screening factor, for the CSF, and for the critical radius of the electron orbit for Circular Rydberg States (CRS) in this screened Rydberg atom. The results are derived for any general form of the screened Coulomb potential and are applied to the particular case of the Debye potential. We also show that CRS can temporarily exist above the ionization threshold and are therefore the classical counterparts of quantal discrete states embedded into continuum. The results are significant not only to Rydberg plasmas, but also to fusion plasmas, where Rydberg states of multi-charged hydrogen-like ions result from charge exchange with hydrogen or deuterium atoms, as well as to dusty/complex plasmas.

Flannery, M. R.; Oks, E.

2008-04-01

38

Autoionization rate constants of zero electron kinetic energy Rydberg states

NASA Astrophysics Data System (ADS)

We have calculated the vibrational and rotational autoionization rate constants for diatomic molecules H2, N2, and HCl in high Rydberg states by employing the density matrix formulation with the inverse Born-Oppenheimer approximation basis set. The purpose is to simulate the main radiationless processes occurring in zero electron kinetic energy (ZEKE) spectroscopy. The quantum numbers and the energy dependences of the calculated autoionization rate constants are represented as the scaling laws via nonlinear regression. These data provide a suitable starting point for quantitative study of the intricate dynamics involved in ZEKE Rydberg states.

Mineo, H.; Wang, Y. H.; Chao, S. D.; Lin, S. H.

2012-03-01

39

Coherent excitation of a single atom to a Rydberg state

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

40

Vibrational autoionization from nf Rydberg states of nitric oxide

NASA Astrophysics Data System (ADS)

The multiphoton ionization spectra of vibrationally excited nf Rydberg states of nitric oxide (NO) molecules are taken by using two-photon double resonance excitation via NO A 2Sigma + states. The optical transition intensities from NO A state to nf Rydberg states were calculated and the results agree very well with the experiment. These results combined with circular dichroism method help us assign the fine structure of nf Rydberg states even in a spectrum of relatively low resolution. Reported in this thesis are the energy levels of these nf (nu, R, N) Rydberg levels converging to NO X 1E+ (nu+ = 1 and 2) with total angular momentum (excluding electronic spin), N from 15 to 28, and principle quantum number, n, from 9 to 18 and ion core rotational quantum number, R, from 14 to 29. Multipole interactions between the Rydberg electron and the ion core is used to explain the fine structure and a corresponding model is used to fit the energy levels to obtain the quadrupole moment and polarizability of the NO+. Energy- and angle-resolved photoelectron spectroscopy (PES) is also used to study the vibrational autoionization from individual nf (nu = 2, R, N) Rydberg levels. The photoelectron spectra are taken and vibrational distribution, rotational distribution, and photoelectron angular distributions are measured. We found (1) the Deltanu = 1 propensity rule is loosely obeyed; (2) Deltanu = 1 and Deltanu = 2 decay paths have dramatically different dynamics; (3) both decay paths involve the angular momentum exchange between the outgoing electron and the molecular-ion core, which can not be explained by multipole interactions or other existing models.

Zhao, Runchuan

41

Interacting Rydberg and valence states in radicals and molecules

NASA Astrophysics Data System (ADS)

This review discusses low-lying (n = 3) Rydberg electronic states of molecules and radicals, in particular those that result in mixed configurations and participate in non-adiabatic interactions. Rydberg-valence interactions are ubiquitous in molecules and radicals and have important effects on potential energy surface shapes, spectroscopy, and dissociation dynamics. The review emphasises selected properties that are affected by these interactions and illustrates them with several examples, mostly involving free radicals, in which collaboration between experimental and theoretical investigations has been crucial for understanding. Specifically, the cases of substituted methyl, vinyl, and hydroxyalkyl radicals are described, as well as Rydberg states of diazomethane and the ethyl radical. The issue of triple conical intersections is also briefly discussed.

Reisler, Hanna; Krylov, Anna I.

42

Resonant collisions of sodium atoms in Rydberg states

A careful numerical solution of the equations of the two-state theory of resonant collisions is presented. The particular process investigated is that of collisions of two sodium atoms in Rydberg states in the presence of a weak static electric field for which measurements have been carried out recently. Dipole-dipole interaction between the atoms is assumed as the interaction responsible for

E. Fiordilino; G. Ferrante; B. M. Smirnov

1987-01-01

43

Rydberg energies using excited state density functional theory.

We utilize excited state density functional theory (eDFT) to study Rydberg states in atoms. We show both analytically and numerically that semilocal functionals can give quite reasonable Rydberg energies from eDFT, even in cases where time dependent density functional theory (TDDFT) fails catastrophically. We trace these findings to the fact that in eDFT the Kohn-Sham potential for each state is computed using the appropriate excited state density. Unlike the ground state potential, which typically falls off exponentially, the sequence of excited state potentials has a component that falls off polynomially with distance, leading to a Rydberg-type series. We also address the rigorous basis of eDFT for these systems. Perdew and Levy have shown using the constrained search formalism that every stationary density corresponds, in principle, to an exact stationary state of the full many-body Hamiltonian. In the present context, this means that the excited state DFT solutions are rigorous as long as they deliver the minimum noninteracting kinetic energy for the given density. We use optimized effective potential techniques to show that, in some cases, the eDFT Rydberg solutions appear to deliver the minimum kinetic energy because the associated density is not pure state v-representable. We thus find that eDFT plays a complementary role to constrained DFT: The former works only if the excited state density is not the ground state of some potential while the latter applies only when the density is a ground state density. PMID:19045011

Cheng, Chiao-Lun; Wu, Qin; Van Voorhis, Troy

2008-09-28

44

Rydberg energies using excited state density functional theory

We utilize excited state density functional theory (eDFT) to study Rydberg states in atoms. We show both analytically and numerically that semilocal functionals can give quite reasonable Rydberg energies from eDFT, even in cases where time dependent density functional theory (TDDFT) fails catastrophically. We trace these findings to the fact that in eDFT the Kohn-Sham potential for each state is computed using the appropriate excited state density. Unlike the ground state potential, which typically falls off exponentially, the sequence of excited state potentials has a component that falls off polynomially with distance, leading to a Rydberg-type series. We also address the rigorous basis of eDFT for these systems. Perdew and Levy have shown using the constrained search formalism that every stationary density corresponds, in principle, to an exact stationary state of the full many-body Hamiltonian. In the present context, this means that the excited state DFT solutions are rigorous as long as they deliver the minimum noninteracting kinetic energy for the given density. We use optimized effective potential techniques to show that, in some cases, the eDFT Rydberg solutions appear to deliver the minimum kinetic energy because the associated density is not pure state v-representable. We thus find that eDFT plays a complementary role to constrained DFT: The former works only if the excited state density is not the ground state of some potential while the latter applies only when the density is a ground state density.

Cheng, C.-L.; Wu Qin; Van Voorhis, Troy [Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States)

2008-09-28

45

Rydberg energies using excited state density functional theory

NASA Astrophysics Data System (ADS)

We utilize excited state density functional theory (eDFT) to study Rydberg states in atoms. We show both analytically and numerically that semilocal functionals can give quite reasonable Rydberg energies from eDFT, even in cases where time dependent density functional theory (TDDFT) fails catastrophically. We trace these findings to the fact that in eDFT the Kohn-Sham potential for each state is computed using the appropriate excited state density. Unlike the ground state potential, which typically falls off exponentially, the sequence of excited state potentials has a component that falls off polynomially with distance, leading to a Rydberg-type series. We also address the rigorous basis of eDFT for these systems. Perdew and Levy have shown using the constrained search formalism that every stationary density corresponds, in principle, to an exact stationary state of the full many-body Hamiltonian. In the present context, this means that the excited state DFT solutions are rigorous as long as they deliver the minimum noninteracting kinetic energy for the given density. We use optimized effective potential techniques to show that, in some cases, the eDFT Rydberg solutions appear to deliver the minimum kinetic energy because the associated density is not pure state v-representable. We thus find that eDFT plays a complementary role to constrained DFT: The former works only if the excited state density is not the ground state of some potential while the latter applies only when the density is a ground state density.

Cheng, Chiao-Lun; Wu, Qin; van Voorhis, Troy

2008-09-01

46

Spectroscopy and dynamics of vibrationally autoionizing nitric oxide Rydberg states

NASA Astrophysics Data System (ADS)

Vibrationally autoionizing Rydberg states of nitric oxide are studied to learn about the dynamics of this nonadiabatic (Born-Oppenheimer violating) process. Most of chemical physics is described in terms of the Born-Oppenheimer approximation, in which the nuclei are assumed to be moving too slowly to interact with the motion of the electrons. This thesis presents the study of a specific case where this approximation breaks down. A new theoretical development based on multichannel quantum defect theory (MQDT) is derived, demonstrating the energy dependence of photoelectron dynamics through a weakly autoionizing Rydberg state. This model of resonance mediated photoionization is compared to a first order perturbation theory model of bound-continuum mixing. The two models are shown to predict equivalent results for angular distribution measurements from optically prepared, weakly autoionizing Rydberg states with minimal contribution from direct photoionization. Spectra are reported for Rydberg states converging to the NO+ X (v+ = 1) with total angular momentum, N, from 19--27, and principal quantum number, n, from 11--18. The spectra were recorded by measuring ion current produced by vibrational autoionization of the prepared states. Spectral features were identified by a combination of techniques, including simulations and circular dichroism. Resonant energies were fit to an MQDT expression using a nonlinear least-squares algorithm to extract phase shift parameters of closed-channel K matrix for s, p, and d channels. Eigen defects deduced from this fit are reported for the (v = 1) musd1sigma, mu sd2sigma, mud pi, muddelta, mu psigma, and mup pi channels. Time-of-flight photoelectron spectra and photoelectron angular distributions are reported for seven Rydberg states in the NO (v = 1) s--d complex. A previously reported analysis of the 14 s(v = 1, R = 20) Rydberg state is corrected, and the conclusions from that report are re-evaluated. Significant lambda mixing resulting from vibrational autoionization is confirmed, indicating significant contribution from long-range coupling between the bound states and the continuum.

Konen, Ian Michael

47

Lifetimes of heavy-Rydberg ion-pair states formed through Rydberg electron transfer

NASA Astrophysics Data System (ADS)

The lifetimes of K+..Cl-, K+..CN-, and K+..SF6- heavy-Rydberg ion-pair states produced through Rydberg electron transfer reactions are measured directly as a function of binding energy using electric field induced detachment and the ion-pair decay channels discussed. The data are interpreted using a Monte Carlo collision code that models the detailed kinematics of electron transfer reactions. The lifetimes of K+..Cl- ion-pair states are observed to be very long, >100 ?s, and independent of binding energy. The lifetimes of strongly bound (>30 meV) K+..CN- ion pairs are found to be similarly long but begin to decrease markedly as the binding energy is reduced below this value. This behavior is attributed to conversion of rotational energy in the CN- ion into translational energy of the ion pair. No long-lived K+..SF6- ion pairs are observed, their lifetimes decreasing with increasing binding energy. This behavior suggests that ion-pair loss is associated with mutual neutralization as a result of charge transfer.

Cannon, M.; Wang, C. H.; Dunning, F. B.; Reinhold, C. O.

2010-08-01

48

Lifetimes of Heavy-Rydberg Ion-Pair States Formed through Rydberg Electron Transfer

The lifetimes of K{sup +}-Cl{sup -}, K{sup +}-CN{sup -}, and K{sup +}-SF{sub 6}{sup -} heavy-Rydberg ion-pair states produced through Rydberg electron transfer reactions are measured directly as a function of binding energy using electric field induced detachment and the ion-pair decay channels discussed. The data are interpreted using a Monte Carlo collision code that models the detailed kinematics of electron transfer reactions. The lifetimes of K{sup +}-Cl{sup -} ion-pair states are observed to be very long, >100 {micro}s, and independent of binding energy. The lifetimes of strongly bound (>30 meV) K{sup +}-CN{sup -} ion pairs are found to be similarly long but begin to decrease markedly as the binding energy is reduced below this value. This behavior is attributed to conversion of rotational energy in the CN{sup -} ion into translational energy of the ion pair. No long-lived K{sup +}-SF{sub 6}{sup -} ion pairs are observed, their lifetimes decreasing with increasing binding energy. This behavior suggests that ion-pair loss is associated with mutual neutralization as a result of charge transfer.

Cannon, M. [Rice University; Wang, C. H. [Rice University; Dunning, F. B. [Rice University; Reinhold, Carlos O [ORNL

2010-01-01

49

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

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

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

1996-05-01

50

NASA Astrophysics Data System (ADS)

We provide a scheme with which the transfer of the entangled state and the entanglement swapping can be realized in a system of neutral atoms via the Rydberg blockade. Our idea can be extended to teleport an unknown atomic state. According to the latest theoretical research of the Rydberg excitation and experimental reports of the Rydberg blockade effect in quantum information processing, we discuss the experimental feasibility of our scheme.

Deng, Li; Chen, Ai-Xi; Zhang, Jian-Song

2011-11-01

51

Auto transfer to Rydberg states during ion-atom collisions

Electron capture by slow multiply charged ions colliding on rare-gas targets is known to populate highly excited states of the projectile. On the basis of experimental measurement of energy and angle differential cross-sections we have shown that capture to a resonant doubly excited state may lead to Autoionizing Double Capture (ADC) as well as to True Double Capture (TDC). In this model TDC appears as a two step post-collisional process, the state populated by the collision decays to (or delutes into) a dense adjacent Rydberg series, followed by radiative deexcitation of the inner electron of the (3,n) Rydberg states. We report here new experimental observations in electron spectra measured in [ital N][sup 7+]+[ital He]. Auto transfer to Rydber states has also important consequences on the determination of the lifetime of the autoionizing states, some discrepancies between theoretical width values for low [ital N][sup 5+](4,4) resonant states will be discussed and partially resolved.

Bachau, H.; Harel, C. (Laboratoire des Collisions Atomiques, Unite Propre de Recherche 260 du CNRS, Universite Bordeaux I, 351 Cours de la Liberation, 33405 Talence (France)); Barat, M.; Roncin, P. (Laboratoire des Collisions Atomiques et Moleculaires, Unite associee 281 du CNRS, Universite de Paris Sud, Batiment 351, 91405 Orsay (France)); Bordenave-Montesquieu, A.; Moretto-Capelle, P.; Benoit-Cattin, P.; Gleizes, A.; Benhenni, M. (IRSAMC, Unite associee 770 du CNRS, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse (France))

1993-06-05

52

Optical spectroscopy of high-L Rydberg states of nickel

Binding energies of 23 Rydberg fine-structure levels of Ni with n = 9 and L{>=}5 were measured using resonant excitation Stark ionization spectroscopy. From this spectrum, the quadrupole moment and the scalar and tensor dipole polarizability of the {sup 2}D{sub 5/2} ground state of Ni{sup +} were determined to be Q=-0.474(2), {alpha}{sub d,0}=7.92(6), and {alpha}{sub d,2}=1.15(14) a.u. The electric hexadecapole moment was determined to be -0.33(21) a.u.

Keele, Julie A.; Woods, Shannon L.; Hanni, M. E.; Lundeen, S. R.; Sturrus, W. G. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States); Department of Physics, Youngstown State University, Youngstown, Ohio 44555 (United States)

2010-02-15

53

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

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

Leif Holmlid

1998-01-01

54

Excitation of weakly bound molecules to trilobitelike Rydberg States.

We observe "trilobitelike" states of ultracold ^{85}Rb_{2} molecules, in which a ground-state atom is bound by the electronic wave function of its Rydberg-atom partner. We populate these states through the ultraviolet excitation of weakly bound molecules, and access a regime of trilobitelike states at low principal quantum numbers and with vibrational turning points around 35 Bohr radii. This demonstrates that, unlike previous studies that used free-to-bound transitions, trilobitelike states can also be excited through bound-to-bound transitions. This approach provides high excitation probabilities without requiring high-density samples, and affords the ability to control the excitation radius by selection of the initial-state vibrational level. PMID:23952391

Bellos, M A; Carollo, R; Banerjee, J; Eyler, E E; Gould, P L; Stwalley, W C

2013-07-29

55

Rydberg states of chloroform studied by VUV photoabsorption spectroscopy

NASA Astrophysics Data System (ADS)

The VUV photoabsorption spectra of CHCl3 and CDCl3 in the energy region 6.2-11.8 eV (50,000-95,000 cm-1) have been investigated using synchrotron radiation from the Indus-1 source. Rydberg series converging to the first four ionization limits at 11.48, 11.91, 12.01 and 12.85 eV corresponding to excitation from the 1a2, 4a1, 4e, 3e, orbitals of CHCl3 respectively are identified and analyzed. Quantum defect values are observed to be consistent with excitation from the chlorine lone pair orbitals. Vibrational progressions observed in the region of 72,500-76,500 cm-1 have been reassigned to ?3 and combination modes of ?3+?6 belonging to the 1a2?4p transition in contrast to earlier studies where they were assigned to a ?3 progression superimposed on the 3e?4p Rydberg transition. The assignments are further confirmed based on isotopic substitution studies on CDCl3 whose VUV photoabsorption spectrum is reported here for the first time. The frequencies of the ?3 and ?6 modes in the 4p Rydberg state of CHCl3 (CDCl3) are proposed to be ~454 (409) cm-1 and~130 (129) cm-1 respectively based on the vibronic analysis. DFT calculations of neutral and ionic ground state vibrational frequencies support the vibronic analysis. Experimental spectrum is found to be in good agreement with that predicted by TDDFT calculations. This work presents a consolidated analysis of the VUV photoabsorption spectrum of chloroform.

Singh, Param Jeet; Shastri, Aparna; D'Souza, R.; Jagatap, B. N.

2013-11-01

56

Dissociative ionization of sodium molecules via repulsive Rydberg states

NASA Astrophysics Data System (ADS)

In this thesis, an investigation of two color resonance multiphoton ionization (REMPI) and fragmentation processes in Na2 has been performed in combination with Linear Time-of-Flight Mass Spectrometry technique. The ionization and dissociative ionizations channels in the energy range up to 2500cm -1 above the dissociative ionization threshold into Na(3s)+Na ++e have been studied. After a mild supersonic expansion from the beam source, neutral sodium dimers in the ground state have been produced. Two tunable, pulsed lasers excite Na2 molecules via the intermediate A1S+u state to a single ro-vibrational level of the second intermediate 21pig state. Following absorption of a third photon, the total energy is above the dissociation limit into Na(3s) + Na+ + e. Typically, a small portion of atomic ions is produced under our experimental conditions. By varying the total available energy below and through the doubly excited states correlating with the Na(3p)+Na(4s) atom pair, there is no evidence that the doubly excited states positioned in the ionic continuum get involved. By calculation of the expected transition probabilities for all possible channels which can decay directly and indirectly into atomic ions, I find that direct dissociative ionization via 12S+u is impossible. The transition probabilities for dissociative ionization via the repulsive Rydberg states with principal quantum numbers n from 5˜12 converging toward the 12S+u state are three to four orders of magnitude larger than those for direct ionization into the continuum of the X2S+g ground state. These repulsive Rydberg states are much more likely to play a role in the photo-ionization through the intermediate 21Pg state. A semi-classical model which was originally developed for negative ion dissociative attachment (O'MAL'67) describes how dissociative ionization occurs along the repulsive Rydberg states. Its prediction concerning the ratio of atomic to molecular ion production as a function of initial state and excess energy is compared with the experimental findings. The model agrees reasonable well both with the trend and the quantitative magnitude of the experimental results. This thesis also includes some measurements of the polarization dependence of the TOF spectra as well as an analysis of the angular distributions of the slow fragment Na+. Reference: (O'MAL'67) O'Malley, T. F., Phys. Rev.155,59(1967)

Chen, Hong

57

Enhanced electron attachment to Rydberg states in molecular hydrogen volume discharges

We review recent studies on negative ion formation and studies in other areas that are relevant to the role of high-Rydberg states of H{sub 2} and H{sub 3} in hydrogen negative ion sources. Possible mechanisms for the formation of these excited states are discussed, including the formation of long-lived superexcited (core-excited) Rydberg states. Experimental evidence for negative ion formation via electron attachment to core-excited Rydberg states in a glow discharge apparatus is presented. An expression for the dissociative electron attachment rate constant for Rydberg molecules is derived based on electron capture by a Rydberg molecule due to polarization interaction. {copyright} {ital 1999 American Institute of Physics.}

Pinnaduwage, L.A.; Ding, W.X.; McCorkle, D.L. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6122 (United States); Lin, S.H.; Mebel, A.M. [Institute of Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10764, Taiwan, Republic of (China); Garscadden, A. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States)

1999-05-01

58

Bound states using the R-matrix method: Rydberg states of HeH

A method is presented for adapting scattering calculations performed with the molecular R-matrix method to find bound states based on the atomic method of Seaton. Quantum defect theory is used to determine initial energy grids and to determine whether all the bound states have been located. This method is particularly suited to the Rydberg states of electron plus molecular ion

B. K. Sarpal; S. E. Branchett; J. Tennyson; L. A. Morgan

1991-01-01

59

Infrared vibrational spectroscopy of cis-dichloroethene in Rydberg states

NASA Astrophysics Data System (ADS)

We have measured the infrared (IR) vibrational spectrum for cis-dichloroethene (cis-ClCH=CHCl) in excited Rydberg states with the effective principal quantum numbers n*=9, 13, 17, 21, 28, and 55 using the vacuum ultraviolet-IR-photoinduced Rydberg ionization (VUV-IR-PIRI) scheme. Although the IR frequencies observed for the vibrational bands ?11* (asymmetric C-H stretch) and ?12* (symmetric C-H stretch) are essentially unchanged for different n* states, suggesting that the IR absorption predominantly involves the ion core and that the Rydberg electron behaves as a spectator; the intensity ratio for the ?11* and ?12* bands [R(?11*/?12*)] is found to decrease smoothly as n* is increased. This trend is consistent with the results of a model ab initio quantum calculation of R(?11*/?12*) for excited cis-ClCH=CHCl in n*=3-18 states and the MP2/6-311++G(2df,p) calculations of R(?11/?12) and R(?11+/?12+), where R(?11/?12)[R(?11+/?12+)] represents the intensity ratio of the ?11(?11+) asymmetric C-H stretching to the ?12(?12+) symmetric C-H stretching vibrational bands for cis-ClCH=CHCl (cis-ClCH=CHCl+). We have also measured the IR-VUV-photoion (IR-VUV-PI) and IR-VUV-pulsed field ionization-photoelectron depletion (IR-VUV-PFI-PED) spectra for cis-ClCH=CHCl. These spectra are consistent with ab initio calculations, indicating that the IR absorption cross section for the ?12 band is negligibly small compared to that for the ?11 band. While the VUV-IR-PIRI measurements have allowed the determination of ?11+=3067+/-2 cm-1, ?12+=3090+/-2 cm-1, and R(?11+/?12+)~1.3 for cis-ClCH=CHCl+, the IR-VUV-PI and IR-VUV-PFI-PED measurements have provided the value ?11=3088.5+/-0.2 cm-1 for cis-ClCH=CHCl.

Wang, P.; Woo, H. K.; Lau, K.-C.; Xing, X.; Ng, C. Y.; Zyubin, A. S.; Mebel, A. M.

2006-02-01

60

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

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

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

2006-12-15

61

Helium Resources of the United States, 2007.

National Technical Information Service (NTIS)

Technical Note 429, Helium Resources of the United States2007, is an assessment of the total estimated helium reserves and resources of the United States. This assessment is made using estimates of natural gas resources from the Potential Gas Committee (P...

N. Pacheco S. F. Ali

2008-01-01

62

New measurement of the Rydberg constant by two-photon spectroscopy of hydrogen Rydberg states

We have made wavelength measurements of the three transitions 2S-8D, 2S-10D, and 2S-12D in atomic hydrogen and deuterium to determine a new value for the Rydberg constant, R?=109 737.315 709 (18) cm-1, currently the most precise one. As reference we made use of an I2-stabilized He-Ne laser, compared to the standards of the Bureau International des Poids et Mesures. The

F. Biraben; J. C. Garreau; L. Julien; M. Allegrini

1989-01-01

63

NASA Astrophysics Data System (ADS)

The variations in the population densities of Rydberg states (with principal quantum number n ~ 50 — 100) in an expanding ultracold laser plasma (Ne ~ 109 — 104 cm-3, Te ~ 10 — 0.5 K) are calculated. The electron temperature measurement from the population densities of Rydberg states (T C Killian et al., Phys. Rev. Lett., vol. 86, p. 3759, 2001) is shown to be described by the conventional three-body recombination theory with the inclusion of recombination heating of free electrons.

Tkachev, Aleksei N.; Yakovlenko, Sergei I.

2001-12-01

64

Sub-Poissonian Statistics of Rydberg-Interacting Dark-State Polaritons

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

65

Absorption Spectrum of CO in the Hopfield Helium Continuum Region.

National Technical Information Service (NTIS)

The high resolution absorption spectrum of CO has been reinvestigated in the Hopfield helium continuum region, particularly from 960 to 1080A. One Rydberg State was extended and other Rydberg states, which are converging to the ground state of CO, have be...

S. Ogawa M. Ogawa

1973-01-01

66

Fundamental Constants and Tests of Theory in Rydberg States of Hydrogenlike Ions

A comparison of precision frequency measurements to quantum electrodynamics (QED) predictions for Rydberg states of hydrogenlike ions can yield information on values of fundamental constants and test theory. With the results of a calculation of a key QED contribution reported here, the uncertainty in the theory of the energy levels is reduced to a level where such a comparison can yield an improved value of the Rydberg constant.

Jentschura, Ulrich D. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8420 (United States); Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Mohr, Peter J.; Tan, Joseph N. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8420 (United States); Wundt, Benedikt J. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

2008-04-25

67

Fundamental constants and tests of theory in Rydberg states of hydrogenlike ions.

A comparison of precision frequency measurements to quantum electrodynamics (QED) predictions for Rydberg states of hydrogenlike ions can yield information on values of fundamental constants and test theory. With the results of a calculation of a key QED contribution reported here, the uncertainty in the theory of the energy levels is reduced to a level where such a comparison can yield an improved value of the Rydberg constant. PMID:18518170

Jentschura, Ulrich D; Mohr, Peter J; Tan, Joseph N; Wundt, Benedikt J

2008-04-22

68

The Rydberg constant is one of the most important constants of atomic physics bemuse of its connection with the fundamental atomic constants (e, h, mc, c), and because of the high accuracy with which it can be determined. In this review the Rydberg constant is seen in its historical context, in relation to the spectra of hydrogen and ionized helium,

1974-01-01

69

Magnetic stabilization of a Rydberg quasimolecule in circular states

NASA Astrophysics Data System (ADS)

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

Flannery, M. R.; Oks, E.

2006-01-01

70

Magnetic stabilization of a Rydberg quasimolecule in circular states

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

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

2006-01-15

71

New measurement of the Rydberg constant by two-photon spectroscopy of hydrogen Rydberg states

We have made wavelength measurements of the three transitions 2S-8D, 2S-10D, and 2S-12D in atomic hydrogen and deuterium to determine a new value for the Rydberg constant, R/sub infinity/ = 109 737.315 709 (18) cm/sup -1/, currently the most precise one. As reference we made use of an I/sub 2/-stabilized He-Ne laser, compared to the standards of the Bureau International des Poids et Mesures. The H-D isotopic shifts have also been measured and a value for the proton-to-electron mass ratio deduced: m/sub p//m/sub e/ = 1836.152 59 (24).

Biraben, F.; Garreau, J.C.; Julien, L.; Allegrini, M.

1989-02-06

72

Two-color photoexcitation of Rydberg states via an electric quadrupole transition

We report the observation of an electric quadrupole transition between the 4s{sup '}[1/2]{sub 0}{sup o} and 3d[3/2]{sub 2}{sup o} states in the spectrum of argon and use it in the first step of a scheme to excite Rydberg states. The initial identification of the transition is based on one-color, two-photon photoionization. A different experiment utilizing two-color, two-photon photoexcitation to Rydberg states confirms the identification. Despite the unavoidable background of one-color, two-photon photoionization, the latter experimental technique makes possible two-photon spectroscopy of Rydberg states using a resonant intermediate state populated by an electric quadrupole transition.

Li Leping; Gu Quanli; Knee, J. L. [Department of Chemistry, Wesleyan University, Middletown, Connecticut 06459 (United States); Wright, J. D.; DiSciacca, J. M.; Morgan, T. J. [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States)

2008-03-15

73

Excited state positronium collisions with helium

NASA Astrophysics Data System (ADS)

Calculations of the discrete positronium (Ps) transition Ps(2s) ? Ps(2p) in collisions with ground state helium are reported. Results are presented at total and single differential levels. Calculations are made within the first born approximation (FBA). The Hartley Walters approximation is used to sum over all possible final excited atom states. In addition, impulse approximation (IA) calculations are reported for Ps(2s) and Ps(2p) fragmentation collisions with ground state helium, where the atom does not change state. Again, the FBA with the HWA is used to account for collisions in which the atom is excited or ionized.

Starrett, C.; Walters, H. R. J.; McAlinden, Mary T.

2008-02-01

74

High-resolution spectroscopy of Rydberg states in an ultracold cesium gas

NASA Astrophysics Data System (ADS)

Transitions between high Rydberg states of 133Cs atoms have been studied by high-resolution millimeter-wave spectroscopy of an ultracold sample. The spectroscopic measurements were performed after releasing the atoms from a magneto-optical trap. Switching off all trapping fields and compensating the stray electric and magnetic fields to below 1 mV/cm and 2 mG, respectively, prior to the spectroscopic measurement enabled the recording of millimeter-wave spectra of Rydberg states with principal quantum number beyond n=100 under conditions where the inhomogeneous broadening by stray fields is minimal and no dephasing of the Rydberg-atom sample can be detected over measurement times up to 60 ?s. The Fourier-transform-limited line widths of better than 20 kHz enabled the observation of the hyperfine structure of nS and nP Rydberg states of Cs beyond n=90. The analysis of the line shapes of transitions to Rydberg states with n?230 indicated that field inhomogeneities across the atomic sample represent the dominant cause of spectral broadening at high n values. The analysis also revealed that the initial polarization of the atomic sample (F=4, MF=4) is preserved for several tens of microseconds, the depolarization being caused by slow precession along the magnetic stray fields.

Saßmannshausen, H.; Merkt, F.; Deiglmayr, J.

2013-03-01

75

Fine structure measurements of high-L Rydberg states of H2.

NASA Astrophysics Data System (ADS)

Measurement of the fine structure pattern of high-angular momentum Rydberg states provides information about the basic properties of the ion core, such as the polarizability. Recently a resonant excitation Stark ionization spectroscopy (RESIS) apparatus has been constructed at the SUNY Fredonia campus. A Doppler-tuned CO2 laser resonantly excites transitions in a fast molecular beam, which are detected by Stark ionization. We report here our experimental progress in the fine structure measurements of high-L Rydberg states of the ground vibrational state of molecular hydrogen.

Svanidze, Eteri; Johnson, Spencer; Snow, Erica

2008-05-01

76

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

77

NASA Astrophysics Data System (ADS)

Infrared spectra of phenol-rare gas clusters in high- n Rydberg states were measured. Both free and hydrogen-bonded OH stretching vibrations were observed in the infrared spectra. ? ? H site switching of rare gas was observed even in high- n Rydberg states.

Miyazaki, Mitsuhiko; Tanaka, Shinya; Ishiuchi, Shun-Ichi; Dopfer, Otto; Fujii, Masaaki

2011-09-01

78

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

The ({ital X} {sup 2}{Sigma}{sup +}{sub {ital g}}){ital np} Rydberg states converging to the {ital X} {sup 2}{Sigma}{sup +}{sub {ital g}}, {ital v}{sup +}{ge}9 ionization thresholds of molecular hydrogen were excited by double-resonance excitation via the {ital E},{ital F} {sup 1}{Sigma}{sup +}{sub {ital g}}, {ital v} = 6 level. The energy region of interest (139 500--140 000 cm{sup {minus}1}) included the {ital X} {sup 2}{Sigma}{sup +}{sub {ital g}}, {ital v}{sup +}=9, {ital N}{sup +}=0--3 ionization thresholds as well as the energetic threshold for ion pair formation. The decay of the autoionizing Rydberg states was studied by both conventional and constant-ionic-state photoelectron spectrometry. The results support the {Delta}{ital v}=minimum propensity rule for vibrational autoionization of Rydberg states with a high level of vibrational excitation. However, the relative intensities of the ({ital X} {sup 2}{Sigma}{sup +}{sub {ital g}}){ital np}, {ital v}{prime}{ge} 9 Rydberg series converging to different rotational levels of the ion are dramatically different from those for the analogous Rydberg series with {ital v}{prime}{le}2. In addition, the two-color photoelectron spectrum via the {ital E},{ital F} {sup 1}{Sigma}{sub {ital g}}{sup +}, {ital v}=6 level shows considerable intensity in the {ital v}{sup +}=7 and 8 photoelectron bands both on and off resonance, in marked contrast with the single-color photoelectron spectrum obtained for the same intermediate levels. These observations may be due to the dependence of the transition dipole matrix elements on the internuclear distance and to the presence of doubly excited electronic states that cross the H{sub 2+} {ital X} {sup 2}{Sigma}{sup +}{sub {ital g}} potential curve at a total energy close to that accessed by the two-color excitation scheme.

Pratt, S.T.; Dehmer, P.M.; Dehmer, J.L. (Argonne National Laboratory, Argonne, Illinois 60439 (United States))

1992-09-01

79

NASA Astrophysics Data System (ADS)

Photodissociation efficiency spectrum of anionic oxygen atom produced via ion-pair dissociations of carbon dioxide is recorded by means of the synchrotron radiation excitation (XUV photon energy 17.40-20.00 eV). The present spectrum is assigned as the Rydberg-like excited ion-pair states, i.e., Tanaka-Ogawa and Henning series, tilde C2?g+ (CO+2) vibrational ground-state and excitation series. Three Rydberg series, np?u, np?u, and nfu, converging to tilde C2?g+ (0, 0, 0), show the higher cross sections.

Feng, Qiang; Xu, Yun-Feng; Sun, Jin-Da; Tian, Shan-Xi; Shan, Xiao-Bin; Liu, Fu-Yi; Sheng, Liu-Si

2009-10-01

80

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

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

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

2012-01-01

81

Microwave and laser spectroscopy of high-L Rydberg states of H(2) and its isotopes

NASA Astrophysics Data System (ADS)

The highest-L (>=4), n = 9, 10 Rydberg levels of H2, HD, and D2 were studied in a fast molecular beam, using both optical and microwave spectroscopy. This is the first systematic study of high-L Rydberg states in all three isotopes. Both spectroscopic methods were based on Stark ionization of Rydberg levels resonantly excited by a Doppler-tuned CO2 laser. The laser excitation spectrum gave optical spectra with linewidths of ~300 MHz (0.01 cm-1). Microwave spectra were obtained using the selective laser excitation for detection of microwave-induced transitions, which gave linewidths of about 1 MHz. The Rydberg fine structure revealed in the optical spectroscopy was almost identical in all three isotopes. Some differences in the structure, due to differences in the quadrupole moments of the three ions, were clearly observed, especially for the heteronuclear HD+ ion. However, the most significant variations in the spectra, observed for the three isotopes, were in the relative line intensities. The Pauli exclusion principle favored odd R rotational states in H2, favored even R rotational states in D2, and had no effect on the asymmetric HD molecule. Microwave spectroscopy was used to study high-L Rydberg fine structure of the H2 and D2 n = 9, 10 Rydberg levels bound to the ground (? = 0,R = 0) states of H2+ and D2+. The measured fine structure intervals were analyzed within the polarization model, and yielded precise values for the scalar adiabatic dipole polarizabilities of both ion ground states. The measured polarizabilities were, for (0,0)H2+,/ ?s=3.1680(7)/ ao3 and, for (0,0)D2+,/ ?s=3.0716(4)/ ao3. These measurements have already motivated improvements to existing theoretical treatments of this simplest molecule.

Jacobson, Phillip Lee

1998-11-01

82

Structure and dynamics of higher vibronic levels in the methyl radical Rydberg 3s state

The structure and dynamics of vibronic levels in the methylradical Rydberg 3s state above the origin were examined by far-ultraviolet resonance Raman spectroscopy. Rotationally resolved Raman excitation profiles were obtained for the CD{sub 3} [0100] level of the Rydberg 3s state. The dissociation rates from the CD{sub 3} [0100] level were observed to be 2 times faster than those from the [0000] level. The Raman excitation profile analysis yields 47 271 cm{sup {minus}1} for the band origin of the [0100]-[0100] ground to Rydberg 3s absorption (X {sup 2}A{sub 2}{sup {double_prime}} {r_arrow} B {sup 2}A{sub 1} {sup {prime}}). The out-of-plane bend frequency, v{sub 2}{sup prime}, in the Rydberg 3s state is determined to be 1094 cm{sup {minus}1}. The structure and dynamics of the CH{sub 3} [1000]-[0000] vibronic transition were examined. Q branch excitation profiles of the v{sub 1} and 2v{sub 1} Raman features place the [1000]-[000] band origin at 206.85 nm. The Rydberg 3s state symmetric stretching frequency, v{sub 1}{sup prime}, is consequently estimated to be 2040 cm{sup {minus}1}. The dephasing nm. The Rydberg 3s state symmetric stretching frequency, v{sub 1}{sup prime}, is consequently estimated to be 2040 cm{sup {minus}1} The dephasing constant in the [1000] level is determined to be approximately 400 cm{sup {minus}1}, corresponding to a predissociation lifetime of 13 fs. 27 refs., 7 figs., 2 tabs.

Westre, S.G.; Gansberg, T.E.; Kelly, P.B. [Univ. of California, Davis, CA (United States)] [and others

1992-04-30

83

Perturbations in the Spectra of High Rydberg States: Channel Interactions, Stark and Zeeman Effects

NASA Astrophysics Data System (ADS)

Rydberg states of principal quantum number n?50 have been prepared by irradiation of an atomic beam of xenon with vacuum ultraviolet (VUV) radiation. Narrowband submillimeter-wave (THz) radiation was then used to record spectra of transitions from these Rydberg states to higher or lower-lying Rydberg states. The transitions were detected by selective field ionization and recording either the electrons or the ions, the latter offering the advantage of mass selection. Rydberg states of high principal quantum number are extremely sensitive to their environment, which can be exploited to characterize the experimental conditions under which the spectroscopic measurements are carried out. The high resolution achieved in the experiments (better than 100 kHz) enabled the study of the spectral lineshapes and line positions in dependence of weak electric (down to below 100?V/cm) and magnetic fields (down to a few ?T), and of the density of Rydberg atoms and ions generated in the experimental volume. The experiments rely on the use of a pulsed, broadly tunable, laser-based source of THz radiation for survey scans, and of a phase- and frequency-stabilized submillimeter-wave backward-wave oscillator-based radiation source for precision measurements. To illustrate the use of these sources, we present the results of the spectroscopic investigations of the hyperfine structure of 129Xe Rydberg states in spectral regions where s-d interactions are expected to play a role. F. Merkt and A. Osterwalder Int. Rev. Phys. Chem. 21, 385, (2002). J. Liu and F. Merkt Appl. Phys. Lett. 93, 131105, (2008). M. Schäfer, M. Andrist, H. Schmutz, F. Lewen, G. Winnewisser and F. Merkt J. Phys. B: At. Mol. Opt. Phys. 39, 831, (2006).

Haase, Christa; Schäfer, Martin; Hogan, Stephen D.; Merkt, Frédéric

2011-06-01

84

GHz Rabi Flopping to Rydberg States in Hot Atomic Vapor Cells

NASA Astrophysics Data System (ADS)

We report on the observation of Rabi oscillations to a Rydberg state on a time scale below 1 ns in thermal rubidium vapor. We use a bandwidth-limited pulsed excitation and observe up to 6 full Rabi cycles within a pulse duration of ˜4ns. We find good agreement between the experiment and numerical simulations based on a surprisingly simple model. This result shows that fully coherent dynamics with Rydberg states can be achieved even in thermal atomic vapor, thus suggesting small vapor cells as a platform for room-temperature quantum devices. Furthermore, the result implies that previous coherent dynamics in single-atom Rydberg gates can be accelerated by 3 orders of magnitude.

Huber, B.; Baluktsian, T.; Schlagmüller, M.; Kölle, A.; Kübler, H.; Löw, R.; Pfau, T.

2011-12-01

85

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

86

NASA Astrophysics Data System (ADS)

A mode-locked tunable Ti:Sapphire oscillator has been synchronized with the time structure of a storage ring and used to study the photoionization of noble gases. In multi-bunch operation of the ring the setup permits the observation of the dynamics from a few nanoseconds down to the tens of picoseconds range. The characteristics of the setup are demonstrated by following the two-color ionization of helium (via the 1s3p 1Po state) and argon (via the 3p5 (2P3/2) 3d state). In the CW mode we have also examined the two-color ionization of neon via the 2p5 (2P1/2) 3d? state. In neon the nf? Rydberg series was followed up to n˜50, and the quantum defect was determined.

Moise, Angelica; Alagia, Michele; Banchi, Luca; Ferianis, Mario; Prince, Kevin C.; Richter, Robert

2008-04-01

87

Production of autoionizing Rydberg states by transfer excitation in high energy ion atom collisions

The method of zero-degree Auger spectroscopy was used to study the production of autoionizing Rydberg states in collisions of carbon and oxygen projectiles incident at several MeV on He gas and carbon foils. The autoionization electrons were measured with high resolution so that the quantum defect corresponding to the angular momenta of the Rydberg electrons could be observed. The main purpose of the present experiment is to gain information about the n and l distribution of the Rydberg electron captured in the collision. The well-known n/sup -3/ law is confirmed. For the He gas target it is found that the angular momenta p and d are predominantly produced. For the foil target the higher angular momenta are clearly enhanced. 15 refs., 6 figs.

Stolterfoht, N.; Miller, P.D.; Krause, H.F.; Yamazaki, Y.; Dittner, P.F.; Pepmiller, P.L.; Sellin, I.A.; Datz, S.

1986-01-01

88

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

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

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

2011-11-15

89

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

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

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

2009-08-14

90

Ab initio study of valence and Rydberg states of CH3Br.

We performed configuration interaction ab initio calculations on the valence and 5s, 5p(a(1)), and 5p(e) Rydberg bands of the CH(3)Br molecule as a function of the methyl-bromide distance for frozen C(3v) geometries. The valence state potential energy curves are repulsive, the Rydberg state ones are similar to the one of the CH(3)Br(+) ion with a minimum at short distance. One state emerging from the 5p(e) band has valence and ion-pair characters as distance increases and the corresponding potential curve has a second minimum at large distance. This state has a very strong parallel electric dipole transition moment with the ground state and plays a central role in UV photon absorption spectra. It is also responsible for the parallel character of the anisotropy parameters measured in ion-pair production experiments. In each band, there is a single state, which has a non-negligible transition moment with the ground state, corresponding to a transition perpendicular to the molecular axis of symmetry, except for the 5p(e) band where it is parallel. The perpendicular transition moments between ground and valence states increase sharply as methyl-bromide distance decreases due to a mixing between valence and 5s Rydberg band at short distance. In each band, spin orbit interaction produces a pair of states, which have significant transition moments with the ground one. In the valence band, the mixing between singlet and triplet states is weak and the perpendicular transition to the (1)Q(1) state is dominant. In each Rydberg band, however, spin-orbit interaction is larger than the exchange interaction and the two significant transition moments with the ground state have comparable strengths. The valence band has an additional state ((1)Q(0)) with significant parallel transition moment induced by spin-orbit interaction with the ground state at large distance. PMID:19566152

Escure, Christelle; Leininger, Thierry; Lepetit, Bruno

2009-06-28

91

Dynamical stabilization of the initial state in a periodically kicked three-dimensional Rydberg atom

NASA Astrophysics Data System (ADS)

We present the dynamical stabilization of the initial state of a three-dimensional Rydberg atom subjected to a periodic train of half-cycle pulses. It is shown as an existence of a broad maximum of the survival probability at train repetition frequencies close to the classical orbital frequency. Population of the initial state for train repetition frequencies from this plateau is almost constant, even for trains consisting of a large number of pulses. We find this phenomenon very well observable for the initial redshifted Stark states. It is shown that for initial states with high and intermediate values of the angular quantum number, the dynamical stabilization of the initial state occurs only partially. We show that for extreme members of the Stark manifold as the initial states, results are fully consistent with appropriate results for a one-dimensional Rydberg atom.

Kopyciuk, T.

2012-08-01

92

Predissociation of Rydberg states of CO investigated by the detection of theC( 3P J ) fragment

Carbon atom generation following the predissociation of Rydberg states of CO has been investigated. The Rydberg states of CO were prepared by two-color double resonant excitation through the3s?B1?+ state and the atomic carbon fragment was detected by resonance-enhanced multiphoton ionization. The4s–6s(v = 0), 5s(v = 1), 4p(v = 0), 3d?(v = 0, 1), 5d?(v = 0), 4f–5f(v = 0) Rydberg

Takayuki Ebata; Takumichi Sutani; Naohiko Mikami

1995-01-01

93

An {ital ab} {ital initio} electronic structure technique has been developed to study highly excited states of molecules by combining Schwinger variational methods of collision theory with generalized quantum defect theory. The technique exploits methods of scattering theory to study the region of highly excited Rydberg levels below and across ionization thresholds for molecules. The reaction matrix {ital K}, which describes the interaction of the Rydberg electron with the ionic core, is found at arbitrary negative electron energies by employing an unbounded Coulomb Green's function in the Lippmann--Schwinger equation for the electronic wave function. Quantal conditions are imposed to obtain discrete molecular energy levels, associated Rydberg wave functions, and quantum defect functions, all as a function of the internuclear distance. Results within the static-exchange approximation for the {sup 1,3}{Sigma}{sup +}{sub {ital u}}(1{sigma}{sub {ital g}n}{sigma}{sub {ital u}}) and {sup 1,3}{Pi}{sub {ital u}}(1{sigma}{sub {ital g}n}{pi}{sub {ital u}}) Rydberg states of H{sub 2}, for {ital n}=2--20 and {ital R}=1.2--5.0 {ital a}{sub 0}, are presented and discussed.

Stephens, J.A.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125 (United States))

1992-12-01

94

Final-state distributions in charge transfer from sodium Rydberg atoms near the matching velocity

Reports measurements of the distribution of final n states that are populated in charge transfer collisions of Na+ ions with Na in highly-excited Rydberg states. Relative cross sections for final principal quantum numbers n'=18-42 are shown for laser-excited Na initial states 24d, 25s, 28d, 29s, 33d and 34s at kinetic energies 550-2000 eV. These results span the velocity-matching region in

R. G. Rolfes; K. B. MacAdam

1982-01-01

95

Rotational autoionization and energy levels of triplet nf, v=0 Rydberg states of H2s

We have measured the energy levels and purely rotational autoionization rates of 25 different triplet Rydberg states of the H2 molecule with quantum numbers n=14-29, L=3, v=0, and R=2-4. Electron impact excites the ground-state molecules in a beam to the metastable c(2p) 3 Piu states. Two-color laser excitation from two counterpropagating single-mode cw dye laser beams excites the metastable molecules

M. D. Lindsay; F. M. Pipkin

1997-01-01

96

Confined helium: Excited singlet and triplet states

NASA Astrophysics Data System (ADS)

Energies for the first four singlet and triplet S states of a helium atom confined at the center of an impenetrable sphere are reported. All calculations used explicitly correlated Hylleraas basis sets. The first triplet state is shown to lie below the first excited singlet state only when the confinement radius is greater than 0.988a0. A simple configuration interaction calculation was performed in parallel with Hylleraas calculation. The one-electron atomic orbitals of the configuration treatment provide insight into the physical concepts behind the numerical results of the Hylleraas treatment. This was particularly helpful in understanding the level crossing and avoided crossings observed with changing confinement radius.

Montgomery, H. E.; Pupyshev, Vladimir I.

2013-11-01

97

Doppler-free three-photon spectroscopy of 3snf Rydberg states of Mg

High-resolution two-photon resonant three-photon spectroscopy was applied to investigate the 3snf Rydberg series of Mg. Hyperfine-induced level shifts were detected for the /sup 1,3/F states of the odd isotope /sup 25/Mg. From these measurements the hyperfine coupling constant a/sub 3s/ of the /sup 25/Mg/sup +/-ion ground state was derived.

Beigang, R.; Schmidt, D.; Timmermann, A.

1984-05-01

98

Shedding new light on the role of the Rydberg state in the photochemistry of aniline.

Efficient electronic relaxation following the absorption of ultraviolet light is crucial for the photostability of biological chromophores, so understanding the microscopic details of the decay pathways is of considerable interest. Here, we employ femtosecond time-resolved photoelectron imaging to investigate the ultrafast intramolecular dynamics of aniline, a prototypical aromatic amine, following excitation just below the second absorption maximum. We find that both the second ??* state and the Rydberg state are populated during the excitation process. Surprisingly, the dominant non-radiative decay pathway is an ultrafast relaxation mechanism that transfers population straight back to the electronic ground-state. The vibrational energy resolution and photoelectron angular distributions obtained in our experiments reveal an interesting bifurcation of the Rydberg population to two non-radiative decay channels. The existence of these competing non-radiative relaxation channels in aniline illustrates how its photostability arises from a subtle balance between dynamics on different electronically excited states and importantly between Rydberg and valence states. PMID:22710758

Spesyvtsev, Roman; Kirkby, Oliver M; Vacher, Morgane; Fielding, Helen H

2012-06-19

99

Half-cycle-pulse-train induced state redistribution of Rydberg atoms

Population transfer between low-lying Rydberg states independent of the initial state is realized using a train of half-cycle pulses with pulse durations much shorter than the classical orbital period. We demonstrate experimentally the population transfer from initial states around n=50 with 10% of the population de-excited down to n<40 as well as up to the continuum. This is a demonstration of a state-independent de-excitation technique applicable to the currently produced state distribution of antihydrogen. The measured population transfer matches well to a model of the process for one-dimensional atoms.

Mandal, P. K.; Speck, A. [Rowland Institute at Harvard, Cambridge, Massachusetts 02142 (United States)

2010-01-15

100

NASA Astrophysics Data System (ADS)

This paper is dedicated to the implementation of a generalized approach for calculating quantum defects in high Rydberg states of polar molecules with an account for the dipole moment of the molecular core and l uncoupling of the Rydberg electron. Adiabatic (Born-Oppenheimer) and nonadiabatic (inverse Born-Oppenheimer) regions of the spectrum are considered. The nonadiabatic case with a nonzero projection of the core momentum on the core axis is considered and is illustrated by the example of the SO molecule.

Dorofeev, Dmitry L.; Elfimov, Sergei V.; Zon, Boris A.

2012-02-01

101

NASA Astrophysics Data System (ADS)

Dissociative electron attachment cross sections (DEA) on vibrationally excited H2 molecule taking place via the 2?g+ Rydberg-excited resonant state are studied using the local complex potential (LCP) model for resonant collisions. The cross sections are calculated for all initial vibrational levels (vi = 0-14) of the neutral molecule. In contrast to the previously noted dramatic increase in the DEA cross sections with increasing vi, when the process proceeds via the X 2?u+ shape resonance of H2, for the 2?g+ Rydberg resonance the cross sections increase only gradually up to vi = 3 and then decrease. Moreover, the cross sections for vi ? 6 exhibit pronounced oscillatory structures. A discussion of the origin of the observed behavior of calculated cross sections is given. The DEA rate coefficients for all vi levels are also calculated in the 0.5-1000 eV temperature range.

Celiberto, R.; Janev, R. K.; Wadehra, J. M.; Tennyson, J.

2012-04-01

102

Double Rydberg formula and applications to doubly excited states of highly charged ions

The screening constant in the double Rydberg formula is estimated using the intrashell configuration-interaction states. Its explicit dependence on the bending rovibrational quantum numbers is included. Comparison of the energy levels so obtained with elaborate numerical results indicates its utility for doubly excited states of highly charged ions and also points to its geometrical origin. Procedures are introduced to generalize the formula to intershell doubly excited states and to doubly excited states of multielectron atoms. A number of specific numerical results are presented.

Lin, C.D.; Watanabe, S.

1987-06-01

103

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

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

104

Spectroscopic observation and characterization of H(+)H(-) heavy Rydberg states.

A series of discrete resonances was observed in the spectrum of H2, which can be unambiguously assigned to bound quantum states in the 1/R Coulombic potential of the H+H- ion-pair system. Two-step laser excitation was performed, using tunable extreme ultraviolet radiation at lambda = 94-96 nm in the first step, and tunable ultraviolet radiation in the range lambda = 310-350 nm in the second step. The resonances, detected via H+ and H2+ ions produced in the decay process, follow a sequence of principal quantum numbers (n = 140-230) associated with a Rydberg formula in which the Rydberg constant is mass scaled. The series converges upon the ionic H+H- dissociation threshold. This limit can be calculated without further assumptions from known ionization and dissociation energies in the hydrogen system and the electronegativity of the hydrogen atom. A possible excitation mechanism is discussed in terms of a complex resonance. Detailed measurements are performed to unravel and quantify the decay of the heavy Rydberg states into molecular H2+ ions, as well as into atomic fragments, both H(n = 2) and H(n = 3). Lifetimes are found to scale as n3. PMID:19921940

Vieitez, M O; Ivanov, T I; Reinhold, E; de Lange, C A; Ubachs, W

2009-11-26

105

NASA Astrophysics Data System (ADS)

An efficient method to study highly excited states at the ab initio level has been introduced and applied to ultralong Rydberg CsNe molecules. Vibrational properties of Rydberg CsNe molecules are investigated on corresponding potential energy curves obtained by perturbation theory. The Rydberg CsNe molecules are associated with a Rydberg Cs(ns/np) atom (n = 20-60) and a ground state Ne(1S0) atom. The starting point for the perturbation treatment of corresponding Rydberg molecular potential energy curves is to generate accurate atomic Rydberg states from realistic ab initio effective core potential. According to the authors' knowledge this is a good reference for ultralong range molecules (order of 1000 Bohr radii) to be studied at the ab initiolevel.

Liu, Xiaomeng; Yang, Yonggang; Zhao, Jianming; Xiao, Liantuan; Jia, Suotang

2013-08-01

106

An efficient method to study highly excited states at the ab initio level has been introduced and applied to ultralong Rydberg CsNe molecules. Vibrational properties of Rydberg CsNe molecules are investigated on corresponding potential energy curves obtained by perturbation theory. The Rydberg CsNe molecules are associated with a Rydberg Cs(ns?np) atom (n = 20-60) and a ground state Ne((1)S0) atom. The starting point for the perturbation treatment of corresponding Rydberg molecular potential energy curves is to generate accurate atomic Rydberg states from realistic ab initio effective core potential. According to the authors' knowledge this is a good reference for ultralong range molecules (order of 1000 Bohr radii) to be studied at the ab initio level. PMID:23927257

Liu, Xiaomeng; Yang, Yonggang; Zhao, Jianming; Xiao, Liantuan; Jia, Suotang

2013-08-01

107

Using the Doppler-free two-photon absorption technique, we observe the 2S-8D and 2S-10D transitions in atomic hydrogen and deuterium with a relative line width of 1.8 · 10-9. The comparison of the wave-length of these transitions to the one of an iodine stabilized He-Ne laser provides a new determination of the Rydberg constant R? = 109 737.315 69(6) cm-1. This measurement

F. Biraben; J. C. Garreau

1986-01-01

108

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

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

2008-10-04

109

Dynamical stabilization of the initial state in a periodically kicked one-dimensional Rydberg atom

NASA Astrophysics Data System (ADS)

We investigate the dynamical stabilization of the initial state of a one-dimensional Rydberg atom subjected to a periodic train of half-cycle pulses. A survival probability of the initial state as a function of pulse repetition frequency is presented for different values of momentum transferred to the electron. This survival probability exhibits a broad maximum at train repetition frequencies close to the classical orbital frequency provided that the momentum is negative. There is no such behaviour for positive momentum transferred to the electron.

Kopyciuk, T.; Parzy?ski, R.

2009-11-01

110

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

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

111

Ionization of naphthalene via the Rydberg states using a femtosecond 775 nm pulse

NASA Astrophysics Data System (ADS)

Photoelectron spectroscopic studies on naphthalene excited with a femtosecond 775 nm laser pulse reveal two ionization paths via the Rydberg states: a resonance-enhanced, non-relaxed process and one that goes through internal conversion of an undetermined intermediate. Varying the pulse duration with several hundred femtosecond causes only small change in the spectra. Compared to the ionization mechanism of anthracene, the reduced molecular size changes the ionization behavior due to a slower internal conversion rate and the presence of atomic-like Freeman resonances.

Goto, Motoshi; Hansen, Klavs

2012-01-01

112

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

We show that strongly polarized very-high-n (n~600) potassium Rydberg atoms can be produced by manipulating lower-n (n~350) polarized atoms using a tailored sequence of ultrashort half-cycle pulses (HCPs). The protocol for this involves first a weak HCP that generates transient phase-space localization whereupon a second large HCP of opposite polarity excites the electron to a broad distribution of highly elongated states. This distribution is then refocused by a short periodic train of HCPs using the properties of (un)stable manifolds near fixed points in phase space.

Zhao, W. [Rice University; Mestayer, J. J. [Rice University; Lancaster, J. C. [Rice University; Dunning, F. B. [Rice University; Reinhold, Carlos O [ORNL; Yoshida, S. [Institute for Theoretical Physics, Vienna University of Technology, Austria; Burgdorfer, J. [Institute for Theoretical Physics, Vienna University of Technology, Austria

2005-10-01

113

Rydberg state ionization by half-cycle-pulse excitation: strong kicks create slow electrons.

The asymptotic velocity distribution of electrons ionized in half-cycle-pulse excitation of high Rydberg states (n=34), placed in a static electric field, is studied using electron velocity-map imaging. At weak half-cycle pulse strengths, the electrons escape over the saddle point in the potential. For strong half-cycle pulses, the electrons are emitted in the direction of the field kick. The much slower and less intense half cycle of opposite polarity, which necessarily follows the main half-cycle pulse, strongly affects the momentum distribution and reduces the excess energy of the electrons significantly. PMID:12513203

Wetzels, A; Gürtler, A; Noordam, L D; Robicheaux, F; Dinu, C; Muller, H G; Vrakking, M J J; van der Zande, W J

2002-12-19

114

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

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

115

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

116

Alteration of the lifetimes of autoionizing Rydberg states by a circularly polarized microwave field

Autoionizing Rydberg states in zero field exhibit lifetimes scaling as the cube of the principal quantum number, n{sup 3}, but in a linearly polarized static or microwave field the lifetimes scale as n{sup 4} due to l mixing. To mimic the effects of collisions with charged particles we have examined the effect of a circularly polarized field on the decay rate and find longer lifetimes than in a linearly polarized field, but not an n{sup 5} dependence. {copyright} {ital 1997 American Institute of Physics.}

Jones, R.R.; Fu, P.; Gallagher, T.F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22901 (United States)

1997-03-01

117

Photodissociation dynamics of doubly excited Rydberg states of molecular hydrogen

We have applied photofragment ion imaging to investigate the dissociation dynamics of low-lying, doubly excited states of molecular hydrogen. A doubly excited electronic state is one in which both of the hydrogen electrons reside in excited molecular orbitals. Two-step, two-color multiphoton excitation of H{sub 2}, first via 201.8 nm, two-photon excitation into the {ital E}, {ital F} {sup 1}{Sigma}{sup +}{sub {ital g}}({ital v}{sub {ital E}}=0, {ital J}=1) state, followed by {similar to}563 nm, 1+{ital m} ({ital m}=1, 2) excitation through the {ital B}{double prime} {sup 1}{Sigma}{sup +}{sub {ital u}}({ital v}=0, {ital J}=0, 2), {ital D} {sup 1}{Pi}{sub {ital u}}({ital v}=2, {ital J}=1, 2), and {ital B}{prime} {sup 1}{Sigma}{sup +}{sub {ital u}}({ital v}=4, {ital J}=0, 2) states provides a ready means of populating several low-lying doubly excited states of H{sub 2} at increasing internuclear separations. From these doubly excited repulsive states, both dissociation and autoionization processes are possible. Because the excitation energy remains relatively constant as each intermediate state is accessed, differences in the photodissociation dynamics via each state can be ascribed directly to the effects of changing internuclear separation and electronic symmetry of the intermediate and dissociative states. H{sup +} fragments detected from each photodissociation pathway are distinguished by their differing velocities, determined from an ion image.

Buntine, M.A. (Department of Chemistry, Stanford University, Stanford, California 94305 (United States)); Baldwin, D.P.; Chandler, D.W. (Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550 (United States))

1992-04-15

118

Resonance ionization spectroscopy of HCO and DCO. I. The 3 p sup 2. Pi. Rydberg state

Resonance two-photon ionization (R2PI) spectroscopy has been used for medium resolution studies of HCO and DCO at wavelengths from 208 to 222 nm. Vibronic analysis of subband positions originating from both {ital A}{prime} and {ital A}{double prime} symmetry components of the 3{ital p} {sup 2}{Pi} Rydberg states of HCO and DCO yields values for the Renner--Teller parameter {Epsilon}, dipolar vibronic parameter {ital g}{sub {ital k}}, quartic anharmonicity constant {ital g}{sub 22}, harmonic bending vibrational frequency {omega}{sub 2}, anharmonicity constant {ital x}{sub 22}, and spin--orbit splitting constant {ital A}. Values of the harmonic frequencies {omega}{sub 2} and anharmonicity constants {ital x}{sub 22} for the bending vibrations of the HCO and DCO {ital {tilde X}} {sup 2}{ital A}{prime} ground states are also determined. Previously unidentified two-photon subbands, thought to be excitations of the 3{ital s} {sup 2}{Sigma}{sup +} Rydberg state, are assigned to the symmetric {ital A}{prime} component of the 3{ital p} {sup 2}{Pi} state.

Song, X.; Cool, T.A. (School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States))

1992-06-15

119

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

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 they are determined by the interplay among the ring geometry, the structure of the atomic resource states, and the collectivity in the photon emission which is controlled by the lattice spacing. The system permits the creation of versatile single-photon sources and two-photon entangled states.

Olmos, B.; Lesanovsky, I. [Midlands Ultracold Atom Research Centre (MUARC), The University of Nottingham, School of Physics and Astronomy, Nottingham NG7 2RD (United Kingdom)

2010-12-15

120

Diatomics-in-molecules approximation for Rydberg states of H/sub 3/

Electronic energies for excited Rydberg states of H/sub 3/ in D/sub 3h/ or C/sub 2nu/ nuclear configurations are calculated by use of the diatomics-in-molecules method and spline fits to accurate potential curves for 22 states of the H/sub 2/ molecule. Explicit formulas expressing the energy levels of H/sub 3/ for D/sub 3h/ configurations in terms of the H/sub 2/ potential curves are given for all states corresponding to two ground-state atoms in consort with a third atom excited to any s or p state. The available data permit evaluation of the elevels for all states involving 2s or 2p excitation or II-type 3p excitation, as well as a few higher excitation. The results agree well (within approx. 0.01 hartree) with ab initio calculations. 12 references, 2 figures, 3 tables.

Raynor, S.; Herschbach, D.R.

1982-01-01

121

Molecular detection using Rydberg, autoionizing, and cluster states. Progress report

Continuing investigations of multiphoton ionization processes in naphthalene have established the geometry and spectroscopy of trimer and tetramer cluster states. A new, highly efficient ionization mechanism has been identified in the trimer. It is closely related to autoionization of 2-electron atoms by resonant 2-photon excitation and to exciton fusion in larger clusters.

Wessel, J.

1989-08-17

122

Multiphoton spectroscopy of Rydberg states of small molecules

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

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

1990-01-01

123

NASA Astrophysics Data System (ADS)

Mass spectra were recorded for one-colour resonance enhanced multiphoton ionization (REMPI) of HiBr (i = 79, 81) for the two-photon resonance excitation region 79 040-80 300 cm-1 to obtain two-dimensional REMPI data. The data were analysed in terms of rotational line positions, intensities, and line-widths. Quantitative analysis of the data relevant to near-resonance interactions between the F1?2(v' = 1) and V1?+(v' = m + 7) states gives interaction strengths, fractional state mixing, and parameters relevant to dissociation of the F state. Qualitative analysis further reveals the nature of state interactions between ion-pair states and the E1?+ (v' = 1) and H1?+(v' = 0) Rydberg states in terms of relative strengths and J' dependences. Large variety in line-widths, depending on electronic states and J' quantum numbers, is indicative of number of different predissociation channels. The relationship between line-widths, line-shifts, and signal intensities reveals dissociation mechanisms involving ion-pair to Rydberg state interactions prior to direct or indirect predissociations of Rydberg states. Quantum interference effects are found to be important. Moreover, observed bromine atom (2 + 1) REMPI signals support the importance of Rydberg state predissociation channels. A band system, not previously observed in REMPI, was observed and assigned to the k3?0(v' = 0) <--<-- X transition with band origin 80 038 cm-1 and rotational parameter Bv'=7.238 cm-1.

Long, Jingming; HróÐmarsson, Helgi Rafn; Wang, Huasheng; Kvaran, Ágúst

2012-06-01

124

Many-body spin interactions and the ground state of a dense Rydberg lattice gas.

We study a one-dimensional atomic lattice gas in which Rydberg atoms are excited by a laser and whose external dynamics is frozen. We identify a parameter regime in which the Hamiltonian is well approximated by a spin Hamiltonian with quasilocal many-body interactions which possesses an exact analytic ground state solution. This state is a superposition of all states of the system that are compatible with an interaction induced constraint weighted by a fugacity. We perform a detailed analysis of this state which exhibits a crossover between a paramagnetic phase with short-ranged correlations and a crystal. This study also leads us to a class of spin models with many-body interactions that permit an analytic ground state solution. PMID:21405236

Lesanovsky, Igor

2011-01-11

125

Many-Body Spin Interactions and the Ground State of a Dense Rydberg Lattice Gas

NASA Astrophysics Data System (ADS)

We study a one-dimensional atomic lattice gas in which Rydberg atoms are excited by a laser and whose external dynamics is frozen. We identify a parameter regime in which the Hamiltonian is well approximated by a spin Hamiltonian with quasilocal many-body interactions which possesses an exact analytic ground state solution. This state is a superposition of all states of the system that are compatible with an interaction induced constraint weighted by a fugacity. We perform a detailed analysis of this state which exhibits a crossover between a paramagnetic phase with short-ranged correlations and a crystal. This study also leads us to a class of spin models with many-body interactions that permit an analytic ground state solution.

Lesanovsky, Igor

2011-01-01

126

Many-Body Spin Interactions and the Ground State of a Dense Rydberg Lattice Gas

We study a one-dimensional atomic lattice gas in which Rydberg atoms are excited by a laser and whose external dynamics is frozen. We identify a parameter regime in which the Hamiltonian is well approximated by a spin Hamiltonian with quasilocal many-body interactions which possesses an exact analytic ground state solution. This state is a superposition of all states of the system that are compatible with an interaction induced constraint weighted by a fugacity. We perform a detailed analysis of this state which exhibits a crossover between a paramagnetic phase with short-ranged correlations and a crystal. This study also leads us to a class of spin models with many-body interactions that permit an analytic ground state solution.

Lesanovsky, Igor [Midlands Ultracold Atom Research Centre (MUARC), School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2011-01-14

127

Quantum defect theory of dipole and vibronic mixing in Rydberg states of CaF.

The Rydberg spectra of CaF combine the simplicity of a single electron outside a doubly closed-shell Ca2+F- ion core with the exceptional polarity of the ion core. A global multichannel quantum defect (MQDT) fit to 612 previously assigned levels, 507 from n approximately = 12-18, N=0-14, v+=1, 97 from n approximately = 9-10, N=0-14, v+=2, and 8 from n approximately = 7, N=3-10, v+=3, produces the complete L=0-3 quantum defect matrix mu (with the exception of one element) and 19 of 20 elements of the partial differentialmu/differentialR matrix, as well as the molecular constants of the CaFX 1sigma+ state [omega(e)+=694.58(14), omega(e)x(e+)=2.559(40), B(e+)=0.373 07(16) cm(-1), and the v=0, N=0 to v(+)=0, N(+)=0 ionization energy, 46,996.40(8) cm(-1)]. This experimentally determined mu(R) matrix is unusual in the completeness of its representation of the spectrum of both core-penetrating and nonpenetrating Rydberg series, including both local perturbations and vibrational autoionization rates, as well as all dynamical processes encoded in the spectrum that result from the scattering (at negative energy) of the Rydberg electron off the Ca2+F- ion core. The MQDT theory is presented in a form that clarifies the relationships of the reaction (K) and phase (P) matrices of MQDT to effective Hamiltonian models for local interactions between accidentally near degenerate levels. In particular, a Hund's case (b) like representation of the Hamiltonian is described in which the rovibronic K matrix is diagonalized and the P matrix, which contains information about the v+, N+ eigenstates of the ion, becomes nondiagonal. PMID:15918711

Field, R W; Gittins, C M; Harris, N A; Jungen, Ch

2005-05-01

128

NASA Astrophysics Data System (ADS)

New and existing spectroscopic data on N2, obtained using a wide variety of experimental techniques, are interpreted using a coupled-channel Schrödinger-equation (CSE) model of the structure and predissociation dynamics for the interacting Rydberg and valence states of 3?u symmetry. As a result, v>0 levels of the 3p?uG3 3?u Rydberg state are assigned correctly for the first time, leading to the identification of very strong perturbations in the G3-state vibrational structure. A four-channel CSE model, which includes the 3s?gF3 3?u and 3p?uG3 3?u Rydberg states and the C' 3?u and C 3?u valence states, indicates strong Rydberg-Rydberg coupling between the F3 and G3 states, strong Rydberg-valence coupling between the G3 and C' states, and weaker coupling between the F3 and C' states.

Lewis, B. R.; Heays, A. N.; Gibson, S. T.; Lefebvre-Brion, H.; Lefebvre, R.

2008-10-01

129

Term energies of 1s2nf high Rydberg states for the lithium atom

NASA Astrophysics Data System (ADS)

Ionization potentials and quantum defects of 1s2nf bound states and their adjacent continuum states for the lithium atom are calculated with the R-matrix theory; then the quantum defect function (QDF) of the 1s2nf channel is obtained, which varies smoothly with the energy based on the quantum defect theory. The original QDF is calibrated from a more accurate literature value and used to calculate quantum defects, ionization potentials and term energies (relative to the 1s22s ground state) of 1s2nf high Rydberg states of the lithium atom. The term energies in this work are, on the whole, in good agreement with the experimental data in the literature.

Chen, Chao

2013-10-01

130

Photoinduced Rydberg ionization spectroscopy of the B~ state of benzonitrile cation

NASA Astrophysics Data System (ADS)

Photoinduced Rydberg ionization (PIRI) spectra of the second excited electronic state of benzonitrile cation were recorded via the origin and 6a1 and 6b1 vibrational levels of the cation ground electronic state. This B~<--X~ transition was verified to be a forbidden 2B2<--2B1 transition with an origin at 17 225 cm-1 above the ground ionic state. By the use of vibronic coupling calculations, as well as symmetry analysis and comparison of the PIRI spectra via different ground vibrational levels, a nearly complete assignment of the vibrational structure was made, and the vibrational frequencies of the B~ 2B2 state of benzonitrile cation were obtained based on the assignments. Comparisons of the experimental spectra with simulations from the vibronic structure calculations are also used to validate the theoretical procedures used in the simulations.

Xu, Haifeng; Johnson, Philip M.; Sears, Trevor J.

2006-10-01

131

Stark spectra of Rydberg states in atomic cesium in the vicinity of n = 18

NASA Astrophysics Data System (ADS)

The Stark structures in a cesium atom around n = 18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and those with a large |m| shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in ultracold atomic cesium. Atoms initially in 6P3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to the field, and Stark spectra with |m| = 1/2, 3/2, 5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.

Dong, Hui-Jie; Wang, Ting; Li, Chang-Yong; Zhao, Jian-Ming; Zhang, Lin-Jie

2013-07-01

132

The lowest Rydberg state of NO has been observed to fluoresce with unity quantum yield in solid Ar, Kr, and Xe hosts. The purely radiative lifetimes lengthen in the sequence vacuum, Ar, Kr, Xe, thus directly demonstrating an increasing delocalization of the Rydberg wavefunction in media with increasing dielectric coefficient. A simple, semiquantitative theory of the relative stability of bubble

Julie Goodman; L. E. Brus

1977-01-01

133

Interfacing Rydberg atoms with superconducting circuits

NASA Astrophysics Data System (ADS)

Hybrid quantum system are promising candidates for future quantum computing architectures because they provide the potential to combine the best properties of different physical systems. Here, we bring together Rydberg atoms and microwave photons emanating from a co-planar waveguide with the ultimate goal to interface long-lived Rydberg atoms with well-controllable superconducting qubits. In our cryogenic experiment, helium atoms pass over microwave electrodes hosted on a printed circuit board. By applying resonant microwave pulses, we induce transitions between Rydberg states with principal quantum number n=31-35 and observe coherent Rabi oscillations with typical oscillation periods of about 50ns [1]. From spectral measurements we can characterize the interaction between the atoms and surface fields leading to decoherence. The analysis of the inhomogeneously broadened lineshapes indicates that the stray electric field strength decreases with the inverse square of the atom-surface distance [2]. In experiments in preparation we plan to employ on-chip superconducting resonators to study the strong interaction of Rydberg atoms with few or individual microwave photons.[4pt] [1] S.D. Hogan et al., PRL 108, 063004 (2012).[0pt] [2] J.D. Carter and J.D.D. Martin, PRA 83, 032902 (2011).

Filipp, S.; Thiele, T.; Stammeier, M.; Wallraff, A.; Hogan, S. D.; Agner, J. A.; Merkt, F.

2013-03-01

134

Explicitly correlated Gaussian calculations of the {sup 2}D Rydberg states of the boron atom

Accurate non-relativistic variational calculations are performed for the seven lowest members of the {sup 2}D Rydberg series (1s{sup 2}2s2p{sup 2}, and 1s{sup 2}2s{sup 2}nd, n= 3, Horizontal-Ellipsis , 8) of the boron atom. The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian basis functions and the effect of the finite nuclear mass is directly included in the calculations allowing for determining the isotopic shifts of the energy levels. The Gaussian basis is optimized independently for each state with the aid of the analytic energy gradient with respect to the Gaussian parameters. The calculations represent the highest accuracy level currently achievable for the considered states. The computed energies are compared with the available experimental data.

Sharkey, Keeper L. [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States); Bubin, Sergiy [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Adamowicz, Ludwik [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States); Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2012-08-14

135

We report the first experimental observation of magnetic field effects on dielectronic recombination (DR) via highly excited Rydberg levels. Crossed static electric and magnetic fields E{sub y} and B{sub z} were imposed on the collision region in high resolution DR measurements with Li-like Cl{sup 14+} ions at the heavy ion storage ring TSR in Heidelberg. Enhancement of DR rate coefficients {alpha} for the group of high Rydberg states attached to the 2p{sub 1/2} and 2p{sub 3/2} series limits was observed when motional electric fields E{sub y} up to 380thinspthinspV/cm were introduced. The associated enhancement rate d{alpha}/dE{sub y} which we found to be constant at least for E{sub y}{le}100 V/cm decreased by almost a factor of 2 when the longitudinal field B{sub z} was increased from 20 to 69thinspthinspmT. {copyright} {ital 1999} {ital The American Physical Society}

Bartsch, T.; Schippers, S.; Mueller, A.; Brandau, C. [Institut fuer Kernphysik, Universitaet Giessen, 35392 Giessen (Germany); Gwinner, G.; Saghiri, A.A.; Beutelspacher, M.; Grieser, M.; Schwalm, D.; Wolf, A. [Max-Planck-Institut fuer Kernphysik and Physikalisches Institut der Universitaet Heidelberg, 69117 Heidelberg (Germany); Danared, H. [Manne Siegbahn Laboratory, Stockholm University, 10405 Stockholm (Sweden); Dunn, G.H. [JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)

1999-05-01

136

A variational method, based on some results due to T. Kato [Proc. Phys. Soc. Jpn. 4, 334 (1949)], and previously discussed is here applied to the hydrogen atom in uniform magnetic fields of tesla in order to calculate, with a rigorous error estimate, energy eigenvalues, energy eigenfunctions, and oscillator strengths relative to Rydberg states up to just below the field-free

P. Falsaperla; G. Fonte

1994-01-01

137

The intervals between hyperfine levels of high ns and nd (n=68-76) Rydberg states of {sup 83}Kr have been determined by millimeter-wave spectroscopy. The hyperfine structure of the Rydberg states has been analyzed using multichannel quantum defect theory. Improved eigenquantum defects for the ns and nd Rydberg series and quantitative information about the s-d interaction at the energy of the {sup 2}P{sub 3/2} threshold have been obtained, and improved values of the hyperfine structure of the {sup 2}P{sub 3/2} ground state of {sup 83}Kr{sup +} have been derived.

Schaefer, Martin; Merkt, Frederic [Laboratorium fuer Physikalische Chemie, ETH Zuerich, CH-8093 Zurich (Switzerland)

2006-12-15

138

An Ordered State of Dislocations in Solid Helium

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

139

The newly developed technique of photoinduced Rydberg ionization (PIRI) spectroscopy has been successfully applied to study the B˜?X˜ transition in the phenol and phenol-d6 cations. Vibrationally resolved spectra have been obtained for the B˜ state in phenol ion via the origin and the ?6, and ?12 vibrations of the ground ionic state. Similarly, vibrationally resolved spectra for the B˜ state

J. E. LeClaire; R. Anand; P. M. Johnson

1997-01-01

140

Probing state-to-state reaction dynamics using H-atom Rydberg tagging time-of-flight spectroscopy.

In the last decade or so, the H-atom Rydberg tagging time-of-flight (HRTOF) technique has made a significant impact in the study of state-to-state reaction dynamics, and especially in the study of transition state dynamics of elementary chemical reactions and quantum state resolved dynamics of molecular photodissociation of important molecules. In this perspective, we will discuss mainly the state-to-state dynamics of three important elementary reactions: H + H(2), O((1)D) + H(2) and F + H(2) that have been studied in our laboratory in recent years using the HRTOF method. In addition, we will also mention briefly the experimental results of other reactive systems. In the end, we will also present a brief research outlook in the study of molecular reaction dynamics using this powerful experimental method. PMID:21479311

Yang, Xueming

2011-04-09

141

The role of high Rydberg states in the generation of negative ions in negative-ion discharges

The generation of substantial yields of H{sup {minus}} ions in a laser excited H{sub 2} gas has been reported by Pinnaduwage and Christoforu. These H{sup {minus}} yields have been attributed to (2 + 1) REMP photoexcitation processes leading to dissociative attachment of doubly-excited or superexcited states (SES), or dissociative attachment of high Rydberg product states. The new feature of these experiments is the implied large dissociative attachment rates, of order 10{sup {minus}6} cm{sup 3} sec{sup {minus}1}, values that are orders-of-magnitude larger than the dissociative attachment of the vibrationally excited levels of the ground electronic state. While these laser excitations are not directly applicable to a hydrogen negative-ion discharge, the implication of large dissociative attachment rates to the high Rydberg states may affect both the total negative-ion density and the interpretation of discharge performance. Within the discharge energetic electrons will collisionally excite the higher Rydberg states, and the relative contribution of the dissociative attachment of these states when compared with the dissociative attachment to the ground state vibrational levels, is the topic of this paper.

Hiskes, J.R.

1995-11-28

142

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

143

A new detector for state analysis of multicharged ions, excited in high Rydberg states, at kinetic energies of the order of keV is described. It is composed of a field-ionizing lens system (FILS), associated with two electrostatic spectrometers; the first one, in front of the FILS, selects the q-times charged excited ions of interest, and the second one, behind the

A. Pesnelle; H. J. Andrä

1997-01-01

144

The newly developed technique of photoinduced Rydberg ionization (PIRI) spectroscopy has been successfully applied to study the {tilde B}â{tilde X} transition in the phenol and phenol-dâ cations. Vibrationally resolved spectra have been obtained for the {tilde B} state in phenol ion via the origin and the Î½â, and Î½ââ vibrations of the ground ionic state. Similarly, vibrationally resolved spectra for

J. E. Leclaire; R. Anand; P. M. Johnson

1997-01-01

145

Sulfur difluoride radicals in their ground state have been produced by a ``laser-free'' pulsed dc discharge of the SF6\\/Ar gas mixtures in a supersonic molecular beam and detected by mass-selective resonance-enhanced multilphoton ionization (REMPI) spectroscopy in the wavelength range of 408-420 nm. Analyses of the (3+1) REMPI excitation spectrum have enabled identification of three hitherto unknown Rydberg states of this

Qun Zhang; Xiaoguo Zhou; Quanxin Li; Shuqin Yu; Xingxiao Ma

2008-01-01

146

NASA Astrophysics Data System (ADS)

Transitions between Rydberg states of atomic chlorine have been detected between 1477 and 1507 cm-1 by the technique of carbon monoxide laser magnetic resonance (LMR). Transitions have been observed in both emission and absorption. The spectra have been assigned for those transitions involving levels which have been identified previously. However, several more resonances are unassigned, revealing the presence of previously unidentified states of atomic chlorine. Many of the lines show resolved nuclear hyperfine structure.

Brown, J. M.; Comben, E. R.; Bohle, W.; Zeitz, D.; Urban, W.

1987-02-01

147

NASA Astrophysics Data System (ADS)

We elaborate the quantum-mechanical analysis using the two-state vector model to investigate the formation of intermediate Rydberg states of multiply charged ions (core charge Z ? 1, principal quantum number nA ? 1) interacting with solid surfaces in the grazing incidence geometry. For the fixed initial and final states of the active electron, the two wavefunctions are used to describe the transitional electron state at the time t. Considering the projectile motion classically, the effect of projectile velocity is taken into account in accordance with Galilean invariance. The population probabilities of the intermediate Rydberg states are obtained in the analytical form, which enables an analysis of the localization and the selectivity of the process, for various ion-surface parameters. Ions ArZ+, KrZ+ and XeZ+ with Z ? [5, 35] interacting with Al-surface are considered as an example. The results are compared with the classical overbarrier predictions and the measured kinetic energy gain due to the image acceleration of the ions. It is demonstrated that the ionic velocity influences the ion-surface distance at which the formation of the particular intermediate Rydberg state is mainly localized, as well as the probability for this formation.

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

2012-11-01

148

Investigation of Rydberg states of nitrogen dioxide with high-power laser

NASA Astrophysics Data System (ADS)

A survey of the Rydberg states of NO2 accessed in optical-optical two-color double-resonant (OODR) manner by the technique of multi-photon ionization (MPI) spectroscopy is presented. The pump laser is the double-frequency output of a Nd:YAG laser. While the probe laser is an optical parameter generator and optical parameter amplifier (OPG/OPA) pumped by the triple-frequency output 355nm of the former. The OODR-MPI spectrum of NO2 is obtained by scanning the probe laser in the range of 465-535nm under the condition that the pump laser is unfocused and the probe laser is focused on the center of the pump laser beam. The ionization peaks could be attributed to E2?u<--A2B2<--X2A1(1+2) resonant transitions. This means that NO2 molecule is excited to the appropriate level of the first excited A2B2 state by absorbing one pump laser (?1) photon. Then from the first excited state it should take three probe photons (?2) and via final resonant E2?u state for the ionization. The bending vibration frequency of NO2 E2?u state obtained from above ionization spectrum is (608.6+/-2.2)cm-1. It is consistent with the literature.

Zhang, GuiYin; Zhang, Lianshui; Han, Xiaofeng; Sun, Bo

2005-01-01

149

Excited state spectroscopy on helium using a color center laser

The recent application of optogalvanic detection for observing weak transitions in the visible was adapted to infrared spectroscopy. For Doppler limited spectroscopy, infrared optogalvanic detection has proven particularly sensitive to those states which the highest angular quantum number; and the observed signal strengths are in good agreement with a steady state model of the optogalvanic effect in the helium positive

D. J. Jackson

1981-01-01

150

A combined experimental and theoretical investigation of the role of electronic and nuclear spins in molecular photoionization is reported. Photoionization spectra of autoionizing p Rydberg states belonging to series converging on the X {sup 2}{sigma}{sub g}{sup +}(v{sup +}=0,N{sup +}=3) level of ortho-H{sub 2}{sup +} have been measured in the range of principal quantum number n=50-200 from the long-lived H {sup 1}{sigma}{sub g}{sup +}(v=0,J=3) level. The use of a pulsed near-Fourier-transform-limited laser with a bandwidth of less than 10 MHz resulted in a Doppler-limited linewidth of 25 MHz which sufficed to partially resolve the hyperfine structure of the Rydberg states. Below n{approx_equal}70, the exchange interaction between the ion core and Rydberg electrons is larger than the hyperfine interactions in the ion core and the observed levels can be understood in terms of Hund's angular momentum coupling case (d). With increasing value of n, the hyperfine interactions in the core lead to a mixing of singlet and triplet characters of the Rydberg states and eventually to a complete decoupling of the Rydberg electron spin from the core spins that results in distinct series converging on the hyperfine components of the ion. Several intermediate coupling cases have been identified and two of them completely characterized. Most interestingly, the total spin angular momentum has been found to be a good quantum number up to n{approx_equal}150 at least, i.e., far beyond the region where the ionic hyperfine structure starts dominating the coupling hierarchy. Multichannel quantum defect theory including nuclear and electron spins has been extended to treat autoionization and predict spectral intensities. The comparison with the experimental spectra has revealed a satisfactory agreement between calculated and measured line positions, linewidths, and intensities and has enabled us to extract, by extrapolation, a more accurate term value for the H {sup 1}{sigma}{sub g}{sup +}(v=0,J=3) level. The calculations have been used to characterize the role of hyperfine, spin-rotational, and pf interactions in rotational autoionization and have revealed a very strong dependence of the autoionization lifetimes of high Rydberg states on the value of the total angular momentum quantum number F.

Woerner, H. J.; Mollet, S.; Merkt, F. [Laboratorium fuer Physikalische Chemie, ETH-Zuerich, 8093 Zurich (Switzerland); Jungen, Ch. [Laboratoire Aime-Cotton du CNRS, Universite de Paris-Sud, 91405 Orsay Cedex (France)

2007-06-15

151

Atomic orientation following predissociation of the C 3?g Rydberg state of molecular oxygen.

(2 + 1) resonance enhanced multiphoton ionization in combination with time-of-flight mass spectroscopy (TOF-MS) has been used to detect both the O((3)P) and O((1)D) fragments produced as a result of predissociation of the C (3)?g (v = 0) and (v = 1) Rydberg states of O2, accessed via two-photon absorption from the ground X (3)?g(-) state. In particular, TOF profiles have been recorded at various fixed two-photon absorption wavelengths within the two bands, with circular polarized probe laser light used to probe the angular momentum orientation of these photofragments. All photofragments are found to display coherent orientation resulting from interference between two possible two-photon absorption pathways. The measured orientation is affected by rotational depolarization due to the long lifetime of the excited C state; once this effect is accounted for the orientation is found to be nearly constant over all dissociation wavelengths. The origin of the coherent orientation is attributed to two-photon absorption to different spin-orbit components of the C state. PMID:23758371

Gilchrist, A J; Ritchie, G A D

2013-06-01

152

Mass spectra were recorded for (2 + n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 88865-89285 cm(-1) region to obtain two-dimensional REMPI data. Band spectra due to two-photon resonance transitions to number of Rydberg states (?' = 0, 1, and 2) and the ion-pair state V((1)?(+)(?' = 0)) for H(35)Cl and H(37)Cl were identified, assigned, and analyzed with respect to Rydberg to ion-pair interactions. Perturbations show as line-, hence energy level-, shifts, as well as ion signal intensity variations with rotational quantum numbers, J', which, together, allowed determination of parameters relevant to the nature and strength of the state interactions as well as dissociation and ionization processes. Whereas near-resonance, level-to-level, interactions are found to be dominant in heterogeneous state interactions (?? ? 0) significant off-resonance interactions are observed in homogeneous interactions (?? = 0). The alterations in Cl(+) and HCl(+) signal intensities prove to be very useful for spectra assignments. Data relevant to excitations to the j(3)?(0(+)) Rydberg states and comparison with (3 + n) REMPI spectra allowed reassignment of corresponding spectra peaks. A band previously assigned to an ? = 0 Rydberg state was reassigned to an ? = 2 state (?(0) = 88957.6 cm(-1)). PMID:21528955

Matthíasson, Kristján; Long, Jingming; Wang, Huasheng; Kvaran, Ágúst

2011-04-28

153

NASA Astrophysics Data System (ADS)

Mass spectra were recorded for (2 + n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 88865-89285 cm-1 region to obtain two-dimensional REMPI data. Band spectra due to two-photon resonance transitions to number of Rydberg states (?' = 0, 1, and 2) and the ion-pair state V(1?+(?' = 0)) for H35Cl and H37Cl were identified, assigned, and analyzed with respect to Rydberg to ion-pair interactions. Perturbations show as line-, hence energy level-, shifts, as well as ion signal intensity variations with rotational quantum numbers, J', which, together, allowed determination of parameters relevant to the nature and strength of the state interactions as well as dissociation and ionization processes. Whereas near-resonance, level-to-level, interactions are found to be dominant in heterogeneous state interactions (?? ? 0) significant off-resonance interactions are observed in homogeneous interactions (?? = 0). The alterations in Cl+ and HCl+ signal intensities prove to be very useful for spectra assignments. Data relevant to excitations to the j3?(0+) Rydberg states and comparison with (3 + n) REMPI spectra allowed reassignment of corresponding spectra peaks. A band previously assigned to an ? = 0 Rydberg state was reassigned to an ? = 2 state (?0 = 88957.6 cm-1).

Matthíasson, Kristján; Long, Jingming; Wang, Huasheng; Kvaran, Ágúst

2011-04-01

154

Extensive double-excitation states in atomic helium

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

Domke, M.; Xue, C.; Puschmann, A.; Mandel, T.; Hudson, E.; Shirley, D.A.; Kaindl, G. (Institut fuer Experimentalphyik, Freie Universitaet Berlin, D-1000 Berlin 33, Germany (DE)); Greene, C.H.; Sadeghpour, H.R. (Joint Institute of Laboratory Astrophysics and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (USA)); Petersen, H. (Berliner Electronenspeicherring enGesellschaft fuer Synchrotronstrahlung (BESSY) GmbH, D-1000 Berlin 33 (Germany))

1991-03-11

155

Spectroscopy of high angular momentum Rydberg states with (2)S(1/2) ion cores

NASA Astrophysics Data System (ADS)

The fine structure intervals of n=17 and 20 have been measured in magnesium and barium for a range, 7 ? L ? 13, of angular momentum states. This systematic study used microwave spectroscopy with selective laser excitation for detection of Rydberg levels by Stark ionization. These precise measurements lead to up to two orders of magnitude improvement from past experimental determinations of the induced polarizabilities of the ground state ionic cores. The measured polarizabilities are, for Mg+, alphad = 35.02(4) a30 and alphaQ = 202(54) a50 , and for Ba+, alphad = 124.09(27) a30 and alphaQ = 4238(643) a50 . An opportunity to test the adequacy of the long-range model, historically used to treat high-angular momentum fine structure data, is possible with the availability of independent theoretical calculations. Previously, studies have revealed excellent agreement with calculated values of the induced dipole polarizability of the ion core. A large discrepancy is found, however, between experiment and the best theoretical calculations for the induced quadrupole polarizability. These previous disagreements between theory and experiment for 2S1/2 systems have been largely resolved in this work. In addition, the inclusion of core fine structure in the long-range model will be shown to describe the spin-orbit splittings of high-L barium states.

Snow, Erica Lynn

156

In this paper, we discuss the photoionization dynamics of the {ital D} {sup 2}{Sigma}{sup {minus}}(1{pi}{sup 2}3{ital p}{sigma}) and 3 {sup 2}{Sigma}{sup {minus}}(1{pi}{sup 2}4{ital s}{sigma}) Rydberg states of OH, emphasizing the critical role that Rydberg orbital evolution plays at intermediate to larger internuclear distances in determining vibrational and rotational molecular ion distributions. The orbital evolution process is discussed in terms of diabatic and adiabatic molecular states, united atom--separated atom correlation rules, and quantum defect functions. Vibrationally resolved photoelectron spectra and angular distributions for resonance enhanced multiphoton ionization (REMPI) of OH via the {ital D} {sup 2}{Sigma}{sup {minus}}(1{pi}{sup 2}5{sigma}) and 3 {sup 2}{Sigma}{sup {minus}}(1{pi}{sup 2}6{sigma}) Rydberg states are considered as examples. The results and conclusions are relevant to vibrationally and rotationally resolved REMPI studies of all first-row molecular hydrides, due to the similarity of their electronic structure and correspondence to their associated united atom.

Stephens, J.A.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA (USA))

1990-12-01

157

Observing Superradiant Decay of Excited-State Helium Atoms Inside Helium Plasma

NASA Astrophysics Data System (ADS)

Using femtosecond transient absorption spectroscopy on excited-state helium atoms in a plasma created through optical field ionization, we measured the decay of 2S3-2P3 excitation with sub-ps temporal resolution. The population evolution shows that initial decay is significantly faster than the electron-atom collisions and three orders of magnitude faster than the single atom spontaneous decay rate. This indicates on superradiant coherent behavior of the atomic system inside the plasma.

Xia, Hui; Svidzinsky, Anatoly A.; Yuan, Luqi; Lu, Chao; Suckewer, Szymon; Scully, Marlan O.

2012-08-01

158

State selective Rydberg charge transfer and ionization in low energy ion-atom collisions

NASA Astrophysics Data System (ADS)

The Classical Trajectory Monte Carlo (CTMC) simulation method with a core modified interaction potential has been used to study the single charge transfer in Na+ and Ar+ ions colliding with a variety of state selected Na Rydberg atom targets (n=24, 28, 33, 40 and l=2) in the reduced velocity region v=0.2-2.0. The experimentally observed structures in the total capture cross section versus reduced velocity curves are reproduced by CTMC method. The n-distribution of final capture state has got two peaks viz. first one at nf=ni and the second one at a higher nf depending on the initial angular momentum in the velocity regime 0.4-0.6. These structures have been explained in terms of quasimolecular-ion formation and a classical model proposed by Roy et al. (B.N. Roy, D.N. Tripathi, D.K. Rai, Phys. Rev. A 5 (1972) 1252). The CTMC ionization cross section results are benchmarked with the recent experimental measurement of Makarov et al. (O.P. Makarov, D.M. Homan, O.P. Sorokina, K.B. MacAdam, in: F. Aumayr, G. Betz, H.P. Winter (Eds.), Proceedings of the 20th International Conference on the Physics of Electronics and Atomic Collisions, Vienna, 1997, p. FR052) for Na+-Na(24d).

Perumal, A. N.; Tripathi, D. N.

1998-10-01

159

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

160

Results of combined theoretical and experimental studies of photoelectron spectra resulting from (2+1) resonance enhanced multiphoton ionization (REMPI) via the {ital f} {sup 1}{Pi}(3{ital p}{sigma}), {ital g} {sup 1}{Delta}(3{ital p}{pi}), and {ital h} {sup 1}{Sigma}{sup +}(3{ital p}{pi}) Rydberg states of NH are reported. The overall agreement between these calculated and measured spectra is encouraging. Strong {Delta}{ital N}={ital N}{sup +}{minus}{ital N}{prime}=even peaks, particularly for {Delta}{ital N}=0, are observed in these spectra. Low-energy Cooper minima are predicted to occur in the l=2 wave of the {ital k}{pi}({sup 1}{Sigma}{sup +}), {ital k}{pi}({sup 1}{Sigma}{sup {minus}}), and {ital k}{pi}({sup 1}{Delta}) photoelectron channels for the {ital f} state, the {ital k}{pi}({sup 1}{Delta}), {ital k}{delta}({sup 1}{Pi}), and {ital k}{delta}({sup 1}{Phi}) channels for the {ital g} state, and the {ital k}{pi}({sup 1}{Sigma}{sup +}) and {ital k}{delta}({sup 1}{Pi}) channels for the {ital h} state of NH. Depletion of the {ital d} wave (l=2) contributions to the photoelectron matrix element in the vicinity of these Cooper minima subsequently enhances the relative importance of the odd l waves. The observed {Delta}{ital N} transitions are also affected by strong l mixing in the electronic continuum induced by the nonspherical molecular potential. Interference of continuum waves between degenerate ionization channels also determines the spectral pattern observed for photoionization of the {ital f} {sup 1}{Pi} state of NH. Photoelectron angular distributions and the angular momentum compositions of photoelectron matrix elements provide further insight into the origin of these Cooper minima.

Wang, K.; Stephens, J.A.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125 (United States)); de Beer, E.; de Lange, C.A.; Westwood, N.P.C. (Laboratory for Physical Chemistry, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam (Netherlands))

1992-07-01

161

Applicability of equations of state for modeling helium systems

NASA Astrophysics Data System (ADS)

Proper design of helium systems with large number of components and involved configurations such as helium liquefiers/refrigerators requires the use of tools like process simulators. The accuracy of the simulation results, to a great extent, depends on the accuracy of property data. For computation of thermodynamic properties of helium, the 32-parameter MBWR equation of state proposed by McCarty and Arp [1] is widely used. However, it is computationally involved, makes the simulation process more time-consuming and sometimes leads to computational difficulties such as numerical oscillations, divergence in solution especially, when the process operates over a wide thermodynamic region and is constituted of many components. Substituting MBWR EOS by simpler equations of state (EOS(s)) at selected thermodynamic planes, where the simpler EOS(s) have the similar accuracy as that of MBWR EOS may enhance ease of computation. In the present paper, the methodology to implement this concept has been elucidated with examples of steady state and dynamic simulation of helium liquefier/refrigerator based on Collins cycle. The above concept can be applied to thermodynamic analysis of other process cycles where computation of fluid property is involved.

Thomas, Rijo Jacob; Dutta, Rohan; Ghosh, Parthasarathi; Chowdhury, Kanchan

2012-07-01

162

ERIC Educational Resources Information Center

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

Harbola, Varun

2011-01-01

163

Rydberg atom spectroscopy enabled by blackbody radiation ionization

We have excited helium atoms from their metastable 2 {sup 3} S state to Rydberg states in the range 13

Lu Xiaoxu; Sun Yuan; Metcalf, Harold [Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800 (United States)

2011-09-15

164

Collision Dynamics of Rydberg Atoms and Molecules at Ultralow Energies.

National Technical Information Service (NTIS)

First Major Highlight: Collisional Stark Mixing at ultralow energies in Rydberg Plasmas. Atoms in high (n,l) states formed in cold Rydberg plasmas decay to the ground state in a succession of radiative transitions populating intermediate excited states. W...

M. R. Flannery

2005-01-01

165

Excited state spectroscopy on helium using a color center laser

NASA Astrophysics Data System (ADS)

The recent application of optogalvanic detection for observing weak transitions in the visible was adapted to infrared spectroscopy. For Doppler limited spectroscopy, infrared optogalvanic detection has proven particularly sensitive to those states which the highest angular quantum number; and the observed signal strengths are in good agreement with a steady state model of the optogalvanic effect in the helium positive column. Doppler free optogalvanic spectra were also studied. Holtzmark broadening of the helium linewidth makes it difficult to retrieve spectroscopic information on the fine structure intervals from spectra taken in a discharge; on the other hand, potentially useful information on the processes of the discharge can be extracted from the linewidths and signal strengths.

Jackson, D. J.

1981-08-01

166

Mass spectra were recorded for (2 + n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 88865-89285 cm?1 region to obtain two-dimensional REMPI data. Band spectra due to two-photon resonance transitions to number of Rydberg states (?? = 0, 1, and 2) and the ion-pair state V(1?+(?? = 0)) for H35Cl and

Kristja´n Matthi´asson; Jingming Long; Huasheng Wang; A´gu´st Kvaran

2011-01-01

167

Mass spectra were recorded for (2 + n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 88865-89285 cm-1 region to obtain two-dimensional REMPI data. Band spectra due to two-photon resonance transitions to number of Rydberg states (Omega' = 0, 1, and 2) and the ion-pair state V(1Sigma+(Omega' = 0)) for H35Cl and

Kristján Matthíasson; Jingming Long; Huasheng Wang; Ágúst Kvaran

2011-01-01

168

A spectroscopic study of the Rydberg states of excimer complexes of inert elements and oxygen

Excimer compounds of inert gases and oxygen were investigated by the luminescent analysis of these elements in solid solutions. Results are presented for both low-energy valence complexes and high-energy Rydberg excimers. It is shown that free matrix excitons, which lead to the dissociation of impurity oxygen molecules, play the leading role in the excimer excitation process.

E. M. Iurtaeva; I. Ia. Fugol; A. G. Belov

1990-01-01

169

We report the first experimental observation of magnetic field effects on dielectronic recombination (DR) via highly excited Rydberg levels. Crossed static electric and magnetic fields Ey and Bz were imposed on the collision region in high resolution DR measurements with Li-like Cl14+ ions at the heavy ion storage ring TSR in Heidelberg. Enhancement of DR rate coefficients alpha for the

T. Bartsch; S. Schippers; A. Mueller; C. Brandau; G. Gwinner; A. A. Saghiri; M. Beutelspacher; M. Grieser; D. Schwalm; A. Wolf; H. Danared; G. H. Dunn

1999-01-01

170

The present work involves the study of a simplified atomic system to gain better understanding of controlling and manipulating Rydberg-like systems. Detailed simulations of the classical hydrogen atom have been carried out using, first, the nonrelativistic Lorentz-Dirac classical equation of motion for a charged point particle under the action of a Coulombic binding force, plus applied radiation, then progressing to

Yi Zou

2004-01-01

171

Rydberg atom data register: A use of atomic electronic states for information storage

Quantum computation has experienced a steady growth in interest in recent years. With the rapid development of quantum technologies, the quantum mechanical nature of physical systems is becoming an increasingly important part of future industrial technology. The Rydberg atom is one of the best test tubes in which to attempt programmable coherent control because of our in-depth understanding of both

Jaewook Ahn

2002-01-01

172

NASA Astrophysics Data System (ADS)

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

Sprecher, Daniel; Jungen, Christian; Merkt, Frédéric

2013-10-01

173

NASA Astrophysics Data System (ADS)

(2 + n) resonance enhanced multiphoton ionization mass spectra for resonance excitations to diabatic E1?+ (v') Rydberg and V 1?+ (v') ion-pair states (adiabatic B1?+(v') states) of HiCl (i = 35,37) and HiBr (i = 79,81) were recorded as a function of excitation wavenumber (two-dimensional REMPI). Simulation analyses of ion signal intensities, deperturbation analysis of line shifts and interpretations of line-widths are used to derive qualitative and quantitative information concerning the energetics of the states, off-resonance interactions between the E states and V states, closest in energy as well as on predissociation channels. Spectroscopic parameters for the E1?+ (v')(v' = 1) for H35Cl and v' = 0 for H79Br states, interaction strengths for E - V state interactions and parameters relevant to dissociation of the E states are derived. An overall interaction and dynamical scheme, to describe the observations for HBr, is proposed.

Long, Jingming; Wang, Huasheng; Kvaran, Ágúst

2013-01-01

174

The influence of the half-cycle pulse (HCP) kick on the asymptotic velocity of the ejected electron has been studied for excited xenon atoms (n{sup *}=34) in the presence of a static electric field (220 V cm{sup -1}). We find that the HCP does not change the momentum distribution perpendicular to the kick direction. Therefore half-cycle pulse ionization and electron velocity map imaging can be used to obtain two-dimensional momentum distributions of atomic Rydberg states. Semiclassical and quantum mechanical calculations complement the experimental results.

Wetzels, A.; Guertler, A.; Rosca-Pruna, F.; Zamith, S.; Vrakking, M.J.J. [FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); Robicheaux, F. [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States); Zande, W.J. van der [FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); Department of Molecule and Laser Physics, University of Nijmegen, Nijmegen (Netherlands)

2003-10-01

175

Rotationally resolved spectroscopy and dynamics of the 3p(x)?(1)A(2) Rydberg state of formaldehyde.

The rotational structure of the lowest three vibrational levels (0(0), 6(1) and 4(1)) of the 3p(x)?(1)A(2) Rydberg state of formaldehyde has been studied by doubly-resonant three-photon ionization spectroscopy. A strong a-type Coriolis interaction between the in-plane rocking (?(6)) and out-of-plane bending (?(4)) modes results in the observation of vibronically forbidden transitions to the 6(1) level from the intermediate Ã(1)A(2) (2(1) 4(3)) level. The full widths at half maximum of the rovibronic transitions to the 4(1) state are considerably larger than to the vibrational ground state and the 6(1) level. The band origin (T(0) = 67?728.939(82) cm(-1)), the rigid rotor rotational constants (A = 9.006(19) cm(-1), B = 1.331(20) cm(-1), and C = 1.135(22) cm(-1)), the Coriolis coupling constant (? = 8.86(89) cm(-1)) and the deperturbed fundamental wave numbers of both vibrational modes (v[combining tilde](6) = 808.88(25) cm(-1) and v[combining tilde](4) = 984.92(26) cm(-1)) have been determined for the 3p(x)?(1)A(2) Rydberg state. Polarization effects originating from the double-resonance technique have been exploited to detect the Coriolis interaction and investigate how it affects the predissociation dynamics. PMID:20733971

Meisinger, M; Schulenburg, A M; Merkt, F; Radi, P P

2010-08-23

176

In order to assess the long-term threat posed to plant and animal life by ozone depletion and the resulting increase of ultraviolet (UV) radiation, the United States Department of Agriculture has established a UV irradiance monitoring program, with emphasis on the UV-B wavelength region between 290 nm and 320 nanometers. However, there is serious concern over the long-term stability of conventional instruments used to measure the UV-B flux. We have recently demonstrated the feasibility of using resonance ionization to monitor specific wavelengths in the UV-B band. However, instead of using high-intensity lasers to detect a few atoms as is typically done in resonance ionization experiments, the UV-B monitor is based upon using a relatively high pressure (about 10{sup -5} Torr) of vapor-phase cesium, rubidium, and/or potassium to detect photons. Specific Rydberg states formed by resonant absorption of UV-B radiation in these vapors can be identified by their unique voltage threshold for ionization. Our initial work has established that there is a high correlation between the detected Rydberg state and the wavelength of the absorbed light, so that it should be possible to construct a UV-B detector with an internal, absolute wavelength calibration. The initial work will be discussed and the prospect for making a UV-B detector will be examined.

Whitaker, T.; Bekov, G. [Atom Sciences, Inc., 114 Ridgeway Center, Oak Ridge, TN, 37830 (United States)

1995-04-01

177

NASA Astrophysics Data System (ADS)

As a major constituent of the terrestrial atmosphere, the O2 molecule plays an important role both in the attenuation of solar radiation and in the spectrum of the airglow and aurora. Photo absorption by O 2 to its complex excited state structure leads to predissociation and involves a host of other kinetic and radiative processes. Part of the work presented in the thesis constitutes a complete and critical review of what is presently known about the electronic structure of O2 in four broad areas: (1)the detailed electronic structure of the first six bound states of O2 (the 0 to ~ 5 eV region), (2)the electronic structures around the B S

Morrill, Jeff Stanley

1999-09-01

178

Magnetic Trapping of Long-Lived Cold Rydberg Atoms

We report on the trapping of long-lived strongly magnetized Rydberg atoms. {sup 85}Rb atoms are laser cooled and collected in a superconducting magnetic trap with a strong bias field (2.9 T) and laser excited to Rydberg states. Collisions scatter a small fraction of the Rydberg atoms into long-lived high-angular momentum 'guiding-center' Rydberg states, which are magnetically trapped. The Rydberg atomic cloud is examined using a time-delayed, position-sensitive probe. We observe magnetic trapping of these Rydberg atoms for times up to 200 ms. Oscillations of the Rydberg-atom cloud in the trap reveal an average magnetic moment of the trapped Rydberg atoms of {approx_equal}-8{mu}{sub B}. These results provide guidance for other Rydberg-atom trapping schemes and illuminate a possible route for trapping antihydrogen.

Choi, J.-H.; Guest, J.R.; Povilus, A.P.; Hansis, E.; Raithel, G. [FOCUS Center, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

2005-12-09

179

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

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

D. Porcelli; G. J. Wasserburg

1995-01-01

180

Collective quantum jumps of Rydberg atoms.

We study an open quantum system of atoms with a long-range Rydberg interaction, laser driving, and spontaneous emission. Over time, the system occasionally jumps between a state of low Rydberg population and a state of high Rydberg population. The jumps are inherently collective, and in fact, exist only for a large number of atoms. We explain how entanglement and quantum measurement enable the jumps, which are otherwise classically forbidden. PMID:22324684

Lee, Tony E; Häffner, H; Cross, M C

2012-01-09

181

Long-range ultracold Rydberg molecules

NASA Astrophysics Data System (ADS)

The dipole-dipole interaction between two Rydberg atoms has a non-zero contribution in first-order perturbation theory, due to the large number of non-core-penetrating states which retain the angular-momentum degeneracy characteristic of atomic hydrogen. The combination of dipole-dipole attraction ( ˜ R-3) and quadrupole-quadrupole repulsion ( ˜ R-5) produces a set of electronic potential curves, which may support many vibrational states at large internuclear distances R and which are relatively stable against predissociation, autoionization and radiative decay. The strongest binding in each Rydberg-Rydberg manifold corresponds to both electrons being in the most stretched Stark dipole states aligned in the same direction along the internuclear axis. Such diatoms possess significant net dipole moments and can therefore form larger clusters. Directed-valence Rydberg orbitals so introduced are basic to Rydberg-Rydberg interactions. Research supported by AFOSR, Grant 49620-02-1-0338 and NSF Grant 01-00890.

Flannery, M. Raymond; Ostrovsky, Valentine; Vrinceanu, Daniel; Prudov, N.

2003-10-01

182

The spectroscopic measurements of Houston and of Chu pertinent to the Rydberg constant have been adjusted to a new wavelength value (5015.6779+\\/-0.0003 A in air) for the helium line used as a standard by them. This new wavelength, based primarily on recent measurements by the author and by Series and Field, replaces the value 5015.675 A accepted by Houston and

William C. Martin

1959-01-01

183

The newly developed technique of photoinduced Rydberg ionization (PIRI) spectroscopy has been successfully applied to study the {tilde B}{l_arrow}{tilde X} transition in the phenol and phenol-d{sub 6} cations. Vibrationally resolved spectra have been obtained for the {tilde B} state in phenol ion via the origin and the {nu}{sub 6}, and {nu}{sub 12} vibrations of the ground ionic state. Similarly, vibrationally resolved spectra for the {tilde B} state in phenol-d{sub 6} ion have been obtained via the origin and {nu}{sub 6} vibration. Calculations to date have suggested the character of the half-filled orbital is {pi} type, and experimental evidence for the {tilde B}-state assignment so far has been inconclusive. In contrast to previous featureless photoelectron spectra, the main feature in all of the spectra presented here is the presence of several long, low frequency Frank{endash}Condon progressions, suggestive of a large geometry change in the transition. Configuration interaction singles 6-31G{sup {asterisk}} calculations, allowing full geometry optimization, show that the first excited {sigma} state has the OH group rotated 90{degree} from the planar ground state. Therefore, the symmetry for the {tilde B} state in phenol cation is assigned to be 2p{sigma} instead of {pi}, corresponding to that of benzene and several other monosubstituted benzenes. Further support for this assignment is found in a calculation of the normal mode vibrations, based on the geometry optimized for the excited {sigma} state. These show three low frequency normal modes having a large amount of OH torsion, one of which has a ring motion identical to one of the two normal modes that induces the {tilde B}{l_arrow}{tilde X} transition in the benzene cation. This calculated normal mode is, therefore, assigned to the most intense and most extensive progression observed in the photoinduced Rydberg ionization spectra. {copyright} {ital 1997 American Institute of Physics.}

LeClaire, J.E.; Anand, R.; Johnson, P.M. [Department of Chemistry, The State University of New York at Stony Brook, Stony Brook, New York 11794-3400 (United States)

1997-05-01

184

The hyperfine structure of ns and nd Rydberg states of {sup 83}Kr has been measured in the range n=30-190 below the {sup 2}P{sub 3/2} ionization threshold by pulsed-field ionization following single-photon excitation from the {sup 1}S{sub 0} ground state using a narrow-bandwidth vacuum-ultraviolet laser system. A multichannel quantum defect theory (MQDT) treatment of the hyperfine structure in Rydberg states of the rare-gas atoms has been developed that quantitatively accounts for the effects of the nuclear spin on the spectral structures over the entire range of principal quantum number investigated. The model allows the parametrization of the hyperfine structure of the Rydberg states in terms of the ionic hyperfine structure and relies on the assumption that the interaction with the nuclear spin is negligible in the close-coupling region of the electron-ion collision, an assumption that is also expected to be valid in other atomic and molecular systems. Improved eigen quantum defects for the ns and nd Rydberg series with J=1 and 2 have been derived from the MQDT analysis, and the hyperfine structure of the two {sup 2}P{sub 3/2} and {sup 2}P{sub 1/2} spin-orbit components of the ground state of {sup 83}Kr{sup +} has been determined.

Woerner, H. J.; Hollenstein, U.; Merkt, F. [Laboratorium fuer Physikalische Chemie, ETH Zuerich, CH-8093 Zurich, (Switzerland)

2003-09-01

185

Ultrafast Laser Studies of Molecular Rydberg Wave Packets.

National Technical Information Service (NTIS)

The goal of this work is to investigate the formation and detection of Rydberg wave packets in molecules and to explore their possible use in quantum information processing. Very few coherent superpositions of molecular Rydberg states have been experiment...

S. R. Leone S. Gilb V. Nestorov E. Torres A. Arrowsmith

2005-01-01

186

Ultrafast Laser Studies of Molecular Rydberg Wave Packets.

National Technical Information Service (NTIS)

Wave packet preparation and probing is investigated in molecules, with particular emphasis on the formation of Rydberg wave packets. A new apparatus has been developed to investigate Rydberg state excitation with ultrafast lasers. It consists of an ultraf...

S. R. Leone

2002-01-01

187

NASA Astrophysics Data System (ADS)

The electronic states of the BBr molecule, including 12 valence states and 12 low-lying Rydberg states, have been studied at the theoretical level of MR-CISD+Q with all-electron aug-cc-pVQZ basis sets and Douglas-Kroll [Ann. Phys. (N.Y.) 82, 89 (1974)] scalar relativistic correction. The spin-orbit coupling effect in the valence states was calculated by the state interaction approach with the full Breit-Pauli Hamiltonian. This is the first multireference ab initio study of the excited electronic states of BBr. Potential energy curves of all states were plotted with the help of the avoided crossing rule between electronic states of the same symmetry. The structural properties of these states were analyzed. Computational results reproduced most experimental data well. The transition properties of the a 3?0+, a 3?1, and A 1?1 states to the ground state X 1?0++ transitions were obtained, including the transition dipole moments, the Franck-Condon factors, and the radiative lifetimes. The evaluated radiative lifetime of the a 3?0+, and a 3?1 states are near 1 ms, much longer than that of the A 1?1 state.

Yang, Xinzheng; Boggs, James E.

2006-05-01

188

Non-Franck--Condon effects in photoionization of the 3 sup 3. Pi. Rydberg state of NH

Strong non-Franck--Condon behavior is predicted to occur in the vibrationally resolved photoionization spectra of NH for (3+1) resonance enhanced multiphoton ionization processes via the 3 {sup 3}{Pi} Rydberg state. The non-Franck--Condon effects are interpreted on the basis of rapid orbital evolution, Cooper minima, and internuclear distance dependence of the dipole transition moment and cross sections. A Cooper minimum occurs in the 5{sigma}{r arrow}{ital k}{pi} channel at small internuclear distances, where NH resembles its united atom, oxygen. The iterative Schwinger variational method and multiplet-specific ion potentials are employed in the calculation of the photoelectron continuum wave functions. Cross sections and asymmetry parameters for photoionization of the NH ground state leading to the {ital X} {sup 2}{Pi}, {ital a} {sup 4}{Sigma}{sup {minus}}, and {ital A} {sup 2}{Sigma}{sup {minus}} ions are also reported.

Wang, K.; Stephens, J.A.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA (USA))

1990-12-01

189

NASA Astrophysics Data System (ADS)

Mass analyzed threshold ionization (MATI) experiments have enabled mapping of the n-dependent Rydberg state survival probability for a series of molecules. Utilizing vacuum and extreme ultraviolet (VUV/XUV) photons, one photon Rydberg manifold spectra of argon, hydrogen chloride, nitrogen, benzene, and oxygen were produced, and the prospects of photoinduced Rydberg ionization (PIRI) experiments examined. It was found that the widths of Rydberg manifolds for the molecules studied are quite different. Hydrogen chloride and nitrogen have the narrowest manifold width, followed by benzene, and then oxygen. These varying widths are most strongly correlated with the angular momentum (i.e., quantum defect) of the initially prepared Rydberg orbital. PIRI experiments required the use of a static cell, rather than a molecular jet assembly, for the more efficient production of higher amounts of VUV/XUV radiation, and hence more Rydberg signal needed to observe PIRI. Armed with the ability to produce tunable VUV/XUV radiation, and to determine the feasibility of a PIRI experiment, the MATI and fragment PIRI spectra of trans-1,3-butadiene (BD) were recorded. The MATI spectrum is vibrationally resolved and was analyzed with the help of ab initio calculations and other published results. The fragment PIRI spectrum of the A<==X transition of BD+ is not vibrationally resolved, but information regarding the wavelength dependence of fragmentation pathways has been gathered and interpreted. It was found that at low photodissociation photon energies, production of C3H3+ dominates, but at higher photon energies, C2H4 + is also produced. The production of each fragment showed a definite PIRI wavelength dependence.

Hofstein, Jason David

1999-11-01

190

Unnatural parity states of helium with screened Coulomb potentials

NASA Astrophysics Data System (ADS)

Effect of screened Coulomb (Yukawa) potentials on the doubly excited meta-stable bound states and the resonance states with unnatural parities of the helium atom have been investigated in the framework of stabilization method using CI-type basis functions. A total of 54 resonances (6 each of 1Do and 3Do states, 12 each of 1Fe and 3Fe states, 9 each of 1Go and 3Go states) below the He+(3P) thresholds have been estimated by calculating the density of resonance states using a stabilization method. The resonances belong to the different 3lnlprime (n ge 3) series. We have also calculated the doubly excited 1,3Fe and 1,3Go meta-stable bound states of He atom below the He+ (2P) thresholds. The resonance energies and widths along with the meta-stable bound states energies are reported for various screening parameters. In free atom case, some of the F-wave resonance states and most of the cases, F- and G-wave resonance widths are reported for the first time.

Kar, Sabyasachi; Ho, Y. K.

191

Helium resources of the United States, 1993. Information circular\\/1995

This report uses several criteria to determine reserves, marginal reserves, and subeconomic resources, including helium content, proximity to major gas transmission lines, and size of field. Refinements in evaluating other occurrences of helium and undiscovered resources also have been made for this report. As of this report, there is 33.7 Bcf of helium stored in Bush Dome at Cliffside Gasfield.

J. E. Hamak; D. L. Driskill

1995-01-01

192

Excitation of autoionizing states of helium by electron impact

NASA Astrophysics Data System (ADS)

We report results of calculations for excitation of autoionizing (2s^2)^1S, (2p^2)^1D and (2s2p)^1P states of helium by electron impact. The calculations have been carried out with inclusion of the Coulomb interaction in the final state and expansion of two-electron excitation amplitude in the Born series over the projectile-target interaction through the second order. Spatial electron correlation has been taken into account using multi-configurational Hartree-Fock (MCHF) wavefunctions. Results of the calculations are compared to (e,2e) experimental data of McDonal and Crowe for 200 eV electron impact.

Godunov, A. L.; McGuire, J. H.

2002-05-01

193

Stimulated emission of bremsstrahlung radiation by electrons in high Rydberg states is analysed theoretically. This approach to bremssstrahlung masers is shown to overcome some of the previous difficulties in realizing a practical value for the bremsstrahlung gain in the millimeter-wave regime by allowing volumetric production of mono-energetic electrons within a time period which is short compared to the thermalization time of the electron energy distribution, and by relaxing the criteria on the energy dependence bremsstrahlung gain coefficient.

Palmer, A.J.

1986-08-15

194

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

195

Rydberg state population due to multicapture processes in Kr[sup q+] (q=17-18) on Kr collisions

Initial population distributions in principal quantum numbers n of excited states were obtained in multicapture processes for Kr[sup q+] (q=17-18) on Kr collisions at low energy ([approx]5 keV/u). Radiative decay curves of Rydberg transitions of the projectivle ions have been measured by shifting the target gas jet along the projectile beam, i.e. perpendicularly to the observation axis. As a result for Kr[sup 18+] projectiles, we have found that an Kr[sup 16+] constant initial population from n=14 to n=19 allows the observed Kr XVII 14--15 radiative decay curve to reproduce relatively well. In addition to this, coincidence time of flight spectroscopy between recoil ion photons and recoil ions have been performed in order to determine the decay curves of recoil ion transitions. We found an initial population distribution centered around n=20 for the 7i--8k transition of Kr VII recoil ion.

Martin, S.; Denis, A.; Delon, A.; Desesquelles, J. (LASIM Universite Lyon 1, Campus de la Doua, F-69622 Villeurbanne Cedex (France)); Ouerdane, Y. (TSI Universite de Saint-Etienne, 23 rue du Dr Paul Michelon, F-4202, Saint-Etienne (France))

1993-06-05

196

An experimental determination of the Rydberg constant

The wavelengths of components of the Balmer- alpha line in dueterium and tritium have been determined in terms of the 86Kr 606 nm primary standard to establish a value for the Rydberg constant. Improved resolution of the fine structure was achieved by using a discharge cooled in liquid helium to reduce the Doppler width. Positions and intensities of the fine

B. P. Kibble; W. R. C. Rowley; R. E. Shawyer

1973-01-01

197

The Rydberg states of Xe{sub 2} in the region between 76,,000 and 84,000 cm{sup -1} were studied by using a combination of two-photon excitation and velocity map ion imaging. The electronic states in this region are based on the Xe({sup 1}S{sub 0})+Xe 6p and 5d dissociation limits, and the large number of states leads to numerous curve crossings and distorted potentials. These Rydberg states can decay by predissociation or fluorescence or can be photoionized, dissociatively photoionized, or photodissociated by the absorption of a single additional photon. Furthermore, the molecular ion can be photodissociated as well. While numerous other techniques have been applied to this problem, velocity map ion imaging provides a high resolution approach to determine the operative processes. When combined with existing data obtained by other methods, the present experiments allow a more complete understanding of the assignment and behavior of these states.

Shubert, V. A.; Rednic, M.; Pratt, S. T. (Chemical Sciences and Engineering Division); (Univ. of Illinois)

2010-01-01

198

Rydberg Atom - Atom Interactions and Collisions

NASA Astrophysics Data System (ADS)

The interaction between highly excited Rydberg atoms exerts a crucial role in such modern issues as ultracold Rydberg plasmas, Rydberg matter, dipole blockade and quantum computing. For two-electron states in a Rydberg-Rydberg dimer Rg_2, the dipole-dipole interaction ( ˜ 1/R^3) between the Rydberg atoms Rg with internuclear distance R can be both attractive or repulsive, depending on electronic state. For the two-electron states with maximum dipole-dipole attraction, the next term in the potential energy originates from the quadrupole-quadrupole interaction which is repulsive. Since the attraction prevails at larger internuclear separations R and repulsion dominates at smaller R, the related potential curve exhibits a minimum at separation R = (10 ?5/3?2) n^2. For such large R, the autoionization width is small and long-living vibrational states are possible. In the simplest case of H(n=2)-H(n=2) pair, the potential well supports several tens of vibrational bound states. Estimates for higher n are provided. A theory of ?-mixing intrashell transitions in Rydberg-Rydberg collisions induced by the dipole-dipole interaction will also be presented. Research supported by AFOSR, Grant 49620-02-1-0338 and NSF Grant 01-00890.

Flannery, Raymond; Ostrovsky, Valentin; Prudov, N.; Vrinceanu, Daniel

2003-05-01

199

NASA Astrophysics Data System (ADS)

Mass spectra were recorded for (2+n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 81 710-82 870 cm-1 region to obtain two-dimensional REMPI data. Small but significant fragmentations and H+, Cl+, as well as HCl+ formations are found to occur after resonance excitations to the triplet Rydberg states f 3?2(v'=0), f 3?1(v'=0), and g 3?+(1)(v'=0). Whereas insignificant rotational line shifts could be observed, alterations in relative ion signal intensities, due to perturbations, clearly could be seen, making such data ideal for detecting and analyzing weak state interactions. Model analysis of relative ion signal intensities, taking account of the major ion formation channels following excitations to Rydberg states, its near-resonance interactions with ion-pair states as well as dissociations and/or photodissociations were performed. These allowed verification of the existence of all these major channels as well as quantifications of the relative weights of the channels and estimates of state interaction strengths. The proposed mechanisms were supported by ion signal power dependence studies.

Kvaran, Ágúst; Matthiasson, Kristján; Wang, Huasheng

2009-07-01

200

NASA Astrophysics Data System (ADS)

A simple Mathematica (version 7) code for computing S-state energies and wave functions of two-electron (helium-like) ions is presented. The elegant technique derived from the classical papers of Pekeris is applied. The basis functions are composed of the Laguerre functions. The method is based on the perimetric coordinates and specific properties of the Laguerre polynomials. Direct solution of the generalized eigenvalues and eigenvectors problem is used, distinct from the Pekeris works. No special subroutines were used, only built-in objects supported by Mathematica. The accuracy of the results and computation times depend on the basis size. The ground state and the lowest triplet state energies can be computed with a precision of 12 and 14 significant figures, respectively. The accuracy of the higher excited states calculations is slightly worse. The resultant wave functions have a simple analytical form, that enables calculation of expectation values for arbitrary physical operators without any difficulties. Only three natural parameters are required in the input.The new version of Mathematica code takes into account the fact that the negative hydrogen ion has only one bound state.

Liverts, Evgeny Z.; Barnea, Nir

2012-03-01

201

Semiclassical theory of the helium atomic spectrum

A semiclassical theory of the excitations of two-electron atoms is developed, based on the collective coordinate method and the 1/N expansion, and its application to the s-state helium spectrum is considered. The leading approximation, where quantum fluctuations due to the kinetic term are quenched, while attendant effects are accommodated by an effective potential, provides an inset to delineate spontaneous symmetry rearrangement of the system. The cumulative spectral content of the fragmentation or single-particle regime and the affiliated electron regime as reflected by the doubly excited states, is a Rydberg series within a Rydberg series. The collective regime promotes novel molecular features, such as vibrational s states, due to the underlying geometrical configurations of the affiliated electrons. The work also touches on issues such as quantum defect theory, topological quantization, and rotational effects.

van der Merwe, P.d.T.

1984-12-20

202

(2 + n) resonance enhanced multiphoton ionization mass spectra for resonance excitations to diabatic E(1)?(+) (v') Rydberg and V (1)?(+) (v') ion-pair states (adiabatic B(1)?(+)(v') states) of H(i)Cl (i = 35,37) and H(i)Br (i = 79,81) were recorded as a function of excitation wavenumber (two-dimensional REMPI). Simulation analyses of ion signal intensities, deperturbation analysis of line shifts and interpretations of line-widths are used to derive qualitative and quantitative information concerning the energetics of the states, off-resonance interactions between the E states and V states, closest in energy as well as on predissociation channels. Spectroscopic parameters for the E(1)?(+) (v')(v' = 1) for H(35)Cl and v' = 0 for H(79)Br states, interaction strengths for E - V state interactions and parameters relevant to dissociation of the E states are derived. An overall interaction and dynamical scheme, to describe the observations for HBr, is proposed. PMID:23387585

Long, Jingming; Wang, Huasheng; Kvaran, Ágúst

2013-01-28

203

The initial state alignment effect vs relative velocity is measured for a state-to-state Ca Rydberg collisional energy transfer process. The stimulated emission detection method is used to determine the alignment effect for the n,l-changing transition: Ca(4s17d 1D2)+Xe?Ca(4s18p 1P1) +Xe+?E=?1.7 cm?1. The rate of electronic energy transfer in this state-changing collision is observed to vary with the direction of the Rydberg

Eileen M. Spain; Mark J. Dalberth; Paul D. Kleiber; Stephen R. Leone; Stefan S. Op de Beek; Jan P. J. Driessen

1995-01-01

204

Rydberg atoms in ultracold plasmas

NASA Astrophysics Data System (ADS)

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

Rolston, Steven

2009-05-01

205

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

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

2011-05-15

206

Very accurate variational nonrelativistic calculations are performed for the five lowest Rydberg {sup 2}D states (1s{sup 2}nd{sup 1}, n=3,...,7) of the lithium atom ({sup 7}Li). The finite-nuclear-mass approach is employed and the wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian function. Four thousand Gaussians are used for each state. The calculated relative energies of the states determined with respect to the {sup 2}S 1s{sup 2}2s{sup 1} ground state are systematically lower than the experimental values by about 2.5 cm{sup -1}. As this value is about the same as the difference between the experimental relative energy between {sup 7}Li{sup +} and {sup 7}Li in their ground-state energy and the corresponding calculated nonrelativistic relative energy, we attribute it to the relativistic effects not included in the present calculations.

Sharkey, Keeper L. [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States); Bubin, Sergiy [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Adamowicz, Ludwik [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States); Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2011-01-15

207

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

208

IR+UV double resonant ion-dip and ion-enhancement spectroscopies are employed to study the nu3 asymmetric CH stretch vibration fundamental of CH3 in the ground and 3p(z) Rydberg electronic states. CH3 radical is synthesized in the supersonic jet expansion by flash pyrolysis of azomethane (CH3NNCH3) prior to the expansion. The Q band of the 3(1) (1) 3p(z)<--X transition of CH3, not detected by conventional UV resonantly enhanced multiphoton ionization (REMPI) spectroscopy, is determined to lie at 59,898 cm(-1) using IR+UV REMPI spectroscopy. Energy of the asymmetric CH stretch of CH3 in the 3p(z) Rydberg state, nu3(3p(z)), is 3087 cm(-1), redshifted by approximately 74 cm(-1) with respect to ground state nu3(X). PMID:16392920

Fu, H B; Hu, Y J; Bernstein, E R

2005-12-15

209

Collisions and interactions in ultracold Rydberg plasmas

NASA Astrophysics Data System (ADS)

A new branch of atomic physics - the interactions and collisions in ultracold Rydberg plasmas (T1 K) systems- has naturally evolved from recent advances in the cooling and trapping of neutral gases. Here we discuss the key collisional processes-- three-body recombination. electron-impact ionization of Rydberg atoms, radiative cascade of Rydberg atoms and Rydberg -Rydberg interactions --important to the evolution of the plasma. Quantal and classical radiative cascades are illustrated, together with the ``trajectory" in nl space followed during the cascade. Theory and cross sections for ionization of Rydberg atoms in n, l states by collision with electrons is presented. The full dependence of the cross sections on the initial angular momentum l of the target is revealed, with interesting physical characteristics. Analytical curvefits for the cross sections are then provided so as to extract the rates for three-body capture into state n,l from detailed balance. Three-body recombination followed by Stark mixing produce Rydberg atoms with a broad distribution of l states. These states are sufficiently flexible that permanent dipole and higher permanent multipoles are created quite easily out of the large number ˜n^2 of degenerate angular momentum states l within the energy shell. First-order interactions between Rydbergs therefore exist. We present the physics of the first-order long-range interaction between these polar Rydberg atoms and investigate the possible formation of long-range molecules from two Rydberg atoms with the same (or different) principal quantum numbers n, but with a broad superposition of many degenerate angular momentum states l.

Flannery, Raymond

2005-05-01

210

Ground-state properties of one-dimensional matter and the Zel'dovich effect in Rydberg atoms

NASA Astrophysics Data System (ADS)

The following dissertation consists of three parts. The first two concern ground-state properties of one-dimensional matter, while the third describes an experimental realization of the Zel'dovich effect in Rydberg atoms. Motivated by emerging experimental possibilities to confine atoms and molecules in quasi-one-dimensional geometries, in Chapters 1 and 2 we analyze ground-state properties of strictly one-dimensional molecular matter comprised of identical particles of mass m interacting by a Morse potential between nearest neighbors. We find that due to zero-point motion, the system first undergoes a discontinuous evaporation transition into a diatomic gas followed by a continuous dissociation transition into a monoatomic gas. In particular we find that spin-polarized isotopes of hydrogen and 3He are monoatomic gases, 4He is a diatomic gas, while molecular hydrogen and heavier substances are Luttinger liquids. We also investigate the effect of finite pressure on the properties of the liquid and monoatomic gas phases. In particular we estimate a pressure at which molecular hydrogen undergoes an inverse Peierls transition into a metallic state which is a one-dimensional analog of the transition predicted by Wigner and Huntington in 1935. In Chapter 2, we show that dissociation of the Luttinger liquid is a process initiated at the system edge. The latter becomes unstable against quantum fluctuations at a value of De Boer's number which is smaller than that of the bulk instability which parallels the classical phenomenon of surface melting. 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. In Chapter 3 we demonstrate that along the Periodic Table of elements the Zel'dovich effect manifests itself as a 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.

Timmins, Michael Anthony

211

NASA Astrophysics Data System (ADS)

Two-color resonance-enhanced multiphoton ionization (REMPI) spectra of jet-cooled (?6-C6H6)2Cr(1), (?6-C6D6)2Cr(2), and (?6-C6D6)(?6-C6D5H)Cr(3) have been measured with use of the 3dz2-->R4px,y Rydberg transition as the first step of the electronic excitation. The 000 Rydberg component shifts by 59 and 54 cm-1 to red when one goes from 1 to 2 and 3, respectively. Surprisingly, the REMPI spectra of 1-3 show very rich vibronic structures revealing both totally symmetric vibrations and degenerate vibrational modes. Presence of intense peaks corresponding to the e2g modes in the spectra of 1 and 2 is indicative of Jahn-Teller coupling in the R4px,y Rydberg state. Additional REMPI resonances appear on going from 1 and 2 to 3 as a result of the symmetry reduction. The vibronic components in the spectra of 1-3 were assigned on the basis of the selection rules and comparison with the vibrational frequencies of the 1 and 2 ground-state molecules. The frequencies of over 10 normal vibrations have been determined for the gas-phase 1-3 Rydberg-state molecules from the REMPI experiment. The wavenumber corresponding to the lowest-energy mode (the ring torsion vibration) appears to be 40 cm-1 in 1 and 35 cm-1 in the deuterated complexes. The REMPI peaks are homogeneously broadened. The lower lifetime limits for the upper-state components increase on going from the vibrationless level to higher-lying vibronic states and on going from 1 to the deuterated derivatives.

Ketkov, Sergey Yu.; Selzle, Heinrich L.; Schlag, Edward W.

2004-07-01

212

The results of rotationally resolved resonance enhanced multiphoton ionization photoelectron spectroscopy and zero kinetic energy-pulsed field ionization studies on HBr via various rotational levels of the {ital F}{sup 1}{Delta}{sub 2} and {ital f}{sup 3}{Delta}{sub 2} Rydberg states are reported. These studies lead to an accurate determination of the lowest ionization threshold as 94098.9{plus_minus}1 cm{sup {minus}1}. Observed rotational and spin{endash}orbit branching ratios are compared to the results of {ital ab} {ital initio} calculations. The differences between theory and experiment highlight the dominant role of rotational and spin{endash}orbit interactions for the dynamic properties of the high-{ital n} Rydberg states involved in the pulsed field ionization process. {copyright} {ital 1996 American Institute of Physics.}

Wales, N.P.; Buma, W.J.; de Lange, C.A. [Laboratory for Physical Chemistry, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam (The Netherlands); Lefebvre-Brion, H. [Laboratoire de Photophysique Moleculaire, Bat. 213, Universite de Paris-Sud, 91405 Orsay Cedex (France); Wang, K.; McKoy, V. [Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125 (United States)

1996-04-01

213

Microwave spectroscopy of S, P, and D states of sodium Rydberg atoms

NASA Astrophysics Data System (ADS)

The transition frequencies of the nS-->nP and nD-->(n+1)P sodium atom series were measured within the 53-350-GHz range for the main quantum number n=22-32. More precise values of ls splitting and quantum defects for P1/2,3/2 and D3/2,5/2 terms were determined. The frequencies were measured with an accuracy of better than 50 kHz. The results were treated using the Rydberg formula E(n,l,j)=-RNa/(n-?nlj)2. The quantum defect was calculated by using the expression ?nj=?lj+?lj/n*2. The constants ?lj and ?lj that result from this work are ?1/2=0.855 444 58(14), ?1/2=0.112 668 (90), ?3/2=0.854 625 83(12), and a3/2=0.112 878(81) for the P term and ?3/2=0.014 909 19(38), a3/2=-0.042 19(25), ?5/2=0.014 925 82(55), and a5/2=-0.043 33(35) for the D term. The ls-splitting constants determined from the expression ??l=Al/n*3 are Ap=5 384 790(420) MHz for the P term and Ad=97 340(680) MHz for the D term.

Dyubko, S.; Efimenko, M.; Efremov, V.; Podnos, S.

1995-07-01

214

NASA Astrophysics Data System (ADS)

In this paper, we accurately estimate the ground-state energy and the atomic radius of the helium atom and a helium-like Hookean atom by employing the uncertainty principle in conjunction with the variational approach. We show that with the use of the uncertainty principle, electrons are found to be spread over a radial region, giving an electron cloud. Our calculation also shows how the Coulomb interaction between electrons affects their distribution. This leads to a physical picture of how electrons are located with respect to each other in these atoms. Finally, we also obtain through our calculations a general formula for the estimate of ground-state energy and radius of two electron atoms and ions with atomic number Z.

Harbola, Varun

2011-11-01

215

Collective quantum jumps of Rydberg atoms

NASA Astrophysics Data System (ADS)

A quantum system under constant observation may occasionally switch between two metastable states. These quantum jumps are usually observed in a single object, like an atom, electron, or superconducting qubit. We report on a collective type of quantum jump in a group of atoms with long-range Rydberg interaction, laser driving, and spontaneous emission. Over time, the system occasionally jumps between a state of low Rydberg population and a state of high Rydberg population. The jumps are inherently collective and in fact exist only for a large number of atoms. We explain how entanglement and quantum measurement enable the jumps, which are otherwise classically forbidden.

Lee, Tony; Haeffner, Hartmut; Cross, Michael

2012-02-01

216

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

217

Rydberg crystallization detection by statistical means

NASA Astrophysics Data System (ADS)

We investigate an ensemble of atoms which can be excited into a Rydberg state. Using a disordered quantum Ising model, we perform a numerical simulation of the experimental procedure and calculate the probability distribution function P(M) to create a certain number of Rydberg atoms M, as well as their pair-correlation function. Using the latter, we identify the critical interaction strength above which the system undergoes a phase transition to a Rydberg crystal. We then show that this phase transition can be detected using P(M) alone.

Breyel, D.; Schmidt, T. L.; Komnik, A.

2012-08-01

218

Stimulated emission studies of ultracold Rydberg atoms

NASA Astrophysics Data System (ADS)

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

Brekke, Erik Gallup

219

Quantum-classical lifetimes of Rydberg molecules

NASA Astrophysics Data System (ADS)

A remarkable property of Rydberg atoms is the possibility of creating molecules formed by one highly excited atom and another atom in the ground state. The first realization of such a Rydberg molecule has opened an active field of physical investigations, and showed that its basic properties can be described within a simple model regarding the ground state atom as a small perturber that is bound by a low-energy scattering process with the Rydberg electron (Greene et al 2000 Phys. Rev. Lett. 85 2458). Besides the good agreement between theory and the experiment concerning the vibrational states of the molecule, the experimental observations yield the astonishing feature that the lifetime of the molecule is clearly reduced as compared to the bare Rydberg atom (Butscher et al 2011 J. Phys. B: At. Mol. Opt. Phys. 44 184004). With focus on this yet unexplained observation, we investigate in this paper the vibrational ground state of the molecule in a quantum-classical framework. We show that the Rydberg wavefunction is continuously detuned by the presence of the moving ground state atom and that the timescale on which the detuning significantly exceeds the natural linewidth is in good agreement with the observed reduced lifetimes of the Rydberg molecule.

Junginger, Andrej; Main, Jörg; Wunner, Günter

2013-04-01

220

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

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

2010-03-15

221

Multiphoton Microwave Ionization of Rydberg Atoms

NASA Astrophysics Data System (ADS)

This thesis describes a series of multiphoton microwave experiments on Rydberg atoms when the microwave frequency is much greater than the classical Kepler frequency of the excited atoms. A new kHz pulse repetition frequency dye laser system was constructed for Rydberg lithium excitation with a linewidth as narrow as 3 GHz. This new laser system is used for first experiments of multiphoton microwave ionization of Rydberg lithium approaching the photoionization limit using 17 and 36 GHz microwave pulses. A multi-channel quantum defect model is presented that well describes the experimental results, indicating that these results are due to the coherent coupling of many atomic levels both above and below the classical ionization limit. Finally, preliminary results of measuring the final-state distributions of high lying Rydberg states after 17 GHz microwave pulses are presented.

Gurian, Joshua Houston

222

Effects of electric fields on doubly excited autoionizing Rydberg states of barium

NASA Astrophysics Data System (ADS)

We report the effects of static electric fields on the doubly excited 6p12nl states of barium in the region n*=12. Using a three-step laser excitation scheme we have measured the electric-field dependence of the positions and autoionization widths of the 6p12-17s,16p,15d,12l (l=4-10),12f, and 16s states at field values of up to 4.92 kV/cm. The photoexcitation spectra of the autoionizing states exhibit interference effects which are well understood and provide a better understanding of the character of these states in electric fields. The systematic study of the spectra and positions allows us to explain the field dependence of the autoionization widths in terms of electric-field mixing of the discrete portions of the auoionizing states. The relationship of these effects to dielectronic recombination rates of ions and electrons in plasma microfields is discussed.

Safinya, K. A.; Delpech, J. F.; Gallagher, T. F.

1980-09-01

223

Antiferromagnetic phase transition in a nonequilibrium lattice of Rydberg atoms

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

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

2011-09-15

224

NASA Astrophysics Data System (ADS)

Proposed studies of parity non-conservation in Ba^+ ions[1] will depend on precise knowledge of calculated atomic matrix elements for their interpretation. Independent experimental checks of those calculations depend on precise measurements of Ba^+ properties, such as transition probabilities, light shifts, and polarizabilities. Using the fast beam RESIS technique[2], fine structure intervals in the n=9 and 10 levels of Ba Rydberg states have been measured, and the fine structure pattern has been used to determine both the dipole and quadrupole polarizabilities of the 6s ground state of Ba^+. Because the excitation energy of the 5d state is small ( ˜ 5000 cm-1) the quadrupole polarizability is large, and plays an unusually prominent role in the Rydberg fine structure[3]. * Permanent address: Youngstown State University, Youngstown, OH 44555 [1] Norval Fortson, Phys. Rev. Lett. derline 70, 2383 (1993) [2] F.J. Deck, E.A. Hessels, and S.R. Lundeen, Phys. Rev A derline 48, 4400 (1993) [3] T.F. Gallagher, R. Kachru, and N.H. Tran, Phys. Rev. A derline 26, 2611 (1982) Supported by the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Science, Office of Science, U.S. Dept. of Energy

Snow, E. L.; Komara, R. A.; Gearba, M. A.; Sturrus, W. G.; Lundeen, S. R.

2004-05-01

225

Path integral ground state with a fourth-order propagator: Application to condensed helium

NASA Astrophysics Data System (ADS)

Ground state properties of condensed helium are calculated using the path integral ground state (PIGS) method. A fourth-order approximation is used as short (imaginary) time propagator. We compare our results with those obtained with other quantum Monte Carlo (QMC) techniques and different propagators. For this particular application, we find that the fourth-order propagator performs comparably to the pair product approximation, and is far superior to the primitive approximation. Results obtained for the equation of state of condensed helium show that PIGS compares favorably to other QMC methods traditionally utilized for this type of calculation.

Cuervo, Javier E.; Roy, Pierre-Nicholas; Boninsegni, Massimo

2005-03-01

226

Influence of Thermal Blackbody Radiation on the Evolution of a Cold Rydberg Gas

Cold Rydberg gases are dynamical systems subject to multiple state-changing and ionizing collision processes. Blackbody radiation can modify the dynamics of Rydberg gases in various ways. The Rydberg atoms undergo thermal redistribution and ionization, affecting the bound-state redistribution and (partial) plasma formation. Plasma electrons in the presence of ion fields can also couple to the blackbody radiation field. We present

A. Walz-Flannigan; J. R. Guest; J.-H. Choi; G. Raithel

2004-01-01

227

Probing the photoinduced Rydberg ionization process

NASA Astrophysics Data System (ADS)

The photophysical processes behind the new technique of photoinduced Rydberg ionization (P1RI) spectroscopy have been investigated for benzene. The major limitation to the signal-to-noise attainable using this method has been found to be caused by spontaneous autoionization of the prepared Rydbergs. In addition, some evidence has been found to suggest that the autoionizing transitions, which form the basis of the PIRI technique, only take place when the Rydberg electron is of lower n (and therefore I) than the typical n = 100-200 employed in pulsed field ionization experiments. A new method of recording photoinduced ion core transitions, employing multiphoton photodissociation of the Rydberg core, is also reported. The lighter masses of the fragment ions enable them to be separated from the background of parent ions created by spontaneous autoionization. This method allows the core excitation transition to originate from a vibrationally excited state which previously had produced a prohibitively large background as a result of vibrational autoionization.

Goode, J. G.; Leclaire, I. E.; Johnson, P. M.

1996-12-01

228

CORRIGENDUM: Ab initio potential energy curves of Rydberg, valence and continuum states of NO

An input mistake was found in the outer region step of our calculations of the potential energy curves of NO at some internuclear distances. The resulting errors, although small, affect the reported positions of the higher intruder states, which are slightly lowered in energy. The corrected results for the NO symmetries 2?+ and 2?, corresponding to figures 4 - 7,

I. Rabadán; J. Tennyson

1998-01-01

229

The halfium model is presented and its application to 1Sigma+g ionization channels of H2 is described. Ab initio calculations of the (2psigma)2 doubly excited state of H2 are presented and compared with previous calculations. The connection with a fully ab initio study of the H2 dissociative recombination process is outlined.

Mourad Telmini; Christian Jungen; Soumaya Bezzaouia; Houaida Oueslati

2005-01-01

230

NASA Astrophysics Data System (ADS)

The halfium model is presented and its application to 1?+g ionization channels of H2 is described. Ab initio calculations of the (2p?)2 doubly excited state of H2 are presented and compared with previous calculations. The connection with a fully ab initio study of the H2 dissociative recombination process is outlined.

Telmini, Mourad; Jungen, Christian; Bezzaouia, Soumaya; Oueslati, Houaida

2005-01-01

231

High-resolution optogalvanic study of the c4(0)1?u, c'5(0)1?u+, and a''(0)1?g+ Rydberg states of N2

NASA Astrophysics Data System (ADS)

A new optogalvanic technique with an rf discharge was applied to a high-resolution study of the Rydberg states of N2. The Ledbetter band, c4(0)1?u <-- a''(0)1?g+, and a new visible band, c'5(0)1?u+ <-- a''(0)1?g+, were studied at a Doppler-limited resolution of 0.05 cm-1. A Doppler-free method was also applied to resolve overlapped lines. Precise wavenumbers were determined for the rotational transitions of the two Rydberg bands. The rotational and the centrifugal constants for the lowest Rydberg state, a''(0)1?g+, were determined to be B0 = 1.913748(42) cm-1 and D0 = 6.088(99) × 10-6 cm-1, where the numbers in parentheses are the standard deviation and apply to the last digits. Present address: Technical Research Center, Komatsu, Ltd., 2597 Shinomiya, Hiratsuka, Kanagawa 254, Japan.

Suzuki, Tananori; Kakimoto, Masao

1982-06-01

232

Lifetimes of Rydberg states in ions of the group II elements

NASA Astrophysics Data System (ADS)

Total probabilities A nl of spontaneous radiative transitions, which determine lifetimes ? nl = 1/ A nl of nS-, nP-, nD- and nF-states in singly charged ions of the group IIa (Be+, Mg+, Ca+, Sr+, Ba+) and IIb (Zn+, Cd+, Hg+) elements, were calculated in the single-electron Fues' model potential (FMP) method. An asymptotic dependence is determined for highly excited states with small angular momentums and presented in the form ? nl = ? {/l (0)} n 3 Q l (1/ n) and numerical values of the factors ? {/l (0)} and coefficients of the cubic polynomial Q l ( x) are calculated, which approximate results of numerical computations with relative error below 2% in the range of states with principal quantum numbers from n = 7 to n ? 2000. The comparison of the numerical results with data in literature is presented, and applicability and reliability of single-electron model calculations are discussed in detail for positive singly charged ions of the group II elements.

Glukhov, I. L.; Nikitina, E. A.; Ovsiannikov, V. D.

2013-07-01

233

NASA Astrophysics Data System (ADS)

Rovibrational levels and widths of the positive parity 3d electronic states of BeH and BeD are calculated by a multi-state complex scaling method. Ab initio adiabatic potential energy curves of all n = 3 Rydberg states and the valence state C 2icons/Journals/Common/Sigma" ALT="Sigma" ALIGN="TOP"/>+, along with their mutual couplings (radial between states of the same symmetry and rotational-electronic between states differing in icons/Journals/Common/Lambda" ALT="Lambda" ALIGN="TOP"/> by one) have been included in the calculations. The results of the seven-state calculations show extensive predissociation of the levels of all the n = 3 2icons/Journals/Common/Sigma" ALT="Sigma" ALIGN="TOP"/>+ states in both BeH and BeD. The positive parity 3p (B 2icons/Journals/Common/Pi" ALT="Pi" ALIGN="TOP"/>+) and 3d (D 2icons/Journals/Common/Pi" ALT="Pi" ALIGN="TOP"/>+ and 1 2icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/>+) Rydberg states are also predissociated to differing extent, depending on the vibrational and rotational level. Significant mixing is found among the 3d states, as expected, but also between the levels of 1 2icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> v = 0 and those of B 2icons/Journals/Common/Pi" ALT="Pi" ALIGN="TOP"/> v = 2 in BeH, which in the present calculations are found to be in near coincidence.

Petsalakis, Ioannis D.; Papadopoulos, Demetrios; Theodorakopoulos, Giannoula; Buenker, Robert J.

1999-07-01

234

One-Dimensional Rydberg Gas in a Magnetoelectric Trap

We study the quantum properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap which is superimposed by a homogeneous electric field. Trapped Rydberg atoms can be created in long-lived electronic states exhibiting a permanent electric dipole moment of several hundred Debye. The resulting dipole-dipole interaction in conjunction with the radial confinement is demonstrated to give rise to an effectively one-dimensional ultracold Rydberg gas with a macroscopic interparticle distance. We derive analytical expressions for the electric dipole moment and the required linear density of Rydberg atoms.

Mayle, Michael [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany); Hezel, Bernd [Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, D-69120 Heidelberg (Germany); Lesanovsky, Igor [Institut fuer Theoretische Physik, Universitaet Innsbruck, A-6020 Innsbruck (Austria); Schmelcher, Peter [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany); Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, D-69120 Heidelberg (Germany)

2007-09-14

235

Electric-Field Induced Dipole Blockade with Rydberg Atoms

High resolution laser Stark excitation of np (60

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

2007-08-17

236

Cooper minima are predicted to occur in the 3{ital p}{sigma}{r arrow}{ital k}{sigma}({ital l}=2) and 3{ital p}{sigma}{r arrow}{ital k}{pi}({ital l}=2) channels in the resonance enhanced multiphoton ionization of NO via the {ital D} {sup 2}{Sigma}{sup +}(3{ital p}{sigma}) Rydberg state. The low energy {ital k}{sigma}({ital l}=2) Cooper minimum leads to the observed {Delta}{ital N}={ital N}{sup +}{minus}{ital N}{prime}=0 photoelectron peak, in addition to the {Delta}{ital N}={plus minus}1, {plus minus}3 peaks seen in the rotational spectra. The Cooper minima are accompanied by significant {ital l} mixing in the continuum due to the nonspherical molecular potential and result in a strong dependence of rotational branching ratios and angular distributions on photoelectron kinetic energy. A Cooper minimum is also predicted in the 3{ital p}{pi}{r arrow}{ital k}{delta}({ital l}=2) channel for photoionization of the {ital C} {sup 2}{Pi}(3{ital p}{pi}) Rydberg state. The effect of this Cooper minimum on photoelectron spectra and photoelectron angular distributions is also investigated.

Wang, K.; Stephens, J.A.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California (USA))

1991-11-01

237

Heavy-Rydberg ion-pair formation in collisions of Rydberg atoms with attaching targets

NASA Astrophysics Data System (ADS)

Collisions between K(np) Rydberg atoms and electron attaching targets can lead to the creation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair orbiting at large internuclear separations. The lifetimes of such states and their correlation with binding energy and the channels available for decay, which can be controlled by varying n, the Rydberg atom velocity, and the target species, are being investigated. The ion-pair states are produced in a small collision cell and allowed to exit to form a beam that passes between a pair of electrodes where their number and binding energy distribution is determined by electric field induced dissociation. Ion-pair production is analyzed with the aid of a Monte Carlo collision code that models both initial Rydberg electron capture and the subsequent evolution of the product ion pair. Research supported by the Robert A Welch Foundation.

Wang, Changhao; Kelley, Michael; Dunning, F. Barry

2012-06-01

238

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

NASA Astrophysics Data System (ADS)

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

Prozument, Kirill; Colombo, Anthony P.; Zhou, Yan; Park, G. Barratt; Petrovi?, Vladimir S.; Coy, Stephen L.; Field, Robert W.

2011-09-01

239

New and existing spectroscopic data on N(2), obtained using a wide variety of experimental techniques, are interpreted using a coupled-channel Schrodinger-equation (CSE) model of the structure and predissociation dynamics for the interacting Rydberg and valence states of (3)Pi(u) symmetry. As a result, v>0 levels of the 3ppi(u)G(3) (3)Pi(u) Rydberg state are assigned correctly for the first time, leading to the identification of very strong perturbations in the G(3)-state vibrational structure. A four-channel CSE model, which includes the 3ssigma(g)F(3) (3)Pi(u) and 3ppi(u)G(3) (3)Pi(u) Rydberg states and the C(') (3)Pi(u) and C (3)Pi(u) valence states, indicates strong Rydberg-Rydberg coupling between the F(3) and G(3) states, strong Rydberg-valence coupling between the G(3) and C(') states, and weaker coupling between the F(3) and C(') states. PMID:19045265

Lewis, B R; Heays, A N; Gibson, S T; Lefebvre-Brion, H; Lefebvre, R

2008-10-28

240

High-order-harmonic generation from Rydberg states at fixed Keldysh parameter

NASA Astrophysics Data System (ADS)

Because the commonly adopted viewpoint that the Keldysh parameter ? determines the dynamical regime in strong field physics has long been demonstrated to be misleading, one can ask what happens as relevant physical parameters, such as laser intensity and frequency, are varied while ? is kept fixed. We present results from our one- and fully three-dimensional quantum simulations of high-order-harmonic generation (HHG) from various bound states of hydrogen with n up to 40, where the laser intensities and the frequencies are scaled from those for n=1 in order to maintain a fixed Keldysh parameter ?<1 for all n. We find that as we increase n while keeping ? fixed, the position of the cutoff scales in a well-defined manner. Moreover, a secondary plateau forms with a new cutoff, splitting the HHG plateau into two regions. The first of these subplateaus is composed of lower harmonics, and has a higher yield than the second one. The latter extends up to the semiclassical Ip+3.17Up cutoff. We find that this structure is universal, and the HHG spectra look the same for all n?10 when plotted as a function of the scaled harmonic order. We investigate the n, l, and momentum distributions to elucidate the physical mechanism leading to this universal structure.

Bleda, E. A.; Yavuz, I.; Altun, Z.; Topcu, T.

2013-10-01

241

Very accurate variational non-relativistic calculations are performed for four higher Rydberg {sup 2}D states (1s{sup 2}nd{sup 1}, n= 8, ..., 11) of the lithium atom ({sup 7}Li). The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions and finite nuclear mass is used. The exponential parameters of the Gaussians are optimized using the variational method with the aid of the analytical energy gradient determined with respect to those parameters. The results of the calculations allow for refining the experimental energy levels determined with respect to the {sup 2}S 1s{sup 2}2s{sup 1} ground state.

Sharkey, Keeper L. [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States); Bubin, Sergiy [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Adamowicz, Ludwik [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States); Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2011-05-21

242

Structure of heavy helium isotopes via the isobaric analog states in Lithium

Study of nuclei far removed from the valley of stability provide an opportunity to test the models of nuclear structure. In particular, heavy isotopes of helium attract much attention due to their extreme neutron to proton ratio. In this work we studied the T=5\\/2 states in ^9Li and T=3\\/2 states in ^7Li, isobaric analog states of ^9He and ^7He respectively.

G. V. Rogachev; A. Aprahamian; P. Boutachkov; M. Quinn; J. J. Kolata; B. Skorodumov; A. Woehr; V. Z. Goldberg; G. Chubarian; A. Fomichev; M. S. Golovkov; Yu. Ts. Oganessian; A. Rodin; R. S. Slepnev; G. Ter-Akopian; R. Wolski; W. H. Trzaska; D. V. Aleksandrov; P. A. Deyoung; G. F. Peaslee; P. J. Mears; F. D. Becchetti; Y. Chen

2003-01-01

243

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`.

244

Tunneling from Electronic Bubble States in Liquid Helium through the Liquid-Vapor Interface

The escape of electrons from their bubble state in liquid helium through the free liquid surface into the vapor phase is investigated. The measured escape rates are calculated in terms of a tunneling model which predicts a unique temperature and electric field dependence in excellent agreement with the experimental data. A fit of this model to the data yields the

W. Schoepe; G. W. Rayfield

1973-01-01

245

Formation of Excited Molecular States in the Positive Column of a Helium Discharge.

National Technical Information Service (NTIS)

Excited molecular states are shown to be populated in the positive column of a glow discharge in helium by electron excitation of metastable molecules. At higher pressures in the range 2-20 torr, metastable molecules are formed primarily by three-body con...

M. P. Teter W. W. Robertson

1966-01-01

246

Measurement of the Hyperfine Structure of the Ground State of Muonic Helium(3).

National Technical Information Service (NTIS)

Polarization measurements by the muon spin rotation method yielded the detection that in the formation of sup 3 He mu exp - e exp - the hfs states are occupied differently. In pure helium(3) a residual polarization of 2.6(4)% of the ( sup 3 He mu exp - ) ...

K. P. Arnold

1984-01-01

247

A nonlinear programming approach to lower bounds for the ground-state energy of helium

Lower-bound estimates for the ground-state energy of the helium atom are determined using nonlinear programming techniques. Optimized lower bounds are determined for single-particle, radially correlated, and general correlated wave functions. The local nature of the method employed makes it a very severe test of the accuracy of the wave function.

Porras, I.; Feldmann, D.M.; King, F.W. [Univ. of Wisconsin, Eau Claire, WI (United States). Dept. of Chemistry

1999-02-20

248

Theoretical energies of low-lying states of light helium-like ions

A rigorous quantum electrodynamical calculation is presented for energy levels of the 1 {sup 1}S, 2 {sup 1}S, 2 {sup 3}S, 2 {sup 1}P{sub 1}, and 2 {sup 3}P{sub 0,1,2} states of helium-like ions with the nuclear charge Z=3,...,12. The calculational approach accounts for all relativistic, quantum electrodynamical, and recoil effects up to orders m{alpha}{sup 6} and m{sup 2}/M{alpha}{sup 5}, thus advancing the previously reported theory of light helium-like ions by one order in {alpha}.

Yerokhin, Vladimir A.; Pachucki, Krzysztof [Center for Advanced Studies, St. Petersburg State Polytechnical University, Polytekhnicheskaya 29, St. Petersburg 195251 (Russian Federation); Institute of Theoretical Physics, University of Warsaw, Hoza 69, PL-00-681 Warsaw (Poland)

2010-02-15

249

Momentum correlation of the final-state wavefunction for (e, 3e) collisions on helium

NASA Astrophysics Data System (ADS)

Based on our earlier paper, the momentum correlation of the four bodies in the final state is further considered for (e, 3e) processes on helium. A fivefold differential cross section (FDCS) for electron-impact double ionization of helium is calculated by use of the modified model for high incident energy (1-5.6keV). It has been found that the present results give a better description for the experimental data, as compared with the results of our earlier paper.

Zhang, Sui-Meng

2004-04-01

250

Trapping Rydberg Atoms in an Optical Lattice

NASA Astrophysics Data System (ADS)

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

Anderson, Sarah E.

2012-06-01

251

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

252

Multiphoton Processes in Systems of Rydberg Atoms.

National Technical Information Service (NTIS)

Multiphoton nonlinear effects and Raman processes of Rydberg systems (Rydberg atom gas or Rydberg matter) by intense laser fields are considered. Some experiments and basic elements of quantum theory of Rydberg matter are briefly reviewed. A correlation b...

E. A. Manykin

2002-01-01

253

Spectroscopy of electrons in image-potential--induced surface states outside liquid helium

We report a spectroscopic study of electronic transitions from the ground state to several excited states in the potential well lying outside the free surface of liquid helium formed by the long-range attractive-image potential and the short-range electron--atom repulsive potential. These electric dipole transitions were observed at frequencies from 130 to 220 GHz by measuring the microwave absorption derivative at

C. C. Grimes; T. R. Brown; Michael L. Burns; C. L. Zipfel

1976-01-01

254

The first metastable valence excited states and the first Rydberg states of the MgKr and MgXe molecules have been characterized by resonance two-photon photoionization (R2PI) spectroscopy. The Mg(3s3p 3PJ)?RG(3&Pgr;0+,0?) metastable states, produced by expanding the products of a laser-ablated magnesium rod in Kr\\/Ar or Xe\\/Ar gas mixtures into a supersonic expansion, were excited by a dye laser pulse to several

John G. Kaup; Allen W. K. Leung; W. H. Breckenridge

1997-01-01

255

Nonequilibrium phase transition in a dilute Rydberg ensemble.

We demonstrate a nonequilibrium phase transition in a dilute thermal atomic gas. The phase transition, between states of low and high Rydberg occupancy, is induced by resonant dipole-dipole interactions between Rydberg atoms. The gas can be considered as dilute as the atoms are separated by distances much greater than the wavelength of the optical transitions used to excite them. In the frequency domain, we observe a mean-field shift of the Rydberg state which results in intrinsic optical bistability above a critical Rydberg number density. In the time domain, we observe critical slowing down where the recovery time to system perturbations diverges with critical exponent ?=-0.53±0.10. The atomic emission spectrum of the phase with high Rydberg occupancy provides evidence for a superradiant cascade. PMID:24074087

Carr, C; Ritter, R; Wade, C G; Adams, C S; Weatherill, K J

2013-09-10

256

Nonequilibrium Phase Transition in a Dilute Rydberg Ensemble

NASA Astrophysics Data System (ADS)

We demonstrate a nonequilibrium phase transition in a dilute thermal atomic gas. The phase transition, between states of low and high Rydberg occupancy, is induced by resonant dipole-dipole interactions between Rydberg atoms. The gas can be considered as dilute as the atoms are separated by distances much greater than the wavelength of the optical transitions used to excite them. In the frequency domain, we observe a mean-field shift of the Rydberg state which results in intrinsic optical bistability above a critical Rydberg number density. In the time domain, we observe critical slowing down where the recovery time to system perturbations diverges with critical exponent ?=-0.53±0.10. The atomic emission spectrum of the phase with high Rydberg occupancy provides evidence for a superradiant cascade.

Carr, C.; Ritter, R.; Wade, C. G.; Adams, C. S.; Weatherill, K. J.

2013-09-01

257

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

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

1988-01-01

258

Study of Rydberg-Rydberg interactions for quantum gates with neutral atoms

NASA Astrophysics Data System (ADS)

The fast phase gate scheme, in which the qubits are atoms confined in sites of an optical lattice, and gate operations are mediated by excitation of Rydberg states, was proposed in [1]. The logic gate is implemented using a blockade of the simultaneous excitation of atoms into a Rydberg state. Strong coupling between atoms is required for the experimental realization of such proposal. In this work, we study Rydberg-Rydberg interactions that are resonantly enhanced by the Foster processes [2]. Such resonances may provide sufficiently strong Rydberg-Rydberg interactions in low electric fields to realize a blockade necessary for the gate operations. Comparative calculations are done for alkali atoms to determine if this entanglement scheme may be better suited for a specific system.[1] D. Jaksch, J.I. Cirac, P. Zoller, S.L.Rolston, R. Côt'e, and M.D. Lukin, Phys. Rev. Lett. 85, 2208 (2000).[2] Thad G. Walker and Mark Saffman, J. of Phys. B 38, S309 (2005).

Arora, Bindiya; Safronova, M. S.; Clark, Charles W.

2006-05-01

259

Dynamics and equilibration of Rydberg excitations in dissipative atomic ensembles

NASA Astrophysics Data System (ADS)

We study resonant optical excitations of strongly interacting Rydberg states of atoms in the presence of relaxations. We employ the quantum stochastic (Monte Carlo) wavefunctions to simulate the dissipative dynamics of tens of atoms in two-dimensional lattices. We show that under typical experimental conditions involving the slow Rydberg state decay and sizable relaxation of atomic coherences, on the timescale of several ?s the atomic ensemble approaches a stationary state in which much of the quantum correlations between the atoms have decayed away. The steady state, however, exhibits strong classical correlations of Rydberg excitation probabilities.

Petrosyan, David

2013-07-01

260

Cryogenic MOT and Trap for Cold Rydberg Atoms

NASA Astrophysics Data System (ADS)

Cold Rydberg gases offer many opportunities for studying strong interactions between Rydberg atoms, the formation of ultracold neutral plasmas^i , and the subsequent dynamics of plasma components and Rydberg atom populations. In recent experiments in our laboratory, we have observed the spontaneous evolution of Rydberg atom gases into long-lived high angular momentum states^ii . However, the lifetime of these states has been severely limited in the presence of room-temperature black-body radiation, thus restricting our studies to times relatively short compared to the natural lifetimes of high-l Rydberg atoms. We report on our effort to extend our studies by performing them in a cryogenic environment. We have constructed a double-MOT system in which an LVIS MOT is used to seed a secondary, cryogenic MOT. Having eliminated blackbody-induced decay, the interaction time of atoms in the cold Rydberg atom gas is then limited by the gas expansion. Future goals include the demonstration of a trap for Rydberg atoms by utilizing their large magnetic moments to confine them within the weak magnetic field of the MOT. This will allow for studies of interacting Rydberg atoms over much longer time scales with greater control over the gas/plasma density. *Funding provided by NSF i. T.C. Killian, et.al, Phys. Rev. Lett. 83, 4776 (1999). M.P. Robinson, et. al., Phys. Rev. Lett. 85, 4466 (2000) ii. S K Dutta et. al., Phys. Rev. Lett. 86, 3993 (2001)

Walz-Flannigan, Alisa; Guest, Jeffrey R.; Raithel, Georg

2002-05-01

261

In this paper, we extend a previous formulation of molecular resonance enhanced multiphoton ionization (REMPI) photoelectron spectra of diatomic molecules to treat rotationally resolved photoionization of nonlinear polyatomic molecules. Useful parity selection rules, which govern changes of angular momenta {Delta}{ital K}{sub {ital a}} and {Delta}{ital K}{sub {ital c}}, are also derived. As an example, we use this formulation to study rotational branching ratios and photoelectron angular distributions resulting from (3+1{prime}) REMPI of H{sub 2}O via the {ital C} {sup 1}{ital B}{sub 1} (3{ital pa}{sub 1}) Rydberg state. Cooper minima are predicted to occur in the {ital d} wave ({ital l}=2) of the {ital ka}{sub 1} ({lambda}=0) and {ital kb}{sub 1} ({lambda}=1) photoelectron continua. The effects of these Cooper minima on rotationally resolved photoelectron spectra are also investigated.

Lee, M.; Wang, K.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125 (United States)); Machado, L.E. (Departamento de Fisica, Universidade Federal de Sao Carlos, Caixa Postal 676, 13560 Sao Paulo (Brazil))

1992-09-15

262

NASA Astrophysics Data System (ADS)

RESIS microwave techniques [1] have been used to directly measure the fine structure intervals between several n=17 and 20 high-L states of magnesium. The precision of these measurements and the access to higher-L Rydberg levels provide more than an order of magnitude improvement on the precision of the ionic polarizabilities as compared with previous experiment. [2] This offers an excellent experimental check on the a-priori atomic structure calculations. [1] R.A. Komara, M.A. Gearba, C.W. Fehrenbach and S.R. Lundeen, J. Phys. B: At. Mol. Opt. Phys. 38 S87 (2005). [2] B. J. Lyons and T. F. Gallagher, Phys. Rev. A 57, 2426 (1998).

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

2006-05-01

263

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

264

Excited-State Positronium Formation from Helium, Argon, and Xenon

NASA Astrophysics Data System (ADS)

The cross sections for the formation of positronium in the 2P state in collisions of positrons with He, Ar, and Xe atoms have been determined by measuring coincidences between the remnant ion and the Lyman-? photon from positronium. The maximum fractional contributions of these to the total Ps formation cross sections increase from approximately 0.06±0.01 in He to 0.12±0.04 in Ar and 0.26±0.09 in Xe. In the case of He, good agreement is found with a coupled-state calculation; for Ar and Xe, measurements are compared with a distorted-wave Born approximation.

Murtagh, D. J.; Cooke, D. A.; Laricchia, G.

2009-04-01

265

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

266

Discovery of antiproton trapping by long-lived metastable states in liquid helium

Delayed annihilation of antiprotons stopped in liquid helium has been observed, revealing that about 3.6% of stopped antiprotons are trapped in long-lived metastable states. No delayed component was found either in liquid nitrogen or in liquid argon. The observed time distribution of delayed annihilation shows fast-decaying components followed by a major part with a decay time constant of 3 musec.

M. Iwasaki; S. N. Nakamura; K. Shigaki; Y. Shimizu; H. Tamura; T. Ishikawa; R. S. Hayano; E. Takada; E. Widmann; H. Outa; M. Aoki; P. Kitching; T. Yamazaki

1991-01-01

267

NASA Astrophysics Data System (ADS)

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 ?2 = 136(45) fs. The lifetime of the 3p Rydberg state in quadricyclane is ?1 = 320(31) and the lifetime of the 3s Rydberg state in norbornadiene is ?3 = 394(32).

Rudakov, Fedor; Weber, Peter M.

2012-04-01

268

Surface-Electrode Rydberg-Stark Decelerator

NASA Astrophysics Data System (ADS)

Hydrogen atoms in Rydberg states with principal quantum numbers between 23 and 70 have been accelerated, decelerated, and electrostatically trapped using a surface-electrode Rydberg-Stark decelerator. By applying a set of oscillating electrical potentials to a two-dimensional array of electrodes on a printed circuit board (PCB), a continuously moving, three-dimensional electric trap with a predefined velocity and acceleration is generated. From an initial longitudinal velocity of 760m/s, final velocities of the Rydberg atoms ranging from 1200m/s to zero velocity in the laboratory-fixed frame of reference were achieved. Accelerated or decelerated atoms were detected directly by pulsed electric-field ionization. Atoms trapped at zero mean velocity above the PCB were reaccelerated off the PCB before field ionization.

Hogan, S. D.; Allmendinger, P.; Saßmannshausen, H.; Schmutz, H.; Merkt, F.

2012-02-01

269

Ionization of Rydberg H2 molecules at doped silicon surfaces.

The present study focuses on the interaction of H2 Rydberg molecules with doped silicon semiconductor surfaces. Para-H2 Rydberg states with principal quantum numbers n = 17-21 and core rotational quantum number N(+) = 2 are populated via resonant two-colour two-photon (vacuum ultraviolet-ultraviolet) excitation and collide at grazing incidence with a surface. For small Rydberg-surface separation, the Rydberg states are ionized due to the attractive surface potential experienced by the Rydberg electron and the remaining ion-core is detectable by applying a sufficiently strong external electric field. It is found that the surface ionization profiles (ion signal vs applied field) of H2 on p-type doped Si surfaces show a higher detected ion signal than for n-type Si surfaces, while an Au surface shows lower detected ion signal than either type of Si surface. It is shown that ion detectability decreases with increasing dopant density for both types of Si surfaces. Higher-n Rydberg states show higher ion detectability than lower-n Rydberg states but this variation becomes smaller when increasing the dopant density for both p- and n-type surfaces. Theoretical trajectory simulations were developed with a 2D surface potential model and using the over-the-barrier model for the ionization distance; the results help to explain the observed variations of the experimental surface ionization profiles with dopant density and type. PMID:23534640

Sashikesh, G; Ford, M S; Softley, T P

2013-03-21

270

National Technical Information Service (NTIS)

A recently developed variational formalism for the determination of the reduced single-particle density matrix, correct to second order, is applied to the ground state of the helium isoelectronic sequence. For a Slater-determinant-type trial wave function...

V. Sahni J. B. Krieger J. B. Gruenebaum

1974-01-01

271

The first examination of the predissociation dynamics of the methyl radical [tilde B] [sup 2]A[prime][sub 1] state has been performed. The Raman excitation profile technique was utilized to obtain J[prime]-resolved Raman excitation profiles of CH[sub 3] and CD[sub 3] in resonance with the [0000]-[0000] [tilde B] [sup 2]A[prime][sub 1]-[tilde X][sup 2]A[double prime][sub 2] absorption. The structure and dynamics of vibronic levels above the Rydberg 3 s origin level were examined. The predissociation of the CD[sub 3] [0100]Rydberg 3 s level was examined by rotationally resolved Raman excitation profile analysis. The excitation profile analysis places the band origin of the [0100]-[0100] vibronic feature at 47271 cm[sup [minus]1]. The out-of-plane bend frequency, [nu][sub 2][prime], in the Rydberg 3 s state is determined to be 1094 cm[sup [minus]1]. Q branch excitation profiles of the [nu][sub 1] and 2[nu][sub 1] Raman features yield a band origin of 206.85 nm for the [1000]-[0000] transition. The symmetric stretching frequency in the Rydberg 3 s state is estimated to be 2040 cm[sup [minus]1]. The Q branch excitation profiles yield a dephasing constant in the [1000] level of approximately 400 cm[sup [minus]1]. The methyl radical ground state ([tilde X] [sup 2]A[double prime][sub 2]) stretching potential was experimentally investigated. Resonance Raman spectra of isotopomers CH[sub 3], Ch[sub 2]D, CHD[sub 2] and CD[sub 3] were obtained. The bonding in the methyl radical was compared to a variety of sp[sup 2] hybridized ethylenic molecules. The Morse harmonic frequency and anharmonicity constant indicate the bonding in the methyl radical and ethylenic molecules is primarily a function of the sp[sup 2] hybridization of the central carbon. The local mode-coupled Morse oscillator analysis reveals that the vibrational states of the methyl radical are described by wavefunctions containing a significant percentage of normal model character.

Westre, S.G.

1992-01-01

272

The question of the desirability of a governmental program of recovering and storing helium from helium-rich natural gas for the low-cost supply of future helium demands is considered. The geologic occurence and distribution of helium, most of which is found in the United States, are discussed, and difficulties in the assessment of helium resources are presented. Uncertainties of future large-scale

E. Cook

1979-01-01

273

Equation of state and electronic structure of liquid Helium at high pressure

NASA Astrophysics Data System (ADS)

As the second most abundant element, the properties of fluid Helium form an important part of our understanding of stellar and giant planetary structure. Yet the physics of Helium at pressure-temperature conditions characteristic of these bodies is uncertain. We perform first principles molecular dynamics simulations of fluid Helium over a wide range of pressure (< 1 Gbar) and temperature (< 5 eV). The simulations are based on finite-temperature density functional theory in the generalized gradient approximation, and are performed in the canonical ensemble with a Nose thermostat. We find that both temperature and compression have a strong influence on the electronic structure as revealed by the band gap. At a density of 1 g cm-3 the band gap varies from 20 eV for the static crystal to 0 for the fluid at 4 eV. The gap is closed at all temperatures for density greater than 20 g cm-3. We find that the equation of state varies smoothly through the band gap closure transition with no indication of a high-order phase transformation. The decrease in band gap with increasing temperature at constant density results from enhanced mixing of 1s- and 2s-like states with increasing disorder (i.e., enhanced vibrational amplitudes and melting) that has profound implications for understanding the deep interiors of planets.

Stixrude, Lars; Jeanloz, Raymond

2006-03-01

274

Equation of state and electronic structure of liquid Helium at high pressure

NASA Astrophysics Data System (ADS)

As the second most abundant element, the properties of fluid Helium form an important part of our understanding of stellar and giant planetary structure. Yet the physics of Helium at pressure-temperature conditions characteristic of these bodies is uncertain. We perform first principles molecular dynamics simulations of fluid Helium over a wide range of pressure (< 1 Gbar) and temperature (< 5 eV). The simulations are based on finite-temperature density functional theory in the generalized gradient approximation, and are performed in the canonical ensemble with a Nose thermostat. We find that both temperature and compression have a strong influence on the electronic structure as revealed by the band gap. At a density of 1 g cm-3 the band gap varies from 20 eV for the static crystal to 0 for the fluid at 4 eV. The gap is closed at all temperatures for density greater than 20 g cm-3. We find that the equation of state varies smoothly through the band gap closure transition with no indication of a high-order phase transformation. The decrease in band gap with increasing temperature at constant density results from enhanced mixing of 1s- and 2s-like states with increasing disorder (i.e., enhanced vibrational amplitudes and melting) that has profound implications for understanding the deep interiors of planets.

Stixrude, Lars; Jeanloz, Raymond

2007-03-01

275

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

Helium-3 spin-echo measurements of resonant scattering from the Si(111)-(1 × 1)H surface, in the energy range 4-14 meV, are presented. The measurements have high energy resolution yet they reveal bound state resonance features with uniformly broad linewidths. We show that exact quantum mechanical calculations of the elastic scattering, using the existing potential for the helium/Si(111)-(1 × 1)H interaction, cannot reproduce the linewidths seen in the experiment. Further calculations rule out inelastic and other mechanisms that might give rise to losses from the elastic scattering channels. We show that corrugation in the attractive part of the atom-surface potential is the most likely origin of the experimental lineshapes. PMID:21828452

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

2009-06-11

276

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

277

NASA Astrophysics Data System (ADS)

The photoexcitation of very-high-n, n˜ 300, potassium Rydberg atoms in the presence of an rf driving field at, or near, the Kepler frequency of the final state is examined and allows the realization of quantum-optical protocols in truly mesoscopic atoms. When directly exciting 4s ->np transitions using a uv laser, application of the drive field leads to the appearance of new features in the excitation spectrum that lie approximately midway between the np states. Whereas the size of these features increases with increasing drive field amplitude their positions remain largely unchanged. As the rf frequency is detuned from resonance, the features split, the separation of the components being equal to twice the detuning. The new features are attributed to multiphoton transitions to final ns and nd states that involve the absorption or emission of rf photons. Measurements further suggest that while the electron motion in the product states is locked to the drive field this results from post-excitation interactions with the field rather than the excitation process per se. The results are analyzed using Floquet theory.

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

2012-06-01

278

Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble

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

279

NASA Astrophysics Data System (ADS)

In this paper, we present theoretical results for the process of non-sequential two-photon double ionization of helium at the photon energy 42 eV. Our approach is based on solving the time-dependent Schrödinger equation in a B-spline based numerical framework. Information about the process is obtained by extracting the double-ionized component by means of uncorrelated final states. The total (generalized) cross section for the process is extracted, as well as differential cross sections resolved in electron energies and ejection angles. We focus on the impact the final-state correlation has on the accuracy of the cross sections.

Simonsen, Aleksander S.; Askeland, Sigurd; Førre, Morten

2013-02-01

280

Evolution dynamics of a dense frozen Rydberg gas to plasma

NASA Astrophysics Data System (ADS)

Dense samples of cold Rydberg atoms have previously been observed to spontaneously evolve to a plasma, despite the fact that each atom may be bound by as much as 100cm-1 . Initially, ionization is caused by blackbody photoionization and Rydberg-Rydberg collisions. After the first electrons leave the interaction region, the net positive charge traps subsequent electrons. As a result, rapid ionization starts to occur after 1?s caused by electron-Rydberg collisions. The resulting cold plasma expands slowly and persists for tens of microseconds. While the initial report on this process identified the key issues described above, it failed to resolve one key aspect of the evolution process. Specifically, redistribution of population to Rydberg states other than the one initially populated was not observed, a necessary mechanism to maintain the energy balance in the system. Here we report new and expanded observations showing such redistribution and confirming theoretical predictions concerning the evolution to a plasma. These measurements also indicate that, for high n states of purely cold Rydberg samples, the initial ionization process which leads to electron trapping is one involving the interactions between Rydberg atoms.

Li, Wenhui; Noel, Michael W.; Robinson, Michael P.; Tanner, Paul J.; Gallagher, Thomas F.; Comparat, Daniel; Laburthe Tolra, Bruno; Vanhaecke, Nicolas; Vogt, Thibault; Zahzam, Nassim; Pillet, Pierre; Tate, Duncan A.

2004-10-01

281

Evolution dynamics of a dense frozen Rydberg gas to plasma

Dense samples of cold Rydberg atoms have previously been observed to spontaneously evolve to a plasma, despite the fact that each atom may be bound by as much as 100 cm{sup -1}. Initially, ionization is caused by blackbody photoionization and Rydberg-Rydberg collisions. After the first electrons leave the interaction region, the net positive charge traps subsequent electrons. As a result, rapid ionization starts to occur after 1 {mu}s caused by electron-Rydberg collisions. The resulting cold plasma expands slowly and persists for tens of microseconds. While the initial report on this process identified the key issues described above, it failed to resolve one key aspect of the evolution process. Specifically, redistribution of population to Rydberg states other than the one initially populated was not observed, a necessary mechanism to maintain the energy balance in the system. Here we report new and expanded observations showing such redistribution and confirming theoretical predictions concerning the evolution to a plasma. These measurements also indicate that, for high n states of purely cold Rydberg samples, the initial ionization process which leads to electron trapping is one involving the interactions between Rydberg atoms.

Li Wenhui; Noel, Michael W.; Robinson, Michael P.; Tanner, Paul J.; Gallagher, Thomas F.; Comparat, Daniel; Laburthe Tolra, Bruno; Vanhaecke, Nicolas; Vogt, Thibault; Zahzam, Nassim; Pillet, Pierre; Tate, Duncan A. [Department of Physics, University of Virginia, McCormick Road, Charlottesville, Virginia 22903 (United States); Laboratoire Aime Cotton, CNRS II Campus d'Orsay, 91405 Orsay Cedex (France); Department of Physics and Astronomy, Colby College, Waterville, Maine 04901 (United States)

2004-10-01

282

Dislocation-mediated melting of one-dimensional Rydberg crystals

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

283

Collisions and Interactions in Ultracold Rydberg Plasmas

NASA Astrophysics Data System (ADS)

A new branch of atomic physics with many applications- the interactions, dynamics and collisions in ultracold (T? 1K) systems- has naturally evolved from recent advances in the cooling and trapping of neutral gases. Cold Rydberg plasmas, wherein electrons and ions coexist with atoms Ry(n?) in highly excited Rydberg states n,? have been recently produced by laser ionization of atoms initially prepared at sub-millikelvin temperatures. Three-body recombination permits Rydberg production over a broad range of angular momentum states ?=n-1, n-2,...,2,1,0. The plasma is maintained by electron-ionization, de-excitation and recombination. The variation of the ionization cros section with ? is therefore of key interest. In this paper, the full dependence of the cross sections on the initial angular momentum ? of Rydberg atoms is revealed, with interesting physical characteristics which are explained. Rates for three-body capture into state n,? are then deduced from detailed balance. Analytic expressions for the ionization cross section are also derived within the classical impulse approximation and compared with the classical trajectory results.

Flannery, Raymond; Vrinceanu, Daniel

2004-09-01

284

Results of theoretical studies of rotational ion distributions in the {ital X} {sup 2}{Pi}{sub 1/2} ground state of HBr{sup +} resulting from (2+1) resonance enhanced multiphoton ionization (REMPI) via the {ital S}(2) branch of the {ital F} {sup 1}{Delta}{sub 2} Rydberg state are reported. These results show a strongly parity-favored ion distribution with about 80% population in the ({minus}) component of the {Lambda} doublet of {ital J}{sup +} rotational levels. The 20% population in the other parity component of the {Lambda} doublet can be seen to be due to odd partial wave contributions to the photoelectron matrix elements which arise primarily from non-atomic-like behavior of the electronic continuum. This, in turn, is due to angular momentum coupling in the photoelectron orbital brought about by the torques of the nonspherical molecular ion potential. We demonstrate that the effect of alignment on these ion distributions, although not large, is important. Photoelectron angular distributions and alignment of the {ital J} levels of the HBr{sup +} ions are also presented. Rotational branching ratios and photoelectron angular distributions resulting from (2+1{prime}) REMPI of HBr via several {ital S} branches of the {ital F} {sup 1}{Delta}{sub 2} state are also shown for near-threshold photoelectron energies.

Wang, K.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California (USA))

1991-12-01

285

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

286

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

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

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

2011-08-26

287

Electron capture from Rydberg atoms by highly-charged ions

We report cross sections in electron capture from circular Rydberg atoms by highly charged ions A^q+ for charge states q ranging from 1 to 40. The initial Rydberg state has n,l=25,24 as its principal and angular momentum quantum numbers, respectively. The collision speed is chosen between 0.4 to 4 times the electron orbital speed, corresponding to collision energies from 6.4

J. Wang; J. H. McGuire; R. E. Olson; J. Burgdoerfer

1996-01-01

288

Ultrafast structural dynamics and isomerization in Rydberg-exited Quadricyclane

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

289

Imaging Spatial Correlations of Rydberg Excitations in Cold Atom Clouds

We use direct spatial imaging of cold {sup 85}Rb Rydberg atom clouds to measure the Rydberg-Rydberg correlation function. The results are in qualitative agreement with theoretical predictions [F. Robicheaux and J. V. Hernandez, Phys. Rev. A 72, 063403 (2005)]. We determine the blockade radius for states 44D{sub 5/2}, 60D{sub 5/2}, and 70D{sub 5/2} and investigate the dependence of the correlation behavior on excitation conditions and detection delay. Experimental data hint at the existence of long-range order.

Schwarzkopf, A.; Sapiro, R. E.; Raithel, G. [FOCUS Center, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2011-09-02

290

NASA Astrophysics Data System (ADS)

We have investigated the effects of screened Coulomb (Yukawa) potentials on the bound 1,3D states and the doubly excited 1,3 De resonance states of helium atom using highly correlated exponential basis functions. The Density of resonance states are calculated using stabilization method. Highly correlated exponential basis functions are used to consider the correlation effect between the charged particles. A total of 18 resonances (nine each for 1 De and 3 De states) below the n = 2 He + threshold has been calculated. For each spin states, this includes four members in the 2pnp series, three members in the 2snd series, and two members in 2pnf series. The resonance energies and widths for various screening parameters ranging from infinity to a small value for these 1,3 De resonance states are reported along with the bound-excited 1s3d 1,3 D state energies. Overall behavior of the spectral profile of 1s3d 1D state of helium atom due to electron-electron and electron-nucleus screening are also presented. Accurate resonance energies and widths are also reported for He in vacuum.

Kar, Sabyasachi; Ho, Y. K.

291

We are reporting electron spectra resulting from the inelastic scattering of 45-eV electrons from helium atoms through a scattering angle of 12° in the presence of an intense carbon dioxide laser. The spectra presented are in the region of the 2 1S and 2 1P states of helium. These data show additional structure when the laser is present at scattered

B. Wallbank; J. K. Holmes; A. Weingartshofer

1989-01-01

292

NASA Astrophysics Data System (ADS)

Two previous studies of Rydberg fine structure in barium have determined the dipole and quadrupole polarizabilities of Ba^+ [1,2]. The measured dipole polarizability appears to be in good agreement with theoretical calculations, but the quadrupole polarizability and the contribution to it from the single lowest D state are in very poor agreement with the most precise calculations [2]. In an effort to resolve this apparent discrepancy, microwave measurements of higher L fine structure intervals were conducted. RESIS microwave techniques [3,4] have been used to directly measure the fine structure intervals between several n=17 and 20 high-L states. It is hoped that the increased precision of these measurements and the access to higher L levels will clarify the comparison with theory. [1] T.F. Gallagher, R. Kachru, and N.H. Tran, Phys. Rev. A 26, 2611 (1982) [2] E.L. Snow, M.A. Gearba, R.A. Komara, and S.R. Lundeen, (to be published) Phys. Rev. A (2005) [3] P.W. Arcuni, E.A. Hessels, and S.R. Lundeen, Phys. Rev. A 41, 3648 (1990). [4] R.A. Komara, M.A. Gearba, C.W. Fehrenback and S.R. Lundeen, J. Phys. B: At. Mol. Opt. Phys. 38 S87 (2005).

Snow, E. L.

2005-05-01

293

Recent advances in experimental technique now allow study of the behaviour of Rydberg atoms subject to pulsed unidirectional electric fields, termed half-cycle pulses (HCPs), whose duration is much less that the classical electron orbital period. Such HCPs simply deliver an impulsive momentum transfer or \\

F. Barry Dunning

2002-01-01

294

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

295

Excitation of the n=2 states of helium by positron impact

A high-resolution (DELTAEapprox55 meV) trap-based positron beam has been used to measure absolute scattering cross sections for the excitation of the resolved 2 {sup 1}S,P states of helium at energies between threshold and 38 eV. The experimental integral cross sections, which have typical uncertainties of 10% or less, are compared with several theoretical calculations, and the agreement is generally very favorable. In particular, a new convergent close-coupling approach shows excellent agreement with the experimental data.

Caradonna, Peter; Sullivan, James P.; Jones, Adric; Makochekanwa, Casten; Slaughter, Daniel; Mueller, Dennis W.; Buckman, Stephen J. [ARC Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, Australian National University Canberra, Australian Capital Territory 0200 (Australia)

2009-12-15

296

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

2013-09-01

297

Progress towards the creation of an on-demand single photon source using Rydberg atoms

NASA Astrophysics Data System (ADS)

This dissertation describes experiments performed on Rydberg atoms in order to facilitate the construction of an on-demand, single-photon source. We performed two-photon excitation on atoms in a Magneto-Optical Trap (MOT) up to high n-level Rydberg states. We developed a novel technique for measuring the linewidths of atomic transitions at timescales shorter than 100 mus, and measured the linewidths of the 5S ? i Rydberg transitions to be 8 MHz for Rydberg principal quantum number 28, 43, and 58. We also employ another novel technique, a state-probe laser which stimulates atomic emission out of the Rydberg level and allows us to observe the timescale of Rydberg atom transitions. By employing the state-probe laser and observing trap loss from the MOT, we are able to determine that atoms are transferred out of the Rydberg state faster than collisional processes and blackbody transition rates. We have developed a model of superradiance which predicts the transition rates we observe in the experiment. Based on this, we have concluded that superradiant emission out of the Rydberg excitation state is a much greater factor in the mus-scale Rydberg transfer rates observed in the literature than any other study had previously reported. We have performed non-degenerate four-wave mixing through Rydberg states using a non-collinear geometry as a precursor to an on-demand, single-photon source. In addition, this is among the first demonstrations of the coherent manipulations of Rydberg atoms found in the literature. We have developed a model of four-wave mixing that agrees with our observations of the phase-matched count rate and fraction of phase-matched light to within a factor of 3. With the excitation beams detuned from the two-photon Rydberg transition, we observe up to 50% of the emitted light radiated into the preferred phase-matched direction.

Day, Jason Owen

298

Electron dynamics in double Rydberg wavepackets

NASA Astrophysics Data System (ADS)

The experiments described here represent the first time-dependent study of highly excited double Rydberg wavepackets. There are two main experiments that are described in this dissertation. The first experiment is a study of the decay of an autoionizing Rydberg wavepacket in calcium. This experiment shows the decay of autoionizing wavepackets to occur in the form of stair-steps and be critically dependent on the phase of the constituent states. We have been able to control the phase of the components of the wavepackets to vary the decay rates by more than a factor of five. The second experiment is the creation of a controlled double Rydberg wavepacket in barium where the two outermost electrons are excited into independently controlled wavepackets at adjustable relative delays. This study provides an experimental realization of a controlled three-body Coulomb problem. We monitor the decay products of autoionization of the double Rydberg wavepacket for different initial energies of the wavepackets and as a function of the delay between exciting the wavepackets. We have been able to use an intuitive semi-classical picture to explain the features that are observed in the experiments. The two experiments that have been described here help in a better understanding of electron dynamics in two-electron atoms.

Pisharody, Santosh Narayanan

299

NASA Astrophysics Data System (ADS)

Droplets of about 10^{4} helium atoms generated in a supersonic expansion, represent a nanometer-sized superfluid medium of 0.4 K temperature and can be doped with one or several atoms or molecules that may form complexes in this cold environment. Using two-laser excitation schemes, we were able to identify the alkali trimers K_3, Rb_3, K_2Rb and KRb_2 in their lowest quartet states formed on helium droplets loaded with potassium and rubidium atoms and assign several excited states that underlie both Jahn-Teller and spin-orbit coupling. As helium provides a gentle and only weakly perturbing matrix, it appeared desirable to look for ways to measure fine and hyperfine structure directly in the microwave or radiofrequency regime. In preparation for experiments involving optical detection of electron spin transitions in cold molecules, we studied the electronic spin relaxation in alkali atoms and molecules that reside on the surface of a droplet. Measurements of the circular dichroism in the presence of a magnetic field showed that the populations of Zeeman sublevels in alkali atoms are not thermalized, while for dimers and trimers a temperature of 0.4 K was found, implicitly providing a first determination of the droplet's surface temperature. Optical detection of spin resonance is achieved in an optical pump-probe experiment with the electron spin transition induced in a microwave cavity in a magnetic field between the pump and probe regions. With the pump laser depleting a particular spin state by desorption of the species from the droplet beam or by optical pumping, the probe laser detects the successful spin flip induced by the microwave field. Examples will be presented showing up to 50 Rabi cycles of an electron spin transition on an alkali doped helium droplet during the flight time of 57 ?s through the cavity. J. Nagl, G. Auböck, A. W. Hauser, O. Allard, C. Callegari, and W. E. Ernst, Phys. Rev. Lett. 100, 063001(2008)} G. Auböck, J. Nagl, C. Callegari, and W. E. Ernst, J. Chem. Phys. 129, 114501(2008). J. Nagl,G. Auböck, C. Callegari, and W. E. Ernst, Phys. Rev. Lett. 98, 075301 (2007). G. Auböck, J. Nagl, C. Callegari, and W. E. Ernst, J. Phys. Chem. A 111, 7404(2007). G. Auböck, J. Nagl, C. Callegari, and W. E. Ernst, Phys. Rev. Lett. 101, 035301(2008)

Ernst, Wolfgang E.

2009-06-01

300

NASA Astrophysics Data System (ADS)

Several peaks have been observed, in the electron energy range up to 20 eV, due to Coster-Kronig electrons from the autoionizing Rydberg states emitted from 2 MeV u-1 Si5+ ions excited through a carbon foil. To obtain a better understanding of these low-energy electron spectra and their production mechanisms, we synthesize the expected electron spectrum which is compared with the observed electron spectrum. Two theoretical methods, namely the perturbation theory of Z-expansion (MZ code) and the multiconfiguration Hartree-Fock method (Cowan code), are used to calculate the necessary Auger electron energies and emission rates. It has been found that the 1s22pnl-1s22s 2S and 1s22s2pnl-1s22s2 1S decays give the most significant contributions to the observed electron spectrum from threshold up to the 20 eV region. The synthetic electron spectra have also been found to reproduce the observed electron spectra quite nicely when the charge distributions of the projectile Si ions after thin carbon foils are taken into account.

Sataka, M.; Imai, M.; Kawatsura, K.; Komaki, K.; Tawara, H.; Vasilyev, A.; Safronova, U. I.

2002-01-01

301

Toward a Rydberg constant measurement on circular atoms

A high-resolution spectroscopy experiment on the microwave transitions connecting circular states of lithium atoms was performed. A measurement of the Rydberg constant, directly in frequency units, with an uncertainty of less than 10-10 is reported. This experiment involves a continuous excitation of circular Rydberg atoms and requires typically a 1 ms interaction time with a 300-500 GHz microwave field. To

J. Hare; A. Nussenzweig; C. Gabbanini; M. Weidemuller; P. Goy; M. Gross; S. Haroche

1993-01-01

302

Design of a Rydberg gate quantum logic experiment

NASA Astrophysics Data System (ADS)

We present a design for implementation of a neutral atom quantum logic testbed based on Rydberg atom interactions. Detailed calculations of expected decoherence rates and fidelities for 1 and 2 qubit logical operations are described. We discuss geometries for efficient implementation of crosstalk free row-parallel Rydberg gate operations. A novel solution for elimination of excited state motional decoherence is presented. We will report on experimental progress towards single atom loading into micron sized FORT traps.

Chutia, S.; Day, J. O.; Urban, E.; Johnson, T. A.; Kulatunga, P. B.; Walker, T. G.; Saffman, M.

2003-05-01

303

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

Wang, K.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California (USA))

1991-12-15

304

Collisional loss of cesium Rydberg atoms in a magneto-optical trap

The collisional loss rates of 63S{sub 1/2} Rydberg atoms in cesium magneto-optical trap are measured by using the state-selective pulse field ionization technique and used to investigate the interaction between Rydberg atoms. The collisional loss rate coefficients due to collisions with Rydberg atoms and ground-state atoms are obtained by fitting the experimental data. The results indicate that the large collisional loss mainly comes from the strong long-range interaction between ultracold Rydberg atoms, and the loss rate is significantly increased under a weak electric field.

Feng Zhigang; Zhang Hao; Che Junling; Zhang Linjie; Li Changyong; Zhao Jianming; Jia Suotang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, College of Physics and Electronics Engineering, Shanxi University, Taiyuan 030006 (China)

2011-04-15

305

Interactions in a frozen Rydberg gas

NASA Astrophysics Data System (ADS)

This thesis is an attempt to discover the properties of interactions between highly excited atoms with very low kinetic energies. A magneto-optical trap is used as the basis for achieving a dense frozen Rydberg gas where the atoms are essentially stationary on the time scale of the experiments. The experiments contained within are at the intersection of atomic, condensed matter, and plasma physics. Dipole-dipole interactions in this frozen Rydberg gas are examined. The low kinetic energies and large dipole moments of the Rydberg atoms make it possible to observe many-body interactions. Specifically, the resonance widths of the dipole-dipole energy transfer process Rb25s1/2+Rb33 s1/2?Rb24p 1/2+Rb34p3/2 1 resonant at fields of 3.0 and 3.4 V/cm are larger than expected considering only the strength of the interaction. A variant of the Ramsey interference method is used to explicitly show the importance of two omnipresent and always resonant dipole-dipole interactions, Rb25s1/2+Rb24 p1/2?Rb24p 1/2+Rb25s1/2 2 and Rb33s1/2+Rb34 p3/2?Rb34p 3/2+Rb33s1/2 .3 The density dependent dephasing of the Ramsey interference fringes is of the same order as the broadening of the resonance line and is attributed to the simultaneous interaction of more than two atoms. The spontaneous evolution of a cold dense gas of Rydberg atoms into an ultra-cold plasma is also observed. The build up of space charge due to many different slow ionization processes is examined and modelled. The avalanche ionization process that ensues once the space charge is large enough to trap electrons of kinetic energies comparable to the binding energy of the Rydberg atoms is studied in detail. The avalanche ionization is examined in terms of the collision rate of the electrons. A model based on a rate equation is put forth that qualitatively reproduces the features in both time and density. The evolution is examined in terms of initial Rydberg state, initial density, and time delay. DC electric fields and radio-frequency fields are used to suppress and enhance the avalanche process, and the slow ionization process is slowed by suppression of hot background Rydberg atoms.

Robinson, Michael Parker

2002-09-01

306

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

Prior studies have shown that the abundance of helium relative to hydrogen in the solar wind is a highly variable quantity. Kasper, et al. (2007) used observations from the Wind spacecraft to show that that the helium abundance in slow solar wind is strongly correlated with sunspot number. During the penultimate solar minimum, helium abundance was a linear function of

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

2010-01-01

307

XUV frequency-comb metrology on the ground state of helium

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

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

2011-12-15

308

Collisional perturbation of states in atomic ytterbium by helium and neon

Results of an investigation of collisional deexcitation of the metastable 6s6p&hthinsp;{sup 3}P{sub 0} state in atomic ytterbium by helium and neon buffer gases are reported. We find upper limits for the quenching cross sections to be {sigma}{sub He}{lt}13{times}10{sup {minus}22}&hthinsp;cm{sup 2} and {sigma}{sub Ne}{lt}8{times}10{sup {minus}22}&hthinsp;cm{sup 2}. The small cross sections may allow an ytterbium parity nonconservation experiment to be performed in a vapor cell. We have also measured the pressure broadening and shift of the 6s6p&hthinsp;{sup 3}P{sub 0}{r_arrow}6s7s&hthinsp;{sup 3}S{sub 1} and 6s{sup 2}&hthinsp;{sup 1}S{sub 0}{r_arrow}6s6p&hthinsp;{sup 3}P{sub 1} transitions by helium and neon. {copyright} {ital 1999} {ital The American Physical Society}

Kimball, D.F.; Clyde, D.; Budker, D.; Freedman, S.J.; Rochester, S.; Stalnaker, J.E. [Physics Department, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Budker, D.; Freedman, S.J. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); DeMille, D. [Physics Department, Yale University, New Haven, Connecticut 06520 (United States); Zolotorev, M. [Center for Beam Physics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

1999-08-01

309

Supersymmetry in Rydberg-dressed lattice fermions

NASA Astrophysics Data System (ADS)

Supersymmetry is a powerful tool that allows the characterization of strongly correlated many-body systems, in particular in the case of supersymmetric extensions of the fermionic Hubbard model [1]. At the same time, these models can exhibit rich and exotic physics on their own, such as flat bands with a vanishing dispersion relation. We show that such lattice models can be realized with Rydberg-dressed fermions in optical lattices. Strong interactions within the ground state manifold of the atoms can be realized by admixing a weak contribution of a highly excited Rydberg state [2]. We discuss the unique possbilities of ultracold atoms for the detection of supersymmetry and the effects of tuning the system away from the supersymmetric point.[4pt] [1] P. Fendley, K. Schoutens, J. de Boer, PRL 90, 120402 (2003).[0pt] [2] J. Honer, H. Weimer, T. Pfau, H. P. B"uchler, PRL 105, 160404 (2010).

Weimer, Hendrik; Huijse, Liza; Gorshkov, Alexey; Pupillo, Guido; Zoller, Peter; Lukin, Mikhail; Demler, Eugene

2012-06-01

310

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

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

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

2010-02-19

311

Inelastic electron collisions with Rydberg atoms

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

312

R-matrix with Pseudo-States Calculations for Electron Impact Excitation of Helium.

NASA Astrophysics Data System (ADS)

We have extended our previous R-matrix with pseudo-states work on electron impact excitation of the n=2 states of helium [1] to include transitions to the physical n=3 states. The predictions for total cross sections from both the ground state and the metastable (1s2s)^1,3S states agree very well with the convergent-close-coupling results of Fursa and Bray [2], while some disagreement remains with the recent experimental data of Lagus et al. [3]. However, excellent agreement between theory and experiment [2,4] is obtained for various electron impact coherence parameters, particularly for excitation of the 3^1,3D states. 1. K. Bartschat, E.T. Hudson, M.P. Scott, P.G. Burke, and V.M. Burke, 1. Phys. Rev. A 54 (1996), R998-1001; J. Phys. B29 (1996), 2875 & 5513 2. D.V. Fursa and I. Bray, J. Phys. B 30 (1997), 757-785 3. M.E. Lagus, J.B. Boffard, L.W. Anderson, and C.C. Lin, Phys. Rev. 3. A 53 (1996), 1505-18 4. A. Crowe (1997), private communication

Bartschat, Klaus

1998-05-01

313

The dipole moment and magnetic hyperfine properties of the {ital A} {sup 2}{Sigma}{sup +} Rydberg state of nitric oxide have been evaluated at a variety of levels of theory with extended correlation consistent basis sets. Using the finite field approach to compute the dipole moment, restricted coupled cluster RCCSD(T) and complete active space-configuration interaction CAS-CI+Q methods yield values (1.09--1.12 D) that are essentially identical to experiment. In contrast, dipole moments computed as an expectation value of the dipole moment operator typically differ from experiment by 0.1--0.6 D. The rather unfavorable comparisons with experiment reported in previous theoretical studies may stem, in part, from the method chosen to evaluate the dipole moment. Magnetic hyperfine properties were evaluated using a variety of unrestricted and restricted open-shell Hartree--Fock-based methods. We estimated the full CI limiting properties by exploiting the convergence behavior of a sequence of MRCI wave functions. The isotropic component {ital A}{sub iso}({sup 14}N) of 39{plus_minus}1 MHz evaluated in this fashion is in excellent accord with the experimental value of 41.4{plus_minus}1.7 MHz. Highly correlated UHF-based methods [e.g., CCSD(T) and QCISD(T)] yield comparable values of 40--41 MHz that are in good agreement with both experiment and the apparent full CI limit. However, for {ital A}{sub iso}({sup 17}O), the full CI limit ({minus}97{plus_minus}2 MHz) and the UHF-based results (ca.{minus}118 MHz) differ by roughly 20 MHz. It remains unclear how to reconcile this large discrepancy. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Glendening, E.D.; Feller, D. [Environmental Molecular Sciences Laboratory, Pacific Northwest Laboratory, Richland, Washington 99352 (United States); Peterson, K.A. [Department of Chemistry, Washington State University and Environmental Molecular Sciences Laboratory, Pacific Northwest Laboratory, Richland, Washington 99352 (United States); McCullough, E.A. Jr. [Department of Chemistry and Biochemistry, Utah State University 0300, Logan, Utah 84322 (United States); Miller, R.J. [Atomic and Molecular Spectroscopy, Pacific Northwest Laboratory, Richland, Washington 99352 (United States)

1995-09-01

314

Topological matter with collective encoding and Rydberg blockade

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

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

2010-11-15

315

Linewidth broadening in edge-magnetoplasmon resonance of helium surface state electrons

NASA Astrophysics Data System (ADS)

We employed edge-magnetoplasmon (EMP) resonance technique to study magneto-transport properties of 2DES where edge states play an important role. We measured EMP frequencies and linewidths of 2DES on liquid helium surface under various lateral con nement potentials. The experimental results show that as the lateral con nement potential is reduced measured EMP linewidth takes minimum at a certain strength of con nement potential and broad signal was obtained on further potential reduction. This broadening behavior is absolutely unexpected from the exsisting theories of conventional EMP. We consider that an oscillation mode transition is responsible for the linewidth broadening. The linewidth behavior in the strong con nement region is reasonably explained by conventional EMP, while the broad signals in the weak con nement region is not. We show our experimental data and discuss the origin of the line broadening.

Arai, T.; Yamanaka, S.; Yayama, H.; Sawada, A.; Fukuda, A.

2012-12-01

316

NASA Astrophysics Data System (ADS)

We have investigated the doubly excited P1,3e , D1,3o , and F1,3e nonautoionizing states of helium atom with Coulomb and screened Coulomb (Yukawa) potentials in the framework of Ritz variational principle. Highly accurate correlated exponential wave functions with exponents generated by a quasirandom process are used to represent the correlation effect. For the Coulomb case, the metastable bound-excited 2pnp P1e (3?n?5) , 2pnp P3e (2?n?5) , 2pnd D1,3o (3?n?9) , and 2pnf F1,3e (4?n?9) states energies are reported. Our upper-bound results for the 2pnd D1o (3?n?7) , 2pnf F1e (4?n?8) , D3o and F3e states are the lowest values up to this date. For the screened Coulomb case, the lower-lying metastable bound states energies for different screening parameters and for each spin states are also reported.

Kar, Sabyasachi; Ho, Y. K.

2009-06-01

317

Two-photon absorption and emission by Rydberg atoms in coupled cavities

NASA Astrophysics Data System (ADS)

We study the dynamics of a system composed of two coupled cavities, each interacting with a single Rydberg atom. The interplay between Rydberg-Rydberg interaction and photon hopping enables the transition of the atoms from the collective ground state to the double Rydberg excitation state by individually interacting with the optical normal modes and suppressing the upconversion process between them. The atomic transition is accompanied by the two-photon absorption and emission of the normal modes. Since the energy level structure of the atom-cavity system is photon number dependent there is only a pair of states being in the two-photon resonance. Therefore, the system can act as a quantum nonlinear absorption filter through the nonclassical quantum process, converting coherent light field into a nonclassical state. Meanwhile, the vacuum field in the cavity inspires the Rydberg atoms to simultaneously emit two photons into the normal mode, resulting in obvious emission enhancement of the mode.

Wu, Huaizhi; Yang, Zhen-Biao; Zheng, Shi-Biao

2013-10-01

318

Dynamic Stabilization of the Kicked Rydberg Atom

NASA Astrophysics Data System (ADS)

We present a detailed study of the behavior of 1D and 3D Rydberg atoms subject to a train of unidirectional impulses. Depending on the characteristics of the train and on the initial state of the atom, this system is found to be either fully chaotic or characterized by a mixed phase space with various families of fully stable islands within which the atom is not ionized. This system is realized experimentally by exposing potassium np Rydberg atoms with nagt 380 to a sequence of up to 50 half-cycle pulses whose duration is much less than the classical electron orbital period. Measured and calculated survival probabilities provide clear evidence of dynamic stabilization for pulse repetition frequencies of the order of the classical orbital frequency.

Reinhold, C. O.; Yoshida, S.; Burgdörfer, J.; Frey, M. T.; Dunning, F. B.

1998-05-01

319

NASA Astrophysics Data System (ADS)

In this paper we present 4-state, 5-dimensional Vibronic Coupling Hamiltonians for cyclobutanone and cyclopentanone. Wave packet calculations using these Hamiltonians reveal that for cyclobutanone the (n,3s) to (n,?*) internal conversion involves direct motion in nuclear modes coupling the two states leading to fast population transfer. For cyclopentanone, internal vibrational energy redistribution is a bottleneck for activating reactive nuclear modes leading to slower population transfer.

Kuhlman, T. S.; Sauer, S. P. A.; Sølling, T. I.; Møller, K. B.

2013-03-01

320

Wave-packet approach to Rydberg resonances in dissociative recombination

We report the time-dependent approach to resonant electron capture into Rydberg states in collisions with molecular cations at low impact energy, as an alternative to the method based on multichannel quantum defect theory (MQDT), and present the results for the HD{sup +} ion. The propagation of the initial wave function on 13 Rydberg states (besides one valence state) correctly describes the indirect dissociative recombination mechanism in the time domain. Notably, the nonlocal coupling operator between the ionization and dissociation channels is accounted for in the indirect process, extending previous work on the case of direct coupling. The present approach compares to the MQDT framework with remarkable precision: resonant structures in the cross section correctly emerge from the wave-packet propagation; the time-dependent result also forms a cross section envelope for the dense series of ultrafine MQDT resonances corresponding to the quasicontinuous part of the Rydberg state manifold.

Morisset, Sabine; Pichl, Lukas; Orel, Ann E.; Schneider, Ioan F. [Laboratoire des Interactions Ioniques et Moleculaires, Universite de Provence - Centre National de la Recherche Scientifique, Centre Saint-Jerome, Equipe SdM, Service 242, 13397 Marseille cedex 20 (France); Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden (Germany); Department of Applied Science, University of California, Davis, California 95616 (United States); Laboratoire de Mecanique, Physique et Geosciences, Unite de Formation et de Recherche Sciences et Techniques, Universite du Havre, 25, rue Philippe Lebon, BP 540, 76058, Le Havre (France)

2007-10-15

321

Magic-wavelength optical traps for Rydberg atoms

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

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

2011-10-15

322

Entropic enhancement of spatial correlations in a laser-driven Rydberg gas

NASA Astrophysics Data System (ADS)

Laser-driven Rydberg gases are many-body quantum systems that exhibit a pronounced collective excitation behavior due to the strong interaction between atoms in high-lying electronic states. Atoms located within a so-called blockade volume share a single Rydberg excitation, which is dynamically created and annihilated. For sufficiently long times, this driven system approaches a steady state, which lends its properties from a maximum entropy state of a Tonks gas. Using this connection, we show that spatial correlations between Rydberg atoms are controlled by the number of atoms contained within a blockade volume. For a small number, the system favors a disordered arrangement of Rydberg atoms, whereas in the opposite limit, Rydberg atoms tend to arrange in an increasingly ordered configuration. We argue that this is an entropic effect which is observable in current experiments. Our work demonstrates how ordered structures can spontaneously emerge in a strongly interacting, closed many-body system out of equilibrium.

Ates, C.; Lesanovsky, I.

2012-07-01

323

High precision calculation of helium and atom energy levels

This work is concerned with the high-presicion calculation of the energies of the gound and excited states of the helium atom (or other light helium-like ions) to match the recent advances in experimental laser spectroscopic studies of transitions between these states with a precision of better than 10{sup {minus}4} cm{sup {minus}1}. At this level of accuracy it is essential to include mass-polarization effects through 2nd order, relativistic effects properly scaled by appropriate powers of the reduced mass, and quantum electrodynamic (QED) effects. In recent work on excited states of helium we have attained this level of accuracy for all the non-QED effects. Our results are in good agreement with those obtained independently by G. W. F. Drake. We are proceeding with a high-precision evaluation of the Bethe logarithm, which is the principal source of uncertainty in the theoretically determined QED effects. The refinement of these calculations at the 10{sup {minus}5} cm{sup {minus}1} level and beyond is expectd to stimulate further advances both theoretical and experimental, both in the calculations of 0({alpha}{sup 4}) Rydberg relativistic and QED effects and in the high-precision measurement of transition wavelengths.

Baker, J.; Hill, R.N.; Morgan, J.D. III (Department of Physics, University of Delaware, Newark, DE 19716 (USA))

1989-06-15

324

As a major constituent of the terrestrial atmosphere, the O2 molecule plays an important role both in the attenuation of solar radiation and in the spectrum of the airglow and aurora. Photo absorption by O 2 to its complex excited state structure leads to predissociation and involves a host of other kinetic and radiative processes. Part of the work presented

Jeff Stanley Morrill

1999-01-01

325

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

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

326

Controlled many-body interactions in a frozen Rydberg gas

Previous resonant dipole-dipole energy-transfer experiments of cold Rydberg gases [Anderson et al., Phys. Rev. Lett. 80, 249 (1998); Mourachko et al., Phys. Rev. Lett. 80, 253 (1998)] have been interpreted as providing evidence of many-body, as opposed to purely binary, effects. Here we separate two-body and many-body interactions by introducing an additional Rydberg state, which does not participate directly in the energy-transfer process, but is strongly coupled to one of the final states. We observe broadening of the energy-transfer resonances due to this added Rydberg state, which clearly demonstrates the many-body nature of the dipole-dipole interactions in such a system.

Mourachko, I.; Li Wenhui; Gallagher, T.F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

2004-09-01

327

Electron attachment to photofragments and Rydberg states in laser-irradiated CCl{sub 2}F{sub 2}

We report electron attachment measurements on ArF-excimer-laser irradiated CCl{sub 2}F{sub 2}, obtained using an improved experimental technique that allows simultaneous measurements on multiple electron attaching species. Compared to a maximum electron attachment rate constant of {approximately}2{times}10{sup {minus}9}thinspcm{sup 3}thinsps{sup {minus}1} for the ground electronic state of CCl{sub 2}F{sub 2}, we measure an order of magnitude larger rate constant for the CClF{sub 2} radical produced via laser photodissociation. However, the highly excited electronic states of CCl{sub 2}F{sub 2} produced by the laser irradiation have an associated electron attachment rate constant that is at least four orders of magnitude larger compared to the ground electronic state value. Implications of these findings for plasma processing discharges using CCl{sub 2}F{sub 2} are discussed. {copyright} {ital 1998 American Institute of Physics.}

Pinnaduwage, L.A.; Datskos, P.G. [Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831-6122 (United States)]|[Department of Physics, University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Tav, C. [Department of Physics, University of Tennessee, Knoxville, Tennessee 37996-1200 (United States)

1998-10-01

328

Measurement of the oscillator strength distribution in helium

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

329

Calculation of electron-photon coincidence parameters for singlet-triplet mixed 4F states of helium

NASA Astrophysics Data System (ADS)

We present the theoretical formalism required to interpret the electron-photon coincidence measurements of the helium 4F state by Cvejanovi? and Crowe [Phys. Rev. Lett. 80, 3033 (1998)]. The results of the convergent close-coupling theory are compared with experiment and found to be in good qualitative agreement. We demonstrate that the singlet-triplet mixing in the 4F states does not affect the calculated results significantly.

Fursa, Dmitry V.; Bray, Igor

1999-02-01

330

The binding energies of high-L Rydberg levels of Pb{sup +} with n=19 or 20 and 6{<=}L{<=}10 were measured with resonant excitation Stark ionization spectroscopy (RESIS). When combined with previous measurements of members of the nh Rydberg series in Pb{sup +}, and analyzed with the long-range polarization model, these determined the polarizability of the 5d{sup 10}6s{sup 2} ground state of Pb{sup 2+} to be {alpha}{sub d} = 13.62(8) a.u. This value is substantially larger than the estimate published recently based on the measured lifetime of the 6s6p{sup 1}P{sub 1} resonance level of Pb{sup 2+}, 7.9(6) a.u. The difference is mostly due to the polarizability of Pb{sup 4+}, the 5d{sup 10} core of the Pb{sup 2+} ion. This was established by observation of resolved fine structure in the excitation of n=39, high-L Rydberg levels of Pb{sup 3+}, using the same RESIS technique. Analysis of this spectra determined the polarizability of Pb{sup 4+} to be {alpha}{sub d} = 3.61(4) a.u. Reanalysis of optical spectra of nh and ng levels in Pb{sup +} and Pb{sup 3+} in view of the polarizabilities determined in the RESIS studies indicates revised ionization energies of both ions, E{sub I}(Pb{sup +}) = 121245.28(6) cm{sup -1} and E{sub I}(Pb{sup 3+}) = 341 435.1(8) cm{sup -1}.

Hanni, M. E.; Keele, Julie A.; Lundeen, S. R.; Fehrenbach, C. W.; Sturrus, W. G. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States); J. R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas 66506 (United States); Department of Physics, Youngstown State University, Youngstown, Ohio 44555 (United States)

2010-04-15

331

Echo Experiments in a Strongly Interacting Rydberg Gas

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

Raitzsch, Ulrich; Bendkowsky, Vera; Heidemann, Rolf; Butscher, Bjoern; Loew, Robert; Pfau, Tilman [5. Physikalisches Institut, Universitaet Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany)

2008-01-11

332

Rydberg Excitation of Bose-Einstein Condensates

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 {sup 87}Rb 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.

Heidemann, Rolf; Raitzsch, Ulrich; Bendkowsky, Vera; Butscher, Bjoern; Loew, Robert; Pfau, Tilman [5. Physikalisches Institut, Universitaet Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany)

2008-01-25

333

Rydberg excitation of Bose-Einstein condensates.

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. PMID:18232977

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

2008-01-22

334

Photon-Photon Interactions via Rydberg Blockade

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

335

Deceleration and electrostatic trapping of hydrogen Rydberg molecules

NASA Astrophysics Data System (ADS)

Recent progress in the development of methods by which to decelerate and manipulate the translational motion of Rydberg atoms in the gas phase using static and time-varying inhomogeneous electric fields [1] has led to the experimental realization of Rydberg atom optics elements including a lens [2], a mirror [3] and two- and three-dimensional traps [4,5]. These experiments exploit the very large electric dipole moments associated with Rydberg Stark states, and have demonstrated the possibility to stop a seeded, pulsed, supersonic beam of atomic hydrogen traveling with an initial velocity of 700 ms-1 within 2 mm and only ˜5 ?s using electric fields of a few kVcm-1. We have now extended these techniques to manipulate the translational motion of molecular hydrogen, for applications in precision spectroscopy and in studies of molecular collisions at low temperature or with a high degree of control over collision energies. The results of recent experiments in which we have been able to load hydrogen Rydberg molecules into a three-dimensional electrostatic traps will be summarized. These experiments have relied upon the preparation of nonpenetrating (l>=3) Rydberg-Stark states, with principal quantum number in the range n=20-30, using circularly polarized laser radiation. The rate of decay of these states in the trap has been determined providing, for the first time, experimental information on the predissociation of nonpenetrating molecular Rydberg states.[4pt] [1] S. R. Procter et al., Chem. Phys. Lett., 374, 667 (2003).[0pt] [2] E. Vliegen et al., Eur. Phys. J. D, 40, 73 (2006).[0pt] [3] E. Vliegen and F. Merkt, Phys. Rev. Lett., 97, 033002 (2006).[0pt] [4] E. Vliegen et al., Phys. Rev. A, 76, 023405 (2007).[0pt] [5] S. D. Hogan and F. Merkt, Phys. Rev. Lett., 100, 043001 (2008).

Hogan, Stephen

2009-05-01

336

Collisional transfers induced in the n-italic = 6--13 Li Rydberg states by H/sub 2/, N/sub 2/, and CO molecules have been experimentally studied in a heat-pipe oven. The l-italic-mixing cross sections have been deduced from the fast component of the population relaxations following pulsed laser excitation. The order of magnitude of these cross sections (10/sup 3/ A-circle/sup 2/) is well predicted by the existing theories. For large n-italic, the cross sections stay approximately constant. This can be partly explained by the influence of inelastic processes such as n-italic changing. In the particular case of H/sub 2/, n-italic-changing collisions have been identified by the fluorescence starting from the n-italic' = n-italic +- 1, n-italic-2 levels. Cross sections of the order of 10 A-circle/sup 2/ have been measured. The systematic study of the n-italic-changing cross sections as a function of the transferred energy shows some evidence of resonance phenomena corresponding to an energy exchange between the Rydberg electron and the molecular rotation. This effect is also observed when H/sub 2/ is replaced by D/sub 2/. These resonances are well described by the theory of Petitjean and Gounand based on the e-italic-quadrupolar interaction.

Dubreuil, B.; Harnafi, M.

1986-08-01

337

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

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

1986-04-01

338

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

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

339

Equilibrium charge-state fractions of 0.2 to 6.5 MeV helium ions in carbon

The fractions of He0, He+, and He2+ present in helium beams scattered at 0° through thin carbon foils have been measured. Singly and doubly ionized beams of both 3He and 4He were used to obtain velocities corresponding to alpha particle energies from 0.2 to 6 5 MeV. The scattered ions were magnetically analysed and the three charge states were simultaneously

J. C. Armstrong; J. V. Mullendore; W. R. Harris; J. B. Marion

1965-01-01

340

We report results from recent investigations of the interior structure of Jupiter using state-of-the-art computer simulations of dense fluid hydrogen and helium. Thermodynamic properties used in the models were obtained using density-functional molecular dynamics (DFT-MD) simulations on a grid of temperature and density points spanning the interiors of the planets. In addition to calculations for pure hydrogen, simulation results for

B. Militzer; J. Vorberger; W. Hubbard

2006-01-01

341

NASA Astrophysics Data System (ADS)

A simple two-channel quantum defect theory approach accounts for resonance positions in the np Rydberg series of 11BH. The transition from Hund's case (b) to (d) in the interacting levels of this np series represents a fundamental example of electron orbital <==> cation core rotational coupling, and frame transformation theory offers a means to connect close-coupled electronically excited-state potentials and l-uncoupled Rydberg positions. This evolving interaction of the np Rydberg electron with the rotational and the vibrational motion of the 11BH+ core is formulated in terms of quantum defects, ??(v+).

Viteri, C. Ricardo; Gilkison, Andrew T.; Grant, Edward R.

2012-06-01

342

NASA Astrophysics Data System (ADS)

Configuration interaction studies on MHe and MHe2 (where M = Na, K) systems have revealed several interesting characteristics in the properties of their low-lying electronic states. Binding energy values of the 12?1/2, 3/2 states in MHe systems are found to be lower than the values of 12?u (1/2, 3/2) states in the He-M-He systems by a margin of more than 200 cm-1, indicating better exciplex stabilities of the latter systems. Excited states of the other variety of the linear MHe2 (M-He-He) systems are almost repulsive. The characteristic energy barrier of the first excited spin-orbit state of alkali metal-helium systems is found to be only 15 cm-1 in KHe and 19 cm-1 in He-K-He. For the Na*He and K*He exciplexes, predicted radiative lifetime values of 18.5 ns and 29.8 ns, respectively, are in excellent agreement with the experimental values. The red-tail portions of their emission bands are contributed by M*He2 exciplexes with relatively high radiative lifetimes. The repulsive excited state of 2?+1/2 (or 2?+g,1/2) symmetry in these van der Waals systems is likely to play an important role in the pumping of the blue side of the ns2S1/2 ? np2P3/2 transition, which eventually may give rise to the np2P1/2 ? ns2S1/2 lasing transition.

Chattopadhyay, Anjan

2011-08-01

343

Photo-excited states in germanium at liquid-helium temperatures

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

Culbertson, J.C.

1982-12-01

344

Electrometry near a dielectric surface using Rydberg electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Electrometry near a dielectric surface is performed using Rydberg electromagnetically induced transparency. The large polarizability of high-n-state Rydberg atoms gives this method extreme sensitivity. We show that dipoles produced by adsorbates on the dielectric surface produce a significant electric field that responds to an applied field with a time constant of order 1 s. For transient applied fields (with a time scale of less than 1 s) we observe good agreement with calculations based on numerical solutions of Laplace’s equation using an effective dielectric constant to simulate the bulk dielectric.

Abel, R. P.; Carr, C.; Krohn, U.; Adams, C. S.

2011-08-01

345

Collective Many-Body Interaction in Rydberg Dressed Atoms

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

346

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

347

Minerals yearbook, 1988: Helium

Grade-A helium (99.995% or better) sales volume in the United States by private industry and the Bureau of Mines was 1,911 million cubic feet (MMcf) in 1988. Grade-A helium exports by private producers were 663 MMcf, for total sales of 2,574 MMcf of U.S. helium. The price of Grade-A helium, f.o.b. plant, was about $37.50 per thousand cubic feet (Mcf) for both the Bureau and private industry. The Bureau price for bulk liquid helium was $45.00 per Mcf with additional costs for container services and rent. The liquid helium price of private industry was also about $45.00 per Mcf with some producers posting surcharges to this price. Topics discussed in the report include domestic data coverage, legislation and government programs, domestic production, consumption and uses, stocks, resources, transportation, prices, foreign trade, world review, and technology.

Leachman, W.D.

1988-01-01

348

Minerals Yearbook 1989: Helium

Grade-A helium (99.995% or better) sales volume in the United States by private industry and the Bureau of Mines was 2,083 million cubic feet (MMcf) in 1989. Grade-A helium exports by private producers were 796 MMcf, for total sales of 2,879 MMcf of U.S. helium. The price of Grade-A helium, f.o.b. plant, was about $37.50 per thousand cubic feet (Mcf) for both the Bureau and private industry. The Bureau price for bulk liquid helium was $45.00 per Mcf with additional costs for container services and rent. The liquid helium price for private industry was also about $45.00 per Mcf with some producers posting surcharges to the price.

Leachman, W.D.

1989-01-01

349

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

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

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

2009-12-15

350

Optogalvanic Measurement of Even Parity Rydberg Levels in Krypton Gas.

National Technical Information Service (NTIS)

An optogalvanic detection scheme, in conjunction with a single-step pulsed laser excitation has been used to measure the energy of even parity Rydberg levels in krypton. The excitation scheme starts from the 5s(3/2)2 and 5s'(1/2)0 metastable states, which...

M. S. Kandola

1984-01-01

351

Identification of isomeric hydrocarbons by Rydberg photoelectron spectroscopy

Many saturated and unsaturated organic hydrocarbons can assume multiple isomeric forms. At high temperatures, the identification of such isomers is difficult with conventional spectroscopic techniques, posing a challenge to the exploration of important processes such as the combustion of hydrocarbons. A recently developed technology using resonance enhanced multi-photon ionization via Rydberg states shows promise as an analytical technique, because the

Job D. Cardoza; Fedor M. Rudakov; Nils Hansen; Peter M. Weber

2008-01-01

352

Quantum information with Rydberg atoms

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

Saffman, M.; Walker, T. G.; Moelmer, K. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States); Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2010-07-15

353

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 ?(2) = 136(45) fs. The lifetime of the 3p Rydberg state in quadricyclane is ?(1) = 320(31) and the lifetime of the 3s Rydberg state in norbornadiene is ?(3) = 394(32). PMID:22482548

Rudakov, Fedor; Weber, Peter M

2012-04-01

354

Correlations of Rydberg excitations in an ultracold gas after an echo sequence

We show that Rydberg states in an ultracold gas can be excited with strongly preferred nearest-neighbor distance if densities are well below saturation. The scheme makes use of an echo sequence in which the first half of a laser pulse excites Rydberg states while the second half returns atoms to the ground state, as in the experiment of Raitzsch et al. [Phys. Rev. Lett. 100, 013002 (2008)]. Near the end of the echo sequence, almost any remaining Rydberg atom is separated from its next-neighbor Rydberg atom by a distance slightly larger than the instantaneous blockade radius halfway through the pulse. These correlations lead to large deviations of the atom-counting statistics from a Poissonian distribution. Our results are based on the exact quantum evolution of samples with small numbers of atoms. Finally, we demonstrate the utility of the {omega} expansion for the approximate description of correlation dynamics through an echo sequence.

Wuester, S.; Stanojevic, J.; Ates, C.; Pohl, T.; Rost, J. M. [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden (Germany); Deuar, P. [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw (Poland); Corney, J. F. [ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072 (Australia)

2010-02-15

355

Anisotropic interaction potential between a Rydberg electron and an open-shell ion

NASA Astrophysics Data System (ADS)

We develop a theoretical description of the anisotropic interaction between a Rydberg electron and an ionic core. An adiabatic formulation expresses the anisotropic nature of the interaction through angular-momentum operators of the core and the Rydberg electron. Terms with odd tensorial structure, such as a vector hyperpolarization proportional to L-->c.l-->, emerge in the long-range potential. Computed energies of neon n=10 Rydberg states are compared with recent experimental measurements. The vector term improves agreement between theory and experiment. The vector hyperpolarizability is calculated explicitly, along with some standard polarizabilities of Ne+.

Clark, William; Greene, Chris H.; Miecznik, Gregory

1996-04-01

356

Antiprotonic helium and CPT invariance

NASA Astrophysics Data System (ADS)

We review recent progress in the laser and microwave spectroscopy of antiprotonic helium atoms (\\barpHe^+ \\equiv \\rme^\\--\\barp - He^{++}) carried out at CERN's Antiproton Decelerator facility (AD). Laser transitions were here induced between Rydberg states (n, ell) and (n ± 1, ell - 1) of \\barpHe^+ (n ~ 40 and ell ? n - 1 being the principal and orbital angular momentum quantum numbers of the antiproton orbit). Successive refinements in the experimental techniques improved the fractional precision on the \\barpHe^+ frequencies from 3 parts in 106 to ~1 part in 108. These included a radiofrequency quadrupole decelerator, which reduced the energy of the antiprotons from 5.3 MeV (the energy of the beam emerging from AD) to ~100 keV. This enabled the production of \\barpHe^+ in ultra-low density targets, where collisional effects with other helium atoms are negligible. A continuous wave pulse-amplified dye laser, stabilized against a femtosecond optical frequency comb, was then used to measure the \\barpHe^+ frequencies with ppb-scale precision. This progress in the experimental field was matched by similar advances in computing methods for evaluating the expected transition frequencies in three-body QED calculations. The comparison of experimental (?exp) and theoretical (?th) frequencies for seven transitions in \\barp^4He^+ and five in \\barp^3 He^+ yielded an antiproton-to-electron mass ratio of m_\\bar p/m_{\\rme} = 1836.152\\,674(5) . This agrees with the known proton-to-electron mass ratio at the level of ~2 × 10-9. The experiment also set a limit on any CPT-violating difference between the antiproton and proton charges and masses, (Q_p - |Q_{\\barp}|)/Q_p \\sim (m_p - m_{\\barp})/m_p < 2 \\times 10^{-9} to a 90% confidence level. If on the other hand we assume the validity of the CPT invariance, the m_{\\barp}/m_{\\rme} result can be taken to be equal to mp/me. This can be used as an input to future adjustments of fundamental constants. The hyperfine structure of a state in \\barp^4He^+ has also been measured by microwave spectroscopy to a precision of 3 × 10-5. This corresponds to the accuracy of the most precise three-body QED calculations. Further increases in the experimental precision may soon yield an improvement in the value of the antiproton magnetic moment.

Hayano, Ryugo S.; Hori, Masaki; Horváth, Dezso; Widmann, Eberhard

2007-12-01

357

Deflection Schemes Using Rydberg Atom Mirror

NASA Astrophysics Data System (ADS)

We are investigating two schemes for deflecting Rydberg atoms in our atom mirror experiment. We plan to excite the Li Rydberg states (n=15) by a 3-step process(G.D. Stevens et al.)., Phys. Rev. Lett. 75, 3402 (1995).. The atoms then travel between a pair of plates that create an inhomogeneous elctric field. Li atoms will evolve along one of the levels of the Stark manifold, the energy changing with the position in the field. The velocity component along the field gradient will be changed, resulting in deflection. In our field configuration we can obtain a gradient of 1000 V/cm across 1 mm, corresponding to a change in energy of 23 cm-1. We compare two possible deflection schemes: 1) atoms going across the field gradient with an initial velocity until reversed, and then steered back towards high/low fields (for high/low field seeker states) or 2) atoms going along the field gradient and simply increasing their transverse momentum. For the first case we study the velocity-dependent nature of the deflection, while for the second case we calculate an optimum deflection angle of about 15^circ for our experimental conditions (beam velocity v ~2000 m/s, field variation 0-1000 V/cm, n=15). We have successfully implemented a Pt-Ir hotwire detector for the beam profile.

Tudorica, F.; Kritsun, O. A.; Stevens, G. D.; Metcalf, H.

1998-05-01

358

Rydberg spectroscopy of Fr-like thorium and uranium ions

NASA Astrophysics Data System (ADS)

The binding energies of high L Rydberg levels of Th 3+ were measured using the resonant excitation Stark ionization spectroscopy (RESIS) technique. When analyzed using the long range polarization model the measured energies determine the dipole and quadrupole polarizability of the Th4+ ion: alphad = 7.61(6) a.u. and alphaQ = 45(4) a.u. The RESIS technique and apparatus constructed for this study are discussed in this work. Modifications to the original design of the detector are presented. The modifications to the detector increased the energy resolution of the beams in the detector. It was determined that a significant source of background present in the observations of the U5+ Rydberg fine structure is due to the presence of auto-ionizing Rydberg states attached to metastable excited ion cores. These auto-ionizing states severely limit the fine structure observations, preventing the successful observation of any U5+ Rydberg fine structure.Also discussed are future directions that could lead to an increase in the signal to noise in the Th3+ fine structure observations and to a successful measurement of the dipole polarizability of U6+ .

Hanni, Mark Earl

359

New Measurement of the Rydberg Constant Using Polarization Spectroscopy of Halpha

We have determined a new Rydberg value, R?=109 737.314 76(32) cm-1, from an absolute wavelength measurement of the 2S12-3P12 component of the hydrogen Balmer-alpha line. Polarization spectroscopy of a mild helium-hydrogen discharge with a cw dye laser provided a threefold higher accuracy than the only previous Doppler-free measurement. Another twofold improvement can be obtained by a more precise wavelength measurement

J. E. M. Goldsmith; E. W. Weber; T. W. Hänsch

1978-01-01

360

New measurement of the Rydberg constant using polarization spectroscopy of H\\/sub b

We have determined a new Rydberg value, R\\/sub infinity\\/ = 109 737.314 76(32) cm-Â¹, from an absolute wavelength measurement of the 2Sââ - 3Pââ component of the hydrogen Balmer-..cap alpha.. line. Polarization spectroscopy of a mild helium-hydrogen discharge with a cw dye laser provided a threefold higher accuracy than the only previous Doppler-free measurement. Another twofold improvement can be obtained

J. E. M. Goldsmith; E. W. Weber; T. W. Haensch

1978-01-01

361

Fermionic Collective Excitations in a Lattice Gas of Rydberg Atoms

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

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

2009-10-30

362

Attosecond Two-Photon Interferometry for Doubly Excited States of Helium

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 noncoincident single-electron spectra. We analyze the interferometric signal in terms of a semianalytical model which is validated by a numerical solution of the time-dependent two-electron Schroedinger equation in its full dimensionality.

Feist, J. [ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Nagele, S.; Burgdoerfer, J. [Institute for Theoretical Physics, Vienna University of Technology, 1040 Vienna, Austria, EU (Austria); Ticknor, C.; Collins, L. A. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Schneider, B. I. [Office of Cyberinfrastructure, National Science Foundation, Arlington, Virginia 22230 (United States)

2011-08-26

363

Dipole effects in a cold Rydberg gas

NASA Astrophysics Data System (ADS)

This dissertation is a continuing study of the dipole effects between cold Rydberg atoms in a MOT (Magneto Optical Trap). The dipole-dipole interaction is commonly used to explain the plasma forming process and dipole blockade effects. However, no direct measurements have been made for such interaction. This dissertation is designed to directly measure this interaction and study the effects induced by the dipole interaction. To achieve this, a few experiments were carried out. First, a millimeter wave spectroscopy experiment was performed to determine quantum defects of higher angular momentum f and g states, which then allows us to accurately identify these states. Moreover, the higher angular momentum states play an important role in the plasma forming process. The next experiment examined the oscilloscope trace collected through field ionization pulses on which all our experiments are based, which leads to the conclusion that the side peaks other than the main peak can be due to the field ionization pulse sweeping through the resonances. Based on the knowledge of identifying states obtained from these two experiments, a third experiment was carried out to understand the interactions between cold Rydberg atoms. It was found that the second order dipole-dipole interaction, the van der Waals interaction, commonly exists between the atoms in our atomic sample, and when we excite the atoms from the ns to (n + 1)s states using a narrow band microwave pulse, an asymmetric broadening, which is attributed to the nsns to ns(n + 1) s molecular state transition, was observed. Furthermore, the van der Waals long range molecule is studied, which provides another way to study the two-body to multi-body transition.

Han, Jianing

364

High-precision eigenvalues for the 1s2p /sup 1/P and /sup 3/P states of helium

The double basis set method in Hylleraas coordinates described previously (G. W. F. Drake, Nucl. Instrum. Methods B31, 7 (1988)) is applied to the calculation of high-precision eigenvalues for the 1s2p /sup 1/P and /sup 3/P states of helium. Convergence to a few parts in 10/sup 14/ is obtained for the nonrelativistic energies. The new wave functions are used to calculate mass-polarization, relativistic, relativistic reduced mass, and quantum-electrodynamic corrections. A comparison of the P-state energies, together with the previously calculated S- and D-state energies, with the experimental energy levels tabulated by Martin (Phys. Rev A 36, 3575 (1987)) yields well-defined discrepancies of the order of 0.001 cm/sup -1/, which can be attributed to higher-order relativistic and quantum-electrodynamic effects.

Drake, G.W.F.; Makowski, A.J.

1988-10-01

365

1Po resonances of helium below the n=4 threshold of He+

NASA Astrophysics Data System (ADS)

In this work the lowest eleven 1Po resonances of helium below the n=4 threshold of He+ have been investigated. The QHQ eigenvalues of these states have been calculated and found to be lower than the QHQ results of Oberoi and of Herrick and Sinanog?lu. The saddle-point energies of these resonances are found to be generally in good agreement with the experimental results of Madden and Codling and of Woodruff and Samson. The oscillator strengths from both the 11Se and 21Se states to these autoionizing levels are also calculated together with various pertinent expectation values which allow us to arrange the eleven states into six Rydberg series, one of which we identify as the resonant series seen in the experiments.

Davis, Brian F.; Chung, Kwong T.

1982-11-01

366

Entanglement of Two Individual Neutral Atoms Using Rydberg Blockade

We report the generation of entanglement between two individual {sup 87}Rb atoms in hyperfine ground states |F=1,M=1> and |F=2,M=2> which are held in two optical tweezers separated by 4 {mu}m. Our scheme relies on the Rydberg blockade effect which prevents the simultaneous excitation of the two atoms to a Rydberg state. The entangled state is generated in about 200 ns using pulsed two-photon excitation. We quantify the entanglement by applying global Raman rotations on both atoms. We measure that 61% of the initial pairs of atoms are still present at the end of the entangling sequence. These pairs are in the target entangled state with a fidelity of 0.75.

Wilk, T.; Gaeetan, A.; Evellin, C.; Wolters, J.; Miroshnychenko, Y.; Grangier, P.; Browaeys, A. [Laboratoire Charles Fabry, Institut d'Optique, CNRS, Univ Paris-Sud, Campus Polytechnique, RD 128, 91127 Palaiseau cedex (France)

2010-01-08

367

Processes of decay of Rydberg plasma

The lifetime of a molecule consisting of two Rydberg atoms with respect to electron release is determined from computer simulation of two classical electrons in the field of Coulomb centers. From this, the cross section of the Penning process of collision of two Rydberg atoms with electron release is obtained. The rate constant for ionization of Rydberg atoms is evaluated for the Rydberg plasma within the Thomson model. On the basis of these processes, the kinetics is analyzed for the decay of a Rydberg plasma. Comparison with experimental data shows that these decay processes are responsible for the first stage of the decay of a magnetized and nonmagnetized Rydberg plasma located in a magnetic superconducting trap, whereas other processes become important at a subsequent stage of the plasma evolution.

Andreev, E. A. [Russian Academy of Sciences, Semenov Institute of Chemical Physics (Russian Federation); Kashtanov, P. V., E-mail: kashtan@maryno.net; Smirnov, B. M. [Russian Academy of Sciences, Institute for High Temperatures (Russian Federation)

2006-10-15

368

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

369

NASA Astrophysics Data System (ADS)

The interpretation of the almost 300 diffuse interstellar bands (DIBs) is one of the most long-standing problems in interstellar spectra. The only model showing agreement with a large number of DIBs (>60 bands) is based on transitions in doubly excited atoms embedded in the condensed phase named Rydberg Matter (RM). A similar model is now used to precisely calculate all intense bands from the high-resolution survey by Galazutdinov et al., 63 bands in total. Thus, the RM model interprets at present 120 DIBs accurately in a consistent manner, almost half of the number of DIBs. The origin of almost all intense DIBs is shown to be absorption during electron transitions between co-planar doubly excited He atoms inside RM, and from singly excited He atoms to doubly excited He atoms inside RM. The average error in the assignments is 4 cm-1 (1.4 Å), comparable to the band width. The intense but broad DIB 578.0 nm is part of a series of 10 bands interpreted as RM transitions from n'' = 5 to the conduction band limit. The shape of DIB 579.7 nm is consistent with a rotational band from symmetric top RM clusters at approximately 100 K. Good agreement with observational results like band shapes and correlations among various bands is found.

Holmlid, Leif

2008-02-01

370

NASA Astrophysics Data System (ADS)

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

Hessels, E. A.

2003-05-01

371

Mechanical Effect of van der Waals Interactions Observed in Real Time in an Ultracold Rydberg Gas

We present time-resolved spectroscopic measurements of Rydberg-Rydberg interactions between two Rydberg atoms in an ultracold gas, revealing the pair dynamics induced by long-range van der Waals interactions between the atoms. By detuning the excitation laser, a specific pair distribution is prepared. Penning ionization on a microsecond time scale serves as a probe for the pair dynamics under the influence of the attractive long-range forces. Comparison with a Monte Carlo model not only explains all spectroscopic features but also gives quantitative information about the interaction potentials. The results imply that the interaction-induced ionization rate can be influenced by the excitation laser. Surprisingly, interaction-induced ionization is also observed for Rydberg states with purely repulsive interactions.

Amthor, T.; Reetz-Lamour, M.; Westermann, S.; Denskat, J.; Weidemueller, M. [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg (Germany)

2007-01-12

372

Mechanical effect of van der waals interactions observed in real time in an ultracold Rydberg gas.

We present time-resolved spectroscopic measurements of Rydberg-Rydberg interactions between two Rydberg atoms in an ultracold gas, revealing the pair dynamics induced by long-range van der Waals interactions between the atoms. By detuning the excitation laser, a specific pair distribution is prepared. Penning ionization on a microsecond time scale serves as a probe for the pair dynamics under the influence of the attractive long-range forces. Comparison with a Monte Carlo model not only explains all spectroscopic features but also gives quantitative information about the interaction potentials. The results imply that the interaction-induced ionization rate can be influenced by the excitation laser. Surprisingly, interaction-induced ionization is also observed for Rydberg states with purely repulsive interactions. PMID:17358604

Amthor, T; Reetz-Lamour, M; Westermann, S; Denskat, J; Weidemüller, M

2007-01-10

373

NASA Astrophysics Data System (ADS)

We investigate a hybrid quantum system that consists of a superatom coupled to a surface phonon-polariton. We apply this hybrid quantum system to subtract individual photons from a beam of light. A Rydberg atom blockade is used to attain absorption of a single photon by an atomic microtrap. Surface phonon-polariton coupling to the superatom then triggers the transfer of the excitation to a storage state, a single Rydberg atom. The approach utilizes the interaction between a superatom and a Markovian bath that acts as a controlled decoherence mechanism to irreversibly project the superatom state into a single Rydberg atom state that can be read out.

Kübler, H.; Booth, D.; Sedlacek, J.; Zabawa, P.; Shaffer, J. P.

2013-10-01

374

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

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

2009-10-15

375

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

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

2012-02-01

376

Rydberg-Rydberg interaction profile from the excitation dynamics of ultracold atoms in lattices

We propose a method for the determination of the interaction potential of Rydberg atoms. Specifically, we consider a laser-driven Rydberg gas confined in a one-dimensional lattice and demonstrate that the Rydberg atom number after a laser excitation cycle as a function of the laser detuning provides a measure for the Rydberg interaction coefficient. With the lattice spacing precisely known, the proposed scheme only relies on the measurement of the number of Rydberg atoms and thus circumvents the necessity to map the interaction potential by varying the interparticle separation.

Mayle, Michael [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States); Zeller, Wolfgang; Tezak, Nikolas; Schmelcher, Peter [Zentrum fuer Optische Quantentechnologien, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany)

2011-07-15

377

Remeasurement of the Rydberg constant

We report a remeasurement of the Rydberg constant via a single-photon determination of the Balmer-..cap alpha.. wavelength. The new value refects the redefinition of the meter, a reexamination of corrections, and improvements of the experimental apparatus. The result is R = 109 737.315 69(7) cmâ»Â¹, where c = 299 792 458 m\\/s by definition. This result does not significantly disagree

Ping Zhao; W. Lichten; H. P. Layer; J. C. Bergquist

1986-01-01

378

Infrared detection using Rydberg atoms. Final report, 1 March 1979-30 November 1987

This is the final report on a program of research on Rydberg atoms and radiation. The goal of the program was to use Rydberg atoms to explore new types of fundamental radiative phenomena. As demonstrated by the research generated by this line of inquiry in laboratories in the U.S. and abroad, the program has been successful. A new area of study called Cavity Quantum Electrodynamics has emerged in the last few years. Research under this grant on inhibited spontaneous emission is often regarded as seminal in that development. The Principal Investigator was awarded the 1986 Davisson-Germer Prize of the American Physical Society for research on Rydberg Atoms in applied fields: research under this grant was central to that achievement. Early work under the grant involved developing techniques for studying radiative transfer of Rydberg atoms on a level-by level basis. During this time the P.I. conceived the idea of of turning off spontaneous emission by Rydberg atoms. A closely related idea - the inhibition of black-body radiative transfer - was demonstrated shortly thereafter. Full demonstration of inhibited spontaneous emission required the development of a technique for transferring atoms to the so-called circular Rydberg states. These are states of the highest-possible angular momentum for a given principal quantum number. The author's method has been adapted in other laboratories, and is now being employed in Rydberg-atom studies and in a new type of measurement of the Rydberg constant. The most-exciting advance under the grant has been the demonstration that spontaneous emission can indeed be switched off.

Kleppner, D.

1988-04-01

379

Population transfer in the Na s-p Rydberg ladder by a chirped microwave pulse

While quantum defects of nl Rydberg states of Na with l{>=}2 are nearly equal to zero, the quantum defects of ns and np states of Na are quite large due to the finite size of its ionic core. Since the Na ns and np states are energetically isolated from the higher angular momentum states of the same n, we can think of the Na ns and np Rydberg states as a specific example of a simple multilevel ladder system consisting of only alternating s and p angular momentum states. Here we report that population transfer in the Na s-p Rydberg ladder can be effectively achieved using a frequency-chirped microwave pulse, which couples only s and p states under suitable conditions.

Maeda, H. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904-4714 (United States); Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Sagamihara, Kanagawa 252-5258 (Japan); Gurian, J. H.; Gallagher, T. F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904-4714 (United States)

2011-12-15

380

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

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

381

Quantum phases of strongly interacting Rydberg atoms in triangular lattices

NASA Astrophysics Data System (ADS)

We present a theoretical study on the system of laser-driven strongly interacting Rydberg atoms trapped in a two-dimensional triangular lattice, in which the dipole-dipole interactions between Rydberg states result in exotic quantum phases. By using the mean-field theory, we investigate the steady state solutions and analyze their dynamical stabilities. We find that in the strong-interaction limit, the dynamics of the system is chaotic and exhibits random oscillations under appropriate laser detunings. The Lyapunov exponent criterion is introduced to confirm the existence of this chaotic behavior. In addition, we present a full quantum calculation based on a six-atom model, and find that the system exhibits some biantiferromagnetic properties in every triangular cell when the one-photon detuning is exactly resonant or blue shifted.

Qian, Jing; Zhou, Lu; Zhang, Weiping

2013-06-01

382

Dynamical entanglement and chaos: The case of Rydberg molecules

A Rydberg molecule is composed of an outer electron that collides on the residual ionic core. Typical states of Rydberg molecules display entanglement between the outer electron and the core. In this work, we quantify the average entanglement of molecular eigenstates and further investigate the time evolution of entanglement production from initially unentangled states. The results are contrasted with the underlying classical dynamics, obtained from the semiclassical limit of the core-electron collision. Our findings indicate that entanglement is not simply correlated with the degree of classical chaos, but rather depends on the specific phase-space features that give rise to inelastic scattering. Hence mixed phase-space or even regular classical dynamics can be associated with high entanglement generation.

Lombardi, M.; Matzkin, A. [Laboratoire de Spectrometrie physique (CNRS Unite 5588), Universite Joseph-Fourier Grenoble-1, Boite Postale 87, 38402 Saint-Martin d'Heres (France)

2006-06-15

383

Dipole-dipole-coupled double-Rydberg molecules

NASA Astrophysics Data System (ADS)

We show that the dipole-dipole interaction between two Rydberg atoms can give rise to long-range molecules. The binding potential arises from two states that converge to different separated-atom asymptotes. These states interact weakly at large distances, but start to repel each other strongly as the van der Waals interaction turns into a resonant dipole-dipole interaction with decreasing separation between the atoms. This mechanism leads to the formation of an attractive well for one of the potentials. If the two separated-atom asymptotes come from the small Stark splitting of an atomic Rydberg level, which lifts the Zeeman degeneracy, the depth of the well and the location of its minimum are controlled by the external electric field. We discuss two different geometries that result in a localized and a donut-shaped potential, respectively.

Kiffner, Martin; Park, Hyunwook; Li, Wenhui; Gallagher, T. F.

2012-09-01

384

Precision Measurements of the Rydberg Constant

Five recent measurements of the frequencies of optical spectral lines in atomic hydrogen and deuterium have improved the accuracy of the Rydberg constant beyond 1 part in 109. We review these experiments and discuss the importance of the Rydberg constant in atomic theory and in relation to the other fundamental physical constants. We discuss the limitations of these recent experiments

D. H. McIntyre; T. W. Hänsch

1988-01-01

385

A measurement of the Rydberg constant

THE Rydberg constant is of key importance in spectroscopy and, because it may be expressed as the product of several fundamental physical constants, it also plays an important part as an auxiliary constant in the evaluation of the fundamental constants of physics1. We report here a value of the Rydberg constant that is derived from the measurement of three of

B. W. Petley; K. Morris

1979-01-01

386

Excitation of Rydberg wave packets with chirped laser pulses

NASA Astrophysics Data System (ADS)

We study Rydberg wave packets produced by pairs of time separated femtosecond laser pulses. The time separation ranges from femtosecond to picosecond time scales. The wave packets consist predominantly of f states of principal quantum numbers n=22-32 in Li. With a direct analysis of the field ionization spectra the n-level-resolved classical orbit times are displayed. By chirping the second excitation pulse we demonstrate controlled amplitude oscillations of n-level amplitudes on femtosecond time scales.

Preclíková, J.; Kozák, M.; Fregenal, D.; Frette, Ø.; Hamre, B.; Hjertaker, B. T.; Hansen, J. P.; Kocbach, L.

2012-12-01

387

Calculation of Rydberg energy levels for the francium atom

NASA Astrophysics Data System (ADS)

Based on the weakest bound electron potential model theory, the Rydberg energy levels and quantum defects of the np2Po1/2 (n = 7-50) and np2Po3/2 (n = 7-50) spectrum series for the francium atom are calculated. The calculated results are in excellent agreement with the 48 measured levels, and 40 energy levels for highly excited states are predicted.

Huang, Shi-Zhong; Chu, Jin-Min

2010-06-01

388

Calculation of Rydberg energy levels for the francium atom

Based on the weakest bound electron potential model theory, the Rydberg energy levels and quantum defects of the np2Po1\\/2 (n = 7-50) and np2Po3\\/2 (n = 7-50) spectrum series for the francium atom are calculated. The calculated results are in excellent agreement with the 48 measured levels, and 40 energy levels for highly excited states are predicted.

Shi-Zhong Huang; Jin-Min Chu

2010-01-01

389

Bidirectionally kicked Rydberg atoms: Population trapping near the continuum

The behavior of high-n Rydberg atoms subject to a periodic sequence of short half-cycle pulses (HCPs) that alternate in sign is reexamined. Each HCP delivers an impulsive momentum transfer or 'kick' to the electron and the net average field it experiences is zero. The data show that the excited electron energy distribution initially moves toward the continuum, i.e., toward states

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

2006-01-01

390

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

391

Investigation of cold rubidium Rydberg atoms in a magneto-optical trap

This paper reports on the results of experiments with cold rubidium Rydberg atoms in a magneto-optical trap. The specific feature of the experiments is the excitation of Rydberg atoms in a small volume within a cloud of cold atoms and the sorting of measured signals and spectra according to the number of detected Rydberg atoms. The effective lifetime of the 37P Rydberg state and its polarizability in a weak electric field are measured. The results obtained are in good agreement with theoretical calculations. It is demonstrated that the localization of the excitation volume in the vicinity of the zero-magnetic-field point makes it possible to improve the spectral resolution and to obtain narrow microwave resonances in Rydberg atoms without switching off the quadrupole magnetic field of the trap. The dependence of the amplitude of dipole-dipole interaction resonances in Rydberg atoms on the number of atoms is measured. This dependence exhibits a linear behavior and agrees with the theory for a weak dipole-dipole interaction.

Tretyakov, D. B.; Beterov, I. I.; Entin, V. M.; Ryabtsev, I. I. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)], E-mail: ryabtsev@isp.nsc.ru; Chapovsky, P. L. [Russian Academy of Sciences, Institute of Automation and Electrometry, Siberian Branch (Russian Federation)

2009-03-15

392

The goal of this work is to bridge the gap between physics and engineering aspects of helium fluids to encourage their use and enhance their usefulness in low-temperature systems. Topics covered include thermodynamic laws, electrical and thermal conductivities, spin systems, virial expansion, liquid He I, transport properties, density of helium as a quantum fluid, vortices and turbulence in He II,

Van Sciver

1986-01-01

393

The results of studies of ionic rotational branching ratios and photoelectron angular distributions resulting from (2+1{prime}) resonance enhanced multiphoton ionization of NO via various high {ital J} ({approx}21.5) rotational branches of the {ital E}{sup 2}{Sigma}{sup +}(4{ital s},3{ital d}) and {ital H}{sup 2}{Sigma}{sup +}(3{ital d},4{ital s}) Rydberg states are presented. The rotational branching ratios show the expected {Delta}N=even rotational propensity rule with very small {Delta}N=odd signals. The branching ratios for the {ital E}{sup 2}{Sigma}{sup +} state are seen to be independent of photoelectron energy with the {Delta}N=+2 signals strongest and no appreciable higher rotational transfer peaks ({vert bar}{Delta}N{vert bar}{ge}3). The higher rotational transfer signal for ionization of the {ital H}{sup 2}{Sigma}{sup +} state are also negligible but the rotational branching ratios are strongly energy dependent due to a Cooper minimum in the {ital l}=3 partial wave of the {ital k}{sigma}- and {ital k}{pi}-continua at a photoelectron kinetic energy of 2.6 eV and 2.9 eV, respectively. This leads to a strong rotational selectivity that can be exploited to produce ions in a specific rotational level. These consequences of Cooper minima close to threshold are quite general and their influence on rotational distributions should be readily observable in other molecular systems. The photoelectron angular distributions via both states show a strong energy dependence with a rapid change in the angular distributions around the Cooper minimum associated with the {ital H}{sup 2}{Sigma}{sup +} state.

Rudolph, H.; McKoy, V. (Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA (USA))

1990-11-15

394

NASA Astrophysics Data System (ADS)

In this dissertation, I study the structure and dynamics of Rydberg two-electron atoms. Specifically, I study the core polarization effect of the Rydberg electron on the ground state ion of strontium and the autoionization of barium atoms in an external static field in the low field regime. The autoionization studies show that it is possible to measure the contribution to dielectronic recombination (DR) of energetically unresolved high ? states by measuring the recombination rate as a function of electric field. I also present the experimental observation that the ejected electrons from autoionizing states in an electric field have a directional preference that depends on the orientation of the Rydberg Stark state wavefunctions. Finally, I present the spectroscopy of the Stark autoionizing states in the low field regime using a high resolution dye-amplified diode laser.

Nunkaew, Jirakan

395

We are reporting electron spectra resulting from the inelastic scattering of 45-eV electrons from helium atoms through a scattering angle of 12{degree} in the presence of an intense carbon dioxide laser. The spectra presented are in the region of the 2 {sup 1}S and 2 {sup 1}P states of helium. These data show additional structure when the laser is present at scattered electron energies which correspond to an increase or decrease in electron kinetic energy of the equivalent of one laser quantum. These measurements demonstrate the simultaneous electron-photon excitation of an atom at high incident-electron energies.

Wallbank, B.; Holmes, J.K.; Weingartshofer, A. (Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia, Canada B2G1C0 (CA))

1989-11-01

396

Review of cold Rydberg atoms and their applications

NASA Astrophysics Data System (ADS)

We present an introductory review of the latest advancements cold Rydberg atom research. First, we briefly summarize the exaggerated properties of Rydberg atoms, and we discuss the new perspectives of Rydberg atom research that has been enabled by laser cooling and trapping technique. We then highlight the latest developments and achievements in the newly emerged research fields for Rydberg molecules and cold neutral plasmas. Various applications of the Rydberg blockade effect for quantum optics and quantum information science are also reviewed.

Lim, Jongseok; Lee, Han-gyeol; Ahn, Jaewook

2013-08-01

397

Wigner crystallization of single photons in cold Rydberg ensembles.

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

2013-09-09

398

Physics of Ultra-cold and Rydberg Plasmas

Here we discuss collective processes and plasma effects that can be found in ultra-cold matter. First, we consider the ultra-cold atomic gas that can be produced in a magneto-optical trap. Due to the existence of long-range repulsive forces, new collective oscillation can take place, resembling sound waves but with a cut-off frequency. We also examine new phenomena in Rydberg plasmas, resulting from laser ionization of the ultra-cold gas. In these very low temperature plasmas a large amount of excited Rydberg states can exist, leading to a new dispersion relation for the electromagnetic waves. Enhanced magnetic field generation will also be considered. Finally, we discuss the collective properties of Bose Einstein condensates, showing a strong analogy with collective plasma processes. Two related examples are given as an illustration: Bogoliubov oscillations in the condensate, and two-stream instabilities of counter-streaming BECs.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2010-06-15

399

Quantal and Classical Radiative Cascade in Rydberg Plasmas

NASA Astrophysics Data System (ADS)

Atoms in high (n, ?) states formed in cold Rydberg plasmas decay to the ground state in a succession of radiative transitions populating intermediate excited states. Which states are populated during cascading and with what probability can be obtained from known transition probabilities. A classical model simplifies the calculation considerably, reveals the ``trajectory" in n? space followed during the cascade, scaling rules and other aspects hidden within the quantal approach. Quantal-Classical correspondence in radiative decay is directly demonstrated. Classical transition probabilities based on the Heisenberg correspondence principle are in excellent agreement with quantal transition probabilities, even for moderate quantum numbers.

Flannery, Raymond; Vrinceanu, Daniel

2003-05-01

400

Remeasurement of the Rydberg constant

We report a remeasurement of the Rydberg constant via a single-photon determination of the Balmer-..cap alpha.. wavelength. The new value refects the redefinition of the meter, a reexamination of corrections, and improvements of the experimental apparatus. The result is R = 109 737.315 69(7) cm/sup -1/, where c = 299 792 458 m/s by definition. This result does not significantly disagree with the preceding measurement by Amin et al, significantly disagrees with the measurement by Hildum et al., and agrees very well with a recent measurement by Biraben and Julien.

Zhao, P.; Lichten, W.; Layer, H.P.; Bergquist, J.C.

1986-12-01

401

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

402

Two body and multibody interaction in a cold Rydberg gas

NASA Astrophysics Data System (ADS)

Cold Rydberg atoms trapped in a Magneto Optical Trap (MOT) are not isolated and they tend to bond through dipole-dipole and multiple-multiple interactions between Rydberg atoms. The dipole-dipole interaction and van der Waals interaction between two atoms have been intensively studied. However, the fact that the dipole-dipole interaction and van der Waals interaction show the same size of broadening, studied by Raithel's group, and there is transition between two molecular states, studied by Farooqi and Overstreet, can not be explained by the two atom picture. The purpose of this paper is to show the multibody nature of a dense cold Rydberg gas by studying the molecular state microwave spectrum. Specifically, single body, two body and three body interaction regions are separated. Moreover, the multibody energy levels for selected geometries are calculated. In addition, multibody blockade will be discussed. [3pt] [1] A. Reinhard, K. C. Younge, T. Cubel Liebisch, B. Knuffman, P. R. Berman, and G. Raithel, Phys. Rev. Lett. 100, 233201 (2008).[0pt] [2] 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).[0pt] [3] K. Richard Overstreet, Arne Schwettmann, Jonathan Tallant, and James P. Shaffer, Phys. Rev. A 76, 011403 (2007).

Han, Jianing; Gallagher, Tom

2009-05-01

403

The goal of this work is to bridge the gap between physics and engineering aspects of helium fluids to encourage their use and enhance their usefulness in low-temperature systems. Topics covered include thermodynamic laws, electrical and thermal conductivities, spin systems, virial expansion, liquid He I, transport properties, density of helium as a quantum fluid, vortices and turbulence in He II, Kapitza conductance, acoustic mismatch theory, nucleate boiling heta transfer, surface effects, general considerations of internal flow, ideal liquefaction, stirling cycle, and the helium-3 isotope.

Van Sciver, S.W.

1986-01-01

404

Two-Stage Melting in Systems of Strongly Interacting Rydberg Atoms

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

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

2010-12-03

405

Dependences of sticking coefficient on amount of the absorbed helium and a sorbent temperature and dependences of critical and limiting sorption capacities on a sorbent temperature have been obtained.

L. S. Gurevich; V. V. Petrovsky; A. V. Pustovoit

1990-01-01

406

Communication: Atomic and molecular Rydbergs from water

NASA Astrophysics Data System (ADS)

We report the formation of energetic neutral Rydberg hydrogen atoms and transient Rydberg molecular ions, [(H2O)q+]? in ion-impact dissociation of isolated water molecules. The kinetic energy spectra of the neutral Rydberg H atoms are determined from the complete study of (H*, H+, O+) dissociation channel. This channel of water dissociation is suggested as a possible additional source of the energetic neutrals detected in upper atmospheres of extra solar planets, and of slow electrons which are known to play a major role in radiation induced damage to living cells.

Rajput, Jyoti; Safvan, C. P.

2011-05-01

407

Quantal and classical radiative cascade in Rydberg plasmas

NASA Astrophysics Data System (ADS)

Atoms in high-(n,l) states formed in cold Rydberg plasmas decay to the ground state in a succession of radiative transitions populating intermediate excited states. A classical treatment presents radiative cascade in a physically transparent way and reveals the “trajectory” in nl space obeyed by the cascade, scaling rules, and other aspects hidden within the quantal approach. Quantal-classical correspondence in radiative decay is directly demonstrated. Classical transition probabilities are also presented and are in excellent agreement with quantal transition probabilities, even for moderate quantum numbers.

Flannery, M. R.; Vrinceanu, D.

2003-09-01

408

Quantal and Classical Radiative Cascade in Ultracold Rydberg Plasmas

NASA Astrophysics Data System (ADS)

Atoms in high (n, ?) states formed in cold Rydberg plasmas decay to the ground state in a succession of radiative transitions populating intermediate excited states. A classical treatment presents radiative cascade in a physically transparent way and reveals the ``trajectory" in n? space obeyed by the cascade, scaling rules and other aspects hidden within the quantal approach. Quantal-Classical correspondence in radiative decay is directly demonstrated. Classical transition probabilities are also presented and are in excellent agreement with quantal transition probabilities, even for moderate quantum numbers. Research supported by AFOSR, Grant 49620-02-1-0338 and NSF Grant 01-00890.

Flannery, M. Raymond; Vrinceanu, Daniel

2003-10-01

409

Adiabatic quantum computation with Rydberg-dressed atoms

NASA Astrophysics Data System (ADS)

We study an architecture for implementing adiabatic quantum computation with trapped neutral atoms. Ground-state atoms are dressed by laser fields in a manner conditional on the Rydberg blockade mechanism, thereby providing the requisite entangling interactions. As a benchmark, we study the performance of quantum annealing to the ground state of an Ising spin lattice. We model a proof-of-principle experiment in a realistic architecture, including details of the atomic implementation, with qubits encoded in the clock states of 133Cs. Numerical simulation yields fidelities >0.98 for up to four qubits, and implementations of 10–20 qubits are within the range of current technology.

Keating, Tyler; Goyal, Krittika; Jau, Yuan-Yu; Biedermann, Grant W.; Landahl, Andrew J.; Deutsch, Ivan H.

2013-05-01

410

Quantal and classical radiative cascade in Rydberg plasmas

Atoms in high-(n,l) states formed in cold Rydberg plasmas decay to the ground state in a succession of radiative transitions populating intermediate excited states. A classical treatment presents radiative cascade in a physically transparent way and reveals the 'trajectory' in nl space obeyed by the cascade, scaling rules, and other aspects hidden within the quantal approach. Quantal-classical correspondence in radiative decay is directly demonstrated. Classical transition probabilities are also presented and are in excellent agreement with quantal transition probabilities, even for moderate quantum numbers.

Flannery, M.R. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); ITAMP, Harvard-Smithsonian Center for Astrophysics, Harvard University, Cambridge, Massachusetts 02138 (United States); Vrinceanu, D. [ITAMP, Harvard-Smithsonian Center for Astrophysics, Harvard University, Cambridge, Massachusetts 02138 (United States)

2003-09-01

411

Mesoscopic Rydberg Gate Based on Electromagnetically Induced Transparency

We demonstrate theoretically a parallelized C-NOT gate which allows us to entangle a mesoscopic ensemble of atoms with a single control atom in a single step, with high fidelity and on a microsecond time scale. Our scheme relies on the strong and long-ranged interaction between Rydberg atoms triggering electromagnetically induced transparency. By this we can robustly implement a conditional transfer of all ensemble atoms between two logical states, depending on the state of the control atom. We outline a many-body interferometer which allows a comparison of two many-body quantum states by performing a measurement of the control atom.

Mueller, M.; Lesanovsky, I.; Zoller, P. [Institute for Theoretical Physics, University of Innsbruck, and Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); Weimer, H.; Buechler, H. P. [Institute for Theoretical Physics III, University of Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany)

2009-05-01

412

Dynamic formation of Rydberg aggregates at off-resonant excitation

NASA Astrophysics Data System (ADS)

The dynamics of a cloud of ultracold two-level atoms is studied at off-resonant laser driving to a Rydberg state. We find that resonant excitation channels lead to strongly peaked spatial correlations associated with the buildup of asymmetric excitation structures. These aggregates can extend over the entire ensemble volume, but are in general not localized relative to the system boundaries. The characteristic distances between neighboring excitations depend on the laser detuning and on the interaction potential. These properties lead to characteristic features in the spatial excitation density, the Mandel Q parameter, and the total number of excitations. As an application an implementation of the three-atom cswap or Fredkin gate with Rydberg atoms is discussed. The gate not only exploits the Rydberg blockade, but also utilizes the special features of an asymmetric geometric arrangement of the three atoms. We show that continuous-wave off-resonant laser driving is sufficient to create the required spatial arrangement of atoms out of a homogeneous cloud.

Gärttner, Martin; Heeg, Kilian P.; Gasenzer, Thomas; Evers, Jörg

2013-10-01

413

Time-Dependent Electron Interactions in Double-Rydberg Wavepackets

NASA Astrophysics Data System (ADS)

We consider the evolution of double-Rydberg wavepackets in which the two valence electrons in Ba are radially localized via sequential short-pulse laser excitation. Following the launch of the wavepackets, the atoms are exposed to a subpicosecond, half-cycle electric field pulse (HCP). The atoms either directly ionize during the HCP or are further excited by it, autoionizing to a distribution of Ba^+ Rydberg states. These ions are then subjected to a field ramp which ionizes the most highly excited Ba^+ to Ba^2+. The Ba^2+ signal is recorded as a function of the relative launch times of the two electrons and as a function of the HCP delay. The data show a dramatic reduction in the Ba^2+ yield when the HCP arrives after the excitation of the second wavepacket, suggesting that autoionization occurs almost instantly. This conclusion is supported by both full quantum and classical Monte Carlo calculations. The quantum calculations numerically solve the time dependent Schrodinger equation using a radial grid of points for each electron and coupled spherical harmonics. These calculations do not include the HCP but clearly show that more than 80% of the atoms ionize within one Rydberg period and the character of the ionization depends on the relative launch times.

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

2012-06-01

414

NASA Astrophysics Data System (ADS)

Light propagation through an ensemble of ultracold Rydberg atoms in an electromagnetically-induced-transparency (EIT) configuration is studied. In strongly interacting Rydberg EIT media, nonlinear optical effects lead to a nontrivial 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, because 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.

Gärttner, Martin; Evers, Jörg

2013-09-01

415

Advanced helium magnetometer for space applications

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

Robert E. Slocum

1987-01-01

416

Stabilization of circular Rydberg atoms by circularly polarized infrared laser fields

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

417

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

418

Rydberg constant and fundamental atomic physics

A detailed report on the current status of measurements of the Rydberg constant is given. Our recently reported value of R?=109 737.315 73(3) cm-1 has been confirmed by three other laboratories within experimental error. An additional check on the iodine cell, the heart of our wavelength and frequency reference, confirms a negligible pressure shift. The possible role of the Rydberg

Ping Zhao; W. Lichten; Zhi-Xiang Zhou; H. P. Layer; J. C. Bergquist

1989-01-01

419

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

NASA Astrophysics Data System (ADS)

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

Grusdt, F.; Fleischhauer, M.

2013-04-01

420

National Technical Information Service (NTIS)

Some theoretical potential curves are reported for the 1 sigma sub u(+) (2s,1So), 1 sigma sub g(+) (2s,1So), 1 sigma sub g(+) (2po,1So), 3 sigma sub g(+) (2Po,1So), 3 sigma sub g(+) (2s,3 sub 1), and 3 sigma sub g(+) (2Po,3S SUB 1) states of the helium mo...

J. C. Browne

1964-01-01

421

NASA Astrophysics Data System (ADS)

We report new results of triple differential cross sections for the single ionization of helium by 1-KeV electron impact at the ejection energy of 10 eV. Investigations have been made for both the perpendicular plane and the plane perpendicular to the momentum transfer geometries. The present calculation is based on the three-Coulomb wave function. Here we have also incorporated the effect of target polarization in the initial state. A comparison is made between the present calculation with the results of other theoretical methods and a recent experiment [Dürr M, Dimopoulou C, Najjari B, Dorn A, Bartschat K, Bray I, Fursa D V, Chen Z, Madison D H and Ullrich J 2008 Phys. Rev. A 77 032717]. At an impact energy of 1 KeV, the target polarization is found to induce a substantial change of the cross section for the ionization process. We observe that the effect of target polarization plays a dominant role in deciding the shape of triple differential cross sections.

Sun, Shi-Yan; Ma, Xiao-Yan; Li, Xia; Miao, Xiang-Yang; Jia, Xiang-Fu

2012-07-01

422

Carbon Monoxide Triplet Rydberg Series in the f Complex Region.

Using a multistep state-selective excitation scheme, fluorescence-dip spectra of carbon monoxide have been recorded in the energy region between 106 100 and 112 200 cm(-1). Prominent groups of bands were tentatively identified as transitions into the 6f em leader10f (v=0) and 9psigma em leader11psigma (v=0) triplet Rydberg series. For the f complex states, molecular constants have been calculated. The triplet f levels show an unusually large rotational constant and are located at higher energies than their singlet counterparts. Copyright 2001 Academic Press. PMID:11281691

Mellinger, Axel; Rohwer, Erich G.; Vidal, Carl Rudolf

2001-04-01

423

Storage and Control of Optical Photons Using Rydberg Polaritons

NASA Astrophysics Data System (ADS)

We use a microwave field to control the quantum state of optical photons stored in a cold atomic cloud. The photons are stored in highly excited collective states (Rydberg polaritons) enabling both fast qubit rotations and control of photon-photon interactions. Through the collective read-out of these pseudospin rotations it is shown that the microwave field modifies the long-range interactions between polaritons. This technique provides a powerful interface between the microwave and optical domains, with applications in quantum simulations of spin liquids, quantum metrology and quantum networks.

Maxwell, D.; Szwer, D. J.; Paredes-Barato, D.; Busche, H.; Pritchard, J. D.; Gauguet, A.; Weatherill, K. J.; Jones, M. P. A.; Adams, C. S.

2013-03-01

424

Storage and control of optical photons using Rydberg polaritons.

We use a microwave field to control the quantum state of optical photons stored in a cold atomic cloud. The photons are stored in highly excited collective states (Rydberg polaritons) enabling both fast qubit rotations and control of photon-photon interactions. Through the collective read-out of these pseudospin rotations it is shown that the microwave field modifies the long-range interactions between polaritons. This technique provides a powerful interface between the microwave and optical domains, with applications in quantum simulations of spin liquids, quantum metrology and quantum networks. PMID:23521254

Maxwell, D; Szwer, D J; Paredes-Barato, D; Busche, H; Pritchard, J D; Gauguet, A; Weatherill, K J; Jones, M P A; Adams, C S

2013-03-04

425

Electron capture from Rydberg atoms by highly-charged ions

The authors report cross sections in electron capture from circular Rydberg atoms by highly charged ions A{sup q+} for charge states q ranging from 1 to 40. The initial Rydberg state has n,l=25,24 as its principal and angular momentum quantum numbers, respectively. The collision speed is chosen between 0.4 to 4 times the electron orbital speed, corresponding in collision energies from 6.4 to 640 eV/u. Also studied are the final