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1

Interaction of Helium Rydberg State Atoms with Superfluid Helium

NASA Astrophysics Data System (ADS)

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

Fiedler, Steven L.; Eloranta, Jussi

2014-03-01

2

Rydberg states of helium - A new recoil term

NASA Technical Reports Server (NTRS)

It is shown that the mass-polarization shift in the energy levels of 1sNL Rydberg states of helium contains a term of second order, in the ratio of the electron mass to that of the nucleus, that is independent of L. The derivation of this new recoil term, based on the method of Drachman (1986), is very simple. It yields a correction of significance for the calculation of absolute ionization energies.

Drachman, Richard J.

1988-01-01

3

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

4

NASA Technical Reports Server (NTRS)

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

Au, C. K.

1989-01-01

5

Energies for the high-L Rydberg states of helium: Asymptotic analysis

The asymptotic expansion method based on a core polarization potential for the Rydberg electron is reviewed and extended to the high angular momentum states of helium up to L=15. A comparison with recent large-scale configuration interaction calculations for the nonrelativistic energies shows that there is good agreement for L=7, but there are serious systematic disagreements for the states of higher angular momentum. A possible explanation is that there is an important class of configurations missing from the CI calculations.

El-Wazni, Rida; Drake, G. W. F. [Department of Physics, University of Windsor, Windsor, Ontario, N9B 3P4 (Canada)

2009-12-15

6

Black-body induced ionization rate of Rydberg states in helium

NASA Astrophysics Data System (ADS)

The probabilities of photoionization by the black-body radiation (BBR) were calculated for singlet and triplet S-, P-, and D-Rydberg states of a neutral helium atom. The numerical values obtained on the basis of the Fues model potential for states with the principal quantum number n ranging from 8 to 45 were used to derive a formula which not only reproduces the asymptotical behavior of the ionization rate for n --> ? but also describes exactly its maximums. The n-independent constants in this formula are determined by a third order polynomial in powers of the absolute temperature with coefficients derived from the calculated data for the temperature range from 200 to 2000 K.

Glukhov, I. L.; Ovsiannikov, V. D.

2007-07-01

7

Rydberg State Stark Spectroscopy and Applications to Plasma Diagnostics.

National Technical Information Service (NTIS)

Rydberg state Stark spectroscopy of triplet and singlet helium has been applied to measure the electric field profile in DC glow discharges. Stark splittings of triplet helium were used to map the field profile in the cathode sheath of a parallel plate di...

J. R. Shoemaker

1990-01-01

8

Rydberg states in condensed matter

The Wannier formula is unable to fit the energy of the lowest level (n=1) simultaneously with that of the higher states (n>=2) in materials exhibiting a weak dielectric screening. We discuss the theory and the use of the Rydberg formula in condensed matter. We show that it describes all levels (n=1 and n>=2) and provides values for the energy gaps

L. Resca; R. Resta

1979-01-01

9

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

10

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

11

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

12

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 3858 nm and large intensities up to 100 TW/cm{sup 2} are considered. The emphasis is laid on convergence of the results with respect to the quality of the Gaussian basis sets (typically limited by a number of partial waves, density, and spatial extent of the basis functions) as well as to the quality of the basis set of field-free states (typically limited by the maximum rotational quantum number and maximum excitation of the lower electron). Particular attention is paid to stability of the results with respect to varying complex scaling parameter. Moreover, the study of the dynamics is preceded by a thorough check of helium energies and oscillator strengths as they are obtained with the exponentially tempered Gaussian basis sets, being also compared with yet unpublished emission wavelengths measured in electric discharge experiments.

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

2013-09-14

13

Analysis of Autoionizing Rydberg States in HI and CH31. Comments on Rydberg Electron Wavefunctions.

National Technical Information Service (NTIS)

Three Rydberg series, ns, np, and nd, converging to the doublet E(1/2) and doublet Pi(1/2) states of CH3I(+) and HI(+), respectively, are identified on the basis of their photoionization spectra. Splittings observed in the Rydberg peaks of CH3I are attrib...

B. P. Tsai T. Baer

1974-01-01

14

Millimetre wave spectroscopy of high Rydberg states

We have recently developed high-resolution vacuum ultraviolet laser sources and combined these with millimetre waves in double-resonance experiments to achieve a spectral resolution of up to 60 kHz in the spectra of high Rydberg states. The article describes the main features of our experimental procedure and presents studies in which we have used millimetre wave spectroscopy (a) to obtain information

F. Merkt; A. Osterwalder

2002-01-01

15

Supersymmetry and radial squeezed states for Rydberg wave packets

NASA Technical Reports Server (NTRS)

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

Bluhm, Robert; Kostelecky, V. Alan

1994-01-01

16

Preparation of Entangled and Antiferromagnetic States by Dissipative Rydberg Pumping

NASA Astrophysics Data System (ADS)

We propose and analyze an approach for preparation of high fidelity entanglement and antiferromagnetic states using Rydberg mediated interactions with dissipation. Using asymmetric Rydberg interactions the two-atom Bell singlet is a dark state of the Rydberg pumping process. Master equation simulations demonstrate Bell singlet preparation fidelity F=0.998. Antiferromagnetic states are generated on a four-spin plaquette in agreement with results found from diagonalization of the transverse field Ising Hamiltonian.

Carr, A. W.; Saffman, M.

2013-07-01

17

Alignment of D-state Rydberg molecules.

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

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

2014-04-11

18

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

19

Atomic Fock state preparation using Rydberg blockade.

We use coherent excitation of 3-16 atom ensembles to demonstrate collective Rabi flopping mediated by Rydberg blockade. Using calibrated atom number measurements, we quantitatively confirm the expected ?N Rabi frequency enhancement to within 4%. The resulting atom number distributions are consistent with an essentially perfect blockade. We then use collective Rabi ? pulses to produce N=1, 2 atom number Fock states with fidelities of 62% and 48%, respectively. The N=2 Fock state shows the collective Rabi frequency enhancement without corruption from atom number fluctuations. PMID:24580449

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

2014-01-31

20

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

21

Rydberg States of Benzene in Rare-Gas Matrices.

National Technical Information Service (NTIS)

The paper presents experimental evidence for the observation of Rydberg states of benzene in solid Ar, Kr, and Xe. On the basis of semiquantitative theoretical evidence it is argued that molecular Rydberg-type states of a guest molecule are amenable to ex...

B. Katz M. Brith B. Sharf J. Jortner

1968-01-01

22

Threshold Photoionization Spectroscopy with Heavy Rydberg States

NASA Astrophysics Data System (ADS)

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

Hepburn, John W.

2002-05-01

23

The absorption spectrum of S2 has been observed down to 400 Ĺ on the SA63 line of SUPERACO (LURE) in Orsay, France. Two already reported Rydberg Series converging to the X2?g ground state of S+2, ?4u?2gX3??g ? ?4u?g(?unp)3??u and ?4u?2gX3??g ? ?4u?g(?unp)3?u, have been extended up to n = 10. Eight new series have been observed, giving ionization energies of

J. Breton; F. Remy; I. Dubois; H. Bredohl; D. Macauhercot; J. M. Esteva; E. Some

1995-01-01

24

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

25

Analysis of a controlled phase gate using circular Rydberg states

NASA Astrophysics Data System (ADS)

We propose and analyze the implementation of a two-qubit quantum gate using circular Rydberg states with maximum orbital angular momentum. The intrinsic quantum gate error is limited by the finite Rydberg lifetime and finite Rydberg blockade shift. Circular states have much longer radiative lifetimes than low orbital angular momentum states and are therefore candidates for high-fidelity gate operations. We analyze the dipole-dipole interaction of two circular state Rydberg atoms and present numerical simulations of quantum process tomography to find the intrinsic fidelity of a Rydberg blockade-controlled phase gate. Our analysis shows that the intrinsic gate error can be less than 9×10-6 for circular Cs atoms in a cryogenic environment.

Xia, T.; Zhang, X. L.; Saffman, M.

2013-12-01

26

Retardation or Casimir Effects in a Rydberg Helium Atom and Other Atomic Systems.

NASA Astrophysics Data System (ADS)

A retardation effect, an effect due to the finiteness of the speed of light, can manifest itself in the interaction between two polarizable systems as a change in the form of the long-range interaction potential. With the interaction viewed as mediated by virtual photons, retardation effects become important when the time required for a photon to travel back and forth between the two systems becomes larger than or of the order of the characteristic period of the motion of either system. The form of the potential under retardation is characterized in general by the dynamic electric dipole polarizabilities alpha_ {d}(omega) of each of the systems, where omega is the virtual photon frequency, the separation r of the systems, hbar, and c. The high-precision verification of a retardation effect on the potential V(r) between a pair of systems probably demands that the systems be microscopic and form a bound state. The ideal pair would seem to be a helium ionic core (an alpha particle and an electron in the 1 s state) interacting with an electron in a state with n and l not too small, possibly in a high Rydberg state. Making use of time-ordered Feynman diagrams, with the electrons treated nonrelativistically, an expression for V(r) valid for r greater than several a _0 is obtained. The approach can be interpreted as an extension of the physical arguement that for r > 137alpha_0 the retardation component of V(r) follows easily from considerations of the interactions between electromagnetic vacuum fluctuations and each member of the pair, with each member characterized solely by its frequency-dependent electric dipole polarizability, alpha_{d}(omega); the extension from r > 137 a_0 down to just several a _0 is achieved by including in the characterization of each member not only its alpha_ {d}(omega), but its frequency-dependent nonadiabatic dipole polarizability, beta( omega). Effects originating in the finite nuclear mass are discussed. Retardation effects for Rydberg systems with many-electron cores are also of interest and so a qualitative discussion of retardation effects is provided to help one guess, for a given system with l ~ n gg 1, whether the size of the retardation energy shift is such as to warrant consideration.

Babb, James Frederick

27

Squeezing a helium nanodroplet with a Rydberg electron.

We have investigated, by means of density functional theory, the structure of a "scolium", that is, an electron circulating around a positively charged 4He nanodroplet, temporarily prevented from neutralization by the helium-electron repulsion. The positive ion core resides in the center of the nanodroplet where, as a consequence of electrostriction, a strong increase in the helium density with respect to its bulk value occurs. The electron enveloping the 4He cluster exerts an additional electrostatic pressure which further increases the local 4He density around the ion core. We argue that under such pressure, sufficiently small 4He nanodroplets may turn solid. The stability of a scolium with respect to electron-ion recombination is investigated. PMID:17983211

Ancilotto, F; Pi, M; Mayol, R; Barranco, M; Lehmann, K K

2007-12-13

28

State-dependent energy shifts of Rydberg atoms in a ponderomotive optical lattice.

We demonstrate the state dependence of the ponderomotive energy shift of Rydberg atoms in an optical lattice using microwave spectroscopy. Unique to Rydberg atoms, this dependence results from a state-dependent aspect ratio between Rydberg-atom size and lattice period. A semiclassical simulation reproduces all features observed in the microwave spectra and indicates the presence of trapped Rydberg atoms. PMID:20482104

Younge, K C; Knuffman, B; Anderson, S E; Raithel, G

2010-04-30

29

Field-induced dissociation of Rydberg ion-pair states

NASA Astrophysics Data System (ADS)

A theoretical study is presented on the dissociation of H+..F- and K+.. Cl- heavy-Rydberg ion pairs induced by a ramped electric-field, a technique used experimentally to detect and probe ion-pair states.

Reinhold, C. O.; Yoshida, S.; Dunning, F. B.

2012-11-01

30

Dark entangled steady states of interacting Rydberg atoms.

We propose a scheme for rapid generation of high fidelity steady-state entanglement between a pair of atoms. A two-photon excitation process toward long-lived Rydberg states with finite pairwise interaction, a dark-state interference effect in the individual atoms, and spontaneous emission from their short-lived excited states lead to rapid, dissipative formation of an entangled steady state. We show that for a wide range of physical parameters, this entangled state is formed on a time scale given by the strengths of coherent Raman and Rabi fields applied to the atoms, while it is only weakly dependent on the Rydberg interaction strength. PMID:23909321

Rao, D D Bhaktavatsala; Mřlmer, Klaus

2013-07-19

31

Dark Entangled Steady States of Interacting Rydberg Atoms

NASA Astrophysics Data System (ADS)

We propose a scheme for rapid generation of high fidelity steady-state entanglement between a pair of atoms. A two-photon excitation process toward long-lived Rydberg states with finite pairwise interaction, a dark-state interference effect in the individual atoms, and spontaneous emission from their short-lived excited states lead to rapid, dissipative formation of an entangled steady state. We show that for a wide range of physical parameters, this entangled state is formed on a time scale given by the strengths of coherent Raman and Rabi fields applied to the atoms, while it is only weakly dependent on the Rydberg interaction strength.

Rao, D. D. Bhaktavatsala; Mřlmer, Klaus

2013-07-01

32

A note on the assignments of Rydberg states of COS

NASA Technical Reports Server (NTRS)

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

Wu, C. Y. R.

1982-01-01

33

Spectroscopy of High-L Rydberg States of Nickel

NASA Astrophysics Data System (ADS)

In this study, the fine structure of high-L Rydberg states of nickel is measured. In these high-L Rydberg states, a highly excited ``spectator electron'' reveals, by the details of its binding energy, certain properties of the Ni+ ion which it ``orbits''. These special states are created and measured by a technique called RESIS: Resonant Excitation Stark Ionization Spectroscopy. This method involves creating a fast beam of Ni+ ions which travel through a Rb 9F Rydberg target where many of them capture a single electron to form Rydberg states of neutral nickel with population concentrated near n=9. Any unneutralized Ni+ ions are blocked by a high electric potential. The fast Ni Rydberg atoms then pass through a Doppler-tuned CO2 laser which may excite them from n=9 to n=19 or 20, and any atoms so excited are ionized by a strong electric field and collected and counted. As the CO2 laser is tuned across the excitation resonance, the complex fine structure of n=9 L > 5 levels is fully resolved, and analysis of the fine structure pattern determines properties of the Ni+ ion such as its quadrupole moment and polarizabilitiy. Currently, the data of the study is being analyzed to give unprecedented results for these properties of Ni+.

Voigt, Kristen; Lundeen, Stephen; Keele, Julie; Woods, Shannon

2009-10-01

34

Study on ionic Rydberg states of calcium

NASA Astrophysics Data System (ADS)

Using five-laser resonance excitation, we observe the 0953-4075/31/24/016/img1p Rydberg series with n from 39 to 92. The energy levels calculated using the self-consistent-field method and quantum defect theory are in good agreement with the experimental results.

Xu, C. B.; Xie, X. P.; Zhao, R. C.; Sun, W.; Xue, P.; Zhong, Z. P.; Huang, W.; Xu, X. Y.

1998-12-01

35

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

36

Pressure Shift and Broadening of Alkali Rydberg States

We have studied the broadening and shift of spectral lines involving Rydberg states of alkali atoms, due to collisions with ground-state alkali atoms. The technique of Doppler-free two- photon spectroscopy allowed this work to be carried out at low pressures, so that only binary collisions are important. Thermionic ionization detection was used, making possible the study of levels with high

David Charles Thompson

1986-01-01

37

NASA Astrophysics Data System (ADS)

On the basis of analytical expressions in the Fues model potential approach for the second-order Stark effect on single-electron Rydberg states in atoms and ions, general equations are derived for coefficients of polynomials in powers of the principal quantum number n in asymptotic presentations of static scalar and tensor dipole polarizabilities. The power dependence for polarizabilities of isolated Rydberg states |nl> at n ? 1 scales as n7, in contrast with that of polarizabilities for hydrogenic states, degenerate in the orbital quantum number l ? n ? 1, which scales as n6. This difference is demonstrated analytically in the asymptotic dependencies of the second-order matrix elements, determining the Stark shifts of the isolated and degenerate states. Analytical equations for polynomial coefficients use the data on quantum defects determined from the level energies of corresponding series of states. Numerical values of coefficients are presented for S-, P- and D-series of Rydberg states in neutral atoms of alkali-metal elements and helium in comparison with existing data of the literature. The analytical equations are also used for determining numerical values of coefficients in asymptotic polynomials for polarizabilities of Rydberg states in positive ions of alkaline-earth-metal elements.

Kamenski, A. A.; Ovsiannikov, V. D.

2014-05-01

38

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

39

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

40

Microwave multiphoton transitions between Rydberg states driven by chirped pulses

We observe microwave multiphoton transitions in Rydberg states of potassium using intense pulses of chirped microwave radiation. Pulses of microwaves with frequencies between 0.6 and 0.9 GHz with frequency chirp times from 5 ns (4 cycles) to 200 ns (150 cycles) are generated with peak fields of 15 V\\/cm. We are able to drive high order multiphoton transitions using these

C. W. S. Conover; M. C. Doogue; D. A. Perry

1998-01-01

41

State-selective Rydberg excitation with femtosecond pulses

NASA Astrophysics Data System (ADS)

We show that multipulse excitation of Rydberg atoms with a sequence of short time-delayed femtosecond pulses results in strong n selection of the final-state amplitudes. In the experiment, a 150 fs laser pulse, which alone populates n levels from 22-32 in Li, is chopped into four time-delayed excitation pulses, which results in a strong modification of the n-level distribution. The mechanism demonstrated in the experiment is derived theoretically: With more pulses, it is shown that the population of a single or a few n levels can be performed on demand and varied as long as the central laser frequency is given.

Kozák, M.; Preclíková, J.; Fregenal, D.; Hansen, J. P.

2013-04-01

42

Elliptic Rydberg states as direction indicators

The orientation in space of a Cartesian coordinate system can be indicated by the two vectorial constants of motion of a classical Keplerian orbit: the angular momentum and the Laplace-Runge-Lenz vector. In quantum mechanics, the states of a hydrogen atom that mimic classical elliptic orbits are the coherent states of the SO(4) rotation group. It is known how to produce these states experimentally. They have minimal dispersions of the two conserved vectors and can be used as direction indicators. We compare the fidelity of this transmission method with that of the idealized optimal method.

Lindner, Netanel H.; Peres, Asher; Terno, Daniel R. [Department of Physics, Technion--Israel Institute of Technology, 32 000 Haifa (Israel)

2003-10-01

43

Helium resources of the United States, 1989

The helium resources base of the United States was estimated by the Bureau of Mines to be 894.6 Bcf as of January 1, 1989. These resources are divided into four categories in decreasing degree of the assurance of their existence: (1) helium in storage and in proved natural gas reserves, 282.4 Bcf; (2) helium in probable natural gas resources, estimated

Richard D. Miller; John E. Hamak

1990-01-01

44

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

45

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 512 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

46

Accurate lifetime calculation of high Rydberg states in Rb

NASA Astrophysics Data System (ADS)

In view of recent accurate measurements of the lifetimes for high-Rydberg (n=32-45) states, we have extended our previous calculations for Rb to higher states(21

Theodosiou, Constantine

2003-05-01

47

Rydberg States of Lithium and Other Systems

NASA Technical Reports Server (NTRS)

The interesting calculation of retardation corrections to excited atomic state energies is facilitated by the existence of good calculations of the nonrelativistic and nonretarded energies, to which retardation corrections can be added. Here I describe a perturbation method, applicable when the angular momentum is high enough which generates an asymptotic series for the energy. It makes use of generalized polarizabilities of the atomic or ionic core (numerically obtained) but otherwise is completely analytic. It is applied here to the lithium atom in detail, and its application to hydrogen molecular ions is outlined.

Drachman, Richard J.

1999-01-01

48

Transitions to Atomic Rydberg States Perturbed by Foreign Gases.

NASA Astrophysics Data System (ADS)

Collisional interactions of neutral, ground state foreign gases with highly excited atomic states have been experimentally investigated. Transitions to Rydberg states of Na, Rb and Sr are pumped using a tunable dye laser and two-photon excitation techniques. States studied include the 4d('2)D(,J) and 5s('2)S(, 1/2) states of Na, the nd('2)D(,J) and ns('2)S(, 1/2) series of Rb and the 5snd ('1.3)D(,2) and 5sns ('1)S(,0) series of Sr. Absorption lineshapes were recorded while these transitions were collisionally perturbed by various foreign gases. Perturber gases included He, Ar, Kr, Xe and N(,2) at densities that range from 0.05 to 2.5 relative density. Lineshape parameters for energy shift and line broadening have been measured for Na and Rb transitions as functions of principal and angular momentum quantum numbers. The variations of these parameters were also measured as functions of perturber gas species and density. These results were related to the theory of Alekseev and Sobelman which models perturbed lineshapes in terms of independent elastic and inelastic collisional processes. Sr transitions yield more diverse results. For high Rydberg levels (n (GREATERTHEQ) 20) lineshape parameters and the Alekseev -Sobelman theory provide an adequate description of the interaction processes. Intermediate states (12 (LESSTHEQ) n (LESSTHEQ) 20) demonstrate enhanced inelastic processes due to energy level perturbations and complete lineshapes are required for analysis. Low lying transitions (6 (LESSTHEQ) n (LESSTHEQ) 10) have extended absorption lineshapes. Again complete lineshapes are necessary to account for the observed red-wing and satellite structures using the unified theory of Anderson and Talman.

Bruce, Douglas Maitland

49

Infrared vibrational spectroscopy of cis-dichloroethene in Rydberg states.

We have measured the infrared (IR) vibrational spectrum for cis-dichloroethene (cis-ClCH[Double Bond]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 nu(11) (*) (asymmetric C-H stretch) and nu(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 nu(11) (*) and nu(12) (*) bands [R(nu(11) (*)nu(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(nu(11) (*)nu(12) (*)) for excited cis-ClCH[Double Bond]CHCl in n(*)=3-18 states and the MP26-311++G(2df,p) calculations of R(nu(11)nu(12)) and R(nu(11) (+)nu(12) (+)), where R(nu(11)nu(12))[R(nu(11) (+)nu(12) (+))] represents the intensity ratio of the nu(11)(nu(11) (+)) asymmetric C-H stretching to the nu(12)(nu(12) (+)) symmetric C-H stretching vibrational bands for cis-ClCH[Double Bond]CHCl (cis-ClCH[Double Bond]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[Double Bond]CHCl. These spectra are consistent with ab initio calculations, indicating that the IR absorption cross section for the nu(12) band is negligibly small compared to that for the nu(11) band. While the VUV-IR-PIRI measurements have allowed the determination of nu(11) (+)=3067+/-2 cm(-1), nu(12) (+)=3090+/-2 cm(-1), and R(nu(11) (+)nu(12) (+)) approximately 1.3 for cis-ClCH=CHCl(+), the IR-VUV-PI and IR-VUV-PFI-PED measurements have provided the value nu(11)=3088.5+/-0.2 cm(-1) for cis-ClCH=CHCl. PMID:16483210

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

2006-02-14

50

NASA Astrophysics Data System (ADS)

The formation of heavy-Rydberg ion-pair states through electron transfer in collisions between K(np) Rydberg atoms and molecules that attach low-energy electrons is investigated. The measurements show that low-n collisions with a wide variety of target species (SF6, c-C7F14, C6F6, and CCl4) can lead to formation of bound ion-pair states and that, under appropriate conditions, a small fraction of these can subsequently dissociate as free ions through internal-to-translational energy transfer. Analysis of the data suggests that those ion pairs that do dissociate typically have lifetimes of ~1 ?s, although some can have lifetimes of 5 ?s or longer.

Cannon, M.; Dunning, F. B.

2009-01-01

51

Microwave spectroscopy of high-L Rydberg states of nickel

NASA Astrophysics Data System (ADS)

High-L non-penetrating Rydberg levels of nickel display a fine structure pattern consisting of six levels for each value of L. This pattern was studied recently with the optical RESIS technique, determining initial values of the quadrupole moment and polarizabilities of the ^2D5/2 ground state of Ni^+ [1]. Measurements are now in progress using the microwave RESIS technique [2], which promises much more precise measurements of the fine structure and of the related core properties, including the permanent hexadecapole moment.[4pt] [1] Julie A. Keele, et. al., to be published, Phys. Rev. A[0pt] [2] M.E. Hanni, et. al., Phys. Rev. A 78, 062510 (2008)

Lindsay, Mark D.; Keele, Julie A.; Woods, Shannon L.; Lundeen, Stephen R.

2010-03-01

52

Dopant low- n Rydberg states in CF 4 and CH 4 near the critical point

NASA Astrophysics Data System (ADS)

Dopant low- n Rydberg states perturbed by dense CF 4 and CH 4 were investigated using vacuum ultraviolet photoabsorption spectroscopy at noncritical temperatures and on an isotherm near (+0.5 °C) the perturber critical temperature. A full analysis of these data using semi-classical line shape theory was performed. The perturber induced energy shift was extracted from the simulated bands and demonstrates a perturber critical point effect on the energy of low- n Rydberg states in these molecular fluids.

Li, Luxi; Shi, Xianbo; Findley, G. L.; Evans, C. M.

2009-11-01

53

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

A method is presented for calculating the wave function and energy of Rydberg excited states of molecules. A good estimate of the Rydberg state orbital is obtained using ground state density functional theory including Perdew-Zunger self-interaction correction and an optimized effective potential. The total energy of the excited molecule is obtained using the Delta Self-Consistent Field method where an electron is removed from the highest occupied orbital and placed in the Rydberg orbital. Results are presented for the first few Rydberg states of NH3, H2O, H2CO, C2H4, and N(CH3)3. The mean absolute error in the energy of the 33 molecular Rydberg states presented here is 0.18 eV. The orbitals are represented on a real space grid, avoiding the dependence on diffuse atomic basis sets. As in standard density functional theory calculations, the computational effort scales as NM(2) where N is the number of orbitals and M is the number of grid points included in the calculation. Due to the slow scaling of the computational effort with system size and the high level of parallelism in the real space grid approach, the method presented here makes it possible to estimate Rydberg electron binding energy in large molecules. PMID:24320311

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

2013-11-21

54

A critical re-assignment of the Rydberg states of iodomethane based on new polarization data

NASA Astrophysics Data System (ADS)

2- and 3-photon excitation of components of the lower Rydberg states of iodomethane (CH3I) using linearly and circularly polarized light, followed by ionization with one more photon, is used to determine their molecular term symbol, ?, values as well as quantum defects. These ? values, together with a detailed theoretical analysis, require a re-assignment of the 7s and 8s states to various components of the 5d and 6d states, but there is evidence of (n+2)s/nd hybridization in the pairs of ? = 1 states. Predissociation sets in for all Rydberg states beyond 6d based on the ground (2?3/2) state of the core, but sharp autoionizing resonances based on the 2?1/2 core state are assigned to the 9s, 7d, and 5f states. The dominant effect of the singlet/triplet character of the Rydberg states on their accessibility from the ground state, seen in bromomethane and chloromethane, is again apparent and a concordant interpretation of the Rydberg spectra of CH3I can now be presented. Evidence for coupling of some ? = 1 and ? = 0+ Rydberg states with a repulsive valence state and an ion-pair state, respectively, is also put forward.

Donovan, Robert J.; Hennessy, John T.; Lawley, Kenneth P.; Ridley, Trevor

2013-04-01

55

Need for high resolution in VUV Rydberg state spectroscopy

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

56

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

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

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

2014-03-28

57

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

58

Experimental investigation of long-lived Rydberg states in ultracold argon

NASA Astrophysics Data System (ADS)

We report on our investigation of the formation and survival of long-lived Rydberg states in argon produced by pulsed laser excitation of ultracold metastable state argon atoms in a magneto-optical trap. The states studied have a 2P1/2 core. Low angular momentum Rydberg states with this core normally autoionize rapidly. If, however, atoms are excited in the presence of electric fields, higher angular momentum states, traditionally termed ZEKE states (ZEKE is derived from zero kinetic energy) can be formed. The lifetime of these states can be orders of magnitude greater than low angular momentum states. In this paper, we report on the time dependence of ZEKE Rydberg state population in an ultracold environment.

Ranjit, G.; Sukenik, C. I.

2013-03-01

59

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

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

Bookless, W.

1980-12-01

60

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

NASA Astrophysics Data System (ADS)

The structure and dynamics of high-n Rydberg states belonging to series converging to the (v+ = 0, N+ = 0-2) levels of the X^+ ^2? _g^+ electronic ground state of HD+ were studied by high-resolution spectroscopy from the GK ^1? _g^+ (v = 1, N = 1) state under field-free conditions. Three effects of g/u-symmetry breaking were detected: (i) Single-photon transitions from the GK (v = 1, N = 1) state of gerade symmetry to the 30d21 and 31g22 Rydberg states of gerade symmetry were observed after careful compensation of the stray electric fields. (ii) The singlet 61p12 Rydberg state of ungerade symmetry was found to autoionize to the N+ = 0, ? = 2 ionization continuum of gerade symmetry with a lifetime of 77(10) ns. (iii) Shifts of up to 20 MHz induced by g/u-symmetry mixing were measured for members of the np11 Rydberg series which lie close to nd21 Rydberg states. These observations were analyzed in the framework of multichannel quantum-defect theory. From the observed level shifts, the off-diagonal eigenquantum-defect element ? _pd of singlet-? symmetry was determined to be 0.0023(3) and the corresponding autoionization dynamics could be characterized. The ionization energy of the GK (v = 1, N = 1) state of HD was determined to be 12 710.544 23(10) cm-1.

Sprecher, Daniel; Merkt, Frédéric

2014-03-01

61

NASA Astrophysics Data System (ADS)

A supersonic beam of metastable He_2^* a ^3?_{u}^+ molecules was generated using a pulsed discharge at the exit of a pulsed valve prior to the gas expansion into vacuum. Transitions to high np Rydberg states were recorded using photoionization and Rydberg-state-resolved threshold ionization spectroscopy. Overview scans at moderate resolution (0.3 cm^{-1}) were obtained with ionization fields ranging from 1.3 to 133 V/cm, lowering the ionization thresholds by 5.5 and 55 cm^{-1}, respectively. Using a solid-state UV laser system with a 20 MHz bandwidth, high-resolution spectra of Rydberg series with n up to 150 and with resolved fine structure of the initial He_2^* a ^3?_{u}^+ (N'') state were recorded. The assignment of the observed Rydberg states is based on multichannel quantum defect theory calculations from a recent study^a of pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron and photoionization spectra of He_2 (see following talk). The extrapolation of the observed Rydberg series to their limits enabled the determination of the ionization energy of the a ^3?_{u}^+ state and the rotational structure of the He_2^+ ion with a precision of better than 20 MHz. M. Raunhardt, M. Schäfer, N. Vanhaecke, F. Merkt}, J. Chem. Phys. 128, 164310 (2008). R. Seiler, U. Hollenstein, G. M. Greetham, F. Merkt, Chem. Phys. Lett. 346, 201 (2001). R. Seiler, Th. A. Paul, M. Andrist, F. Merkt}, Rev. Sci. Instr. 76, 103103 (2005). M. Raunhardt, M. Schäfer, N. Vanhaecke, F. Merkt, J. Chem. Phys. 128, 164310 (2008).

Liu, Jinjun; Sprecher, Daniel; Raunhardt, Matthias; Schäfer, Martin; Merkt, Frédéric

2009-06-01

62

The ns and nd Rydberg states of O2 described by Hund's case (e).

Using Hund's case (e) representation, we have obtained a simulation of the 5s Rydberg states of O(2) for J=2 by fitting the experimental data obtained recently by Sheard et al. [J. Chem. Phys. 118, 8781 (2003)]. Our analysis permits us to include evidence of not only the mixing of Hund's case (a) states by spin-orbit interaction, but also by L and S uncouplings. This mixing is even more important for the nd Rydberg states. For the 3d Rydberg state, J=2, we have been able to suggest for the first time an assignment for both the 3d sigma (1)Pi(g) and the 3d delta (1)Pi(g) states. PMID:16238390

Lefebvre-Brion, Hélčne; Ridley, Trevor

2005-10-01

63

Highly excited Rydberg states of a rubidium atom: Theory versus experiments

NASA Astrophysics Data System (ADS)

There has been increasing interest in the energy spectrum of highly excited Rydberg states. The energy spectra of the s, p, and d highly excited Rydberg states of a rubidium atom have been measured by different groups. However, there is a discrepancy between the reported data concerning the energy levels of highly excited s and d states of Rb. We address this issue by performing accurate calculations of Rb(ns ,np,nd) energy levels using the parametric one-electron valence potential [Marinescu, Sadeghpour, and Dalgarno, Phys. Rev. A 49, 982 (1994), 10.1103/PhysRevA.49.982] with spin-orbit coupling. We compare results with reference data from the National Institute of Standards and Technology and from available experiments. This enables us to recommend energy levels of highly excited Rydberg states of Rb that can be used as reference values.

Pawlak, M.; Moiseyev, N.; Sadeghpour, H. R.

2014-04-01

64

Populations of Rydberg states of ions emerging from solid surfaces.

National Technical Information Service (NTIS)

Analysis of decays of Rydberg ions produced in beam-foil conditions shows that populations are observed to emerge in the form n(sup -(beta)), where n is the principal quantum number and the index (beta) is significantly less than the value 3 expected from...

H. J. Hay P. B. Treacy

1989-01-01

65

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

66

The distribution of principal quantum numbers for high-Rydberg states of lithium, produced in a thermal atomic beam by electron impact excitation, has been determined after passage of the beam through gaseous targets. Target densities were selected for an approximately tenfold reduction of the on-axis flux of Rydberg atoms. The state distribution, determined by electric field ionization, is markedly affected by

Carl A. Kocher; Chester L. Shepard

1981-01-01

67

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

68

CH 3I low- n Rydberg states in supercritical atomic fluids near the critical point

NASA Astrophysics Data System (ADS)

Vacuum ultraviolet photoabsorption spectra of CH 3I 6s and 6s' Rydberg states doped into supercritical argon, krypton, and xenon perturbers were measured from low density to the density of the triple point liquid at noncritical temperatures and on an isotherm near the perturber critical temperature. A full line shape analysis of these spectra was performed using a single set of intermolecular potential parameters for each dopant/perturber system. The resulting perturber induced shift of the simulated adiabatic transition of the 6s and 6s' Rydberg states is presented as a function of perturber number density, and this shift illustrates a perturber critical point effect on the excitation energies of the molecular low- n Rydberg states.

Li, Luxi; Shi, Xianbo; Evans, C. M.; Findley, G. L.

2009-06-01

69

Photoexcitation of n?305 Rydberg states in the presence of an rf drive field

NASA Astrophysics Data System (ADS)

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

2012-10-01

70

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

71

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

72

Photoionization from excited states of helium

NASA Technical Reports Server (NTRS)

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

Jacobs, V. L.

1973-01-01

73

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

NASA Astrophysics Data System (ADS)

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, 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 -characters of the 3<=<=5 core-nonpenetrating 2?+ states and to characterize their mixing with the core-penetrating states. We conclude that the mixing of the =4, N-N+=-4(g(-4)) state with lower- 2?+ states is stronger than documented in our previous multichannel quantum defect theory and long-range fits to zero-field spectra.

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

2009-08-01

74

The dynamics of high autoionizing Rydberg states of Ar

In this paper we present a theoretical study of the autoionization dynamics of high 2P1\\/2np?[3\\/2]1 Rydbergs (with the principal quantum numbers n=100280) of Ar in weak homogeneous electric fields (F=0.011.0 V\\/cm), which were experimentally interrogated by time-resolved zero-electron kinetic energy (ZEKE) spectroscopy [M. Mu¨hlpfordt and U. Even, J. Chem. Phys. 103, 4427 (1995)], and which exhibit a marked dilution (i.e.,

M. Bixon; Joshua Jortner

1995-01-01

75

Theoretical Studies of Rydberg Atom Collisions.

National Technical Information Service (NTIS)

During the last two years, theoretical studies were performed on a variety of topics related to collisions involving Rydberg atoms. Progress was made towards the understanding of ion-Rydberg atom, Rydberg atom-Rydberg atom, and ground state atom-Rydberg a...

R. E. Olson

1981-01-01

76

Theoretical Studies of Rydberg Atom Collisions.

National Technical Information Service (NTIS)

Theoretical studies were performed on a variety of topics related to collisions involving Rydberg atoms. Progress was made towards the understanding of ion-Rydberg atom, Rydberg atom-Rydberg atom, and ground state atom-Rydberg atom collisions. A strong dc...

R. E. Olson

1984-01-01

77

Applying a method based on some results due to Kato [Proc. Phys. Soc. Jpn. 4, 334 (1949)], we show that series of Rydberg eigenvalues and Rydberg eigenfunctions of hydrogen in a uniform magnetic field can be calculated with a rigorous error estimate. The efficiency of the method decreases as the eigenvalue density increases and as [gamma][ital n][sup 3][r arrow]1, where [gamma] is the magnetic-field strength in units of 2.35[times]10[sup 9] G and [ital n] is the principal quantum number of the unperturbed hydrogenic manifold from which the diamagnetic Rydberg states evolve. Fixing [gamma] at the laboratory value 2[times]10[sup [minus]5] and confining our calculations to the region [gamma][ital n][sup 3][lt]1 (weak-field regime), we obtain extremely accurate results up to states corresponding to the [ital n]=32 manifold.

Falsaperla, P.; Fonte, G. (Dipartimento di Fisica, Universita di Catania, Corso Italia 57, I-95129 Catania (Italy) Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia 57, I-95129 Catania (Italy))

1993-05-01

78

Two-dimensional REMPI of CF 3 Br: Rydberg states and photofragmentation channels

NASA Astrophysics Data System (ADS)

Mass spectra were recorded for (2 + n) REMPI of CF 3Br as a function of resonance excitation energy in the 71 320-84 600 cm -1 region to obtain two-dimensional REMPI data. CF3+, iBr + ( i = 79,81) and C + ions were detected. Laser power dependence experiments were performed for ion signals. CF3+ signals due to resonance transitions from the ground state CF 3Br to number of Rydberg states and various vibrational states followed by CF3+ and Br - ion-pair formation via intersystem crossings, were identified. Bromine atom production by predissociation channels via two-photon excitation to the Rydberg states is proposed, based on detecting bromine atom (2 + 1) REMPI.

Kvaran, Ágúst; Sveinbjörnsson, Kári; Long, Jingming; Wang, Huasheng

2011-11-01

79

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

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

2003-01-01

80

Resonances in the population of circular Rydberg states formed in beam-foil excitation

NASA Astrophysics Data System (ADS)

By directing fast moving 164 MeV F2656e ion beam on 90 ?g/cm2 thick carbon foil we have studied the unresolved decay of short-lived 2p (?2p?3.3 fs) and long-lived 2s (?2s?350.6 ps) states of H-like Fe in the time range 1.6×104-9.2×105?2p, where, ?2p and ?2s are, respectively, radiative lifetimes of the 2p and 2s levels. At such large times four resonances have been observed as the humps riding on the decay curve of the beam-foil-excited 2s state. This unusual behavior is explained as consequence of the sequential cascading of circular Rydberg states (l=n-1) to 2p state, which modifies the time dependent photon intensity, I(t), of the 2p?1s transition from an exponential to hump-like structures for tť?2p. From the detailed study of the cascading process the relative population of circular Rydberg states is determined. It is observed that certain circular Rydberg states are unexpectedly and profusely populated when fast H-like Fe ions emerge from the back surface of a thin solid foil.

Mishra, Adya P.; Nandi, T.; Jagatap, B. N.

2013-05-01

81

Two-color three-photon excitation studies of thallium Rydberg states

NASA Astrophysics Data System (ADS)

We present new data on the even-parity Rydberg states of atomic thallium using two-step three-photon laser excitation technique in conjunction with a thermionic diode ion detector. Atoms are excited from the 6p 2P 1/2 ground state to the 7p 2P 1/2 intermediate state via two-photon excitation and subsequently promoted to the high lying ns 2 S 1/2 and nd 2D 3/2 Rydberg states. The first ionization potential of thallium is determined as 49,266.66(1) cm -1 using data for the ns 2 S 1/2 (25 ? n ? 54) and nd 2D 3/2 (24 ? n ? 65) Rydberg series. This value is believed to be more accurate because the contribution due to the hyperfine structure splitting of the 7p 2P 1/2 state (0.07185 cm -1) is much smaller as compared to that of the 6p 2P 1/2 ground state (0.711 cm -1).

Riaz, M.; Anwar-ul-Haq, M.; Ali, Raheel; Baig, M. A.

2010-12-01

82

NASA Astrophysics Data System (ADS)

We study resonant optical excitations of spatially frozen atoms in 1D trapping potentials and lattices to strongly-interacting Rydberg states. In the steady-state of strong uniform driving, correlations of Rydberg excitation probabilities exhibit exponentially decaying spatial oscillations with the period approaching one collective excitation per Rydberg blockade distance (superatom). For few atoms per blockade distance, the system is well described by a rate equation model with hard sphere superatoms. For higher densities approaching a continuous limit, we find via numerical simulations that the superatoms develop soft boundaries. For the case of an additional lattice we derive an effective master equation with non-local damping. We give analytic expressions for the many-body steady state and the correlation length of the Rydberg quasi-crystal or antiferromagnetic order and discuss conditions when it can approach infinity.

Hoening, Michael; Petrosyan, David; Fleischhauer, Michael

2012-06-01

83

Helium resources of the United States, 1989. Information Circular\\/1990

The helium resources base of the United States was estimated by the Bureau of Mines to be 894.6 Bcf as of January 1, 1989. These resources are divided into four categories in decreasing degree of the assurance of their existence: (1) helium in storage and in proved natural gas reserves, 282.4 Bcf, (2) helium in probable natural gas resources, estimated

R. D. Miller; J. E. Hamak

1990-01-01

84

NASA Astrophysics Data System (ADS)

Adiabatic potential energy curves of forty doublet electronic states of CF have been determined by configuration interaction calculations, over the range of internuclear distances R from 1.8 to 50.0 bohr. Rydberg states of CF converging to excited electronic states of the cation are calculated above the ground state of CF + at short R. Rydberg-valence interactions result in a complicated pattern of avoided crossings at intermediate R, leading to predissociation of the Rydberg states as well as to a rationalization of production of ground state F( 2P0) + C( 3P), and F( 2P0) + C( 1D) fragments from the dissociative recombination of CF + + e -.

Petsalakis, Ioannis D.; Theodorakopoulos, Giannoula

2011-05-01

85

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

NASA Astrophysics Data System (ADS)

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

Hagström, Magnus; Davidsson, Jan; Holmlid, Leif

1998-02-01

86

Radiative Decay of Helium Doubly Excited States

NASA Astrophysics Data System (ADS)

A theoretical study of the radiative decay of low-lying doubly excited ^1P^o states of Helium in the energy region below the He^+(N=2) threshold is presented. We calculated the oscillator strength from the ground state, the Auger and radiative decay rates, and the natural widths of these states. These rates are used to obtain the photon emission and metastable atom yield spectra to compare with experimental measurements, including those from Odling-Smee et al.(M. K. Odling-Smee, E. Skoell, P. Hammond, and M. A. MacDonald, Phys. Rev. Lett. 84), 2598 (2000). and Rubensson et al.(J.-E. Rubensson, C. Sĺthe, S. Cramm, B. Kessler, S. Stranges, R. Richter, M. Alagia, and M. Coreno, Phys. Rev. Lett. 83), 947 (1999).. We showed that the lifetimes of the long-lived doubly excited states are determined by the radiative rates.

Liu, Chien-Nan; Chen, Ming-Keh; Lin, C. D.

2001-05-01

87

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

NASA Technical Reports Server (NTRS)

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

Victor, G. A.; Sando, K.

1971-01-01

88

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

One of the great successes of quantum physics is the description of the long-lived Rydberg states of atoms and ions. The Bohr model is equally applicable to donor impurity atoms in semiconductor physics, where the conduction band corresponds to the vacuum, and the loosely bound electron orbiting a singly charged core has a hydrogen-like spectrum according to the usual BohrSommerfeld formula, shifted to the far-infrared because of the small effective mass and high dielectric constant. Manipulation of Rydberg states in free atoms and ions by single and multiphoton processes has been tremendously productive since the development of pulsed visible laser spectroscopy. The analogous manipulations have not been conducted for donor impurities in silicon. Here, we use the FELIX pulsed free electron laser to perform time-domain measurements of the Rydberg state dynamics in phosphorus- and arsenic-doped silicon and we have obtained lifetimes consistent with frequency domain linewidths for isotopically purified silicon. This implies that the dominant decoherence mechanism for excited Rydberg states is lifetime broadening, just as for atoms in ion traps. The experiments are important because they represent a step toward coherent control and manipulation of atomic-like quantum levels in the most common semiconductor and complement magnetic resonance experiments in the literature, which show extraordinarily long spin lattice relaxation timeskey to many well known schemes for quantum computing qubitsfor the same impurities. Our results, taken together with the magnetic resonance data and progress in precise placement of single impurities, suggest that doped silicon, the basis for modern microelectronics, is also a model ion trap.

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

2008-01-01

89

Microwave Spectroscopy of High-L, n=10 Rydberg states of Silicon

NASA Astrophysics Data System (ADS)

Using the RESIS/microwave technique [1], we have measured two fine structure intervals between high-L, n=10 Rydberg states of Silicon. A fast Si beam was obtained from an 8 keV Si^+ beam by charge exchange in an n=10 Rb Rydberg target. Individual n=10 Rydberg levels with L=6-9 were selectively detected by upwards excitation to n=31, using a Doppler tuned CO2 laser, followed by Stark ionization of the n=31 level and collection of the resulting ions. This L-selective detection was then used to detect microwave-induced transitions from L=7 to L=8 and from L=8 to =9. The measured intervals give a much improved determination of the dipole polarizability of the ground state of Si^+,^ (3p ^2 P1/2). An unexpected observation is the large ``spin-splitting" between the two levels formed by coupling Jc to L. The observed splittings are more than an order of magnitude larger than expected from magnetic interactions. [1] R.A. Komara, M.A. Gearba, C.W. Fehrenback and S.R. Lundeen, J. Phys. B: At. Mol. Opt. Phys. 38 S87 (2005).

Komara, R. A.; Fehrenbach, C. W.

2005-05-01

90

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

91

NASA Astrophysics Data System (ADS)

The UV-VUV photoabsorption spectrum of dibromomethane (CH2Br2) in the energy region 4.3-11.8 eV (35,000-95,000 cm-1) is investigated using synchrotron radiation. Rydberg series converging to the first four ionization limits at 10.52, 10.74, 11.21 and 11.30 eV corresponding to excitations from the 3b1, 2b2, 1a2, and 4a1 orbitals of CH2Br2 are identified and analyzed. Quantum defect values are observed to be consistent with excitation from the bromine lone pair orbitals. Assignments of the ns Rydberg series are revised and the np and nd Rydberg series are assigned for the first time. Observed vibrational features accompanying the 5p and 4d Rydberg states are assigned exclusively to the totally symmetric (a1) -CBr symmetric stretching mode (?3) in contrast to the earlier assignment to ?3 and -CH2 bending (?2) modes. The Rydberg and valence transitions observed in the present experiment are found to be in good agreement with the vertical excited states calculated using the TDDFT method. The calculations are further used to infer the valence transitions responsible for the broad intensity pedestals underlying the Rydberg transitions. The assignments are confirmed using isotopic substitution studies on CD2Br2 whose UV-VUV photoabsorption spectrum is reported here for the first time. This work presents a consolidated analysis of the UV-VUV photoabsorption spectrum of dibromomethane.

Mandal, Anuvab; Singh, Param Jeet; Shastri, Aparna; Kumar, Vijay; Sekhar, B. N. Raja; Jagatap, B. N.

2014-09-01

92

Coupled internal-state and center-of-mass dynamics of Rydberg atoms in a magnetic guide

NASA Astrophysics Data System (ADS)

We study cold rubidium Rydberg atoms, initially prepared in state 59D5/2, guided along a two-wire magnetic atom guide. The evolution of the atoms is driven by the combined effects of internal-state transitions and dipole forces acting on the center-of-mass degree of freedom. State-selective field ionization, applied at a variable delay time, is used to investigate the evolution of the internal-state distribution. We observe a broadening of the field ionization spectrum caused by population transfer between Rydberg states. At late times, the distribution of the remaining Rydberg atoms becomes biased toward states with high principal quantum numbers. The population transfer is attributed to thermal transitions and, to a lesser extent, initial state mixing due to Rydberg-Rydberg collisions. Characteristic components in spatially and temporally resolved distributions of the ion signal are interpreted in the context of the underlying physics. The system is simulated with a model in which the center-of-mass dynamics are treated classically, while the internal-state dynamics are treated quantum mechanically. The simulation qualitatively reproduces most experimental findings and provides experimentally inaccessible information.

Traxler, M.; Sapiro, R. E.; Lundquist, K.; Power, E. P.; Raithel, G.

2013-05-01

93

Interaction of the NO 3p? Rydberg state with Ar: Potential energy surfaces and spectroscopy

NASA Astrophysics Data System (ADS)

We present the experimental and simulated (2+1) REMPI spectrum of the C~ 2? state of the NO-Ar complex, in the vicinity of the 3p Rydberg state of NO. Two Rydberg states of NO are expected in this energy region: the C2? (3p?) and D2?+ (3p?) states, and we concentrate on the former here. When the C2? (3p?) state interacts with Ar at nonlinear orientations, the symmetry is lowered to Cs, splitting the degeneracy of the 2? state to yield C~(2A'') and C~(2A') states. For these two states of NO-Ar, we calculate potential energy surfaces using second order Mřller-Plesset perturbation theory, exploiting a procedure to converge the reference Hartree-Fock wavefunction to describe the excited states, the maximum overlap method. The bound rovibrational states obtained from the surfaces are used to simulate the electronic spectrum, which is in excellent agreement with experiment, providing assignments for the observed spectral lines from the calculated rovibrational wavefunctions.

Ershova, Olga V.; K?os, Jacek; Harris, Joe P.; Gardner, Adrian M.; Tamé-Reyes, Victor M.; Andrejeva, Anna; Alexander, Millard H.; Besley, Nicholas A.; Wright, Timothy G.

2013-06-01

94

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

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

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

2005-12-01

95

NASA Astrophysics Data System (ADS)

We consider problems of short-time dynamics of a polyelectronic atomic nonstationary state, V , assumed to be formed as a wave packet at t=0 . We focus on two cases, for which the role of the quasicontinuum of the upper part of the Rydberg states, with which the V state has nonzero coupling matrix elements, is investigated. In the first case, the position of the V state is just above the ionization threshold, E=0 , and so V dissipates into the free electron continuum as an autoionizing state. The question is how the presence of the Rydberg series converging to E=0 affects the time evolution of the autoionizing V . In the second case, the position of V is embedded in the quasicontinuum of the Rydberg series below threshold. The question is whether there are distinct features in the time evolution of this V , although its position is in the discrete part of the energy spectrum. In this case, by focusing on short times and by evaluating analytically certain infinite sums, analogous to Fourier integrations, the following result is obtained: For small times, the V state evolves as an exponentially decaying state. However, in addition to the term describing exponential decay, there is a term, entering with a small coefficient, which describes exponential growth and eventually dominates. It is shown that exponential decay holds for times shorter than the time tp needed by the wave packet to reach the outer classical turning point. For the decay to be physically meaningful, this time must be smaller than the time td which equals the inverse of the half-width in atomic units. We examined a model system of V -Rydberg state interaction based on the Boron S2 spectrum. The results indicate that the effect is observable on the scale of femtoseconds.

Komninos, Yannis; Nicolaides, Cleanthes A.

2005-09-01

96

NASA Astrophysics Data System (ADS)

We present a proposal for generation of a robust tripartite Greenberger-Horne-Zeilinger state among three-individual neutral Rydberg atoms. By modulating the relation between two-photon detuning and Rydberg interaction strength $U_{ij}(r)$, an effective Raman coupling is obtained between the hyperfine ground states $|F=2,M=2\\rangle$ of three $^{87}$Rb atoms and the Rydberg states $|rrr\\rangle$ via the third-order perturbation theory. This method is also capable of implementing a three-qubit controlled-phase gate with each qubit encoded into the hyperfine ground states $|F=1,M=1\\rangle$ and $|F=2,M=2\\rangle$. As an extension, we generalize our scheme to the case of multipartite GHZ state and quantum gate in virtue of high-order perturbation theory.

Shao, Xiao-Qiang; Zheng, Tai-Yu; Oh, C. H.; Zhang, Shou

2014-04-01

97

High-field-seeking Rydberg atoms orbiting a charged wire

NASA Astrophysics Data System (ADS)

Pulsed supersonic beams of helium atoms in the high-field-seeking 52p Rydberg state have been guided while following helical trajectories in the electrostatic field of a charged wire suspended along the axis of a grounded cylindrical metallic tube. The operation of this electrostatic wire guide for samples in high-field-seeking Rydberg-Stark states has been investigated with dc and pulsed electric potentials applied to the wire while the guided atoms were detected by pulsed electric-field ionization. The acceptance of the guide has been determined through numerical particle trajectory simulations.

Ko, H.; Hogan, S. D.

2014-05-01

98

Radiative transitions from Rydberg states of lithium atoms in a blackbody radiation environment

NASA Astrophysics Data System (ADS)

The radiative widths induced by blackbody radiation (BBR) were investigated for Rydberg states with principal quantum number up to n = 1000 in S-, P- and D-series of the neutral lithium atom at temperatures T = 100-3000 K. The rates of BBR-induced decays and excitations were compared with the rates of spontaneous decays. Simple analytical approximations are proposed for accurate estimations of the ratio of thermally induced decay (excitation) rates to spontaneous decay rates in wide ranges of states and temperatures.

Glukhov, I. L.; Ovsiannikov, V. D.

2012-05-01

99

Ultrafast dynamics of the ns (n = 3,4) and 3d Rydberg states of O2.

The ultrafast dynamics of the lowest optically accessible Rydberg states of molecular oxygen (O2) has been studied by time resolved transient ionization. The process was triggered by the absorption of two pump photons in the 304 nm-220 nm range which corresponds to an energy range of 8.2 eV-11.3 eV, and probed by ionization with photons at 800 nm. From the analysis of the experimental data different time constants ranging from a few femtoseconds to hundreds of picoseconds were found. The identification of the states responsible for the measured lifetimes revealed important facts about the dynamics of the Rydberg states in this energy range, underlying the importance of the coupling between Rydberg and valence states in the relaxation mechanisms of the molecule. PMID:23435804

Peralta Conde, A; Montero, R; Ovejas, V; Fernández-Fernández, M; Castańo, F; Longarte, A

2013-04-14

100

Mass-resolved (2 + n) resonance-enhanced multiphoton ionization (REMPI) spectra of CH2Br2 in the two-photon resonance excitation region from 71?200 to 82?300 cm(-1) were recorded and analyzed. Spectral structures allowed characterization of new molecular Rydberg states. C*((1)D2) was found to be an important intermediate in the photodissociation processes. A broad spectral feature peaking at about 80?663 cm(-1) in the C(+) spectrum and frequently seen in related studies is reinterpreted and associated with switching between three- and two-photon ionization of C*((1)D2). Analysis of band structures due to transitions from the A(2)? state of CH* that were seen in the CH(+) and C(+) REMPI spectra allowed characterization of three electronic states of CH, assigned as E(2)?, D(2)?, and F(2)?(+), which clarifies a long-term puzzle concerning the energetics of the CH radical. Predissociation of the E, D, and F states to form C*((1)D2) occurs. Bromine atomic lines were observed and are believed to be associated with bromine atom formation via predissociation of CH2Br2 Rydberg states. PMID:24527983

Long, Jingming; Wang, Huasheng; Kvaran, Ágúst

2014-03-13

101

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

102

NASA Astrophysics Data System (ADS)

The complementary threshold ionization techniques of MATI and ZEKE spectroscopy have been used to reveal well-resolved, long-lived (>10 ?s) hydrogenic Rydberg series (50?n?98) in a van der Waals complex formed between a polyatomic molecule and a diatomic molecule for the first time. The series are observed within 50 cm-1 of the adiabatic ionization threshold as well as two core-excited thresholds corresponding to excitation of up to two quanta in the van der Waals vibrational mode.

Cockett, Martin C.; Watkins, Mark J.

2004-01-01

103

Photoelectron imaging of propanal by resonant multiphoton ionization via the 3s Rydberg state.

We report the conformationally- and vibrationally-selected photoelectron spectroscopy of propanal obtained by resonance-enhanced multiphoton ionization (REMPI) using photoelectron imaging. These photoelectron spectra, employing (2 + 1) ionization via the (n, 3s) Rydberg transitions in the range from 365 to 371 nm, confirm that there are two stable conformer origins in the lowest ionic state, the cis conformer with a co-planar CCCO geometry and a gauche conformer with a approximately 119 degrees CCCO dihedral angle. From ab initio calculations at the B3LYP/6-311++G** level, we find the gauche conformer is slightly more stable, with the energy difference between two conformers determined to be only 65 cm(-1). In our photoelectron spectra, the vertical ionization potential (IP) for the cis conformer of propanal was then determined to be 9.999 (+/-0.003) eV, while that of the gauche conformer of propanal was estimated to be 9.944 eV. A long vibrational progression in the in-plane CCCO deformation vibrational mode, v, for the cis conformer is systematically observed in all photoelectron spectra in which this mode is excited, suggesting that the geometry of the ground ionic state is significantly different from that of the 3s Rydberg state, particularly along the v(15) coordinates. PMID:16880905

Hwa Kim, Myung; Shen, Lei; Suits, Arthur G

2006-07-01

104

Core effect on the diamagnetic spectrum of barium Rydberg states

NASA Astrophysics Data System (ADS)

We study the core effect of nonhydrogenic alkaline-earth-metal barium in its diamagnetic spectrum by one photon transition from the ground state 6s2 1S0 experimentally and theoretically. The non-Coulombic potential of the ion core introduces an extra energy shift compared with hydrogen and a level anticrossing between different n manifolds, characterized by the quantum defect of the concerned angular momentum states. With a complex rotation coordinate technique and a B-spline expansion method, we develop a matrix-form Hamiltonian based on an effective potential incorporating the angular-dependent quantum defect into the angular rotation term. The nonhydrogen core effects are investigated by sweeping the quantum defects of different channels in the calculation. Results show that quantum defects of p and f states have a undeniable effect on the intensities and positions of the spectral lines, although barium is closely hydrogenlike in the energy range examined. The anticrossing spectral lines are also identified with the aid of theoretical calculations. The calculations are in good agreement with the experimental observations.

Yang, H. F.; Gao, W.; Quan, W.; Liu, X. J.; Liu, H. P.

2012-03-01

105

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

106

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

107

Steady-state crystallization of Rydberg excitations in an optically driven lattice gas

NASA Astrophysics Data System (ADS)

We study the conditions for attaining crystalline order in the stationary state of a continuously driven, open many-body system. Specifically, we consider resonant optical excitations of atoms in a one-dimensional lattice to the Rydberg states interacting via the van der Waals potential. Strong blockade of excitations at neighboring lattice sites steers the system toward a crystalline state while competing with the fluctuations associated with relaxation. We analyze the stationary state of the many-body system and the dynamics of its buildup employing numerically exact time-dependent density-matrix renormalization-group simulations for two- and three-level excitation schemes. We also present an approximate rate equation model which provides qualitative conditions for attaining crystalline order.

Höning, Michael; Muth, Dominik; Petrosyan, David; Fleischhauer, Michael

2013-02-01

108

NASA Astrophysics Data System (ADS)

In the range 0-45 cm^{-1} below the ionization limit, the separation between adjacent electronic states (Rydberg states with principal quantum number n>50) of atoms and molecules is smaller than 2 cm^{-1}. In order to resolve the fine or hyperfine structure of these states, it is necessary to combine high-resolution vacuum ultraviolet (VUV) laser radiation, which is required to access the Rydberg states from the ground state, with millimeter wave radiation. Such double-resonance experiments have been used to study the hyperfine structure of high Rydberg states of ^{83}Kr, H_2 or D_2. Millimeter wave transitions (240-350 GHz) between n? (52? n?64, ??3) Rydberg states of different xenon isotopes were detected by pulsed field ionization followed by mass-selective detection of the cations. Because of the high polarizability of high-n Rydberg states (? n^7, 10^4 MHz cm^{2} V^{-2} for n? 50), it is necessary to reduce the electric stray fields to values of the order of mV/cm (or less) in order to minimize the (quadratic) Stark shift of the millimeter wave transitions. Some p and d Rydberg states of Xe are nearly degenerate and efficiently mixed by small stray fields, making it possible to observe transitions forbidden by the ??=ą1 selection rule or transitions exhibiting a linear Stark effect, which is typical for the degenerate high-? Rydberg states. Multichannel quantum defect theory (MQDT) was used to analyze the millimeter wave data and to determine the hyperfine structures of the ^2P_{3/2} ground electronic states of ^{129}Xe^+ and ^{131}Xe^+. C. Fabre, P. Goy, S. Haroche, J. Phys. B: Atom. Mol. Phys. 10, L183-189 (1977). F. Merkt, A. Osterwalder, Int. Rev. Phys. Chem. 21, 385-403 (2002). M. Schäfer, M. Andrist, H. Schmutz, F. Lewen, G. Winnewisser, F. Merkt, J. Phys. B: At. Mol. Opt. Phys. 39, 831-845 (2006) M. Schäfer, F. Merkt, Phys. Rev. A, 74, 062506 (2006). A. Osterwalder, A. Wüest, F. Merkt, Ch. Jungen, J. Chem. Phys., 121, 11810-11838 (2004). H. A. Cruse, Ch. Jungen, F. Merkt, Phys. Rev. A 77, 04502 (2008)

Schäfer, Martin; Raunhardt, Matthias; Merkt, Frédéric

2009-06-01

109

Electric-field-induced dissociation of heavy Rydberg ion-pair states

NASA Astrophysics Data System (ADS)

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

Reinhold, C. O.; Yoshida, S.; Dunning, F. B.

2011-05-01

110

Electric-field-induced dissociation of heavy Rydberg ion-pair states

NASA Astrophysics Data System (ADS)

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

Reinhold, Carlos; Yoshida, Shuhei; Wang, Changhao; Dunning, Barry

2011-06-01

111

Three-body bound states in dipole-dipole interacting Rydberg atoms.

We show that the dipole-dipole interaction between three identical Rydberg atoms can give rise to bound trimer states. The microscopic origin of these states is fundamentally different from Efimov physics. Two stable trimer configurations exist where the atoms form the vertices of an equilateral triangle in a plane perpendicular to a static electric field. The triangle edge length typically exceeds R?2 ?m, and each configuration is twofold degenerate due to Kramers degeneracy. The depth of the potential wells and the triangle edge length can be controlled by external parameters. We establish the Borromean nature of the trimer states, analyze the quantum dynamics in the potential wells, and describe methods for their production and detection. PMID:24476267

Kiffner, Martin; Li, Wenhui; Jaksch, Dieter

2013-12-01

112

NASA Astrophysics Data System (ADS)

We report diamagnetic spectra of sodium atoms observed in a strong magnetic field up to 3 T and compare them with theoretical calculations based on the formulation of an exact quantum-defect theory. We focus on one-photon absorption processes from the ground 3s state to the excited np Rydberg states whose magnetic quantum numbers are determined by the polarization of the laser field. The calculations employ B-spline basis expansion and the complex spatial coordinate rotation technique, and their results agree well with the observed ones when atomic core effects are appropriately taken into account. When graphed against magnetic field, level anticrossings and core-induced interaction of the np states provide clear signatures for studying the effects of quantum defect on the diamagnetic spectra.

Gao, W.; Yang, H. F.; Cheng, H.; Liu, X. J.; Liu, H. P.

2012-07-01

113

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

114

Numerous infrared transitions between Rydberg states of neon and argon have been measured by optogalvanic spectros- copy in commercial hollow cathode lamps using a color center laser operating in the range 3600-4100 cm-'. Transitions in lithium and barium atoms sputtered from the cathodes were also detected. The generality and high sensitivity of this technique indicates potential applications for frequency calibration

Marianne H. BEGEMANN; Richard J. SAYKALLY

1982-01-01

115

National Technical Information Service (NTIS)

The effect of solvation by nonpolar solvents on the (n,3s) Rydberg states of 1,4- diazabicyclo(2.2.2) octane (DABCO) and azabicyclo(2.2.2) octane (ABCO) is investigated through mass resolved excitation spectroscopy of their van der Waals complexes. The so...

Q. Y. Shang P. O. Moreno C. Dion E. R. Bernstein

1993-01-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

117

Spectroscopy of High-L N = 10 Rydberg States of Carbon, Oxygen, and Neon.

NASA Astrophysics Data System (ADS)

The high angular momentum fine structure of the n = 10 to 27 transitons in neutral Carbon, Oxygen, and Neon has been measured using Resonant Excitation Stark Ionization Spectroscopy (RESIS). This structure has been interpreted in terms of an effective polarization potential model to allow extraction of the quadrupole moments and dipole polarizibilities of the singly charged ion in each species to a precision of 0.2%. Further radio frequency studies in n = 10 Oxygen and Neon have directly determined the relative energies of high angular momentum fine structure levels to a precision of better than 0.3 MHz, allowing for greater precision in extraction of these core parameters. The RF data also allows the first test of predicted geometric phase effects in Rydberg atoms with a P-state core.

Ward, Ralph Franklin, Jr.

118

Ionization Potentials and Quantum Defects of 1s2np2P Rydberg States of Lithium Atom

NASA Astrophysics Data System (ADS)

In this work, ionization potentials and quantum effects of 1s2np2P Rydberg states of lithium are calculated based on the calibrated quantum defect function. Energy levels and quantum defects for 1s2np2P bound states and their adjacent continuum states are calculated with the R-matrix theory, and then the quantum defect function of the 1s2np (n >= 7) channel is obtained, which varies smoothly with the energy based on the quantum defect theory. The accurate quantum defect of the 1s27p2P state derived from the experimental data is used to calibrate the original quantum defect function. The new function is used to calculate ionization potentials and quantum effects of 1s2np2P (n >= 7) Rydberg states. Present calculations are in agreement with recent experimental data in whole.

Chen, Chao

2008-09-01

119

NASA Astrophysics Data System (ADS)

The term energies and linewidths of the Rydberg states of NO are determined experimentally in a vacuum chamber at 1-10 microtorr, using a collimated pulsed supersonic molecular beam and a three-stage pulse-amplified CW dye laser with linewidth 0.002/cm. Results for transitions from the ground state to the A 2Sigma(+) 3s(sigma) v = 1 state and from the A state to the 7f, 12f, and 15f v = 1 states are presented in extensive tables and graphs and characterized in detail. The v = 0 ionization potential is calculated, on the basis of the combined measurements, as 74,721.7 (standard deviation 1).

Biernacki, D. Therese; Colson, Steven D.; Eyler, E. E.

1988-09-01

120

Far infrared stimulated emission from the ns and nf Rydberg states of NO.

We report directional far-infrared emission from the ? = 0 vibrational levels of the 9s?, 10s?, 11s?, 9f, and 10f Rydberg states of NO in the gas phase. The emission around 28 and 19 ?m from the 9f state was identified as the downward 9f ? 8g and subsequent 8g ? 7f cascade transitions, respectively. The emission around 38 and 40 ?m from the 10f state was identified as the 10f ? 9g and 10f ? 9d?? transition, respectively. Following the excitation of the 9s?, 10s?, and 11s? states, the emission around 40, 60, and 83 ?m was assigned as the 9s? ? 8p?, 10s? ? 9p?, and 11s? ? 10p? transitions, respectively. In addition to these emission systems originated from the laser-prepared levels, we found the emission bands from the 8f, 9f, and 10f states which are located energetically above the 9s?, 10s?, and 11s? states, respectively. This observation suggests that the upward 8f ? 9s?, 9f ? 10s?, and 10f ? 11s? optical excitation occurs. Since the energy differences between nf and (n + 1)s? states correspond to the wavelength longer than 100 ?m, the absorption of blackbody radiation is supposed to be essential for these upward transitions. PMID:23822248

Furukawa, Hiroki; Araki, Mitsunori; Umeki, Hiroya; Tsukiyama, Koichi

2013-06-28

121

NASA Technical Reports Server (NTRS)

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

Drachman, Richard J.

2006-01-01

122

NASA Astrophysics Data System (ADS)

Photoionization spectra and Rydberg-state-resolved threshold-ionization spectra of the gerade triplet np Rydberg states of 4He2 located in the vicinity of the X^+ ^2? _u^+ (v^+=0) ionization threshold were recorded from the 2s? a ^3? _u^+ metastable state. An accuracy of 0.01 cm-1 was achieved for the experimental term values of the observed Rydberg states. The data were combined with spectroscopic data on low-lying triplet np and nf Rydberg states from the literature to derive energy- and internuclear-distance-dependent eigenquantum-defect parameters of multichannel quantum-defect theory (MQDT). The MQDT calculations reproduce the experimental data within their experimental uncertainties and enabled the derivation of potential-energy curves for the lowest triplet p Rydberg states (n = 2-5) of He2. The eigenquantum-defect parameters describing the p -f interaction were found to be larger than 0.002 at the energies corresponding to the high-n Rydberg states, so that the p -f interaction plays an important role in the autoionization dynamics of np Rydberg states with v+ = 0. By extrapolating the experimental term values of triplet np Rydberg states of 4He2 in the range of principal quantum number n between 87 and 110, the positions of the (v+ = 0, N+ = 3) and (v+ = 0, N+ = 5) levels of the ground state of 4He_2^+ were determined to lie 70.937(3) cm-1 and 198.369(6) cm-1, respectively, above the (v+ = 0, N+ = 1) ground rotational level.

Sprecher, D.; Liu, J.; Krähenmann, T.; Schäfer, M.; Merkt, F.

2014-02-01

123

Photoionization spectra and Rydberg-state-resolved threshold-ionization spectra of the gerade triplet np Rydberg states of (4)He2 located in the vicinity of the X(+) (2)?(u)(+) (?(+) = 0) ionization threshold were recorded from the 2s? a (3)?(u)(+) metastable state. An accuracy of 0.01?cm(-1) was achieved for the experimental term values of the observed Rydberg states. The data were combined with spectroscopic data on low-lying triplet np and nf Rydberg states from the literature to derive energy- and internuclear-distance-dependent eigenquantum-defect parameters of multichannel quantum-defect theory (MQDT). The MQDT calculations reproduce the experimental data within their experimental uncertainties and enabled the derivation of potential-energy curves for the lowest triplet p Rydberg states (n = 2-5) of He2. The eigenquantum-defect parameters describing the p?-f interaction were found to be larger than 0.002 at the energies corresponding to the high-n Rydberg states, so that the p?-f interaction plays an important role in the autoionization dynamics of np Rydberg states with v(+) = 0. By extrapolating the experimental term values of triplet np Rydberg states of (4)He2 in the range of principal quantum number n between 87 and 110, the positions of the (v(+) = 0, N(+) = 3) and (v(+) = 0, N(+) = 5) levels of the ground state of (4)He(+)(2) were determined to lie 70.937(3)?cm(-1) and 198.369(6)?cm(-1), respectively, above the (v(+) = 0, N(+) = 1) ground rotational level. PMID:24527912

Sprecher, D; Liu, J; Krähenmann, T; Schäfer, M; Merkt, F

2014-02-14

124

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

125

NASA Astrophysics Data System (ADS)

MRCI results are reported for the vertical excitation energies (VEE) and oscillator strengths f of doublet states of OClO up to 11 eV, including 3b1 --> 4s, 4p, 3d, 5s, 5p, 4d, and most 1a2, 8a1, 5b2 --> 4s and 4p Rydberg states. The lowest Rydberg states 3b1 --> 4s and 3b1 --> 4px have mixed valence-Rydberg character. The observed spectral bands were reassigned to include valence states which have generally higher oscillator strengths. The well-known valence state 12A2 has a VEE of 3.63 eV, and a relatively high f of 0.042. Overall, the calculated oscillator strengths are in good agreement with measured values. The lowest quartet state, 14B2, lies at 6.95 eV. Quartet Rydberg states start with 1a2 --> 4s at 9.28 eV. According to calculated vertical ionization potentials (VIP) of OClO, the second VIP at 12.59 eV is reassigned from 13B1 to 13B2 (ionization from 1a2, rather than 8a1), and the third VIP at 12.63 eV from 11B1 to 13B1 (ionization from 8a1). Vertical electron detachment energies of OClO- have been calculated up to 8.9 eV. There is good agreement with experimental values.

Grein, Friedrich

2011-07-01

126

The photochemistry of the pyrrole-ammonia cluster is analyzed theoretically. Whereas in neat pyrrole the dominant photochemical reaction is H-atom cleavage, recent experiments show that in pyrrole-ammonia clusters the major reaction is H-transfer to form the NH(4) radical (solvated by ammonia molecules in the case of large clusters) and the pyrrolyl radical. A mechanism involving the hydrogen-bonded Rydberg state is offered to account for these results and verified computationally. Two minima are located on the lowest excited singlet PES. Both of them are Rydberg states, one leads to the formation of NH(4) and pyrrolyl radicals, the other is connected to the ??* state through a relatively high barrier, leading to a 3-body dissociation reaction to form a pyrrolyl radical, ammonia and an H-atom. The former is the energetically and statistically preferred one. PMID:22337489

Zilberg, Shmuel; Kahan, Anat; Haas, Yehuda

2012-07-01

127

Properties of Th^3+ from Optical Spectroscopy of High-L Rydberg states of Th^2+

NASA Astrophysics Data System (ADS)

The Fr-like Thorium ion, Th^3+, has one valence electron outside a Rn-like closed shell, but its ground electronic state is ^2F5/2 instead of ^2S1/2 due to the high nuclear charge [1]. The positions of the lowest seven levels of this ion have been established by optical spectroscopy [2], but no other properties have been measured previously. We measure the properties of the Th^3+ ground state that control its long-range interactions, such as polarizabilities and permanent moments, by attaching a single electron in a non-penetrating Rydberg state and measuring the details of its binding energy using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique [3]. A typical transition is n=29 to n'=72. The laser excitation partially resolves the complex fine structure pattern in the lower state caused by the long-range interactions, and this leads to measurements of the core ion properties controlling those interactions.[4pt] [1] U.I. Safronova, et. al., Phys. Rev. A 76, 042504 (2007)[0pt] [2] URL = http://www.lac.u-psud.fr/Database/Contents.html[0pt] [3] M.E. Hanni, et. al. Phys. Rev. A 82, 022512 (2010)

Keele, Julie; Woods, Shannon; Lundeen, Stephen; Fehrenbach, Charles

2011-06-01

128

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 Quadrupole moment and polarizability. Resonant Excitation Stark Ionization Spectroscopy (RESIS) uses a Doppler-tuned CO2 laser to resonantly excite transitions in a fast molecular beam, which are detected by Stark ionization. Reported here is the analysis of the fine structure measurements of the high-L Rydberg states of the rotationally excited (R=2) ground vibrational level of molecular hydrogen. This determines the Quadrupole moment and scalar and tensor dipole polarizabilities of H2^+. The experimental progress made using a novel approach to the detection techniques of RESIS which will allow the first measurements of the higher rotational levels of H2 that were previously unattainable due to their fast autoionization rates will also be discussed.

Snow, Erica

2012-06-01

129

NASA Astrophysics Data System (ADS)

Crossed magnetic and electric fields are observed to extend the lifetime of high molecular Rydberg states of DABCO (1,4-Diazabicyclo[2.2.2]octane) well into the microsecond range. The experimental and computational (using classical mechanics and for a diatomic polar core) results agree both on the magnitude of the effect and on its decrease with increasing electrical field. Theoretical considerations suggest that this time-stretching effect is only present for high Rydberg states and/or for not too weak fields. The computed lifetime increases as the magnetic-field strength is decreased but it requires a finite magnetic field for the onset of the effect. The experimental technique of detection of the surviving Rydberg states via their ionization in a delayed field pulse (known as ZEKE spectroscopy) is most easily implemented for high (say, n>100) but not too high (n<400) Rydberg states. In this regime, the magnetic field required for the additional time stretching is larger than that due to the earth but can be significantly weaker than that required to induce extensive chaotic behavior. The results of the numerically exact classical simulations are interpreted using equations of motion, cast in the form of a mapping, which retain terms up to second order in the fields. (The first-order terms are qualitatively and quantitatively not, by themselves, sufficient.) As is to be expected on physical grounds, the origin of the effect is the slow, periodic modulation of the magnitude of the magnetic quantum number ml of the electron due to terms second order in the magnetic field. Since the angular momentum l of the electron is bounded from below by ml, and since it requires a low l for the electron to couple effectively to the molecular core, the presence of the magnetic field provides for an elongation of the time scale which is over and above that made possible due to the periodic motion of l due to the dc electric field.

Mühlpfordt, Annette; Even, U.; Rabani, Eran; Levine, R. D.

1995-05-01

130

Far infrared stimulated emission from the ns and nf Rydberg states of NO

We report directional far-infrared emission from the {upsilon}= 0 vibrational levels of the 9s{sigma}, 10s{sigma}, 11s{sigma}, 9f, and 10f Rydberg states of NO in the gas phase. The emission around 28 and 19 {mu}m from the 9f state was identified as the downward 9f{yields} 8g and subsequent 8g{yields} 7f cascade transitions, respectively. The emission around 38 and 40 {mu}m from the 10f state was identified as the 10f{yields} 9g and 10f{yields} 9d{sigma}{pi} transition, respectively. Following the excitation of the 9s{sigma}, 10s{sigma}, and 11s{sigma} states, the emission around 40, 60, and 83 {mu}m was assigned as the 9s{sigma}{yields} 8p{sigma}, 10s{sigma}{yields} 9p{sigma}, and 11s{sigma}{yields} 10p{sigma} transitions, respectively. In addition to these emission systems originated from the laser-prepared levels, we found the emission bands from the 8f, 9f, and 10f states which are located energetically above the 9s{sigma}, 10s{sigma}, and 11s{sigma} states, respectively. This observation suggests that the upward 8f Leftwards-Arrow 9s{sigma}, 9f Leftwards-Arrow 10s{sigma}, and 10f Leftwards-Arrow 11s{sigma} optical excitation occurs. Since the energy differences between nf and (n+ 1)s{sigma} states correspond to the wavelength longer than 100 {mu}m, the absorption of blackbody radiation is supposed to be essential for these upward transitions.

Furukawa, Hiroki; Araki, Mitsunori; Umeki, Hiroya; Tsukiyama, Koichi [Graduate School of Chemical Sciences and Technology, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601 (Japan)

2013-06-28

131

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

132

Exploring the high-order harmonic generation from Rydberg states with a fixed Keldysh parameter

NASA Astrophysics Data System (ADS)

The commonly adopted viewpoint that the Keldysh parameter ? determines the dynamical regime of ionization in strong field physics has long been demonstrated to be a misleading one. One can then ask what happens in strong field ionization as relevant parameters, such as laser intensity and frequency, are varied while keeping ? fixed. We present results from our simulations of high-order harmonic generation (HHG) from Rydberg states of a hydrogen atom. We calculate high harmonic spectra from various initial states with n up to 42, where the laser intensities and the frequencies are scaled from those for n=1 in order to maintain a fixed Keldysh parameter ?<1. We find that as we go up in n for a fixed ?, the position of the cut-off scales as 1/n^2 in terms of the cut-off law predicted by the three-step model for n=1. However, a secondary cut-off structure forms below this, which moves to lower harmonics as n is increased. This second cut-off splits the plateau into two regions, one higher in yield and below the second cut-off, and the second with lower yield following it. We further investigate the final n-distributions for some of the interesting cases to elucidate the physical mechanism leading to this structure

Ata Bleda, Erdi; Yavuz, Ilhan; Altun, Zikri; Topcu, Turker

2012-06-01

133

The influence of charge-transfer and rydberg (f\\u000a \\u000a n?1\\u000a d) states on the luminescence of lanthanides and actinides (more specifically hexavalent uranium) is demonstrated. Optical\\u000a transitions between the ground state and these excited states, and their dependence on electron configuration and crystallographic\\u000a surroundings of the complex involved, are discussed first. The influence of charge-transfer and f\\u000a \\u000a n?1\\u000a d states on emission

G. Blasse

134

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

135

NASA Astrophysics Data System (ADS)

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

Martin, James D. D.

1999-11-01

136

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

137

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

138

A new spectrum of the autoionizing triplet states of gerade symmetry of H2 has been recorded from the ?? = 14, N? = 13 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 ?+ = 14, N+ = 05 levels of the X+ 2?(g)+ ground state of H2+. Numerous perturbations caused by sd 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). PMID:23428200

Sprecher, Daniel; Jungen, Christian; Merkt, Frédéric

2013-10-01

139

NASA Astrophysics Data System (ADS)

Electric dipole and quadrupole transitions probabilities between two atomic Rydberg states ?l,?'l' have been calculated using three methods. From comparison of results we deduce a new method from which any radial integrals may be obtained very easily using only two functions of the difference s=?-?'. These functions are g0(s) and g1(s) which have been calculated in the dipole case [J. Picart, A. R. Edmonds, N. Tran Minh, and R. Pullen, J. Phys. B 11, L651 (1978); A. R. Edmonds, J. Picart, N. Tran Minh, and R. Pullen, J. Phys. B 12, 2781 (1979)].

Oumarou, B.; Picart, J.; Tran Minh, N.; Chapelle, J.

1988-03-01

140

Multiatom entanglement in cold Rydberg mixtures

NASA Astrophysics Data System (ADS)

We present an efficient method for generating maximum entanglement in one-dimensional atomic lattices. The proposed method relies on adiabatic rapid transfer into two Rydberg states with strongly asymmetric interactions. The method is suitable for Rydberg S states in the absence of applied electrostatic fields. We show numerical simulations of entanglement generation in rubidium atoms using calculated van der Waals potentials under realistic experimental conditions. We study the effect of the chosen Rydberg states on the final entanglement.

Cano, Daniel; Fortágh, József

2014-04-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

142

Helium resources of the United States, 1977. Information circular 1979

This Bureau of Mines publication estimates that U.S. helium resources as of January 1977 were 710 billion cubic feet. These resources are broken down into four classifications, as follows: Helium in measured natural gas resources and in storage, 201 billion cubic feet; helium in indicated natural gas resources, 150 billion cubic feet; helium in hypothetical natural gas resources, 175 billion

1979-01-01

143

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

144

National Technical Information Service (NTIS)

SOlvent induced singlet (2p3s) Rydberg state relaxation dynamics of diazabicyclooctane (DABCO) are studied in van der Waals clusters generated in a supersonic jet expansion. The excited state decay is determined by a pump (excitation)/probe(ionization) ma...

Q. Y. Shang P. O. Moreno E. R. Bernstein

1994-01-01

145

First observation of the v=3 level of the B 1?+ Rydberg state of CO

A new diffuse vuv band of 12C16O at 92 800 cm?1 has been observed in absorption and assigned to the BX(30) transition. The assignment is based on the excellent agreement found between the observed band and a calculated spectrum of the BX(30) transition, where a previously optimized two channel close-coupling model of the B 1?+D 1?+ Rydbergvalence predissociation interaction has

Jacob Baker; Paul S. Julienne

1995-01-01

146

Attosecond pump-probe of doubly excited states in helium

NASA Astrophysics Data System (ADS)

Pump--probe experiments using two attosecond light pulses promise to provide unprecedented temporal resolution of electronic wave packet dynamics and have thus been called the ``holy grail'' of attosecond physics. Their experimental realization has up to now been out of experimental reach because of the limited intensity of attosecond sources. We study such setups for probing doubly excited states of helium, which present a prototypical example for correlated electron dynamics. We will present schemes to achieve sufficient yields for the experimental realization of such a setup. Furthermore, we will discuss the novel information that can be gained about the dynamics of the system and that is not available in conventional spectroscopy.

Feist, Johannes; Nagele, Stefan; Burgdörfer, Joachim; Ticknor, Christopher; Collins, Lee A.; Schneider, Barry I.

2011-06-01

147

Properties of Fr-like Th^3+ from microwave spectroscopy of high-L Rydberg states of Th^2+

NASA Astrophysics Data System (ADS)

Spectroscopy of high-L n= 28 Rydberg levels of Th^2+ was recently reported using the optical RESIS method [1]. Because the ground state of Fr-like Th^3+ is a ^2F5/2 level, each (n,L) Rydberg level of Th^2+ is split into six eigenstates whose relative positions are determined by long-range e-Th^3+ interactions. Measurements of those positions can be used to determine the Th^3+ properties that control those interactions, such as polarizabilities and permanent moments. We report a much improved study of n=28 levels with 9 <= L <= 12, obtained with the microwave/RESIS method. The higher precision measurements allow improved determinations of a wider range of Th^3+ properties and a better test of theoretical calculations [2].[4pt] [1] Julie A. Keele, M.E. Hanni, Shannon L. Woods, S.R. Lundeen, and C.W. Fehrenbach, Phys. Rev. A 83, 062501 (2011)[0pt] [2] U.I. Safronova, W.R. Johnson, and M.S. Safronova, Phys. Rev. A 74, 042511 (2006)

Keele, Julie; Smith, Chris; Woods, Shannon; Lundeen, Stephen; Fehrenbach, Charles

2012-06-01

148

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

NASA Astrophysics Data System (ADS)

Autoionizing high-Rydberg states formed during the initial electron capture phase of dielectronic recombination (DR) provide a unique access to spectroscopic information of highly charged heavy ions. This paper summarizes recent experimental and theoretical studies on the low energy 1s 22p jnlj' ( j=1/2, 3/2) Be-like DR resonances associated with the 2s 1/2?2p j core excitations of the Li-like ions 19779Au 76+, 20892Pb 79+ and 23892U 89+. An extrapolation of the resonance energies of the 1s 22p 1/2nlj' ( n?20) Rydberg series to the series limits ( n??) yields the 2s 1/2-2p 1/2 transition energies. The experimental precision of below 100 meV for all three ions obtained with this photonfree spectroscopic method is comparable to the best optical measurements available and allows to test quantum electrodynamics of strong central fields on a level of below 7% of the ?2 contributions. Furthermore, our theoretical calculations show that the observed DR resonance positions sensitively depend on the charge distribution within the atomic nucleus.

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

2003-05-01

149

Production of high-n strontium Rydberg atoms

NASA Astrophysics Data System (ADS)

The photoexcitation of strontium Rydberg atoms with n ~ 300 is being examined using a crossed laser-atom beam approach to enable study of quasi-stable two-electron excited states and of strongly-coupled Rydberg systems.

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

2014-04-01

150

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

151

Rydberg tomography of an ultracold atomic cloud

NASA Astrophysics Data System (ADS)

One of the most striking features of the strong interactions between Rydberg atoms is the Rydberg blockade effect, which allows only a single excitation to the Rydberg state within the volume of the blockade sphere. Here we present a method that spatially visualizes this phenomenon in an inhomogeneous gas of ultracold rubidium atoms. In our experiment we scan the position of one of the excitation lasers across the cold cloud and determine the number of Rydberg excitations detected as a function of position. Comparing this distribution to the one obtained for the number of ions created by a two-photon ionization process via the intermediate 5P level, we demonstrate that the blockade effect modifies the width of the Rydberg excitation profile. Furthermore, we study the dynamics of the Rydberg excitation and find that the time scale for the excitation depends on the atomic density at the beam position.

Valado, M. M.; Malossi, N.; Scotto, S.; Ciampini, D.; Arimondo, E.; Morsch, O.

2013-10-01

152

Wireless Network Control of Interacting Rydberg Atoms

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

153

Wireless network control of interacting Rydberg atoms.

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

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

2014-04-25

154

NASA Astrophysics Data System (ADS)

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

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

2006-07-01

155

NASA Astrophysics Data System (ADS)

A detailed theoretical analysis of the high-resolution X-ray absorption spectra of condensed long-chain alkane molecules (hexatriacontane, C 36H 74 and heptatriacontane, C 37H 76) suggests that the resonance at 287.7 eV, which is the dominating feature in the near-edge X-ray absorption spectra of saturated long-chain hydrocarbons, is due to transitions into Rydberg states. These findings, which are at variance with the previous interpretation, are corroborated by the identification of a previously unresolved resonance at 288.2 eV in the high-resolution X-ray absorption spectra and of the observation of a strong quenching of the X-ray absorption resonances upon physisorption on a Cu(111)-metal surface.

Bagus, P. S.; Weiss, K.; Schertel, A.; Wöll, Ch.; Braun, W.; Hellwig, C.; Jung, C.

1996-01-01

156

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 ionization threshold. Making use of a basis (parabolic Sturmian basis) with a size varying from 990 up to 5050, we obtain, over the energy range of [minus]190 to [minus]24 cm[sup [minus]1], all of the eigenvalues and a good part of the oscillator strengths with a remarkable accuracy. This, however, decreases with increasing excitation energy and, thus, above [similar to][minus]24 cm[sup [minus]1], we obtain results of good accuracy only for eigenvalues ranging up to [similar to][minus]12 cm[sup [minus]1].

Falsaperla, P.; Fonte, G. (Dipartimento di Fisica,Universita di Catania, Corso Italia 57, I-95129 Catania (Italy) Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia 57, I-95129 Catania (Italy))

1994-10-01

157

(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

158

Investigation of the state of helium implanted into molybdenum lattice by alpha-particle bombardment

Knowledge of the state and behaviour of helium in reactor components is needed in order to understand such phenomena as void swelling and high temperature radiation embrittlement. The X-ray diffraction method of lattice parameter measurement can provide useful information about the state of helium in radiation damaged lattices of metals if the effects of irradiation induced lattice defectsvacancies and interstitials

V. F. Reutov; Yu. I. Abdrashitov; A. A. Loktionov; S. F. Kramar

1983-01-01

159

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

160

Electronic spectroscopy of the 3d Rydberg states of NO-Rg (Rg=Ne,Ar,Kr,Xe) van der Waals complexes

We have employed (2+1) resonance-enhanced multiphoton ionization spectroscopy to record electronic absorption spectra of NO-Rg (Rg=Ne,Ar,Kr) van der Waals complexes. The nitric oxide molecule is the chromophore, and the excitation corresponds to an electron being promoted from the 2ppi* orbital to 3dsigma, 3dpi, and 3ddelta Rydberg states. We review the ordering of the 3dlambda states of NO and use this

Denis E. Bergeron; Adam Musgrave; Robert T. Gammon; Victoria L. Ayles; James A. E. Silber; Timothy G. Wright; Bo Wen; Henning Meyer

2006-01-01

161

Interactions between Rydberg-dressed atoms

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

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

2010-09-15

162

NASA Astrophysics Data System (ADS)

Three 1sigma Rydberg states of the NCl molecule, accessed from the NCl a1 state, have been investigated by multiphoton ionization spectroscopy. NCl was prepared from the Cl + N3 reaction and the excited 1sigma states were observed via the 2-photon resonance enhancements they provide in the multiphoton ionization spectrum of NCl a1 . Assignment of the initial and final electronic states associated with each band was achieved by rotational band contour simulations, least-squares fitting of the resolved rotational structure, recording spectra with linearly and circularly polarized radiation and recording spectra in the N35Cl+ and N37Cl+ mass channels. The +/- character of each excited state as well as the dominant electronic configuration at spectroscopically accessible bond lengths was established by multireference double excitation configuration interaction (MRDCI) calculations.

Boggis, S. A.; Dyke, J. M.; Tabrizchi, M.; Richter, R.

1999-07-01

163

Semiclassical quantization of Bohr orbits in the helium atom

NASA Astrophysics Data System (ADS)

We use the complex WKB-Maslov method to construct the semiclassical spectral series corresponding to the resonance Bohr orbits in the helium atom. The semiclassical energy levels represented as the Rydberg tetra series correspond to the doubly symmetrically excited states of helium-like atoms. This level series contains the Rydberg triple series reported by Richter and Wintgen in 1991, which corresponds to the Z2+e-e- configuration of electrons observed by Eichmann and his collaborators in experiments on the laser excitation of the barium atom in 1992. The lower-level extrapolation of the formula obtained for the semiclassical spectrum gives the value of the ground state energy, which differs by 6% from the experimental value obtained by Bergeson and his collaborators in 1998. We also calculate the fine structure of the semiclassical spectrum due to the spin-orbit and spin-spin interactions of electrons.

Belov, V. V.; Maksimov, V. A.

2007-05-01

164

NASA Astrophysics Data System (ADS)

About 3% of antiprotons (bar{p}) stopped in helium are long-lived with microsecond lifetimes, against picoseconds in all other materials. This unusual longevity has been ascribed to the trapping of bar{p} on metastable bound states in bar{p}He+ helium atom-molecules thus named atomcules. Apart from their unique dual structure investigated by laser spectroscopy - a near-circular quasi-classical Rydberg atom with l n - 1 37 or a special diatomic molecule with a negatively charged bar{p} nucleus in high rotational state with J = l - the chemical physics aspects of their interaction with other atoms or molecules constitute an interesting topic for molecular physics. While atomcules may resist to million collisions in helium, molecular contaminants such as H2 are likely to destroy them in a single one, down to very low temperatures. In the Born-Oppenheimer framework, we interpret the molecular interaction obtained by ab initio quantum chemical calculations in terms of classical reactive channels, with activation barriers accounting for the experiments carried out in He and H2. From classical trajectory Monte Carlo simulations, we show that the thermalization stage strongly quenches initial populations, thus reduced to a recovered 3 % trapping fraction. This work illustrates the pertinence of chemical physics concepts to the study of exotic processes involving antimatter. New insights into the physico-chemistry of cold interstellar radicals are anticipated.

Sauge, Sébastien

2012-10-01

165

Electronic spectroscopy of NO(Rg)x complexes (Rg=Ne,Ar) via the 4s and 3d Rydberg states

We have employed (2+1) resonance enhanced multiphoton ionization spectroscopy to investigate the 3d and 4s Rydberg states of the NO molecule when bound to the surface of Rgx clusters (Rg=rare gas). We observe that the spectra of the NO-Arx species converge in appearance as x increases, and this is discussed in terms of two Rg atoms interacting with the NO+

Denis E. Bergeron; Adam Musgrave; Victoria L. Ayles; Robert T. Gammon; James A. E. Silber; Timothy G. Wright

2006-01-01

166

Electronic spectroscopy of NO(Rg)x complexes (Rg=Ne,Ar) via the 4s and 3d Rydberg states

We have employed (2+1) resonance enhanced multiphoton ionization spectroscopy to investigate the 3d and 4s Rydberg states of the NO molecule when bound to the surface of Rgx clusters (Rg=rare gas). We observe that the spectra of the NOArx species converge in appearance as x increases, and this is discussed in terms of two Rg atoms interacting with the NO+

Denis E. Bergeron; Adam Musgrave; Victoria L. Ayles; Robert T. Gammon; James A. E. Silber; Timothy G. Wright

2006-01-01

167

Ground-state energetics of helium and deuterium fermion fluids

NASA Astrophysics Data System (ADS)

The method of correlated basis functions (CBF) is applied to the evaluation of the ground-state energy of atomic fermion fluids as a function of density. As a first step, liquid 3He in both unpolarized and fully polarized spin configurations is considered variationally, using Slater-Jastrow trial wave functions. Results are reported for a conventional analytic choice of the state-independent two-body correlation function f(r) and for the optimal f(r) determined by the solution of a suitable Euler equation. The Jastrow treatment is found to be inadequate in that (i) the energy expectation value lies above the experimental equilibrium energy by some 1.5 K, and (ii) the polarized phase is predicted to be more stable than the unpolarized one. For a given polarization, a correlated basis is formed by application of the assumed Jastrow correlation factor to the elements of a complete set of noninteracting-Fermi-gas Slater determinants. The exact ground-state energy may be developed in a perturbation expansion in the correlated basis, the leading term being the Jastrow energy expectation value. Considerable improvement on the Jastrow description of the unpolarized phase is achieved upon inclusion of the correlated two-particle-two-hole component of the second-order CBF perturbation correction. At the experimental equilibrium density, this contribution, which incorporates important momentum- and spin-dependent correlations, can amount to some 0.6-1.1 K [depending on the choice of f(r)]. The required correlated-basis matrix elements are calculated by Fermi hypernetted-chain (FHNC) techniques, crucial Pauli effects of the elementary diagrams being introduced through the FHNC/C algorithm. The Euler equation is approximated within the same framework. The momentum-space integrations in the second-order perturbation correction are evaluated by a Monte Carlo procedure. One may reasonably expect that further refinements of the CBF method will lead to an accurate microscopic description of the ground-state energetics of liquid 3He. Bulk atomic deuterium with all electronic spins aligned is treated at the same level of approximation as applied to helium. Three choices of nuclear-spin distribution are examined, with a single spin state present, or two or three equally populated nuclear spin states. The finite-density energy minimum is found to lie very close to zero energy in all three examples; a very precise many-body calculation will thus be needed to decide their liquid or gaseous nature at zero temperature under zero external pressure.

Krotscheck, E.; Smith, R. A.; Clark, J. W.; Panoff, R. M.

1981-12-01

168

NASA Astrophysics Data System (ADS)

The Stark spectra of autoionizing Rydberg states of Xe converging to the second ionization limit 5p5 2P1/2 have been investigated as a function of applied electric field over the range 26-2362 V/cm. Single-photon excitation from the Xe ground state was achieved using coherent radiation near 92.5 nm, generated by frequency tripling the pulsed output of a frequency-doubled dye laser in a free jet of rare-gas atoms. For the lowest electric field only the ns' and nd' series were observed. As the electric field was increased the np' series appeared because of the mixing of wave functions with different l values. Further increase of the electric field caused the appearance of hydrogenlike Stark manifolds. The Stark spectrum was simulated in a two-step procedure with no adjustable parameters. Using a jl-coupling basis set the Hamiltonian matrix was diagonalized to determine the energy levels and corresponding eigenfunctions for a given electric field strength. The intensities and line shapes were then calculated using the formalism developed by Fano for a many-discrete-level-single-continuum configuration interaction. This treatment was sufficient to reproduce the positions, widths, and shapes of most observed features. At field strengths between 1000 and 2000 V/cm, however, an additional modulation structure with a spacing of about 2.7 cm-1 appeared on top of the ||M||=1 autoionizing resonances, which could not be explained by our simple theoretical model.

Ernst, W. E.; Softley, T. P.; Zare, R. N.

1988-06-01

169

Two-Electron Excitation of an Interacting Cold Rydberg Gas

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

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

2010-11-19

170

NASA Astrophysics Data System (ADS)

The dynamics a model Rydberg atom prepared initially in a mixed state is investigated in a classical laser field. The possibility of interference stabilization regime is studied and the influence of parameters of initial mixed state on the ionization process is analyzed. In the case when initial atomic mixed state is formed due to entanglement with few-photon non-classical light the possibility to extract the information about initial atomic density matrix from the atomic behavior in the further applied classical laser field is discussed.

Sharapova, P. R.; Tikhonova, O. V.

2014-04-01

171

NASA Astrophysics Data System (ADS)

The binding energies of high-L Rydberg levels of Pb+ 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+, and analyzed with the long-range polarization model, these determined the polarizability of the 5d106s2 ground state of Pb2+ to be ?d = 13.62(8) a.u. This value is substantially larger than the estimate published recently based on the measured lifetime of the 6s6p1P1 resonance level of Pb2+, 7.9(6) a.u. The difference is mostly due to the polarizability of Pb4+, the 5d10 core of the Pb2+ ion. This was established by observation of resolved fine structure in the excitation of n=39, high-L Rydberg levels of Pb3+, using the same RESIS technique. Analysis of this spectra determined the polarizability of Pb4+ to be ?d = 3.61(4) a.u. Reanalysis of optical spectra of nh and ng levels in Pb+ and Pb3+ in view of the polarizabilities determined in the RESIS studies indicates revised ionization energies of both ions, EI(Pb+) = 121245.28(6) cm-1 and EI(Pb3+) = 341 435.1(8) cm-1.

Hanni, M. E.; Keele, Julie A.; Lundeen, S. R.; Fehrenbach, C. W.; Sturrus, W. G.

2010-04-01

172

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

173

Robust Rydberg-interaction gates with adiabatic passage

NASA Astrophysics Data System (ADS)

We show that with adiabatic passage, one can reliably drive two-photon optical transitions between the ground states and interacting Rydberg states in a pair of atoms. For finite Rydberg-interaction strengths an adiabatic pathway towards the doubly Rydberg excited state is identified when a constant detuning is applied with respect to an intermediate optically excited level. The Rydberg interaction among the excited atoms provides a phase that may be used to implement quantum gate operations on atomic ground-state qubits.

Rao, D. D. Bhaktavatsala; Mřlmer, Klaus

2014-03-01

174

Electron Capture Process in Collisions of Proton with Excited State of Helium

NASA Astrophysics Data System (ADS)

Total and state-selective cross sections for single electron capture (SEC) from then = 2 excited state of helium colliding by protons are calculated in the energy range of 1.0-100.0keV/u by using the two-center atomic orbital close-coupling method. The interaction of the active electron with helium ion is represented by a model potential. Total SEC cross sections show a monotonic decreasing trend with increasing collision energy, and display a different behavior compared with the case from the ground state of helium. It is also found that the dominant reaction channel is captured to the H(2p) state up to 40keV/u, and then the capture to the H(1s) or H(2s) state becomes more pronounced. Moreover, the alignment dependence on the initial states is obtained for the electron capture from He(2p0) and He (2p1).

Wang, Xue-Rong; Liu, Ling; Wang, Jian-Guo

2010-12-01

175

Summary form only given. The equation of state and opacity of warm dense helium (1

helium are sparse, and in particular none exist in

J. Eggert; P. Celliers; G. Collins; D. Hicks; S. Brygoo; P. Loubeyre; R. Jeanloz; R. McWilliams; T. Boehly

2005-01-01

176

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

177

NASA Astrophysics Data System (ADS)

We demonstrate that the frequency-selected enhancement of high-order-harmonic generation (HHG) can be achieved by a few-cycle laser pulse interacting with a coherent superposition state, which is prepared by the ground state and two degenerate Rydberg states. The degenerate states have the same orbital radius and hence have a large overlap in the electronic density distribution. By controlling the relative phase between the two degenerate states, the constructive or destructive interference of them can markedly change the initial density distribution of the Rydberg electron, thereby we can manipulate the characteristics and the conversion efficiency of HHG. Specifically, a significant enhancement in the continuous harmonics near HHG cutoff can be obtained, hence an intense isolated pulse with a duration less than 100 attoseconds is straightforwardly generated. On the other hand, since there exists a specific dependence of the harmonic efficiency on the relative phase of the two degenerate states, one can expect that the relative phase may be probed by examining the corresponding harmonic intensity. In practice, we may apply a weak static electric field in the whole dynamic process to obtain an asymmetry electron density distribution at a large radius; hence similar HHG results can be obtained.

Chen, Jigen; Wang, Ruquang; Zhai, Zhen; Chen, Jing; Fu, Panming; Wang, Bingbing; Liu, Wu-Ming

2012-09-01

178

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

179

Ionization of Rydberg atoms by blackbody radiation

NASA Astrophysics Data System (ADS)

We have studied ionization of alkali-metal Rydberg atoms by blackbody radiation (BBR). The results of theoretical calculations of ionization rates of Li, Na, K, Rb and Cs Rydberg atoms are presented. The calculations have been performed for nS, nP and nD states for principal quantum numbers n=8-65 at ambient temperatures of 77, 300 and 600 K. The calculations take into account the contributions of BBR-induced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of the measured ionization rates and their n dependence. A Cooper minimum for BBR-induced transitions between bound Rydberg states of Li has been found. The calculated ionization rates are compared with our earlier measurements of BBR-induced ionization rates of Na nS and nD Rydberg states with n=8-20 at 300 K. Good agreement for all states except nS with n>15 is observed. Useful analytical formulae for quick estimates of BBR ionization rates of Rydberg atoms are presented. Application of BBR-induced ionization signal to measurements of collisional ionization rates is demonstrated.

Beterov, I. I.; Tretyakov, D. B.; Ryabtsev, I. I.; Entin, V. M.; Ekers, A.; Bezuglov, N. N.

2009-01-01

180

National Technical Information Service (NTIS)

Two color, 1 + 1, mass resolved excitation spectroscopy (MRES) is used to obtain molecular Rydberg (3s left arrow n) spectra of azabicyclo(2.2.2)octane (ABCO) and diazabicyclo(2.2.2)octane (DABCO) clustered with argon. Nozzle/laser timing delay studies ar...

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

1993-01-01

181

Complete active space self-consistent field (CASSCF) and multireference CI with singles and doubles (MR-CISD) calculations [including extensivity corrections, at MR-CISD+Q and multireference averaged quadratic coupled cluster (MR-AQCC) levels] have been performed to characterize the low-lying valence and the Rydberg states of 2H-tetrazole. The highest level results (MR-AQCC/d'-aug'-cc-pVDZ) indicate the following ordering of the valence singlet excited states: S(1) (n-pi*), 6.06 eV; S(2) (n-pi*), 6.55 eV; S(3) (pi-pi*), 6.55 eV. The MR-CISD+Q/d'-aug'-cc-pVDZ results indicate the same ordering, but at slight higher energies: 6.16, 6.68, and 6.69 eV, respectively. According to our MR-CISD+Q/d'-aug'-cc-pVDZ results, the next two states are Rydberg states, at 7.69 eV (pi-3s) and 7.89 eV (n-3s). The calculated energies of these two states, as well as their proximity, are consistent with the conclusion reached by Palmer and Beveridge (Chem Phys 1987, 111, 249) that the first band of the photoelectron spectrum of 2H-tetrazole is likely to be associated to the first two ionizations processes (of pi and N lone pair electrons), at energies close to 11.3 eV. PMID:18942735

de Souza, Miguel A F; Ventura, Elizete; Araújo, Regiane C M U; Ramos, Mozart N; do Monte, Silmar A

2009-05-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

183

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

184

Efficient Grover search with Rydberg blockade

NASA Astrophysics Data System (ADS)

We present efficient methods to implement the quantum computing Grover search algorithm using the Rydberg blockade interaction. We show that simple ?-pulse excitation sequences between ground and Rydberg excited states readily produce the key conditional phase shift and inversion-about-the-mean unitary operations for the Grover search. Multi-qubit implementation schemes suitable for different properties of the atomic interactions are identified and the error scaling of the protocols with system size is found to be promising for experimental investigation.

Mřlmer, Klaus; Isenhower, Larry; Saffman, Mark

2011-09-01

185

The Excitation of the Ground State of Helium to the 2(1)p State by Fast Electrons.

National Technical Information Service (NTIS)

The first Born approximation is used to calculate the cross section for electron excitation of the ground state of helium to the 2(1)P state. Various ground- and excited-state wave functions are employed and the calculations are performed using both the l...

D. J. Kennedy A. E. Kingston

1967-01-01

186

NASA Astrophysics Data System (ADS)

The 3p?uD 3?u+ Rydberg state of N2 is studied experimentally using two high-resolution spectroscopic techniques. First, the forbidden D 3?u+-X 1?g+ transition is observed for the first time via the (0,0) band of 14N2 and the (1,0) band of 15N2, using 1 extreme-ultraviolet +1 ultraviolet two-photon-ionization laser spectroscopy. Second, the Rydberg-Rydberg transition D 3?u+-E 3?g+ is studied using near-infrared diode-laser photoabsorption spectroscopy, thus extending the previous measurements of Kanamori et al. [J. Chem. Phys. 95, 80 (1991)], to higher transition energies, and thereby revealing the (2,2) and (3,3) bands. The combined results show that the D(v=0-3) levels exhibit rapidly increasing rotational predissociation as v increases, spanning nearly four orders of magnitude. The D-state level structure and rotational predissociation signature are explained by means of a coupled-channels model which considers the electrostatically coupled 3?u Rydberg-valence manifold, together with a pure-precession L-uncoupling rotational interaction between the 3p?uD 3?u+ and 3p?uG 3?u Rydberg p-complex components.

Lewis, B. R.; Baldwin, K. G. H.; Heays, A. N.; Gibson, S. T.; Sprengers, J. P.; Ubachs, W.; Fujitake, M.

2008-11-01

187

NASA Astrophysics Data System (ADS)

We develop practical formulas for the calculation of the matrix elements of the interaction of the electromagnetic field with an atomic state, beyond the long-wavelength approximation. The atom-plus-field Hamiltonian is chosen to have the multipolar form, containing the electric, paramagnetic, and diamagnetic operators. The final workable expressions include the interactions to all orders and are derived by first expanding the fields in partial waves. The electric-field operator reaches a constant value as the radial variable becomes large, contrary to the result of the electric-dipole approximation (EDA) where the value of the corresponding operator increases indefinitely. Applications are given for Rydberg states of hydrogen up to n=50 and for free-free transitions in a Coulomb potential. Such matrix elements are relevant to a number of real and virtual processes occurring during laser-atom interactions. The computation is done numerically, using a combination of analytic with numerical techniques. By comparing the results of the EDA with those of the exact treatment, it is shown that the former is inadequate in such cases. This finding has repercussions on the theory and understanding of the physics of quantum systems in high-lying Rydberg levels and wave packets or in scattering states.

Komninos, Yannis; Mercouris, Theodoros; Nicolaides, Cleanthes A.

2002-04-01

188

NASA Astrophysics Data System (ADS)

Velocity map photoelectron imaging was used to study the photoionization of Xe2 in several low-lying 5d and 6p Rydberg states. The Rydberg states were prepared by two-photon excitation and ionized by either one additional photon from the pump laser (2+1 ionization), or by one photon of a second color (2+1' ionization). The 2+1 images and associated photoelectron spectra were consistent with previous results, although some adjustment of previously proposed equilibrium bond lengths was necessary to fit the spectra with Franck-Condon factor calculations. The 2+1' images provided higher resolution photoelectron spectra and, in conjunction with the Xe2+ potentials reported by Zehnder and co-workers [J. Chem. Phys. 128, 234306 (2008)] and the 6p and 5d Xe2* potentials calculated by Jonin and Spiegelmann [J. Chem. Phys. 117, 3059 (2002)], provided a means for improving the Xe2* potentials. New experimental data are also presented for photoionization populating the Xe2+ I(1/2g) state, and are used to provide a better description of its potential curve.

Shubert, V. Alvin; Pratt, Stephen T.

2011-01-01

189

How to excite and control a particular state in a Hamiltonian system without a feedback and using a perturbation? A solution to this problem by passage through resonances and adiabatic synchronization is discussed. The idea is based on capturing the system into persistent (auto-) resonance with chirped frequency driving perturbations such that the driving amplitude exceeds a threshold. Among other

Lazar Friedland

2005-01-01

190

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

191

{alpha}{sup 4}R corrections to singlet states of helium

Corrections of order {alpha}{sup 4}R are calculated for the singlet states 1 {sup 1}S{sub 0} and 2 {sup 1}S{sub 0} of the helium atom. The result for the 1 {sup 1}S{sub 0} state is in slight disagreement with that of Korobov and Yelkhovsky [Phys. Rev. Lett. 87, 193003 (2001)]. The results obtained lead to a significant improvement of the transition frequencies between low-lying levels of the helium atom. In particular theoretical predictions for the 2 {sup 1}S{sub 0}-1 {sup 1}S{sub 0} transition are found to be in disagreement with experimental values.

Pachucki, Krzysztof [Institute of Theoretical Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland)

2006-08-15

192

Hyperfine-Structure Measurements in the Rydberg S and P States of Rubidium and Cesium.

National Technical Information Service (NTIS)

The hyperfine structure in many highly-excited S and P states of Rb87 and Cs133 is measured. The results for the magnetic-dipole coupling constants are, in MHz, for Rb87: A(10(2)S sub 1/2) = 56.3(2), A(11(2)S sub 1/2) = 37.4(3); and for Cs133: A(9(2)S sub...

J. Farley P. Tsekeris R. Gupta

1976-01-01

193

EDITORIAL: Special issue on Rydberg physics

NASA Astrophysics Data System (ADS)

Atoms and molecules in highly excited electronic states ('Rydberg atoms') have been the object of broad scientific research for almost a century. Despite this long history, the field of research has never lost its buoyancy, and recent years in particular have seen a tremendous revival of interest in the physics of Rydberg atoms and molecules from many different perspectives. Rydberg systems touch a wide range of research areas including, among others, ultralong-range molecules, artificial ('designer') atoms, quantum chaos, quantum information, ultracold Rydberg gases and plasmas, and anti-hydrogen formation. Due to the many fields involved, the physical insight and technical know-how are scattered over different communities. The goal of this special issue is to provide an integral overview of the latest developments in this highly innovative research field and to make the physical knowledge available to a wide audience. Groups from various fields of atomic, molecular and optical physics as well as condensed matter and plasma physics have contributed to this issue, which therefore spans a wide range of areas connected through the common theme: 'Rydberg physics'. This name was given to a four-week International Workshop and Seminar which was held from 19 April to 14 May 2004 at the Max-Planck-Institut für Physik Komplexer Systeme in Dresden, Germany, and organized by the three of us. The workshop and seminar programme was a very successful mixture of topics bringing together colleagues working in different but related areas of research centred about the physics of highly excited Rydberg atoms and molecules. We would like to take this opportunity to express our gratitude to the organization team of the MPI-PKS Dresden, especially the Director, Jan-Michael Rost, and the Visitors' Programme coordinator, Mandy Lochar. The generous support of the Max Planck Society, which made this successful workshop and seminar possible, is also gratefully acknowledged. Inspired by the great response to the 'Rydberg physics' conference we thought that it would be timely and appropriate to recognize the importance of Rydberg physics with a special issue of a scientific journal. The 'unbureaucratic' and highly efficient editorial and publishing team of Journal of Physics B: Atomic, Molecular and Optical Physics (J. Phys. B) allowed this to become a reality; it was a real pleasure for us to serve as guest editors. Unlike a conventional conference proceedings, this special issue has not been restricted to participants of the 'Rydberg physics' conference, and all the original papers contained in it have been peer-reviewed to the usual high standards of J. Phys. B. The variety and integrated discussion on the physics of Rydberg systems during the 'Rydberg physics' conference is reflected in the papers presented here. We have tried to group the papers according to the subject areas which are addressed. The first part of this special issue is devoted to high-resolution spectroscopy revealing deeper insights into the structure of Rydberg atoms and molecules as well as electronic interaction processes. The second part contains experimental and theoretical investigations on the influence of external static and oscillatory fields on Rydberg atoms. The third part takes account of the newly established field of ultracold Rydberg gases and plasmas with special emphasis on the appearance of ultralong-range interactions in these systems. Finally, the issue is concluded by articles on new developments including 'exotic' Rydberg systems. We would like to thank all of the participants of the 'Rydberg physics' workshop and seminar, and, in particular, the contributors to this special collection of papers, for their involvement. We are deeply indebted to the J. Phys. B editorial and publishing team both for making its realization possible in an extremely efficient way, and for the journal's commitment to the physics of Rydberg systems. We are impressed by the continuing progress in this fascinating and rapidly growing field of research and we look forward to many

Côté, Robin; Pattard, Thomas; Weidemüller, Matthias

2005-01-01

194

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. PMID:17930435

Mayle, Michael; Hezel, Bernd; Lesanovsky, Igor; Schmelcher, Peter

2007-09-14

195

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

196

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

197

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

198

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`.

199

Excited-state relaxation of Ag8 clusters embedded in helium droplets.

Neutral silver clusters Ag(N) are grown in ultracold helium nanodroplets. By exploiting a strong absorption resonance recently found for Ag8, first photoelectron spectra of this neutral species are recorded. Variation of the laser photon energy reveals that direct vertical two-photon ionization is hindered by rapid relaxation into the lower edge of a long-living excited state manifold. The analysis of the dynamics gives a precise value of (6.89+/-0.09) eV for the vertical ionization potential of Ag8. The influence of the helium matrix on photoemission is discussed. PMID:15169149

Radcliffe, Paul; Przystawik, Andreas; Diederich, Thomas; Döppner, Tilo; Tiggesbäumker, Josef; Meiwes-Broer, Karl-Heinz

2004-04-30

200

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

201

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

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

2013-10-15

202

Electromagnetically induced transparency and fluorescence in blockaded Rydberg atomic system.

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

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

2013-10-28

203

Measurement of the lifetime of excited-state electron bubbles in superfluid helium

We report on the measurement of the lifetime of bubbles in superfluid helium that contain an electron in the 1P state. The 1P bubbles are produced by laser excitation of ground-state bubbles, and are detected by ultrasonic cavitation. Our measurements show that the lifetime of these excited bubbles is much less than the calculated lifetime for radiative decay and, hence, is determined by a nonradiative mechanism.

Ghosh, Ambarish; Maris, Humphrey J. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States)

2005-08-01

204

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

205

Light-induced states in attosecond transient absorption spectra of laser-dressed helium

NASA Astrophysics Data System (ADS)

Laser-dressed absorption in atomic helium is studied, both theoretically and experimentally, by transient absorption spectroscopy using isolated 400-as pulses centered at 22 eV and 12-fs near-infrared (NIR) pulses with 780-nm central wavelength. Multiple features in the helium singly excited bound-state spectrum are observed only when the NIR and attosecond pulses are overlapped in time. Theoretical analysis indicates that these light-induced structures (LISs) are the intermediate states in resonant, second-order processes that transfer population to multiple dipole forbidden states. The use of broadband, coherent extreme ultraviolet (XUV) radiation allows observation of these LISs without specifically tuning to a two-photon resonance, as would be required with narrowband XUV light. The strength and position of the LISs depend strongly on the NIR intensity and the pump-probe delay.

Chen, Shaohao; Bell, M. Justine; Beck, Annelise R.; Mashiko, Hiroki; Wu, Mengxi; Pfeiffer, Adrian N.; Gaarde, Mette B.; Neumark, Daniel M.; Leone, Stephen R.; Schafer, Kenneth J.

2012-12-01

206

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

207

CASSCF and MR-CISD study of the n-4s and n-4pe Rydberg states of the CF3Cl

NASA Astrophysics Data System (ADS)

The low-lying n-4s (S2 and T2) and n-4pe (S3 and T3) Rydberg states of the CF3Cl have been studied at the CASSCF, MR-CISD, MR-CISD + Q and MR-AQCC levels using the mixed aug-cc-pVDZ/d-aug-cc-pVDZ and aug'-cc-pVTZ/d'-aug'-cc-pVTZ basis sets. Spin-orbit corrections for the singlet energies, vertical excitation energies and oscillator strengths have been computed. The effect of the inclusion of K + L or only the K inner shell chlorine orbitals in the frozen core space at the post-CASSCF levels has also been discussed. Good agreement with available experimental and with previous high-level theoretical results has been achieved.

de Medeiros, Vanessa C.; Ventura, Elizete; do Monte, Silmar A.

2012-09-01

208

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

209

Production and trapping of cold circular Rydberg atoms

NASA Astrophysics Data System (ADS)

Cold circular Rydberg atoms are produced and magnetically trapped. The trap is characterized by direct spatial imaging of ion distributions, ion counting, and state-selective field ionization. At room temperature, we observe about 70% of the trapped atoms remaining after 6 ms. We measure a trap oscillation frequency increase of the circular Rydberg atom trap relative to the ground-state atom trap due to the larger magnetic moment of the circular Rydberg atoms. Simulations of the center-of-mass and internal-state evolution of circular states in our magnetic trap are performed and results are in good agreement with experimental observations.

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

2013-09-01

210

Debye equation of state for fluid helium-3.

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

Huang, Yonghua; Chen, Guobang; Arp, Vincent

2006-08-01

211

Spin Squeezing in a Rydberg Lattice Clock

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

212

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

213

Ionization of Rydberg H2 molecules at doped silicon surfaces

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

214

Collisons of Rydberg atoms with neutral particles

The results of theoretical investigations of the excitation, quenching, ionization and broadening of the Rydberg atomic levels in inelastic collisions with ground-state atoms of buffer or parent gases are presented. The different physical mechanisms of these processes due to the scattering of the perturbing neutral particle on the quasifree electron and on the core of the Rydberg atom are considered. In particular the role of the potential and resonance scattering of the slow electron on the perturbing atoms in the quenching and broadening processes is discussed. The effects of the nonadiabatic transfer of the Rydberg electron energy to the kinetic energy of the colliding atoms and to the energy of the electronic shell of the quasimolecular ion are also considered. The results of calculations of the cross sections and the rate constants of the quenching, boradening and ionziation processes for some physcial systems are presented and are compared with available experimental data.

Lebedev, V.S. (P. N. Levedev Physical Institute, Academy of Sciences of the USSR, 53, Leninsky prospect, Moscow (USSR))

1990-06-01

215

Radiative and Relativistic Effects in the Decay of Highly-Excited States in Helium

NASA Astrophysics Data System (ADS)

A recent experimental study(J.- E. Rubensson, C. Sĺthe, S. Cramm, B. Kessler, S. Stranges, R. Richter, M. Alagia, and M. Coreno, Phys. Rev. Lett. 83), 947 (1999) measured a significant fluorescence yield of the He(2l n l^') photoexcited resonances, showing major qualitative differences from non-relativistic predictions. We present a further theoretical analysis of these states, and perform detailed R-matrix multichannel quantum defect theory calculations, including radiative optical potential and spin-orbit frame transformation methods, to extract fluorescence and ionization cross sections, giving results in excellent agreement with new, higher-resolution measurements. The principal effect of the spin-orbit operator has been quantified as an oscillatory perturbation below threshold, causing strong mixing between all seven 2l nl^' J=1 resonance series, and redistribution of fluorescence and ionization cross sections at regular intervals. These results should be applicable for highly-excited states in general, whenever there are multiple Rydberg series capable of interacting, and emphasize that careful consideration of radiative and relativistic effects is necessary to characterize threshold spectra.

Gorczyca, Thomas W.

2000-06-01

216

Following our work on the study of helium droplets and film doped with one electronically excited rubidium atom Rb(?) ((2)P) [M. Leino, A. Viel, and R. E. Zillich, J. Chem. Phys. 129, 184308 (2008)], we focus in this paper on the second excited state. We present theoretical studies of such droplets and films using quantum Monte Carlo approaches. Diffusion and path integral Monte Carlo algorithms combined with a diatomics-in-molecule scheme to model the nonpair additive potential energy surface are used to investigate the energetics and the structure of Rb(?)He(n) clusters. Helium films as a model for the limit of large clusters are also considered. As in our work on the first electronic excited state, our present calculations find stable Rb(?)He(n) clusters. The structures obtained are however different with a He-Rb(?)-He exciplex core to which more helium atoms are weakly attached, preferentially on one end of the core exciplex. The electronic absorption spectrum is also presented for increasing cluster sizes as well as for the film. PMID:21241108

Leino, Markku; Viel, Alexandra; Zillich, Robert E

2011-01-14

217

Plasma formation from ultracold Rydberg gases

Recent experiments have demonstrated the spontaneous evolution of a gas of ultracold Rydberg atoms into an expanding ultracold plasma, as well as the reverse process of plasma recombination into highly excited atomic states. Treating the evolution of the plasma on the basis of kinetic equations, while ionization/excitation and recombination are incorporated using rate equations, we have investigated theoretically the Rydberg-to-plasma transition. Including the influence of spatial correlations on the plasma dynamics in an approximate way, we find that ionic correlations change the results quantitatively but not qualitatively.

Pohl, T.; Pattard, T.; Rost, J. M. [MPI for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden, (Germany)

2003-07-01

218

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

219

NASA Technical Reports Server (NTRS)

High-quality ab initio electronic structure calculations have been performed on the 2D Rydberg series in Al I. The configuration 3s3p2(2D) is shown to contribute substantially to the lowest four 2D Rydberg states. The same configuration also contributes substantially to a 2D state embedded in the ionization continuum. Computed oscillator strengths for the first six members of the 2D Rydberg transitions are given: these should be of substantially higher accuracy than currently available values.

Taylor, Peter R.; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

1988-01-01

220

NASA Technical Reports Server (NTRS)

High quality ab initio electonic structure calculations were performed on the 2D Rydberg series in Al I. The configuration 3s3p2(2D) is shown to contribute substantially to the lowest four 2D Rydberg states. The same configuration also contributes substantially to a 2D state embedded in the ionization continuum. Computed oscillator strengths for the first six members of the 2D Rydberg transitions are given: these should be of substantially high accuracy than currently available values.

Taylor, Peter R.; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

1987-01-01

221

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

222

NASA Astrophysics Data System (ADS)

An exact spin-dependent localized Hartree-Fock (LHF) exchange potential is derived for both close-shell and open-shell of atomic systems. The LHF exchange potential is free of the Coulomb self-interaction, has the correct long-range behavior, requires only the occupied orbitals, and thus implies the requirements for the investigation of the excited states. An effective procedure of the exact exchange density-functional theory (DFT), the spin-polarized LHF density-functional method, is presented based on the LHF exchange potential for the multiply excited states of the atomic systems. This method is applied to the calculations of singly, doubly, and especially triply excited Rydberg states of He- and Li- like ions. The exchange-only (X-only) results are found to be surprisingly close to those of the Hartree-Fock (HF) method. The correlation effects are considered by incorporating the Lee-Yang-Parr (LYP) correlation potential into the LHF exchange potential. The results are in overall agreement with the available theoretical and experimental data in light of the typical errors of the DFT calculations of the excited states.

Zhou, Zhongyuan; Chu, Shih-I.

2004-05-01

223

Muon transfer from ground state deuterium to helium nuclei and its temperature dependence

NASA Astrophysics Data System (ADS)

The energy and time distributions of the decay X-rays of excited, metastable, molecular (dľHe)*-resonances were measured. The comparison of the observed energy spectra with calculated ones suggests that decay from the rotational state J = 1 dominates at the investigated conditions. The muon transfer rates from ground state deuterium to the helium isotopes 3He and 4He at low temperatures were determined from the time distributions of these spectra. Additionally, the temperature dependence of the muon transfer rate was clearly established in deuterium / 4He mixtures.

Gartner, B.; Ackerbauer, P.; Augsburger, M.; Breunlich, W. H.; Cargnelli, M.; Chatellard, D.; Egger, J.-P.; von Egidy, T.; Hartmann, F. J.; Jacot-Guillarmod, R.; Jeannet, E.; Kammel, P.; King, R. C.; Kosak, A.; Lauss, B.; Marton, J.; Mühlbauer, M.; Mulhauser, F.; Petitjean, C.; Piller, C.; Prymas, W.; Schaller, L. A.; Schellenberg, L.; Schneuwly, H.; Schott, W.; Thalmann, Y. A.; Tresch, S.; Werthmüller, A.; Zmeskal, J.

1999-06-01

224

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

225

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

226

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

227

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

228

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of H{sub 2} molecules. By selectively shortening the lifetimes of states with higher principal quantum number n as compared to those of lower n, this method for the first time provides access to all initially populated metastable states of {ital {bar p}}He{sup +} atoms. This was demonstrated by observing the transitions (n,l)=(38,l){r_arrow}(39,l+1), l=35,36,37 and (n,l)=(37,l){r_arrow}(38,l+1), l=34,35,36. {copyright} {ital 1997} {ital The American Physical Society}

Ketzer, B.; Hartmann, F.; von Egidy, T.; Maierl, C.; Pohl, R. [Physik-Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)] [Physik-Department, Technische Universitaet Muenchen, D-85747 Garching (Germany); Eades, J.; Widmann, E.; Yamazaki, T. [CERN, CH-1211 Geneva 23 (Switzerland)] [CERN, CH-1211 Geneva 23 (Switzerland); Kumakura, M.; Morita, N. [Institute for Molecular Science, Myodaiji, Okazaki 444 (Japan)] [Institute for Molecular Science, Myodaiji, Okazaki 444 (Japan); Hayano, R.; Hori, M.; Ishikawa, T.; Torii, H. [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 (Japan)] [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 (Japan); Sugai, I. [Institute for Nuclear Study, University of Tokyo, 3-2-1 Midori-cho, Tanashi, Tokyo 188 (Japan)] [Institute for Nuclear Study, University of Tokyo, 3-2-1 Midori-cho, Tanashi, Tokyo 188 (Japan); Horvath, D. [Central Research Institute for Physics, Research Institute for Particle and Nuclear Physics, H-1525 Budapest (Hungary)] [Central Research Institute for Physics, Research Institute for Particle and Nuclear Physics, H-1525 Budapest (Hungary)

1997-03-01

229

NASA Astrophysics Data System (ADS)

The low energy electron impact cross sections of helium from some low excited states are calculated in the R-matrix method. The convergences of the cross sections are checked systematically by using 5 sets of high quality target states; i.e., 5, 11, 19, 29 and 39 physical target states.

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

2014-04-01

230

C-NOT gate based on ultracold Rydberg atom interactions

NASA Astrophysics Data System (ADS)

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

Rashid, Muhammad; Maarten, Hoogerland; Yasir, Jamil

2013-11-01

231

Photon mediated transport and crystallization in optically driven Rydberg gases

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

232

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

233

Guiding of Rydberg atoms in a high-gradient magnetic guide

NASA Astrophysics Data System (ADS)

We study the guiding of 87Rb 59D5/2 Rydberg atoms in a linear, high-gradient, two-wire magnetic guide. Time-delayed microwave ionization and ion detection are used to probe the Rydberg atom motion. We observe guiding of Rydberg atoms over a period of 5 ms following excitation. The decay time of the guided-atom signal is about five times that of the initial state. We attribute the lifetime increase to an initial phase of l-changing collisions and thermally induced Rydberg-Rydberg transitions. Detailed simulations of Rydberg-atom guiding reproduce most experimental observations and offer insight into the internal-state evolution.

Traxler, M.; Sapiro, R. E.; Hempel, C.; Lundquist, K.; Power, E. P.; Raithel, G.

2012-08-01

234

NASA Astrophysics Data System (ADS)

We report a combined experimental and theoretical study of photoionization (PI) of the NO2 molecule into the NO2+ (X 1?g+) ground state and the photodissociation of NO2 into the NO+(1?+) + O-(2P) ion pair. These processes were induced by 10.9 eV-13 eV synchrotron radiation and the products were detected using electron-ion or O--NO+ coincident momentum spectroscopy. The results demonstrate the strong influence of [R*(4b2)-1, nl?i, v2'] Rydberg states vibrationally resolved in the v2' bending modes for both processes. In particular, we emphasize two regions around 11.5 eV and 12.5 eV that were studied in more detail for their relevance to 400 nm multiphoton ionization induced by femtosecond pulses. The photoelectron energy spectra and asymmetry parameters support the existence of two PI mechanisms, as probed with the help of fixed-nuclei frozen-core Hartree-Fock calculations. We found significant deviations from Franck-Condon ionization predictions which may be assigned to vibronic coupling of NO2* states such as that induced by a conical intersection. The limited agreement between theory and experiment, even for the non-resonant processes, indicates the need for calculations that go beyond the approximations used in the current study. Ion pair formation leads to strong vibrational and rotational excitation of the NO+(1?+,v) product, with an ion fragment angular anisotropy depending on both the v2' bending quantum number of the excited parent molecule and the v vibrational level of the fragment.

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

2013-07-01

235

We report a combined experimental and theoretical study of photoionization (PI) of the NO2 molecule into the NO2(+) (X (1)?g(+)) ground state and the photodissociation of NO2 into the NO(+)((1)?(+)) + O(-)((2)P) ion pair. These processes were induced by 10.9 eV-13 eV synchrotron radiation and the products were detected using electron-ion or O(-)-NO(+) coincident momentum spectroscopy. The results demonstrate the strong influence of [R(?)(4b2)(-1), nl?(i), v2(')] Rydberg states vibrationally resolved in the v2(') bending modes for both processes. In particular, we emphasize two regions around 11.5 eV and 12.5 eV that were studied in more detail for their relevance to 400 nm multiphoton ionization induced by femtosecond pulses. The photoelectron energy spectra and asymmetry parameters support the existence of two PI mechanisms, as probed with the help of fixed-nuclei frozen-core Hartree-Fock calculations. We found significant deviations from Franck-Condon ionization predictions which may be assigned to vibronic coupling of NO2(?) states such as that induced by a conical intersection. The limited agreement between theory and experiment, even for the non-resonant processes, indicates the need for calculations that go beyond the approximations used in the current study. Ion pair formation leads to strong vibrational and rotational excitation of the NO(+)((1)?(+),v) product, with an ion fragment angular anisotropy depending on both the v2(') bending quantum number of the excited parent molecule and the v vibrational level of the fragment. PMID:23901984

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

2013-07-28

236

NASA Astrophysics Data System (ADS)

Fluorescence excitation functions produced through photoexcitation of N2 using synchrotron radiation in the spectral region between 80 and 100 nm have been studied. Two broadband detectors were employed to simultaneously monitor fluorescence in the 115-320 nm and 300-700 nm region, respectively. The peaks in the VUV Fluorescence excitation functions are found to correspond to excitation of absorption transitions from the ground electronic state to the Rydberg states of b, cn (with n= 4-9), and o3 of N2. The relative fluorescence production cross sections for the observed peaks are determined. No fluorescence has been produced through excitation of the most dominating absorption features of the b-X transition except the (1,0), (5,0), and (6,0) bands, in excellent agreement with the recent lifetime measurements [1] and theoretical calculations [2]. In addition, fluorescence peaks correlate with the long vibrational progression of the c4 (v = 0-7) has also been observed. Weak fluorescence excitation peaks are also found to correlate with the excitation of the (1,0), (2,0), and (3,0) bands of the o3 VX transition. The present results provide important information for further unraveling of complicated and intriguing interactions among the excited electronic states of N2. Furthermore, solar photon excitation of N2 leading to the production of c4(0) may provide useful data required for evaluation and analysis of dayglow models of the c4(0) issue of the Earth's atmosphere [3]. Detailed results will be presented. This research is based on work supported by NSF grant ATM-0096761. [1] Sprengers, J. P., W. Ubachs, and K. G. H. Baldwin, J. Chem. Phys., 122, 144301 (2005). [2] Lewis, B. R., S. T. Gibson, W. Zhang, H. Lefebvre-Brion, and J.-M. Robbe, J. Chem. Phys., 122, 144302 (2005). [3] e.g., Meier, R. R., Space Sci. Rev., 58, 1 (1991).

Wu, R. C.; Judge, D. L.; Singh, T. S.; Mu, X. L.; Nee, J. B.; Chiang, S. Y.; Fung, H. S.

2006-12-01

237

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

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

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

2009-04-17

238

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

239

Rydberg atoms in hollow-core photonic crystal fibres

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

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

2014-01-01

240

Rydberg atoms in hollow-core photonic crystal fibres.

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

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

2014-01-01

241

Rydberg atoms in low-frequency fields : fundamental aspects and applications

In this thesis we investigate highly excited atoms, so-called Rydberg atoms, in oscillating fields with frequencies from the megahertz to the terahertz domain. The strong interaction of Rydberg atoms with external fields is used to establish a connection between the ionization of Rydberg atoms by radiofrequency fields and the field ionization process of ground-state atoms by high-power laser pulses, which

Andreas Stefan Gürtler

2003-01-01

242

Experiments with bubbles containing electrons in excited states in liquid helium

NASA Astrophysics Data System (ADS)

When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms, which is referred to as an electron bubble. It represents a fine example of a quantum-mechanical particle confined in a potential well. The electron bubble has been the subject of extensive experimental study and its main properties are well understood. However, most of the work in the past has been done with bubbles containing electrons in ground states. We expanded the field of study by investigating the effect of bubbles containing electrons in excited states on cavitation in the liquid. The cavitation of excited-state bubbles was observed for the first time and the magnitude of explosion pressure was in good agreement with theoretical predictions. We also investigated the effect of these bubbles on cavitation over a range of temperatures and pressures. The results depend in a complicated way on these parameters and are not completely understood. In a second series of experiments, we have studied the effect of light on the mobility of electron bubbles. The mobility of ions was measured by a time-of-flight technique over a range of temperatures and pressures and a number of interesting phenomena, such as the trapping of ions into quantized vortices in the liquid, were observed. We then investigated the interaction of light with trapped ions and obtained some quantitative results. We also made an attempt to observe the so called exotic ions which are charged objects with mobility higher then that of electron bubbles. We have also studied the nucleation of bubbles in bubble chambers and proposed a simple model for this process. The theoretical predictions of this model turned out to be in good agreement with experimental results.

Konstantinov, Denis

243

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

244

Observation of the stark-tuned Förster 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 Förster resonance using the Stark effect. The observed resonance line shapes are in good agreement with numerical Monte Carlo simulations. PMID:20366877

Ryabtsev, I I; Tretyakov, D B; Beterov, I I; Entin, V M

2010-02-19

245

Inelastic electron collisions with Rydberg atoms

NASA Astrophysics Data System (ADS)

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.; Myasnikov, M. I.; Smirnov, B. M.

2009-01-01

246

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

247

The Distribution of Angular Correlation in Two-Electron Atoms. I. The 2(1)S State of Helium.

National Technical Information Service (NTIS)

Calculations of the distribution of angular correlation in the 2(1)S state of helium were made for the case of t = 0. The nodal region in the wave function has a marked effect upon angular correlation in that it changes the angular interaction from repuls...

J. P. Tatum

1968-01-01

248

Infrared Detection Using Rydberg Atoms.

National Technical Information Service (NTIS)

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 i...

D. Kleppner

1988-01-01

249

NASA Astrophysics Data System (ADS)

A possible extension (?') of the ? curve of liquid helium beyond the T, p boiling line, i.e., into the region of a metastable liquid state, is examined. The relation between the slope of the ? curve dp/dT? and the sign of the thermal expansion coefficient of liquid helium ap is discussed. Experimental data for ap are analyzed using thermodynamic equations to reveal that the derivative dp/dT? changes sign in the metastable region. As a result, the shape of the ?' extension becomes similar to that of the pressure-shifted Bose-condensation line of an ideal 4He gas. The position of the ?' curve is not entirely arbitrary due to the spinodal nature of stretched liquid helium.

Skripov, Vladimir P.

2000-05-01

250

NASA Astrophysics Data System (ADS)

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

Colombo, Anthony P.; Zhou, Yan; Prozument, Kirill; Coy, Stephen L.; Field, Robert W.

2013-01-01

251

Quantum nonlinear optics using cold Rydberg atoms

NASA Astrophysics Data System (ADS)

Although photons do no a ect each other in vacuum, interactions between individual photons could enable a wide variety of scienti c and engineering applications. Here we report on the creation of a quantum nonlinear medium with large photon-photon interactions at the single photon level. Our approach relies on Electromagnetically Induced Transparency (EIT) techniques, in which individual photons are coherently mapped onto strongly interacting Rydberg atoms. Under EIT conditions, photons traveling in the medium are best described as part-matter part-light quantum particles, called polaritons, which experience long-range interactions through the Rydberg blockade. In particular, we demonstrate coherent photon-photon interactions, akin to those associated with conventional massive particles, paving the way for novel photonics states and quantum simulation with light.

Peyronel, T.; Firstenberg, O.; Liang, Q.-Y.; Gorshkov, A.; Lukin, M. D.; Vuletic, V.

2014-02-01

252

Entangling quantum gate in trapped ions via Rydberg blockade

NASA Astrophysics Data System (ADS)

We present a theoretical analysis of the implementation of an entangling quantum gate between two trapped Ca+ ions which is based on the dipolar interaction among ionic Rydberg states. In trapped ions, the Rydberg excitation dynamics is usually strongly affected by mechanical forces due to the strong couplings between electronic and vibrational degrees of freedom in inhomogeneous electric fields. We demonstrate that this harmful effect can be overcome using dressed states that emerge from the microwave coupling of nearby Rydberg states. At the same time. these dressed states exhibit long-range dipolar interactions which we use to implement a controlled adiabatic phase gate. Our study highlights a route toward a trapped ion quantum processor in which quantum gates are realized independently of the vibrational modes.

Li, Weibin; Lesanovsky, Igor

2014-01-01

253

Impact broadening of Rydberg atomic levels in inelastic collisions with alkali-metal atoms

The theory of impact broadening of the isolated spectral lines of the Rydberg atomic series perturbed by neutral particles is developed within the framework of the impulse approximation. The analysis of the broadening process is based on the consideration of the inelastic nl to n' transitions between highly excited states of the Rydberg atom. The role of the potential and

V. S. Lebedev; V. S. Marchenko

1987-01-01

254

Two-atom Rydberg blockade using direct 6S to nP excitation

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

255

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

256

Feshbach projection approach to study plasma effects on doubly excited autoionizing states in helium

NASA Astrophysics Data System (ADS)

We have implemented a method based on the Feshbach formalism along with an explicitly correlated configuration interaction method to perform a systematic study on the behavior of resonance parameters (energies and lifetimes) of the autoionizing states of plasma-embedded He 1,3Se, 1,3Po, and 1,3De, as a function of the screening strength. In particular, we study the evolution of the lowest states in the series located below the He+(N=2) ionization threshold in the unscreened case. At variance with one-electron atoms (where shape resonance widths vary monotonically with the screening strength) the evolution of the Auger width with respect to screening is found to be different for each series represented by (K,T)A pseudoquantum numbers until resonances merge into the upper electronic continuum, when crossing the He+(2s) threshold. We conclude from our ab initio calculations that, although resonances pertaining to the same (K,T)A series share a similar tendency in their widths against the screening strength, general propensity rules for the robustness of lifetimes, based on the isomorphic series in the (K,T)A classification, cannot be established in plasma-embedded helium.

Ordóńez-Lasso, Andrés Felipe; Cardona, Juan Carlos; Sanz-Vicario, José Luis

2013-07-01

257

The Vacuum Ultraviolet Spectrum of Selenium Hydride. II. Rydberg Transitions

NASA Astrophysics Data System (ADS)

Electronic transitions between Rydberg levels and the ground state in the SeH molecule have been observed in absorption after flash photolysis in the wavelength region 1600 to 1330 Ĺ. Rotational constants have been determined for these Rydberg states as well as for the 2?i ground state. The corresponding transitions for the SeD molecule have also been observed and analysed. The ionisation potential for SeH is estimated to be 9.06 ą 0.01 eV (73 070 ą 100 cm-1).

Bollmark, P.; Lindgren, B.; Sassenberg, U.

1980-01-01

258

Due to strong electron correlation effects and electron coupling with nuclear motion, the molecular inner-valence photoionization is still a challenge in electron spectroscopy, resulting in several interesting phenomena such as drastic changes of angular dependencies, spin-orbit induced predissociation, and complex interplay between adiabatic and nonadiabatic transitions. We investigated the excited electronic states of HCl(+) in the binding energy range 27.5-30.5 eV using synchrotron radiation based high-resolution inner-valence photoelectron spectroscopy with angular resolution and interpreted the observations with the help of ab initio calculations. Overlapping electronic states in this region were disentangled through the analysis of photoelectron emission anisotropies. For instance, a puzzling transition, which does not seem to obey either an adiabatic or a nonadiabatic picture, has been identified at ?28.6 eV binding energy. By this study, we show that ultrahigh-resolution photoelectron spectroscopy with angular selectivity represents a powerful tool to probe the highly excited ionic molecular electronic states and their intricate couplings. PMID:25007894

Patanen, M; Nicolas, C; Linguerri, R; Simőes, G; Travnikova, O; Liu, X-J; Hochlaf, M; Bozek, J D; Miron, C

2014-07-10

259

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

260

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

261

Imaging the evolution of an ultracold strontium Rydberg gas

NASA Astrophysics Data System (ADS)

Clouds of ultracold strontium 5s48s1S0 or 5s47d1D2 Rydberg atoms are created by two-photon excitation of laser-cooled 5s21S0 atoms. The spontaneous evolution of the cloud of low orbital angular momentum (low-?) Rydberg states towards an ultracold neutral plasma is observed by imaging resonant light scattered from core ions, a technique that provides both spatial and temporal resolution. Evolution is observed to be faster for the S states, which display isotropic attractive interactions, than for the D states, which exhibit anisotropic, principally repulsive interactions. Immersion of the atoms in a dilute ultracold neutral plasma speeds up the evolution and allows the number of Rydberg atoms initially created to be determined.

McQuillen, P.; Zhang, X.; Strickler, T.; Dunning, F. B.; Killian, T. C.

2013-01-01

262

Stationary three-dimensional entanglement via dissipative Rydberg pumping

NASA Astrophysics Data System (ADS)

We extend the recent result of a bipartite Bell singlet [A. W. Carr and M. Saffman, Phys. Rev. Lett. 111, 033607 (2013), 10.1103/PhysRevLett.111.033607] to a stationary three-dimensional entanglement between two-individual neutral Rydberg atoms. This proposal makes full use of the coherent dynamics provided by a Rydberg-mediated interaction and the dissipative factor originating from the spontaneous emission of a Rydberg state. The numerical simulation of the master equation reveals that both the target state negativity N (accent="true">???) and fidelity F (accent="true">???) can exceed 99.90%. Furthermore, a steady three-atom singlet state |S3> is also achievable based on the same mechanism.

Shao, Xiao-Qiang; You, Jia-Bin; Zheng, Tai-Yu; Oh, C. H.; Zhang, Shou

2014-05-01

263

NASA Astrophysics Data System (ADS)

Fine structure intervals separating high-L, n=19 levels of Si^+ have been measured using the fast beam RESIS/microwave technique[1]. All intervals between L=9 and L=15 have been measured, and transitions up to the L=18 level have been resolved and used for studies of stray electric fields. The pattern of fine structure intervals is used to determine a precise value of the polarizability of the Mg-like core of this Rydberg system. Significant corrections for Stark shifts due to stray fields are required. The Rydberg ions are formed by charge transfer in a Rb Rydberg target [2] from a beam of Si^2+ ions and selectively detected using a Doppler tuned CO2 laser. [1] R.A. Komara, M.A. Gearba, S.R. Lundeen, and C.W. Fehrenbach, Phys. Rev. A derline 67, 062502 (2003) [2] C.W. Fehrenbach, S.R. Lundeen, and O.L Weaver, Phys. Rev. A derline 51, R910 (1995)

Komara, R. A.; Gearba, M. A.; Lundeen, S. R.; Fehrenbach, C. W.

2004-05-01

264

Photoassociation of long-range nD Rydberg molecules.

We observe long-range homonuclear diatomic nD Rydberg molecules photoassociated out of an ultracold gas of Rb87 atoms for 34?n?40. The measured ground-state binding energies of Rb87(nD+5S1/2) molecular states are larger than those of their Rb87(nS+5S1/2) counterparts, which shows the dependence of the molecular bond on the angular momentum of the Rydberg atom. We exhibit the transition of Rb87(nD+5S1/2) molecules from a molecular-binding-dominant regime at low n to a fine-structure-dominant regime at high n [akin to Hund's cases (a) and (c), respectively]. In the analysis, the fine structure of the nD Rydberg atom and the hyperfine structure of the 5S1/2 atom are included. PMID:24815648

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

2014-04-25

265

Quantum statistics of light transmitted through an intracavity Rydberg medium

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

266

Photoassociation of Long-Range nD Rydberg Molecules

NASA Astrophysics Data System (ADS)

We observe long-range homonuclear diatomic nD Rydberg molecules photoassociated out of an ultracold gas of Rb87 atoms for 34?n ?40. The measured ground-state binding energies of Rb87(nD +5S1/2) molecular states are larger than those of their Rb87(nS +5S1/2) counterparts, which shows the dependence of the molecular bond on the angular momentum of the Rydberg atom. We exhibit the transition of Rb87(nD +5S1/2) molecules from a molecular-binding-dominant regime at low n to a fine-structure-dominant regime at high n [akin to Hund's cases (a) and (c), respectively]. In the analysis, the fine structure of the nD Rydberg atom and the hyperfine structure of the 5S1/2 atom are included.

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

2014-04-01

267

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

2008-01-25

268

Code of Federal Regulations, 2010 CFR

...except for the value of the helium extracted. The United States...necessary for the extraction of helium. The extraction of helium shall not cause substantial delays in the delivery of natural gas produced to the purchaser...

2010-07-01

269

Code of Federal Regulations, 2010 CFR

...except for the value of the helium extracted. The United States...necessary for the extraction of helium. The extraction of helium shall not cause substantial delays in the delivery of natural gas produced to the purchaser...

2009-07-01

270

NASA Astrophysics Data System (ADS)

The relaxation rates of the monopole, magnetic dipole, and electric quadrupole moments have been determined for the 31P state of helium excited by electron impact, The data are determined from atomic lifetimes using linear and circular polarization analyzed radiation with the electron-photon delayed coincidence technique. This has permitted the direct observation of the time dependence of all the off-diagonal elements of the density matrix of the excited state. The implications for atomic state information determined from polarization and angular correlation methods are indicated.

Williams, J. F.; Mikosza, A. G.; Wang, J. B.; Wedding, A. B.

1992-08-01

271

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

NASA Astrophysics Data System (ADS)

We demonstrate spatially resolved, coherent excitation of Rydberg atoms on an atom chip. Electromagnetically induced transparency (EIT) is used to investigate the properties of the Rydberg atoms near the gold-coated chip surface. We measure distance-dependent shifts (~10 MHz) of the Rydberg energy levels caused by a spatially inhomogeneous electric field. The measured field strength and distance dependence is in agreement with a simple model for the electric field produced by a localized patch of Rb adsorbates deposited on the chip surface during experiments. The EIT resonances remain narrow (<4 MHz) and the observed widths are independent of atom-surface distance down to ~20 ?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.; van Linden van den Heuvell, H. B.; Spreeuw, R. J. C.

2010-06-01

272

Slow-light polaritons in Rydberg gases

NASA Astrophysics Data System (ADS)

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

Fleischhauer, Michael

2012-02-01

273

Dipoledipole induced global motion of Rydberg-dressed atom clouds

NASA Astrophysics Data System (ADS)

We consider two clouds of ground-state alkali atoms in two distinct hyperfine ground states. Each level is far off-resonantly coupled to a Rydberg state, which leads to dressed ground states with a weak admixture of the Rydberg state properties. Due to this admixture, for a proper choice of the Rydberg states, the atoms experience resonant dipoledipole interactions that induce mechanical forces acting on all atoms within both clouds. This behaviour is in contrast to the dynamics predicted for bare dipoledipole interactions between Rydberg superatoms, where only a single atom per cloud is subject to dipoledipole induced motion (Möbius et al 2013 Phys. Rev. A 88 012716).

Genkin, M.; Wüster, S.; Möbius, S.; Eisfeld, A.; Rost, J. M.

2014-05-01

274

On the self-shift and broadening of doppler-free Rydberg 2S spectral lines in alkali atoms

The shift and broadening of Doppler-free, two-photon transitions to Rydberg states of alkali atoms are analyzed for the case of Rb in the framework of a molecular approach to collisions of ground state and Rydberg atoms. The overall features of the observed spectra are determined by the electrostatic interactions between the two atoms and are calculated using the impact theory

Yitzhak Rabin; Frank Rebentrost

1982-01-01

275

Spectroscopy of high-L Rydberg levels of nickel

NASA Astrophysics Data System (ADS)

The complex fine structure pattern in high-L ( L > 4) Rydberg levels of nickel were studied using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique. A beam of Ni^+ ions, obtained from a Colutron ion source, captured a single electron from a Rb 9F Rydberg target to become highly excited Rydberg levels of neutral Ni. Levels with n=9 and L=5,6,7, and 8 were excited to n=19 or 20 using a Doppler-tuned CO2 laser, resolving the n=9 fine structure pattern, which consists of six levels for each value of L. Analysis of the pattern using the long-range polarization model determined several properties of the 3d^9 ^2D5/2 ground state of Ni^+, including its permanent quadrupole moment and its scalar and tensor dipole polarizabilities.

Keele, Julie A.; Woods, Shannon L.; Hanni, Mark E.; Voigt, Kristen; Lundeen, Stephen R.

2010-03-01

276

Semianalytical model for nonlinear absorption in strongly interacting Rydberg gases

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

277

Electrometry near a dielectric surface using Rydberg electromagnetically induced transparency

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. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)

2011-08-15

278

Strongly coupled plasmas via Rydberg blockade of cold atoms.

We propose and analyze a new scheme to produce ultracold neutral plasmas deep in the strongly coupled regime. The method exploits the interaction blockade between cold atoms excited to high-lying Rydberg states and therefore does not require substantial extensions of current ultracold plasma experiments. Extensive simulations reveal a universal behavior of the resulting Coulomb coupling parameter, providing a direct connection between the physics of strongly correlated Rydberg gases and ultracold plasmas. The approach is shown to reduce currently accessible temperatures by more than an order of magnitude, which opens up a new regime for ultracold plasma research and cold ion-beam applications with readily available experimental techniques. PMID:23829735

Bannasch, G; Killian, T C; Pohl, T

2013-06-21

279

Strongly Coupled Plasmas via Rydberg Blockade of Cold Atoms

NASA Astrophysics Data System (ADS)

We propose and analyze a new scheme to produce ultracold neutral plasmas deep in the strongly coupled regime. The method exploits the interaction blockade between cold atoms excited to high-lying Rydberg states and therefore does not require substantial extensions of current ultracold plasma experiments. Extensive simulations reveal a universal behavior of the resulting Coulomb coupling parameter, providing a direct connection between the physics of strongly correlated Rydberg gases and ultracold plasmas. The approach is shown to reduce currently accessible temperatures by more than an order of magnitude, which opens up a new regime for ultracold plasma research and cold ion-beam applications with readily available experimental techniques.

Bannasch, G.; Killian, T. C.; Pohl, T.

2013-06-01

280

Strongly Interacting Rydberg Excitations of a Cold Atomic Gas

NASA Astrophysics Data System (ADS)

Highly excited Rydberg atoms have many exaggerated properties. In particular, the interaction strength between such atoms can be varied over an enormous range. In a mesoscopic ensemble, such strong, long-range interactions can be used for fast preparation of desired many-particle states. We generated Rydberg excitations in an ultra-cold atomic gas and subsequently converted them into light. As the principal quantum number n was increased beyond ?70, no more than a single excitation was retrieved from the entire mesoscopic ensemble of atoms. These results hold promise for studies of dynamics and disorder in many-body systems with tunable interactions and for scalable quantum information networks.

Dudin, Y. O.; Kuzmich, A.

2012-05-01

281

All-optical quantum information processing using Rydberg gates.

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

Paredes-Barato, D; Adams, C S

2014-01-31

282

Formation of Antihydrogen Rydberg atoms in strong magnetic field traps

It is shown that several features of antihydrogen production in nested Penning traps can be described with accurate and efficient Monte Carlo simulations. It is found that cold deeply-bound Rydberg states of antihydrogen (H-bar) are produced in three-body capture in the ATRAP experiments and an additional formation mechanism -Rydberg charge transfer-, particular to the nested Penning trap geometry, is responsible for the observed fast (hot) H-bar atoms. Detailed description of the numerical propagation technique for following extreme close encounters is given. An analytic derivation of the power law behavior of the field ionization spectrum is provided.

Pohl, T.; Sadeghpour, H. R. [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States)

2008-08-08

283

Photoionization rates of Cs Rydberg atoms in a 1064-nm far-off-resonance trap

Experimental measurements of photoionization rates of nD{sub 5/2} Rydberg states of Cs (50{<=}n{<=}75) in a 1064-nm far off-resonance dipole trap are presented. The photoionization rates are obtained by measuring the lifetimes of Rydberg atoms produced inside of a 1064-nm far off-resonance trap and comparing the lifetimes to corresponding control experiments in a magneto-optical trap. Experimental results for the control experiments agree with recent theoretical predictions for Rydberg state lifetimes and measured photoionization rates are in agreement with transition rates calculated from a model potential.

Tallant, J.; Booth, D.; Shaffer, J. P. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, Oklahoma 73019 (United States)

2010-12-15

284

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

285

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

NASA Astrophysics Data System (ADS)

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

Topcu, Turker; Derevianko, Andrei

2014-02-01

286

One-dimensional Rydberg gas in a Magneto-Electric Trap

NASA Astrophysics Data System (ADS)

We investigate the possibility to trap and align ultracold Rydberg atoms in the regime where both the (coupled) center of mass and electronic motion of the Rydberg atom are of quantum nature. First we explore the properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap being commonly used in ultracold atomic physics experiments. A computational scheme projecting on a single n-manifold and incorporating an adiabatic separation of the electronic and ultracold center of mass motion is developed. An analysis of the resulting adiabatic potential energy surfaces for the center of mass motion demonstrates the possibility of trapping for a class of large angular momentum electronic states. In a second step 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 here 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 quantum Rydberg gas with a macroscopic interparticle distance. We derive analytical expressions for the electric dipole moment and the required linear density of Rydberg atoms. References: I. Lesanovsky and P. Schmelcher, Phys.Rev.Lett. 95, 053001 (2005)B. Hezel, I. Lesanovsky and P. Schmelcher, Phys.Rev.Lett. 97, 223001 (2006)M. Mayle, B. Hezel, I. Lesanovsky and P. Schmelcher, Phys.Rev.Lett. 99, 113005 (2007)

Schmelcher, Peter

2008-05-01

287

A two-state vibrational wave packet is prepared in a low-lying 4d[1/2]{sub 1 or 2} Rydberg state of jet cooled Br{sub 2} (4d, v{prime}=3 and v{prime}=4) by two-photon excitation with 266.5 nm pulses from an ultrafast laser. The wave packet is detected by autoionization following excitation with time-delayed 800 nm pulses to the n=8 (v{sup +}=4) and n=9 (v{sup +}=3) Rydberg states in the {sup 2}{Pi}{sub 1/2} angular momentum core state. Autoionization of each state occurs to the {sup 2}{Pi}{sub 3/2} state of the ion through spin-orbit ionization. Photoelectron spectroscopy is used to differentiate between the n=8 and n=9 ejected photoelectrons. Detection of the wave packet recurrences via the n=8 and n=9 Rydberg states reveals a {pi} phase-shift difference of the recurrences between the two final states. In each case, {Delta}v {ne} 0 transitions are observed since wave packet recurrences are detected. By fitting the observed phase change of the recurrences with a simple model for the overlap amplitudes and assumptions about the potentials, we estimate, within the context of the model, that approximately 0.6% of the transitions may be attributed to {Delta} v = {+-} 1 transitions between the initial Rydberg superposition state and the final Rydberg detection state.

Stavros, V.G.; Lau, L.; Strasser, D.; Leone, S.R.

2006-02-06

288

Spatial correlations of Rydberg excitations in optically driven atomic ensembles

NASA Astrophysics Data System (ADS)

We study many-body correlations in the stationary state of a continuously driven, strongly interacting dissipative system. Specifically, we examine resonant optical excitations of Rydberg states of atoms interacting via long-range dipole-dipole and van der Waals potentials employing numerical and analytical techniques. Collection of atoms within a blockade distance form a superatom that can accommodate at most one Rydberg excitation. The superatom excitation probability saturates to (1)/(2) for coherently driven atoms but is significantly higher in the presence of dephasing, approaching unity as the number of atoms increases. Using the exact numerical solution of the density-matrix equations for a small system, we demonstrate that strong dephasing of the optically driven dipoles renders the many-body problem amenable to semiclassical Monte Carlo simulations. We employ the Monte Carlo algorithm for a large number of atoms and find that in the steady state of a uniformly driven, extended one-dimensional system, the saturation of superatoms leads to quasicrystallization of Rydberg excitations whose correlations exhibit damped spatial oscillations. We show that the behavior of the system under the van der Waals interaction potential can be approximated by a rate-equations model based on a hard-rod interatomic potential, and by solving it we obtain the period and correlation length for the density wave of Rydberg excitations.

Petrosyan, David; Höning, Michael; Fleischhauer, Michael

2013-05-01

289

Properties of Rn-like Th^4+ from microwave spectroscopy of high-L n=37 Rydberg states of Th^3+

NASA Astrophysics Data System (ADS)

A recent microwave/RESIS study of n=37 Rydberg levels of Th^3+ led to the first measurements of dipole and quadrupole polarizabilities of Rn-like Th^4+ [1]. We report additional measurements that extend the data pattern to include the L=8 level and improve the precision of the L = 14 and L = 15 levels. Together these new measurements allow improved determinations of both polarizabilities and a more precise test of theoretical calculations [2].[4pt] [1] Julie A. Keele, S.R. Lundeen, and C.W. Fehrenbach, Phys. Rev. A 83, 062509 (2011)[0pt] [2] U.I Safronova and M.S. Safronova, Phys. Rev. A 84, 052515 (2011)

Smith, Chris; Keele, Julie; Lundeen, Stephen; Fehrenbach, Charles

2012-06-01

290

The spectroscopy of Rydberg excited iodine-argon van der Waals complexes

NASA Astrophysics Data System (ADS)

The Rydberg excited I 2-Ar complex formed in a supersonic free jet has been observed using mass resolved (2+1 ) REMPI spectroscopy. The present work has concentrated on the [ 2? 3/2] g 7s, ?= 1, 2 Rydberg series of I 2-Ar. The spectrum exhibits anharmonic progressions in the I 2 Ar van der Waals stretching mode for each Rydberg state with ? e values of 59ą2 and 53ą2 cm -1 for the two states. The corresponding zero-point dissociation energies, calculated from the observed spectral red-shifts were determined to be 568ą5 and 504ą5 cm -1. All the experimental data indicate that the complex has a T-shaped geometry in both Rydberg states.

Cockett, M. C. R.; Goode, J. G.; Lawley, K. P.; Donovan, R. J.

1993-10-01

291

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

292

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

NASA Technical Reports Server (NTRS)

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

Musacchia, X. J.

1973-01-01

293

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

Wolfgang E. Ernst

2009-01-01

294

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

295

Rydberg atoms in a linear magnetic atom guide

NASA Astrophysics Data System (ADS)

We study the trapping and guiding of Rydberg atoms in a high-gradient two-wire magnetic atom guide. Samples of several hundred cold 59D5/2 Rb Rydberg atoms are prepared at densities of order 2x10^8 cm-3. The atoms are ionized after a variable delay time using a microwave pulse. The resulting ions are imaged onto a position-sensitive microchannel plate detector, and time-domain multi-scaler traces as well as gated CCD images of the ion signals are obtained. We observe guiding of Rydberg atoms over a period of 5 ms following excitation. There is a brief initial period during which about 7% of the Rydberg atoms undergo Penning ionization. The decay time of the guided atom signal is about five times that of the initial state lifetime. We attribute the increase in lifetime to an initial phase of l-changing collisions concurrent with the Penning ionization phase and also to thermal electric-dipole transitions. A Monte Carlo simulation reproduces most experimental observations and offers insight into the internal-state dynamics.

Traxler, Mallory; Sapiro, Rachel; Hempel, Cornelius; Lundquist, Karl; Power, Erik; Raithel, Georg

2012-06-01

296

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

NASA Astrophysics Data System (ADS)

Metastable pionic helium (?He+) is a three-body atom composed of a helium nucleus, an electron occupying the 1s ground state, and a negatively charged pion ?- in a Rydberg state with principal and orbital angular momentum quantum numbers of n ?+116. We calculate the spin-independent energies of the ?3He+ and ?4He+ isotopes in the region n =15-19. These include relativistic and quantum electrodynamics corrections of orders R??2 and R??3 in atomic units, where R? and ? denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the ?- and the radiative and Auger decay rates of the states are also calculated. Some states (n,?)=(16,15) and (17,16) retain nanosecond-scale lifetimes against ?- absorption into the helium nucleus. We propose the use of laser pulses to induce ?- transitions from these metastable states to states with large (1011 s-1) Auger rates. The ?He2+ ion that remains after Auger emission of the 1s electron undergoes Stark mixing with the s, p, and d states during collisions with the helium atoms in the experimental target. This leads to immediate nuclear absorption of the ?-. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge. A resonance curve is obtained from which the ?He+ transition frequency can in principle be determined with a fractional precision of 10-8-10-6 provided the systematic uncertainties can be controlled. By comparing the measured ?He+ frequencies with the calculated values, the ?- mass may be determined with a similar precision. The ?He+ will be synthesized by allowing a high-intensity (>108 s-1) beam of ?-produced by a cyclotron to come to rest in a helium target. The precise time structure of the ?- beam is used to ensure a sufficient rate of coincidence between the resonant laser pulses and the ?He+ atoms.

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

2014-04-01

297

Two-dimensional crystals of Rydberg excitations in a resonantly driven lattice gas

NASA Astrophysics Data System (ADS)

The competition between resonant optical excitation of Rydberg states of atoms and their strong, long-range van der Waals interaction results in spatial ordering of Rydberg excitations in a two-dimensional lattice gas, as observed in a recent experiment of Schauß [Nature (London)NATUAS0028-083610.1038/nature11596 491, 87 (2012)]. Here we use semiclassical Monte Carlo simulations to obtain stationary states for hundreds of atoms in finite-size lattices. We show the formation of regular spatial structures of Rydberg excitations in a system of increasing size, and find highly sub-Poissonian distribution of the number of Rydberg excitations characterized by a large negative value of the Mandel Q parameter which is nearly independent of the system size.

Petrosyan, David

2013-10-01

298

NASA Astrophysics Data System (ADS)

Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium-oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the homogeneous-glow-like ?-mode plasma with oxygen admixtures up to 1% were investigated. The results are compared with a one-dimensional numerical simulation, which includes a semi-kinetical treatment of the pronounced electron dynamics and the complex plasma chemistry (in total 20 species and 184 reactions). Very good agreement between measurement and simulation is found. The main formation mechanisms for metastable helium atoms are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

Niemi, K.; Waskoenig, J.; Sadeghi, N.; Gans, T.; O'Connell, D.

2011-10-01

299

High Angular Momentum Rydberg Wave Packets

NASA Astrophysics Data System (ADS)

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

Wyker, Brendan

300

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

301

Coherent Control of Population Transfer in Rydberg Atoms via Chirped Microwave Pulses

We present a comprehensive and ab initio nonperturbative investigation of the coherent population transfer among the 3D high-lying Rydberg hydrogen and alkali atomic states via linearly polarized chirped microwave pulses. The time-dependent Schrodinger equation for the dynamical evolution of Rydberg atoms is accurately and efficiently solved by means of the time-dependent generalized pseudospectral method. For atomic H, the population transfer

Juan J. Carrera; Shih-I Chu

2007-01-01

302

Spectroscopy of high-L Rydberg levels of Fr-like U and Th Ions

NASA Astrophysics Data System (ADS)

High-L Rydberg levels of Fr-like U^5+ and Th^3+ have been studied using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique. Beams of Rn-like U^6+ and Th^4+, obtained from a 14 GHz permanent magnet ECR source at Kansas State University, capture a single electron from a dense Rb Rydberg target, becoming Fr-like ions in very highly excited states, n 50. These Rydberg states are selectively excited to much higher levels, using a Doppler-tuned CO2 laser, partially resolving the fine structure of the lower Rydberg level. Analysis of the spectrum with the long-range polarization model can be used to determine the polarizability of the Rn-like ion cores. The technique is analogous to previous studies of Kr^5+ Rydberg levels [1], but is more challenging because of the presence of background due to auto-ionizing Rydberg levels bound to metastable Rn-like ions.[4pt] [1] S.R. Lundeen and C.W. Fehrenbach, Phys. Rev. A 75, 032523(2007)

Hanni, Mark E.; Lundeen, Stephen R.; Fehrenbach, Charles W.

2010-03-01

303

Density dependence of the ionization avalanche in ultracold Rydberg gases

NASA Astrophysics Data System (ADS)

We report on the behavior of the ionization avalanche in an ensemble of ultracold 87Rb atoms coupled to a high-lying Rydberg state and investigate extensions to the current model by including the effects of three-body recombination and plasma expansion. To separate the two effects we study the time dependence of the plasma formation at various densities as well as for different nS and nD states. At medium densities and low n we observe the onset of the avalanche as has been reported in other experiments, as well as a subsequent turn-off of the avalanche for longer excitation times, which we associate with plasma expansion. At higher densities and for higher-lying Rydberg states we observe a disappearance of the avalanche signature, which we attribute to three-body recombination.

Siercke, M.; Oon, F. E.; Mohan, A.; Wang, Z. W.; Lim, M. J.; Dumke, R.

2014-02-01

304

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

305

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

306

The state-resolved differential cross sections for both the 1s{sup 2} {sup 1}S{sub 0}{yields}1s2s {sup 1}S{sub 0} monopolar transition and the 1s{sup 2} {sup 1}S{sub 0}{yields}1s2p {sup 1}P{sub 1} dipolar transition of atomic helium had been measured over a large momentum transfer region by high-resolution inelastic x-ray scattering (IXS). The almost-perfect match of the present measurement with the theoretical calculations gives a stringent test of the theoretical method and the calculated wave functions. Our results demonstrate that high-resolution IXS is a powerful tool for studying the excitations in atoms and molecules.

Xie, B. P.; Yang, K.; Zhou, B.; Feng, D. L. [Department of Physics, Surface Physics Laboratory (National Key Laboratory), and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (China); Zhu, L. F.; Wang, E. L. [Hefei National Laboratory for Physical Sciences at Microscale, Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Hiraoka, N.; Cai, Y. Q. [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Yao, Y.; Wu, C. Q. [Department of Physics, Fudan University, Shanghai 200433 (China)

2010-09-15

307

Ionization of Rydberg atoms of sodium by 360-4400 eV alkali-metal ions

NASA Astrophysics Data System (ADS)

Impact ionization by singly charged ions from Rydberg Na(24d) and Na(25s) states has been investigated over the reduced velocity region v~=0.5-2.2. The ions of Na+, K+, and Li+ were accelerated to energies from 360 to 4400 eV and used to bombard the laser-excited Rydberg atoms. Electrons released in the ionization of Rydberg atoms were collected from the collision volume and registered by a channel electron multiplier. Measured relative ionization cross sections from Na(24d) and Na(25s) states show maxima at v~=1.6-1.7 and agree moderately well with classical-trajectory Monte Carlo calculations.

Makarov, Oleg; MacAdam, K. B.

1999-09-01

308

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

309

Electrically dressed ultra-long-range polar Rydberg molecules

NASA Astrophysics Data System (ADS)

We investigate the impact of an electric field on the structure of ultra-long-range polar diatomic rubidium Rydberg molecules. Both the s-wave and p-wave interactions of the Rydberg electron and the neutral ground-state atom are taken into account. In the presence of the electric field the angular degree of freedom between the electric field and the internuclear axis acquires vibrational character and we encounter two-dimensional oscillatory adiabatic potential energy surfaces with an antiparallel equilibrium configuration. The electric field allows shifting of the corresponding potential wells in such a manner that the importance of the p-wave interaction can be controlled and the individual wells are energetically lowered at different rates. As a consequence the equilibrium configuration and corresponding energetically lowest well move to larger internuclear distances for increasing field strength. For strong fields the admixture of nonpolar molecular Rydberg states leads to the possibility of exciting the large angular momentum polar states via two-photon processes from the ground state of the atom. The resulting properties of the electric dipole moment and the vibrational spectra are analyzed with varying field strength.

Kurz, Markus; Schmelcher, Peter

2013-08-01

310

NASA Astrophysics Data System (ADS)

An investigation was made of spontaneous Raman scattering of YAG:Nd3+ laser radiation with the wavelength ?=1.064? by the metastable state 21S of the helium atom and the 2p53p[5/2]2 state of neon, both excited in a hollow-cathode discharge. This scattering produced radiation at the wavelengths of 56.9 and 62.8 nm, respectively. The spectral brightness of the source was 1.5×1015 and 1.0×1014 photonsˇsec-1ˇcm-2ˇsr-1ˇcm when the population of the He(21S) state was 1.4×1011cm-3 and the population of the Ne(2/p53p[5/2]2) state was 3.5×108cm-3. It was found that the Raman scattering by the atomic or ionic levels excited in a gas-discharge plasma made it possible to generate strong far ultraviolet radiation and could be used for plasma diagnostics.

Mailyan, A. É.; Nersisyan, G. Ts; Papanyan, V. O.

1986-05-01

311

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

312

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

313

Two-photon dynamics in coherent Rydberg atomic ensemble.

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

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

2014-04-01

314

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

315

NASA Technical Reports Server (NTRS)

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

Sutton, J. F.

1972-01-01

316

Photoinitiated collisions between cold Cs Rydberg atoms

Experimental studies of a photoinitiated collision in an ultracold Cs Rydberg gas are presented. The process is characterized by measuring the laser intensity dependence of the absorption, the number of particles leaving each collision, and the recoil velocity of the collision fragments. The results of the experiment are compared to ab initio Rydberg pair interaction potentials.

Overstreet, K. Richard; Schwettmann, Arne; Tallant, Jonathan; Shaffer, James P. [University of Oklahoma, Homer L. Dodge Department of Physics and Astronomy, 440 West Brooks Street, Norman, Oklahoma 73019 (United States)

2007-07-15

317

Coherence in Rydberg Atoms: Measurement and Control

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.

Mary Kutteruf

2010-01-01

318

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

319

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

320

Controlling ultracold Rydberg atoms in the quantum regime.

We discuss the properties of Rydberg atoms in a magnetic Ioffe-Pritchard trap being commonly used in ultracold atomic physics experiments. The Hamiltonian is derived, and it is demonstrated how tight traps alter the coupling of the atom to the magnetic field. We solve the underlying Schrödinger equation of the system within a given n manifold and show that for a sufficiently large Ioffe field strength the 2n;{2}-dimensional system of coupled Schrödinger equations decays into several decoupled multicomponent equations governing the center of mass motion. An analysis of the fully quantized center of mass and electronic states is undertaken. In particular, we discuss the situation of tight center of mass confinement outlining the procedure to generate a low-dimensional ultracold Rydberg gas. PMID:17155797

Hezel, Bernd; Lesanovsky, Igor; Schmelcher, Peter

2006-12-01

321

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

2013-09-13

322

Wigner Crystallization of Single Photons in Cold Rydberg Ensembles

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

323

Theory of two-photon double ionization of helium at the sequential threshold

We analyze in this paper the process of double-electron ejection through two-photon absorption from the fundamental state of helium. We focus on the case of photon energies close to 2 a.u., which marks the threshold between direct and sequential double-ionization regimes. We demonstrate the crucial role of two-photon excitation-plus-ionization process of nlk{sup '}l{sup '} Rydberg series. We show that the latter channel must be taken into account in the theory in order to properly describe two-electron ejection. A simple expression is derived for the electron energy spectrum, leading to better insights into the physics underlying two-photon absorption close to the sequential threshold.

Bachau, H. [Centre des Lasers Intenses et Applications, Universite Bordeaux I-CNRS-CEA, 33405 Talence Cedex (France)

2011-03-15

324

A universal approach to Rydberg spectral line shapes in plasmas

NASA Astrophysics Data System (ADS)

A universal approach for the calculation of Rydberg atom line shapes in plasmas is developed. This approach goes far beyond the calculation capabilities of the standard models. It is based on analytical formulae for the intensity distribution in radiation transitions n - n' between highly excited atomic states with large values of principal quantum numbers n, n' Gt 1, with Dgrn = n - n' Lt n, and on the frequency fluctuation model to account for ion thermal motion effects. The theory allows us to describe a transition from the static to the impact broadening domains for every hydrogen spectral line. The specific cases of broadening of Hn-agr(Dgrn = 1) and Hn-bgr(Dgrn = 2) lines are considered in detail for various values of plasma parameters. The line shapes are presented in a universal manner as functions of the relative frequency splitting and of the fluctuation rate ngr of the ion plasma microfield, using dimensionless variables. For small values of ngr, the static line shapes which generalize the well-known Underhill-Waddell data for the Rydberg state case are presented. For large values of ngr, the transition to impact ion broadening is observed, resulting in a narrowing effect. A comparison with the hydrogen Hagr line shape calculations shows a good agreement between the universal approach for Rydberg lines and traditional spectral line shapes.

Mossé, C.; Calisti, A.; Stamm, R.; Talin, B.; Bureyeva, L. A.; Lisitsa, V. S.

2004-03-01

325

Dynamics of oxygen Rydberg atom generation following O 1s inner-shell excitation of H2O

NASA Astrophysics Data System (ADS)

The emission of low-energy electrons from H2O has been investigated at photon excitation energies in the vicinity of the O 1s ionization threshold. Neutral oxygen Rydberg atoms (O*) were found to form, and the correlation between the initial inner-shell excited state of H2O and the Rydberg state of O* was determined. The initially excited electron in a Rydberg orbital is shown to remain associated with O* even after the cleavage of two O-H bonds. We also show that the energy discrepancy between two Rydberg states of H2O and O* can be explained by the influence of the post-collision interaction, which becomes stronger as the excitation energy approaches the 1s ionization threshold.

Gejo, T.; Ikegami, T.; Honma, K.; Takahashi, O.; Shigemasa, E.; Hikosaka, Y.; Tamenori, Y.

2014-06-01

326

Dynamics of oxygen Rydberg atom generation following O 1s inner-shell excitation of H2O.

The emission of low-energy electrons from H2O has been investigated at photon excitation energies in the vicinity of the O 1s ionization threshold. Neutral oxygen Rydberg atoms (O*) were found to form, and the correlation between the initial inner-shell excited state of H2O and the Rydberg state of O* was determined. The initially excited electron in a Rydberg orbital is shown to remain associated with O* even after the cleavage of two O-H bonds. We also show that the energy discrepancy between two Rydberg states of H2O and O* can be explained by the influence of the post-collision interaction, which becomes stronger as the excitation energy approaches the 1s ionization threshold. PMID:24908011

Gejo, T; Ikegami, T; Honma, K; Takahashi, O; Shigemasa, E; Hikosaka, Y; Tamenori, Y

2014-06-01

327

Accurate local Kohn-Sham potentials have been constructed for the ground 1s21S state and, in particular, for the lowest triplet 1s2s3S state of the helium atom, using electron densities from many-body calculations and the procedure of van Leeuwen and Baerends. The resulting Kohn-Sham orbitals reproduce the many-body densities very accurately; furthermore, we have demonstrated that the negative of the energy eigenvalue

I. Lindgren; S. Salomonson; F. Möller

2005-01-01

328

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

329

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

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

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

2010-06-04

330

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. PMID:19518767

Müller, M; Lesanovsky, I; Weimer, H; Büchler, H P; Zoller, P

2009-05-01

331

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

332

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

333

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

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

Cabral, F.; Kalos, M.H.

1981-02-01

334

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

The A(e,eK+)X reaction has been investigated at Jefferson Laboratory. Data were taken for Q{sup 2} approx. 0.35 GeV{sup 2} at a beam energy of 3.245 GeV for 1H,3He and 4He targets. Evidence for Lambda-hypernuclear bound states is seen for 3,4He targets. This is the first time that the electroproduction of these hypernuclei has been observed.

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

2005-05-01

335

Electroproduction of strangeness on {sub {lambda}}{sup 3,4}H bound states on Helium

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

Dohrmann, F. [Argonne National Laboratory (United States); Forschungszentrum Rossendorf (Germany); Abbott, D.; Carlini, R.; Dunne, J.; Ent, R.; Fenker, H.; Garrow, K.; Lung, A.; Mack, D.; Meekins, D.; Mitchell, J.; Wood, S.; Yan, C. [Thomas Jefferson National Accelerator Laboratory (United States); Ahmidouch, A. [NC A and T State University (United States); Hampton University (United States); Kent State University (United States); Ambrozewicz, P.; Martoff, C.J. [Temple University (United States); Armstrong, C.S. [Thomas Jefferson National Accelerator Laboratory (United States); College of William and Mary (United States); Arrington, J.; Bailey, K.; Cummings, W.J. [Argonne National Laboratory (United States)] [and others

2005-05-06

336

Resonant collisions of K Rydberg atoms

We have studied the collisional energy transfer process K (ns) +K (n-2) d {yields} K (np) +K (n-1) p which is tuned into resonance with an applied static electric field. The initial Rydberg states are excited stepwise with two dye laser pulses. The resonant energy transfer is detected by selectively field ionizing the final K(np) state as the static field is swept over many laser shots. Due to fine structure splitting of the d and p levels 45 resonances are energetically allowed at n{sub s}=25. The actual number of resonances that are observed depends on the polarization of the laser light, the dipole-dipole selection rules, and the n state excited. Above n{sub s}=29 all resonances are energically forbidden. We have measured the position of the resonances in electric field from n{sub s}=25 to n{sub s}=29 and found them to be in good agreement with calculated positions.

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

1993-05-01

337

We show that the dynamics of a laser driven Rydberg gas in the limit of strong dephasing is described by a master equation with manifest kinetic constraints. The equilibrium state of the system is uncorrelated but the constraints in the dynamics lead to spatially correlated collective relaxation reminiscent of glasses. We study and quantify the evolution towards equilibrium in one and two dimensions, and analyze how the degree of glassiness and the relaxation time are controlled by the interaction strength between Rydberg atoms. We also find that spontaneous decay of Rydberg excitations leads to an interruption of glassy relaxation that takes the system to a highly correlated nonequilibrium stationary state. The results presented here, which are in principle also applicable to other systems such as polar molecules and atoms with large magnetic dipole moments, show that the collective behavior of cold atomic and molecular ensembles can be similar to that found in soft condensed-matter systems. PMID:24313500

Lesanovsky, Igor; Garrahan, Juan P

2013-11-22

338

Information Storage and Processing in Rydberg Atoms.

National Technical Information Service (NTIS)

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

R. R. Jones

2008-01-01

339

Helium and minor ions in the corona and solar wind - Dynamics and charge states

NASA Technical Reports Server (NTRS)

A theoretical model of the acceleration region of the solar wind with major species (p, alpha, e) and minor ions (e.g., He-3, C, O, Mg, Si) is presented. Observed n(e)-profiles and the equations of continuity and momentum are used to calculate profiles of T, n, and u for all species, as well as charge states of minor ions. The disagreement of the results of a pure p-e model with observations is discussed in some detail, and it is shown that a model consistent with observations both in the corona and at 1 AU requires a finite abundance of He(2+). This model predicts a strong enhancement of He/H in the lower corona. The results for the frozen-in charge states in the p-alpha-e model are in agreement with measurements in the low speed solar wind, especially for the well determined pair O(6+)/O(7+). Finally, a model for a coronal hole is investigated and it is found that wave pressure is necessary to model successfully the observed solar wind speeds and abundances. Although various simplifying assumptions had to be introduced, care was taken to ensure that the model remains physically consistent, i.e., that the same physics is used for the major species as well as the minor ions.

Buergi, A.; Geiss, J.

1986-01-01

340

The local Kohn-Sham potential is constructed for the 1s2s S-3 state of the helium atom, using the procedure proposed by van Leeuwen and Baerends (Phys. Rev. A, 49, 2138 (1994)) and the many-body electron density, obtained from the pair-correlation program of Salomonson and Oster (Phys. Rev. A, 40, 5559 (1989)). The Kohn-Sham orbitals reproduce the many-body density very accurately, demonstrating

Sten Salomonson; F. Moller; Ingvar Lindgren

2005-01-01

341

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

342

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 12Pi1\\/2, 3\\/2 states in MHe systems are found to be lower than the values of 12Piu (1\\/2, 3\\/2) states in the He-M-He systems by a margin of more than

Anjan Chattopadhyay

2011-01-01

343

Mobilities of ground-state and metastable O/+/, O2/+/, O/2+/, and O2/2+/ ions in helium and neon

NASA Astrophysics Data System (ADS)

The ionic mobilities of O(+), O2(+), O(2+), and O2(2+) in helium and neon have been measured using a selected-ion drift apparatus (SIDA). It is found that the mobilities of both O(+) and O2(+) ions in the metastable states (2D or 4Pi u) are measurably smaller than those of the same ions carried out by using known, state-selective ion-molecule reactions. A similar mobility differentiation of ground-state and metastable ions was not observed for the O(2+) and O2(2+) ions.

Johnsen, R.; Biondi, M. A.; Hayashi, M.

1982-09-01

344

Ab initio potentials and the equation of state of condensed helium at high pressure

NASA Astrophysics Data System (ADS)

The equation of state of condensed 4He, at room temperature and at pressures between ~10 and ~50 GPa, is computed by Path Integral Monte Carlo simulations. Recently proposed, ab initio pair and three-body potentials are utilized. Results are compared to available experimental data, as well as to predictions obtained with two- and three-body potentials used in previous studies. If only two-body interactions are included, the pressure is overestimated by as much as 56% at the highest compression considered here. A relatively modest improvement is offered by the recently developed SAPT over the more commonly adopted Aziz potential. The introduction of three-body forces, modeled using two different potentials, causes instead a significant underestimation of the pressure. In the range of density explored here, agreement with experiment cannot be obtained simply by rescaling the strength of the attractive part of the three-body potential, as had been empirically found in previous work. The results suggest that either four-body terms are more important than previously thought, or, possibly, that the entire approach based on a static potential may be inadequate. Three-body forces are found to have a negligible effect on structural properties and on the single-particle kinetic energy, for which estimates are provided.

Chang, Soon-Yong; Boninsegni, Massimo

2001-08-01

345

NASA Astrophysics Data System (ADS)

The rotationally excited 2 1P (L = 1) and 2 3P (L = 1) states in the inftyHe, 3He and 3He helium atoms are considered by using our multi-box variational procedure (Frolov 2001 Phys. Rev. E 64 036704). In particular, the total non-relativistic energies of these states for the inftyHe atom have been determined to very high accuracy. These energies are -2.123 843 086 498 101 357 17 au (2 1P state) and -2.133 164 190 779 283 204 14 au (2 3P state). A number of bound state properties for these two states in the inftyHe atom are also presented. The total energies of the 2 1P (L = 1) and 2 3P (L = 1) states in 3He and 4He have been determined. Some astrophysical applications of the rotationally excited 2 1P (L = 1) and 2 3P (L = 1) states in the helium atoms are briefly discussed.

Frolov, Alexei M.

2003-07-01

346

National Technical Information Service (NTIS)

Although the zero-point energy dominates the properties of the solid helium isotopes at low densities, more and more experimental evidence is accumulating to show that, except perhaps at a few singular points or limited regions of very low density, the th...

J. S. Dugdale

1964-01-01

347

Direct Experimental Observations of a Phase Space Turnstile in a Rydberg System

NASA Astrophysics Data System (ADS)

Rydberg atoms exposed to alternating positive and negative electric field pulses (kicks) are an example of a chaotic atomic system. Chaotic ionization in this system is organized by a phase space turnstile which represents a mechanism that promotes electrons from their bound to unbound state. Only the electrons that are inside the turnstile ionize after one kicking period. We present theoretical and experimental results for the turnstile signature in the chaotic ionization of Rydberg atoms. We create a Rydberg wave packet and subject it to alternating kicks, after which we measure the ionization fraction. The signature of the turnstile manifests itself in the step-function-like behavior of the ionization fraction as a function of the kick strength. We show that this behavior persists for different values of kicking periods and starting electron energies.

Mitchell, Kevin; Burke, Korana; Ye, Shuzen; Wyker, Brendan; Dunning, Barry

2011-06-01

348

NASA Astrophysics Data System (ADS)

We present an improved superatom model for examining nonlinear optical responses of cold Rydberg atoms in the regime of electromagnetically induced transparency (EIT). By going beyond the weak-probe approximation, we find that several higher-order collective states should be included to correctly describe the coherent Rydberg excitation of superatoms. Otherwise, numerical results based on the simple ladder system of superatoms will contribute wrong predictions on light intensity and photon correlation of the transmitted probe field. In particular, a great photon-bunching effect will be improperly expected somewhere out of the EIT window in one dilute atomic sample. The essence of this improved superatom model lies in that it can provide reliable predictions on the nonlinear Rydberg-EIT phenomena even in dense atomic samples and may be extended to realize lossless conditional light interactions in appropriate multilevel systems exhibiting dipole blockade.

Liu, Yi-Mou; Yan, Dong; Tian, Xue-Dong; Cui, Cui-Li; Wu, Jin-Hui

2014-03-01

349

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

NASA Astrophysics Data System (ADS)

We present a mechanism that permits the parallel execution of multiple quantum gate operations within a single long linear ion chain. Our approach is based on large coherent forces that occur when ions are electronically excited to long-lived Rydberg states. The presence of Rydberg ions drastically affects the vibrational mode structure of the ion crystal, giving rise to modes that are spatially localized on isolated subcrystals which can be individually and independently manipulated. We theoretically discuss this Rydberg mode shaping in an experimentally realistic setup and illustrate its power by analyzing the fidelity of two conditional phase flip gates executed in parallel. The ability to dynamically shape vibrational modes on the single-ion level might find applications in quantum simulators and quantum computation architectures.

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

2013-05-01

350

Dipole-dipole interaction between cold Rydberg atoms in RF fields

NASA Astrophysics Data System (ADS)

Already for some time, dipole-dipole interaction between cold Rydberg atoms is promising as application in quantum information. This promise drives the research on this interaction. In this context we report two aspects: 1) Coherence. When a quantum-mechanical state energetically shifts under the influence of some external perturbation, the effect of a periodic perturbation will show up as side bands. When this shift is linear (e.g. a dipole in an electric field) the population of this side band is described by Bessel-functions. Here we treat the situation that the shift of the state is quadratic under an external perturbation (a polarizable state in an electric field). Now not only the population of the sidebands is a (known but complicated) function of the perturbation, but also the energy of the state and its sidebands is no longer constant. Both the energy and the population of the sidebands are probed by introduction a second state, which is insensitive for the perturbation and that is weakly couple to the first state. This weak coupling is dipole-dipole interaction between two Rydberg atoms. This coupling leads to an avoided crossing between the externally perturbed and the unperturbed states. This particular realization allows for an alternative interpretation of the population of sidebands, in particular of the minima, in terms of Stückelberg oscillations. These oscillations are measured in the sidebands of the resonant interaction between Rb 49s and 41d states with 49p and 42p states and are used to obtain information about the coherent nature of the interaction. 2) Surfaces. In addition we report on the effect of a conducting surface nearby a Rydberg atoms. This issue is particularly relevant in case the conducting surface is an atom chip. The Rydberg atoms are probed by means of electromagnetically induced transparency (EIT) induced in Rb 5s-5p-Rydberg ladder schemes.

van Linden van den Heuvell, H. B.

2009-05-01

351

Thermal shifts and broadening of Rydberg levels in Be II ions

NASA Astrophysics Data System (ADS)

The effect of a thermal field on Rydberg states of the nS-, nP- and nD-series in beryllium ions Be+ is investigated. The blackbody radiation-induced depopulation rates caused by transitions to upper (excitations) and lower (decays) bound levels and to the continuum (ionization) are calculated in wide ranges of the principal quantum numbers n and ambient temperatures. Simple and reliable approximations for natural lifetimes and stimulated by thermal radiation depopulation rate components are proposed. The blackbody-radiation-induced shifts of Rydberg levels are also calculated and their qualitative and quantitative properties are analysed.

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

2013-11-01

352

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

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

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

2011-04-29

353

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

354

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

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

2006-08-15

355

NASA Astrophysics Data System (ADS)

This is a theoretical study of argon plasma under conditions, where Ne- and Na-like ionization stages are dominant. Balance equations are generalized to treat 37 3l states of Ne-like ion and 37 adjacent series of Rydberg states of Na-like ion simultaneously. This allows us to include in the kinetics a diffusion-like motion of the state of the system "Ne-like ion plus one electron" through the multitude of excited levels spread over an energy region of 50 eV. The populations Ni - i (i = (1, ..., 37)) of the Ne-like ion states are introduced explicitly; those of adjacent 37 Rydberg series are accounted for through continuous functions Ni(?). These functions describe the population distribution within each Rydberg series dependent on the Rydberg electron enegy ?. The elementary processes of the collisionalradiative model connecting all Ne- and Na-like states, as well as processes of redistribution of populations inside each Rydberg series, are accounted for. The rate coefficients for all processes within the Ne-like residue have been calculated previously, using a detailed many-body relativistic theory. The dielectric capture cross sections and autoionization probabilities are presented as analytical continuation of the collisional excitation cross sections. The excited-excited states transitions are included. The rest of the processes are treated in a simple semiclassical approximation. The Lotz formula is generalized by unambiguous analytical continuation to cover the case of bound-bound transitions between Rydberg states of Na-like ions. The radiation reabsorption in a long plasma cylinder is included through Biberman-Holstein coefficients for all transitions. The inclusion of Na-like states, accounting for diffusion-like processes, increases the population inversion for the "lasing candidates" by at least a factor of two for a wide range of plasma conditions. This is important for the ionization equilibrium too. Besides, the functions Ni(?) bear diagnostic information. Detailed calculations have been done for the homogeneous steady-state Maxwellian plasma. The role of transient processes in the population inversion creation is under discussion.

Ivanov, L. N.; Ivanova, E. P.; Knight, L. V.; Molchanov, A. G.

1996-06-01

356

The kicked Rydberg atom: Regular and stochastic motion

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

Burgdoerfer, J.

1988-01-01

357

Landau-Zener Transitions in Frozen Pairs of Rydberg Atoms

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

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

2010-04-02

358

Atom control and gravity measurements using Rydberg positronium

NASA Astrophysics Data System (ADS)

We consider some of the obstacles that will have to be overcome in order to perform a direct measurement of the gravitational free-fall of positronium atoms. Foremost among these are the production of positronium atoms in a cryogenic environment, efficient excitation of these atoms to suitably long-lived Rydberg states, and their subsequent control via the interaction of their large electric dipole moments with inhomogeneous electric fields. Recent developments in all of these areas can be directly applied to a positronium free-fall gravity measurement, making such an endeavour both timely and feasible.

Cassidy, D. B.; Hogan, S. D.

2014-05-01

359

High-Rydberg Xenon Submillimeter-Wave Detector

NASA Technical Reports Server (NTRS)

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

Chutjian, Ara

1987-01-01

360

Strongly correlated excitation of a quasi-1D Rydberg gas

NASA Astrophysics Data System (ADS)

Rydberg excitation dynamics of a 87-Rb cold atom cloud is investigated in an effective one-dimensional geometry. We measure the excitation dynamics and the full counting statistics for resonant and off-resonant excitation to the 70S state. While for a resonant laser excitation the counting distributions have a strong sub-Poissonian character, we find strongly bimodal counting distributions in the off-resonant regime. The n-th central moments, up to n = 4, of the counting distributions are derived from the measured counting distributions.

Malossi, N.; Valado, M. M.; Scotto, S.; Morsch, O.; Arimondo, E.; Ciampini, D.

2014-04-01

361

Resonant Dipole-Dipole Collisions of Rydberg Atoms in a Magneto-Optical Trap

I present a study of resonant energy transfer via a dipole-dipole interaction between alkali atoms in Rydberg states. We have studied such interactions between atoms prepared in a magneto-optical trap (MOT). In binary collisions the atomic density plays no role in the collision dynamics, however, using laser cooling and trapping techniques we have been able to enter a new regime

W. R. Anderson

1998-01-01

362

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

Quantum defects of ns and np Rydberg states of Na are quite large, deltas= 1.35 and deltap=0.85, respectively, while for nl states with l>=2 values of deltal are nearly zero. Therefore Na ns and np states are energetically isolated from the higher angular-momentum states in the same n manifold. Together with the fact that energy spacing between ns and np

H. Maeda; J. H. Gurian; T. F. Gallagher

2007-01-01

363

Chaotic Energy Hopping in Bidirectionally Kicked Rydberg Atoms

NASA Astrophysics Data System (ADS)

A highly excited (n 306) quasi one-dimensional Rydberg atom exposed to periodic alternating external electric field pulses exhibits chaotic behavior. Time evolution of this system is governed by a geometric structure of phase space called a homoclinic tangle and its turnstile. The turnstile is responsible for organizing chaotic ionization. We present and explain the results from an experiment designed to probe the structure of the phase space turnstile. We create time-independent Rydberg wave packets, subject them to alternating electric field kicks, and measure the ionization fraction. We present the behavior of the ionization fraction as a function of the applied kick strength and show that this behavior is directly connected to the size and shape of the underlying turnstile. For short kicking periods the ionization fraction as a function of the applied kick strength exhibits step-function-like behavior that changes into s-shape behavior for large kicking periods. Next we use the geometric structure of phase space to design a short pulse sequence that quickly and efficiently transfers electronic wave packet from a high energy state to a much lower energy state. Finally, we show how the phase space geometry influences the efficiency of the transport between energy states.

Burke, Korana; Mitchell, Kevin; Ye, Shuzhen; Dunning, F. Barry

2012-06-01

364

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/sub infinity/ = 109 737.315 73(3) cm/sup -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 constant in fundamental atomic physics lies in tests of quantum electrodynamics and in improvement of the realization of the meter. We propose that the hydrogen spectrum be used to realize the meter in the optical domain, as an alternative to the current frequency chains. For the realization to be useful, improvement of the current precision of the Rydberg constant by a factor of 2 or more is required.

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

1989-03-15

365

Interacting Fibonacci anyons in a Rydberg gas

NASA Astrophysics Data System (ADS)

The physics of interacting Fibonacci anyons can be studied with strongly interacting Rydberg atoms in a lattice, when due to the dipole blockade the simultaneous laser excitation of adjacent atoms is forbidden. The Hilbert space maps then directly on the fusion space of Fibonacci anyons. Interactions between anyons are generated and controlled by the intensity and frequency of the excitation laser. Fusion outcomes of neighboring anyons can be determined experimentally via the measurement of three-point correlations among three consecutive atoms. Our work shows that a Rydberg lattice gas constitutes a natural physical platform for the experimental exploration of topological quantum liquids of non-Abelian anyons.

Lesanovsky, Igor; Katsura, Hosho

2012-10-01

366

van der Waals-stabilized Rydberg aggregates

NASA Astrophysics Data System (ADS)

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

Zoubi, H.; Eisfeld, A.; Wüster, S.

2014-05-01

367

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

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

1983-08-01

368

NASA Astrophysics Data System (ADS)

We present three techniques for suppressing predissociation of the nitric oxide Rydberg states normally excited in pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy. By applying a combination of appropriate dc and microwave fields it is possible to inhibit predissociation by resonantly mixing Stark states of adjacent principal quantum number n, with similar parabolic quantum number k. Lifetime enhancement is also obtained by using an appropriate radio-frequency field to resonantly mix Stark states of the same n. Finally, in the absence of dc fields, microwaves are used to stabilize optically excited nf Rydberg states, by inducing transitions to higher angular momentum states with longer lifetimes, specifically to the n+/-1, l>=4 states.

Murgu, Elena; Martin, J. D. D.; Gallagher, T. F.

2001-10-01

369

Linear Atom Guides: Guiding Rydberg Atoms and Progress Toward an Atom Laser

NASA Astrophysics Data System (ADS)

In this thesis, I explore a variety of experiments within linear, two-wire, magnetic atom guides. Experiments include guiding of Rydberg atoms; transferring between states while keeping the atoms contained within the guide; and designing, constructing, and testing a new experimental apparatus. The ultimate goal of the atom guiding experiments is to develop a continuous atom laser. The guiding of 87Rb 59D5/2 Rydberg atoms is demonstrated. The evolution of the atoms is driven by the combined effects of dipole forces acting on the center-of-mass degree of freedom as well as internal-state transitions. Time delayed microwave and state-selective field ionization, along with ion detection, are used to investigate the evolution of the internal-state distribution as well as the Rydberg atom motion while traversing the guide. The observed decay time of the guided-atom signal is about five times that of the initial state. A population transfer between Rydberg states contributes to this lengthened lifetime, and also broadens the observed field ionization spectrum. The population transfer is attributed to thermal transitions and, to a lesser extent, initial state-mixing due to Rydberg-Rydberg collisions. Characteristic signatures in ion time-of-flight signals and spatially resolved images of ion distributions, which result from the coupled internal-state and center-of-mass dynamics, are discussed. Some groups have used a scheme to make BECs where atoms are optically pumped from one reservoir trap to a final state trap, irreversibly transferring those atoms from one trap to the other. In this context, transfer from one guided ground state to another is studied. In our setup, before the atoms enter the guide, they are pumped into the | F = 1, mF = --1> state. Using two repumpers, one tuned to the F = 1 ? F' = 0 transition (R10) and the other tuned to the F = 1 ? F' = 2 transition (R12), the atoms are pumped between these guided states. Magnetic reflections within the guide are also studied. Design and construction of a new linear magnetic atom guide is detailed. This guide beta has many improvements over the original guide alpha: a Zeeman slower, magnetic injection, a physical shutter, and surface adsorption evaporative cooling are some of the main changes. Testing of this new system is underway. It is hoped that the improvements to guide beta will yield an atom density sufficient to reach degeneracy, thereby forming a continuous BEC at the end of the guide. The BEC, which will be continuously replenished by the atoms within the guide, will be outcoupled to form a continuous atom laser.

Traxler, Mallory A.

370

Adiabatic quantum computation with neutral atoms via the Rydberg blockade

NASA Astrophysics Data System (ADS)

We study a trapped-neutral-atom implementation of the adiabatic model of quantum computation whereby the Hamiltonian of a set of interacting qubits is changed adiabatically so that its ground state evolves to the desired output of the algorithm. We employ the ``Rydberg blockade interaction,'' which previously has been used to implement two-qubit entangling gates in the quantum circuit model. Here it is employed via off-resonant virtual dressing of the excited levels, so that atoms always remain in the ground state. The resulting dressed-Rydberg interaction is insensitive to the distance between the atoms within a certain blockade radius, making this process robust to temperature and vibrational fluctuations. Single qubit interactions are implemented with global microwaves and atoms are locally addressed with light shifts. With these ingredients, we study a protocol to implement the two-qubit Quadratic Unconstrained Binary Optimization (QUBO) problem. We model atom trapping, addressing, coherent evolution, and decoherence. We also explore collective control of the many-atom system and generalize the QUBO problem to multiple qubits.

Goyal, Krittika; Deutsch, Ivan

2011-06-01

371

Population coherent control of Rydberg potassium atom via adiabatic passage

NASA Astrophysics Data System (ADS)

The time-dependent multilevel approach (TDMA) and B-spline expansion technique are used to study the coherent population transfer between the quantum states of a potassium atom by a single frequency-chirped microwave pulse. The Rydberg potassium atom energy levels of n = 6-15, l = 0-5 states in zero field are calculated and the results are in good agreement with other theoretical values. The time evolutions of the population transfer of the six states from n = 70 to n = 75 in different microwave fields are obtained. The results show that the coherent control of the population transfer from the lower states to the higher ones can be accomplished by optimizing the microwave pulse parameters.

Jiang, Li-Juan; Zhang, Xian-Zhou; Jia, Guang-Rui; Zhang, Yong-Hui; Xia, Li-Hua

2013-02-01

372

Cooperative Excitation and Many-Body Interactions in a Cold Rydberg Gas

NASA Astrophysics Data System (ADS)

The dipole blockade of Rydberg excitations is a hallmark of the strong interactions between atoms in these high-lying quantum states [M. Saffman, T. G. Walker, and K. Mřlmer, Rev. Mod. Phys. 82, 2313 (2010)RMPHAT0034-686110.1103/RevModPhys.82.2313; D. Comparat and P. Pillet, J. Opt. Soc. Am. B 27, A208 (2010)JOBPDE0740-322410.1364/JOSAB.27.00A208]. One of the consequences of the dipole blockade is the suppression of fluctuations in the counting statistics of Rydberg excitations, of which some evidence has been found in previous experiments. Here we present experimental results on the dynamics and the counting statistics of Rydberg excitations of ultracold rubidium atoms both on and off resonance, which exhibit sub- and super-Poissonian counting statistics, respectively. We compare our results with numerical simulations using a novel theoretical model based on Dicke states of Rydberg atoms including dipole-dipole interactions, finding good agreement between experiment and theory.

Viteau, Matthieu; Huillery, Paul; Bason, Mark G.; Malossi, Nicola; Ciampini, Donatella; Morsch, Oliver; Arimondo, Ennio; Comparat, Daniel; Pillet, Pierre

2012-08-01

373

Interstellar Helium Atom Flux Halo

NASA Astrophysics Data System (ADS)

Relative motion of the Sun with respect to the surrounding local interstellar medium (LISM) results in interstellar helium atoms entering the heliosphere. These atoms have been experimentally studied in detail by observing their glow, measuring as pickup ions, and by directly detecting them on the Ulysses and IBEX space missions. Local helium fluxes are characterized by velocity distributions with their angular width and direction determined by the velocity, temperature, and number density of helium in the LISM. Dynamics of atom propagation to an observational point in the gravitational field of the sun and atom losses are well understood. The observed wings [e.g., Bzowski et al., Ap. J. Suppl., 198(2), 12, 2012] of directional distributions of interstellar helium fluxes show higher intensities than predicted by conventional theoretical models. This wing enhancement (in contrast to the flux core), the helium flux halo, could be caused by non-Maxwellian conditions in the LISM, which is not in a state of thermodynamical equilibrium, and by interactions of helium atoms in the heliosphere. The nature of the interstellar helium flux halo is examined, constraining its possible physical causes.

Gruntman, M.

2012-12-01

374

Autodissociating Rydberg states of positronium hydride

NASA Technical Reports Server (NTRS)

Consequences of the nonrelativistic Coulomb Hamiltonian with a fixed proton are considered for positronium hydride (PsH). An optical-potential method and certain simplifying assumptions are used to compute the lowest s-wave resonance parameters on the basis of the /e(+)H(-)/ configuration. Resonance parameters corresponding to a Ps scattering energy of 4.0190 eV and a width of 0.0303 eV are obtained. These results are shown to be in very close agreement with those of previous studies.

Drachman, R. J.

1979-01-01

375

Measurement of Atomic Oscillator Strength Distribution from the Excited States

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

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

2008-10-22

376

NASA Astrophysics Data System (ADS)

The four-body boundary corrected first Born approximation (CB1-4B) is used to calculate the single electron capture cross sections for collisions between fully stripped ions (He2+, Be4+, B5+ and C6+) and helium target at intermediate and high impact energies. The main goal of this study is to assess the usefulness of the CB1-4B method at intermediate and high impact energies for these collisions. Detailed comparisons with the measurements are carried out and the obtained theoretical cross sections are in reasonable agreement with the available experimental data.

Man?ev, Ivan; Milojevi?, Nenad; Belki?, Devad

2013-11-01

377

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

We investigate the single-photon double ionization of helium at photon energies of 440 and 800 eV. We observe doubly charged ions with close to zero momentum corresponding to electrons emitted back to back with equal energy. These slow ions are the unique fingerprint of an elusive quasifree photon double ionization mechanism predicted by Amusia et al. nearly four decades ago [J. Phys. B 8, 1248 (1975)]. It results from the nondipole part of the electromagnetic interaction. Our experimental data are supported by calculations performed using the convergent close-coupling and time-dependent close-coupling methods. PMID:23862999

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

2013-07-01

378

Rydberg electrons spy conformational dynamics of hot molecules

NASA Astrophysics Data System (ADS)

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

Weber, Peter M.

2007-03-01

379

Quantum-defect analysis of 3p and 3d H{sub 3} Rydberg energy levels

In this work, Rydberg energy levels of the triatomic hydrogen molecule (H{sub 3}) are studied with multichannel quantum-defect theory. We extract the body-frame p-wave quantum defects from highly accurate ab initio electronic potential surfaces and calculate the quantum defects of higher angular-momentum states in a long-range multipole potential model. Laboratory-frame quantum-defect matrices emerge from a rovibrational-frame transformation carried out with accurate rovibrational states of H{sub 3}{sup +}. Finally, we use the laboratory-frame quantum defects to calculate Rydberg energy levels for the fundamental neutral triatomic molecule H{sub 3}.

Wang Jia; Greene, Chris H. [Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309 (United States)

2010-08-15

380

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

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

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

2010-11-15

381

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

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

Patton, Kelly R; Fischer, Uwe R

2013-12-13

382

Polarizabilities of two-electron positive ions and Rydberg levels of lithium

NASA Technical Reports Server (NTRS)

Second-order sums are computed for the two-electron positive ions Li(+), Be(2+), and B(3+) by representing the intermediate states as discrete pseudostates. The Hamiltonian for the system is given and translated to semi-Jacobi variables for its derivation in reduced Rydberg units. The interaction potential is developed in its multipole form and employed in second-order perturbation theory. The perturbation is always a multipole-potential term, and the initial and intermediate states are constructed from two-particle Hylleraas basis sets. The resulting pseudostates are shown to represent the continuum with good convergence, and the asymptotic-optical-potential method is applied to the two-body quantities to determine the energy levels of three-electron systems in high Rydberg states. The method is shown to give accurate values for the polarizabilities of the two-electron isoelectronic systems.

Bhatia, A. K.; Drachman, Richard J.

1992-01-01

383

Ion beam generation by field ionization of laser-excited Rydberg atoms

Sodium atoms (10/sup 8/--10/sup 11/ cm/sup -3/) effused from an oven where excited by two pulsed dye lasers (--8--15 ns, --100 ..mu..J) from the ground state 3s, via an intermediate state 3p, to a Rydberg state ns or nd (20less than or equal tonless than or equal to25). About 50 ns after the laser irradiation, a pulsed electric field (0.5--5.5 kV/cm) was applied to the Rydberg atoms to ionize them and accelerate the resulting ions. Thus, a pulsed ion beam was obtained with a maximum total electric charge of --5 pC, corresponding to a peak current of --25 ..mu..A with an output pulse of --200 ns full width at half-maximum.

Oomori, T.; Ono, K.; Fujita, S.; Murai, Y.

1987-01-12

384

Electromagnetically induced transparency in strongly interacting Rydberg gases

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

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

2011-04-15

385

NASA Astrophysics Data System (ADS)

In this work we employ ab initio electronic structure theory at a very high level to resolve a long standing experimental controversy; the interaction between helium and the MgO (100) surface has been studied extensively by other groups, employing diverse experimental approaches. Nevertheless, the binding energy of the lowest bound state is still unclear: the existence of a state at around -5.5 meV is well established but a state at -10 meV has also been reported. The MgO (100)-He system captures the fundamental physics involved in many adsorption problems; the weak binding is governed by long-range electronic correlation for which a fully predictive theory applicable to the solid state has been elusive. The above-mentioned experimental controversy can now be resolved on the basis of the calculations presented in this work. We performed three-dimensional vibrational dynamics calculations on a highly accurate potential-energy surface. The latter was constructed using a method which systematically approaches the exact limit in its treatment of electronic correlation. The outcome is clear: our calculations do not support the existence of a bound state around -10 meV.

Martinez-Casado, Ruth; Usvyat, Denis; Maschio, Lorenzo; Mallia, Giuseppe; Casassa, Silvia; Ellis, John; Schütz, Martin; Harrison, Nicholas M.

2014-05-01

386

Trapping Rydberg Atoms in an Optical Lattice

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

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

2011-12-23

387

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

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

2011-01-01

388

Silane molecules have been embedded in helium droplets and studied via infrared laser depletion spectroscopy in the range of 2190 cm(-1). We found that the R1 and Q2 lines of the nu(3) band have satellites shifted by about 2.3 cm(-1) towards low frequency and having similar intensity to the main lines. We assigned this perturbation in the spectrum to the coupling of the J=2 levels in nu(3) and close lying nu(1) vibration states. The strength of the coupling is a factor of about 50 larger in He droplets than in free molecules and have the same selection rules implied by the tetrahedral symmetry of SiH(4) molecules. The perturbation, which cannot be explained within the framework of a Hamiltonian of free molecules, is evidence of strong coupling of the molecule with some He excitations in the molecular vicinity. PMID:20059045

Skvortsov, Dmitry; Marinov, Daniil; Sartakov, Boris G; Vilesov, Andrey F

2009-12-28

389

Probing Surface Patch Fields with Rydberg Atoms

NASA Astrophysics Data System (ADS)

The stray electric patch fields present at a Au(111) surface are investigated by studying the ionization of Rydberg atoms incident at near-grazing angles. Measurements of the threshold conditions for observation of the resulting ions are used to estimate the size, and other characteristics, of the stray fields. This is accomplished using an iterative procedure and calculating the threshold conditions for different assumed field parameters using a simple over-the-barrier model of surface tunneling. Excellent fits to the experimental data are obtained over a broad range of n and angles of incidence and indicate that the stray fields can be as large as 10^3 V/cm 100nm from the surface decreasing to 20V/cm 500 nm from the surface. The use of lithographically-patterned electrode arrays to further study the effects of stray fields is being explored. Simulations suggest that engineered electrode structures, which can generate localized fields approaching 10^4 V/cm, will help evaluate the potential of Rydberg atoms as a tool to detect and characterize stray fields as well as allow the detection of low-n (n 10) Rydberg atoms.

Pu, Yu; Neufeld, Dean; Dunning, Barry

2011-06-01

390

Negative ion formation by Rydberg electron transfer: Isotope-dependent rate constants

The formation of negative ions during collisions of rubidium atoms in selected ns and nd Rydberg states with carbon disulfide molecules has been studied for a range of effective principal quantum numbers (10 {le} n* {le} 25). For a narrow range of n* near n* = 17, rate constants for CS{sub 2}{sup {minus}} formation are found to depend upon the isotopic composition of the molecule, producing a negative ion isotope ratio (mass 78 to mass 76, amu) up to 10.5 times larger than the natural abundance ratio of CS{sub 2} isotopes in the reagent. The isotope ratio is found to depend strongly upon the initial quantum state of the Rydberg atom and perhaps upon the collision energy and CS{sub 2} temperature. 32 refs., 5 figs., 1 tab.

Carman, H.S. Jr.; Klots, C.E.; Compton, R.N.

1991-01-01

391

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

We study the Rydberg blockade in a system of three atoms arranged in different two-dimensional geometries (linear and triangular configurations). In the strong blockade regime, we observe high-contrast, coherent collective oscillations of the single excitation probability and an almost perfect van der Waals blockade. Our data are consistent with a total population in doubly and triply excited states below 2%. In the partial blockade regime, we directly observe the anisotropy of the van der Waals interactions between |nD> Rydberg states in the triangular configuration. A simple model that only uses independently measured two-body van der Waals interactions fully reproduces the dynamics of the system without any adjustable parameter. These results are extremely promising for scalable quantum information processing and quantum simulation with neutral atoms. PMID:24856694

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

2014-05-01

392

Rydberg-wave-packet evolution in a frozen gas of dipole-dipole-coupled atoms

NASA Astrophysics Data System (ADS)

We have studied the evolution of Rydberg wave packets in the presence of interatomic dipole-dipole interactions in a frozen Rb gas. Rb atoms in a magneto-optical trap (MOT) are first laser excited to ns Rydberg eigenstates. A picosecond THz pulse further excites them into coherent superposition states involving the initial-level and neighboring np states. A second, identical, time-delayed THz pulse probes the wave-packet dynamics. As the wave packets evolve they are influenced by dipole-dipole interactions, predominantly pairwise excitation-exchange processes of the form |s >|p>?|p>|s>. The coherent electronic evolution of the ensemble dephases due to the variation in dipole-dipole coupling strength between atom pairs in the MOT. The experimental results are in good agreement with numerical calculations that simulate the interactions between nearest neighbors in a frozen gas.

Zhou, Tao; Li, Sha; Jones, R. R.

2014-06-01

393

Phases and collective modes of Rydberg atoms in an optical lattice

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

394

Hybrid model for Rydberg gases including exact two-body correlations

NASA Astrophysics Data System (ADS)

A model for the simulation of ensembles of laser-driven Rydberg-Rydberg interacting multilevel atoms is discussed. Our hybrid approach combines an exact two-body treatment of nearby atom pairs with an effective approximate treatment for spatially separated pairs. We propose an optimized evolution equation based only on the system steady state, and a time-independent Monte Carlo technique is used to efficiently determine this steady state. The hybrid model predicts features in the pair-correlation function arising from multiatom processes which existing models can only partially reproduce. Our interpretation of these features shows that higher-order correlations are relevant already at low densities. Finally, we analyze the performance of our model in the high-density case.

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

2012-12-01

395

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

396

Laser resonance photoionization spectroscopy of Rydberg levels in Fr

We investigated for the first time the high-lying Rydberg levels in the rare radioactive element francium (Fr). The investigations were conducted by the highly sensitive laser resonance atomic photoionization technique with Fr atoms produced at a rate of about 10/sup 3/ atoms/s in a hot cavity. We measured the wave numbers of the 7p/sup 2/P/sub 3/2/..-->..nd/sup 2/D (n = 22--33) and 7p/sup 2/P/sub 3/2/..-->..ns/sup 2/S (n = 23, 25--27,29--31) transitions and found the binding energy of the 7p/sup 2/P/sub 3/2/ state to be T = -18 924.8(3) cm/sup -1/, which made it possible to establish accurately the ionization potential of Fr.

Andreev, S.V.; Letokhov, V.S.; Mishin, V.I.

1987-09-21

397

Decoherence of high-l Rydberg wave packets

NASA Astrophysics Data System (ADS)

Quantum revivals in very-high-n (n ~ 300) high-l Rydberg wave packets generated from parent np states are used to examine decoherence induced by the application of 'coloured' noise from a random pulse generator and by collisions. In the absence of external perturbations, the high-l wave packets maintain their coherence for periods ~ 1 ľs, i.e. for many hundreds of orbits. This coherence can be destroyed on sub-microsecond timescales by the application of even very small amounts of electrical noise at a rate that depends markedly on the spectral characteristics of the noise. In contrast, measurements over similar timescales with CO2 target gas densities of ~ 1011 cm-3 provided no evidence of collisional dephasing. The mechanisms responsible for decoherence are discussed with the aid of classical and quantum simulations. The results of these simulations are in good accord with the experimental data.

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

2011-09-01

398

Rydberg-atom population transfer by population trapping in a chirped microwave pulse

We demonstrate that Rydberg atoms can be transferred to states of lower principal quantum number by exposing them to a frequency chirped microwave pulse. Specifically, we have transferred n=75 atoms to n=66 with a 400-ns pulse chirped from 7.8 to 11.8 GHz. In spite of the large number of coupled levels, using a simplified model we can describe the process

J. Lambert; Michael W. Noel; T. F. Gallagher

2002-01-01

399

Rydberg-Atom Population Transfer By Population Trapping in a Chirped Microwave Pulse

We demonstrate that Rydberg atoms can be transferred to states of lower principal quantum number by exposing them to a frequency chirped microwave pulse. Specifically, we have transferred n=75 atoms to n=66 with a 400-ns pulse chirped from 7.8 to 11.8 GHz. In spite of the large number of coupled levels, using a simplified model we can describe the process

J. Lambert; Michael W. Noel; T. F. Gallagher

2002-01-01

400

Ionization and entanglement of two interacting Rydberg atoms in a strong laser field

NASA Astrophysics Data System (ADS)

Dynamics of ionization and entanglement of two Rydberg atoms interacting with each other and with external strong laser field is investigated. The phenomenon of interference stabilization of the bipartite atomic system is established in a strong field limit. The production of highly-entangled state of the studied atoms is shown to be realized. The possibility to control the evolution and time-dependent entanglement of the examined multilevel q-dit system is demonstrated.

Burenkov, Ivan A.; Tikhonova, Olga V.

2014-04-01

401

Ionization of sodium and rubidium nS , nP , and nD Rydberg atoms by blackbody radiation

NASA Astrophysics Data System (ADS)

Results of theoretical calculations of ionization rates of Rb and Na Rydberg atoms by blackbody radiation (BBR) are presented. Calculations have been performed for nS , nP , and nD states of Na and Rb, which are commonly used in a variety of experiments, at principal quantum numbers n=8 65 and at three ambient temperatures of 77, 300, and 600K . A peculiarity of our calculations is that we take into account the contributions of BBR-induced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of measured ionization rates and shapes of their dependences on n . The calculated ionization rates are compared with the results of our earlier measurements of BBR-induced ionization rates of Na nS and nD Rydberg states with n=8 20 at 300K . A good agreement for all states except nS with n>15 is observed. We also present the useful analytical formulas for the quick estimation of BBR ionization rates of Rydberg atoms.

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

2007-05-01

402

We present a detailed analysis and design of a neutral atom quantum logic device based on atoms in optical traps interacting via dipole-dipole coupling of Rydberg states. The dominant physical mechanisms leading to decoherence and loss of fidelity are enumerated. Our results support the feasibility of performing single- and two-qubit gates at MHz rates with decoherence probability and fidelity errors

M. Saffman; T. G. Walker

2005-01-01

403

Spatial correlations between Rydberg atoms in an optical dipole trap

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

404

NASA Astrophysics Data System (ADS)

Collisions that produce a change in the total angular momentum and quenching processes involving the triplet z 3° titanium excited level and noble gases have been studied by laser perturbation and time-resolved spectroscopy. Titanium atoms are produced in a hollow-cathode discharge, and the analysis of resonance and sensitized fluorescence light decays enable us to determine total-angular-momentum-changing (J-changing) and quenching cross sections induced by collisions with helium, neon, and argon atoms. The thermally averaged J-changing cross section (z 3F ° i-->z 3F ° j) in units of 10-16 cm2 are ?Ż4-->2=1.7+/-0.5, 0.7+/-0.06, 3.1+/-1 ?Ż4-->3=11+/-2, 1.4+/-0.1, 11+/-1 ?Ż3-->2=7+/-2, 2.2+/-0.3, 14+/-2, respectively, for helium, neon, and argon colliding partners. As for alkali-metal-noble-gas collisions, a pronounced minimum of the J-changing cross sections is obtained for the titanium (z 3F °)-neon collisions. Radiative destruction probabilities of the z 3F ° j (j=4,3,2) titanium sublevels have been measured also, and good agreement with accepted values is found.

Dezert, D.; Quichaud, V.; Degout, D.; Catherinot, A.

1986-12-01

405

Helium, which was first discovered on the sun with the help of spectral analysis, plays, together with hydrogen, a principal\\u000a role in astrophysics. We consider here two fundamental quantities: primordial helium abundance formed during Big Bang nucleosynthesis\\u000a and the current initial helium abundances in nearby stars. It is shown that stellar atmospheres are enriched in helium during\\u000a the main-sequence stage.

L. S. Lyubimkov

2010-01-01

406

A large helium liquefier is described which produces 7.5 liters of liquid helium per hour through a Joule-Thomson expansion valve when operated from a compressor giving 21 cu ft.\\/min. flow at a pressure head of 320 lb.\\/sq. in. The liquid helium can readily be transferred into exterior cryostats. The consumption of liquid hydrogen, used to pre-cool the helium gas, during

J. G. Daunt; H. L. Johnston

1949-01-01

407

NASA Astrophysics Data System (ADS)

The core-valence-Rydberg Becke's three-parameter exchange (B3)+Lee-Yang-Parr (LYP) correlation functional (CVR-B3LYP) is proposed as a means to improve descriptions of Rydberg excitations of core-valence B3LYP (CV-B3LYP). CV-B3LYP describes excitations from both core and occupied valence orbitals to unoccupied valence orbitals with high accuracy but fails to describe those to Rydberg orbitals. CVR-B3LYP, which adopts the appropriate portions of Hartree-Fock exchange for unoccupied valence and Rydberg regions separately, overcomes the disadvantage of CV-B3LYP. Numerical assessment confirms that time-dependent density functional theory calculations with CVR-B3LYP succeed in describing not only core excitations but also Rydberg excitations with reasonable accuracy.

Nakata, Ayako; Imamura, Yutaka; Nakai, Hiromi

2006-08-01

408

Properties of Ni^+ from microwave spectroscopy of n=9 Rydberg levels of Nickel

NASA Astrophysics Data System (ADS)

The microwave/RESIS method was used to determine the relative positions of 15 of the n=9 Rydberg levels of Nickel with L >= 6. Because the ground state of the Ni^+ ion is a ^2D5/2 level, each Rydberg level (n,L) splits into six eigenstates whose relative positions are determined by long-range e-Ni^+ interactions present in addition to the dominant Coulomb interaction. A previous study with the optical RESIS method determined these positions with precision of +/- 30 MHz [1]. Using the microwave/RESIS method improves that precision by a factor of 300, and leads to much improved determinations of the Ni+ properties that control the long-range interactions. [4pt] [1] Julie A. Keele, Shannon L. Woods, M.E. Hanni, and S.R. Lundeen Phys. Rev. 81, 022506 (2010)

Woods, Shannon; Keele, Julie; Smith, Chris; Lundeen, Stephen

2012-06-01

409

Thermal Casimir-Polder shifts in Rydberg atoms near metallic surfaces

The Casimir-Polder (CP) potential and transition rates of a Rydberg atom above a plane metal surface at finite temperature are discussed. As an example, the CP potential and transition rates of a rubidium atom above a copper surface at 300 K are computed. Close to the surface we show that the quadrupole correction to the force is significant and increases with increasing principal quantum number n. For both the CP potential and decay rates one finds that the dominant contribution comes from the longest wavelength transition and the potential is independent of temperature. We provide explicit scaling laws for potential and decay rates as functions of atom-surface distance and principal quantum number of the initial Rydberg state.

Crosse, J. A.; Clements, Kate; Buhmann, Stefan Y.; Scheel, Stefan [Quantum Optics and Laser Science, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Ellingsen, Simen A. [Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim (Norway)

2010-07-15

410

Inelastic and quasielastic collisions of Rydberg atoms with the heavy rare-gas atoms

The authors develop a semiclassical theory of collisions of Rydberg atoms with neutral targets. The impact-parameter approach is combined with the normalized perturbation theory. The transition probabilities and cross sections are represented in terms of scaled variables and analyzed in terms of dependence on an inelasticity parameter and a collision strength parameter. They show that the standard scattering length approximation, widely used for the Rydberg-atom-rare-gas-atom collisions, is not valid for heavy rare-gas atoms. Inelastic processes involving these atoms are substantially affected by the Ramsauer-Townsend effect. The authors present the results for quenching of the Rb atoms in nS, nD, and nF states in collisions with Ar, Kr, and Xe. They compare the theory with experimental data in a wide range of the principal quantum numbers and transition energy defects.

Lebedev, V.S.; Fabrikant, I.I. [Univ. of Nebraska, Lincoln, NE (United States)

1996-05-01

411

The nonlinear interaction of Rydberg Na atoms (P-series) with IR and millimeter radiation

NASA Astrophysics Data System (ADS)

The nonlinear resonant interaction of CO2-laser radiation (lambda = 10.6 microns) and of tunable millimeter radiation at wavelengths of 3.8-5.6 mm with Rydberg Na atoms excited in the nP state with n = 11 and 36. The Rydberg Na atoms were obtained in an atomic beam under three-stage excitation according to the 3S(1/2)-3P(3/2)-4S(1/2)-nP(1/2, 3/2) scheme. Pulsed tunable organic-dye lasers and a laser utilizing F2(-) color centers in the LiF crystal were used. It is concluded that, under the present experimental conditions, the saturation effects are largely due to the Stark effect in an inhomogeneous field; this significantly reduces the coherent interaction time. Saturation of the two-photon absorption at the 36P-37P transition is observed.

Beterov, I. M.; Vasilenko, G. L.; Fateev, N. V.

1988-07-01

412

Oxygen atom Rydberg emission in the equatorial ionosphere from radiative recombination

NASA Astrophysics Data System (ADS)

Radiative recombination of O+ generates a variety of O-atom Rydberg levels, which then radiatively cascade to the ground state. The last two steps in the cascade produce 844.6 nm and 130.2-130.6 nm radiation in the triplet set of Rydberg levels and 777.2-777.5 nm and 135.6 nm radiation in the quintets. These four emissions are well known from ionospheric observations, and the higher members of the cascades are sometimes seen in auroral spectra but rarely in the nightglow. Sky spectra taken in 2000 at the Keck II telescope with the ESI echelle spectrograph reveal 20 members of the Rydberg transitions in the 390-930 nm region not previously observed in the nightglow. Most of these are not seen in earlier Keck spectra, taken at solar minimum. We are able to quantify the relative intensities of the emissions across the entire wavelength region using standard star spectra, allowing comparisons to be made with theoretical calculations. As the atmosphere is optically thin for the quintet transitions, corrections for radiative scattering are not necessary, and relative agreement between theory and observations is excellent. For the triplets the data agree more closely with the optically thick calculations. The relationship between the intensities of the quintet 3d-3p (926-926.6 nm) and the triplet 3p-3s (844.6 nm) multiplets is investigated and found to be linear. Accurate wavelengths are determined for the Rydberg quintets on the basis of observations with the high-resolution (40,000) Keck I/HIRES system. For the triplets the multiplets are incompletely resolved. Examples of spectra are presented where the 844.6 nm multiplet is the only OI Rydberg emission observed. We argue that the cause is Bowen fluorescence, a consequence of photoexcitation of the OI 3d-2p transition by H Lyman-? radiation in the geocorona. The fact that so many of the oxygen Rydberg lines have been identified in this study and that their intensities are consistent with cascade models of radiative recombination is a strong confirmation of the importance of this process in the tropical nightglow near solar maximum.

Slanger, T. G.; Cosby, P. C.; Huestis, D. L.; Meier, R. R.

2004-10-01

413

NASA Technical Reports Server (NTRS)

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

Cook, Joseph

1996-01-01

414

NASA Astrophysics Data System (ADS)

The electronic spectrum of the C 0+, D 1 ? X 0+ transitions of KrXe has been studied at high resolution in the vicinity of the Kr(1S0)+Xe 6p[5/2]2 dissociation limit by resonance-enhanced (1 + 1') two-photon ionization spectroscopy. The rotational structure of 13 bands, 5 and 8 of which correspond to transitions to levels of 0+ and 1 symmetry, respectively, were observed in the spectra of several isotopomers. The hyperfine structure in the spectrum of the ? = 1 levels of 84Kr129Xe was determined. The five transitions to levels of 0+ symmetry form a regular progression of bands characterized by a regular rotational structure and corresponding to high vibrational levels (with v = 16-20) of the C 0+ state. The C 0+ state is found to possess significant X 1/2, A1 3/2 and A2 1/2 ion-core character in combination with an excited electron of 6p?, 6p? and 6s? character, respectively, and to correlate adiabatically to the Kr(1S0)+Xe 6s[1/2]1o dissociation limit. The transition to the eight levels of ? = 1 symmetry form a very irregular progression both as far as spectral positions and intensities are concerned. Rotational levels of f-symmetry, accessed via Q-branch transitions, are weakly predissociated by a repulsive level associated with the Kr(1S0)+Xe 6s[1/2]0o limit. A local perturbation in the rotational structure of the fourth level of ? = 1 symmetry enabled the identification of a so far unobserved predissociative level of ? = 1 or ? = 2 symmetry with band center near 77318.5 cm-1. The determination of the band centers, rotational constants and isotopic shifts of the ? = 1 levels led to the conclusion that the level structure is affected by homogeneous perturbations and that at least two electronic states of ? = 1 symmetry contribute to the spectrum of KrXe in this spectral region. Modelling the observed rovibronic structure using a coupling model involving low vibrational levels of a weakly bound ? = 1 state associated with the Kr(1S0)+Xe 6s[1/2]1o dissociation limit and high vibrational levels of a more strongly bound state associated with the Kr(1S0) + Xe 6p[5/2]2 dissociation limit enabled us to reproduce the observed values of the rotational constants, vibronic positions and intensity distribution in a qualitatively satisfactory manner. However, the model failed to account for the observed isotopic shifts. Rotationally resolved photoelectron spectra of the KrXe+ X 1/2 ? KrXe C 0+ and KrXe+ A1 3/2 ? KrXe C 0+ ionizing transitions were recorded from selected rotational levels of selected isotopomers of KrXe. The rotational levels of the X 1/2 state of KrXe+ group as pairs of levels of opposite parity and have a spin-rotation coupling constant ? of approximately -2B, as a consequence of pure precession. The rotational level structure of the low-lying electronic states of KrXe+ thus appears to form the same patterns as the corresponding states of ArXe+.

Piticco, Lorena; Merkt, Frédéric

2013-02-01

415

CW Measurement of the Upward-Going Temperature Wave in the Helium-4 Self-Organized Critical State

We describe the first continuous-wave (CW) measurements of the upward-going temperature wave in the self-organized-critical (SOC) state which forms in 4He under conditions of downward heat flow near T{lambda} under gravity. The CW technique permits measurements with extremely low (<1 nK) excitation amplitudes, allows continuous measurement of the wave velocity as the SOC state grows, and has yielded the first quantitative measurements of the attenuation. The CW measurements appear to support predictions for the velocity but disagree with predictions for the attenuation. This new technique may help us understand the underlying mechanism of the SOC state.

Boyd, S. T. P.; Sergatskov, D. A.; Duncan, R. V. [Department of Physics and Astronomy, University of New Mexico, Albuquerque NM 87131 (United States)

2006-09-07

416

Creating and Detecting Shaped Rydberg Wave Packets

Inherently quantum mechanical, transient nanostructures with dynamics on a picosecond time scale can be produced by controlling the quantum dynamics of Rydberg electrons. Ultrashort, tailored light pulses are used to build structures in position and/or momentum space from the wave function of an electron. The optimal laser pulses required to make these structures can be computed and synthesized in the laboratory. As an example, we present a structure consisting of five peaks which acts as a time-dependent grating and can be detected via ultrafast extreme ultraviolet diffraction. {copyright} {ital 1997} {ital The American Physical Society}

Krause, J.L. [Quantum Theory Project, P.O. Box 118435, University of Florida, Gainesville, Florida 32611-8435 (United States)] [Quantum Theory Project, P.O. Box 118435, University of Florida, Gainesville, Florida 32611-8435 (United States); Schafer, K.J. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States)] [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Ben-Nun, M.; Wilson, K.R. [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093 (United States)] [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093 (United States)

1997-12-01

417

Radiatively assisted collisions of K Rydberg atoms

We have observed radiatively assisted collisions between velocity-selected K Rydberg atoms in radio-frequency (rf) fields. The low relative velocity of the atoms leads to long collision times, or equivalently, narrow, 1-MHz, collisional resonances. We have carried out systematic measurements with rf fields in the strong-field regime, and have shown that the cross sections agree quantitatively with the predictions of the strong-field theory. We have also shown experimentally and theoretically that the sum over {ital m} of the cross sections for {ital m} photon-assisted cross sections is larger than the resonant-collision cross section in the absence of a rf field.

Thomson, D.S.; Renn, M.J.; Gallagher, T.F. (Department of Physics, University of Virginia, Charlottesville, Virginia 22901 (United States))

1992-01-01

418

The continuing u.s. Helium saga.

Helium, resident in relatively high concentrations in certain natural gas fields in the United States, can be lost to the atmosphere when the natural gas is burned as fuel. In 1960, Congress amended the Helium Act of 1925 to provide for stripping natural gas of its helium, for purchase of the separated helium by the government, and for its long-term storage. In 1971, after about 28 billion cubic feet had been stored, the purchase program was terminated by the government, an action that unleashed several lawsuits and not a little acrimony. After more than a decade of controversy, much of the litigation has been concluded, much of the helium that could have been saved has been wasted to the atmosphere, and the gas fields supplying the helium are almost depleted. A new rich source of helium has been discovered in southwestern Wyoming that could ensure adequate supplies for many decades if an appropriate new federal policy on helium is developed and implemented. PMID:17737740

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

1984-02-24

419

NASA Technical Reports Server (NTRS)

A number of future space missions require liquid helium for cooling scientific payloads. These missions will require the long term storage and resupply of liquid helium at temperatures of 1.4 - 2.1 Kelvin. In addition, some of the proposed instruments will require refrigeration to temperatures as low as 50 mK. A variety of liquid helium based refrigerator systems could provide this subkelvin cooling. The status of helium storage and refrigeration technologies and of several alternative technologies is presented here along with areas where further research and development are needed. (Helium resupply technologies are the topic of another presentation at this symposium). The technologies covered include passive and dynamic liquid helium storage, alternatives to liquid helium storage, He -3 refrigerators, He -3/He -4 dilution refrigerators, and alternative sub-kelvin coolers.

Kittel, Peter

1987-01-01

420

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

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

2010-05-14

421

Interaction-induced stabilization of circular Rydberg atoms

We discuss a candidate solution for the controlled trapping and manipulation of two individual Rydberg atoms by means of a magnetic Ioffe-Pritchard trap that is superimposed by a constant electric field. In such a trap Rydberg atoms experience a permanent electric dipole moment that can be of the order of several hundred debye. The interplay of electric dipolar repulsion and three-dimensional magnetic confinement leads to a well controllable equilibrium configuration with tunable trap frequency and atomic distance. We thoroughly investigate the trapping potentials and analyze the interaction-induced stabilization of two such trapped Rydberg atoms. Possible limitations and collapse scenarios are discussed.

Hezel, Bernd [Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, DE-69120 Heidelberg (Germany); Mayle, Michael; Schmelcher, Peter [Zentrum fuer Optische Quantentechnologien, Universitaet Hamburg, Luruper Chaussee 149, DE-22761 Hamburg (Germany)

2011-12-15

422

Dressed multi-wave mixing process with Rydberg blockade.

We investigate the way to control multi-wave mixing (MWM) process in Rydberg atoms via the interaction between Rydberg blockade and light field dressing effect. Considering both of the primary and secondary blockades, we theoretically study the MWM process in both diatomic and quadratomic systems, in which the enhancement, suppression and avoided crossing can be affected by the atomic internuclear distance or external electric field intensity. In the diatomic system, we also can eliminate the primary blockade by the dressing effect. Such investigations have potential applications in quantum computing with Rydberg atom as the carrier of qubit. PMID:23736395

Zheng, Huaibin; Zhao, Yan; Yuan, Chenzhi; Zhang, Zhaoyang; Che, Junling; Zhang, Yiqi; Zhang, Yunguang; Zhang, Yanpeng

2013-05-20

423

Chaotic Ionization of Bidirectionally Kicked Rydberg Atoms

NASA Astrophysics Data System (ADS)

A highly excited quasi one-dimensional Rydberg atom exposed to periodic alternating external electric ?eld pulses exhibits chaotic behavior. The ionization of this system is governed by a geometric structure of phase space called a homoclinic tangle and its turnstile. We present and explain the results from an experiment designed to probe the structure of the phase space turnstile. We create time-dependent Rydberg wave packets, subject them to alternating applied electric fields (kicks), and measure the survival probability. We show that the survival probability of the electron depends not only on the initial electron energy, but also on the phase space position of the electron with respect to the turnstile--the portion of the electron wave packet inside the turnstile ionizes quickly, after one period of the applied field, while that portion outside the turnstile ionizes after multiple kicking periods. Finally, we use the turnstile geometry to explain the dependence of ionization on the kicking period. This procedure describes a very robust yet simple way to control chaotic ionization of an atomic system.

Burke, Korana; Mitchell, Kevin; Ye, Shuzhen; Dunning, F. Barry; Wyker, Brendan

2012-02-01

424

Fidelity of a Rydberg-blockade quantum gate from simulated quantum process tomography

NASA Astrophysics Data System (ADS)

We present a detailed error analysis of a Rydberg blockade mediated controlled-not quantum gate between two neutral atoms as demonstrated recently in Isenhower [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.010503 104, 010503 (2010)] and Zhang [Phys. Rev. A1050-294710.1103/PhysRevA.82.030306 82, 030306 (2010)]. Numerical solutions of a master equation for the gate dynamics, including all known sources of technical error, are shown to be in good agreement with experiments. The primary sources of gate error are identified and suggestions given for future improvements. We also present numerical simulations of quantum process tomography to find the intrinsic fidelity, neglecting technical errors, of a Rydberg blockade controlled phase gate. The gate fidelity is characterized using trace overlap and trace distance measures. We show that the trace distance is linearly sensitive to errors arising from the finite Rydberg blockade shift and introduce a modified pulse sequence which corrects the linear errors. Our analysis shows that the intrinsic gate error extracted from simulated quantum process tomography can be under 0.002 for specific states of 87Rb or Cs atoms. The relation between the process fidelity and the gate error probability used in calculations of fault tolerance thresholds is discussed.

Zhang, X. L.; Gill, A. T.; Isenhower, L.; Walker, T. G.; Saffman, M.

2012-04-01

425

NASA Technical Reports Server (NTRS)

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

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

1971-01-01

426

We describe a (1)H polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T?30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T<90 K, a new probe system using cold helium gas for both sample-cooling and -spinning was developed. The novel system can sustain a low sample temperature between 30 and 90K for a period of time >10 h under MAS at ?(R)?3 kHz with liquid He consumption of ?6 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T?34 K, (1)H DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules. PMID:23079589

Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi

2012-12-01

427

NASA Astrophysics Data System (ADS)

We describe a 1H polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T ? 30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T ? 90 K, a new probe system using cold helium gas for both sample-cooling and -spinning was developed. The novel system can sustain a low sample temperature between 30 and 90 K for a period of time >10 h under MAS at ?R ? 3 kHz with liquid He consumption of ?6 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T ? 34 K, 1H DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules.

Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi

2012-12-01

428

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

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

Stipanovi?, P; Marki?, L Vranje; Boronat, J; Kei?, B

2011-02-01

429

Experimental investigation of non-hydrogenic orbits in helium recurrence spectra

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