Charge Impurities in Cold Atomic andMolecular Systems

July 19-21, 2017Organizers:

Svetlana Kotochigova (NIST & Temple)Tommaso Calarco (Ulm)

Sponsored by:

Institute for Theoretical Atomic, Molecular and Optical Physics*

Harvard - Smithsonian Center for Astrophysics60 Garden St., Cambridge, MA

https://www.cfa.harvard.edu/itamp-event/charge-impurities-cold-atomic-and-molecular-systems

Abstracts, Program, Participants, and Guide to ITAMP

*Funded by the National Science Foundation

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Harvard-Smithsonian Center for AstrophysicsITAMP

MS-14, B-32660 Garden Street

Cambridge, MA 02138 USA

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INDEX

Welcome 4Synopsis 6Participants 7Program 9

Rudro Biswas 12Lauriane ChomazMarkus Deiss 14Eugene Demler 15Michael Drewsen 16Alexander Glaetzle 17Rosario González-Férez 18Eric Hudson 19Thomas Killian 20Michael KÖhl 21Ming Li 22Henri Lopez 23Floarian Meinert 24Antonio Negretti 25Herwig Ott 26Roee Ozeri 27Jesús Pérez-RÍos 28Peter Schmelcher 29Winthrop Smith 31Thierry Stoecklin 32Michal Tomza 34 Tomasz Wasak 35Andrey Vilesov 36Vladan Vuletic 37

ITAMP Guide 38 Notes 42

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Abstracts

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Notes

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Welcome Notes

ITAMP began life in 1989 at the Harvard-Smithsonian Center for Astrophysics. It is the only theoretical AMO "user facility" in the United States. It hosts workshops (3-days) and topical group meetings (1-4 weeks), and visitors (short- and long-term), has a flagship speaker series, the Joint Atomic Physics colloquia held in Harvard Physics, and a rigorous postdoctoral program. ITAMP workshops are web-cast, when possible, and beginning in 2010, workshop lectures are available on the ITAMP YouTube channel. There are on average 4-5 workshops each year. A Call for Proposal to organize workshops and a list of workshops & topical groups are available at http://itamp.harvard.edu. The postdoctoral program has been a recognized success, placing energetic fellows into junior positions at universities and national labs.

ITAMP thrives in the larger Cambridge-area AMO physics ecosystem, drawing upon the considerable depth and breadth of experimental expertise. The mission of ITAMP continues to be in furthering the cause of theoretical AMO physics by providing resources, centrality of location, and scientific and administrative expertise, to enhance collaborative efforts between theory and experiment, and to be broad in advocating for theoretical AMO.

H. Sadeghpour

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ITAMP Guide

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Synops is ITAMP Guide

The workshop will bring together experts in the field of quantum hybrid ion-neutral systems with controllable properties. This workshop will initiate a dialog about recent advances in many-body simulations with ultracold atomic and molecular gases coupled to one or more ions, novel species-independent techniques of cooling and trapping, and chemical reactivity at the ultra-cold single-to-few ion limit. We will also discuss advances in the closely-related hybrid many-body system, namely, that of one or more Rydberg atoms embedded in a gas of ultra-cold atoms.

Organizers:

Svetlana Kotochigova (NIST & Temple University)Tommaso Calarco (University of Ulm)

c. Part I section, your SSNb. Part II Section, your Signature and DateNote: Do not e-mail this form that contains your SSN. This confidential data will not be stored and it will be destroyed. If you will be faxing the documents, use +1-617-495-5970, which is a private fax line.4) Foreign Individual Vendor Request Form. This form is for Foreign Nationals. Please follow the instructions to your individual specifications and fill in the following information:1) Your name2) SSN if applicable (if none, enter N/A)3) Your Mailing address4) Your Email5) Your Visa Type5) Federal Awards Travel Reimbursement Exception Form. This for is for the traveler who uses non-U.S. Flag air carrier. If applicable, please sign in at the bottom of the form where “Reimbursee Signature” and “Date” is. Thank you for helping us to get your reimbursements back to you quickly as possible. Your check will be sent about a month after we process your paper work. Please contact us with any questions or concerns that you might have.

Important Note: In case your expenses are being paid by your institute, you do not need to fill out these forms. Instead we will need an invoice from your institute that contains the information below:• Invoice number• Invoice date• Bill to: Harvard College Observatory 60 Garden Street, MS 14 Cambridge, MA 02138• Make Payment To: NAME & ADDRESS of your University• Description of your visit• Balance due• Wire Transfer information (only for international participants with

more than 1000 support)

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Par t i c ipan ts ITAMP Guide

Nisreen AlshehriKing Saud UniversityPhysnis@Gmail.Com

James BabbITAMPjbabb@cfa.harvard.edu

Rudro BiswasPurdue University rrbiswas@purdue.edu

Tommaso Calarco University of Ulm Tommaso.Calarco@Uni-Ulm.De

Lorraine ChomazUniversity of Innsbruck lauriane.chomaz@uibk.ac.at

Markus DeissUniversity of Ulmmarkus.deiss@uni-ulm.de

Eugene DemlerHarvard University demler@physics.harvard.edu

Michael DrewsenAarhus Universitydrewsen@phys.au.dk

Alexander GlaetzleOxford Universityglaetzle@gmail.com

Rosario González-FérezGranada Universityrogonzal@ugr.es

Shinsuke HazeInstitute For Laser Science, Uec Haze@Ils.Uec.Ac.Jp

Eric HudsonUCLAericrhudson@gmail.com

Thomas KillianRice Universitykillian@rice.edu

Michael KöhlUniversity of Bonnmichael.koehl@uni-bonn.de

Svetlana KotochigovaNIST & Templesvetlana.kotochigova@temple.edu

Jonathan KwolekUniversity of ConnecticutKwolek.Jonathan@Gmail.Com

Ming Li Temple UniversityMing.Li@Temple.edu

Yen-Wei LinHarvard UniversityYenweilin@G.Harvard.edu

Henri LopezUniversity of Heidelberg lopez@physi.uni-heidelberg.de

Constantinos MakridesUniversity of MarylandMakrides@Umd.edu

Florian MeinertUniversity of Stuttgartf.meinert@physik.uni-stuttgart.de

Rick MukherjeeRice UniversityRm47@Rice.edu

Instructions for Reimbursement Forms

If you have been promised support to help cover your expenses, the following forms will be required paperwork for your reimbursement. Please, only use the attached forms if you have already received an offer of support. If you feel there has been a mistake or are unsure about your support, please ask and we can assist you. We will only need receipts that will total up to your promised support in your invitation letter. If your receipts total over that amount, you will simply just be reimbursed up to that promised amount. Here are the directions for filling out the following forms.1) The Non-Employee Reimbursement Form. This form is submitted to the University and must be filled out in a specific way. We will fill in the details of your expenses. Please provide the following information:a. Your name in the box marked “Reimbursee Name” b. Affiliationc. Your citizenship and resident information d. SIGN the bottom at “Reimbursee Signature” and fill in the check mailing address section below your signature. e. Leave the back page blank

Leave the following sections blank:• Business Purpose Section and• The box below of “All expenses must be itemized…” Section.2) Missing Receipt Affidavit. You will only need this document if anything you send does not fit the receipt policy. Harvard’s receipt policy is on the back of this form. If you do not believe there will be a problem, you do not need to submit this form. It is included here, in case of a problem. We would however encourage you to sign this form in any event to quicken the process.3) W-9 Request for Taxpayer Identification Number and Certification Form. This form should be signed by U.S. citizens or U.S. Residents. Please fill in the following information:a. Nameb. Address, City, State and Zip code

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Par t i c ipan ts ITAMP Guide

Antonio NegrettiUniversity of Hamburganegrett@physnet.uni-hamburg.de

Kang-Kuen NiHarvard UniveristyNi@Chemistry.Harvard.edu

Herwig OttUniversity of Kaiserslauternott@physik.uni-kl.de

Roee Ozeri Weizmann Institute of ScienceRoee.Ozeri@weizmann.ac.il

Igor PikovskiITAMPIgor.Pikovski@Cfa.Harvard.edu

Jesús Pérez-RíosPurdue University jperezri@purdue.edu

Seth RittenhouseUnited States Naval Academyrittenho@usna.edu

Hossein Sadeghpour ITAMPhsadeghpour@cfa.harvard.edu

Peter Schmelcher University of Hamburgpschmelc@physnet.uni-hamburg.de

Richard SchmidtITAMPRichard.Schmidt@Cfa.Harvard.edu

Dries SelsBoston UniversityDsels@Bu.edu

Winthrop Smith University of Connecticut Winthrop.Smith@Uconn.edu

Thierry Stoecklin University of Bordeaux thierry.stoecklin@u-bordeaux.fr

Eite Tiesinga NIST & JQIEite.Tiesinga@Nist.Gov

Michal TomzaUniversity of Warsawmichal.tomza@chem.uw.edu.pl

Alban UrvoyMITUrvoy@Mit.edu

Andrey VilesovUniversity of Southern California vilesov@usc.edu

Vladan VuleticMIT Vuletic@Mit.edu

Daniel Vrinceanu Texas Southern UniversityVrinceanud@Tsu.edu

Dominik WildHarvard UniversityWild@G.Harvard.edu

Tomasz WasakUniversity of WarsawTomasz.Wasak@Fuw.edu.Pl

Jhih-Shih YouHarvard UniversityJhihshihyou@Gmail.Com

Public Transportation and Taxicabs Buses servicing Harvard Square & CfA area are Buses # 72, 74, 75 and 78Bus to Harvard Square to MIT is Bus #1Buses to Watertown and Belmont are #71, #73Harvard Square to Boston: Red Line Train to Park Street StationHarvard Square to Airport: Red Line Train to South Station. Take the Silver line to Logan Airport. Silver line stops at all terminals. To see the schedule of buses visit http://www.mbta.com/schedules_and_maps/bus/

TaxicabsAmbassador: 617 492-1100 Yellow: 617 547-3000

Dining in and around ITAMP

At the Observatory The Cart In the Perkin Lobby Open from 9:30 to 2:30

Near the Observatory Sarah’s Market, 200 Concord Ave. The Village Kitchen, 359 Huron Ave. Full Moon, 344 Huron Ave. House of Chang, 282 Concord Ave. Trattoria Pulcinella, 147 Huron Ave. Armanado’s Pizza, 163 Huron Ave. Hi-Rise Bread CO, 208 Concord Ave. Formaggio Kitchen, 244 Huron Ave

Massachusetts Ave. Chang-Sho, 1712 Mass. Ave. Temple Bar, 1688 Mass. Ave. Simons Coffee House, 1736 Mass. Ave. Stone Hearth Pizza Co., 1782 Mass. Ave. Super Fusion, 1759 Mass. Ave. Cambridge Common, 1667 Mass Ave. Lizard Lounge, 1667 Mass. Ave.

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Program ITAMP Guide

Charge impurities in cold atomicand molecular systems

July 19, 2017 - July 21, 2017 Phillips Auditorium

Wednesday, July 19, 2017

Chair: Hossein Sadeghpour8:30 am Registration - Coffee & Pastries9:00 am Welcome and Introduction Svetlana Kotochigova & Tommaso Calarco9:30 am Peter Schmelcher Mesoscopic Molecular Ions in Ultracold Atom-Ion Hybrid Systems10:10 am Rosario González-Férez Rydberg Optical Feshbach Resonances in Cold Gases 10:50 am Coffee11:20 am Jesús Pérez-Ríos A single Rydberg atom in a high density media: a chemistry-assisted new world12:00 pm Florian Meinert Photo-association of trilobite Rydberg molecules via resonant spin-orbit coupling12:40 pm Lunch

Chair: James Babb2:00 pm Antonio Negretti Controlled atom-ion interactions2:40 pm Herwig Ott Electrons and ions meet ultracold atoms3:20 pm Alex Glaetzle Adiabatic Quantum Computing and Quantum Spin Lenses with Ultra-Cold Rydberg Atoms4:00 pm Coffee

Welcome to ITAMP ITAMP Office: 60 Garden St.Cambridge, MA 02138 B-326 MS-14Fax: 617 496-7668Fax: 617 495-5970 (for confidential material e.g. tax forms, reference letters etc.)

Who to Contact:Naomi Tariri Tel: 617 495-9524 Office B-326Alice Kalemkiarian Tel: 617 495-0402 Office B-323

Computer SupportThe Center for Astrophysics has a large computer network and there are many options for connectivity. In this section, we describe the easiest ways to get on-line. Jim Babb, B-318, can help with questions about how to get connected and related issues. There is also a Computer Help Desk on the second floor, near Room B-215.

Internet AccessMost wireless devices will connect to the “Harvard Guest” account. This works fine and there is no paperwork involved in getting internet access. Other connections are available, should this not work for you for some reason. Please see Jim Babb if you run into problems.

Copiers/Faxing and Phone AccessCopy Machines are located throughout the building (see map) The access code for copy machines throughout the CfA is 9635.

Telephone System To call outside the University you must dial 9 before the number. The Univer-sity prefix three digits are 495 and 496. To dial on campus, you simply need to dial the “5” or “6” and the last four digits. For example, ITAMP Admin office’s number is 617-495-9524. You can dial 5-9524 to call internally. The Institute is not permitted to pay for long distance calls.

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4:30 pm Thomas Killian From Ultralong-range Molecules to Rydberg Polarons in a Bose Gas5:10 pm Lauriane Chomaz Observation of the roton mode in a dipolar quantum gas 6:00 pm Reception - Perkin Lobby

Thursday, July 20, 2017

Chair: Eite Tiesinga8:30 am Michael Köhl Dynamics of spin impurities in a strongly-interacting Fermi gas9:10 am Eric Hudson Hybrid traps, molecular ions, and radioactive qubits9:50 am Ming Li Excited State Atom-Ion Charge-Exchange10:30 am Coffee11:00 am Michael Drewsen Coherent internal state manipulation of single atomic and molecular ions by frequency combs11:40 am Tomasz Wasak Application of ultracold atom-atom and atom-ion systems for magnetic field sensing12:20 pm Lunch

Chair: Constantinos Makrides2:00 pm Roee Ozeri Ultracold trading: the observation of momentum, spin and electronic-excitation exchange in atom-ion collisions 2:40 pm Vladan Vuletic Strongly interacting traveling Rydberg polaritons3:20 pm Coffee3:50 pm Eugene Demler Polarons in Electron Systems and Ultracold Atoms

Strongly interacting travelingRydberg polaritons

Vladan VuleticDepartment of Physics

Massachusetts Institute of Technology

By coherently coupling light to Rydberg excitations in a dense atomic medium, it is possible to realize tunable strong long-range interaction between individual Rydberg polaritons. By implementing exchange collisions between selected Rydberg levels, we realize a robust π/2 collisional phase shift that is determined by the interaction symmetry rather than the precise experimental parameters. This may enable advances towards more general symmetry-protected many-body states. I will also discuss recent advances on cavity cooling of atoms at large detuning from atomic transitions as a possible scheme for laser cooling arbitrary particles.

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4:30 pm Andrey Vilesov X-ray coherent diffractive imaging of quantum vortices in helium droplets

Friday, July 21, 2017

Chair: Daniel Vrinceanu8:30 am Rudro Biswas Charged and topological impurities in quantum states of matter9:10 am Markus Deiss State-to-state chemistry of a few-body process in the ultracold domain9:50 am Henry Lopez Sympathetic cooling of OH- by a laser-cooled buffer gas10:30 am Coffee11:00 am Thierry Stoecklin Vibrational sympathetic cooling of BaCl+ by Ca atoms: theoretical11:40 am Michal Tomza Towards ultracold quantum regime in ion-atom systems12:20 pm Winthrop Smith The UConn cold ion-neutral hybrid trap

1:00 pm Adjournment

X-ray coherent diffractive imaging of quantum vortices in helium droplets

Andrey F. VilesovDepartment of Chemistry

University of Southern California, Los Angeles

We investigate the rotation of single, superfluid 4He droplets (D=200-2000 nm) via single-shot femtosecond X-ray coherent diffractive imaging [1-4] at Linac Coherent Light Source. As indicated by large centrifugal deformations, the droplets’ angular velocities span a range from vanishing to those close to the disintegration limit [1, 4]. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from Xe clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than observed in bulk liquid He. The images of the vortex filaments in the droplets, such as in Figure 1, were obtained from the diffraction images via recently developed phase retrieval techniques [2]. Excessive doping by Xe changes equilibrium arrangement of vortices in the droplet and leads to stabilization of widely spaced configurations [3]. Evidence for non-stationary vortex dynamics comes from observations of asymmetric formations of vortices in some droplets.

References

[1] L. F. Gomez et al., Science 345, 906 (2014).[2] R. M. P. Tanyag et al., Structural Dynamics 2, 051102 (2015).[3] C. Jones et al., Phys. Rev. B. 93, 180510(R) (2016).[4] C. Bernando et al., Phys. Rev. B 95, 064510 (2017).

Figure 1: Image of a 600 nm diameter superfluid 4He droplet (blue) with six vortex filaments (red) as obtained from the x-ray diffraction pattern shown in the background [2].

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Charged and topological impurities inquantum states of matter

Rudro Rana Biswas

Purdue University

Idealizations of clean quantum states, while convenient for analytical tractability, are seldom realized in practice. Conversely, impurities provide unique ways of probing the quantum state they inhabit, or they may be utilized to modify the properties of the host in ways that make the latter technologically relevant. The study of the physical properties of realistic and technologically relevant materials thus inevitably requires the study of the impurities which naturally occur in them, or are deliberately introduced into them. In this talk I shall first recapitulate the well-understood theory of short-ranged impurities in Fermi liquids. I will contrast this with progressively different behaviors exhibited by (i) short-range and (ii) unscreened long-ranged charged impurities in chiral nodal electronic states with vanishing Fermi surfaces. Finally, I will consider (iii) long-range topological defects hosted within topological states. Time permitting, I will comment on experimental implications.

Application of ultracold atom-atom and atom-ion systems for magnetic field sensing

Tomasz Wasak1, Krzysztof Jachymski2, Zbigniew Idziaszek1, Paul S. Julienne3, Antonio Negretti4, and Tommaso Calarco5

1 Faculty of Physics, University of Warsaw, Poland2 Institute for Theoretical Physics III, University of Stuttgart, Germany

3 Joint Quantum Institute, University of Maryland, USA4 Zentrum für Optische Quantentechnologien and

The Hamburg Centre for Ultrafast Imaging,Universität Hamburg, Germany

5 Institute for Complex Quantum Systems & Center for Integrated QuantumScience and Technologies (IQST), Universität Ulm, Germany

An emerging field of quantum technologies may lead to substantial advances in various areas, such as communication and sensing. In quantum metrology, the performance of measuring devices used for determination of external fields can be improved by exploiting quantum coherence or entanglement. Due to their high degree of controllability, ultracold systems offer a promising platform for implementing quantum sensing protocols. Recent advances in preparing hybrid systems of atoms interacting with atomic or ionic impuritiesoffer the possibility of constructing devices with potential applications for metrology. The interaction between impurity and atoms might result in effects that are sensitive to external fields and thus potentially used as their precise probe. I will discuss here a scheme of a sensor that is based on the collisional properties of the system composed of atoms and the impurity. The interplay of the confinement and controllable interaction can result in resonances that are sensitive to the external magnetic field. Basing on the Fisher information approach, I provide the bound on the maximum attainable precision of inferring the value of that field along with the conditions for which the sensitivity of the device is the highest. I will also discuss the possibility of further improving the sensitivity by using entangled states of atoms.

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Observation of the roton modein a dipolar quantum gas

Lauriane ChomazUniversity of Innsbruck

The concept of a roton, a special kind of elementary excitation, forming a minimum of energy at finite momentum, has been essential to understand the properties of superfluid 4He. In quantum liquids, rotons arise from strong in-terparticle interactions, whose microscopic description remains debated. In the realm of highly controllable quantum gases, a roton mode has been predicted to emerge due to dipolar interparticle interactions despite of their weakly inter-acting character. Yet it has remained elusive to observations. Here we report measurements of the momentum distribution of dipolar quantum gases of high-ly-magnetic erbium atoms, revealing the existence of the long-sought roton. The population of the roton mode is induced by performing a controlled quench of the interaction strength in the quantum gas. When the dominantly dipolar re-gime is reached, we observe the appearance of reproducible symmetric peaks at a well-defined momentum matching the inverse of the tight confinement length as expected for dipolar rotons. By modifying the trap geometry and the interac-tion parameters, we investigate further the special properties of the roton mode. Our combined theoretical and experimental work demonstrates unambiguous-ly the roton softening of the excitation spectrum in axially elongated dipolar quantum gases and provides a further step in the quest towards supersolidity emerging from the intrinsic interparticle interactions.

Towards ultracold quantum regimein ion-atom systems

Michał Tomza1

1Centre of New Technologies, University of Warsaw, Warsaw, Poland

Hybrid systems of laser-cooled trapped ions and ultracold atoms combined in a single experimental setup have recently emerged as a new platform for fundamental research in quantum physics. Reaching ultracold s-wave quantum regime is one of the most important challenges in this field at the moment. Unfortunately, the lowest attainable temperatures in experiments using the Paul ion trap are limited by the potential rf-field-induced heating related to the micromotion [1]. I will discuss two possible solutions to this problem. The first approach, which can allow reaching the s-wave regime, is the use of ion-atom mixtures with the large ion/atom mass ratio [1]. The Yb+/Li combination is the best candidate. The radiative charger transfer and association losses theoretically predicted for this system to be small [2] have been recently experimentally confirmed [3] opening the way for sympathetic cooling and applications in quantum simulations [4]. Additionally, accurate measurements of charge transfer rates for ions in electronically exited states provide an excellent test for ab inito molecular structure calculations. The second approach, which proposes reaching the quantum scattering regime, is the use of a specific type of a homonuclear S-state Rydberg molecule with a small reduced mass to initialize the scattering event [5]. After the ionization of this molecule, the obtained ion-atom scattering wave packet can have temperature as small as 10 µK, which can additionally be controlled with external electric field. The scattering properties of a produced ion-atom system can be probed by both the time-resolved microscopy of evolving wave packet and the probability of molecular ion formation. The new way of measuring ion-atom scattering length in such a scenario is proposed.

References

[1] M. Cetina, A. T. Grier, and V. Vuletic, Phys. Rev. Lett. 109, 253201 (2012)[2] M. Tomza, C. P. Koch, R. Moszynski, Phys. Rev. A 91, 042706 (2015)[3] J. Joger, H. Furst, N. Ewald, T. Feldker, M. Tomza, R. Gerritsma (2017)[4] R. Gerritsma et al., Phys. Rev. Lett. 109, 080402 (2012)[5] T. Schmid, C. Veit, N. Zuber, T. Dieterle, R, Löw, T. Pfau, M. Tarana, M. Tomza (2017)

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State-to-state chemistry of a few-bodyprocess in the ultracold domain

Markus Deiss1, Joschka Wolf1, Artjom Krükow1, Eberhard Tiemann2, Brandon P. Ruzic3, Yujun Wang4, José P. D’In-cao5, Paul S. Julienne3, and Johannes Hecker Denschlag1

1Institut für Quantenmaterie and Center for Integrated Quantum Science and Technology IQST, Universität Ulm, Germany

2Institut für Quantenoptik, Leibniz Universität Hannover, Germany3Joint Quantum Institute, University of Maryland and NIST, College Park,

MD4American Physical Society, 1 Research Rd., Ridge, NY

5JILA, NIST and Department of Physics, University of Colorado, Boulder, CO

Understanding chemical reactions in all details, including the dynamics of all involved spins of electrons and nuclei is a long-standing goal for both physicists and chemists. However, tackling this aim is challenging as experimental investigation requires both the preparation of the reactants in precisely-defined quantum states and the probing of the product population distribution in a quantum-state resolved way. Furthermore, the theoretical treatment is notoriously difficult since the number of product channels is in general large, particularly for a system of more than two reactive constituents. Making use of the high level of control attainable for ultracold quantum gases we perform state-to-state measurements for a few-body process. Specifically, in our experiments we investigate the recombination of three neutral rubidium atoms, which leads to the formation of a rubidium dimer. We present a method to detect diatomic molecular product states with a resolution down to the hyperfine levels. For the studied regime of nonresonant interparticle interactions a broad population distribution of final molecular states is observed and the loss rate constants due to the three-body recombination into the individual product channels are determined. These results are compared to state-of-the-art numerical calculations. From our studies we extract first propensity rules for the molecular reaction products gaining deep insights into the three-body recombination process.

Fig. 1 Comparison between the close-coupling vibrational quenching rate coefficients kcc (T)with the statistical capture formula ksc for five different colliding systems with the diatomic cation in the initial state (ν=1, j=0)..

References

[1] Hansen, A.K. et al. Efficient Rotational Cooling of Coulomb-Crystallized Molecular Ions by a Helium Buffer Gas. Nature 508, 76-79 (2014)[2] Hutzler, N.R., Lu, H.I., and Doyle, J.M. The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules. Chem. Rev.112, 4803 (2012).[3] Campbell, W.C et al., Time-Domain Measurement of Spontaneous Vibrational Decay of Magnetically Trapped NH. Phys. Rev. Lett. 100,083003 (2008).[4] Rellergert, W.G. et al. Evidence for Sympathetic Vibrational Cooling of Translationally Cold Molecules. Nature 495, 490-495 (2013).[5] T. Stoecklin and P. Halvick, M. A. Gannouni and M. Hochlaf, S. Kotochigova and E. R. Hudson, Explanation of efficient quenching ofmolecular ion vibrational motion by ultracold atoms, Nature Communications 7:11234 (2016).

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Polarons in Electron Systems andUltracold Atoms

Eugene DemlerHarvard University

The idea of polarons was originally introduced in condensed matter physics to describe electrons interacting with lattice vibrations in solids. This concept was later applied to understand many other phenomena including dynamics of charge carriers interacting with magnetic excitations in Mott insulators, response of electron systems to time dependent perturbations, Kondo effect, optical and transport properties of mesoscopic systems. In the last few years several new types of polaronic systems have also been realized experimentally using ultracold atoms. I will discuss recent theoretical and experimental work in this area and show how cold atoms shed new light on the open problems in polaronic systems.

Vibrational sympathetic cooling of BaCl+ by Ca atoms: theoretical study

T. Stoecklin (a) and P. Halvick(a), A. Gannouni(b) and M. hochlaf(b), Svetlana Kotochigova(c) and Eric R. Hudson(d)

(a) UMR5255-CNRS, Institut des Sciences Moléculaire, Université de Bordeaux, 351 cours de la Libération, 33405 Talence Cedex, France.

e-mail: thierry.stoecklin@u-bordeaux.fr(b) Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle,

MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France(c) Department of Physics, Temple University, Philadelphia, Pennsylvania 19122,

USA 2. Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan

(d) Department of Physics and Astronomy, University of California,Los Angeles, California 90095, USA

The internal structure of molecules offers a host of scientific and technological opportunities, including the manipulation of quantum information, critical insight into quantum chemistry, and improved tests of the Standard Model. To utilize this potential of molecules typically requires the preparation of molecular samples at very low temperatures, where only a single quantum state is occupied. Unfortunately, experiments attempting to reach these temperatures by buffer gas cooling have found that though the molecular motion and rotation are quickly cooled to the cryogenic temperature [1,2], the molecular vibration relaxes at impractically long timescales [3]. Here, we theoretically explain the recently observed exception to this rule: efficient vibrational cooling of BaCl+ by a laser-cooled Ca buffer gas [4]. We perform intense close-coupling calculations that agree with the experimental result, and use both quantum defect theory and a statistical capture model to provide an intuitive understanding of the system. This result establishes that, in contrast to the commonly held opinion, there exists a large class of systems that exhibit efficient vibrational cooling and therefore supports a new route to realize the long-sought opportunities offered by molecular structure [5].

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Coherent internal state manipulation of single atomic and molecular ions

by frequency combs

Michael DrewsenAarhus University

The talk will focus on coherent manipulation of the internal states of single atomic and molecular ions through the exposure of such ions to optical frequency comb (OFC). By only stabilizing and tuning the repetition rate of the OFC, Raman transitions between any atomic and molecular states separated by up to several tens of THz can be driven efficiently by using essentially all the power available in the comb. With coherent manipulation of the population between the metastable3d 2D3/2- and 3d 2D5/2-levels in the Ca+ ion separated by 1.8 THz, we will discuss our next experiments on coherent rotational state manipulation of the MgH+ ion, as well as comment on the perspective in using this manipulation technique in connection with investigations of cold neutral-ion interactions.

The UConn cold ion-neutralhybrid trap – review and prospects

Winthrop Smith and Jonathan Kwolek1, Douglas Goodman2, James Wells3 and Reinhold Blumel4

1U. of Connecticut, Storrs, 2Wentworth Inst., Boston, 3Keck Science, Claremont Colleges, CA and 4Wesleyan Univ., CT

Recent experiments will be reviewed involving cold ion-neutral collisions, sympathetic ion cooling, Ca+ on Na charge exchange reactions and channels, and the total Na+ on Na collision rate from MOT loss-rate measurements, in comparison with theory and simulations. Nonlinear saturated-ion behavior in a Paul trap versus loading rate from a MOT will also be discussed briefly.

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Adiabatic Quantum Computing and Quantum Spin Lenses with Ultra-Cold Rydberg Atoms

Alexander Glaetzle University of Oxford and CQT Singapore

There is a significant ongoing effort in realizing quantum annealing with different physical platforms. The challenge is to achieve a fully programmable quantum device featuring coherent adiabatic quantum dynamics. In this talk, I will show that combining the well-developed quantum simulation toolbox for Rydberg atoms with the recently proposed Lechner-Hauke-Zoller (LHZ) architecture allows one to build a prototype for a coherent adiabatic quantum computer with all-to-all Ising interactions and, therefore, a novel platform for quantum annealing and machine learning. In LHZ a infinite-range spin-glass is mapped onto the low energy subspace of a spin-1/2 lattice gauge model with quasi-local 4-body parity constraints. This spin model can be emulated in a natural way with Rubidium and Cesium atoms in a bipartite optical lattice involving laser-dressed Rydberg-Rydberg interactions, which are several orders of magnitude larger than the relevant decoherence rates. This makes the explo-ration of coherent quantum enhanced optimization protocols accessible with state-of-the-art atomic physics experiments. In the second part of this talk I will propose and discuss linear and nonlin-ear ‘quantum spin- lenses’ and their physical realization with cold atoms and ions. I will discuss application as a (novel) quantum atom-light interface, where incident photonic qubits are sequentially stored in an atomic array, and focused to a quantum register of spatially localized spin-qubits. More generally, we will discuss the design of non-linear spin-lenses, adding finite range (repulsive) spin-spin interactions to the spin-lens Hamiltonian. Thus, focusing dynamics will be conditional to the number of initial spin excitations, and an initial quan-tum superposition state of delocalized spins will be mapped to superposition of spatial spin patterns.

References:[1] A. Glaetzle, R. van Bijnen, P. Zoller, W. Lechner, A Coherent Quantum Annealer with Rydberg Atoms, Nature Comm. (2017), arXiv:1611.02594 [2] A. W. Glaetzle, K. Ender, D. S. Wild, S. Choi, H. Pichler, M. D. Lukin, P. Zoller, Quantum Spin Lenses in Atomic Spin Lenses in Atomic Arrays, arXiv:1704.08837

taking atom-ion and atom-atom correlations fully into account. We show the existence of a critical atom number at which dissociation occurs, resulting in an unbound fraction which forms a background gas for the molecule. Moreover, we present the self-localization behavior of the ion, originating from the generation of an effective mass and an effective trap. Our study is carried out by means of the Multi Layer Multi-Configuration Time-Dependent Hartree method for Bosons (ML-MCTDHB), an ab initio approach to simulate the correlated quantum many-body dynamics.

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Rydberg Optical FeshbachResonances in Cold Gases

Rosario González-Férez Instituto Carlos I de Física Teórica y Computacional

and Departamento de Física Atómica, Molecular y NuclearUniversidad de Granada, 18071 Granada

In this work, we present a novel scheme to efficiently tune the scattering length of two colliding ground-state atoms by off-resonantly coupling the scattering-state to an excited Rydberg-molecular state using laser light. For the s-wave scattering of two colliding 87Rb atoms, we demonstrate that the effective optical length and pole strength of this Rydberg optical Feshbach resonance can be tuned over several orders of magnitude, while incoherent processes and losses are minimised [1]. Due to the ubiquity of Rydberg molecular states, this technique should be generally applicable to homonuclear atomic pairs, non bi-alkali mixtures, as well as to other atomic mixtures with s -wave scattering and p-wave scattering.

References

[1] N. Sandor, R. González-Férez, P. S. Julienne and G. Pupillo, arXiv:1611.07091

Mesoscopic Molecular Ions in UltracoldAtom-Ion Hybrid Systems

Peter Schmelcher

Centre for Optical Quantum Technologies andHamburg Centre for Ultrafast Imaging

University of HamburgLuruper Chaussee 149

22761 Hamburg, Germany

We explore the structure and dynamics of individual ions immersed into a sea of ultracold bosons in a quasi one-dimensional trapping environment. As a first step we investigate the situation by which the ion is strongly localized such that its motion can be effectively neglected. With the development of a model potential for the atom-ion interaction, we are able to numerically obtain the exact many-body ground state of the atomic ensemble in the presence of an ion. We analyse the influence of the atom number and the atom-atom interaction on the ground state properties. Interestingly, for weakly interacting atoms, we find that the ion impedes the transition from the ideal gas behaviour to the Thomas-Fermi limit. We show that this effect can be exploited to infer the presence of the ion both in the momentum distribution of the atomic cloud and by observing the interference fringes occurring during an expansion of the quantum gas. In the strong interacting regime, the ion modifies the fragmentation process in dependence of the atom number parity which allows a clear identification of the latter in expansion experiments. In a next step we explore the quantum dynamics in the course of a sudden creation of the ion. The dynamics is analyzed via a cluster expansion approach, which provides a comprehensive understanding of the occurring many-body processes. After a transient during which the atomic ensemble separates into fractions which are unbound and bound with respect to the ion, we observe an oscillation in the atomic density which we attribute to the additional length and energy scale induced by the attractive long- range atom-ion interaction. This oscillation is shown to be the main source of spatial coherence and population transfer between the bound and the unbound atomic fraction. Finally we show how a single ion can bind multiple atoms on mesoscopic scales, forming a correlated bound many-body compound. We explore these mesoscopic molecular ions from weak to strong atomic repulsion, thereby

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Hybrid traps, molecular ions, and radioactive qubits

Eric HudsonUCLA

Sympathetic cooling with laser-cooled atomic ions and neutral atoms promises to enable the production and study of trapped, ground state molecular ions. I will discuss recent progress along two fronts of this research. First, using atomic ions immersed in a laser-cooled neutral atom cloud we have explored the limits of kinematic cooling in an ion trap, finding a surprising bifurcation in the thermodynamic steady state that depends on the ion initial conditions. This work offers an explanation of some of the observed limits to sympathetic cooling in an ion trap. Second, we have recently observed and characterized the reaction of a polyatomic molecular ion with laser-cooled Ca atoms. The reaction exhibits an interesting dependence on electron spin and produces a novel (and somewhat surprising) non-stoichiometric molecule. I will conclude with a diversion into recent work with Prof. Wes Campbell at UCLA, where we have demonstrated trapping and laser cooling of a radioactive isotope of barium that holds promise for quantum information processing. The method of production of this ion may be of interest to the molecular ion community.

A single Rydberg atom in a high density media: a chemistry-assisted new world

Jesús Pérez-RíosDepartment of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA and School of Natural Sciences and Technology, Universiad

del Turabo, Gurabo, PR00778, USA

A single Rydberg atom in a Bose-Einstein condensate (BEC) where thousands of neutral atoms are within the Rydberg orbit experiences an intriguing fast decay depending on its principal quantum number n, in comparison with the natural decay rate of Rydberg atoms in vacuum (~n^(-3)) [1]. The physics behind this phenomenon has remained unexplored until the present work, where it is shown that the decay mechanism of a Rydberg atom in a high density medium is due to both reactive and non-reactive ultracold chemical processes: l-mixing collisions and chemi-ionization. These chemical reactions have been studied by means of a new theoretical framework including explicitly the role of the Rydberg electron on the dynamics of the Rydberg-neutral energy landscape, as well as the short-range Rydberg core-neutral potential energy curves coming from quantum chemistry calculations [2]. This theoretical approach may open up new pathways for the optical trapping of ions. On the other hand, several Rydberg atoms in a BEC may form ultra-long Rydberg molecules through light-assisted chemical reactions, where a photon provides the necessary energy for binding the Rydberg atom to a neutral one leading to the formation of Rydberg molecules. The reaction products of this reaction are studied, with primary interest in the so-called butterfly molecules: homonuclear molecules with giant permanent dipole moment [3,4]. In particular, the exceptional alignment of these molecules in an external electric field is employed to formulate initial studies in dipolar quantum gases in the strong coupling regime [5].

[1]J. B. Balewski et al. “Coupling a Single Electron to a Bose-Einstein Condensate”, Nature, 502, 664 (2013).[2] M. Schlagmüller et al. “Ultracold Chemical Reactions of a Single Rydberg Atom in a Dense Gas”, Phys. Rev. X 6, 031020 (2016).[3] E. L. Hamilton, C. H. Greene and H. R. Sadeghpour, “Shape-resonance-induced long-range molecular Rydberg states”. J. Phys. B: At. Mol. Opt. Phys. 35, L199 (2002).[4] T. Niederprüm et al, “Observation of pendular butterfly Rydberg molecules”, Nat. Commun. 7, 12820 (2016).[5] M. T. Eiles, H. Lee, J. Pérez-Ríos and C. H. Greene “Anisotropic blockade using pendular long-range Rydberg molecules”, Phys. Rev. A 95, 052708 (2017).

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From Ultralong-range Molecules to Rydberg Polarons in a Bose Gas

Thomas C. KillianRice University, Department of Physics and Astronomy and

Rice Center for Quantum Materials, Houston, Texas, USA 77251

I will describe the excitation of Rydberg atoms in a Bose-Einstein conden-sate of strontium atoms. In a few-body regime, we observe a dense, highly structured spectrum reflecting excitation of ultralong-range molecules con-sisting of one or more ground-state atoms bound to the Rydberg core in po-tential wells formed by the Rydberg-electron wave function. In a many-body regime, with hundreds of ground-state atoms within the Rydberg orbital, the Rydberg atoms can be viewed as an impurity in a quantum gas, connecting to important concepts in condensed matter physics. The spectrum for impurity excitation displays signatures of polaronic states, in which the Rydberg atom significantly perturbs the density of the background Bose gas. In particular, detailed analysis of the red-detuned tail of the excitation spectrum reveals the intrinsic excitation spectrum of Rydberg polarons, free from non-linear effects, density averaging, and the perturbing influences of shape resonances. All features of the spectrum are well described using functional determinant theory to solve the many-body Hamiltonian. I will also describe progress towards creating Rydberg polarons in a quantum degenerate Fermi gas.

Research supported by the AFOSR, NSF and the Robert A, Welch Foundation

Collaborators

F. B. Dunning1, F. Camargo1, J. Whalen1, R. Ding1, H. R. Sadeghpour2, R. Schmidt2,3, E. Demler3, S. Yoshida4, J. Burgdorfer4

1Rice University, Department of Physics and Astronomy and Rice Center for Quan-tum Materials, Houston, Texas2ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cam-bridge, Massachusetts3Department of Physics, Harvard University, Cambridge, Massachusetts 4Institute for Theoretical Physics, Vienna University of Technology, Vienna,Austria, EU

Ultracold trading: the observation ofmomentum, spin and electronic-excitation

exchange in atom-ion collisions

Ziv Meir, Tomas Sikorsky, Ruti Ben-Shlomi, Meirav Pinkas, Yehonatan Dallal, Nitzan Akerman and Roee Ozeri

Department of Physics of Complex SystemsWeizmann Institute of Science

Rehovot 7610001, Israel

Here I’ll review recent experiments on Rb-Sr+ ultracold collisions. We initialize the ion in the ground-state of a linear Paul trap and overlap it with a cloud of atoms at μK temperature trapped in an optical dipole trap. We observe the following dynamics in which the ion acquires a non-thermal energy distribution with a power-law tale of high energies. We further study the spin dynamics of the ion in the presence of atoms and show when the atomic cloud is polarized spin-exchange aligns the ion-spin with that of the atomic bath. Finally we study the quenching of a meta-stable electronic excitation of the ion due to atomic collisions.

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Dynamics of spin impurities in a strongly-interacting Fermi gas

Michael KÖhlUniversity of Bonn

We investigate the dynamics of spin-impurities in a strongly interacting Fermi gas subject to a continuous driving. We determine the excitation spectrum of the impurities and find that they cause a collective mode corresponding to the Higgs mode of the strongly interacting superfluid. We measure the collective mode frequency as a function of the interaction strength of the superfluid and find good agreement with theoretical simulations.

Electrons and ions meet ultracold atoms

Herwig OttUniversity of Kaiserslautern and Research Center OPTIMAS

Bringing together ultracold atoms and charged particle beams opens up new research directions in atomic physics. On the one hand, electrons and ions can be used to probe and control ultracold atomic gases. On the other hand, a sample of ultracold atoms is an ideal starting point to generate well controlled ultracold electron and ion beams. In this talk, I will show that a focused electron beam can be used to image and manipulate ultracold quantum gases with high spatial resolution. To this end, we have adapted a scanning electron microscope for the study of ultracold quantum gases [1,2]. Thereby, the imaging principle relies on the electron impact ion-ization of cold atoms with subsequent ion detection. The technique also allows to realize localized dissipative impurities in a quantum gas [3]. Secondly, I will present results on the generation of a high-repetition de-terministic single ion source based on photoionization of ultracold atoms.

References

[1] T. Gericke et al., Nature Physics 4, 949 (2008).[2] P. Würtz et al., Phys. Rev. Lett. 103, 080404 (2009).[3] G. Barontini et al., Phys. Rev. Lett. 110, 035302 (2013).

Excited State Atom-Ion Charge-Exchange

Ming LiTemple University

We theoretically investigate the possible exothermic charge-exchange reactions that occur when the ground-state positive ion-impurities are embedded in a neutral atomic cloud in a MOT that contains excited-state atoms. In particular, we focus on ground-sate Yb+ ions that can collide with excited Ca*(4s4p 1P) atoms in a Ca MOT. Collisions between an excited atom and an ion are guided by two major contributions to the long-range interaction potentials, the induction C4/R

4 and charge-quadrupole C3/R3 potentials, and their coupling by the electron-exchange interaction. Our model of these forces leads to close-coupling equations for multiple reaction channels. We find several avoided crossings between the potentials that couple to the nearby asymptotic limits of Yb*+Ca+, some of which can possibly provide large thermally averaged charge exchange rate coefficients above 10-10 cm3/s that can lead to fast ion losses.

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Controlled atom-ion interactions

Antonio NegrettiUniversity of Hamburg

In my talk I shall present our recent theoretical investigations on how to control the interaction of an atom and an ion either via Rydberg dressing [1] or via confinement-induced resonances [2]. In the first case, we exploit the strong polarizabilities of the Rydberg levels, which increase the interaction strength between atoms and ions by many orders of magnitude, as compared to the case of ground state atoms, and may be mediated over micrometers. We calculate that such interactions can be used to generate entanglement between an atom and the motion or internal state of an ion. Interestingly, no ground state cooling of the ion or atom is required and the setup allows for full dynamical control. Moreover, the scheme is to a large extent immune to the micromotionof the ion. In the second part of my talk, I shall briefly illustrate recent investigations of a static ion colliding with an atom in a waveguide. Due to the large-range of the atom-ion interaction an “isotope-like” effect of the confinement-induced atom-ion resonance is found, namely the position of the resonance relies on the atom mass as well, contrarily to the atom-atom scenario. Our findings are of interest for developing hybrid quantum information platforms and for implementing quantum simulations of solid-state physics.

References

[1] T. Secker, R. Gerritsma, A. Glaetzle, A. Negretti, Phys. Rev. A 94, 013420 (2016).[2] V. Melezhik, A. Negretti, Phys. Rev. 94, 022704 (2016).

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Sympathetic cooling of OH- by alaser-cooled buffer gas

Henry Lopez, Jonas Tauch, Bastian Höltkemeier,Matthias Weidemüller

Physics Institute, Heidelberg University, Germany

Sympathetic cooling is a versatile tool that is applied when other standard cooling methods like laser cooling are not applicable. In the last few years there has been discussion about its limitations when applied to ions stored in radio-frequency traps: is it possible to cool down trapped ions in a system where the coolant is heavier than the cooled particle? By using a spatially confined buffer gas – e.g., in a magneto-optical trap - and a higher pole-order radio frequency trap for ions, we could show theoretically that sympathetic cooling of ions in such hybrid systems becomes feasible [1, 2]. We report latest progress in our experiment to demonstrate sympathetic cooling of molecular anions, in particular OH-, using laser-cooled Rb atoms. The atoms are confined in a dark spontaneous-force optical trap loaded from a 2D-MOT. The ions are stored in an 8-pole rf trap made of thin wires, guaranteeing optical access into the trapping region. For probing the temperature of the ions we apply photodetachment tomography of the negative ions and time-of-flight detection of ions extracted from the trap. We observe first evidence for sympathetic cooling and non-thermal energy distribution of the ions, as predicted by our model.

References[1]B. Höltkemeier, P. Weckesser, H. Lopez, M. Weidemüller, Buffer-Gas Cooling of a Single Ion in a Multipole Radio Frequency Trap Beyond the Critical Mass Ratio, Phys. Rev. Lett. 116, 233003 (2016)[2] B. Höltkemeier, P. Weckesser, H. Lopez, M. Weidemüller, Dynamics of a single trapped ion immersed in a buffer gas, Phys. Rev. A 94, 062703 (2016)

Photo-association of trilobite Rydbergmolecules via resonant spin-orbit coupling

Florian MeinertUniversity of Stuttgart

Rydberg molecules, consisting of a neutral ground-state atom bound to a Rydberg electron via electron-neutral scattering, offer a unique possibility to prepare diatomic molecules with large permanent electric dipole moments. Of particular interest in this context are so called trilobite-molecules, which attain extreme dipolar character as a consequence of the scattering-induced admixture of high-L Rydberg orbits. Yet, these states are generally difficult to laser associate due to angular momentum conservation. Here, I will present experiments demonstrating that for suitable principal quantum numbers resonant coupling of the orbital motion of the Rydberg electron with the nuclear spin of the ground-state atom, mediated by electron-neutral scattering, hybridizes the trilobite molecular potential with the more conventional S-type molecular state. This provides a general path to associate trilobite molecules with large electric dipole moments. Spectroscopic data including the determination of the dipole moment is presented and compared to calculated potential energy curves.

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