Papers by Silke Ospelkaus
We analyse rovibrational transitions of the (2)Σ–X(1)Σ system of LiSr and find the energy levels ... more We analyse rovibrational transitions of the (2)Σ–X(1)Σ system of LiSr and find the energy levels of the (2)Σ state to be perturbed by coupling between the (2)Σ and (1)Π states. We present an analysis of the coupled system yielding molecular parameters for the lowest vibrational levels of the (2)Σ state and for higher vibrational levels of the (1)Π state together with molecular coupling constants. Improved Dunham coefficients for the rovibrational levels of the X(1)Σ state are also obtained, where the correlation with the parameters of the excited states is removed completely. Supplementary material for this article is available online
ABSTRACT We have produced near quantum degenerate ^40K^87Rb polar molecules in their rovibrationa... more ABSTRACT We have produced near quantum degenerate ^40K^87Rb polar molecules in their rovibrational ground state using magneto-association followed by STIRAP transfer. Preliminary measurements show that trap lifetime of these fermion molecules is limited to ˜ 100 ms. We are investigating the KRb loss in the presence of either K or Rb atoms to look for evidence of chemical reactions at ultracold temperatures. This work is supported by the NSF and NIST.
Submitted for the DAMOP08 Meeting of The American Physical Society Toward Creation of an Ultracol... more Submitted for the DAMOP08 Meeting of The American Physical Society Toward Creation of an Ultracold Dense Gas of Polar Molecules KANG-KUEN NI, SILKE OSPELKAUS, A. PE’ER, M. MIRANDA, B. NEYENHUIS, J. ZIRBEL, JILA, S. KOTOCHIGOVA, Temple University, P. JULIENNE, NIST Gaithersburg, J. YE, D. JIN, JILA, NIST and the University of Colorado, Boulder — We present experimental efforts toward the creation of ultracold gas of KRb polar molecules. We start by creating extremely weakly bound molecules using a magnetic-field Feshbach resonance. This ultracold dense sample of Feshbach molecules provides a starting point for coherent optical transfer schemes aimed at creating tightly bound, polar molecules. Starting with Feshbach molecules, we have performed two-photon and one-photon spectroscopy. We have also demonstrated coherent optical transfer of Feshbach molecules to a more deeply bound state in the electronic ground state. We will discuss suitable routes to extend this work to even more deep...
We spectroscopically investigate a pathway for the conversion of NaK Feshbach molecules into rovi... more We spectroscopically investigate a pathway for the conversion of NaK Feshbach molecules into rovibronic ground state molecules via STImulated Raman Adiabatic Passage (STIRAP). Using photoassociation spectroscopy from the diatomic scattering threshold in the aΣ potential, we locate the resonantly mixed electronically excited intermediate states |B1Π, v = 8〉 and |c3Σ+, v = 30〉 which, due to their singlet-triplet admixture, serve as an ideal bridge between predominantly aΣ Feshbach molecules and pure XΣ ground state molecules. We investigate their hyperfine structure and present a simple model to determine the singlet-triplet coupling of these states. Using Autler-Townes spectroscopy, we locate the rovibronic ground state of the NaK molecule (|X1Σ+, v = 0, N = 0〉) and the second rotationally excited state N = 2 to unambiguously identify the ground state. We also extract the effective transition dipole moment from the excited to the ground state. Our investigations result in a fully cha...
Physical Review Research, 2021
We present and analyze a toolbox for the controlled manipulation of ultracold polar molecules, co... more We present and analyze a toolbox for the controlled manipulation of ultracold polar molecules, consisting of detection of molecules, atom-molecule entanglement, and engineering of dissipative dynamics. Our setup is based on fast chemical reactions between molecules and atoms leading to a quantum Zeno-based collisional blockade in the system. We demonstrate that the experimental parameters for achieving high fidelities can be found using a straightforward numerical optimization. We exemplify our approach for a system comprised of NaK molecules and Na atoms and we discuss the consequences of residual imperfections such as a finite strength of the quantum Zeno blockade.
STIRAP (stimulated Raman adiabatic passage) is a powerful laser-based method, usually involving t... more STIRAP (stimulated Raman adiabatic passage) is a powerful laser-based method, usually involving two photons, for efficient and selective transfer of populations between quantum states. A particularly interesting feature is the fact that the coupling between the initial and the final quantum states is via an intermediate state, even though the lifetime of the latter can be much shorter than the interaction time with the laser radiation. Nevertheless, spontaneous emission from the intermediate state is prevented by quantum interference. Maintaining the coherence between the initial and final state throughout the transfer process is crucial. STIRAP was initially developed with applications in chemical dynamics in mind. That is why the original paper of 1990 was published in The Journal of Chemical Physics. However, from about the year 2000, the unique capabilities of STIRAP and its robustness with respect to small variations in some experimental parameters stimulated many researchers t...
arXiv: Atomic Physics, 2020
Precision spectroscopy has been the driving force for progress of our physical understanding and ... more Precision spectroscopy has been the driving force for progress of our physical understanding and still is a promising tool for the investigation of new physics. Molecules offer transitions which allow tests that are not possible in atomic systems. However, usually precision spectroscopy of molecules is challenging due to the lack of cycling transitions for state preparation and state detection. For molecular ions, this obstacle can be overcome by quantum logic spectroscopy, where dissipation for state preparation and detection is provided by a co-trapped atomic ion exploiting the shared eigenstates of motion. Here, we propose a full quantum logic spectroscopy scheme for molecular oxygen ions and theoretically investigate the feasibility of quantum logic assisted state detection and preparation. Furthermore, we provide coupling rates for a direct single-photon quadrupole excitation of a vibrational overtone transition that can serve as a sensitive transition for tests of a possible v...
Bulletin of the American Physical Society, 2010
ABSTRACT We prepare a near-quantum-degenerate gas of fermionic KRb molecules, with all the molecu... more ABSTRACT We prepare a near-quantum-degenerate gas of fermionic KRb molecules, with all the molecules in the absolute lowest energy state. We observe atom-exchange chemical reactions in a regime where the reaction rates are determined by the quantum statistics of the molecules, single partial wave scattering, and quantum threshold laws [1].[4pt] [1] S. Ospelkaus, K.-K. Ni, D. Wang, M. H. G. de Miranda, B. Neyenhuis, G. Qu'em'ener, P. S. Julienne, J. L. Bohn, D. S. Jin, J. Ye, Quantum-State Controlled Chemical Reactions of Ultracold KRb Molecules, Science (in press).
Ultracold polar molecules are new model quantum systems that promise study of quantum phase trans... more Ultracold polar molecules are new model quantum systems that promise study of quantum phase transitions, quantum simulations of condensed matter spin systems, and new schemes for quantum information. These proposals require a high phase-space-density gas of polar molecules ...
arXiv: Quantum Gases, 2020
We report the creation of ultracold bosonic dipolar $^{23}\textrm{Na}^{39}\textrm{K}$ molecules i... more We report the creation of ultracold bosonic dipolar $^{23}\textrm{Na}^{39}\textrm{K}$ molecules in their absolute rovibrational ground state. Starting from weakly bound molecules immersed in an ultracold atomic mixture, we coherently transfer the dimers to the rovibrational ground state using an adiabatic Raman passage. We analyze the two-body decay in a pure molecular sample and in molecule-atom mixtures and find an unexpectedly low two-body decay coefficient for collisions between molecules and $^{39}\textrm{K}$ atoms in a selected hyperfine state. The preparation of bosonic $^{23}\textrm{Na}^{39}\textrm{K}$ molecules opens the way for future comparisons between fermionic and bosonic ultracold ground-state molecules of the same chemical species.
Submitted for the DAMOP14 Meeting of The American Physical Society Dipolar gases of ground state ... more Submitted for the DAMOP14 Meeting of The American Physical Society Dipolar gases of ground state molecules: NaK in Hannover MATTHIAS W. GEMPEL, TORBEN A. SCHULZE, TORSTEN HARTMANN, Institut für Quantenoptik, Leibniz Universität Hannover, IVO I. TEMELKOV, Institut für Quantenoptik, Leibniz Universität Hannover; Department of Physics, Sofia University, HORST KNÖCKEL, ALESSANDRO ZENESINI, EBERHARD TIEMANN, SILKE OSPELKAUS, Institut für Quantenoptik, Leibniz Universität Hannover — In the coming years, dipolar interactions will be one of the most promising tools in the field of ultracold atoms. Since the first realization of degenerate gases of dipolar atoms and the creation of large diatomic molecular samples in their rovibrational groundstate [1], a lot of experimental and theoretical interest has been focused on long-range interactions, anisotropy, exotic phase transitions and other peculiar phenomena. We will update you on our work in Hannover with details on the NaK experimental app...
We have produced heteronuclear Feshbach molecules from an ultracold gas mixture of K40-Rb87 in an... more We have produced heteronuclear Feshbach molecules from an ultracold gas mixture of K40-Rb87 in an optical dipole trap. We can create more than 30,000 molecules at about 100 nK and we have observed molecule lifetimes as long as 20 ms near the Feshbach resonance ...
KCa was produced in a heatpipe oven and its thermal emission spectrum around 8900 cm was recorded... more KCa was produced in a heatpipe oven and its thermal emission spectrum around 8900 cm was recorded by a high resolution Fourier transform spectrometer. In addition, many selected transitions of this spectrum between deeply bound vibrational levels of the X(1)Σ and (2)Σ states were studied using laser excitation to facilitate the assignment of the lines. The ground state is described for v′′ = 0 – 5 and the (2)Σ state for v′ = 0 – 8 with rotational levels up to 175. For both states, Dunham coefficients, spin-rotation parameters and potential energy curves are derived.
We prepare mixtures of ultracold K atoms in various hyperfine spin states and NaK molecules in an... more We prepare mixtures of ultracold K atoms in various hyperfine spin states and NaK molecules in an optical dipole trap at a fixed magnetic field and study inelastic two-body atommolecule collisions. We observe atom-molecule loss that is hyperfine dependent with a two-body loss rate far below the universal limit. We analyze the two-body loss dynamics based on the derivation of general and easy applicable analytic solutions for the differential equations describing the loss of an arbitrary number γ of particles in a single collisional event.
We present a detailed study of interspecies Feshbach resonances of the bosonic Na+K mixture for m... more We present a detailed study of interspecies Feshbach resonances of the bosonic Na+K mixture for magnetic fields up to 750 G in various collision channels. A total of fourteen Feshbach resonances are reported, as well as four zero crossings of the scattering length and three inelastic two-body loss features. We use the observed magnetic field locations of the resonant features together with the known data on Na+K to refine the singlet and triplet ground state potentials of NaK and achieve a consistent description of Feshbach resonances for both, the Bose-Bose mixture of Na+K as well as the Bose-Fermi mixture of Na+K. We also discuss the influence of the interplay between inelastic two-body and three-body processes on the observation of a Feshbach resonance.
Physical Review Letters
We probe photo-induced loss for chemically stable bosonic 23 Na 87 Rb and 23 Na 39 K molecules in... more We probe photo-induced loss for chemically stable bosonic 23 Na 87 Rb and 23 Na 39 K molecules in chopped optical dipole traps where the molecules spend a significant time in the dark. We expect the effective two-body decay to be largely suppressed in chopped traps due to the small expected complex lifetimes of about 13 µs and 6 µs for 23 Na 87 Rb and 23 Na 39 K respectively. However, instead we do observe near-universal loss even at the lowest chopping frequencies we can probe. Our data thus either suggest a drastic underestimation of the complex lifetime by at least one to two orders of magnitude or a so far unknown loss mechanism.
Physical Review A
We create weakly bound bosonic 23 Na 39 K molecules in a mixture of ultracold 23 Na and 39 K. The... more We create weakly bound bosonic 23 Na 39 K molecules in a mixture of ultracold 23 Na and 39 K. The creation is done in the vicinity of a so far undetected Feshbach resonance at about 196 G which we identify in this work by atom-loss spectroscopy. We investigate the involved molecular state by performing destructive radio frequency binding energy measurements. For the constructive molecule creation we use radio frequency pulses with which we assemble up to 6000 molecules. We analyze the molecule creation efficiency as a function of the radio frequency pulse duration and the atom number ratio between 23 Na and 39 K. We find an overall optimal efficiency of 6 % referring to the 39 K atom number. The measured lifetime of the molecules in the bath of trapped atoms is about 0.3 ms.
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Papers by Silke Ospelkaus