M. Olshanii [Phys. Rev. Lett. 81, 938 (1998)] recently solved the atom-atom scattering problem with a pseudopotential interaction in the presence of transverse harmonic confinement, i.e. within an 'atom waveguide', deriving an effective one-dimensional coupling constant that diverged at a "confinement induced resonance" (CIR). Here, we report numerical results for finite range potentials that corroborate this resonance. In addition, we now present a physical interpretation of this effect as a novel type of Feshbach resonance in which the transverse modes of the waveguide assume the roles of 'open' and 'closed' scattering channels. [1,2,3,4,5,6,7,8]. One goal of such experiments is to reach the 'single-mode' or quasi-1D regime, where only the ground state of transverse motion is significantly populated at thermal equilibrium. This regime is of great practical interest due to the potential for ultra-sensitive rotation and gravitational gradient detection with guided single-mode atom interferometers. In addition to such applications, reaching the quasi-1D regime is of significant theoretical interest as the 1D delta-interacting boson gas represents one of the few known fully integrable quantum field theories. In a finite system with infinitely strong (hard-core) deltafunction interactions, boson many-body states in 1D have been shown to correspond via a one-to-one mapping with the highly-correlated states of the corresponding noninteracting Fermi gas [9]. The properties of this TonksGirardeau gas have been a topic of significant current theoretical interest [9,10,11,12,13,14,15] in anticipation of future atom-waveguide experiments. Additionally, the homogeneous 1D Bose with arbitrary-strength delta-function interactions, known as the Lieb Liniger model, is also a fully integrable system [16].To make the connection between experiments in tightly confining waveguides and theoretical models in 1D, it is necessary to know the relationship between the effective 1D coupling constant, g 1D , and the 3D scattering length, a. This problem was first addressed rigorously in [22], where it was predicted that a 'confinement induced resonance' (CIR) modifies the effective interaction, resulting in an effective 1D coupling strength which can be tuned from −∞ to +∞ by varying the transverse width of the * Electronic address: thbergeman@notes.cc.sunysb.edu † Electronic address: mmoore@cfa.harvard.edu ‡ Electronic address: olshanii@phys4adm.usc.edu waveguide, a ⊥ over a small range in the vicinity of the resonance at a ⊥ = Ca, where C = 1.4603 . . .. Hence this resonance clearly has significant implications for atomwaveguide experiments. Until now, however, there has been no convincing physical explanation for the effect, thus raising questions concerning its appearance in systems with finite-range interactions.The primary goal of this Letter, therefore, is to present numerical calculations of scattering in the presence of a cylindrical harmonic potential using finite-range atomatom potentials, confirming the existence of the CIR. ...

We demonstrate the production of ultracold polar RbCs molecules in their vibronic ground state, via photoassociation of laser-cooled atoms followed by a laser-stimulated state transfer process. The resulting sample of X 1 Σ + (v = 0) molecules has a translational temperature of ∼ 100 µK and a narrow distribution of rotational states. With the method described here it should be possible to produce samples even colder in all degrees of freedom, as well as other bi-alkali species.PACS numbers: 33.80. Ps, 39.25.+k, 33.80.Wz, 33.70.Ca Samples of ultracold, polar molecules (UPMs) can provide access to new regimes in many phenomena. Ultracold temperatures allow trapping, and polarity can be used to engineer large, anisotropic, and tunable interactions between molecules. These features make UPMs attractive as qubits for quantum computation [1], as building blocks for novel types of many-body systems [2], and for the study of chemistry in the ultracold regime [3]. Furthermore, UPMs can be used as uniquely sensitive probes of phenomena beyond the Standard Model of particle physics [4].Methods such as buffer-gas cooling [5], Stark-slowing [6], billiard-like collisions [7], and velocity filtering [8] have produced samples of polar molecules at temperatures of ∼ 10-100 mK. Formation of heteronuclear molecules from pre-cooled atoms via photoassociation (PA) [9,10,11,12] or Feshbach resonance techniques [13] promises access to much lower temperatures; however, these processes leave molecules in highly excited vibrational levels, which have vanishingly small polarity [14] and are unstable to collisions [15,16]. The possibility of transferring such molecules to their vibronic ground state, via optical processes such as stimulated Raman transitions, has been discussed extensively (see e.g. [1,17,18,19,20]); however, insufficient data on the structure of experimentally accessible molecules has made it difficult to identify specific pathways for efficient transfer.Here we report the production of UPMs via PA of laser-cooled Rb and Cs atoms, followed by a two-step stimulated emission pumping (SEP) process. This yields RbCs molecules in their absolute vibronic ground state X 1 Σ + (v = 0). These polar molecules (calculated electric dipole moment µ ≈ 1.3 D [21]) have a translational temperature of ∼ 100 µK. The distribution of rotational states is also quite narrow, so the resulting sample of X 1 Σ + state molecules is cold in all degrees of freedom. Figure 1 shows the methods by which we produce and detect UPMs. A pair of colliding, ultracold Rb and Cs atoms is photoassociated, i.e., the pair absorbs a photon and is driven to an electronically excited molecular level [22]. This level decays rapidly, with branching fraction of ∼ 7% into the long-lived a 3 Σ + (v = 37) level [9]. After a period of PA, a resonant laser pulse ("pump" pulse) transfers these metastable, vibrationally excited molecules to an intermediate, electronically excited state (i). The population of state i is monitored by applying an intense laser pulse ("ionizat...

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We have produced ultracold, polar RbCs * molecules via photoassociation in a laser-cooled mixture of Rb and Cs atoms. Using a model of the RbCs * molecular interaction which reproduces the observed rovibrational structure, we infer decay rates in our experiments into deeply bound X 1 Σ + ground state RbCs vibrational levels as high as 5×10 5 s −1 per level. Population in such deeply bound levels could be efficiently transferred to the vibrational ground state using a single stimulated Raman transition, opening the possibility to create large samples of stable, ultracold polar molecules.PACS numbers: 32.80. Pj, 33.80.Ps, 34.50.Gb, 34.50.Rk Ultracold polar molecules, due to their strong, longrange, anisotropic dipole-dipole interactions, may provide access to qualitatively new regimes previously inaccessible to ultracold atomic and molecular systems. For example, they might be used as the qubits of a scalable quantum computer [1]. New types of highly-correlated many-body quantum states could become accessible such as BCS-like superfluids [2], supersolid and checkerboard states [3], or "electronic" liquid crystal phases [4]. Ultracold chemical reactions between polar molecules have been discussed [5], and might be controlled using electric fields [6]. Finally, the sensitivity of current moleculebased searches for violations of fundamental symmetries [7] might be increased to unprecedented levels.Cold, trapped polar molecules have so far only been produced using either buffer-gas cooling [8] or Starkslowing [9], at temperatures of ∼10-100 mK [8,9]. This is much higher than the ∼1-100 µK accessible with atoms, and attempts to bridge this gap with evaporative cooling may run afoul of predicted molecular Feshbach resonances [10] or inelastic losses [11].Another approach is to extend well-known techniques for producing ultracold (non-polar) homonuclear diatomic molecules in binary collisions of ultracold atoms, either through photoassociation [12,13,14,15,16], or Feshbach resonance [17,18]. In these methods, the translational and rotational temperatures of the molecules are limited only by the initial atomic sample, possibly providing access all the way to the quantum-degenerate regime [15,18]. An important limitation, however, is that the molecules are typically formed in weakly bound vibrational levels near dissociation, which may have vanishing electric dipole moments [19], and are unstable with respect to inelastic collisions [10,11,15]; therefore, a method for transferring them to the vibrational ground state is desirable [14].Several authors have discussed the extension of these methods to the formation of (heteronuclear) polar molecules in collisions between different atomic species [20,21,22,23]. In recent experiments NaCs + and RbCs + ions formed in the presence of near-resonant light have indeed been observed in small numbers [21]; however, these observations did not permit an analysis of their formation mechanism, nor demonstrate a method for producing neutral, ultracold polar molecules.In this Letter, we ...