Production of Ultracold, PolarRbCs*Molecules via Photoassociation

Abstract

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 ...

Fourier-transform spectroscopy and coupled-channels deperturbation treatment of theA 1Σ+–b 3Πcomplex of KCs

“…[14] within few cm −1 near a minimum of these functions; (see Eq. (8). However, the present empirical A so ± (r) functions evaluated near the equilibrium distance r e of the triplet b-state are smaller on 20-25 cm −1 than their ab initio counterparts corresponding to the pure (c) Hund's coupling case [15] (see Table IV).…”

“…Due to proximity of K(4p) and Rb(5p) energies, the energy of low-lying electronic states of KCs is similar to the ones in the RbCs molecule, however, KCs possess larger permanent electric dipole moment. The RbCs molecule has been already studied in ultracold conditions [7,8,9]. In particular, the recent quantum dynamics simulation of the mixed A 1 Σ + and b 3 Π Ω states of RbCs in a time-dependent wave-packet approach [6] demonstrated that the pump -dump picosecond pulsed laser scheme could be efficient to form ultracold heteronuclear diatomic molecules in highly bonded ground X 1 Σ + state.…”

XΣ+1andaΣ+Staanum1, Pashov2, Knöckel3 et al. 2007Phys. Rev. A1199592View full textAdd to dashboardCite

“…Cold heteronuclear alkali dimers are subject to a large interest since they can be formed at temperatures below 1 mK [1,2,3,4,5] and possess a large permanent electric dipole moment for deeply bound singlet levels [6,7]. This combination of properties enables electric field control of ultracold collisions [8,9] and cold chemical reactions [10,11] and holds promises for applications in quantum computation [12].…”

Boson-fermion coherence in a spherically symmetric harmonic trap

“…Two recent experiments have led to the observation of heteronuclear Feshbach resonances in Bose-Fermi mixtures of 6 Li and 23 Na [11] in one case, and of 87 Rb and 40 K in the other [12]. We also mention recent experiments by Kerman et al [13], who produced metastable RbCs molecules in their lowest triplet state starting from a laser-cooled mixture of 85 Rb and 133 Cs by photoassociation. Major current experimental and experimental efforts are directed towards the exploration of the crossover between the Bardeen-Cooper-Schrieffer (BCS) state of fermionic atoms and BEC of bosonic molecules as the system crosses a Feshbach resonance [14].…”