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Production of Ultracold, Polar RbCs* Molecules via Photoassociation  [PDF]
Andrew J. Kerman,Jeremy M. Sage,Sunil Sainis,David DeMille,Thomas Bergeman
Physics , 2003, DOI: 10.1103/PhysRevLett.92.033004
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 singlet ground state RbCs vibrational levels as high as 5 x 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.
Production and state-selective detection of ultracold, ground state RbCs molecules  [PDF]
Andrew J. Kerman,Jeremy M. Sage,Sunil Sainis,Thomas Bergeman,David DeMille
Physics , 2004, DOI: 10.1103/PhysRevLett.92.153001
Abstract: Using resonance-enhanced two-photon ionization, we detect ultracold, ground-state RbCs molecules formed via photoassociation in a laser-cooled mixture of 85Rb and 133Cs atoms. We obtain extensive bound-bound excitation spectra of these molecules, which provide detailed information about their vibrational distribution, as well as spectroscopic data on the RbCs ground a^3\Sigma^+ and excited (2)^3\Sigma^+, (1)^1\Pi states. Analysis of this data allows us to predict strong transitions from observed excited levels to the absolute vibronic ground state of RbCs, potentially allowing the production of stable, ultracold polar molecules at rates as large as 10^7 s^{-1}.
Optical Production of Ultracold Polar Molecules  [PDF]
J. M. Sage,S. Sainis,T. Bergeman,D. DeMille
Physics , 2005, DOI: 10.1103/PhysRevLett.94.203001
Abstract: 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 $X ^1\Sigma^+ (v=0)$ molecules has a translational temperature of $\sim100 \mu$K 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.
Photoassociative Production and Trapping of Ultracold KRb Molecules  [PDF]
D. Wang,J. Qi,M. F. Stone,O. Nikolayeva,H. Wang,B. Hattaway,S. D. Gensemer,P. L. Gould,E. E. Eyler,W. C. Stwalley
Physics , 2004, DOI: 10.1103/PhysRevLett.93.243005
Abstract: We have produced ultracold heteronuclear KRb molecules by the process of photoassociation in a two-species magneto-optical trap. Following decay of the photoassociated KRb*, the molecules are detected using two-photon ionization and time-of-flight mass spectroscopy of KRb$^+$. A portion of the metastable triplet molecules thus formed are magnetically trapped. Photoassociative spectra down to 91 cm$^{-1}$ below the K(4$s$) + Rb (5$p_{1/2}$) asymptote have been obtained. We have made assignments to all eight of the attractive Hund's case (c) KRb* potential curves in this spectral region.
Formation of ultracold RbCs molecules by photoassociation  [PDF]
N. Bouloufa-Maafa,M. Aymar,O. Dulieu,C. Gabbanini
Physics , 2011, DOI: 10.1134/S1054660X12100039
Abstract: The formation of ultracold metastable RbCs molecules is observed in a double species magneto-optical trap through photoassociation below the ^85Rb(5S_1/2)+^133Cs(6P_3/2) dissociation limit followed by spontaneous emission. The molecules are detected by resonance enhanced two-photon ionization. Using accurate quantum chemistry calculations of the potential energy curves and transition dipole moment, we interpret the observed photoassociation process as occurring at short internuclear distance, in contrast with most previous cold atom photoassociation studies. The vibrational levels excited by photoassociation belong to the 5th 0^+ or the 4th 0^- electronic states correlated to the Rb(5P_1/2,3/2)+Cs(6S_1/2) dissociation limit. The computed vibrational distribution of the produced molecules shows that they are stabilized in deeply bound vibrational states of the lowest triplet state. We also predict that a noticeable fraction of molecules is produced in the lowest level of the electronic ground state.
Dispersion interactions and reactive collisions of ultracold polar molecules  [PDF]
Svetlana Kotochigova
Physics , 2010, DOI: 10.1088/1367-2630/12/7/073041
Abstract: Progress in ultracold experiments with polar molecules requires a clear understanding of their interactions and reactivity at ultra-low collisional energies. Two important theoretical steps in this process are the characterization of interaction potentials between molecules and the modeling of reactive scattering mechanism. Here, we report on the {\it abinitio} calculation of isotropic and anisotropic van der Waals interaction potentials for polar KRb and RbCs colliding with each other or with ultracold atoms. Based on these potentials and two short-range scattering parameters we then develop a single-channel scattering model with flexible boundary conditions. Our calculations show that at low temperatures (and in absence of an external electric field) the reaction rates between molecules or molecules with atoms have a resonant character as a function of the short-range parameters. We also find that both the isotropic and anisotropic van der Waals coefficients have significant contributions from dipole coupling to excited electronic states. Their values can differ dramatically from those solely obtained from the permanent dipole moment. A comparison with recently obtained reaction rates of fermionic $^{40}$K$^{87}$Rb shows that the experimental data can not be explained by a model where the short-range scattering parameters are independent of the relative orbital angular momentum or partial wave.
Linking Ultracold Polar Molecules  [PDF]
A. V. Avdeenkov,J. L. Bohn
Physics , 2002, DOI: 10.1103/PhysRevLett.90.043006
Abstract: We predict that pairs of polar molecules can be weakly bound together in an ultracold environment, provided that a dc electric field is present. The field that links the molecules together also strongly influences the basic properties of the resulting dimer, such as its binding energy and predissociation lifetime. Because of their long-range character these dimers will be useful in disentangling cold collision dynamics of polar molecules. As an example, we estimate the microwave photoassociation yield for OH-OH cold collisions.
Ultracold dense samples of dipolar RbCs molecules in the rovibrational and hyperfine ground state  [PDF]
Tetsu Takekoshi,Lukas Reichs?llner,Andreas Schindewolf,Jeremy M. Hutson,C. Ruth Le Sueur,Olivier Dulieu,Francesca Ferlaino,Rudolf Grimm,Hanns-Christoph N?gerl
Physics , 2014, DOI: 10.1103/PhysRevLett.113.205301
Abstract: We produce ultracold dense trapped samples of 87Rb133Cs molecules in their rovibrational ground state, with full nuclear hyperfine state control, by stimulated Raman adiabatic passage (STIRAP) with efficiencies of 90%. We observe the onset of hyperfine-changing collisions when the magnetic field is ramped so that the molecules are no longer in the hyperfine ground state. A strong quadratic shift of the transition frequencies as a function of applied electric field shows the strongly dipolar character of the RbCs ground-state molecule. Our results open up the prospect of realizing stable bosonic dipolar quantum gases with ultracold molecules.
Creation of ultracold $^{87}$RbCs molecules in the rovibrational ground state  [PDF]
Peter K. Molony,Philip D. Gregory,Zhonghua Ji,Bo Lu,Michael P. K?ppinger,C. Ruth Le Sueur,Caroline L. Blackley,Jeremy M. Hutson,Simon L. Cornish
Physics , 2014, DOI: 10.1103/PhysRevLett.113.255301
Abstract: We report the creation of a sample of over 1000 ultracold $^{87}$RbCs molecules in the lowest rovibrational ground state, from an atomic mixture of $^{87}$Rb and Cs, by magnetoassociation on an interspecies Feshbach resonance followed by stimulated Raman adiabatic passage (STIRAP). We measure the binding energy of the RbCs molecule to be $h c \times 3811.576(1)$ cm$^{-1}$ and the $|v''=0, J''=0>$ to $|v''=0, J''=2>$ splitting to be $h \times 2940.09(6)$ MHz. Stark spectroscopy of the rovibrational ground state yields an electric dipole moment of 1.225(3)(8) D, where the values in parentheses are the statistical and systematic uncertainties, respectively. We demonstrate that a space-fixed dipole moment of 0.355(2)(4) D is accessible in RbCs, which is substantially higher than in previous work.
Inelastic Collisions of Ultracold Polar Molecules  [PDF]
John L. Bohn
Physics , 2000, DOI: 10.1103/PhysRevA.63.052714
Abstract: The collisional stability of ultracold polar molecules in electrostatic traps is considered. Rate constants for collisions that drive molecules from weak-field-seeking to strong-field-seeking states are estimated using a simple model. The rates are found to be quite large, of order 10^{-12} - 10^{-10} cm^3/sec, and moreover to grow rapidly in an externally applied electric field. It is argued that these results are generic for polar molecules, and that therefore polar molecules should be trapped by other than electrostatic means.
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