Ultracold LiCs molecules in the absolute ground state X1Sigma+, v'' = 0, J'' = 0 are formed via a single photoassociation step starting from laser-cooled atoms. The selective production of v'' = 0, J'' = 2 molecules with a 50-fold higher rate is also demonstrated. The rotational and vibrational state of the ground state molecules is determined in a setup combining depletion spectroscopy with resonant-enhanced multiphoton ionization time-of-flight spectroscopy. Using the determined production rate of up to 5 x 10(3) molecules/s, we describe a simple scheme which can provide large samples of externally and internally cold dipolar molecules.
Ultracold collisions between Cs atoms and Cs2 dimers in the electronic ground state are observed in an optically trapped gas of atoms and molecules. The Cs2 molecules are formed in the triplet ground state by cw photoassociation through the outer well of the 0-(g) (P3/2) excited electronic state. Inelastic atom-molecule collisions converting internal excitation into kinetic energy lead to a loss of Cs2 molecules from the dipole trap. Rate coefficients are determined for collisions involving Cs atoms in either the F=3 or F=4 hyperfine ground state, and Cs2 molecules in either highly vibrationally excited states (nu'=32-47) or in low vibrational states (nu'=4-6) of the a3 summation(u)+ triplet ground state. The rate coefficients beta approximately 10(-10) cm3/s are found to be largely independent of the vibrational and rotational excitation indicating unitary limited cross sections.
Abstract.We present the first observation of ultracold LiCs molecules. The molecules are formed in a two-species magneto-optical trap and detected by two-photon ionization and time-of-flight mass spectrometry. The production rate coefficient is found to be in the range 10 −18 cm 3 s −1 to 10 −16 cm 3 s −1 , at least an order of magnitude smaller than for other heteronuclear diatomic molecules directly formed in a magneto-optical trap.
We recently reported the formation of ultracold LiCs molecules in the rovibrational ground state et al., PRL 101, 133004 (2008)]. Here we discuss details of the experimental setup and present a thorough analysis of the photoassociation step including the photoassociation line shape. We predict the distribution of produced ground state molecules using accurate potential energy curves combined with an ab-initio dipole transition moment and compare this prediction with experimental ionization spectra. Additionally we improve the value of the dissociation energy for the X 1 Σ + state by high resolution spectroscopy of the vibrational ground state.
The rate coefficients for hyperfine-changing collisions of ground-state 133Cs and 7Li atoms trapped in a quasielectrostatic trap (QUEST) were investigated. The rate coefficients G(4,4) for hyperfine-changing collisions of Cs atoms in the upper hyperfine ground state |F=4 was found to be 1.1 x 10-11 cm3s-1 in the temperature range between 30 and 130 K. Absorption imaging was used to detect the Cs atom number, density and temperature. It was concluded that the behavior of a mixture of Li and Cs atoms that was analyzed using coupled rate equations can result the rate coefficients for all possible combinations of hyperfine ground states
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