Experimental versus theoretical rates for photoassociation and for formation of ultracold molecules

Drag, Cyril; Tolra, B. Laburthe; Dulieu, Olivier; Comparat, D.; Vatasescu, Mihaela; Boussen, Salah; Guibal, S.; Crubellier, A.; Pillet, P.

doi:10.1109/3.892556

Cited by 63 publications

(63 citation statements)

References 43 publications

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“…2b showing that the predicted PA rate in a MOT environment is comparable to the rates observed with various heteronuclear diatomic species. We recall that the PA rate for Cs 2 at 140 µK [39] was larger than most of the PA rates observed under MOT conditions, as it was enhanced by the presence of a long-range double-well in the excited PEC. The large magnitude of the atom/molecule PA rate under QD conditions shows that such an experiment is achievable just like its Li-Li counterpart of Ref [41].…”

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confidence: 94%

“…The large magnitude of the atom/molecule PA rate under QD conditions shows that such an experiment is achievable just like its Li-Li counterpart of Ref [41]. [39], and several experimental rates for LiK [43], LiRb [44], RbCs [45], Na2 [42], and Li2 [41].…”

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confidence: 99%

“…As the detuning is assumed to be small, the |i → |f transition dipole moment is taken as the one for the 6 2 S 1/2 → 6 2 P 3/2 transition, leading to the corresponding atomic Rabi frequency Ω if and saturation intensity I 0 = 1.1 mW/cm 2 [28]. For the purpose of comparison among various experimental implementations, it is useful to define the normalized PA rate K PA (T ) = R PA (T )/n mol /φ PA (conveniently expressed in cm 5 ) where φ PA = I PA λ PA /hc is the PA laser photon flux at the wavelength λ PA [29,39]. The results for K PA (T ) are displayed in Fig.…”

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Theory of Long-Range Ultracold Atom-Molecule Photoassociation

2015

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The creation of ultracold molecules is currently limited to diatomic species. In this letter we present a theoretical description of the photoassociation of ultracold atoms and molecules to create ultracold excited triatomic molecules, thus being a novel example of light-assisted ultracold chemical reaction. The calculation of the photoassociation rate of ultracold Cs atoms with ultracold Cs2 molecules in their rovibrational ground state is reported, based on the solution of the quantum dynamics involving the atom-molecule long-range interactions, and assuming a model potential for the short-range physics. The rate for the formation of excited Cs3 molecules is predicted to be comparable with currently observed atom-atom photoassociation rates. We formulate an experimental proposal to observe this process relying on the available techniques of optical lattices and standard photoassociation spectroscopy.Ultracold dilute gases at temperatures much lower than 1 mK offer new opportunities for the study of elementary reactive processes between atoms and molecules. As emphasized in seminal review articles [1,2] this socalled ultracold chemistry is freed from averaging on large velocity distributions. Thus in this regime the quantum nature of the processes can be accessed, like the presence of resonances, or the sensitivity to long-range interactions which can induce anisotropic arrangements prior to the reaction. One of the most advanced experiments in this direction is undoubtedly under progress in JILA at Boulder, where quantum threshold collisions induced by tunneling through a centrifugal barrier between fermionic ultracold KRb molecules have been detected [3,4] [9] have been detected through atom trap losses. Three-body recombination in a Rb quantum gas has been characterized [10], and features associated to universal N -body (up to N = 5) resonances induced by collisions between atoms and weaklybound molecules have been observed in quantum degenerate gases [11][12][13][14][15][16].However the deep understanding of the collisional dynamics is still to come as none of these achievements were able to characterize the nature and the state distribution of the final products [17,18]. The heavy mass of alkalimetal species leads to a huge density of resonant states related to the numerous rovibrational levels accessible during an atom/molecule or a molecule/molecule collision, preventing them to be individually characterized. Models connecting the standard treatment of long-range interactions between particles to a statistical description of the resonances mostly resulting from short-range couplings have been developed [18][19][20][21]. The main quantitative uncertainty of such models arises from the estimation of the actual amount of resonant states which are indeed active during the collision.In this letter, we propose to use the well-known photoassociation (PA) process to get more insight into such collisions between ultracold atoms and molecules. PA of an ultracold atom pair is a laser-assisted collision creating an ...

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Theory of Long-Range Ultracold Atom-Molecule Photoassociation

2015

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“…Saturation was not observed in this experiment. Saturation was observed in two other lower precision experiments [22,23], but these experiments were performed in a magneto-optical trap, where the temperatures were greater than 100 K and the corresponding unitaritylimited rates were quite small, of the order of 1 s ÿ1 or less.We report precise measurements of both the rate of PA and the spectral shift in a quantum degenerate gas of 7 Li atoms as a function of laser intensity. The rate is observed to saturate at the highest intensities, where the corresponding rate constants are nearly 2 orders of magnitude larger than any previously measured.…”

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Intensity Dependence of Photoassociation in a Quantum Degenerate Atomic Gas

et al. 2003

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We have measured the intensity dependent rate and frequency shift of a photoassociation transition in a quantum degenerate gas of 7 Li. The rate increases linearly with photoassociation laser intensity for low intensities, whereas saturation is observed at higher intensities. The measured rates and shifts agree reasonably well with theory within the estimated systematic uncertainties. Several theoretically predicted saturation mechanisms are discussed, but a theory in which saturation arises because of quantum mechanical unitarity agrees well with the data. DOI: 10.1103/PhysRevLett.91.080402 PACS numbers: 03.75.Nt, 33.20.Kf, 33.70.-w, 34.20.Cf Photoassociation (PA) of ultracold atoms has been a remarkably useful tool for determining scattering lengths characterizing ultracold atom collisions, for producing ultracold molecules, and for providing extremely precise measurements of atomic radiative lifetimes (see Refs. [1,2] for reviews). This utility is largely a consequence of the spectroscopic precision afforded by the small thermal broadening in a laser or evaporatively cooled gas. Quantum degenerate gases are especially interesting because the coherence of the atomic field may enable the formation of a molecular Bose-Einstein condensate (BEC) from an atomic one by coherent Raman transitions [3,4], stimulated Raman adiabatic passage [5], or by other coherent adiabatic population transfer schemes [6,7].There have been extensive theoretical studies of the rate of PA [8][9][10][11][12]. The rate is predicted to increase linearly with intensity at low intensities, while various mechanisms have been proposed that cause saturation of the rate at higher intensities. Among these mechanisms are the quantum mechanical unitarity limit on the rate of atomic collisions [11], a breakdown of the two-mode approximation [4,13] for PA of Bose condensates caused by coupling to noncondensed atomic modes [12,14 -16], and the depletion of the atomic pair correlation function [15]. Photoassociation resonances are also predicted to exhibit a spectral shift proportional to the light intensity caused by coupling to the continuum of free-atom states [11,[17][18][19]. In contrast to theory, there are relatively few experimental measurements, and only two that could be considered ''precise'' (which we define as measurements with uncertainties of less than a factor of 2). We previously measured the spectral light shift using quantum degenerate 7 Li and obtained good agreement with theory [20]. Both the spectral shift and the PA rate constant were recently measured in a Na condensate, and good agreement with two-body theory was found [21]. Saturation was not observed in this experiment. Saturation was observed in two other lower precision experiments [22,23], but these experiments were performed in a magneto-optical trap, where the temperatures were greater than 100 K and the corresponding unitaritylimited rates were quite small, of the order of 1 s ÿ1 or less.We report precise measurements of both the rate of PA and the spectral shift in...

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Ultracold Molecules: Formation, Detection

Dulieu

2003

Dissociative Recombination of Molecular Ions With Electrons

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Experimental versus theoretical rates for photoassociation and for formation of ultracold molecules

Cited by 63 publications

References 43 publications

Theory of Long-Range Ultracold Atom-Molecule Photoassociation

Theory of Long-Range Ultracold Atom-Molecule Photoassociation

Intensity Dependence of Photoassociation in a Quantum Degenerate Atomic Gas

Ultracold Molecules: Formation, Detection

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