arXiv subjects

Pascal Naidon

Publications and source records attributed to Pascal Naidon.

40 records · Page 3Linked to original sources

arXiv2007

Two-color photoassociation spectroscopy of ytterbium atoms and the precise determinations of s-wave scattering lengths

By performing high-resolution two-color photoassociation spectroscopy, we have successfully determined the binding energies of several of the last bound states of the homonuclear dimers of six different isotopes of ytterbium. These spectroscopic data are in excellent agreement with theoretical calculations based on a simple model potential, which very precisely predicts the s-wave scattering lengths of all 28 pairs of the seven stable isotopes. The s-wave scattering lengths for collision of two atoms of the same isotopic species are 13.33(18) nm for ^{168}Yb, 3.38(11) nm for ^{170}Yb, -0.15(19) nm for ^{171}Yb, -31.7(3.4) nm for ^{172}Yb, 10.55(11) nm for ^{173}Yb, 5.55(8) nm for ^{174}Yb, and -1.28(23) nm for ^{176}Yb. The coefficient of the lead term of the long-range van der Waals potential of the Yb_2 molecule is C_6=1932(30) atomic units $(E_h a_0^6 \approx 9.573\times 10^{-26}$ J nm^6).

physics.atom-ph↗

arXiv2006

Optical Feshbach resonances of Alkaline-Earth atoms in a 1D or 2D optical lattice

Motivated by a recent experiment by Zelevinsky et al. [Phys. Rev. Lett. 96, 203201], we present the theory for photoassociation and optical Feshbach resonances of atoms confined in a tight one-dimensional (1D) or two-dimensional (2D) optical lattice. In the case of an alkaline-earth intercombination resonance, the narrow natural width of the line makes it possible to observe clear manifestations of the dimensionality, as well as some sensitivity to the scattering length of the atoms. Among possible applications, a 2D lattice may be used to increase the spectroscopic resolution by about one order of magnitude. Furthermore, a 1D lattice induces a shift which provides a new way of determining the strength of a resonance by spectroscopic measurements.

physics.atom-ph↗

arXiv2005

Photoassociation and optical Feshbach resonances in an atomic Bose-Einstein condensate: treatment of correlation effects

In this paper we formulate the time-dependent many-body theory of photoassociation in an atomic Bose-Einstein condensate with realistic interatomic interactions, using and comparing two approximations: the first-order cumulant approximation, originally developed by Kohler and Burnett [Phys. Rev. A 65, 033601 (2002)], and the reduced pair wave approximation, based on a previous paper [Phys. Rev. A 68 033612 (2003)] generalizing to two channels the Cherny-Shanenko approach [Phys. Rev. E 62, 1046 (2000)]. The two approximations differ only by the way a pair of condensate atoms is influenced by the mean field at short interatomic separations. For these approximations we identify two different regimes of photoassociation: the adiabatic regime and the coherent regime. The threshold for the so-called "rogue dissociation" [Phys. Rev. Lett. 88, 090403 (2002)] (where mean-field theory breaks down) is found to be different in each regime, which sheds new light on the experiment of McKenzie et al [Phys. Rev. Lett. 88, 120403 (2002)] and previous theoretical calculations. We then use the two approximations to investigate numerically the effects of rogue dissociation in a sodium condensate under conditions similar to the McKenzie et al experiment. We find two different effects: reduction of the photoassociation rate at short times, and creation of correlated pairs of atoms, confirming previous works. We also observe that the photoassociation line shapes become asymmetric in the first-order cumulant approximation, while they remain symmetric in the reduced pair wave approximation, giving the possibility to experimentally distinguish between the two approximations.

cond-mat.other↗

arXiv2004

Pair dynamics in the formation of molecules in a Bose-Einstein condensate

We revisit the mean-field treatment of photoassociation and Feshbach resonances in a Bose-Einstein condensate previously used by various authors. Generalizing the Cherny and Shanenko approach (Phys. Rev. E 62, 1646-59 (2000) ) where the finite size of the potentials is explicitly introduced, we develop a two-channel model for a mixed atomic-molecular condensate. Besides the individual dynamics of the condensed and non-condensed atoms, the model also takes into account their pair dynamics by means of pair wave functions. We show that the resulting set of coupled equations can be reduced to the usual coupled Gross-Pitaevskii equations when the time scale of the pair dynamics is short compared to that of the individual dynamics. Such time scales are discussed in the case of typical photoassociation experiments with cw lasers. We show that the individual dynamics plays a minor role, demonstrating the validity of the rates predicted by the usual models describing photoassociation in a nondegenerate gas.

cond-mat.other↗