Manipulation of photoassociation of ultracold Cs atoms with tunable scattering length by external magnetic fields

Abstract

We demonstrate that for ultracold, optically trapped Cs atoms the photoassociation (PA) can be manipulated by using external uniform magnetic fields due to the alteration of the scattering wavefunction in the region of the free–bound optical transition. We present PA–induced atom loss measurements with the same intensity for PA laser but different external magnetic fields, and analyze main contributions of the PA to the variation of the number of atoms in the trap. The PA rate exhibits a strong dependence on the changing uniform magnetic field. The experimental data are simulated within the model of a single–channel one–well rectangular potential, whose depth is adjusted so as to assure the predicted variation of the scattering length with the magnetic field. The computational and experimental results are in a reasonable agreement to each other. The same model is used to illustrate some general properties of the two–body quantum system in the near–threshold state.

Cosine-type Absorbing Optical Potential for the Modeling of Quantum Dynamics with the Fourier Grid and Optimizer Packages

“…Modern spectroscopic experiments on the PA of ultracold atoms via magnetically tuned near-dissociation Feshbach resonances (see [18] and references therein) require a description of the Feshbach resonances at very low energies, corresponding to very long oscillation lengths (several hundreds of Bohr radii or even more). The numerical tests presented in Table 2 were done with lengths of the absorption zone of no less than the oscillation length, which required dealing with very long zones to simulate these near-dissociation features.…”

“…Probably the most efficient way to enhance the PA process, and hence to increase the production of such ensembles, is by using magnetically tuned near-dissociation Feshbach resonances [16][17][18][19].…”

Effect of external magnetic field on the shift of resonant frequency in photoassociation of ultracold Cs atoms

“…[33] was used to calculate the atomic scattering length near a Feshbach resonance, and this model was used to explain the enhanced PA by magnetic field. [34] Here, a single channel square-well potential with a tunable depth is considered to generate a versatile wavefunction of Cs atoms in the effective PA range in Fig. 4(a) and then applied to the obtained variation of the slope of the frequency shift with the magnetic field in Fig.…”