Short-pulse photoassociation in rubidium below theD1line

Abstract

Photoassociation of two ultracold rubidium atoms and the subsequent formation of stable molecules in the singlet ground and lowest triplet states is investigated theoretically. The method employs laser pulses inducing transitions via excited states correlated to the 5S + 5P 1/2 asymptote. Weakly bound molecules in the singlet ground or lowest triplet state can be created by a single pulse while the formation of more deeply bound molecules requires a two-color pump-dump scenario. More deeply bound molecules in the singlet ground or lowest triplet state can be produced only if efficient mechanisms for both pump and dump steps exist. While long-range 1/R 3 -potentials allow for efficient photoassociation, stabilization is facilitated by the resonant spin-orbit coupling of the 0 + u states. Molecules in the singlet ground state bound by a few wavenumbers can thus be formed. This provides a promising first step toward ground state molecules which are ultracold in both translational and vibrational degrees of freedom.

Enhancing photoassociation rates by nonresonant-light control of shape resonances

“…This enhancement is due to shape resonances and scattering states becoming bound, causing a larger number of atom pairs to be quasi-trapped at sufficiently short interatomic separations to be photoassociated. Since the photoassociation rate is limited by the low pair density at or near the Condon radius [22,32], applying strong non-resonant light during photoassociation overcomes the main obstacle toward forming larger numbers of molecules. The enhancement of the photoassociation rate is accompanied by strong hybridization of the angular motion, which we have fully accounted for in a rigorous treatment of the coupled rovibrational motion.…”

Dynamical interferences to probe short-pulse photoassociation of Rb atoms and stabilization ofRb2dimers

“…The pulse is centered at t P = 50 ps, with τ C = 10 ps, χ = 4.41 × 10 −2 ps −2 , and E pulse = 41 nJ focused on σ = 2.8 × 10 −3 cm 2 . We choose χ > 0 to maximize the population transfer [25].…”

Probing ultracold collisional dynamics with frequency-chirped pulses

“…The cold atoms fill in the depleted pair distribution rather slowly. Finally, we point out that our depletion effect is closely related to the production of a "hole" in the ground-state collisional wavefunction [9,12]. Such a hole is associated with mixing bound levels into the continuum state and is predicted to lead directly to the production of weakly-bound ground-state molecules.…”

“…Laser cooling and evaporative cooling of atoms [1] and the coherent control of excitation processes in molecules [2,3] represent prime examples. The possibility of combining these two areas, i.e., applying coherent control techniques to ultracold systems, has generated a great deal of interest, especially in the context of using short laser pulses to produce ultracold molecules by photoassociating ultracold atoms [4,5,6,7,8,9,10,11,12,13,14,15]. Part of the appeal is the prospect of controlling the internal state distribution of the resulting molecules.…”