Cold collisions of alkali atoms in a laser field

+134hlm.;24c

High-precision calculations of van der Waals coefficients for heteronuclear alkali-metal dimers

Van der Waals coefficients for the heteronuclear alkali-metal dimers of Li, Na, K, Rb, Cs, and Fr are calculated using relativistic ab initio methods augmented by high-precision experimental data. We argue that the uncertainties in the coefficients are unlikely to exceed about 1%.Comment: 11 pages, 2 figs, graphicx.st

Observation of a shape resonance in cold-atom scattering by pulsed photoassociation

We observe the time dependence of a cold-atom collision in a pulsed photoassociation experiment. For a g-wave shape resonance in the 85Rb+85Rb system we measure the time needed to build up the resonant state by tunneling through the centrifugal barrier. Combining this with time-independent 85Rb and 87Rb photoassociation we determine the resonance energy and find evidence for the decay of the shape resonance into inelastic channels. We also determine the 85Rb+85Rb and 87Rb+87Rb C6 coefficient and triplet scattering lengths without relying on ab initio calculations

Role of collisions in creation of overlapping Bose condensates

We study the elastic scattering length and inelastic decay rate associated with collisions of [Formula Presented] and [Formula Presented] atoms in different hyperfine states: one with atoms in the [Formula Presented] and one with atoms in the [Formula Presented] state. For Na the real part of the [Formula Presented] scattering length for 22〉+1-1〉 collisions is predicted to be positive and equal to 65±5 Bohr length units [Formula Presented] for small B. The zero-temperature low-field decay rate is of the order of a typical exchange rate: [Formula Presented]=(1.5±0.7)[Formula Presented] [Formula Presented] [Formula Presented], showing that a two-condensate experiment is not feasible for a Na gas sample in a static magnetic trap. For the case of Rb atoms the present knowledge of the singlet interaction does not allow a similar calculation. The extreme suppression of [Formula Presented] demonstrated by a recent experiment is shown to be very restrictive for the value of the singlet accumulated phase

Time-independent and time-dependent photoassociation of spin-polarized rubidium

We extract information about collisions of ultra-cold ground-state rubidium atoms from observations of a g-wave shape resonance in the 85Rb + 85Rb system via time-independent and time-dependent photoassociation. The shape resonance arises from a quasi-bound state inside a centrifugal barrier that enhances the excitation to the bound electronically excited state by the photoassociation laser in the time-independent experiment. The shape resonance is sufficiently long-lived that its build-up through the barrier can be observed by first depleting it via a photoassociation laser pulse and then measuring the rate of photoassociation by a second laser pulse with a variable delay time. A combined method of analysis of the time-independent and time-dependent experiments is presented. We discuss the spectroscopy of states of two particles with spin trapped inside a centrifugal barrier, interacting via direct and indirect spin-spin interactions