Quantum suppression of collisional loss rates in optical traps

We present a coupled-channel study of optical collisions, restricted to a single atom-laser manifold. Outside of a resonance region around the Condon point, we find a simple representation of the solution in terms of propagating complex dressed states. The probability flux for the ${}_{}{}^2{}_{}{}^{}$ ${\mathit{P}}_{3/2}$+S state at small interatomic distances can be interpreted in terms of two such interfering dressed states. The coupled-channel solution displays some features that have previously been obtained with semiclassical optical-Bloch-equation methods. An important quantum effect, however, is a strong reduction of atom loss rates at low collision energies that is roughly proportional to ${\mathit{E}}^{\mathrm{-}2}$.