Inelastic losses in radiofrequency-dressed traps for ultracold atoms

Abstract

We calculate the rates of inelastic collisions for ultracold alkali-metal atoms in radiofrequency-dressed traps, using coupled-channel scattering calculations on accurate potential energy surfaces. We identify an rf-induced loss mechanism that does not exist in the absence of rf radiation. This mechanism is not suppressed by a centrifugal barrier in the outgoing channel, and can be much faster than spin relaxation, which is centrifugally suppressed. We explore the dependence of the rf-induced loss rate on singlet and triplet scattering lengths, hyperfine splittings and the strength of the rf field. We interpret the results in terms of an adiabatic model of the collision dynamics, and calculate the corresponding nonadiabatic couplings. The loss rate can vary by 10 orders of magnitude as a function of singlet and triplet scattering lengths. $^{87}$Rb is a special case, where several factors combine to reduce rf-induced losses; as a result, they are slow compared to spin-relaxation losses. For most other alkali-metal pairs, rf-induced losses are expected to be much faster and may dominate.