Evaporative cooling in a radio-frequency trap

Abstract

A theoretical investigation for implementing a scheme of forced evaporative cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing the atoms to be trapped in a combination of a dc magnetic field and a rf field at frequency ω1, the cooling procedure is facilitated using a second rf source at frequency ω2. This second rf field produces a controlled coupling between the spin states dressed by ω1. The evaporation is then possible in a pulsed or continuous mode. In the pulsed case, atoms with a given energy are transferred into untrapped dressed states by abruptly switching off the ω2 coupling. In the continuous case, it is possible for energetic atoms to adiabatically follow the doubly dressed states and escape out of the trap. Our results also show that when ω1 and ω2 are separated by at least the Rabi frequency associated with ω1, additional evaporation zones appear which can make this process more efficient. © 2006 The American Physical Society.