Evaporative cooling in a radio-frequency trap

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 1, the cooling procedure is facilitated using a second rf source at frequency 2. This second rf field produces a controlled coupling between the spin states dressed by 1. 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 2 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 1 and 2 are separated by at least the Rabi frequency associated with 1, additional evaporation zones appear which can make this process more efficient