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 ${\omega }_1$, the cooling procedure is facilitated using a second rf source at frequency ${\omega }_2$. This second rf field produces a controlled coupling between the spin states dressed by ${\omega }_1$. 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 ${\omega }_2$ 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 ${\omega }_1$ and ${\omega }_2$ are separated by at least the Rabi frequency associated with ${\omega }_1$, additional evaporation zones appear which can make this process more efficient.

• Received 31 August 2006

DOI:https://doi.org/10.1103/PhysRevA.74.053413