RECTIFIED FORCES ON A 3-LEVEL ATOM - THE CASCADE CONFIGURATION

We calculate the force on a stationary three-level atom in the presenc e of a bichromatic standing wave whose two frequencies are nearly reso nant with the two transitions of the cascade configuration. We see sig nificant rectification of the force, i.e., the force does not vanish w hen averaged over an optical wavelength. Such a unidirectional force a llows the creation of deep potential wells for the atom. In the case o f two-photon resonance, the force can be fully rectified, which preven ts channeling of atoms on the optical wavelength scale.