We report a new cooling scheme used to actively collimate an atomic beam of 85 Rb with onedimensional optical molasses. The atoms' transverse velocity is damped by a standing wave of circularly polarized light in a magnetic field of -20 /iT to 2 cm/s (rms), well below the Doppler velocity v D -(lhy/20M) U2~-\0 cm/s for one-dimensional optical molasses. The minimum measured velocity is limited only by the experimental geometry. We have developed a model in which the mixing by the field and optical pumping combine to form a cycle that cools below the Doppler limit, in agreement with our measurements.

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