We present a scheme for stabilizing the difference frequency of two independent lasers. The scheme is based on simple electronics and makes use of the frequency-dependent phase shift experienced by a signal when it propagates through a delay line of coaxial cable. The stabilized difference frequency can be tuned over a wide range. Difference frequencies in the radio-frequency domain (100 MHz–10 GHz) can be controlled with long-term stability of better than 1 MHz.

Abstract. We investigate collisional properties of lithium and cesium which are simultaneously confined in a combined magneto-optical trap. Trap-loss collisions between the two species are comprehensively studied. Different inelastic collision channels are identified, and inter-species rate coefficients as well as cross sections are determined. It is found that loss rates are independent of the optical excitation of Li, as a consequence of the repulsive Li * -Cs interaction. Li and Cs loss by inelastic inter-species collisions can completely be attributed to processes involving optically excited cesium (fine-structure changing collisions and radiative escape). By lowering the trap depth for Li, an additional loss channel of Li is observed which results from ground-state Li-Cs collisions changing the hyperfine state of cesium.

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We have trapped cesium atoms over many minutes in the focus of a CO 2 -laser beam employing an extremely simple laser system. Collisional properties of the unpolarized atoms in their electronic ground state are investigated. Inelastic binary collisions changing the hyperfine state lead to trap loss, which is quantitatively analyzed. Elastic collisions result in evaporative cooling of the trapped gas from 25 K to 10 K over a time scale of about 150 s.

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