Cesium coverage due to Cs+bombardment of a polycrystalline molybdenum surface was investigated in the incident energy range below 500 eV. When the surface is exposed to a Cs+beam the work function decreases until steady state is reached with a total dose of less than ape;1times;1016ions/cm2. The steady state work function reaches a minimum at an incident energy of ape;100 eV and slowly increases with bombarding energy. Cesium coverage of a target is proportional to the ratio (1minus;bgr;)/ggr;, where bgr; is the reflection coefficient and ggr; is the sputter yield. This ratio is large for molybdenum because of its low mass and high binding energy. Implications of these results for Hminus;surface conversion sources are discussed.
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