Kinetic Ejection of Electrons from Tungsten by Cesium Ions

Measurements of ${\gamma }_i$ (number of electrons per incident ion) for cesium ions on atomically clean tungsten surfaces are reported. Vacuum conditions were such that subsequent to heating the tungsten to 2400°K a monolayer of gas was formed on the surface in ∼4 hours. Since measurements were taken within 30 seconds after heating the tungsten to this temperature, the surface contamination is