SECONDARY-ELECTRON EMISSION FROM SURFACES IMPACTED BY MULTIPLY-CHARGED POLYATOMIC IONS

In this paper, results are presented on the emission of secondary electrons from various surfaces under collisional excitation by incident energetic multiply-charged macro-molecular ions from an electrospray source. The impact velocities fall in the range nu = 30 to 90 km/s, above the threshold for kinetic electron emission. The secondary electron yield varies dramatically for different targets. The yield is proportional to (nu2 - a), where a is a constant which depends on projectile mass and charge state and on the target material. For graphite, the secondary electron yield is proportional to mass, whereas for Al2O3 it is proportional to M0.74. A simple model is proposed to explain an observed modulation of the electron yield with primary ion charge state and conformation.