INCIDENT ANGLE DEPENDENCE OF SECONDARY-ELECTRON EMISSION FROM A TA SURFACE BY MULTIPLY CHARGED IONS

The incident angle dependence of secondary electron emission yield-gamma from a clean polycrystalline Ta target has been investigated for keV Ne(q+) (q = 0-3) and Ar(q+) (q = 0-3) over the angle-theta ranging from 0 to 80-degrees to the surface normal. Generally the observed gamma is found to increase as theta increases. The gamma for kinetic emission of ions, gamma(KE), is estimated from the gamma for q = 0, neutral atoms. An analysis of the incident angle dependence of gamma using gamma(KE) shows that the gamma for Potential emission, gamma(PE), is constant. Furthermore, we concluded that the incident angle dependence of gamma is due to excited atoms which are not completely relaxed into their ground state when they arrive at the surface.