Angle-resolved spectroscopy of low-energy secondary electrons from surfaces emitted by highly charged ion impact

Abstract

Secondary electron emission is a key energy dissipation mechanism during the impact of highly charged ions on material surfaces. While total electron yields have been well studied across a wide range of ion velocities and charge states, angle- and energy-resolved data of low-energy secondary electrons remains scarce. To address this, we installed a portable electron beam ion source at the ASPHERE III setup at DESY, which features a hemispherical energy analyser for angle-resolved ion-induced electron emission spectroscopy (ARIIEES). Our results show that the angular distribution of emitted electrons varies with ion charge state: For singly charged ions, emission follows a cosine distribution, but with higher charge states, the distribution flattens, favouring emission at larger angles. This suggests that at high yields, repulsion due to space charge effects reduces electron emission normal to the surface We will present these findings and discuss their implications for related experimental techniques.