Effect of molecular axis orientation of 3.6 MeV Si2+projectiles on the ion-induced secondary electron emission from a carbon foil

We study ion-induced secondary electron emission from solid surfaces. This work focuses on the dependence of the energy distribution of secondary electrons on the orientation of Si-dimers impinging on thin carbon foils. The orientation was determined by the foil-induced Coulomb explosion method. Furthermore, the electron energy was measured with a retarding field analyzer. The correlation between the electron energy distribution and the cluster orientation was obtained through simultaneous measurements. A comparison of the electron energy distribution for parallel and perpendicular orientations indicated that the electron yields at an energy below 20 eV are lower for parallel orientation. This reduction can be explained by the orientation dependence of the energy loss of Si2+ in carbon. It was suggested that the orientation effect is due to the distant collision between the cluster and the target atom, in which low-energy electrons are produced.