Cluster-induced force acting on the photoemitted electron. Cluster-induced force (Equation 9) acting on the electron moving away from the center of the cluster (N = 20, rs = 4) as a function of the electron position. We consider the cases without and with a localized hole at the center of the cluster. The electron moves with a constant velocity: (a) υ = 1 a.u. (Inset, for cluster-induced force for a larger cluster with 556 electrons, the hole is not included. The horizontal dotted line corresponds to the stopping power in an homogeneous electron gas with rs = 4.) and (b) υ = 1.5 a.u. Vertical dashed lines correspond to the radius of the cluster, Rcl = 10.86 a.u.