population inversion   arises for typically 100 femtoseconds during the interaction of a slow highly charged ion (HCI) with a solid surface. Despite this limited lifetime, the formation and decay of a hollow atom can be conveniently studied from ejected electrons and soft X-rays, and the trajectories, energy loss and final charge state distribution of surface-scattered projectiles.
population inversion occurs typically for 100 femtoseconds during the interaction of a slow, highly charged ion (HCI) with a solid surface. Despite its short lifetime, the formation and decay of a hollow atom can be studied from ejected electrons and soft X-rays, as well as the trajectories, energy loss, and final charge state distribution of surface-scattered projectiles.