Abstract
It is pointed out that the quasiparticle picture, which has been found to be valid for both outer valence and core electrons and is commonly used in atomic, molecular and solid-state physics, may completely break down in the inner valence region. Many-body calculations of inner valence ionisation potentials and their relative intensities are reported for several atomic and molecular systems. The calculations demonstrate that the absence of quasiparticles is a common phenomenon.