  Driven by recent developments in time-resolved photoemission spectroscopy, we
extend the successful method of photoemission orbital tomography (POT) to
excitons. Our theory retains the intuitive orbital picture of POT, while
respecting both the entangled character of the exciton wave function and the
energy conservation in the photoemission process. Analyzing results from three
organic molecules, we classify generic exciton structures and give a simple
interpretation in terms of natural transition orbitals. We validate our
findings by directly simulating pump-probe experiments with time-dependent
density functional theory.
