3D mapping of photoemission from a single oriented H2O molecule

3D O 1s photoelectron angular distributions from a fixed-in-space H2O molecule have been observed for the first time by quadruple coincidence measurements of photoelectron−O+−H+−H+. Obtained results for the non-axially symmetric molecules reveal the symmetry-imposed restrictions of the C2v symmetry group on the angular distributions and their strong orientation. Characteristic features of the angular distributions are explained with full quantum mechanical calculations and also in terms of Huygens' approach on electron de Broglie waves.