Complete photo-fragmentation of the deuterium molecule

All properties of molecules - from binding and excitation energies to their geometry - are determined by the highly correlated initial-state wavefunction of the electrons and nuclei. Details of these correlations can be revealed by studying the break-up of these systems into their constituents. The fragmentation might be initiated by the absorption of a single photon(1-6), by collision with a charged particle(7,8) or by exposure to a strong laser pulse(9,10): if the interaction causing the excitation is sufficiently understood, the fragmentation process can then be used as a tool to investigate the bound initial state(11,12). The interaction and resulting fragment motions therefore pose formidable challenges to quantum theory(13-15). Here we report the coincident measurement of the momenta of both nuclei and both electrons from the single-photon-induced fragmentation of the deuterium molecule. The results reveal that the correlated motion of the electrons is strongly dependent on the inter-nuclear separation in the molecular ground state at the instant of photon absorption.