Molecular-frame (e,2e) experiment for N2 at large momentum transfer

We report molecular-frame (e,2e) cross sections for N₂ at large momentum transfer, obtained using the electron-electron-fragment ion triple-coincidence technique. The measured angular distribution of the (e,2e) cross section for the inner-valence 2σ_g orbital appears to show that the spatial character of the orbital has been directly observed in momentum space. On the other hand, experimental results for ionization to states above the double-ionization threshold suggested a larger intensity in the direction perpendicular to the molecular axis rather than parallel, an observation that our plane-wave impulse-approximation calculations fail to reproduce.