Electron Transfer from Sodium to Oriented Nitromethane, CH₃NO₂:  Probing the Spatial Extent of Unoccupied Orbitals

Beams of sodium atoms with energies of a few eV are crossed with a beam of oriented CH3NO2 molecules to study the effect of collision energy and orientation on electron transfer. The electron transfer produces Na+ ions and free electrons, parent negative ions (CH3NO2-), and fragmentation ions NO2- and O- in proportions that depend on the collision energy. The steric asymmetry is very small or zero and suggests that production of all of the ions is favored by sideways attack with respect to the permanent dipole along the C−N axis. In these experiments, the electron appears to be transferred into the 2B1 state of the anion comprising mainly the π*NO LUMO, producing a valence-bound state rather than a dipole-bound state.