Electronic structure of helium hydride

Seven new electronic states of helium hydride have been observed, allowing the first determination of ionization potentials and quantum defects. From the rotational analysis and the observed intensities of the six new emission bands, the characters of the electronic states and the correlation to united atom orbitals were obtained. Thus the first clear picture of the electronic structure of this fundamental molecule is presented. Strong perturbations and interference effects between states with Δl=±1 were found. The excited HeH molecules were produced by neutralization of a fast ${\mathrm{HeH}}^{+}$ beam.