Photoelectron Spectroscopy of NH3 and ND3 Using Molecular Beams

Ammonia and ammonia‐d₃ have been examined with high resolution photoelectron spectroscopy using the 584‐ Å resonance line of helium. The spectra consist of two electronic states which are formed as a result of severe geometrical changes in the ground state molecule. The onset for the first state, consisting of a vibrational envelope of the ${\nu }_2$ out of plane banding mode, was at 10.175 ± 0.010 eV in NH₃, 10.180 ± 0.010 eV in ND₃. The second electronic state of NH₃ and ND₃ is complex. Onset was found to be 14.94 ± 0.03 eV for both NH₃ and ND₃. The band in NH₃ apparently consists of two consecutive vibrational series (I and II) having different frequency intervals and are superimposed on a continuum. In ND₃ series I is missing, although series II is present with a spacing consistent with an isotope effect of some unknown vibrational mode.