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 ν2 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.