Electronic spectra of aliphatic carbonyl compounds by electron impact spectroscopy: III. Unsaturated compounds

Electron impact energy loss spectra at an impact energy of 100 eV and a scattering angle of 2 degrees are presented for propenal (CH₂ = CHCHO) and methyl vinyl ketone (CH₂ = CHCOCH₃). The spectra are tentatively assigned using quantum defects and term values derived from ionization potentials measured by photoelectron spectroscopy. The duality of Rydberg and valence transition assignments in propenal is discussed. It is shown that a transition earlier assigned by Walsh to be π → π* is most probably a Rydberg transition.