Electronic structure and spectra of small rings. V Photoelectron and electron impact spectra of cyclopropenone

The photoelectron and electron impact spectra of cyclopropenone are presented and are interpreted with the aid of Gaussian orbital calculations of double-zeta quality. The spectra and the calculations all lead to the conclusion that there is an unusually large interaction between both the pi and lone pair orbitals in the carbonyl portion of the molecule with the pi and sigma orbitals of the olefin portion. The first ionization potential (9.57 eV) involves ionization of an electron from the oxygen lone pair, whereas the second (11.19 eV) involves ionization of an electron from the olefin pi bond. The most vertical ionization is from the 7a1 MO (16.11 eV), the second lone pair orbital on oxygen. Rydberg series are observed in the electron impact energy loss spectrum converging upon each of these three ionization potentials.