Etude par spectrometrie de photoelectrons de la structure electronique des enynes conjugues

We have measured by UV excited photoelectron spectroscopy the ionization potentials of 22 conjugated alkynes, in particular, those associated with three π orbitals (π_, π_, π₊. The corresponding bands appear in this order in the spectrum. We have also calculated the orbital energies of these compounds by two semi-empirical quantum mechanical methods (INDO and SPINDO).Discussion of the ionization potential variations in terms of polar effects confirms the spatial distribution of the orbitals predicted by calculation.The vibrational structure of the photoelectron bands confirms their attribution and the role predicted for the orbitals associated with the chemical bonds of these compounds.