Electron-Impact Spectroscopy Investigation of Diketene

The electronic spectrum of diketene was investigated by the technique of variable-angle, electron energy loss spectroscopy, using the impact energies of 25 and 50 eV, and varying the scattering angle from 10° to 90°. Transitions have been observed at 4.36, 5.89, 6.88, and 7.84 eV. On the basis of the intensity variation of these transitions with impact energy and scattering angle, and through analogy with simpler molecules, the first three are tentatively assigned to an n → π* transition, a π → σ*(3s) Rydberg transition, and a π → π* transition.