Electron-Impact Spectroscopy Investigation of Diketene

Abstract

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 f π* transition, a π f σ*(3s) Rydberg transition, and a π f π* transition.

UV-Induced Unimolecular Photochemistry of Diketene Isolated in Cryogenic Inert Matrices

“…The second transition in the electronic spectrum of DK was reported at 5.89 eV (∼210.5 nm) and assigned to a π → σ*­(3s) Rydberg transition . This assignment is again in agreement with the present NBO calculations that predict the LUMO+2 to be of the Rydberg type.…”

“…When irradiation at 280 nm was applied, the IR spectrum of the DK monomer started to decrease noticeably, while new bands due to photogenerated species appeared in the spectrum. The energy of 4.36 eV (∼284.4 nm) was earlier tentatively assigned to an n → π* transition of monomeric DK, in an experimental study of the electronic spectrum of DK by the technique of variable-angle, electron energy loss spectroscopy . The NBO calculations performed in the present study confirm the assignment reported before .…”

“…The energy of 4.36 eV (∼284.4 nm) was earlier tentatively assigned to an n → π* transition of monomeric DK, in an experimental study of the electronic spectrum of DK by the technique variable-angle, electron energy loss spectroscopy. 39 The NBO calculations performed in the present study confirm the assignment reported before. 39 The energies of the frontier and several adjacent molecular orbitals calculated at the DFT and MP2 levels of theory are presented in Figure 3.…”

“…39 The NBO calculations performed in the present study confirm the assignment reported before. 39 The energies of the frontier and several adjacent molecular orbitals calculated at the DFT and MP2 levels of theory are presented in Figure 3. The highest occupied molecular orbital (HOMO) is occupied by the lone electron pair of the carbonyl oxygen atom of DK and is of σ-type.…”

“…The second transition in the electronic spectrum of DK was reported at 5.89 eV (∼210.5 nm) and assigned to a π → σ*(3s) Rydberg transition. 39 This assignment is again in agreement with the present NBO calculations that predict the LUMO+2 to be of the Rydberg type. Furthermore, it was gratifying to find that when one reduced the wavelength of the UV-tunable laser to λ = 225 nm (in a separate experiment), the photochemical behavior of DK resulted in different relative amounts of photoproducts (compared to the longer wavelength excitations described above), thus clearly indicating the involvement in the phototransformations of a new excited electronic state of DK.…”