Electron energy loss and dissociative electron attachment spectroscopy of methyl vinyl ether and related compounds

The triplet and singlet excited states of methyl vinyl ether have been char acterized by electron energy loss spectroscopy and multireference density f unctional theory with configuration interaction (DFT/MRCI). The electron at tachment energy was determined from the excitation functions for vibrationa l excitation to be 2.3 eV. Dissociative electron attachment spectra have be en measured with a mass spectrometer having a trochoidal monochromator in t he incident electron beam. Fragment anion bands peaking at 3 eV, 6.5 eV and 9.5 eV have been found in methyl vinyl ether. The first band is assigned t o the (2)(pi*) shape resonance, the second band to a resonance where an ele ctron is loosely bound by dipole and polarization forces to the target mole cule in its valence excited (1)(pi, pi*) state, and the third band to Feshb ach resonances with occupation of Rydberg orbitals. CH3O- and H2CC- are for med at 3 eV, CH3O- and HCC- at 6.5 and 9.5 eV. The fragmentation pattern of ethyl vinyl ether at 3 eV is similar, yielding ethanolate and vinylidene a nions, but with the unexpected addition of the deprotonated acetaldehyde an ion CH2CHO-. The fragmentation patterns of methyl allyl ether and benzyl me thyl ether are dominated by the methanolate anions with high intensity, ind icating that dissociation of C-O bond in unsaturated ethers is much faster if this bond does not lie in the plane of the pi system. (C) 2001 Elsevier Science B.V.