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

Abstract

The triplet and singlet excited states of methyl vinyl ether have been characterized by electron energy loss spectroscopy and multireference density functional theory with configuration interaction (DFT/MRCI). The electron attachment energy was determined from the excitation functions for vibrational excitation to be 2.3 eV. Dissociative electron attachment spectra have been measured with a mass spectrometer having a trochoidal monochromator in the 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 to the 2(π∗) shape resonance, the second band to a resonance where an electron is loosely bound by dipole and polarization forces to the target molecule in its valence excited 1(π, π∗) state, and the third band to Feshbach resonances with occupation of Rydberg orbitals. CH 3O − and H 2CC − are formed at 3 eV, CH 3O − 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 anions, but with the unexpected addition of the deprotonated acetaldehyde anion CH 2CHO −. The fragmentation patterns of methyl allyl ether and benzyl methyl ether are dominated by the methanolate anions with high intensity, indicating that dissociation of C–O bond in unsaturated ethers is much faster if this bond does not lie in the plane of the π system.