ELECTRON-SPECTROSCOPY OF RESONANCE-ENHANCED VIBRATIONAL EXCITATIONS OF GASEOUS AND SOLID TETRAHYDROFURAN

We report intramolecular vibrational excitation of tetrahydrofuran (TH F) in both the gas and solid phase induced by 1-30 eV electrons. High- resolution electron-energy-loss spectra reveal selective vibrational e nhancement of THF for different impact energies, indicating the presen ce of at least three resonances (i.e., temporary anion states), locate d near 4, 7.5, and 10 eV, as well as many possibly overlapping higher- lying resonances. We also report electron-energy-loss spectra for diff erent THF film thicknesses. Besides fundamental vibrational excitation , we observe several energy loss peaks due to overtones and combinatio n vibrational modes. The present vibrational losses are assigned in co mpliance with published optical measurements. The similarities between the solid THF and gaseous cyclopentane spectra suggest that the reson ances in both molecules could have a common origin and hence need not be attributed to the presence of the oxygen nonbonding electrons in TH F. (C) 1998 American Institute of Physics. [S0021-9606(98)70438-6].