OBSERVATION OF TEMPORARY-NEGATIVE-ION STATES IN CONDENSED METHANOL VIA VIBRATIONAL-EXCITATION INDUCED BY SLOW-ELECTRON SCATTERING

We report the measurements of electron-impact vibrational excitation o f amorphous methanol condensed an a polycrystalline Pt substrate over incident energies of 1-20 eV at a large off-specular angle. The spectr a obtained show that vibrations within solid methanol in its ground st ate are rather sensitive to the variation of impact energy and then is tangible evidence of the formation of at least three compound tempora ry-negative-ion (TNI) states. The low-energy feature lying between 3 a nd 6 eV is assigned tentatively to a (2)A' valence-shape resonance wit h a (2)[N,(8a'sigma)(1)] configuration, whose parent state is the gro und state (1)A' of the molecule. The origin of the second broad struct ure centered around 7.0 eV in the excitation functions may be threefol d: a Feshbach-type resonance (2)A'' of the electronic configuration (2 )[(2a'')(1),(3sa')(2)] (about 7 eV); a nearby shape resonance (2)A' of (2)[(N,(9a' sigma)(1)] (about 8 eV); and probably also a minor contr ibution from another (2)[((7a')(1),(3sa')(2)] Feshbach resonance (2)A' (about 9 eV). The third broad bandlike resonant feature, extending fr om 11 up to 17 eV, may consist of overlapping TNI states, dominated by the 2[(6a')(1),(3sa')(2)] Feshbach resonance (2)A'. Plausible decay c hannels from their configurations are discussed.