LOW-ENERGY ELECTRON-ENERGY-LOSS SPECTROSCOPY OF SOLID METHANOL - VIBRATIONAL AND ELECTRONIC EXCITATIONS

We report electron-energy-loss spectra for 19-eV electrons incident on a solid film of methanol (30 layers) condensed at 15 K. The vibrational energy losses compare more closely to the infrared absorption spectrum of solid methanol in its amorphous phase. The first electronic excitation is found around 7.7 eV with a threshold at 6.7 eV. It Is followed by a weak band around 9.5 eV. These two excitation features are identified to the gas-phase transitions (3,1)A'' (2a''-->3s) and (3,1)A' (7a'-->3s), blueshifted by 1.0-1.4 eV in the condensed phase. At higher energy loss, we have a large maximum around 15.5 eV due to various transitions from the ground state to free-electron conduction bands and to the ionization cross section of the solid.