ELECTRON-ENERGY-LOSS SPECTROSCOPY IN MONOSUBSTITUTED BENZENES

The electron energy-loss spectra of toluene, monochlorobenzene, phenol , nitrobenzene and aniline vapours have been obtained at 70 eV impact energy and 0 degrees scattering angle. Interpretation of the spectra h as been attempted with the aid of previous experimental data and quant um chemical calculations in the literature. The excited states observe d are generally in good agreement with those obtained in vacuum ultrav iolet optical absorption studies. In extending the measurements beyond the first ionization potentials, unreported transitions have been obt ained and are assigned to Rydberg states on the basis of term values w ith respect to ionization potentials determined by photoelectron spect roscopy. Apparent optical oscillator strength distributions were deriv ed from the energy-loss data under the assumption that the Born approx imation is valid at energies as low as 70 eV.