Inner shell excitation and ionization of the monohalobenzenes

Energy loss (excitation) spectra of the gaseous monohalobenzenes, C 6H 5X (X = F, Cl, Br and I), were obtained by fast electron impact in the regions of the respective carbon 1 s, chlorine 2 p and 2 s, bromine 3 d and iodine 4 d edges. Gas phase X-ray PES measurements of the binding energies of these levels are also reported. Structure observed below the ionization limits has been interpreted with the aid of term values derived from the two sets of measurements.