On the origin of the additional bands observed in the photoelectron spectra obtained with Ne or Ar resonance lines

Photoelectron spectra of benzene, fluorobenzene and pyridine ionized by the Ne (16.85 and 16.67 eV) or by the Ar (11.83 eV and 11.62 eV) resonance lines are reinvestigated with a spherical-grid kinetic energy analyzer. Some other hydrogenated and non-hydrogenated molecules are also studied. In the spectra of the hydrogenated molecules a band not observed with the He I (21.22 eV) resonance line is generally visible. It is shown that this additional band can be interpreted as being due to the Lyman α line (10.195 eV). Hydrogen coming from the target molecules is probably responsible for the occurrence of this impurity line.