Vibrational fine structure on the core level photoelectron lines of small polyatomic molecules

The C 1s and O 1s photoelectron spectra of CH4, CD4, CF4, C2H6 and CO2 have been measured with high photon energy resolution. Vibrational fine structure on the main line (single hole state) could be resolved for all molecules except CF4. Even in the case of C2H6 where several modes are expected to couple, two prominent progressions are visible. The fine structure on the C 1s line of CO2 results, as expected, from the totally symmetric stretching mode, whereas the O 1s main line is dominated by the antisymmetric stretching mode of ?u symmetry due to vibronic coupling.