A study of the valence shell photoionisation dynamics of CH3CN and CF3CN

Valence shell angle resolved photoelectron spectra of CH₃CN and CF₃CN have been recorded in the photon energy range 14–120 eV, thereby allowing asymmetry parameters and branching ratios to be derived. The carbon and nitrogen K-shell photoabsorption spectra of these two molecules exhibit features ascribed to shape resonantly enhanced transitions. Energy dependent variations observed in the asymmetry parameters and branching ratios provide evidence of shape resonances influencing the valence shell photoionisation dynamics. In addition to the main lines associated with single-hole states, complex satellite structure appears in the inner valence region of the photoelectron spectrum due to many-electron effects. The experimental spectra have been interpreted using previously reported ionisation energies and spectral intensities obtained from Green's function calculations.