A study of valence level photoelectron cross sections for the metallocenes of vanadium, chromium, cobalt and nickel from 20 to 100 eV☆

Abstract Relative partial photoionization cross sections and photoelectron branching ratios have been measured for the valence bands of the bis-η 5 -cyclopentadienyl compounds of vanadium, chromium, cobalt and nickel over the photon energy range 20 to 80 or 100 eV. The d bands show cross section features attributable to 3d resonant photoemission in the vicinity of the 3p → 3d giant resonance absorption. These features are stronger for V and Cr than for Co and Ni. Other intensity maxima are attributed to shape resonances in f ionization channels for the a 1 ′ and e 2 ′ ionizations those for the a 1 ′ being stronger than those for the e 2 ′ bands. The 2 e 1 ″ bands of Co(η-C 5 H 5 ) 2 and Ni(η-C 5 H 5 ) 2 show particularly strong shape resonances. Evidence is presented for d orbitals covalency in the 1 e 1 ″ orbitals. Previous assignments for the a 1 ′ ionizations are confirmed.