Theoretical study of the photoionization shape resonances of cobaltocene and nickelocene

The outer valence photoionization cross-section profiles of cobaltocene and nickelocene have been calculated and compared with experimental data. The main features observed in the experiment are well reproduced by the theory and are ascribed to shape resonances. The continuum wave function calculated for photoelectron energies corresponding to the resonances is then analyzed, taking advantage of a procedure which keeps the only one non-zero contribution to the dipole transition moment of the initial state with the final continuum. This procedure allows to ascribe unambiguously the observed features to various mechanisms such as trapping of f waves onto the encaged metal atom, shape resonances to ligand quasi-bound orbitals and the splitting of continuum orbitals in the molecular effective field. (C) 2001 Elsevier Science B.V. All rights reserved.