Theoretical study of the correlation effects in the photoelectron spectrum of bis(*-allyl)nickel

CI calculations of the photoelectron spectrum of bis(pgreco-allyl)nickel have been performed in several model spaces. The most importante effects are found to be associated with a quasidegenerate space corresponding to the allyl p-greco and Ni 3d orbitals, with significant contribution up to 4h-3p excitations. Inclusion of single and double excitations in the remaining virtual space, with perturbative selection of configurations, gives a good reproduction of the upper experimental spectrum recovering the errors given by previous ab-initio treatments.