title: Two-dimensional Penning ionization electron spectroscopy of open-shell metallocenes: outer valence ionic states of vanadocene and nickelocene.
abstract: In order to investigate outer valence ionic states of open-shell metallocenes, we have applied two-dimensional collision-energy/electron-energy-resolved Penning ionization electron spectroscopy (2D-PIES) upon collision with metastable He*(2(3)S) excited atoms as well as a high level ab initio molecular orbital calculation (the partial third-order quasiparticle theory of the electron propagator (P3)) to ionization from neutral ground states of vanadocene ((4)A2g) and nickelocene ((3)A2g). Assignments of observed Penning ionization electron/He I ultraviolet photoelectron spectra were consistent with the P3 calculation results for ionization of α and β spin electrons except for electron correlation bands observed by PIES. Negative collision energy dependence of partial Penning ionization cross-sections (CEDPICS) indicate attractive interaction with He*(2(3)S) around the molecule. Results by model potential calculation utilizing Li(2(2)S) instead of He*(2(3)S) for interaction between He*(2(3)S) and open-shell metallocenes do not explain the strong negative CEDPICS of the bands observed in PIES.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan. kishimoto@m.tohoku.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Kishimoto
authors.forename: Miku
authors.initials: M
authors.lastname: Kimura
authors.forename: Koichi
authors.initials: K
authors.lastname: Ohno