The band 12 issue of norbornane: a study of higher shake-up states.

ABSTRACT

In line with a recent study of the electronic structure of the cage compound norbornane (J. Chem. Phys. 121 (2004), 10525; J. Phys. Chem. A 109 (2005), 4267), symmetry adapted cluster expansion configuration interaction (SAC-CI) general R calculations have been performed and compared with results obtained by the third order algebraic diagrammatic construction scheme [ADC(3)]. Comparison has been made with previously performed electron momentum spectroscopy (EMS) and ultraviolet photo-electron measurements. The region around ~25 eV (band 12), characterized by an elaborated band in the EMS spectrum which is missing in previous Green's function and ADC calculations, is investigated. This study is completed with outer-valence Green's function (OVGF) and SAC-CI/SD-R calculations, and results are obtained by employing (single and double) ionization extended second order ADC [ADC(2)-x]. Since ADC(3) only includes 2h-1p shake-up states, while SAC-CI general-R also includes higher order states, the agreement between both methods assures that the higher order shake-up states do not play an important role in the ionization spectrum of norbornane. While the band-12 issue of norbornane is therefore still open for further discussion, a tentative description in terms of ultrafast nuclear dynamical effects and autoionization processes has become more plausible.