Experimental momentum-space orbital density study of valence-shell electronic structure and many-body effects of trans-dichloroethylene by symmetric noncoplanar (e, 2e) spectroscopy Original Research Article

The valence-shell electronic structure of trans-dichloroethylene has been investigated by symmetric noncoplanar (e, 2e) spectroscopy. lonization energy (IE) spectra of the valence shell (6–46 eV) have been obtained at relative azimuthal angles of 0° and 8° and compared with literature photoelectron (PE) data. The present work confirms the presence of extensive many-body features in the inner-valence region (> 18 eV), reported by previous PE studies and predicted by a literature Greenʹs function calculation. Momentum distributions (MDs) of selected valence-shell ionic states of trans-dichloroethylene have been determined for the first time, and they are compared with MDs of the corresponding orbitals generated from ab initio self-consistent field wavefunctions of 4-31 G, 6-31 G and 6-31++ G∗∗ basis sets. Good agreement between experiment and calculations is found only for a limited number of ionic states including the D(9ag) −1, E(2au)−1, and H(7bu)−1 states. Discrepancies are noted particularly in the lower-momentum region of the MDs of the X(3au)−1, A(10ag)−1 +B(9bu)−1 +C(2bg)−1, and F(8bu)−1 + G(8ag)−1 outer-valence ionic states, as well as of the many-body (satellite) states corresponding to the removal of electrons from the 7ag and 6ag orbitals in the inner-valence region. The observed discrepancies in the MDs generally indicate the inadequacies of the basis sets, which are useful for further development of precise electronic wavefunction for trans-dichloroethylene on an orbital-by-orbital basis. Furthermore, the orbital assignments for the close-lying D and E ionic states have been definitively clarified by examining their characteristic MDs. Finally, MD measurements of selected satellite states above 26 eV have provided support for the hypothesis that these many-body states are dominated by the removal of electrons from the innermost valence orbital 6ag.