EXPERIMENTAL MOMENTUM-SPACE ORBITAL DENSITY STUDY OF VALENCE-SHELL ELECTRONIC-STRUCTURE AND MANY-BODY EFFECTS OF TRANS-DICHLOROETHYLENE BY SYMMETRICAL NONCOPLANAR (E, 2E) SPECTROSCOPY

The valence-shell electronic structure of trans-dichloroethylene has b een investigated by symmetric noncoplanar (e, 2e) spectroscopy. Ioniza tion energy (IE) spectra of the valence shell (6-46 eV) have been obta ined at relative azimuthal angles of 0-degree and 8-degrees and compar ed with literature photoelectron (PE) data. The present work confirms the presence of extensive many-body features in the inner-valence regi on (> 18 eV), reported by previous PE studies and predicted by a liter ature Green's function calculation. Momentum distributions (MDs) of se lected valence-shell ionic states of trans-dichloroethylene have been determined for the first time, and they are compared with MDs of the c orresponding orbitals generated from ab initio self-consistent field w avefunctions of 4-31G, 6-31G 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(9a(g))-1, E(2a(u))-1, and H(7b(u))-1 states. Discrepancies are noted particularly in the lower-momentum reg ion of the MDs of the X(3a(u))-1, A(10a(g))-1 + B(9b(u))-1 + C(2b(g))- 1, and F(8b(u))-1 + G(8a(g))-1 outer-valence ionic states, as well as of the many-body (satellite) states corresponding to the removal of el ectrons from the 7a(g) and 6a(g) orbitals in the inner-valence region. The observed discrepancies in the MDs generally indicate the inadequa cies of the basis sets, which are useful for further development of pr ecise electronic wavefunction for transdichloroethylene on an orbital- by-orbital basis. Furthermore, the orbital assignments for the close-l ying D and E ionic states have been definitively clarified by examinin g their characteristic MDs. Finally, MD measurements of selected satel lite 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 6a(g).