An electron momentum spectroscopy and density functional theory study of theouter valence electronic structure of stella-2,6-dione

Abstract

We report on the first electron momentum spectroscopy (EMS)study into the outer valence electronic structure of the groundelectronic state for the organic molecule stella-2,6-dione (C8H8O2).Experimentally measured binding-energy spectra are compared against a He(Iα)photoelectron spectroscopy result, while our derived momentum distributions(MDs) are compared against corresponding results from the plane wave impulseapproximation (PWIA) level calculations. These computations employeddensity functional theory (DFT) basis states at the triple zeta valencepolarization (TZVP) level, with a range of exchange-correlation (XC)functionals. A detailed comparison between the experimental and PWIADFT-XC/TZVP calculated MDs enabled us to evaluate the accuracy of thevarious functionals, the Becke–Perdew (BP) XC functional being found to providethe most accurate description here. The importance of the through-bondinteraction to the molecular orbitals (MOs) of stella-2,6-dione is demonstratedusing the orbital imaging capability of EMS. Finally we show that themolecular geometry of this molecule, as derived from BP/TZVP, is in quitegood agreement with corresponding independent experimental data.