Electron momentum spectroscopy study of a conformationally versatile molecule: n-propanol

As a continued study of structural versatile molecules, n-propanol (CH3CH2CH2OH) has been investigated with our newly developed electron momentum spectrometer. n-propanol is a straight-chain molecule with one more carbon atom than ethanol. In order to verify the validity of the plane wave impulse approximation (PWIA), the measurements were conducted at impact energies of 1200 eV and 600 eV. The theoretical calculations of five known conformers: Tt, Tg, Gt, Gg, Gg' were performed by B3LYP/aug-cc-pVTZ and OVGF/6-311++G** methods with thermodynamic population analysis. This process can well simulate the measurements. Both measurements and theoretical simulations show that the one-electron binding energies and momentum distributions highly depend on the conformation. Depending on the conformation, a given orbital (e.g. MO11) may contribute to different bands in the (e, 2e) ionization spectrum. It was found that the momentum distributions can reflect the distortions and topological changes that molecular orbitals undergo due to the internal rotation of the hydroxyl and the distortion of the carbon chain.