The K-shell spectra of tetrahydrofuran studied by electron energy loss spectroscopy and ab initio calculations

Ab initio calculations have been carried out in order to assign the bands observed in the carbon and oxygen K-shell spectra of gaseous tetrahydrofuran (THF), measured using inner-shell electron energy loss spectroscopy (ISEELS). The good agreement between the theoretical and the measured spectra allows us to re-assign precisely most of the peaks. The ionisation energies are calculated for the first time and found to be consistent with a quantum defect analysis of the core excitation energies. The calculated spectra for the C2v, C2 and Cs geometries of the molecule show very small differences. Thus, K-shell spectroscopy cannot be used to solve the controversy on the geometry of THF.