Threshold photoelectron spectra of tetrahydrofuran over the energy range 9-29Â eV

Threshold photoelectron spectra of the tetrahydrofuran (THF) molecules, C4H8O have been measured over the photon energy range 9-29 eV using synchrotron radiation. For the lowest photoelectron band at 9.3-10.5 eV, due to ionization from the oxygen atom lone-pair 9b/12a′ orbital (C2/Cs conformations), vibrational structures have been observed superimposed on a broad maximum. The resolved vibrational series have been attributed to ionization transitions from the C2 conformation of the THF molecule with an adiabatic energy of 9.427 eV. The underlying broad maximum has been assigned to ionization from the Cs conformation of the THF molecule with a vertical energy of 9.73 eV. This is the first observation of the ionization transitions from two conformations of a pseudorotating molecule. New photoelectron bands have been also identified in the photon energy region 16-26 eV.