THE CORRELATION STATES OF FURAN AND THIOPHENE BY HIGH-RESOLUTION SYNCHROTRON PHOTOELECTRON-SPECTROSCOPY

The high resolution synchrotron photoelectron spectra (PES) of furan and thiophene are obtained at 90-200 eV photon energy. Several ionization peaks attributed to inner valence orbitals and correlation (satellite) states are resolved for the first time. By using the photon energy dependence of the ionization cross sections of the valence orbitals and the correlation states, significant insight into the dominant character of the valence orbitals and correlation states of furan and thiophene is attained. Two classes of a1-type molecular orbitals in furan, two classes of b2-type molecular orbitals in furan and two types of correlation (satellite) states in thiophene are distinguished by the present procedure. Some limitations of the photon energy dependence of molecular photoionization cross sections are also discussed.