HIGH-RESOLUTION THRESHOLD PHOTOELECTRON-SPECTROSCOPY OF MOLECULAR FLUORINE

The threshold photoelectron spectrum of molecular fluorine has been re corded in the 15.6-21.9 eV photon energy range, at resolutions ranging from 3 to 12 meV, using synchrotron radiation and a penetrating-field electron spectrometer. In addition to observing the three known band systems of F-2(+) at higher resolution than previously achieved with c onventional photoelectron spectroscopy, extensive vibrational structur e is found in the Franck-Condon gaps between the main electronic syste ms of F-2(+). This extended vibrational structure is attributed to res onance autoionization of neutral Rydberg states.