High-resolution threshold photoelectron spectroscopy of molecular fluorine Original Research Article

The threshold photoelectron spectrum of molecular fluorine has been recorded in the 5.6–21.9 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 F2+ at higher resolution than previously achieved with conventional photoelectron spectroscopy, extensive vibrational structure is found in the Franck-Condon gaps between the main electronic systems of F2+. This extended vibrational structure is attributed to resonance autoionization of neutral Rydberg states.