Threshold photoelectron spectroscopy of boron trifluoride Original Research Article

The threshold photoelectron spectrum of boron trifluoride has been recorded over the entire outer valence ionization region (15–37 eV) under high-resolution conditions using synchrotron radiation and employing the penetrating-field threshold electron collection method. By means of a direct comparative study with the photoelectron spectrum of BF3 over the same binding energy region numerous autoionization effects are identified in the ionic band systems in the threshold photoelectron spectrum. Extensive vibrational “filling-in” is found in the Franck–Condon gap regions between the four lowest ionic-state band systems that are attributed to resonance autoionization of Rydberg states lying in these binding-energy regions. Extensive vibronic coupling effects are found in all band systems of BF3+ in general agreement with theory. Analysis of the vibrational structure in most band systems of BF3+ suggests that interstate vibronic coupling via pseudo-Jahn–Teller interactions may be more complicated than previously assumed. There is some evidence that a shape resonance involving the 5e′ molecular orbital of BF3 is important in populating the (D 2E′) and (E 2A1′) states of BF3+ as observed in the attendant band systems of the threshold photoelectron spectrum.