Threshold photoelectron spectroscopy of boron trifluoride

Abstract

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 BF 3 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 BF 3 + in general agreement with theory. Analysis of the vibrational structure in most band systems of BF 3 + 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 BF 3 is important in populating the (D 2 E ′ ) and (E 2 A 1 ′ ) states of BF 3 + as observed in the attendant band systems of the threshold photoelectron spectrum.