THE INFLUENCE OF NONADIABATIC EFFECTS ON THE OUTER VALENCE SHELL PHOTOIONIZATION DYNAMICS OF BORON-TRIFLUORIDE

The entire valence shell photoelectron spectrum of boron trifluoride h as been studied using synchrotron radiation in the photon energy range 20-120 eV. Photoelectron angular distributions and branching ratios f or the six outer valence orbitals have been measured and compared with theoretical predictions. The strongest evidence for the e' shape reso nance affecting the valence shell photoionisation dynamics appears in the asymmetry parameter associated with the 4a(1)' orbital. Strong vib ronic coupling effects are observed in the vibrational structure exhib ited by the E (2)A(1)' state and asymmetry parameters are reported for several vibrational components. The data demonstrate that the asymmet ry parameters associated with the photoelectron peaks induced through vibronic coupling are characteristic of the ionic state through which they derive their intensity. Complex structure, associated with ionisa tion from the 2e' and 3a(1)' inner valence orbitals, is observed in th e photoelectron spectrum for binding energies between 26 and 50 eV. Th is structure is compared with pole strengths calculated using the many -body Green's function approach. (C) 1998 Elsevier Science B.V.