Angle-resolved photoelectron study of the valence levels ofBF3in the range17≤hν≤28eV

Photoelectron branching ratios and angular distributions have been measured for the six outermost levels of ${\mathrm{BF}}_3$ in the range $17\le h\nu \le 28$ eV with the use of synchrotron radiation. Comparisons are made with a recent multiple-scattering model calculation which indicates that a shape resonance in the $e^{\prime }$ electronic continuum should appear in five of the six channels studied. Good agreement between experiment and theory is found in a majority of the comparisons; however, experimental evidence for the expected $e^{\prime }$ shape resonance is clear in some cases but absent in others. The results are discussed in the context of other cases in which shape resonances, well known from inner-shell spectra, are obscured in valence-shell properties. Experiments which would help clarify the role of the $e^{\prime }$ shape resonance in the photoionization dynamics of ${\mathrm{BF}}_3$ are suggested.